JPH02182522A - Suspension control device - Google Patents

Abstract

PURPOSE:To make it possible to wholly secure driving force for the driving wheels of a car at its maximum by detecting an axle load on each driving wheel, and controlling the axle load so that the axle load of the driving wheel having the minimum axle load may be changed to correct the reduction of the driving force of the same car. CONSTITUTION:A series circuit having a throttle valve 11 and an accumulator 12 is connected to each port 10a of hydraulic cylinders 10 (10FL-10RR) attached to front and rear wheels on both sides, and a hydraulic control circuit for an axle load regulating mechanism is connected to each port 10b of the cylinders 10, and composed of a hydraulic pump 13, a shut-off valve 21 and a pressure control valve 23 (23FL-23RR) corresponding to each hydraulic cylinder 10. In this case, the axle load sensors 27, 28 are provided to detect the axle load on each driving wheel, and their outputs are inputted into a controller 26, and then the axle load on a fixed driving wheel is changed on the detected axle load. Thus the pressure control valve 23 is controlled to increase the axle load on the driving wheel having the minimum axle load.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a suspension control device that secures maximum driving force by controlling a suspension and moving wheel loads.

(Prior Art) As a conventional suspension control device of this type, for example, Japanese Patent Application Laid-Open No. 62-275814, which was previously filed by the applicant of the present application,
There is something described in the No.

This device adjusts the wheel load by placing a mechanical spring that supports the wheel load in parallel between the vehicle body and the wheels, and a hydraulic cylinder that acts as a shock absorber that generates the desired damping force and absorbs vibrations. In an active suspension system, the cornering force (hereinafter referred to as CF) of the wheel is generated by shifting the load according to the driving condition.
) is controlled to an appropriate value. In other words, this device changes the wheel load distribution in a direction that suppresses changes in yaw moment due to changes in the driving condition, depending on the braking/driving force and lateral acceleration (hereinafter referred to as machine G) used for the driving condition. , the vehicle turning characteristics are improved by realizing a desired load movement to compensate for changes in wheel CF.

(Problem to be Solved by the Invention) However, the above-mentioned conventional suspension control device simply performs control to correct changes in wheel CF in response to changes in braking/driving force and lateral G in driving conditions. However, when the driving force of the driving wheels decreases due to a decrease in the wheel load while driving, there is no control to ensure the maximum driving force of the driving wheels as a whole, which causes the following problems. arise. In other words, when one drive wheel (for example, the left rear wheel) slips and the wheel load decreases while driving, the differential limiting device (Limited S pDif
In vehicles that are not equipped with a ferential (hereinafter referred to as LSD), the driving force is not transmitted between the left and right drive wheels, so in response to the decrease in the drive force of that drive wheel, the drive force of the other drive wheel (in this case, the right The driving force of the rear wheels (rear wheels) decreases to the same level as the decreased driving force, and the driving force of the drive wheels as a whole also decreases significantly. - In vehicles equipped with an LSD, even if the wheel load on one drive wheel decreases due to slipping, etc., the driving force is transmitted between the left and right drive wheels due to the action of the LSD. The side drive wheels can exert normal driving force according to the wheel load, but
As shown in Figure 5, the driving force of a vehicle exhibits non-linear characteristics with respect to the wheel load, so the driving force of the driving wheels as a whole decreases according to the difference in wheel load between the left and right driving wheels. Comparing when the load difference is O and when it is 2.Δ, the total wheel load is the same, but the driving force per wheel is 0 at point A in the diagram.
1 to 02 at point B) The present invention aims to solve the above-mentioned problem by performing control to correct the decrease in driving force by changing the wheel load of a predetermined wheel when the wheel load decreases. do.

