JP2852660B2 - Vehicle height control method for vehicle with vehicle height adjustment device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vehicle height control method for a vehicle with a vehicle height adjustment device.

2. Description of the Related Art Vehicles with a vehicle height adjustment function that controls the vehicle height in zones such as high, normal, and low have been known in the past. Vehicles for adjusting the vehicle height have been developed conventionally, and are disclosed in, for example, Japanese Patent Application Laid-Open No. 62-139709.

Problems to be Solved by the Invention Suspension sensors for detecting the vertical relative displacement of suspensions, that is, suspension strokes, are provided for all four front, rear, left and right suspensions, and each suspension is detected based on the suspension stroke information of each suspension detected by the suspension stroke sensors. In a vehicle that performs independent vehicle height control for each vehicle, each suspension is controlled to match the reference vehicle height, for example, when the vehicle body is distorted or when the degree of tire wear is different for each wheel. Therefore, the balance of the ground load of each wheel is deteriorated.

That even if the distortion on the vehicle body as shown in the schematic drawing of FIG. 3 is generated, the suspension 1 ₁ of the left and right front wheels, 1 ₂ and left and right rear wheels of the suspension 1 _3, 1 ₄ reference vehicle height suspension length together Since it tries to keep it constant according to the set value,
The contact load of the left front wheel and the right rear wheel tire increases, and the contact load of the right front wheel and the left rear wheel tire decreases. In FIG. 3, the tires are represented by springs S, the tires having a large contact load are contracted, and the tires having a small contact load are extended.

If the grounding load varies as described above, the tire spring and the mount spring of the suspension are non-linear springs. Even if the suspension spring is a linear spring, it is a non-linear spring as a whole. Shaking of the vehicle body is likely to occur around the line XX connecting the points, resulting in an unstable state.

Such variation in the grounding load of each wheel occurs not only when the vehicle body is distorted or when the tires are worn, but also when the sensor link of the suspension stroke sensor is deformed or the sensor is displaced due to a sensor failure.

An object of the present invention is to address the above-described conventional problems.

Means for Solving the Problems The present invention detects a suspension stroke of all suspensions of all four wheels and controls the vehicle height independently for each suspension so as to maintain a set reference vehicle height. In the device-equipped vehicle, the controller obtains, for each suspension, an integrated value SD of a predetermined time width of an absolute value of a difference between each of the suspension strokes and the set reference vehicle height in a straight running state of the vehicle, and one diagonal position. When the difference between the sum of the integral values SD of the suspension of the other suspension and the sum of the integral values SD of the suspension at the other diagonal position is equal to or larger than a predetermined value,
The above-mentioned reference vehicle height of the suspension of all the wheels or all four wheels is corrected so that the suspension having a small SD is low and the suspension having a large SD is high, and the vehicle height is controlled so as to maintain the corrected reference vehicle height. It is a feature.

Effect In a vehicle that performs height control independently for each suspension based on the suspension stroke information for each suspension so as to maintain the set reference vehicle height, the tire ground load varies as shown in Fig. 3 due to vehicle body distortion and the like. When the vehicle body shakes, the expansion and contraction vibration of each suspension stroke during straight running becomes relatively small in a suspension of a wheel having a large ground load and relatively large in a suspension of a wheel having a small ground load. Therefore, as described above, the integral value SD of a predetermined time width of the absolute value of the difference between each suspension stroke and the set reference vehicle height during straight running is obtained for each suspension, and the integral value SD of the suspension at one diagonal position is obtained. By observing the difference between the sum of SD and the sum of the integral values SD of the suspension at the other diagonal position, it is possible to determine whether or not the ground contact load is unbalanced. A wheel having a small ground contact load and a small SD can be determined to have a large ground contact load.

Therefore, suspensions of wheels with a small SD, that is, wheels with a large ground load, lower the reference vehicle height to reduce the ground load, and suspensions of wheels with a large SD, that is, wheels with a small ground load, raise the reference vehicle height. By performing the control of increasing the ground contact load, the imbalance of the tire ground load is removed, and the vehicle body shake and the unnecessary vehicle height adjustment operation accompanying it are eliminated.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a system diagram showing an example of a control system for active suspension should be applied the present invention, 1 _1, 1
₂ left and right front wheels of the suspension, 1 _3, 1 ₄ Suspension of the left and right rear wheels, the oil chamber of the gas spring section D that partitioning the gas chamber B which is sealed with the oil chamber A in the diaphragm C is a respective suspensions A and an oil chamber F of an oil cylinder E are communicated via an orifice G. One end of the oil cylinder E (for example, the bottom surface of the cylinder) is connected to a wheel-side member such as a suspension arm, and the other end (for example, a piston rod) is connected to the other end. The oil is circulated through the orifice G between the oil chamber and the oil chambers F and A of the gas spring portion to generate an appropriate damping force with respect to the vertical load, and the diaphragm C is coupled to the vehicle body side member. A conventionally known hydro-pneumatic suspension having a spring action by a volume elasticity of a gas sealed in the gas chamber B via the gas chamber B is adopted. The shows.

