JPH072254Y2 - Circuits for vehicle fluid suspension - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a circuit of a fluid suspension using a fluid such as air, which is used for suspension of a vehicle.

[Prior Art] Since it is relatively easy to change the suspension characteristics of an air suspension, it is often used in combination with an electronic control device for advanced control.

Among such suspension control items are vehicle height adjustment and vehicle attitude adjustment, etc., but all of these controls supply an appropriate amount of air to the air chamber of the air suspension of each wheel, It is discharged from the. However, in order to perform advanced suspension control, it is necessary to set the air supply / exhaust speed to an appropriate value according to each control purpose. Especially when adjusting the vehicle height,
It is preferable that the vehicle height is as high as possible and the vehicle speed is as low as possible from the viewpoint of passenger comfort.

Regarding the technology of controlling the vehicle height adjustment speed, in order to change the air supply speed to the air suspension according to the purpose, a reservoir tank for storing compressed air is provided in the circuit, and the suspension unit of each wheel and A device has been proposed in which two pipes, a thick one and a thin one, are provided between the air chamber and the air chamber (Actual No. 60-119623).

Further, in Japanese Patent Publication No. 50-28589 and Japanese Utility Model Publication No. 61-27711, a high pressure reservoir tank and a low pressure reservoir tank are provided, and a compressor compresses air from the low pressure reservoir tank and supplies it to the high pressure reservoir tank. The configuration is shown.

[Problems to be Solved by the Invention] Conventionally, the former of the above-mentioned conventional techniques is also of the same type, but various proposals have been made for changing the vehicle height adjusting speed during ascent or descent. However, little consideration was given to equalizing the ascending speed and the descending speed.

Raising and lowering the vehicle height with the fluid suspension means supplying and discharging the fluid to the fluid suspension, but if these supply and discharge speeds are not the same, the rising and lowering speeds will be different. Therefore, when turning, for example, one of the left and right wheels is supplied with air and the other is exhausted, which may give an occupant a discomfort.

For example, as shown in the latter of the above-mentioned prior art, there is a configuration in which high-pressure and low-pressure reservoir tanks are provided, fluid is supplied from the high-pressure reservoir tank to the fluid suspension, and the fluid discharged therefrom is put into the low-pressure reservoir tank. is there.

The volume of the fluid chamber of the fluid suspension must be variable in order to adjust the vehicle height. Therefore, although a flexible diaphragm or the like is usually used, it is difficult to maintain the pressure inside the fluid chamber at a very high value from the viewpoint of pressure resistance and durability, and it is set to a relatively low pressure. . On the other hand, the high-pressure reservoir tank is designed to hold the fluid at a considerably high pressure, particularly from the viewpoint of volume efficiency in passenger cars and the like. Therefore, assuming that the pressure of the fluid chamber is Pa, the pressure of the high-pressure reservoir tank is Ph, and the pressure of the low-pressure reservoir tank is Pl, there is generally a relationship of Ph-Pa> Pa-Pl (1). In the conventional fluid suspension circuit, no consideration has been given to this pressure difference, so there is a speed difference between the supply and discharge of fluid, which impairs the ride comfort of the vehicle occupant and complicates the control of the valve opening time. Was forced to.

The present invention has been made in order to compensate for the above-mentioned drawbacks of the prior art and basically to make the difference between the fluid supply / discharge speeds small and ideally equal in the control of the fluid suspension.

Configuration of the Invention [Means for Solving the Problems] The present invention made to solve the above problems includes a fluid suspension provided on a wheel of a vehicle and a first valve. It has a high-pressure passage for supplying high-pressure fluid to the fluid suspension by opening the valve, a high-pressure reservoir tank provided in the high-pressure passage, and a second valve, and the fluid is opened by opening the second valve. In a vehicle fluid suspension circuit including a low-pressure passage for discharging fluid from a suspension and a low-pressure reservoir tank provided in the low-pressure passage, the effective passage cross-sectional area of the high-pressure passage is smaller than that of the low-pressure passage. It is also characterized by being small.

As an embodiment of the present invention, the high-pressure reservoir tank is connected to the high-pressure passage through a third valve,
By providing the low-pressure reservoir tank directly in the low-pressure passage, it is possible to show that the effective passage sectional area of the high-pressure passage is smaller than the effective passage sectional area of the low-pressure passage.

[Operation] In the fluid suspension circuit of the present invention, since the effective passage cross-sectional area of the high pressure passage is smaller than the effective passage cross-sectional area of the low pressure passage, the pressure difference represented by the above formula (1) is different from the effective passage cross-sectional area. Are canceled by each other, and the supply speed of the fluid to the fluid chamber and the discharge speed from the fluid chamber become substantially equal.

In the configuration of the embodiment, the high pressure passage from the high pressure reservoir tank to the fluid suspension has a third valve and the first valve, while the low pressure passage from the fluid suspension to the low pressure reservoir tank has a second valve. Since there are only valves, the flow resistance of the fluid in the high-pressure passage increases, and the effective passage area becomes smaller than that of the low-pressure passage.

[Example] An example in which the present invention is applied to an air suspension system for an automobile will be described below. FIG. 1 is a circuit diagram of this system. This system is roughly divided into compressed air supply / exhaust system 10,
Left and right front and rear wheel suspension systems 20, 22, 24, 26, and front and rear reservoir systems 30, including high and low pressure reservoir tanks,
It is divided into 32. The four suspension systems are front wheel system 21 including left and right front wheel systems 20, 22 and left and right rear wheel systems 24, 26.
Rear wheel system 25 including
30 and 32 are provided for each of the lines 21 and 25.

The left and right suspension systems 20 and 22 for the front wheels are connected by an air supply pipe 40 and an exhaust pipe 41. The left and right suspension systems 24 and 26 for the rear wheels are also connected by an air supply pipe 40R and an exhaust pipe 41R.

Air supply and exhaust pipes 42 and 43 are connected between the compressed air supply and exhaust system 10 and the air supply pipe 40 and the exhaust pipe 41 of the front wheel system 21. Similarly, air supply and exhaust pipes 44, 45 are connected between the front wheel system 21 and the rear wheel system 25.

The compressed air supply / exhaust system 10 is provided with a pump 3 having an inlet 1 and an outlet 2. The suction port 1 of the pump 3 has a check valve 4
An exhaust pipe 43 is connected between the intake port 1 and the check valve 4 via a flow control return valve 5 although it communicates with the atmosphere via the flow control return valve 5. The pipe connected to the suction port 1 branches in the middle and communicates with the piston lower chamber 3a of the pump 3, which is for reducing the torque load at the time of starting and operating the pump 3.

A check valve 6, an air dryer 7, a one-way throttle valve 8, and a flow control main valve 9 are provided in the air supply pipe 42 connected to the discharge port 2 of the pump 3. Check valve 6 on the air supply side
An exhaust valve 11 to the atmosphere is provided between the air dryer 7 and the air dryer 7.

The one-way throttle valve 8 of the air supply pipe 42 and the flow control main valve 9 and the exhaust pipe 43 are connected by a bypass pipe 12, and the bypass pipe 12 is provided with a flow control bypass valve 13.

The front and rear reservoir systems 30, 32 have the same structure, so the front wheel system
The reservoir system 30 of 21 will be described. The reservoir system 30 includes a high pressure reservoir tank 33 and a low pressure reservoir tank 34. The high-pressure reservoir tank 33 is connected via a front reservoir high-pressure valve 35 to an air supply pipe 40 that connects the left and right front wheel suspension systems 20, 22. Low pressure reservoir tank 34
Is an exhaust pipe that connects the left and right suspension systems 20 and 22.
It is directly inserted in the middle of 41. Each of the tanks 33 and 34 is provided with pressure sensors 36 and 37 and relief valves 38 and 39. For convenience of the following description, the elements corresponding to the reservoir system 32 and the pipes of the rear wheel system 25 are denoted by R after the element numbers in the front wheel system.

Since the structure and operation of the suspension system of each wheel are the same, the suspension system 20 of the left front wheel will be described.
The suspension system 20 includes an air suspension main body 54 having an air chamber 50, a leveling valve 56 inserted in the air supply pipe 40, and a discharge valve 58 inserted in the exhaust pipe 41. The air supply pipe 40 and the exhaust pipe 41 meet immediately before the air chamber 50 of the air suspension body 54, and a pressure sensor 64 is provided there. Air suspension body 54
In addition to the air chamber 50, a shock absorber 66 having a variable damping force is also provided, and therefore an actuator 68 for changing the damping force is provided. The air suspension 54 is fixed to a vehicle body (not shown) in the upper portion 52 of the air chamber 50, and is fixed to a suspension arm (not shown) below the shock absorber 66. For convenience of the following description, the right front wheel 22, the left rear wheel 24,
FR after the corresponding element number in each system of the right rear wheel 26, respectively,
Attach RL and RR.

In the above pneumatic circuit, air suspension 54, 54F
The air chambers 50, 50FR, 50RL and 50RR of R, 55RL and 54RR correspond to the fluid suspension of the present invention, and the air supply pipes 40 and 40R and the exhaust pipes 41 and 41R to the high pressure passage and the low pressure passage of the present invention, and the leveling valve. 56, 56FR, 56RL, 56RR and discharge valves 58, 58FR, 58RL, 58RR correspond to the first valve and the second valve, respectively. The front and rear reservoir high pressure valves 35, 35R correspond to the third valve of the embodiment.

In this embodiment, the high pressure reservoir tanks 33, 33
The air pressure R ₃₃ in the R is considerably higher than the normal set pressure R ₅₀ (about 6.5 atm gauge pressure) of the air chambers 50, 50FR, 50RL, 50RR in order to increase the volumetric efficiency and the air supply speed. The air pressure P ₃₄ in the low-pressure reservoir tanks ₃₄ , 34R is high (about 0 atm in gauge pressure), while it is high and set at about 15 atm in gauge pressure. However, depending on usage conditions, P ₃₃ changes to about 10 to 15 atmospheres, and P ₃₄ changes to about 0 to 5 atmospheres. However, since the system of this embodiment forms a substantially closed circuit, the sum of P ₃₃ and P ₃₄ always maintains a substantially constant value. For example, when P ₃₄ becomes 1 atm, P ₃₃ becomes 14
It changes like atmospheric pressure.

The above is a description of circuits related to air pressure. Next, circuits related to electrical pressure will be briefly described. The pressure sensors are connected to an electronic control unit (not shown), and pressure signals of the tanks and the air chambers are input to the electronic control unit. Each wheel is provided with a vehicle height sensor (not shown), and the vehicle height value at each wheel is also input to the electronic control unit. Further, each of the above valves is composed of a two-position solenoid valve, and is normally placed at a shutoff position as shown in FIG. 1 by a spring, but is placed at a communication position by a drive current from the electronic control unit.

The electronic control unit calculates based on the input signals from each pressure sensor, vehicle height sensor and other sensors according to a predetermined program for suspension characteristic control or attitude control, and supplies it to the air chamber of each wheel. Calculate the amount of air to be discharged or the amount of air to be discharged from the air chamber. Based on the values thus calculated, the electronic control unit can
A drive current is supplied to the position solenoid valve to perform predetermined vehicle height adjustment, suspension characteristic change, and vehicle attitude control. At this time, the damping force of the shock absorber 66 is also changed.

Hereinafter, the operation of the system when the vehicle height rises and falls, which is a portion related to the present invention, will be described.

First, the operation for increasing the vehicle height will be described. For example, by the signal from the vehicle height sensor provided on each wheel,
If it is detected that the vehicle height has decreased, the electronic control unit returns the vehicle height to the original value by adjusting the air suspension 54, 54F.
The air is supplied to the air chambers 50, 50FR, 50RL and 50RR of the R, 65RL and 54RR. Specifically, the valves 35 and 35R of the front and rear high pressure reservoir tanks 33 and 33R and each suspension system
20, 22, 24, 26 leveling valves 56, 56FR, 56RL, 56
By supplying a drive current to the solenoid of RR, they are brought into the communicating position, and high pressure air is supplied from the high pressure reservoir tanks 33, 33R to the air chambers 50, 50FR, 50RL, 50RR. At this time, all the other solenoid valves are placed in the shut-off position, and the energization time to the solenoid of each valve is
It is calculated according to the amount of decrease in vehicle height.

Next, the operation for decreasing the vehicle height will be described.
When it is determined that the vehicle height is increased by the signal from the vehicle height sensor provided on each wheel, the electronic control unit starts the execution of a predetermined routine, and the air suspension 54, 54FR is returned in order to restore the vehicle height to the original level. , 54RL, 54RR air chamber 50, 50FR, 50R
Perform processing to discharge air from L and 50RR. In particular,
By supplying drive current to the solenoids of the discharge valves 58, 58FR, 58RL, 58RR of each suspension system 20, 22, 24, 26, they are placed in the communicating position, and each air chamber 5
Air is discharged from 0, 50FR, 50RL, 50RR to the low pressure tanks 34, 34R in the front and rear. At this time as well, the other solenoid valves are all placed in the shut-off position, and the energization time of the solenoid of each valve is calculated according to the amount of decrease in vehicle height.

As described above, when air is supplied to the air chambers 50, 50FR, 50RL, and 50RR, for example, in the case of the left front wheel, the passage from the high pressure reservoir tank 33 is connected to the front reservoir high pressure valve 35, It comprises an air pipe 40, a leveling valve 56, and a passage 40a between the leveling valve 56 and the air chamber 50. On the other hand, the passage from the air chamber 50 to the low-pressure tank 34 is the discharge valve from the air chamber 50.
It is composed of a passage 41a up to 58 (this is partly common with the passage 40a), a discharge valve 58 and an exhaust pipe 41. The effective cross-sectional area of each of these passages is It is calculated by the formula. Here, S _{i is} the effective passage cross-sectional area in the case of air supply, S _{o is} the effective passage cross-sectional area in the case of exhaust, and S _xx is the effective passage cross-sectional area due to each element (number xx) of each passage.

Since the high-pressure reservoir tank 33 and the low-pressure reservoir tank 34 are usually placed close to each other, the air supply pipe 40 and the exhaust pipe
The effective passage cross-sectional areas S ₄₀ and S ₄₁ of ₄₁ are equal, and S _40a and
S _41a , S ₅₆ and S ₅₈ also correspond to each other and are equal, so
S _i is smaller than S _o by the amount of 1 / S ² ₃₅ term (in the denominator).

On the other hand, the difference P ₃₃ -P ₅₀ between the air pressure in the high pressure reservoir tank 33 and the pressure in the air chamber 50 is larger than the pressure difference P ₅₀ -P ₃₄ between the air chamber 50 and the low pressure reservoir tank 34, as described above. .

Therefore, the difference in the effective passage area cancels out the pressure difference, and eventually the air supply speed and the air discharge speed become substantially equal. As a result, the speed when the vehicle height rises and the speed when the vehicle height descends become substantially equal, and the vehicle height can be adjusted naturally for the occupant. Further, when performing other controls, it is not necessary to consider the speed difference between the air supply and the air discharge, so that the control program and the like are simplified.

If the reservoir high pressure valve 35
If the pressure difference cannot be offset by just installing
It is also possible to put an appropriate throttle in the air supply pipe 40.

In the above embodiment, the high pressure reservoir tank 33 is provided with the reservoir high pressure valve 35, so that it also has the following effects. First, when air is supplied to the air chamber 50, the air supply source is set to the high pressure reservoir tank 33 as in the above embodiment.
In addition to the above, by shutting off the reservoir high pressure valve 35, it is possible to supply the air directly from the compressor 3 to the air chamber 50. As a result, the air supply speed can be changed in two steps. Further, as another effect, when the air is discharged from the air chamber 50, it is directly discharged to the low pressure reservoir tank 34 as in the above embodiment, and a reservoir high pressure valve.
By shutting off 35 and opening the bypass valve 13,
Air chamber 50-Air supply pipe 40-Air supply pipe 42-Bypass passage 12-
It is also possible to take the route of exhaust pipe 43-exhaust pipe 41 to discharge to the low pressure reservoir tank 34. Also in this case, the air discharge speed can be changed in two steps.

Effects of the Invention A high-pressure reservoir tank normally holds a fluid at a considerably high pressure, while a fluid suspension has a structural constraint that it must have a flexible member in order to have a variable volume. Is set relatively low. Therefore, in the conventional configuration, the supply speed of the fluid from the high-pressure reservoir tank to the fluid suspension is higher than the discharge speed from the fluid suspension to the low-pressure tank, and there is a difference between the vehicle ascending speed and the vehicle descending speed, or compensation is made for it. Therefore, the control was complicated.

On the other hand, in the fluid suspension circuit of the present invention,
Since the effective passage cross-sectional area of the high-pressure passage from the high-pressure reservoir tank to the fluid suspension is set smaller than the effective passage cross-sectional area of the low-pressure passage from the fluid suspension to the low-pressure tank, such pressure difference is canceled out, The difference between the fluid supply speed to the suspension and the discharge speed can be reduced. For this reason, the vehicle height ascending speed and the descending speed become substantially equal to each other, and it is possible to perform the riding height adjustment that is naturally felt by the occupant of the vehicle. Further, even when other control is performed, the calculation of the valve opening / closing time at the time of supplying and discharging the fluid is simplified, and quick control can be performed.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an air suspension system for a vehicle according to an embodiment of the present invention. 33,33R …… High pressure reservoir tank, 34,34R …… Low pressure reservoir tank, 35,35R …… Reservoir high pressure valve, 40,40a, 4
0R …… Air supply pipe, 41,41a, 41R …… Exhaust pipe, 50,50FR, 50RL, 50RR …… Air chamber 56,56FR, 56RL, 56RR …… Leveling valve 58,58FR, 58RL, 58RR …… Discharge valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hajime Uezama 1 Toyota-cho, Toyota-shi, Aichi Prefecture Toyota Motor Corporation (56) References JP 61-64509 (JP, A) JP 60- 110516 (JP, A) Actually open Sho 60-26909 (JP, U)

Claims (2)

[Scope of utility model registration request] 1. A high-pressure passage having a fluid suspension provided on a wheel of a vehicle and a first valve, the high-pressure passage supplying high-pressure fluid to the fluid suspension by opening the first valve, and the high-pressure passage. A high pressure reservoir tank, a second valve, a low pressure passage for discharging the fluid from the fluid suspension by opening the second valve, and a low pressure reservoir tank provided in the low pressure passage. A circuit for fluid suspension of a vehicle, comprising: a circuit for fluid suspension of a vehicle, wherein an effective passage sectional area of the high-pressure passage is smaller than an effective passage sectional area of the low-pressure passage. 2. The high-pressure reservoir tank is connected to the high-pressure passage through a third valve, and the low-pressure reservoir tank is directly provided in the low-pressure passage.
The circuit for fluid suspension of a vehicle according to claim 1, wherein the effective passage sectional area of the high-pressure passage is smaller than the effective passage sectional area of the low-pressure passage.