GB2165502A - A power-assisted steering gear - Google Patents
A power-assisted steering gear Download PDFInfo
- Publication number
- GB2165502A GB2165502A GB08425828A GB8425828A GB2165502A GB 2165502 A GB2165502 A GB 2165502A GB 08425828 A GB08425828 A GB 08425828A GB 8425828 A GB8425828 A GB 8425828A GB 2165502 A GB2165502 A GB 2165502A
- Authority
- GB
- United Kingdom
- Prior art keywords
- shafts
- neutral condition
- valve
- spring
- relative
- 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
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
A power-assisted steering gear has a steering input shaft 9 and a pinion shaft 4 which are co-axially coupled together through a torsion bar 13 so that the shafts 4 and 9 are capable of restricted rotation relative to each other. The input shaft 9 includes a valve rotor 10 which is received within a valve sleeve 3 rotatable with the output shaft 4. Mounted on the shaft 9 is a C-shaped spring 18 to provide an additional biasing force to restore the rotary valve to its neutral condition. Preferably the C-spring 18 is pre-loaded so that this pre-load has to be overcome before the rotary valve can be displaced from its neutral condition. <IMAGE>
Description
SPECIFICATION lk power assisted steering gear
Technical field and background art
This invention relates to a power assisted steering gear of the type having a rotary valve which is operated in response to a steering input to control flow of hydraulic fluid to and from a servo motor to assist in the steering manoeuvre. In such a gear, which may be incorporated as part of a rack and pinion steering assembly as is well known in the art and currently favoured as a most efficient, reliable and inexpensive assembly, it is usual to have co-axial input and output shafts, the former of which is rotatable in response to a steering manoeuvre and the latter of which rotates to drive, for example, a pinion or other component from which an output is derived from the gear.These shafts are capable of restricted rotation relative to each other and this relative rotation is utilised to adjust valve means for controlling fluid flow. Conventionally the valve means has a valve sleeve rotatable with one of the shafts and a valve rotor in the sleeve which is rotatable with the other of the shafts and it is the relative rotation between the sleeve and rotor which serves to provide the necessary control of fluid flow. To provide adequate feel and self centralising for the valve means a biasing means is provided which biases the sleeve rotationally relative to the rotor and to a neutral condition of the valve means so that during a steering manoeuvre a rotational displacement between the rotor and sleeve from the neutral condition will result in the development of a restoring force which opposes that manoeuvre.A well known and widely adopted form of biasing means for the valve means is a torsionally responsive component which provides a co-axial coupling between the input and output shafts so that relative rotation between the shafts from the neutral condition is resisted by twisting of the component to energise the latter and bias the shafts and thereby the valve means in a sense to return it to the neutral condition. The torsionally responsive component is usually in the form of a rod or bar examples of which are to be found in many of our prior Patents on rack and pinion steering gears such as G.B. 1,470,975 and 2,122,151A.
The modern rotary valve is manufactured to extremely close tolerances and may be regarded as a sophisticated design which lends itself to economical manufacture and provides a very accurate and safe performance. The combination of such a rotary valve with biasing means in the form of a torsion bar or similar component have generally
proved acceptable. However, it is becoming apparent that with modern high performances vehicles where steering manoeuvres are made when driving a vehicle fast, the self centering characteristics
of the torsion bar (or the ability of the torsion bar to return the valve means to its neutral condition following a steering manoeuvre) are effected at a
slower rate and with less precision than that which
is considered desirable.The reason for this is that when manoeuvring at high speed it is likely that only a relatively small angular displacement will be effected (between the valve sleeve and rotor) from the neutral condition and this small displacement will provide a correspondingly small energisation of the torsion bar. Consequently when a slight steering manoeuvre is completed only a small energy in the bar is available to return the valve means to its neutral condition so that the rotary valve responds slowly and can take an unacceptably long period before it "settles down" in its neutral condition.On the contrary, and as has been determined from long experience, the torsion bar has proved itself fully satisfactory in providing adequate response to the rotary valve following a steering manoeuvre with relatively large angular displacements (between the valve sleeve and rotor) from the neutral condition as would be encountered during a steering manoeuvre at slow speed.
