JPH03182830A - Suspension control device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a suspension control device, and more specifically, the present invention relates to a suspension control device, and more specifically, the present invention relates to a suspension control device, and more specifically, it is equipped with a shock absorber that can vary the setting of damping force, and is configured to adjust the shock based on the driving condition of the vehicle. The present invention relates to a suspension control device that controls the generation pattern of damping force of an absorber.

[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 is performed based on unevenness of the road surface, brake operation, etc. It is known that when the force suddenly changes, the generation pattern of the damping force for the movement of the shock absorber is quickly switched to a smaller value side (for example, Japanese Patent Laid-Open No. 6
4-67407). Since the rate of change in damping force is a signal with extremely high responsiveness, such a suspension control device can quickly follow changes in the damping force pattern to changes in road surface conditions and maintain 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, after switching the damping force setting, there is a problem in that simply continuing that state for a certain period of time does not adequately respond to the road surface condition.In other words, when driving on a rough road, In this case, the rate of change of the damping force fluctuates up and down rapidly, so if the period during which the damping force generation pattern is maintained in a soft manner is short, the frequency of switching the damping force increases, causing a sense of discomfort. This also has a negative impact on the durability of the shock absorber. On the other hand, if the period of keeping the damping force soft is too long, when driving on a relatively flat road surface, the damping force setting will be kept soft for an unnecessarily long time after passing over a small bump, etc. It invites the problem of loss of sexuality. As a result, the driving feeling may deteriorate.

The suspension control device of the present invention solves the above problems,
To control damping force setting using a damping force change rate in accordance with road surface conditions, and to improve riding comfort and steering stability when a flat road or a rough road continues.

4. Structure of the Invention The structure of the present invention that achieves the above object will be explained below.

[Means for Solving the Problems] The suspension control device of the present invention, as illustrated in FIG. Based on the damping force change rate detection means M2 that detects the change rate of the damping force of the absorber M1, and the magnitude relationship between the detected damping force change rate and the damping force adjustment reference value,
a damping force control means M3 for changing the damping force setting of the shock absorber S; and when the damping force setting is changed by the damping force control means M3, the damping force setting after the change is continued for a predetermined holding period. a suspension control device comprising a damping force switching and holding means M4 that detects a state of a road surface on which the vehicle runs based on a change in the setting of the damping force by the damping force control means M3; When it is determined that either a flat road or a rough road condition continues based on M5 and the detected road surface condition, the damping force control means M3 controls the setting of the damping force. , a damping force adjustment/correction means M6 that corrects the damping force to the average value side set respectively on a flat road and a rough road 1, and the state of the previous correction of the damping force by the damping force adjustment/correction means M6. and a holding period correction means M7 for correcting the holding period in the damping force switching and holding means M4 based on the damping force switching and holding means M4.

[Function] The suspension control device of the present invention having the above configuration has the following features:
The rate of change in the damping force of the shock absorber M1 provided in the suspension S of the vehicle is detected by the damping force change rate detection means M2, and based on the magnitude relationship between the rate of change in the damping force and a reference value for adjusting the damping force. , the damping force control means M3+ switches the setting of the damping force of the shock absorber M1. After the switching, the damping force is held by the damping force switching and holding means M4 without being switched for a predetermined holding period, regardless of the magnitude of the damping force change rate and the adjustment reference value. Furthermore, it performs the following actions.

The road surface condition detecting means M5 detects the state of the road surface on which the vehicle is traveling based on the change in the damping force setting by the damping force control means M3, for example, the switching frequency and switching cycle in a configuration in which the damping cover turns are switched in several stages. Detect. When it is determined that either a flat road or a rough road continues based on the road surface state detected in this way, the damping force adjustment correction means M6 controls the damping force controlled by the damping force control means M3. The force setting is corrected to the average value of the damping force set respectively on flat roads and rough roads.

