JPH0326053Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial application field> The invention sends the working fluid discharged from the pump to the power steering device through the throttle passage, and recirculates the surplus flow to the suction side through the bypass passage. The present invention relates to a flow control device for a power steering device.

<Prior Art> In a pump that supplies working fluid to a power steering device, for example, as shown in FIG. 20
A metering orifice 61 and a spool 22 provided in the supply passage 60 divert more than a predetermined amount of fluid to the bypass port 13 , and the diverted fluid is returned to the suction port 2 of the pump P through the first suction passage 63 . Fluid discharged from the hydraulic actuator A is returned to the reservoir 65 through a passage 66. Therefore, the second suction passage 6 supplies the insufficient fluid from the reservoir 65 to the pump P.
4 is opened in the vicinity of the bypass port 13 of the first suction passage 63, and the pump P rotates at high speed by utilizing the supercharge effect due to the ejector effect of the fluid flowing from the bypass port 13 into the first suction passage 63. This prevents cavitation from occurring due to insufficient suction.

<Problems to be solved by the invention> However, in such conventional technology, the pump P rotates at a higher speed (for example, 4000 to 5000 r.pm).
When this happens, the supercharge action reaches its limit, resulting in insufficient suction, causing cavitation and erosion of the rotor, plates, etc. of the pump P, resulting in a problem of reduced durability.

<Means for Solving the Problems> In order to solve the above-mentioned problems, the present invention includes a first restriction passage having a large diameter at the center of the fluid passage, and a first restriction passage having a large diameter in the center of the fluid passage. A second throttle passage with a small diameter is formed on a circumference radially spaced apart from the throttle passage, and a projection that fits into and closes the first throttle passage is provided on the throttle member side of the control spool; and a closing surface having a step and closing the second throttle passage.

<Operation> The present invention opens all of the first and second throttle passages during low-speed rotation, closes only the first throttle passage during medium-speed rotation, and further closes all of the first and second throttle passages during high-speed rotation. and move the control spool to the fully open position. As a result, all the fluid discharged from the pump is bypassed on the suction side, and insufficient suction is eliminated.

<Example> Hereinafter, an example of the present invention will be described based on the drawings. 1 to 3 show an embodiment of a flow rate control device according to the present invention. In this embodiment, a flow rate control device 20 is incorporated in a pump housing 10 of a fluid pump. 20
The main components include a union 21, a spool 22 for adjusting flow rate, a control spool 23, and a throttle member 24 forming a throttle passage.

This pump housing 10 is provided with a storage hole 11 passing through it, a union 21 is screwed into one end of the storage hole 11 in a fluid-tight manner, and a stopper 25 is attached to the other end of the storage hole 11. are fitted in a liquid-tight manner. The outer circumference of the inner end of the union 21 and the storage hole 11
A supply passage 1 provided in the pump housing 10 is provided in between.
2 into the storage hole 11 at all times.
is formed. When the discharge flow rate of the working fluid supplied to the supply passage 12 increases, this fixed throttle 31 causes the supply passage 12 and the storage hole 1 to
It acts to create a pressure difference between the two. Note that the delivery hole 21 formed at the outer end of the union 21
a is connected to a normally open type servo valve device of a power steering device, and a supply passage 12 is communicated with a discharge chamber of a fluid pump.

The spool 22 is connected to the union 21 in the storage hole 11.
The first valve chamber 32 and the second valve chamber 33 are slidably inserted between the stopper 25 and the stopper 25 .
is formed. Further, the spool 22 is biased by a spring 26 interposed in the second valve chamber 33 and comes into elastic contact with the union 21, and the supply passage 12
and a bypass passage 1 provided in the pump housing 10
Communication with 3 has been cut off. Note that the bypass passage 13 communicates with the suction chamber of the fluid pump.

The control spool 23 is slidably inserted into the inner hole of the union 21, and is attached by a spring 27 interposed between it and the throttle member 24 fitted on the outer end side of the inner hole of the union 21. The union 21 is biased to resiliently abut against the inner end step 21b of the inner hole of the union 21. This control spool 23 has a communication hole 23a formed in its center, and a through hole 23d extending diagonally in the outer diameter direction on the throttle member 24 side, and communicates the through hole 23d with the fluid chamber 34. .

As shown in FIG. 2, the aperture member 24 includes:
A first throttle passage 24a with a large diameter is located on the center line of the control spool 23, and a pair of second throttle passages with a small diameter are arranged on a circumference spaced apart in the radial direction around the first throttle passage 24a.
A throttle passage 24b is formed.

Further, on the end face of the control spool 23 on the throttle member 24 side, there is a protrusion 50 that fits into and closes the first throttle passage 24a, and has a step with this protrusion 50 to close the second throttle passage 24b. Occlusion surface 51
is formed.

The first valve chamber 32 and the fluid chamber 3 are connected to each other through the communication hole 23a and the first and second throttle passages 24a and 24b.
4 and the delivery hole 21a of the union 21 are communicated with each other.

The throttle member 24 has first and second throttle passages 24.
In addition to a and 24b, a small hole 24c is formed, and the small hole 24c, the union 2
1 and the communication hole 21 provided in the pump housing 10
It communicates with the second valve chamber 33 through d and 14. As a result, the first and second throttle passages 24a, 24
A part of the downstream fluid b is guided into the second valve chamber 33, and the pressures before and after the first and second throttle passages 24a, 24b act on both end surfaces of the spool 22, and the The spool 22 moves in the axial direction, and the opening degree of the bypass passage 13 is adjusted to maintain the pressure difference constant.

Further, a pressure chamber 40 is formed between the step end surface of the control spool 23 and the inner hole end surface of the union 21. This pressure chamber 40 communicates with the supply passage 12 through a pressure introduction hole 41 provided in the union 21, and the control spool 23 slides against the spring 27 according to the differential pressure before and after the fixed throttle 31. It's getting old.

In the flow control device configured in this way,
When the fluid pump is driven by the vehicle engine,
The working fluid is supplied from the discharge chamber of the fluid pump to the supply passage 12
is supplied to The supplied working fluid is supplied to the first valve chamber 32 through the fixed throttle 31, and from the first valve chamber 32 to the circulation hole 23a, the first and second throttle passages 24.
It is fed from the delivery hole 21a of the union 21 to the power steering device via the channels a and 24b.

By the way, when the rotational speed of the liquid pump is low, the discharge flow rate of the working fluid is small, so the spool 2
2 closes the bypass passage 13 as shown in FIG. 1, and the control spool 23 moves slightly to the right in FIG.
b are not moved unless they are occluded. Therefore, the entire amount of working fluid is transferred to the first and second restricting passages 24.
The flow rate shown at low speed in FIG. 4 is fed to the power steering device through the channels a and 24b.

When the rotational speed of the fluid pump increases to a medium speed, the control spool 23 further moves to the right in FIG. 1, and the protrusion 50 fits into the first throttle passage 24a and closes it. Therefore, the working fluid passes through the small-diameter second throttle passage 24b, reduces the flow rate to the flow rate shown at the middle speed in FIG. 4, and is fed to the power steering device.

In addition, when the fluid pump rotates at a high speed as the vehicle moves to high-speed running and the discharge flow rate of the working fluid supplied to the supply passage 12 increases, the flow resistance in the fixed throttle 31 causes the flow inside the supply passage 12 to increase. As a fluid pressure difference is created, the pressure in the supply passage 12 is introduced into the pressure chamber 40 through the pressure introduction passage 41, pushing the control spool 23 against the spring 27 to the right end as shown in FIG. As a result, the closing surface 51 at the end of the control spool 23 is
The throttle passage 24b is closed and the first,
The second throttle passages 24a and 24b are all closed, and the entire amount of fluid discharged from the pump is bypassed to the bypass passage 13. As a result, the suction efficiency of the pump is improved and cavitation is prevented from occurring.

<Effects of the invention> As described above, in the present invention, a large-diameter first throttle passage and a small-diameter throttle passage are formed in the throttle member provided in the fluid passage, and the control spool has the large-diameter first throttle passage. The configuration includes a protrusion that fits into and closes the first throttle passage, and a closing surface that has a step with the protrusion and closes the small diameter second throttle passage. The flow rate of the working fluid supplied to the power steering system is controlled to be gradually reduced in stages, providing a smooth steering feel and eliminating insufficient suction from the pump during high-speed rotation, which prevents cavitation. It has the effect of preventing

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of the flow control device according to the present invention, showing the state when the pump rotation is stopped. Fig. 2 is a front view of the throttle member, Fig. 3 is a vertical cross-sectional view of the flow control device at high speed, Fig. 4 is a graph showing changes in flow control characteristics with respect to pump rotation speed, and Fig. 5 is the structure of the prior art. It is a diagram. 12... Supply passage, 13... Bypass passage, 2
1a... Delivery hole, 22... Spool valve, 23...
Control spool, 23a...flow hole, 24...throttle member, 24a...first throttle passage, 24b...second
Throttle passage, 50...Protrusion, 51...Closing surface.

Claims (1)

[Scope of utility model registration request] A throttle member is provided in the fluid passage leading from the pump to the power steering device, and the throttle member includes a first throttle passage having a large diameter at the center of the fluid passage, and a circle spaced apart in the radial direction around the first throttle passage. 2nd small diameter on the circumference
A fixed throttle is provided upstream of these throttle passages, and the opening degree of a bypass passage that slides by the pressure of the working fluid before and after the throttle passage and recirculates the excess flow to the inflow side of the pump is adjusted. A flow rate adjustment spool to be adjusted is provided, a control spool is provided that slides by the pressure of the working fluid before and after the fixed throttle passage and has a flow hole, and the control spool is pressed between the control spool and the throttle member. A spring is interposed, and a protrusion that fits into and closes the first throttle passage is formed on the throttle member side of the control spool, and a closing surface that has a step with the protrusion and closes the second throttle passage. A flow control device for a power steering device, characterized by: