JP2754809B2 - 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 including a shock absorber capable of varying a predetermined damping force, and 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.

[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 with respect to the movement of the shock absorber is quickly switched to a small value side (for example, see
64-67407).

On the other hand, depending on the condition of the road surface, the cycle is relatively long, about 1 second, and vibrations of the vehicle body (so-called “tilting”) that may cause motion sickness may occur. There is a suspension control device described in Japanese Unexamined Patent Publication No. Sho 62-80111. This suspension control device detects the tilt of the vehicle body based on the data of the vehicle height, and if a tilt occurs, sets the shock absorber's damping force pattern to the higher side to make the suspension harder, It was to prevent.

[Problems to be Solved by the Invention] These various suspension control devices are excellent in controlling the setting of the damping force of the vehicle to improve ride comfort and prevent tilt, but for example, when the traveling road surface is In the case of a so-called composite road surface where gently undulating undulations on the vehicle body are overlapped with fine irregularities such as unpaved road surfaces,
There is a problem that the ride comfort may be impaired by any control. For example, if the suspension is set to be hard to prevent tilt, the vehicle may vibrate under the influence of unevenness of the road surface, and the ride comfort may be impaired. On the other hand, in this case, if the suspension is kept soft according to the damping force change rate caused by the unevenness of the road surface, the ride comfort is impaired due to the occurrence of tilt.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems, achieve a balance between damping force control and swing control on a complex road surface, and improve the riding comfort of a vehicle.

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

[Means for Solving the Problems] A first suspension control device of the present invention is provided on a suspension S of a vehicle and can set a generation pattern of a damping force, as exemplified by a solid line in FIG. M1; damping force change rate detecting means M2 for detecting a change rate of the damping force of the shock absorber M1; and a shock absorber M1 based on a magnitude relationship between the detected change rate of the damping force and a switching reference value. And a damping force control unit M3 for changing the setting of the damping force of the suspension control device, wherein the change of the setting of the damping force by the damping force control unit M3 includes a change frequency, a magnitude of the changed damping force, Parameter detecting means M4 for detecting a damping force change parameter such as a frequency at which the rate of change of the damping force exceeds a learning reference value set at a value smaller than the switching reference value; Additional parameters to match the target value,
A switching reference value of the damping force control means, an adjustment reference value learning means M5 for learning at predetermined intervals, and a sprung resonance detecting means M6 for detecting vibration near a sprung resonance frequency occurring in the vehicle body during running of the vehicle. In setting the learning period by the adjustment reference value learning means M5 according to the magnitude of the sprung resonance detected, a learning period shortening means M7 for shortening the learning period as the sprung resonance increases. It is characterized by having.

Further, the second suspension control device is different from the first suspension control device in the configuration of the first suspension control device in that the learning period shortening means M7 is replaced by a broken line in FIG. Accordingly, the gist is that the target value correction means M8 for correcting the target value of the damping force change parameter in the adjustment reference value learning means M5 to the side where the setting of the damping force becomes relatively large is provided. I do.

[Operation] The first suspension control device having the above configuration includes:
The rate of change of the damping force of the shock absorber M1 provided on the suspension S of the vehicle is detected by damping force change rate detecting means M2, and damping force control is performed based on the magnitude relationship between the rate of change of the damping force and the switching reference value. The means M3 performs the following operation on the premise of a technique for changing the setting of the damping force of the shock absorber M1.

In the first and second suspension control devices having the above configuration, the parameter detecting means M4 detects the damping force change parameter. Here, the damping force change parameter is a parameter relating to the setting of the damping force changed by the damping force control means M3, and the change frequency, the magnitude of the damping force after the change, and the rate of change of the damping force are the switching reference value. It is a parameter such as a frequency exceeding a learning reference value set with a smaller value. In the first and second suspension control devices, the adjustment reference learning unit M5 uses the damping force control unit M3 to adjust the damping force change parameter to the target value.
The switching reference value is learned for each predetermined period, and during the running of the vehicle, the sprung resonance detecting means M6 detects vibration near the sprung resonance frequency generated in the vehicle body B.

Here, in the first suspension control device, the learning period shortening unit M7 sets the learning period by the adjustment reference value learning unit M5 according to the magnitude of sprung resonance detected by the sprung resonance detecting unit M6. The larger the sprung resonance, the shorter the learning period. As a result, if the vibration (so-called tilt) of the vehicle body B near the sprung resonance frequency increases, the learning of the switching reference value for setting the damping force of the shock absorber M1 is performed in a short period of time. Therefore, when traveling on a composite road surface, the setting of the damping force of the shock assover M1 is controlled to a large value in a short period of time.

On the other hand, in the second suspension control device, as the detected sprung resonance increases, the damping force change parameter in the adjustment reference value learning means M5 is increased by the target value correction means M8 provided in place of the learning period shortening means M7. The target value is corrected so that the setting of the damping force becomes relatively large. As a result, even in the second suspension control device, the setting of the damping force of the shock absorber M1 is controlled to a larger value when traveling on a complex road surface, as in the first device.

The setting of the learning period and the correction of the target value may be performed independently for each wheel, may be performed commonly for the front two wheels and the rear two wheels, or may be performed commonly for all the wheels.

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 a main part of the shock absorber. It is a part enlarged sectional view.

As shown in FIG. 2, the suspension control device 1 of the present embodiment includes shock absorbers 2FL, 2FR, 2RL, and 2RR capable of changing the damping force in two stages, and is connected to each of these shock absorbers to control the damping force. And an electronic control unit 4. Each shock absorber 2FL, 2FR, 2RL, 2R
R is provided between the suspension lower arms 6FL, 6FR, 6RL, 6RR of the left and right front and rear wheels 5FL, 5FR, 5RL, 5RR and the vehicle body 7 together with coil springs 8FL, 8FR, 8RL, 8RR.

Next, the structure of each of the shock absorbers 2FL, 2FR, 2RL, and 2RR will be described.
Since the structures of 2RL and 2RR are all the same, here the left front wheel 5
A description will be given using the shock absorber 2FL on the FL side as an example. Further, in the following description, reference numerals of the respective members provided on the respective wheels indicate, as necessary, the left front wheel 5FL, the right front wheel 5FR, the left rear wheel 5RL,
Subscripts FL, FR, RL, and RR corresponding to the right rear wheel 5RR shall be added, and if there is no difference between the respective wheels, the subscripts will 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
Thereby, 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 leaf valve 31 and the collar 32 are pressed and fixed respectively to the backup member 28 side. Also, leaf valve
A main valve 34 and a spring 35 are interposed between the 31 and the backup member 28, and bias the leaf valve 31 toward the main piston 18.

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.
That is, when the piezo actuator 27 expands due to the application of a high voltage, the shock absorber 2 switches its damping force characteristic from a state of a large damping force (hard) to a small damping force (soft) side. The damping force characteristic is returned to the damping force (hard) state.

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 the arrow B (contraction direction) is larger than when the main piston 18 moves in the direction of the arrow A (extension direction). Become. 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. Further, a hydraulic oil supply path 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, an integrator 71 that integrates an output signal of the damping force change rate detection circuit 70 and outputs a damping force signal, Bandpass filter (BPF) 72 that extracts only specific frequency components from force signals, steering sensor 50
And a waveform shaping circuit 72 connected to the vehicle speed sensor 51, a high voltage application circuit 75 connected to the piezo actuator 27, and a power supply from a battery 77 via an ignition switch 76 to output a driving voltage for driving the piezo actuator. Switching regulator type high voltage power supply circuit 7
9. A constant voltage power supply circuit 80 for changing the voltage of the battery 77 to generate the operating voltage (5 V) of the electronic control unit 4 is provided. Shift position sensor 52, stop lamp switch 53,
The damping force change rate detection circuit 70, the BPF 72, and the waveform shaping circuit 73 are 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
It consists of four detection circuits provided corresponding to R, RL and RR. Each detection circuit takes out the electric charge accumulated in the piezo load sensor 25 as a voltage signal by a circuit of a predetermined impedance according to the acting force received by the shock absorber 2 from the road surface, and takes this as a damping force change rate V of the shock absorber 2. Is output to the CPU 61 via the input unit 67.

The damping force change rate signal V is also input to the integrator 71, where it is integrated and converted into a signal corresponding to the damping force. The BPF72 that this signal passes next has a frequency of 1.0
Since the filter passes only signals near the sprung resonance frequency of not less than [Hz] and not more than 1.5 [Hz], the signal output from the BPF72 should correspond to the magnitude of the slow body vibration caused by sprung resonance. Become. Damping force change rate V
FIG. 5 (A) shows how only the damping force signal corresponding to the sprung resonance is extracted from the damping force signal obtained by integrating
It was shown to. The damping force signal corresponding to the sprung resonance is hereinafter referred to as a sprung resonance signal SVup.

The waveform shaping circuit 73 is a circuit that shapes detection signals from the steering sensor 50 and the vehicle speed sensor 51 into a signal suitable for processing in the CPU 61 and outputs the signal. Therefore, the CPU 61 of the electronic control unit 4 controls the damping force change rate detection circuit 70, BPF7
2 and the output signal from the waveform shaping circuit 73, as well as the own processing result and the like, it is possible to determine the road surface state, the running state of the vehicle, and the like. CPU 61, based on such a determination,
A control signal is output to a high voltage application circuit 75 provided corresponding to each wheel.

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 is in a small state. On the other hand, when the electric charge is discharged by a negative voltage to contract the Piuzo actuator 27, As the oil flow rate decreases, the damping force becomes large. Note that once the electric charge accumulated in the piezo actuator 27 is discharged, even if the negative voltage is removed, the piezo actuator 27 remains in a contracted state, and the shock absorber 2 maintains a large damping force state.

Next, damping force control performed by the suspension control device 1 according to the present embodiment having the above-described configuration will be described with reference to the flowcharts of FIGS. 6, 7, 8, and 9. Each routine shown in each figure is repeatedly executed at predetermined time intervals by interrupt processing. Note that these processes are
The processing is executed for each of the shock absorbers 2FL, FR, RL, and RR of each wheel. However, since the processing for each wheel is 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. 6) The piezo actuator 27 is switched based on the change rate V of the damping force to set the damping force to a large state or a small state.

Frequency Detection Interrupt Routine (FIG. 7) The rate of change of the damping force within a predetermined time is equal to the learning reference value VrefG.
Is detected as the frequency N corresponding to the damping force change parameter.

Switching Reference Value Vref Learning Routine (FIG. 8) The switching reference value Vref used for switching the damping force is learned based on the magnitude of the switching frequency N.

Learning Period Change Routine (FIG. 9) The period i for learning the switching reference value Vref is changed based on the magnitude of the sprung resonance frequency component, that is, the magnitude of the slow vibration of the vehicle body.

The frequency detection interrupt routine and the switching reference value Vref learning routine refer to the time measurement variable C and the frequency N to learn the switching reference value Vref, and learn the learned switching reference value Vr.
Using ef, the damping force pattern switching control routine executes the switching control of the damping force. In addition, the learning timing in the switching reference Vref learning routine is changed by the learning period change routine, and if the vibration near the sprung resonance frequency is large, the learning is performed in a short period of time. For details of each routine, see the damping force pattern switching control routine (6th
) Will be described in order.

When this damping force pattern switching control routine is started,
First, from the damping force change rate detection circuit 70 via the input unit 67,
A process of reading the rate of change V of the damping force of each shock absorber 2 is performed (step 100).
Is greater than the switching reference value Vref learned in the switching reference value learning routine (FIG. 8) (step 110). If the damping force change rate V is smaller than the switching reference value Vref, it is determined whether or not the flag FHS indicating that the characteristics of the suspension is set to software is 1 (step 120). If not 1,
Control the suspension hard (Step 130)
This routine is ended once. The process of step 130 is such that immediately after the setting of the damping force of the shock absorber 2 is switched from software to hardware, -100 volts from the high voltage application circuit 75 is supplied to the piezo actuator 27 by the control signal from the output unit 68. This is performed by reducing the voltage by applying the voltage, and holding the piezoelectric actuator 27 as it is in a contracted state.