As a result of this correction, for example, when an extremely flat road continues for a predetermined period or longer, the damping force generation pattern of the shock absorber S is corrected from a large damping force setting to a small one, resulting in two consecutive runs on a rough road. In this case, the damping force is corrected from a small setting to a large damping force. As a result, deviations in the damping force generation pattern are quickly corrected, resulting in suspension characteristics with an excellent balance between shock absorption and ground contact.

The damping force that has been corrected and set after switching as described above is continued and maintained within the correction range by the damping force switching and holding means M4 for a certain period of time after switching, as described above. However, the holding period is corrected based on the state of the previous damping force correction by the damping force correction adjustment means M6. That is, once the damping force adjustment correction means M6 judges the road surface condition and corrects the damping force, the holding period correction means M7 switches the damping force after a period corresponding to the road surface condition reflected in the correction. Therefore, the period during which the damping force state set within the correction range is maintained, that is, the holding period is corrected.

In this way, in the suspension control device of the present invention, the 8-holding period after switching the damping force setting is corrected based on the correction that reflects the road surface condition by the damping force correction adjustment means M6, so that It becomes possible to appropriately switch the damping force accordingly.

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.

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

FIG. 2 is a schematic configuration diagram showing the overall configuration of this suspension control device 1, FIG. 3(A) is a partially cutaway sectional view of the shock absorber, and FIG. 3(B) is a main part of the shock absorber. FIG.

As shown in FIG. 2, the suspension control device 1 of 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, 5 respectively.
RL, 5RR suspension lower arm 6FL
, between 6FR, 6RL, 6RR and the vehicle body 7,
Coil springs 8FL, 8FR.

It is located alongside 8RL and 8RR.

Shock absorber 2FL, 2FR, 2RL,
2RR [as described later, shock absorber 2FL
, 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 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 FL corresponding to left rear wheel 5R1, right rear wheel 5RR,
F.R.

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

The shock absorber 2, as shown in FIG. 3(A),
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 upper end of the rod 13 inserted through the cylinder]1 is fixed to the suspension lower arm 6 via the bearing 7a and the vibration isolating rubber 7b. It is fixed to the vehicle body 7 together with a coil spring 8.

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 18 that slides along the inner peripheral surface of the cylinder 11 are disposed. An internal cylinder 15 connected to the rod 13 of the shock absorber 2 houses a piezo load sensor 25 and a piezo actuator 27 .

The main piston 18 is fitted onto the outside of the cylindrical member 17, and a sealing material]9 is interposed on the outer periphery of the main piston 18, which fits into the cylinder 11. Therefore, the inside of the cylinder 11 is divided into a first liquid chamber 21 and a second liquid chamber 23 by the main piston 18. A backup member 28 is screwed onto the tip of the cylindrical member 17, and between the cylindrical member 17 and the main piston 18,
Spacer 29 and leaf valve 30 on the cylindrical member 17 side,
Backup member 28 for leaf valve 31 and collar 32
Each side is pressed and fixed. Further, a main valve 34 and a spring 35 are interposed between the leaf valve 31 and the backup member 28.
1 in the direction of the main piston 18.

These leaf valves 30, 31 are connected to the main piston 18.
When the main piston is stopped, the extension side and the contraction narrow passage 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 18 moves, the hydraulic oil filled in both the liquid chambers 21 and 23 flows through both passages 18a and 23.
18b, and moves between the two liquid chambers 21 and 23. In this manner, when the movement of hydraulic oil between the two liquid chambers 21 and 23 is limited to both passages 128a and 18b, the damping force generated against the movement of the rod 13 is large, and the suspension characteristics are hard. becomes.

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
The spool 41, 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 filler 45a provided in the plate valve 45.
As a result, when the spool 41 moves in the direction of arrow B, the first liquid chamber 21 and the second liquid chamber 2
The flow rate of the hydraulic oil flowing between 3 and 3 increases. In other words, when the piezo actuator 27 expands due to high voltage application, the shock absorber 2 switches its damping force characteristic from a high damping force (hard) state to a low damping force (soft) state, and when the electric charge is discharged and contracts, the shock absorber 2 attenuates. Change the force characteristics to large damping force (
hard) state.

