JPH03511A - Car height control method for vehicle with car height adjuster - Google Patents

Abstract

PURPOSE:To conduct the dynamic change of a turning characteristic by detecting a horizontal acceleration at the time of turning, and adjusting the car heights of respective wheels so that the tire ground contact load difference of turning inner and outer wheels may be so made that the load of one of the front wheels and the rear wheels is made large and the load of the other is made small. CONSTITUTION:A horizontal g sensor 13 detects a horizontal g which accompanies turning, and inputs it at a controller 3. The controller 3 controls the car heights of respective wheels by means of the detection g of the horizontal g sensor 13, and the degree of an understair is made to be of a strong stair characteristic by increasing the tire ground contact load of the outer wheel on the front wheel side and decreasing the tire ground contact load of the outer wheel on the rear wheel side, at the time of turning. Or, it is made to be of a weak stair characteristic by controlling car heights in a reverse direction. For example, at the time of left turn, a right front wheel car height is increased and a left front wheel car height is decreased and a right side rear wheel car height is decreased and left side rear wheel car height is increased, and a strong stair characteristic is made. As a result, the characteristic of turning can be changed dynamically.

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.

BACKGROUND ART AND PURPOSE OF THE INVENTION Suspension stroke sensors for detecting changes in suspension expansion/contraction strokes, that is, suspension strokes, are provided on the front, rear, left, and right four-wheel suspension wheels. ) Vehicles have been developed that allow each wheel to adjust the vehicle height independently.
For example, it is disclosed in Japanese Patent Application Laid-Open No. 139709/1983.

The vehicle height adjustment device described above sensitively detects any deviation from the standard suspension length and controls the vehicle to always maintain the target attitude by adjusting the deviation to zero. However, in the present invention, in a vehicle equipped with such a vehicle height adjustment device, by adding a vehicle height adjustment function according to the turning state of the vehicle to the vehicle height adjustment device, the turning characteristics of the vehicle can be dynamically adjusted. The main purpose is to allow changes.

Components of the Invention The present invention provides a vehicle height adjustment device having a controller that detects changes in the vertical stroke of each suspension suspension as described above and performs vehicle height adjustment control independently for each suspension so as to maintain the reference vehicle height. In vehicles equipped with this system, the lateral acceleration when the vehicle turns is detected, and depending on the magnitude of the lateral acceleration, the tire ground load difference between the inner and outer wheels is increased for either the front wheel or the rear wheel while the other is The controller is characterized in that the controller is provided with control logic for controlling the vehicle height adjustment of each wheel so as to reduce the height of the vehicle.

Effect Based on the above, for example, the tire ground load difference between the inner and outer wheels during turning can be calculated as follows:
When the vehicle height is adjusted so that the front wheels are large and the rear wheels are small, the understeer tendency becomes stronger, and when the vehicle height is adjusted so that the front wheels are small and the rear wheels are large, the understeer tendency is weakened. The steering characteristics can be freely controlled, making it easy to match the steering characteristics to the driver's preference or change them depending on the vehicle speed.

Example Embodiments of the present invention will be described below with reference to both figures.

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 includes an oil chamber A and a sealed gas chamber B which are separated by a diaphragm C, and the oil chamber A and the oil cylinder at the gas spring section. E
The oil chamber F is communicated with 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 between the oil cylinder and the oil chambers F and A of the gas spring part through the orifice G to generate an appropriate damping force against the vertical load, and the oil flows through the diaphragm C to the gas chamber B. This figure shows an example in which a conventionally known hydro-pneumatic suspension is used, which obtains a spring action by the volume elasticity of a gas sealed in the air.

2+, 2+, 23, and 2a are control valves that supply oil to the oil chamber F of the oil cylinder E of each suspension and discharge oil from the oil chamber F, and each of these control valves 2+, 22t23e24 is controller 3, which will be described later.
They are each independently controlled by valve drive signals from the valves.

4 is an oil tank, and 5 is an oil pump. The oil pump 5 is rotationally driven by the engine 6, but in the illustrated embodiment, the oil pump 5' for power steering and the oil pump 5 are in tandem, and the oil pump 5 is driven by the engine 6. An example is shown in which the re-extraction pumps 5 and 5' are driven to rotate at the same time.

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, 11 is a load φ unload valve,
The loading/unloading valve 11 is switched to the illustrated unloading state by a signal issued by the controller 3 based on a signal from the pressure sensor 81 that detects that the high pressure accumulator 8 has reached a predetermined set pressure, and the oil pump 5 discharges. The oil is made to flow to the oil cooler 9 side and flow into the oil tank 4.

Each of the suspensions 11-12+13e14 is provided with a suspension stroke sensor 12 that detects the vertical relative displacement between the sprung mass and the unsprung mass, that is, the stroke change of the suspension, and the detection signal of the suspension stroke sensor 12 is inputted to the controller 3. , and a lateral i sensor 13 (hereinafter referred to as lateral 2) that detects the lateral acceleration of the vehicle (hereinafter referred to as lateral 2).
(including a device that calculates the lateral 2 from each signal of the vehicle speed sensor and a steering angle sensor, or a device that calculates the lateral 2 from the steering torque or steering assist force, etc.), and the detection signal of the lateral 2 sensor 13 is also controlled by the controller. 3 is input.

