JP2600471B2 - Suspension rigidity control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a suspension rigidity control device suitable for use in an automobile.

2. Description of the Related Art For vehicles such as automobiles, there have been developed ones in which the rigidity of a suspension can be adjusted according to, for example, a driver's preference.

As a mechanism for adjusting the rigidity of such a suspension, a mechanism that adjusts the roll rigidity by changing a mounting point of a stabilizer, or a mechanism that adjusts the rigidity of a suspension bush that elastically attaches a suspension to a vehicle body is used. There are types.

[Problems to be Solved by the Invention] In a motor vehicle, a so-called handle shimmy in which the handle vibrates in the circumferential direction may occur, and this handle shimmy undesirably deteriorates the handle grip feeling of the drive. Therefore, in order to suppress such handle shimming, measures to increase the handle inertia moment or to interpose a spring or the like in the middle of the handle shaft are generally considered. However, since all of these means only lower the sensitivity of the steering wheel, the suppression of shimmy is uncertain, and at present it is not a fundamental solution to the steering shimmy.

In such a handle shimmy, since engine vibration and suspension vibration are transmitted to the steering shaft system to induce torsional vibration of the steering shaft, torsional vibration of the steering shaft is particularly large due to resonance or the like. The shimmy gets bigger.

Therefore, changing the vibration characteristics (natural frequencies) on these vibration-generating sides can be a fundamental solution to handle shimmy. In particular, since the vibration characteristics of the suspension vary greatly depending on the slight rigidity balance of the suspension, it is possible to expect suppression of handle shimmy by adjusting the rigidity of the suspension.

The present invention has been devised in view of such a problem, and provides a suspension stiffness control device that can appropriately adjust suspension stiffness to suppress the handle shimmy when the vehicle has handle shimmy. The purpose is to provide.

[Means for Solving the Problems] For this reason, the suspension rigidity control device of the present invention includes:
Suspension longitudinal rigidity adjusting means capable of adjusting longitudinal rigidity of a suspension provided in a vehicle, suspension lateral rigidity adjusting means capable of adjusting lateral rigidity of the suspension, suspension longitudinal rigidity adjusting means and suspension lateral rigidity adjusting means Control means for controlling the vehicle, and steering wheel vibration detecting means for detecting a state of the steering wheel vibration of the vehicle, wherein the control means controls the vibration of the steering wheel based on information from the steering wheel vibration detecting means so that the vibration of the steering wheel exceeds an allowable level. A handle vibration reduction control unit that outputs a control signal to the suspension rigidity adjusting means to adjust the longitudinal rigidity or the lateral rigidity of the suspension so as to suppress the handle vibration when the handle vibration is reduced; Mainly in the region where the suspension is large Is characterized in that it is set mainly to suppress the handle vibration by adjusting the transverse stiffness of the suspension is adjusted region suppressing handle vibration handle vibration is small.

[Operation] In the suspension rigidity control device of the present invention described above, when the control means detects that the handle vibration has become larger than the allowable level based on the information from the handle vibration detecting means, the control means reduces the handle vibration reduction control. Controls the suspension stiffness adjustment means to adjust the suspension rigidity mainly by adjusting the suspension front and rear stiffness in the region where the handle vibration is large, and to suppress the handle vibration mainly by adjusting the lateral stiffness of the suspension in the region where the handle vibration is small Output a signal. Thereby, when the steering wheel vibration is in a large region, the front-rear rigidity of the suspension of the vehicle is adjusted through the suspension rigidity adjusting means, so that the steering wheel vibration is suppressed to a small region.
By adjusting the lateral stiffness of the suspension of the vehicle through the suspension stiffness adjusting means, the steering wheel vibration is suppressed to within an allowable range of an even smaller area.

[Embodiment] Hereinafter, a suspension rigidity control device as one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration, and FIG. 2 (b) is a sectional view taken along the line IIb-IIb in FIG. 2 (a), and FIG. 2 (c) is a sectional view taken along IIc-IIc in FIG. 2 (a). FIG. 3 is a schematic view showing an example of mounting on the suspension viewed in the vehicle length direction, FIG. 4 is a schematic plan view showing an example of mounting on the suspension, and FIG. FIG. 6 is a detailed diagram showing the mounting example of the vehicle as viewed in the vehicle length direction, FIG. 6 is a flowchart showing the control operation thereof, and FIG. 7 is a graph showing a threshold value used for the control. Is shown.

