JPH03178820A - Suspension control device - Google Patents

Abstract

PURPOSE:To control a suspension, depending upon a road condition by retaining the setting of a changed damping force for the predetermined time when the damping force is changed from a high level to a low level, and making an increasing correction for the retaining time, if a road surface is rough during that time, respectively in the subject suspension control device having a damping force variable cushioning device. CONSTITUTION:The damping force change rate of a shock absorber M1 is detected with a damping force change rate detection means M2, and a damping force control means M3 changes the setting of a damping force, according to a relationship in magnitude between the damping force and a reference value for damping force adjustment. When the damping force is changed from a high level to a low level, a damping force changeover retaining means M4 retains the changed setting level for the predetermined time. During this retaining time, a road condition judgement means M5 judges the rough state of a travel road. when the road is judged to be rough, a retaining time correction means M6 increasingly corrects the retaining time. According to the aforesaid construction, a road condition can be reflected on the control of a suspension S.

Description

[Detailed Description of the Invention] [Industrial Field of Application] 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 that is equipped with a shock absorber that can vary the setting of damping force, and that adjusts 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 force is increased based on unevenness of the road surface, brake operation, etc. It is known that when a sudden change occurs, the generation pattern of the damping force against the movement of the shock absorber is quickly switched to a smaller value (for example,
4-67407). Since the rate of change in damping force is a signal with extremely high responsiveness, these suspension control devices 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] Although this suspension control device uses the rate of change of damping force (it has excellent responsiveness), the signal of the rate of change is not used as the standard for adjustment, such as when driving on rough roads. When the damping force goes up or down in a short period of time, the damping force settings are changed one by one according to the magnitude relationship with respect to the adjustment reference value. If the damping force setting exceeds this value, it is necessary to maintain the damping force setting for a certain period of time. However, simply continuing that state for a certain period of time after switching the damping force setting is insufficient to adequately respond to the road surface condition. There was a problem that there was no
When driving on a so-called rough road, the rate of change in damping force fluctuates dramatically up and down, so it is important to maintain a soft damping force generation pattern for a short period of time ('L damping force switching frequency becomes high). It also has a negative effect on the durability of the shock absorber.On the other hand, if the period of keeping the shock absorber soft is too long, when driving on a relatively flat road surface, after going over a small bump etc. This causes the problem that the damping force setting is kept soft for an unnecessarily long period of time, resulting in a loss of ground contact.As a result, the drive feeling may deteriorate.

The suspension control device of the present invention solves the above problems,
The purpose of this invention is to control the setting of damping force using the damping force change rate in accordance with road surface conditions.

The configuration of the present invention that achieves the above objectives will be described below.

[Means for Solving the Problems] A suspension control device of the present invention (1: as illustrated in FIG. 1).

A shock absorber M1 provided in the suspension S of the vehicle is capable of setting a generation pattern of damping force; a damping force change rate detection means M2 that detects a rate of change in the damping force of the shock absorber M1; Based on the magnitude relationship between the rate of change of and the reference value for damping force adjustment,
a damping force control means M3 for changing the damping force setting of the shock absorber M]; damping force switching and holding means M4 that lasts for a holding period; road surface condition determining means M5 that judges whether the road surface on which the vehicle has traveled within the holding period is rough; and the road surface condition determining means M5 determines that the road surface is rough. and a retention period correction means M6 for increasing the retention period when the retention period is exceeded.

[Operation] The suspension control device of the present invention having the above configuration (9) detects the rate of change in the damping force of the shock absorber M1 provided in the suspension S of the vehicle by the damping force change rate detection means M2, and detects the rate of change in the damping force. The damping force control means M3 changes the setting of the damping force of the shock absorber M1 based on the magnitude relationship between the damping force adjustment reference value and the damping force adjustment reference value.

When the damping force setting is changed from large to small by the damping force control means M3, the damping force set to a small value is maintained for a predetermined holding period by the damping force switching and holding means M4.

The degree of roughness of the road surface on which the vehicle traveled during the holding period is determined by the road surface condition determination means M5, and it is determined that the road surface is not rough. (The holding period correction means M6 increases the period during which the damping force setting is kept small.

Therefore, in the suspension control device of the present invention, the damping force setting is switched to a small state (1), and this state is always maintained for a certain period or more, and during that period, depending on the roughness of the road surface on which the vehicle is traveling, the damping force setting is changed to a small state. It is determined whether to discontinue the setting of the damping force that has been set or to increase the holding period of the reduced damping force, making it possible to appropriately switch the damping force depending on the road surface condition.

Incidentally, such control may be carried out independently for each wheel, or may be carried out in common for the two front wheels and the rear two wheels, or may be carried out in common for all wheels.

[Examples] In order to further clarify the structure and operation of the present invention described above, first, 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 this 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 device 4.

Each shock absorber 2FL, 2FR, 2RL,
2RRt, 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,
2RRf As will be explained 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 they all have the same structure, the shock absorber 2FL on the left front wheel Sr1 side will be explained here as an example. In addition, in the following explanation, the numbers of each member provided on each wheel (above) will be changed as necessary to indicate left front wheel 5, right front wheel 5, Subscripts FL, F
R.

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

As shown in FIG. 3(A), the shock absorber 2 is fixed to the suspension lower arm 6 at the lower end on the cylinder 11 side via the axle side member 11a. At the upper end, it is fixed to the vehicle body 7 together with a coil spring 8 via a bearing 7a and a vibration isolating rubber 7b.

Inside the cylinder 11 (internal cylinder 15 connected to the lower end of the rod 13, connecting member 16 and cylindrical member) 7
and a main piston 18 that is slidable along the inner circumferential surface of the cylinder 11. Shock absorber 2
A piezo load sensor 25 and a piezo actuator 27 are housed in an internal cylinder 15 connected to a rod 13.

The main piston 18 is fitted onto the outside of the cylindrical member 17, and a sealing material 19 is interposed on the outer periphery that fits into the cylinder 11. Therefore, the main piston 18 allows the first liquid to be It is divided into a chamber 21 and a second liquid chamber 23. A backup member 28 is screwed to the tip of the cylindrical member 17, and a spacer 29 is provided between the cylindrical member 17 and the main piston 18. The leaf valve 30 is pressed and fixed on the cylindrical member 7 side, and the leaf valve 31 and collar 32 are respectively pressed and fixed to the backup member 28 side. A valve 34 and a spring 35 are interposed, and the leaf valve 31 is connected to the main piston 18.
It is biased in the direction.

These leaf valves 30, 31 [i.

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, the hydraulic oil (
As the main piston 18 moves, both passages 18a
, 18b, and moves 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 suspension characteristics are hard. Become.

A piezo load sensor 2 is housed inside the internal cylinder 15.
5 and piezo actuator 27 (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, the output of the piezo load sensor 25 can be taken out as a voltage signal by a circuit with a predetermined impedance. rate can be detected.

The piezo actuator 27 (which 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) 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 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. The flow path 17 in the cylindrical member 17 passes through this sub flow path 39blt and an oil filler 45a provided in the plate valve 45.
Since the spool 41 is moved in the direction of the arrow B, the flow rate of the hydraulic oil flowing between the first liquid chamber 21 and the second liquid chamber 23 increases as a result. In other words,
Shock absorber 2 (Zhi piezo actuator 27)
When it expands due to high voltage application, its damping force characteristics switch from the state of high damping force (hard) to the damping wheel (soft) side, and when the electric charge is discharged and contracts, the damping force characteristic changes to the state of high damping force (hard). restore the condition.

The amount of movement of the leaf valve 31 provided on the lower surface of the main piston 18 is regulated by the upper spring 351 compared to the leaf valve 30.
5 (the oil container 45b, which has a larger diameter than the oil container 45a,
When the plate valve 45 moves in the direction of the bush 39 against the biasing force of the spring 46, it can move through the hydraulic oil (upper oil inlet 45b). Therefore, the position of the spool 41 Regardless of the case, the flow rate of hydraulic oil when the main piston 18 moves in the direction of arrow B is greater than when the main piston 18 moves in the direction of the arrow.In other words, the damping force varies depending on the direction of movement of the main piston 18. In addition, a hydraulic oil supply path 38 is provided between the oil-tight chamber 33 and the first liquid chamber 2 along with a check valve 38a. , the flow rate of hydraulic oil in the oil-tight chamber 33 is kept 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 for each shock absorber 2 as a sensor for detecting the running state of the vehicle, a steering sensor 50 for detecting the steering angle of a steering wheel (not shown), and a steering sensor 50 for detecting the steering angle of a steering wheel (not shown), and a steering sensor 50 for detecting the steering angle of a steering wheel (not shown). A vehicle speed sensor 51 that detects a shift position of a transmission (not shown), a shift position sensor 52 that detects a shift position of a transmission (not shown), a stop lamp switch 53 that issues a signal when a brake pedal (not shown) is depressed, and the like are connected.

The electronic control device 4 outputs control signals to the piezo actuator 27 described above based on these detection signals, etc. (configured as an arithmetic and logic operation circuit centered on the well-known CPU 61, ROM 62, and RAM 64, and communicates with these through a common bus 65). The connected input section 67 and output section 68 perform input/output with the outside.

In addition to the electronic control unit 4, the piezo load sensor 25
, a waveform shaping circuit 73 connected to the steering sensor 50 and vehicle speed sensor 51 , a high voltage application circuit 75 connected to the piezo actuator 27 , and an ignition switch 76 connected to the battery. A so-called switching regulator type high voltage power supply circuit 79 receives power supply from 77 and outputs a drive voltage for driving the piezo actuator, and transforms the voltage of the battery 77 to generate an operating voltage (5V) for the electronic control unit 4. A constant voltage power supply circuit 80 and the like are 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 the output is output from the 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
CPtJ6 as damping force change rate of shock absorber 2
It is configured to output to 1. In addition, a waveform shaping circuit 73 (above) is a circuit that shapes the detection signal from the steering sensor 50 and vehicle speed sensor 51 into a signal suitable for processing in the CPU 61 and outputs the waveform.
1L! ,.

Based on the output signals from the damping force change rate detection circuit 70 and the waveform shaping circuit 73, as well as its own processing results, the road surface condition, vehicle running condition, etc. can be determined. C.P.
Based on this determination, U61 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, this attenuation In response to the force switching signal, the piezo actuator 27 expands (when +500 volts is applied) or contracts (when -100 volts is applied), the hydraulic oil flow rate is switched, and the damping force characteristic of the shock absorber 2 is switched between soft and hard. In other words, the damping force characteristics of each shock absorber 2 (by applying a high voltage to the piezo actuator 27
When the spool 4 is extended (see Fig. 3 (B)), the hydraulic oil flowing between the first liquid chamber 21 and the second liquid chamber 23 in the shock absorber 2 is expanded. As the flow rate increases, the damping force becomes small, and when the piezo actuator 27 is contracted by discharging the charge with a negative voltage (as the hydraulic oil flow rate decreases, the damping force becomes large). , piezo actuator 2
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 1 of this embodiment having the above-described configuration will be explained based on the flowcharts shown in FIGS. 5, 6, and 7. Each routine shown in each figure is repeatedly executed at regular intervals by interrupt processing.

It should be noted that these processes are executed for each of the shock absorbers 2 FL, FR, RL, and RR of each wheel, but since there is no difference in the process for each wheel, the explanation will be made without making any particular distinction. The processing contents of each routine are as follows.

(2) Damping cover turn switching control routine (Fig. 5) The piezo actuator 27 is switched based on the rate of change V of the damping force, and the damping force is set to a large state or a 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 processing implementation routine for implementing switching reference value V ref learning processing, etc. (FIG. 7) The switching reference value V ref used for switching the damping force is learned based on the magnitude of the switching frequency N. Furthermore, based on the switching frequency N, the roughness of the road surface on which the vehicle was traveling while the damping force was maintained in a small state is determined.

The above-described frequency detection interrupt routine and learning processing execution routine (time measurement variable C1 frequency Nt) learn the switching reference value V ref by referring to each other, and using the learned switching reference value V ref, The damping cover turn switching control routine executes the damping force switching control based on the judgment result of the road surface condition in the learning process execution routine.The damping cover turn switching control routine executes the damping force switching control. The details of each routine will be explained in order from the attenuation cover turn switching control routine (FIG. 5) with reference to FIG.

When this routine is started, first, the damping force change rate V of each shock absorber 2 is read from the damping force change rate detection circuit 70 via the input section 67 (step 100), and the damping force change rate V is larger than the switching reference value V ref learned in the learning process implementation routine (FIG. 7) (step 105). When the damping force change rate V is smaller than the switching reference value V ref (), it is determined whether the flag FHS indicating that the suspension characteristics are set to soft is the value 1 (
In step 110), if the flag FHS is not set to the value 1, that is, if it is not set to soft, then the suspension is controlled to hard (step 1] 5), and this routine is temporarily terminated. Immediately after the damping force setting of the shock absorber 2 is switched from soft to hard, 1100 volts is applied to the piezo actuator 27 from the high voltage application circuit 75 according to the control signal from the output section 68. This is done by contracting the piezoactuator 27 and holding it as it is if the piezoactuator 27 is already in a contracted state.

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)
, the process of starting the timer, that is, setting the timer variable T to the value 0
Then, to set the suspension characteristics to soft, the flag FHS is set to the value 1 (step 120).
25). Thereafter, a high voltage of +500 volts is applied from the high voltage recirculating circuit 75 to the piezo actuator 27 to switch and control the damping force of the shock absorber 2 to a small state (step 130), and this routine ends.

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
(start and decay of the timer mentioned above)
The control to reduce the force is repeated, but when the damping force change rate V becomes equal to or less than the switching reference value V ref (step 05), the value of the flag FH5 is checked.Step 10), the value of the flag FH3 If is 1, it is determined whether the timer variable T exceeds a preset reference value T b 5hrt (step 135). Reference value Tb5hrtLL This is a value set so that after the shock absorber 2 is switched to a state with a small damping force, that state is always maintained for a certain period of time. Therefore,
If the timer variable is less than or equal to the reference value T b 5hrt, this 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 140 and 130). Therefore, the suspension is kept soft.

After that, if the damping force change rate V is changed again to the switching reference value V re
exceed f ('L At that time (time t2 in Figure 8),
The process moves to steps 120 to 130 where control is performed to start the timer and reduce the damping force.

On the other hand, after the damping force of the shock absorber 2 is once switched from large to small (after time t in FIG. 8), when the damping force change rate V becomes equal to or less than the switching reference value V ref, a predetermined period of time ( In other words, the time corresponding to the reference value T b 5hrt)
Until the time elapses, the damping force change rate V is equal to the switching reference value V re
If f is not exceeded (this condition is satisfied from time t3 to time t4 in FIG. 8), the judgment at step 135 is rYESJ, and after that, the holding time [( FIG. 8 From time t1 to time t3
flag F indicating whether or not the road surface on which the vehicle traveled during the time period) + (T b 5hrt) ] was rough.
roug (step] 45). Note that the period from time t1 to time t3 in FIG. 8 is hereinafter referred to as Ta.

Flag F rougI & retention time (T a + T b
The condition of the road surface on which the vehicle is traveling during the period of 5 hours) is determined by the routine shown in FIG. .

When the flag Froug is reset to the value O in step 145, the flag FHS is reset to the value 01 (step 150), and the damping force of the shock absorber 2 is controlled to a large state (step 15). , during the holding time (T a + T b 5hrt) (2) When the road surface on which the vehicle is traveling is not rough b 5 hours) only.

On the other hand, when the flag Froug is set to the value 1 in step 145, the timer variable T is incremented by the value 1 (step 155).Then, the timer variable T is set to a value longer than the reference value T b 5hrt. As a result, when the timer variable is determined to be smaller than the reference value T b long (step 160), the damping force of the shock absorber 2 is controlled to be small (step 130). ),
This routine ends once.

The reference value T b long is the retention time (T a +T
This value is set to extend the time during which the damping force of the shock absorber 2 is maintained at a low level when the road surface on which the vehicle is traveling is rough for a period of 5 hours.

In other words, time (T b long - T b 5hrt)
This value is set to increase the time during which the damping force of the shock absorber 2 is maintained in a small state.

When it is determined that the timer variable T exceeds the reference value T b long thus set (step 155)
, reset the flag FHS to the value O (step) 50
), the damping force of the shock absorber 2 is controlled to be large (step 115). That is, when the road surface is rough, the damping force of the shock absorber 2 is changed to a smaller state (after time t1 in FIG. 8), (T a
After a time period of 10 T b long), the state is switched to the large state.

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), immediately set to a small state. The time from time t] to t4 in Figure 8, that is, the holding time (, T a + T
b 5hrt) is always kept as small as it is. Then, the retention time (T a + T b 5
The damping force of the shock absorber 2 is switched to a large state after the holding time (Ta+Tb5hrt). If it is determined that (T a + T
b 5hr) after 1; Tblong-T b 5hr
The damping force of the shock absorber 2 is held in a small state for a period of time t, and then switched to a large state.

