JPS6347570Y2 - - Google Patents

Description

[Detailed description of the invention] This invention sends the pressure fluid discharged from the pump to the power steering device through the throttle passage, and the flow rate of the working fluid for power steering that returns the surplus flow to the suction side from the bypass passage. The present invention relates to a control device, particularly a flow rate control device that variably controls an orifice by a control spool that is displaced based on an increase in discharge flow rate due to an increase in pump rotation speed, and lowers the flow rate sent to a power steering device as the pump rotation speed increases. It is something.

In a power steering pump that incorporates a flow rate adjustment valve, a throttle passage is provided in the supply passage through which pressure fluid is discharged, and the pressure difference between before and after the throttle passage is created by an increase in the pump discharge flow rate due to an increase in pump rotation speed. For example, a device that variably controls the orifice by displacing the control spool in response to the
It is publicly known as shown in the publication No.

In such a flow control device that variably controls the orifice according to the pump rotation speed, as shown in Fig. 1, two sets of orifices 2 and 3 are opened in parallel in a union 1 fixed to the pump housing. A control spool 5 that is displaced based on an increase in the discharge flow rate due to an increase in the pump rotation speed is inserted into the orifice forming body 4, and one of the two sets of orifices 2 is closed by the control spool 4 for power steering. By reducing the flow rate sent to the device, flow rate control can be easily performed with a simple configuration.

However, in the configuration shown in FIG. 1, when the handle is steered during a transition period when the clearance h between the shaft end of the control spool 5 that opens and closes the orifice 2 and the orifice forming body 4 becomes small, the parallelism between the two becomes smaller. Low frequency pressure fluctuations may occur depending on factors such as temperature and assembly accuracy. This occurs because the shaft end of the control spool 5 and the orifice forming body 4 act like a flapper valve, and the flow near the orifice becomes unsteady due to the influence of the parallelism mentioned above. considered to be a thing.

Therefore, an object of the present invention is to provide a flow rate control device that eliminates pressure fluctuations and enables stable operation of the control spool, regardless of the parallelism or assembly accuracy between the orifice forming body and the control spool. That's true.

Embodiments of the present invention will be described below with reference to the drawings.
In FIG. 2, 10 indicates a pump housing, and this pump housing 10 has a valve housing hole 11.
A union 12 is screwed into one end of the valve storage hole 11, and a stopper 13 is fitted into the other end. The union 12 has a substantially cylindrical shape, one end of which is thrust into the valve housing hole 11, the outer periphery of its tip is loosely fitted into the valve housing hole 11, and the other end is fitted with a normal oven type servo valve of the power steering device. A pressure fluid outlet 23 connected to the device is open. A supply passage 14 and a bypass passage 15 are opened in the valve housing hole 11 and are spaced apart from each other in the axial direction.
is constantly communicated with the inside of the valve housing hole 11 through an annular throttle passage 16 formed between the outer periphery of one end of the union 12 and the valve housing hole 11. The throttle passage 16 is configured such that when the pump discharge flow rate supplied to the supply passage 14 increases, a pressure difference is generated between the upstream side and the downstream side, that is, between the supply passage 14 and the valve storage hole 11 due to the flow passage resistance. It's summery. Although not shown, the supply passage 14 communicates with the discharge chamber of the pump, and the bypass passage 15 communicates with the suction chamber of the pump.

A flow rate adjustment spool valve 1 is installed in the valve housing hole 11 in order to close the communication path between the supply passage 14 and the bypass passage 15 and to adjust the degree of opening of the communication passage.
A first valve chamber 18 and a second valve chamber 19 are formed on both sides of the spool valve 17. The second valve chamber 19 is provided with a spring 20 that presses the spool valve 17 toward the first valve chamber 18, and the force of this spring 20 normally holds the spool valve 17 in a position where it collides with the union 12. However, communication between the supply passage 14 that opens into the first valve chamber 18 and the bypass passage 15 is blocked.

An orifice forming body 24 is fitted into the union 12 in proximity to the outlet 23, and the first valve chamber 18 and the outlet 23 are communicated with the center of the orifice forming body 24 via a fluid passage described later. First thing to do
An orifice 25 is formed. A control nozzle 2 is provided between the orifice forming body 24 and the outlet 23.
7 is opened, and this control nozzle 27 is connected to the union 1.
2 and the second valve chamber 19 through communication holes 28 and 29 formed in the pump housing 10. As a result, the fluid that has passed through the orifice 25 is guided to the second valve chamber 19, so the spool valve 1
Since the pressure before passing through the orifice 25 and the pressure after passing through the orifice 25 act on both end faces of the spool valve 17, the spool valve 17 is moved in the axial direction according to the pressure drop at the orifice 25, and the bypass valve 17 is moved to keep the pressure drop at a constant value. Adjust the opening degree of the passage 15.

A control spool 30 is slidably inserted into the union 12, and a fluid passage 31 that communicates between the first valve chamber 18 and the orifice 25 penetrates the control spool 30. A control shaft portion 32 having an outer diameter slightly larger than the inner diameter of the first orifice 25 is protruded from one end of the control spool 30, and the control shaft portion 32 controls the opening and closing of the first orifice 25. A notch 26 is formed in the tip surface of the control shaft portion 32 in the diameter direction as shown in Fig. 3, and this notch 26 forms a second orifice 26 that opens into the first orifice 25 between the control shaft portion 32 and the orifice forming body 24. Therefore, even after the control shaft portion 32 abuts against the orifice forming body 24, the communication relationship between the first valve chamber 18 and the delivery port 23 is maintained via the second orifice 26. The passage area of the second orifice 26 is set to be sufficiently smaller than the passage area of the first orifice 25 .

The control spool 30 and the orifice forming body 24
A spring 33 is inserted between the spring 33 and the spring 33 in a resilient state, and the force of the spring 33 causes the control spool 30 to move toward the stepped portion 3 formed in the union 12.
4, the control shaft portion 32 of the control spool 30 is held in the position where it locks into the orifice forming body 24.
The first orifice 25 is opened at a distance from the first orifice. Further, the union 12 includes a control spool 30 isolated from the fluid passage 31 and a union stepped portion 34.
A pressure introduction hole 36 that opens at the joint surface with the supply passage 14 is bored, and this pressure introduction hole 36 communicates with the supply passage 14 . The diameter of the pressure introduction hole 36 is narrowed to provide a damping effect so that the control spool 30 does not vibrate due to fluctuations in the supply pressure.

Next, the operation of the device of the present invention constructed as described above will be explained.

When a pump rotor is rotationally driven by an automobile engine, working fluid in a suction chamber is sucked into the pump chamber through a suction port, and pressurized fluid is discharged into a discharge chamber through a discharge port. The pressure fluid discharged into the discharge chamber is supplied to the valve housing hole 1 via the supply passage 14 and from the throttle passage 16 between the union 12 and the valve housing hole 11.
1, and this first valve chamber 18
The fluid then passes through the fluid passage 31, the first orifice 25, and is delivered from the delivery port 23 to the power steering device.

When the pump rotation speed is low, the pump discharge flow rate is also small, so the spool valve 17 closes the bypass passage 15 and the entire pump discharge flow rate is sent to the power steering device via the first orifice 25. As the pressure rises, the discharge flow rate also increases, and the spool valve 17 is slid to keep the pressure difference before and after the orifice 25 constant.
5 to bypass the excess flow to the bypass passage 15. As a result, the pressure fluid delivered to the power steering device is maintained at a predetermined amount Q1 determined by the first orifice 25.

When the pump rotational speed further increases as the automobile shifts to high-speed running, and the pump discharge flow rate supplied to the supply passage 14 increases, the fluid pressure in the supply passage 14 increases due to the passage resistance in the throttle passage 16. , a pressure difference is created between the supply passage 14 and the first valve chamber 18. The pressure of the supply passage 14 is introduced between the joint surfaces of the control spool 30 and the union 12 through the pressure introduction hole 36, and the pressure of the control spool 3
0 acts as an axial thrust that presses against the spring 33. As mentioned above, as the pump discharge flow rate increases, the pressure in the supply passage 14 increases, and the axial thrust becomes a force generated by the spring 33. Once raised to the point of overcoming, control spool 30 begins to be displaced against spring 33. Therefore, the first orifice 25 is gradually restricted by the control shaft portion 32 of the control spool 30, and is finally closed as shown in FIG. Even after
Since the valve chamber 18 and the outlet 23 are maintained in communication via the second orifice 26 formed at the shaft end of the control spool 30, the pressure fluid sent to the power steering device is as shown in FIG. is reduced to a predetermined amount Q2 determined by the second orifice 26. As a result, when driving at high speeds, the driver can enjoy the steering reaction force obtained by reducing the flow rate supplied to the power steering device, improving high-speed stability and achieving horsepower savings when driving at high speeds. be done.

In this way, the present invention replaces the second orifice with the first orifice.
Since the control spool is formed diametrically at the shaft end of the control spool that controls the opening and closing of the orifice, the flow direction of the fluid passing through the orifice can be kept almost constant at all times. Regardless of parallelism, assembly accuracy, etc., pressure fluctuations do not occur even when the handle is steered when the first orifice is closed, making it extremely easy to manage processing accuracy and assembly accuracy. is played.

Moreover, the present invention has a configuration in which a throttle passage is formed between the outer periphery of the union attached to one end of the valve housing hole and the inner periphery of the valve housing hole, and a control spool is incorporated within the union. It is also possible to control the flow rate with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of essential parts showing an example of a flow rate control device, FIG. 2 is a cross-sectional view of a power steering working fluid flow rate control device showing an embodiment of the present invention, and FIG. 4 is a diagram showing the flow rate characteristics with respect to the pump rotation speed, and FIG. 5 is an operating state diagram of FIG. 2. 10... Pump housing, 11... Valve housing hole, 12... Union, 14... Supply passage, 15
...Bypass passage, 16... Throttle passage, 17...
Spool valve for flow rate adjustment, 23... Delivery port, 24...
... Orifice forming body, 25 ... First orifice, 26 ... Second orifice, 30 ... Control spool, 32 ... Control shaft portion, 36 ... Pressure introduction hole.

Claims (1)

[Scope of utility model registration request] A power steering system in which the pressurized fluid discharged from the pump is sent from the supply passage through the orifice to the power steering device, and the surplus flow is returned to the suction side of the pump by a flow rate adjustment spool valve that adjusts the opening degree of the bypass passage. A flow rate control device for a working fluid for use includes a housing, a valve housing hole formed in the housing and into which the flow rate adjusting spool valve is slidably fitted, a union attached to one end of the valve housing hole, and a union attached to one end of the valve housing hole. A throttle passage formed between the outer periphery of the union and the inner periphery of the valve housing hole to throttle the fluid flowing through the supply passage, and a throttle passage slidably housed within the union to increase the discharge flow rate by increasing the pump rotation speed. a control spool that is displaced in response to a pressure difference before and after the throttle passage that occurs in response to the pressure difference and variably controls the orifice; ,
a second orifice cut diametrically at the axial end of the control spool; and after the first orifice is closed by the axial end of the control spool, the pressure fluid is powered through the second orifice. A flow rate control device for a working fluid for power steering, characterized in that the flow rate control device is configured to send a working fluid to a steering device.