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 (time corresponding to TS) elapses, at step 170 Is YES, the flag FHS is reset to 0 (step 190), and the damping force of the shock absorber 2 is controlled to a large value (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 damping force change rate (FIG. 7) in order to determine the damping force switching reference value Vref referred to in the damping force switching control routine (FIG. 6).
Will be described. When this interrupt routine is started,
First, a process of incrementing a variable C for counting the number of times of activation 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. If the current pattern is determined to be soft with reference to the value of the flag FHS, the current switching reference value Vref is multiplied by a value of 0.8 × 0.5 (step 212). The current switching reference value Vref is multiplied by the value 0.8 (step 214) to calculate the learning reference value VrefG.

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 detection of 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. 8, when the switching reference value learning routine is started, first, the stop lamp switch 53 and the steering sensor 5 are input via the input unit 67.
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, the processing for switching the switching reference value Vref is performed to prepare for such processing (step 315). .

On the other hand, when it is determined that the running state of the vehicle does not require the anti-dip 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. 7 is executed once, and the time required to determine the magnitude of the frequency N based on the value of the variable C (the ninth time).
That is, it is determined whether the learning period change routine shown in FIG. If it is determined that the frequency of execution of the frequency detection interrupt routine is small (C <i) and 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.
It is determined as a function f1 (Sp) that increases as SP increases.

Next, a process for obtaining a frequency deviation ΔN between the frequency N counted in the frequency detection interrupt routine (FIG. 7) and the frequency reference value Nref is performed (step 360), and whether or not the frequency deviation ΔN is larger than 0 Is determined (step 370).
If the frequency deviation ΔN is larger than the value 0, the correction value ΔV is changed to the value β
(Step 380). On the other hand, if the frequency deviation ΔN is equal to or smaller than 0, the correction value ΔV is decremented by the value β (step 390), and the correction value ΔV is added to the reference base value Vbase. A process for calculating the switching reference value Vref is performed (step 400). As a result, the vehicle speed Sp
The switching reference value Vref is changed in accordance with, but the correction value ΔV learned up to that time is stored and used continuously. After the execution of step 400, the frequency N is reset to a value in preparation for the subsequent frequency detection (step 410), and this routine ends.

By executing the switching reference value learning routine described above, the switching reference value Vref is set based on the vehicle speed Sp, and is learned based on the frequency N relative to the frequency reference value Nref. That is, in this example, the frequency reference value Nr
ef is a target value of the frequency N as a damping force change parameter.

The period of such learning is determined by the magnitude of the variable i. The learning of this variable i will be described based on the learning period change routine in FIG. This routine is an interrupt routine that is started at predetermined time intervals.
Perform the process of calculating the sprung resonance signal SVup (step
500). First, the sprung resonance signal SV read from the BPF72
up may be used directly, but the sprung resonance signal
The average value of the sprung resonance signal VSup may be obtained by averaging the weight of the SVup with the average value obtained so far (so-called averaging process), and this may be used thereafter.

Next, the sprung resonance signal SVup is set to a predetermined comparison value SVref.
It is determined whether or not the value is larger than the reference value (step 510). If the sprung resonance signal SVup is equal to or smaller than the comparison value SVref, an initial value i0 is set as a variable i (step 520), and the frequency reference value Nre is further set.
A process for setting f to the initial value N0 is also performed (step 530).

On the other hand, if the sprung resonance signal SVup is larger than the comparison value SVref, the function value h1 (SVup) of the sprung resonance signal SVup is set to the variable i corresponding to the learning period (step 540), and the frequency reference value Nref is also sprung. A process of setting a function value h2 (SVup) of the resonance signal SVup is performed (step 550). Function value h1 (SVu
The variable i given as p) is determined as a value that decreases as the sprung resonance signal SVup increases as shown in FIG. 5 (B). The reason why the frequency reference value Nref is updated in accordance with the update of the variable i is that if the learning period is short, the frequency at which the damping force change rate V exceeds the switching reference value Vref becomes a small value within that period. This is to guarantee. The variable i and the frequency reference value Nref corresponding to the learning period are set such that h2 (SVup) / h1 (SVup) ≦ N0 / i0.

After setting the variable i and the frequency reference value Nref (steps 520 to 550), the process exits to "RTN" and ends this routine.

By executing the processing shown in the flowcharts of FIGS. 6 to 9 sequentially described above, the generation pattern of the damping force of each shock absorber 2 of the vehicle, and consequently, the hardness of the suspension are controlled as follows. You.

[I] When the vehicle is continuously traveling on a flat road, the damping force change rate V becomes very large.
Is controlled to a large state. 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. 7), and the damping force change rate V is changed to the switching reference value during a predetermined period (period corresponding to the variable i). The frequency N exceeding Vref is a small value. Therefore, the switching reference value Vref is learned to a smaller value by the value β (step 390 in FIG. 8). As a result, the damping force change rate V becomes equal to the switching reference value V.
ref can easily be exceeded, and the damping force can be switched to a small state due to small irregularities or the like while traveling on a flat road. When the value of the switching reference value Vref is reduced in this way, the learning reference value VrefG also becomes a small value, and the damping force change rate V becomes the learning reference value during a predetermined period.
The frequency exceeding VrefG increases. As a result, the switching reference value Vref is updated to a value larger by + β, and while repeating such processing, the switching reference value Vref becomes a value at which the switching frequency is appropriate, that is, a value at which the frequency N becomes equal to the frequency reference value Nref. Will be learned.

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,
As the learning reference value VrefG is learned, the switching reference value Vref is gradually reduced, so that the shock absorber 2 has a small damping force, that is, the suspension characteristics can be easily switched to soft. 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.

When traveling on a flat road, the sprung resonance signal SVup is usually smaller than the comparison value, and the learning period (i) is kept at the initial value i0, but the road surface has gentle undulations. Occurs, the learning period (i) has a small value (h2
(SVup)), and the learning of the above-described switching reference value Vref is performed in a shorter time as compared with a road surface having no undulation.

[II] On the other hand, when the vehicle is continuously running on a rough road having unevenness on the road surface such as an unpaved road, the 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. 7),
The frequency N at which the damping force change rate V exceeds the switching reference value Vref during a predetermined period (a period corresponding to the variable i) is a large value. Therefore, the switching reference value Vref is learned to a larger value by the value β (step 380 in FIG. 8). As a result, the damping force change rate V does not easily exceed the switching reference value Vref, so that the damping force characteristics can be easily switched to hardware even when traveling on a rough road. 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 to a value smaller by -β, and by repeating this processing, the switching reference value Vref is 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 gradually increased, so that the damping force characteristic of the shock absorber 2 becomes large, that is, the suspension characteristic is easily switched to hardware. As a result, it is possible to appropriately cope with the insufficient contact property, which is conventionally known, that is, the so-called low waist around the underbody, when the running on the rough road continues, and the steering stability is remarkably improved.

[III] When the vehicle is traveling on the rough road described in [II] and there is a gradual undulation with a period considerably larger than the unevenness of the road surface (running on a so-called composite road) Case), the change of the damping force change rate V is large,
Suspension characteristics show a tendency to be controlled softly like when traveling on rough roads, but if the soft state continues,
As described in [II], learning of the switching reference value Vref is performed in a direction in which control is easily performed by hardware.

By the way, in the case of a complex road surface, the variable i corresponding to the learning period is set to a small value based on the magnitude of the sprung resonance signal SVup by the learning period changing routine shown in FIG. FIG. As a result, in the suspension control device according to the present embodiment, the switching reference value Vref is updated in a shorter period of time than when traveling on a simple rough road, and the tendency to control the suspension hard as a whole increases. . Therefore, on the composite road surface, it is possible to prevent the occurrence of the tilt to some extent and to absorb the unevenness of the road surface to some extent, thereby improving the overall riding comfort.

As described above, according to the suspension control device 1 of the present embodiment, it is possible to improve the contact property when traveling on a flat road or a rough road, and to achieve both the riding comfort and the steering stability of the vehicle. In addition, on a so-called complex road surface where there are fine irregularities on a gently undulating road surface, if the vibration due to the sprung resonance of the vehicle body increases, the time required for learning will be shortened and the suspension state will be set earlier and hard. Facilitates and improves ride quality on complex road surfaces. In particular, in the present embodiment, the riding comfort on a complex road surface is improved by using learning control (learning control of the switching reference value Vref) for improving the riding comfort and steering stability on a flat road or a rough road. The advantage is that the configuration is simple and the control is simple.

In addition, in the suspension control device 1 of the present embodiment, the reference base value Vbase for calculating the switching reference value Vref is obtained based on the vehicle speed Sp. Can be reflected in

In the present embodiment, the learning period (variable i) is calculated based on the value of the sprung resonance signal SVup (FIG. 9 step).
540), since the sprung resonance signal SVup is a signal that changes between plus and minus as shown in FIG. 5 (A), a certain time after the sprung resonance signal SVup once falls outside the range of the comparison value ± SVref. May be configured to shorten the learning time.
During this period, the learning period (i) may be sequentially reduced at a predetermined rate.

Next, a second embodiment of the present invention will be described. The suspension control device as the second embodiment has the same device and configuration as the first embodiment, and instead of the configuration (FIG. 9) for changing the learning period (i), a switching reference value learning routine (8th embodiment)
3), a configuration for correcting the frequency reference value Nref is provided. That is, in the switching reference value learning routine, as shown in FIG. 10, the reference base value Vbase is calculated (step 350), and then the frequency reference value Nref is set based on the sprung resonance signal SVup. (Step 35
5) Then, the frequency deviation ΔN in the step is calculated (step 360). As shown in FIG. 11, the frequency reference value Nref is set in step 355 because the sprung resonance signal SVup increases as the sprung resonance signal SVup increases, that is, as the vibration near the sprung resonance frequency of the vehicle body increases.
It's like setting ef to a small value.

As a result, when the switching reference value learning routine shown in FIGS. 10 and 8 is performed together with other routines (FIGS. 6 and 7), on a road surface where sprung resonance occurs in the vehicle body,
The switching reference value Vref is learned to a value larger by the repetition value β (steps 360 to 400 in FIG. 8), and the damping force of the shock absorber 2 is easily set to be hard. Therefore, the damping force change rate V greatly varies on a so-called composite road surface where the road surface is rough and has gradual undulations. However, the suspension control device 1 of the present embodiment also provides a shock absorber similarly to the first embodiment. 2 is easier to set as a whole as compared with a case of simply traveling on a rough road, and it is possible to prevent so-called tilting while maintaining a balance with the riding comfort.

In the above embodiment, the damping force change rate detecting circuit 70 which receives the input signals from the piezo weight sensors 25FL, 25FR, 25RL, 25RR has a first feature.
The CPU 61 executes the control processing shown in the flowchart of FIG. 5 for the high voltage application circuits 75FL, 75FR, 75RL, 75RR and the piezo actuators 27FL, 27FR, 27RL, 27RR. By doing so, the "damping force control means" in claim 1 is constituted, and the CPU 61 executes the control processing shown in the flowchart of FIG. Then, the CPU 61 executes the control processing shown in the flowchart of FIG. 8 to constitute the "adjustment reference value learning means" according to claim 1, and has a sprung resonance having a frequency of not less than 1.0 [Hz] and not more than 1.5 [Hz]. Bandpass filter BPF that passes only signals near the frequency
The CPU 61 executes step 540 of the control processing shown in the flowchart of FIG. 9 to constitute the "learning period shortening means" in claim 1, In the example where the CPU 61 executes the control processing shown in the flowchart of FIG. 10 instead of FIG.
By performing step 5, the "target value correcting means" in claim 2 is constituted.