2 ₁ , 2 ₂ , 2 ₃ , 2 ₄ are control valves for supplying oil to and discharging oil from the oil chamber F of the oil cylinder E of each of the above-mentioned suspensions. Valve 2 ₁ , 2
_2, 2 _3, 2 ₄ are controlled independently by a valve drive signal from the controller 3 to be described later.

Reference numeral 4 denotes an oil tank, and 5 denotes an oil pump. The oil pump 5 is rotated by an engine 6. In the illustrated embodiment, the oil pump 5 'for power steering and the oil pump 5 are tandemly operated by the engine 6. An example is shown in which both oil pumps 5, 5 'are driven to rotate simultaneously.

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

Reference numeral 10 denotes a relief valve, 11 denotes a load / unload valve, and the load / unload valve 11 receives a signal from the controller 3 based on a signal from a pressure sensor 81 that detects that the high-pressure accumulator 8 has reached a predetermined set pressure. The state is switched to the unloading state shown in the figure, and the oil discharged from the oil pump 5 flows to the oil cooler 9 and flows into the oil tank 4.

Above each suspension 1 _1, 1 _2, 1 _3, 1 _4, suspension stroke sensor 12 for detecting the vertical relative displacement of the sprung and unsprung
The detection signal of the suspension stroke sensor 12 is input to the controller 3 respectively, and a straight running state detecting means 13 comprising a combination of a vehicle speed sensor and a steering angle sensor, for example, is provided. The detection signal of the means 13 is also input to the controller 3.

A suspension stroke detection signal of each suspension detected by the suspension stroke sensor 12 is input to the controller 3, and the controller 3 passes through the dead zone circuit, for example, a few mm.
For example, a vehicle speed switch (a switch for switching between a low normal reference vehicle height and a high reference vehicle height suitable for driving on a rough road, etc.) is selected for a signal in a range exceeding that displacement. Oil is injected into the suspension that is displaced in the contraction direction based on the reference vehicle height,
The suspension which is displaced in the extension direction issues a valve drive signal to discharge oil, and controls to keep the vehicle height at the reference vehicle height.

In a vehicle equipped with a vehicle height adjustment device that performs high-resolution vehicle height control in units of mm, the suspension is always controlled to be constant, so that the vehicle body is distorted as shown in FIG. 3, for example. Imbalance occurs between the tire and the ground contact load of the tire, and the vehicle body is liable to sway around the line XX connecting two contact points on the diagonal line where the contact load is large, for example, the left front wheel and the right rear wheel. As described above, such a situation is caused by uneven wear of each tire,
The same occurs when the sensor link of the suspension stroke sensor is deformed or the sensor is displaced due to a failure.

In order to address the above-described problem, the present invention determines whether or not the vehicle body has been shaken due to the imbalance of the ground contact load of the tire in the controller 3 and determines whether the vehicle body has been shaken when the vehicle body has been shaken. And a control logic for performing oil injection and discharge control of each suspension so as to correct the reference vehicle height set by the vehicle height switch or the like and maintain the corrected reference vehicle height.

That is, the controller 3 first detects the straight traveling state detecting means 13
When it is determined that the vehicle is in the straight running state from the detection signal, the difference ΔD between each of the suspension strokes and the set reference vehicle height based on the detection signal of each of the suspension stroke sensors 12 during the straight traveling.
Is observed, and the absolute value | △ D | of the の D of each suspension is integrated over a predetermined time T ₀ (set to a value larger than the natural vibration period of the vehicle) to obtain SD.

The SD value of each suspension does not differ so much when the contact load of each tire is substantially the same, but for example, as shown in FIG.
When the ground contact load of the wheel is large and the vehicle body shakes around X-X, the suspension stroke vibration is large and the SD shows a large value in the suspension of the wheel with the small ground load, In the suspension, the suspension stroke vibration is small and the SD value is small.

Therefore, the sum of two diagonal wheels, that is, the sum SD of the right front wheel and the left rear wheel SD _FR + SD _RL, and the other diagonal two wheel SD
, Ie, the difference between the SD of the left front wheel and the SD of the right rear wheel, _SDFL + SD _RR △ SD is obtained by SDSD = ( _SDFR + _SDRL ) + ( _SDFL + _SDRR ), and △ SD exceeds the allowable setting range. In this case, as described above, it is determined that the ground load of each wheel is out of balance due to an abnormality such as a twisting of the vehicle body, a variation in tire wear, or a deviation in the sensing of the suspension stroke, as shown below. Setting reference vehicle height H _FL0 , H
_FR0, performs H _RL0, correction of H _RR0, performs the corrected vehicle height control to match the reference vehicle height (injection of the oil, the discharge control).

In other words, if △ SD is positive and exceeds the allowable setting range, (a) the reference vehicle height for the right front wheel is increased (H _FR0 → H _FR0 + △ H) (b), the reference standard for the left front wheel _{Reduce the} vehicle height (H _FL0 → H _{FL0 −ΔH} ) (c), _{reduce the} reference vehicle height for setting the right rear wheel (H _RR0 → H _{RR0 −ΔH} ) (d), _{Increase the} reference vehicle height (H _RL0 → H _RL0 + △ H) Any two or four of the above (a), (b), (c) and (d) are corrected simultaneously.

