GB2199000A - A valve assembly for a power assisted steering system - Google Patents
A valve assembly for a power assisted steering system Download PDFInfo
- Publication number
- GB2199000A GB2199000A GB08630373A GB8630373A GB2199000A GB 2199000 A GB2199000 A GB 2199000A GB 08630373 A GB08630373 A GB 08630373A GB 8630373 A GB8630373 A GB 8630373A GB 2199000 A GB2199000 A GB 2199000A
- Authority
- GB
- United Kingdom
- Prior art keywords
- valve
- sleeve
- carrier part
- valve sleeve
- valve assembly
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 230000007935 neutral effect Effects 0.000 claims abstract description 25
- 239000012530 fluid Substances 0.000 claims abstract description 18
- 238000003466 welding Methods 0.000 claims abstract description 6
- 238000006073 displacement reaction Methods 0.000 claims description 7
- 230000000295 complement effect Effects 0.000 claims description 5
- 230000000452 restraining effect Effects 0.000 claims description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 230000000712 assembly Effects 0.000 description 2
- 238000000429 assembly Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000013459 approach Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
- B62D5/08—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle characterised by type of steering valve used
- B62D5/083—Rotary valves
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Power Steering Mechanism (AREA)
Abstract
The imput shaft (2) has a valve rotor (3) received in a valve sleeve (16) of the output shaft (5) and relative rotation between the rotor (3) and sleeve (16) from a neutral condition of a valve which they form controls fluid flow for power assistance. A torsion rod (7) extends between the shafts (2) and (5) to bias the rotor (3) and sleeve (16) to the neutral condition. Secured on the shaft (5) for rotation therewith is a carrier (10) within radial bores (12) of which are mounted balls (14) that are radially displaceable in response to fluid pressure thereon to engage in seats (13) in the shaft (2). As fluid pressure on the balls (14) increases they are urged into engagement with the shaft (2) to restrain relative rotation between the shafts (2) and (5) for reducing power assistance which is available. The sleeve (16) is initially coupled through sliding surfaces (17, 18) to the carrier (10) so that, on setting up of the valve, the sleeve (16) can be rotated relative to an optimum position of engagement between the balls (14) and their seats (13) to ensure that the valve is in its neutral condition. Following such setting up the surfaces (17, 18) are secured for example by welding, bonding, peening or pinning. <IMAGE>
Description
TITLE
"A valve assembly for a power assisted steering system"
TECHNICAL FIELD & BACKGROUND ART
The present invention relates to a valve assembly for a power assisted steering system of the kind having relatively rotatable and coaxial input and output components one of which components has a valve sleeve and the other of which has a valve rotor received in the sleeve to form a valve. The valve is rotationally adjusted from a neutral condition by relative rotation between the input and output components in response to a steering input or manoeuvre to control the flow of fluid under pressure for providing appropriate power assistance to the steering manoeuvre in known manner.With such known valve assemblies it is conventional to provide spring means such as a torsion bar or C-spring unit which reacts between the input and output components and rotationally biases those components relative to each other and into the neutral condition of the valve.
It is preferred that power assisted steering systems are speed proportional in the sense that as vehicle speed increases there is a reduction in the power assistance which is normally provided (so that the steering "feel" approaches that of a manual system) and as vehicle speed decreases, the power assistance which is available increases (so that maximum power assistance is provided for slow moving manoeuvres). A means of achieving such speed proportional power assisted steering is disclosed in our
G.B. Patent No. 1,465,901 in which displaceable balls are carried by the valve sleeve to be displaceable into engagement with seats in the rotor.The balls are displaceable under fluid pressure which pressure varies in response to vehicle speed so that as the speed increases the pressure increases to urge the balls into engagement with their seats and thereby restrain relative rotation between the valve rotor and sleeve from the neutral condition of the valve to reduce the power assistance available as vehicle speed increases and conversely the power assistance increases as vehicle speed decreases when the fluid pressure on the balls is reduced.In our aforementioned British Patent the balls are radially displaceable between the sleeve and rotor but alternative proposals are known having a similar effect where the balls are replaced by other forms of displaceable members (such as pistons or generally cylindrical elements) and where the displaceable members are displaced axially rather than radially in response to fluid pressure as vehicle speed increases to restrain relative rotation between the valve sleeve and rotor. Further examples of valve assemblies having the characteristics discussed above are disclosed in
Japanese Publications Nos. 86/12469 and 86/18566 and U.S.
Patent No. 4,593,783.
It is usual practice for the seatings with which the displaceable members engage to be in the form of recesses having cam surfaces which are profiled to provide predetermined characteristics for the resistance which is presented to restrain relative rotation between the input and output components when the members engage with their seatings under a particular hydraulic fluid pressure.
These profiled seatings are conventionally symmetrical so that when the displaceable members engage with central positions in their seatings, the resistance characteristics to relative rotary displacement between the input and output members is symmetrical for both directions of such displacement. When the displaceable members are located relative to their seatings so that they will engage in the aforementioned central positions the valve should be in its neutral condition.If this is not the case then the valve assembly and steering gear can present different characteristics when the displaceable members are urged under fluid pressure into engagement with their seatings when the input and output components are rotated relative to each other from the neutral condition in one sense of direction as compared with the effect from relative rotation in the opposite sense of direction so that the feel of the power assisted sSteering system is not symmetrical. Consequently the valve assembly should be set-up with the valve in its neutral condition while the fluid pressure displaceable members are located to engage centrally with their respective seatings and it is an object of the present invention to provide a valve assembly by which this may be achieved relatively simply and inexpensively.
STATEMENT OF INVENTION & ADVANTAGES
According to the present invention there is provided a valve assembly for a power assisted steering system, which assembly has relatively rotatable and coaxial input and output components, a first of said components having a valve sleeve and the second component having a valve rotor which is received in said sleeve to comprise a valve which is rotationally adjusted by relative rotation between the first and second components, spring means rotationally biasing the input and output components relative to each other and to a neutral condition of the valve; displaceable means carried by the first component and being responsive to fluid under pressure to engage in seating means carried by the second component for restraining relative rotation between those components and thereby restraining adjustment of the valve from its neutral condition and wherein said displacement means is located in a carrier part of the first component remote from the valve sleeve and said valve sleeve is mechanically coupled to the carrier part by adjustment means which, in setting up of the assembly, permits relative rotation between the valve sleeve and the carrier part to rotationally position the valve sleeve relative to the displacement means and seating means for said valve to be in its neutral condition and which adjustment means can be locked following said setting up for the valve sleeve to rotate in unison with the carrier part.
By the present invention it is envisaged that when the input and output components are assembled coaxially the carrier part can be located so that the displaceable means (which will usually be in the form of balls, pistons or plungers as previously discussed) can be accurately aligned to engage centrally with the respective seatings in the component having the valve rotor - thereby ensuring that from this condition, any relative rotation between the rotor and the carrier part in either sense of direction will develop reactions between the displaceable means and their seatings which are symmetrical for both directions of rotation.During this initial setting up of the valve assembly the adjustable means which mechanically couples the valve sleeve to the carrier part will permit the valve sleeve to be rotationally adjusted relative to the carrier part; as a consequence the valve sleeve can now be rotationally adjusted relative to the carrier part and to the rotor which the valve sleeve accommodates until the valve sleeve is positioned relative to the valve rotor for the valve to be in its neutral condition. With the valve in its neutral condition, the valve sleeve is now locked to the carrier part to rotate in unison therewith and with the input or output component having the carrier part; from this it will follow that, when the valve is in its neutral condition, the displaceable means will be positioned relative to their respective seatings so that they will engage centrally with those seatings for developing reactions which are symmetrical for relative rotation in either sense of direction between the displaceable means and the seating means.
The adjustment means between the carrier part and the valve sleeve may simply comprise respective surfaces which slide over each other during rotational adjustment and which can be locked together following adjustment by a welding, bonding, peening or pinning technique.
Preferably the adjustment means comprises an annular flange or ring carried to rotate in unison with one of the carrier part and valve sleeve and which is slidably received in a complementary annular recess of the other of the carrier part and valve sleeve so that when the sleeve and carrier part have been rotated relative to each other to set the valve in its neutral condition, the aforementioned annular flange or ring can be locked within the recess to ensure that the carrier part and valve sleeve rotate in unison.
The displaceable means can be displaced into engagement with the seating means axially, radially or otherwise as is known in the art.
In addition to having the advantage that the valve assembly of the present invention can be set-up initially so that the valve in its neutral condition will correspond with the most desirable positioning in which the displaceable means should co-operate with the seating means, the location of the displaceable means in the carrier part remote from the valve sleeve permits an effective increase in the diameter at which the displaceable means can co-operate with the respective seating means on the input or output component having the valve rotor. Consequently the aforementioned diameter can be independent of the diameter of the valve sleeve and thereby provide, for a given hydraulic pressure on the displaceable means, a greater reaction between the displaceable means and the seating means to restrain relative rotation between the valve rotor and valve sleeve.