(Means for Solving the Problems) For this purpose, the suspension control device of the present invention provides wheel load adjustment capable of adjusting at least one of the amount of load transfer between the left and right wheels and the amount of load distribution between the front and rear wheels. In a suspension control device having a mechanism, a wheel load detection means for detecting a wheel load or a wheel load equivalent amount of each drive wheel;
A wheel load changing means for changing the wheel load of a predetermined wheel by the wheel load adjustment mechanism based on the detected wheel load or wheel load equivalent, and in this case, for example, the wheel load Changing the wheel load by changing means is as follows:
The wheel load of the drive wheel with the smallest detected wheel load or wheel load equivalent is increased.

(Function) While the vehicle is running, the wheel load detection means detects the wheel load or wheel load equivalent of each drive wheel.

By the way, if one of the drive wheels is likely to slip while driving, the driving force of the drive wheels as a whole will decrease due to the decrease in the wheel load of that drive wheel, as described above, regardless of whether an LSD is installed or not. (Especially in vehicles without LSD, the driving force decreases significantly).

Therefore, the wheel load changing means changes the wheel load of a predetermined wheel using a wheel load adjustment mechanism based on the detected wheel load or wheel load equivalent. Note that this change in wheel load is performed, for example, by controlling the drive wheel with the minimum wheel load to increase the wheel load.

As a result, the wheel load difference between the left and right drive wheels is reduced, and the driving force of the vehicle's drive wheels as a whole is restored to almost the same level as when there is no reduction in the wheel load, thereby securing the maximum amount. Can be done.

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

FIG. 1 is a diagram showing the configuration of a first embodiment of the suspension control device of the present invention, and this example employs an active suspension using hydraulic cylinders. 1 in the diagram
0PL, 10PR, 10RL, and 10RR are hydraulic cylinders for the left and right front and rear wheels, respectively.

Hydraulic cylinder l0FL, l0PR, l0RL, l0
The RR is mounted so that its upper end in the figure is supported by the vehicle body and its lower end in the figure is supported by the wheels, and each wheel (not shown) is independently suspended. Hydraulic cylinder boat 10
A series circuit of a throttle valve 11 and an accumulator 12 having a shock absorber function is connected to the boat 1.
0b is supplied with a control pressure P-(PCl
, PcZ, Pc:I, Pc4). When these hydraulic cylinders supply control pressure Pc to the boat 10b, this control pressure Pc is supplied to the oil chamber 10e through the communication hole 10d of the cylinder 10c, and is also supplied to the oil chamber 10g via the communication hole 10f. The size of the area causes a force to move the cylinder IOc upward in the drawing, and the load applied to the vehicle body at that time causes a force to move the cylinder 10c downward in the drawing, so the cylinder 10c stops at a position where these forces are balanced. . The accumulator 11 and the throttle valve 12 exhibit a shock absorber function by damping vibrations when there is a sudden change in load such as vibration of the vehicle body, and the accumulator 11 acts as a spring. Note that the above hydraulic cylinder and the following hydraulic control circuit constitute a wheel load adjustment mechanism as a whole.

Next, the hydraulic control circuit will be explained. 13 is a hydraulic pump, check valves 14, 15, 16, accumulator 17,
The unload valve 18, oil cooler 19, tank 20, and shutoff valve (fail-safe valve) 21 constitute a hydraulic pressure supply circuit. That is, when the hydraulic pump 13 starts supplying hydraulic pressure, the internal pressure of the accumulator 17 increases, and the unload valve 18 and the shutoff valve 21 are pressurized. Here, when the ignition key is turned OFF and the engine is stopped, the shutoff valve 21 is in the cut-off position shown in the figure to cut off the supply of source pressure and prevent the vehicle's attitude from changing. Supplied individually. Note that when the internal pressure of the accumulator 17 exceeds a predetermined value, the unload valve 18 becomes the communication position and drains the hydraulic pressure into the tank 20 via the oil cooler 19.

