JPS5910398Y2 - power steering pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a pump for supplying pressure fluid to a power steering system used as a power steering device for automobiles and the like.

In this type of power steering pump, for example, when a steering operation is performed and the rudder is turned all the way, the load increases infinitely, so that the discharge pressure of the pump increases to its maximum value.

Therefore, in the past, even in such cases, the pump discharge pressure was regulated so that it did not exceed a certain set value, thereby maintaining the stability of the circuit and preventing excessive loads from being placed on the various components that make up the steering mechanism. Generally, the pump has a built-in relief valve to prevent this from happening.

During its control operation, the relief valve normally opens the bypass ports of the flow control valve and returns the fluid released therefrom to the pump suction chamber.

Therefore, while the relief valve is in operation, the pump sucks fluid released from the bypass port of the flow control valve and the relief valve, and the discharge side is directed toward the power steering system when the rudder is turned fully. Since the external circuit is closed, a so-called closed circuit is formed in which the entire amount of fluid sucked from the pump suction chamber is returned to the pump suction chamber through the bypass port and relief valve of the flow control valve. Fluid is circulated between the pump and the Noleaf valve without using the fluid in the fluid reservoir provided surrounding it.

This circulating fluid is only a limited amount of the power steering circuit, and it is subject to changes from high pressure to low pressure and from low pressure to high pressure, especially during pressure drops from high pressure to low pressure. A part of it is converted into thermal energy, and therefore, if the relief pressure is large and the pressure drop is large, the temperature of the fluid suddenly increases.

Naturally, the temperature rise of the fluid is related to the frequency of steering operations, which causes a decrease in the viscosity of the fluid and causes an oil film to run out on the sliding parts of the pump, resulting in premature wear and seizure of the pump. This could cause a catastrophic failure.

Furthermore, fluids exposed to high temperatures are more susceptible to deterioration;
This also affects the life of the pump.

It is therefore an object of the invention to provide an improved power steering pump of this kind, which eliminates the above-mentioned drawbacks.

Hereinafter, an example of the implementation of the present invention will be described based on the attached drawings. A power steering pump 1 includes a drive shaft 6 rotatably supported on a casing 2 via ball bearings 3, 4 and an oil seal 5. The drive shaft 6 is rotatably driven by an engine of an automobile or the like through a pulley 8 which is connected to a key 7 at its end.

The casing 2 has a pump mechanism 9 therein which is rotatably driven through the drive shaft 6, and its outer periphery is covered with a pump force bar 11 that forms a fluid reservoir 10.

The pump mechanism 9 may be of any type, but in this embodiment, the knock pin 12 connects the casing 2.
A type of pump is shown in which a rotor 15 rotates carrying a plurality of pages 14 that move radially following the contour of a hole in a cam ring 13 fixed to the cam ring 13 .

For this purpose, the pump mechanism 9 further includes a cam ring 1.
It is equipped with the various parts necessary to create the side play H6.17 that supports 3 from both sides and other operating structures.

Further, in front of the pump mechanism 9, a partition element 19 is provided which is fixed to the casing 2 by a locking ring 18, and a pressure chamber 20 is isolated from the fluid reservoir 10 within the casing 2 by this partition element 19. are divided.

A flow control valve 22 is installed below the pump mechanism 9 and located in a valve hole 21 formed in the casing 2.

The flow rate control valve 22 controls the pressure fluid that is sent to the power steering system as the rotational speed increases when the power steering pump 1 is rotated by the engine of an automobile or the like as a function of the vehicle speed. A device with a flow damping characteristic that suppresses the tendency of the flow rate to increase and maintains the flow rate at a predetermined level, and, if necessary, reduces the flow rate of the pressure fluid sent to the power steering system from a certain rotation speed. It can be anything.

In this embodiment, an inlet port 23 and a bypass port 24 are opened in the valve hole 21, respectively, and the inlet port 23 communicates with the pressure chamber 20 on the side of the pump mechanism 9, and the bypass port 24 is an annular pump suction chamber 2 formed between the casing 2 and the outer periphery of the pump mechanism 9.
5, and at the same time, it also communicates with the fluid reservoir 10 through a through hole 26 cut in the casing 2, as seen in FIG.

A control spool 27 is slidably inserted into the valve hole 21 to connect and disconnect the bypass port 24 from the inlet port 23. and a back chamber 29, and the right end of the control spool 27 and the valve hole 21.
A coil spong 30 is interposed between the end wall and the end wall.

The artificial port 23 is always open to the front chamber 28 and is only opened through the front chamber 28 when the control spool 27 retracts to the right while compressing the spring 30 to open the bypass port 24 into the valve hole 21. It also connects to bypass port 24.

A nipple 137 is screwed into the left end opening of the valve hole 21.

This nipple 31 is for directing the pressure fluid sent from the pump mechanism 9 to the front chamber 28 through the pressure chamber 20 and the inlet port 23 toward the power steering system.

Further, an adjustment rod 32 integrally projects from the left end of the control spool 27 toward the inside of the nipple 137.
Although it is hidden by the nipple 137 in the drawing,
As is known, these nipples 137 and adjustment rods 32
An orifice is formed between the control spool 27 and the opening area from a predetermined position as the control spool 27 retreats to the right, and the downstream side of this orifice is a through hole 33 (no. (see Figure 2) into the back chamber 29.

As a result, the pump mechanism 9 sucks the fluid in the fluid reservoir 10 from the through hole 26 through the bypass pole 24 and the annular pump suction chamber 25 as the rotor 15 rotates, and discharges it as pressure fluid. It is forced out from the port 34 into the pressure chamber 20 and from this pressure chamber 20 through the inlet port 23, the front chamber 28 and the nipple 31 to the power steering system.

Meanwhile, return fluid from the power steering system is routed through a nipple 35 mounted through the pump power bar 11.
From there, the flow returns to the fluid reservoir 10.

Thus, all the pressurized fluid sent from the pump mechanism 9 to the power steering system will flow through the orifice formed between the nipple 137 and the adjusting rod 32, and will flow before and after this orifice. , a pressure difference occurs that corresponds to the flow rate of the pressure fluid at that time.

The pressure on the upstream side of this orifice acts directly on the left end surface of the control spool 27 from the front chamber 28, and the pressure on the downstream side acts on the right end surface of the control spool 27 through the through hole 33 and the back chamber 29. Therefore, the control spool 27 retreats to the right while compressing the spring 30 in response to the pressure difference between the front and rear of the orifice, and the bypass port 2
Open 4.

Therefore, the characteristics of the flow rate control valve 22 should be selected in advance so that the control spool 27 starts opening the bypass port 24 when the flow rate of the pressure fluid sent to the power steering system reaches a predetermined value. For example, even if the flow rate of the pressure fluid discharged from the pump mechanism 9 changes greatly in response to an increase or decrease in the rotational speed of the rotor 15 in the pump mechanism 9, the flow rate control valve 22 can
The control spool 27 is controlled to the left and right under the influence of the pressure difference generated before and after the onofice, and the opening area of the bypass port 24 is appropriately selected to control the flow rate of the pressurized fluid escaping from the front chamber 28 through the bypass port 24. In this way, the flow rate of the pressure fluid sent to the power steering system side is kept almost constant, and when the rotational speed of the rotor 15 exceeds a certain level, the opening area of the orifice is reduced and the flow rate control valve 22 is controlled. It provides flow damping characteristics and works to reduce the flow rate of pressure fluid sent to the power steering system.

On the other hand, in order to prevent the discharge pressure of the pressurized fluid discharged from the pump mechanism 9 from rising to the maximum value as when the rudder is turned all the way, the inside of the control spool 27 in the flow rate control valve 22 is A beam 1-f valve 36 is provided.

This relief valve 36 connects the load pressure normally generated on the power steering system side to the back chamber 29 from the through hole 33.
When the load pressure is about to rise above the set value, it opens and allows the pressure fluid to escape from the through hole 37 in the control spool 27 to the bypass port 24, thus reducing the discharge pressure of the pump mechanism 9 to this renovator. Pressurized fluid is returned from the front chamber 28 to the bypass port 24 through the opening of the control spool 27 and the relief valve 36 while maintaining the set pressure of the valve 36 .

Therefore, during the operation of the relief valve 36, the pump mechanism 9 is connected to the opening of the control spool 27 and the relief valve 3.
6, the fluid released into the bypass port 24 is sucked in from the pump suction chamber 25, and the fluid is returned as pressure fluid to the pump suction chamber 25 through the opening of the control spool 27 and the relief valve 36. , which is accompanied by a sudden increase in temperature of the fluid in a harmful manner.

In this case, when the flow rate control valve 22 normally operates to return excess pressure fluid from the front chamber 28 to the bypass port 24 side, when the fluid flows out from the bypass port 24 to the pump suction chamber 25, the fluid reservoir Since the fluid in the pump mechanism 9 is sucked all at once, the pressure in the pump suction chamber 25 increases in proportion to the load pressure, and especially when the relief valve 36 is activated, the entire flow from the pump mechanism 9 flows into the pump suction chamber 25. We know by experiment that it shows the highest pressure to return.

This increase in pressure within the pump suction chamber 25 to a certain extent is effective in providing pre-pressure for the pump mechanism 9 to perform a suction action.

Therefore, in the present invention, a check valve 38 is provided for the pump suction chamber 25, which is activated by detecting the pressure increase in the pump suction chamber 25 when the relief valve 36 is activated.
When the relief valve 36 is actuated, a part of the fluid returned from the opening of the control spool 27 and the relief valve 36 to the pump suction chamber 25 through the bypass port 24 is returned to the fluid reservoir 10 from the check valve 38. It is.

That is, in the case of this embodiment, since the casing 2 of the pump mechanism 9 originally has a hole 39 (normally this is covered with a lid) when processing the bypass port 24, this hole 39 is The valve seat I/member 40 and the cap body 41 and the spring 4 are inserted therein.
A check valve 38 containing a ball 43 energized at step 2 is fitted.

As a result, the check valve 38 maintains the pressure in the pump suction chamber 25 at the pressure necessary for pre-pressurizing the pump mechanism 9 when the relief valve 36 is activated, and also prevents the fluid returning to the pump suction chamber 25 from increasing. A portion of the fluid is released into the fluid reservoir 10, and at the same time, an amount of fluid corresponding to the amount of fluid returned from the check valve 38 to the fluid reservoir 10 is transferred from the fluid reservoir 10 through the through hole 26 and the bypass port 24 to the pump suction chamber 24.
5 will be sucked in.

Thus, according to the present invention, when the relief valve 36 is activated, a part of the fluid is sent to the fluid reservoir 10 although the circuit is closed.
A path is constructed to exchange the fluid in the fluid reservoir 10, and thereby the fluid in the fluid reservoir 10 is also circulated, effectively circulating the limited amount of fluid in the power steering circuit and increasing the temperature rise rate of the fluid. With this extremely simple structure, the temperature rise of the fluid can be suppressed to a low level, and early wear and seizure of the sliding parts of the pump mechanism 9 can be effectively prevented. This also prevents deterioration and significantly extends the life of the pump.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view showing one embodiment of a power steering pump according to the present invention, and FIG. 2 is a longitudinal sectional side view along line II-III in FIG. 1. 1...Power steering pump, 2...
...Casing, 9...Pump mechanism, 10
...Fluid reservoir, 25...Pump suction chamber, 38...Check valve.

Claims (1)

[Scope of utility model registration request] The fluid released into the bypass port 24 from the opening of the control spool 27 and the relief valve 36 is transferred to the casing 2.
Suction is drawn into the pump suction chamber 25 in the pump mechanism formed inside, giving pre-pressure to the pump suction chamber 25, and the fluid is returned to the pump suction chamber 25 through the opening of the control spool 27 and the relief valve 36 as pressure fluid. In a power steering pump with an internal circulation mechanism that returns
The casing 2 is provided with a check valve 38 that opens in response to the internal pressure when the internal pressure in the pump suction chamber 25 exceeds a predetermined value. A power steering pump in which a portion of the pressure oil inside is communicated to a fluid reservoir on the outer periphery of the casing.