JP2000103218A - Controller of vehicle suspension mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller for generating a damping force maximizing signal only in the vicinity of a resonance point of a car body and a wheel by a damping force variable hydraulic shock absorber capable of switching maximum or minimum two damping force characteristics at a high speed. SOLUTION: This suspension mechanism has a highly responsive damping force variable hydraulic shock absorber 4 where a low speed area characteristic of a piston becomes a viscous damper, a vertical acceleration sensor 2 for detecting vertical acceleration of a car body 3, a vertical acceleration sensor 6 for detecting vertical acceleration of a wheel 7 and an electronic controller 20 for generating an ON.OFF signal on the basis of a vertical speed of the phase-corrected car body 3 and a vertical speed of the piston of the hydraulic shock absorber 4. Damping force of the hydraulic shock absorber 4 is switched to a maximum or a minimum by the ON.OFF signal of the electronic controller 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic control unit for generating an ON / OFF signal (binary switching signal) using the vertical speed of a piston of a hydraulic shock absorber and the vertical speed of a vehicle body whose phase has been corrected. Switch damper damping force between maximum and minimum
The present invention relates to a control device for a vehicle suspension mechanism that performs ON / OFF control.

[0002]

2. Description of the Related Art In general, in a vehicle suspension mechanism using a hydraulic shock absorber having an invariable damping force characteristic, characteristics of the hydraulic shock absorber are set in consideration of a vehicle type, a vehicle type, ride comfort, steering stability and the like. In this case, since the mass of the vehicle body is several times (6 to 10 times) larger than the mass of the wheel (tire), the damping force characteristics of the hydraulic shock absorber are determined as shown in FIG. As described above, the wheel resonance is substantially suppressed. However, there is a problem that the road surface input blocking property (having a large effect on ride comfort) in a vibration region between the vehicle body resonance point and the wheel resonance point is deteriorated.

Accordingly, a semi-active vehicle suspension mechanism having a variable damping force type hydraulic shock absorber having a response (for example, about 25 to 50 msec) required to suppress the body resonance (1 to 2 Hz) has been developed. By setting the minimum characteristic of the damping force of the shock absorber low, the road surface input cutoff property is improved.
However, as shown in FIG. 15, the above-described semi-active vehicle suspension mechanism does not have a responsiveness to suppress wheel resonance. Therefore, the minimum characteristic of the damping force of the hydraulic shock absorber is set to be high so as to appropriately suppress wheel resonance. Need to be kept. The limitation of the minimum characteristic of the damping force of the hydraulic shock absorber will determine the limit of road surface input cutoff. In order to further improve the riding comfort of a vehicle, a high-response variable damping force type hydraulic shock absorber that suppresses wheel resonance is required.

