JPH0481313A - Active suspension device for vehicle - Google Patents

Abstract

PURPOSE:To maintain a steering characteristic constant to improve the steering stability at the time of turning a vehicle by obtaining the control pressure of oil pressure support means in response to the lateral acceleration working to a car body, and setting a distribution ratio of the control pressure against oil pressure support means in front and rear of the car body in response to a rise of the speed. CONSTITUTION:In suspension units 12 as an oil pressure support means respectively provided in right and left front wheels and right and left rear wheels, a suspension spring 13 and a hydraulic actuator 14 are interposed between a car body 7 and a wheel 8. The operation of a control valve 17 and a switching valve 22 of the suspension unit 12 is controlled by a controller 30 forming an oil pressure control means on the basis of the detecting signal from a lateral G sensor 31 and a speed sensor 34 or the like. In this case, when a steering characteristic of a vehicle is moved to an under-steer side in response to a rise of the speed, the controller 30 can change a distribution ratio of the control pressure to be distributed to the suspension units 12 in front and rear of the car body to deny an under-steer quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an active suspension device for a vehicle that reduces roll of a vehicle body when turning and at the same time improves vehicle maneuverability.

(Prior Art) This type of active suspension device has a hydraulic actuator consisting of a hydraulic cylinder installed between the vehicle body and each wheel, and supports the vehicle body via these hydraulic actuators, that is, with hydraulic pressure. That's what I do. Therefore, if the vehicle body is supported hydraulically in this way, the control pressure of the hydraulic actuator is calculated according to the magnitude of the lateral acceleration acting on the vehicle body when the vehicle turns, and each hydraulic pressure is adjusted based on this control pressure. By controlling the hydraulic pressure of the actuator, the roll of the vehicle body can be reduced or prevented using the control pressure. Specifically, when the vehicle turns, control pressure is applied to the hydraulic pressure of the hydraulic actuator on the outer wheel of the turn to increase the oil pressure, while the oil pressure of the hydraulic actuator of the inner wheel of the turn is reduced by the amount of control pressure. By doing so,
It becomes possible to reduce or prevent the roll of the vehicle body and maintain a constant posture of the vehicle body.

Further, according to this type of active suspension device, when the vehicle turns, the hydraulic pressure of the hydraulic actuators at the front and rear of the vehicle body is adjusted based on the control pressure distribution obtained by distributing the control pressure, according to the steering state of the steering wheel. It is known that if controlled, the roll stiffness changes between the front and rear of the vehicle body, thereby making it possible to control the steering characteristics of the vehicle body.

In other words, when the amount of steering from the steering wheel is large, if the distribution of control pressure is varied to increase the roll stiffness at the rear of the vehicle, the steering characteristics will become oversteer, making it easier for the vehicle to turn. .

(Problem to be Solved by the Invention) However, it is known that the steering characteristics of a vehicle change depending on the vehicle speed. Specifically, as the vehicle speed increases, the steering characteristics of the vehicle change. , when turning, there is a tendency to shift to the understeer side. That is, this can be recognized from the fact that as the vehicle speed increases, the stability factor decreases, as shown in FIG. 7, which shows the relationship between vehicle speed and stability factor. Here, the stability factor S can be calculated from the following equation.

S=-(m/j22) ・(Af -Kf -E
r - Kr ) / (Kf - Kr ) In the above formula, m is the inertial weight of the vehicle, l is the wheel pace, l[ is the distance between the center of gravity and the front axle, and 1r is the distance between the center of gravity and the rear axle. Kf indicates the cornering power of the front wheels, and Kr indicates the cornering power of the rear wheels.

The above-mentioned phenomenon is that as the vehicle speed increases, the wind pressure acting on the vehicle body increases rapidly, so even if you turn the steering wheel, the wind pressure acts as resistance to this steering, and this causes the vehicle to It is thought that the steering characteristics tend to understeer. Therefore, in the above-mentioned vehicle steering characteristic control, the control pressure distribution ratio is varied only according to the steering condition of the steering wheel, so as the vehicle speed increases, the vehicle steering characteristic changes to the desired level. This would deviate from the characteristics of

For this reason, it is conceivable to mount an aerodynamic device such as an air spoiler on the vehicle body, and use this aerodynamic device to cancel out changes in steering characteristics during high-speed driving. However, even when a vehicle such as a passenger car travels at high speed, the effect of the aerodynamic device is small, and the aerodynamic device is often insufficient to counteract the tendency of the vehicle to understeer.

This invention was made based on the above-mentioned circumstances, and
The purpose is to provide an active suspension device for a vehicle that can effectively reduce vehicle body roll and at the same time eliminate the tendency of understeer in steering characteristics associated with an increase in vehicle speed, thereby improving its steering performance. There is a particular thing.

(Means for Solving the Problems) The present invention includes hydraulic support means that are inserted between the vehicle body and each wheel to support the vehicle body, lateral acceleration detection means that detects lateral acceleration acting on the vehicle body, A control pressure calculation means for calculating a control pressure for the hydraulic support means to reduce roll of the vehicle body based on the lateral acceleration, and a hydraulic control means for controlling supply and discharge of hydraulic pressure to each hydraulic support means based on the control pressure. In the active suspension device for a vehicle, the active suspension device of the present invention includes a vehicle speed detection means for detecting the vehicle speed of the vehicle, and a vehicle speed detecting means that detects the vehicle speed when the steering characteristic of the vehicle shifts to the understeer side as the vehicle speed increases. In order to cancel out the difference, the system includes a distribution rate variable means for varying the distribution rate of the control pressure distributed to the hydraulic support means at the front and rear of the vehicle body.

(Function) According to the active suspension device of the present invention, when the vehicle turns while traveling at high speed, the distribution ratio of the control pressure calculated to perform roll control of the vehicle body is The ratio of the control pressure of the hydraulic support means is varied so as to increase as the vehicle speed increases. If the distribution ratio of the control pressure is varied in this manner, the roll stiffness of the rear portion of the vehicle body increases, so that the steering characteristics of the vehicle body tend to oversteer. Therefore, this oversteer tendency is
Since the understeer tendency caused by an increase in vehicle speed is canceled out, the vehicle can turn in accordance with the steering of the steering wheel.

(Example) FIG. 1 shows the configuration of a hydraulic active suspension system for a vehicle. This figure shows a suspension unit 12 as a hydraulic support means provided for each wheel, that is, front left and right wheels and rear left and right wheels, and a suspension spring 13 of this suspension unit 12 and a single-acting hydraulic cylinder. A hydraulic actuator 14 consisting of
are interposed between the vehicle body 7 and the wheels 8. Furthermore, the first
In the figure, a suspension unit combined with one wheel is representatively illustrated.

The control valve 17 of the suspension unit 12 is inserted between an oil passage 16 communicating with the hydraulic chamber 15 of the hydraulic actuator 14, and a supply oil passage 14 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 2o 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 cusp spring action is exerted. A first throttle 19 is disposed in the middle of the branch path 16a, and this first throttle 19
regulates the amount of hydraulic oil flowing between the accumulator 20 and the hydraulic chamber 15 of the hydraulic actuator 14, thereby achieving a desired vibration damping effect.

A first throttle 1 is provided between the oil passage 16 and the accumulator 20.
A bypass path 16b that bypasses 9 is connected,
A second throttle 21 and a switching valve 22 are arranged in this bypass passage 16b.

The second aperture 21 has a larger orifice diameter than the first aperture 19. The switching valve 22 is in a closed state (the state shown in the figure) when the switching valve 22 is not energized, and when the switching valve 22 is switched to the open state, the hydraulic oil is transferred to the switching valve 2 in the open state.
2 and the second throttle 21 can flow between the accumulator 20 and the hydraulic chamber 15, thereby weakening the vibration damping effect. That is, by opening and closing the switching valve 22, the spring rigidity of the suspension unit 12 changes in two stages.

