JPH07112766B2 - Suspension controller - Google Patents

Description

The present invention relates to a suspension control device, and more particularly to a suspension control device, which is equipped with a shock absorber capable of varying the setting of a damping force, and which is based on the running state of a vehicle. The present invention relates to a suspension control device that controls a generation pattern of damping force.

[Prior Art] As a suspension control device of this type, the rate of change of the damping force of a shock absorber is detected, and when this rate of change reaches or exceeds a predetermined level, that is, the damping force is increased based on road surface irregularities or 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 smaller value side (for example, JP-A-64
-67407). Since the rate of change of damping force is a signal with extremely excellent responsiveness, such a suspension control device
Make the pattern of damping force quickly follow the changes in the road surface condition,
It is possible to maintain a good ride comfort.

[Problems to be Solved by the Invention] Although the suspension control device using the rate of change of the damping force is excellent in responsiveness as described above, the signal of the rate of change is used as an adjustment reference when driving on a rough road. In the case of going up and down 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 one by one according to the magnitude relationship with the adjustment reference value. When the value exceeds the value, it becomes necessary to hold the setting of the damping force for a predetermined period. However, after switching the setting of the damping force, there is a problem in that the state of the road surface cannot be sufficiently dealt with by simply maintaining that state for a certain period of time. That is, when running on a so-called bad road with a rough road surface, the rate of change of the damping force fluctuates rapidly, so if the soft holding period for softly holding the pattern of generation of the damping force is short,
The switching frequency of the damping force becomes high, which causes a feeling of strangeness. Also,
It also has a negative effect on the durability of the shock absorber. On the other hand, if the soft holding time is too long, the ride comfort is reduced and the ground contact property is impaired.

The suspension control device of the present invention solves the above problems,
The purpose of the present invention is to set a soft holding period according to the road surface condition using the damping force change rate to achieve both riding comfort and steering stability.

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

[Means for Solving the Problem] A first suspension control device of the present invention is provided in a suspension S of a vehicle and is a shock absorber capable of setting a generation pattern of a damping force, as illustrated by a solid line in FIG. M1, a damping force change rate detecting means M2 for detecting a changing rate of the damping force of the shock absorber M1, and a magnitude relationship between the detected changing rate of the damping force and a damping force adjusting reference value, In a suspension control device including a damping force control unit M3 that changes the setting of the damping force of the shock absorber M1, the damping force control unit M3 is configured such that the rate of change of the damping force is outside the range of the first reference value S1. When it is determined that, the damping force switching means M4 for changing the setting of the damping force 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, Decrease When it is determined that the rate of change of the weakening force has continued for a preset first predetermined period T1 or more within the range of the second reference value S2 whose absolute value is smaller than the first reference value S1, the attenuation A first damping force returning means M5 for changing the setting of force from small to large and a soft holding period until the setting of the damping force is changed by the damping force switching means M4 and is returned by the first damping force returning means M5. And a soft holding period calculating means M6 for calculating, and a second for changing the setting of the damping force from small to large when it is determined that the calculated soft holding period exceeds a preset second predetermined period T2. The gist is that the damping force restoring means M7 is provided.

On the other hand, the second suspension control device of the present invention is the first suspension control device.
As indicated by a broken line in the figure, in the first suspension control device, instead of the second damping force restoring means M7 or together with the second damping force restoring means M7, the soft holding period calculating means M6 calculates When it is determined that the soft holding period has exceeded the preset third predetermined period T3, the absolute value of the second reference value is gradually increased and / or the value of the first predetermined period T1 is gradually decreased. The gist is that the reference value correcting means M8 is provided.

Further, the third suspension control device of the present invention, when added by the alternate long and short dash line in FIG. 1, when the second suspension control device determines that the degree of correction of the reference value correction means M8 is large. An initial value correcting means M9 for increasing and / or decreasing the initial value of the second reference value S2 at the start of the soft holding period and / or decreasing the initial value of the first predetermined period T1. Is the gist.

[Operation] In the first, second, and third suspension control devices of the present invention having the above-described configuration, the damping force change rate detection means M2 detects the change rate of the damping force of the shock absorber M1 provided in the suspension S of the vehicle. The damping force control means detects the damping force and based on the magnitude relationship between the rate of change of the damping force and the damping reference value.
Use M3 to change the damping force setting of shock absorber M1.

