JPH03208716A - Suspension control device - Google Patents

Abstract

PURPOSE:To improve drive feeling, securing the steering stability, by correcting the suspension characterisic of a suspension means to a hard side on the basis of the operation state of a vehicle which generates the tilt of the vehicle attitude and fixing the suspension characteristic to a hard state according to the operation state. CONSTITUTION:The suspension characteristic such as the damping force generation pattern and the spring constant of a suspension means M1 installed between a wheel and a car body is controlled by a means M3 on the basis of the vibration state of a vehicle which is detected by a means M2. In this device, the operation state of the vehicle which generates the tilt of the vehicle attitude is detected by a means M4. Further, the suspension characteristic of the suspension means M1 is corrected to a hard side as a whole by a means M5 when the degree of tilt of the attitude which is estimated from the detected operation state of the vehicle is the first standard value or more. Further, when the degree of the tilt of the attitude is over the second standard value or more, the suspension characteristic of the suspension means M1 is fixed to a hard state by a means M6 independently of the vibration state of the vehicle.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a suspension control device, and more specifically, the present invention relates to a suspension control device, and more specifically, the present invention relates to a suspension control device that is equipped with a suspension means that can vary characteristics such as a damping force generation pattern and a spring constant, and is The present invention relates to a suspension control device that changes characteristics of suspension means based on vibration conditions.

[Prior Art] As a suspension control device of this type, one is known that detects the vibration state of a vehicle by the displacement of a suspension system, and adjusts the spring constant of a suspension spring, which is one of the characteristics of the suspension system. For example, (1) Japanese Patent Application Laid-Open No. 60-94810).

With such a device (when the vibration of a companion vehicle becomes large, the spring constant is reduced to soften the suspension characteristics and improve ride comfort, it is possible to improve the suspension stability by reducing the pattern of damping force generated by the shock absorber). A similar effect can be obtained by making it softer.

On the other hand, if the suspension characteristics are simply softened based on the displacement of the suspension system, it will be sufficient to suppress the tilting of the vehicle due to dives, squats, and rolls, as well as the backlash that occurs during sudden acceleration, deceleration, and turns. Can not do it.

As a result, the ground contact of the wheels is impaired and the steering stability is also reduced. Therefore, when a driving condition that results in a change in vehicle posture such as a dive or roll (such as sudden acceleration, braking or steering operation, or vehicle speed) is detected, the standard value for switching the suspension system characteristics to soft is increased by 12 corrections. A device that attempts to suppress the occurrence of dies, rolls, etc. has also been proposed (Japanese Unexamined Patent Publication No. 64-67407).

[Problems to be Solved by the Invention] Such a device suppresses the tilt of the vehicle's posture during driving and has excellent steering stability, but it does not require a standard value for softly switching the characteristics of the suspension system. Therefore, when the displacement of the suspension system is large, such as during sudden acceleration/deceleration or high-speed turning, there is a problem in that the characteristics of the suspension system inevitably switch to soft. For this reason,
It was thought that during sudden acceleration/deceleration or sharp turns, the vehicle's contact with the ground ↑ and, as a result, the steering stability would become insufficient. However, since the characteristics of the suspension system are set to be hard during sudden acceleration/deceleration or turning (it is possible that the ride comfort during slow braking, slow acceleration, or slow turning may become insufficient).

The suspension control device of the present invention solves the above problems,
The objective is to achieve both ride comfort and handling stability even in driving conditions that result in a tilted vehicle posture.

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 is provided between a wheel and a vehicle body, and is configured to
Suspension means M1 that can vary characteristics such as a spring constant; Vibration state detection means M2 that detects the vibration state of the vehicle; Suspension characteristic control that controls the characteristics of the suspension means M1 based on the detected vibration state. a driving state detection means M4 for detecting a driving state of the vehicle that causes an inclination of the vehicle attitude; a correction means M5 for correcting the characteristics of the suspension means M1 controlled by the suspension characteristic control means M3 to the hard side as a whole; and prediction from the detected driving state of the vehicle. If the degree of inclination of the posture is equal to or greater than a second reference value that is larger than the first reference value, the characteristics of the suspension means M1 are fixed to a hard state regardless of the vibration state of the vehicle. The present invention is characterized in that it includes suspension characteristic fixing means M6 for controlling.

