JPH02175403A - Suspension control device - Google Patents

Abstract

PURPOSE:To ensure driving stability even at a decreased air pressure in a tire while turning by arranging a tire air pressure detecting means which detecting each air pressure in the tires of front and rear wheels, and a wheel load changing means which changes the wheel load of a given wheel through a wheel load adjusting mechanism according to detected air pressure. CONSTITUTION:Tire air pressure P1 - P4 and lateral G are read by respective tire air pressure sensors 27 - 30 and a lateral acceleration (lateral G) sensor 31, and as turning driving when lateral G is beyond prescribed level G0, the wheel loads of right and left rear wheels are relocated so that the wheel load of a rear outer wheel may increase with the decrease in the air pressure of a front wheel tire if at least either of air pressure P1 or P2 of a right or left front wheel tire is under an abnormal condition of air pressure in the front wheel tire. When both air pressure P1 and P2 are beyond a prescribed level and air pressure P3 or P4 in a right or left rear wheel tire is under an abnormal condition of air pressure in a rear wheel tire which is below the prescribed level, the wheel loads of right and left front wheels are relocated so that the wheel load of a front outer wheel may increase with the decrease in the air pressure of a rear wheel. This makes a correction so that the steering characteristics of a vehicle may be neutralized.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention improves the turning characteristics of a vehicle by controlling the suspension and adjusting the cornering force of the wheels to an appropriate value by shifting the wheel load. The present invention relates to a suspension control device.

(Prior Art) As a conventional suspension control device of this type, there is one described in, for example, Japanese Patent Laid-Open No. 62275814, which was previously filed by the applicant of the present invention.

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 lateral 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, in the above-mentioned conventional suspension control device, control is performed to correct changes in wheel CF in response to changes in braking/driving force and lateral G in the driving state. However, if the tire air pressure of the wheels changes while the vehicle is running, no correction control is performed, resulting in the following problems. In other words, if the tire pressure of one of the front wheels, for example, the front outer wheel (the front wheel that is on the outer side during a turn) decreases while turning, the CF of that wheel decreases, so the total amount of CP of the front wheel decreases. As the cornering power (hereinafter referred to as CP) of the front wheels decreases, the steering characteristics of the vehicle tend to understeer, making it difficult to ensure running stability during turns.

An object of the present invention is to solve the above-mentioned problem by performing control to correct the decrease in CF by changing the wheel load of a predetermined wheel when the tire air pressure decreases.

(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. A suspension control device having a mechanism includes a tire air pressure detection means for detecting tire air pressure of front and rear wheels, 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 tire air pressure. In this case, for example, when the tire pressure of at least one of the left and right front wheels decreases below a predetermined value, the wheel load changing means changes the wheel load by changing the wheel load of the rear wheel on the outer periphery of the turn when the tire pressure of at least one of the left and right front wheels decreases below a predetermined value. The wheel load is increased, and when the tire air pressure of at least one of the left and right rear wheels decreases below a predetermined value, the wheel load of the front wheel on the outer circumferential side of the turn is increased.

(Function) While the vehicle is running, the tire pressure detection means detects the tire pressures of the left and right front wheels and the left and right rear wheels.

By the way, when the tire pressure decreases in the front or rear wheels when the vehicle turns, the CF of the front or rear wheels as a whole decreases, and the steering characteristics of the vehicle tend to understeer or oversteer, respectively. Therefore, the wheel load changing means changes the wheel load of a predetermined wheel using a wheel load adjustment mechanism based on the detected tire air pressure. This change in wheel load is performed, for example, by controlling the wheel load of the rear outer wheel (or front outer wheel) when the tire pressure of one or both of the left and right front wheels (or rear wheels) decreases below a predetermined value. .

As a result, the steering characteristics of the vehicle are neutralized by equivalently canceling the aforementioned understeer or oversteer tendency, and sufficient running stability during turns can be ensured even when tire pressure fluctuates. 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
0FL, 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 left end in the figure is supported by the vehicle body and its right 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 control pressure P, (P-+
, Pcz, P-z, P-4). When these hydraulic cylinders supply a 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 10e through the communication hole 10f.
0g, a force is applied to move the cylinder 10c to the left in the drawing depending on the size of the pressure receiving area, and a force to move the cylinder 10c to the right in the drawing is applied to the load applied to the vehicle body at that time, 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 when the load ΔW changes suddenly due to vibrations of the vehicle body, the throttle valve 12 damps vibrations, 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 1. Unload valve 18 and 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. Furthermore, the accumulator 17
When the internal pressure of
Drain.

When the ignition key is turned on, the source pressure that passes through the shutoff valve 21 is sent to each wheel individually, for example, in the case of the left (right) front wheel, it is sent to the hydraulic cylinder l0FL (1,0PR) via the accumulator 22F and the pressure control valve 23PL (23FR). It is supplied as a control pressure PC1 (pcz) (the same applies to the left and right rear wheels). Electromagnetic proportional pressure control valve 23F11.23
When the source pressure is supplied, PR, 23RL, and 23RR are in the communication state shown in the figure to 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 directs the hydraulic pressure of the hydraulic cylinder to the orifices 24L and 2.
4R, 25L or 25R, shutoff valve 2I, check valve 16 and oil cooler 19, and drains to tank 20.

