JPH0459408A - Active suspension device for vehicle - Google Patents

Abstract

PURPOSE:To enhance the riding comfortableness by detecting vibration input substances in front of vehicles, comparing the signals output in response to their sizes with a specified upper limit after corrected in response to car speed, and lessening the supporting rigidity of an oil pressure supporting means only when it is less than the specified upper limit. CONSTITUTION:Vibration input substances such as projections, etc., in front of vehicles are detected by a preview sensor 33 and input to a controller 30. Also, detected car speed is input to the controller 30 from a car speed sensor 54. Then, the controller 30 corrects the upper and lower limit threshold values to perform optimum preview control in response to the input car speed. And, the detected signal of the preview sensor 33 is compared against this corrected shreshold value, and a changeover valve 22 is switched to lessen the rigidity of an oil pressure supporting means 12 only when it does not exceed the upper limit threshold value. Thus, a discrimination error accompanies car speed change is corrected making control accurate.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an active suspension device for a vehicle, which is used in a vehicle such as an automobile, and which uses a hydraulic actuator (hydraulic support means) to reduce the impact force when driving over a projection, etc. Regarding.

(Prior Art) Conventionally, so-called active suspension devices have been proposed that absorb and alleviate vertical vibrations of a vehicle.

This active suspension system has a hydraulic actuator interposed between each wheel and the vehicle body, the hydraulic chamber of this hydraulic actuator is connected to an accumulator via an orifice, and the hydraulic chamber of each hydraulic actuator is connected from an oil pump to the hydraulic chamber of each hydraulic actuator. A control valve consisting of a proportional electromagnetic valve is arranged in the middle of an oil path that supplies hydraulic oil. When using this active suspension to control the vertical vibration of the vehicle, the controller controls the operation of the control valve described above based on the vibration input information from the sprung G sensor, thereby reducing vibrations generated in the vehicle body. That's what I do.

(Problems to be Solved by the Invention) Such conventional active suspension devices can effectively suppress vertical vibrations of the vehicle body, but they can suppress shocks that occur when driving over bumps or on pavement joints. It was not possible to sufficiently suppress vibrations.

In order to suppress such impactful vibrations, the support rigidity of the hydraulic support means must be reduced to the extent that the so-called full stroke of the suspension unit does not occur when the impact is large, so that the input impact can be sufficiently absorbed. We need to make a change.

Incidentally, since an ultrasonic sensor is used to detect vibration input objects such as protrusions, vehicle speeds that deviate from the predetermined vehicle speed, which is the sensitivity setting vehicle speed, will cause a decrease in the output of the detection signal due to the Doppler effect, causing a decrease in the detection signal output of the vibration input object. There is a problem in that the size cannot be detected accurately, and therefore, it cannot be accurately determined whether or not to generate a full stroke.

When the suspension is fully stroked, the suspension unit etc. violently collide with the vehicle body, generating a shock.
On the contrary, it may worsen the riding comfort.

The present invention was made to solve such problems, and it accurately determines the size of a vibration input object such as a protrusion even when the vehicle speed changes, and prevents the suspension unit from reaching its full stroke. An object of the present invention is to provide an active suspension device for a vehicle that is capable of optimal hydraulic control of a hydraulic support means in response to input impact vibrations.

(Means for solving the problem) In order to achieve the above-mentioned object, the active suspension device for a vehicle of the present invention is interposed between the vehicle body and the wheels, and changes support rigidity by controlling the supply and discharge of hydraulic pressure. vibration input detection means for detecting a vibration input object in front of the vehicle and outputting a detection signal according to the size of the vibration input object; vehicle speed detection means for detecting vehicle speed; and the vibration input detection means When detects a vibration input object, outputs a command signal to change the supply and discharge of hydraulic pressure to the hydraulic support means only when the output signal value of the vibration input detection means does not exceed a predetermined upper limit value, and controls the hydraulic support means. hydraulic control means for reducing support rigidity, and when determining whether or not the output signal value exceeds the predetermined upper limit value, a determination error caused by a change in vehicle speed is eliminated.
It is characterized in that the correction is made in accordance with the vehicle speed detected by the vehicle speed detection means.

