JPH03169734A - Suspension control device - Google Patents

Abstract

PURPOSE:To make riding sensation compatible with drive stability with excellent response by a method wherein, when either a flat or an adverse road state is continued, setting of a damping force is corrected according to the magnitude of a deviation between variation frequency and target frequency of a given parameter. CONSTITUTION:The rate of change of the damping force of a shock absorber M1 mounted to a suspension S of a vehicle is detected by a means M2, and a damping force is controlled by a means M3 according to the magnitude of a deviation between a detecting value and a reference value. The state of a road on which a vehicle runs is detected by a means M4, a damping force is regulated and corrected to an average value of a flat or an adverse road by a means M5, based on a detecting result from the road state detecting means. In above device, it is detected by a means M6 whether a difference is produced between the states of set variation of a damping force by means of the means M3. When the difference is produced, the reference value for regulation of a damping force or target frequency of variation of setting is regulated and correction is effected by a means M7 so that a control difference is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a suspension control device, and more specifically, the present invention relates to a suspension control device, and more specifically, it is equipped with a shock absorber that can vary the setting of damping force, and is capable of controlling the shock based on the driving condition of the vehicle. The present invention relates to a suspension control device that controls the generation pattern of damping force of an absorber to improve ride comfort and handling stability.

[Prior Art] This type of suspension control device detects the rate of change in the damping force of a shock absorber, and when this rate of change exceeds a predetermined value, that is, the damping force is increased based on unevenness of the road surface, brake operation, etc. It is known that when a sudden change occurs, the damping force generation pattern of the shock absorber is quickly switched to a smaller value side, thereby increasing the responsiveness of the shock absorber control. Furthermore, there is also a suspension control device that attempts to further improve ride comfort by changing the magnitude of the reference value for adjusting the rate of change in damping force, which determines when to switch the damping force setting, based on vehicle driving conditions such as vehicle speed. Proposed(
For example, Japanese Patent Application Laid-Open No. 64-67407).

[Problems to be Solved by the Invention] Such a suspension control device is excellent in maintaining good ride comfort by quickly following changes in the damping force pattern to changes in road surface conditions. If the above continues, there is a problem that the ride comfort and steering stability are not necessarily sufficient.For example, when driving continuously on a flat road, the shock absorber is maintained at a large damping force, so the suspension is hard (
(Hard), small irregularities on the road surface may become more noticeable. On the other hand, if the vehicle continues to drive on a rough road, the shock absorber will continue to maintain its damping force at a low level, resulting in a loss of ground contact and possibly impairing the driving feeling.

In order to solve this problem, the applicant has separately applied for a technology that determines whether a flat road or a rough road continues and performs control according to the determination result, but the actual driving conditions etc. This problem becomes even more complex depending on the situation. In other words, the damping force characteristics of the shock absorber for the front and rear wheels of a vehicle often differ due to the state of weight distribution between the front and rear wheels, such as the number of passengers and loaded cargo, or the difference in the suspension type between the front and rear wheels. While there is a risk of unbalanced control between the front and rear wheels, a similar problem also occurs between the left and right wheels.

The suspension control device of the present invention solves the above problems,
The purpose is to improve the ride comfort and steering stability when the road is flat or rough, and also to prevent the occurrence of imbalance in control at each wheel of the vehicle.

The structure of the present invention that achieves the above object will be explained below.

[Means for Solving the Problems] As illustrated in FIG. 1, the suspension control device of the present invention includes: a shock absorber M1 provided in each suspension S of a vehicle and capable of setting a damping force generation pattern; A damping force change rate detecting means M2 detects the rate of change in the damping force of each shock absorber M1, and a damping force change rate detecting means M2 detects the rate of change in the damping force of each shock absorber M1, and the a damping force control means M3 that changes the setting of the damping force for the absorber M1; and a condition of the road surface on which the vehicle runs based on the difference between the frequency at which the setting of the damping force is changed by the damping force control means M3 and a target frequency. a road surface condition detecting means M4 for detecting the road surface; Setting the damping force to be controlled,
A suspension control device comprising a damping force adjustment/correction means M5 for correcting the damping force to an average value set respectively on a flat road and a rough road, wherein each shock absorber M is controlled by the damping force control means M3. control difference detection means M6 for detecting whether or not a difference has occurred between the change situations of the damping force settings for the shock absorbers M1 and 1; When it is detected that a difference has occurred between the change situations, the adjustment reference value and/or the target The present invention is characterized by comprising a control difference correction means M7 that directly or indirectly corrects the frequency and adjusts the detected difference to a value that reduces the detected difference.

[Function] The suspension control device of the present invention having the above configuration has the following features:
Damping force change rate detection means M detects the rate of change in damping force of each shock absorber M1 provided in each suspension S of the vehicle.
2, and the damping force control means M3 changes the damping force setting of each shock absorber M1 based on the magnitude relationship between the rate of change of the damping force and a reference value for adjusting the damping force. In addition, it performs the following functions.

The road surface condition detecting means M4 detects, based on the difference between the frequency of changing the damping force setting by the damping force controlling means M3 and the target frequency,
Detects the condition of the road surface on which the vehicle is running. When it is determined that either a flat road or a rough road continues based on the road surface state detected in this way, the damping force adjustment correction means M5 controls the damping force controlled by the damping force control means M3. The force setting is corrected to the average value of the damping force set respectively on flat roads and rough roads.

As a result of such correction, for example, when an extremely flat road continues for a predetermined period of time or more, the damping force generation pattern of the shock absorber S is corrected from a large damping force setting to a small one, and when the vehicle continues to drive on a rough road. , the damping force is corrected from a small setting to a large one. As a result, the damping force generation pattern is not biased to one side, and the shock absorption and
Suspension characteristics with excellent ground contact balance.

Furthermore, in parallel with executing such control, the control difference detection means M6 detects whether a difference has occurred between the changes in the damping force setting for each shock absorber M1. For example, whether there is a difference between the damping force switching frequency for one shock absorber M1 and the damping force switching frequency for another shock absorber M1,
Alternatively, it is detected whether a difference has occurred between the time during which one shock absorber M1 is switched to soft mode and the time during which another shock absorber M1 is switched to soft mode.

