JPH03200415A - Suspension controller - Google Patents

Abstract

PURPOSE:To allow for both riding comfort and steering stability by setting a soft retention period for a predetermined duration according to a rate of change in damping force when damping force is restored after it is changed from large to small and restoring the damping force from small to large when required. CONSTITUTION:A rate of change in damping force in a shock absorber M1 provided on a vehicle suspension S is detected by a means M2 as well as the damping force is controlled by a means M3 based on the detection value and a reference value of the damping force. In such an apparatus, when the rate of change in damping force is out of a range of a first reference value, the damping force is changed from large to small by a means M4. When the rate of change in damping force is maintained for a first period or longer within a range of a second smaller reference value, the damping force is restored from small to large by a means M5. A soft retention period from the change in the damping force to the recovery is calculated by a means M6. When the soft retention period exceeds a second period, the damping force is restored from small to large by a means M7.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention [Field of Industrial Application] The present invention relates to a suspension control device, and more specifically, the present invention relates to a suspension control device, which includes a shock absorber whose damping force can be varied, and which adjusts the shock absorber based on the running condition of the vehicle. The present invention relates to a suspension control device that controls a damping force generation pattern.

[Prior Art] This type of suspension control device detects the rate of change in the damping force of a shock absorber, and when this rate of change exceeds a predetermined value, that is, the damping force is increased based on unevenness of the road surface, brake operation, etc. It is known that when a sudden change occurs, the damping force generation pattern for the movement of the shock absorber is quickly switched to a smaller value side (for example ('L, Japanese Patent Application Laid-open No. 64-67407).The rate of change of the damping force is Since the signal has extremely high responsiveness, it is possible for these suspension control devices to quickly follow changes in the damping force pattern to changes in road surface conditions, thereby maintaining good ride comfort.

[Problems to be Solved by the Invention] The suspension control device that uses the rate of change in damping force has excellent responsiveness, but when driving on rough roads, the rate of change signal is not the standard for adjustment. If the damping force goes up or down in a short period of time, there is no point in controlling the damping force if the damping force setting is changed according to the magnitude relationship with respect to the adjustment reference value. If the value is exceeded, it becomes necessary to maintain the damping force setting for a predetermined period of time. However, there is a problem in that simply continuing the damping force setting for a certain period of time after switching the damping force setting does not adequately respond to the road surface condition. That is,
When driving on rough roads, the rate of change in damping force fluctuates up and down rapidly. Therefore, it is important to keep the damping force generation pattern soft for a short period of time. This results in an uncomfortable feeling.It also has a negative impact on the durability of the shock absorber.

On the other hand, if the soft retention period is too long, problems arise in that ride comfort is reduced and ground contact is impaired.

The suspension control device of the present invention solves the above problems,
The purpose is to use the rate of change in damping force to set a soft retention period depending on the road surface condition, thereby achieving both ride comfort and handling stability.

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 first suspension control device of the present invention, as illustrated by the solid line in FIG. an absorber M1, a damping force change rate detection means M2 that detects a rate of change in damping force of the shock absorber M1, and a damping force change rate detecting means M2 that detects a rate of change in damping force of the shock absorber M1, based on the magnitude relationship between the detected rate of change in damping force and a reference value for adjusting the damping force. ,
and a damping force control means M3 for changing the setting of the damping force of the shock absorber M1, wherein the rate of change of the damping force by the damping force control means M31 is outside the range of the first reference value S]. a damping force switching means M4 that changes the damping force setting of the shock absorber M1 from large to small when it is determined that the damping force setting of the shock absorber M1 is changed from large to small; The rate of change of the damping force is the first reference value S]
A first damping force that changes the setting of the damping force from small to large when it is determined that the damping force has continued for a preset first predetermined period T1 or more within the range of a second reference value S2 having a smaller absolute value. a return means M5 and a soft retention period calculation means M for calculating a soft retention period until the setting of the damping force is changed by the damping force switching means M4 and the damping force is restored by the first damping force return means M5;
6, and a second damping force return means M7 that changes the setting of the damping force from small to large when it is determined that the calculated soft retention period exceeds a second predetermined period T2 set in advance. The main points are as follows.

On the other hand, in the second suspension control device of the present invention (as indicated by the broken line in FIG. 1), in the first suspension control device, the second damping force Together with the return means M7, when it is determined that the software retention period calculated by the software retention period calculation means M6 has exceeded a preset third predetermined period T3, the absolute value of the second reference value S2 is gradually corrected. and/or the first predetermined period T].