There is therefore a requirement for a power assisted steering gear which incorporates a rotary valve of the kind discussed above and has a biasing means which provides a rapid response to return the valve to its neutral condition following a relatively small angular displacement between the valve sleeve and the rotor and which response is an improvement over that exhibited by the conventional torsion bar (or similar torsional biasing) and which will also have the advantages attributable to the torsion bar (or similar torsional biasing) for a relatively large angular displacement (between the valve sleeve and rotor) from the neutral condition. It is an object of the present invention to satisfy the above mentioned requirement.
Statement of invention and advantages
According to the present invention there is provided a power assisted steering gear comprising co-axial input and output shafts which are capable of restricted rotation relative to each other and which input shaft is rotatable in response to a steering input and rotation of the output shaft follows from rotation in the input shaft; valve means having a valve sleeve rotatable with one of said shafts and a valve rotor in said sleeve rotatable with the other of said shafts, relative rotation between said sleeve and rotor from a neutral condition serving to control fluid flow for power assistance; and means biasing the valve means to the neutral condition, the biasing means comprising a torsionally responsive component which provides a co-axial coupling between the shafts so that relative rotation between the shafts from the
neutral condition is resisted by the component which is torsionally energised to bias the valve
means to its neutral condition, and a spring means acting in a plane that extends radially relative to said shafts and is energised by relative rotation between the shafts from the neutral condition to provide additional biasing to return the valve means to its neutral condition.
By the proposal of the present invention two dis
crete biasing devices are provided which serve to
bias the valve means to its neutral condition and
both of these biasing devices are energised simul taneously upon angular rotational displacement between the valve sleeve and valve rotor from the neutral condition. However, for a relatively small angular displacement a self centering force exerted by the spring means is intended to predominate to restore the valve to its neutral condition following a steering manoeuvre whereas for a large angular displacement between the sleeve and rotor the self centering force which is exerted by the torsionally responsive component may predominate to restore the valve to its neutral condition.With this arrangement and by appropriately matching the torsionally responsive component and the spring means it is possible to provide a rotary valve arrangement which has a rapid response and precise control to positively locate the valve means in its neutral condition irrespective of the extent, frequency and speed of steering manoeuvres. It also has the advantage that when the valve is in its neutral condition the restraining effect of the spring means will maintain the valve means in that condition against deflecting forces which may result other than from a steering manoeuvre, for example by road vibration.
The spring means is preferably in the form of a
C-shaped spring member (or so-called "circa" spring) which is mounted to one of the shafts in a radial plane thereof with the mouth of the C-spring engaging an abutment on that shaft. This abutment restrains the spring from rotating as a whole relative to the shaft on which it is mounted. The spring mouth is arranged to engage with a second abutment that is rotatable with the other shaft so that, during relative rotation between the two shafts from the neutral condition, the two abutments are displaced circumferentially and the spring is diametrically enlarged and energised (by the reaction through its mouth against the two abutments) to bias the valve means to its neutral condition.The immediate biasing effect presented by the "circa" or C-shaped spring provides the desirable positive centralising on the valve means to achieve the required precise control for the valve means to revert rapidly to its neutral condition.
Preferably the spring means is pre-loaded so that it is necessary to overcome this load before relative rotary movement can take place between the valve sleeve and rotor. It will be appreciated that during initial displacement of the valve means from its neutral condition, the restoring force on the valve means will predominantly be presented by the spring means albeit that the torsionally responsive component will be energised by the twisting action to which it is subjected during relative rotation between the input and output shafts. However, as the extent of relative rotation between the valve sleeve and rotor is increased, the restoring force provided by the torsionally responsive component will progressively increase so that eventually the latter component will predominate.
It has hitherto been proposed to provide a Cshaped spring in a rotary valve for a power assisted steering gear to bias the valve to its neutral condition, see for example our G.B. Patent No.
2,109,757A. However, in prior proposals the Cshaped spring has provided the sole biasing to the valve to restore it to its neutral condition and while this restoring force was adequate for relatively small angular displacement between valve sleeve and rotor from the neutral condition, it did not increase progressively in proportion to the increase in that angular displacement so that it was somewhat inefficient for large rotational displacements between the sleeve and rotor.Consequently, the use of a C-spring as the sole means of biasing the rotary valve has the disadvantage of not providing a fast positive control of the valve for large rotational displacements between the valve sleeve and rotor; it was not until the realisation of the present invention of combining both the spring means (such as the C-shaped spring or circa spring) with the torsionally responsive component (such as a torsion bar) in a rotary valve that the considerable advantage could be achieved of providing a fast and precise control for restoring the valve means in its neutral condition following a steering manoeuvre irrespective of the extent of the relative rotation which is imparted between the valve sleeve and rotor during that manoeuvre.