When the control difference detection means M6 detects that there is a difference between the changes in the damping force settings for each shock absorber M1, the control difference correction means M7
Directly or indirectly correcting the adjustment reference value and/or target frequency for at least one of the shock absorbers M1 in which a difference in the damping force setting change situation has occurred;
Adjustment is made to a value that reduces the difference detected by the control difference detection means M6.

As a result, the difference between the changes in the damping force setting for each shock absorber M is eliminated through the control by the damping force control means M3 and/or the control by the damping force adjustment correction means M5.

The control difference correction means M6 is, for example, a device that detects a control difference between the front and rear wheels, a device that detects a control difference between the left and right wheels, or a device that detects a control difference between the front and rear wheels and the left and right wheels. Alternatively, it may be possible to detect whether or not there is a control difference between the torsion relationship, for example, between the left front wheel and the right rear wheel.

Furthermore, it may be possible to compare the four wheels completely independently and detect the occurrence of a control difference between one wheel and the other three wheels. Of course, the number of wheels is not limited to four, and the number of wheels may be more or less than that (however, two or more wheels).

Further, the control difference correction means M7 may be set to a value that eliminates the difference in the adjustment reference value and/or target frequency for one of the shock absorbers M1 for which it is determined that there is a difference, for example, by increasing one of the shock absorbers M1. Both may be adjusted by decreasing the other. Furthermore, this control difference correction means M7 may correct the difference as soon as it occurs, or
A configuration may be adopted in which the correction is performed when the difference exceeds a predetermined value.

In addition, the correction by the damping force adjustment correction means M5 {for shock absorbers that can control the damping force steplessly, it is sufficient to simply increase or decrease the damping force; This can be achieved by changing the adjustment reference value for switching.

[Examples] In order to further clarify the configuration and operation of the present invention described above, preferred embodiments of the suspension control device of the present invention will be described below.

FIG. 2 is a schematic configuration diagram showing the entire configuration of the suspension control device 1 of the first embodiment, FIG. 3(A) is a partially cutaway sectional view of the shock absorber, and FIG.
) is an enlarged sectional view of the main part of the shock absorber.

As shown in FIG. 2, the suspension control device 1 of this embodiment includes shock absorbers 2FL, 2FR, 2RL, and 2RR (hereinafter, all will be referred to as 2FL, FR) that can change the damping force in two stages. , RL,
It is abbreviated as RR.

(Other members will be described in the same manner) and an electronic control device 4 connected to each of these shock absorbers and controlling their damping force.
It is composed of. Each shock absorber 2 FL
, FR, RL, and RR are the left and right front and rear wheels, respectively.
Coil springs 8 FL, FR, RL, RR are installed between the suspension lower arms 6FL, FR, RL, RR of L, FR, RL, RR and the vehicle body 7.
It is attached with.

The shock absorbers 2 FL, FR, RL, and RR are the shock absorbers 2 FL, F, as described later.
A piezo load sensor that detects the force acting on R, RL, and RR, and a shock absorber 2 FL, FR, and R
It has a built-in piezo actuator for switching the setting of the damping force generation pattern for L and RR.

Next, each of the above-mentioned shock absorbers 2 FL, FR,
The structures of the shock absorbers 2 FL, FR, RL, and RR are all the same, so the shock absorber 2FL on the left front wheel 5FL side will be explained here as an example. In addition, in the following explanation, the reference numbers of each member provided on each wheel are as necessary: front left wheel 5 FL, front right wheel 5 FR, rear left wheel 5 R.
L, subscripts FL, FR, corresponding to right rear wheel 5RR,
RL and RR shall be added, and if there is no difference regarding each wheel, the subscripts shall be omitted.

The shock absorber 2, as shown in FIG. 3(A),
The lower end of the cylinder 11 side is fixed to the suspension lower arm 6 via the axle side member 11a.Meanwhile, the upper end of the rod 13 inserted through the cylinder 11 is fixed to the vehicle body 7 via the bearing 7a and the anti-vibration rubber 7b. is fixed together with a coil spring 8.

Disposed inside the cylinder 11 are an internal cylinder 15 connected to the lower end of the rod 13, a connecting member 6, a cylindrical member 17, and a main piston 18 that is slidable along the inner surface of the cylinder 1. ing. An internal cylinder 15 connected to the rod 13 of the shock absorber 2 houses a piezo load sensor 25 and a piezo actuator 27.

The main piston 18 is fitted onto the outside of the cylindrical member 17, and a sealing material]9 is interposed on the outer periphery of the main piston 18, which fits into the cylinder 11. Therefore, the inside of the cylinder 11 is divided into a first liquid chamber 21 and a second liquid chamber 23 by the main piston 18. A backup member 28 is screwed onto the tip of the cylindrical member 17, and between the cylindrical member 17 and the main piston 18, two spacers and a leaf valve 30 are placed on the cylindrical member 17 side, and a leaf valve 31 and a leaf valve 30 are placed on the cylindrical member 17 side. Rikira 3
2 are pressed and fixed to the backup member 28 side, respectively. In addition, the leaf valve 31 and the backup member 2
A main valve 34 and a spring 35 are interposed between the leaf valve 31 and the leaf valve 8, and bias the leaf valve 31 in the direction of the main piston 18.

These leaf valves 30, 31 are connected to the main piston 18.
When the main piston 18 is stopped, the extension and contraction passages 18a and 18b provided in the main piston 18 are closed on one side, and as the main piston 18 moves in the direction of arrow A or arrow B, and open to one side. Therefore, as the main piston 18 moves, the hydraulic oil filled in both the liquid chambers 21 and 23 moves between the two liquid chambers 21 and 23 through either of the passages 18a and 18b. In this way, the movement of the hydraulic oil between both the liquid chambers 21 and 23 is achieved through both passages 18a and 1.
8b, the damping force generated against the movement of the rod 13 is large and the suspension characteristics become hard.

