JPH0113666Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a control valve for a power steering device, and more specifically, includes a conversion mechanism that converts relative rotational displacement between two shafts coaxially supported in a housing into axial displacement; A power steering system comprising a spool valve that is displaced in the axial direction by this conversion mechanism, and a valve sleeve that is interposed between the spool valve and the housing and forms a switching valve part of a center-open four-way switching valve together with the spool valve. Regarding the control valve of the device.

In general, in this type of control valve, the valve sleeve is made of a material such as cast iron that has good affinity for lubricating oil, in consideration of sliding properties and wear resistance against the valve sleeve when the spool valve is displaced in the axial direction. The spool valve is made of a material with good wear resistance, such as steel. For this reason, the valve sleeve is made of a material with a smaller coefficient of linear expansion than the spool valve, and as the temperature of the hydraulic oil inside the control valve increases, the valve between the spool valve and the valve sleeve Clearance (several μm) decreases. Additionally, in general, in this type of control valve, the pressure receiving surfaces of the valve sleeve that receive the operating hydraulic pressure are located at both ends of the switching valve part, and the pressure receiving area is larger on the outer circumferential surface than on the inner circumferential surface of the valve sleeve. big. Therefore, both ends of the switching valve portion of the valve sleeve tend to undergo hydraulic deformation in the direction of diameter reduction due to the influence of the hydraulic pressure during operation of the control valve. As a result, the valve clearance between both ends of the switching valve section and the spool valve decreases due to hydraulic deformation of the valve sleeve, and this, together with the decrease in valve clearance due to the rise in oil temperature, reduces the smoothness of the spool valve. displacement is obstructed, and smooth steering sensation cannot be obtained. Furthermore, if the reduction in valve clearance due to hydraulic pressure deformation and oil temperature rise increases, there is a risk that the spool valve will become stuck (valve lock phenomenon). Therefore, in reality, in this type of control valve, the valve clearance is set large considering the reduction in each valve clearance described above, but as a result, the flow of hydraulic fluid between the spool valve and the valve sleeve is reduced. As the leakage increases, the amount of hydraulic fluid supplied from the hydraulic pump becomes insufficient, making it impossible to obtain a smooth steering feel.

The present invention was developed in light of these circumstances, and its main purpose is to maintain smooth displacement of the spool valve by suppressing the decrease in valve clearance caused by the above-mentioned oil temperature rise and hydraulic deformation. At the same time, the valve clearance is set small to suppress leakage of hydraulic oil occurring between the spool valve and the valve sleeve, thereby providing a smooth steering feeling in the power steering device.

Hereinafter, the present invention will be explained based on the drawings. FIGS. 1 and 2 show an example of a control valve of a power steering device according to the present invention. The control valve 10 is
It has a housing 12 that is fluid-tightly fixed to the gearbox 11, and an input shaft 2 is disposed inside the housing 12.
0 and the output shaft 30 are a pair of ball bearings 13,
A cylindrical spool valve 40 and a valve sleeve 50 are coaxially supported via the input shaft 2.
It is placed concentrically with 0. The input shaft 20 has its lower end joined to the upper end of the output shaft 30 via a needle bearing 15, and is connected to the output shaft 30 by a torsion bar 21 inserted through its axis. The torsion bar 21 is assembled with its upper end connected to the upper end of the input shaft 20 by a pin 22 and its lower end connected to the output shaft 30 by a pin 23. Further, as shown in FIG. 2, on the lower outer periphery of the input shaft 20, a pair of spiral grooves 24, 24 having a V-shaped cross section and a pair of notches 25, 25 are provided.
A ball 2 is provided in each spiral groove 24.
6 is accommodated.

The output shaft 30 has a pair of protruding pieces 31, 31 that protrude into each notch 25 of the input shaft 20, and a guide pin 32 is fixed to each of these protruding pieces 31 in the radial direction. Each guide pin 32 is fitted into a pair of axial guide grooves 41, 41 provided opposite to each other at the lower end of the spool valve 40 to guide the axial movement of the spool valve 40. Further, each protruding piece 31 of the output shaft 30 is arranged with a predetermined gap in the circumferential direction within each notch 25 of the input shaft 20, so that the input shaft 20 rotates relative to the output shaft 30. It is becoming possible to do so.

The spool valve 40 is fitted into the valve sleeve 50 so as to be movable in the axial direction, and a pair of through holes 42, 42 in which the balls 26 are fitted in a rolling manner are provided in the lower end thereof in the radial direction. It is being Spool valves 40 located on both sides of each through hole 42
A pair of annular grooves 44, 44 are provided on the outer peripheral surface of the retainer ring 4.
6 is supported, and each ball 26 is held rotatably in each spiral groove 24 by this retainer ring 46.

The valve sleeve 50 constitutes a center-open four-way switching valve together with the spool valve 40, and the switching valve portion thereof selectively communicates with annular grooves 47, 48, and 49 formed on the outer circumferential surface of the spool valve 40. A radial communication hole 58 is provided that constantly communicates with the pair of annular grooves 57, 59 and the annular groove 48 at the center of the spool valve 40. The valve sleeve 50 is disposed at a predetermined position between the housing 12 and the spool valve 40 by engagement with a support member 33 fitted to the upper end of the output shaft 30 so as to be relatively rotatable. Note that the communication hole 58 of the valve sleeve 50 communicates with the pressure oil supply port 12A of the housing 12 connected to a hydraulic pump (not shown). Further, each annular groove 57, 59 of the valve sleeve 50 communicates with each inlet port 12B, 12C connected to each oil chamber of a power cylinder (not shown). Note that the reference numeral 12D is an outlet connected to a reservoir (not shown).

In the control valve 10, the spool valve 4
0 vibration isolators 60 are provided. In this vibration isolator 60, an annular retainer member 61 fitted to the upper end of the spool valve 40 forms an annular oil chamber R isolated from the inside of the spool valve 40. An annular orifice 62 formed between the peripheral surface and the outer peripheral surface of the input shaft 20 communicates with the inside of the spool valve 40, and the retainer member 61 and the ball bearing 1
A type of oil damper is constructed by interposing a coil spring 63 with a predetermined mounting load between the three inner races 13a. In the control valve 10 employing the vibration isolating device 60 having such a configuration, when the spool valve 40 is in its neutral position, each ball 26 is elastically moved to one side of each helical groove 24 by the action of the coil spring 63. It is held so that it does not vibrate by being pressed against it. In this state, when the input shaft 20 rotates while twisting the torsion bar 21 by steering the steering wheel, the ball 26 rolls along one side of the spiral groove 24, and the spool valve 40 moves upward or downward from its neutral position. Pressure oil displaced downward and flowing in from the supply port 12A is supplied to one oil chamber of the power cylinder of the steering device through the inflow port 12B or 12C, and at the same time, discharged oil from the other oil chamber is supplied to the inflow port 12C or 12C. 12B and reflux to the reservoir through the outlet 12D. When a hydraulic pressure fluctuation occurs in the pressure oil during operation, the oil in the oil chamber R isolated by the retainer member 61 flows through the orifice 62 and buffers the vibrations applied to the spool valve 40.

Therefore, the spool valve 4 of the control valve 10
The valve sleeve 50 is made of cast iron, which has a high affinity for hydraulic oil and has a smaller coefficient of linear expansion than steel. This valve sleeve 50 includes
As shown in FIG. 1, a pair of annular notch grooves 51 are provided inside the upper end portion of the switching valve portion and inside the lower portion of the switching valve portion.
a, 51b are formed, and each notch groove 51a,
Ring members 52a and 52b are press-fitted and fixed to 51b. Each ring member 52a, 52b has the same inner diameter as the inner diameter of the valve sleeve 50, and is made of a material such as an aluminum alloy that has a larger coefficient of linear expansion than cast iron.

In the control valve 10 configured as described above, since the linear expansion coefficients of the spool valve 40 and the valve sleeve 50 are different, the valve clearance between the spool valve 40 and the valve sleeve 50 decreases due to an increase in the temperature of the hydraulic oil. The valve clearance between both ends of the switching valve portion of the valve sleeve 50 and the spool valve 40 tends to decrease due to hydraulic deformation during operation of the control valve 10. However, each of the ring members 52a and 52b press-fitted into the valve sleeve 50 expands as the temperature of the hydraulic oil increases, thereby expanding the inner diameter of the valve sleeve 50. Therefore, due to the expanding action of each of the ring members 52a and 52b, the clearance of each valve is reduced due to an increase in the temperature of the hydraulic oil and hydraulic deformation due to the hydraulic pressure, and in particular, the switching valve in the valve sleeve 50 due to hydraulic deformation is The decrease in valve clearance between both ends of the spool valve 40 and the spool valve 40 is sufficiently suppressed. As a result,
Smooth displacement of the spool valve 40 is maintained,
A smooth steering feeling can be obtained in the power steering device. Further, since the valve clearance can be set small, leakage of hydraulic oil occurring between the spool valve 40 and the valve sleeve 50 is suppressed, and from this point as well, a smooth steering feeling can be obtained.

In this embodiment, an example of a control valve is described in which a conversion mechanism for converting relative rotational displacement of both shafts 20 and 30 into axial displacement is configured by a spiral groove 24, a ball 26, a guide pin 32, a guide groove 41, etc. However, it is of course possible to change this to an appropriate conversion mechanism capable of converting the relative rotational displacement of both shafts 20 and 30 into axial displacement, and it is also possible to omit the vibration isolator 60.

As explained above, the present invention includes a spool valve and a valve sleeve that together forms the switching valve part of a center-open four-way switching valve, and the valve sleeve is made of a material with a smaller coefficient of linear expansion than the spool valve. In the control valve of the power steering device, ring members made of a material with a larger coefficient of linear expansion than the valve sleeve are press-fitted and fixed on both inner sides of the valve sleeve on the end side from the switching valve part. There is a characteristic of its composition.
Therefore, according to the present invention, the expansion action of the ring member on the valve sleeve caused by the increase in the temperature of the hydraulic oil reduces the reduction in valve clearance caused by the increase in the temperature of the hydraulic oil and the hydraulic deformation caused by the hydraulic pressure. In addition, the valve clearance can be set small, and a smooth steering feeling can be obtained in the power steering device.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional view taken along the - line in Fig. 2 showing an example of the control valve of the present invention;
FIG. Explanation of symbols, 10... Control valve, 12... Housing, 20... Input shaft, 24... Spiral groove, 26...
... Ball, 30 ... Output shaft, 40 ... Spool valve, 50 ... Valve sleeve, 51a, 51b
...Notch groove, 52a, 52b...Ring member.

Claims (1)

[Scope of utility model registration request] a conversion mechanism that converts relative rotational displacement between both shafts coaxially supported within the housing into axial displacement;
The conversion mechanism includes a spool valve that is displaced in the axial direction, and a valve sleeve that is interposed between the spool valve and the housing and forms a switching valve part of a center-open four-way switching valve together with the spool valve. In the control valve of the power steering device, the control valve is formed of a material having a linear expansion coefficient smaller than that of the spool valve, and a linear expansion coefficient compared to the valve sleeve is provided on both inner sides of the end portion of the valve sleeve from the switching valve portion. A control valve for a power steering device, characterized in that ring members made of a material with a large coefficient of expansion are press-fitted and fixed.