GB1564760A

GB1564760A - Rack and pinion units

Info

Publication number: GB1564760A
Application number: GB1529577A
Authority: GB
Original assignee: TRW Steering Systems Ltd
Current assignee: TRW Steering Systems Ltd
Priority date: 1972-07-18
Filing date: 1978-04-04
Publication date: 1980-04-16

Description

(54) IMPROVEMENTS IN OR RELATING TO RACK AND PINION UNITS (71) We, CAM GEARS LIMITED, of 45 Wilbury Way, Hitchin, Hertfordshire, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: The invention relates to a rack and pinion unit for a vehicle steering gear and is an improvement in or modification of the rack and pinion unit which is the subject of our U.K. Patent No. 1,422,122.

According to the invention there is provided a rack and pinion unit for a vehicle steering gear which comprises a longitudinally displaceable rack bar having a rack co-operating with a rotatable pinion, both of which rack bar and pinion are mounted within a unitary housing, and in which the unitary housing is an assembly comprising at least two pre-moulded (as hereinafter defined) metal components which are assembled and secured together once and for all so that the housing defines a first tubular portion within which the rack bar is displaceable and a second portion within which the pinion is rotatably mounted.

More particularly, the invention provides that the unitary housing comprises a pinion casing portion (as hereinafter defined) and a tubular rack bar casing portion which extends from the pinion casing portion to enclose at least a part length of the rack bar; and in which the housing is an assembly comprising at least two premoulded metal shell-like components each of which integrally incorporates a part of the pinion casing portion and a part of the rack bar casing portion, said components being assembled and secured together once and for all.

By the term "pinion casing portion" is meant the portion of the unitary housing in which is located the pinion and bearing means by which the pinion is rotatably mounted in that portion.

By the term "pre-moulded" or "premoulding" is meant construction of the metal components by pressing, stamping, moulding, rolling and other metal preforming techniques as is appropriate to the material and design of those components.

The unitary housing is preferably formed from two metal shell-like components which are appropriately moulded as by pressing into concave formations to provide recesses and seatings as necessary for the pinion (or more usually for bearings in which the pinion is rotatably mounted), the rack bar and possibly means for supporting the rack bar in engagement with the pinion. To facilitate assembly, the housing will usually be formed from two pre-moulded components which are preferably arranged to have split lines in a plane which is substantially parallel to the axis of rotation of the pinion and which extends in the longitudinal direction of the rack bar through the tubular portion within which the rack bar is located.

Preferably the tubular rack bar casing portion is provided with an appropriate seating in which is located and retained a bush or yoke in which the rack bar is slidably supported, such a bush usually being located in the rack bar casing at a position longitudinally remote from the pinion.

To construct a rack and pinion unit in accordance with the invention two or more metal shell-like components are premoulded of appropriate dimensions and shape so that they can be assembled to form the housing by abutment on aDDropriate split lines. Preferably the shell-like components are then secured together once and for all by welding or brazing around the split lines to form the unitary housing into which the rack bar, pinion and such bearings as are required can then be inserted and the rack and pinion unit assembled for operation in conventional manner. Alternatively, but less usually, the rack bar and pinion (together with such bearings as are required can be mounted for co-operation with each other in conventional manner in one of the shell-like components and thereafter the other pre-moulded component or components can be assembled around the rack bar and pinion and then all of the pre-moulded components can be secured together once and for all, for example by welding over abutting faces of the shell-like components at the split lines.

A considerable advantage afforded by the invention is that since the shell-like components are pre-moulded such recesses as are necessary for the internal elements of the rack and pinion unit can be accurately moulded in, thereby alleviating machining requirements for the housing and also the requirement for fixing plugs or other retaining means for the internal elements. Usually each shell-like component for the housing of the rack and pinion unit will be pressed from sheet steel.

Further according to the invention there is provided a method of constructing a rack and pinion unit for a vehicle steering gear which unit comprises a longitudinally displaceable rack bar having a rack cooperating with a rotatable pinion both of which rack bar and pinion are enclosed within a unitary housing, and which method comprises pre-moulding (as hereinbefore defined) at least two metal shelllike components, assembling said components along split lines and securing the components together once and for all to form the unitary housing. Preferably the method includes locating and assembling the rack bar and pinion elements (together with such bearings as are required) in the unitary housing subsequent to the shelllike components being secured together.

Alternatively the method can include locating the rack bar and pinion in co-operative engagement with each other in one of said shell-like components; assembling the other shell-like component or components around the co-operating rack bar and pinion; and securing the shell-like components together once and for all to form the unitary housing.

The present invention further includes a rack and pinion unit when constructed in accordance with the method specified in the immediately preceding paragraph.

The unitary housing of the rack and pinion unit of the present invention was primarily developed for such units as are intended for use in vehicle steering gears in conventional manner and in an attempt to provide a relatively inexpensive housing structure which is capable of meeting the technical requirements of reliability and efficiency for steering gears. Still further according to this invention therefore there is provided a vehicle steering gear which incorporates a rack and pinion unit constructed in accordance with the invention.

One embodiment of a rack and pinion unit for a vehicle steering gear and constructed in accordance with the invention will now be described, by way of example, with reference to the accompanying illustrative drawings in which: Figure 1 is a first shell-like component for the housing of the unit view along the axis of a rack bar casing portion which is to be partly formed thereby; Figure 3 shows the first shell-like component of Figure 1 when viewed along the axis of a pinion casing portion which is to be partly formed thereby; Figure 3 is a plan view of the shell-like component shown in Figure 1; Figure 4 is a perspective view of the shell-like component shown in Figure 1; Figure 5 is a perspective view of a second shell-like component for mating with the component shown in Figure 4 to form a housing; Figure 6 is a perspective view of the shell-like components shown in Figures 4 and 5 mated and assembled to form a housing, and Figure 7 diagrammatically illustrates the manner in which two abutting edges of the two shell-like components in Figure 6 are to be joined.

The rack bar, pinion and other internal elements such as bearings for the pinion are conventional in the rack and pinion unit of the invention and are therefore not shown.

The first and second shell-like components 1 and 2 respectively are substantially complementary concave pressings of sheet steel, for example 16G sheet steel, having a substantially 'X' configuration and edges 3, 3', 4, 4' and 5, 5', 6, 6' respectively, which abut on assembly to form a housing as shown in Figure 6, the two pressings being welded together once and for all along the abutting edges to form a unitary housing.

The configuration of the two shell-like components may most easily be described by noting that the assembled housing in Figure 6 has the shape of two substantially intersecting cylindrical tubes providing respectively a relatively shorter pinion casing portion 7 and a relatively longer rack casing portion 8. The portions 7 and 8 intersect in plan view at an inclined (that is other than normal) angle which is consistent with the desired angle of engagement between the rack and pinion which are to be mounted in the housing and have longitudinal axes which are offset from each other (that is which do not meet). The major part lengths of the abutting edges 3, 4, 5, 6 lie substantially in respective planes which are each substantially parallel to the axis about which the pinion is to be rotatable and to the longitudinal axis along which the rack bar is to be displaceable. Furthermore the split lines formed by the abutting edges 3 and 5 and 4 and 6 for the casing portion 8 are substantially in a plane which includes the axis along which the rack bar is to be longitudinally displaceable and the split lines formed by the abutting edges 3 and 5 and 4 and 6 for the casing portion 7 are substantially in a plane which includes the axis about which the pinion is to be rotatable. The short edge portions 3', 4', 5', 6' are approximately perpendicular to the aforementioned planes and connect the major part lengths of the abutting edges 3, 4, 5, 6.

One of the shell-like components may be formed with a joggled or rebated edge 9 as shown in Figure 7 to facilitate mating of the two components on assembly of the housing prior to the application of a welding fillet 9'.

The shell-like components may be grooved or nipped at 10, 11 and 12, 13 to provide annular internal ribs for locating bearings or bushes which receive pinion shafts by which the pinion is rotatably mounted. Such grooves are shown on the pinion casing portion only but may be provided on the rack casing portion if a bearing, yoke or bush is required for sum porting the rack bar. Dimples 14 (or other projections or recesses) in the walls of the shells may be provided for the same purpose of location.

A jig may be used to retain the two pressings 1 and 2 in mated relationship during welding.

Following its construction the unitary housing is assembled with the other elements of the rack and pinion unit. In particular the pinion (not shown) is inserted in the casing portion 7 and rotatably mounted in bearings (not shown) which are located in the seatings formed at the ends of the casing portion 7 adjacent to the ribs 10 and 12. These bearings and the pinion can be retained in the portion 7 by appropriate end caps. The rack bar (not shown) is now fed through the tubular portion 8 and into engagement with the pinion in conventional manner, if required a yoke or a bush can be provided in the portion 8 to maintain the rack in engagement with the pinion WHAT WE CLAIM IS 1. A rack and pinion unit for a vehicle steering gear which comprises a longitudinally displaceable rack bar having a rack co-operating with a rotatable pinion, both of which rack bar and pinion are mounted within a unitary housing, and in which the unitary housing is an assembly comprising at least two pre-moulded (as hereinbefore defined) metal components which are assembled and secured together once and for all so that the housing defines a first tubular portion within which the rack bar is displaceable and a second portion within which the pinion is rotatably mounted.

2. A rack and pinion unit as claimed in claim 1 in which the unitary housing comprises a pinion casing portion (as hereinbefore defined) and a tubular rack bar casing portion which extends from the pinion casing portion to enclose at least a part length of the rack bar; and in which the housing is an assembly comprising at least two pre-moulded metal shell-like components each of which integrally incorporates a part of the pinion casing portion and a part of the rack bar casing portion, said components being assembled and secured together once and for all.

3. A rack and pinion unit as claimed in either claim 1 or claim 2 in which the pre-moulded components are pressed from metal sheets and include moulded-in seatings for location of bearings within which the pinion is rotatably mounted.

4. A rack and pinion unit as claimed in any one of the preceding claims in which the pre-moulded components are pressed from metal sheets and include moulded-in seatings for location of support means by which the rack bar is displaceably supported in co-operation with the pinion.

5. A rack and pinion unit as claimed in any one of the preceding claims in which the housing is formed from premoulded components having edges which abut in substantially complementary manner and are secured together along said regions of abutment.

6. A rack and pinion unit as claimed in claim 5 in which at least of one said components has a rebated edge which mates in overlying manner with the edge of the other, or the adjacent, component along said regions of abutment.

7. A rack and pinion unit as claimed in any one of the preceding claims in which the housing is formed from two substantially complementary pre-moulded components which are secured together along split lines which are substantially located in at least one plane which is substantially parallel to the axis of rota

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Claims

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is other than normal) angle which is consistent with the desired angle of engagement between the rack and pinion which are to be mounted in the housing and have longitudinal axes which are offset from each other (that is which do not meet). The major part lengths of the abutting edges 3, 4, 5, 6 lie substantially in respective planes which are each substantially parallel to the axis about which the pinion is to be rotatable and to the longitudinal axis along which the rack bar is to be displaceable. Furthermore the split lines formed by the abutting edges 3 and 5 and 4 and 6 for the casing portion 8 are substantially in a plane which includes the axis along which the rack bar is to be longitudinally displaceable and the split lines formed by the abutting edges 3 and 5 and 4 and 6 for the casing portion 7 are substantially in a plane which includes the axis about which the pinion is to be rotatable. The short edge portions 3', 4', 5', 6' are approximately perpendicular to the aforementioned planes and connect the major part lengths of the abutting edges 3, 4, 5, 6.

One of the shell-like components may be formed with a joggled or rebated edge 9 as shown in Figure 7 to facilitate mating of the two components on assembly of the housing prior to the application of a welding fillet 9'.

The shell-like components may be grooved or nipped at 10, 11 and 12, 13 to provide annular internal ribs for locating bearings or bushes which receive pinion shafts by which the pinion is rotatably mounted. Such grooves are shown on the pinion casing portion only but may be provided on the rack casing portion if a bearing, yoke or bush is required for sum porting the rack bar. Dimples 14 (or other projections or recesses) in the walls of the shells may be provided for the same purpose of location.

A jig may be used to retain the two pressings 1 and 2 in mated relationship during welding.

Following its construction the unitary housing is assembled with the other elements of the rack and pinion unit. In particular the pinion (not shown) is inserted in the casing portion 7 and rotatably mounted in bearings (not shown) which are located in the seatings formed at the ends of the casing portion 7 adjacent to the ribs 10 and 12. These bearings and the pinion can be retained in the portion 7 by appropriate end caps. The rack bar (not shown) is now fed through the tubular portion 8 and into engagement with the pinion in conventional manner, if required a yoke or a bush can be provided in the portion 8 to maintain the rack in engagement with the pinion WHAT WE CLAIM IS 1. A rack and pinion unit for a vehicle steering gear which comprises a longitudinally displaceable rack bar having a rack co-operating with a rotatable pinion, both of which rack bar and pinion are mounted within a unitary housing, and in which the unitary housing is an assembly comprising at least two pre-moulded (as hereinbefore defined) metal components which are assembled and secured together once and for all so that the housing defines a first tubular portion within which the rack bar is displaceable and a second portion within which the pinion is rotatably mounted.
2. A rack and pinion unit as claimed in claim 1 in which the unitary housing comprises a pinion casing portion (as hereinbefore defined) and a tubular rack bar casing portion which extends from the pinion casing portion to enclose at least a part length of the rack bar; and in which the housing is an assembly comprising at least two pre-moulded metal shell-like components each of which integrally incorporates a part of the pinion casing portion and a part of the rack bar casing portion, said components being assembled and secured together once and for all.
3. A rack and pinion unit as claimed in either claim 1 or claim 2 in which the pre-moulded components are pressed from metal sheets and include moulded-in seatings for location of bearings within which the pinion is rotatably mounted.
4. A rack and pinion unit as claimed in any one of the preceding claims in which the pre-moulded components are pressed from metal sheets and include moulded-in seatings for location of support means by which the rack bar is displaceably supported in co-operation with the pinion.
5. A rack and pinion unit as claimed in any one of the preceding claims in which the housing is formed from premoulded components having edges which abut in substantially complementary manner and are secured together along said regions of abutment.
6. A rack and pinion unit as claimed in claim 5 in which at least of one said components has a rebated edge which mates in overlying manner with the edge of the other, or the adjacent, component along said regions of abutment.
7. A rack and pinion unit as claimed in any one of the preceding claims in which the housing is formed from two substantially complementary pre-moulded components which are secured together along split lines which are substantially located in at least one plane which is substantially parallel to the axis of rota

tion of the pinion and which extends substantially parallel to the longitudinal direction in which the rack bar is displaceable.
8. A rack and pinion unit as claimed in any one of the preceding claims in which the second portion of the housing is tubular and said first and second tubular portions intersect at an angle consistent with the desired angular relationship required between the axis of the pinion and the longitudinal direction of displacement of the rack bar for co-operation of the pinion with the rack.
9. A rack and pinion unit as claimed in claim 8 when appendent to claim 2 in which the housing is formed from two pre-moulded components which are substantially complementary and are each of substantially 'X' configuration.
10. A rack and pinion unit as claimed in claim 9 wherein the first tubular portion has split lines between said pre-moulded components which split lines are substantially located in a plane which includes the longitudinal axis along which the rack bar is displaceable and which plane is displaced from, but substantially parallel to, the axis of rotation of the pinion, and the second tubular portion has split lines between said pre-moulded components which latter split lines are substantially located in a plane which includes the axis of rotation of the pinion and which is displaced from, but substantially parallel to, the axis along which the rack bar is displaceable.
11. A rack and pinion unit as claimed in any one of the preceding claims in which the pre-moulded components are formed from sheet steel and such components are secured together by welding.
12. A rack and pinion unit substantially as herein described with reference to the accompanying illustrative drawings.
13. A method of constructing a rack and pinion unit for a vehicle steering gear which unit comprises a longitudinally displaceable rack bar having a rack co-operating with a rotatable pinion both of which rack bar and pinion are enclosed within a unitary housing, and which method comprises pre-moulding (as hereinbefore defined) at least two metal shell-like components, assembling said components along split lines and securing the components together once and for all to form the unitary housing.
14. A method as claimed in claim 13 which comprises mounting the rack bar and pinion elements in the unitary housing subsequent to the shell-like components being secured together.
15. A method as claimed in claim 13 which comprises locating the rack bar and pinion in co-operative engagement with each other in one of said shell-like components; assembling the other shell-like component or components around the cooperating rack bar and pinion, and securing the shell-like components together once and for all to form the unitary housing.
16. A method as claimed in any one of claims 13 to 15 which comprises premoulding the shell-like components by pressing or stamping from sheet steel.
17. A method as claimed in claim 16 which comprises securing the shell-like components together by welding along abutting edges of said components.
18. A method as claimed in any one of claims 13 to 17 which comprises premoulding the shell-like components to include seatings for location of bearings or support means for mounting the pinion or rack bar in the housing.
19. A method as claimed in claim 13 and substantially as herein described.
20. A rack and pinion unit for a vehicle steering gear when constructed by the method as claimed in any one of claims 13 to 19.
21. A vehicle steering gear when incorporating a rack and pinion unit as claimed in any one of claims 1 to 12 or claim 20.