Furthermore, the third suspension control device of the present invention has a first
As indicated by a dashed line in the figure, when the second suspension control device determines that the degree of correction by the reference value correction means M8 is poor, the second suspension control device at the start of the soft retention period The gist of the present invention is to include an initial value correcting means M9 for increasing the initial value of the reference value S2 and/or decreasing the initial value of the first predetermined period T1.

[Operation] The first aspect of the present invention having the above configuration. Second. The third suspension control device detects the rate of change in the damping force of the shock absorber M provided in the suspension S of the vehicle using the damping force change rate detection means M2, and uses the rate of change in the damping force and the damping force for adjustment. Based on the magnitude relationship with the reference value, the damping force control means M3 changes the setting of the damping force of the shock absorber M.

Here, in the first suspension control device, the damping force setting (first, the rate of change of the damping force is set to the first reference value S1).
When the damping force is outside the range, the damping force is changed from large to small by the damping force switching means M4. After this change, when it is determined that the rate of change of the damping force has continued within the range of the second reference value S2 for the first predetermined period of time 11 or more, the damping force setting is changed from small to small by the first damping force return means M5. greatly changed. When the setting of the damping force is changed from dog to small, the soft retention period until the damping force is restored by the first damping force restoration means M5 is calculated by the soft retention period calculation means M6, but this soft retention period is the second
When it is determined that the predetermined period T2 has been exceeded, the setting of the damping force is changed from small to large by the second damping force return means M71.

That is, when the rate of change in the damping force falls outside the range of the first reference value S1, the setting of the damping force of the shock absorber M is switched from large to small, and thereafter this rate of change is set to the second reference value S2.
If the damping force setting continues for more than the first predetermined period T1 within the range of In this case, the damping force setting is changed from small to large.

On the other hand, the second suspension control device of the present invention provides a second damping force return main stage M of the suspension control device of the first invention.
7, or together with the second damping force return main stage M7, a reference value correction means M8 is provided. When it is determined that the soft retention period has exceeded the third predetermined period T3, the absolute value of the second reference value S2 Gradual increase correction The value of the first predetermined period T1 is gradually decreased. In other words, the conditions under which the damping force setting can return from small to large are relaxed, and the soft holding period ends more easily. Note that both the gradual increase correction and the gradual decrease correction may be performed, or either one of them may be performed.

Furthermore, the third suspension control device of the present invention includes a second
In the suspension control device, the reference value correction means M
When the degree of correction of No. 8 is large, the initial value correction means M9 increases the initial value of the second reference value S2.
The initial value of the predetermined period T1 is corrected to decrease. In other words, if the degree of correction of the second reference value S2, which is a condition value that allows the damping force setting to return from small to large, and the first predetermined period T1 is large, the initial value is changed to the initial value after the soft retention period ends. The damping force is corrected to the easier side, and the number of corrections required to return the damping force setting from small to large is reduced. Note that both the increase correction and the decrease correction may be performed, or either one may be performed.

Therefore, in the first to third suspension control devices of the present invention, the soft holding period from when the damping force setting is switched from large to small until it returns to normal is limited to This becomes situation-specific, and furthermore, it prevents soft retention from continuing for a long period of time.

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

[Example] In order to further clarify the structure and operation of the present invention described above, preferred embodiments of the suspension control device of the present invention will be described below.

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

As shown in FIG. 2, the suspension control device 1 of the present embodiment includes shock absorbers 2FL, 2FR, 2RL, and 2RR that can change the damping force in two stages, and is connected to each of these shock absorbers to control the damping force. It is composed of an electronic control unit 4 that performs the following operations.

Each shock absorber 2FL, 2FR, 2RL,
2RR has left and right front and rear wheels 5FL, 5FR,
5RL, 5RR suspension lower arm 6F
Coil springs 8FL and 8FR are installed between L, 6FR, 6RL, and 6RR and the vehicle body 7.

It is located alongside 8RL and 8RR.

Shock absorber 2FL, 2FR, 2RL,
2RR is a shock absorber 2FL as described later.
, 2FR.

A piezo load sensor that detects the force acting on 2RL and 2RR, and shock absorbers 2FL, 2FR, and 2
R.L.

Each set includes a piezo actuator that switches the setting of the damping force generation pattern in the 2RR.

Next, each of the above-mentioned shock absorbers 2FL and 2FR.

