JPH02246812A - Level control of car with leveling device - Google Patents

Abstract

PURPOSE:To prevent unbalanced grounding load and floated wheels by reading suspension strokes for each wheel at the time of speed zero and finding the deformation amount of a road from a difference between the suspension strokes for right and left front wheels and rear wheels to allow the change of a reference level set in each suspension device in accordance with the deformation amount. CONSTITUTION:At the time of speed zero, a controller 3 reads suspension strokes D'FL, D'FR for right and left front wheels and suspension strokes D'RL, D'RR for right and left rear wheels in accordance with input signals from respective suspension stroke sensors 13 to compute the deformation amount of a road from the difference of the strokes. The reference levels DFLD-DRRO of respective wheels are changed in setting to D'FLO-D'RRO, based on the deformation amount of the road. Then, in accordance with the changed reference levels D'FLO-D'RRO, level control is performed. Such constitution permits prompt adaption to road conditions and prevents unbalanced grounding load.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a vehicle height control method for a vehicle equipped with a vehicle height adjustment device.

Conventional technology Vehicles with a vehicle height adjustment function that controls the vehicle height in zones such as high, normal, and low have been known for a long time. Vehicles with vehicle height adjustment have also been developed in the past, for example, in Japanese Patent Application Laid-open No. 1397-1983.
It is published in Publication No. 09, etc.

Problems to be Solved by the Invention Generally, when a car is stopped on a distorted road surface, some suspensions are in an extended state and others are in an equilibrium state in a compressed state. .

Especially in vehicles that adjust the vehicle height independently on all four wheels with high resolution (for example, vehicles equipped with active suspension), the suspension tries to reach the target standard vehicle height, so it is difficult to adjust the height of the vehicle like a regular vehicle without a vehicle height adjustment function. The distortion of the road surface cannot be absorbed by the expansion and contraction of the suspension, but is absorbed only by the elastic deformation of the tires on each wheel.The spring constant of tires is usually about 10 times the spring constant of the suspension, so the distortion of each wheel is The balance of the ground load becomes unbalanced, and in the worst case, the vehicle height adjustment control will never finish or one wheel will float.
There is a risk that a situation may occur.

The main purpose of the present invention is to deal with the above-mentioned problems.

Means for Solving the Problems The present invention provides a vehicle equipped with a vehicle height adjustment device that detects the suspension strokes of the front, rear, left, and right four-wheel suspensions and independently controls each suspension to maintain a set standard vehicle height. When the value becomes zero, read the suspension stroke of each suspension, calculate the amount of road surface distortion from the suspension stroke difference between the left and right front wheels, and the suspension stroke difference between the left and right rear wheels, and adjust all four wheels to absorb the amount of road surface distortion. The present invention is characterized in that the set standard vehicle height of the suspension is changed and the vehicle height is controlled to maintain the changed standard vehicle height.

Effect According to the above, when the vehicle is stopped on a road surface where there is no deviation in the suspension stroke difference between the left and right front wheels and the suspension stroke difference between the left and right rear wheels, the amount of road surface distortion is zero, so the suspension of all four wheels is adjusted to the initial position. The vehicle height is controlled to maintain the standard vehicle height, but if the vehicle is stopped on a distorted road surface, there will be a difference in the suspension stroke between the left and right front wheels and between the left and right rear wheels, and this difference will be absorbed by the suspension of all four wheels. The standard vehicle height setting for each suspension is changed and the vehicle height is controlled to maintain the newly set standard vehicle height.In a short period of time, the installed load of each tire approaches the ideal condition. Additionally, the vehicle body approaches a nearly horizontal position, eliminating previous problems.

Example Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a system diagram showing an example of an active suspension control system to which the present invention is applied.
12 is a suspension for the left and right front wheels, 13.14 is a suspension for the left and right rear wheels, and each suspension has an oil chamber A and a sealed gas chamber B separated by a diaphragm C. Oil cylinder E
The oil chamber F is connected to the oil chamber F through an orifice G, and one end (for example, the bottom surface of the cylinder) of the oil cylinder E is connected to a wheel side member such as a suspension arm, and the other end (for example, a piston rod) is connected to a vehicle body side member. The oil flows through the oil cylinder and between the oil chambers F and A of the gas spring part through the orifice G to generate an appropriate damping force, and also through the diaphragm C. This figure shows an example in which a conventionally known hydro-pneumatic suspension is used, which obtains a spring action by the volumetric elasticity of the gas sealed in the gas chamber B.