The amount of movement of the leaf valve 31 provided on the lower surface of the main piston 18 is controlled by a spring 35.
It is regulated compared to Further, the plate valve 45 is provided with an oil filler 45b having a larger diameter than the oil filler 45a on the outside of the oil filler 45a, and the plate valve 45 is connected to the spring 4.
When it moves in the direction of the bush 39 against the urging force of 6, the hydraulic oil becomes movable through the oil reservoir 45b. Therefore,
Regardless of the position of the spool 4], the main piston 1
The hydraulic oil flow rate when the main piston 18 moves in the direction of the arrow B is larger than when the main piston 18 moves in the direction of the arrow B. In other words, the damping force is changed depending on the direction of movement of the main piston 18, and the characteristics as a shock absorber are changed. 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 21 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 generation pattern of the damping force of the shock absorber 2 described above will be explained using FIG. 4.

This electronic control device 4 includes a piezo load sensor 25 (tL) of each shock absorber 2 as a sensor for detecting the running state of the vehicle;
A vehicle speed sensor 51 that detects the running speed of the vehicle, 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 depressed, etc. are connected. has been done.

The electronic control device 41 outputs control signals to the piezo actuator 27 based on these detection signals and the like, and the well-known CPLI 61. ROM62. It is constructed as an arithmetic and logic operation circuit centering on a RAM 64. Input and output with the outside is performed through an input section 67 and an output section 68 which are connected to each other 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 voltage connected to the piezo actuator 27. An application circuit 75 receives power from a battery 77 via an ignition switch 76, and converts the voltage of the battery 77 into a so-called switching regulator type high voltage power supply circuit 79 which outputs a drive voltage for driving a piezo actuator 6-. A constant voltage power supply circuit 80 that generates an operating voltage (5V) for the electronic 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;
High voltage application circuit 75. The high voltage power supply circuit 79 has an output section 68
are connected to each.

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 (Yo) This circuit shapes the detection signals from the steering sensor 50 and vehicle speed sensor 51 into signals suitable for processing in the CPLJ 61 and outputs them. Therefore, the CPU 6
1 is this damping force change rate detection circuit 70 and waveform shaping circuit 7
It is possible to determine the road surface condition, the driving condition of the vehicle, etc. based on the output signals from 3 and the own processing results. Based on this determination, the CPU 61- outputs a control signal to the high voltage application circuit 75 provided corresponding to each wheel.

This high voltage application circuit 75 is a circuit that applies a voltage of +500 volts or 1100 volts output from the 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 characteristic of each shock absorber 2 is such that when a high voltage is applied to extend the piezo actuator 27, the first damping force in the shock absorber 2 is 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 piezo actuator 27 is contracted by discharging the electric charge with a negative voltage, the hydraulic oil Since the flow rate decreases, the damping force becomes large. Note that once the electric charge accumulated in the piezo actuator 27 is discharged, the piezo actuator 27 remains in a contracted state even if the negative voltage is removed, and the shock absorber 2 maintains a state with a large damping force. .

Next, the damping force control performed by the suspension control device 1 of this embodiment having the above-described configuration will be explained in FIGS. 5 and 6.
This will be explained based on the flowcharts shown in FIGS. Each routine shown in each figure is repeatedly executed at fixed time intervals by interrupt processing.

Note that these processes apply to each shock absorber 2 of each wheel.
Although the processing is executed for each of the FL, FR, RL, and RR, there is no difference in the processing for each wheel, so the description will be made without making any particular distinction. The processing contents of each routine are as follows.

■ Damping cover turn switching control routine (Fig. 5) 9- Piezo actuator 27 based on the rate of change of damping force V
to set the damping force to a large or small state.

■ Frequency detection interrupt routine (Fig. 6) The rate of change of damping force within a predetermined time reaches the learning reference value V re
The number of times that fG is exceeded is detected as frequency N.

■ Learning process implementation routine for implementing switching reference value V ref learning process, etc. (FIG. 7) The switching reference value V ref used for switching the damping force is learned and corrected based on the magnitude of the switching frequency N.

Also, based on the correction of the switching reference value V ref, the flag referred to in the above-mentioned (2) damping cover turn switching control routine is set/reset.

The above-described frequency detection interrupt routine and learning process execution routine mutually refer to the time measurement variable C1 frequency N to learn the switching reference value V ref. Using this learned switching reference value V ref and referring to the flag processed in the learning process execution routine, the damping cover turn switching control routine executes damping force switching control. The details of each routine will be described with reference to FIG. 8, which shows the relationship between the switching reference value V ref and the damping force change rate V, the control state of the suspension 2, etc.
The attenuation cover turn switching control routine (FIG. 5) will be explained in order.

When this routine starts, first, the rate of change in damping force of each shock absorber 2 is read from the damping force change rate detection circuit 70 via the input section 67 (step 100), and this damping force change rate V is , it is determined whether or not it is larger than the switching reference value V ref learned in the learning process implementation routine (FIG. 7) (step 105). If the damping force change rate V is smaller than the switching reference value V ref, it is determined whether the flag FliS indicating that the suspension characteristics are set to soft is 1 (step 110), and the flag FH5 is set to soft. If the value is not 1, that is, if it is not set to soft, the suspension is controlled to be hard (step 115), and this routine is temporarily terminated. In addition, in the process of step 115, immediately after the damping force setting of the shock absorber 2 is switched from soft to hard, 1100 volts is applied from the high voltage application circuit 75 to the piezo actuator 27 by the control signal from the output section 68. This is done by applying a voltage, contracting it, and if the piezo actuator 27 is already in a contracted state, it is held as it is.

On the other hand, when the damping force change rate V becomes larger than the switching reference value V ref (time tl in FIG. 8), (step 105)
, refers to the flag Finc that is processed in a routine for implementing learning processing, etc., which will be described in detail later (step 120). Flag F
inc is set to the value 1 when the switching reference value V ref is corrected to be larger by the learning process. When the correction is made to a smaller value (2 is the flag that is reset to the value O.As will become clear in the later explanation of the learning processing etc. execution routine, when the flag Finc is set to the value 1, the flag is reset to the value O. It can be assumed that the road surface on which the vehicle is running immediately before the routine is carried out is rough.

If the flag Finc is set to value], the variable T
Step 12: Set the reference value T b long to s.
5) On the other hand, if the flag Finc has been reset to the value O, the reference value Tb5hrt is set to the variable Ts (step 130).

The reference values T b long and T b 5hrt are both values set to maintain the damping force in that state for a certain period of time after the damping force setting is switched from large to small, and The reference value T b long is greater than the reference value Tb 5hrt. Therefore, if the variable Ts is set to the reference value T b long, the time during which the damping force is kept small becomes longer, and the reference value Tb5hrt
If set to , the time will be shortened.

After step 125 or 130, the timer is started, that is, the timer variable is set to the value O (step 135), and the flag FHS is set to the value 1 to set the suspension characteristics to soft. Then, processing is performed (step 140). after that,
Step 14: Apply a high voltage of +500 volts 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.
5) End this routine.

23- After switching the damping force of the shock absorber 2 to a small state in this way, the damping force change rate V becomes the switching reference value V ref
If it exceeds the switching reference value Vref, the above-mentioned setting of the variable Ts, start of the timer, and control to reduce the damping force are repeated. However, when the damping force change rate V becomes less than the switching reference value Vref, the flag "1" is set. Check the value of -1s (step 110), and if the value of the flag FHS is 1, the timer variable Ts has become a definite value (reference value Tblon).
g or Tb5hrt) is exceeded (step 150).

If the timer variable is less than the determined value Ts, the timer variable is incremented by 1 and the process of controlling the damping force of the shock absorber 2 to a small state is continued (steps 155 and 145). Therefore, the suspension is kept soft.

After that, if the damping force change rate V exceeds the switching reference value Vref again before the time corresponding to the fixed value Ts has elapsed, at that time (t2 in Figure 8), the setting of the variable Ts and the timer The process moves to steps 120 to 145 in which control is performed to reduce the start and damping force.

On the other hand, after the damping force of the shock absorber 2 is switched from large to small (after time t1 in FIG. Until the time (time corresponding to the value Ts) has elapsed,
Unless the damping force change rate V exceeds the switching reference value V ref (this condition is satisfied at time t3 in FIG. 8(A)).
to t4 (from time t3 to t5 in FIG. 8(B)), the determination at step 150 is rYESJ, and the flag FH3 is reset to the value O (step) 60.
The damping force of the shock absorber 2 is controlled to a large state (step 115).

As described above, when this routine is repeatedly executed, the damping force of the shock absorber 2 of each wheel changes when the damping force change rate V exceeds the switching reference value V ref (time t in Figure 8).
l), based on the result of the flag Finc that was immediately set to a small state and referenced at time t3 in FIG.
g or T b 5hrt, and during that time (reference value T
b long or Tb5hrt), return the damping force setting from the small state to the large state.

Next, a routine (see Fig. 6) for detecting the change frequency N of the damping force change rate V used to determine the switching reference value V ref for damping force switching referred to in this damping force switching control routine (see Fig. 5) is performed. ) will be explained.

When this interrupt routine is started, a process is first performed in which a variable C that counts the number of executions of this routine is incremented by a value of 1 (step 200), and then it is determined whether the current suspension setting is hard or soft. is performed (step 210). The damping cover turn of the shock absorber 2 is controlled by the damping cover turn switching control routine shown in FIG. 5, and the current pattern is determined to be soft by referring to the value of the flag FHS. ref is multiplied by the value 0.8 x 0,5 (step 212), and if it is determined to be hard, the current switching reference value V ref is multiplied by the value 0.8 (step 214), and each learning reference value is set. Calculate V refG.

After determining the learning reference value V refG in this way, it is determined whether the current damping force change rate V is larger than the learning reference value V refG (step 220). If the damping force change rate V is equal to or less than the learning reference value V refG, the flag "" is reset to the value 0 (step 230), and this routine is immediately terminated.

On the other hand, if it is determined that the damping force change rate V exceeds the learning reference value V refG, check the value of the flag F (step 240), and check the value of the flag F (step 240). Immediately after exceeding the learning reference value VrefG, the frequency N is incremented by the value 1 in step 2.
50), and sets the value 1 to the flag FF (step 26).
0), this routine is temporarily ended. Therefore, this flag FF indicates that the damping force change rate V exceeds the learning reference value V refG, and the frequency N is not incremented during that time (step 2).
7 whelk 240). In other words, the frequency N is incremented only when it is newly determined that the damping force change rate V exceeds the learning reference value V refG.

By repeatedly executing the frequency detection interrupt routine described above, the learning reference value V refG is updated based on the switching reference value ref, and the frequency N in which the damping force change rate exceeds the learning reference value V refG is determined. A process of detecting this will be performed.

Next, a learning process for learning the switching reference value V ref used in this process and a learning process for setting/resetting the flag Finc used in the attenuation cover turn switching control routine will be described below.

As shown in FIG. 7, when the learning processing etc. execution routine is started, first, the stop lamp switch 53. Steering sensor 50, vehicle speed sensor 5], etc. are used to read the driving conditions (step 300).
), and based on the running state, it is determined whether or not to perform anti-dive, anti-roll, etc. control 28- (step 310).
. When the brake is stepped on or the steering wheel is suddenly turned, anti-dive processing etc. are performed, and the switching reference value V ref is changed in preparation for these processing (step 315), and this routine continues as is. finish.

On the other hand, if it is determined that the running state of the vehicle does not require anti-dive processing, it is determined whether the variable C has become equal to the value i (step 320).
is a value that is incremented each time the frequency detection interrupt routine shown in FIG. It is determined whether or not the set amount of time has elapsed. The number of executions of the frequency detection interrupt routine is small (C
1) If it is determined that the timing to judge the frequency has not arrived yet, exit to rRTNJ and temporarily end this routine.

