JPH0260808A - Damping force control device for shock absorber - Google Patents

Abstract

PURPOSE:To improve comfortability and steering stability by obtaining amplitude and wave length of fluctuation waveform of relative variation between a wheel and the body, and changing over and setting up damping force of a shock absorber to high damping force for an appointed time when the standard values thereof changing depending upon on the amplitude and the wave length are exceeded. CONSTITUTION:An electric control device 42 inputs signals from a vehicle speed sensor 40, a wheel height sensors 36, 38 for a front wheel and a rear wheel, operates relative displacement between front wheels 12, 14 and the body, namely difference between detected wheel height and a standard wheel height, and obtains amplitude and wave length of fluctuation waveform thereof. And, when amplitude of the fluctuation waveform exceeds a standard value, damping force of shock absorbers 20, 22 is changed over to high damping force for an appointed time. The standard value is set up so as to shift gradually toward small amplitude side as increase in wave length of the fluctuation waveform due to increase on vehicle speed, therefore damping force is surely set up to high damping force for suppressing the body on stirring motion in a case of low frequency, and becomes in low damping force in a case of high frequency. Thus, it can be intended to improve comfortability and steering stability.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a shock absorber incorporated into a suspension of a vehicle such as an automobile, and more particularly to a damping force control device for a shock absorber.

Problems to be Solved by the Prior Art and the Invention As one of the damping force control devices for a shock absorber incorporated in the suspension of a vehicle such as an automobile, for example, Japanese Patent Laid-Open No. 61-3
As described in No. 751-1, Japanese Patent Application Laid-Open No. 62-168704, and Japanese Utility Model Application No. 62-11010, when the relative displacement between the wheel and the vehicle body exceeds a reference value, the shock absorber is damped. A damping force control device is known that is configured to switch and set a force to a high damping force for a predetermined period of time.

In such a damping force control device, switching of the damping force of the shock absorber is determined only depending on whether or not the relative displacement amount between the wheel and the vehicle body exceeds a reference value. Even when a vibration input is received, if the amount of relative displacement exceeds a reference value, the damping force is switched to a high damping force, resulting in a problem that the ride comfort of the vehicle is impaired. In addition, each time the relative displacement amount exceeds the reference value, the damping force of the shock absorber is switched between low damping force and high damping force. There is a problem in that the frequency of switching increases significantly and the durability of the shock absorber and its actuator deteriorates.

Furthermore, JP-A-62-152913 discloses a damping force control configured to set the damping force to a high damping force when the frequency of the fluctuation waveform of the relative displacement amount is low, and to set the damping force to a low damping force when the frequency is high. The equipment is described. However, even if the unsprung vibration is a high-frequency vibration, if its amplitude is large, it may cause the vehicle body to tilt. In this case, a damping force control device configured to uniformly set the damping force to a low damping force cannot effectively prevent the vehicle body from tilting, and therefore the handling stability of the vehicle may be affected. cannot be improved.

In view of the above-mentioned problems with conventional shock absorber damping force control devices, the present invention can improve both ride comfort and handling stability of a vehicle without deteriorating the durability of the shock absorber or its actuator. It is an object of the present invention to provide an improved damping force control device for a shock absorber.

Means for Solving the Problems According to the present invention, relative vibration between the wheels and the vehicle body is damped, and the damping force is switched between at least a high damping force and a low damping force. A damping force control device for a shock absorber configured as described above includes a displacement amount detection means for detecting a relative displacement amount between the wheel and the vehicle body, and a signal indicating the relative displacement amount from the displacement amount detection means. control means configured to determine the amplitude and wavelength of a fluctuation waveform of the relative displacement amount, and to switch and set the damping force of the shock absorber to a high damping force for a predetermined time when the amplitude of the fluctuation waveform exceeds a reference value. The reference value is achieved by a damping force control device configured to gradually shift the amplitude of the fluctuating waveform to a smaller side as the wavelength of the fluctuating waveform increases.

Effects and Effects of the Invention According to the configuration as described above, the control means determines the amplitude and wavelength of the fluctuation waveform of the relative displacement amount, and when the amplitude of the fluctuation waveform exceeds the reference value, the damping force of the shock absorber is kept at high damping for a predetermined period of time. The reference value is set to increase the wavelength of the fluctuation waveform, and gradually shift to the smaller amplitude side of the fluctuation waveform, so the fluctuation waveform of the relative displacement amount becomes lower. If the fluctuation waveform is a high frequency waveform, the damping force is set to a high damping force to ensure that vehicle body tilting is suppressed, and if the fluctuation waveform is a high frequency waveform and its amplitude is relatively small, the damping force By setting the damping force to a low damping force, the ride comfort of the vehicle is ensured, and conversely, when the amplitude is large, the damping force is set to a high damping force to suppress the vehicle body from tilting. The steering stability of the vehicle can be improved without deteriorating the ride comfort of the vehicle.

Further, according to the above-described configuration, when the fluctuation waveform of the relative displacement amount is high frequency, the reference value is set to a high value. The frequency of switching to the shock absorber and its actuator can be reduced, thereby avoiding a decrease in the durability of the shock absorber and its actuator.

Further, in the damping force control device of the present invention, it is preferable that the predetermined time period for setting the shock absorber to a high damping force is set to be relatively long, for example, one period or more of the fluctuation waveform. According to this configuration, the frequency at which the damping force of the shock absorber is switched between low damping force and high damping force is further reduced, thereby further reliably avoiding a decrease in the durability of the shock absorber and its actuator. can do.

When the vehicle is running, the wheels are always in substantially contact with the road surface, so in this specification, the term "relative displacement between the wheels and the vehicle body" refers to the amount of change in vehicle height, that is, the road surface. It should be noted that this concept includes the amount of change in distance between and the vehicle body.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be explained in detail below by way of example embodiments with reference to the accompanying figures.

Embodiment FIG. 1 is a schematic configuration diagram showing one embodiment of a damping force control device according to the present invention, and FIG. 2 is a Pronk diagram showing the electric control device shown in FIG. 1.

In Figure 1, 10 indicates the vehicle body, 12.14,
] 6.18 shows the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. The corresponding suspensions of the wheels 12-]8 are provided with shock absorbers 20, 22, 24, 26. The damping force of each of the shock absorbers 20 to 26 is switched and set to high damping force or low damping force by actuators 28, 30, 32, and 34, respectively. The actuators 28 to 34 are controlled by an electric control device 42 based on signals from vehicle height sensors 36, 38 and vehicle speed sensors 40 provided corresponding to the front right wheel and the rear left wheel.

As shown in FIG. 2, electrical control device 42 includes a microcomputer 44. As shown in FIG. The microcomputer 44 is a general type (1'4) as shown in FIG.
Central processing unit (CPU) 4
6, a read-only memory (ROM) 48, a random access memory (RAM) 50, and an input port device 5.
2 and an output port device 54, which are connected to each other by a bidirectional common bus 56.

A signal indicating the vehicle speed V is inputted from the vehicle speed sensor 40 to the input port device 52, and the vehicle height Hr of the front wheel (right front wheel) and the vehicle height Hr of the rear wheel (left rear wheel) are inputted from the vehicle height sensors 36 and 38, respectively.
A signal indicating this is input. Filters 58 and 60 are provided between the vehicle height sensors 36 and 38 and the input port device 52 to remove DC components determined by the number of occupants in the vehicle from the output from the vehicle height sensors. The human power port device 52 appropriately processes signals indicating the vehicle speed V and vehicle height H1% Hr, and uses the CPU and RAM 5 according to instructions from the CPU 46 based on the program stored in the ROM 48.
The signal processed to 0 is output. R.O.
M48 stores a map etc. corresponding to the control flow shown in FIG. 3 and the graph shown in FIG. 4. Figure 4 shows the 1/2 wavelength color of the relative displacement variation waveform, the maximum absolute value A of the relative displacement amount, and the shock value for the low speed range V1, medium speed range V2, and high speed range V3 of the vehicle speed V. It shows the relationship between the damping force of the absorber.

Next, the operation of one embodiment of the present invention based on the flowchart shown in FIG. 3 will be described with reference to FIGS. 1 through 6.

First, in the first step 1, the vehicle height Hr detected by the vehicle height sensor 36 is read, and then the process proceeds to step 2.

In step 2, the vehicle speed V detected by the vehicle speed sensor 40 is read, and then the process proceeds to step 3.

In step 3, set the vehicle height of the front wheels to H1'.

As, △Hr-Hr-Hr.

The deviation of the vehicle height of the front wheels, that is, the amount of relative displacement between the front wheels and the vehicle body is calculated, and the process then proceeds to step 4.

In step 4, it is determined whether the damping force of the front wheel shock absorbers 20 and 22 is low damping force or not, and when it is determined that the damping force is not low damping force, step 18 If it is determined that the damping force is a low damping force, the process proceeds to step 5.

In step 5, △H calculated in step 3
The absolute value of fn and 1 of the flowchart shown in FIG.
△Hfn-1 calculated in step 3 before the cycle
It is determined whether the product with the absolute value of is negative or not, and when it is determined that this product is negative, step 12
If it is determined that this product is not negative, the process advances to step 6.

In step 6, it is determined whether or not the TV timer related to the 1/2 wavelength time Tv of the waveform of ΔHf' is activated, and when it is determined that the Tw timer is not activated, The process proceeds to step 9, and if it is determined that the Tv timer is activated, the process proceeds to step 7.

In step 7, △H calculated in step 3
The absolute value of fn and 1 of the flowchart shown in FIG.
△Hrn-+ calculated in step 3 before the cycle
It is determined whether the deviation from the absolute value of If the determination fails, the process advances to step 8.

In step 8, the absolute value of △Hf'n and △Hrn
The larger of the absolute values of -+ is stored in the RAM 50 as the maximum absolute value of the relative displacement, and the process then proceeds to step 9.

In step 9, T is determined regarding the time To from when ΔHr becomes substantially 0 to when the damping force of the shock absorber is switched to high damping force.

It is determined whether the timer is activated or not.
When it is determined that the o timer is not activated, the process proceeds to step 20, and when it is determined that the to timer is activated, the process proceeds to step 0.

In step 10, it is determined whether the time To has elapsed or not, and when it is determined that the time To has not elapsed, the process proceeds to step 20, where it is determined that the time To has elapsed. If so, proceed to step 11.

In step 11, the front wheel shock absorber 20
and setting the damping force of 22 to a high damping force,
After that, the process proceeds to step 21.

In step]2, it is determined whether or not the Tv timer is activated, and when it is determined that the Tv timer is not activated, the process proceeds to step 17;
When it is determined that the w timer is activated, the process advances to step 13.

In step 13, the vehicle speed V1 read in step 2 is calculated as shown in FIG. It is determined whether the damping force to be controlled is high or low based on the map stored in the ROM 48 corresponding to the graph, and then the process proceeds to step 4.

In step 13, the operation of the 7w timer is stopped,
After that, proceed to Step 5.

In step 15, it is determined whether the damping force of the front wheel shock absorbers 20 and 22 determined in step 13 is a high damping force or not, and it is determined whether the damping force is not a high damping force. When the determination is made, the process proceeds to step 20, and when it is not determined that the damping force is a high damping force, the process proceeds to step 16.

In step 16, the operation of the To timer is started,
After that, proceed to step 20.

In step 17, the operation of the Tv timer is started,
After that, proceed to step 20.

In step 18, the front wheel shock absorber 20
It is determined whether or not a time T1 for setting the damping force of step 22 to a high damping force has elapsed. If it is determined that T1 has not elapsed, the process advances to step 21, and the time T1 is set to a high damping force.
If it is determined that the time has elapsed, the process advances to step 19.

In step 19, the operation of the T1 timer is stopped;
After that, proceed to step 20.

In step 20, the front wheel shock absorber 20
and setting the damping force of 22 to a low damping force,
After that, the process proceeds to step 21.

In step 21, the front wheel shock absorber 20
A control signal is outputted from the output port device 54 to the actuators 30 and 32 via the drive circuits 62 and 64 so that the damping force of and 22 becomes the damping force set in step 11 or 20, and then the process proceeds to step 22. move on.

In step 22, the vehicle height H1' is replaced with the vehicle height Hr of the rear wheels detected by the vehicle height sensor 38, and the vehicle height deviation ΔH' is replaced with the vehicle height deviation ΔHr of the rear wheels. Third
Vehicle height deviation △Hr one cycle before the flowchart shown in the figure
Similarly, n-+ is the rear wheel deviation △Hr n-
+, and the time TOsTITw is T 6 respectively.
The damping force of the rear wheel shock absorbers 24 and 26 is controlled in the same steps as steps 1 to 21 described above, except that T HT v ' is replaced.

When step 22 is completed, the process returns to step 1 and steps 1 to 22 are repeated.

In addition, the time To is Tw/2 in To or 1/4-1/f in To, where f is the frequency of the fluctuation waveform of the general relative displacement amount, so that the time To is as shown in Fig. 5. , may be set to end near the brightest peak Pi of the fluctuating waveform after the measurement of time Tw ends.

Also, T1 is T H 1,000 2 ・Tv or 1/f in T1 or 3 in Ti
The fluctuation waveform may be set to end at the second to fourth peaks from the peak P1, such as: - TV or 3/2 - 1/f or T 4 - TV or T 1,200/f.

Moreover, To and T1 do not need to be constant values, and between steps 13 and 14 of the flowchart in FIG. It may be configured to be variably set according to the 1/2 wavelength Tw.

Thus, in the illustrated embodiment, when a relative displacement of the vehicle body occurs, for example as shown in FIG.
If ΔHf' crosses the horizontal axis, a yes determination is made in step 5, and step 1
In step 2, a negative determination is made, and in step 17, Tw
The timer starts running. Next, a YES determination is made in step 6, and when the absolute value of ΔHf reaches the maximum value, a YES determination is made in step 7, and a YES determination is made in step 9.
A negative determination is made in .

When ΔHr crosses the horizontal axis again, yes is determined in steps 5 and 12, the damping force of the shock absorber is determined in step 13, and T is determined in step 14.
The operation of the v-timer is stopped, and it is determined whether the damping force determined in step 15 is a high damping force.