The suspension stroke change detection signals of each suspension stroke detected by the suspension stroke sensor 12 are input to the controller 3, which removes displacements of, for example, several millimeters or less through a dead band circuit, and removes displacements of, for example, several millimeters or less, and removes displacements of less than a few mm. is, for example, based on the standard vehicle height selected with the vehicle height switch (a switch for switching between a low normal standard vehicle height and a high standard vehicle height suitable for driving on rough roads), and is displaced in the contraction direction from that point. Oil is injected into the suspension that is currently in position, and a valve drive signal is issued to discharge oil from the suspension that is displacing in the extension direction, and control is performed to maintain the vehicle height at the reference vehicle height.

In a vehicle equipped with a vehicle height adjustment device such as the one described above, if control is performed to raise the vehicle height of just one wheel when the vehicle is in its normal position, for example, the suspension stroke sensor as shown in Figure 1 will increase the vehicle height up to a certain range. If the suspension stroke sensor measures without including the length of the spring (height dimension of gas chamber B), deflection of the spring and tire will occur, and if the suspension stroke sensor measures including the length of the spring, the tire will bend. Deflection occurs, and the vehicle height becomes lower than the target high vehicle height by the amount of deflection, and the tire ground load on that one wheel increases. Conversely, if control is performed to lower the vehicle height of only one wheel, the tire ground contact load will be reduced without achieving the target vehicle height.

That is, the tire ground load can be controlled by adjusting the vehicle height.

The present invention utilizes the fact that the tire ground load can be controlled by adjusting the vehicle height in this manner, and the turning characteristics when the vehicle turns are variably controlled in accordance with the sideways movement that occurs when turning.

Generally, the roll stiffness of a vehicle is constant due to each suspension spring and the torsion spring of the stabilizer that connects the left and right wheels, and the ratio of the roll stiffness of the front wheels to the roll stiffness of the rear wheels (front-rear ratio) is also constant. ing.

Therefore, the front-to-back ratio of the amount of load transfer during cornering is also fixed, and in order to change the cornering characteristics, conventional general vehicles had to change elements such as tires, suspension springs, and stabilizers.

In the present invention, by providing the controller 3 with a control logic for controlling the vehicle height as described below, the turning characteristics can be easily changed and controlled.

For example, when the two lateral sensors 13 detect a left turn of the vehicle, (a) Increase the vehicle height of the right front wheel (front outer wheel) by Δh.

(b) The vehicle height of the left front wheel (front inner wheel) is reduced by Δh.

(C) The vehicle height of the right rear wheel (rear outer wheel) is reduced by Δh.

(d) Increase the vehicle height of the left rear wheel (rear inner wheel) by Δh.

(However, Δh≧O, Δhee horizontal 2) When the above (a), (b), (c), and (d) controls are performed, the tire ground load on the front outer wheel increases, and the tire ground load on the rear outer wheel increases. decreases, the amount of load transfer to the front wheels increases and the cornering power of the front wheels decreases, and conversely the amount of load transfer to the rear wheels decreases and the cornering power of the rear wheels increases, resulting in a decrease in the degree of understeer. Strong steering characteristics.

Further, when the sideways sensor 13 detects a left turn of the vehicle, contrary to the above, (ao), the vehicle height of the right front wheel (front outer wheel) is lowered by Δh.

(b'), the vehicle height of the left front wheel (front inner wheel) is set to Δh7. Boo.

(C') Increase the vehicle height of the right rear wheel (rear outer wheel) by Δh.

(do), reduce the vehicle height of the left rear wheel (rear inner wheel) by Δh.

(However, Δh≧O, Δhacm, ?) Above (a'), (b”), (c”),
When (d”) is controlled, (a), (b),
Contrary to the control in (c) and (d), the tire contact load on the front outer wheel decreases, the load transfer amount on the front wheel decreases, the front wheel cornering power increases, and the tire contact on the rear outer wheel decreases. The load increases, the amount of load transfer to the rear wheels increases, and the cornering power to the rear wheels decreases, resulting in steering characteristics with a weak degree of understeer.

The above will be explained in more detail.

The cornering power relative to the ground load of the tire is expressed by an upwardly convex curve as shown in Figure 2.

When the lateral 2 when the vehicle turns is Y, and the amount of load movement is ΔW, ΔW: MYH/2tr ・・・・・・・・・・・・・・・
(1) (where M is the vehicle weight, H is the vehicle center of gravity height - roll center ground clearance, and tr is the tread) Therefore, the load movement amount ΔW can be considered to be proportional to the lateral width Y.

In a conventional vehicle that does not perform the above-mentioned vehicle height control when the vehicle turns, the front wheel side load movement amount ΔWf.

and rear wheel side load movement amount ΔWr (ratio r to 1 is constant,
Since ΔWfo+ΔWr6=ΔW, the amount of load movement on the front and rear wheels ΔWf and ΔWr) is the tire ground load Wf of the front inner and outer wheels during a turn, and the ground load Wr of the rear inner and outer wheels before turning. The tire ground load of the front and rear wheels of W f
If o e W r o, then the second
The cornering power of each wheel can be calculated from the graph in the figure.

Here, when the vehicle turns, the above (a), (b), (c
), (d), on the front wheel side, the tire ground load on the outer wheel increases, the tire ground load on the inner wheel decreases, and the difference in tire ground load between the inner and outer wheels increases. On the rear wheel side, the tire ground load on the outer wheel decreases, the tire ground load on the inner wheel increases, and the difference in tire ground load between the inner and outer wheels decreases.

As shown in Figure 2, the curve of the graph is upwardly convex, so due to the characteristics of this curve, for example, the tire ground load on the outer tire increases,
When the tire contact load on the inner wheel decreases, the decrease in cornering power on the inner wheel is greater than the increase in the cornering power on the outer wheel, so the total value of cornering power on the inner and outer wheels decreases, and conversely, the tire contact load on the outer wheel decreases. When the tire ground load of the inner wheel increases, the total cornering power of the inner and outer wheels increases because the increase in the cornering power of the inner wheel is greater than the decrease in the cornering power of the outer wheel.

In other words, as the difference in tire ground load between the inner and outer wheels increases, the total cornering power decreases, and as the difference between the inner and outer wheels decreases, the total cornering power increases.

Therefore, as mentioned above, (a), (b), (C)
, (d), the cornering power on the front wheel side decreases and the cornering power on the rear wheel side increases, resulting in a stronger degree of understeer, (a''), (b').

When (c') and (d') are performed, the front wheel cornering power increases, the rear wheel cornering power decreases, and the degree of understeer is weakened.

By dynamically changing the vehicle height from the reference vehicle height in accordance with the size of the generation tank 2 during turning as described above, the turning characteristics of the vehicle can be freely controlled.

For example, if a driver prefers a weak understeer tendency, the above (a''), (b'), (
For those who prefer a strong understeer tendency, the settings are set to perform the control of (a), (b), (c), and (d').
(d) is set to perform the control, and in the angle control Δ
By increasing or decreasing the value of the proportionality constant 4 of h=4Y according to each person's preference, the degree of strength of weak understeer and strong understeer can be arbitrarily determined. Steering characteristics can also be controlled according to constant vehicle speeds to improve stability by providing strong understeer at high vehicle speeds.

Note that the present invention is not limited to the embodiment shown in FIG. 1, but detects the suspension stroke of all four wheels, front, rear, left, and right, and adjusts each suspension to maintain the reference vehicle height based on the information on each suspension stroke. It is applicable to all vehicles equipped with a vehicle height adjustment device that has a controller that independently controls the vehicle height.

Effects of the Invention As described above, the present invention has a suspension stroke sensor that detects the suspension stroke of each of the four suspensions, and independently controls each suspension to maintain the reference vehicle height based on the information on each suspension stroke. In a vehicle equipped with a controller that controls the vehicle height, a lateral lateral sensor is installed to detect lateral 2 when the vehicle turns, and the tire ground load difference between the inner and outer wheels when turning is determined according to the size of lateral 2 detected by the lateral i sensor. By providing the above controller with control logic that adjusts the vehicle height of each wheel so that one of the front and rear wheels is increased and the other is decreased, for example, the front wheel side can adjust the tire ground load difference between the inner and outer wheels when turning. If the steering characteristics are controlled so that the steering characteristics are large and the rear wheels are small, the understeer tendency will be strengthened, and if the front wheels are small and the rear wheels are large, the understeer tendency will be weakened. It is possible to easily obtain steering characteristics according to the driver's preference or to change the steering characteristics depending on the vehicle speed, and it can bring about great practical effects.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of a 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 diagram showing the relationship between tire ground load and cornering power. 11.12, 13.14... Suspension, 21°22 * 23 + 24... Control valve, 3... Controller, 12... Suspension stroke sensor, 13...
・Lateral hit sensor. that's all

Claims (1)

[Claims] It has a suspension stroke sensor that detects changes in the vertical stroke of each of the four suspensions on the front, rear, left, and right wheels, and maintains the vehicle height at a preset standard vehicle height based on information about changes in the vertical stroke of the suspension detected by the suspension stroke sensor. In a vehicle equipped with a vehicle height adjustment device having a controller that independently performs vehicle height adjustment control for each suspension, a lateral g detecting means for detecting lateral acceleration generated when the vehicle turns is provided, and the controller is configured to control the lateral g Depending on the magnitude of the lateral acceleration detected by the detection means, the vehicle height of each wheel is adjusted so that the tire ground load difference between the inner and outer wheels during the turn is made larger on either the front wheel side or the rear wheel side and smaller on the other side. A vehicle height control method for a vehicle with a vehicle height adjustment device, characterized in that the vehicle height is controlled.