JPH02182520A - Suspension control device - Google Patents

Abstract

PURPOSE:To effectively dissolve unbalanced axle load in the case of the occurrence of the unbalance of the axle load which may make a wheel attain the limit of characteristics, by controlling the axle load to prevent the wheel from attaining the limit of its characteristics by changing the axle load on a fixed wheel. 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 rate of change in cornering force to load movement quantity of each wheel is determined on each wheel load detected by wheel load sensors 29-32 and driving force for each wheel computed on the output of a throttle sensor 27 and a shift position sensor 28 to control each pressure control valve 23 on the above-mentioned rate of change.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a suspension control device that maximizes the limits of the characteristics of the vehicle as a whole by controlling the suspension and moving wheel loads. It is.

(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 tank G) used for the driving condition. , the vehicle characteristics are improved by realizing the desired load movement so as to correct the change 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, there is no control to prevent either the left or right front wheels or the left or right rear wheels from reaching their characteristic limits while the vehicle is running, resulting in the following problems.

In other words, the wheel load on the wheels due to load transfer during driving, etc. changes from point A (linear region) to point B (nonlinear region), and from point B to 0 on the characteristic diagram of CF against wheel load W (see Figure 5). , increases from point 0 to point D, 8CF/ΔW, which is the rate of change of the increase in CF ΔCF with respect to the amount of load movement ΔW, decreases as the wheel load W increases. This decreasing tendency of ΔCF/ΔW becomes more pronounced in the nonlinear region, and becomes a small value extremely close to 0 near the limit (point D). Therefore, when the total amount of CF decreases due to an imbalance between the left and right wheels due to an increase in wheel load and a wheel reaches its characteristic limit, the left (or right) wheel paired with this wheel has not yet reached its characteristic limit. Despite this, the limits of the characteristics of the vehicle as a whole are undesirably lowered.

The present invention solves the above-mentioned problem by controlling the wheel load of a predetermined wheel to prevent the wheel from reaching the limit of its characteristics when an unbalance of the wheel load occurs such that the wheel of the wheel reaches the limit of its characteristics. The purpose is to solve the problem.

(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 wheel, a driving force detection means for detecting a driving force or a driving force equivalent amount of each wheel, and a wheel load detection means for detecting a wheel load or a wheel load equivalent amount of each wheel, and a Cornering force change rate determining means for determining a cornering force change rate for each wheel based on the load or wheel load equivalent and the driving force or the driving force equivalent, and based on the obtained cornering force change rate, A wheel load changing means for changing the wheel load of a predetermined wheel by the wheel load adjusting mechanism is provided. In this case, for example, changing the wheel load by the wheel load changing means changes the obtained cornering. The wheel load of the drive wheel with the minimum force change rate shall be reduced.

(Function) While the vehicle is running, the wheel load detection means detects the wheel load or wheel load equivalent of each wheel, and the driving force detection means detects various driving forces or driving force equivalents, and determines the rate of change in cornering force. The means calculates the rate of change in cornering force with respect to the amount of load movement based on the obtained wheel load or wheel load equivalent and the driving force or driving force equivalent.

By the way, when a wheel load imbalance occurs that causes a wheel to reach the limit of its characteristics while driving, the left (or right) wheel paired with this wheel may not be able to reach the limit of its characteristics yet, but the entire wheel is This results in an undesirable reduction in the limits of its properties.

Therefore, the wheel load changing means changes the wheel load of a predetermined wheel using a wheel load adjustment mechanism based on the obtained cornering force change rate. Note that this change in wheel load is performed, for example, by controlling to reduce the wheel load of the wheel with the smallest cornering force change rate.

This eliminates the wheel load imbalance by reducing the wheel load difference between the left and right wheels, so by ensuring the total amount of 01 for the left and right wheels, it is possible to prevent the wheels from reaching their characteristic limits, and improve the overall vehicle performance. The limits of the characteristics can be secured to the maximum.

(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
0FL, 10PR, 10RL, and 10RR are hydraulic cylinders for the left and right front and rear wheels.

