GB2249067A - Rack-and-pinion power-assisted steering mechanism - Google Patents
Rack-and-pinion power-assisted steering mechanism Download PDFInfo
- Publication number
- GB2249067A GB2249067A GB9023376A GB9023376A GB2249067A GB 2249067 A GB2249067 A GB 2249067A GB 9023376 A GB9023376 A GB 9023376A GB 9023376 A GB9023376 A GB 9023376A GB 2249067 A GB2249067 A GB 2249067A
- Authority
- GB
- United Kingdom
- Prior art keywords
- rack
- pinion
- housing
- pinion housing
- cylinder
- 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.)
- Withdrawn
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
- B62D5/20—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle specially adapted for particular type of steering gear or particular application
- B62D5/22—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle specially adapted for particular type of steering gear or particular application for rack-and-pinion type
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Power Steering Mechanism (AREA)
Abstract
The rack (10) carries a piston (18) slidably located in the rack housing (11) which defines the cylinder. The pinion is rotatably mounted on a shaft (26) in pinion housing (29) which is mounted on the rack housing (11) so that it is capable of limited movement axially of the rack (10). Resilient elements, eg wave spring washers (36), Belleville washers or elastomeric elements act upon the pinion housing (29) to bias it towards a central position and a control valve (46) is responsive to movement of the pinion housing (29), eg by being connected thereto by control rod (45), to control flow of fluid to and from opposite ends of the cylinder (17). <IMAGE>
Description
POWER ASSI8TED STEERING NECHANI8M8 The present invention relates to power assisted steering mechanisms for vehicles.
According to one aspect of the present invention a power assisted steering mechanism for a vehicle comprises a rack and pinion assembly, the rack being slidably located in a rack housing and being adapted to be connected at opposite ends to different wheels of the vehicle by which the vehicle may be steered, the rack housing defines a cylinder and a piston is provided on the rack, the piston being slidably sealed in the cylinder, the pinion is mounted on a pinion shaft which is adapted to be connected to a steering wheel for rotation thereby, the pinion shaft is located in a bearing formation within a pinion housing, the pinion housing being slidably located on a plurality of pins longitudinally of the rack so that the pinion engages the rack, the pinion housing being capable of limited axial movement relative to the rack, resilient means acts upon the pinion housing to bias it towards a central position and control means is associated with the pinion housing so that movement of the pinion housing will selectively connect opposite ends of the cylinder to a source of fluid under pressure or to drain.
With the above power steering mechanism, when the steering wheel is turned to steer the vehicle in one direction, the reaction between the pinion and rack will force the pinion housing in the other direction, against the load applied to the pinion housing by the resilient means. This movement of the pinion housing, through the control means, will connect one end of the cylinder to fluid under pressure and the other end to drain, so that a load will be applied to the piston on the rack, reinforcing the effort applied to the steering wheel and providing power assistance. When the effort is removed from the steering wheel the pinion housing will return to its central position under the influence of the resilient means and the control means will connect both ends of the cylinder to drain, removing the power assitance and permitting the wheels to return to the straight ahead position.
According to a preferred embodiment of the invention, the pins upon which the pinion housing is slidably located, are provided with longitudinal bores and radial ports, which correspond to ports in the pinion housing to control flow of the fluid to and from the cylinder.
The invention is now described, by way of example only, with reference to the accompanying drawings, in which:
Figure 1 shows an exploded assymetric view of a power steering mechanism in accordance with the present invention;
Figure 2 is a part section through the steering mechanism illustrated in Figure 1;
Figure 3 is a partial exploded view showing a modification to the steering mechanism illustrated in Figure 1; and
Figures 4 to 6 are schematic illustrations of the valving arrangement of the steering mechanism illustrated in Figure 3.
The steering mechanism illustrated in Figures 1 and 2 has a rack 10 which is slidably located in a rack housing 11 through bushes 12. The rack housing 11 has a pair of lugs 13 by which it may be secured to a vehicle transversely thereof. The rack 10 is adapted to be connected to opposite wheels of the vehicle by means of track rod ends 14 (only one shown), in conventional manner.
As illustrated in Figure 2, the bushes 12 are mounted on internal baffles 15 within the rack housing 11. Seals 16 are provided on the internal diameter of these baffles facing inwardly, to provide a seal with the rack 10 and define a closed cylinder 17. A piston 18 is located on the rack 10 intermediate of the baffles 15 and is sealed to the wall of the cylinder 18 by sealing element 19. Inlets 20 and 21 are provided to the cylinder 17, one adjacent each end of the cylinder 17.
A pinion 25 is mounted on a pinion shaft 26 for rotation therewith. The pinion shaft 26 is mounted in bearings 27, 28 in a pinion housing 29. One end of the pinion shaft 26 emerges from the pinion housing 29 and is provided with splines 30 by means of which it may be drivingly connected, via a steering column, to the steering wheel of the vehicle.
The pinion housing 29 is slidably mounted between the end of rack housing 11 and an end plate 31 on three pins 32, 33 and 34, which are angularly spaced around and extend longitudinally of the rack 10. The pins 32, 33 and 34 threadably engage in the end of rack housing 11, the end plate 31 being secured to the opposite ends of the pins 32, 33 and 34 by means of nuts 35. The separation between the end of the rack housing 11 and the end plate 31 is greater than the width of the pinion housing 29, so that the pinion housing 29 is capable of limited longitudinal movement relative to the rack 10. -Wave spring washers 36 are provided between each end of the pinion housing 29 and the adjacent end of the rack housing 11 and end plate 31 respectively, to bias the pinion housing 29 to a central position.
A spring loaded yolk 38 of conventional design is located in a cylindrical casing 39 on the pinion housing 29 and acts on the back of the rack 10 opposite to the pinion 25 to urge the pinion 25 into mesh with the teeth 40 on the rack 10. A lug 41 is provided on the pinion housing 29 by which the pinion housing 29 may be connected to the control rod 45 of a spool valve 46. The spool valve 46 is mounted externally on the rack housing 11.
As illustrated in greater detail in Figure 2, the spool valve 46 which is of conventional design, has a cylinder 47 with a spool 48 slidably mounted therein. The cylinder 47 has five ports 49, 50, 51, 52 and 53 which open into the cylinder 47 at axially spaced locations. The spool 48 has a pair of axially spaced circumferential grooves 54 and 55 thus defining three land formations 56, 57 and 58 which sealingly engage the internal diameter of the cylinder 47.
The spool 48 is capable of movement within the cylinder 47 under the control of the pinion housing 29 via the control rod 45.
The grooves 54 and 55 and ports 49, 50, 51, 52 and 53 are dimensioned and located such that port 52 will open into groove 54 and port 53 will open into groove 55 over the full range of movement of the spool 48 in the cylinder 47.
When the spool 48 is in a position corresponding to the central position of the pinion housing 29, the land 57 between grooves 54 and 55 will close port 50 and ports 49 and 50 will open into grooves 54 and 55 respectively.
Movement of the spool 48 to the left (as illustrated in
Figure 2) will close port 51, opening port 50 to groove 55 while port 49 will remain open to groove 54. Likewise, movement of the spool 48 to the right will close port 49 opening port 50 to groove 54 while port 51 remains open to groove 55.
Ports 49 and 51 are connected by return lines to a fluid reservoir, port 50 is connected to a pump by which fluid may be delivered under pressure from the reservoir to the port 50, port 52 is connected to the inlet 21 at one end of cylinder 17 and port 53 is connected to inlet 20 at the other end of cylinder 17.
With the power steering mechanism described above, the reaction between the pinion 25 and teeth 40 of rack 10 upon initial movement of the vehicle steering wheel, will cause pinion housing 29 to move to one side, compressing the wave spring 36 on that side. Continued movement of the steering wheel will then be transmitted via the pinion 25 and teeth 40 on rack 10 to move the rack 10 in the appropriate direction. Movement of the pinion housing 29 is transmitted via lug 41 and control rod 45 to the spool valve 46, thereby connecting the cylinder 17 on one side of piston 18 to fluid under pressure and the cylinder 17 on the other side of piston 18 to drain, so that the effort applied to the steering wheel is reinforced by the pressure differential across piston 18. For example, when turning to the right, the initial reaction between the pinion 25 and rack 10 will force the pinion housing 29 to the left, thereby pulling the spool 48 to the left so that port 49 is closed and port 50 is opened via groove 54 and port 52 to the inlet 21 thereby permitting fluid under pressure to be pumped to the portion of cylinder 17 to the right of piston 18. At the same time, the cylinder 17 to the left of piston 18 is open to drain via inlet 20, port 53, groove 55 and port 51. The pressure differential across piston 18 will thereby apply a load to rack 10 urging it to the left.
When the effort is removed from the steering wheel, the pinion housing 29 returns to its central position under the influence of wave springs 36 so that the spool 48 of spool valve 46 also returns to its central position closing port 50 and opening both sides of cylinder 17 to drain via inlet 20, port 52, groove 54 and port 49; and inlet 21, port 53, groove 55 and port 51. The power assistance to the rack 10 is thereby removed, permitting the wheels of the vehicle to move back to their straight ahead position.
In the modification illustrated in Figures 3 to 6, instead of using movement of the pinion housing 29 to control an external spool valve 46, movement of the pinion housing 29 is used to control the flow of fluid directly.
As illustrated in Figures 3 to 6, a flange formation 60 is provided at the end of the rack housing 11 adjacent to pinion housing 29. The ends of the pins 32, 33 and 34 are located through the flange formation 60 and are secured thereto in suitable manner.
The pins 32, 33 and 34 have axial bores 61, 62 and 63 which extend from the ends thereof secured through flange formation 60 and are closed adjacent the ends of the pins 32, 33 and 34 secured to end plate 31. Radial bores 64, 65 and 66 open into the axial bores 61, 62, 63 respectively.
The ends of the pins 32, 33 and 34 which extend throughflange formation 60 are provided with fluid connections 67, 68 and 69.
As illustrated in Figures 4 to 6, the bores 70, 71 and 72 in pinion housing 29, through which the pins 32, 33 and 34 extend, are provided with pairs of annular grooves 73, 74; 75, 76; and 77, 78 respectively. Seals 89 are provided on either side of each pair of grooves 73, 74; 75, 76; and 77, 78 to sealingly engage the pins 32, 33 and 34. Grooves 73 and 74 are located with respect to radial bore 64 in pin 32, such that; when the pinion housing 29 is in its central position the bore 64 will engage and be closed by the land 79 formed between grooves 73 and 74; and when the pinion housing 29 is displaced to the right or left, bore 64 will be aligned with groove 73 or groove 74 respectively.Grooves 75 and 76 are located with respect to the radial bore 65 in pin 33 such that; when the pinion housing 29 is in its central position or is displaced to the left, bore 65 will be aligned with groove 76; and when the pinion housing 29 is displaced to the right, bore 65 will be aligned with groove 75. In similar manner, grooves 77 and 78 are located with respect to radial bore 66 in pin 34 such that; when the pinion housing 29 is in its central position or is displaced to the right, bore 66 will be aligned with groove 77; and when the pinion housing 29 is displaced to the left, bore 66 will be aligned with groove 78.
Grooves 73, 74, 75, 76, 77 and 78 are interconnected by internal passages within the pinion housing 29, groove 73 being connected to groove 75 by passage 80, groove 74 being connected to groove 78 by passage 81 and grooves 76 and 77 being connected to an outlet 82 by passages 83 and 84 respectively.
The connection 67 at the end of pin 32 is connected to a feedline 85 by which fluid may be delivered under pressure from a reservoir, by pump means; connection 68 at the end of pin 33 is connected by pipe 86 to inlet 21 of cylinder 17; connection 69 at the end of pin 34 is connected by pipe 87 to inlet 20 of cylinder 17; and the outlet 82 is connected by a return line 88 back to the fluid reservoir.
With this modified steering mechanism, when the pinion housing 29 is in its central position as illustrated in
Figure 4, both sides of cylinder 17 will be connected to the return line 88 via inlets 20, 21; pipes 87, 86; bores 63, 62 and 66, 65; grooves 77, 76; passages 84, 83; and outlet 82; while the feed from line 85 will be shut off by engagemen,t of bore 64 by land 79.
Upon steering to the right, the pinion housing 29 will move to the left as illustrated in Figure 5, aligning bore 64 with groove 74, bore 65 will remain aligned with groove 76 and bore 66 will be aligned with groove 78. The lefthand end of cylinder 17 will now be connected via inlet 20, pipe 87, bores 63 and 66, groove 78, passage 81, groove 74 and bores 64 and 61 to the feedline 85, from which fluid will be pumped under pressure into cylinder 17. The righthand end of cylinder 17 will be connected via inlet 21, pipe 86, bores 62 and 65, groove 76, passage 83 and outlet 82 to the return line 88. A pressure differential will thus be established across the piston 18, reinforcing the steering effort to the right. Similarly, upon steering to the left the pinion housing 29 will move to the right as illustrated in Figure 6.In this position, bore 64 will be aligned with groove 73, bore 65 will be aligned with groove 75 and bore 66 will be aligned with groove 77. The righthand end of cylinder 17 will now be connected via inlet 21, pipe 86, bores 62 and 65, groove 75, passage 80, groove 73 and bores 64 and 61 to the feedline 85. The lefthand end of cylinder 17 will be connected via inlet 20, pipe 87, bores 63 and 66, groove 77, passage 84 and outlet 82 to the return line 88. A pressure differential will thus be established across piston 18 reinforcing the steering effort to the left.
Various modifications may be made without departing from the invention. For example, in place of the wave spring washers 36, individual Belleville washers may be provided on each of the pins 32, 33 and 34, at either end of the pinion housing 29. Alternatively, a resilient elastomeric element may be provided at both ends of the pinion housing 29 which in addition to serving to bias the pinion housing 29 to its central position, will also prevent the ingress of dirt etc. into the mechanism.
Claims (8)
1. A power assisted steering mechanism for a vehicle comprising a rack and pinion assembly, the rack being slidably located in a rack housing and being adapted to be connected at opposite ends to different wheels of the vehicle by which the vehicle may be steered, the rack housing defines a cylinder and a piston is provided on the rack, the piston being slidably sealed in the cylinder, the pinion is mounted on a pinion shaft which is adapted to be connected to a steering wheel for rotation thereby, the pinion shaft is located in a bearing formation within a pinion housing, the pinion housing being slidably located on a plurality of pins longitudinally of the rack so that the pinion engages the rack, the pinion housing being capable of limited axial movement relative to the rack, resilient means acts upon the pinion housing to bias it towards a central position and control means is associated with the pinion housing so that movement of the pinion housing will selectively connect opposite ends of the cylinder to a source of fluid under pressure or to drain.
2. A power assisted steering mechanism according to claim 1 in which the pinion housing is slidably mounted between an end of the rack housing and an end plate on three pins, the pins being spaced angularly with respect to the rack housing and extending longitudinally of the rack.
3. A power assisted steering mechanism according to claim 1 or 2 in which the pinion housing is interconnected to an external spool valve so that movement of the pinion housing will control the spool valve to selectively connect opposite ends of the cylinder to a source of fluid under pressure or to drain.
4. A power assisted steering mechanism according to claim 1 or 2 in which the pins provide fluid connection between opposite ends of the cylinder and the source of fluid under pressure or drain, ports being associated with the pins and with the pinion housing to selectively connect the opposite ends of the cylinder to the source of fluid under pressure or to drain, depending upon the position of the pinion housing.
5. A power steering mechanism according to claim 4 in which the pinion housing is slidably mounted on three angularly spaced pins, each pin having an axial bore closed at one end and having a fluid connection at the other end, a port being provided by a transverse bore adjacent the closed end of each pin; each pin being slidably located in a bore through the pinion housing, a pair of axially spaced grooves being provided in each bore in the pinion housing; a first of said pins being connected to a source of fluid under pressure, a second of the pins being connected to one side of the cylinder, and a third of the pins being connected to the other side of the cylinder; the grooves associated with the first pin being positioned such that when the pinion housing is in the central position, the port in the first pin will be intermediate of the grooves and when the pinion housing is displaced to one side or the other, the port in the pin will be aligned with one of said grooves and connected via such groove to grooves associated with either the second or third pin depending on the side to which the pinion housing is displaced, the other grooves associated with the second and third pins being connected to drain.
6. A power steering mechanism according to any one of the preceding claims in which when the pinion housing is in its central position, both sides of the cylinder are connected to drain.
7. A power steering mechanism according to any one of the preceding claims in which when the pinion housing is displaced to one side or the other, the corresponding side of the cylinder is connected to a source of fluid under pressure and the other side of the cylinder is connected to drain, so as to provide a pressure differential across the piston, said pressure differential applying a load to the rack which will reinforce the steering effort.
8. A power steering mechanism substantially as described herein, with reference to, and as shown in Figures 1 and 2 or Figures 3 to 6 of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9023376A GB2249067A (en) | 1990-10-26 | 1990-10-26 | Rack-and-pinion power-assisted steering mechanism |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9023376A GB2249067A (en) | 1990-10-26 | 1990-10-26 | Rack-and-pinion power-assisted steering mechanism |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9023376D0 GB9023376D0 (en) | 1990-12-05 |
| GB2249067A true GB2249067A (en) | 1992-04-29 |
Family
ID=10684430
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9023376A Withdrawn GB2249067A (en) | 1990-10-26 | 1990-10-26 | Rack-and-pinion power-assisted steering mechanism |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2249067A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19647797A1 (en) * | 1996-11-19 | 1998-05-20 | Zahnradfabrik Friedrichshafen | Rack and pinion power steering |
| DE10334112A1 (en) * | 2003-07-25 | 2005-03-17 | Toyota Motorsport Gmbh | Valve arrangement for a servo system |
| WO2012021184A1 (en) * | 2010-08-10 | 2012-02-16 | Parker Hannifin Corporation | Power steering system |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1144052A (en) * | 1966-03-10 | 1969-03-05 | Cam Gears Luton Ltd | Improvements in or relating to power assisted steering |
| US4141432A (en) * | 1977-10-05 | 1979-02-27 | The Bendix Corporation | Rack and pinion steering device |
-
1990
- 1990-10-26 GB GB9023376A patent/GB2249067A/en not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1144052A (en) * | 1966-03-10 | 1969-03-05 | Cam Gears Luton Ltd | Improvements in or relating to power assisted steering |
| US4141432A (en) * | 1977-10-05 | 1979-02-27 | The Bendix Corporation | Rack and pinion steering device |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19647797A1 (en) * | 1996-11-19 | 1998-05-20 | Zahnradfabrik Friedrichshafen | Rack and pinion power steering |
| US6193008B1 (en) | 1996-11-19 | 2001-02-27 | Zf Friedrichshafen Ag | Rack-and-pinion assisted steering system |
| DE10334112A1 (en) * | 2003-07-25 | 2005-03-17 | Toyota Motorsport Gmbh | Valve arrangement for a servo system |
| WO2012021184A1 (en) * | 2010-08-10 | 2012-02-16 | Parker Hannifin Corporation | Power steering system |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9023376D0 (en) | 1990-12-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |