JP2576649B2 - Suspension control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension control device, and more particularly, to a suspension control device including a shock absorber capable of changing a setting of a damping force, and a shock absorber based on a running state of a vehicle. The present invention relates to a suspension control device that controls a generation pattern of a damping force.

[Prior Art] As this type of suspension control device, a change rate of a damping force of a shock absorber is detected, and when the change rate becomes a predetermined value or more, that is, a damping force is determined based on unevenness of a road surface or a brake operation. It is known that when a sudden change occurs, the generation pattern of the damping force with respect to the movement of the shock absorber is quickly switched to a small value side (for example, see
64-67407). Since the rate of change of the damping force is a signal having extremely excellent response, such a suspension control device can quickly follow the pattern of the damping force to the change in the road surface condition, and can maintain a good ride comfort.

[Summary of Problems to be Solved by the Invention] The suspension control device using the change rate of the damping force is excellent in responsiveness, but the signal of the change rate is used as an adjustment reference signal when driving on a rough road. If the damping force is changed in a short time with respect to the value, it is meaningless to control the damping force by switching the setting of the damping force each time according to the magnitude relation with the adjustment reference value. When the value is exceeded, it is necessary to hold the setting of the damping force for a predetermined period. However, there is a problem in that simply switching the setting of the damping force and continuing the state for a certain period of time does not sufficiently cope with the state of the road surface. That is, when the vehicle is traveling on a so-called rough road with a rough road surface, the rate of change of the damping force moves up and down sharply. Becomes uncomfortable. In addition, the durability of the shock absorber is also negative. On the other hand, if the soft maintenance period is too long, when traveling on a relatively flat road surface, the damping force setting is maintained soft for an unnecessarily long time after a small step, etc. This leads to the problem that the performance is impaired. As a result, the drive feeling may be reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problem and to make the control of the setting of the damping force using the damping force change rate according to the road surface condition.

Configuration of the Invention The configuration of the present invention that achieves the above object will be described below.

[Means for Solving the Problems] A suspension control device of the present invention is provided on a suspension S of a vehicle, as shown in FIG. 1, and is capable of setting a damping force generation pattern; Damping force change rate detecting means M2 for detecting a change rate of the damping force of the absorber M1, and a shock absorber M1 based on a magnitude relationship between the detected change rate of the damping force and a damping force adjustment reference value. A damping force control unit M3 for changing the setting of the damping force, wherein the damping force control unit M3 determines that the rate of change of the damping force is out of the range of the first reference value S1. When the damping force setting means M4 changes the damping force setting of the shock absorber M1 from large to small, and after the damping force setting is changed to small by the damping force switching means M4, the rate of change of the damping force changes. However, when it is determined that the state in which the absolute value is within the range of the second reference value S2 having a smaller absolute value than the first reference value S1 has continued for a predetermined period or more, the damping force setting is changed from small to large. And a damping force return means M5.

[Operation] The suspension control apparatus of the present invention having the above-described configuration detects the rate of change of the damping force of the shock absorber M1 provided on the suspension S of the vehicle by the damping force change rate detecting means M2, and determines the rate of change of the damping force. And the damping force adjustment reference value based on the magnitude relationship between the damping force adjustment reference value and
Change the setting of the damping force of the shock absorber M1. The damping force is set by first setting the rate of change of the damping force to the first reference value.
When it is out of the range of S1, it is changed from large to small by the damping force switching means M4. After this change, when the rate of change of the damping force has continued for a predetermined time within the range of the second reference value S2, the setting of the damping force is changed from small to large by the damping force return means M5.

That is, when the rate of change of the damping force is out of the range of the first reference value S1, the setting of the damping force of the shock absorber M1 is switched from large to small, and thereafter, this rate of change falls within the range of the second reference value S2. , The damping force setting returns from small to large. Conversely, once the second reference value S2
If this does not continue for a predetermined period, the damping force is not restored.

Therefore, in the suspension control device of the present invention, the holding period from when the setting of the damping force is changed from large to small and before the damping force is restored depends on the road surface condition that is reflected in the state of the damping force change rate. .

Note that such control may be performed independently for each wheel, may be performed commonly for the front two wheels and the rear two wheels, or may be performed commonly for all the wheels.

