JPH03197227A - Suspension control device - Google Patents

Abstract

PURPOSE:To reduce the frequency of setting suspension characteristics at a soft side when the vibration of a vehicle exceeds an allowable vibration range, and increase the stability of the vehicle against a lateral force by expanding the allowable vibration range according to an increase in lateral force acting on the vehicle. CONSTITUTION:When the vibration condition of a vehicle detected with a vibration condition detection means M1 on the basis of a road condition change, exceeds an allowable vibration range, the hardness and soft characteristics of a vehicle suspension device M2 drop and the suspension characteristics thereof are set at the soft side with a characteristics setting means M3. In the aforesaid constitution, the magnitude of a lateral force F acting on the vehicle due to a lateral wind is detected with a lateral force detection means M4. Also, the allowable vibration range is so set with an allowable vibration range setting means M5 as to expand, according to an increase in lateral force F. Consequently, the frequency of setting the suspension characteristics at the soft side is lessened and the average of the suspension characteristics is shifted to the hard side. According to the aforesaid construction, the stability of the vehicle against the lateral force can be increased.

Description

[Detailed Description 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 in accordance with the vibration state of the vehicle. , relates to a suspension control device that controls suspension characteristics.

[Prior art] A suspension system that improves vehicle stability by increasing the damping force of shock absorbers and the spring constant of air suspensions to make suspension characteristics harder (rigid) when crosswinds exceed a predetermined level. There is a control device (for example, JP-A-61-163009). According to this, it is possible to eliminate the problems that hitherto caused the stability of the vehicle to be impaired due to crosswinds, causing the vehicle to be swept away, and causing discomfort due to the generation of yaw angular velocity.

[Problems to be Solved by the Invention] Such a configuration is excellent in improving the stability of the vehicle when subjected to crosswinds, but if the crosswinds exceed a predetermined magnitude, the suspension characteristics will deteriorate regardless of the road surface condition. There was a problem in that the ride comfort could be sacrificed depending on the road surface conditions.

The suspension control device of the present invention solves the above problems,
The purpose is to improve the stability of the vehicle in the event of crosswinds while ensuring excellent ride comfort.

Composition for soothing sleep [Means for solving the problem] The suspension control device of the present invention, as illustrated in FIG. When the detected vibration state of the vehicle exceeds the permissible vibration range, the suspension control device includes a characteristic setting means M3 that reduces the hardness and softness characteristics of the vehicle suspension system M2 to set the suspension characteristics to the soft side. lateral force detection means M4 for detecting the magnitude of lateral force F acting on the lateral force F; and permissible vibration range setting means M5 for expanding the permissible vibration range as the lateral force F becomes stronger. .

[Operation] In the suspension control device of the present invention having the above configuration, the vibration state of the vehicle based on changes in road surface conditions is detected by the vibration state detection means M1 while the vehicle is running, and the detected vibration state of the vehicle falls within the allowable vibration range. If the suspension characteristic exceeds this value, the characteristic setting means M3 reduces the hardness and softness characteristics of the vehicle suspension system M2 to set the suspension characteristics to the soft side. Furthermore, in the present invention, the permissible vibration range in which the characteristic setting means M3 determines the vibration state of the vehicle is expanded by the permissible vibration range setting means M5 as the lateral force detected by the lateral force detecting means M4 increases.

Therefore, as the crosswind becomes stronger and the lateral force F increases, the permissible vibration range widens, and even under the same road surface condition, the characteristic setting means M3 determines that the vibration state of the vehicle exceeds the permissible vibration range and sets the suspension characteristics to the soft side. The frequency of setting will be reduced. As a result, when the lateral force F is large, even if the suspension characteristics are controlled according to the road surface condition, the average suspension characteristics will shift toward the stiff side. Achieve stability.

[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 1 of this embodiment includes a shock absorber (hereinafter simply referred to as "shock absorber 2") 2FL 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.

In the 2RR, a piezo actuator that switches the setting of the generation pattern of damping force with respect to the stroke is used.
Each set is built-in.

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 5F and front right wheel 5FR, as necessary.

Left rear wheel 5R[, subscript FL corresponding to 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, as shown in FIG. 3(A),
At the lower end of the cylinder 11 side, it is fixed to the suspension lower arm 6 via the axle-side member]]a.On the other hand, at the upper end of the rod 13 inserted through the cylinder It is fixed to the vehicle body 7 together with a coil spring 8.

Cylinder ]] Inside is an internal cylinder 15 . connected to the lower end of the rod 13 . A connecting member 16 and a cylindrical member] 7, 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 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 cylinder 11 side is divided into a first liquid chamber 2 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 there is a gap between the back-up member 28 and 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]7 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 3] and the backup member 28, and urge the leaf valve 3] in the main piston direction.

