JPH04176723A - Suspension controller for vehicle - Google Patents

Abstract

PURPOSE:To efficiently improve the convergence performance of the vibration of a car body by controlling the timing for the restoration of the damping force of a suspension by directly detecting the passing of a wheel on an uneven road surface from the output of a G sensor in the vertical direction. CONSTITUTION:When the G value in the vertical direction which is detected by a G sensor 31 on a spring is over a prescribed value, and accordingly, after the lapse of a prescribed time from the time where a wheel 8 passes through a projection detected by a preview sensor 33, and the vibration over a prescribed value is generated on a car body, a selector valve 22 is closed. At this time, the second orifice 21 is closed, and only the first orifice 19 is interposed between a hydraulic actuator 14 and an accumulator 20, and the flow resistance of the orifice for the variation of the hydraulic actuator 14 increases, and the damping force increases. Accordingly, the vibration after the riding over the projection can be converged efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvements in suspension control devices used in vehicles such as automobiles.

(Prior Art) Conventionally, for example, as shown in Japanese Patent Publication No. 2-40522, a non-contact road sensor is used to predict the unevenness of the road surface in front of the wheels, and the wheel passes over the unevenness. Suspension control devices that softly change suspension characteristics in accordance with timing are known.

(Problem to be Solved by the Invention) However, when the road surface sensor is placed at the front end of the vehicle facing downward as in the conventional example above, the time required for the wheels to reach the unevenness of the road surface can be detected relatively accurately. Although it is possible to do so, it only detects road surface irregularities slightly in front of the wheels, so when driving at high speeds, the time from when road surface irregularities are detected until the wheels reach them is extremely short, making it difficult to execute control. There is a problem in that the vehicle speed range in which the effects of predictive control of road surface irregularities can be obtained is extremely limited.

For this reason, it is conceivable to use a road surface sensor that detects the presence or absence of unevenness on the road surface in front of the vehicle, but if such a road surface sensor is used, it will be difficult to detect the presence or absence of unevenness within a certain predetermined distance in front of the vehicle. Therefore, when road surface unevenness is detected, the distance between the road surface unevenness and the wheel tends to vary, and it becomes difficult to detect with high accuracy the point in time when the wheel passes through the unevenness. For this reason, the time for softening the suspension characteristics must be set to a certain length while taking detection errors into account.

If such settings are made, the suspension characteristics may remain soft for a relatively long time even after the wheels pass over an uneven road surface, and in such cases, the vibration damping performance deteriorates and the ride comfort actually deteriorates. The problem is getting worse.

(Means for Solving the Problems) The present invention has been devised in view of the above points, and includes a damping force changing means that can change the damping force of a suspension that supports wheels on a vehicle body, and a damping force changing means that can change the damping force of a suspension that supports wheels on a vehicle body. A road surface sensor detects the presence or absence of unevenness, a vehicle speed sensor detects the running speed of the vehicle, a vertical G sensor detects the vertical acceleration of the vehicle body near the wheels, and the damping force is determined based on the detection output of each of the sensors. control means for controlling the operation of the changing means; when the road surface sensor detects an unevenness of the road surface, the control means calculates the point in time when the wheel reaches the unevenness based on the output of the vehicle speed sensor; activating the damping force control means so that the damping force decreases at the point, and then activating the damping force changing means after a predetermined period of time after detecting a predetermined fluctuation in the output of the vertical G sensor. This is a suspension control device for a vehicle, characterized in that it is configured to restore the suspension.

(Function) According to the present invention, by using a road surface sensor that detects the presence or absence of road surface irregularities in front of the vehicle, road surface irregularities can be predicted in a relatively wide vehicle speed range, and the damping force is reduced when passing through the irregularities. As a result, it is possible to efficiently absorb shocking human force due to vibrations and improve riding comfort when passing over uneven surfaces.

In particular, in the present invention, the return operation of the damping force changing means after reducing the damping force is performed a predetermined time after the vertical G sensor directly detects that the wheel has passed over an uneven surface. Therefore, the timing at which the damping force returns is not significantly delayed from the time when the wheels pass over an uneven surface, and the vehicle body vibration is also excellently suppressed. In addition, since the vertical G sensor is used, the vibration of the vehicle body can be directly detected, and the convergence of vehicle body vibration can be efficiently improved. The timing for reducing the damping force is controlled by predicting when the wheel will pass over an uneven road surface, while the timing for restoring the damping force is controlled by directly detecting when the wheel has passed over an uneven surface using the output of the vertical G sensor. , it is possible to expand the range in which predictive control can be performed, thereby improving riding comfort and at the same time improving stability after passing over uneven surfaces.

(Example) Hereinafter, an example of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a system configuration diagram of this embodiment.

In FIG. 1, an oil pump 1 is provided to suck oil stored in a reserve tank 3 through an oil passage 2 and discharge the oil to a supply oil passage 4. As shown in FIG. Supply oil path 4
An oil filter 9 and a check valve 10 are interposed therein, and the check valve 10 prohibits oil from flowing from the downstream side to the upstream side. An accumulator 1 for maintaining line pressure is located downstream of the check valve 10 in the supply oil line 4.
1 is connected to the accumulator 11, and a suspension unit 12 is connected to the downstream side of the accumulator 11. 1st
Although one suspension unit 12 is shown as a representative in the figure, the suspension unit 12 is provided for each wheel, and each suspension unit is also connected to a discharge oil path 6 that communicates with the reservoir tank 3. has been done.

Each suspension unit 12 has the same structure, with a suspension spring 13 and a single-acting hydraulic actuator 14 between the vehicle body 7 and the wheels 8.
The hydraulic actuator 1 is provided with
The supply and discharge of hydraulic pressure to and from the hydraulic chamber 15 of No. 4 is controlled. The control valve 17 controls the pressure acting on the hydraulic actuator 14 by controlling the flow rate of oil flowing from the supply oil path 4 side to the discharge oil path 6 side, and controls the valve opening according to the supplied current value. It has become something that will be done. Therefore, this control valve 17 can control the pressure within the hydraulic actuator 14 in proportion to the supplied current value, and the larger the supplied current value, the greater the supporting force generated by the hydraulic actuator 14. It has become something to do.

Further, an oil passage 15 communicating with the hydraulic chamber of the hydraulic actuator 14 is connected to an accumulator 2 via a first orifice 19.
0 is connected, and the first orifice 19 exhibits a vibration damping effect, and the accumulator 20 is filled with gas to exhibit a gas spring action. Further, a second orifice 21 is provided between the accumulator 20 and the oil passage 15 in parallel with the first orifice 19, and a switching valve 22 is provided between the second orifice 21 and the accumulator 20. , which switches communication and cutoff between the second orifice 21 and the accumulator 20. And these first orifices 19. The second orifice 21 and the switching valve 22 constitute variable orifice means, and the second orifice 21 has an orifice diameter larger than that of the first orifice 19. Further, the switching valve 22 constitutes a damping force changing means, and is normally turned off and in the cutoff state shown in the figure.

The operation of the control valve 17 and the switching valve 22 is controlled by a controller 30 comprised of a microcomputer. This controller 30 includes a detection output of a sprung G sensor 31 that detects the vertical acceleration acting on the vehicle body corresponding to each wheel, and a vehicle height sensor 32 that is provided for each wheel and detects the stroke amount of the wheel.
, the detection output of the underside preview sensor 33 that detects the presence of a protrusion on the road surface in front of the vehicle, and the detection output of the vehicle speed sensor 28 that detects the running speed of the vehicle are manually operated. , the controller 30 controls the operating states of each control valve 17 and each switching valve 22 for each wheel based on the detection outputs of these sensors.

This controller 30 has a configuration corresponding to a control means.

The preview sensor 33 includes an ultrasonic sensor arranged at the front of the vehicle body and tilted downward, and is provided for each left and right wheel.

The control operations for control valve 17 performed within controller 30 are represented by the control block diagram shown in FIG. That is, the output of the sprung G sensor 31 is
The output of the vehicle height sensor 32 is differentiated by a differentiator 37 and then multiplied by KP by an amplifier 38. The outputs of the amplifiers 36 and 38 are input to an adder 39 and added to the control amount for maintaining the vehicle height stored or calculated in the controller 30.
The output of the adder 39 is outputted to the control valve 17 via the valve drive unit 40, and the operation of the control valve 17 is controlled.This causes the hydraulic actuator 14 to expand and contract to absorb the input vibration, thereby providing a soft ride. It's something you can get.

On the other hand, the control operation of the switching valve 22 for each wheel performed within the controller 30 is represented by the control flowchart shown in FIG.

To explain the flowchart shown in Figure 3,
First, in step S1, a counter N is set as an initial setting.
and each flag A-D is set to 0, followed by step S2
Then, the outputs of each sensor 31 to 34 are read. After that, the process proceeds to step S3, and it is determined from the output of the preview sensor 33 whether or not there is a protrusion or step (hereinafter simply referred to as protrusion) in front of the vehicle. If it is determined that there is no protrusion, the counter N is determined in step S4. It is determined whether or not the counter N is 0. Initially, the counter N is O, so in this case, the process returns to step S2.

On the other hand, if it is determined in step S that there is a protrusion, the process proceeds to step S5. In step S5, it is determined whether the counter N is 0 or not.
is O, the process proceeds to step S6, and the delay time T until the wheel reaches the protrusion on the road surface is determined based on the output of the vehicle speed sensor 32. is calculated. That is, this delay time T.

As shown in Figure 4, is the distance between the protrusion on the road surface in front of the vehicle and the wheel (for the front wheel, L for the rear wheel).
+f) and the vehicle speed V detected by the vehicle speed sensor 34. In this case, preview sensor 3
3 detects the presence or absence of a protrusion at a predetermined distance in front of the vehicle body, and the above L value is a fixed value. Then, in step S6, the time T until the wheel reaches the protrusion. After has been calculated, the process proceeds to step S7 where the flag A is set to 1, and in the following step S8, the timer T is reset. Then, when the process proceeds to step S9, 1 is added to the value of the counter N, and since the counter N is initially 0, the counter N becomes 1. After passing step S9, step 5
Proceeding to step 10, the calculation cycle INT is added to the value stored in the timer T1, and the value of the timer T1 is rewritten. In the following step SIO, it is determined whether or not the count value of the timer T1 is greater than or equal to the delay time T calculated in the aforementioned step S6, and the value of the timer T is T. If it is less than , the process returns to step S2.

After returning to step S2 through the above processing, if the preview sensor 33 continues to detect the presence of a protrusion, the process proceeds from step S3 to step S5, but the counter N is set to 1.
Therefore, the process advances to step S12 and flag 8 is set to 0.
It is determined whether or not.

In this case, since the flag A is set to 1 in step S7 described above, the processing in steps S10 and S11 described above is performed.

Furthermore, the value of timer T is T. If the protrusion detection signal from the preview sensor 33 disappears before reaching , the process proceeds from step S3 to step S4, but since the counter N is 1 at this time, the process proceeds to step S13 to set the flag A.
After setting 0 to 0, the process of step 510.11 described above is performed.

Also, the value of timer T is T. If the protrusion detection signal from the preview sensor 33 disappears before reaching , and then the detection signal is generated again, the process proceeds to step 512 via step S3.5, and it is determined whether flag A is O or not. However, at this time, flag A is set to O in step 513, so the process proceeds to step 314, where flag 8 is set to 1. Thereafter, in the aforementioned step S, 1 is added to the counter N, and after the counter N becomes 2, the processing of the aforementioned step 510.11 is performed.

Then, the value of timer T1 is T. The above process is repeated until the number of protrusions is reached, and each time a new protrusion is detected, the counter N is incremented, and the count value N becomes the count value of the number of protrusions present in front of the vehicle. Note that flag A is provided to avoid counting the same protrusion over and over again.

The elapsed time T from when the preview sensor 33 detects the first protrusion is the time T when the wheel reaches the protrusion.

When reaching this point, the process advances from step Sll to step S15. In this step 3.15, the switching valve 22 is turned on, the second orifice 21 and the accumulator 20 are communicated via the switching valve 22, and the hydraulic actuator 1
4 and the accumulator 20 increases, the damping characteristics of the suspension become softer, and the vibration absorption characteristics when riding over a protrusion are efficiently improved.

After step S15 has passed, it is determined in step S16 whether flag B indicating that the switching valve 22 is in the open state is 1, and since it is initially 0, step S17
Then, flag B is set to 1. Next step S1
At step 8, 1 is added to the counter N, so that the value of the counter N becomes 1 more than the number of protrusions that are predicted to pass. Thereafter, the timer T is reset in step S19, and after the elapse of step S19 and if it is determined that the flag B is 1 in the aforementioned step 516, the value stored in the timer T3 is calculated in step S20. Period I
NT is added and the value of timer T3 is rewritten. The timer T3 is for counting the continuous open time of the switching valve 22, and after step S20, in step S21, the count value of the timer T3 is set in advance for the maximum continuous open time T,... 0.5 seconds).

Initially, the count value of the timer T3 is smaller than T lla M, so the process proceeds from step S21 to step S22, and it is determined whether the value of the counter N is 1 or not. Since the value of N is 2 or more, the process advances to step S23. In step S23, the value of the vertical G detected by the sprung G sensor 31 is a predetermined value G. If it is Go or higher, that is, if the wheel 8 passes the protrusion and a vibration of a predetermined value or more is generated in the vehicle body, the process proceeds to step S24, and it is determined whether the flag D is 1 or not. It is determined. In this case, since the flag D is initially O, the process proceeds to step S25 and sets the flag D to 1. In step S26, 1 is subtracted from the value of the counter N, and the process returns to step S2. Also,
The upper and lower G values are the predetermined values G. If step S24 is reached again in the above state, flag D is already set to 1), so the process returns to step S2 and the subtraction in step 326 is not executed. Furthermore, up and down G
The value is the predetermined value G. If not, the process advances from step S23 to step S27, where the flag D is set to 0, and the process returns to step S2, so that the upper and lower G values are then set to the predetermined value G again. When the value exceeds the value, the counter N is decremented in step S26.

In this way, according to the processes of steps 323 to 27, the wheels drive over the protrusions and the vehicle body receives a predetermined G.

Since the value of the counter N is decremented each time the above-described vertical G occurs, the value of the counter N becomes 1 when the vehicle passes over as many protrusions as detected by the preview sensor 33.

Then, when the value of the counter N becomes 1, step S22
The process then proceeds to step S28, where it is determined whether or not flag C is 1. Since it is initially 0, flag C is set to 1 in step S29.

In the following step 530, timer T2 is reset,
After step S30 has passed and if flag C is determined to be 1 in step 528, step S3
At step 1, the calculation cycle INT is added to the stored value of the timer T2, and the value of the timer T2 is rewritten. The timer T2 is for counting the elapsed time since the wheel passes the last protrusion, and after step 531 has passed, in step S32, the count value of the timer T2 is preset for a predetermined time T. (about 0.1 seconds) or not is determined.

In step S32, the count value of timer T2 is T. In the following cases, the process returns to step S2, but the count value of timer T2 is T. If it becomes larger, the process proceeds to step S33 and the switching valve 22 is closed, thereby returning the damping performance of the suspension to the normal state and improving the convergence of the vibrations of the vehicle body. After step S33, in step S34, the counter N and each flag A to D are set to 0, as in the initial setting, and the processes from step S2 onwards are repeated.

In addition, in the process that goes through step S32, when the wheel actually passes over the protrusion and a vertical G of more than a predetermined value occurs, the counter N
However, in actual driving conditions, there may be cases where the user does not actually go over a protrusion due to false detection by the preview sensor or a change in course, so the maximum continuous open time T and X described above are not executed. is set. As a result, if the control to close the switching valve 22 via step S32 is not executed within T*a x time after opening the switching valve 22, the value of the timer T will change to T in step S21. When it is determined that the value is equal to or greater than X, the process directly proceeds from step S21 to step S33, thereby forcibly closing the switching valve 22.

Next, the operation of the above embodiment will be explained.

According to the above configuration, as shown in FIG. 5, the switching valve 22 is opened after a time To (when the wheel 8 passes the protrusion) after the presence of the protrusion on the road surface in front of the vehicle is detected. This opens the second orifice 21, and because the orifice diameter of the second orifice 21 is larger than the first orifice 19, the substantial orifice diameter interposed between the hydraulic actuator 14 and the accumulator 20 increases greatly. . As a result, the damping force against high-frequency vibrations is significantly reduced, and at the same time, the vibration transmission force to the vehicle body is also reduced, making it possible to significantly reduce the feeling of pushing up when going over a bump.

Also, the wheel goes over the protrusion and G. When time Tc elapses after the above vertical acceleration occurs, the switching valve 22 closes. As a result, the second orifice 21 closes and only the first orifice 19 is interposed between the hydraulic actuator 14 and the accumulator 20, so the flow resistance of the orifice against fluctuations in the hydraulic actuator 14 increases and the damping force increases. Therefore, vibrations after riding over the protrusion can be efficiently converged. Fig. 6 is a characteristic diagram showing the change in vertical G when the switching valve 22 is closed and left open after going over the protrusion. It is clear that this can improve the convergence of vehicle body vibration.

