JPH05104924A - Variable damping force type shock absorber control device - Google Patents

Abstract

PURPOSE:To prevent the generation of noise caused by the vibration of a support part by providing a limiting means for limiting a command signal outputted from a command signal output means, to the value at the noise genera tion start time or less. CONSTITUTION:In a step 508, the vibration of a support part 1 is estimated from the damping force detected in a step 502. In a step 509, the upper limit value of the damping force is computed from the allowed level of vibration in steps 506, 507 and the vibration of the support part 1 estimated in the step 508. The upper limit value VSB of command value (damping coefficient) that can be set in the following control cycle up to the time of the estimated vibration of the support part 1 reaching the allowed level is computed from the computed upper limit value of the damping force and the expansion speed of a shock absorber 6 detected in a step 503. In a step 510, the command value VSA computed in a step 505 is compared with the upper limit value VSB computed in the step 509, and the smaller value is outputted as command signal voltage VS to an actuator drive unit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a damping force variable shock absorber control device in which a switching actuator such as a piezo actuator is provided so as to vary the damping force.

[0002]

2. Description of the Related Art Conventionally, as a known shock absorber control device for improving riding comfort and steering stability, an optimum damping force (target damping force) is calculated from a physical quantity according to a running state, and an actual damping force is calculated. A device that outputs a control command value to the actuator driving means so as to match the target damping force to drive the actuator (for example, Japanese Patent Laid-Open No. 1-111513).
Issue).

[0003]

However, in the conventional device, when the followability to the target damping force is increased (the gain is increased) in order to improve the control performance, the deviation between the target damping force and the actual damping force becomes large. When it is larger, the command value to the actuator driving means changes suddenly, so that the damping force changes rapidly. If the damping force suddenly changes, there is a problem in that the support portion interposed between the shock absorber and the vehicle body vibrates and an unpleasant sound is generated, which gives an occupant an uncomfortable feeling.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a shock absorber control device that suppresses the generation of sound due to the vibration of the support portion.

[0005]

In order to achieve the above object, the shock absorber control apparatus of the present invention, as shown in FIG. 1, includes actuator drive means for driving a switching actuator for switching the damping force of the shock absorber of a vehicle. A damping force detecting means for detecting a damping force of the shock absorber, a target damping force calculating means for calculating a target damping force from a physical quantity according to a running state, and a damping force detected by the damping force detecting means. And a command signal output unit for outputting a command signal to the actuator driving unit so that the target damping force calculated by the target damping force calculation unit is obtained, and the shock absorber is attached to the vehicle body via a support portion. In the damping force variable shock absorber controller, the damping force is detected by the damping force detecting means. Estimates the vibration of the support portion from 衰力,
Setting means for setting the value of the command signal when the sound caused by the vibration of the support portion starts to be generated, and the command signal output from the command signal output means is limited to the value at the time when the sound starts to be generated or less. The gist is to provide the limiting means.

[0006]

In the control device having the above structure, the vibration of the support portion is estimated from the damping force to set the value of the command signal when the sound due to the vibration of the support portion starts to be generated, and the command signal output means is provided. Since the command signal output from is limited to a value equal to or less than the value at which the sound starts to be generated, the support does not vibrate so much that the sound caused by the vibration of the support is generated.

[0007]

Embodiments of the shock absorber control device of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a sectional view of the main part of the shock absorber 6. In FIG. 2, the internal space of the cylinder 401 of the shock absorber 6 is vertically divided by a main piston 402 into hydraulic chambers 4a and 4b, respectively, and the main piston 402 is fixed to a piston rod 403 penetrating the center thereof. The piston rod 403 is connected to the lower end of a shaft 404 extending upward.

On the outer periphery of the main piston 402,
A contraction side fixed orifice 405 and an extension side fixed orifice 406 are formed therethrough, and plate-like check valves 407 and 4 provided on the upper surface and the lower surface of the main piston 402, respectively.
It is opened and closed by 08. A sub-channel 409 is formed in the shaft 404. The sub-channel 409 extends downward from the side surface facing the upper hydraulic chamber 4a through the center of the rod. The sub-channel 409 is formed by an annular groove on the outer periphery of a spool valve 410 that operates vertically. The flow path cross-sectional area can be changed.