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

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 8 moves, the hydraulic oil filled in both the liquid chambers 21 and 23 flows through both passages 18a and 23.
18b, and moves between the two liquid chambers 21 and 23. In this state where the movement of hydraulic oil between the two liquid chambers 21 and 23 is limited to both passages 18a and 18b, the damping force generated against the movement of the rod 3 is large, and the suspension characteristics become hard. Become.

The piezo load sensor 2 is housed inside the internal cylinder] 5.
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 generated in 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 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-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 chamber 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 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 is provided with an oil chamber 45b having a larger diameter than the oil chamber 45a on the outside of the oil chamber 45a.
When the bushing 39 moves against the urging force of the bushing 39, the hydraulic oil becomes movable through the oil chamber 45b. Therefore, regardless of the position of the spool 41, the main piston 18
The hydraulic oil flow rate when the main piston 18 moves in the direction of the arrow 8 is larger than when the main piston 18 moves in the direction of the arrow. That is, the damping force is changed depending on the moving direction of the main piston 18, 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 to check the check valve 38a.
The hydraulic oil flow rate 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 steering sensor 50 for detecting the steering angle of a steering wheel (not shown), which is an imitation of the piezo load sensor 25 of each shock absorber 2, as a sensor for detecting the running state of the vehicle, and a steering sensor 50 for detecting the steering angle of a steering wheel (not shown). Connected are a vehicle speed sensor 51 that detects speed, a differential pressure sensor 52 that detects the difference in pressure between the left and right sides of the vehicle, and a stop lamp switch 53 that issues a signal when a brake pedal (not shown) is depressed. Among these, the differential pressure sensor 52 is connected to conduits 52A and 52B that open on the left and right sides of the vehicle, as shown in FIG. 2, and changes its output voltage in accordance with the pressure difference between the left and right sides.

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° ROM 62. RAM6
The input section 67 and the output section 68 are connected to each other via a common bus 65 to perform input/output with the outside.

In addition to the electronic control device 4 (erroneous), the piezo load sensor 25
A damping force change rate detection circuit 70 and a steering sensor 50 . vehicle speed sensor 5], a waveform shaping circuit 73 to which a differential pressure sensor 52, etc. are connected, and a piezo actuator 2
A so-called switching regulator-type high-position piezoelectric circuit receives power supply from a battery 77 via a high voltage application circuit 75 and an ignition switch 76 and outputs a drive voltage for driving a piezo actuator.
9. A constant voltage power supply circuit 80 that transforms the voltage of the battery 77 to generate an operating voltage (5 V) for the electronic control device 4 is 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 and the high voltage power supply circuit 79 are connected to the output section 68.

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 is a steering sensor 50. Vehicle speed sensor 51. This circuit shapes the detection signal from the differential pressure sensor 52 into a signal suitable for processing in the CPLI 61 and outputs the signal. Therefore, the CPU 61 can determine the road surface condition, the running condition of the vehicle, 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.

The high voltage application circuit 75 applies a voltage of +500 volts or -100 volts output from the high voltage power supply circuit 79.
This is a circuit that applies voltage to the piezo actuator 27 in response to a control signal from CP[J61. 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), the hydraulic oil flow rate is switched, and the damping force characteristics of the shock absorber 2 are changed. Can be switched to soft or hard. That is, the damping force characteristics of each shock absorber 2 are determined by applying a high voltage to the piezo actuator 27.
When the spool 4] (3rd
(B)), the flow rate of the hydraulic oil flowing between the first liquid chamber 21 and the second liquid chamber 23 in the shock absorber 2 increases, resulting in a state where the damping force is small, and the negative voltage causes an electric charge. When the piezo actuator 27 is contracted by being discharged, the hydraulic oil flow rate decreases, resulting in a state of large damping force.

Next, the damping force control performed by the suspension control device 1 of this embodiment having the above-mentioned configuration 2 will be explained in FIGS. 5 and 6.
This will be explained based on the flowchart shown in the figure. 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.

■ Damping cover turn switching control routine (Fig. 5) This routine is executed independently for each wheel 5FL, 5FR, 5RL, and 5RR, and sets the rate of change V of the damping force that changes depending on the road surface condition and the switching reference value. The piezo actuator 27 is switched based on the magnitude relationship with the switching reference value V ref set in routine ■, and each wheel 5FL,
The damping force is switched to a large state (hard) or a small state (soft) for each of 5FR, 5RL, and 5RR.

■ Switching reference value setting routine (Figure 6) Find the magnitude of the lateral force F that acts on the vehicle due to crosswinds, and if the lateral force F is large, set the switching reference value V ref, which is referred to in the damping cover turn switching control routine ■, to a large value. Change to

The details of each routine will be explained in order starting from the attenuation cover turn switching control routine (FIG. 5). Note that since there is no difference in the processing for each wheel, the explanation will be made without making any particular distinction.

When this routine is started, the rate of change V of the damping force of the shock absorber 2 is read from the damping force change rate detection circuit 70 via the input section 67 (step 100).
), it is determined whether the damping force change rate V is larger than the switching reference value V ref (step 110). The switching reference value Vref is set in a switching reference value setting routine (FIG. 6).

If the damping force change rate V is smaller than the switching reference value V ref (step] ] 0), then the flag FH3 indicating that the suspension characteristics are set to soft is set to the value 1.
A determination is made as to whether or not (step) 20). Flag F)
If -18 is not the value 1 (step 20), that is, if it is not set to soft, the suspension is controlled to hard (step 130), 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, 1100 volts is applied from the high voltage application circuit 75 to the piezo actuator 27 by the control signal from the output section 68. Apply and reduce this, and already the piezo actuator 27
If it is in a shrunken state, this is done by holding it as it is.

On the other hand, if the damping force change rate V is larger than the switching reference value V ref (step 110), a process is performed to start the timer, that is, a process to reset the timer variable T to the value 0 (step) 40, and further the suspension is adjusted. Assuming that the characteristic is set to soft, processing is performed to set the flag FH8 to a value of 1 (step 150). 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 (soft).]6
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 (step) 10, the above-described starting of the timer and control to reduce the damping force are repeated. After that, the damping force change rate V becomes the switching reference value V re
When the value is equal to or less than f (step 110), flag FH is set.
After checking the value of 3 (step 120), it is determined whether the timer variable T exceeds a preset reference value TS (step 70). The reference value TS is a value set so that, after the shock absorber 2 is once switched to a state with a small damping force, the state is maintained for a certain period of time. Therefore, if the timer variable Te is less than the reference value TS (step 170), this variable Te value is incremented by 1 (step 80), and the process of controlling the damping force of the shock absorber 2 to a small state is continued. (Step] 60).

Further, if the damping force change rate V does not exceed the switching reference value Vref until a predetermined time (time corresponding to TS) has elapsed since the damping force change rate V became equal to or less than the switching reference value Vref, step 170 Since the judgment is rYESJ, the flag FH3 is then reset to the value 0 (step 90), and the damping force of the shock absorber 2 is controlled to a large state (step 30).

Therefore, for example, when the road surface is rough and the damping force change rate V exceeds the switching reference value V ref, the damping force of the shock absorber 2 is immediately set to a small state (soft), and when the road surface becomes rough, the damping force change rate V After the value becomes less than or equal to the switching reference value V ref, the state (soft) is maintained as it is for at least the time corresponding to the reference value TS. In this way, when a predetermined period of time has elapsed with the damping force change rate V remaining below the switching reference value V ref and the fear of the vehicle vibrating is eliminated,
Set the damping force to a large state (hard) again.

Next, a switching reference value setting routine for setting the switching reference value V ref referred to in the above-described damping cover turn switching control routine in accordance with the magnitude of the lateral force F will be described (FIG. 6).

When this routine starts, the vehicle speed S is first read from the waveform shaping circuit 73 via the input section 67 (step 20
0), a process (step 210) is performed to determine whether the vehicle speed S is low, that is, less than 5LOW, a low vehicle speed at which the influence of the lateral force F on the stability of the vehicle can be ignored. If the vehicle speed S is less than the low vehicle speed 5LOW (step 210), a process of setting the switching reference value V ref to the normal value VN is performed (step 220). The normal value VN to be set as the switching reference value V ref is the value that is used when controlling the switching of the damping force generation pattern of the shock absorber 2 according to the road surface condition without considering the lateral force F. This value provides the best balance of comfort.

On the other hand, if the vehicle speed S is higher than the low vehicle speed stow (step 2
10) Next, read the differential pressure P from the waveform shaping circuit 73 via the input unit 67 (step 230), and calculate the lateral force F from the differential pressure P and vehicle speed S (step 240).
Do this. The reason why the vehicle speed S is taken into account in the calculation of the lateral force F is that the detected differential pressure P changes depending on the vehicle speed S. For details on the calculation of the lateral force F, see, for example, "Prior Art"
For details, refer to JP-A No. 61-163009 explained in the column.
Since this is a well-known matter, its explanation will be omitted.

Next, it is determined whether the calculated lateral force F is greater than or equal to the reference force F ref (step 250). The lateral force F is the reference force F r
If it is greater than or equal to ef (step 250), it is determined that the influence of lateral force F on vehicle stability cannot be ignored, and the switching reference value V ref is set to a value VL that is slightly larger than the normal value VN.
A process of setting (step 260) is performed. The value VL to be set is the attenuation cover turn switching control routine (fifth
When the damping force switching control is performed according to the road surface condition by executing the procedure shown in the figure), the suspension characteristics shift to the hard side on average, as will be explained later, and the value is such that the stability of the vehicle against the lateral force F can be achieved. .