Here, in the first suspension control device, the setting of the damping force is first changed from large to small by the damping force switching means M4 when the rate of change of the damping force is outside the range of the first reference value S1. It After this change, the rate of change of damping force is the second
When it is determined that the first predetermined time T1 has been continued for the first predetermined time T1 or more within the range of the reference value S2, the damping force setting means M5 changes the damping force setting from small to large. The soft holding period until the setting of the damping force is changed from large to small and the damping force is restored by the first damping force restoring means M5 is calculated by the soft holding period calculating means M6. This soft holding period is the second predetermined value. When it is determined that the period T2 has been exceeded, the setting of the damping force is changed from small to large by the second damping force restoring means M7.

That is, when the rate of change of the damping force is outside 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 then this rate of change is within the range of the second reference value S2. The setting of the damping force returns from small to large when it continues for the first predetermined period T1 or more. However, when the soft holding period until this return exceeds the second predetermined period T2, the damping force is reduced. The force setting is changed from small to large.

On the other hand, the second aspect of the present invention and the suspension control device are the first aspect.
Second damping force recovery main stage of the suspension control device of the present invention
Instead of M7, or with the second damping force recovery main stage M7, the reference value correction means M8 is provided, and when it is determined that the soft holding period exceeds the third predetermined period T3, the absolute value of the second reference value S2 is The value is gradually increased and the value of the first predetermined period T1 is gradually decreased. That is, the condition under which the attenuation factor setting can be returned from small to large is relaxed, and the soft holding period is easily ended. Both the gradual increase correction and the gradual decrease correction may be performed, or either one of them may be performed.

Further, the third suspension control device of the present invention is the second suspension control device.
In the suspension control device, the reference value correction means M8
When the degree of correction is large, the initial value correction means M9 increases the initial value of the second reference value S2 and decreases the initial value of the first predetermined period T1. That is, the second reference value S, which is a condition value that allows the damping force setting to return from small to large.
2, If the degree of correction in the first predetermined period T1 is large, the initial value is corrected to the side where the soft holding period is likely to end,
Decrease the number of corrections until the damping force setting returns from small to large. Both the increase correction and the decrease correction may be performed, or either one of them may be performed.

Therefore, in the first to third suspension control devices of the present invention, the soft holding period from when the setting of the damping force is switched from large to small and then until the setting is restored, the soft holding period of the road surface reflected in the state of the damping force change rate. This will be appropriate for the situation, and it is possible to prevent the soft holding from continuing for a long time.

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

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

FIG. 2 is a schematic configuration diagram showing the overall configuration of the suspension control device 1 showing an embodiment of the first to third suspension control devices of the present invention, and FIG. 3 (A) is a cross-sectional view of the shock absorber partially broken. FIG. 3 (B) is an enlarged sectional view of a main part of the shock absorber.

As shown in FIG. 2, the suspension control device 1 of the present embodiment is provided with a shock absorber 2FL, 2FR, 2RL, 2RR capable of changing the damping force in two steps, and connected to each of these shock absorbers to control the damping force. And an electronic control unit 4 that operates. Shock absorber 2FL, 2FR, 2RL, 2RR
Are installed 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 the coil springs 8FL, 8FR, 8RL, 8RR.

The shock absorbers 2FL, 2FR, 2RL, 2RR are, as described later, a piezo load sensor that detects the force acting on the shock absorbers 2FL, 2FR, 2RL, 2RR, and the shock absorber 2F.
A pair of piezo actuators that switch the setting of the damping force generation patterns for L, 2FR, 2RL, and 2RR are built in each.

Next, the structure of each of the shock absorbers 2FL, 2FR, 2RL, 2RR will be described. The above shock absorbers 2FL, 2FR, 2R
Since the structures of L and 2RR are all the same, here the front left wheel 5FL is used.
Take the shock absorber 2FL on the side as an example. Further, in the following description, the reference numerals of the respective members provided on the respective wheels refer to the left front wheel 5FL, the right front wheel 5FR, the left rear wheel 5RL,
The subscripts FL, FR, RL, RR corresponding to the right rear wheel 5RR shall be added, and the subscripts shall be omitted when there is no difference between the respective wheels.

The shock absorber 2 is, as shown in FIG. 3 (A),
The lower end of the cylinder 11 side is fixed to the suspension lower arm 6 via the axle side member 11a, while the cylinder 11
At the upper end of the rod 13 which is inserted into the vehicle body 7, it is fixed to the vehicle body 7 together with the coil spring 8 via a bearing 7a and a vibration-proof rubber 7b.

Inside the cylinder 11, an internal cylinder 15, a connecting member 16 and a tubular member 17 connected to the lower end of the rod 13 are provided.
1 A main piston 18, which is slidable along the inner peripheral surface, is installed side by side. The internal cylinder 15 connected to the rod 13 of the shock absorber 2 accommodates a piezo load sensor 25 and a piezo actuator 27.

The main piston 18 is externally fitted to the tubular member 17, and a seal material 19 is provided on the outer periphery fitted to the cylinder 11. Therefore, the inside of the cylinder 11 is partitioned by the main piston 18 into a first liquid chamber 21 and a second liquid chamber 23.
A backup member 28 is screwed onto the tip of the tubular member 17, and between the tubular member 17 and the main piston 18,
The spacer 29 and the leaf valve 30 are pressed and fixed to the tubular member 17 side, and the leaf valve 31 and the collar 32 are pressed and fixed to the backup member 28 side, respectively. Further, a main valve 34 and a spring 35 are interposed between the leaf valve 31 and the backup member 28 to urge the leaf valve 31 toward the main piston 18.

When the main piston 18 is stopped, the leaf valves 30 and 31 close the expansion side passage 18a and the contraction side passage 18b provided on the main piston 18 on one side, and the main piston 18 indicates the arrow. It opens to one side as it moves in the A or B direction. Therefore, the hydraulic oil filled in both liquid chambers 21 and 23 moves between both liquid chambers 21 and 23 through either of the passages 18a and 18b as the main piston 18 moves. In this way, when the movement of the hydraulic oil between the liquid chambers 21 and 23 is limited to the passages 18a and 18b, the damping force generated with respect to the movement of the rod 13 is large, and the suspension characteristic becomes hard. .

Piezo load sensor 25 housed inside the internal cylinder 15
The piezo actuator 27 is shown in FIGS. 3 (A) and (B).
As shown in FIG. 5, an electrostrictive element laminate is obtained by laminating piezoelectric ceramic thin plates between electrodes. Each electrostrictive element of the piezoelectric load sensor 25 is polarized by the force acting on the shock absorber 2, that is, the 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 damping force can be detected.

The piezo actuator 27 is formed by stacking electrostrictive elements that expand and contract with good response when a high voltage is applied to increase the expansion and contraction amount, 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. In this way, when the spool 41 at the position (origin position) shown in FIG. 3B moves in the direction B in the drawing, the sub-channel 16c connected to the first liquid chamber 21 and the bush 39 connected to the second liquid chamber 23. Sub flow path 39b
Will be communicated with. The sub-flow passage 39b is further provided with a tubular member 1 through an oil hole 45a provided in the plate valve 45.
Since the flow path 17a in the inside 7 is communicated, when the spool 41 moves in the direction of the arrow B, as a result, the first liquid chamber 21 and the second liquid chamber 21
The flow rate of hydraulic oil flowing between the liquid chamber 23 and the liquid chamber 23 increases. That is, the shock absorber 2 is connected to the piezo actuator 27.
When the voltage is extended by applying a high voltage, the damping force characteristic is switched from the high damping force (hard) state to the low damping force (soft) side, and when the charge is discharged and contracts, the damping force characteristic is changed to the high damping force (hard). Restore the condition.

A leaf valve provided on the lower surface of the main piston 18
The movement amount of 31 is regulated by the spring 35 as compared with the leaf valve 30. In addition, the plate valve 45 has an oil hole 45
An oil hole 45b having a diameter larger than a is provided outside the oil hole 45a.When the plate valve 45 moves in the direction of the bush 39 against the urging force of the spring 46, the hydraulic oil passes through the oil hole 45b. Can be moved. Therefore, regardless of the position of the spool 41, the hydraulic oil flow rate when the main piston 18 moves in the arrow B direction becomes larger than when the main piston 18 moves in the arrow A direction. That is, the damping force is changed according to the moving direction of the main piston 18 to further improve the characteristics of the shock absorber. 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 hydraulic oil flow rate in the oil tight chamber 33 constant.

Next, the electronic control unit 4 for controlling the switching of the damping force generation pattern of the shock absorber 2 will be described with reference to FIG.

The electronic control unit 4 includes, as sensors for detecting the traveling state of the vehicle, 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. A vehicle speed sensor 51 for detecting a shift position, a shift position sensor 52 for detecting a shift position of a transmission (not shown), a stop lamp switch 53 for issuing a signal when a brake pedal (not shown) is depressed, and the like are connected.

The electronic control unit 4 that outputs a control signal to the above-mentioned piezo actuator 27 based on these detection signals is a well-known CP.
U61, ROM62, RAM64 are mainly configured as an arithmetic logic operation circuit, and an input section 6 and an output section 68 which are connected to each other through a common bus 65 perform input / output with the outside.

The electronic control unit 4 further includes a damping force change rate detection circuit 70 to which a piezo load sensor 25 is connected and a steering sensor.
A waveform shaping circuit 73 to which the vehicle speed sensor 51 and the vehicle speed sensor 51 are connected, a high voltage applying circuit 75 connected to the piezo actuator 27,
A high voltage power supply circuit 79 of a so-called switching regulator type which receives a power supply from a battery 77 via an ignition switch 76 and outputs a drive voltage for driving a piezoelectric actuator, and an operating voltage of the electronic control unit 4 by transforming the voltage of the battery 77. A constant voltage power supply circuit 80 for generating (5v) is provided. The shift position sensor 52, the stop lamp switch 53, the damping force change rate detection circuit 70, and the waveform shaping circuit 73 are connected to the input section 67, while the high voltage application circuit 75 and the high voltage power supply circuit 79 are provided.
Are connected to the output units 68, respectively.

The damping force change rate detection circuit 70 is for each piezo load sensor 25FL, FR,
It consists of four detection circuits provided for RL and RR,
Each of the detection circuits has a shock absorber 2 from the road surface.
The voltage signal V output from the circuit including the piezo load sensor 25 according to the acting force received by the CPU is output to the CPU 61 as the damping force change rate of the shock absorber 2. The waveform shaping circuit 73 is a circuit that waveform-shapes the detection signals from the steering sensor 50 and the vehicle speed sensor 51 into a signal suitable for processing by 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, the processing result of itself, and the like. The CPU 61 outputs a control signal to the high voltage applying circuit 75 provided corresponding to each wheel based on such a determination.

This high voltage application circuit 75 outputs the voltage of +500 V or −100 V output from the high voltage power supply circuit 79 to the CPU 61.
This circuit is applied to the piezo actuator 27 in accordance with a control signal from. Accordingly, the damping force switching signal causes the piezo actuator 27 to expand (when +500 V is applied) or contract (when -100 V is applied), 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 the high voltage is applied to extend the piezo actuator 27, the first shock absorber 2 inside the shock absorber 2 is caused by the spool 41 (FIG. 3 (B)) described above. Since the flow rate of the hydraulic oil flowing between the liquid chamber 21 and the second liquid chamber 23 increases, the damping force becomes small, and when the piezoelectric actuator 27 is contracted by discharging the electric charge by the negative voltage, the hydraulic oil is reduced. The damping force becomes large because the flow rate decreases. Note that once the 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 a large damping force.

Next, damping force control performed by the suspension control device 1 of the present embodiment having the above configuration will be described based on the flowchart of FIG. This damping force control is
3 is an example of processing performed by the first and second suspension control devices of the present invention. This damping force control interrupt control routine is
In the initialization process (not shown) when the power is turned on, after the flags FS, FA, etc., which will be described later, are reset to the value 0, they are repeatedly executed at regular time intervals. Although these processings are executed for each shock absorber 2FL, FR, RL, RR of each wheel, the processing for each wheel is the same and will be described without making a distinction.

When the processing routine shown in FIG. 5 is started, first, the processing for reading the damping force change rate V of each shock absorber 2 from the damping force change rate detection circuit 70 via the input unit 67 is performed (step 100), It is determined whether or not the absolute value of the damping force change rate V (hereinafter simply referred to as the damping force change rate V) is larger than the first reference value V1 (step 110). The first reference value V1 is provided to judge the magnitude of the damping force change rate V and to switch the characteristics of the shock absorber 2 softly, and may be a predetermined value or a vehicle speed. The value may be set by another routine (not shown), or may be learned based on the switching frequency of the damping force setting of the shock absorber 2 or the like.