Hydraulic cylinder l0FL, l0FR, 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
Connect a series circuit of a throttle valve 11 and an accumulator 2, which have a shock absorber function, to a)
10b receives a control pressure Pe (Pc
l, PCZ, Pc3. Pc4) is supplied. When these hydraulic cylinders supply control pressure P to the boat 10b, this control pressure P 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 through the communication hole 10f. , a force is exerted to move the cylinder 10c upward in the figure depending on the size of the pressure receiving area, and a force is exerted to move the cylinder 10c downward in the figure due to the load ΔW applied to the vehicle body, so the cylinder 10c stops at a position where these forces are balanced. do. The accumulator 11 and the throttle valve 12 exhibit a shock absorber function by damping the vibrations when there is a sudden change in the load Δ due to vehicle body vibrations, etc., 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. 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, and when the ignition key is turned ON, the shutoff valve 21 is in the communicating position to allow the source pressure to flow to each source. 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). P
ct(P, is supplied as ri (the same applies to the left and right rear wheels). Electromagnetic proportional pressure control valves 23FL, 23FR
, 23RL.

23RI? When the source pressure is supplied, the cylinders are in the communication state shown in the figure and supply 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, 25.
L or 25R1 Shutoff valve 21° Check valve 16
and drains into the tank 20 via the oil cooler 19.

The above feedback pressure is transferred to the solenoid 23a of the pressure control valve.
The control pressures Pc+ to Pc4 are controlled by controlling the drive currents 1+, Iz, 13.14. A controller 26 is provided to control this solenoid drive current, and the controller 26 receives signals from a throttle sensor 27, a shift position sensor 28, and wheel load sensors 29 to 32 representing the throttle opening T)l, respectively, and a signal indicating the shift position S of the automatic transmission.
A signal indicating wheel load WFL, l(□r WIL+-
Input the signal representing □. Note that in this example, the control pressure p
Focusing on the fact that c+~Pc4 is proportional to the wheel load, for example, a pressure sensor is used as the wheel load sensor, but it is not limited to this, and detects parameters that can estimate wheel load movement such as longitudinal G and lateral G. A sensor 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 throttle opening TH, shift position S, wheel load W (FL,
-□, Wet, W*++), step 10
In step 2, the driving force Q of each wheel is determined from TH and S.

In the next step 103, the cornering force CF of each wheel is determined from the driving force Q and the wheel load W, and in step 104, the cornering force change rate ΔCF/ΔW of each wheel is determined from the cornering force CF and the wheel load W.

In step 105, Δ of each ring obtained in this way is
CF/Δ- is compared and the wheel with the minimum value is determined. Based on this determination, suspension control is performed in the next step 106 to reduce the wheel load of the relevant wheel.

Note that the amount of decrease in this wheel load is, for example, ΔCF/
It may be determined according to the magnitude of Δ-.

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 △W, the wheel loads of the other wheels are uniquely determined, and the left rear wheel is +△匈, and the left front wheel is increased by △W.) and the right rear wheel is set as 8-, and the wheel load movement of the wheels on the diagonal is made equal)
.

By the way, the cornering force CF of a wheel shows a relationship as shown in Figure 5 with respect to the wheel load W when the driving force is constant, and a relationship as shown in Figure 6 with respect to the driving force Q when the wheel load is constant. . In other words, CF can be determined as a function of W and Q. Therefore, when executing step 103 of the control program in FIG. 4, if a plurality of maps of the W-CF characteristics and Q-CF characteristics are stored in a memory (not shown), the CF can be read from these maps. , Further, in step 104, the cornering force change rate ΔCF/Δ− with respect to the load movement amount is determined from this CF.
can be found.

Step 1: ΔCF/ΔW of each wheel obtained in this way.
The wheel with the smallest ΔCP/Δ− is determined by comparison in step 05, and the wheel load of this wheel is reduced in step 106, thereby reducing the wheel load difference between the left and right wheels and effectively eliminating the wheel load imbalance. This makes it possible to prevent the wheel from reaching the limit of its characteristics, and to ensure the maximum limit of the characteristics of the vehicle as a whole.

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 51 driven by the compressor 51 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 56PL, 56FR, 56RL, and 56RR. Here, a main valve 57 is provided in parallel with the chain 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.

The supply and exhaust valves 56FL, 56FR, 56RL, and 56RR are three-position switching valves 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. Illustration when driving (C)
At this point, 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 transferred to the suspension device 58FL.
, 58FR, 58RL, and 58RR, and is also supplied to a pressure sensor 59 provided to monitor the air pressure thereof, and further supplied to a sub-tank 61 via a cut valve 60. These suspension devices are operated by the air pressure Pc++PC2 supplied to the air chamber 58a.
゜The vehicle height is adjusted according to PC3+PC4,
It 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, con)0-ra26
will be established. Note that the inputs to the controller 26 are the throttle opening TH, shift position S, and wheel load WFL+ WFR+ from each of the sensors 27 to 32 described above, as in the first embodiment.
0 controller 26 using WRL+WRR is the first
As in the embodiment, the suspension control of the present invention is performed by executing the control program shown in FIG.

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, when the wheel load of the right rear wheel is made uniform, the supply and exhaust valve 56
This is carried out by setting RR to the exhaust position and releasing the air pressure of the right rear wheel suspension system to the atmosphere to obtain a weak wheel load to - (this quantitative control of - to H is performed by the feedback of the pressure sensor 59) (performed by)

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, oil passage 7 connecting oil chambers 70b and 71a
4 is provided with an accumulator 75.

Next, the effect will be explained. If the piston 70c of the hydraulic cylinder 70 moves by ΔXt due to the force ΔFt applied from the front wheel side, if XF is 0 to the stroke of the piston 71C of the hydraulic cylinder 71 on the rear wheel side, the piston 71c is pushed upward in the figure. The force Δf (−ΔF
, ) work, and a stabilizing effect can be obtained.

Now, considering when the wheel load increases, the force that tries to press the hydraulic cylinders 70 and 71 from above in the figure increases, so when looking at the vehicle system as a whole, the cam F or △F that is applied from the wheel side relatively. The situation is similar to when a force is applied in the opposite direction.

Therefore, the mechanism shown in FIG. 3 is provided for the left front wheel system and the right front wheel system, respectively, and the controller 26, throttle sensor 27, shift position sensor 28, and wheel load sensors 29 to 32 are also provided as in the first and second embodiments. In the vehicle, based on the control program shown in FIG.
By performing active wheel load transfer control that controls one or both of P, the same effects as the first embodiment can be obtained, and the weight and cost reduction effects of the system of the second embodiment can be obtained. You can also get

(Effects of the Invention) Thus, as described above, the suspension control device of the present invention changes the wheel load of a predetermined wheel to reach the limit of the characteristic when an unbalance of the wheel load occurs that causes the wheels to reach the limit of the characteristic. Since we have performed control to prevent this from happening, it is possible to effectively eliminate the unbalance of the wheel loads and ensure the maximum characteristics of the vehicle as a whole.

[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. 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 cornering force with respect to wheel load; The figure is a characteristic diagram showing the characteristics of cornering force with respect to driving force. 10FL, l0PR, l0RL, l0RR... Hydraulic cylinder 11... Accumulator 12... Throttle valve 13... Hydraulic pump 21... Shutoff valve 23FL, 23FR, 23RL, 23RR.
...Pressure control valve 26...Controller 27...
・Throttle sensor 28...Shift position sensor 29
~32...Wheel load sensor 50...Motor
51... Compressor 55... Main tank 56FL, 56FR, 56RL, 56RR... Supply/exhaust valve 57... Main valve

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, the wheel load of each wheel is or a wheel load detection means for detecting a wheel load equivalent amount, a driving force detection means for detecting a driving force or a driving force equivalent amount of each wheel, the obtained wheel load or a wheel load equivalent amount, and a driving force or driving force. cornering force change rate determination means for determining a cornering force change rate for each wheel based on the amount of load movement; and based on the obtained cornering force change rate, the wheel load adjustment mechanism changes the wheel load of a predetermined wheel. What is claimed is: 1. A suspension control device comprising a wheel load changing means. 2. The suspension control device according to claim 1, wherein the wheel load changing means changes the wheel load so as to reduce the wheel load of the drive wheel with the minimum cornering force change rate.