(Function) The hydraulic support means changes the support rigidity of the vehicle body by changing the supply and discharge of hydraulic pressure in response to command signals from the hydraulic control means.If the magnitude of the impact exceeds the upper limit, the hydraulic support means changes the support rigidity of the vehicle body. When the support rigidity of the hydraulic support means is changed to a small value, the suspension unit is moved to a full stroke, so when the output signal value of the vibration input detection means exceeds a predetermined upper limit value, it is prohibited to change the support rigidity of the hydraulic support means to a small value. do. At this time, the detection signal of the vibration input detection means has an output drop at a vehicle speed that deviates from a predetermined speed, which is the vehicle speed to which the vibration input detection means is sensitive, and cannot accurately predict the full stroke of the suspension unit.

In order to prevent the suspension/control unit from reaching a full stroke, the hydraulic control means corrects the vehicle speed for a determination error when comparing and determining the output signal value of the vibration input detection means with a predetermined upper limit value. For this vehicle speed correction, the gain of the output signal value of the vibration input detection means may be corrected in accordance with the vehicle speed, or the predetermined upper limit value may be corrected in accordance with the vehicle speed.

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

FIG. 1 shows the configuration of an active suspension device for an automobile according to the present invention. This figure shows a suspension unit 12 provided for each wheel (the suspension unit for one wheel is shown as a representative), and a suspension spring 13 of this suspension unit I2 and a single-acting hydraulic Actuator I
4 is interposed between the vehicle body 7 and the wheels 8.

The control valve I7 of the suspension unit 12 is interposed between an oil passage 16 communicating with a hydraulic chamber I5 of the hydraulic actuator 14, and a supply oil passage 4 and a discharge oil passage 6, which will be described later. One end of a branch passage 16a is connected to the middle of the oil passage 16, and an accumulator 20 is connected to the other end of the branch passage 16a. Gas is sealed in the accumulator 20, and due to the compressibility of the gas, a so-called gas spring action is exerted. A throttle (first orifice) 19 is disposed in the middle of the branch path 16a, and a hydraulic chamber 1 of the accumulator 20 and the hydraulic actuator 14 is arranged.
By regulating the amount of hydraulic oil flowing between
Vibration damping effect is demonstrated.

A bypass passage 16b that bypasses the orifice 19 is connected between the oil passage 16 and the accumulator 20, and a second orifice 21 and a switching valve 22 are connected to the bypass passage 16b.
is installed. The second orifice 21 has a larger orifice diameter than the first orifice 19, and the switching valve 2
2 is in an off state (the state shown in the figure) when not energized, and when the switching valve 22 is opened, the hydraulic oil flows into the accumulator 2 through the opened switching valve 22 and the orifice 21.
0 and the pressure chamber 15, which weakens the vibration damping effect. That is, the support rigidity of the suspension unit 12 changes in two stages by turning the switching valve 22 on and off.

The other end of the supply oil passage 4 mentioned above is connected to the discharge side of the oil pump 1, and the suction side of the oil pump 1 communicates with the inside of the reserve tank 3 via the oil passage 2. Therefore, when the oil pump 1 operates, the hydraulic oil stored in the reserve tank 3 is discharged to the oil supply path 4 side. Supply oil path 4
From the oil pump 1 side, there is an oil filter 9, a check valve 10, and an accumulator 11 for maintaining line pressure.
is installed. The check valve 10 is connected to the oil pump 1
This check valve 10 only allows the flow of hydraulic oil from the side toward the suspension unit 12 side, and this check valve 10 allows high-pressure hydraulic oil to be stored in the accumulator 11.

The control valve 17 is of a type that changes the valve opening in proportion to the supplied current value, and the amount of oil flowing from the supply oil path 4 side to the discharge oil path 6 side is adjusted according to this valve opening degree. The pressure acting on the hydraulic actuator 14 is controlled by controlling the pressure. The larger the current value supplied to the control valve 17, the more the hydraulic actuator 14
The structure is such that the supporting force (supporting load) generated by the bearing is increased. The hydraulic oil discharged from the control valve 17 to the discharge oil path 6 side is returned to the reserve tank 3 described above.

The control valve 17 and the switching valve 22 are connected to the controller 3
It is electrically connected to the output side of controller 3.
The operation is controlled by a drive signal from 0. On the input side of the controller 30, various sensors for controlling the suspension unit 12 are provided, for example, for each wheel.
A sprung G sensor 31 detects the vertical acceleration acting on the vehicle body, a vehicle height sensor 32 is provided for each wheel and detects the stroke amount of the wheel, and a vehicle height sensor 32 detects protrusions on the road surface in front of the vehicle. A preview sensor 33 that outputs an output signal value according to the size, a vehicle speed sensor 34 that detects the traveling speed of the vehicle, etc. are connected. The aforementioned control valve (7) and switching valve 22, which are arranged for each wheel, are operated and controlled based on detection signals from these sensors.

It should be noted that an ultrasonic sensor is used as the preview sensor 33, and this sensor 33 is attached to the front part of the vehicle body facing diagonally downward (see FIG. 2).

During normal driving, the switching valve 22 is closed.
Slight vibrations input to the vehicle body from the road surface are absorbed and attenuated because the hydraulic chamber 15 of the hydraulic actuator 14 communicates with the accumulator 20 via the orifice 19. The control valve 17 also includes a sprung G sensor 3.
A current of a required magnitude is supplied in response to the first output signal, and the working pressure supplied to the hydraulic actuator 14 is PJ.
D control is performed, thereby suppressing vertical vibration of the vehicle body.

On the other hand, when the preview sensor 33 detects a vibration input object such as a protrusion in front of the vehicle body, the controller 30 switches the switching valve 22 to
Decrease the support rigidity of

To explain in more detail the control of support rigidity by switching the switching valve 22, the controller 30 constantly monitors the output signal value of the preview sensor 33, and detects protrusions etc. based on changes in this signal value. As will be described in detail later, at this time the controller 30 controls the preview sensor 3.
A command signal for switching the switching valve 22 is output only when the output signal value of No. 3 is within a predetermined range optimal for performing preview control.

That is, as shown in FIG.
Since the output signal of the 2000 includes noise components corresponding to small protrusions that do not affect the ride quality, performing preview control on all input signals would cause the suspension to be affected more than necessary. This will change the support rigidity of the unit 12. To prevent this, a lower threshold value V1 is set for separating the noise component and performing optimal preview control. On the other hand, if the support rigidity of the suspension unit 12 is reduced even in the case of a protrusion with a large impact force, a so-called full stroke phenomenon of the suspension unit will occur, which will actually worsen the riding comfort. In order to prevent this, an upper threshold value V2 is set for performing optimal preview control within a range in which the full stroke of the suspension unit 12 does not occur. Here, V is the waiting time ΔT(V+
This is set as the signal value after the time (time from measurement to measurement of v2) has elapsed.

Further, as described above, an ultrasonic sensor is used as the preview sensor 33, but the sensor is set at a certain predetermined vehicle speed in consideration of the Doppler effect. The frequency is adjusted to obtain maximum sensitivity.

Therefore, this predetermined vehicle speed U. At vehicle speeds outside of this range, the reception sensitivity of the sensor decreases, and the output signal value appears to decrease. To prevent this, the controller 30 sets the aforementioned threshold values VI and V2 to the vehicle speed sensor 34.
is set according to the detected vehicle speed, and the vehicle speed is thereby corrected (see FIG. 9).

As a result, the controller 30 controls the preview sensor 3
A command signal for switching the switching valve 22 is output only when the output signal value of No. 3 is within the preview control region set here.

Then, depending on the vehicle speed detected by the vehicle speed sensor 34, the time delay from the time when a protrusion is detected until the wheel passes over the protrusion is predicted, and the switching valve 22 is opened before the wheel passes over the protrusion. When riding over a protrusion or the like, the support rigidity of the suspension unit I2 is switched to small.

Furthermore, after passing over the protrusion, the switching valve 22 is closed again.

Next, a procedure for controlling the switching valve 22 (preview control) when the controller 30 moves over a protrusion or the like will be described with reference to FIGS. 4, 6, 7, and 8.

The control routine for preview control is executed as follows (FIG. 4).

First, the controller 30 detects the vehicle speed U from the vehicle speed sensor 34.
is detected (step S6). Then, the detected vehicle speed U
Using the correction map shown in FIG. 9 showing the relationship between the preset threshold value and the vehicle speed U, the lower threshold value v1 and the upper threshold value V2 corresponding to the vehicle speed U are respectively determined (
Step S8).

Further, the controller 30 constantly monitors the signal value of the preview sensor 33, and reads the output signal value V of the input ultrasonic reflected wave (step 510).

Then, it is determined whether or not the read output signal value of the preview sensor 33 exceeds the lower limit threshold value (■) for separating the noise component set as described above.
Step 512).

If the determination result in step S12 is negative (No),
Steps 86 to S12 are repeated.

If the determination result in step S12 is affirmative (Yes), a timer for measuring the aforementioned waiting time ΔT is started (step 514).

Next, the controller 30 reads the output signal value ■ of the preview sensor 33 (step 516).

It is determined whether the output signal value V exceeds the maximum signal value V max detected after the time point when the output signal value V1 exceeds the threshold value V1 (step 818).

If the determination in step 318 is affirmative (Yes), the output signal value V is rewritten as the maximum signal value V max (step 520).

If the determination in step 318 is negative (No), or after the rewriting of the maximum signal value V max in step S20 is completed, it is determined whether the above-described waiting time ΔT has elapsed (step 1. step 522). .

If the determination in step S22 is negative (No), step 316. S18. S20 is executed, and the maximum signal value V max is rewritten.

If the determination result in step S22 is affirmative (Yes), the maximum signal value V measured from the time when the output signal value of the preview sensor 33 exceeds the lower limit threshold v1 until the elapse of the waiting time ΔT It is determined whether or not max exceeds the upper threshold value V2 set to prevent the suspension unit 12 from reaching a full stroke (step 524).

If the determination result in step S24 is affirmative (Yes), that is, if it is determined that the detected protrusion is small and the suspension unit 12 will not make a full stroke even if the support rigidity of the suspension unit 12 is reduced when passing over this protrusion. In step S30, a command signal for switching the switching valve 22 is output.

If the determination result in step S24 is negative (No), that is, if the detected protrusion is large and it is determined that reducing the support rigidity of the suspension unit 12 when passing over this protrusion will cause the suspension unit to make a full stroke. , the preview output in step S30 described above is not executed, and the timer reset and V ma
Deletion of the x value (step 526) is executed and the routine ends.

Then, detection of the vehicle speed, setting of the threshold values V+ and Vz, and monitoring of the output signal value of the preview sensor 33 are started again to prepare for the arrival of the next protrusion, etc. (steps 86 to S1
．． O).

Here, various aspects of detected protrusions are shown with reference to FIG. 6. In the case of the output signal shown by curve A, the maximum signal value Vmax (=VA
2) exceeds the upper limit threshold V2, the preview output in step S30 is not executed. Further, in the case of the output signal shown by curve B, the maximum signal value Vmax (=V++t) until the waiting time ΔT has elapsed does not exceed the upper limit threshold V2, so the preview output in step S30 is executed. .

Note that, although the waiting time ΔT is set according to the vehicle speed as described above, it may be a constant value.

Furthermore, the reason why the magnitude of the output signal value after ΔT has elapsed is not subject to evaluation is that for so-called gentle protrusions, the support rigidity of the suspension unit 12 is reduced even if the absolute value is large. This is because it is predicted that the full stroke of the suspension unit will not occur.

Next, a preview control output routine executed when the above-mentioned command signal is output will be explained with reference to FIGS. 7 and 8.

First, the delay time T is calculated (step 532).

This delay time is used to time the timing at which the switching valve 22 is opened immediately before the wheel passes over the protrusion after receiving the command signal from the aforementioned control routine (time t2 in FIGS. 3 and 8). and the following formula (1),
Calculated by (2).

T-(Ll +Lx)/U-ΔT...(1
)T-(Ll +L2 +Lv)/U-ΔT-(2)
Here, equation (1) is used to find the delay time for the front wheels, and equation (2) is used to find the delay time for the rear wheels. Ll is the minimum detection distance between the sensor 33 and the detected protrusion, L2 is the distance between the sensor 33 and the front wheel, Ll is the distance between the wheels (wheelbase), and U is the vehicle speed detected by the vehicle speed sensor 34 (the (See Figure 2). And ΔT
is the waiting time mentioned above.

Next, the process proceeds to step S34, where a delay timer and a holding timer are set to timer values T and T', which will be described later, respectively, and then started.

This delay timer is for counting the delay time T set in step S32 described above, and this timer is
Available for front wheels and rear wheels. Further, holding timers are also prepared for the front wheels and the rear wheels, respectively, and the timer value T° to be set is calculated by the following equation (3).

T' ” T + T o...
(3) Here, To is a holding time for maintaining the switching valve 22 in an open state, and is set to, for example, 0.1 sec. Further, T is the delay time calculated by the above equation (1) or (2).

The former delay timer is an up counter that outputs an on signal when it counts up to the set timer value, and at the time of counting up (time t3 in Figure 8), Switching valve 22
is opened (steps S36 and 838). As a result, in addition to the first orifice 19, the second orifice 21
Since the condition is also reversed, the support rigidity of the suspension unit 12 is switched to a small value. Therefore, when the wheel rides over a protrusion or the like, the impact force can be appropriately alleviated without causing a full stroke of the suspension unit.

The latter holding timer also has a set timer value T'
This is an up-counter that outputs an on signal when it counts up to the point where it counts up (t in Figure 8).
4) at the corresponding switching valve 2 on the front or rear wheel side.
2 is closed (steps S40 and 542), and the routine ends. As a result, the preview sensor 33
The support rigidity of the suspension unit 12 is maintained at a high state until the next time a vibration input object such as a protrusion is detected and the control routine of the controller 30 determines that it is optimal for performing preview control. Ru.

Figure 5 shows the preview control routine (Figure 4) described above.
This figure shows the determination procedure of the second embodiment, which simplifies the determination procedure of .

In addition, the explanation of the structure of the active suspension device for a vehicle in FIG. 1 in the first embodiment described above, the explanation of the preview sensor 33 in FIG. 2, and the explanation of the switching valve 2 in FIG.
The explanation of the second control area is also common to this embodiment, so the explanation thereof will be omitted.

First, the controller 30 detects the vehicle speed U from the vehicle speed sensor 34.
is detected (step S6°). Then, using the detected vehicle speed U, the lower limit threshold V1 and the lower limit threshold V corresponding to the vehicle speed U are determined from the correction map showing the relationship between the preset threshold value and the vehicle speed U shown in FIG. ! are determined (step 38').

Further, the controller 30 constantly monitors the output signal value of the preview sensor 33, and reads the output signal value V of the input ultrasonic reflected wave (step SlO').

Then, it is determined whether or not the read output signal value of the preview sensor 33 exceeds the lower limit threshold V1 for separating the noise component (step S I
2').

If the determination result in step 812' is negative (No), steps S6° to S12' are repeated.

If the determination result in step 312' is affirmative (Yes), a timer for measuring the aforementioned waiting time ΔT is started (step S14').

Next, wait for the waiting time ΔT to elapse (step 822').
At the time when the elapsed time has elapsed, the output signal value ■ of the preview sensor 33 is read as Vt2 (step S23').

Then, it is determined whether or not this output signal value Vt2 exceeds an upper threshold value v2 set to prevent the suspension unit from going full stroke (step 824M).

If the determination result in step 324' is affirmative (Yes), that is, if it is determined that the suspension unit does not make a full stroke even if the support rigidity of the suspension unit 12 is reduced when passing over the detected protrusion, etc., the switching Step S30 of outputting a command signal for switching the valve 22 is executed.

If the determination result in step S24° is negative (No), that is, if it is determined that reducing the support rigidity of the suspension unit 12 when passing over the detected protrusion will cause the suspension unit to make a full stroke, the above-mentioned The preview output in step S30 is not executed, but the timer reset (step 326°) is executed and the routine ends. Then, detection of the vehicle speed, setting of the threshold values V+ and Vt, and monitoring of the output signal value of the preview sensor 33 are started again to prepare for the arrival of the next protrusion, etc. (steps 86° to S10').