2 + + 2212312 a C A control valve for supplying oil to the oil chamber F of the oil cylinder E of each of the above-mentioned units and discharging oil from the oil chamber F, and each of these control valves 21. 22 and 2i24 are each independently controlled by a valve drive signal from a controller 3, which will be described later.

4 is an oil tank, 5 is an oil pump, and 1. The oil pump 5 is rotationally driven by an engine 6, but in the illustrated embodiment, the power steering oil pump 5' and the oil pump 5 are arranged in tandem, and the engine 6 rotates both pumps 5 and 5' at the same time. An example is shown below.

The oil discharged from the oil pump 5 passes through the check valve 7 and is accumulated in the high-pressure accumulator 8. When one or more of the control valves is switched to the injection side, the oil is discharged from the control valve switched to the injection side. High pressure oil is supplied to the oil chamber of one or more suspensions, and when one or more of the control valves is switched to the discharge side, one of the control valves switched to the discharge side Alternatively, oil is discharged from the oil chambers of two or more suspensions and flows into the oil tank 4 through the oil cooler 9.

10 is a relief valve, and 11 is a load/unload valve. The oil pump 5 is switched to the unloaded state shown in the figure, and the oil discharged from the oil pump 5 is made to flow to the oil cooler 9 side and flow into the oil tank 4.

Each of the suspensions 1+, 12, 13, and 14 is provided with a suspension stroke sensor 13 that detects the vertical relative displacement between the sprung mass and the unsprung mass, and inputs suspension stroke information to the controller 3 for each suspension. It has become.

A reference vehicle height signal from a vehicle height adjustment switch 12 that can select and set a reference vehicle height is input to the controller 3, and the vehicle height adjustment switch 12 selects and sets, for example, a normal reference vehicle height. In this case, the controller 3 compares the suspension stroke signal of each suspension inputted from the suspension stroke sensor 13 of each suspension with the normal reference vehicle height signal of the vehicle height adjustment switch 12, and determines whether the control valve of the suspension that is contracted is On the injection side,
The control valves of the extended suspensions each issue a valve drive signal to be switched to the exhaust side, and control to maintain the normal standard vehicle height is performed independently for each suspension.

When the vehicle height adjustment switch 12 is switched to a high standard vehicle height,
In the same way as above, oil injection and drainage are controlled independently for each suspension so that all suspensions are maintained at a high standard vehicle height.

The input signal from the suspension stroke sensor 13 is passed through a dead band circuit provided in the controller 3 so that it does not react to minute displacements of, for example, several layers or less.

As mentioned above, a vehicle height adjustment device such as an active suspension that has a suspension stroke sensor 13 in at least each suspension part, observes the vehicle height with high resolution (in units of 1 crow), and controls the vehicle height independently for each suspension. For example, when a vehicle is stopped on a distorted road surface as shown in the model diagram in Figure 2, the suspension gears 11 and 14 on the left front wheel and the right rear wheel run onto a relatively high point on the road surface, and The suspensions 12 and 13 for the front right wheel and the rear left wheel are located relatively low on the road surface and are extended by ΔD' from the reference value. Then, a signal is input from the suspension stroke sensor 13 of each suspension to the controller 3, and control is performed to return all the suspensions to their standard values as described above. Oil is injected into the suspensions 11 and 14 of the rear wheels and they expand, and the oil in the suspensions 12 and 13 of the right front wheel and the left rear wheel, which are located low on the road surface, is discharged and contracts, causing all the suspensions to expand. Try to make the lengths the same.

The distortion of the road surface can then be absorbed only by the elasticity of the tires of each wheel (the elasticity of the tires is represented by the spring S in Figure 2), but the spring constant of the tires is generally about 10 the spring constant of the suspension. Because it is about twice as large, it is difficult to absorb the distortion of the road surface, and the tires that are low on the road surface tend to lift up, resulting in poor balance.
If the distortion of the road surface is large, there is a risk that one wheel will be completely lifted off the ground, causing a problem in which control to return each suspension to its standard value will not be completed.

Therefore, the present invention solves the above-mentioned problems by incorporating control logic as described below into the controller 3.

First, when the vehicle speed reaches OK m/H, the left and right front wheel suspension strokes D'FL * D'FR1 Left and right rear wheel suspension strokes D'LL, D'RR are determined from the signals input from each stroke sensor 13. Read the standard vehicle heights DFLO, DFRO of the left and right front wheels and the standard vehicle height DRL11 of the left and right rear wheels. DRRO is changed and set using the following formulas (1) to (4), and each of the changed reference vehicle heights D;
, D'FR11, D'RLO, and D'11RO, oil injection and discharge control is performed for each of the four suspension wheels (front, rear, left, and right) so as to substantially match the values of D'FR11, D'RLO, and D'11RO.

DFLO = DFLO 10% ((D'FL - D'FR) -
(D'RL-D'1lR) )・・・・・・・・・(1
)DFRO=Drt+o-%((D'FL -D'FR
)−(D'RL−D'RR) )・・・・・・・・・(
2) DRLO=DRLO-X ((D'FL-DFR)
-(D'RL-D'RI+) )・・・・・・・・・(
3) DRRII = DRRO + genus ((D'rt-D'
FR)-(D'RL-D'RR))...
・(4) In the above formulas (1) to (4), (DFL-D
'FR) and (D'RL-DRII) respectively represent the left-right inclination of the front wheels and the left-right inclination of the rear wheels (in both cases, the inclination of the vehicle body upward to the right with respect to the road surface is positive). The inside represents the difference in inclination between the front and rear left and right directions, that is, the amount of distortion of the road surface.

If the above control is applied to the case where the vehicle stops on a distorted road surface as shown in Fig. 2, since p Fl <D'FR,(D'FL - D'FR) is negative, and D'RL>
Since DRR, (D'RL - D'RR) is positive.

Therefore, in equations (1) to (4), the value inside the curly brackets is negative.

Therefore, the suspension 11 of the left front wheel and the suspension 14 of the right rear wheel are set to the standard vehicle height D'rto*D'**o, which is smaller than the initial standard vehicle height DrtomDRRO, and the suspension 12 of the right front wheel and the suspension 13 of the left rear wheel are Reference vehicle height D' that is greater than the initial reference vehicle height DFRO, DRLG
Since the vehicle height is controlled to approach FRO and D'RLO, the vehicle height of each wheel is lower where the road surface is higher and higher where the road surface is lower, and the ground load of each tire is almost equalized, and the vehicle body is It will be controlled so that it is almost horizontal.

If the four-wheel suspension does not fall within the control dead zone (standard vehicle height number 1) at the same time during the above control,
Read the suspension stroke of the transformation suspension, perform vehicle height adjustment control by setting the same reference vehicle height change as above, and repeat the rereading cycle of each suspension stroke until the four-wheel suspension enters the dead zone for rotation. is the minimum time required for normal vehicle height adjustment.

In the above control, when the vehicle is stopped on a road surface where there is no distortion or little distortion and the difference between the suspension stroke difference between the left and right front wheels and the suspension stroke difference between the left and right rear wheels is within the range of the dead zone.

D'++a "Drto, D'rRo-i" DF*o,
D's+oki DRLO.

DRRO: DRRo, which is almost the same as normal vehicle height control.

The present invention is not limited to the embodiment shown in Fig. 1, but detects the suspension strokes of all four wheels (front, rear, left, and right), and independently detects the suspension strokes of each suspension to maintain the reference vehicle height based on the information on each suspension stroke. It can be effectively applied to any suspension structure that adjusts the vehicle height by controlling the vehicle height.

Effects of the Invention As described above, according to the present invention, when a vehicle with a vehicle height adjustment function is stopped on a distorted road surface, each tire almost matches the undulations of the distorted road surface in a very short time and balances each tire. The length of each suspension can be adjusted to maintain good contact with the ground, and unlike conventional models, the balance of the ground load between each tire may become unbalanced, or one of the wheels may float up, causing the vehicle height adjustment to never end. It is possible to completely eliminate any defects, and it can bring about great practical effects.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an example of the vehicle height adjustment control system of a vehicle with a vehicle height adjustment device to which the present invention is applied, and Fig. 2 is a model showing the expansion and contraction states of each suspension when the vehicle is stopped on a distorted road surface. FIG. 1+, 12, 13. i4... Suspension, 21°22.23.24... Control valve, 3... Controller, 12... Vehicle height adjustment switch, 3... Suspension stroke sensor.

Claims (1)

[Claims] At least, it has a means for detecting the suspension stroke of each of the four suspensions, and independently detects the suspension stroke of each suspension so as to maintain the vehicle height at a preset standard vehicle height based on the suspension stroke information of each suspension. For vehicles equipped with a vehicle height adjustment device that has a controller that adjusts the vehicle height, the suspension strokes of all four wheels are read when the vehicle speed reaches zero, and the suspension stroke difference between the left and right front wheels and the suspension stroke difference between the left and right rear wheels are calculated. Determine the amount of road surface distortion from , change the set reference vehicle height of all four wheels of suspension to absorb the amount of road surface distortion, and perform vehicle height control to maintain the changed reference vehicle height. A vehicle height control method for a vehicle equipped with a vehicle height adjustment device.