As shown in FIG. 1, the structure of the suspension rigidity control device includes a suspension bush 1 having a rigidity adjusting mechanism as suspension rigidity adjusting means, and a controller serving as control means for controlling the suspension rigidity adjusting means (suspension bush) 1. 11 and a steering angle sensor 12b and an acceleration sensor (handle vibration sensor) 12i as steering wheel vibration detecting means for detecting a state of steering wheel vibration of the vehicle.

Suspension bush 1 with rigidity adjustment mechanism
Is capable of adjusting the vertical rigidity and longitudinal rigidity of the suspension, and its operation is controlled by a hydraulic pressure by a hydraulic control system 10. The suspension bush with the rigidity adjusting mechanism is also referred to as a rigidity adjusting actuator 1.

This suspension bush 1 with a rigidity adjusting mechanism is
As shown in FIGS. 2 (a) to 2 (c), a case 2 is mounted on the vehicle body side, a shaft 3 is mounted on the suspension side, and the shaft Rubber members 4 and 6 are provided as elastic support members for elastically supporting 3 in case 2.

Among them, the rubber body 4 is provided such that both ends thereof are fixed to the inner wall of the case 2 at an intermediate portion in the first direction [the vertical direction in FIG. Spaces 7a and 7b as first oil chambers are formed on both sides of 4. Thus, the rubber body 4 elastically supports the shaft 3 inside the rubber body 4 in the first direction.

The rubber body 6 has both ends fixed to the inner wall of the case 5 at an intermediate portion in the second direction [the left-right direction in FIG. 2A] in the inner case 5 built in the rubber body 4. Spaces 8a and 8b as second oil chambers are formed on both sides of the rubber body 6. Thereby, the rubber body 6
Supports the shaft 3 therein elastically in the second direction.

Then, the support rigidity in the first direction changes according to the oil pressure supplied into the oil chambers 7a and 7b, and the support rigidity in the second direction changes according to the oil pressure supplied into the oil chambers 8a and 8b. The support stiffness changes.

Reference numeral 9 denotes a reinforcing member incorporated in each of the rubber members 4, 6, and the reinforcing members 9 make the rubber members 4, 6 have a certain tension (rigidity). Reference numerals 20a to 20d denote hydraulic supply / discharge ports for the oil chambers 7a, 7b, 8a, 8b.

The first and second oil chambers 7a, 7b, 8a, 8b are connected to a hydraulic control system 10 for controlling the oil pressure inside the oil chambers 7a, 7b, 8a, 8b, These oil chambers 7a, 7b, 8
A stiffness adjusting mechanism 1A for adjusting the suspension stiffness is composed of the a, 8b and the hydraulic control system 10.

In this example, the first direction [vertical direction in FIG. 2 (a)] is the front-rear direction of the vehicle body, and the second direction [lateral direction in FIG. 2 (a)] is the lateral direction of the vehicle body. It is installed so that it becomes.

The hydraulic control system 10 is configured as shown in the upper part of FIG. 1. In FIG. 1, 10a and 10b are control valves connected to supply / discharge ports 20a to 20d, and 11 is a control valve 10a and 10b. A controller for outputting a control signal; 12, a sensor group such as a steering angle sensor 12b and a steering wheel vibration sensor 12i connected to the controller 11; 13, an orifice; 14, an oil pump;
Is an accumulator, 16 is a relief valve, 17 is a one-way valve, and 19 is an oil reservoir.

Among the control valves 10a and 10b, the control valve 10a is a longitudinal rigidity control valve, and an oil chamber arranged in the longitudinal direction of the vehicle body so as to adjust the longitudinal rigidity of the suspension.
Connected to 7a, 7b. The control valve 10b is a lateral rigidity control valve, and is connected to oil chambers 8a and 8b arranged in the lateral direction of the vehicle body so that the lateral rigidity of the suspension can be adjusted.

These control valves 10a, 10b are connected to the oil chambers 7a, 7b, 8
a, an open state communicating between the inside of 8b and the accumulator 18 side,
Oil supply chambers 7a, 7b, 8a, 8b are closed by closing supply / drain ports 20a, 20b, 20c, 20d of oil chambers 7a, 7b, 8a, 8b and oil chambers 7a, 7b, 8a, 8b from supply / drain ports 20a, 20b, 20c, 20d.
It is configured to be able to take a drain state in which the hydraulic pressure in the inside is discharged.

Therefore, for example, if the control valve 10a is open, the oil driven by the oil pump 14
The pressure is appropriately adjusted at 7 and stored in the accumulator 18, and is supplied from the control valve 10a to the oil chambers 7a and 7b of the actuator (suspension bush) 1 through the supply / discharge ports 20a and 20b. When the pressure inside each of the oil chambers 7a, 7b reaches a predetermined pressure, the control valve 10a is closed, whereby the oil chambers 7a, 7b
The internal pressure is kept constant at a predetermined level. Further, when the control valve 10a is set to the drain state, the oil in the oil chambers 7a, 7b is discharged, and the pressure in the oil chambers 7a, 7b decreases.

Further, the control valve 10b operates in a similar manner.

Suspension bush 1 with rigidity adjustment mechanism described above
Can be installed on various types of rear wheel suspensions.For example, when installed on a strut type suspension, as shown in FIGS.
The suspension bush 1 has a shaft 3 oriented in the vehicle width direction and a vehicle length in a first direction [vertical direction in FIG. 2 (a)]. The vehicle is installed so that a second direction [left-right direction in FIG. 2 (a)] is directed in the vehicle width direction.

In the drawing, 21 is a wheel, 22 is a strut, 27 is a rubber bush that rotatably supports the inner end of the strut 22 around a vehicle length direction axis, 25 is a bush 27 and a shaft 3 of the actuator 1.
And a connection joint for connecting

More specifically, it is configured as shown in FIG. In FIG. 5, the same reference numerals as those in FIGS.
Reference numeral 21a denotes a knuckle, 23 denotes a joint between the knuckle 21a and the outer end of the lower arm 24, and 28 denotes a spring.

By the way, as shown in FIG.
The controller 11 controls the control valves 10a and 10b to any one of the above-described states. The controller 11 controls the control valves 10a and 10b based on information from various sensors (sensor groups) 12. A handle vibration control unit 11f that controls the control valves 10a and 10b based on information from the vibration sensor 12i is provided.

The handle vibration handling control unit 11f determines the magnitude of the handle signal based on the information from the handle vibration sensor 12i.
When G | exceeds the tolerance (here, acceleration G ₃ ),
A control signal is output to the suspension bush 1 with the rigidity adjusting mechanism so as to obtain the longitudinal rigidity or the lateral rigidity of the suspension so as to suppress the handle vibration.

Specifically, as shown in FIG. 7, for the magnitude | G | of the steering wheel vibration, threshold values G ₂ , G ₃ (G ₂ > G ₃ ) corresponding to the vehicle speed
Is provided, and the magnitude | G |
Beyond the _{threshold) G 3 (| G |>} G 3) and performs the handle vibration-control. In particular, for example, as in G ₁ shown in FIG. 7, the magnitude of the handle vibration | G | is the threshold (second
Threshold) G ₂ which exceeds large area (| G | In> G _2), primarily by adjusting the longitudinal stiffness of the suspension, the size of the handle vibration | G | exceeds a small threshold G ₃ than the threshold G ₂ In such a region (G ₂ > | G |> G ₃ ), it is set so as to suppress the steering wheel vibration mainly by adjusting the longitudinal rigidity of the suspension.

This is because the front-rear stiffness of the suspension is more likely to affect the handle vibration than the lateral stiffness, so the adjustment of the front-rear stiffness of the suspension makes it easy to greatly adjust the handle vibration characteristics. This is because the adjustment of the lateral rigidity makes it easy to fine-tune the handle vibration characteristics.

Therefore, | G |> of the time G _2, first, after roughly reduce handle vibration by adjusting the longitudinal stiffness of the suspension is set to slightly reduce handle vibration by adjusting the lateral stiffness , G ₂ > | G |> G ₃ , the lateral rigidity is adjusted so that the steering wheel vibration is slightly reduced.

In addition, the adjustment of the longitudinal rigidity and the lateral rigidity of the suspension is performed by adjusting the rigidity by a minute amount, thereby feeding back the increase / decrease result of the handlebar vibration and performing control.

Note that if the suspension stiffness changes during turning, there is a problem such as deterioration of the steering feeling. Therefore, the above-described steering vibration response control by adjusting the suspension stiffness is performed only at a low steering angle based on information from the steering angle sensor 12b. It is set to do so.

Since the suspension stiffness control device as one embodiment of the present invention is configured as described above, in the suspension bush 1 with the stiffness adjusting mechanism, the controller 11 uses the information from the sensors 12 such as the handle vibration sensor 12i. The control valves 10a and 10b are controlled.

That is, as shown in FIG. 6, control is started in conjunction with turning on the ignition and the like. First, in step S1, each control parameter and the like are initialized to values such as initializing the control flags FL1 to FL4 to 0. I do.

It should be noted that the control flag FL1 is set to 1 when performing control to lower (that is, soften) the longitudinal rigidity of the suspension.
The control flag FL2 is set to 1 when performing control to increase (ie, soften) the longitudinal rigidity of the suspension.
The control flag FL3 is set to 1 when performing control to lower (ie, soften) the lateral rigidity of the suspension, and the control flag FL4 is set to 1 when performing control to increase (ie, soften) the lateral rigidity of the suspension. It is said.

Next, in step S2, information (data) from the sensors 12, such as the steering angle sensor 12b and the steering wheel vibration sensor 12i, is read.

Then, in step S3, it is determined whether or not the magnitude | θ | of the steering angle is larger than a threshold value θ ₀ (θ ₀ is a small value) based on information from the steering angle sensor 12b and the like. The magnitude of the steering angle | theta | is proceeds with the step S15 is greater than the threshold value theta ₀ each control flag FL1~FL4 is reset to 0, and ends this control cycle. Also, the magnitude of the steering angle | theta | if there is no greater than the threshold theta _0, the process proceeds to step S4.

In step S4, the handle vibration sensor 12i handle magnitude of the vibration | G | determines whether greater than the first threshold value G _3. | G | <unless G _3, handle vibration-control for controlling the handle vibration is controlled not performed without, | G |> if G _3, the process proceeds to step S5.

In step S5, the size of the handle vibration from the information of the steering wheel vibration sensor 12i | G | determines whether greater than the second threshold value G _2.

| G |> unless G _2, since the need to suppress the handle vibration but the extent of the oscillation is not too large, in order to fine-tune the steering wheel vibration characteristics, so as to perform the handle vibration suppressed by adjusting the transverse stiffness of the suspension To step S12.

| G |> if G _2, since the degree of the steering wheel vibration is not large, in order to increase the size handle vibration characteristics, the process proceeds to step S6 to perform a steering wheel vibration suppressed by adjusting the longitudinal stiffness of the suspension.

In step S6, it is determined whether or not the control flag FL1 is "1". At the start of control, the control flag FL1 is "0", so that the process proceeds to step S7.

In step S7, it is determined whether or not the control flag FL2 is 1. At the start of the control, since the control flag FL2 is 0, the process proceeds to step S8.

In step S8, the control flag FL1 is set to 1, and the process proceeds to step S9 so that the longitudinal rigidity is reduced (down).
The control valve 10a is controlled. In other words, a control signal is output from the handle vibration control unit 11f of the controller 11 to the control valve 10a so that the control valve 10a is in a drain state.
The oil in each of the oil chambers 7a, 7b of the actuator (suspension bush) 1 is discharged from the supply / discharge ports 20a, 20b through the supply / discharge ports 20a, 20b, thereby lowering the longitudinal rigidity of the suspension. However, the amount by which the rigidity is reduced in this manner is set to an appropriately minute constant amount.

 Then, the control cycle ends.

In the next control cycle, | θ | <θ, | θ |>
If G _2, since the control flag FL1 is 1, step S
From S2, S3, S4, S5, S6, the process proceeds to step S10, where it is determined whether or not the steering wheel vibration has been reduced from the rate of change of | G | (||). If the magnitude | G | of the handle vibration has decreased, the process proceeds to step S9 again to control the control valve 10a so that the longitudinal rigidity further decreases.

On the other hand, if the magnitude | G | of the steering wheel vibration is not reduced, the control flag FL1 is set to 0 in step S11, and the control flag
With FL2 set to 1, the process proceeds to step S13.