The lower end of the shaft 404 is formed in a cylindrical shape, and the piezo actuator 4 is provided in the cylinder.
The piezo actuator 4 is configured by laminating a large number of piezoelectric ceramic plates such as PZT, and expands and contracts according to a drive voltage supplied from a drive device of the actuator via a lead wire 412. A piston 413 is provided in contact with the lower end of the piezo actuator 4, an oil-tight chamber 414 is formed below the piston 413, and a plunger 415 facing the oil-tight chamber 414 and vertically movable is disposed. The plunger 415 is connected to the spool valve 410.

However, during the contraction operation in which the main piston 402 moves downward, the enclosed oil circulates between the hydraulic chambers 4a and 4b via the large-diameter contraction-side fixed orifice 405, and the damping coefficient becomes slightly small, resulting in small damping. On the other hand, at the time of extension operation in which the force is generated and the main piston 402 moves upward, the enclosed oil circulates between the hydraulic chambers 4a and 4b via the small diameter extension side fixed orifice 406, and the damping coefficient is slightly increased to a large damping force. Occurs.

These damping forces can be continuously changed by operating the spool valve 410 by the piezo actuator 4 and continuously changing the flow passage cross-sectional area of the sub flow passage 409. That is, as shown in FIG. 3, the damping coefficient is arbitrarily changed between the characteristics x and y when the flow passage cross-sectional area is increased and between the characteristics x ′ and y ′ when the flow passage cross-sectional area is reduced to be arbitrary. It is possible to generate a damping force of.

The upper end of the shock absorber 6 is
As shown in FIG. 4, it is fixed to the vehicle body 2 with bolts 8 and nuts 9 via a support portion 1. Next, the piezo actuator driving device 3 for driving the piezo actuator 4 will be described. FIG. 5 shows a circuit diagram of the piezo actuator driving device 3. The piezo actuator drive device 3 is provided corresponding to the piezo actuator 4 of each wheel, and each piezo actuator drive device 3 has a DC / DC system in which the battery voltage is boosted to 600V.
The output voltage of the converter 301 is supplied. Also,
The command signal voltage Vs from the electronic control unit 7 is compared with the voltage of the charge amount detection capacitor 307 of the piezo actuator 4 fed back via the buffer 306 in the comparator 302. When the command voltage Vs is higher than the voltage of the charge detection capacitor 307, the comparator 302 outputs a “1” level signal. As a result, the photocoupler 303a is extinguished and the output F
The ET 304a becomes conductive, and the high voltage generated by the DC / DC converter 301 is applied to the piezo actuator 4 to charge it. The charging current at this time is kept constant by the current feedback circuit 305a.

When the voltage of the piezoelectric actuator 4 increases and the voltage of the charge amount detecting capacitor 307 exceeds the command signal voltage Vs, the comparator 302 outputs a signal of "0" level. Then this time, photo coupler 3
03b is extinguished and the output FET 304b becomes conductive, and the electric charge stored in the piezo actuator 4 is discharged. The discharge current at this time is the current feedback circuit 30.
It is kept constant by 5b.

Thus, the amount of charge stored in the piezoelectric actuator 4, that is, the amount of expansion thereof, is in accordance with the signal level of the command voltage Vs output from the electronic control unit 7, and the damping coefficient of the shock absorber 6 depends on the command voltage Vs. It can be changed continuously.

Next, a method of preventing the sound generated due to the vibration of the support portion 1 will be described. It can be considered that the sound transmitted in the vehicle compartment is almost proportional to the amplitude of the vibration of the support portion 1. Therefore, the damping force is first considered as the input, and the support portion 1
Create a mathematical model that outputs the vibration of (the speed of vibration / acceleration of vibration may be used). Specifically, as shown in FIG. 6, it is approximated by a secondary vibration model etc. taught by vibration engineering etc. In FIG. 6, s is the Laplace operator,
a, b, and c are coefficients that differ depending on the shock absorber 6, the support portion 1, and the like. As a result, if the damping force that is the input to the mathematical model is detected, the vibration of the support portion 1 that is the output can be estimated. For example, when the support portion 1 in the measurement time T _A previously a damping force as shown in FIG. 7 (a) occurs in measurement time T _A not vibrate, the vibration of the measurement time T _A after the support portion 1 A time chart showing the estimation of is as shown in FIG. The measurement have support unit 1 vibrates measurement time T _A previous time T _A
Assuming that no damping force is generated thereafter, the time chart showing the estimation of the vibration of the supporting portion 1 after the measurement time T _A is as shown by the broken line in FIG.