Embodiment In order to further clarify the configuration and operation of the present invention described above, a preferred embodiment of a suspension control device of the present invention will be described below.

FIG. 2 is a schematic configuration diagram showing the entire configuration of the suspension control device 1. FIG. 3 (A) is a cross-sectional view of the shock absorber partially cut away, and FIG. 3 (B) is an essential diagram of the shock absorber. It is a part enlarged sectional view.

As shown in FIG. 2, the suspension control device 1 of the present embodiment includes shock absorbers 2FL, 2FR, 2RL, and 2RR capable of changing the damping force in two stages, and is connected to each of these shock absorbers to control the damping force. And an electronic control unit 4. Each shock absorber 2FL, 2FR, 2RL, 2R
R is provided between the suspension lower arms 6FL, 6FR, 6RL, 6RR of the left and right front and rear wheels 5FL, 5FR, 5RL, 5RR and the vehicle body 7 together with coil springs 8FL, 8FR, 8RL, 8RR.

As described later, the shock absorbers 2FL, 2FR, 2RL, 2RR are a piezo load sensor that detects the force acting on the shock absorbers 2FL, 2FR, 2RL, 2RR, and a shock absorber.
A piezo actuator for switching the setting of the generation pattern of the damping force in 2FL, 2FR, 2RL, and 2RR is incorporated in each one set.

Next, the structure of each of the shock absorbers 2FL, 2FR, 2RL, and 2RR will be described.
Since the structures of 2RL and 2RR are all the same, here the left front wheel 5
A description will be given using the shock absorber 2FL on the FL side as an example. Further, in the following description, reference numerals of the respective members provided on the respective wheels indicate, as necessary, the left front wheel 5FL, the right front wheel 5FR, the left rear wheel 5RL,
Subscripts FL, FR, RL, and RR corresponding to the right rear wheel 5RR shall be added, and if there is no difference between the respective wheels, the subscripts will be omitted.

As shown in FIG. 3 (A), the shock absorber 2 is fixed to the suspension lower arm 6 via an axle-side member 11a at the lower end on the cylinder 11 side, while the upper end of a rod 13 inserted into the cylinder 11 , Is fixed to the vehicle body 7 together with the coil spring 8 via the bearing 7a and the 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 slidable along the inner peripheral surface of the cylinder 11,
It is arranged. A piezo load sensor 25 and a piezo actuator 27 are housed in the internal cylinder 15 connected to the rod 13 of the shock absorber 2.

The main piston 18 is externally fitted to the cylindrical member 17,
A seal member 19 is interposed on the outer periphery fitted to the cylinder 11. Therefore, the main piston 18
Thus, a first liquid chamber 21 and a second liquid chamber 23 are defined. A backup member 28 is screwed into the distal end of the cylindrical member 17, and a spacer 29 and a leaf valve 30 are provided between the cylindrical member 17 and the main piston 18 on the cylindrical member 17 side. The collar 32 is pressed and fixed to the backup member 28 side. A main valve 34 and a spring are provided between the leaf valve 31 and the backup member 28.
35 is interposed, and the leaf valve 31 is connected to the main piston
Energized in 18 directions.

When the main piston 18 is stopped, the leaf valves 30 and 31 close the extension side and the contraction side passages 18a and 18b provided on the main piston 18 on one side, respectively. It opens to one side as it moves in the A or B direction. Accordingly, the hydraulic oil filled in the two liquid chambers 21 and 23 moves between the two liquid chambers 21 and 23 through one of the two passages 18a and 18b as the main piston 18 moves. In the state where the movement of the hydraulic oil between the two liquid chambers 21 and 23 is limited to the two passages 18a and 18b, the damping force generated for the movement of the rod 13 is large, and the characteristics of the suspension become hard. .

Piezo load sensor 25 housed inside internal cylinder 15
3 (A) and 3 (B).
As shown in FIG. 1, an electrostrictive element laminate is obtained by laminating piezoelectric ceramic thin plates with electrodes interposed therebetween. Each electrostrictive element of the piezo load sensor 25 is polarized by a force acting on the shock absorber 2, that is, a damping force. Therefore, the piezo load sensor
If the output of 25 is taken out as a voltage signal by a circuit having a predetermined impedance, the rate of change of the damping force can be detected.