Each time the frequency detection interrupt routine is executed, the determination at step 320 is rY E SJ, and then the variable C
(step 330), and read the vehicle speed SP (step 330).
Step 340) is executed.

Based on the vehicle speed Sp read in this way, a process is then performed to calculate the reference base value vbase (step 3).
50). The reference base value Vbase is the switching reference value V r
This is to set the magnitude of ef to a value according to the vehicle speed Sp, and as shown in FIG. 9, the function fl(Sp
) is determined as

Next, a process is performed to obtain a frequency deviation △N between the frequency N counted in the frequency detection interrupt routine (Fig. 6) and a preset frequency reference value Nref (step 360), and this frequency deviation △N is , is greater than, less than, or equal to the value O (step 370). If the frequency deviation ΔN is smaller than the value O, after decrementing the correction value ΔV by the value β, the flag Finc is reset to the value 01 (steps 380, 390);
If N is larger than the value O, the correction value △V is incremented by the value β, and then the flag Fine is set to the value 1 (
Steps 400, 410). Incidentally, if the frequency deviation ΔN is equal to the value O, the flag Finc is reset to the value 01 with the correction value unchanged (steps 420, 3).
90).

After step 390 or 410, by adding the correction value ΔV to the reference base value V base, the switching reference value V
A process of calculating ref is performed (step 430).

As a result, the switching reference value V ref is changed according to the vehicle speed Sp, but the correction value △V learned up to that point is saved.
It will continue to be used.

Thereafter, the frequency N is reset to the value O in preparation for subsequent frequency detection (step 440), and this routine ends.

By executing the learning process etc. execution routine described above, the switching reference value V ref is set based on the vehicle speed Sp,
Learning is performed based on the frequency N. Also,
When the switching reference value Vref becomes large, the flag Fi
If nc is set to the value 1 and the bill switching reference value V ref becomes small or remains unchanged, the flag Finc is set to
It is reset to the value 0 and becomes 1-. That is, if the (-) damping force change rate V frequently exceeds the learning reference value V refG, the flag Finc will be set to the value 1, and this is because the vehicle was running immediately before this routine was executed. This means that the road you are on is rough. This also means that the road surface on which the vehicle will be traveling immediately after this is likely to be rough.

(d) On the other hand, the damping force change rate V is the learning reference value V refG
If the frequency of exceeding (Y) is low, the flag Finc will be reset to the value O, which means that the road surface on which the vehicle is traveling immediately before this routine is executed is relatively flat. This means that there is a high possibility that the road surface on which the vehicle will drive immediately after is also relatively flat.

By executing the processes shown in the flowcharts of FIGS. 5 to 7 explained above, the switching reference value is changed from the time when the damping force change rate V exceeds the switching reference value V ref (time tl in FIG. 8). Until Vref is no longer exceeded (time t3 in FIG. 8), the setting of the damping force of the shock absorber 2 is maintained at a small state. Then, just before time t3, the switching reference value V r
If ef has been corrected to be large, it is determined that the road surface on which the vehicle is traveling after time t3 is likely to be rough, and the damping force of the shock absorber 2 is maintained for a relatively long period of time T b long. The setting is kept small (FIG. 8(A)).

On the other hand, if the switching reference value V ref is corrected to be small just before time t3, it is determined that the road surface on which the vehicle is traveling at time t341 is likely to be relatively flat, and the The damping force of the shock absorber is maintained in a small state for a short period of time (FIG. 8(B)).

In this way, the suspension control device 1 of the present embodiment switches the holding period depending on the road surface condition, and at the same time, the switching reference value V ref is learned and corrected, so that the switching of the damping force is made easier. [1] When the damping force change rate V is not so large and the damping force characteristic of the shock absorber 2 is controlled to be large, the learning reference value V refG
is calculated as a value of 80% of the switching reference value V ref (step 214 in FIG. 6), and the damping force change rate V reaches the switching reference value V in a predetermined period (period corresponding to the count value 1).
The frequency N exceeding ref is a small value. Therefore, the switching reference value V ref is learned to be smaller by the value β (step 380 in FIG. 7). As a result, the damping force change rate V easily exceeds the switching reference value V ref, and the damping force can be switched to a small state even when the vehicle is traveling on a flat road and there are small irregularities. Even if the damping force is switched in this way, the switching reference value V ref is corrected to be smaller, so the damping force setting of the shock absorber 2 is determined to be such that the road surface on which the vehicle is running is not so rough. is held in a small state only for a short time, and then immediately changed to a large state. Therefore, even in situations where the road surface does not continue to be rough, the suspension settings return to hard within a short period of time, and ride comfort is maintained.

As described above, when the vehicle runs on a flat road, the damping force change rate V
is relatively small and the suspension tends to be maintained hard, the switching reference value V ref is gradually decreased by detecting the frequency N, updating the switching reference value ref, and learning the learning reference value V refG. Therefore, the shock absorber 2 can be easily switched to a state with a small damping force. As a result, when the vehicle continues to drive on a flat road, small irregularities on the road surface, which have been a problem in the past, can be dealt with appropriately, and ride comfort is significantly improved. Further, by referring to the correction of the learning reference value VrefG, the suspension settings are not kept soft for an unnecessarily long period of time, and the ground contact performance is not impaired.

[11] On the other hand, the damping force change rate V is equal to the switching reference value Vre
f is frequently exceeded and the suspension characteristics are softly controlled, the learning reference value V refG continues to be calculated as a value of 40% of the switching reference value V ref (6th
Step 212), the frequency N in which the damping force change rate V exceeds the switching reference value Vref□ during a predetermined period (period corresponding to the count value i) becomes a large value.

Therefore, the switching reference value V ref is learned to a large value (step 410 in FIG. 7). If the switching reference value V ref has been corrected to become larger in this way, it can be concluded that the road surface on which the vehicle is driving continues to be quite rough.2 Keep the damping force in a small state. Increase the time (continuously hold for a time corresponding to the reference value T b long). Therefore, the frequency of switching the damping force does not become unnecessarily high. As a result, there is no discomfort when driving the vehicle, and the durability of the shock absorber 2 is also improved.

In this way, once the damping force is set to a small state, that state is maintained for a long time depending on the road surface condition, but if the vehicle continues to drive on a rough road for a long time, the switching reference value V r
As ef is gradually increased, the damping force of the shock absorber 2 becomes easier to maintain gradually in a large state. As a result, it is possible to suitably deal with insufficient ground contact, which has been a concern in the past when driving on rough roads, so-called lack of stiffness in the suspension, and the steering stability is significantly improved.

[II+] In addition, in this example, the length of the holding time for keeping the damping force setting at a small state is determined by the flag Finc, and the flag Finc is set for a certain period of time immediately before the holding time is determined. =36~ Since the damping force faithfully reflects the road surface conditions on which the vehicle traveled, the damping force closely reflects the road surface conditions.

As described above, according to the suspension control device of this 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 the above embodiment, if the switching reference value V ref is not corrected, the flag Finc is reset to the value O. In that case, the holding period is only Tb5hrt. This is because steering stability is more important than ride comfort. If ride comfort is more important than handling stability, the holding period may be set to Tblong if the switching reference value Vref is not corrected.

Further, in the above embodiment, the holding time for keeping the damping force setting in a small state is set to either T b long or Tb5hrt, but the switching reference value V ref may be corrected by an amount corresponding to the frequency deviation △N. , the holding time (ie, the variable Ts) may be set according to a function of the correction amount. In this configuration, the holding period is proportional to the roughness of the road surface on which the vehicle travels, so the setting of the damping force becomes more responsive to the road surface condition.

Although several embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way.
For example, there is a configuration in which the reference value correction amount Vrvs is referred to in the form of a three-dimensional map of the frequency deviation ΔN and the vehicle speed, a configuration in which the frequency deviation ΔN is determined based on the number of times the damping force is actually switched, or a configuration in which the frequency deviation ΔN is calculated based on the number of times the damping force is actually switched, or the frequency reference value N ref Each front, rear, left and right wheel 5F
It goes without saying that the invention can be implemented in various ways without departing from the spirit of the invention, such as a configuration in which different values are used for each of L, FR, RL, and RR.

Effects of the Invention As detailed above, according to the suspension control device of the present invention, the holding period of the damping force setting after switching is determined based on the magnitude relationship between the damping force change rate and the adjustment reference value. ,
Since the damping force is corrected based on the damping force correction that reflects the road surface conditions of the damping force adjustment correction means, the damping force setting that has been switched can be continued for a period of time depending on the road surface condition on which the vehicle is traveling. be effective. Therefore, for example, when driving over a small step on a relatively flat road, the damping force setting tends to return to hard in a short period of time, whereas when driving on a rough road, the damping force setting continues to be set to soft (maintaining two). As a result, the damping force setting is not unnecessarily maintained at a soft setting for a long period of time, thereby impairing ground contact, or the damping force setting is not changed frequently, causing the driver to feel uncomfortable. In addition, there are also benefits to the durability of the device.

In particular, in the present invention, the decision to increase or decrease the period during which the damping force setting is held is made in accordance with the damping force correction that reflects the road surface condition on which the vehicle was traveling immediately before the decision, so it is extremely accurate to the road surface condition. Suspension control can be carried out according to the conditions.

Furthermore, according to the suspension control device of the present invention, if the condition of either a flat road or a rough road continues, the damping force setting by the damping force control means is corrected. It can effectively deal with small irregularities on rough roads, significantly improving ride comfort, and also solving the problem of insufficient ground contact, or lack of stiffness in the suspension, which has been a concern in the past when driving on rough roads. It can be dealt with in a suitable manner, and has the extremely excellent effect of significantly improving steering stability and maintaining a good driving feeling. Therefore, according to the suspension control device of the present invention, it is possible to achieve both ride comfort and steering stability of the vehicle when driving on flat roads and rough roads with good responsiveness.

[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 part of the shock absorber=40=bar 2, FIG. 4 is a block diagram showing the configuration of the electronic control device 4 of this embodiment, FIG. 5 is a flowchart showing the damping cover turn switching control routine, FIG. 6 is a flowchart showing the frequency detection interrupt routine. FIG. 7 is a flowchart showing the learning processing etc. execution routine.
A graph showing the relationship between switching reference value Vref and damping force change rate V, control status, etc., Figure 9 shows vehicle speed SP and reference base value V
This is a graph showing the relationship with base. 1... Suspension control device 2 FL, FR, RL, RR... Shock absorber 4... Electronic control device 25 FL, FR, RL, RR... Piezo load sensor 27 FL, FR, RL, RR... ... Piezo actuator 51 ... - Vehicle speed sensor 70 ... Damping force change rate detection circuit

Claims (1)

[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 the rate of change in the damping force of the shock absorber, and a damping force change rate detection means that detects the rate of change in the damping force detected by the shock absorber. and a damping force control means for changing the damping force setting of the shock absorber based on the magnitude relationship between the damping force and the damping force adjustment reference value, and when the damping force setting is changed by the damping force control means. ,
and a damping force switching and holding means that continues the damping force setting after the change for a predetermined holding period. a road surface condition detection means for detecting the condition of the road surface on which the vehicle is traveling; and when it is determined that either the flat road or the rough road condition continues based on the detected road surface condition, the damping force is increased. a damping force adjustment correction means for correcting the setting of the damping force controlled by the control means to the average value of the damping force set respectively on a flat road and a rough road; A suspension control device comprising: a holding period correcting means for correcting a holding period in the damping force switching holding means based on the situation of the immediately preceding correction.