A piezo load sensor 25 and a piezo actuator 27 housed inside the internal cylinder 15 (Fig. 3(A),
As shown in (B), this is an electrostrictive element laminate in which thin plates of piezoelectric ceramics are stacked with electrodes in between. Each electrostrictive element of the piezo load sensor 25 is polarized by the force acting on the shock absorber 2, that is, the damping force. Therefore, by extracting the output of the piezo load sensor 25 as a voltage signal using a circuit with a predetermined impedance, the rate of change in damping force can be detected.

The piezo actuator 27 (which is made by stacking electrostrictive elements that expand and contract with good response when a high voltage is applied to increase the amount of expansion and contraction) directly drives the piston 36.

When the piston 36 is moved in the direction of arrow B in FIG. 3(B), the plunger 37 and H
The spool 41, which has a letter-shaped cross section, is also moved in the same direction. When the spool 4 in the position shown in FIG. 3 (8) (origin position) moves in the direction B in the figure, the first liquid chamber 2
The sub-channel 16c connected to the pump 1 and the sub-channel 39b of the push 39 connected to the second liquid chamber 23 are communicated with each other. This sub-flow path 39b is further connected to the flow path 17a in the cylindrical member 17 via an oil hole 45a provided in the plate valve 45.
As a result, when the spool 41 moves in the direction of arrow B, the first liquid chamber 21 and the second liquid chamber 23
The flow rate of hydraulic oil flowing between the two increases. In other words, when the shock absorber 2 (yo piezo actuator 27) expands due to high voltage application, its damping force characteristics are switched from a high damping force (hard) state to a low damping force (soft) state, and when the electric charge is discharged and the piezo actuator 27 contracts, it decreases. Change the force characteristics to large damping force (
hard) state.

The amount of movement of the leaf valve 31 provided on the lower surface of the main piston 18 is determined by the spring 35.
It is regulated compared to Further, the plate valve 45 is provided with an oil hole 45b having a larger diameter than the oil hole 45a on the outside of the oil hole 45a.
When the hydraulic oil moves in the three push directions against the urging force of No. 6, the hydraulic oil becomes movable through the oil hole 45b. Therefore,
Regardless of the position of the spool 41, the main piston]
The hydraulic fluid flow rate when the main piston 8 moves in the direction of the arrow B is larger than when the main piston] 8 moves in the direction of the arrow 8. That is, the damping force is changed depending on the direction of movement of the main piston 18, thereby improving the characteristics as a shock absorber. Further, a hydraulic oil supply path 38 is connected to a check valve 38 between the oil-tight chamber 33 and the first liquid chamber 21.
a, and keeps the flow rate of hydraulic oil in the oil-tight chamber 33 constant.

Next, the electronic control device 4 that switches and controls the generation pattern of the damping force of the shock absorber 2 described above will be explained with reference to FIG. The sensors include a 4 m piezo seedling weight sensor 25 of each shock absorber 2, a steering sensor 50 that detects the steering angle of a steering wheel (not shown), a vehicle speed sensor 51 that detects the running speed of the vehicle, and a shift position of a transmission (not shown). A shift position sensor 52 that detects the shift position is connected to a stop lamp switch 53 that issues a signal when a brake pedal (not shown) is depressed.

The electronic control device 4 that outputs control signals to the piezo actuator 27 described above based on these detection signals etc. is configured as an arithmetic and logic operation circuit centering on a well-known CPU 61, ROM 62, and RAM 64. The connected input section 67 and output section 68 perform input/output with the outside.

In addition, the electronic control device 4 includes a damping force change rate detection circuit 70 connected to the piezo load sensor 25, a waveform shaping circuit 73 connected to the steering sensor 50 and the vehicle speed sensor 51, and a high voltage connected to the piezo actuator 27. A battery 77 is charged via an application circuit 75 and an ignition switch 76. A high-voltage power supply circuit 79 of a so-called switching regulator type that outputs the driving voltage for the piezo 7 quetuator and the battery 77
A constant voltage power supply circuit 80 and the like is provided, which transforms the voltage of the electronic control unit 4 to generate an operating voltage (5V) for the electronic control device 4. The shift position sensor 52, stop lamp switch 53, damping force change rate detection circuit 70, and waveform shaping circuit 73 are connected to the input section 67.
On the other hand, the high voltage application circuit 75 and the high voltage power supply circuit 79 are respectively connected to the output section 68.

The damping force change rate detection circuit 70 connects each piezo load sensor 2 to 5.
It consists of four detection circuits provided corresponding to FL, FR, RL, and RR, and each detection circuit outputs an output from a circuit including the piezo load sensor 25 according to the acting force that the shock absorber 2 receives from the road surface. The CPU outputs the voltage signal as the damping force change rate V of the shock absorber 2.
61. Further, the waveform shaping circuit 73 is a circuit that shapes the detection signals from the steering sensor 50 and the vehicle speed sensor 51 into signals suitable for processing in the CPU 61 and outputs the waveform-shaped signals. Therefore, the CPU
61 can determine road surface conditions, vehicle running conditions, etc. based on the output signals from the damping force change rate detection circuit 70 and the waveform shaping circuit 73, as well as its own processing results. Based on this determination, the CPU 61 outputs a control signal to the high voltage application circuit 75 provided corresponding to each wheel.

This high voltage application circuit 75 is a circuit that applies a voltage of +500 volts or -100 volts output from the high voltage power supply circuit 79 to the piezo actuator 27 according to a control signal from the CPU 61. Therefore, in response to this damping force switching signal, the piezo actuator 27 expands (when +500 volts is applied) or contracts (when -100 volts is applied), and the hydraulic oil flow rate is switched to change the damping force characteristics of the shock absorber 2 from soft to hard. can be switched to That is, the damping force characteristic of each shock absorber 2 is such that when a high voltage is applied to extend the piezo actuator 27, the first damping force in the shock absorber 2 is As the flow rate of the hydraulic oil flowing between the liquid chamber 21 and the second liquid chamber 23 increases, the damping force becomes small, and when the electric charge is discharged by the negative voltage and the Viezo actuator 27 is contracted, Since the hydraulic oil flow rate decreases, the damping force becomes large.

Next, the damping force control performed by the suspension control device 1 of this embodiment having the above-described configuration will be explained in FIGS. 5 and 6.
This will be explained based on the flowchart of FIG. 7 and FIG. Each routine is repeatedly executed for each of the shock absorbers 2 FL, FR, RL, and RR at predetermined time intervals by interrupt processing. In addition, in this example, special 12, front wheel 5 FL, FR side shock absorber 2 FL,
The processing for the FR and the processing for the rear wheels 5 RL and shock absorbers 2 RL and RR on the RR side are executed as one group.

The processing contents of each routine are as follows.

■ Damping force pattern switching control routine (Fig. 5) The piezo actuator 27 is switched based on the rate of change of damping force V, and the damping force is set to a large state. Minausumi ■ Frequency detection interrupt routine (Fig. 6) The rate of change of damping force within a predetermined time reaches the learning reference value V re
The number of times that fG is exceeded is detected as frequency N.

(2) Switching reference value learning routine (Fig. 7) The switching reference value V ref used for switching the damping force is learned based on the magnitude of the switching frequency N.

The above frequency detection interrupt routine and switching reference value learning routine (reference the time measurement variable C and frequency N to each other to learn the switching reference value V ref, and using the learned switching reference value V ref , the damping force pattern switching control routine executes damping force switching control.The details of each routine will be explained in order starting from the damping force pattern switching control routine (FIG. 5).

When this routine is started, first, the damping force change rate V of each shock absorber 2 is read from the damping force change rate detection circuit 70 via the input section 67 (step 100), and the damping force change rate V is larger than the switching reference value V ref learned in the switching reference value learning routine (FIG. 7) (step 110). ．．
If the damping force change rate ■ is smaller than the switching reference value V ref, it is determined whether the flag FHS, which indicates that the suspension characteristics are set to soft, has a value of 1 (
In step 120), if the flag FHS is not set to 1, that is, if it is not set to soft, the suspension is controlled to be hard (step 13o), and this routine is temporarily terminated. In addition, in the process of step 130, immediately after the damping force setting of the shock absorber 2 is switched from soft to hard, -100 volts is applied from the high voltage application circuit 75 to the piezo actuator using the control signal 12 from the output section 68. This is done by applying a voltage to the piezo actuator 27 to contract it, and if the piezo actuator 27 is already in a contracted state, it is held as it is.

On the other hand, when the damping force change rate V becomes larger than the switching reference value V ref (step 11o), a process of starting the timer, that is, a process of resetting the timer variable T to the value ○ is performed (step 14o), and further Assuming that the suspension characteristics are set to soft, processing is performed to set the flag FHS to "value" (step 15o). after that,
A high voltage of +500 volts is applied from the high voltage application circuit 75 to the piezo actuator 27 to switch and control the damping force of the shock absorber 2 to a small state (step 16
0), this routine ends.

After switching the damping force of the shock absorber 2 to a small state in this way, the damping force change rate V becomes the switching reference value V ref
If it exceeds the switching reference value Vref, the above-mentioned timer start and control to reduce the damping force are repeated, but when the damping force change rate V becomes less than the switching reference value Vref (if the value of the flag FHS is checked) After that (step 120), it is determined whether or not the timer variable lower exceeds a preset reference value Ts (step 170). This value is set to 12 to continue the state for a certain period of time after the timer variable T.
If it is less than s, this variable is incremented by the value 1, and the process of controlling the damping force of the shock absorber 2 to a small state is continued (step 160).
. Therefore, the suspension is kept soft.

In this way, after the damping force change rate V once becomes equal to or less than the switching reference value Vref, a predetermined period of time (time corresponding to the reference values T, s)
The damping force change rate V must not exceed the switching reference value V ref until the time elapses.
Since YESJ is obtained, the flag FHSe value is then reset to O (step 190), and the damping force of the shock absorber 2 is controlled to a large state (step 130).

Therefore, when this routine is repeatedly executed, the damping force of the shock absorber 2 of each wheel is set to a small state as soon as the damping force change rate V exceeds the switching reference value Vref. The state is maintained as it is for at least the time corresponding to the reference value Ts after the value becomes equal to or less than the value V ref. Thereafter, when a predetermined period of time has elapsed while the damping force change rate V remained below the switching reference value V ref, the damping force is again controlled to a large state.

Next, a routine (Fig. 6) for detecting the change frequency N of the damping force change rate in order to determine the switching reference value V ref for damping force switching referred to in this damping force switching control routine (Fig. 5). I will explain about it. When this interrupt routine is started, first a process is performed to increment the variable C, which counts the number of times this routine has been executed, by a value of 1 (step 2 0 0), and then whether the current suspension setting is hard or soft. A determination is made (step 21o)
). The damping force pattern of the shock absorber 2 is controlled by the damping force pattern switching control routine 1 shown in FIG. Switching reference value Vr
Multiply ef by the value 0.8XO, 5 (Step 2] 2),
On the other hand, if it is determined to be hard, the current switching reference value V r
ef has value 0. Each learning reference value V refG is calculated by multiplying by 8 (step 214).

After determining the learning reference value V refG in this way, it is determined whether the current damping force change rate V is larger than the learning reference value V refG (step 22o). If the damping force change rate V is equal to or less than the learning reference value V refG, the flag FF is reset to the value O (step 230), and this routine is temporarily ended.

On the other hand, if it is determined that the damping force change rate V exceeds the learning reference value V refG, the value of the flag F is checked (step 240), and the flag FF is set to the value O, that is, the damping force change rate. Immediately after ■ exceeds the learning reference value VrefG, the frequency N is incremented by 1 (step 2
50), set the value 1 to the flag "F" (step 26
0), this routine is temporarily ended. Therefore, this flag "" indicates that the damping force change rate V exceeds the learning reference value V refG, and the frequency N is not incremented during that time (step 240 ).In other words, the frequency N is incremented only when it is newly determined that the damping force change rate V exceeds the learning reference value V refG.

By repeatedly executing the frequency detection interrupt routine described above, the learning reference value V refG is updated based on the switching reference value V ref, and the damping force change rate V exceeds the learning reference value V refG. A process of detecting the frequency N will be performed. These processes are executed independently on the front wheels 5 FL, FR side and the rear wheels 5 RL, RR side as described above, and the frequency NF for the front wheels 5 FL, FR side shock absorbers 2 FL, FR and the rear wheels 5 R are calculated.
The frequency NR for the shock absorber 2 RL and RR on the L and RR sides is determined.

A learning routine for the switching reference value V ref used in such processing will be described next. As shown in Figure 7,
When the switching reference value learning routine is started, first, the driving condition is read from the stop lamp switch 53, the steering sensor 50, the vehicle speed sensor 51, etc. via the input unit 67 (step 300), and the driving condition is read based on the driving condition. Then, it is determined whether control such as anti-dive or anti-roll should be executed (step 310). When you step on the brake or suddenly turn the steering wheel, anti-dive processing etc. are performed, and in preparation for these processings, the switching reference value V ref is switched (
Step 315), this routine is ended immediately.

On the other hand, if it is determined that the running state of the vehicle does not require anti-dive processing or the like, it is determined whether the variable C has become equal to the value i (step 320). Variable C is a value that is incremented each time the frequency detection interrupt routine shown in FIG. It is determined whether or not a preset period (preset) has elapsed. The number of executions of the frequency detection interrupt routine is small (C1
), if it is determined that the timing for determining the frequency has not yet arrived, the program exits to li rRTNJ and temporarily ends this routine.

Each time the frequency detection interrupt routine is executed once, the determination at step 320 is rYEsJ, and then the variable C is reset (step 330) and the vehicle speed sp is read (step 340).

Based on the vehicle speed Sp read in this way, the next step is to calculate a reference base value Vbase (step 350). The reference base value Vbase is the switching reference value V
This is to set the magnitude of ref to a value according to the vehicle speed sp, and as shown in FIG. 8, the function fl(S
p) is determined as.

Next, a process is performed to obtain the frequency deviation ΔN between the frequency N counted in the frequency detection interrupt routine (FIG. 6) and the preset frequency reference value Nref (step 360), and this frequency deviation ΔN is the value A determination is made as to whether the value is greater than O (step 370).

If the frequency deviation ΔN is thicker than the value O, then the correction value ΔV is the value β
(step 380); on the other hand, if the frequency deviation ΔN is less than or equal to the value O, the correction value ΔV is decremented by the value β (step 390), and this correction value ΔV is added to the reference base value V base. Then, the process of calculating the switching reference value V ref is performed (step 400).
. Next, the frequency NF obtained for the front wheel 5 FL, shock absorber 2 FL on the FR side, FR, and the shock absorber 2 FL, on the rear wheel 5 RL, RR side.
The difference (front and rear wheel frequency difference) ΔNFR between the calculated frequency NR and the FR is calculated (step 405). Note that the frequencies NF and NR are for left and right wheels 5FL-FR and 5RL-RR.
Calculated as the average value of Based on the thus calculated front and rear wheel frequency difference ΔNFR, a process is performed in which a front and rear wheel difference correction amount V cmp is added to the switching reference value V ref calculated at step 400 (step 407).

This front and rear wheel difference correction amount Vcmp is the front and rear wheel frequency difference ΔNFR
According to the switching reference value V of the front and rear wheels, whichever is more frequent
Increase ref and set the switching reference value V with the smaller frequency.
This is the correction amount for reducing ref, and as shown in FIG. 9, the front wheel side correction amount VcmpF (solid line in the figure) and the rear wheel side correction amount VcmpR are determined according to the value of the front and rear wheel frequency difference ΔNFR.
(dotted line in the figure) is set in advance. Note that when the front and rear wheel frequency difference ΔNFR is zero, that is, when there is no difference between the front and rear wheels, the front wheel side correction amount VcmpF and the rear wheel side correction amount VcmpR are both zero, which is the same as not making any correction. It is.

After calculating the switching reference value V ref based on whether the road continues to be flat or rough and whether there is a difference in the change status of the damping force between the front and rear wheels, the switching reference value V ref is calculated in preparation for subsequent frequency detection. N is reset to the value O (step 410), and this routine ends.

In this way, the front wheels 5 FL, FR side and the rear wheels 5 RL, R
Respective switching reference values V refF, V r on the R side
efR is calculated in the damping force pattern switching control routine (Fig. 5) and the frequency detection interrupt routine (Fig. 6).
Based on these values V refF and V refR, respective processes are executed for each shock absorber 2 FL, FR, RL, and RR.

In this way, the flowchart 1 of FIGS. 5 to 7
By executing the process shown in FIG. 2, the generation pattern of the damping force of each of the shock absorbers 2 FL, FR, RL, and RR of the vehicle, as well as the stiffness of the suspension, are controlled as follows.

[1] FIG. 10(A) illustrates the state of control when the vehicle is continuously traveling on a flat road. As shown in the figure, when the vehicle is traveling on a flat road, the damping force change rate V is not so large, and the damping force characteristics of the shock absorber 2 are controlled to be large. At this time, the learning reference value V re
fG is calculated as a value of 80% of the switching reference value Vref (step 214 in FIG. 6), and the damping force change rate V increases to the switching reference value Vref in a predetermined period (period corresponding to the value i).
The frequency N exceeding this becomes a small value. Therefore, the switching reference value V ref is learned to be smaller by the value β (step 390 in FIG. 7). As a result, the damping force change rate V easily exceeds the switching reference value V ref, and the damping force is switched to a small state due to small irregularities etc. while driving on a flat road (10th
Figure (A) time tl, t2). In this way, the switching reference value V
When the value of ref is decreased, the learning reference value V ref
G also becomes a small value, and the frequency with which the damping force change rate V exceeds the learning reference value V refG during a predetermined period increases. As a result, the switching reference value V ref is updated to a larger value by +β. As this process is repeated, the switching reference value V ref
f is learned to a value that makes the switching frequency appropriate.

Therefore, even when the vehicle is running on a flat road and the damping force change rate V is relatively small and the suspension tends to be maintained hard, the switching reference value V ref gradually decreases by detecting and switching the frequency N. As a result, the shock absorber 2 can be easily switched to a state where the damping force is small, that is, the suspension characteristics can be switched to soft. As a result, when the vehicle continues to drive on a flat road, small irregularities on the road surface, which have been a problem in the past, can be dealt with appropriately, and ride comfort is significantly improved.

[11] On the other hand, when driving continuously on a rough road, the damping force change rate V
changes greatly, and the suspension characteristics are softly controlled. At this time, the learning reference value VrefG is the switching reference value V
It is calculated as a value of 40% of ref (step 212 in Fig. 6), and the frequency N at which the damping force change rate V exceeds the switching reference value Vref during a predetermined period (period corresponding to the value i) is a large value. .

Therefore, the switching reference value V ref is learned to be larger by the value β (step 380 in FIG. 7). As a result, the damping force change rate V becomes difficult to exceed the switching reference value V ref, and the damping force characteristic remains hard even when driving on a rough road. When the switching reference value V refO increases in this way, the learning reference value V refG also becomes a large value, and the frequency at which the damping force change rate V exceeds the learning reference value V refG during a predetermined period becomes smaller. As a result, the switching reference value Vref is updated to a value smaller by -β. By repeating this process, the switching reference value Vref is learned to an appropriate value.

Therefore, even when the vehicle is driving on a rough road and the damping force change rate V is relatively large and the suspension tends to be kept soft, the frequency N is detected, the switching reference value V ref is updated, and the learning reference value V refG is By performing this learning, the switching reference value V ref is gradually increased, and the damping force characteristic of the shock absorber 2 becomes large, that is, the suspension characteristic is easily switched to a hard state. As a result, when the vehicle continues to drive on rough roads, it is possible to suitably deal with the conventional problem of insufficient ground contact, so-called lack of stiffness in the suspension, and the steering stability is significantly improved.

[III ”J Furthermore, the frequency of switching the damping force in the shock absorbers 2 FL, FR on the front wheels 5 FL, FR side may vary depending on the arrangement of passengers and cargo loading conditions.
and rear wheel 5RL, RR side shock absorber 2RL
, If there is a difference between the damping force switching frequency NR in RR, for example, if the front and rear wheel frequency difference ΔNFR is a positive value,
The front wheel 5FL, FR side switching reference value V refF is corrected to a large value by the positive correction amount Vcmp F.
The switching reference value V refR for the rear wheels 5 RL and RR is corrected to a small value by a negative correction amount V cmpR (step 407 in FIG. 7). As a result, the switching frequency N
Front wheel 5 had a large switching reference value V on the FL and FR sides.
refF becomes relatively large and the rear wheels 5 RL, R
It is harder to enter soft than the R side, and the rear wheel 5 RL,
On the RR side, on the contrary, the switching reference value V refR becomes relatively small, making it easier to enter the soft state. Therefore, control is executed in a direction in which the front and rear wheel frequency difference ΔNFR becomes zero.

As a result, in the above-mentioned control when the flat road or rough road continues, the front and rear wheels will not be in an unbalanced control state.

As described above, the suspension control device 1 of the present embodiment absorbs small vibrations when continuously traveling on a flat road, improves ground contact when continuously traveling on a rough road, It is possible to achieve both ride comfort and steering stability of the vehicle.

In addition, since control is performed to eliminate the frequency difference ΔNFR between the front and rear wheels, the above-mentioned ride comfort and handling stability can be achieved even when the weight distribution between the front and rear wheels, suspension types, and damping force characteristics settings are different. When performing control to achieve this, the damping force switching between the front and rear wheels will not become unbalanced. Therefore, control can be executed in accordance with the driving conditions of the actual vehicle, and the driver does not feel that the front wheels are stiff or the rear wheels are stiff, and the vehicle can always be driven with a stable sense of control.

Next, a modification will be described in which the frequency difference ΔNFR between the front and rear wheels is canceled by a method other than adding the front and rear wheel frequency difference correction amount V cmp when a difference in damping force switching frequency occurs between the front and rear wheels.

The learning reference value V refG in the above-mentioned embodiment is expressed as follows.

\/ro4n=-\/rof Y Kc. nft
KIcnt... (1) where Ksoft is a soft coefficient, and has a value of 0 when the suspension characteristics are softly controlled in the damping force pattern control routine.
．． 5, otherwise the value 1. 0 (steps 212 and 214 in FIG. 6). Also, K
lcnt is a learning value coefficient, and in the above example, the value is 0.
．． It is fixed at 8 (steps 212 and 214 in Figure 6).
.

This modification proposes a system that achieves the same effects as the above-mentioned embodiment by correcting this learned value coefficient K Icnt.

That is, in the modified example (instead of the processing in step 407 of the switching reference value learning routine of the embodiment), the front and rear wheel frequency difference Δ
A process of changing the learning value coefficient Klcnt based on the value of NFR is executed (step 1407 in FIG. 11), and in calculating the learning reference value V refG of the frequency detection routine of the embodiment, the change is made to the switching reference value V ref. Fixed value 0.8 (
6) Instead of steps 212 and 214) in FIG.
It is the one that carries out the br
Steps 1212 and 1214 in FIG. 12). Note that the learning value coefficient K lcnt is determined according to the front and rear wheel frequency difference ΔNFR.
This is a correction amount that increases the learning reference value V refG of the front and rear wheels with a higher frequency and decreases the learning reference value V refG of the front and rear wheels with a lower frequency, as shown in FIG. 13. When the value of is greater than or equal to a predetermined value ±ΔNFR1, the front wheel side value KlcntF (shown as a solid line) and the rear wheel side value KIcntR (shown as a dotted line) are set in advance to increase or decrease to different values. .

As a result, for example, the damping force switching frequency NFh on the front wheels 5 FL, FR side is less than the switching frequency NR on the rear wheels 5 RL, RR side.
If the difference reaches a predetermined value of 10ΔN FRI, then the front wheels 5 FL, FR
Change the learned value coefficient K IcntF on the side to a large value and change the learned value coefficient KlcntR on the rear wheels 5 RL and RR side.
The learned value coefficients K IcntF and K Ic are changed to a small value to eliminate the frequency difference ΔNFR between the front and rear wheels.
ntR is set (step 1407).