In step S13, the control valve 10a is controlled so that the front-back rigidity is improved (up). In other words, the control valve 10a
A control signal is output so that the
The oil in the oil chambers 7a, 7b of the actuator (suspension bush) 1 is supplied from the oil supply / discharge ports 20a, 20b through 10a, so that the longitudinal rigidity of the suspension is enhanced. However, the amount of improvement in rigidity is set to an appropriate minute constant amount.

Usually, by repeating such suitable cycle down or up longitudinal stiffness, the size of the handle vibration | G | is reduced, the threshold G ₂ or less, or becomes a threshold G ₃ below.

The size of the handle vibration | G | is if below the threshold G _3, in the next control cycle, the process proceeds from step S4 to step S15, a special control, that is, although not performed rigidity adjusting the suspension, the steering wheel vibration magnitude | G | if the threshold G ₃ or the threshold G ₂ or less, the step S16 from step S5
Then, the lateral rigidity of the suspension is controlled.

If the magnitude | G | of the handle vibration does not decrease due to the control of the longitudinal rigidity of the suspension, step S12
Then, the process proceeds to step S14 to initialize the control flag FL2 to 0, and then proceeds to step S17 to control the lateral rigidity of the suspension.

To control the lateral rigidity of such a suspension, first,
In step S16, the control flag FL1 and the control flag FL2 are both set to 0 (there may be already 0), and the process proceeds to step S17.

In step S17, it is determined whether or not the control flag FL3 is 1. When the control is started, the control flag FL3 is 0, so that the process proceeds to step S18.

In step S18, it is determined whether or not the control flag FL4 is 1. Since the control flag FL4 is now 0,
Proceed to step S19.

In step S19, the control flag FL3 is set to 1, and the process proceeds to step S20 so that the lateral rigidity is reduced (down).
The control valve 10b is controlled. That is, a control signal is output from the handle vibration control unit 11f of the controller 11 to the control valve 10b so that the control valve 10b is in a drain state.
The oil in each of the oil chambers 8a, 8b of the actuator (suspension bush) 1 is discharged from the supply / drain ports 20c, 20d through the supply / discharge ports 20c, 20d, thereby reducing the rigidity of the suspension. However, the amount by which the rigidity is reduced in this manner is set to an appropriately minute constant amount.

 Then, the control cycle ends.

In the next control cycle, | θ |> θ, G ₂ > |
theta | if> G _3, the control flag FL3 is 1, the process proceeds from step S2, S3, S4, S5, S16, S17 to step S21,
It is determined from the rate of change of | G | whether or not the steering wheel vibration has been reduced. If the magnitude of the handle vibration | G |
Proceeding to step S20 again, so that the longitudinal rigidity decreases,
The control valve 10b is controlled.

On the other hand, if the magnitude | G | of the steering wheel vibration is not reduced, the control flag FL3 is set to 0 in step S22, and the control flag
With FL4 set to 1, the process proceeds to step S23.

In step S23, the control valve 10b is controlled so that the lateral rigidity is improved (up). That is, controller 1
The control signal is output from the handle vibration control unit 11f of the first control valve 10 so that the control valve 10b is opened.
The oil is supplied from the supply / discharge ports 20c, 20d to the respective oil chambers 7a, 7b of the actuator (suspension bush) 1 through b to improve and enhance the rigidity of the suspension. However, the amount of improvement in rigidity is set to an appropriate minute constant amount.

Usually, by repeating such a lateral stiffness of the down or appropriate cycles up, the size of the handle vibration | G | is reduced, equal to or less than the threshold value G _3.

As a result, the occurrence of steering wheel vibration (steering wheel shimmy) can be suppressed, and the driver does not feel discomfort due to the steering wheel vibration during driving, and can perform comfortable driving.

Further, a large adjustment of the steering wheel vibration characteristic is mainly performed by adjusting the front and rear rigidity of the suspension, which is relatively easy to influence the steering wheel vibration, and a fine adjustment of the steering wheel vibration characteristic is mainly relatively small in the influence on the steering wheel vibration. Since the adjustment is performed by adjusting the lateral stiffness of the suspension, the handle vibration can be efficiently and appropriately suppressed.

The suspension rigidity adjusting means is not limited to the suspension bush 1 with the rigidity adjusting mechanism described above, but other adjusting means capable of controlling rigidity in a plurality of directions,
Adjustment means capable of controlling the rigidity only in one direction may be provided in combination.

[Effect of the Invention] As described above in detail, according to the suspension rigidity control device of the present invention, suspension longitudinal rigidity adjusting means capable of adjusting the longitudinal rigidity of the suspension provided in the vehicle, and adjusting the lateral rigidity of the suspension A suspension lateral rigidity adjusting means, a suspension longitudinal rigidity adjusting means and a control means for controlling the suspension lateral rigidity adjusting means, and a steering wheel vibration detecting means for detecting a state of a steering wheel vibration of the vehicle. The control means, based on the information from the handle vibration detecting means, when the handle vibration becomes larger than the tolerance, adjusts the longitudinal rigidity or the lateral rigidity of the suspension so as to reduce the handle vibration to the suspension rigidity adjusting means. A handle vibration reduction control unit for outputting a control signal; The vibration reduction control unit is set to suppress the handle vibration by adjusting the front and rear rigidity of the suspension mainly in the region where the handle vibration is large, and to suppress the handle vibration mainly by adjusting the lateral rigidity of the suspension in the region where the handle vibration is small With this configuration, the occurrence of steering wheel vibration (steering wheel shimmy) can be suppressed more efficiently and appropriately, so that the driver can operate the steering wheel more comfortably and can further contribute to improving the riding comfort. is there.

[Brief description of the drawings]

1 to 7 show a suspension stiffness control apparatus according to an embodiment of the present invention. FIG. 1 is a block diagram showing the configuration of the apparatus, and FIG. 2 (b) is a sectional view taken along the line IIb-IIb in FIG. 2 (a), and FIG. 2 (c) is a sectional view taken along the line IIc-IIc in FIG. 2 (a). FIG. 3 is a schematic view showing an example of mounting on the suspension in the vehicle length direction, FIG. 4 is a schematic plan view showing an example of mounting on the suspension,
FIG. 5 is a detailed view showing an example of mounting on the suspension viewed in the vehicle length direction, FIG. 6 is a flowchart showing the control operation, and FIG. 7 is a graph showing threshold values used for the control. 1 ... suspension rigidity adjusting means (suspension bush with rigidity adjusting mechanism or actuator for rigidity adjusting), 1A ... rigidity adjusting mechanism, 2 ... case, 3 ... axis,
4, 6 ... rubber body as elastic support member, 5 ... inner case, 7a, 7b ... space as first oil chamber, 8a, 8b ... second
9: Reinforcing material, 10: Hydraulic control system, 10a: Front / rear rigidity control valve, 10b: Lateral rigidity control valve, 11: Controller, 11f: Handle vibration control unit, 12 …… Sensor group, 12b …… Steering angle sensor, 12i…
... Acceleration sensor (handle vibration sensor) as handle vibration detection means, 13 ... orifice, 14 ... oil pump, 15,18 ... accumulator, 16 ... relief valve, 17 ... one-way valve, 19 ... oil Reservoir, 20a
~ 20d …… Supply / discharge port, 21 …… Wheel, 21a …… Knuckle, 22…
… Strut, 23 …… Joint, 24 …… Lower arm,
25 ... joint joint, 26 ... body, 28 ... spring.

Continuation of the front page (72) Inventor Takao Morita 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (56) References JP-A-63-22712 (JP, A)

Claims (1)

(57) [Claims] 1. A suspension longitudinal rigidity adjusting means capable of adjusting longitudinal rigidity of a suspension provided in a vehicle, a suspension lateral rigidity adjusting means capable of adjusting lateral rigidity of the suspension, the suspension longitudinal rigidity adjusting means, and the suspension. Control means for controlling the lateral rigidity adjustment means; and handle vibration detection means for detecting a state of handle vibration of the vehicle, wherein the control means controls the vibration of the handle based on information from the handle vibration detection means. A handle vibration reduction control unit that outputs a control signal to the suspension rigidity adjusting means to adjust the front-rear rigidity or the lateral rigidity of the suspension so as to suppress the handle vibration when the handle vibration becomes larger than the tolerance. Section is mainly used in suspension A suspension stiffness control device characterized in that the front and rear stiffness of the suspension is adjusted to suppress steering wheel vibration, and in a region where the steering wheel vibration is small, the lateral stiffness of the suspension is mainly adjusted to suppress steering wheel vibration.