Although several embodiments of the present invention have been described above,
The present invention is not limited to these examples in any way,
For example, instead of increasing or decreasing the switching reference value Vref based on the frequency N, the switching reference value Vref is updated by the time during which the damping force change rate V exceeds the damping force reference value Vref. Similarly, the suspension is switched softly. Configuration for updating the switching reference value Vref with time, or frequency reference value Nref
Can be implemented in various modes without departing from the gist of the present invention, such as a configuration in which the values are different for each of the front, rear, left, and right wheels 5FL, FR, RL, and RR.

Effect of the Invention As described in detail above, when traveling on a so-called complex road having unevenness such as a non-paved road and a gentle undulation, the first suspension control device sets the switching reference as the sprung resonance increases. The learning period of the value is shortened, and the second suspension control device corrects the target value of the damping force change parameter such that the larger the sprung resonance, the larger the setting of the damping force becomes. Therefore, vibration on the complex road surface near the sprung resonance frequency of the vehicle body (so-called tilt)
While appropriately preventing vibrations on rough road surfaces,
It has an extremely excellent effect of dramatically improving ride comfort. In addition, according to the suspension control device of the present invention, it is possible to preferably maintain the riding comfort and the steering stability of the vehicle when traveling on a flat road or a rough road.

[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 illustrating an overall configuration of a suspension control device as an embodiment of the present invention, and FIG. 3 (B) 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, and FIG. 5 (A) damping. FIG. 5 (B) is a graph showing an example of a force signal, FIG. 5 (B) is a graph showing a relationship between a sprung resonance signal SVup and a learning period (i), FIG. 6 is a flowchart showing a damping force pattern switching control routine, FIG. Is a flowchart showing a frequency detection interrupt routine, FIG. 8 is a flowchart showing a switching reference value Vref learning routine, FIG. 9 is a flowchart showing a learning period change routine, and FIG. 10 is a control in the second embodiment of the present invention. The main part of FIG. 11 is a graph showing the relationship between the sprung resonance signal SVup and the frequency reference value Nref. 1 ... Suspension controller 2FL, FR, RL, RR ... Shock absorber 4 ... Electronic controller 25FL, FR, RL, RR ... Piezo load sensor 27FL, FR, RL, RR ... Piezo actuator 51 ... Vehicle speed Sensor 70: Damping force change rate detection circuit, 71: Integrator 72: Bandpass filter (BPF) 75: High voltage application circuit, 79: High voltage power supply circuit

Continuing from the front page (72) Inventor Hiroyuki Kawada 1-1-1, Showa-cho, Kariya-shi, Aichi, Japan Inside Denso Corporation (72) Inventor Akira Fukami 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Corporation (72 ) Inventor Yutaka Suzuki 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Examiner, Takushi Koyama in Denso Co., Ltd. (56) References JP-A-64-67407 (JP, A) JP-A-62-80111 (JP, A (58) Field surveyed (Int.Cl. ⁶ , DB name) B60G 17/015

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 rate of change of the force and a switching reference value, wherein the damping force is controlled by the damping force control means. With respect to the setting change, a damping force change parameter such as a change frequency, a magnitude of the damping force after the change, and a frequency at which the rate of change of the damping force exceeds a learning reference value set at a value smaller than the switching reference value is detected. Parameter detecting means for adjusting the switching reference value of the damping force control means at predetermined intervals so that the damping force change parameter matches the target value. A reference value learning unit, a sprung resonance detection unit that detects vibration near a sprung resonance frequency generated in the vehicle body during running of the vehicle, and the adjustment reference value learning unit according to the detected magnitude of the sprung resonance. A suspension control device, comprising: a learning period shortening unit that shortens the learning period as the sprung resonance increases when setting the learning period. 2. The suspension control device according to claim 1, wherein, instead of the learning period shortening means, the larger the detected sprung resonance is, the more the damping force change parameter in the adjustment reference value learning means becomes. A suspension control device provided with target value correction means for correcting a target value to a side on which a setting of a damping force becomes relatively large.