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 the illustrated time t1, the suspension characteristic becomes soft. Whether or not the flag FS indicating that the flag is set is 1 is determined (step 120). If the flag FS is not 1, the suspension is controlled by hardware (step 130) and this routine is once executed. finish. Incidentally, the processing of step 130 for controlling the suspension to the hardware is performed by the control signal from the output section 68 from the high voltage applying circuit 75 to −100 immediately after the setting of the damping force of the shock absorber 2 is switched from software to hardware. This is done by applying a bolt to the piezo actuator 27 to reduce it, and if the piezo actuator 27 has already been contracted, hold it 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), it is determined whether the flag FS is 0 (step 140),
When the flag FS has a value of 0, that is, when the damping force setting at the time of this determination is hard, a reset process of the timer variable Ts that is a process for starting the timing of the soft hold time is performed (step 150). ). If the setting of the damping force is software, the processing of step 150 is skipped and the timer variable Ts is incremented by the value 1 in order to measure the timer by software (step 16).
0). Subsequently, it is determined whether or not this timer variable Ts is equal to or less than the soft reference time T2 set for determining the timing for changing the return condition of the damping force setting (step 170),
If "YES" is determined, the value 1 is set in the flag FS (step 180), and then the high voltage applying circuit 75 outputs +500.
Apply a high voltage of volt to the piezo actuator 27,
The damping force of the shock absorber 2 is switched / controlled to a small state, that is, the suspension is softly controlled (step 190), and this routine is once ended. Since the timer variable Ts is incremented by 1 each time this routine is executed, the determination in step 170 is made while the timer variable Ts corresponding to the soft hold time does not exceed the soft reference time T2. "YES" is set and the damping force setting is held in software. Also, the timer variable Ts is the soft reference time.
The case of exceeding T2 will be described later, but until then Ts
The description will be continued assuming that ≦ T2.

Eventually, as shown at time t2 in FIG. 6, when the damping force change rate V becomes equal to or lower than the first reference value V1, the determination in step 110 is “N
"O", and after checking the value of the flag FS (Step 1
20) Whether or not the damping force change rate V is smaller than a second reference value V2 (which is used to determine the return condition of the damping force setting and is set to a value smaller than the first reference value). Make a decision (step 200). In the period from time t2 to t3, this judgment is "NO", and the flag FA indicating that the damping force change rate V is below the second reference value V2 is reset to the value 0 (step 210), The process shifts to step 140 and above. Even in this case, the setting of the damping force of the shock absorber 2 is still held soft (step 190), and this routine is once terminated.

When this process is repeated and time t3 elapses, the step
The determination of 200 is "YES", and it is determined whether the value of the flag FA is 0 (step 220). This flag FA has V <V2
After that, the value is set to 1. Accordingly, immediately after the rate of change V of the water reduction force falls below the second reference value V2, it is determined that FA = 0 and a value 1 is set to the flag FA (step 230).
<Processing for starting the timer corresponding to the duration of the state of V2, that is, processing for resetting the timer variable Ta to the value 0 (step 240).

After this process, or if "NO" is determined in step 220, the timer variable Ta is incremented by 1 in order to measure the timer by software (step 250). Then, it is determined whether or not this timer variable Ta is equal to or longer than the preset reference time T1 for fitting (step 260), and if “NO” is determined, step 140
Then, the damping force of the shock absorber 2 is kept soft. The standard time T1
Is a return condition for setting the damping force based on the time period during which the state of V <V2 is continued.

If “YES” is determined in step 260, flag FS
Is reset to the value 0 (step 270), the setting of the damping force of the shock absorber 2 is switched from software to hardware (step 130), and this routine is once ended. That is,
When the time period in which the damping force change rate V continues to be smaller than the second reference value V2 becomes longer than the set reference time T1, the damping force setting is switched to hard.

Therefore, as shown in FIG. 6, after the time t3, the determination in step 200 becomes “YES”, and the timer variable Ta is compared with the set reference time T1 in step 260.
Since the period of t4 is settled and is shorter than the reference time T1, the damping force setting is held softly, and after time t4, the step
The judgment of 200 (V <V2) becomes “NO”, and the setting of the damping force is still held in software. Similarly, from time t5 to t7, the damping force setting is held soft, but at time t7
After passing, the time (Ta) in which the damping force change rate V continues to be a value smaller than the second reference value V2 is settled and is longer than the reference time T1. Therefore, the determination in step 260 (Ta ≧ T1) is “ YES "
And the time after the reference time T1 has passed since the time t7
The damping force setting is switched to hard at t8.

Next, as shown in FIG. 7, a process when the damping force change rate V is smaller than the second reference value V2 and does not continue for the set reference time T1 or more will be described.

In this case, the determination at step 200 or step 260 in FIG. 5 is "NO", and the damping force setting is held in software, but the timer variable Ts corresponding to this software holding time is set.
When exceeds the soft reference time T2, the determination in step 170 becomes “NO”, and the process proceeds to step 280 and thereafter.

First, the second reference value V2 is increased by the value x (step 28
0), and the set reference time T1 is decreased by the value y (step 290). That is, the determination condition in steps 200 and 260 is changed to the side that is likely to be “YES”. Next, the soft reference time T2 is increased by the value z (z> T1) (step 300). That is, the determination condition of step 170 is changed, and the time to start the processing of step 280 and thereafter is set. Next, it is determined whether or not the increased soft reference time T2 is equal to or less than a preset upper limit soft upper limit T2lim (step 310), and if “YES” is determined, it is further increased. The second upper limit value V2, which is a preset upper limit value for the second reference value V2
It is determined whether or not it is less than or equal to lim (step 320). Also in this determination, if "YES" is determined, the processing of step 180 and thereafter is started, and the setting of the damping force is still held in software. That is, when the number of times the increase process of steps 280 and 300 is performed is small and the soft reference value T2 and the second reference value V2 are less than the soft upper limit value T2lim and the second upper limit value V2lim, respectively, the damping force is still set. It is held soft.

When the processing of steps 280 to 300 is repeated and the judgment of step 310 or step 320 becomes “NO” (FIG. 7 time te or when the second reference value V2 increases to V2e), the second reference value V2 is changed to A process of returning the set reference time T1 to the initial value T10, the soft reference time T2 to the initial value T20, and the soft reference time T2 to the initial value V20 are performed (steps 330 to 350). Then, the process proceeds to step 270 and thereafter, the flag FS is reset to the value 0 (step 270), the damping force setting is restored to hardware (step 130), and this routine is once ended.

When the damping force control routine described above is repeatedly executed, the damping force of the shock absorber 2 of each wheel is immediately set to a small state when the damping force change rate V exceeds the first reference value V1 (FIG. 6). At time t1), the damping force change rate V is the reference value
After V1 or less, the damping force change rate V becomes the second reference value V2.
It is held in this state until it falls below the time T1 and continues for the reference time T1 or more (time t8). After the elapse of this time, the shock absorber 2 is controlled to a state where the damping force is large again. Further, if the damping force change rate V falls below the second reference value V2 and does not continue for a reference time T1 or longer, that is, in a situation where traveling on a flat road does not last long, the second reference value V2 By correcting the set reference time T1 and the set reference time T1, the judgment condition is changed to the side where the setting of the damping force easily returns to hardware. Furthermore, if the damping force setting does not return to hardware even after this correction is repeated, the soft reference time T2 or the second reference value V2 is the soft upper limit value.
When T2lim or the second upper limit value V2lim or more, the setting of the damping force is once returned to hardware.

Therefore, the suspension control device 1 of the present embodiment uses the damping force change rate V, which is an extremely responsive signal, to generate the damping force generation pattern of each shock absorber 2 of the vehicle.
It is possible to quickly control to an appropriate state according to the state of the road surface. 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 the state of V <V2, and the shock absorber 2 is reduced in damping force. The time for holding in a state with small characteristics is also set short. Therefore, when a small step or the like is crossed on a flat road surface, the damping force is returned to the hard setting within a short time, and the riding comfort is kept good. As a result, the setting of the damping force is not unnecessarily kept soft for a long time and the grounding property is not impaired.

[II] On the other hand, when the vehicle is traveling on a rough road, the damping force change rate V greatly changes, and the damping force change rate V becomes the first reference value V1.
After exceeding once, the state of exceeding the second reference value V2 frequently appears. Therefore, once the suspension characteristics are softly controlled, the time to maintain the state of V <V2 becomes shorter,
The soft holding time becomes long, and the frequency of switching the damping force does not unnecessarily increase. Further, since the upper limit value is set for the time period during which the soft holding is continued, the setting of the damping force does not continue to be softly controlled. As a result, there is no discomfort in driving the vehicle, and the shock absorber 2
The durability of is also 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 using the damping force change rate, which is a signal with excellent responsiveness, and at the same time, a small step at the time of traveling on a flat road can be obtained. It is possible to optimally switch the time for maintaining the damping force to a small state between the case of overriding and the like and the case of traveling on a rough road, and it is possible to achieve both the riding comfort and the steering stability of the vehicle.

In this embodiment, the damping force is reset based on the soft upper limit value T2lim and the second upper limit value V2lim. However, it is also possible to use only the soft upper limit value T2lim to restore the damping reference time. The return condition may be changed by changing only T1 or the second reference value V2.

Next, regarding the setting of the second reference value V2 and the initial value of the settling reference time T1 which give the condition for returning the setting of the damping force from the software to the hardware in the damping force control interrupt processing routine shown in FIG. A description will be given with reference to the flowchart of FIG. This initial value correction routine is repeatedly executed at regular intervals, and its cycle is much longer than the cycle of the processing shown in FIG. This process is an example of the process performed by the third suspension control device of the present invention.

First, during the predetermined period when the damping force control device shown in FIG. 5 is repeatedly executed, the correction frequency N1 is calculated from the increase correction circuit of the second reference value V2, and the soft reference time T2 is the soft upper limit value T2lim. From the number of times it exceeds, the upper limit frequency N2
Is calculated from the number of times the second reference value V2 exceeds the second upper limit value V2lim (step 400). Then, it is determined whether the upper limit reaching frequency N2 or the upper limit reaching frequency N3 is less than or equal to a preset upper limit reference frequency NA (step 410), and if “YES” is determined, the correction frequency N1 is further set in advance. It is determined whether or not the correction reference frequency NB is equal to or lower than the set correction reference frequency NB. If this determination or the determination in step 410 is "NO", the initial value V20 of the second reference value V2 is increased by the value a (step 430), and the initial value T10 of the set reference time T1 is further reduced by the value b. The number is decreased (step 440) and this routine is once ended.

If the determination in step 420 is "YES", the correction frequency
It is determined whether or not N1 is equal to or more than the preset minimum correction frequency NC (NB> NC) (step 450). If “YES”, this routine is temporarily terminated, and if “NO”, , The initial value V20 of the second reference value V2 is decreased by the value a (step 460), and the initial value T10 of the reference time T1 is set to the value b.
Only (step 470) and this routine is once terminated.

Therefore, when the upper limit reaching frequency N2, N3 or the correction frequency N1 exceeds the upper limit reference frequency NA and the correction reference frequency NB, respectively, the initial values V20, T10 are increased and decreased, respectively. The number of corrections until the setting of the damping force in the processing returns from software to hardware is reduced, and the software holding time is shortened. That is, when the correction frequency N1 is large, it means that the vehicle is traveling on a bad road and the software holding time is originally long.Therefore, in order to timely set the damping force according to the ever-changing road surface condition, Reduce the number of times and the soft hold time.

On the other hand, when the correction frequency N1 is less than the correction minimum frequency NC, the initial values V20 and T10 are respectively decreased and increased, and therefore, when rough road running is started, damping in the damping force control processing of FIG. The number of corrections until the force setting returns from software to hardware increases, and the software holding time increases. That is, when the correction frequency N1 is small, the soft holding time is originally short, so the number of corrections is increased to maintain the soft state to some extent, and the soft holding time is increased.

Therefore, by this initial value correction processing, the soft holding time extremely suitable for the road surface condition is set, and the effect in the first embodiment is further improved. That is, it is possible to make the riding comfort of the vehicle and the steering stability extremely compatible with each other.

