JP3023558B2 - Suspension device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a suspension device for controlling the attitude of a vehicle.

(Prior Art) In a suspension device such as an active suspension, which can control the attitude of a vehicle, a cylinder of a suspension unit is used to adjust the height of the vehicle and to suppress a change in the attitude of the vehicle caused by rolling during driving. The pressure fluid is appropriately supplied and discharged, and a pressure source for supplying the pressure fluid to the suspension unit is provided.

Conventionally, there has been a suspension apparatus of this type, for example, as shown in FIG.

This is composed of a suspension unit 1 and a pressure source 2 for supplying a pressure fluid (oil liquid) to the suspension unit 1. The suspension unit 1 moves wheels (not shown) to a vehicle body (not shown). A cylinder 3 for moving the vehicle relatively up and down, and a supply line 4 for supplying a pressure fluid from a pressure source 2 to the cylinder 3 and a reservoir (tank) for controlling the posture of the vehicle body. A control valve 7 for appropriately switching the return line 5 for returning the pressure fluid to 6 to supply / discharge the pressure fluid to / from the cylinder 3, an accumulator 8 connected to the cylinder 3 and serving as a spring element, and a control valve 7 for the cylinder 3 and the accumulator 8 And a damping force generating mechanism 9 for generating damping force. In addition,
The control valve 7 is an electromagnetic three-port three-position switching valve. In the position, the pressure fluid is supplied from the pressure source 2 to the cylinder 3 to increase the vehicle height. In the position, the pressure fluid is returned from the cylinder 3 to the reservoir 6. The vehicle height is lowered, and the position is a neutral position in which the supply and discharge of the pressure fluid is not performed. The amount of supply and discharge of the pressure fluid to and from the cylinder 3 is set by the valve opening time or the valve opening amount of the control valve 7.

The pressure source 2 is operated by the rotation of the engine E of the vehicle, and supplies a fixed displacement pump 11 that sucks and discharges the pressure fluid in the reservoir 6 through the pipe 10 and supplies the fixed displacement pump 11 and the suspension unit 1. An accumulator 13 provided in the middle of a pipe 12 connecting the pipe 4 and storing the pressurized fluid; a check valve 14 for preventing backflow of the pressurized fluid from the accumulator 13 to the fixed displacement pump 11; Constant flow rate control for supplying a pressure fluid at a predetermined flow rate regardless of the number of rotations of the pump, and the pressure fluid discharged from the fixed displacement pump 11 when the supply pressure of the pressure fluid to the suspension unit 1 reaches a predetermined value. And a control mechanism 15 for performing unload control for returning to the reservoir 6.

The constant flow rate control by the control mechanism 15
A throttle 16 is provided in the middle, and a flow control valve 18 at two ports and two positions is provided in a pipe 17 connecting the fixed capacity pump 11 side of the throttle 16 and the pipe 10. This is operated when the pressure difference between the front and the rear becomes larger than a predetermined value, and a part of the pressure fluid discharged from the fixed displacement pump 11 is returned to the pipeline 10.

In the unload control, a 2-port 2-position switching valve 20 is provided in a pipe 19 connecting the pipe 12 and the return pipe 5, and the switching valve 20 is connected between the check valve 14 and the suspension unit 1. When the pressure of the pressure fluid reaches a predetermined value, the pressure fluid is switched to return the pressure fluid discharged from the fixed displacement pump 11 to the reservoir 6.

In the drawing, R is a relief valve for returning the pressure fluid to the pipeline 10 when the pressure of the pressure fluid abnormally rises, for example, when the switching valve 20 for performing the unload control is damaged, In the figure, C denotes a cooling pipe for cooling the pressurized fluid which has been compressed in the fluid circuit and has become high temperature.

To explain the operation of this conventional suspension device,
The rotation of the engine E activates the fixed displacement pump 11 to draw fluid from the reservoir 6 and to drive the suspension unit 1
The fluid is discharged to the side and the pressurized fluid is stored in the accumulator 13. At this time, when the number of revolutions of the engine E increases and the discharge flow rate of the pressure fluid from the fixed displacement pump 11 increases,
When the pressure difference before and after the pressure increases, the flow control valve 18 starts operating and part of the pressure fluid discharged from the fixed displacement pump 11
Return to 10 and only the specified flow rate
Is not supplied. When the supply pressure of the pressure fluid supplied to the suspension unit 1 reaches a predetermined value, the switching valve
20 is switched, the pressure fluid flows to the return line 5, and the unload control is performed.

(Problems to be Solved by the Invention) However, the above-mentioned conventional suspension device has the following problems.

From the start of the engine E, the fixed displacement pump 11 constantly inhales, compresses and discharges the pressurized fluid with a constant displacement volume, and the discharge flow rate increases in proportion to the rotation speed of the engine E. On the other hand, the amount of pressure fluid to be supplied / discharged to / from the suspension unit, that is, the consumption of the pressure fluid, is limited to a predetermined range without being directly related to the rotation speed of the engine E. The discharge flow rate of the fixed displacement pump 11 is set so that the consumption of the pressure fluid can be secured. For this reason, at the time of high rotation of the engine E, the discharge flow rate of the fixed displacement pump 11 increases with the number of rotations of the engine E, and the fixed displacement pump 11 exceeds the above-mentioned required amount of consumption of the pressure fluid, Compression and discharge are repeated to apply a large load to the engine E, and the discharged excess pressure fluid is returned to the pipeline 10 by the constant flow rate control of the flow rate control valve 18. Will be performed.

In the unload control, the fixed displacement pump 11
Is only returned to the reservoir 6 via the switching valve 20 and the pipeline 19, so that the fixed displacement pump 11
Causes almost no load. For this reason, when the fixed displacement pump 11 repeats the normal compression operation and the unload control operation at the time of high-speed rotation of the engine E, the load on the engine E fluctuates greatly, and the shock at the time of the switching is changed by the occupant of the vehicle. And there were problems such as giving discomfort.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a suspension device capable of keeping a discharge flow rate from a pump substantially constant regardless of an increase in the engine speed. Is to do.

(Summary Means for Solving the Problems) The suspension device of the present invention is a suspension device that controls the posture of a vehicle body by supplying and discharging a pressure fluid to and from a suspension unit interposed between the vehicle body side and the wheel side. A pressure source for supplying a pressure fluid to the suspension unit is driven by an engine, and a variable displacement pump capable of continuously controlling a displacement according to a pressure introduced to the variable means; A throttle provided in the side pipe, introducing pressures before and after the throttle as pilot pressure, and communicating the variable means with the reservoir side or the discharge side pipe in accordance with a difference between these pressures, thereby making the variable And a switching valve for controlling the discharge flow rate of the displacement pump to be substantially constant.

(Operation) According to this configuration, when the discharge flow rate of the variable displacement pump changes according to the change in the engine speed, the pressure difference before and after the throttle provided in the discharge side pipe of the variable displacement pump changes, and this pressure changes. The switching valve communicates the variable means of the variable displacement pump with the reservoir side or the discharge side pipe line in accordance with the change in the difference, thereby adjusting the pressure introduced into the variable means,
The discharge flow rate of the variable displacement pump is controlled to be substantially constant, whereby the load on the engine of the variable displacement pump can be maintained substantially constant.

Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a view showing the configuration of the present embodiment, FIG. 2 is a longitudinal sectional view showing an example of a variable displacement pump used in the present embodiment,
FIG. 3 is a sectional view taken along line III-III of FIG. Further, in the configuration of the present embodiment, the suspension unit 1 is the same as that described in the related art, so the same reference numerals are given and the description is omitted, and the pressure source 22 having the control mechanism 21 will be described in detail. .

The engine E of the vehicle includes a variable displacement pump 23 which will be described in detail later.
Is connected, and the variable displacement pump 23
Works. A pipe 25 for sucking fluid (oil liquid) from the reservoir 6 is connected to a suction port 24 of the variable displacement pump 23, and a pipe 27 for supplying a pressure fluid to the suspension unit 1 to a discharge port 26. Is connected. Line 27
Is provided with an accumulator 28 for storing the pressure fluid and a check valve 29 for preventing the pressure fluid from flowing back from the accumulator 28 to the variable displacement pump 23 side.

Here, an example of the variable displacement pump 23 is shown in FIGS.
Description will be made based on the drawings.

A shaft 31 connected to the rotation shaft of the engine E and transmitting the rotation is rotatably supported in the main body 30 by bearings 32 and 33. The shaft 31 has a plurality of cylinder holes in a circumferential direction. The pump cylinder 34 is coupled so as to be relatively displaceable in the axial direction and to rotate integrally with each other in the rotational direction. A pump piston 35 is slidably fitted in each cylinder hole of the pump cylinder 34. One end of the pump piston 35 is formed in a spherical shape, and the spherical portion is formed in a spherical shape corresponding to the sliding member 36. It is received in the recess 36a, and is slidably rotatable within the recess 36a, but is coupled inseparably.

In addition, a tilting member 37 is provided in the main body 30, and the tilting member 37 can be changed in angle by a hemispherical member 38 provided at each one position on both sides of the paper surface in a direction perpendicular to the paper surface of the drawing. The angle is changed according to the movement of a piston 40 (variable means) slidably fitted to a cylinder 39 (variable means) formed in the main body 30. The sliding member 36 is mounted on the inclined surface of the tilting member 37 so as to be slidable in the circumferential direction. The pump is driven by the rotation of the sliding member 36 along the tilting member 37 as the shaft 31 rotates. The piston 35 repeats reciprocating motion in the axial direction within the cylinder hole of the pump cylinder 34.

The tilting member 37 moves until the inclined surface on which the sliding member 36 slides becomes perpendicular to the shaft 31 as shown in FIG. 2, but further movement is not shown. Disabled by means.

The cylinder 39 is provided with a small hole (not shown) at a predetermined position, and the piston 40 moves, so that the inclined surface of the tilting member 37 is substantially perpendicular to the axis of the shaft 31 (for example, about 89 °).
When the piston 40 moves to the position where
The inner chamber communicates with the small hole. The small hole communicates with the suction port 24 through a passage (not shown), and serves as a throttle that slightly releases the pressure fluid in the cylinder 39 to the suction port 24. For this reason,
A predetermined pressure is held in the chamber in the cylinder 39 by allowing the pressure fluid slightly discharged from the variable displacement pump 23 to escape to the suction port 24 through the small hole during the unload control described later.

With this configuration, when the pump piston 35 moves in the extension direction, fluid is sucked into the pump cylinder 34 from the semicircular groove 24a of the suction port 24, and when the pump piston 35 moves in the contraction direction, the discharge port 26 The pressure fluid in the pump cylinder 34 is discharged from the semi-circular groove 26a to perform pumping. At this time, the angle of the inclined surface of the tilting member 37 changes according to the fluid pressure introduced into the cylinder 39. Thus, the discharge flow rate can be continuously changed.

Next, the control mechanism 21 for performing the constant flow rate control and the unload control will be described.

A throttle 41 is provided in the pipeline 27 on the discharge side of the variable displacement pump 23. A three-port, two-position flow control valve 42 (switching valve) that is activated by a pressure difference before and after the throttle 41 is provided. Of the three ports of the flow control valve 42, the pump port P1 is a variable displacement pump. 23, the tank port T1 is connected to the suction side pipe 25 of the variable displacement pump 23, and the cylinder port C1 is connected to the tank port T2 of the switching valve 43 for unload control described later. Have been. And, at the position of the flow control valve 42, the cylinder port
C1 communicates with the tank port T1, and at the position, the pump port P1 communicates with the cylinder port C1.

A switching valve 43 provided for performing unload control by the pressure of the pressure fluid between the check valve 29 and the suspension unit 1 is a three-port two-position switching valve.
Pump port P2 is a variable displacement pump
The tank port T2 is connected to a cylinder port C1 of the flow control valve 42, and the cylinder port C2 is connected to a cylinder 39 formed in the main body 30 of the variable displacement pump 23. ing. At the position of the switching valve 43, the tank port T2 communicates with the cylinder port C2, and at the position, the pump port P2 communicates with the cylinder port C2.

The pipes 44, 45, and 46 shown by broken lines in the figure are pilot pipes, and the flow control valve 42 and the switching valve 43 are appropriately switched according to the pressure detected by the pilot pipes 44, 45, 46.

 The operation of the suspension device having the above configuration will be described.

The operation of the variable displacement pump 23 is started by the rotation of the engine E. At the start, the flow control valve 42, the switching valve 43
Is in the state shown in FIG.
Is activated, and the pressure fluid sucked from the reservoir 6 is discharged to the suspension unit 1 side and stored in the accumulator 28.

When the attitude control of the vehicle is performed, the control valve 7 is appropriately switched to supply and discharge the pressurized fluid to and from the cylinder 3.

When the rotation speed of the engine E increases, the discharge flow rate of the variable displacement pump 23 increases, but a large pressure difference occurs before and after the throttle 41, so that the flow control valve 42 moves in the direction of switching from the position to the position, Pressure fluid is pumped from pump port P1 through cylinder port C1
The tilting member 37, which is introduced into the cylinder 39, is moved in a direction in which the inclination becomes smaller, and the displacement is reduced to return to a predetermined discharge flow rate. Then, the discharge flow rate decreases and the
When the pressure difference before and after 41 becomes smaller and reaches a predetermined pressure difference, the flow control valve 42 moves again in the direction of switching from the position to the position, and the communication between the pump port P1 and the cylinder port C1 is cut off. The introduction of the pressure fluid to the cylinder 39 of the nozzle 23 is stopped, and the predetermined discharge flow rate is maintained. Further, when the rotation speed of the engine E drops from this state, the discharge flow rate of the variable displacement pump 23 decreases, and the pressure difference before and after the throttle 41 decreases. Along with this, the flow control valve 42 further moves in the direction of switching from the position to the position, and the cylinder port C1 communicates with the tank port T1 so that the flow of the pressure fluid introduced into the cylinder 39 of the variable displacement pump 23 is reduced. The part is returned to the reservoir 6. Then, the tilting member 37 moves in the direction in which the tilt increases, the displacement of the variable displacement pump 23 increases, and the tilting member 37 returns to the predetermined discharge flow rate. As described above, the flow rate control valve 42 is appropriately switched according to the pressure difference between before and after the throttle 41, so that the variable displacement pump 23 supplies the suspension unit 1 with a pressure fluid having a substantially constant flow rate.

The rotational speed N of the engine E and the variable displacement pump described above
FIG. 5 shows the relationship between the discharge flow rate Q of 23 and the power consumption P of the engine E.

Next, when the pressure of the pressure fluid in the accumulator 28 becomes larger than a predetermined value, the switching valve 43 switches from the position to the position, and the pressure fluid discharged from the variable displacement pump 23 is supplied to the cylinder 39 of the variable displacement pump 23 and 37 is moved so that the surface on which the sliding member 36 slides becomes almost perpendicular to the axis of the shaft 31. This allows the pump piston
Even if 35 rotates, it moves only slightly in the axial direction, and the variable displacement pump 23 does not perform any operation other than the suction and discharge operations of the pressure fluid to maintain the pressure in the cylinder 39.

As described above, the flow rate of the pressure fluid discharged from the variable displacement pump 23 during the constant flow rate control is made substantially constant, and the discharge amount is made a small amount during the unload control.
Can be greatly reduced.

In this embodiment, the variable displacement pump 23 that changes the discharge amount by the tilting member 37 is used. However, the present invention is not limited to this, and the discharge amount can be changed using the pressure of the pressure fluid. If so, another type such as a vane pump may be used.

(Effect of the Invention) As described above in detail, the present invention provides a pressure source for supplying a pressure fluid to a suspension unit including a variable displacement pump, a throttle and a switching valve, and a variable displacement pump in accordance with a change in engine speed. When the discharge flow rate of
The pressure difference before and after the throttle changes, and the switching valve adjusts the pressure introduced to the variable means by connecting the variable means of the variable displacement pump to the reservoir side or the discharge side pipe in accordance with the change in the pressure difference. Then, since the discharge flow rate of the variable displacement pump is controlled to be substantially constant, the load on the engine can be maintained substantially constant, and the engine output can be improved.

Further, even when the variable displacement pump repeats the normal compression operation and the unload control operation at the time of high-speed rotation of the engine, the range of fluctuation of the load applied to the engine is small. It is almost as small as ever and does not cause any discomfort to passengers.

[Brief description of the drawings]

FIG. 1 is a view showing a configuration of a suspension device according to an embodiment of the present invention. FIG. 2 is a longitudinal sectional view showing an example of a variable displacement pump. FIG. 3 is a sectional view taken along line III-III of FIG. FIG. 4 is a diagram showing an example of the configuration of a conventional suspension device. FIG. 5 is a diagram showing an embodiment of the present invention shown in FIG. It is a figure which shows the relationship with power consumption. 1 ... Suspension unit 21 ... Control mechanism 22 ... Pressure source 23 ... Variable displacement pump 27 ... Pipe line 41 ... Throttle 42 ... Flow control valve

Claims (1)

(57) [Claims] 1. A suspension device for controlling the attitude of a vehicle body by supplying and discharging a pressure fluid to and from a suspension unit interposed between a vehicle body side and a wheel side. A pressure source driven by the engine and capable of continuously controlling a displacement according to a pressure introduced into the variable means; a throttle provided in a discharge-side pipe of the variable capacity pump; The pressure before and after the throttle is introduced as pilot pressure, and the discharge flow rate of the variable displacement pump is controlled to be substantially constant by communicating the variable means with the reservoir side or the discharge side pipe according to the pressure difference. A suspension device, comprising: a switching valve.