If the damping force determined in step 13 is a low damping force, the damping force is maintained at a low damping force in steps 20 and 21. On the other hand, if the damping force determined in step 13 is a high damping force, the operation of the To timer is started in step 16, YES is determined in step 4, and step 5 is performed. No determination is made in step 6 and 6, yes determination is made in step 9, and when time To has elapsed, yes determination is made in step 10, and in steps 11 and 21, the shock absorber is damping force is controlled to a high damping force.

From the above explanation, according to the illustrated embodiment, the damping force of the shock absorber is appropriately switched and set according to the wavelength (frequency) and amplitude of the fluctuation waveform of the relative displacement amount, thereby deteriorating the ride comfort of the vehicle. In particular, as shown in Fig. 6, the vibration of the sprung mass (vehicle body) due to the vibration of the unsprung mass (wheel) of high frequency and large amplitude (Ad) is effectively damped without causing any vibration. Even when the vehicle body vibrates with high amplitude (Au), the vibration of the vehicle body is well damped, and the damping force switching control is performed every time the relative displacement amount exceeds a predetermined value. It will be appreciated that the frequency is reduced, thereby increasing the durability of the load absorber and its actuator.

In addition, according to the illustrated embodiment, the reference value for switching the damping force of the shock absorber between high damping force and low damping force changes as the vehicle speed V increases, the 1/2 wavelength T of the fluctuation waveform of the relative displacement amount increases.
Since the maximum value A of the absolute value of w and the amount of relative displacement is set to gradually shift to the smaller side, good ride comfort of the vehicle in the low vehicle speed range is ensured, and it is also ensured that the maximum value A of the absolute value of the relative displacement amount is It will be understood that it is possible to ensure good handling stability of the vehicle, and thereby to control the ride comfort and handling stability of the vehicle in accordance with the vehicle speed.

In the illustrated embodiment, the time Tw is calculated as the time of 1/2 wavelength, but it is calculated as twice the time of 1/4 wavelength, that is, when the fluctuation waveform of the relative displacement amount is horizontal. It may be determined as twice the time from the time when the axis is crossed to the peak.

Further, in the illustrated embodiment, the electric control device is a digital control device, but it may be configured as an analog control device.

Furthermore, in the illustrated embodiment, the damping forces of the front and rear shock absorbers are controlled independently of each other, or are controlled based on the amount of relative displacement between either wheel and the vehicle body. The damping force of all shock absorbers may be controlled, or the damping force of each shock absorber may be controlled independently of each other.

Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments are possible within the scope of the present invention. This will be clear to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one embodiment of the damping force control device according to the present invention, FIG. 2 is a block diagram showing the electric control device shown in FIG. 1, and FIG. 3 is a block diagram showing an embodiment of the damping force control device according to the present invention. A flowchart showing the control flow in one embodiment of the damping force control device, FIG. 4 is a flowchart showing the control flow in one embodiment of the damping force control device.
, for high-speed range V3, 1/2 of the relative displacement fluctuation waveform
A graph showing the relationship between the wavelength TW, the maximum absolute value A of the relative displacement amount, and the damping force of the shock absorber, and FIG. 5 shows the operation of the embodiment shown in FIGS. 1 to 4. FIG. 6 is an illustrative graph showing high-frequency, large-amplitude unsprung vibration and low-frequency, high-amplitude sprung vibration that are well damped according to the present invention. . 10...Vehicle body, 12-18...Wheel, 20-26.
・・Shock absorber, 28-34・・Actuator 36. 38・・Vehicle height sensor, 40・Vehicle speed sensor. 42... Electric control device, 44... Microcomputer 46... CPU, 48... ROM, 50... RAM
, 52...Input port device, 54...Output port device, 58.60...Filter, 62-68...Drive circuit patent Applicant Toyota Motor Corporation Agent Akira Patent Attorney
Takeshi Ishi Figure 2 42 Electric control device 44 Microcomputer

Claims (1)

[Claims] A damping force control device for a shock absorber configured to damp relative vibration between a wheel and a vehicle body and configured to switch the damping force between at least a high damping force and a low damping force,
displacement amount detection means for detecting the amount of relative displacement between the wheels and the vehicle body; and a signal indicating the relative displacement amount is inputted from the displacement amount detection means, and the amplitude and wavelength of the fluctuation waveform of the relative displacement amount is detected control means configured to determine the amplitude of the fluctuation waveform and switch and set the damping force of the shock absorber to a high damping force for a predetermined time when the amplitude of the fluctuation waveform exceeds a reference value, the reference value being the wavelength of the fluctuation waveform. a damping force control device configured to gradually shift the amplitude of the fluctuating waveform to a smaller side as the amplitude of the fluctuating waveform increases.