The above feedback pressure is transferred to the solenoid 23a of the pressure control valve.
Drive current I+, h, 13. Control pressures PC1 to PC4 are controlled by controlling I4. A controller 26 is provided to control this solenoid drive current, and the controller 26 includes a tire air pressure sensor 2 provided for each wheel.
From 7 to 30, tire pressure P l, P z, P s
, P4, and a signal representing the lateral acceleration (lateral G) of the vehicle is input from the lateral G sensor 31. In this example, the sensors 27 to 30 are a tire air pressure sensor (combined with a Bourdon tube and a reed switch) described in Japanese Patent Application Laid-open No. 58-223896, which was previously filed by the applicant of the present application, to detect changes in tire air pressure at an oscillation frequency. Although a sensor capable of non-contact measurement is used as a change in tire pressure, the present invention is not limited to this, and any sensor capable of measuring tire air pressure may be used.

Further, instead of using the lateral G sensor, the turning state of the vehicle may be estimated using a combination of the vehicle speed V and the steering angle θ.

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 tire pressure sensor 27 is
~30 and lateral G sensor 31 tire air pressure PI+P
! , h, P4, and lateral G are read, and in step 102 it is determined whether the lateral G is a predetermined value of 60 or more.

If the lateral G is less than 60, the control is ended as it is not turning, and if the lateral G is 00 or more, step 1
From 03 onwards, the tire pressure will be determined for each front and rear wheel.

That is, in step 103, the tire pressure p of the left and right front wheels is
, , p is greater than or equal to a predetermined value. Note that this predetermined value may be, for example, 0.3 kgf/, which is the boundary value at which the tire pressure sensor described above generates an alarm output.
cm2 is used. If this determination is No, that is, if at least one of the tire pressures p, , p is abnormal and the front tire pressure is less than a predetermined value, then in the next step 104, the wheel load on the rear outer wheel is adjusted according to the amount of decrease in the front tire air pressure. Suspension control is performed to shift the wheel load between the left and right rear wheels so that the load increases. Note that which of the left and right rear wheels corresponds to the rear outer wheel is determined based on the polarity (positive or negative) of the lateral G read in step 101, and the wheel load shift described above is carried out front and rear on the side of the wheel corresponding to the rear outer wheel. This may also be done by changing the amount of load distribution between the wheels.

On the other hand, if the determination in step 103 is Yes, that is, if the tire pressures P, , P, are both equal to or higher than the predetermined value and the front tire pressure is normal, the tire pressures Ps, Pg of the left and right rear wheels are determined in step 105 in the same manner as step 103. A determination is made as to whether or not the predetermined value is greater than or equal to the predetermined value. If this determination is NO (rear wheel tire pressure abnormality), the wheel load of the left and right front wheels is shifted (step 104 The suspension control may also be performed by changing the load distribution amount between the front and rear wheels in the same way as in step 105.
If it is an ES, both the front and rear tires have normal tire pressure, so
Terminates control as is.

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

-i In hydraulic active suspensions, the wheel load of each wheel can be controlled independently, but in order to avoid changes in the vehicle's attitude, it is necessary to It is necessary to equalize the difference and eliminate moment changes (for example, if the wheel load on the right front wheel is increased by Δ-, the wheel loads on the other wheels are uniquely determined, and the left rear wheel is increased by +△, and the left front wheel is increased by +△). and right rear wheel Δ
The wheel loads of the wheels on the diagonal are equal as W).

By the way, when the tire air pressure of the wheels decreases while the vehicle is running, especially when turning, the CF of the wheels decreases in the same way as when the wheel load decreases, so the steering characteristics of the vehicle tend to understeer when the CFF measurement of the front wheels decreases. , when the total CF amount of the rear wheels decreases, auto-steer tends to occur.

Here, as a method to correct this decrease in CF, since the total amount of load transfer between the left and right wheels in the front and rear wheels is a constant amount determined according to the lateral G, the tire pressure of the front and rear wheels decreases. One method is to control the wheel load of the wheel on the side where the tire pressure is normal, and the other is to control the wheel load on the wheel where the tire pressure is normal. However, since it is more effective to control the tire pressure on the normal side, the latter is adopted. Therefore, when the tire air pressure of the front wheels decreases, the wheel load of the rear outer wheels is increased according to the amount of decrease in the air pressure of the front wheels by executing steps 103 and 104 in FIG.
Steps 105 and 106 when the rear tire air pressure decreases.
By executing this, the wheel load on the front outer wheels is increased in accordance with the amount of air pressure reduction in the rear wheels.

As a result, the desired yaw moment is obtained, and the steering characteristics of the vehicle are neutralized by equivalently canceling the above-mentioned understeer or oversteer tendency. Therefore, sufficient running stability can be ensured.

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 the dryer 53, this air pressure is stored in the main tank 55 via the check valve 54, and is also stored in the main tank 55 through the air supply/exhaust valve 561? It is supplied to each wheel individually via L, 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 within the main tank 55 at a constant value and supplies air pressure 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 normal state (a) shown in the figure, the air pressure source and the suspension device are cut off, and when the solenoid 56a is driven, they are communicated in the position (b) shown in the drawing to supply air pressure from the pneumatic source to the suspension device. Illustration of the solenoid 56b being driven (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.
, 58FR, 58RL, 58RIi air chamber 58a
It is also supplied to a pressure sensor 59 provided to monitor the air pressure, and further supplied to a sub tank 61 via a cut valve 60. These suspension devices are connected to the air pressure PC1+PC supplied to the air chamber 58a.
2゜It adjusts the vehicle height according to PC31PC4 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, tire air pressures P, -P4 and lateral G from the sensors 27 to 31 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 loads of the right front wheel and left rear wheel are +Δd, and the wheel loads of the left front wheel and right rear wheel are -Δ, the compressor 51 is driven at the same time as the main valve 57 is opened, and the air supply and exhaust gas are Valve 5
6FR, 561? By connecting L and increasing the air pressure to the suspension system for the right front wheel and left rear wheel, 4△-
(This quantitative control of +Δ is performed by feedback from the pressure sensor 59), and the supply and exhaust valves -56FL, 56R1? By setting the wheel to the exhaust position and releasing the air pressure of the suspension devices of the left front wheel and the right rear wheel to the atmosphere, a wheel load of - is 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.
will be established. Similarly, an accumulator 75 is provided in the oil passage 74 connecting the oil chambers 70b and 71a.

Next, the effect will be explained. The piston 70c of the hydraulic cylinder 70 moves ΔX due to the force ΔF applied from the front wheel side.

Assuming a long stroke, the hydraulic cylinder 7 on the rear wheel side
If the stroke Δχ of the piston 71C in E is O, then
The force △f(
rΔPr ) works, and a stabilizing effect can be obtained.

Considering the relationship with tire air pressure, when the tire air pressure decreases, the wheel load decreases, and the hydraulic cylinder T0
．． Since the force that tries to press 71 from above in the figure decreases, when looking at the vehicle system as a whole, the cam F is relatively pushed from the wheel side.
, or ΔFr is added.

Therefore, the mechanism shown in FIG. 3 is provided in the left front and rear wheel system and the right front and rear wheel system, respectively, and the controller 26, tire pressure sensors 27 to 30, and lateral G
In the vehicle equipped with the sensor 31, active wheel load shift control is performed to control one or both of the accumulator pressures ΔPryΔP for the left and right front and rear wheel systems, respectively, based on the control program shown in FIG. 4 described above. If carried out, the same effects as those of the first embodiment can be obtained, and furthermore, the effects of weight reduction and cost reduction of the system of the second embodiment can also be obtained. Note that if the vehicle configured in this way is a front-wheel drive vehicle (front-wheel drive vehicle), even if the wheel load transfer control described above is not performed, the passive effect of increasing the wheel load on the outer wheel side and making the steering characteristics neutral is generated. is obtained.

(Effects of the Invention) Thus, as described above, the suspension control device of the present invention changes the wheel load of a predetermined wheel when the tire air pressure decreases, thereby controlling the CF.
Since the decrease in the steering characteristics of the vehicle is corrected to neutralize the steering characteristics of the vehicle, it is possible to sufficiently ensure running stability during turns even when the tire air pressure fluctuates.

[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 configuration of the third embodiment. Diagram showing the principle configuration. FIG. 4 is a flowchart showing the control program of the controller in the first, second and third embodiments. 1, OFL, 1. OFR, l0RL, l0RR...
・Hydraulic cylinder 11...Accumulator 12...
- Throttle valve 13...Hydraulic pump 21...Shutoff valve 23FL, 23F11.23RL, 23RR
...Pressure control valve 26...Controller 27-30...Tire air pressure sensor 31...Lateral G sensor 50...Motor 51.
...Compressor 55...Main tank 56P
L, 56FR, 56RL, 56RR... Supply and 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 the left and right wheels and the amount of load distribution between the front and rear wheels, the tire air pressure of the front and rear wheels is adjusted. What is claimed is: 1. A suspension control device comprising: tire air pressure detection means for detecting tire air pressure; and wheel load changing means for changing the wheel load of a predetermined wheel by the wheel load adjustment mechanism based on the detected tire air pressure. 2. Changing the wheel load by the wheel load changing means increases the wheel load of the rear wheel on the outer periphery of the turn when the tire pressure of at least one of the left and right front wheels decreases to a predetermined value or less. 2. The suspension control device according to claim 1, wherein when the air pressure of one tire decreases below a predetermined value, the wheel load of the front wheel on the outer circumferential side of the turn is increased.