There is also the advantage that the location of the displaceable means within the carrier part remote from the valve sleeve may alleviate axial tipping forces on the valve sleeve (as a reaction from the engagement of the displaceable means with the seating means) and thereby permit a smoother operation of the valve.
DRAWINGS
One embodiment of a valve assembly for a rack and pinion power assisted steering system constructed in accordance with the present invention will now be described, by way of example only, with reference to the accompanying illustrative drawings in which:
Figure 1 is an axial section through the valve assembly, and
Figure 2 is a section of the valve assembly taken on the line II - II of Figure 1.
DETAILED DESCRIPTION OF DRAWINGS
The valve assembly illustrated is for a rack and pinion power assisted steering system of which the structure and components not illustrated may be considered as conventional. The valve assembly has a housing 1 with a stepped cylindrical bore which will usually be mounted to communicate from a pinion housing (not shown) of the rack and pinion gear. Extending into the housing 1 is an input shaft 2 having a valve rotor 3 and a radially outwardly extending flange 4 axially spaced from the rotor 3. An output shaft 5 is mounted within the housing 1 coaxially with the shaft 2 and has a pinion 6 (for engagement with a rack bar in conventional manner) axially remote from the input shaft 2. The input shaft 2 is tubular and receives a torsion bar 7 which projects axially from the input shaft into a recess 8 in the output shaft 5.The torsion bar 7 is pinned at 9 to the input shaft 2 for rotation therewith while the end of that bar in the recess 8 is splined to the output shaft for rotation therewith. Consequently the torsion bar 7 provides a conventional form of spring means which rotationally biases the input and output shafts relatively to each other and to a predetermined condition.
Located on the output shaft 5 within the housing 1 is a tubular and generally annular carrier 10 which is secured for rotation with the output shaft 5 by any convenient means such as a press fit, bonding, welding or pinning.
The carrier 10 is mounted within the housing 1 in needle rollers 11 which provide bearings for the output shaft 5.
The carrier 10 includes a skirt 10a which extends axially over the flange 4 on the input shaft 2. Located in the skirt 10a is a circumferentially spaced array of four bores 12 which extend radially through the wall of the skirt in the same radial plane as the flange 4. Located in the periphery of the flange 4 are four seatings 13 which are disposed in a circumferentially spaced array corresponding to the array of the bores 12. In the present example the seatings 13 are shown as part cylindrical recesses but can be of any required recessed cam profile.With the torsion bar 7 coupled at 8 and 9 to the output and input shafts respectively and in an unstressed condition, the bores 12 are arranged to directly oppose the respective seatings 13 with the axes of the bores 12 extending radially of the input shaft 2 and passing through the respective centres of the seatings 13 so that the profile of each seating is symmetrical circumferentially about the aforementioned axis of the respective bores 12.
Each bore 12 houses a displaceable member in the form of a ball 14 which is a close sliding fit within the respective bore in which it is housed. The balls 14 are capable of engaging with the respective seatings 13, for example in generally complementary manner as shown in
Figure 2. The housing 1 includes a port 15 through which hydraulic fluid under pressure is admitted into the bores 12 on the side of the displaceable balls 14 remote from the rotor shaft 2. As the fluid pressure in port 15 increases and greater pressure is applied to the balls 14 to urge them into their respective seatings 13, there is a greater resistance to relative rotation between the input shaft 2 and the carrier 10 (and thereby between the input and output shafts).In accordance with conventional practice the fluid pressure at 15 can be directly proportional to the speed of a vehicle which incorporates the steering system so that as vehicle speed increases the pressure increases and vice versa as is well known for vehicle speed responsive or speed proportional feel steering gears.
The valve rotor 3 is received in the housing 1 within a valve sleeve 16. The valve rotor and sleeve include fluid control surfaces and ports which may be regarded as conventional for a hydraulic valve so that relative rotation between the sleeve and rotor from a neutral condition of the valve controls flow of hydraulic fluid to and from a power assistance means of the steering gear in known manner. To provide this fluid control the rotor 3 will rotate with the input shaft 2 while the valve sleeve 16 will rotate in unison with the carrier 10 and thereby with the output shaft 5 as permitted by twisting of the torsion bar 7 in response to a steering torque being applied to the input shaft 2 and a resistance being applied to rotation of the output shaft 5.
However, for reasons previously discussed for efficient steering characteristics and feel of the gear, the radial alignment of the balls 14 centrally with their respective seatings 13 when the torsion bar 7 is unstrained (that is without a steering torque being applied to the input shaft 2) should correspond with the valve comprising the rotor 3 and sleeve 16 being in a neutral condition.
To facilitate the setting up of the assembly in such a desirable condition, the sleeve 16 is constructed separately from the carrier 10 but is mechanically linked thereto so that the sleeve can be rotationally adjusted relative to the carrier 10 (and thereby relative to the rotor 3) so that the valve can be set-up in its neutral condition. With this in mind the end of the sleeve 16 adjacent to the output shaft 5 has mounted thereon an annular collar 17 which is slidably received within a complementary axially extending recess 18 in the adjacent end of the skirt 10a of the carrier 10. The collar 17 is provided with a radially extending pin 19 which is received as a close sliding fit within an axially extending slot 20 in the end of the sleeve 16 so that the sleeve and collar will rotate in unison.Consequently during the initial construction of the valve assembly, the sleeve 16 can be rotated relative to the carrier 10 and thereby relative to the output shaft 5 by rotationally sliding the collar 17 within the complementary recess 18 - the collar 17 being rotated in unison with the sleeve 16 by the drive transmitted through the pin 19.
The sleeve 16 is rotated relative to the carrier 10 and thereby relative to the rotor 3 until the valve is in its predetermined neutral condition. With the valve in this latter condition, the collar 17 is locked to the carrier sleeve 10a by any convenient means such as welding, bonding, peening or pinning so that the sleeve 16 and carrier 10 will then rotate in unison.
It will be appreciated that the initial setting-up of the valve to its neutral condition as aforementioned and the locking of the collar 17 to the carrier 10 will usually occur prior to the input and output shafts (and the respective parts and components carried thereby) being located as a sub-assembly within the housing 1.
Claims (13)
1. A valve assembly for a power assisted steering system, which assembly has relatively rotatable and coaxial input and output components, a first of said components having a valve sleeve and the second component having a valve rotor which is received in said sleeve to comprise a valve which is rotationally adjusted by relative rotation between the first and second components; spring means rotationally biasing the input and output components relative to each other and to a neutral condition of the valve; displaceable means carried by the first component and being responsive to fluid under pressure to engage in seating means carried by the second component for restraining relative rotation between those components and thereby restraining adjustment of the valve from its neutral condition and wherein said displacement means is located in a carrier part of the first component remote from the valve sleeve and said valve sleeve is mechanically coupled to the carrier part by adjustment means which, in setting up of the assembly, permits relative rotation between the valve sleeve and the carrier part to rotationally position the valve sleeve relative to the displacement means and seating means for said valve to be in its neutral condition and which adjustment means can be locked following said setting up for the valve sleeve to rotate in unison with the carrier part.
2. A valve assembly as claimed in claim 1 in which the adjustment means comprises respective surfaces of the carrier part and the valve sleeve which slide over each other during rotational adjustment between the valve sleeve and the carrier part.
3. A valve assembly as claimed in either claim 1 or claim 2 in which the adjustment means comprises an annular flange or ring carried to rotate in unison with one of the carrier part and the valve sleeve and which is slidably received in a complementary annular recess of the other of the carrier part and the valve sleeve so that, when the valve sleeve and carrier part have been rotationally adjusted relative to each other, the annular flange or ring can be locked within the annular recess.
4. A valve assembly as claimed in any one of the preceding claims in which the adjustment means is locked for the valve sleeve to rotate in unison with the carrier part by welding, bonding, peening or pinning.
5. A valve assembly as claimed in any one of the preceding claims in which, with the adjustment means locked, the valve sleeve is rotatable in unison with the carrier part through means by which the valve sleeve can be displaced axially relative to the carrier part.
6. A valve assembly as claimed in claim 5 in which the valve sleeve is rotatable in unison with the carrier part through a pin which closely engages in an axially extending slot so that the valve sleeve is displaceable axially relative to the carrier part.
7. A valve assembly as claimed in claim 6 when appendant to claim 3 in which the pin and slot engagement is provided between the annular flange or ring and the valve sleeve.
8. A valve assembly as claimed in any one of the preceding claims in which the carrier part comprises a tubular component within which the first of the input and output components is received and which is secured for rotation with that first component.
9. A valve assembly as claimed in claim 8 in which the tubular component is secured to the first component by a press fit, bonding, welding or pinning.
10. A valve assembly as claimed in either claim 8 or claim 9 in which the tubular component has a part which overlies the seating means and in which part is located the displacement means.
11. A valve assembly as claimed in any one of the preceding claims in which the first component comprises an output shaft and the second component comprises an input shaft which is rotatable in response to a steering input.
12. A valve assembly substantially as herein described with reference to the accompanying illustrative drawings.
13. A power assisted steering system which includes a valve assembly as claimed in any one of the preceding claims.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8630373A GB2199000B (en) | 1986-12-19 | 1986-12-19 | A valve assembly for a power assisted steering system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8630373A GB2199000B (en) | 1986-12-19 | 1986-12-19 | A valve assembly for a power assisted steering system |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8630373D0 GB8630373D0 (en) | 1987-01-28 |
| GB2199000A true GB2199000A (en) | 1988-06-29 |
| GB2199000B GB2199000B (en) | 1990-09-26 |
Family
ID=10609281
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8630373A Expired - Lifetime GB2199000B (en) | 1986-12-19 | 1986-12-19 | A valve assembly for a power assisted steering system |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2199000B (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2212463A (en) * | 1987-11-14 | 1989-07-26 | Burman & Sons Ltd | Power-assisted steering gear |
| WO1992020560A1 (en) * | 1991-05-24 | 1992-11-26 | A.E. Bishop & Assoicates Pty. Limited | Rotary valve for power steering |
| WO1993009019A1 (en) * | 1991-10-29 | 1993-05-13 | Trw Steering & Suspension Australia Limited | Rotary valve for hydraulic power steering |
| FR2748071A1 (en) * | 1996-04-25 | 1997-10-31 | Daimler Benz Ag | REACTION SYSTEM ON A SERVOVALVE DEVICE |
| WO1998024678A1 (en) * | 1996-12-05 | 1998-06-11 | Mercedes-Benz Lenkungen Gmbh | Feedback system for a servo valve system |
-
1986
- 1986-12-19 GB GB8630373A patent/GB2199000B/en not_active Expired - Lifetime
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2212463B (en) * | 1987-11-14 | 1991-12-11 | Burman & Sons Ltd | Power-assisted steering gear |
| GB2212463A (en) * | 1987-11-14 | 1989-07-26 | Burman & Sons Ltd | Power-assisted steering gear |
| US5251669A (en) * | 1991-05-24 | 1993-10-12 | A. E. Bishop & Associates Pty. Limited | Power steering valves |
| WO1992020560A1 (en) * | 1991-05-24 | 1992-11-26 | A.E. Bishop & Assoicates Pty. Limited | Rotary valve for power steering |
| WO1992020561A1 (en) * | 1991-05-24 | 1992-11-26 | A.E. Bishop & Associates Pty. Limited | Rotary valve for power steering |
| EP0609353B1 (en) * | 1991-10-29 | 1996-02-07 | TRW STEERING & SUSPENSION AUSTRALIA LIMITED | Rotary valve for hydraulic power steering |
| WO1993009019A1 (en) * | 1991-10-29 | 1993-05-13 | Trw Steering & Suspension Australia Limited | Rotary valve for hydraulic power steering |
| FR2748071A1 (en) * | 1996-04-25 | 1997-10-31 | Daimler Benz Ag | REACTION SYSTEM ON A SERVOVALVE DEVICE |
| GB2314054A (en) * | 1996-04-25 | 1997-12-17 | Daimler Benz Ag | Reaction arrangement and centering device in a steering servo valve |
| GB2314054B (en) * | 1996-04-25 | 1998-06-10 | Daimler Benz Ag | Reaction arrangement on a servo valve arrangement |
| US6009903A (en) * | 1996-04-25 | 2000-01-04 | Daimlerchrysler Ag | Steering reaction force control arrangement for a power steering servo valve |
| WO1998024678A1 (en) * | 1996-12-05 | 1998-06-11 | Mercedes-Benz Lenkungen Gmbh | Feedback system for a servo valve system |
| US6227244B1 (en) | 1996-12-05 | 2001-05-08 | Mercedes-Benz Lenkungen Gmbh | Feedback system for a servo valve system |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8630373D0 (en) | 1987-01-28 |
| GB2199000B (en) | 1990-09-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20011219 |