If _ΔSD is negative and exceeds the allowable setting range, (a), the reference vehicle height set for the right front wheel is reduced (H _FR0 → H _{FR0 −ΔH} ) (b), the reference vehicle height set for the left front wheel (H _FL0 → H _FL0 + _ΔH ) (c), Setting the reference height of the right rear wheel large (H _RR0 → H _RR0 + _ΔH ) (d), Setting reference of the left rear wheel _{Decreasing the} vehicle height (H _RL0 → H _RL0 − △ H) Any two or four of the above (a), (b), (c) and (d) are simultaneously corrected. ΔH is set to the control resolution, that is, about several mm.

When the set reference vehicle height is corrected as described above, oil is injected and discharged so as to match the corrected reference vehicle height, and as a result, the suspension of the wheel having a large ground load is reduced by ΔH. On the other hand, the suspension of the wheel having a small contact load extends by ΔH, and the degree of unbalance of the contact load decreases.

The above-described correction of the reference vehicle height is repeatedly performed at a certain time period T _H (approximately equal to the time required for one vehicle height adjustment). Is completed, and unnecessary shaking of the vehicle body is eliminated.

By performing the above, when the tire ground load becomes unbalanced due to an abnormality such as a twist of the vehicle body, a variation in the wear of each tire, and a deformation range of the sensor link due to a sensor failure, a failure occurs. As shown in FIG. 2, the balance of the tire contact load of each wheel represented by the spring S is improved in a relatively short time, the body of the vehicle does not sway during traveling, and the vehicle height adjustment is completed forever. The conventional problem of consuming unnecessary energy without being used is eliminated.

The present invention is not limited to the embodiment of FIG. 1, but detects the suspension strokes of all four front, rear, left and right suspensions and independently controls each suspension so as to maintain the reference vehicle height based on the information of each suspension stroke. The present invention is applicable to all vehicles with a vehicle height adjustment device that performs vehicle height control.

Effects of the Invention As described above, according to the present invention, a suspension stroke sensor for detecting the suspension stroke of each of all four suspensions is provided, and the suspension is independently provided for each suspension so as to maintain the reference vehicle height based on the information of each suspension stroke. In a vehicle having a controller that performs vehicle height control, a straight traveling state detecting means for detecting that the vehicle is in a straight traveling state is provided, and a target stroke of each suspension stroke (that is, a reference vehicle height) in the straight traveling state is provided. The integral value of the absolute value of the difference of the predetermined time width is obtained for each suspension, and the difference between the sum of the integral values of the suspension at one diagonal position and the sum of the integral values of the suspension at the other diagonal position is obtained. When the value is equal to or more than the predetermined value, the contact load of each wheel is in an unbalanced state, the contact load of the wheel having a large integral value is small, and the contact load of the wheel having a small integral value is large. The control logic for correcting the reference vehicle height of an arbitrary two-wheel suspension or all four-wheel suspensions to a higher value for a suspension with a smaller ground load and a lower value for a suspension with a larger ground load is determined by the controller. The vehicle height control is performed so as to maintain the corrected reference vehicle height, thereby eliminating an inconvenience such as occurrence of vehicle body shake due to unbalance of tire contact load, and an unnecessary vehicle based on the vehicle body shake. It can eliminate energy consumed for high adjustment, and can bring a great effect in practical use.

[Brief description of the drawings]

FIG. 1 is an explanatory view 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 FIGS. 2 and 3 show expansion and contraction states of each suspension when the vehicle body is distorted. FIG. 2 is a perspective view schematically illustrating a case where FIG. 2 is controlled by the present invention, and FIG. 1 ₁ , 1 ₂ , 1 ₃ , 1 ₄ …… Suspension, 2 ₁ , 2 ₂ , 2 ₃ , 2 ₄ … Control valve, 3… Controller, 12… Suspension sensor, 13… Straight running state detection means.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B60G 17/015

Claims (1)

(57) [Claims] A means for detecting at least the suspension stroke of each of the front, rear, left and right suspensions, and for each suspension so as to maintain the reference vehicle height set in advance based on the information of the suspension stroke of each suspension. In a vehicle with a vehicle height adjustment device having a controller that independently performs vehicle height adjustment control, a straight traveling state detection unit that detects that the vehicle is traveling straight is provided, and the above-described suspension stroke in the straight traveling state is provided. An integral value of a predetermined time width of an absolute value of a difference from the set reference vehicle height is obtained for each suspension, and a sum of the integral value of the suspension at one diagonal position and the integral value of the integral value of the suspension at the other diagonal position are obtained. When the difference from the sum is equal to or greater than a predetermined value, the above-mentioned reference vehicle height of any two or four suspensions is changed to a suspension having a smaller integral value. A vehicle height control for a vehicle with a vehicle height adjusting device, wherein a control logic for correcting a suspension having a low integral value and a large value is provided in the controller, and the vehicle height is controlled so as to maintain the corrected reference vehicle height. Method.