JP2724754B2 - Suspension control device - Google Patents

Description

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

[Prior Art] As this type of suspension control device, a change rate of a damping force of a shock absorber is detected, and when the change rate becomes a predetermined value or more, that is, a damping force is determined based on unevenness of a road surface or a brake operation. It is known that when a sudden change occurs, the generation pattern of the damping force of the shock absorber is promptly switched to a smaller value to increase the responsiveness of control of the shock absorber. Further, there is also a suspension control device that changes the magnitude of the reference value for adjusting the rate of change of damping force, which determines switching of the setting of damping force, based on the driving state of the vehicle, such as the vehicle speed, to further improve ride comfort. It has been proposed (for example, JP-A-64-67407).

[Problem to be Solved by the Invention] Such a suspension control device is excellent in keeping a good ride comfort by quickly following a pattern of a damping force to a change in road surface condition. In the case where the above is continued, there is a problem that the riding comfort and the driving stability are not always sufficient. This is because, for example, when the vehicle is running on a flat road, the shock absorber is maintained in a state of a large damping force, so that the suspension is hard (hard) and small irregularities on the road surface may be conspicuous. is there. On the other hand, if the vehicle continues to travel on a rough road, the shock absorber may be kept in a state of a small damping force, which may result in sacrificing the ground contact property and impairing the driving feeling.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems and to improve the riding comfort and the steering stability with good responsiveness when a flat road or a bad road continues.

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

[Means and Actions for Solving the Problems] A suspension control device according to the present invention is provided on a suspension S of a vehicle and sets a damping force generation pattern as exemplified in FIG. 1 and illustrated in FIG. Shock absorber M1, a damping force change rate detecting means M2 for detecting a change rate of the damping force of the shock absorber M1, and a magnitude relationship between the detected change rate of the damping force and a reference value for adjusting the damping force. And a damping force control means M3 for changing the setting of the damping force of the shock absorber M1 based on the frequency control means M4 for detecting a frequency of a change in a parameter related to the damping force, A difference between the detected frequency and the target frequency, a frequency deviation calculating means M5 for calculating as a frequency deviation, based on a state of change of the setting of the damping force by the damping force control means M3. A road surface state detecting means M6 for detecting the state of the road surface on which the vehicle travels; and, when it is determined that the flat road is continued based on the detected road surface state, the adjustment reference value is subjected to a frequency deviation. And a damping force adjustment correcting means M7 for correcting the adjustment reference value to a large value in accordance with the amount of the frequency deviation when it is determined that the rough road is continuing. It is characterized by having.

[Operation] The suspension control apparatus of the present invention having the above-described configuration detects the rate of change of the damping force of the shock absorber M1 provided on the suspension S of the vehicle by the damping force change rate detecting means M2, and determines the rate of change of the damping force. And the damping force adjustment reference value based on the magnitude relationship between the damping force adjustment reference value and
It is based on the technology of changing the setting of the damping force of the shock absorber M1, and further performs the following operation.

The frequency detecting means M4 is a frequency of a change in a parameter related to the damping force, for example, a frequency of switching the damping force characteristics in two stages, and a frequency at which the characteristics are actually switched or a frequency at which the damping force exceeds a predetermined threshold. Is detected. Of course, in a configuration including a shock absorber that can switch the damping force steplessly, the number of times that the damping force is changed by a predetermined value or more may be detected as the frequency. The difference between the frequency thus obtained and the target frequency is calculated as a frequency deviation by the frequency deviation calculating means M5.

On the other hand, the road surface state detecting means M6 is adapted to drive the vehicle based on the state of the change in the setting of the damping force by the damping force control means M3, for example, in a configuration in which the damping force pattern is switched in several stages, based on the switching frequency and the switching cycle. The condition of the road surface to be detected is detected. Based on the detected road surface condition,
When it is determined that the flat road is continuing, the damping force adjustment correction unit M7 corrects the adjustment reference value to a small value according to the amount of the frequency deviation.

On the other hand, when it is determined that the rough road continues, the damping force adjustment correction means M7 corrects the adjustment reference value to a large value according to the amount of the frequency deviation.

With this correction, for example, when an extremely flat road surface continues for a predetermined period or more, the generation pattern of the damping force of the shock absorber changes from a large damping force setting to a small damping force by the correction value of the adjustment reference value. It is easy to switch to the side. In addition, as the frequency of change of the parameter related to the damping force greatly deviates from the target frequency, that is, as the deviation between the two increases, the adjustment reference value is corrected to be a smaller value. You.

Further, when the vehicle continues to travel on a rough road, the larger the frequency deviation is, the larger the correction is made from a small damping force to a large damping force. As a result, the bias in the pattern of the generation of the damping force is quickly corrected, and the suspension characteristics are excellent in the balance between the shock absorbing property and the contact property.

Further, as described in claim 2, in the suspension control device according to claim 1, the damping force control means is configured as a means capable of changing the setting of the damping force steplessly, and the damping force adjustment correction is performed. As means, when it is determined based on the detected state of the road surface that the flat road is continued, the damping force set by the damping force control means is lowered according to the amount of frequency deviation. And when it is determined that the rough road continues, the damping force set by the damping force control means is corrected to a higher state in accordance with the amount of frequency deviation. The above object can also be achieved by a suspension control device having a correction means.

According to the suspension control device of the second aspect, when the flat road is continuous, the damping force is corrected to be lower, so that the impact due to the small unevenness of the road surface can be absorbed. In this case, the damping force is corrected to be relatively high, so that the contact property can be improved. However, since the above correction is performed according to the magnitude of the frequency deviation,
This is exactly the same as the first aspect in that the larger the deviation is, the larger the correction is made and the deviation is quickly eliminated.

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

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

As shown in FIG. 2, the suspension control device 1 according to the present embodiment includes shock absorbers 2FL, 2FR, 2RL, 2RR (hereinafter, all of which are referred to as 2F, which can change the damping force in two stages).
Abbreviated as L, FR, RL, RR. Other members are described similarly)
And an electronic control unit 4 connected to each of the shock absorbers and controlling the damping force. Each shock absorber 2FL, FR, RL, RR is left and right front and rear wheel 5F
L, FR, RL, RR suspension lower arm 6FL, FR, RL, RR
And a body 7 together with coil springs 8FL, FR, RL, RR.

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

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

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

Inside the cylinder 11, an internal cylinder 15, a connecting member 16, and a cylindrical member 17 connected to the lower end of the rod 13, and a main piston 18 slidable along the inner peripheral surface of the cylinder 11,
It is arranged. A piezo load sensor 25 and a piezo actuator 27 are housed in the internal cylinder 15 connected to the rod 13 of the shock absorber 2.

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

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

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

The piezo actuator 27 is formed by laminating electrostrictive elements that expand and contract with good responsiveness when a high voltage is applied, and increases the amount of expansion and contraction, and directly drives the piston 36. When the piston 36 is moved in the direction of arrow B in FIG. 3 (B), the plunger 37 and the spool 41 having an H-shaped cross section are also moved in the same direction via the hydraulic oil in the oil-tight chamber 33. Thus, the spool 41 at the position (origin position) shown in FIG.
Move in the direction B in the drawing, the sub-flow path 16c connected to the first liquid chamber 21 and the sub-flow path 3 of the bush 39 connected to the second liquid chamber 23
9b will be communicated. The sub flow path 39b is further connected to the flow path 17a in the tubular member 17 via an oil hole 45a provided in the plate valve 45, so that the spool 41
Moves in the direction of arrow B, as a result, the flow rate of hydraulic oil flowing between the first liquid chamber 21 and the second liquid chamber 23 increases.
In other words, the shock absorber 2 switches its damping force characteristic from a large damping force (hard) state to a small damping force (soft) side when the piezo actuator 27 expands due to the application of a high voltage. Returns the force characteristics to the state of large damping force (hard).

The amount of movement of the leaf valve 31 provided on the lower surface of the main piston 18 is regulated by a spring 35 as compared with the leaf valve 30. The plate valve 45 has an oil hole
An oil hole 45b having a diameter larger than 45a is provided outside the oil hole 45a, and when the plate valve 45 moves toward the bush 39 against the urging force of the spring 46, the hydraulic oil passes through the oil hole 45b. And can be moved. Therefore, irrespective of the position of the spool 41, the hydraulic oil flow rate when the main piston 18 moves in the direction of arrow B becomes larger than when the main piston 18 moves in the direction of arrow A. That is, the damping force is changed depending on the moving direction of the main piston 18, thereby further improving the characteristics as a shock absorber. Also,
A hydraulic oil supply passage 38 is provided between the oil-tight chamber 33 and the first liquid chamber 21 together with a check valve 38a to keep the flow rate of the hydraulic oil in the oil-tight chamber 33 constant.

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

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

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

The electronic control unit 4 further includes a damping force change rate detection circuit 70 connected to the piezo load sensor 25, a waveform shaping circuit 73 connected to the steering sensor 50 and the vehicle speed sensor 51,
High voltage application circuit 7 connected to piezo actuator 27
5. A so-called switching regulator type high-voltage power supply circuit 79 that receives power from a battery 77 through an ignition switch 76 and outputs a driving voltage for driving a piezo actuator, and transforms the voltage of the battery 77 to A constant voltage power supply circuit 80 for generating an operating voltage (5v) is provided. Shift position sensor 52, stop lamp switch 53, damping force change rate detection circuit 70, waveform shaping circuit 73
Is connected to the input unit 67, while the high voltage application circuit 75 and the high voltage power supply circuit 79 are connected to the output unit 68.

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

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

Next, the damping force control performed by the suspension control device 1 of the present embodiment having the above-described configuration will be described with reference to the flowcharts of FIGS. 5, 6, and 7. Each routine shown in each figure is repeatedly executed at predetermined time intervals by interrupt processing. These processes are executed for each of the shock absorbers 2FL, FR, RL, and RR of each wheel. However, since the processes for each wheel are the same, description will be made without particular distinction. The processing contents of each routine are as follows.

Damping Force Pattern Switching Control Routine (FIG. 5) Piezo actuator 27 based on the rate of change V of damping force
To set the damping force to a large state or a small state.

Frequency Detection Interrupt Routine (FIG. 6) The rate of change of the damping force within a predetermined time becomes equal to the learning reference value VrefG.
Is detected as the frequency N.

Switching Reference Value Vref Learning Routine (FIG. 7) The switching reference value Vref used for switching the damping force is learned based on the magnitude of the switching frequency N.

The frequency detection interrupt routine and the switching reference value Vref learning routine described above learn the switching reference value Vref by referring to the time measurement variable C and the frequency N, and learn the learned switching reference value.
Using Vref, a damping force pattern switching control routine executes damping force switching control. The details of each routine will be described in order from the damping force pattern switching control routine (FIG. 5).

When this routine is started, first, each shock absorber 2 is input from the damping force change rate detection circuit 70 through the input section 67.
Of the change rate V of the damping force of the
100) It is determined whether or not the damping force change rate V is greater than the switching reference value Vref learned in the switching reference value learning routine (FIG. 7) (step 110). Damping force change rate V
Is smaller than the switching reference value Vref, the flag FHS indicating that the suspension characteristics are set to soft
Is determined to be 1 (step 120). If the flag FHS is not 1, that is, if the flag FHS is not set to software, the suspension is hardly controlled (step 130) and this routine is executed once. finish. Step 130
Immediately after the setting of the damping force of the shock absorber 2 is switched from software to hardware, the control signal from the output unit 68 applies -100 volts from the high voltage application circuit 75 to the piezo actuator 27. Is performed, 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 Vref (step 110), a process of starting a timer, that is, a process of resetting a timer variable T to a value 0 is performed (step 140), and the suspension is further performed. Is set to a value of 1 in the flag FHS (step 150). After that, a high voltage of +500 volts is applied from the high voltage application circuit 75 to the piezo actuator 2
7 to switch / control the damping force of the shock absorber 2 to a small state (step 160), and terminate this routine.

After the damping force of the shock absorber 2 is switched to a small state, if the damping force change rate V exceeds the switching reference value Vref, the above-described start of the timer and the control for reducing the damping force are repeated. When the damping force change rate V becomes equal to or less than the switching reference value Vref, after checking the value of the flag FHS (step 120), it is determined whether or not the timer variable T exceeds a preset reference value TS. (Step 170). The reference value TS is a value that is set so that the shock absorber 2 is temporarily switched to a state with a small damping force and then continues that state for a certain period of time. Therefore, if the timer variable T is equal to or less than the reference value TS, the variable T is incremented by 1 and the process for controlling the damping force of the shock absorber 2 to a small state is continued (step 160). Therefore, the suspension is kept soft.