[0017] Then, by combining the time chart shown in FIG. 7 (b) and FIG. 8, the support portion 1 in the measurement time T _A previously no matter by any vibration, damping force is generated in the measurement time T _A Sometimes, the vibration of the support 1 after the measurement time T _A can be estimated. FIG. 9 shows a time chart obtained by superimposing FIG. 7B and FIG.

In the time chart of FIG. 8, if the vibration level of the supporting portion 1 is set to a preset allowable vibration level (the level at which the supporting portion 1 produces a sound due to the vibration),
What kind of damping force is generated after the measurement time T _A causes the vibration to exceed the allowable level, that is, the upper limit value of the damping force that may be generated after the measurement time T _A can be calculated. Specifically, the same vibration allowable level as in FIG. 8 is provided in the time chart of FIG. 9 as well, and the magnitude of the generated damping force shown in FIG. The vibration amplitude of the support portion 1 may be increased, and the damping force value when the vibration amplitude of the support portion 1 in FIG. 9 matches the vibration allowable level may be set as the upper limit value of the damping force.

Here, the damping force means the expansion / contraction speed of the shock absorber 6 and the piezo actuator 4 according to a known technique.
It can be expressed approximately by the product of the damping coefficient that can be changed by. Therefore, the expansion / contraction speed of the shock absorber 6 is known, and the expansion / contraction speed of the shock absorber changes abruptly (considering the dynamics of the vehicle, the expansion / contraction speed of the shock absorber does not change abruptly within the damping coefficient control cycle (for example, about 5 ms). Otherwise, it is possible to calculate the attenuation coefficient from the following equation so that no sound is generated after the measurement time T _A.

[0020]

## EQU1 ## Damping coefficient = (upper limit value of damping force) / (shock expansion / contraction speed) Next, the control process executed by the electronic control unit 7 will be described with reference to FIG.
A description will be given based on the flowchart shown in FIG.

First, in step 501, the data is initialized, and in step 502, the actual damping force of the shock absorber 6 is detected as shown in Japanese Patent Laid-Open No. 1-205512. In step 503, the expansion / contraction speed (relative speed) of the shock absorber 6 is detected, and the vehicle speed and the vertical acceleration of the vehicle body are also detected.

At step 504, the target damping force of the shock absorber 6 is calculated based on the vertical acceleration of the vehicle body detected at 503. Specifically, step 503
The vehicle body up-down velocity is calculated by integrating the vehicle body up-down velocity detected by the above, and the target damping force is a value obtained by multiplying the vehicle body up-down velocity by a coefficient.

In step 505, the command value V _SA to the actuator driving device 3 is calculated from the target damping force calculated in step 504 and the actual damping force detected in 502. In step 506, it is determined whether or not it is time to update the permissible level of vibration of the support portion 1 required in step 509 described later. The allowable vibration level is the upper limit value of the vibration of the support portion 1 in the state where no sound is generated. Specifically, this timing may be about once a second. Here, if it is determined that it is the allowable level update timing,
Go to step 507.

In step 507, the allowable level is updated in accordance with the vehicle speed detected in step 503 by referring to the vehicle speed-vibration allowable level map provided in the electronic control unit 7. This map is designed to increase the allowable level as the vehicle speed increases. This is because, as the vehicle speed increases, the environmental noise and the like increase, and the sound around the shock absorber relatively decreases. By updating the permissible level, the less the restriction on the vibration of the support portion 1 is, the higher the control followability is. On the contrary, the tighter the restriction on the vibration of the support portion 1 is, the less the control followability is.

In step 508, the vibration of the support portion 1 is estimated from the damping force detected in step 502 by superposing the vibration model shown in FIG. 6 and the vibration models shown in FIGS. In step 509, the upper limit value of the damping force is calculated from the allowable level of vibration in steps 506 and 507 and the vibration of the support portion 1 estimated in step 508, and the upper limit value of this damping force and the shock absorber 6 detected in step 503. The upper limit value _VSB of the command value (damping coefficient) that can be set in the next control cycle until the estimated vibration of the support portion 1 reaches the allowable level is calculated from the expansion / contraction speed of.

At step 510, the command value V _SA calculated at step 505 is compared with the upper limit value _VSB of the command value calculated at step 507. If the command value calculated in step 505 is not less than the upper limit value _VSB of the command value calculated in step 507, the process proceeds to step 511, and the command value V _SA calculated in step 505 is used as the command signal voltage Vs for the piezo actuator driving device 3 Output to.