A semi-active suspension mechanism in which a variable damping-type hydraulic shock absorber is disposed between the vehicle body and the wheels is used as a control method for suppressing the vehicle body resonance and improving the road surface input blocking performance.
A device that generates a damping force of a hydraulic shock absorber in proportion to the absolute speed of a vehicle body (skyhook control) is known to be effective, and is widely used in electronically controlled vehicle suspension mechanisms. The resonance frequency of the wheel is estimated by an appropriate frequency-dependent digital filter, and the wheel resonance can be suppressed by adopting the skyhook control for the wheel. However, in the skyhook control, it is necessary to generate a damping force in the hydraulic shock absorber in proportion to the speed of the vibrating body, and an arbitrary voltage or current can be quickly supplied to the drive unit (driver) of the variable damping force type hydraulic shock absorber. In particular, in the case of a variable damping force type hydraulic shock absorber using an electrorheological fluid, a device (high voltage amplifier) for generating a high voltage of several kV is required, which leads to an increase in the manufacturing cost.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a variable damping force type hydraulic shock absorber capable of switching between the maximum and minimum damping force characteristics at high speed, thereby providing resonance between the vehicle body and wheels. An object of the present invention is to provide a control device for a vehicle suspension mechanism that generates a signal that maximizes a damping force only near a point.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a configuration of the present invention comprises a high-response variable damping force type hydraulic shock absorber in which the characteristics of a piston in a low-speed region become a viscous damper, and A vertical acceleration sensor that detects acceleration, a vertical acceleration sensor that detects the vertical acceleration of wheels, and an electronic control unit that generates ON / OFF signals based on the vertical speed of the vehicle body and the vertical speed of the piston of the hydraulic shock absorber with the phase corrected Wherein the damping force of the hydraulic shock absorber is switched between a maximum value and a minimum value according to an ON / OFF signal of the electronic control unit.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A hydraulic shock absorber used in a vehicle suspension mechanism uses a hydraulic fluid, which is a functional fluid, whose electrical fluid characteristic changes, to reduce the damping force generated by the hydraulic shock absorber at high speed. A continuously variable hydraulic shock absorber is under development. For example, when an electrorheological fluid is used as hydraulic oil, the damping force of the hydraulic shock absorber can be increased by increasing the viscosity of the viscous fluid by applying an electric field. When a magnetic viscous fluid is used as the hydraulic oil, the damping force of the hydraulic shock absorber can be increased by applying a magnetic field to increase the viscosity of the viscous fluid. In both cases, there is no mechanical moving part for adjusting the damping force of the hydraulic shock absorber, and the time required for adjusting the damping force of the hydraulic shock absorber is the time required for changing the characteristics of the viscous fluid (about 5 to 10 msec).
And wheel resonance (10 to 15 Hz) can be suppressed.

As described above, when the hydraulic shock absorber capable of adjusting the damping force at a high speed is used in the vehicle suspension mechanism, the characteristics (road surface input blocking property) that makes it difficult to transmit the unevenness of the road surface to the vehicle body and the grounding property of the wheels are maintained. Characteristics (road surface input followability) can be achieved, and the riding comfort can be further improved. Specifically, the resonance of the vehicle body and the resonance of the wheels can be suppressed, so that the minimum characteristic of the damping force generated by the hydraulic shock absorber can be set to be small without limitation, and the road surface input cutoff property can be improved. Suppression of the wheel resonance prevents deterioration of the ground contact of the wheel, and the road surface input followability can be maintained.

According to the present invention, there is provided a high-response variable damping force type hydraulic shock absorber in which two damping force characteristics can be selected and the damping force characteristic of the piston in a low speed range becomes a viscous damper, and the phase-corrected vertical speed of the vehicle body is increased. And an electronic control unit that generates an ON / OFF signal (binary switching signal) from the vertical speed of the hydraulic shock absorber piston, performs ON / OFF control to switch the damping force of the hydraulic shock absorber to the maximum or minimum. Suppresses vehicle body resonance and wheel resonance and reduces the peak value of the vertical acceleration of the vehicle body in almost all vibration regions. It is only necessary to output the ON / OFF signal to the drive unit of the hydraulic shock absorber, reducing the manufacturing unit price it can.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In general, a one-wheel model is used to evaluate the characteristics of road surface input blockability (ride comfort) and road surface input followability (wheel groundability). The configuration and operation of the present invention are shown in FIG.
A description will be given based on the wheel model. If a variable damping force type hydraulic shock absorber is installed in an actual vehicle, the damping force of the hydraulic shock absorber should be taken into account with respect to the inertia force acting on the vehicle body during steering or acceleration / deceleration, taking into account the posture and steering characteristics of the vehicle body. However, description of this point is omitted in the present invention, and the description will be limited to road surface input.

As shown in FIG. 1, the present invention provides a variable damping type hydraulic shock absorber 4 between a vehicle body 3 and an axle 7a of each wheel 7.
And the suspension spring 5 are connected to each other to form an electronically controlled semi-active suspension. A vertical acceleration sensor 2 is provided on a vehicle body 3 and a vertical acceleration sensor 6 is provided on an axle (or a knuckle) 7a.
The damping force of the hydraulic shock absorber 4 is adjusted according to the output of the electronic control device 20 based on the vertical acceleration detected by the above, the vibration received by the vehicle body 3 is suppressed, and the runaway of the wheels 7 is suppressed.

The electronic control unit 20 removes high frequency component noise and low frequency component offset by passing the detection signals of the vertical acceleration sensors 2 and 6 through an analog bandpass filter 8 and converts the signals into digital signals by an AD converter 9. Then, the vertical speed of the vehicle body 3 whose phase has been adjusted by the phase correction filter 18 including the integrator and the vertical speed and the vertical speed of the wheels 7 are input to the central processing unit 10. Central processing unit 10
To generate ON / OFF signals for determining the maximum and minimum damping force of the hydraulic shock absorber 4 suitable for suppressing the vibration of the vehicle body 3 and the wheels 7,
The DO unit 12 outputs an ON / OFF signal (digital signal) corresponding to the maximum / minimum of the damping force of the hydraulic shock absorber 4 from the drive unit (driver) 13 of the hydraulic shock absorber 4 to the high voltage generator 36,
The damping force of the hydraulic shock absorber 4 is adjusted. The cut-off frequency of the analog bandpass filter 8 is selected to be, for example, 0.2 Hz on the low frequency side and 50 Hz on the high frequency side.

As shown in FIG. 2, the hydraulic shock absorber 4 capable of continuously and rapidly adjusting the damping force has an outer cylinder 37, an intermediate cylinder 38 and an inner cylinder 29 connected between an end plate 23 and an end plate 34. And inner cylinder 2
The upper chamber 24 and the lower chamber 31 are defined by inserting a piston 28 into the piston 9 and the rod 21 connected to the piston 28 projects upward through the end plate 23. As shown in FIG. 1, the rod 21 is connected to the vehicle body 3, and the end plate 34 is connected to the axle 7a. The upper chamber 24 is communicated with a chamber 30 between the intermediate cylinder 38 and the inner cylinder 29 by a through hole 24a at the upper end of the inner cylinder 29, and the chamber 30 is communicated by a through hole 30a at the lower end of the intermediate cylinder 38.
The chamber 25 is communicated between the outer cylinder 37 and the intermediate cylinder 38. The chamber 25 is connected to the lower chamber 31 via the check valve 33 in the passage 32 of the end plate 34.
Communicated to A check valve 27 that allows a flow of oil from the lower chamber 31 to the upper chamber 24 is provided in a passage 26 that passes through the piston 28.

One terminal of the high voltage generator 36 is connected to the upper end of the intermediate cylinder 38 insulated by the annular insulating seals 22 and 35, and the high voltage generator 3 is connected to the lower end of the inner cylinder 29.
6 is connected and grounded. Each room 24,
An electrorheological fluid whose viscosity increases in proportion to the applied voltage is filled in 31, 31. The chamber 25 between the outer cylinder 37 and the intermediate cylinder 38 compensates for excess or deficiency of the electrorheological fluid in the upper chamber 24 and the lower chamber 31 due to the elevation of the piston 28. The high voltage generator 36 functions to increase or decrease the voltage applied to the electrorheological fluid in the chamber 30 according to an analog signal (voltage or current) from the drive unit 13. Accordingly, as represented by the line 39 in FIG. 3, the damping force of the hydraulic shock absorber 4 changes in the patterned area according to the voltage applied to the electrorheological fluid.

As described above, the control device for a vehicle suspension mechanism according to the present invention includes a variable damping force type hydraulic shock absorber 4 capable of quickly and intermittently adjusting the damping force, and a vertical acceleration detecting the vertical acceleration of the vehicle body 3. The sensor 2, a vertical acceleration sensor 6 for detecting the vertical acceleration of the wheel 7, an analog bandpass filter 8 for removing noise and offset of the detection values of the acceleration sensors 2 and 6, and passing through the bandpass filter 8. A / D converter 9 for converting the converted analog value into a digital value
And a phase correction filter 18 for adjusting the phases of the vertical speed of the vehicle body 3, the vertical speed of the wheels 7, and the vertical speed of the vehicle body 3, and an ON / OFF signal for determining the maximum and minimum of the damping force of the hydraulic shock absorber 4. A central processing unit 10 and a DO device 1 for outputting digital signals as the maximum and minimum ON / OFF signals of the damping force of the hydraulic shock absorber 4
2 and a drive unit 13 for switching the damping force of the hydraulic shock absorber 4 between maximum and minimum.

As shown in FIG. 4, the vertical speed of the vehicle body 3 and the vertical speed of the piston 28 of the hydraulic shock absorber 4 are integrated with the vertical acceleration MsA of the vehicle body 3 converted into a digital signal by an integrator 71 of a phase correction filter. And the vertical speed MsV of the vehicle body 3,
The vertical acceleration MuA of the wheel 7 converted into the digital signal is integrated by the integrator 72 of the phase correction filter, and the vertical speed MuV of the wheel 7 is calculated. The central processing unit 10 of the electronic control unit 20 subtracts the vertical speed MuV of the wheel 7 from the vertical speed MsV of the vehicle body 3 in the comparator 73 to obtain the vertical speed of the piston 28 of the hydraulic shock absorber 4 (the relative speed between the vehicle body 3 and the wheel 7). Calculate PV). Here, assuming that the upward speed is positive, if PV> 0, the hydraulic shock absorber 4 is in an extended state,
If PV <0, the hydraulic shock absorber 4 is in a contracted state.

As shown in FIG. 5, a vertical displacement of a piston 28 of the hydraulic shock absorber 4 (relative displacement between the vehicle body 3 and the wheels 7) is used instead of the vertical acceleration sensor 6 for detecting the vertical acceleration of the wheels 7.
A vertical displacement sensor that detects PD can be used. In this case, the vertical acceleration MsA of the vehicle body 3 converted into the digital signal is integrated by the integrator 71 of the phase correction filter,
The vertical velocity MsV of the vehicle body 3 and the displacement PD of the piston 28 of the hydraulic shock absorber 4 converted into a digital signal are differentiated by a differentiator 72a of a phase correction filter, and the vertical velocity of the piston 28 is calculated.
Calculate each PV. Here, if the vertical speed of the piston 28 is PV <0, the output of the displacement sensor is adjusted so that the hydraulic shock absorber 4 is in a contracted state.

Next, control in a vibration region (frequency of 3 Hz or less) near the vehicle body resonance point is performed as follows. Signal generator 7
In 6, the ON / O for suppressing the resonance of the vehicle body is determined from the sign of the product of the vertical speed MsV of the vehicle body 3 and the vertical speed PV of the piston 28.
Generate the FF signal S3. That is, an ON signal is generated if MsV · PV> 0, and an OFF signal is generated otherwise. The meaning of the condition of the ON signal is that when the vehicle body 3 is moving with an upward (positive) vertical speed, the vertical speed of the piston 28 of the hydraulic shock absorber 4 is in an extended state (positive), and the vehicle body 3 is directed downward. When a force is applied, an ON signal is generated.

The control in the vibration region (frequency 3 to 8 Hz) between the vehicle body resonance point and the wheel resonance point is performed as follows. In the vibration region higher than the vehicle body resonance point, the vibration level of the vehicle body 3 becomes small, and therefore, the ON state is the same as in the vibration region near the vehicle body resonance point.
When the OFF signal S3 is generated, an excessive damping force is generated in the hydraulic shock absorber 4 with respect to the vibration level of the vehicle body 3, and as a result, the vehicle body 3
A large peak value is generated in the vertical acceleration of.

As shown in FIG. 9, when a road surface input having a frequency of 4 Hz is applied to the wheels 7, the signal generator 76 generates an ON / OFF signal S3. To reduce the ON time t1 of the ON / OFF signal S3 in order to reduce the peak value of the vertical acceleration of the vehicle body 3, there are two ways to delay the rise of the ON signal or advance the fall. It is more effective to proceed. The reason is that the rising signal depends on the reversal of the sign of the vertical speed of the piston 28. Therefore, if the damping force characteristic of the hydraulic shock absorber 4 is set as shown in FIG. This is because a change in the damping force of the hydraulic shock absorber 4 can be reduced. In order to advance the falling of the ON / OFF signal S3, a signal of the vertical speed MsV of the vehicle body 3 is applied to the signal generator 76 after passing through the vehicle speed phase correction filter 19 having characteristics as shown in FIGS. The three types of vehicle speed phase correction filters 19 shown in FIGS. 6 to 8 advance the phase up to a frequency of about 8 Hz. Vertical speed MsV of body 3
Is passed to the vehicle speed phase correction filter 19,
As shown by 0, the fall of the ON / OFF signal S3 advances by the time t2, and the ON time t1 of the ON / OFF signal S3 is shortened.

A vibration region near the wheel resonance point (frequency 8 to 1)
The control at 5 Hz) is performed as follows. In a vibration region near the wheel resonance point, the wheel resonance is suppressed from the vibration of the vehicle body 3. When the vehicle speed phase correction filter 19 is not used, the signal generator 76 generates an ON / OFF signal S3 as shown in FIG.
The ON / OFF signal S3 is a signal for suppressing the vibration of the vehicle body 3 and does not vibrate the vehicle body 3.
The signal of the vertical speed MuV is substantially equal to the signal of the vertical speed PV of the piston 28, and the ON signal may be always generated when the wheel resonance is suppressed to the maximum. Therefore, in order to suppress wheel resonance in the vibration region near the wheel resonance point, the frequency 3
The ON time t1 of the ON / OFF signal S3 is increased without performing the phase correction of the signal of the vertical speed MsV of the vehicle body 3 performed in the vibration region of about 8 Hz. If the time of the ON / OFF signal S3 is not enough, the phase of the signal of the vertical speed MsV of the vehicle body 3 is changed to the time as shown in FIG.
Delay ON time t3 to increase ON time t1 of ON / OFF signal S3.
The vehicle speed phase correction filter 19 having the characteristic shown in FIG. 6 advances the phase of the signal of the vertical speed MsV of the vehicle body 3 so as to correspond to the phase delay amount shown in FIGS. Three types of vehicle speed phase correction filters 1 shown in FIGS.
The rise of the ON / OFF signal S3 in the piston 28
FIG. 7 shows that the change in the damping force of the hydraulic shock absorber 4 when the ON signal is generated can be reduced, so that the vertical acceleration transmission rate of the vehicle body 3 with respect to the road surface input is reduced. It is more effective in not deteriorating. As shown in FIG. 12, the vertical speed Ms of the vehicle body 3 whose phase has been corrected
When VA is used, the ON time t1 of the ON / OFF signal S3 becomes longer.

A vibration region higher than the wheel resonance point (frequency 1)
Control at 5 Hz or more) is performed as follows. In the vibration region higher than the wheel resonance point, neither the vehicle body resonance nor the wheel resonance occurs, so that the ON / OFF signal S3 is not necessary, and the ON / OFF signal S3 ON time t1 is the same as in the vibration region with a vibration frequency of 3 to 8 Hz. The phase of the signal of the vertical speed MsV of the vehicle body 3 is corrected through the vehicle speed phase correction filter 19 so as to shorten the speed.

The digital signal corresponding to the ON / OFF signal S3 is
It is sent to the drive unit 13 of the hydraulic shock absorber 4 by the DO device 12,
The drive unit 13 adjusts the damping force of the hydraulic shock absorber 4 to a maximum or a minimum. Body resonance and wheel resonance are suppressed.

As shown by solid lines 42 and 44 in FIG. 13, according to the present invention, the ON time of the ON / OFF signal S3 for maximizing the damping force of the hydraulic shock absorber 4 near the vehicle body resonance point and the wheel resonance point. t1
By lengthening, the vibration transmissibility is greatly reduced.

[0025]

As described above, the present invention provides a high-response variable damping force type hydraulic shock absorber in which the characteristics of a piston in a low-speed region are a viscous damper, a vertical acceleration sensor for detecting the vertical acceleration of a vehicle body, A vertical acceleration sensor for detecting the vertical acceleration of the wheels; and an electronic control unit for generating an ON / OFF signal based on the vertical speed of the vehicle body with the phase corrected and the vertical speed of the piston of the hydraulic shock absorber. Since the damping force of the hydraulic shock absorber is switched between a maximum value and a minimum value according to the ON / OFF signal, the resonance of the vehicle body and the resonance of the wheels can be suppressed, and the peak value of the vertical acceleration of the vehicle body in almost all vibration regions can be reduced. What is necessary is just to output an ON / OFF signal to the drive part of the hydraulic shock absorber,
Production cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a control device for a vehicle suspension mechanism according to the present invention.

FIG. 2 is a side sectional view of a variable damping type hydraulic shock absorber in the vehicle suspension mechanism.

FIG. 3 is a diagram showing a damping characteristic of the hydraulic shock absorber.

FIG. 4 is a block diagram of a control device for a vehicle suspension mechanism according to the present invention.

FIG. 5 is a block diagram of a control device for a vehicle suspension mechanism according to a modified embodiment of the present invention.

FIG. 6 is a diagram illustrating characteristics of a phase correction filter of the control device.

FIG. 7 is a diagram illustrating characteristics of a phase correction filter of the control device.

FIG. 8 is a diagram illustrating characteristics of a phase correction filter of the control device.

FIG. 9 is a diagram illustrating an operation of the control device near a vehicle body resonance point.

FIG. 10 is a diagram illustrating an operation of the control device near a vehicle body resonance point.

FIG. 11 is a diagram illustrating an operation of the control device near a wheel resonance point.

FIG. 12 is a diagram illustrating an operation of the control device near a wheel resonance point.

FIG. 13 is a diagram illustrating a vibration damping characteristic of a control device for a vehicle suspension mechanism according to the present invention.

FIG. 14 is a diagram showing a vibration control characteristic of a vehicle body of a control device for a conventional vehicle suspension mechanism.

FIG. 15 is a diagram illustrating a vibration damping characteristic of wheels of a control device for a conventional vehicle suspension mechanism.

[Explanation of symbols]

2: Vertical acceleration sensor 3: Vehicle body 4: Hydraulic shock absorber
5: Suspension spring 6: Vertical acceleration sensor 7: Wheel 8:
Bandpass filter 9: AD converter 10: Central processing unit 12: DO unit 13: Drive unit 18: Phase correction filter 19: Vehicle speed phase correction filter 20: Electronic control unit 21: Rod 24: Upper chamber 25: Compensation chamber 2
8: Piston 31: Lower chamber 36: High voltage generator 7
1, 72: integrator 72a: differentiator 73: comparator 7
6: Signal generator

Claims (1)

[Claims] A high-response variable damping force type hydraulic shock absorber in which the characteristics of a piston in a low-speed region are a viscous damper; a vertical acceleration sensor for detecting a vertical acceleration of a vehicle body; An acceleration sensor, and an electronic control unit that generates an ON / OFF signal based on the vertical speed of the vehicle body with the phase corrected and the vertical speed of the piston of the hydraulic shock absorber. A control device for a vehicle suspension mechanism, wherein a damping force of a shock absorber is switched between a maximum value and a minimum value.