JP4305280B2 - Vehicle height adjustment device - Google Patents

Description

  The present invention relates to a vehicle height adjusting device capable of changing a spring constant.

  2. Description of the Related Art Conventionally, there has been known a vehicle height adjusting device in which a communication valve that closes only when air from an air spring is discharged is provided between an air spring and an air chamber that communicates with the air spring (for example, a patent) Reference 1). According to this vehicle height adjusting device, when the vehicle height is lowered, the communication valve is closed, so that the air in the air chamber is not discharged and only the air spring air is discharged. The amount of time required for vehicle height adjustment can be shortened by reducing the amount.

In addition to the above-described pneumatic vehicle height adjusting device, a hydraulic vehicle height adjusting device having a sub gas spring for changing the spring constant is known in addition to the main gas spring (see, for example, Patent Document 2). . In this hydraulic vehicle height adjusting device, the spring constant is changed by connecting / disconnecting the flow path with the auxiliary gas spring using a communication valve. And, like the above air type vehicle height adjustment device, when it is desired to rapidly lower the vehicle height when getting on and off, by closing the communication valve in order to make the flow path with the auxiliary gas spring non-communication The amount of oil discharged can be reduced and the time required for vehicle height adjustment can be shortened.
Japanese Utility Model Publication No. 5-76810 JP 60-25810 A

  Incidentally, in order to reduce the required hydraulic pressure level and reduce power loss, it is common practice to use an absorber and a coil spring together. In the case of such a vehicle height adjusting device, the oil in the hydraulic cylinder is discharged in a state in which the communication valve is closed in order to make the flow path to the auxiliary gas spring non-communication as in the prior art described above. As the vehicle height is lowered, the shared load of the coil spring increases, the spring bends, and the internal pressure of the hydraulic cylinder decreases. At this time, the pressure in the auxiliary gas spring remains maintained because the communication valve is closed. However, in general, the communication valve has a structure that opens when power is not supplied to the communication valve due to ignition OFF or the like (normally open). For this reason, when the communication valve that has been closed due to a drop in vehicle height is opened due to ignition OFF or the like, oil with high pressure in the auxiliary gas spring flows into the hydraulic cylinder, and a sudden change in vehicle height may occur. .

  Even when the coil spring is not used together, the same phenomenon may occur. In other words, when you are hitting the bound stopper when the vehicle height drops, in order to further lower the vehicle height, you must lower the internal pressure of the hydraulic cylinder, but at that time the high pressure oil in the auxiliary gas spring flows If it comes, the vehicle height will rise rapidly.

  Accordingly, an object of the present invention is to provide a vehicle height adjusting device that suppresses a sudden change in vehicle height even after the power is turned off.

In order to solve the above problems, according to one aspect of the present invention,
A fluid pressure cylinder communicates with the fluid chamber of the gas spring partitioned into the fluid chamber and the gas chamber, and by opening and closing a first communication valve provided in a flow path between the fluid chamber and the fluid pressure cylinder, In the vehicle height adjustment device that makes the spring constant of the suspension variable,
The previous SL gas spring comprises a differential pressure reducing means for reducing the pressure difference between the hydraulic cylinder,
The differential pressure reducing means is
A bypass flow path for bypassing the first communication valve;
A second communication valve for opening and closing the flow of the bypass flow path;
An orifice for restricting circulation of the bypass flow path,
After the first communication valve and the second communication valve are closed, and before the first communication valve is opened due to a power cut-off, the second communication valve is opened and the orifice is passed through the orifice. Thus, there is provided a vehicle adjustment device that reduces the differential pressure by circulating the bypass path . As a result, even if power is not supplied to the first communication valve due to ignition OFF or the like and the valve is opened, the differential pressure between the gas spring and the hydraulic cylinder is reduced. Sudden changes in vehicle height due to inflow can be suppressed.

For example , the pressure difference between the gas spring and the hydraulic cylinder is reduced by turning off the second communication valve for a certain period of time after shutting off the power supply by turning off the ignition, etc. Sudden changes in vehicle height can be suppressed.

  According to the present invention, a sudden change in the vehicle height can be suppressed even after the power is shut off.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing an example of a schematic configuration of a vehicle height adjusting device according to the present invention. In brief, the vehicle height adjusting device includes a hydraulic cylinder 1, a main gas spring 15, a sub gas spring 7, and a first communication valve 17. Further, a bypass flow path 14 that bypasses the first communication valve 17 is set, and a second communication valve 18 and an orifice 16 are provided on the bypass flow path 14.

  The hydraulic cylinder 1 is attached to the vehicle body, and a piston 2 is slidably fitted in the hydraulic cylinder 1. The piston 2 includes a piston body 2a and a piston rod 2b. The piston body 2a partitions the hydraulic cylinder 1 into a cylinder upper chamber 3 and a cylinder lower chamber 4, and the piston rod 2b has a lower arm and a wheel knuckle (not shown) at its lower end. ). The piston body 2a has a hole connecting the cylinder upper chamber 3 and the cylinder lower chamber 4, and the vehicle height can be changed by controlling the pressure in the hydraulic cylinder 1. That is, when a pressure in the hydraulic cylinder 1 is applied, the vertical force F generated can be expressed as F = A × P (A: rod cross-sectional area, P: pressure in the hydraulic cylinder 1).

  The oil supplied to the hydraulic cylinder 1 is stored in a reservoir (not shown). Oil is supplied from the reservoir to the hydraulic cylinder 1 by rotating a pump (not shown). Conversely, when a discharge valve (not shown) communicating with the hydraulic cylinder 1 is opened, the oil in the hydraulic cylinder 1 is discharged to the reservoir.

  The main gas spring 15 has a function of absorbing unevenness input from the road surface. Further, a damping force switching mechanism (not shown) may be provided between the cylinder upper chamber 3 and the main gas spring 15, and the main gas spring 15 and the damping force switching mechanism may absorb and attenuate the uneven input from the road surface. . The main gas spring 15 is partitioned by a diaphragm 10 between a gas chamber 11 in which a gas such as high-pressure nitrogen is sealed and a liquid chamber 13 communicating with the cylinder upper chamber 3.

  The cylinder upper chamber 3 also communicates with the auxiliary gas spring 7 and the flow path 6. Similar to the main gas spring 15, the sub gas spring 7 is partitioned by a diaphragm 9 between a gas chamber 12 in which a gas such as high-pressure nitrogen is sealed and a liquid chamber 8 communicating with the cylinder upper chamber 3. ing. A first communication valve 17 is provided in the flow path 6, and the spring constant of the suspension can be made variable by opening and closing it. That is, the spring constant is changed by opening and closing the first communication valve 17 and changing the volume of the chamber filled with oil. By opening the first communication valve 17 and lowering the spring constant, for example, it is possible to improve riding comfort during straight traveling. On the other hand, by closing the first communication valve 17 and increasing the spring constant, for example, the amount of roll during steering can be suppressed.

  The first communication valve 17 is also used when it is desired to rapidly lower the vehicle height when getting on and off. In this case, it is necessary to discharge the oil in the cylinder upper chamber 3. However, since the oil in the auxiliary gas spring 7 is also discharged together through the cylinder upper chamber 3, it takes extra time to adjust the vehicle height accordingly. For this reason, by closing the first communication valve 17, the oil in the auxiliary gas spring 7 is not discharged, but only the oil in the cylinder upper chamber 3 is discharged. The time required for high adjustment is shortened.

  Although the main gas spring 15 and the auxiliary gas spring 7 are provided in each wheel, for example, one front wheel and one rear wheel may be provided.

  Further, a bypass passage 14 that bypasses the first communication valve 17 is provided. The bypass passage 14 includes a second communication valve 18 that opens and closes the flow of the bypass passage 14 and an orifice 16 that restricts the flow.

  Note that the opening and closing of the first communication valve 17 and the second communication valve 18 are controlled by a not-shown electronic control device (hereinafter referred to as ECU) according to a control operation described later.

  Next, the operation of the vehicle height adjusting device according to the embodiment of the present invention will be described with reference to FIG. FIG. 2 is a flowchart showing the control operation of the vehicle height adjusting device according to the present invention. First, in step 10, the vehicle height down switch is turned on to set the target vehicle height. This vehicle height down switch may be operated by the driver, or may be a vehicle height down signal determined by the ECU.

The ECU that has recognized the vehicle height down switch ON closes the first communication valve 17 and disconnects the flow path 6 to reduce the amount of oil discharged to shorten the vehicle height adjustment time (step 20). . At this time, it is assumed that the second communication valve 18 is closed and the bypass flow path 14 is not in communication. Then, the discharge valve communicating with the cylinder upper chamber 3 is opened, and the oil in the hydraulic cylinder 1 is discharged to the reservoir, thereby lowering the target vehicle height (step 30). The ECU determines whether or not the vehicle height has reached the target vehicle height (step 40). If the vehicle height has reached the target vehicle height, the ECU closes the discharge valve to stop oil discharge (step 50). If the target vehicle height has not been reached, the discharge valve remains open until the target vehicle height is reached.

  If the ignition is turned off after reaching the target vehicle height (step 60), the second communication valve 18 is opened, and the oil in the auxiliary gas spring 7 is discharged via the orifice 16 on the bypass passage 14. Flow into the hydraulic cylinder 1 (step 70). At this time, in order to adjust the deviation from the target vehicle height due to the oil flowing into the hydraulic cylinder 1, the discharge valve is opened again until the target vehicle height is reached (steps 80, 90). When the target vehicle height is reached, the discharge valve is closed (step 100).

  Next, the second communication valve 18 is kept open until a predetermined time elapses to maintain the flow of the bypass flow path 14 (S110), and then the second communication valve 18 is closed to bypass the flow path. 14 is disconnected (S120). That is, when the second communication valve 18 is opened for a certain period of time and the oil slowly flows due to the effect of the restriction of the orifice 16, the differential pressure between the auxiliary gas spring 7 and the hydraulic cylinder 1 is reduced or eliminated, and suddenly It is possible to suppress changes in vehicle height. The predetermined time is preset in design according to the amount of oil in the auxiliary gas spring 7 and the flow rate per unit time through which the orifice 16 can flow, and the differential pressure is sufficiently reduced or eliminated. Value.

  Therefore, even if the driving current or the driving power source of the first communication valve 17 is shut off after a certain time has elapsed and the first communication valve 17 is opened, the differential pressure between the auxiliary gas spring 7 and the hydraulic cylinder 1 is reduced. Since it is eliminated, a sudden change in vehicle height due to the inflow of oil from the auxiliary gas spring 7 does not occur.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  For example, in steps 110 and 120 in FIG. 2, the second communication valve 18 is closed after a predetermined time has elapsed, but the differential pressure between the auxiliary gas spring 7 and the hydraulic cylinder 1 is monitored. A delay circuit that cuts off the drive current or drive power of the first communication valve 17 after the monitored differential pressure value is sufficiently reduced or eliminated may be provided.

  Further, although the embodiment of the hydraulic vehicle height adjusting device has been described as described above, the present invention intends to solve the same problem with an air suspension that switches the air spring constant by increasing or decreasing the air volume. The problem to be solved can be solved. FIG. 3 shows a cross-sectional shape of one air suspension. The air suspension is provided with a main air chamber and a sub air chamber which are connected via a shutoff valve. The spring constant is switched by switching the air volume by opening and closing the shut-off valve. When it is desired to lower the vehicle height, the sub air chamber and the main air chamber are disconnected from each other by a shutoff valve. In other words, the problem to be solved by the present invention can be solved by providing an orifice and a communication valve for bypassing the shutoff valve and operating the vehicle height adjusting device similar to the above-described embodiment by the same control operation. it can.

It is a figure showing an example of the schematic structure of the vehicle height adjusting device of the present invention. It is one flowchart which shows the control action of the vehicle height adjustment apparatus of this invention. It is a figure which shows the cross-sectional shape of one air suspension.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydraulic cylinder 3 Cylinder upper chamber 7 Sub gas spring 14 Bypass passage 15 Main gas spring 16 Orifice 17 1st communication valve
18 Second communication valve

Claims (3)

A fluid pressure cylinder communicates with the fluid chamber of the gas spring partitioned into the fluid chamber and the gas chamber, and by opening and closing a first communication valve provided in a flow path between the fluid chamber and the fluid pressure cylinder, In the vehicle height adjustment device that makes the spring constant of the suspension variable,
The previous SL gas spring comprises a differential pressure reducing means for reducing the pressure difference between the hydraulic cylinder,
The differential pressure reducing means is
A bypass flow path for bypassing the first communication valve;
A second communication valve for opening and closing the flow of the bypass flow path;
An orifice for restricting circulation of the bypass flow path,
After the first communication valve and the second communication valve are closed, and before the first communication valve is opened due to a power cut-off, the second communication valve is opened and the orifice is passed through the orifice. And reducing the differential pressure by circulating the bypass path . 2. The vehicle adjusting device according to claim 1, wherein when the second communication valve is opened, a discharge valve communicating with the hydraulic cylinder is opened until a vehicle height reaches a target vehicle height. The vehicle adjusting device according to claim 2, wherein the second communication valve is closed after the discharge valve is closed.

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