Although the embodiment of the present invention has been described above, the present invention is not limited to such an embodiment. For example, the setting of the second reference value V2 may be performed by setting the absolute values on the positive side and the negative side of the damping force change rate. Different configurations, configurations for correcting only the second reference value V2 or the set reference time T1, and their initial values V2
Needless to say, the present invention can be implemented in various modes without departing from the scope of the present invention, such as a configuration in which only 0 or T10 is corrected.

Effects of the Invention As described above in detail, according to the suspension control device of the present invention, the soft holding time until the damping force is changed from the large setting to the small setting and then the damping force is changed to the second soft holding time.
When the soft holding period exceeds the second predetermined period, the damping force setting is reset from small to large (first invention).
Alternatively, when the soft holding period exceeds the third predetermined period, the determination condition is corrected to the side where the damping force setting easily returns from small to large (second invention), so that the soft holding period suitable for the condition of the road surface. It has an extremely excellent effect that it can be set, and that it is not continuously held in software.
Therefore, for example, when overcoming a small step on a flat road, the damping force setting tends to return to hard in a short time, while on the other hand, the damping force setting tends to be softly maintained when driving on a bad road. Soft retention is prevented. As a result, there is no need to unnecessarily hold the damping force setting for a long period of time to impair the ground contact and the like, or to reduce the riding comfort, and to change the damping force setting frequently to make the driver feel uncomfortable. There is no need to hold him. in addition,
There is also an advantage to the durability of the device. Further, in the third suspension control device of the present invention, in addition to these effects, the degree of correction of the variable serving as the judgment condition for setting the damping force is reduced, so that the timely judgment according to the road surface condition can be made. This makes it possible to set the optimum software holding period.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating the basic configuration of the present invention, FIG. 2 is a schematic configuration diagram showing the overall configuration of a suspension control device as an embodiment of the present invention, and FIG. 3 (A) is a shock absorber 2 3B is a partial sectional view showing the structure of FIG. 3, FIG.
FIG. 6 is a block diagram showing the configuration of the electronic control unit 4 of the present embodiment, FIG. 5 is a flowchart showing a damping force control interrupt routine, and FIGS. 6 and 7 are graphs showing an example of switching of damping force setting. FIG. 8 is a flowchart showing an initial value correction routine. 1 …… Suspension control device 2FL, FR, RL, RR …… Shock absorber 4 …… Electronic control device 25FL, FR, RL, RR …… Piezo load sensor 27FL, FR, RL, RR …… Piezo actuator 51 …… Vehicle speed Sensor 70 …… Attenuation force change rate detection circuit 75 …… High voltage application circuit, 79 …… High voltage power supply circuit

Claims (3)

[Claims] 1. A shock absorber which is provided in a suspension of a vehicle and which can set a generation pattern of a damping force, a damping force change rate detecting means for detecting a changing rate of the damping force of the shock absorber, and the detected damping. And a damping force control means for changing the setting of the damping force of the shock absorber based on the magnitude relation between the rate of change of force and the reference value for adjustment of damping force. The damping force switching means for changing the setting of the damping force of the shock absorber from large to small when it is judged that the rate of change of the damping force is out of the range of the first reference value, and the damping force switching means. After the damping force setting is changed to a small value, the rate of change of the damping force is within a range of a second reference value whose absolute value is smaller than the first reference value, and a preset first predetermined period. When it is determined that the damping force has continued, the first damping force restoring means for changing the setting of the damping force from small to large and the setting of the damping force are changed by the damping force switching means, and the first damping force restoring means Soft holding period calculation means for calculating the soft holding period until restoration, and when it is judged that the calculated soft holding period exceeds a preset second predetermined period, the damping force is set from small to large. And a second damping force restoring means for changing the above. 2. The suspension control device according to claim 1, wherein the soft holding period calculated by the soft holding period calculating unit is used in place of the second damping force returning unit or together with the second damping force returning unit. When it is determined that the preset third preset period has been exceeded, a reference value correction unit is provided for gradually correcting the absolute value of the second reference value and / or gradually reducing the value of the first predetermined period. A suspension control device characterized by the above. 3. The suspension control device according to claim 2, wherein, when it is determined that the degree of correction by the reference value correction means is large, the second reference value of the second reference value at the start of the soft holding period is set. A suspension control device comprising: an initial value correction means for increasing and / or decreasing the initial value in the first predetermined period.