After the damping force change rate V once becomes equal to or less than the switching reference value Vref, if the damping force change rate V does not exceed the switching reference value Vref until a predetermined time (a time corresponding to the reference value TS) elapses, a step is performed. Since the judgment at 170 is "YES",
Next, the flag FHS is reset to 0 (step 19).
0), the damping force of the shock absorber 2 is controlled to a large state (step 130).

Therefore, when this routine is repeatedly executed, the damping force of the shock absorber 2 of each wheel is set to a small value as soon as the damping force change rate V exceeds the switching reference value Vref, and the damping force change rate V becomes equal to the reference value. At least the time corresponding to the reference value TS after the voltage becomes equal to or less than Vref is maintained as it is. Thereafter, when a predetermined time elapses with the damping force change rate V being equal to or less than the switching reference value Vref, the state is again controlled to have a large damping force.

Next, a routine for detecting the change frequency N of the rate of change of the damping force (FIG. 6) in order to determine the damping force switching reference value Vref referred to in the damping force switching control routine (FIG. 5).
Will be described. When this interrupt routine is started,
First, a process of incrementing a variable C for counting the number of executions of this routine by a value of 1 is performed (step 20).
0) Then, it is determined whether the current suspension setting is hard or soft (step 210). The damping force pattern of the shock absorber 2 is controlled by the damping force pattern switching control routine shown in FIG. 5. If the current pattern is determined to be soft with reference to the value of the flag FHS, the current switching is performed. The reference value Vref is multiplied by a value of 0.8 × 0.5 (step 212). On the other hand, if it is determined to be hard, the current switching reference value Vref is multiplied by a value of 0.8 (step 214) to calculate a learning reference value VrefG. I do.

After the learning reference value VrefG is thus determined, it is determined whether or not the current damping force change rate V is larger than the learning reference value VrefG (step 220). If the damping force change rate V is equal to or smaller than the learning reference value VrefG, the flag FF is reset to a value of 0 (step 230), and the present routine is ended once.

On the other hand, when it is determined that the damping force change rate V exceeds the learning reference value VrefG, the value of the flag FF is checked (step 240), and the flag FF is set to a value of 0, that is, the damping force change rate V becomes Immediately after the learning reference value VrefG is exceeded, the frequency N is incremented by 1 (step 250), and the flag FF
Is set to 1 (step 260), and this routine is once ended. Therefore, this flag FF indicates the damping force change rate V
Indicates that the value exceeds the learning reference value VrefG, during which 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 has exceeded the learning reference value VrefG.

By repeatedly executing the frequency detection interrupt routine described above, the learning reference value is obtained based on the switching reference value Vref.
The process of updating VrefG and the process of detecting the frequency N at which the damping force change rate V exceeds the learning reference value VrefG are performed.

A learning routine of the switching reference value Vref used for such processing will be described below. As shown in FIG. 7, when the switching reference value learning routine is started, first, the stop lamp switch 53, the steering sensor 5
0, a process of reading the running state from the vehicle speed sensor 51 or the like is performed (step 300), and based on the running state, it is determined whether or not control such as anti-dive or anti-roll is to be executed (step 310). When the brake is depressed or the steering wheel is suddenly turned, it is determined that processing such as anti-dive is to be performed, and processing for switching the switching reference value Vref is performed in preparation for such processing (step 315), and this routine is terminated as it is. I do.

On the other hand, when it is determined that the running state of the vehicle does not require the anti-dive processing or the like, it is determined whether or not the variable C has become equal to the value i (step 320). Variable C
Is a value that is incremented each time the frequency detection interrupt routine shown in FIG. 6 is executed once, and the time required to determine the magnitude of the frequency N based on the value of the variable C (set in advance) ) Is determined. The frequency of execution of the frequency detection interrupt routine is small (C <
i) If it is determined that the timing for determining the frequency has not been reached, the process exits to "RTN" and ends this routine once.

Every time the frequency detection interrupt routine is executed i times, the determination in step 320 becomes "YES", and then the variable C is reset (step 330), and the vehicle speed Sp is read (step 340).
Execute Next, based on the vehicle speed Sp thus read, a process of calculating a reference base value Vbase is performed (step 350). The reference base value Vbase is for setting the magnitude of the switching reference value Vref to a value corresponding to the vehicle speed Sp.
As shown in the figure, it is determined as a function f1 (Sp) of the vehicle speed Sp.

Next, a process for obtaining a frequency deviation ΔN between the frequency N counted in the frequency detection interrupt routine (FIG. 6) and a preset target frequency Nref is performed (step 370), and a reference is made based on the frequency deviation ΔN. A process of calculating the value correction amount Vrvs is performed (step 380). The reference value correction amount Vrvs determines the amount by which the switching reference value Vref is corrected by one control, and as shown in FIG. The function g of the deviation ΔN (Δ
N). Subsequently, the learning correction value ΔV is updated with the reference value correction amount Vrvs thus obtained (step 390). Therefore, when the frequency N is greater than the target frequency Nref, the learning correction value ΔV is updated in a direction to increase, and is increased as the frequency deviation ΔN increases.

Next, the learning correction value ΔV obtained in this manner is used as a reference base value.
A process of calculating the switching reference value Vref is performed by adding the value to Vbase (step 400). As a result, the switching reference value Vref
Is a learning correction value ΔV based on the frequency deviation ΔN together with the vehicle speed Sp.
Will also be updated. When the vehicle speed Sp changes, the switching reference value Vref is changed, but the learned correction value ΔV learned up to that point is stored and used continuously. After the execution of step 400, the frequency N is reset to a value of 0 in preparation for the subsequent frequency detection (step 410), and this routine ends.

By executing the processing shown in the flowcharts of FIGS. 5 to 7, the generation pattern of the damping force of each shock absorber 2 of the vehicle, and thus the hardness of the suspension, are controlled as follows.

[I] FIG. 10 (A) shows an example of control when the vehicle is traveling on a flat road. As shown in the figure, when traveling on a flat road, 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. At this time, the learning reference value VrefG is calculated as a value of 80% of the switching reference value Vref (step 214 in FIG. 6), and the damping force change rate V is set to the switching reference value during a predetermined period (period corresponding to the count value i). Frequency N above value Vref
Is a small value. Therefore, the frequency deviation ΔN is a negative value, and the reference value correction amount Vr obtained based on this value is
vs also becomes a negative value (see FIG. 9), and the learning correction value Δ
V is greatly learned in the decreasing direction. As a result, the switching reference value Vref is also learned to increase in the decreasing direction (steps 380 to 400 in FIG. 7).

By performing such processing, the damping force change rate V
Easily exceeds the switching reference value Vref, and the damping force is switched to a small state with good responsiveness due to small unevenness or the like during traveling on a flat road (times t1 and t2 in FIG. 10A). When the value of the switching reference value Vref is reduced in this manner, the learning reference value VrefG also becomes a small value, and the frequency at 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 Vref is updated in an increasing direction, and while this process is repeated, the switching reference value Vref is learned to a value at which the switching frequency is appropriate. In addition, since the amount learned in one control depends on the frequency deviation ΔN, the learning is performed promptly, and the switching reference value Vref immediately becomes an appropriate value according to the road surface condition.

Therefore, even when the vehicle travels on a flat road and the damping force change rate V is relatively small and the suspension tends to be maintained hard, detection of the frequency N, update of the switching reference value Vref,
Since the learning reference value VrefG is learned, the switching reference value Vref is changed to a small value with good responsiveness, and the shock absorber 2 is in a state of small damping force, that is, the characteristics of the suspension can be easily switched to soft. is there. As a result, it is possible to appropriately cope with the small unevenness of the road surface, which has conventionally been a concern when the vehicle continues to travel on a flat road, and the riding comfort is remarkably improved.

[II] On the other hand, if you are traveling on rough roads,
As exemplified in FIG. 10 (B), the normal damping force change rate V changes greatly, and the suspension characteristics are controlled softly. At this time, the learning reference value VrefG is 40 times the switching reference value Vref.
% (Step 212 in FIG. 6),
The frequency N at which the damping force change rate V exceeds the learning reference value VrefG during a predetermined period (a period corresponding to the count value i) is a large value. Accordingly, the switching reference value Vref is immediately learned in the direction opposite to the direction [I] when traveling on a flat road (step in FIG. 7).
380-400). As a result, the damping force change rate V is unlikely to exceed the switching reference value Vref, and the damping force characteristic is switched to a hard value even during rough road running (at time t11 in FIG. 10B).
t12). When the value of the switching reference value Vref increases in this way,
The learning reference value VrefG also becomes a large value, and the frequency at which the damping force change rate V exceeds the learning reference value VrefG during a predetermined period decreases. As a result, the switching reference value Vref is updated in a decreasing direction,
By repeating this processing, the switching reference value Vref
Is quickly learned to an appropriate value.

Therefore, even when the vehicle travels on a rough road and the damping force change rate V is relatively large and the suspension tends to be kept soft, the detection of the frequency N, the update of the switching reference value Vref, and the learning of the learning reference value VrefG are performed. Is performed, the switching reference value Vref is learned with a magnitude corresponding to the frequency deviation ΔN, and the damping force characteristic of the shock absorber 2 is large, that is, the suspension characteristic is easily switched to hardware. As a result, it is possible to appropriately cope with the insufficient contacting property, which has conventionally been noticed, that is, the so-called low waist under the suspension, when the driving on the rough road continues, the driving stability is remarkably improved, and the driving feeling is good. Will be kept.

As described above, according to the suspension control device 1 of the present embodiment, a small vibration is absorbed when the vehicle travels on a flat road, and the ground contact property is improved when the vehicle travels on a rough road. It is possible to achieve both the riding comfort of the vehicle and the steering stability. In particular, the switching reference value according to the traveling road condition
Since the learning of Vref is performed with a magnitude corresponding to the frequency deviation ΔN, when the flat road or the bad road continues, the switching reference value Vref can be immediately updated to an appropriate value. Further, since the switching of the damping force characteristic is performed based on the damping force change rate Vref, the control can be performed with good responsiveness. Therefore, for example, even when the switching reference value Vref is learned to a large value on a rough road and the suspension is switched hard, even if the road surface is rougher, the damping force does not have to be increased until the damping force itself increases. It is possible to switch to software immediately based on the value of the force change rate V, and the ride comfort is not impaired.

According to the present embodiment, the state of the road surface on which the vehicle travels, in particular, whether it is a flat road or a bad road, is determined based on the rate of change V of the damping force of the shock absorber 2, so that a new sensor or the like is not required. There is an advantage that the responsiveness is excellent. Furthermore,
In the suspension control device 1 of the present embodiment, the switching reference value
Since the reference base value Vbase for calculating Vref is obtained based on the vehicle speed Sp, the degree of generation of the damping force based on the difference in vehicle speed can be reflected in the suspension characteristics.

Next, another embodiment of the present invention will be described. FIG. 11 shows a main part of the processing in another embodiment. This embodiment has the same device configuration as the above-described embodiment, and calculates a target frequency Nref for obtaining the frequency deviation ΔN in step 370 of the switching reference value learning routine shown in FIG. 7 based on the vehicle speed Sp. (Step 360 in FIG. 11). That is, when the vehicle speed Sp is high, even when the vehicle travels on the same road surface, the damping force change rate V generated in the shock absorber 2 tends to be large. Therefore, as the vehicle speed Sp increases, the solid line in FIG. As shown by F, the target frequency Nref
Are successively smaller values, so that at high speed the switching reference value
It learns Vref to a higher value. As a result, when the vehicle is traveling on a flat road, the control for easily switching the suspension to softness is suppressed as the vehicle speed increases, and traveling stability during high-speed traveling can be ensured.
That is, according to this embodiment, in addition to the effects of the first embodiment, it is possible to further achieve both the riding comfort and the running stability when the vehicle is running over a wide range of the vehicle speed.

Although several embodiments of the present invention have been described above,
The present invention is not limited to such an embodiment. For example, 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, and the damping force is actually switched based on the frequency deviation ΔN. The gist of the present invention, such as a configuration obtained based on the number of times, or a configuration in which the target frequency Nref is set to different values for each of the front, rear, left and right wheels 5FL, FR, RL, and RR as shown by a solid line F and a broken line R in FIG. Of course, the present invention can be implemented in various modes without departing from the scope of the present invention.

Effects of the Invention As described in detail above, according to the suspension control device of the present invention, when the state of either a flat road or a rough road continues, a predetermined correction is made by the damping force adjustment correction means. When traveling continues, it is possible to appropriately cope with small unevenness of the road surface which has been conventionally concerned, and the riding comfort is remarkably improved. It is possible to appropriately cope with the so-called low waist of the undercarriage, and there is an extremely excellent effect that the steering stability is remarkably improved and the driving feeling is kept good. Moreover, since such control is performed in accordance with the magnitude of the deviation between the frequency of change of the parameter relating to the damping force and the target frequency, according to the suspension control device of the present invention,
The riding comfort and the steering stability of the vehicle when traveling on a flat road and a rough road can be compatible with good responsiveness.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a basic configuration of the present invention, FIG. 2 is a schematic configuration diagram showing an overall configuration of a suspension control device as one embodiment of the present invention, and FIG. FIG. 3 (B) is a partial sectional view showing the structure of FIG.
FIG. 4 is an enlarged sectional view of a main part of the shock absorber 2, FIG. 4 is a block diagram showing a configuration of the electronic control unit 4 of the present embodiment, FIG. 5 is a flowchart showing a damping force pattern switching control routine, and FIG. 7 is a flowchart showing a switching reference value Vref learning routine, FIG. 8 is a graph showing a relationship between the vehicle speed SP and a reference base value Vbase, and FIG. 9 is a frequency deviation ΔN and a reference value correction. A graph showing the relationship with the amount Vrvs, FIG. 10 (A) is a graph showing the state of control when traveling on a flat road, and FIG. 10 (B) is a graph showing control when traveling on a rough road. FIG. 11 is a flowchart showing the main part of another embodiment of the present invention, and FIG. 12 is a graph showing the relationship between the vehicle speed and the target frequency Nref. 2FL, FRRL, RR …… Shock absorber 4 …… Electronic control device 25FL, FR, RL, RR …… Piezo load sensor 27FL, FR, RL, RR …… Piezo actuator 51 …… Vehicle speed sensor 70 …… Damping force change rate Detection circuit 75: High voltage application circuit, 79: High voltage power supply circuit

Continuation of the front page (72) Inventor Yoshimichi Hara 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (72) Inventor Eiki 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Corporation ( 72) Inventor Hiroyuki Kawada 1-1-1, Showa-cho, Kariya-shi, Aichi, Japan Inside Denso Co., Ltd. (72) Inventor Akira Fukami 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture, Japan Denso Co., Ltd. 1-1 1-1 Showa-cho, Kariya-shi, Aichi Japan Denso Co., Ltd.

Claims (2)

(57) [Claims] 1. A shock absorber provided on a suspension of a vehicle and capable of setting a damping force generation pattern, a damping force change rate detecting means for detecting a change rate of the shock absorber damping force, and the detected damping force A damping force control means for changing a setting of the damping force of the shock absorber based on a magnitude relationship between a force change rate and a damping force adjustment reference value. Frequency detecting means for detecting the frequency of parameter change; frequency deviation calculating means for calculating the difference between the detected frequency and the target frequency as a frequency deviation; and changing the setting of the damping force by the damping force control means Road surface condition detecting means for detecting the condition of the road surface on which the vehicle is traveling, based on the condition of the vehicle; and determining that the flat road continues based on the detected condition of the road surface. When it is determined, the adjustment reference value is corrected to a small value according to the amount of the frequency deviation, and when it is determined that the rough road continues, the adjustment reference value is corrected according to the amount of the frequency deviation. A suspension control device, comprising: damping force adjustment correction means for correcting to a large value. 2. The suspension control device according to claim 1, wherein the damping force control means is configured as a means capable of changing a setting of the damping force in a stepless manner, and the damping force adjustment correction means is configured to detect the detected damping force. Based on the state of the road surface, when it is determined that the flat road is continued, the damping force set by the damping force control means is corrected to a lower state according to the amount of frequency deviation, When it is determined that the rough road continues, damping force adjustment correction means for correcting the damping force set by the damping force control means to a higher state in accordance with the amount of frequency deviation is provided. A suspension control device.