When the ignition key is turned on, the source pressure passing through the shutoff valve 21 is applied to each wheel individually, for example, in the case of the left (right) front wheel, the control pressure is applied to the hydraulic cylinder l0FL (IOPR) via the accumulator 22F and the pressure control valve 23FL (23FR). Pc
1 (pez) (the same applies to the left and right rear wheels). Electromagnetic proportional pressure control valve 23FL, 23FR
, 23RL.

23RR is in the communication state shown in the figure when the source pressure is supplied, and supplies control pressure to each hydraulic cylinder, but at this time, the pressure corresponding to the source pressure is fed back. When this feedback pressure exceeds a predetermined value, the pressure control valve enters the drain state and drains the hydraulic pressure of the hydraulic cylinders to the orifices 24L, 24R, and 25L.
Alternatively, it is drained into the tank 20 via the 25R1 shutoff valve 21, check valve 16 and oil cooler 19.

The above feedback pressure is transferred to the solenoid 23a of the pressure control valve.
The control pressures PC1 to Pc4 are controlled by controlling the drive currents L+Iz and h+14. A controller 26 is provided to control this solenoid drive current, and the controller 26 includes wheel load sensors 27 and 28 provided for each drive wheel.
Signals Wt and W* representing the wheel load (or wheel load equivalent) of each drive wheel are input. Although the case of a front-wheel drive vehicle or a rear-wheel drive vehicle is shown here, in the case of a four-wheel drive vehicle, four wheel load sensors are used. In addition, as the wheel load sensor, for example, a pressure sensor is used, focusing on the fact that the control pressures Pct to Pc4 are proportional to the wheel load, but the sensor is not limited to this. Sensors that detect parameters that can be estimated may also be used.

The controller 26 executes the control program shown in FIG. 4 to perform the suspension control of the present invention.

That is, first in step 101, the wheel load sensor 27, 28
The wheel load (or wheel load equivalent) of each drive wheel! /J
t.

W is read, and in step 102, the drive wheel with the minimum detected wheel load is determined based on h.

In the next step 103, suspension control is performed to increase the wheel load of the drive wheels. Here, the amount of increase in the wheel load is, for example, the wheel load WL read in step 101.
, W, I The wheel load difference 2・Δ−(2・ΔW=I
wL−w*l). In the case of a four-wheel drive vehicle, the control shown in FIG. 3 is performed for the front wheels and rear wheels, respectively.

The operation of the above control will be explained in detail below.

Generally, in hydraulic active suspensions, the wheel load of each wheel can be controlled independently, but in order to prevent changes in the vehicle's attitude, it is necessary to control the wheel load difference in the longitudinal and lateral directions for each wheel. (For example, if the wheel load of the right front wheel is increased by ΔW, the wheel loads of the other wheels are uniquely determined, and the left rear wheel is changed to +W, the left front wheel and the right rear wheel are increased by ΔW.) The amount of wheel load movement of the wheels on the diagonal is made equal by setting each wheel as one.)

Incidentally, the relationship between the vehicle driving force and the wheel load is shown in FIG. In other words, when the wheel load W is applied equally to the left and right drive wheels (Wt=L+=W), the driving force of each drive wheel is 01 at point A in the figure, and the total drive force of the drive wheels is 2.
Q.

On the other hand, when a wheel load difference occurs between the left and right drive wheels, for example, when the vehicle turns left, a load shift of Δ匈 occurs, and the wheel load WL of the left drive wheel on the inner circumference of the turn becomes W L = W.
1. l = W-Δ-, and when the wheel load 6 of the right driving wheel on the outer circumferential side of the turning becomes 6=-0, =-10ΔW, the driving force of each driving wheel is Qin at the 8 points shown in the figure, and Qin at the 0 point, respectively. becomes 00□. In the case of a vehicle not equipped with an LSD, the driving force of the driving wheels at both stations is determined by the smaller wheel load, as mentioned above, Q! , , and the entire driving wheel is 2・mouth 17
becomes. This driving force 2・Q! The larger the load shift ΔW, the more rapidly M decreases from 2·Ql. In addition, in the case of a vehicle equipped with an LSD, the driving wheels at both stations have a driving force commensurate with the respective wheel loads, that is, Q iR+ corresponding to points B and 0 in the diagram.
(Although, as shown in the figure, the driving force characteristics with respect to the wheel load become more pronounced as the wheel load increases, so the driving force of the entire driving wheel Q4.+Qout = 2.Qz (point shown) decreases from 2.Ql as the load shift ΔW increases.