The structure of 2RL and 2RR will be explained, but each of the above shock absorbers 2FL, 2FR, 2RL, 2RR
Since all of the structures are the same, the shock absorber 2FL on the left front wheel 5FL side will be explained here as an example. In addition, in the following description, the reference numerals of each member provided on each wheel include front left wheel 5 FL and front right wheel 5 FR, as necessary.

Subscript F corresponding to left rear wheel 5RL, right rear wheel 5RR
L, FR.

RL and RR shall be added, and if there is no difference regarding each wheel, the subscripts shall be omitted.

The shock absorber 2, as shown in FIG. 3(A),
The lower end of the cylinder 11 side is fixed to the suspension lower arm 6 via the axle side member 1]a.Meanwhile, the bearing 7 is fixed at the upper end of the rod 3 inserted through the cylinder 1].
It is fixed together with a coil spring 8 to the vehicle body 7 via a vibration-proof rubber 7b.

Inside the cylinder 11 is an internal cylinder 15 connected to the lower end of the rod 13. A connecting member 16, a cylindrical member 17, and a main piston 8 which is slidable along the inner surface of the cylinder] are disposed. A piezo load sensor 25 and a piezo actuator 27 are housed in an internal cylinder 5 connected to a rod 3 of the shock absorber 2 .

The main piston [8] is fitted onto the outside of the cylindrical member [7], and a sealing material 19 is interposed on the outer periphery that fits into the cylinder [1]. Therefore, the cylinder 11 side is divided into a first liquid chamber 21 and a second liquid chamber 23 by this main piston ]8. A backup member 28 is screwed to the tip of the cylindrical member] 7, and a spacer 29 and a leaf valve 30 are attached to the cylindrical member] 7 side together with the main piston 18. Valve 31 and collar 3
2 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 3] and the backup member 28, and urge the leaf valve 3] in the main piston direction.

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

18b are each closed on one side, and the main piston 1
8 opens to one side as it moves in the direction of arrow A or B. Therefore, as the main piston 8 moves, the hydraulic oil filled in both the liquid chambers 21 and 23 flows through both passages 18a and 23.
18b to move between the two liquid chambers 21, 23. In this state where the movement of hydraulic oil between the two liquid chambers 21 and 23 is limited to both passages 18a and 18b, the damping force generated against the movement of the rod 13 is large, and the characteristics of the suspension become hard. .

A piezo load sensor 2 is housed inside the internal cylinder 15.
5 and the piezo actuator 27 are shown in FIG. 3(A),
As shown in (B), this is an electrostrictive element laminate in which thin plates of piezoelectric ceramics are stacked with electrodes in between. Each electrostrictive element of the piezo load sensor 25 is polarized by the force acting on the shock absorber 2, that is, the damping force. Therefore, by extracting the output of the piezo load sensor 25 as a voltage signal using a circuit with a predetermined impedance, the rate of change in damping force can be detected.

The piezo actuator 27 is made by stacking electrostrictive elements that expand and contract with good response when a high voltage is applied to increase the amount of expansion and contraction, and directly drives the piston 36 .

When the piston 36 is moved in the direction of arrow B in FIG. 3(B), the plunger 37 and H
The spool 4, which has a letter-shaped cross section, is also moved in the same direction. When the spool 41 in the position shown in FIG. 3(B) (origin position) moves in the direction B in the figure, the first liquid chamber 2
The sub-flow path 16c connected to the liquid chamber 1 and the sub-flow path 39b of the bushing 39 connected to the second liquid chamber 23 are communicated with each other. This sub-flow path 39b is further connected to the flow path 17a in the cylindrical member 7 via an oil hole 45a provided in the plate valve 45.
As a result, when the spool 41 moves in the direction of arrow B, the first liquid chamber 21 and the second liquid chamber 2
The flow rate of the hydraulic oil flowing between 3 and 3 increases. In other words, when the piezo actuator 27 expands due to high voltage application, the shock absorber 2 switches its damping force characteristic from a high damping force (hard) state to a low damping force (soft) state, and when the electric charge is discharged and contracts, the shock absorber 2 attenuates. Change the force characteristics to large damping force (
hard) state.