On the other hand, the command value V calculated in step 505
_{If SA} is less than the upper limit value _{VSB of} the command value calculated in step 507, the process proceeds to step 512, and the upper limit value _VSB of the command value calculated in step 507 is output to the piezo actuator driving device 3 as the command signal voltage Vs. .. That is, in step 511 or step 512, step 51
Of the values compared with 0, the smaller value (upper limit value or assuming that the damping coefficient increases as the command value increases) is output to the actuator drive device 3 as the command signal voltage Vs.

The actuator driving device 3 receives the command signal voltage Vs output from the electronic control circuit 7 to expand / contract the piezo actuator 4 in accordance with the command signal voltage Vs, thereby changing the damping coefficient and changing the shock absorber 6. Change the damping force of.

As described above, in this embodiment, step 50 is performed.
In step 9, the upper limit value of the command value (damping coefficient) that can be set in the next control cycle is calculated, and in step 510, the command value V _SA calculated in step 505 and the command value V _SA calculated in step 509 are calculated. The upper limit value _VSB is compared and the smaller value is output to the actuator drive device 3 as the command signal voltage Vs. Therefore, even if the command value V _SA calculated in step 505 is larger than the upper limit value _VSB of the command value calculated in step 509, the command signal voltage Vs equal to or lower than the upper limit value is output to the actuator drive device 3. Therefore, the vibration of the support portion 1 does not exceed the allowable level, and the damping force does not suddenly change and no sound is generated due to the vibration of the support portion 1.

In the present embodiment, the actuator driving device 3 corresponds to the actuator driving means, and FIG.
Step 502 of 0 corresponds to damping force detection means, step 504 corresponds to target damping force calculation means, and step 50
5 corresponds to command value calculation means, step 508 corresponds to vibration estimation means, step 502 corresponds to physical quantity detection means, steps 506, 507, 508 and 509 correspond to setting means, and steps 510, 511 and 512 corresponds to the limiting means.

The present invention is not limited to the above-mentioned embodiments, and various modifications can be made, for example, as shown below, without departing from the spirit of the present invention. The permissible level of vibration updated in step 507 may be updated in consideration of a physical quantity corresponding to a traveling state other than vehicle speed such as yaw rate.

[0032]

As described in detail above, according to the damping force variable shock absorber control device of the present invention, the command signal output from the command signal output means is limited to a value equal to or lower than the value at which sound starts to be generated. Therefore, there is an excellent effect that it is possible to prevent the generation of sound due to the vibration of the support portion.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a complaint.

FIG. 2 is a sectional view of a main part of a shock absorber 6.

FIG. 3 is a characteristic diagram showing a generated damping force characteristic of a shock absorber 6.

FIG. 4 is a cross-sectional view showing the vicinity of a support portion 1.

5 is an electric circuit diagram showing a configuration of an actuator drive device 3. FIG.

FIG. 6 is a calculation diagram for calculating the vibration of the support unit 1 from the damping force.

FIG. 7 is a time chart explaining the vibration of the support portion 1.

FIG. 8 is a time chart explaining the vibration of the support portion 1.

FIG. 9 is a time chart explaining the vibration of the support portion 1.

FIG. 10 is a flowchart showing a control process executed by the control device.

[Explanation of symbols]

 3 Actuator drive device 4 Piezo actuator 6 Shock absorber 7 Electronic control device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Takasou 1-1, Showa-cho, Kariya city, Aichi Prefecture Nihondenso Co., Ltd.

Claims (1)

[Claims] 1. A drive unit for driving a switching actuator for switching a damping force of a shock absorber of a vehicle, a damping force detecting unit for detecting a damping force of the shock absorber, and a target damping amount based on a physical quantity according to a running state. Outputting a command signal to the actuator driving means so that the target damping force calculating means for calculating the force and the damping force detected by the damping force detecting means become the target damping force calculated by the target damping force calculating means. In the damping force variable shock absorber control device in which the shock absorber is attached to the vehicle body through the support portion, the vibration of the support portion is generated from the damping force detected by the damping force detection means. Estimate and set the value of the command signal when the sound due to the vibration of the support begins to be generated. Setting means for, the command signal and limiting means for sound command signal outputted from the output means is limited to less than the value at which begins to occur, the damping force variable shock absorber control apparatus comprising: a.