Therefore, if there is a wheel load difference between the left and right drive wheels,
By increasing the wheel load of the drive wheel with the smallest wheel load in accordance with the left and right wheel load difference (2・Δ匈 in the above example), this wheel load difference is almost eliminated and the reduction in the driving force of the wheel is compensated for. Can be corrected.

This makes it possible to maximize the driving force of the entire drive wheels of the vehicle.

FIG. 2 is a diagram showing the configuration of a second embodiment of the suspension control device of the present invention, and this example employs an air suspension. Note that the same reference numerals are used for the same parts as in the first embodiment.

50 is a motor, 51 is a compressor, and the motor 50
The compressor 5I driven by compresses the air taken in from the filter 52 to generate air pressure.

After passing through a dryer 53, this air pressure is stored in a main tank 55 via a check valve 54, and is supplied to each wheel individually via supply/exhaust valves 56FL, 56FR, 56RL, and 56RR. Here, a main valve 57 is provided in parallel with the check valve 54. This main valve 57 maintains the pressure inside the main tank 55 at a constant value, and
Air pressure is supplied from the main tank 55 as desired.

Supply and exhaust valves 56FL, 56FR, 56RL, 56RR
It is a 3-position switching valve that can take three positions: cutoff, communication, and exhaust. That is, in the illustrated normal state (a), the pneumatic pressure source and the suspension device are cut off, and when the solenoid 56a is driven, they are communicated with each other in the illustrated position (b) to supply pneumatic pressure from the pneumatic source to the suspension device. Illustrated when driving (
At position C), the air pressure of the suspension device is exhausted and the air pressure supply is cut off.

The air pressure that passes through the supply and exhaust valves is sent to each suspension device 58FL.
, 5BPR, 58RL, and 58RR, is supplied to a pressure sensor 59 provided to monitor the air pressure, and is further supplied to a sub tank 61 via a cut valve 60. These suspension devices are connected to the air pressure PCI+PC2+P supplied to the air chamber 58a.
It adjusts the vehicle height according to C3+PC4 and has a shock absorber function. The suspension device is also provided with a stroke sensor 62 to detect its stroke. The cut valve 60 controls air pressure by communicating or cutting off the air chamber 58a and the sub-tank 61, and changes the spring constant of the suspension device.

The air pressure is controlled by each solenoid drive current of the supply/exhaust valve, main valve, and cut valve.

In order to control this solenoid drive current, the controller 26
will be established. Note that, as in the first embodiment, signals H, W representing the wheel loads from the wheel load sensors 27.2B described above are used as inputs to the controller 26.

As in the first embodiment, the controller 26 executes the control program shown in FIG. 4 to perform the suspension control of the present invention.

In this example, the effect of this control is similar to that of the first example, but the specific wheel load control method is slightly different. For example, if the wheel load on the left rear wheel is +ΔW and the wheel load on the right rear wheel is -ΔW, the compressor 51 is driven at the same time as the main valve 57 is opened, and the air supply and exhaust valve 56R is opened. By increasing the air pressure to the suspension device of the left rear wheel, a wheel load of +ΔW is obtained (quantitative control of this + to H is performed by feedback from the pressure sensor 59), and the supply and exhaust valve 56RR is moved to the exhaust position. Then, by releasing the air pressure of the right rear wheel suspension system to the atmosphere, a wheel load of 1△ was obtained.

As a result, the same effects as in the first embodiment can be obtained in this example as well, and furthermore, by simplifying the system configuration, it is possible to reduce the weight and cost of the system.

