JPH0671889B2 - Positive displacement pump controller - Google Patents

Description

TECHNICAL FIELD The present invention relates to a control device for a positive displacement pump such as a vane pump that supplies a working fluid to a fluid pressure actuator such as a power steering device.

[Prior art]

Conventionally, as shown in FIG. 3, for example, a control device for a positive displacement pump of this type has a cylinder 21 and a spool 22 slidably provided inside the cylinder 21 and a first chamber 23 on both sides of the spool 22 in the cylinder 21. The flow control valve 20 having the second chamber 24 is formed, and the inlet port 25 and the outlet port 26 opening to the first chamber 23 are connected to the discharge port and the suction port of the positive displacement pump 1, respectively. The discharge port of the positive displacement pump 1 is connected to a fluid pressure actuator 10, such as a servo valve 11 and a power cylinder.
A control throttle 4 is provided in the supply passage 2 connected to the power steering device consisting of 12, and the second chamber 24 is connected to the downstream side of the control throttle 4 in the supply passage 2 via the control passage 7 to connect to the fluid pressure actuator. The control flow rate to be supplied to 10 is controlled. That is, while the pump rotation speed is small, the control flow rate characteristic matches the discharge flow rate characteristic of the positive displacement pump 1 and increases in proportion to the pump rotation rate, but the pump rotation rate increases and the discharge flow rate exceeds a predetermined value. If the pressure loss before and after the control throttle 4 exceeds a predetermined value, the spool 22 is spring-loaded due to the pressure difference between the two sides.
Move against 27 and open exit port 26, return passage 3
The excess discharge flow rate is bypassed to the suction port of the positive displacement pump 1 via the so that the control flow rate characteristic becomes a constant value.

[Problems to be solved by the invention]

In the above-mentioned conventional technique, a predetermined amount of pressure fluid is always supplied to the fluid pressure actuator 10 via the latter half 2b of the supply passage 2 regardless of the operating state of the fluid pressure actuator 10. Since the fluid pressure actuator 10 has a constant flow resistance even in the inactive state, in this inactive state, the predetermined amount of the pressure fluid loses pressure due to the flow resistance of the control throttle 4, the fluid pressure actuator 10 and the piping. And the pressure loss also occurs at the outlet port 26 in response to this, which causes a problem that the positive displacement pump 1 consumes useless energy.

The present invention reduces wasteful energy consumption by the vane pump 1 when the fluid pressure actuator 10 is inactive and the required load pressure is low, for example, when the steering wheel is not operated in the power steering apparatus. The control flow rate characteristic when the fluid pressure actuator 10 is activated and the required load pressure becomes high is intended to be maintained at the same level as the conventional one.

[Means for solving problems]

To this end, the control device for a positive displacement pump according to the invention is
As shown in the embodiment of FIGS. 1 and 2, the cylinder 21 and the spool 22 slidably provided inside the cylinder 21
An inlet port that forms a flow control valve 20 having a first chamber 23 and a second chamber 24 on both sides of a spool 22 inside a 21 and opens to the first chamber 23
25 and the outlet port 26 are respectively connected to the discharge port and the suction port of the positive displacement pump 1, and the control passage 4 is provided in the supply passage 2 connecting the discharge port of the positive displacement pump 1 to the fluid pressure actuator 10. The upstream side of the throttle 4 is connected to the first chamber 23, and the downstream side of the control throttle 4 is connected to the second chamber 23.
A control device for a positive displacement pump that is connected to a control valve 24 and controls the opening of the outlet port 26 by sliding the spool 22 by the differential pressure across the control throttle 4.
Inside the switching cylinder 41, a switching cylinder 41 having a first port 46 connected to 36 and a second port 47 connected to the second chamber 24 and a switching spool 42 slidably provided therein. Of the switching spool 42 is provided with a pressure receiving chamber 43 connected to the downstream side of the control throttle 4 in the supply passage 2, and the switching spool is increased according to an increase in pressure applied to the pressure receiving chamber 43.
The switching valve 40 is formed so that the first port 46 and the second port 47 are slid to communicate with each other when the pressure is small, and are not communicated with each other when the pressure is large.

[Action]

When the fluid pressure actuator 10 is in the inoperative state, the pressure on the downstream side of the control throttle 4 is small, so the pressure in the pressure receiving chamber 43 is also small, and the first port 46 and the second port 47 of the switching valve 40 are communicated with each other. The second chamber 24 of the flow control valve 20 communicates with the discharge passage 36. Therefore, the pressure in the second chamber 24 of the flow rate control valve 20 becomes almost zero, and the spool 22 moves to the first chamber 23 as shown in FIG.
The pressure inside causes the outlet port 26 to fully open. Therefore, in this state, almost all of the working fluid discharged from the positive displacement pump 1 is returned to the return passage 3 without pressure loss.
To be bypassed. When the fluid pressure actuator 10 operates, the pressure on the downstream side of the control throttle 4 increases, so the pressure receiving chamber 43
The internal pressure also becomes large, so that the first port 46 and the second port 47 are not communicated. Therefore, in this state, the second chamber 24 of the flow control valve 20 is communicated only with the downstream side of the control throttle 4, and the control flow characteristic similar to that of the conventional technique shown in FIG. 3 is obtained.

〔The invention's effect〕

As described above, according to the present invention, the fluid pressure actuator 10
In the non-operating state, almost all of the working fluid from the positive displacement pump is bypassed without pressure loss and is not supplied to the fluid pressure actuator, so that wasteful energy is not consumed. Similar control flow characteristics can be obtained. Moreover, in order to obtain the controlled flow rate characteristic, the flow rate control valve that has been conventionally provided is used, and this is controlled by the switching valve to perform the bypass without pressure loss, so that the structure may be so complicated. Absent.

〔Example〕

The embodiment shown in FIGS. 1 and 2 will be described below.
The flow rate control valve 20 is composed of a cylinder 21 and a spool 22 provided therein so as to be slidable in the axial direction. Inside the cylinder 21, a first chamber 23 and a second chamber 24 are formed on both sides of the spool 22. An inlet port 25 and an outlet port 26 are opened in the first chamber 23 with an axial gap therebetween, and the outlet port 26 is provided closer to the spool 22 than the inlet port 25. Entrance port 25
Is communicated with the discharge port of the vane pump (volumetric pump) 1 through the first half 2a of the supply passage 2, and the outlet port
Reference numeral 26 communicates with the suction port of the vane pump 1 via the return passage 3. A spool 22 is provided in the second chamber 24 and a spool 23 is provided in the first chamber 23.
Is provided with a spring 27 that urges it toward the side, and in the free state, the land portion on the first chamber 23 side of the spool 22 is the outlet port.
26 is closed or has a small opening (see FIG. 2).

The first chamber 23 communicates with the fluid pressure actuator 10 through the latter half 2b of the supply passage 2, and the control throttle 4 is provided in a part of the latter half 2b. The fluid pressure actuator 10
In the illustrated embodiment, the power steering apparatus for an automobile comprises a servo valve 11 and a power cylinder 12.
Responds to the manual steering torque applied to the steering wheel, controls the working fluid supplied from the supply passage 2 and sends it to the power cylinder 12 to give an assisting force to the steering device, and the working fluid after use is discharged from the discharge passage 5. It is returned to the reservoir 6.

In the illustrated embodiment, the control throttle 4 is formed in a part of the cylinder 2, and a rod 28a that coaxially passes through the first chamber 23 is fixed to the spool 22 and the plunger 2 is attached to the tip thereof.
8 is provided, the rod 28a is located in the control throttle 4 when the spool 22 has a small opening of the outlet port 26 (see FIG. 2), and when the spool 22 has the outlet port 26 fully opened. The plunger 28 is located in the control diaphragm 4 (see FIG. 1) so that the effective aperture area of the control diaphragm 4 is made small.

In the present embodiment, the control passage connecting the second chamber 24 of the flow control valve 20 and the downstream side of the control throttle 4 of the supply passage 2 is connected.
A switching valve 40 is provided on 30. Switching valve 40 is switching cylinder 41
And a switching spool 42 axially slidably provided therein. A pressure receiving chamber 43 and a low pressure chamber 45 are formed on both sides of the switching spool 42 in the switching cylinder 41.
A switching valve chamber 44 is formed between the left and right lands. In the switching cylinder 41, three ports 46, 47, 48 are opened from the pressure receiving chamber 43 side toward the low pressure chamber 45 side, and the second port 47 is formed.
Is always open to the switching valve chamber 47, and the first and third ports 46,4
8 is selectively opened / closed by sliding of the switching spool 42 and communicated with the switching valve chamber 47. The first port 46 is connected to the reservoir 6 through the discharge passage 36, and the second port 47 is connected to the rear half 30 of the control passage 30.
The third port 48 communicates with the second chamber 24 of the flow rate control valve 20 via b via the front half 30a of the control passage 30 to the downstream side of the control throttle 4 of the supply passage 2. Also, the pressure chamber
43 is connected to the downstream side of the control throttle 4 by the pilot passage 35, and the low pressure chamber 45 is connected to the reservoir 6 by the discharge passage 37. A spring 49 for urging the switching spool 42 toward the pressure receiving chamber 43 side is provided in the low pressure chamber 45. Switching valve 40
In the free state, the switching spool 42 of
Is located on the pressure receiving chamber 43 side, and the second port 47 is connected to the first port 46.
When the pressure receiving chamber 43 receives a predetermined pressure or more, it is located on the low pressure chamber 45 side against the spring 49 and connects the second port 47 to the third port 48.

Next, the operation of the above-described embodiment of the power steering system for an automobile will be described. In the state where the steering wheel is not steered, the working fluid sent to the power steering apparatus 10 through the second half 2b of the supply passage 2 is returned from the discharge passage 5 to the reservoir 6 through the bypass passage in the servo valve 11. In this state, the flow resistance of the servo valve 11 is relatively small, and therefore the pressure on the downstream side of the control throttle 4 is also relatively low. Therefore, as shown in FIG. 1, the switching spool 42 of the switching valve 40 has a spring 49. It is pushed by the force and is located on the pressure receiving chamber 43 side. Therefore, the second chamber 24 of the flow control valve 20 is communicated with the reservoir 6 from the latter half 30b of the control passage 30 through the second port 47, the switching valve chamber 44, the first port 46 and the discharge passage 36 so that the internal pressure is zero. Therefore, the spool 22 is moved to the second chamber 24 side most against the spring 27 by the internal pressure of the first chamber 23, and the outlet port 26 is fully opened.
Through the first half 2a of the supply passage 2, almost all of the working fluid supplied from the vane port 1 to the flow control valve 20 is returned to the vane pump 1 through the return passage 3 without pressure loss.

When the steering wheel is steered, the servo valve 11 responds to the applied manual steering torque, controls the working fluid supplied from the latter half 2b of the supply passage 2 and sends it to the power cylinder 12, so the latter half of the supply passage 2 is controlled. The pressure in 2b rises. This increased pressure is transmitted to the pressure receiving chamber 43 of the switching valve 40 via the pilot passage 35, and thus the switching spool 42 moves to the low pressure chamber 45 side against the biasing force of the spring 49, as shown in FIG. .
As a result, the second chamber 24 of the flow control valve 20 passes from the second half 30b of the control passage 30 through the second port 47, the switching valve chamber 44, the third port 48 and the first half 30a to the control throttle 4 of the supply passage 2. It is connected to the downstream side. That is, in this state, if the amount of working fluid supplied from the inlet port 25 increases or decreases due to fluctuations in the rotational speed of the vane pump 1 driven by the engine, the spool 22 of the flow control valve 20 moves and the outlet port 25 moves.
The opening of 26 is automatically changed so that the control flow rate supplied to the power steering device 10 through the control throttle 4 becomes almost constant, and is controlled by the servo valve 11 to be supplied to the power cylinder 12. Apply normal unstall force to the steering system. Further, in this state, if the rotation speed of the vane pump 1 further increases and exceeds a predetermined value, the effective area of the control throttle 4 is reduced by the plunger 28, and the control flow rate characteristic is further reduced in the high rotation speed range. Will be available. The amount of working fluid supplied to the fluid pressure actuator 10 through the latter half 2b of the supply passage 2 is sucked into the vane pump 1 from the reservoir 6 through the suction passage 3a.

Although the above embodiment has been described with respect to the case where the fluid pressure actuator 10 is a power steering device for an automobile, the present invention has a certain load pressure due to the flow resistance in the inactive state, and this load pressure is obtained in the operating state. Can be applied as long as it is a fluid pressure actuator 10 having a characteristic of increasing, and the positive displacement pump 1 is not limited to a vane pump, but can be a positive displacement pump that continuously supplies a working fluid such as a gear pump or a screw pump. can do.

[Brief description of drawings]

1 and 2 are structural views of an embodiment of a control device for a positive displacement pump according to the present invention, showing operating states at a low pressure and a high pressure, respectively, and FIG. 3 is a structural view of a prior art. Explanation of symbols 1 ... Positive displacement pump, 2 ... Supply passage, 4 ... Control throttle, 10 ... Fluid pressure actuator, 20 ... Flow control valve,
21 ... Cylinder, 22 ... Spool, 23 ... First chamber, 24 ...
… Second room, 25 …… Inlet port, 26 …… Exit port, 36…
… Discharge passage, 40 …… Switching valve, 41 …… Switching cylinder, 42…
… Switching spool, 43 …… Pressure receiving chamber, 46 …… First port, 47
…… Second port, 48 …… Third port.

Claims (1)

[Claims] 1. A flow control valve having a first chamber and a second chamber is formed on both sides of a spool in a cylinder by a cylinder and a spool slidably provided in the cylinder, and the flow control valve is opened in the first chamber. The inlet port and the outlet port are respectively connected to the discharge port and the suction port of the positive displacement pump, and a control throttle is provided in the supply passage that connects the discharge port of the positive displacement pump to the fluid pressure actuator. Is connected to the first chamber, the downstream side of the control throttle is connected to the second chamber, and the spool is slid by the differential pressure before and after the control throttle to control the opening of the outlet port. In a positive displacement pump control device, a switching cylinder having a first port connected to a discharge passage and a second port connected to the second chamber and a switching spool slidably provided therein A pressure receiving chamber connected to a downstream side of the control throttle in the supply passage is provided on one side of the switching spool in the switching cylinder, and the switching spool is slid according to an increase in pressure applied to the pressure receiving chamber. A control device for a positive displacement pump, wherein a switching valve is formed so that the port and the second port are communicated with each other when the pressure is small and are not communicated with each other when the pressure is large.