Drawings
One embodiment of a power assisted steering gear 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 gear, and
Figure 2 is a radial section taken on the line D
D of Figure 1.
Detailed description of drawings
The steering gear is of the type generally known as rack and pinion and has a valve housing 1 forming a cylinder 2 within which is rotationally mounted a conventional valve sleeve 3. Rotatable with the valve sleeve 3 is a pinion shaft 4 on which is formed a pinion 5 that co-operates with a rack on a rack bar (not shown) which is displaceable through a rack bar housing (not shown) in conventional manner to provide a steering output. The valve housing 1 is intended to be bolted or otherwise secured to the rack bar housing through holes 7. The pinion shaft 4 may be integral with the valve sleeve 3 although in the present embodiment it is a separate component which is pinned at 8 to the valve sleeve.
Co-axial with the sleeve 3 and shaft 4 is a tubular input shaft 9 which extends into the valve housing 1 to be rotatable relative to that housing. The input shaft 9 has an inner end 10 in the form of a valve rotor which is received within the bore of the valve sleeve 3. The rotor 10 and sleeve 3 can be regarded as conventional and include ports and passages which are adjusted by relative rotation between the rotor and sleeve to control hydraulic fluid flow through the gear and, for example, by way of ports 11 in the valve housing to a servo motor (such as a double acting piston and cylinder device) operation of which assists in a steering manoeuvre which is applied by rotation of the in put shaft 9 - again in conventional manner.
Extending through the bore 12 of the input shaft is a torsion bar 13, one end of which is secured for rotation with the pinion shaft 4 and the other end of which is secured for rotation with the input shaft 9; in the present example one end of the bar 13 is in splined engagement at 14 with the pinion shaft 4 while the other end is pinned at 15 to the input shaft 9. The arrangement of the torsion bar 13 is conventional as is its function, that is to rotationally bias the sleeve and rotor of the valve means to a neutral condition following relative rotation between the sleeve and rotor in response to a steering manoeuvre applied through the input shaft 9.
When the gear is assembled, the torsion bar 13 is arranged to be in an unstrained condition when the valve means is in its predetermined neutral condition so that relative rotation between the sleeve and rotor from the neutral condition (caused by relative rotation between the shafts 4 and 9) will energise the torsion bar 13 by imparting a twisting effect to the bar which thus biases the valve means to its neutral condition.
Mounted within an annular recess 16 on the input shaft 9 and adjacent to an end face 17 of the valve sleeve 3 is a C-shaped spring member 18.
The spring 18 has a mouth 19 formed by radially extending flanges 20. Received within the mouth 19 is a radially extending pin 21 on the input shaft 9. The flanges 20 abut the pin 21 which latter restrains the C spring 18 from rotating as a whole within the radial plane of the recess 16 and relative to the input shaft 9. Also received within the mouth 19 to be in abutment with the flanges 20 is a pin 22 which is secured to the valve sleeve 3 to extend axially from the end face 17 thereof. The pins 21 and 22 and C spring 18 are arranged so that when both flanges 20 abut both pins 21 and 22 the valve sleeve and rotor are located in the neutral condition of the valve and the spring 18 is arranged to apply a predetermined pre-load in the abutment of its flanges 20 with the pins 21 and 22.
Consequently, immediately there is any rotational or angular displacement between the rotor 10 and sleeve 3 from the neutral condition and in response to a steering input on the shaft 9, there is a circumferential displacement between the pins 21 and 22, the pins thus react on the flanges 20 to open the mouth 19 and diametrically enlarge and energise the spring 18. Consequently, the spring 18 will exert an increased biasing force which, together with the biasing provided by the torsion bar 13, will urge the valve sleeve and rotor to revert to the neutral condition.
Because the C-spring 18 exerts a pre-load on the pins 21 and 22 when in the neutral condition, it is necessary to overcome this pre-load before the valve sleeve and rotor can be displaced from their neutral condition. Consequently, for forces less than the pre-load (for example as may be encountered by road vibration), no relative rotary movement can take place between the sleeve and rotor so that the rotary valve is precisely maintained in its neutral condition.Furthermore, unlike the torsion bar 13 which must necessarily be twisted to progressively increase the biasing force which it exerts to restore the valve to its neutral condition, the C-spring 18 exerts a precise restoring force immediately upon relative circumferential displacement between the pins 21 and 22 so that, depending upon the pre-load of the spring 18, the rotary valve can be quickly restored to its neutral condition in a precise manner and following even a slight steering manoeuvre.The torsion bar 13, unlike the C-spring 18, does not provide an efficient system for positively centering the rotary valve in ite neutral condition; however, when there has been sufficient relative rotation between the valve sleeve and rotor to adequately energise the torsion bar 13, the optimum restoring characteristics of the torsion bar are enjoyed albeit that at this stage the restoring characteristics of the spring 18 may be less apparent.
It is envisaged that the characteristics of the torsion bar 13 and spring 18 will be matched to provide an appropriate "feel" to the rotary valve and generally the forces applied by the pre-load in the
C-spring 18 will be quite low (for example this preload torque may be in the order of 1/2 to 1 Newton
Metres (Nm)) so that the pre-load is sufficient to provide a positive, non-deflecting, centering for the rotary valve in its neutral condition and yet does not require an unacceptable steering effort to be applied to the shaft 9 to operate the rotary valve.
Claims (6)
1. A power assisted steering gear comprising co-axial input and output shafts which are capable of restricted rotation relative to each other and which input shaft is rotatable in response to a steering input and rotation of the output shaft follows from rotation in the input shaft; valve means having a valve sleeve rotatable with one of said shafts and a valve rotor in said sleeve rotatable with the other of said shafts, relative rotation between said sleeve and rotor from a neutral condition serving to control fluid flow for power assistance; and means biasing the valve means to the neutral condition, the biasing means comprising a torsionally responsive component which provides a co-axial coupling between the shafts so that relative rotation between the shafts from the neutral condition is resisted by the component which is torsionally energised to bias the valve means to its neutral condition, and a spring means acting in a plane that extends radially relative to said shafts and is energised by relative rotation between the shafts from the neutral condition to provide additional biasing to return the valve means to its neutral condition.
2. A gear as claimed in claim 1 in which the spring means is pre-loaded so that it is necessary to overcome this load before relative rotary movement can be effected between the valve sleeve and rotor from the neutral condition.
3. A gear as claimed in either claim 1 or claim 2 in which the spring means is located in a plane that extends substantially radially relative to said shafts and is energised in that plane by relative ro tation between the shafts from the neutral condition.
4. A gear as claimed in any one of the preceding claims in which the spring means comprises a
C-shaped spring member which is mounted for rotation with one of said shafts and has a mouth engaging an abutment on that shaft which abutment restrains the spring from rotating relative to the shaft on which it is mounted, said mouth engaging with a second abutment that is rotatable with the other of said shafts so that, during relative rotation between the two shafts from the neutral condition, the two abutments are displaced circumferentially to diametrically enlarge and energise the C-spring for biasing the valve means to its neutral condition.
5. A gear as claimed in claim 4 in which the Cspring is mounted on the input shaft and the second abutment is located on the valve sleeve to be rotatable with the output shaft.
6. A power assisted steering gear substantially as herein described with reference to the accompanying illustrative drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08425828A GB2165502B (en) | 1984-10-12 | 1984-10-12 | A power-assisted steering gear |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08425828A GB2165502B (en) | 1984-10-12 | 1984-10-12 | A power-assisted steering gear |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8425828D0 GB8425828D0 (en) | 1984-11-21 |
| GB2165502A true GB2165502A (en) | 1986-04-16 |
| GB2165502B GB2165502B (en) | 1987-10-14 |
Family
ID=10568095
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08425828A Expired GB2165502B (en) | 1984-10-12 | 1984-10-12 | A power-assisted steering gear |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2165502B (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2188888A (en) * | 1986-04-14 | 1987-10-14 | Trw Cam Gears Ltd | Rotary valve assembly and a method of assembling such |
| EP0336553A1 (en) * | 1988-03-17 | 1989-10-11 | Trw Cam Gears Limited | A vehicle power assisted steering system |
| DE4026983A1 (en) * | 1990-08-25 | 1992-02-27 | Teves Gmbh Alfred | Servo-valve for power assisted steering system - is actuated by relative rotation between steering wheel and pinion of steering mechanism |
| US5251669A (en) * | 1991-05-24 | 1993-10-12 | A. E. Bishop & Associates Pty. Limited | Power steering valves |
| GB2273271A (en) * | 1992-12-10 | 1994-06-15 | Daimler Benz Ag | Servo control device, eg power steering valve. |
| EP0736442A2 (en) * | 1995-04-03 | 1996-10-09 | General Motors Corporation | Motor vehicle power steering gear |
| GB2306928A (en) * | 1995-11-09 | 1997-05-14 | Daimler Benz Ag | Power steering for motor vehicles |
| US10604178B2 (en) | 2017-02-23 | 2020-03-31 | China Automotive Systems, Inc. | Control assembly for power steering |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1470975A (en) * | 1973-07-18 | 1977-04-21 | Cam Gears Ltd | Power assisted steering system |
| GB2109757A (en) * | 1981-11-18 | 1983-06-08 | Cam Gears Ltd | A power assisted steering gear |
| GB2122151A (en) * | 1982-06-18 | 1984-01-11 | Cam Gears Ltd | Power assisted steering gear |
-
1984
- 1984-10-12 GB GB08425828A patent/GB2165502B/en not_active Expired
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1470975A (en) * | 1973-07-18 | 1977-04-21 | Cam Gears Ltd | Power assisted steering system |
| GB2109757A (en) * | 1981-11-18 | 1983-06-08 | Cam Gears Ltd | A power assisted steering gear |
| GB2122151A (en) * | 1982-06-18 | 1984-01-11 | Cam Gears Ltd | Power assisted steering gear |
Cited By (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2188888A (en) * | 1986-04-14 | 1987-10-14 | Trw Cam Gears Ltd | Rotary valve assembly and a method of assembling such |
| EP0245939A2 (en) * | 1986-04-14 | 1987-11-19 | Trw Cam Gears Limited | A process for assembling a rotary valve |
| EP0245939A3 (en) * | 1986-04-14 | 1988-05-25 | Trw Cam Gears Limited | A rotary valve assembly and a method of assembling a rotary valve |
| GB2188888B (en) * | 1986-04-14 | 1989-12-06 | Trw Cam Gears Ltd | A rotary valve assembly and a method of assembling a rotary valve |
| EP0336553A1 (en) * | 1988-03-17 | 1989-10-11 | Trw Cam Gears Limited | A vehicle power assisted steering system |
| DE4026983A1 (en) * | 1990-08-25 | 1992-02-27 | Teves Gmbh Alfred | Servo-valve for power assisted steering system - is actuated by relative rotation between steering wheel and pinion of steering mechanism |
| US5251669A (en) * | 1991-05-24 | 1993-10-12 | A. E. Bishop & Associates Pty. Limited | Power steering valves |
| FR2699135A1 (en) * | 1992-12-10 | 1994-06-17 | Daimler Benz Ag | Servo control, in particular power steering for motor vehicles. |
| GB2273271A (en) * | 1992-12-10 | 1994-06-15 | Daimler Benz Ag | Servo control device, eg power steering valve. |
| DE4241531C1 (en) * | 1992-12-10 | 1994-06-23 | Daimler Benz Ag | Servo control, in particular power steering for motor vehicles |
| US5390755A (en) * | 1992-12-10 | 1995-02-21 | Mercedes-Benz Ag | Power steering servo control for motor vehicles |
| GB2273271B (en) * | 1992-12-10 | 1996-01-31 | Daimler Benz Ag | Servo control device |
| EP0736442A2 (en) * | 1995-04-03 | 1996-10-09 | General Motors Corporation | Motor vehicle power steering gear |
| EP0736442A3 (en) * | 1995-04-03 | 1997-12-10 | General Motors Corporation | Motor vehicle power steering gear |
| GB2306928A (en) * | 1995-11-09 | 1997-05-14 | Daimler Benz Ag | Power steering for motor vehicles |
| GB2306928B (en) * | 1995-11-09 | 1997-09-24 | Daimler Benz Ag | Power steering for motor vehicles |
| US10604178B2 (en) | 2017-02-23 | 2020-03-31 | China Automotive Systems, Inc. | Control assembly for power steering |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8425828D0 (en) | 1984-11-21 |
| GB2165502B (en) | 1987-10-14 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20011012 |