JPH03204325A - Suspension control unit - Google Patents

Abstract

PURPOSE:To improve stability by switching a control carried out by means of a vibration condition control means from independent control for each wheel, into a control in which a pair of, left and right, wheels are synchronized, when acceleration and/or braking conditions of a vehicle are detected. CONSTITUTION:The vibration condition control means M3 of each wheel M2 changes characteristics such as damping force, spring constant, etc., of a vehicle supension device (shockabsorber) in compliance with the vibration condition detected by vibration condition detection means M1 and controls the vibration condition of a vehicle independently of each wheel M2 during traveling. Hereupon, when a traveling condition detection means M4 detects acceleration condition and/or braking condition of the vehicle, a left and right wheel synchronous control means M5 switches control carried out by means of the vibration condition control means M3 into control in which a pair of, left and right, wheels M2R, M2L are synchronized independently of each wheel M2. In this manner, characteristics of the damping force, the spring constant, etc., of the left and right wheels are generally equalized, so that driving force and braking force become equal in left and right wheels to be able to obtain good stability of the vehicle.

Description

[Detailed Description of the Invention] Purpose of the Invention [Field of Industrial Application] The present invention relates to a suspension control device, and more specifically, a suspension control device that changes characteristics such as damping force and spring constant of a vehicle suspension system according to the vibration state of the vehicle. The present invention relates to a suspension control device that independently controls the vibration state of a vehicle for each wheel.

[Prior Art] When the vehicle is in a braking state and the change in vehicle posture due to pitching exceeds a predetermined value, the damping force of the shock absorber and the spring constant of the air suspension are increased to prevent nose dive and other such situations. There are suspension control devices that suppress rollback, which is reaction (for example, Japanese Patent Laid-Open No. 60
-148710).

[Problem to be solved by the invention] However, when the suspension control device to be applied is a device that independently controls the damping force of the shock absorber for each wheel, the above conventional configuration does not cause nose dive during braking. If you attempt to control the Similarly, when attempting to control vehicle vibration during acceleration, the damping force of the shock absorber is switched separately for each wheel, resulting in a decrease in ground contact and making it difficult to ensure vehicle stability. The suspension control device of the present invention, which has been considered in various cases, solves the above problems,
The purpose of this system is to enable a suspension control device that independently controls the vehicle's vibration state for each wheel to ensure good vehicle stability even when the vehicle's vibrations are controlled during acceleration and braking. .

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

1 [Means for Solving the Problems] As illustrated in FIG. 1, the suspension control device of the present invention includes a vibration state detection means M1 for detecting the vibration state of the vehicle, and a vibration state detection means M1 provided at each wheel M2 to detect the vibration state of the vehicle. vibration state control means M3 that controls the vibration state of the vehicle by changing characteristics such as damping force and spring constant of the vehicle suspension system according to the vibration state of the vehicle;
In a suspension control device, the vibration state control means M3 independently controls the vibration state of the vehicle for each wheel M2 while the vehicle is running, the driving state detection detecting the acceleration state and/or braking state of the vehicle. means M4; and when an acceleration state and/or braking state of the vehicle is detected, control of the vibration state of the vehicle by the vibration state control means M3 is changed from independent control for each wheel M2 to a set of left and right wheels; It is characterized by comprising left and right wheel synchronization control means M5 and -4= for switching control to synchronize the wheels M2R and M2L.

[Function] In the suspension control device of the present invention having the above configuration, the vibration state of the vehicle is detected by the vibration state detection means M1, and the braking state control means provided at each wheel M2 is adjusted according to the detected vibration state. M3 changes the characteristics such as the damping force and spring constant of the vehicle suspension system, and while the vehicle is running, each wheel M
The vibration state of the vehicle is controlled independently for each second. At this time, when the running state detection means M4 detects the acceleration state and/or braking state of the vehicle, the left and right wheel synchronization control means M5 controls the vibration state of the vehicle by the vibration state control means M3 independently for each wheel M2. From the control, a set of left and right wheels M2R, M
Switch to synchronized control for 2L. Therefore, even if the vibration state of the vehicle is controlled in the acceleration state and/or braking state, the characteristics such as the damping force and spring constant of the vehicle suspension system for the left and right wheels M2R and M2L will be almost the same, and the ground loads on the left and right wheels will be the same. As a result, driving force and braking force are equalized on the left and right sides, ensuring good vehicle stability.

Although FIG. 1 illustrates a vehicle with four wheels, the present invention may be applied to vehicles with various other numbers of wheels, such as a vehicle with six wheels.

[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 overall configuration of this suspension control device 1, FIG. 3(A) is a partially cutaway sectional view of the shock absorber, and FIG. 3(B) is a main part of the shock absorber. FIG.

As shown in FIG. 2, the suspension control device of this embodiment includes a shock absorber (hereinafter simply referred to as a shock absorber) that can change the damping force in two stages.
It consists of shock absorbers 2FR, 2RL, and 2RR, and an electronic control device 4 that is connected to each of these shock absorbers and controls their damping force. Each shock absorber 2F
L, 2FR, 2RL, 2RR are the suspension lower arms 6FL, 6FR, 6RL of the left and right front and rear wheels 5FL, 5FR, 5RL, and 5RR, respectively.
Between 6RR and car body 7, coil spring 8FL,
8FR.

It is located alongside 8RL and 8RR.

Shock absorber 2FL, 2FR, 2RL,
2RR is a shock absorber 2FL as described later.
, 2FR.

A piezo load sensor that detects the force acting on 2RL and 2RR, and shock absorbers 2FL, 2FR, and 2
R.L.

Each of the 2RRs has a built-in piezo actuator that switches the setting of the damping force generation pattern for each stroke.

Next, each of the above shock absorbers 2FL and 2FR.

The structure of 2RL and 2RR will be explained, but each of the above shock absorbers 2FL, 2FR, 2RL, 2RR
Since all of the structures are the same, the shock absorber 2FL on the left front wheel 5FL side will be explained here as an example. In addition, in the following description, the reference numerals of each member provided on each wheel include front left wheel 5 FL and front right wheel 5 FR, as necessary.

Subscript FL corresponding to left rear wheel 5RL, right rear wheel 5RR,
F.R.

RL and RR shall be added, and if there is no difference regarding each wheel, the subscripts shall be omitted.

The shock absorber 2 is fixed to the suspension lower arm 6 via the axle side member 1]a at the lower end on the cylinder 1 side as shown in FIG. The upper end of the rod 13 is fixed together with a coil spring 8 to the vehicle body 7 via a bearing 7a and a vibration isolating rubber 7b.

Inside the cylinder 11 is 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 peripheral surface of the cylinder]1 are disposed. 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 [8] is fitted onto the outside of the cylindrical member [7], and a sealing material [9] is interposed on the outer periphery that fits into the cylinder 11. Therefore, the inside of the cylinder]1 is divided by the main piston]8 into a first liquid chamber 21 and a second liquid chamber 23. 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,
Spacer 29 and leaf valve 30 on the cylindrical member 17 side,
Leaf valve 3] and collar 32 as backup member 28
Each side is pressed and fixed. Further, a main valve 34 and a spring 35 are interposed between the leaf valve 31 and the backup member 28.
1 is the main piston] It is biased in 8 directions.

These leaf valves 30, 31 are connected to the main piston 18.
When the main piston is at rest, the extension side and the narrow narrow passage provided in the main piston]8a.

18b are each closed on one side, and the main piston]
8 opens to one side as it moves in the direction of arrow A or B. Therefore, as the main piston 18 moves, the hydraulic oil filled in both the liquid chambers 21 and 23 flows through the two speed passages 18a,
18b, and moves between the two liquid chambers 21 and 23. In this state where the movement of the hydraulic oil between the two fluid chambers 21 and 23 is limited to the two speed passages 18a and 18b, the damping force generated against the movement of the rod 13 is large, and the characteristics of the suspension become hard. Become.

A piezo load sensor 2 is housed inside the internal cylinder 15.
5 and the piezo actuator 27 are shown in 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 damping force generated in the shock absorber 2. 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 2 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, and directly drives the piston 36.

When the piston 36 is moved in the direction of arrow B in FIG. 3 (8), the plunger 37 and H
The spool 4, which has a letter-shaped cross section, is also moved in the same direction. In this way, when the spool 41 located at the position shown in FIG. 3(B) (origin position) moves in eight directions in the figure, the first liquid chamber 2
The sub-flow path 16c connected to the liquid chamber 1 and the sub-flow path 39b of the bushing 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 4] moves in the direction of arrow B, the first liquid chamber 21 and the second liquid chamber 2
The flow rate of the hydraulic oil flowing between 3 and 3 increases. In other words, when the piezo actuator 27 expands due to high voltage application, the shock absorber 2 switches its damping force characteristic from a high damping force (hard) state to a low damping force (soft) state, and when the electric charge is discharged and contracts, the shock absorber 2 attenuates. 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 regulated by a spring 35 compared to the leaf valve 30. Further, the plate valve 45 has a 1-oil hole 45b having a larger diameter than the oil hole 45a, and is provided on the outside of the oil hole 45a.
When the plate valve 45 moves toward the bush 39 against the biasing force of the spring 46, the hydraulic oil can move through the oil hole 45b. Therefore, regardless of the position of the spool 41, the flow rate of hydraulic oil when the main piston 18 moves in the direction of arrow B is larger than when the main piston 18 moves in the direction of the arrow claw. That is, the damping force is changed depending on the direction of movement of the main piston] 8, thereby improving the characteristics as a shock absorber. Further, a hydraulic oil supply path 38 is provided between the oil-tight chamber 33 and the first liquid chamber 2, together with a check valve 38a.
The flow rate of hydraulic oil in the oil-tight chamber 33 is kept 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 using FIG. 4.

This electronic control device 4 includes a piezo load sensor 25 (fL) of each shock absorber 2 as a sensor for detecting the running state of the vehicle, a throttle opening sensor 50 (not shown) that detects the opening of the throttle, and a throttle opening sensor 50 that detects the throttle opening (not shown). , a vehicle speed sensor 5 that detects the running speed of the vehicle], a brake oil pressure sensor 52 that detects the pressure of brake oil that increases depending on the degree of depression of the brake pedal (not shown), and a brake oil pressure sensor 52 that detects the pressure of brake oil that increases depending on the degree of depression of the brake pedal (not shown). A stop lamp switch 53 and the like that emit a level signal are connected.

The electronic control device 4 which outputs control signals to the piezo actuator 27 described above based on these detection signals etc. is a well-known CPU 61. ROM62. It is configured as an arithmetic and logic operation circuit centered around the RAM 64, and input/output with the outside is performed through an input section 6 and an output section 68 which are connected to these circuits via a common bus 65.

The electronic control device 4 includes a damping force change rate detection circuit 7o to which a piezo load sensor 25 is connected, and a throttle opening sensor 50. It receives power from the battery 77h1 via a waveform shaping circuit 73 connected to the vehicle speed sensor 51, etc., a high voltage application circuit 75 connected to the piezo actuator 27, and an ignition switch 76, and outputs a drive voltage for driving the piezo actuator. A so-called switching regulator type high voltage power supply circuit 79, a constant voltage power supply circuit 80 which transforms the voltage of the battery 77 to generate an operating voltage (5V) for the electronic control device 4, and the like are provided. Stop lamp switch 53. Damping force change rate detection circuit 70. The waveform shaping circuit 73 is connected to the input section 67, while the high voltage application circuit 75. The high voltage power supply circuits 79 are connected to the output sections 68, respectively.

The damping force change rate detection circuit 70 is connected to each piezo load sensor 25.
It consists of four detection circuits provided corresponding to FL, FR, RL, and RR, and each detection circuit receives 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 voltage signal V that
CPU61 as damping force change rate of shock absorber 2
It is configured to output to . In addition, the waveform shaping circuit 7
3 (Throttle opening sensor 50.Vehicle speed sensor 51
．． The detection signal from the brake oil pressure sensor 52 is
This circuit shapes the waveform of a signal suitable for processing in U61 and outputs the signal. Therefore, the CPU 61 receives output signals from the damping force change rate detection circuit 70 and the waveform shaping circuit 73,
Furthermore, it is possible to determine road surface conditions, vehicle running conditions, etc. based on the own processing results. Based on this determination, the CPLJ 61 outputs a control signal to the high voltage application circuit 75 provided corresponding to each wheel.

The high voltage application circuit 75 is a circuit that applies a voltage of +500 volts or -1100 volts output from the high voltage power supply circuit 79h1 to the piezo actuator 27 in accordance with a control signal from the CPU 61. Therefore, this damping force switching signal causes the piezo actuator 27 to extend (
(when +500 volts are applied) or contract (when -100 volts is applied), the hydraulic oil flow rate is switched, and the damping force characteristic of the shock absorber 2 is switched to soft or hard. That is, when the piezo actuator 27 is extended by applying a high voltage, the damping force characteristics of each shock absorber 2 are as follows:
Due to B)), the flow rate of the hydraulic oil flowing between the first liquid chamber 21 and the second liquid chamber 23 in the shocker 5-absorber 2 increases, resulting in a state of small damping force, and due to the negative voltage. When the electric charge is discharged and the piezo actuator 27 contracts, the hydraulic oil flow rate decreases, resulting in a state of large damping force.

Next, FIGS. 5 and 6 show the damping force control performed by the suspension control device of this embodiment having the above-described configuration.
This will be explained based on the flowcharts shown in FIGS. Each routine shown in each figure is repeatedly executed at fixed time intervals by interrupt processing.

The processing contents of each routine are as follows.

■ Acceleration/braking damping force control routine (Figure 5) Determine whether the vehicle is in a sudden acceleration state or braking state, and if it is in a sudden acceleration state or braking state, the damping force pattern switching control routine ■ By changing the processing content, it is possible to simultaneously control damping force switching for left and right wheels.

■ Attenuation cover turn switching control routine (Figure 6).

(Fig. 7) 6- This is performed independently for each wheel 5FL, 5FR, 5RL, and 5RR, and the piezo actuator 27
Switch each wheel 5FL, 5FR, 5RL,
The damping force is switched to a large state (hard) or a small state (soft) every 5 RR. In this routine, when the sudden acceleration or braking state of the vehicle is checked in the acceleration/braking damping force control routine (2) and the mode flag FM (described later) is set, the processing contents are as follows: (1) Switching of the damping force Control each wheel 5 FL.

From the mode that is performed independently for each of 5FR, 5RL, and 5RR, (2) damping force switching control is applied to the left and right wheels 5 on the front wheel side.
FL.

5FR set and rear left and right wheels 5RL, 5R
The mode is changed to a mode in which the left and right wheels are operated simultaneously for each R group.

The details of each routine will be explained in order starting from the acceleration/braking damping force control routine (FIG. 5).

When this routine starts, first, the output value θth of the throttle opening sensor 50 is read (step 00), and the output value Oth and the immediately preceding output value θthb of the throttle opening read by the previous execution of this routine are combined. The process of determining whether the opening difference 〇 is larger than the comparison angle θref, which is the minimum angle of the opening difference in the sudden acceleration state (step] 0) Do this. The opening difference △θ is larger than the comparison angle θref (Step 11
0), if it is in a sudden acceleration state, the output value θth of the throttle opening sensor 50 read this time is set as the immediately preceding output value θthb (step 115), and the timer is started, that is, the timer variable T] is set to the value 0. Then, assuming that the left and right wheels are to be simultaneously switched, a process is performed to set the mode flag FM to a value of 1 (step 130). If the mode flag FM is the value], the routines described below (Figures 6 and 7)
By executing the process shown in the figure), switching control of the damping force for the left and right wheels simultaneously is realized.

On the other hand, if the opening difference 〇 is smaller than the comparison angle θref (step] ] 0) and there is no sudden acceleration, the output value θth of the throttle opening sensor 50 read this time is set as the immediately preceding output value θthb, and then ( Step 135), reads the output SL of the stop lamp switch 53 (Step 140), and the output of the stop lamp switch 53 is set to the value O.
(Step 50) of determining whether or not the output voltage is at a low level, that is, whether or not the brake is in the braking state.

If the output of the stop lamp switch 53 is 0 and is in a braking state, the timer variable T is set as in the case of a sudden acceleration state.
1 is reset to the value O and a timer is started (step 120), and the mode flag F is set to the value 1 (step 130) to perform simultaneous switching control for the left and right wheels. If the mode flag FM has a value of 1, as in the case of a sudden acceleration state, damping force switching control for the left and right wheels simultaneously is realized by executing a routine (FIGS. 6 and 7) to be described later.

In this way, after setting the mode flag FM to the value 1 by detecting a sudden acceleration state or a braking state and changing the damping force switching control from four-wheel independent to the left and right wheels simultaneously, the opening difference △θ still remains.
exceeds the comparison angle θref (sudden acceleration state step 110), or when the output of the top lamp switch 53 is O (braking state step 50), the above-mentioned timer is started. and the process of setting the value 1 to the mode flag FM are repeated.

After that, in a state of rapid acceleration, 〇 is the comparison angle θr due to the opening difference.
When it becomes below ef (Remove sudden braking state step 1)
O), in the braking state, the stop lamp switch 53
When the output of
50), after checking the value of the flag FM (step) 60), the timer variable T] is set to the preset reference value TS.
It is determined whether the value exceeds 1 (step 170).
).

The reference value TSI is a value set so that the mode flag FM continues to have the value 1 for a certain period of time even after the sudden acceleration state or braking state is released.

Therefore, if the timer variable T1 is less than or equal to the reference value TSI (
Step 170), this variable T] is incremented by value] (Step 80), and the process of setting the mode flag FM to the value 1 is continued (Step 130). In this case, the simultaneous reduction 20-capacity switching control for the left and right wheels is maintained.

Furthermore, from the time when the opening degree difference Δθ becomes equal to or less than the comparison angle θref (step 110), or from the time when the output of the stop lamp switch 53 reaches the value O (step 150), a predetermined period of time (corresponding to TS) is elapsed. If the opening degree difference Δθ does not exceed the comparison angle θref or the output of the stop lamp switch 53 does not reach the value 0,
Since the determination in step]70 is ``YES'', the mode flag FM is then reset to the value 0 (step 19).
0), by executing a routine (FIGS. 6 and 7) to be described later, the damping force switching control is switched to four-wheel independent damping force switching control.

Therefore, in the acceleration/braking damping force control routine, the driving state of the vehicle is a sudden acceleration state or a braking state (if the opening difference Δθ exceeds the comparison angle θref, or if the stop lamp switch 5
3 is the value 0), the mode flag FM is set to the value 1, and the sudden acceleration state or braking state is released (the opening difference is less than the comparison angle θref, or the stop lamp switch 53 is the value 1). After that, the mode flag FM is held at the value 1 at least for a time corresponding to the reference value TS1 in order to perform switching control of the damping force for the left and right wheels simultaneously. After this,
When a predetermined period of time elapses while the sudden acceleration state or braking state is released, the mode flag FM is set to the value 0 in order to perform four-wheel independent damping force switching control.

Below, a damping cover turn switching control routine (Fig. 6,
Fig. 7) will be explained.

The routine shown in the flowchart of FIG.
2RR, and the routine shown in the flowchart of FIG. 7 is executed for the front and rear left wheels 5FL.
, 5RL shock absorber 2FL, 2RL
Each of these is executed separately. In the routines shown in each figure, the processing for the front and rear wheels is the same, so the front and rear wheels will be described without making any particular distinction.

First, right wheels 5FR, 5RR (hereinafter referred to as right wheels 5R)
The damping cover turn switching control routine (FIG. 6) executed for each of the shock absorbers 2FR and 2RR (hereinafter referred to as shock absorber 2R) will be described.

When this routine is started, it is first judged whether or not the mode flag FM is set to the value (step 2).
00). If the mode flag FM is the value O (step 200), it is normal driving, so the damping force change rate detection circuit 70 outputs the damping force change rate VR of the shock absorber 2R of the right wheel 5R via the input section 67. (Step 2] 0), and it is determined whether the damping force change rate VR is larger than the switching reference value Vref (Step 220).

On the other hand, if the mode flag FM is 1 (step 200
), since the running state is a sudden acceleration state or a braking state, the damping force change rate detection circuit 70 detects the damping force change rates VR, VL of the shock absorbers 2R, 2L of the left and right wheels 5R, 5L.
(step 230), and it is determined whether at least one of the left and right damping force change rates VR, V[ is larger than the switching reference value Vref (step 240).

Incidentally, the damping force change rate VL of the shock absorber 2L of the right wheel 5[ read in step 230 is the same as the damping force change rate VL of the shock absorber 2L of the right wheel 5 [ which is the front wheel or rear right wheel 5R targeted by this routine ]. is the damping force change rate v.

As a result of performing the judgment process (step 220 or step 240) according to the value 0 or 1 of the mode flag FM as described above, in normal driving conditions, if the damping force change rate VR is smaller than the switching reference value V ref ( Step 220), when both the left and right damping force change rates VR and VL are smaller than the switching reference value Vref in a sudden acceleration state or braking state (Step 2
40), it is then determined whether the flag FH8R indicating that the suspension characteristics are set to soft is the value (step 250). Flag FH8R has value 1
If not (step 250), that is, if it is not set to soft, the suspension of the right wheel 5R is controlled to be hard (step 260), and this routine is temporarily terminated. Note that the process in step 2603- is performed immediately after the setting of the damping force of the shock absorber 2R is switched from soft to hard.
High voltage application circuits 75 to 100 are controlled by control signals from
This is done by applying a bolt 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, the judgment process (
As a result of steps 220 and 240), if the damping force change rate VR is larger than the switching reference value Vref under normal driving conditions (
Step 220), or the left and right damping force change rate VR in a sudden acceleration state or braking state.

If one of V[ is larger than the switching reference value Vref (step 240), the timer is started, that is, the timer variable T2 is reset to the value O (step 270), and the suspension characteristics are further set to soft. Therefore, processing is performed to set the flag FH8R to a value of 1 (step 280). After that, the high voltage application circuit 7
A high voltage of 5 to +500 volts is applied to the piezo actuator 27 to switch and control the damping force of the shock absorber 2 to a small state (soft) (step 290), and this routine ends.

After switching the damping force of the shock absorber 2R to a small state in this way, if the damping force change rate VR exceeds the switching reference value V ref during normal driving (step 2
20) In the sudden acceleration state or braking state, if either the left or right damping force change rate VR or VL exceeds the switching reference value V ref (step 240), the above-mentioned timer is started and the damping force is set to a small state. This control is repeated. After this, when the damping force change rate VR becomes equal to or less than the switching reference value Vref under normal driving conditions (step 220), both the left and right damping force change rates VR and VL become the switching reference value under sudden acceleration and braking conditions. When it becomes below V ref (step 2
40), after checking the flag FH3RO value (step 250), it is determined whether or not the timer variable T2 exceeds a preset reference value TS2 (step 3).
00). The reference value TS2 is a value set to maintain the state for a certain period of time after the shock absorber 2R is once switched to a state with a small damping force. Therefore,
If the timer variable T2 is equal to or less than the reference value T32 (step 300), this variable T2 is incremented by the value] (step 310), and the process of controlling the damping force of the shock absorber 2R to a small state is continued (step 310).
Step 290).

Furthermore, until a predetermined time (time corresponding to TS2) has elapsed after the damping force change rate VR becomes equal to or less than the switching reference value V ref during normal driving, the left and right damping force change rate VR in the sudden acceleration state and braking state .

The damping force change rate VR1 or the left and right damping force change rates VR until a predetermined time (time corresponding to TS2) has passed after both VL become equal to or less than the switching reference value Vref.

If V[ does not exceed the switching reference value V ref,
Since the determination at step 300 is rYESJ, the flag FH8R is then reset to the value O (step 320
), the damping force of the shock absorber 2 is controlled to a large state (step 260).

Therefore, in normal driving conditions (mode flag FM=70), the damping cover turn switching control is mainly based on the damping force change rate VR applied to the right wheel 5R, which is shown in the area R surrounded by the dashed line in FIG. will be carried out.

That is, when the damping force change rate VR applied to the right wheel 5R exceeds the switching reference value V ref, the damping force of the shock absorber 2R is immediately set to a small state (soft), and the damping force change rate VR is equal to or less than the switching reference value V ref. After that, the state (soft) is maintained as it is for at least the time corresponding to the reference value TS. When a predetermined period of time has elapsed while the damping force change rate VR remains below the switching reference value V ref, the damping force is again set to a large state (hard).

On the other hand, sudden acceleration state, braking state (mode flag FM = 1)
Here, switching control of the damping cover turns is performed based on the left and right damping force change rates VR and VL.

That is, when one of the left and right damping force change rates VR, VL exceeds the switching reference value V ref, the damping force of the shock absorber 2R is immediately set to a small state (soft), and both the left and right damping force change rates VR, VL are set to a small state (soft). The state (soft) is maintained as it is for at least the time corresponding to the reference value TS after it becomes equal to or less than the switching reference value Vref.

Thereafter, when a predetermined period of time has elapsed while both the left and right damping force change rates VR and VL remain below the switching reference value V ref, the damping force is again set to a large state (hard).

Next, a damping cover turn switching control routine (FIG. 7) executed for the shock absorbers 2FL and 2RL (hereinafter referred to as shock absorber 2L) of the left wheels 5FL and 5RL (hereinafter referred to as right wheel 5) will be described.

When this routine starts, it is first determined whether the mode flag FM is the value] or not (step 400), and the mode flag F
If M has a value of 0 and the running condition is normal, the right wheel 5 [
A damping force switching control process (step 410) is performed based on the damping force change rate VLI. This process (step 4)
O) is the same process as the part R surrounded by the dashed line in the flow chart of FIG. 6, that is, the rate of change of the damping force of the left wheel 5L V.
While comparing [ with the switching reference value V ref, the left wheel 5L
This is a process for controlling switching of the damping force of the shock absorber 2L. The details are the same as the portion R surrounded by the dashed line in the flowchart of FIG. 6, and the explanation will be omitted.

If the mode flag FM is the value] (step 400), and if it is a sudden acceleration state or a braking state, then a process is performed to determine whether the flag FH8R indicating the switching state of the damping force of the right wheel 5R is the value 1 or not. (Step 420). For example, if the right wheel flag FH3R has a value of 1, the shock absorber 2 of the left wheel 5L is adjusted to the switching state of the damping force of the right wheel 5R.
A process (step 430) for switching and controlling the damping force to a small state (soft) is executed, and this routine ends. On the other hand, if the flag FH8R of the right wheel 5R is not the value (step 420), the damping force of the shock absorber 2R is switched and controlled to the unattended state (hard) in line with the switching state of the damping force of the right wheel 5R. Then, the routine is completed.

By executing the damping cover turn switching control routine (FIG. 6) for the right wheel 5R and the damping cover turn switching control routine (FIG. 7) for the left wheel 5L as explained above, each wheel 5 FL, 5 FR, 5
Damping force switching control is performed independently for each of RL and 5 RR based on the magnitude relationship between the damping force change rate V and the switching reference value Vref, thereby achieving suspension characteristics with high steering stability.

In a sudden acceleration state or a braking state, the damping force change rates VR, VL and the switching reference value V are determined for each of the front wheel side left and right shock absorbers 2FL and 2FR set, or the rear wheel side left and right shock absorbers 2RL and 2RR set.
The switching control of the damping force of the right wheel 5R is performed based on the magnitude relationship with ref, and in line with the switching control of the damping force of the right wheel 5R controlled in this way, the switching control of the damping force of the left wheel 5L is performed at the same time. Let's do it. As a result of the switching control of the damping force for the left and right wheels being performed simultaneously for each pair of left and right wheels on the front and rear wheels, the shock absorbers 2R and 2L of the left and right wheels are activated during sudden acceleration, during braking, and for a predetermined period thereafter. The magnitude of the damping force is almost the same, the ground load on the left and right sides is the same, the driving force and braking force are equalized on the left and right sides, and good stability of a single vehicle is achieved.

As explained above, according to the suspension control device, the shock absorbers 2R and 2L for the left and right wheels are simultaneously switched during sudden acceleration and braking, so the suspension control system controls the shock absorbers 2 for each of the four wheels independently. The device has the excellent effect of ensuring good vehicle stability even when controlling vehicle vibration during sudden acceleration or braking.

Next, it has the same device configuration as the first embodiment described above,
A second embodiment in which the braking state is determined differently in damping force control will be described.

In the second embodiment, damping force switching control for the left and right wheels is executed simultaneously when the vehicle is in a sudden braking state.

The flowchart in FIG. 8 shows the differences between the acceleration/braking damping force control routine of the second embodiment and the first embodiment. Some of the illustrated processes are replaced with the process of reading the stop lamp switch output SL (step 40) and the process of determining whether the stop lamp switch output SL is the value (step 50) in the flowchart of FIG. This is a possible 32-process. The processing of other parts not shown is the same as the processing shown in the flowchart of FIG. 5, and therefore the description thereof will be omitted.

In the second embodiment, instead of the stop lamp switch 53, the output BP of the brake oil pressure sensor 52 is read (
In step 5o○), a process (step 510) is performed to determine whether the brake oil pressure BP is equal to or higher than a predetermined pressure Pref indicating sudden braking. Brake oil pressure BP is the predetermined pressure P
If the braking condition is greater than or equal to ref and the brake is in a sudden braking state, the mode flag FM is set to the value 1. That is, in the second embodiment, the switching control of the damping force of the left and right wheels is performed simultaneously in the sudden braking state, and if the brake oil pressure BP is in the slow braking state below the predetermined pressure P ref, the damping force of the four wheels is changed independently. Leave switching control as is.

Therefore, according to the second embodiment, in addition to the effects of the first embodiment, when the braking state is in the slow braking state, it is possible to realize control that takes care of ride comfort by controlling damping force switching independently of the four wheels. In a sudden braking state, the damping force switching control for the left and right wheels at the same time has the effect of realizing delicate control that emphasizes control of posture changes.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way, and it goes without saying that it can be implemented in various forms without departing from the gist of the present invention. For example, a suspension control device to which the present invention is applied is not limited to a suspension that uses a shock absorber as in the embodiment, but may also be a suspension control device that controls the vibration state of a vehicle by changing the spring constant of an air suspension. good.

In addition, shock absorbers can be configured to have three or more settings for the amount of damping force they generate,
It may be possible to change the magnitude of the damping force continuously. The vibration state of the wheel may be detected based on other variables, such as a change in the relative vehicle height between the wheel and the vehicle body, in addition to being detected based on the rate of change of the damping force as in the embodiment. In the second embodiment, detection of a sudden braking state is performed using brake oil pressure B.
We have explained the configuration based on the magnitude of P, but for example, when the rise of the damping force change rate becomes large when the four axes are rotated,
It may be configured to determine that the brake system is in a sudden braking state.

Effects of the Invention As detailed above, the suspension control device of the present invention controls the vibration state of the left and right wheels at the same time when the vehicle is in an acceleration state or a braking state. Suspension damping force.

A suspension control device that controls characteristics such as spring constant has the excellent effect of ensuring good vehicle stability even when controlling vehicle vibration during acceleration and braking. Safety will also be improved at the same time.

[Brief explanation of drawings]

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 shock absorber control device as an embodiment of the present invention, and FIG. 3(B) is an enlarged sectional view of main parts of the shock absorber 2; FIG.
35-5 is a flowchart showing a damping force control routine during acceleration and braking. FIG. 6 is a flowchart showing a damping cover turn control routine for the right wheel. FIG. 7 is a flowchart showing the damping cover turn switching control routine for the left wheel. FIG. 8 is a flowchart showing the main part of the damping force control routine during acceleration and braking of the second embodiment. 2... Variable damping force shock absorber 4... Electronic control unit 25... Load sensor 27... Piezo actuator 50... Throttle opening sensor 52... Brake oil pressure sensor 53... Stop Lamp switch 75...High voltage application circuit 79...High voltage power supply circuit

Claims (1)

[Scope of Claims] 1. Vibration state detection means for detecting the vibration state of the vehicle;
vibration state control means for controlling the vibration state of the vehicle by changing characteristics such as damping force and spring constant of a vehicle suspension system, and while the vehicle is running, the vibration state control means independently controls the vehicle for each wheel. A suspension control device for controlling a vibration state of a vehicle, comprising: a driving state detection means for detecting an acceleration state and/or a braking state of the vehicle; and, when an acceleration state and/or a braking state of the vehicle is detected, the vibration state control means A suspension control device comprising: left and right wheel synchronization control means for switching control of the vibration state of the vehicle from independent control for each wheel to synchronized control for a set of left and right wheels.