The piezo actuator 27 is formed by laminating electrostrictive elements that expand and contract with good responsiveness when a high voltage is applied, and increases 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 the spool 41 having an H-shaped cross section are also moved in the same direction via the hydraulic oil in the oil-tight chamber 33. Thus, the spool 41 at the position (origin position) shown in FIG.
Move in the direction B in the drawing, the sub-flow path 16c connected to the first liquid chamber 21 and the sub-flow path 3 of the bush 39 connected to the second liquid chamber 23
9b will be communicated. The sub flow path 39b is further connected to the flow path 17a in the tubular member 17 via an oil hole 45a provided in the plate valve 45, so that the spool 41
Moves in the direction of arrow B, as a result, the flow rate of hydraulic oil flowing between the first liquid chamber 21 and the second liquid chamber 23 increases.
In other words, the shock absorber 2 switches its damping force characteristic from a large damping force (hard) state to a small damping force (soft) side when the piezo actuator 27 expands due to the application of a high voltage. Returns the force characteristics to the state of large damping force (hard).

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 as compared with the leaf valve 30. The plate valve 45 has an oil hole
An oil hole 45b having a diameter larger than 45a is provided outside the oil hole 45a, and when the plate valve 45 moves toward the bush 39 against the urging force of the spring 46, the hydraulic oil passes through the oil hole 45b. And can be moved. Therefore, irrespective of the position of the spool 41, the hydraulic oil flow rate when the main piston 18 moves in the direction of arrow B becomes larger than when the main piston 18 moves in the direction of arrow A. That is, the damping force is changed depending on the moving direction of the main piston 18, thereby further improving the characteristics as a shock absorber. Also,
A hydraulic oil supply passage 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 unit 4 for switching and controlling the generation pattern of the damping force of the shock absorber 2 will be described with reference to FIG.
This will be described with reference to the drawings.

The electronic control unit 4 includes a piezo load sensor 25 of each shock absorber 2, a steering sensor 50 for detecting a steering angle of a steering wheel (not shown), and a traveling speed of the vehicle as sensors for detecting a traveling state of the vehicle. , A shift position sensor 52 for detecting a shift position of a transmission (not shown), a stop lamp switch 53 for emitting a signal when a brake pedal (not shown) is depressed, and the like.

The electronic control unit 4 that outputs a control signal to the piezo actuator 27 based on these detection signals and the like is a known electronic control unit.
The CPU 61, the ROM 62, and the RAM 64 are mainly configured as arithmetic and logic operation circuits, and input / output with the outside is performed by an input unit 67 and an output unit 68 which are connected to the arithmetic and logic circuits via a common bus 65.

The electronic control unit 4 further 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,
High voltage application circuit 7 connected to piezo actuator 27
5. A so-called switching regulator type high-voltage power supply circuit 79 that receives power from a battery 77 through an ignition switch 76 and outputs a driving voltage for driving a piezo actuator, and transforms the voltage of the battery 77 to A constant voltage power supply circuit 80 for generating an operating voltage (5v) is provided. Shift position sensor 52, stop lamp switch 53, damping force change rate detection circuit 70, waveform shaping circuit 73
Is connected to the input unit 67, while the high voltage application circuit 75 and the high voltage power supply circuit 79 are connected to the output unit 68.

The damping force change rate detection circuit 70 is composed of each piezo load sensor 25FL, F
R, RL, and RR are provided for each of the four detection circuits, and each of the detection circuits is a voltage output from a circuit including the piezo load sensor 25 according to the acting force received by the shock absorber 2 from the road surface. It is configured to output the signal V to the CPU 61 as the damping force change rate of the shock absorber 2. Further, the waveform shaping circuit 73 includes a steering sensor
This is a circuit that shapes the detection signal from the vehicle speed sensor 51 or the vehicle speed sensor 51 into a signal suitable for processing in the CPU 61 and outputs the signal. Therefore, the CPU 61 can determine the road surface state, the running state of the vehicle, and the like based on the output signals from the damping force change rate detection circuit 70 and the waveform shaping circuit 73, as well as the result of its own processing. The CPU 61 outputs a control signal to the high voltage application circuit 75 provided for each wheel based on the determination.

The high-voltage applying circuit 75 applies the voltage of +500 volts or -100 volts output from the high-voltage power supply circuit 79 to the CPU 6.
This is a circuit applied to the piezo actuator 27 in response to a control signal from 1. Therefore, the piezo actuator 27 expands (when +500 volts is applied) or contracts (when -100 volts is applied) by this damping force switching signal, and the hydraulic oil flow rate is switched, so that the damping force characteristic of the shock absorber 2 is soft or hard. Is switched to. That is,
The damping force characteristic of each shock absorber 2 is such that when a high voltage is applied to extend the piezo actuator 27, the first liquid chamber in the shock absorber 2 is controlled by the spool 41 (FIG. 3B) described above. When the flow rate of the hydraulic fluid flowing between the second liquid chamber 23 and the second fluid chamber 23 increases, the damping force is in a small state, and when the piezoelectric actuator 27 is contracted by discharging the electric charge by the negative voltage, the hydraulic fluid flow rate is reduced. Because of the decrease, the damping force becomes large. Note that once the electric charge accumulated in the piezo actuator 27 is discharged, even if the negative voltage is removed, the piezo actuator
27 remains in a contracted state and shock absorber 2
Maintains the state of large damping force.

Next, the damping force control performed by the suspension control device 1 of the present embodiment having the above-described configuration will be described with reference to the flowchart of FIG. This damping force control interrupt processing routine is an initialization processing (not shown) when the power is turned on.
After the flags FS, FA, etc., which will be described later, are reset to a value of 0, they are repeatedly executed at regular time intervals. These processes are executed for each of the shock absorbers 2FL, FR, RL, and RR of each wheel. However, since the processes for each wheel are the same, description will be made without particular distinction.

When the processing routine shown in FIG. 5 is started, first, a process of reading the change rate V of the damping force of each shock absorber 2 from the damping force change rate detecting circuit 70 via the input section 67 is performed (step 100). The absolute value of the damping force change rate V (hereinafter, simply referred to as damping force change rate V) is equal to a first reference value V1.
It is determined whether or not it is larger (step 110). The first reference value V1 may be a predetermined value, may be set as a value corresponding to the vehicle speed in another routine (not shown), and may be a switching frequency of the damping force setting of the shock absorber 2. May be learned based on

FIG. 6 is a graph showing an example of the damping force change rate V. When the damping force change rate V is smaller than the first reference value V1 as before time t1, the characteristics of the suspension become soft. It is determined whether or not the flag FS indicating that it is set is a value 1 (step 120). If the flag FS is not a value 1, the suspension is hardly controlled (step 130), and the routine is temporarily stopped. finish. It should be noted that the processing of step 130 for hardly controlling the suspension is such that immediately after the setting of the damping force of the shock absorber 2 is switched from software to hardware, the control signal from the output section 68 causes the high voltage application circuit 75 to output -100 volts. Is applied to the piezo actuator 27 to reduce it, and if the piezo actuator 27 is already in a contracted state, it is held as it is.

On the other hand, as shown at time t1 in FIG. 6, when the damping force change rate V becomes larger than the first reference value V1 (step 11).
0), the value 1 is set to the flag FS (step 140), and then a high voltage of +500 volts is applied from the high voltage application circuit 75 to the piezo actuator 27, and the shock absorber 2
The damping force is switched and controlled to a small state, that is, the suspension is controlled softly (step 150), and this routine ends.

Eventually, as shown at time t2 in FIG. 6, the damping force change rate V
Is less than or equal to the first reference value V1, the determination in step 110 is "NO", and after checking the value of the flag FS (step 120), the damping force change rate V becomes equal to the second reference value V2 (first reference value V2). Is determined (step 160). During the period from time t2 to time t3, this determination is “NO”, and the flag FA indicating that the damping force change rate V has fallen below the second reference value V2 is reset to a value 0 (step 170). The setting of the damping force of the shock absorber 2 is still kept soft (step 150), and this routine ends.

This process is repeated, and when the time t3 has elapsed, the determination in step 160 becomes “YES”, and it is determined whether or not the value of the flag FA is 0 (step 180). This flag FA indicates that V <V
Since the value is set to 1 after reaching 2, the value becomes 0 immediately after the damping force change rate V falls below the second reference value V2. Therefore, if it is determined that FA = 0, a value 1 is set to the flag FA (step 190), and a process of starting a timer, that is, a process of resetting a timer variable Ta to a value 0 is performed (step 200). .

After this processing or in step 180, "NO"
When it is determined, the timer variable Ta is incremented by the value 1 in order to count the timer by software (step 210). Subsequently, it is determined whether or not the timer variable Ta is equal to or longer than a preset reference time T0 (step 220). If "NO" is determined, the process proceeds to step 150, where the damping of the shock absorber 2 is performed. Force settings are still kept soft. Since the timer variable Ta is incremented by 1 each time this routine is executed, the time corresponding to the timer variable Ta is equal to the reference time T0.
Is less than the time period, the determination in step 220 is “NO”.

If “YES” is determined in step 220, the flag
The value of FS is reset to 0 (step 230), the setting of the damping force of the shock absorber 2 is switched from software to hardware (step 130), and this routine is temporarily terminated.

That is, as shown in FIG. 6, after time t3, the determination in step 160 becomes "YES", and in step 220, the timer variable Ta is compared with the reference time T0. Since the time is shorter than the reference time T0, the setting of the damping force is held softly. After the time t4, the determination in step 160 becomes "NO", and the setting of the damping force is still held softly. Similarly, from time t5 to time t7, the setting of the damping force is kept soft, but after time t7, the time during which the damping force change rate V continues to a value smaller than the second reference value V2 is equal to the reference. Since the time is longer than the time T0, the determination in Step 220 is “YES”, and the setting of the damping force is switched to hardware at a time t8 after the elapse of the reference time T0 from the time t7. afterwards,
Until the damping force change rate V exceeds the first reference value V1, the setting of the damping force is held hard.

When the routine of the damping force control described above is repeatedly executed, the damping force of the shock absorber 2 of each wheel is set to a small state immediately after the damping force change rate V exceeds the first reference value V1 (FIG. 6). At time t1), after the damping force change rate V becomes equal to or less than the reference value V1, the damping force change rate V becomes the second reference value.
Until the time falls below V2 and continues for more than the reference time T0 (time
t8), this state is maintained. After the elapse of this time, the shock absorber 2 is again controlled to a state where the damping force is large.

Therefore, the suspension control device 1 of this embodiment uses the extremely responsive signal of the damping force change rate V to change the generation pattern of the damping force of each shock absorber 2 of the vehicle in an appropriate state according to the road surface condition. In addition, it is possible to quickly control. That is, [I] if the vehicle is traveling on a flat road, even if the damping force change rate V exceeds the first reference value V1, it quickly falls into a state where V <V2, and the shock absorber 2 is subjected to the damping force. The time for which the characteristic is kept small is also set short. Therefore, when the vehicle goes over a small step or the like on a flat road surface, the setting of the damping force returns to a hard state within a short time, and the riding comfort is kept good. As a result, the setting of the damping force is kept unnecessarily soft for a long time, and the grounding property is not impaired.

[II] On the other hand, if you are traveling on rough roads,
The damping force change rate V changes greatly, and the damping force change rate V
Not only the state exceeding the reference value V1, but also the state exceeding the second reference value V2 frequently appear. Therefore, once the suspension characteristics are controlled softly, the time for maintaining the state of V <V2 is reduced, and the time for maintaining the softness is prolonged, so that the switching frequency of the damping force does not increase unnecessarily. As a result, the driver does not feel uncomfortable while driving, and the durability of the shock absorber 2 is improved.

As described above, according to the suspension control device 1 of the present embodiment, the characteristics of the suspension are controlled with good responsiveness by using the signal having excellent responsiveness, that is, the damping force change rate, and the small step on the flat road is controlled. It is possible to optimally switch the time during which the damping force is maintained in a small state in the case of overtaking or the like and in the case of traveling on a rough road, thereby achieving both the riding comfort and the steering stability of the vehicle.