When the command signal is output, the preview control output routine shown in FIG. 7 in the first embodiment described above is executed.

In the first and second embodiments described above, the threshold values v1 and V2 for determining whether or not to perform preview control are determined by an approximate characteristic map formed by a combination of straight lines as shown by the solid line in FIG. Although vehicle speed correction is performed, the present invention is not limited to the first and second embodiments described above, and the present invention is not limited to the above-mentioned first and second embodiments. Of course, it is also possible to do so.

Further, in the first and second embodiments described above, the thresholds V1 and V are used to compare the output signal values against a decrease in the output signal values due to the Doppler effect.

However, the present invention is not limited to the first and second embodiments described above, and as shown in FIG. 10, the gain G of the output signal value of the preview sensor 33 is It may be corrected.

(Effects of the Invention) As described above in detail, according to the active suspension device for a vehicle of the present invention, when the wheel passes over a vibration input object, if the impact force is excessive, the support rigidity of the hydraulic support means is reduced. If it is set to a small value, a full stroke of the hydraulic support means is generated, so whether or not to change the support rigidity of the hydraulic support means is determined based on whether the output signal value of the vibration input detection means exceeds a predetermined upper limit value. conduct. When determining whether or not the output signal value of the vibration input means exceeds a predetermined upper limit value, the determination error caused by changes in vehicle speed is corrected according to the vehicle speed detected by the vehicle speed detection means, thereby providing more appropriate support against excessive impact force. Since the rigidity is hydraulically controlled to absorb impact force, ride comfort can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining the schematic configuration of an active suspension device for a vehicle according to the present invention, and FIG. 2 shows a relationship between the position where the preview sensor 33 in FIG. 1 detects a protrusion, etc., and the wheel position. 3 is a graph showing the change in the output signal value of the preview sensor 33 and the change over time to explain the control area of the switching valve 22 in FIG. 1, and FIG. 5 is a flowchart showing the procedure of a control routine of preview control executed by the controller 3o. FIG. 7 is a flowchart showing the procedure of the preview control output routine executed by the controller 30; FIG. FIG. 8 is a graph showing the change over time of the switching signal output to the switching valve 22, and FIG. 9 is a graph showing the relationship between the vehicle speed and the threshold value for determining whether the controller 30 performs preview control. Correction map shown, first
FIG. 0 is a correction map showing the relationship between gain and vehicle speed for explaining vehicle speed correction of the output signal value of the preview sensor 33. 1... Oil pump, 7... Vehicle body, 8... Wheels,
12... Suspension unit (hydraulic support means),
13... Suspension spring, 14... Hydraulic actuator, 15... Hydraulic chamber, 17... Control valve (hydraulic control means), 19... First orifice, 2
0...Accumulator, 21...Second orifice,
22... Switching valve, 30... Controller (hydraulic control means), 33... Preview sensor (vibration input detection means), 34... Vehicle speed sensor. Figure 1 Figure 4 Figure 3 Figure 5 ↑ Figure 6 Figure 8 - Preview publication also output Figure 7

Claims (1)

[Claims] A hydraulic support means is installed between the vehicle body and the wheels and changes the support rigidity by controlling the supply and discharge of hydraulic pressure, and a hydraulic support means that detects a vibration input object in front of the vehicle and outputs a detection signal according to the size of the vibration input object. A vibration input detection means for outputting a vibration input detection means, a vehicle speed detection means for detecting a vehicle speed, and a vibration input detection means for detecting a command signal for changing the supply and discharge of hydraulic pressure to the hydraulic pressure support means when the vibration input detection means detects a vibration input object. hydraulic control means for reducing the support rigidity of the hydraulic support means by outputting the signal only when the output signal value of the means does not exceed the predetermined upper limit; When determining,
An active suspension device for a vehicle, characterized in that a discrimination error caused by a change in vehicle speed is corrected in accordance with a vehicle speed detected by the vehicle speed detecting means.