Note that the preview sensor 3 closes the switching valve 22.
This is after passing the last protrusion detected by step 3. For example, if two protrusions are detected as shown by the broken line in FIG. 5, the second G is detected. T from the occurrence of the above vertical acceleration. After a period of time, the switching valve 22 will close.

In addition, as a countermeasure against not passing through a protrusion due to erroneous detection, etc., the maximum open duration time T□ is set. is set, and when the opening time of the switching valve 22 exceeds T lla M, the switching valve 22 is forcibly closed.

Furthermore, in addition to controlling the switching valve 22 as described above, the control valve 17 is controlled based on the output of the vehicle height sensor and the vertical G sensor.
This control also provides good ride comfort.

According to the above embodiment, it is possible to detect a protrusion, etc. in front of the vehicle and reduce the damping force of the suspension in advance when the protrusion, etc. passes, so it is possible to reduce vibrations generated in the vehicle body when the protrusion, etc. passes, Since the damping force is increased by directly detecting the passage of a protrusion, etc., the damping force can be increased relatively quickly after the passage of a protrusion, etc., which improves the convergence of vehicle body vibrations and improves stability. be effective.

That is, the output of the preview sensor 33 is the output of the switching valve 2.
2 is used for the opening timing, so even if the error is relatively large, as long as the switching valve 22 is opened before the passage of a protrusion, etc., there is no particular problem and the detection distance can be set long and control is possible. It is possible to expand the vehicle speed range, and since the timing for closing the switching valve 22 is set by the upper and lower G, there is an advantage that the convergence of vehicle body vibrations after passing a protrusion or the like can be reliably improved.

Furthermore, the maximum open duration time T□ for the switching valve 22
8, so even if the above settings are used, there is no major inconvenience caused by false detection, and there is an advantage of excellent reliability.

Furthermore, since the above-mentioned control is added to the so-called active suspension, a comfortable ride can be obtained under a wide range of driving conditions.

Note that the present invention is not limited to the above-mentioned embodiments, and may be applied, for example, to shock absorber control in a normal suspension rather than an active suspension, or to a variable control system that can continuously change the orifice diameter. An orifice may also be used. In any case, it goes without saying that various other modifications can be made without departing from the gist of the present invention.

(Effects of the Invention) As described above in detail with the embodiments, according to the present invention, the timing of reducing the damping force is controlled by predicting the passage of the wheel over the unevenness of the road surface based on the outputs of the road surface sensor and the vehicle speed sensor. On the other hand, the timing for restoring the damping force is controlled by directly detecting when the wheel has passed over an uneven surface using the output of the vertical G sensor, and by performing predictive control, it is possible to improve ride comfort when passing over an uneven surface. At the same time, the convergence after passing through unevenness can be reliably improved, and highly reliable predictive control can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a system configuration diagram showing one embodiment of the present invention;
The figure is a control block diagram showing the control operation of the control valve 17, FIG. 3 is a flowchart showing the control operation of the switching valve 22, FIG. 4 is a principle diagram of detecting over a projection using the preview sensor 33, and FIG. 6 is an operation timing chart of the switching valve 22, and FIG. 6 is a characteristic diagram of the vertical acceleration generated in the vehicle body when the vehicle passes over a protrusion. 1...Oil pump, 14...Hydraulic actuator. 17... Control valve, 19... First orifice 20
...Accumulator, 21...Second orifice 22
...Switching hull 1.30-...Controller 31...
Sprung G sensor, 32...Vehicle height sensor 33...Preview sensor, 30...Vehicle speed sensor Fig. 1

Claims (1)

[Claims] a damping force changing means capable of changing the damping force of a suspension that supports the wheels on the vehicle body; a road surface sensor that detects the presence or absence of unevenness on the road surface in front of the vehicle; a vehicle speed sensor that detects the running speed of the vehicle; It has a vertical G sensor that detects the vertical acceleration of the vehicle body, and a control means that controls the operation of the damping force changing means based on the detection output of each of the sensors, and the control means controls the road surface by the road surface sensor. When an unevenness is detected, the time point at which the wheel reaches the unevenness is calculated based on the output of the vehicle speed sensor, and the damping force control means is operated so that the damping force is reduced at the same time. A suspension control device for a vehicle, characterized in that it is configured to restore the operation of the damping force changing means after a predetermined period of time after detecting a predetermined variation in output.