The amount of movement of the leaf valve 31 provided on the lower surface of the main piston 8 is controlled by a spring 35.
It is regulated compared to Further, the plate valve 45 is provided with an oil hole 45b having a larger diameter than the oil hole 45a on the outside of the oil hole 45a.
When the bush moves in the direction of 3 and 9 against the urging force of 6,
The hydraulic oil can move through the oil hole 45b. Therefore, regardless of the position of the spool 4], the flow rate of hydraulic oil when the main piston 18 moves in the direction of arrow B is larger than when the main piston 18 moves in the direction of the arrow. That is, the damping force is changed depending on the direction of movement of the main piston] 8, thereby improving the characteristics as a shock absorber. In addition, the oil-tight chamber 33 and the first
A hydraulic oil supply path 38 is connected between the check valve 3 and the liquid chamber 2 of the check valve 3.
8a, and keeps the flow rate of hydraulic oil in the oil-tight chamber 33 constant.

Next, the electronic control device 4 that switches and controls the damping force generation pattern of the shock absorber 2 described above will be explained using FIG. 4.

This electronic control device 4 includes, as sensors for detecting the running state of the vehicle, a steering sensor 50 for detecting the steering angle of a steering wheel (not shown) of a piezo load sensor 25 of each shock absorber 2, and a steering sensor 50 for detecting the steering angle of a steering wheel (not shown). A vehicle speed sensor 51 that detects speed, a shift position sensor 52 that detects the shift position of a transmission (not shown), a stop lamp switch 53 that issues a signal when a brake pedal (not shown) is stepped on, and the like are connected.

The electronic control device 4 which outputs control signals to the piezo actuator 27 described above based on these detection signals etc. is a well-known CPU 61. ROM62. It is configured as an arithmetic and logic operation circuit centering on a RAM 64, and inputs and outputs to and from the outside through an input section 67 and an output section 68 which are connected to these circuits via a common bus 65.

In addition, the electronic control device 4 includes a damping force change rate detection circuit 70 connected to the piezo load sensor 25, a waveform shaping circuit 73 connected to the steering sensor 50 and the vehicle speed sensor 51, and a high speed The voltage application circuit 75 receives power from the battery 77h1 via the ignition switch 76, and is connected to a so-called switching regulator type high voltage power supply circuit 79 which outputs a drive voltage for driving the piezo actuator, and converts the voltage of the battery 77 to the Ishimuroko. A constant voltage power supply circuit 80 that generates an operating voltage (5V) for the control device 4 is provided. Shift position sensor 52. Stop lamp switch 53. Damping force change rate detection circuit 70. The waveform shaping circuit 73 is connected to the input section 67, while the high voltage application circuit 75. The high voltage power supply circuits 79 are connected to the output sections 68, respectively.

The damping force change rate detection circuit 70 is connected to each piezo load sensor 25.
It consists of four detection circuits provided corresponding to FL, FR, RL, and RR, and each detection circuit receives an output from a circuit including the piezo load sensor 25 according to the acting force that the shock absorber 2 receives from the road surface. The voltage signal V that
CPU61 as damping force change rate of shock absorber 2
It is configured to output to . In addition, the waveform shaping circuit 7
3 is a circuit that shapes the detection signals from the steering sensor 50 and the vehicle speed sensor 51 into signals suitable for processing in the CPU 61 and outputs the signals. Therefore, the CPU 61 can determine the road surface condition, the running condition of the vehicle, etc. based on the output signals from the second damping force change rate detection circuit 70 and the waveform shaping circuit 73, as well as its own processing results. C
Based on this determination, the PU 61 outputs a control signal to the high voltage application circuit 75 provided corresponding to each wheel.

This high voltage application circuit 75 is a circuit that applies a voltage of +500 volts or 1100 volts output from a high voltage power supply circuit 79 to the piezo actuator 27 in accordance with a control signal from the CPU 61. Therefore, in response to this damping force switching signal, the piezo actuator 27 expands (when +500 volts is applied) or contracts (when -100 volts is applied), and the hydraulic oil flow rate is switched to change the damping force characteristics of the shock absorber 2 from soft to hard. can be switched to That is, the damping force characteristics of each shock absorber 2 are determined by applying a high voltage to the piezo actuator 27.
When the spool 4] (3rd
As shown in Figure (B)), the flow rate of the hydraulic oil flowing between the first liquid chamber 2 and the second liquid chamber 23 in the shock absorber 2 increases, resulting in a state where the damping force is small, and due to the negative voltage. When the piezo actuator 27 is contracted by discharging the charge, the flow rate of the hydraulic oil decreases, resulting in a state of large damping force. In addition, the piezo actuator 27
Once the accumulated charge is discharged, even if the negative voltage is removed, the piezo actuator 27 remains contracted, and the shock absorber 2 maintains its large damping force.

Next, the damping force control performed by the suspension control device of this embodiment having the above-described configuration will be explained based on the flowchart of FIG. In addition, this damping force control is
This is an example of processing performed by the first and second suspension control devices of the present invention. This damping force control interrupt processing routine is repeatedly executed at regular intervals after flags FS, FA, etc., which will be described later, are reset to a value O in an initialization process (not shown) when the power is turned on. In addition, these processes are
Shock absorber 2 for each wheel FL, FR, RL
, RR, but the processing for each wheel is the same, so the description will be made without making any particular distinction.

When the processing routine shown in FIG. 5 is started, first, the rate of change V of the damping force of each shock absorber 2 is read from the damping force change rate detection circuit 70 via the input section 67 (step) 00. , it is determined whether the absolute value of this damping force change rate V (hereinafter simply referred to as damping force change rate V) is larger than the first reference value V] (step) ]0
). This first reference value 1 is provided to judge the magnitude of the damping force change rate V and to softly switch the characteristics of the shock absorber 2, and may be a predetermined value, or may be a value depending on the vehicle speed. It may be set in another routine (not shown) as a corresponding value.
The learning may be performed based on the switching frequency of the damping force settings, etc.

FIG. 6 is a graph showing an example of the rate of change in damping force V. If the rate of change in damping force V is smaller than the first reference value 1, as before the time t1 shown in the diagram, then the characteristics of the suspension are The flag FS indicating that it is set to software has a value of 1.
It is determined whether or not (step 12o), and the flag FS is
If the value is not 1, the suspension is controlled hard (step 130), and this routine is temporarily terminated.

In addition, in the process of step 130 for hard controlling the suspension, immediately after the damping force setting of the shock absorber 2 is switched from soft to mood, 1100 volts is applied from the high voltage application circuit 75 by the control signal from the output section 68. is applied to the piezo actuator 271 to contract it, and if the piezo actuator 27 is already in the contracted state, it is held as it is.

On the other hand, as shown at time t1 in FIG.
10), Step 1 to determine whether the flag FS is the value O or not.
40), if the flag FS has a value of 0, that is, if the damping force setting is hard when this judgment is made, the timer variable T is a process to start measuring the soft holding time.
s Glue and paste processing is performed (step 150). If the damping force setting is soft, this step 15o
Skipping the above process, the timer variable Ts is incremented by the value 1 in order to measure the timer by software (step 60). Next, this timer variable Ts
is less than the software reference time T2 set to determine the timing to change the return condition of the damping force setting [step] 70). Set steps] 80),
Thereafter, a high voltage of +500 volts is applied from the high voltage application circuit 75 to the piezo actuator 27 to switch and control the damping force of the shock absorber 2 to a small state, that is, to softly control the suspension (step) 90
), this routine ends once. It should be noted that the timer variable Ts is incremented by the value] each time this routine is executed, so the judgment in step 170 is performed during the period in which the timer variable Ts corresponding to the software retention time does not exceed the software reference time T2. becomes rYESJ, and the damping force setting is kept soft. Furthermore, in the case where the timer variable Ts exceeds the soft reference time T2, as will be described later,
Until then, the explanation will continue assuming that Ts≦T2.

Eventually, as shown at time t2 in FIG. 6, the damping force change rate V
When the damping force change rate V becomes equal to or less than the first reference value V, the judgment in step 110 becomes "NO", and after checking the flag FSO value (step 20), the damping force change rate V becomes the second reference value V.
2 (this is for determining the conditions for restoring the A decaying force setting, and is set to a value smaller than the first reference value) (step 200). During period 1 from time t2 to t3, this determination is "NO".
Therefore, the flag FA indicating that the damping force change rate V has fallen below the second reference value v2 is reset to the value O (step 210), and the process proceeds to step 140 and subsequent steps described above. Even in this case, the damping force setting of the shock absorber 2 should still be kept soft.
), this routine ends once.

When this process is repeated and time t3 has elapsed, the judgment in step 200 becomes rYESJ, and the flag FA
It is determined whether the value of is 0 (step 220). This flag FA is set to the value after V<V2. Therefore, immediately after the damping force change rate V falls below the second reference value V2, the flag FA should be set as FA 20 (step 230), and the time period during which the state of V<V2 continues. A process of starting a timer, that is, a process of resetting the timer variable Ta to the value 0 is performed (step 240).

After this process, or in step 220, rNO
If it is determined that the timer is J, the timer variable Ta is incremented by the value] in order to measure the timer by software (step 250).

Next, it is determined in step 260 whether or not this timer variable Ta is equal to or greater than a preset reference time T1.
), if the determination is "NO", the process moves to step 140, and the setting of the damping force of the shock absorber 2 is still maintained at the sonobutton.

The settling reference time T1 is based on the time during which the state of V<V2 continues, and serves as a condition for returning the damping force setting.

If rYESJ is determined in step 260, the flag FS is reset to the value O (step 270), the damping force setting of the shock absorber 2 is switched from soft to hard (step 30), and this routine is temporarily terminated. That is, when the time during which the damping force change rate V continues to be smaller than the second reference value V2 is longer than the settling reference time T], the damping force setting is switched to hard.

Therefore, as shown in FIG. 6 (2), after time t3,
The judgment at step 200 is rYESJ, and step 2
At step 60, the timer variable Ta is compared with the settling reference time T], but since the period from time t3 to t4 is shorter than the settling reference time T], the setting of the damping force is kept soft. After time t4, the determination in step 200 (V<V2) becomes "NO", and the damping force setting is still kept soft. Similarly, the damping force setting is kept soft from time t5 to t7, but after time t7, the damping force change rate V continues to be smaller than the second reference value v2 (Ta ) is longer than the settling reference time T1, so the judgment in step 260 (Ta≧TI) is rY E
SJ, and the setting of the damping force is switched to hard at time t8, which is after the reference time T1 has passed since time t7.

Next, as shown in FIG. 7, a process will be described in the case where the damping force change rate V is a value smaller than the second reference value v2 and does not continue for more than one time period after settling down.

In this case, step 200 or step 2 in FIG.
The judgment at step 60 is rNOJ, and the damping force setting is held in a soft manner. However, if the timer variable Ts corresponding to this soft holding time exceeds the soft reference time T23, the judgment at step 170 becomes "NO," and the setting of the damping force is held in a soft manner. Proceed to subsequent processing.

First, the second reference value v2 is increased by the value x (step 2
80), the settling reference time T] is decreased by the value y (step 290). That is, the judgment conditions at steps 200 and 260 are changed to the side where rYEsJ is more likely to occur. Next, the soft reference time T2 is increased by a value z (where z>1) (step 300). That is, step 17
The determination condition of step 0 is changed to set the timing for entering the process from step 280 onwards. Then, the increased soft reference time T
2 is a preset upper limit value T21i
Step 310) to determine whether r is less than or equal to m.
When it is determined that Y E SJ , it is further determined whether or not the increased second reference value V2 is less than or equal to the second upper limit value V21im, which is a preset upper limit value (step 32
0). If it is determined that ry E SJ in this determination as well, the process proceeds to step 280 and subsequent steps, and the damping force setting is still maintained at a soft level. That is, step 280
, 300 increase processing is performed less frequently, and the soft reference value T2. The second reference value V2 is the soft upper limit value T
2m, which is less than the second upper limit value V21im, the damping force setting is still kept soft.

The processes of steps 280 to 300 are repeated, and when the judgment of step 310 or step 320 becomes rNOJ (time te in FIG. 7 or the second reference value V2 is V2e
), the second reference value v2 is set to its initial value V
20, processing is performed to return the settling reference time T] to its initial value T10 and the soft reference time T2 to its initial value T20 (steps 330 to 350). And step 27
Moving on to the processing after 0, the flag FS is reset to the value 0 (step 270), and the damping force setting is returned to hard (step 270).
Step 130), this routine is temporarily 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 state that is 1 smaller when the damping force change rate V exceeds the first reference value v1. (Time tl in Figure 6), damping force change rate V
is below the reference value V], this state is maintained until the damping force change rate V remains below the second reference value v2 and continues for the reference time T1 or longer (time t8). After this time has elapsed, the shock absorber 2 is again controlled to have a large damping force. In addition, if the damping force change rate V remains below the second reference value V2 and does not continue for more than the reference time T1, that is, in a situation where driving on a flat road does not continue for a long time, the second reference value V2 By correcting the settling reference time T1, the judgment condition is changed to the side where the damping force setting is more likely to return to hard. Furthermore, if the damping force setting does not return to the hard setting even after this correction is repeated, if the soft reference time T2 or the second reference value V2 exceeds the soft upper limit value T21im or the second upper limit value V21im, - Reset the damping force setting to hard.

Therefore, the suspension control device of the present embodiment uses a very responsive signal called the damping force change rate V to determine the damping force generation pattern of each shock absorber 2 of the vehicle.
It is possible to quickly control the vehicle to an appropriate state depending on the road surface condition. That is, [1] When driving on a flat road, even if the damping force change rate V exceeds the first reference value V1, it quickly settles to a state where V<V2, and the damping force of the shock absorber 2 decreases. The time period for which the characteristics are held in a small state is also set short. Therefore, when the vehicle goes over a small step on a flat road surface, the damping force setting returns to hard within a short period of time, and ride comfort is maintained at a good level. As a result, the damping force setting will not be kept soft for an unnecessarily long period of time, and the ground contact will not be impaired.

[11] On the other hand, when driving continuously on a rough road, the damping force change rate V changes sharply, and after the damping force change rate V once exceeds the first reference value V], the second A state in which the reference value v2 is exceeded frequently appears. Therefore, once the suspension characteristics are softly controlled, the time for which the state of V<V2 continues is shortened, so the soft holding time is lengthened, and the frequency of switching the damping force does not become unnecessarily high. Further, since there is an upper limit value for the time period during which the soft hold is continued, the setting of the damping force will not continue to be under soft control.

As a result, there is no discomfort when driving the vehicle, and the durability of the shock absorber 2 is also improved.

As described above, according to the suspension control device 1 of the present embodiment, the characteristics of the suspension can be controlled with good responsiveness by using a highly responsive signal called the rate of change in damping force, while also controlling small bumps when driving on a flat road. The time during which the damping force is maintained at a low level can be optimally switched between when passing over a car and when driving on a rough road, thereby achieving both ride comfort and handling stability of the vehicle.

In addition, in this embodiment, the soft upper limit value T21im and the second
Although the return setting of the damping force is performed based on the upper limit value V21im, the return setting may be made only based on the soft upper limit value T21im, or the return condition may be set by changing only the settling reference time T1 or the second reference value v2. It may also be something that changes.

Next, in the damping force control interrupt processing routine shown in FIG. 5, a second reference value V2. The setting of the initial value of the settling reference time T] will be explained with reference to the flowchart of FIG. This initial value correction routine (which is repeatedly executed at regular intervals, and whose cycle is much longer than the cycle of the process shown in FIG. 5) should be noted. This is an example of processing performed by the suspension control device.

First, the correction frequency N] is determined from the number of times of increase correction of the second reference value v2 during a predetermined period when the damping force control process shown in FIG. 5 is repeatedly executed.
2 exceeds the soft upper limit value T21im, the upper limit reaching frequency N2 is calculated, and the second reference value V2 is calculated from the second upper limit value V21i.
Calculate the upper limit reaching frequency N3 from the number of times exceeding m (
Step 400). Next, it is determined whether the upper limit reaching frequency N2 or the upper limit reaching frequency N3 is less than or equal to the preset upper limit reference frequency NA (step 410), rYES.
If it is determined to be J, it is further determined whether the correction frequency N1 is equal to or less than a preset correction reference frequency N8. If this judgment or the judgment of step 4]0 is rNOJ, the initial value V20 of the second reference value V2 is increased by the value a (step 430), and the initial value T]O of the reference time T1 is increased by the value a (step 430). (step 440), and this routine is temporarily terminated.

If the determination in step 420 is rYES, 1, the correction frequency N] is the preset correction minimum frequency NC(N
Step 450 to determine whether B>NC) or higher.
), in the case of rYESJ (above), this routine is temporarily terminated, and in the case of "NC", the initial value V20 of the second reference value v2 is decreased by the value a (step 460),
Further, the initial value T10 of the reference time T1 is increased by the value (step 470), and this routine is temporarily terminated.

Therefore, the upper limit reaching frequency N2. N3 or correction frequency N]
exceeds the upper limit reference frequency NA and the corrected reference frequency NB, respectively, the initial value V20. Since the TIO is each corrected by decreasing the force increase by 1, the number of corrections required until the damping force setting returns from soft to hard in the damping force control process shown in FIG. 5 is reduced, and the soft holding time is shortened. That is, if the correction frequency N1 is large, it means that the vehicle is traveling on a rough road and the soft holding time is originally long.
Decrease the number of corrections and reduce the software retention time.

On the other hand, if the correction frequency N1 is less than the minimum correction frequency NC, the initial value V20. Decrease TIO respectively.

Because of the incremental correction, when driving on a rough road starts, the number of corrections required for the damping force setting to return from soft to hard in the damping force control process shown in FIG. 5 increases, and the soft holding time becomes longer. That is, when the correction frequency N] is small (friend) Since the soft holding time is originally short, 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 process, the soft holding time is set that is extremely suitable for the road surface condition, and the effects of the first embodiment are further improved.

In other words, it is possible to achieve both ride comfort and steering stability of the vehicle extremely well.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way. A configuration in which the values are different, a configuration in which only the second reference value V2 or the settling reference time T1 is corrected, a configuration in which only the initial value V20 or TIO is corrected, etc.
It goes without saying that the invention can be implemented in various ways without departing from the gist of the invention.

Effects of the Invention As detailed above, according to the suspension control device of the present invention, the damping force change rate is the same as the soft holding period from when the damping force setting is switched from large to small until it returns to normal.
(first invention), where the damping force is set based on a duration that falls within a reference value range, and when this soft holding period exceeds a second predetermined period, the damping force setting is returned from small to large;
Alternatively, when the soft holding period exceeds a third predetermined period, the judgment condition is corrected to the side where the damping force setting is more likely to return from small to large (second invention), so that the soft holding period is suitable for the road surface condition. can be set, and has the extremely excellent effect of not being held by the software.

Therefore, for example, when driving over a small step on a flat road, the damping force setting tends to return to hard in a short period of time, while when driving on a rough road, the damping force setting tends to remain soft, and it remains unchanged for a long time. Soft retention over an extended period of time is prevented. As a result, the damping force setting is not held soft for an unnecessarily long period of time, which impairs ground contact and reduces ride comfort.In addition, the damping force setting is not changed frequently, which may cause the driver to feel uncomfortable. There's no need to hold her. In addition, the durability of the device is also an advantage. In addition to these effects, the third suspension control device of the present invention reduces the degree of correction of the variables that are the conditions for determining the setting of the damping force, making it possible to make timeless decisions depending on the road surface condition. This makes it possible to set an optimal software retention period.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating the basic configuration of the present invention, FIG. 2 is a schematic configuration diagram showing the overall configuration of a suspension control device as an embodiment of the present invention, and FIG. 3 (A) is a shock absorber 2 Fig. 3 (B) is a partial cross-sectional view showing the structure of
) is an enlarged sectional view of the main parts of the shock absorber 2, and FIG. 4 is a block diagram showing the configuration of the electronic control device 4 of this embodiment.
FIG. 5 is a flowchart showing a damping force control interrupt routine, FIGS. 6 and 7 are graphs showing an example of switching damping force settings, and FIG. 8 is a flowchart showing an initial value correction routine. 1... Suspension control device 2 FL, FR, RL, RR... Shock absorber 4... Electronic control device 5 FL, FR, RL, RR... Piezo load sensor 7 FL, FR, RL, RR・... Piezo actuator] ... Vehicle speed sensor 0 ... Damping force change rate detection circuit

Claims (1)

[Scope of Claims] 1. A shock absorber that is installed in the suspension of a vehicle and can set a damping force generation pattern; a damping force change rate detection means that detects a rate of change in the damping force of the shock absorber; and a damping force control means for changing the setting of the damping force of the shock absorber based on the magnitude relationship between the rate of change of the damping force and a reference value for adjusting the damping force. The damping force switching means changes the damping force setting of the shock absorber from large to small when it is determined that the rate of change of the damping force is outside the range of a first reference value; After the setting of the damping force is changed to a small value by the means, the rate of change of the damping force is within the range of a second reference value whose absolute value is smaller than the first reference value, and the damping force is changed to a preset first value. When it is determined that the damping force has continued for a predetermined period or longer, the first damping force restoration means changes the damping force setting from small to large, and the damping force setting is changed by the damping force switching means, and the first damping force is restored. a soft retention period calculating means for calculating a soft retention period until recovery by a means; A suspension control device comprising: a second damping force return means for changing the damping force from a to a large value. 2. The suspension control device according to claim 1, wherein the soft retention period calculated by the soft retention period calculation means is set in advance in place of or together with the second damping force restoration means. The invention is characterized by comprising a reference value correction means for gradually increasing the absolute value of the second reference value and/or gradually decreasing the value of the first predetermined period when it is determined that the third predetermined period has been exceeded. suspension control device. 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 initial value of the second reference value at the start of the soft retention period is increased. A suspension control device comprising an initial value correcting means for correcting and/or decreasing an initial value for the first predetermined period.