[Function] In the suspension control device of the present invention having the above configuration, the vibration state detection means M2 detects the damping force generation pattern, spring constant, etc. of the suspension means M1 provided between the wheels and the vehicle body. The suspension characteristic control means M3 performs control based on the vibration state of the vehicle, and further performs the following control based on the driving state of the vehicle that causes the tilt of the vehicle posture detected by the driving state detecting means M4.

If the degree of inclination of the posture predicted from the detected driving state is greater than or equal to the first reference value, the correction means M51 corrects the characteristics of the suspension means M1 as a whole to the hard side. In addition, when the degree of inclination of the posture predicted from the driving state of the vehicle is equal to or higher than the second reference value (regardless of the vibration state of the vehicle), the suspension characteristic fixing means M6 sets the suspension characteristic of the suspension means M1. Fix and control characteristics in a hard state.

Here, since the second reference value is a -6 value larger than the first reference value, the suspension means M1 of the vehicle takes ride comfort into consideration when the predicted tilt of the posture is not so large. If the inclination of the predicted posture is greater than that of the control characteristic, the characteristic is forcibly made hard, giving priority to steering stability. As a result, both ride comfort and handling stability can be achieved as a whole.

Note that the correction of the characteristics of the suspension means M1 to the hard side by the correction means M5 is performed by correcting the reference value for soft switching in the case of a type in which the characteristics are controlled by switching the damping force generation pattern in two stages. As a whole, the correction should be made to the hard side (if the setting of the damping force can be controlled steplessly, the setting may be changed to the increasing side).

Moreover, such control may be performed independently for each wheel, or may be performed in common for the two front wheels and the two rear wheels, or may be performed in common for all wheels.

[Embodiment 1] In order to further clarify the structure and operation of the present invention described above, a preferred embodiment 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 1 of this embodiment includes shock absorbers 2FL, 2FR, 2RL, and 2RR whose damping force can be changed in two stages, and which are connected to each of these shock absorbers to change the damping force. It is composed of an electronic control device 4 for controlling.

Each shock absorber 2FL, 2FR, 2RL
, 2RR has left and right front and rear wheels 5FL and 5FR, respectively.
, 5RL, 5RR, coil springs 8FL, 8FR, 8 are installed between the suspension lower arms 6FL, 6FR, 6RL, 6RR and the vehicle body 7.
It is located alongside RL and 8RR.

Shock absorber 2FL, 2FR, 2RL,
2RR is shock absorber 2, as described later.
A piezo load sensor that detects the force acting on FL, 2FR, 2RL, and 2RR, and a shock absorber 2F
A set of piezo actuators for switching the setting of the damping force generation pattern in L, 2FR, 2RL, and -8-2RR are each built in.

Next, each of the above shock absorbers 2FL, 2FR,
The structure of 2RL and 2RR will be explained, but each of the above shock absorbers 2FL, 2FR, 2RL, 2
Since all RR structures are the same, here we use the left front port 5F.
This will be explained by taking the L side shock absorber 2FL as an example.

In addition, in the following explanation, the symbols of each member provided on each wheel (as necessary, front left wheel 5 FL, front right wheel 5 FR)
, left rear wheel 5RL, subscript FL corresponding to right rear wheel 5RR
, FR, RL, and RR shall be added, and if there is no difference regarding each wheel, the suffix shall be omitted.

As shown in FIG. 3(A), the shock absorber 21 is fixed to the suspension lower arm 6 via the axle side member 11a at the lower end of the cylinder 11 side.On the other hand, the upper end 1 of the rod 13 inserted through the cylinder 11 The coil spring 8 is fixed to the vehicle body 7 via a bearing 7a and a vibration isolating rubber 7b.

Inside the cylinder 11, an internal cylinder 15, a connecting member 16, and a cylindrical member 17 connected to the lower end of the rod 13, and a main piston 18 that is slidable along the inner peripheral surface of the cylinder 11 are disposed. There is. shock absorber 20
An internal cylinder 15 connected to the rod 13 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 19 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 this main piston 18. A backup member 28 is screwed to the tip of the cylindrical member 17. Between the cylindrical member 17,
Together with the main piston 18, a spacer 29 and a leaf valve 30 are pressed and fixed to the cylindrical member 17 side, and a leaf valve 31 and a collar 32 are pressed and fixed to the backup member 28 side. Further, a main valve 34 and a spring 35 are interposed between the leaf valve 31 and the backup member 28, and urge 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 B, Therefore, as the main piston 18 moves, the hydraulic oil filled in both the liquid chambers 21 and 23 flows 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 carried out 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 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 force acting on the shock absorber 2, that is, the damping force. Therefore, by extracting the output of the Viezo load sensor 25 as a voltage signal through a circuit with a predetermined impedance, the rate of change in damping force can be detected.

The piezo actuator 27 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(B), the plunger 37 and H
The spool 4, which has a letter-shaped cross section, is also moved in the same direction. When the spool 41 in the position shown in FIG. 3(B) (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.
Therefore, when the spool 41 moves in the direction of the arrow B, -12 As a result, the flow rate of the hydraulic oil flowing between the first liquid chamber 21 and the second liquid chamber 23 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. Returns the force characteristics to a state of high damping force (hard).

The amount of movement of the leaf valve 31 provided on the lower surface of the main piston 18 is controlled by a 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 direction of push 39 against the urging force of 6, it becomes movable through the upper oil hole 45b.
Regardless of the position of the spool 41, the main piston 1
The hydraulic oil flow rate when the main piston 18 moves in the direction of the arrow B becomes larger than when the main piston 18 moves in the eight directions of the arrow 12. That is, the damping force is changed depending on the direction of movement of the main piston 1819, thereby improving the characteristics as a shock absorber. Further, a hydraulic oil replenishment path 38 is provided between the oil-tight chamber 33 and the first liquid chamber 21 together with a check valve 38a to keep the flow rate of the 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 using FIG. 4.

This electronic control device 4 includes, as sensors for detecting the running state of the vehicle, a steering sensor 50 that detects {tL of a piezo load sensor 25 of each shock absorber 2, a steering angle η of a steering wheel (not shown), and a steering sensor 50 that detects a steering angle η of a steering wheel (not shown). A vehicle speed sensor 51 that detects speed S, a shift position sensor 52 that detects the shift position of a transmission (not shown), a hydraulic pressure sensor 53 that detects brake oil pressure P of a brake (not shown), and an opening degree θ of a throttle valve (not shown) A throttle opening sensor 54 and the like for detection is connected.

114- The electronic control device 4 which 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 mainly consisting of a well-known CPU 61, ROM 62, and RAM 64. An input section 67 and an output section 68 which are connected to each other 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 so-called switching regulator type high voltage power supply circuit 79 receives power supply from a battery 77 via an application circuit 75 and an ignition switch 76 and outputs a drive voltage for driving the piezo actuator, and transforms the voltage of the battery 77 to perform electronic control. A constant voltage power supply circuit 80 that generates an operating voltage (5V) for the device 4 is provided. Shift position sensor 52, oil pressure sensor 53, throttle opening sensor 5
4. The damping force change rate detection circuit 15 and the waveform shaping circuit 70 are connected to the input section 67, while the high voltage application circuit 75 and the high voltage power supply circuit 79 are 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 receives an output from a circuit including a piezo load sensor 25 according to the acting force that the shock absorber 2 receives from the road surface. voltage signal V
CPU as the damping force change rate of shock absorber 2
6. It is configured to output to 1. The waveform shaping circuit 73 also includes the steering sensor 50 and the vehicle speed sensor 51.
This circuit shapes the waveform of the detection signal from the CPU 61 into a signal suitable for processing by the CPU 61 and outputs the signal. Therefore, C.P.L.
J61 can determine the running state of the vehicle based on the output signals from the damping force change rate detection circuit 70 and the waveform shaping circuit 73, as well as signals from the oil pressure sensor 53 and the like. Based on this processing, the CPU 61 outputs a control signal to the high voltage application circuit 75 provided corresponding to each wheel.

The high voltage application circuit 75 16-2 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 in accordance with a control signal from the CPU 61. Therefore, according to this damping force switching signal, the piezo actuator 27 expands (when +500 volts is applied) or contracts (when -100 volts is applied), the hydraulic oil flow rate is switched, and the damping force characteristics of the shock absorber 2 are softened. Or you can switch to hardware. That is, the damping force characteristics of each shock absorber 2 are determined by applying a high voltage to extend the piezo actuator 27.
B)) The first liquid chamber 2 in the shock absorber 2
Since the flow rate of the hydraulic oil flowing between the first and second liquid chambers 23 increases, the damping force becomes small, and when the piezo actuator 27 is contracted by discharging the charge with a negative voltage As the flow rate decreases, the damping force becomes large. Note that the electric charge accumulated in the piezo actuator 27 is once discharged. Even if the negative voltage is removed, the piezo actuator 27 will not contract. The shock absorber 2 remains in this state, and the shock absorber 2 maintains its large damping force state.

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 shown in the figure. The outline of the processing in each processing routine and the relationship between the two processings are as follows.

(1) Damping force control interrupt processing routine (Fig. 5) This routine is executed every fixed period of time after each flag FS, FF, etc. is reset to the value O in the initialization processing (not shown) when the power is turned on. This is an interrupt routine that is repeatedly executed, and performs a process of switching the damping force pattern generated by the shock absorber 2 based on the damping force change rate V in the shock absorber 2. In this switching, the control of the damping force generation pattern is changed with reference to the value of the flag FH set in the area determination interrupt routine shown in FIG.

(2) Region determination interrupt routine (Fig. 6) This is an interrupt routine that is executed at shorter intervals than the damping control interrupt processing routine, and determines the region of damping force control based on the driving state of the vehicle. The switching reference value Vref is corrected or the flag FH is set.

Note that these processes apply to each shock absorber 2 of each wheel.
Although the processing is executed for each of the FL, FR, RL, and RR, there is no difference in the processing for each wheel, so the description will be made without making any particular distinction. Of course, the process of hard fixing the damping force setting of shock absorber 2, etc.
It is also preferable to use a configuration in which the left and right wheels are operated at the same time to improve steering stability.

When the processing routine shown in FIG. 5 is started, it is first determined whether or not the flag F is at the value O (step
10). This flag "H" is set by the area determination interrupt routine shown in FIG. 6, and its conditions will be described later. Assuming that the damping force setting is specified as hard, the suspension is controlled to hard (step 120), and this routine is temporarily terminated. , immediately after the damping force setting of shock absorber 2 is switched from soft to hard,
This is done by applying -100 volts from the high voltage application circuit 75 to the piezo actuator 27 in response to a control signal from the output section 68 to contract it, and if the piezo actuator 27 is already in the contracted state, it is held as it is.

On the other hand, if the value of the flag ``0'' is O (step 130), the rate of change V of the damping force of each shock absorber 2 is read from the damping force change rate detection circuit 70 via the input unit 67 (step 130). The force change rate V is the switching reference value V r
It is determined whether the value is larger than ef (step 140).
). In this embodiment, since the damping force setting is switched in a binary manner between hard and soft, the adjustment reference value that serves as the reference for changing the damping force setting is called the "switching reference value"7.
S (This switching reference value V ref is given a predetermined initial value in the initialization routine, etc., but is then corrected in the area determination interrupt routine shown in FIG. 6. Note that the switching reference value V ref may be learned based on the switching frequency of the damping force setting of the shock absorber 2, etc.

Vehicle vibration is small and the damping force change rate V is the switching reference value V r
If it is less than or equal to ef (step 140), it is determined whether FS, which indicates that the damping force setting is under soft control, is 1 (step 150), and it is determined that the damping force setting is already under soft control. If not, the shock absorber 2 is directly controlled in a hard manner (step 120).

On the other hand, if the damping force change rate V becomes larger than the switching reference value V ref (step 140), a process of initializing the timer, that is, a process of setting the timer variable Tb to an initial value is performed (step 160).

Timer variable Tb (friend) This variable is used to measure time by software, and is a variable that determines how long the setting of the shock absorber 2, which has been made soft, will continue after V≦Vref. Tb may be constant regardless of vehicle speed SP, or may be set to a smaller value as vehicle speed SP increases.

After the above processing, the condition for softly controlling the damping force (V>
Since Vref) has been established, a flag indicating this is set as “
S is set to the value 1 (step 170), and then 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 (soft). (step 180), and 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
{ヱ Continuing with the above-mentioned timer variable T. b
Initialization (step 160) and control to reduce the damping force (step 180) are repeated. Eventually, when the damping force change rate V becomes equal to or less than the switching reference value V ref, the determination at step 140 becomes rNOJ, and the value of the flag "S" is checked (step 150). The damping force change rate V becomes -79- Once the switching reference value V ref is exceeded, V≦V ref
f, the flag "S" is set to the value 1. Therefore, the determination at step 150 is "YESJ", and then a determination is made as to whether or not the timer variable Tb has become equal to or less than the value O. (Step 200). The process of decrementing the timer variable Tb by the value 1 (Step 210) and the process of softly controlling the shock absorber 2 (Step 180) are repeated until the timer variable Tb becomes equal to or less than the value O.

When the time corresponding to the timer variable Tb has elapsed since the damping force change rate V became equal to or less than the switching reference value V ref (step 200), the timer variable Tb and the flag "S" are reset to the value O (steps 220, 230). ), hard control the damping force setting of shock absorber 2 (step 1
20). That is, in response to a control signal from the output section 68, -100 volts is applied from the high voltage application circuit 75 to the piezo actuator 27 to reduce the voltage. Then r
Exit to R T NJ and end this routine.

-23- When the above-described damping force control 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 V ref. The rate of change in damping force V is the switching reference value V
After the damping force becomes equal to or less than ref, the damping force setting is maintained in the soft state for a predetermined time (time corresponding to the timer variable Tb). After this time has elapsed, the shock absorber 21 returns to a state where the damping force is large (hard).
controlled by.

Next, the area determination interrupt routine (FIG. 6) will be explained. When this routine starts, first, the rate of change Δθ of the throttle opening θ, the brake oil pressure P
, vehicle speed S, etc. (step 300), and based on these driving conditions, a process is performed to determine the acceleration/deceleration region (step 3.10).
. The acceleration/deceleration region is defined by the relationship between vehicle speed S and brake oil pressure P, or vehicle speed S and throttle opening change rate Δθ, as shown in FIGS. 7(A) and (B).
4-, which is a region preliminarily classified as a driving state that causes a tilt of the vehicle body posture. That is, during braking, the vehicle body leans forward (dives), and the degree of this forward lean becomes greater as the vehicle speed S is higher or the brake oil pressure P is higher. Therefore, the region is divided into three regions: a region where the predicted forward tilt is small, an anti-dive control unnecessary region, a V ref correction region where a certain amount of forward tilt occurs, a hard fixed region. Similarly, the backward tilting (scout) of the vehicle body during acceleration is also divided into anti-scout unnecessary jt Vref correction areas and hard fixed areas, as shown in FIG. 7(B).

In the judgment at step 310, if the hard fixed condition is used, that is, if the vehicle is in a state of sudden acceleration or deceleration and a large inclination of the vehicle body posture is predicted, then the damping force setting of the shock absorber 2 is fixed to a large value. , the flag FH is set to the value 1 (step 320), and this routine is temporarily terminated. As a result of the flag FH being set to the value 1, the shock absorber 2 is immediately controlled hard and maintained as it is -7
'I- is held (step 1 10, 120).

On the other hand, if it is determined that the acceleration/deceleration region is the V ref correction region (step 310), the damping force switching reference value V ref is multiplied by the value (1+α) (correction coefficient α>0
) performs processing to increase this (step 330),
The corrected switching reference value V refO value is compared with the guard value Vgd (step 340), and a process of correcting it to within the guard value Vgd is performed (step 350). Thereafter, the flag F is set to the value O (step 370), and this routine ends. Note that the correction coefficient α to be multiplied may be given as a map of the top vehicle speed S.

As a result of the flag FH being set to the value O and the switching reference value Vref being corrected to increase, the shock absorber 2 is not hard fixed, but changes the damping force in the damping force control interrupt processing routine (Fig. 5). The damping force is controlled to be soft or hard depending on the magnitude of the ratio V, and in this control, the setting of the damping force is made difficult to switch to soft.

On the other hand, if it is determined that the acceleration/deceleration region is in the anti-dive control unnecessary region or the anti-scout control unnecessary region (step 310), the flag "H" is simply set to the value O (step 370). ), this routine ends as is. Therefore, in this case, normal damping force control based on the upper damping force change rate V is performed in the damping force control interrupt processing routine (FIG. 5).

As explained above, the suspension control device 1 of this embodiment uses a highly responsive signal called damping force change rate V to change the damping force generation pattern of each shock absorber 2 of the vehicle as a result of changes in attitude. It is possible to quickly control the vehicle to an appropriate state depending on the driving state and vibration of the vehicle. That is, [1] Even when the vehicle is traveling at a nearly constant speed (e) the damping force change rate V is the switching reference value. When V ref is exceeded, the shock absorber 2 is immediately switched to a state with a small damping force characteristic, and the shock absorber 2 is maintained for a predetermined period of time (T b ) even after falling below the switching reference value V ref.Therefore, the suspension characteristics are quickly softened. It is switched and controlled stably, improving ride comfort.

-27- [11] On the other hand, when the condition is satisfied that acceleration/deceleration is applied to the vehicle body by stepping on the brake or accelerator, ■ a region where it is determined that the driving condition is such that the degree of inclination of the vehicle body posture is not very large (Vref correction region) So 1. Shock absorber 2 damping force switching reference value V ref (1+α)
Since the processing for increasing correction by multiplying is performed, it becomes difficult for the shock absorber 2 to be switched by software. As a result, it becomes possible to take into consideration the riding comfort of the vehicle while improving the steering stability.

■ In a region determined to be a driving state in which the degree of inclination of the vehicle body posture is extremely large (hard fixation region), the shock absorber 2 is immediately controlled to a state where the damping force is set to a large value. Therefore, the suspension is held hard and sufficient steering stability is ensured.

As described above, the suspension control device 1 of this embodiment can skillfully balance the ride comfort and steering stability of the vehicle during acceleration and deceleration of the vehicle.

-28- Next, a second embodiment of the present invention will be described.

The suspension control device 11 of the second embodiment has the same device and configuration as the first embodiment, and only the content of the area determination interrupt routine differs. That is, as shown in FIG. 8(A), the steering angle η,
The vehicle speed S is read (step 400), and the roll region is determined based on these driving conditions (step 410). Here, as shown in FIG. 8(B), the vehicle is traveling almost straight or is running at a low speed and is in an anti-roll control unnecessary area where anti-roll control is not necessary, or the vehicle is at a certain speed S and steering angle η. Determine whether the vehicle is in the V ref correction region where the force to tilt the attitude is predicted to act when turning at a high speed S and the steering angle η, or the hard fixed area where the force to tilt the attitude is predicted to act greatly when the vehicle turns at a high vehicle speed S and steering angle η. That's what I do.

The processing after the determination is the same as in the first embodiment.

In the second embodiment, even if the vehicle is traveling almost straight or at low speed ('L, when the rate of change in damping force V exceeds the switching reference value Vref, the shock absorber 2 is placed in a state with small damping force characteristics. , and is maintained for a predetermined time (T b ) after falling below the switching reference value V ref.Therefore, the suspension characteristics are quickly switched to soft and stably controlled, improving ride comfort.

[11] On the other hand, when the condition is met that a lateral force is applied to the vehicle body when the steering wheel is turned, ■ a region in which the degree of tilt (roll) of the vehicle body posture is determined to be a driving condition in which the degree of inclination (roll) is not very large (V ref
Since the process of multiplying the switching reference value V ref of the damping force of the shock absorber 2 by (1+α) and increasing the correction value is repeated in the correction area), the shock absorber 2 is not switched to the soft state. As a result, This makes it possible to take into account the ride comfort of the vehicle while improving steering stability.

■ Area where the degree of inclination (roll) of the vehicle body posture is judged to be extremely large (hard fixed area)
[1] Immediately control the shock absorber 2 to a state where the damping force is set to a large value. As for the J-30, the suspension is held hard to ensure sufficient steering stability.

In this way, the suspension control device 1 of the second embodiment can skillfully balance the ride comfort and steering stability of the vehicle when the vehicle turns. It should be noted that the judgment of the area in the first embodiment and the judgment in the second embodiment do not have to be exclusive, and if both judgments are made together and either condition is satisfied, the switching reference value is determined. It is also possible to perform V ref correction or hardware fixing control. Further, regarding turning during acceleration/deceleration, it is also preferable to change the V ref correction area and the hard fixation area to lower values, respectively, in order to further ensure steering stability.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way.
A configuration in which the correction coefficient α of the switching reference value Vref in the ref correction region is made variable according to the magnitude of the damping force change rate V.
The present invention may be implemented in various ways without departing from the scope of the invention, such as a configuration in which the spring constant of the air spring is controlled instead of controlling the damping force setting of the shock absorber to change the characteristics of the suspension means. Of course it is possible.

Skin L Effect As detailed above, the suspension control device of the present invention corrects the characteristics of the suspension means to the hard side based on the driving condition of the vehicle that causes the vehicle attitude to tilt, and Since the system is rigidly fixed and controlled, it has the extremely excellent effect of ensuring steering stability while also being able to take ride comfort into account depending on the driving conditions.

[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 suspension control device as an embodiment of the present invention, and FIG. 3 (A) is a shock absorber 2 Fig. 3 (B) is a partial cross-sectional view showing the structure of
) is an enlarged cross-section of the main part of the shock absorber 2, FIG. 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 control interrupt processing routine, and FIG. 6 is the area Flow-32 showing judgment interrupt routine
- Charts, FIGS. 7(A) and (B) are graphs illustrating region determination, FIG. 8(A) is a flowchart showing the main part of the processing of the second embodiment, and FIG. 8(B) is a graph illustrating the area determination. It is a graph showing an example of a roll area in an example. 1... Suspension control device 2 FL, FR, RL, RR... Shock absorber 4... Electronic control device 2 5 FL, FR, RL, RR... Viezo load sensor 2 7 FL, FR, RL, RR...
Piezo actuator 50...steering sensor
51... Vehicle speed sensor 53... Oil pressure sensor 54... Throttle opening sensor 70... Damping force change rate detection circuit

Claims (1)

[Scope of Claims] 1. Suspension means provided between the wheels and the vehicle body and capable of varying characteristics such as a damping force generation pattern and a spring constant; Vibration state detection means for detecting the vibration state of the vehicle; A suspension control device comprising: suspension characteristic control means for controlling characteristics of the suspension means based on the detected vibration state; If the degree of inclination of the posture predicted from the detected driving state of the vehicle is greater than or equal to a first reference value, the characteristics of the suspension means controlled by the suspension characteristic control means are corrected to the hard side as a whole. and a correction means for correcting the vehicle, regardless of the vibration state of the vehicle, if the degree of inclination of the posture predicted from the detected driving state of the vehicle is equal to or higher than a second reference value, which is larger than the first reference value. First, a suspension control device comprising suspension characteristic fixing means for fixing and controlling the characteristics of the suspension means in a hard state.