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 is driven, the reserve tank 3
The hydraulic oil stored therein is discharged to the supply oil path 4 side. An oil filter 9, a check valve 1O, and an accumulator 11 for maintaining line pressure are arranged in the oil supply path 4 in this order from the oil pump 1 side. The check valve IO only allows the flow of hydraulic oil from the oil pump l side toward the suspension unit 12 side, and high-pressure hydraulic oil can be stored in the accumulator 11 by this check valve lO.

The control valve 17 is of a type that changes its valve opening degree in proportion to the supplied current value, and depending on this valve opening degree, the control valve 17 changes the valve opening degree between the supply oil passage 4 side and the discharge oil passage 6 side. It is possible to control the supply and discharge of the amount of oil, that is, the supply and discharge of oil pressure to and from the hydraulic actuator 14. And control valve 17
The structure is such that the higher the current value supplied to the hydraulic actuator 14, the greater the hydraulic pressure within the hydraulic actuator 14, that is, the supporting force generated by the hydraulic actuator 14. The hydraulic oil discharged from the control valve 17 to the discharge oil path 6 side is returned to the reservoir tank 3 as described above.

The control valve 17 and the switching valve 22 are electrically connected to the output side of a controller 3o constituting a hydraulic control means, and their operation is controlled by a drive signal from the controller 30. Therefore, controller 3
Various sensors are connected to the input side of 0, respectively.
These sensors include a lateral G sensor 31 that is attached to the vehicle body 7 and detects the lateral acceleration Gy acting on the vehicle body 7, a vehicle height sensor 32 that is provided for each wheel and detects the stroke amount of the wheel, and a steering wheel of the vehicle. A steering wheel angle sensor 33 that detects the steering angle θH (not shown), and a vehicle speed V of the vehicle.
There is a vehicle speed sensor 34 etc. that detects the vehicle speed.

Therefore, the aforementioned control valve 17 and switching valve 22 are
The operation is controlled by the controller 30 based on the detection signal of each sensor.

During normal driving, the switching valve 22 is closed, and slight vibrations input to the vehicle body from the road surface are suppressed because the hydraulic chamber 15 of the hydraulic actuator 14 communicates with the accumulator 20 via the first throttle I9. , absorbed and attenuated.

Next, the operation of the suspension unit 12 controlled by the controller 30, that is, the roll control and steering characteristic control of the vehicle body 7, will be explained with reference to the block diagram shown in FIG.

First, when the vehicle turns, the lateral acceleration Gy obtained by the lateral G sensor 31 is supplied to the controller 30. In the controller 30, the calculation unit 41 performs roll control based on the lateral acceleration Gy. Pressure ΔP is calculated.

Here, the control pressure ΔP can be calculated from the following equation based on the lateral acceleration Gy.

ΔP=KR-GY Here, the control gain KR is the hydraulic actuator at the left and right wheels that cancels the load movement on the left and right sides of the vehicle body caused by the lateral acceleration GY of the vehicle body 7 when the vehicle turns, that is, the moment force. This is a gain for calculating the control pressure ΔP in 14 based on the lateral acceleration Gy. Therefore, the control gain KR itself can be calculated in advance from the following equation.

KR=M-H/ (L-A) Here, as is clear from FIG. 3, M is the mass of the vehicle body 7, H is the height of the center of gravity of the vehicle body 7, L is the tread, and A is the oil pressure. The effective pressure receiving area of the actuator 14 is shown.

Therefore, when the vehicle turns left, the control pressure of the hydraulic actuator 14 on the right wheel side is Δ
Pl, the control pressure of the hydraulic actuator 14 on the left wheel side becomes -ΔPl.

Then, the vehicle speed V obtained by the vehicle speed sensor 34 is supplied to the calculation unit 42, and the calculation unit 42 calculates the distribution ratio for allocating the control pressure ΔP to the hydraulic actuators 14 on the front wheel side and the rear wheel side.
Here, the distribution ratio γ (0≦γ≦1) as seen from the front wheel side is calculated. Specifically, the distribution ratio γ can be calculated from the map shown in FIG. This map determines the distribution ratio γ based on the vehicle speed V. When the vehicle speed V is lower than a predetermined low speed value VL (for example, 50 km/h), the distribution ratio γ is set to an initial value γ0. Here, the initial value γ0 is a value close to the weight distribution between the front and rear of the vehicle, for example, 0.
It is set to 8. Then, when the vehicle speed V further increases from the low speed value VL, the distribution ratio γ gradually decreases as the vehicle speed V increases, that is, as the understeer tendency of the vehicle becomes stronger, and the vehicle speed 120k
m/h), it is set to γ1 (for example, 0.6). As is clear from FIG. 4, even if the vehicle speed V increases above the high speed value VH, the distribution ratio γ is maintained at γ1.

When the distribution rate γ is set based on the vehicle speed V as described above, this distribution rate γ is then supplied to the calculation unit 43,
Further, the control pressure ΔP obtained by the above-described calculation unit 41 is also supplied to the calculation unit 43. As a result, the calculation section 43
Then, from the distribution ratio γ and the control pressure ΔP, the front wheel side control pressure distribution ΔPf and the rear wheel side control pressure distribution ΔPr for the front wheel side and rear wheel side hydraulic actuators 14 are respectively calculated based on the following equations.

ΔPf=ΔP・γ ΔPr=ΔP・(1−γ) The above ΔPf and ΔPr are the control pressure distribution of the hydraulic actuator 14 at the front and rear of the vehicle body with respect to the right side of the vehicle, that is, when the vehicle turns left. When doing so, the front and rear control pressure distributions for the outer wheel side of the turn are shown, but it goes without saying that the front and rear control pressure distributions for the inner wheel side of the turn are calculated in the same way. Further, (1-γ) indicates the distribution ratio on the rear wheel side.

On the other hand, the steering angle θH obtained from the steering wheel angle sensor 33 is differentiated by the differential calculation unit 44 to calculate the steering angular velocity ΔθH, and the steering angular velocity ΔθH is supplied to the distribution ratio α calculation unit 445. Ru.

Further, the steering angular velocity ΔθH obtained by the differential calculation section 44 is supplied to the steering discrimination section 46, while the steering discrimination section 46 has the following information:
The steering angle θH from the steering wheel angle sensor 33 is also supplied. From the steering angular velocity δH and the steering angle θH, the steering determination unit 46 determines,
The steering wheel is in the cut position, or
This is to determine whether it is in a cutback state. Specifically, the steering wheel is in the neutral position as 00, the steering angle θH is expressed with a sign depending on the steering direction, and then the steering angle θH is expressed based on the sign of the product of the steering angle θH and the steering angular velocity ΔθH. , it is possible to determine whether the steering wheel is in the turned state or the turned back state. In this case, if the sign of the above product is positive, it can be determined that the steering wheel is in the turning state, whereas if the sign of the above product is negative, it can be determined that the steering wheel is in the turning state. can.

Then, in the calculation unit 45 described above, the steering angular velocity ΔθH,
Depending on the steering condition of the steering wheel, that is, whether it is in the turning state or in the turning state, the control pressure Δ as seen from the front wheel side
The distribution ratio α (0≦α≦1) of P is calculated. The distribution ratio α here is different from the distribution ratio γ described above, and is used to actively vary the steering characteristics of the vehicle in accordance with the steering state of the steering wheel. Specifically, the allocation rate α is
From the map shown in FIG. 5, it can be calculated based on the steering angular velocity ΔθH. Here, as is clear from FIG. 5, when the steering angular velocity ΔθH is within a predetermined dead zone area F centered on 0, the distribution ratio α is determined by considering the weight distribution before and after the vehicle and the distribution ratio γ described above. , are set to appropriate initial values. Then, when the steering angular velocity ΔθH exceeds the dead zone region F and increases in the steering direction of the steering wheel,
The distribution ratio α decreases as the steering angular velocity ΔθH increases,
When the steering angular velocity ΔθH is equal to or higher than a predetermined value Δθ, it is maintained at a constant value.

On the other hand, when the steering angular velocity ΔθH increases beyond the dead band region F in the direction in which the steering wheel is turned back, the distribution ratio α increases as the steering angular velocity ΔθH increases, and the steering angular velocity ΔθH exceeds the predetermined value ΔθH2. It is maintained at a constant value.

Therefore, in the calculation unit 45, when the steering wheel is in the turned state, the distribution ratio α is selected from the right side area in FIG. 5 based on the steering angular velocity ΔθH; , the distribution ratio α is set based on the steering angular velocity ΔθH from the left side area in FIG.

When the allocation rate α is set as described above, this allocation rate α is supplied to the correction calculation unit 46.
In step 6, the control pressure distributions ΔPf and ΔP'' from the calculation unit 43 are corrected based on the distribution rate α. That is, when the distribution rate α decreases, the control pressure distribution is adjusted according to the decrease. ΔP" is increased while the control pressure distribution ΔPf is decreased, and on the other hand, when the distribution ratio α increases, conversely,
While reducing the control pressure distribution ΔP', the control pressure distribution ΔPf
These control pressure distributions ΔPf and ΔPr are corrected so as to increase the pressure.

When the control pressure distribution ΔPf and ΔPr are each corrected in the correction calculation unit 46, the controller 3o adjusts the control pressure distribution Δ
Control signals corresponding to Pf and ΔPr are output to the control valves 17 of the corresponding hydraulic actuators 14, and the oil pressure in these hydraulic actuators 14 is controlled according to the control pressure distribution.

Furthermore, as described above, when the vehicle turns, the control pressure distributions ΔPf and ΔPr are applied to each hydraulic actuator 1 on the outer wheel side of the turn.
This is a control amount for controlling the hydraulic pressure of No. 4, and each hydraulic actuator 14 on the inner wheel side of the turn is controlled according to the control pressure distribution ΔPf, -ΔPr calculated in the same way.

Specifically, when the vehicle turns to the left, the hydraulic pressure in the hydraulic actuator 14 before and after the right wheel, which is the outer turning wheel, is increased based on the control pressure distributions ΔPf and ΔPr. The oil pressure in the hydraulic actuator 14 before and after the left wheel, which is the inner wheel of the turning, is determined by the control pressure distribution -ΔPf,
-ΔPr will be respectively depressurized.

When the vehicle turns, if the hydraulic pressure in each hydraulic actuator 14 is controlled as described above, the moment force due to the load movement caused by the vehicle turning can be canceled out by the control pressure ΔP, and thereby, It becomes possible to reduce the roll of the vehicle body 7 and maintain its posture constant.

Further, in this invention, control pressure distribution ΔPf, ΔPr
In calculating the distribution ratio γ determined from the vehicle speed V, it is possible to prevent the steering characteristics of the vehicle from becoming understeer as the vehicle speed V increases. That is, as the vehicle speed V increases from the low speed value VL toward the high speed value VH, the distribution ratio γ decreases as the vehicle speed V increases, as is clear from FIG. , the control pressure distribution ΔPr increases, whereas the control pressure distribution ΔPf decreases.

Therefore, if the hydraulic pressure in each hydraulic actuator 14 is controlled based on these control pressure distributions, the roll stiffness of the rear part of the vehicle body 7 increases, and the steering characteristics of the vehicle tend to oversteer, thereby increasing the vehicle speed V. This makes it possible to cancel out the tendency of understeer associated with this, and to make the steering characteristics of the vehicle constant regardless of the vehicle speed V.

In addition, in the case of this embodiment, the control pressure distribution ΔPf, ΔPr depends on the steering state of the steering wheel and its steering angular velocity Δ
Since the correction is made based on the distribution rate α set from θH, when the steering angular velocity ΔθH is large, the control pressure distribution ΔPr is increased more, whereas the control pressure distribution ΔPf is more The pressure will be reduced. Therefore, in this case, since the roll rigidity of the rear portion of the vehicle body 7 is further increased, the steering characteristics of the vehicle become oversteer, and the turning performance of the vehicle can also be improved. To explain this point in more detail, when correcting the control pressure distribution based on the distribution ratio α set from the steering angular velocity ΔθH, the present invention corrects the understeer tendency of the vehicle caused by the increase in the vehicle speed V. Therefore, the distribution ratio α, that is, the steering angular speed Δθ
Based on H, it becomes possible to optimally control the steering characteristics of the vehicle.

FIG. 6 is a flowchart showing the roll control pressure distribution routine by the controller 30 described above. To briefly explain this flowchart, first, in step S1, the vehicle speed V is read by the vehicle speed sensor 34. Then, it is determined whether the vehicle speed V is between the low speed value VL and the high speed value VH (step S2). If the determination in step S2 is positive (Yes), then it is determined whether or not the control pressure ΔP is output (step S2).
3) If the determination here is also positive, the next step S4 is executed. Specifically, the determination in step S3 can be made based on the presence or absence of a sensor signal from the lateral G sensor 31.

Then, in step S4, the distribution rate γ is determined based on the vehicle speed V.
is set, and then this distribution ratio γ and control pressure Δ
Based on P, the control pressure distributions ΔPf and ΔPr for the hydraulic actuators 14 of the front and rear wheels are respectively calculated and determined (
Step S5), and further, these control pressure distributions are
Corrected according to the distribution ratio α calculated from the steering state of the steering wheel and the steering angular velocity ΔθH (step s6),
It will be output in the next step S7.

This invention is not limited to the one embodiment described above. For example, the configuration of an active suspension device is
Various modifications are possible other than the one shown in FIG. 1, and the controller 3° can actually be constructed from a circuit including a microcomputer.

(Effects of the Invention) As explained above, according to the active suspension device for a vehicle of the present invention, the control pressure of the hydraulic support means is determined according to the lateral acceleration acting on the vehicle body when the vehicle turns, and By controlling the hydraulic pressure of each hydraulic support means based on this control pressure, vehicle body roll is reduced, and the distribution ratio of control pressure to the hydraulic support means at the front and rear of the vehicle body is set in accordance with the increase in vehicle speed. Therefore, when the vehicle speed is increasing, the control pressure distribution of the hydraulic support means at the rear of the vehicle can be increased to increase the roll rigidity of the rear of the vehicle by 4 degrees. When the roll stiffness at the rear of the vehicle body increases in this way, the vehicle's steering characteristics tend to oversteer. This oversteer tendency cancels out the vehicle's understeer tendency caused by an increase in vehicle speed, thereby keeping its steering characteristics constant. This has the effect of improving steering stability by maintaining the

BRIEF DESCRIPTION OF THE DRAWINGS The drawings show an embodiment of the present invention, in which FIG. 1 is a schematic configuration diagram of an active suspension device, FIG. 2 is a block diagram for explaining the operation of the controller, and FIG. Fig. 3 is a diagram for explaining the control pressure that cancels the moment force of the vehicle body when turning, Fig. 4 is a graph showing the distribution ratio γ with respect to the vehicle speed, and Fig. 5 is a graph showing the distribution ratio α with respect to the steering angular speed. FIG. 6 is a flowchart showing the roll control pressure distribution routine, and FIG. 7 is a graph showing the stability factor versus vehicle speed. 7... Vehicle body, 8... Wheel, 14... Hydraulic actuator, 17... Control valve, 30... Controller, 31... Lateral G sensor, 33... Handle angle sensor, 34... ...Vehicle speed sensor.

Claims (1)

[Claims] Hydraulic support means are inserted between the vehicle body and each wheel to support the vehicle body; lateral acceleration detection means detect lateral acceleration acting on the vehicle body; An active suspension device for a vehicle, comprising a control pressure calculation means for calculating a control pressure of a hydraulic support means for reducing roll, and a hydraulic control means for controlling supply and discharge of hydraulic pressure to each hydraulic support means based on the control pressure. In this case, the hydraulic pressure is distributed to a vehicle speed detection means for detecting the vehicle speed of the vehicle, and a hydraulic support means at the front and rear of the vehicle body in order to cancel out the understeer when the steering characteristic of the vehicle shifts to the understeer side as the vehicle speed increases. 1. An active suspension device for a vehicle, comprising a distribution rate variable means for varying a control pressure distribution rate.