Next, a modified example in which the values of the second reference value V2 and the reference time T0 are switched according to the vehicle speed will be described with reference to a part of the flowchart shown in FIG. The processing of steps 121 to 126 shown is performed between step 120 and step 160 in the flowchart shown in FIG.

First, from the waveform shaping circuit 73 to which the vehicle speed sensor 51 is connected,
A process of reading the vehicle speed S is performed (step 121), and it is determined whether the vehicle speed S is higher than a preset reference vehicle speed S0 (step 122). If S> S0, the value V21 is set to the second reference value V2 (step 123), and the value T01 is set to the reference time T0 (step 124). If S ≦ S0, a value V22 smaller than the value V21 is set as the second reference value V2 (step 125), and a value T02 larger than the value T01 is set as the reference time T0 (step 126). That is, the vehicle speed S0
When the vehicle speed is higher than the vehicle speed S0, the second reference value V2 is set larger and the reference time T0 is set shorter than when the vehicle speed is lower than the vehicle speed S0. When the second reference value V2 and the reference time T0 have been set, the process proceeds to the above-described step 160 and subsequent steps. That is, at the time of high speed, the setting of the damping force is easily switched from software to hardware. At high speeds, the damping force change rate V itself generally becomes large. However, by performing this processing, there is no danger that the damping force setting is maintained softly, and the demand for hard orientation at high speeds is met. Can be

Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments at all. For example,
The second reference value V2 is set such that the absolute value differs between the positive side and the negative side of the damping force change rate, and the reference time T0 is determined based on the peak value of the damping force change rate V. It goes without saying that the present invention can be carried out in various modes without departing from the gist of the invention.

Effects of the Invention As described in detail above, according to the suspension control device of the present invention, the holding period from when the setting of the damping force is changed from large to small and before the damping force returns is determined by the damping force change rate that is set to the second reference value. Since it is determined based on the duration within the value range, the setting of the damping force, which is once switched to software, can be continued for a period according to the running state of the vehicle (for example, road surface condition, vehicle speed, etc.). It works. Therefore,
For example, when the vehicle gets over a small step on a flat road, the setting of the damping force tends to return to hard in a short period of time, while the setting of the damping force tends to be continuously maintained softly on a rough road. As a result, there is no need to maintain the soft setting of the damping force unnecessarily for a long period of time, thereby impairing the grounding property or the like, and to prevent the driver from feeling uncomfortable by frequently switching the setting of the damping force. In addition, there are advantages for the durability of the device.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a basic configuration of the present invention, FIG. 2 is a schematic configuration diagram showing an overall configuration of a suspension control device as one embodiment of the present invention, and FIG. FIG. 3 (B) is an enlarged sectional view of a main part of the shock absorber 2, and FIG.
FIG. 5 is a block diagram showing the configuration of the electronic control unit 4 of this embodiment, FIG. 5 is a flowchart showing a damping force control interrupt routine, FIG. 6 is a graph showing an example of switching of damping force setting, and FIG. Is a part of a flowchart showing a main part of a process in another embodiment. 1 ... Suspension controller 2FL, FR, RL, RR ... Shock absorber 4 ... Electronic controller 25FL, FR, RL, RR ... Piezo load sensor 27FL, FR, RL, RR ... Piezo actuator 51 ... Vehicle speed Sensor 70: Damping force change rate detection circuit 75: High voltage application circuit, 79: High voltage power supply circuit

Claims (1)

(57) [Claims] 1. A shock absorber provided on a vehicle suspension and capable of setting a damping force generation pattern, damping force change rate detecting means for detecting a change rate of the damping force of the shock absorber, and the detected damping. A damping force control unit that changes a setting of the damping force of the shock absorber based on a magnitude relationship between a rate of change of the force and a reference value for adjusting the damping force. When it is determined that the rate of change of the damping force is out of the range of the first reference value, damping force switching means for changing the setting of the damping force of the shock absorber from large to small; After the setting of the damping force is changed to a small value, the state in which the rate of change of the damping force is within a range of a second reference value having an absolute value smaller than the first reference value is longer than a predetermined period. When it is determined that continued the suspension control device characterized by comprising a damping force returning means for changing the setting of the damping force from small to large.