JPS6344109B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device that aims to reduce fluid noise caused by working fluid.

As schematically shown in Fig. 1, a general power steering device includes a control unit 1 that increases the steering operation force from the steering wheel using hydraulic pressure to control the operation of a steering linkage (not shown), and an engine or the like as a drive source. Hydraulic pump 2 that generates hydraulic pressure
The control unit 1 and the hydraulic pump 2 are equipped with
are communicated through oil passages 3 and 4 to circulate oil between them.

By the way, in this type of power steering device,
Fluid noise has long been a problem as a type of vehicle noise. In other words, if the oil pressure in the oil passage 4 on the downstream side of the control valve in the control unit 1 is low during operation of the power steering device, cavitation is likely to occur in the oil flow, and this cavitation causes fluid noise. -ing In order to prevent this fluid noise, it is sufficient to suppress the occurrence of cavitation, and for this purpose, it is sufficient to maintain the oil pressure downstream of the control valve at a predetermined value or higher.

For this reason, a configuration can be considered in which a throttle 5 is interposed in the return passage 4 connecting the control section 1 and the hydraulic pump 2 described above to increase the pressure downstream of the control valve, that is, the back pressure of the control section. ing. However, conventionally, a fixed throttle is used as the throttle 5, so when the vehicle is traveling straight or at high speed, the steering force is small and there is no need to operate the power steering device, so fluid noise is almost eliminated. Even in cases where this does not occur often, the back pressure is increased, resulting in a problem that the pressure loss, that is, the drive loss of the hydraulic pump 2 increases.

This invention was made by focusing on such conventional problems, and a back pressure control valve is interposed in the return side passage connecting the control unit and the hydraulic pump.
The above-mentioned problem is solved by keeping the oil pressure low when the steering force is small and the oil pressure is low, and increasing the back pressure only when the steering force increases and the oil pressure increases. The purpose is to

The present invention will be explained below based on the drawings.

FIG. 2 is a diagram showing an embodiment of this invention,
In the figure, 2 is a hydraulic pump, 1 is a control section of the power steering device, and 3 and 4 are an oil supply passage and an oil return passage that communicate between the hydraulic pump 2 and the control section 1, respectively. A back pressure control valve 6 is interposed within 4.

This back pressure control valve 6 has a left-right valve hole 8 formed in a housing 7, and a spool valve 9 consisting of a separately formed spool portion 10 and a plunger portion 11 is mounted in the valve hole 8. The interior is movable. This spool portion 10 is formed with three land portions 12, 13, 14, and these land portions 12, 13, 14 allow oil chambers 15, 16, 17, It defines 18. Note that the land portions 13 and 14 have the same outer diameter, which is larger than the outer diameter of the land portion 12. Further, the right end 1 of the plunger portion 11
1a is located facing boat 19, and passage 2
The right end surface thereof receives the hydraulic pressure of the oil supply passage 3 supplied through the oil supply passage 3. The plunger portion 11 is treated as a separate body in this example because it has a considerably smaller diameter than the land portion 12 since the high hydraulic pressure supplied to the control portion 1 acts on the plunger portion 11.
The plunger portion 11 and the plunger portion 11 may be integrally formed.

On the other hand, an inlet port 21 and an outlet port 22 are formed in the housing 7 so as to be perpendicular to the valve hole 8 . This inlet side port 21 is a small diameter passage 2
3 to the oil chamber 17, and communicates to the oil chamber 16 through the passage 24 and the small diameter passage 25 when the spool valve 9 moves to the right, and further communicates to the oil chamber 15 through the passage 24 and the passage 26. . Further, a passage 27 is connected to the outlet port 22, and passages 28 and 29 formed in the passage 27 communicate with the oil chambers 18 and 17, respectively. Further, it communicates with the oil chamber 16 through the small diameter passage 30 when the spool valve 9 moves to the left, and further communicates with the oil chamber 15 through the orifice 31 and the passage 32 installed in the passage 27. Note that the narrow diameter passages 23, 2
5, 30 and the orifice 31 are set to have diameters that create a predetermined pressure difference between upstream and downstream positions of each passage due to their flow resistance. In the figure, 33 is a stopper for regulating the leftward movement position of the spool valve 9;
34 is a stopper for regulating the rightward movement position.

Next, the action will be explained.

When the steering force is small and the control unit 1 does not operate, and therefore the discharge pressure from the hydraulic pump 2 is lower than a predetermined value, the spool valve 9 is in a position as shown in FIG. That is, the oil chamber 1 at the left end of the spool valve 9
5 and the oil chamber 16 next to it are supplied with the hydraulic pressure of the inlet side port 21, while the oil chamber 18 and the oil chamber 17 at the right end are supplied with the oil pressure of the inlet side port 21.
communicates with the outlet port 22, and the hydraulic pressure of the inlet port 21 is slightly higher than the pressure of the outlet port 22 due to the action of the small diameter passage 23, so the spool valve 9 receives a rightward force. acts to maintain the spool valve 9 in the state shown. In other words,
A force equal to the sum of the area of the land portion 12 and the area difference between the land portions 12 and 13 plus the hydraulic pressure of the inlet side port 21 acts on the spool valve 9 in the right direction, whereas the force in the left direction Only the force that is the excess of the oil pressure of the port 19 acts on the area of the right end of the plunger part 11, and since the oil pressure of the oil supply passage 3 is low when the control part 1 is not operating, the oil pressure of the port 19 is also Therefore, the force acting on the spool valve 9 in the right direction is larger than the force acting in the left direction, and the spool valve 9 is placed at the right end position.

Therefore, the oil flowing through the oil return passage 4 flows from the inlet side port 21 to the small diameter passage 23, the oil chamber 17, and the passage 2.
9 and 27 to the outlet side port 22, and although it is throttled by the slightly narrow diameter passage 23, it has a sufficient passage area compared to the orifice 31, so it returns to the hydraulic pump 2 side with almost no pressure loss. .

On the other hand, when the steering force increases and the oil pressure in the oil supply passage 3 upstream of the control section 1 increases, this oil pressure is supplied to the port 19 and acts on the right end surface of the plunger section 11. By setting the area of this right end face to an appropriate area, when the port 11 oil pressure exceeds a predetermined value, the leftward force acting on the spool valve 9 becomes larger than the rightward force, and the spool valve 9 moves to the left until it is regulated by the stopper 33, resulting in the state shown in FIG. In this state, the small diameter passage 23 and the passage 29 are closed by the land portion 14, and the communication between the small diameter passage 25 and the oil chamber 16 is closed by the land portion 13. Instead, a small diameter passage 30 comes to communicate with the oil chamber 16. Therefore, the oil passages 24 and 26 of the inlet side port 21, the oil chamber 15, and the passage 3
2. The flow passes through the orifice 31 and the passage 27 to the outlet port 22. At this time, the oil greatly increases the oil pressure of the inlet port 21, that is, the back pressure of the control section 1, due to the large throttling effect of the orifice 31. This makes it possible to prevent cavitation in the control section and reduce noise associated with fluid sound.

Here, when the steering force becomes small again,
When the leftward force acting on the spool valve 9 through the plunger portion 11 becomes smaller than the rightward force acting on the left end surface of the spool valve caused by the oil pressure in the oil chamber 15 at the left end of the spool valve, the spool valve 9
returns to the right, but at this time the spool valve 9
Since hysteresis occurs in the force that causes the valve to move to the right or to the left, the spool valve 9 does not vibrate. That is,
As the spool valve 9 moves, the small diameter passages 25 and 30 communicating with the oil chamber 16 are switched, but since the small diameter passage 30 communicates with the downstream side of the orifice 31, it communicates with the upstream side of the orifice 31. The oil pressure supplied to the oil chamber 16 is lower than that of the small diameter passage 25. Therefore, the oil pressure at the port 19 when moving the spool valve 9 to the right must be lower than the oil pressure when the spool valve moves to the left, and this pressure difference becomes hysteresis, causing the spool valve to move to the right or left. It keeps it stable.

As described above, according to the present invention, a back pressure control valve is provided in the oil return passage communicating between the hydraulic pump and the control section of the power steering device, so that when the steering force increases and the oil pressure increases, When the steering force is large and the power steering device is operating, the back pressure of the control section is increased to prevent the generation of noise associated with fluid sound. On the other hand, when the vehicle is traveling straight or at high speed, near neutral where the steering force is small, the increase in back pressure can be suppressed and an increase in pressure loss can be prevented.

[Brief explanation of the drawing]

Figure 1 is a conceptual overall configuration diagram of the power steering device.
FIG. 2 is an overall configuration diagram showing a cross-sectional view of the main parts of the present invention, and FIG. 3 is a cross-sectional view of the main parts for explaining the operation. DESCRIPTION OF SYMBOLS 1... Control part, 2... Hydraulic pump, 3... Oil supply passage, 4... Oil return passage, 6... Back pressure control valve, 9... Spool valve, 10... Spool part, 11... Plunger Part, 12-14...Land part, 15-18...Oil chamber, 19...Port, 2
1...Inlet side port, 22...Outlet side port, 2
3, 25, 30...Small diameter passage, 24, 26, 2
7, 28, 29, 32... passage, 31... orifice.

Claims (1)

[Scope of Claims] 1 The control section of the power steering device and the hydraulic pump are communicated with each other through an oil supply passage and an oil return passage, and a back pressure control valve is installed in the oil return passage, and the oil return passage is provided with a back pressure control valve. The pressure control valve has a passage having an orifice interposed therebetween as a return passage for the oil in its housing, and a passage having a larger passage area than the passage having the orifice interposed therebetween. This spool valve introduces the hydraulic pressure of the oil supply passage into the plunger portion at the end of its shaft, and the force acting on the end face of the plunger portion acts on the large diameter area on the opposite side of the spool valve. A power steering device characterized in that the power steering device is configured to open only the passage in which the orifice is interposed when the force becomes greater than the hydraulic pressure in the oil return passage. 2. In one of the oil chambers on the oil return passage side for applying an acting force to the spool valve, passages communicating with the upstream and downstream sides of the orifice are opened, and each of these passages is opened according to the movement position of the spool valve. Claim 1 wherein the spool valve is closed in the switched state to provide hysteresis to the operation of the spool valve.
The power steering device described in Section 1.