On the other hand, if the lateral force F is less than the reference force F ref (step 250), the influence of the lateral force F on the stability of the vehicle can be ignored, and the switching reference value V ref is set as in the case where the vehicle speed S is small. A process of setting a normal value VN (step 220) is performed.

By executing the damping force pattern switching control routine (Fig. 5) and the switching reference value setting routine (Fig. 6) explained above, for example, when the vehicle speed S is low or when the vehicle speed S
Even if the crosswind is high, if the crosswind is weak and the lateral force F is small, the damping force switching control is based only on the road surface condition. Control is performed to switch the damping force depending on whether or not it exceeds the limit, achieving excellent handling stability and ride comfort suitable for the road surface condition.

On the other hand, if the vehicle speed S is not so low that the influence of the lateral force F can be ignored and the lateral force F is large, the switching reference value V ref should be set to a slightly larger value VL (step 260), and the damping force The rate of change V is the switching reference value Vref (
The damping force is controlled depending on whether the damping force exceeds the value VL). Therefore, during the period until the crosswind subsides, even on the same road surface, the suspension characteristics tend to be less soft than when the damping force is switched, such as when the lateral force F is small. As a result, while driving, the damping force is switched according to the road surface condition to ensure excellent ride comfort, but the average suspension characteristics are shifted to the side of the pigeon, and the vehicle's response to the lateral force F is The stability of the system is improved.

As explained above, according to the suspension control device 1 of the embodiment, when the lateral force F is large, the switching reference value V re
By simply changing the value of f to a larger value VL, it is possible to improve the stability of the vehicle against lateral force F while ensuring excellent ride comfort by controlling the switching of the damping force according to the road surface condition while driving. It has this excellent effect.

Furthermore, in the suspension control device of the embodiment, by adjusting the value VL to be set as the switching reference value V ref when the lateral force F is large, the characteristics of the suspension characteristics when the lateral force F acts can be set in a variety of ways. For example, it has the advantage that it can be set according to the characteristics of various modes, such as a hard sports mode or a soft normal moto mode.

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 only a suspension that uses a variable damping force type shock absorber as in the embodiment, but also a suspension control device that controls the vibration state of a vehicle by changing the spring constant of an air suspension. It may be. Further, the shock absorber may be one in which the setting of the magnitude of the damping force generated by the shock absorber can be switched over three or more stages, or one in which the magnitude of the damping force can be continuously changed. 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.

The lateral force may be detected using a yaw rate sensor and a steering angle sensor, and determined from changes in the output of the yaw rate sensor when changes in the steering angle are small. Furthermore, in the embodiment, the permissible vibration range, that is, the value of the switching reference value Vref, is configured to be changed in two stages according to the value of the lateral force F, but the value of the switching reference value Vref is changed depending on the lateral force F and the vehicle speed. It may be configured to take a value that changes continuously as a function of S, or it may be configured to ask for a price in multiple stages.

Effects of the Invention As detailed above, the suspension control device of the present invention widens the permissible vibration range as the lateral force increases, and changes the suspension characteristics to the soft side when the vibration state of the vehicle exceeds the permissible vibration range while driving. Second, the frequency of setting is reduced and the average suspension characteristics are shifted to the stiffer side, ensuring excellent ride comfort by controlling suspension characteristics according to road conditions, while improving vehicle stability against lateral forces. It has an excellent effect of being able to achieve the desired results.

[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. 2. FIG. 3(B) is an enlarged sectional view of the main part of the shock absorber 2.
FIG. 5 is a block diagram showing the configuration of the electronic control device 4 of this embodiment. FIG. 5 is a flowchart showing the damping cover turn switching control routine. FIG. 6 is a flowchart showing the switching reference value setting routine. 2... Variable damping force shock absorber 4... Electronic control unit 25... Load sensor 27... Piezo actuator 5]... Vehicle speed sensor 52... Differential pressure sensor 75... High voltage application Circuit 79...High voltage power supply circuit

Claims (1)

[Scope of Claims] 1. A vibration state detection means for detecting a vibration state of a vehicle based on a change in road surface conditions; and when the detected vibration state of the vehicle exceeds a permissible vibration range, the hardness and softness characteristics of a vehicle suspension system are reduced. a lateral force detecting means for detecting the magnitude of a lateral force acting on the vehicle due to a crosswind; and as the lateral force increases, A suspension control device comprising: permissible vibration range setting means for expanding the permissible vibration range.