Next, in order to determine the switching reference value V ref for damping force switching referred to in this damping force switching control routine (Fig. 5), a flag F roug indicating the road surface condition is set.
A routine (FIG. 6) for detecting the change frequency N of the damping force change rate V used for resetting 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 21o). The damping cover turn of the shock absorber is controlled by the damping cover turn switching control routine shown in FIG. Multiply Vref by the value 0.8 x 0.5 (
Step 212), and on the other hand, it is determined that it is hard (1) The current switching reference value V ref is multiplied by a value of 0.8 (Step 214), and each learning reference value V refG is calculated.

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 less than or equal to the learning reference value V refG (the family flag FF is reset to the value O (step 230), then this routine is ended.

On the other hand, if it is determined that the damping force change rate V exceeds the learning reference value VrefG (step 240, check the value of the flag FF), the flag FF is set to the value O1, that is, the damping force change rate V is learned. Immediately after exceeding the reference value VrefG (the frequency N is incremented by 1 in step 250), the flag FF is set to the value FF (step 260), and this routine is temporarily terminated. Therefore, this flag FFf & damping force change rate V is the learning reference value V r
This indicates that the state exceeds efG, and during that time, the frequency N is not incremented (step 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 VrefG.

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

The learning process and other implementation routines for implementing the learning process for the switching reference value V ref used in this process and the setting/resetting process for the flag F rogue used in the attenuation cover turn switching control routine will be described below.

As shown in FIG. 7 (2. When the learning processing etc. implementation routine is started, first, the stop lamp switch 53, the steering sensor 50, the vehicle speed sensor 51
etc. (Step 30)
0), it is determined whether anti-dive, anti-roll, etc. control should be executed based on the driving state (step 310). When the driver steps on the brake, suddenly turns the steering wheel, etc., the switching reference value ref is changed in preparation for anti-dive processing (step 315), and the routine ends. do.

On the other hand, if it is determined that the running state of the vehicle does not require anti-dive processing or the like, it is determined whether the variable C has become equal to the value 1 (step 320). Variable C [
i is a value that is incremented each time the frequency detection interrupt routine shown in Figure 6 is executed, and is the time required to determine the magnitude of the frequency N (preset) based on the value of the variable C. The decision is made as to whether or not the current period has elapsed. The number of executions of the frequency detection interrupt routine is small (C
<i) If it is determined that the timing to judge the frequency has not arrived, the routine exits to (J,, rRTNJ and ends this routine once.

Every time the frequency detection interrupt routine is executed i times, the determination at step 320 is rYEsJ, and then the variable C is reset (step 330) and the vehicle speed sp is read (step 340).

Based on the vehicle speed sp read in this way, the next step is to calculate the reference base value Vbase (step 35).
0). The reference base value Vbase is the switching reference value Vre
This is to set the magnitude of f to a value according to the vehicle speed Sp, and as shown in FIG. 9, the function of the vehicle speed Sp + 1 (sp)
is determined as.

Next, a process is performed to obtain the frequency deviation ΔNe between the frequency N counted in the frequency detection interrupt routine (Fig. 6) and the preset frequency reference value Nref (step 360), and this frequency deviation ΔN is determined from the value O. A determination is made as to whether or not dogs are allowed (step 370).

If the frequency deviation ΔN is larger than the value O (the correction value ΔV is the value β
On the other hand, if the frequency deviation ΔN is less than or equal to the value O, the correction value ΔV is decremented by the value β (step 390), and this correction value ΔV is added to the reference base value V base. , performs processing to calculate the switching reference value V ref (step 400).
. As a result, the switching reference value V ref is changed according to the vehicle speed sp, but the correction value ΔV learned up to that point continues to be used.

After execution of step 400 (if the suspension is set to soft (i.e., refer to flag FHS) and whether it is set to the value), the next Carry out a series of steps such as:

After switching the damping force of the shock absorber 2 to a small state (time tl in FIG. 8), a process is performed to obtain the average value N avr of the frequencies N obtained in each of the routines executed up to now (step 420). Next, it is determined whether the value exceeds the reference value Nst (step 430). The reference value NST is used to determine each frequency N used to calculate the average value N avr during the period from time t1 to the time of execution of this routine (i.e., when the average value N avr exceeds this). This value is set to determine that the road surface on which the vehicle was traveling during the period from the first time to the last time is rough.

In step 430, if the average value N avr exceeds the reference value NST (step 440 sets the flag F roug to the value 1), otherwise the flag F roug is immediately reset to 01 (step 440). whelk 1
SO).

Thereafter, the frequency N is reset to the value O in preparation for subsequent frequency detection (step 460), and this routine ends. still,
If it is determined in step 410 that the suspension is set to hard, the average value N avr is set to the value O (
step 470). This is because if the suspension is set to hard, there is no need to refer to the li flag F rogue, and as a result, there is no need to calculate the average value N avr.

By executing the above learning process etc. execution routine, the switching reference value Vrefi is set based on the vehicle speed sp.
Learning is performed based on the frequency N.

In addition, the roughness of the road surface on which the vehicle was traveling from the time the damping force of the shock absorber 2 was switched from the large state to the small state (time ti in Figure 8) to the time this routine was executed is
The determination can be made by comparing avr and NST, and the result can be expressed as the value of the flag F rogue (value 1 when rough). This is because the rougher the road surface, the greater the frequency ΔN, and as a result, Navr becomes larger than Nst.

Therefore, this flag F roug is set to the holding time (Ta+
Immediately after (Tb 5hrt) (2 references li) It is possible to know whether or not the road surface on which the vehicle traveled during the relevant holding time is rough. That is, by referring to the flag F rogue in the damping force switching control routine, The results of determining the roughness of the road surface traveled on from time t1 to time t4 in FIG. 8 are shown.

By executing the processes shown in the flowcharts of FIGS. 5 to 7 explained above, the damping force change rate V will no longer exceed the switching reference value V ref from the time it exceeds it (time tl in FIG. 8). (Time t3 in Figure 8) and T b
5hrt, that is, the retention time (Ta + Tb5hr
t) (the damping force of the suspension is always held in a small state. Then, the holding time (T a +T
b) If it is determined that the road surface on which the vehicle traveled was rough at the time (5 hours), it is determined that the road surface on which the vehicle was traveling is rough (T). b long-T b 5h
rt).

Therefore, using the suspension control device 1 of this embodiment (the damping force change rate V, which is a highly responsive signal), the damping force generation pattern of each shock absorber 2 of the vehicle is calculated.
It is possible to quickly control the vehicle to an appropriate state depending on the road surface condition. That is, even if [11 damping force change rate V exceeds the switching reference value V ref and the damping force of the shock absorber 2 is switched from a large state to a small state, the vehicle is It is determined that the road surface on which the driver is traveling is not rough (after the above-mentioned holding time), and the damping force setting of shock absorber 2 is changed to a large state. Within a short period of time, the suspension settings return to hard and ride comfort is maintained.As a result,
The suspension settings don't stay too soft for too long, compromising ground grip.

[11] On the other hand, if the driver is continuously driving on a rough road, it is determined that the road surface on which the vehicle has traveled within the above holding time is rough, and the time tL and damping force are held in a small state are increased. to correct. 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.

[II+] Also, in this example, (upper damping force change rate V
The condition of the road surface on which the vehicle travels is taken into consideration not only during the time period Ta in which the switching reference value V ref continues to be exceeded or frequently exceeds it, but also during the subsequent predetermined time period (T b 5 hrt). Therefore, the road surface condition from when the damping force is switched to a small state until just before the decision is made as to whether or not to increase the amount of time the damping force is maintained in that state is reflected in that decision. It is possible to control the suspension very precisely according to the situation.

In this way, the suspension control device of this embodiment can control suspension characteristics 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.

Furthermore, in this embodiment, since the switching reference value V ref is changed by learning, the damping force generation pattern of each shock absorber 2 of the vehicle, and by extension the stiffness of the suspension, are controlled as follows.

[A] When driving on a flat road, the damping force change rate (2) is not so large, and the damping force characteristics of the shock absorber 2 are controlled to be large.

At this time, the learning reference value V refG is the switching reference value V r
It is calculated as a value of 80% of ef (step 214 in FIG. 6), and is calculated for a predetermined period (period corresponding to count value i).
The frequency N at which the damping force change rate V exceeds the switching reference value V ref becomes a small value. Therefore, the switching reference value V ref is learned to be smaller by the value β (step 390 in FIG. 7).
). As a result, the damping force change rate V becomes the switching reference value V ref
The damping force can be switched to a smaller state due to small irregularities while driving on a flat road. When the value of the switching reference value V ref is reduced in this way, the learning reference value refG
also becomes a small value, and the frequency with which the damping force change rate V exceeds the learning reference value VrefG during a predetermined period increases. As a result,
The switching reference value V ref is updated to a larger value by +β.
As this process is repeated, the switching reference value V ref will be learned to a value that makes the switching frequency appropriate.

Therefore, even when the vehicle is running on a flat road and the damping force change rate V is relatively small and the suspension tends to be maintained hard, the detection switching reference value V ref of the frequency N is updated and the learning reference value V refG is updated. By performing the learning, the switching reference value V ref is gradually decreased, and the shock absorber 2 becomes in the state 1 where the damping force is small, that is, the suspension characteristics are easily switched to soft. 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.

[B] On the other hand, if you are continuously driving on a rough road (
The damping force change rate V changes greatly, and the suspension characteristics are softly controlled. At this time, the learning reference value V re
fG is calculated as a value of 40% of the switching reference value V ref (Fig. 6, step 2] 2), and the damping force change rate V increases to the switching reference value V ref in a predetermined period (period corresponding to the count value i). The frequency N that exceeds this becomes a large value. Therefore,
The switching reference value V ref is learned to a larger value by the value β (step 380 in FIG. 7). As a result, the damping force change rate V
becomes difficult to exceed the switching reference value V ref, and the damping force characteristic can be switched hard even when driving on a rough road. In this way, when the value of the switching reference value V ref becomes large, the learning reference value V refG also becomes a large value, and the frequency at which the damping force change rate V exceeds the learning reference value V refG during a predetermined period becomes smaller. As a result, the switching reference value V ref is not updated to a smaller value by −β, and by repeating this process, the switching reference value V ref is learned to an appropriate value.

Therefore, even when the vehicle is driving on a rough road and the damping force change rate V is relatively large and the suspension tends to be kept soft, the frequency N is detected, the switching reference value V ref is updated, and the learning reference value V refG is By performing this learning, the switching reference value V ref is gradually increased, and the damping force characteristic of the shock absorber 2 becomes large, that is, the suspension characteristic is easily switched to a hard state. As a result, when the vehicle continues to drive on rough roads, it is possible to suitably deal with the conventional problem of insufficient ground contact, so-called lack of stiffness in the suspension, and the steering stability is significantly improved.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way. The gist of the present invention can be realized by a configuration in which the damping force change rate V is determined based on whether the total period during which it exceeds a predetermined value is long, or a configuration in which the roughness of the road surface is determined based on a signal from a vehicle height sensor, etc. It goes without saying that the invention can be implemented in various ways without departing from the scope.

Effects of the Invention As described in detail above, the suspension control device of the present invention (i) After switching the damping force setting from large to small, maintains the damping force setting in a low state for a predetermined period; l2 Depending on the road surface conditions on which the vehicle was traveling, the damping force setting is switched from small to large, or the period during which the damping force setting is kept small is corrected by increasing the damping force setting. This has an extremely excellent effect in that the settings can be continued for a period of time depending on the driving condition of the vehicle (for example, road surface condition, vehicle speed, etc.).Therefore, for example, when driving over a small step on a relatively flat road, The damping force setting tends to return to the hard setting in a short period of time, while the damping force setting tends to continue to remain soft when driving on rough roads.As a result, the damping force setting becomes unnecessarily soft for a long period of time. There is no need to maintain the damping force, thereby impairing ground contact, or to frequently switch the damping force setting, thereby causing the driver to feel uncomfortable.In addition, there is an advantage in terms of the durability of the device.

In particular, in the present invention, the decision as to whether or not to increase the period during which the damping force is kept small is made immediately before attempting to increase the damping force (
(or immediately before the end of that period) and in response to the road surface conditions on which the vehicle has traveled for a predetermined period immediately before the determination, so the suspension can be controlled extremely accurately in response to the road surface conditions.

[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 the attenuation 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, and Fig. 8 (switching reference value Vref and A graph showing the relationship with the force change rate V, etc., and FIG. 9 is a graph showing the relationship between the vehicle speed SP and the reference base value V, base. 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 ○ Damping force Rate of change 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; 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; a damping force switching and holding means that continues the changed damping force setting for a predetermined holding period when the setting is changed from large to small; and a road surface condition that determines the roughness of the road surface on which the vehicle has traveled within the holding period. A suspension control device comprising: a determination unit; and a retention period correction unit that increases the retention period when the road surface condition determination unit determines that the road surface is rough.