JPH0450013A - Suspension device of vehicle - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a suspension device for a vehicle, and more particularly to a suspension device for a vehicle that adjusts the vehicle height according to the driving condition of the vehicle.

[Conventional technology]

2. Description of the Related Art Recently, various types of vehicle suspension systems have been proposed, such as those called active suspensions, which variably adjust suspension characteristics depending on driving conditions, and those that adjust vehicle height. This type of suspension device detects an overload condition on the wheel by detecting the internal pressure of a fluid cylinder provided between the vehicle body and the wheel, and controls the operating pressure mainly based on the detected value. Suspension characteristics and vehicle height are often adjusted. Or, for example, JP-A-63-
As described in Japanese Patent No. 130418, there is also a vehicle suspension device in which the operating pressure of a fluid cylinder is controlled based on a signal from a vertical acceleration detection means that detects acceleration in the vertical direction of the vehicle body.

[Problem to be solved by the invention]

By the way, for example, in vehicles that are used under harsh conditions such as continuous driving at extremely high speeds for long periods of time, conventional active suspensions that rely exclusively on control systems to change and adjust suspension characteristics and vehicle height are often used as is. It is not possible. This is because it is not easy to deal with problems when they occur, and when the driver's advanced driving skills are required, it is undesirable for controls to be performed that differ from the driver's driving actions. . Furthermore, in the case of ultra-high speed driving,
It is also undesirable that there is a response delay due to feedback control. For example, when you want to increase the speed, there is a delay in lowering the vehicle height, which increases air resistance and prevents the speed from increasing as expected.

The present invention was made in consideration of such circumstances, and an object of the present invention is to provide a suspension device for a vehicle that has no response delay (high safety).

[Means to solve the problem]

A suspension device for a vehicle comprising a shock absorbing means consisting of a spring and a damper installed between the sprung mass and the unsprung mass of the vehicle, and a fluid cylinder for adjusting vehicle height and attitude arranged in series with the shock absorbing means, In order to solve the above problem, a first stroke sensor detects the distance between the sprung mass and the unsprung mass, a second stroke sensor detects the stroke of the fluid cylinder, and a stroke sensor detects the distance between the sprung mass and the unsprung mass, and a second stroke sensor detects the stroke of the fluid cylinder. A control means for adjusting the vehicle height based on the value detected by the sensor is provided.

For example, the control means may be configured to adjust the vehicle height based on the values detected by the second stroke sensor while the vehicle is running and by the first stroke sensor while the vehicle is stopped.

[For production]

The first stroke sensor can detect changes in the stroke of the shock absorbing means, which is a passive suspension, and can detect the vehicle height taking into account the weight of the occupant and the like. Further, the second stroke sensor can detect the stroke of the fluid cylinder without being affected by disturbances such as unevenness of the road surface. Therefore, depending on the driving condition, the detection signal from each stroke sensor is appropriately adopted as a determining factor for adjusting the vehicle height, and the fluid cylinder is driven by a command from the control means to perform the optimal vehicle height adjustment at that time. I can do it.

For example, when stopped or at extremely low speed, a control signal is sent to adjust the distance between the sprung mass and the unsprung mass detected by the first stroke sensor so that the distance becomes a pre-stored reference value. is sent from the control means to a control valve that adjusts the amount of working fluid supplied and discharged from the fluid cylinder, and the vehicle height at that time can be adjusted to the reference vehicle height. When stopped or at very low speeds, there is little variation in the distance between the sprung and unsprung parts due to uneven road surfaces, etc., and the first stroke sensor provides a highly reliable detection value, allowing the vehicle to be adjusted to the correct position, taking into account the weight of the occupants, etc. You can make high adjustments.

While driving other than the above, the vehicle height will be adjusted based on the stroke value of the fluid cylinder detected by the second stroke sensor, and when the vehicle speed exceeds a predetermined value, the vehicle height at that time will be lowered by a predetermined amount than the standard vehicle height. A command to do so is sent from the control means to the control valve for the fluid cylinder, and the vehicle height at that time can be adjusted to be lower than the reference vehicle height by a predetermined amount to reduce air resistance. When the vehicle moves to a speed other than a very low speed, the unevenness of the road surface is absorbed by the buffer means, so the distance between the sprung mass and the unsprung mass detected by the first stroke sensor tends to fluctuate. Therefore, the detected value for adjusting the vehicle height is determined by the second stroke sensor, which is not affected by external disturbances. Since it employs open-loop control that responds to vehicle speed, it can accurately adjust vehicle height by following changes in vehicle speed during high-speed driving without delay in response.

[Effects of the Invention] The vehicle suspension device of the present invention has a shock absorbing means consisting of a spring and a damper and a fluid cylinder arranged in series between the sprung mass and the unsprung mass, so that the shock absorbing means can be used even during high-speed driving. It effectively absorbs road surface irregularities and provides a buffering function that responds to the driver's behavior, improving safety.

The first stroke sensor can reliably detect the distance between the sprung mass and the unsprung mass when the vehicle is stopped or at extremely low speed. Furthermore, while the vehicle is running, the stroke of the fluid cylinder can be detected by the second stroke sensor without being affected by unevenness of the road surface or the like. Therefore, by inputting signals from each stroke sensor to the control means, it is possible to appropriately adjust the vehicle height according to the current driving condition, for example, the vehicle speed.

For example, while driving, the second stroke sensor can adjust the stroke of the fluid cylinder based on the value detected by the first stroke sensor when stopped or at extremely low speeds, and the optimal vehicle height can be adjusted at that time. . Such open-loop control based on vehicle speed makes it possible to adjust the vehicle height without delay in responding to changes in vehicle speed during high-speed driving.

〔Example] The present invention will be explained in detail below based on examples.

The vehicle suspension system shown in this example is used in vehicles that run at high speed for long periods of time, and uses oven loop control while driving to ensure responsive and accurate vehicle height adjustment without being affected by road surface irregularities. , and is configured as follows so that the buffering function can be exhibited in accordance with the driver's maneuvering motion.

As shown in FIG. 1, a damping means 5 consisting of a spring 3 and a damper 4, and a fluid for adjusting the vehicle height attitude are provided between the vehicle body 1 which is on a spring and a pair of front and rear wheels 2F and 2R which are not on a spring. Cylinders 6F and 6R are arranged in series, and a first stroke sensor 7 detects the distance between the sprung mass 1 and the sprung mass 2 on the rear wheel 2R side, and then detects the stroke of the fluid cylinder 6R that supports the wheel 2R. A second stroke sensor 8 is provided, and each detection signal is input to the control means 9. The control means 9 uses the distance X between the sprung mass 1 and the sprung mass 2 detected by the first stroke sensor 7 depending on the traveling state, that is, when stopped or at extremely low speed, and when the vehicle is otherwise traveling. The front and rear fluid cylinders 6F and 6R are operated based on the stroke value X2 of the rear wheel side fluid cylinder 6R detected by a two-stroke sensor 8, and the vehicle height can be adjusted to the optimum vehicle height at that time.

The first stroke sensor 7 and the second stroke sensor 8 are
It is a linear type potentiometer that reads the distance as a resistance value or voltage change using a slider that moves on a resistance wire, and the first stroke sensor 7 is located at the upper end of the rear wheel side shock absorbing means 5, as shown in FIG. and the piston rod 6a of the fluid cylinder 6R. On the other hand, the second stroke sensor 8 is provided between the piston rod 6a and the upper end of the cylinder 6b of the fluid cylinder 6R on the rear wheel side.

Both stroke sensors 7.8 are provided on the left and right rear wheels 2R, and are configured to calculate the average value of the left and right wheels respectively.

The buffering means 5 is a combination of a coil spring 3 and an oil damper 4 in parallel, and exhibits a passive buffering function to flexibly respond to the driver's maneuvering movements and to buffer unevenness on the road surface. I can do it. On the other hand, the fluid cylinder 6 is of a single-acting piston type, and its cylinder 6b is connected to an oil pump 11 and a reserve tank 12 via an electromagnetic three-position direct switching valve 10 that is switched and controlled by a control means 9. The vehicle height can be actively adjusted by the expansion and contraction of the piston rod 6a.

When the spool 10a of the three-position direct switching valve 10 is in the neutral position shown, the fluid in the cylinder 6b is maintained, the stroke does not change, and the vehicle height at that time is maintained. Spool 10
When a is moved downward, fluid is supplied into the cylinder 6b, the piston rod 6a is extended, and the vehicle height becomes higher.
When the piston rod 6a is moved upward, the fluid in the cylinder 6b is returned to the reserve tank 12, and the piston rod 6a is contracted to lower the vehicle height. The oil pump 1] is driven by an on-vehicle engine (not shown), and is driven by an accumulator 17.
It is designed to absorb excess pressure.

The control means 9 is composed of a microcomputer, and performs open loop control with good responsiveness as described later according to a pre-stored program.A first stroke sensor 7 and a second stroke sensor 8 are connected to the input side of the control means 9. On the other hand, a three-position direct switching valve IO provided in each fluid cylinder 6 is connected to the output side. A preferred example of the oven loop control performed by the control means 9 will be described below based on the basic flowchart shown in FIG.

(1) When the ignition switch is turned on, reading of the vehicle speed V starts (Step 1, hereinafter referred to as 31, etc.)
, the vehicle speed V is extremely low speed V. For example, when the speed reaches approximately 4 km/h (S2), the first vehicle height XIA detected by the first stroke sensor 7 is read (S3) and compared with the first reference vehicle height x1° stored in advance. (S4).

(2) If the first vehicle height (S5.S6). This extremely low speed ■. In this case, since there is almost no variation in the first vehicle height XIA due to unevenness of the road surface, it is possible to detect a highly reliable vehicle height that takes into account the weight of the occupant. Thereby, the vehicle height adjustment operation by the fluid cylinder 6 can be made more accurate and quick, and the first vehicle height XIA can be adjusted to the first reference vehicle height X1°.

(3) Next, the second vehicle height XZA detected by the second stroke sensor 8 is read (37), and the value XZA
is set as the second reference vehicle height X2° (S8).

(4) In step 2, the vehicle speed V is extremely low ■. When the vehicle is out of the range, reading of the second vehicle height
The second vehicle height X2B at that time is the second vehicle height that has already been set.
Adjusted to standard vehicle height x2° (Sll.

512). In this speed range, the unevenness of the road surface is mostly buffered by the buffering means 5, so the first vehicle height XIA changes, but there is no change in the stroke of the fluid cylinder 6R.
Second vehicle height X detected by second stroke sensor 8
Since ZB does not fluctuate, it can be easily, stably and accurately adjusted. This allows the vehicle to obtain appropriate downforce and drive smoothly.

(5) In step 10, the vehicle speed V is equal to or higher than a predetermined value, for example 3
When the speed reaches an extremely high speed of 00km/h or more, the second vehicle height Xzml at that time becomes 2III1 higher than the second reference vehicle height XZO.
It is adjusted to be lower by 1 (S13, 514). In this speed range, air resistance increases, so it is necessary to lower the vehicle height and lower the center of gravity to reduce air resistance and increase stability.Moreover, quick and accurate responses are required. Therefore, we decided to adjust the vehicle height with high responsiveness and accuracy using oven loop control that corresponds to vehicle speed. As a result, when accelerating after entering a straight road from a curved road, for example, the vehicle height can be lowered responsively and accurately to reduce air resistance and provide a quick start-up. In addition, by lowering the vehicle height, the center of gravity is lowered, which improves stability and allows you to drive around curves without stalling. In addition, in step 2, the vehicle speed ■ is extremely low ■. Or when it is 0, the first stroke sensor 7R
Read the first vehicle height X1A detected by (S3
). In addition, as described above, in steps 4 to 6, the first vehicle height XIA is changed to the first reference vehicle height X, as described above, when the vehicle height changes due to the weight difference when the passenger is replaced midway.

It is digested by being adjusted to Furthermore, in step 10, how much the vehicle speed should be and how much the vehicle height should be lowered is specific to the vehicle model, etc., and should be considered individually.

Incidentally, if vehicle height adjustment corresponding to fuel consumption is also taken into account, a subflow based on open loop control corresponding to the travel distance may be incorporated into the main flow of FIG. 3, as shown in FIG. That is, after the vehicle height is adjusted in step 11.12 or the vehicle height is lowered in step 13.14, (6) the second vehicle height XZC detected by the second stroke sensor 8 is read again (S15), and the second vehicle height XZC is read again (S15). The value X2c is set as the third reference vehicle height X3° (S
16).

(Next, the mileage at that time is read (S1
7) If the distance traveled exceeds the specified distance (
318), the vehicle height is adjusted so that the second vehicle height XZC at that time is, for example, 2 mm lower than the already set third reference vehicle height X3a (S19S20). Thereby, the buffer means 5 expands by the amount of fuel consumed up to that point, and the increased vehicle height can be corrected.

(8) Furthermore, when the mileage 15 exceeds the predetermined distance L2 (321), the vehicle height is adjusted so that the second vehicle height X2C at that time is, for example, 4 m lower than the third reference vehicle height X30 ( 322, 323).

As described above, according to the vehicle suspension device of the present invention, oven loop control is performed based on the detection values from each stroke sensor as appropriate depending on the driving conditions such as vehicle speed and travel distance, thereby improving the road surface. Vehicle height can be adjusted accurately and with good responsiveness without being affected by unevenness, etc. In addition, passive shock absorbing means is placed in series with the fluid cylinder for vehicle height adjustment.
Suspension characteristics can be passively adapted to the driver's behavior, improving safety.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a general schematic diagram of a suspension device installed on a vehicle, FIG. 2 is a schematic diagram of the suspension device, and FIG. 3 is for explaining the vehicle height adjustment operation. FIG. 4 is a flowchart in which the travel distance is taken into account. 1- sprung mass (vehicle body), 2- sprung mass (wheel), 3 spring, 4
-・Damper 5-Buffer means, 6,6R fluid cylinder,
7-first stroke sensor, 8 second stroke sensor,
9-Control means. Patent applicant Mazda Co., Ltd. agent Patent attorney Katsutoshi (one idiot) Figure 1 Figure 2 Beam (driving accident) Q. Procedural amendment

Claims (2)

[Claims] (1) In a suspension system for a vehicle that includes a shock absorbing means consisting of a spring and a damper installed between the sprung mass and the unsprung mass of the vehicle, and a fluid cylinder for adjusting the vehicle height and attitude arranged in series with the shock absorbing means. , a first stroke sensor that detects the distance between the sprung mass and the unsprung mass, a second stroke sensor that detects the stroke of the fluid cylinder, and based on the values detected by each of the stroke sensors according to the vehicle running state. 1. A suspension device for a vehicle, comprising: a control means for adjusting vehicle height. (2) In place of the above control means, a control means is provided which adjusts the vehicle height based on the value detected by the second stroke sensor while the vehicle is running, and by the first stroke sensor when stopped or at extremely low speeds. The vehicle suspension device according to claim 1, characterized in that: