JPH0144910B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a variable displacement pump suitable for a power steering device.

<Prior Art> Generally, a pump used in a power steering device is constantly driven by an engine regardless of whether or not the power steering device is in operation. Considering the driving conditions of automobiles, most of the time the steering wheel is not operated, and the pump is operated without load. Therefore, in order to improve the fuel efficiency of automobiles, it is important to keep the power loss during no-load operation of the pump as low as possible.

<Object of the Invention> The object of the present invention is to reduce the amount of eccentricity of the cam ring in a variable displacement pump configured to discharge a required flow rate under load by weakening the pressing force of the cam ring by the spring during no-load operation. The objective is to reduce the flow rate and thereby reduce power loss during no-load operation of the pump.

<Examples> Examples of the present invention will be described below based on the drawings. 1 and 2, 10 indicates a pump housing, and this pump housing 10 includes a front housing 11 and a guide housing 12.
and a rear housing 13. A cam ring 14 is accommodated in the inner hole 12a of the guide housing 12 so as to be movable in the radial direction, and a circumferential pressure fluid passage 15 is formed between the peripheral wall of the inner hole 12a and the outer periphery of the cam ring 14. A rotor 17 is rotatably housed in the cam ring 14 and is held slidably in the radial direction with a large number of vanes 16. are combined.

A suction port 21 communicating with the suction area of the pump chamber and a discharge port 22 communicating with the discharge area of the pump chamber are formed on the inner surface of the front housing 11. Suction port 21 is located in front housing 1
1, and the discharge port 22 communicates with the pressure fluid passage 15.

Elongated holes 11a and 19a are formed in the inner surfaces of the front housing 11 and the pressure plate 19, which face each other with the cam ring 14 in between, and both ends of a seal pin 27 extending in the axial direction are fitted into these elongated holes 11a and 19a. are combined. This seal pin 27 is in fluid-tight contact with the upper peripheral wall of the inner hole 12a of the guide housing 12. Furthermore, a fitting groove 14a into which the seal pin 27 can be fitted is formed in the axial direction at a portion of the outer periphery of the cam ring 14 that faces the seal pin 7. This cam ring 14
is pushed upward by the fluid pressure in the pump chamber, causing the fitting groove 14a to tightly fit into the seal pin 27. As a result, the seal pin 27 is attached to the cam ring 1.
4 so as to be slidable in the left and right direction in FIG.
A seal is formed between the peripheral wall of the inner hole and the outer periphery of the cam ring 14. Further, a fitting recess 12b extending in the axial direction is formed in the lower peripheral wall of the inner hole 12a of the guide housing 12, and a gap adjusting member 28 is disposed in the fitting recess 12b. An orifice 29 is formed between 28 and the outer peripheral surface of the cam ring 14, and the orifice 29 and the seal pin 27 connect the pressure fluid passage 15 to the first pressure action chamber 15A communicating with the discharge port 22 and the discharge port 30. The discharge port 30 is connected to the second pressure action chamber 15B, and the supply port of the power steering device is connected to the discharge port 30.

The guide housing 12 has a hole 35 that opens into the second pressure acting chamber 15B, and a hole 35 that opens into the cam ring 14.
The hole 35 is formed in the radial direction, and one end of the hole 35 is closed by a block 36 fixed to the guide housing 12. Spring receiver 3 is in hole 35
7 is slidably fitted, and this spring receiver 3
A ring pressing spring 38 is interposed between one end of the cam ring 7 and the outer peripheral surface of the cam ring 14, and a balance spring 39 is interposed between the other end of the spring receiver 37 and the block 36. The repulsive force of the ring pressing spring 38 urges the cam ring 14 to the left in FIG.
8 and 39 are held in a balanced position.

A valve hole 41 is communicated with a chamber 40 formed between the block 36 into which the balance spring 39 is inserted and the spring receiver 37.
A first spool 42 is slidably inserted into the first spool 1 by a predetermined amount. The first spool 42 is normally held at the upper end in FIG. 3 by the repulsive force of the spring 43, and in this state, the chamber 40 is connected to the reservoir via a communication path 44 provided in the first spool 42. However, when the first spool 42 is slid by a predetermined amount against the spring 43 due to the pressure inside the chamber 40, the communication between the chamber 40 and the discharge port 45 is interrupted. It's starting to shut down. Further, a relief valve 46 is inserted between the chamber 40 and the discharge port 45, and when the pressure inside the chamber 40 reaches a preset relief pressure, the chamber 40
The pressure within 0 is now released to the outlet 45.

Further, a valve hole 48 is formed in the communication passage 47 that communicates the chamber 40 and the second pressure action 15B, and a second spool 49 is slidably inserted into the valve hole 48, and the repulsive force of the spring 50 It is held at the left end in FIG. 2, which normally closes the communication path 47. The second spool 49 does not respond to the pump internal pressure during no-load operation of the pump, but is slid by a predetermined amount against the spring 50 in response to an increase in the pump internal pressure due to handle operation, and the second spool 49 slides a predetermined amount against the spring 50.
7 is opened by a certain aperture area.

Next, the operation in the above configuration will be explained.

When the pump is operated without load, the internal pressure of the pump is low, so the second spool 49 is held in a position where the communication passage 47 is closed, and the first spool 42 is held in a position where the communication passage 44 is connected to the discharge port 45. It is held in a communicating position, and the chamber 40 is opened to the reservoir side. Therefore, due to the pump internal pressure, the spring receiver 37
is slid against the balance spring 39,
As a result, the cam ring 14 and the spring receiver 37
The ring pressing spring 38 inserted between
Since the repulsive force of the cam ring 14 is reduced, the eccentricity of the cam ring 14 is reduced, and the discharge flow rate is reduced. (Dotted line in Figure 4) When the internal pressure of the pump increases due to the operation of the control valve of the power steering device in conjunction with the steering wheel operation, the second spool 49 slides against the spring 50 due to the pressure, and the communication path 47 is opened by a certain throttle opening degree, and the chamber 40 is communicated with the second pressure application chamber 15B via this communication path 47. Therefore, the pressure within the chamber 40 causes the first spool 42 to slide against the spring 43, thereby blocking communication between the communication path 44 and the discharge port 45. This causes the pressure inside the chamber 40 to rise to the second level.
Since the pressure in the pressure action chamber 15B is maintained at the same pressure, the spring receiver 37 is connected to both springs 38, 3.
9 is held in a balanced position, the pressing force of the ring pressing spring 38 against the cam ring 24 is increased, and the cam ring 14 is displaced in a direction that increases the amount of eccentricity, and the discharge flow rate is required for the power steering device. is increased to a predetermined amount. (Solid line in Figure 2) Also, when the internal pressure of the pump reaches a predetermined relief pressure due to an increase in load, the relief valve 46 is activated and the pressure fluid in the second pressure action chamber 15B is transferred to the reservoir side via the chamber 40 and the relief valve 46. leaks into
At this time, the communication path 4 due to the throttle effect of the communication path 47
A pressure difference is created before and after the spring receiver 3.
A difference arises in the fluid pressure acting on both ends of 7. Therefore, the spring receiver 37 is the balance spring 3
Since the cam ring 14 is slid against the repulsive force of the rotor 17, the pressing force against the cam ring 14 by the ring pressing spring 38 is reduced.
The amount of eccentricity is reduced, the pump discharge flow rate is reduced, and a pressure increase exceeding the relief pressure is suppressed.

<Effects of the Invention> As described above, the present invention reduces the pressing force of the cam ring by the spring to reduce the discharge flow path during no-load operation of the pump, and reduces the discharge flow path by increasing the load pressure. Since the pump is designed to increase the required flow rate, the pump drive horsepower during no-load operation can be significantly reduced.
It will be possible to contribute to improving the fuel efficiency of automobiles.

Moreover, according to the present invention, even when the load pressure reaches the relief pressure, the force exerted by the spring on the cam ring can be reduced to reduce the discharge flow rate, which also has the effect of reducing energy loss during relief. be given

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a cross-sectional view of a variable displacement pump, FIG. 2 is a cross-sectional view taken along the line arrow - in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line arrow in FIG. The cross-sectional view in FIG. 4 is a diagram showing the discharge flow rate versus the pump rotation speed. 10... Pump housing, 14... Cam ring, 15A... First pressure action chamber, 15B... Second
Pressure action chamber, 16... vane, 17... rotor,
21...Suction port, 22...Discharge port, 29
... Orifice, 35 ... Hole, 37 ... Spring receiver, 38 ... Spring for pressing ring, 39
...Balance spring, 40... Chamber, 42...
...First spool, 46... Relief valve, 49...
Second spool.

Claims (1)

[Claims] 1. A cam ring is housed in a pump housing so as to be movable in the radial direction, a rotor holding a plurality of vanes is rotatably housed inside the cam ring, and a discharge passage is connected to a discharge port of the pump. an orifice is provided in the pump housing, the upstream and downstream sides of the orifice are communicated with first and second pressure chambers facing both sides of the cam ring, and the pump housing has a hole that opens into the second pressure chamber. A spring receiver is slidably fitted into this hole, a ring pressing spring is inserted between one end of the spring receiver and the cam ring, and the other end of the spring receiver is connected to the pump housing side. A balance spring is inserted in between, and a first spool is provided which communicates the chamber in which the balance spring is inserted with the reservoir side when the pump is not loaded and cuts off the communication when the pump is loaded. A variable displacement pump comprising a second spool that communicates with the second pressure acting chamber via a throttle when under load and blocks the communication when under no load, and communicates the chamber with the reservoir side through a relief valve. 2. The variable displacement pump according to claim 1, wherein the first and second spools are configured to respond to changes in the internal pressure of the pump.