FIG. 3 is a diagram showing the principle structure of a third embodiment of the suspension control device of the present invention, and a variable stabilizer is used in this example.

In the figure, 70 and 71 are hydraulic cylinders for the front and rear wheels, respectively, with the upper part (cylinder tube) supported on the vehicle body side, and the lower part (cylinder tube)
The piston rond) is supported on the wheel side. Hydraulic cylinder 7
The oil chamber 70a of the hydraulic cylinder 71 and the oil chamber 71b of the hydraulic cylinder 71 are connected by an oil passage 72, and an accumulator 73 is provided in the oil passage 72. Similarly, an accumulator 75 is provided in the oil passage 74 connecting the oil chambers 70b and 71a.

Next, the effect will be explained. Now, if the piston 70c of the hydraulic cylinder 70 strokes by 8Xf due to the force ΔFt applied from the front wheel side, if the stroke Δx1 of the piston 71C of the hydraulic cylinder 71 on the rear wheel side is 0, the piston 71c moves upward in the figure. Force to push up Δf (F to ζ
, ) work, and a stabilizing effect can be obtained.

Now, considering when the wheel load decreases, the force that tries to press the hydraulic cylinders 70 and 71 from above in the figure decreases, so when looking at the vehicle system as a whole, a relative force △F or △F is applied from the wheel side. It will be the same as the case.

Therefore, in a vehicle in which the mechanism shown in FIG. 3 is provided in the left front wheel system and the right front wheel system, respectively, and the controller 26 and wheel load sensors 27, 28 are provided similarly to the first and second embodiments, the above-mentioned fourth Based on the control program shown in the figure, the accumulator pressure ΔPf is calculated for the left and right front and rear wheel systems, respectively.
+ΔP, by performing active wheel load movement control that controls one or both of the above, it is possible to obtain the same effects as in the first embodiment, and also to reduce the weight and cost of the system in the second embodiment. You can also get

(Effects of the Invention) Thus, as described above, the suspension control device of the present invention performs control to correct the decrease in the driving force of the vehicle by changing the wheel load of the driving wheel with the smallest wheel load, so that the driving wheel of the vehicle The overall driving force can be maximized.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a first embodiment of the suspension control device of the present invention, FIG. 2 is a diagram showing the configuration of the second embodiment, and FIG. 3 is a diagram showing the principle of the third embodiment. FIG. 4 is a flowchart showing the control program of the controller in the first, second and third embodiments; FIG. 5 is a characteristic diagram showing the characteristics of the driving force with respect to the wheel load. 10FL, l0PR, l0RL, l0RR...1 hydraulic cylinder...accumulator 12...throttle valve 13...hydraulic pump 21...shutoff valve 23PL, 23FR, 23RL, 23RR...
Pressure control valve 26...controller 27.28.
・・Wheel load sensor 50・・Motor 51・
... Compressor 55 ... Main tanks 56FL, 56FR, 56RL, 56RR ... Supply and exhaust valves 57 ... Main valves 58FL, 58PR, 58RL, 58RR ... Suspension device 59 ... Pressure sensor 60.
・Cut valve 61 ・Sub tank 62 ・
...Stroke sensor 70.71...Hydraulic cylinder
73.75...Accumulator Figure 3

Claims (1)

[Scope of Claims] 1. In a suspension control device having a wheel load adjustment mechanism capable of adjusting at least one of the amount of load transfer between left and right wheels and the amount of load distribution between front and rear wheels, A wheel load detection means for detecting a load or a wheel load equivalent amount, and a wheel load changing means for changing the wheel load of a predetermined wheel by the wheel load adjustment mechanism based on the detected wheel load or wheel load equivalent amount. A suspension control device characterized by: 2. The suspension control according to claim 1, wherein the wheel load changing means changes the wheel load so as to increase the wheel load of the drive wheel with the smallest detected wheel load or wheel load equivalent. Device.