Therefore, on the front wheel 5 FL, FR side, the learning reference value V r
As efG increases, the frequency NF decreases and becomes difficult to exceed the target frequency N ref, and accordingly, the switching reference value V ref is gradually decreased (steps 390, 400). That is, the previous situation where the switching reference value V ref tended to be set to a large value because the switching frequency NF was large is resolved. On the other hand, rear wheel 5 RL,
On the RR side, as the learning reference value V refG becomes smaller, the frequency NR increases and becomes easier to exceed the target frequency Nref, and accordingly the switching reference value Vref is gradually increased (steps 380, 400). That is, until now, assuming that the switching frequency NR is small, the switching reference value V re
This eliminates the tendency for f to be set to a small value. As a result, the front wheels are 5FL, and the FR side is also the rear wheels 5RL, RR.
Both sides approach a state where the switching frequency N is almost the same, and while maintaining balance between the front and rear wheels, it is possible to achieve both improvement in ride comfort and improvement in steering stability when the road continues to be flat or rough.

In this manner, the present invention can also be applied to a configuration in which the switching reference value V ref is indirectly corrected.

Furthermore, a second modification will be explained.

In the embodiment described above, the determination as to whether the flat road or the rough road continues is made based on the magnitude relationship between the target frequency N ref and the actual frequency N (step 370 in FIG. 7). Then, if the actual frequency N exceeds the target frequency N ref,
The switching reference value V ref is gradually increased, and if it does not exceed it, it is gradually decreased (steps 380, 390, 400). Therefore,
In the second modification, in order to obtain the same effect as the above-described embodiment and modification, that is, the effect of being able to perform balanced control of the front and rear wheels, a target Execute control to change the frequency N ref.

That is, step 40 of the switching reference value learning routine of the embodiment
Instead of the process in step 7, a process is executed to change the target frequency N ref based on the value of the front and rear wheel frequency difference ΔNFR (step 2407 in FIG. 14), and in the process of the next switching reference value learning routine, this new target Execute learning of switching reference value based on frequency N ref: A f 冫b NISSAN! 100 FFkl,, + 1,000 glc:. rN sword "Ichijin 1 Toshi Uni" originally adopted a configuration in which the change is made in stages according to the vehicle speed Sp (solid line in the diagram), and depending on the front and rear wheel frequency difference ΔNFR, the actual frequency N of the front and rear wheels is higher. target frequency N
Increase ref and set the target frequency N, which is smaller than the actual frequency N.
It is changed to make ref smaller.

That is, when the front and rear wheel frequency difference ΔNFR is the value ΔNFRA, it follows the dotted line shown in the figure, when it is the value ΔNFRB, it follows the dashed line shown in the figure, and when it is the value ΔNFRC, it follows the chain double dotted line shown, so that the target frequencies N refF, Nref are different for the front and rear wheels.
R is set.

As a result, for example, at the vehicle speed Spl, the front wheels 5FL and FR
The switching frequency N of the damping force becomes large on the rear wheel 5RL,
When the difference from the RR side reaches the value ΔNFRA, the first
Based on the relationship shown by the dotted line in Figure 5, the front wheel 5FL,
Set the target frequency N refF on the FR side to a large value N ref
At the same time, the target frequency NrefR for the rear wheels 5RL and RR is changed to a small value NrefAL, and each target frequency N is changed in the direction of eliminating the frequency difference ΔNFR between the front and rear wheels.
Set refF, N refR (step 24
07).

Kuto. Ａ＃＊仝C、rllllD／日If-yst+zu?ヰ100Fwhite=Mr+<dayp frequency Nref is exceeded, and accordingly, the switching reference value Vref is gradually decreased (steps 390, 400). on the other hand,
On the rear wheel 5 RL and RR side, the actual frequency NR is the target frequency N
It becomes easier to exceed ref, and as a result, the switching reference value V
ref is gradually increased (step 380,4
00). As a result, the front wheel is 5 FL, and the FR side is also the rear wheel 5.
The RL and RR sides also gradually approach the appropriate switching reference values V refF and V refR that are well-balanced between the two, and improve ride comfort and control when the road continues to be flat or rough while maintaining a balance between control of the front and rear wheels. It is possible to simultaneously improve stability.

Furthermore, in accordance with the actual driver's requirements,
At high speeds, such control must be executed at early timing to improve responsiveness. Therefore, as the vehicle speed sp increases, the value 1 corresponding to the road surface condition determination period is
It is possible to achieve even better performance by adding control such as reducing . In that case, for example, in a transient state such as during acceleration/deceleration, the reference for road surface judgment becomes unstable, so it is possible to cancel the control, but if road surface judgment is performed even during acceleration/deceleration, it is possible to It can be used for other controls. From this, we can define the value i as vehicle speed sp
It is desirable to execute the control as is while changing it accordingly. Similarly, if we adopt a method of executing the processes from step 330 every fixed distance to improve responsiveness at high speeds, the learning interval will inevitably be shortened at high speeds, and even during transitions due to acceleration/deceleration, This has the effect of executing learning based on accurate road surface judgment. Execution of such processing provides an excellent function and effect in that during high-speed driving, unbalanced control based on unbalanced weight distribution between the front and rear wheels can be quickly resolved.

In addition, if road surface judgment is executed during acceleration, the frequency of exceeding the learning reference value V refG during the road surface judgment period will increase due to squat during acceleration, so even if the road surface judgment period is the same, the switching standard The value V ref is increased, and almost the same effect as anti-squat control can be obtained.

In addition, in the embodiment and each modification, a configuration was adopted in which the unbalanced state of the front and rear wheels was determined based on the difference in the actual frequency N of damping force switching. It is also possible to adopt a configuration in which the determination is made based on the difference between the time during which FL and FR are switched to soft and the time during which shock absorbers 2 RL and RR on the rear wheels 5 RL and RR are switched to soft.

In addition, instead of a configuration that eliminates the imbalance between the front and rear wheels,
A configuration may also be adopted in which the imbalance between the left and right wheels is resolved based on similar means. Furthermore, the configuration may include control difference detection means and control difference correction means for both the front and rear wheels and between the left and right wheels. .

In addition, there is a configuration that eliminates the control difference between wheels in a twisted position, for example, the left front wheel and right rear wheel, or all wheels are compared and, for example, the average switching frequency is calculated, and based on the deviation from this, the above-mentioned Furthermore, it is of course possible to adopt a configuration that executes the same control as in the embodiment or each modification, and is applicable not only to vehicles with four wheels but also to vehicles with more or less than this, but two or more wheels. be.

Further, in such control, in the embodiment and the modified example, the switching reference value Vref and the target frequency N ref are changed for both of the difference comparisons, but a configuration may be adopted in which only one of them is changed. Note that when both are changed, there is an effect that the difference in control can be quickly resolved even if the amount of each change is small.

Further, the switching reference value V ref may be changed and the target frequency N ref may also be changed, and the learning reference value V refG may also be changed.

Although the embodiments and modifications of the present invention have been described above, the present invention is not limited to these embodiments, etc. For example, instead of increasing or decreasing the switching reference value V ref based on the frequency N, the damping force change rate V is the damping force reference value V ref
Cut uV Seri Akl Shiichi I -
-1 Nayote standing [Hand 2nd year C child EyoP/ →←Configuration that updates the switching reference value V ref according to the time that the 7-noh notification is switched to soft, learning reference value Vre
Instead of calculating fG as separate values depending on whether the damping force characteristics are soft or hard, a configuration with two types of frequency reference values Nref, one for soft and one for hard, or a target frequency N
ref for each front, rear, left and right wheel 5 FL, FR, RL,
Within the scope of the present invention, such as a configuration in which different values are set for each RR, and a configuration in which unbalance control is prevented for the left and right wheels, that is, for all four wheels, in addition to preventing unbalance between the front and rear wheels. Of course, it can be implemented in various ways.

Effects of the Invention As detailed above, according to the suspension control device of the present invention, when the condition of either a flat road or a rough road continues, the damping force setting by the damping force control means is corrected. It can effectively deal with small irregularities on the road surface that were a concern when driving continuously, and the ride comfort is significantly improved. The so-called lack of stiffness in the suspension can be suitably addressed, and the driving stability is greatly improved and the driving feeling is maintained in a good manner, which is an extremely excellent effect. Moreover, since such control is performed according to the magnitude of the deviation between the frequency of change of parameters related to damping force and the target frequency, the suspension control device of the present invention allows the vehicle to drive on flat roads and rough roads. The ride comfort and handling stability of
It is possible to achieve both with good responsiveness.

In addition, such control can prevent imbalance between the wheels due to differences in weight distribution between the front and rear wheels or between the left and right wheels.

Therefore, depending on factors on the vehicle side (differences in weight distribution and suspension type), it is possible to perform control with extremely good driving sensation while achieving both ride comfort and handling stability as described above.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating the basic configuration of the present invention, FIG. 2 is a schematic configuration diagram showing the overall configuration of a suspension control device as an embodiment of the present invention, and FIG. 3 (A) is a shock absorber 2. Partial sectional view showing the structure of , Figure 3(B)
4 is a block diagram showing the configuration of the electronic control device 4 of this embodiment. FIG. 5 is a flowchart showing the damping force pattern switching control routine. FIG. 6 is a flowchart showing the damping force pattern switching control routine. Flowchart showing the detection interrupt routine FIG. 7 is a flowchart showing the switching reference value learning routine, FIG. 8 is a graph showing the relationship between vehicle speed sp and reference base value Vbase, and FIG. 9 is a graph showing the relationship between front and rear wheel frequency difference ΔNFR and front and rear wheels. Graph showing the relationship with the difference correction amount V cmp, 10th
Figure (A) is a graph showing the control situation when driving on a flat road, Figure 10 (B) is a graph showing the control situation when driving on a rough road, and Figure 11 is a modified example. FIG. 12 is a flowchart showing a part of the frequency detection interrupt routine. FIG. 13 is a flowchart showing a part of the switching reference value learning routine. FIG. 13 shows the front and rear wheel frequency difference ΔNF in this modification.
Graph showing the relationship between R and learned value coefficient Klcnt, first
FIG. 4 is a flowchart showing part of the switching reference value learning routine of the second modification, and FIG. 15 shows the vehicle speed Sp, the front and rear wheel frequency difference ΔNFR, and the target frequency N r in the second modification.
It is a graph showing the relationship with ef. M1... Shock absorber M2... Damping force change rate detection means M3... Damping force control means M4... Road surface condition detection means M5... Damping force adjustment correction means M6... Control difference detection means M7 ...Control difference correction means 2 FL, FRRL, RR...Shock absorber 4...Electronic control unit 5 FL, FR, RL, RR...Piezo load sensor 7 FL, FR, RL, RR... Piezo actuator 1...Vehicle speed sensor O...Damping force change rate detection circuit

Claims (1)

[Scope of Claims] 1. A shock absorber provided in each suspension of a vehicle and capable of setting a damping force generation pattern; a damping force change rate detection means for detecting a rate of change in damping force of each shock absorber; damping force control means for changing the damping force setting for each of the shock absorbers based on the magnitude relationship between the detected damping force change rate and a damping force adjustment reference value; and a damping force control means for changing the damping force setting for each of the shock absorbers; road surface condition detection means for detecting the condition of the road surface on which the vehicle travels based on the difference between the frequency of change of the setting and the target frequency; When it is determined that either one of the conditions continues, the setting of the damping force controlled by the damping force control means is set to the average value of the damping force set respectively on a flat road and a rough road. A suspension control device comprising damping force adjustment correction means for correcting the damping force, the suspension control device detecting whether or not a difference occurs between changes in damping force settings for each shock absorber by the damping force control means. If the difference detecting means and the control difference detecting means detect that a difference has occurred between the change situations of the damping force settings for each of the shock absorbers, it is determined that a difference has occurred between the change situations. Control difference correction means for directly or indirectly correcting the adjustment reference value and/or the target frequency for at least one of the shock absorbers to a value that reduces the detected difference. A suspension control device characterized by: