JPH04266571A - Rotary valve - Google Patents

Abstract

PURPOSE: To provide a rotary valve that can form a sleeve in extremely thin wall structure by eliminating a sleeve end lock ring, and providing arcuate slots as extended sleeve in order to provide an optimum return passage to discharge oil from the valve. CONSTITUTION: A rotary valve 1 for a hydraulic power steering for a vehicle has arcuate slots 9, 10 in a sleeve 2 and has a slot 11 in an input shaft 3, and several of the slots 10 in the sleeve are so formed as to provide a hydraulic fluid return port 13 in the axial direction of the valve 1 between the sleeve 2 and the input shaft 3. The axial length of the adjacent sleeve slot 10 and input shaft slot 11 is the same at their end parts far from the return port 13.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to rotary valves, and more particularly to rotary valves for hydraulically powered steering of vehicles.

0002

BACKGROUND OF THE INVENTION Typically such valves include an input shaft;
The input shaft is typically connected to the vehicle's steering wheels by a flexible joint and has a plurality of longitudinally extending slots with dead ends separated by flat portions on the outer periphery. The sleeve member supported on the input shaft has in its bore a similar row of dead end slots that fit into the dead end slots of the input shaft but extend longitudinally in overlapping fashion, one of which one slot is wider than the flat portion of the other slot and defines a set of longitudinally extending orifices, said orifices being adapted to open and close upon relative rotation between the input shaft and said sleeve. I am doing it.

Perforated passages in the input shaft and sleeve, along with circumferential grooves around the sleeve, slots in the input shaft and sleeve, engine-driven oil pumps, and right and left hydraulic pressure for the steering gear system. It functions to communicate oil between the auxiliary cylinder chambers.

A torsion rod in the input shaft serves to urge the input shaft and sleeve toward a neutral centering position when no auxiliary power is required. When torque is applied to the steering wheel by the driver, the torsion bar causes relative rotation of the sleeve to deflect from the neutral position of the input shaft and direct oil from the right auxiliary cylinder chamber to the left auxiliary cylinder chamber.

The general method of operating such rotary valves is well known in the power steering field and will not be described in detail herein. A detailed description of this operation is provided in U.S. Pat. No. 3,022,772 (Zeigler), generally recognized as the first specification disclosing the rotary valve concept.

The closest prior art to the present invention is US Pat.
, No. 454,801 (Span). This patent shows a valve that requires an axial straight oil return slot in the internal bore of the sleeve, with an end stop ring press-fit into a counterbore at each end of the sleeve to block the slot. . The straight slots alternate circumferentially as feed and return slots, whereas the feed slots are machined shallow enough to allow end stop rings to hydraulically seal these slots. The return slot is then cut relatively deep to allow oil to return from the sleeve under the end stop ring.

The essence of the invention is the elimination of a sleeve end stop ring as well as the provision of an extended arcuate slot in the sleeve to provide an optimal return path for draining oil from the valve. U.S. Patent No. 4,454,80
The advantages of such a structure over that disclosed in No. 1 (Span) are as follows.

First, the lack of an end stop ring and the need for a counterbore at each end of the sleeve allows the sleeve to have an extremely thin wall construction and therefore for a given internal diameter. Its outer diameter can be reduced,
Additionally, sufficient hoop strength can be provided to withstand stresses applied by hydraulic pressure in the components during operation. The length of the sleeve, measured in the axial direction parallel to the hole, is significantly reduced. The “flow on” reduction in the outer diameter and length of the sleeve and the corresponding reduction in the overall dimensions of the valve and valve housing reduces material usage and therefore the cost and weight of the overall steering system. significantly reduced.

Second, the one-piece sleeve construction is inherently more reliable than the three-piece sleeve construction of the prior art, and eliminates end stop rings that can come loose or leak oil. Not worth it. U.S. Patent No. 3,591,139
(Bishop) clearly points out the advantages of a one-piece sleeve in terms of overall product reliability.

Third, the arcuate cross-section of the oil return slots in the sleeve essentially provides a deep manifold area for oil collection as oil enters these slots through the last trim feed lip. , the oil is forced through a sharp-edged orifice of relatively small cross-sectional area at the point of oil exit from the sleeve.

Such sharp edged orifices are optionally used to provide a suitably small restriction on the oil flow exiting the sleeve. Such a restriction placed in the hydraulic circuit immediately after the last trimming feed edge before oil return can have a significant effect on reducing valve "hiss" noise. The noise is typically generated by the regulating feed edge of the valve during maximum operating pressure conditions (eg, parking operations). This aperture is, for example, 30 to 50 kP.
Although it only results in an increase in the back pressure on the power steering valve, it has a significant effect in reducing oil cavitation as oil exits beyond the regulating feed lip of the valve. Experience has shown that smaller throttles located further downstream in the hydraulic system, ie closer to the final oil return point of the hydraulic vessel, are much less effective in suppressing valve hiss.

As is well known in the automotive power steering art, valve hiss typically increases noise levels as hydraulic oil temperature increases. This is because the vapor pressure of the fluid increases in response to the temperature increase. If the oil flow in the sleeve is constricted, for example by a reduced diameter drilled hole in the valve return port, the back pressure created by this constriction will increase dramatically as the oil temperature increases, due to the aforementioned decrease in oil viscosity. Decrease. The drill hole, which has a length at least twice its diameter, creates a back pressure on the flow due to essentially viscous energy losses due to the laminar nature of the oil flow in such orifices. Therefore, if a simple drill hole is provided as an oil throttle,
The backpressure will be at a minimum at the temperature when the maximum backpressure is actually needed to suppress the hissing noise.

On the other hand, a sharp-edged orifice provided by an elongated arcuate return slot in the sleeve is less dependent on viscosity. That is, the orifice produces an almost constant back pressure for a given flow rate of oil, regardless of oil temperature. A sharp-edged orifice is generally defined as a particular class of orifice, i.e., the cross-sectional area of the orifice is sharply reduced to a minimum area in a single plane perpendicular to the direction of fluid flow; It is defined as an orifice whose cross-sectional area increases rapidly thereafter. The fluid dynamics of sharp-edged orifices versus bore or tube-type orifices are treated in detail in the text "Hydraulic Control Systems" by Herbert E. Merritt (John Willi & Sons, Inc., 1967). Therefore, detailed explanation will be omitted in the main text. Sharp-edged orifices are therefore particularly effective as noise suppressors in power steering valves at high oil temperatures, and such devices can be installed without extra cost and inconvenience due to the shape of the extended, sharp-edged return slot in the sleeve. Can be provided without.

The linear or prismatic oil return slots disclosed in US Pat. It cannot be used to provide aperture. Indeed, in this patent specification, the structure is specifically aimed at reducing the hydraulic backpressure of the power steering valve.

Fourth, the elongated arcuate return slot is arranged to extend into only one end of the sleeve, unlike the straight slot disclosed in US Pat. No. 4,454,801 (Span). can do. The slots in the above patent must necessarily extend to both ends of the sleeve due to the broaching method used in their manufacture. As is known in the power steering field, oil return is typically extracted from only one side of the sleeve. Therefore,
An arcuate slot extending to only one end of the sleeve is much more desirable than the functionally redundant arrangement disclosed in US Pat. No. 4,454,801 (Span).

[0016] Another prior art construction relevant to the present invention is disclosed in US Pat. It differs in that it has an extended arcuate slot in the input shaft for oil return. Because the input shaft is axially extended and therefore the arcuate return slot is relatively deep, the torsional strength of the input shaft is greatly reduced. This is extremely important under fail-safe conditions where the input shaft is required to withstand full manual steering torque in the event of a torsion bar failure. Large diameter input shafts (typically two
2-23mm diameter) reduced torsional strength of 1960
acceptable due to the large extra strength that existed in the design of the components in the 1990s. However, the axially extending oil return slot present in the input shaft is typically quite poor in terms of torsional strength in modern "small" power steering valves with input shafts approximately 18-19 mm in diameter. Not acceptable. From the point of view of torsional strength, it is much more advantageous to extend the slot in the oil return sleeve in the axial direction. This is because this component cannot be subjected to large torsional stresses even in fail-safe operation.

US Pat. No. 3,591,139 (Bishop) is similar to US Pat.
Same as No. 93,608 (Saunders). Therefore, the former structure reduces the torsional strength of the input shaft, which is important in fail-safe operation as described above.

[0018]

SUMMARY OF THE INVENTION The object of the present invention is to provide a rotary valve, particularly for hydraulic power steering of a vehicle, which overcomes the drawbacks of the prior art described above.

[0019]

[Means for Solving the Problems] In order to achieve the above object, the rotary valve of the present invention includes an input shaft supported in a sleeve,
a substantially arcuate first tube formed within the internal bore of the sleeve;
and a second row of slots, at least one of the first slots being stopped beyond the end of the hole;
at least one of the second slots extends to an axial extremity of at least one of said holes to provide a return port for hydraulic fluid, each return port being defined by the circumference of an input shaft and its associated second slot; shaped and in the form of a sharp-edged orifice, said associated first and second slots having substantially the same axial length in an axial direction distal from said respective return port.

In a preferred embodiment of the invention, the slot is in the form of a segment of a circle, and the radius of curvature of the second slot is greater than the radius of curvature of the first slot.

In other embodiments, the maximum radial depth of the second slot is greater than the maximum radial depth of the first slot.

In a preferred embodiment, the arcuate return slot in the sleeve has a relatively large radius and its center of curvature is axially displaced relative to the arcuate feed slot. This has the effect of limiting the radially outward penetration depth of the return slot. Of course, said depth is longer than the feed slot. Sleeves with arcuate internal slots can be manufactured in mass production using, for example, a milling machine of the type disclosed in U.S. Pat. No. 4,154,145 (Bishop). Various slot radii and centers of curvature of the return and feed arcuate slots can be easily achieved during manufacturing by double processing the part with two vertical mills. In an 8-slot type sleeve, for example, the first vertical mill drills four long large radius return slots, and the second
A vertical milling machine can drill four short small radius feed slots.

The response of the rotary valve of the present invention is maximized by maintaining the above-described overlapping relationship of the sleeve slot and input shaft slot over the entire length of the slot's regulating feed edge. This is achieved by the present invention. This is accomplished by axially aligning the ends of the input shaft slot with the associated sleeve slot at a location distal from the associated fluid return port. Misalignment of the ends of the associated sleeve slot and input shaft slot effectively shortens the regulating feed length of the valve and thus reduces its responsiveness. The invention will now be explained with reference to illustrated embodiments.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 show a valve assembly 1 and a part A of the valve assembly 1, which includes a sleeve 2, an input shaft 3, a pinion 4, a torsion rod 5 as main components. including. The torsion rod flexibly connects the input shaft 3 and the pinion 4. The valve assembly 1 along with a number of seals, pins, clips and bearings is housed within a valve housing 6. The valve housing is a housing 7 of a rack and pinion type steering wheel device.
bolted to.

Only the specific operation of the valve assembly 1 with respect to the method of returning oil from the valve assembly to the hydraulic vessel is relevant to the present invention. Therefore, as noted above, a general description of the method of operation of the valve assembly is omitted herein.

The sleeve 2 is, by way of example, of six-slot construction, thus having three supply slots 9 and three return slots 10 spaced circumferentially around the bore 8. These supply slots and return slots are interposed alternately between the six input shaft slots 11 in an overlapping state in the above-mentioned normal rotary valve.

The supply slot 9 is a conventional arcuate dead-ended slot, whereas the arcuate return slot 10 is elongated and directs the return oil flow 12 through the constriction of a sharp-edged orifice 13 to the sleeve 2. discharge in the axial direction. The sharp-edged orifice 13 has an arcuate return slot 10
is formed as a result of intersecting the axial tip 14 of the sleeve 2 adjacent to the outer diameter 22 of the input shaft 3 but within the sleeve skirt portion 15 . The return oil flow 12 then passes through a large annular cavity 16 separating the sleeve skirt 15 and pinion 4 and then passes through the return ports 22, 13.
The oil enters the oil return passage 17 from the power steering valve housing 6 through.

The hydraulic restrictions created by the sharp edged orifices 13 create a pressure differential across these orifices as oil passes through them. The resulting backpressure is therefore applied to the entire hydraulic circuit before these orifices return to the hydraulic pump. As previously mentioned, the sharp-edged shape of these orifices provided by the arcuate shape of return slot 10 makes the magnitude of this additional backpressure relatively invariant to oil temperature, thus reducing valve hiss. It is an ideal and extremely low cost means of reducing noise. The hissing noise typically occurs due to oil cavitation at high temperatures.

As shown in FIGS. 1 and 2, the elongated arcuate return slot 10 in the sleeve 2 has a large radius and has a center of curvature displaced to the right compared to the arcuate feed slot 9. maintains the same axial distance away from return port 22. As previously mentioned, this allows the return slot 10 to "pass through" the axial tip 14 of the sleeve 2 adjacent the outer diameter 22 of the input shaft 3, but the slot 10 is approximately at the depth of the feed slot 9. Limited to equal depth. The structural integrity of the sleeve 2 is therefore not compromised.

3 and 4 correspond to the components of FIGS. 1 and 2 and are shown in US Pat.
and U.S. Patent No. 3,591,139 (Bishop)
Components corresponding to the prior art disclosed in 2006 are given the same reference numerals, so that structural differences between these prior art and embodiments of the present invention will be easily understood.

In the case of FIG. 3, the return slot 10 is linear and the oil returns axially under the retaining ring 18 via a long narrow cavity 19. As previously mentioned, the cavity 19 is not intended as an orifice to provide back pressure to the valve to reduce valve cavitation hiss (quite the contrary in fact). However, if these cavities are designed narrow enough to create such backpressure,
These orifices are too viscous to achieve appreciable valve hiss reduction at high oil temperatures. This is because these cavities are similar to the pipe-type orifices described above.

In the case of FIG. 4, the oil is returned through an elongated arcuate slot 20 in the input shaft 3. The unextended arcuate slot 21 communicates with the oil supply, while the dead end arcuate slot 23 of the sleeve 2 connects to the hydraulic cylinder connection. The method of operation of this rotary valve is different from any of the embodiments of the present invention, and in fact is quite different from that shown in U.S. Pat. No. 4,454,801 (Span), shown in FIG. However, FIG. 3 illustrates the impractical use of an extended arcuate return slot in the input shaft due to the large loss in torsional strength of this component.

[0033] The present invention is not limited to what has been described above, and various modifications can be made within the scope of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a valve assembly of the present invention.

FIG. 2 is an enlarged view of area A in FIG. 1;

FIG. 3 is a view similar to FIG.
FIG. 2 is a diagram showing a structure having essential features of the invention of No. 01 (Span).

FIG. 4 is an enlarged view of the same area as FIG.
91,139 (Bishop) valve assembly.

[Explanation of symbols]

1 Valve assembly 2 Sleeve 3 Input shaft 4 Pinion 5 Torsion rod 6 Housing 7 Steering gear device housing 9 Supply slot 10 Return slot 11 Input shaft slot 12 Return oil flow 13 Orifice 16 Annular cavity part 18 Retaining ring 19 Narrow cavity 20 Extended arcuate slot

Claims (6)

[Claims] 1. An input shaft supported in a sleeve and an array of substantially arcuate first and second slots formed within an internal bore of the sleeve, at least one of the first slots being at least one of the second slots extends to the axial extremity of at least one of the holes to provide hydraulic fluid return ports, each return port being stopped short of the end of the hole; defined by and associated with the input shaft and its associated second slot in the form of a sharp-edged orifice, said associated first and second slots extending substantially axially away from said respective return ports. A rotary valve characterized in that it has the same axial length. 2. Rotary valve according to claim 1, characterized in that the arcuate slot is in the form of a segment of a circle. 3. The rotary valve of claim 2, wherein the center of curvature of the second slot of the row is axially displaced with respect to the center of curvature of the first slot of the row. 4. The rotary valve of claim 2, wherein the radius of curvature of the second slot in the row is greater than the radius of curvature of the first slot in the row. 5. The rotary valve of claim 1, wherein the maximum radial depth of the second slot of the row is greater than the maximum radial depth of the first slot of the row. 6. The first slot of the row is arranged as a supply port for the valve.
The rotary valve described in .