SE542812C2 - Telescopic Shaft and Vehicle - Google Patents

Abstract

A telescopic shaft (1) for a vehicle (3) is disclosed. The telescopic shaft (1) comprises an outer shaft (5), an inner shaft (7) axially movable in the outer shaft (5), and at least two ball tracks (9) extending in an axial direction (ad) of the telescopic shaft (1). Each ball track (9) comprises an inner ball track portion (9’) at the inner shaft (7) and an outer ball track portion (9”) at the outer shaft (5). The telescopic shaft (1) comprises a maximum of two balls (11) arranged in each ball track (9) and each ball track (9) encloses more than 90 % of a circumference of each ball (11). The present disclosure further relates to a vehicle (3) comprising a telescopic shaft (1).

Description

Telescopic Shaft and Vehicle TECHNICAL FIELD The present disclosure relates to a telescopic shaft for a vehicle, such as a steering shaft. The present disclosure further relates to a vehicle comprising a telescopic shaft.

BACKGROUND Heavier vehicles, such as lorries, trucks, and the like, usually have spring suspended cabins which can move in relation to the chassis of the vehicle. Such vehicles may have a steering shaft between the steering wheel and the steering gear in the form of a telescopic shaft, which automatically can change its length during travel with the vehicle. This because the steering wheel is arranged in the cabin of the vehicle while the steering gear is attached to the chassis of the vehicle. Furthermore, some heavier vehicles, such as lorries, trucks, and the like, comprise a cabin which is tiltable relative the chassis, usually in order to gain access to a power source of the vehicle, such as an engine. During tilting of such a cabin, the telescopic shaft must be able to extend its length significantly.

The telescopic shaft may be of different kinds but usually comprise an outer shaft and an inner shaft which are axially movable in relation to each other but locked in relation to each other in a turning joint of the shaft to be able to transmit torque between the steering wheel and the steering gear. Common types of telescopic shafts are ball telescopes with rows of balls arranged in ball tracks between the inner and the outer shaft, needle roller-based telescopes with needle rollers between the inner and outer shaft, and splines telescopes without balls or roller, wherein surfaces slide can against each other at an axial displacement between the inner and outer shaft of the telescope.

Ball telescopes provide low friction during axial movement between the outer shaft and the inner shaft and are usually durable. Ball telescopes usually comprise two or more rows of balls with a plurality of balls in each ball track, such as 4 - 10 balls. Each ball track usually comprises a high number of balls to ensure torsional rigidity of the telescopic shaft.

Furthermore, in order to prevent the balls from abutting against each other, such telescopic shafts usually comprise a ball cage arranged in each ball track. By preventing abutment between the balls, no friction will occur between the balls and wear of the balls is reduced during axial movement between the outer shaft and the inner shaft. A ball gage is a type of cage, usually provided in a polymeric material, used in ball tracks for accommodating the balls in a manner separating the balls from each other.

Telescopic shafts are vital components of vehicles and a malfunction thereof may potentially lead to a loss of steering control of the vehicle. In general, problems associated with telescopic shafts are reliability, torsional rigidity, and stroke length. Furthermore, generally, on today’s consumer market, it is an advantage if products, such as telescopic shafts, have conditions and/or characteristics suitable for being manufactured and assembled in a costefficient manner.

SUMMARY It is an object of the present invention to overcome, or at least alleviate, at least some of the above-mentioned problems and drawbacks.

According to a first aspect of the invention, the object is achieved by a telescopic shaft for a vehicle, wherein the telescopic shaft comprises an outer shaft, an inner shaft axially movable in the outer shaft, and at least two ball tracks extending in an axial direction of the telescopic shaft. Each ball track comprises an inner ball track portion at the inner shaft and an outer ball track portion at the outer shaft. The telescopic shaft comprises a maximum of two balls arranged in each ball track, and each ball track encloses more than 90 % of a circumference of each ball.

Since the telescopic shaft comprises a maximum of two balls arranged in each ball track, i.e. one or two balls only, arranged in each ball track, a short dead length of the telescopic shaft is provided, which provides conditions for a longer stroke length of the telescopic shaft. In addition, since each ball track encloses more than 90 % of a circumference of each ball, a high torsional rigidity of the telescopic shaft is provided despite the fact that each ball track of the telescopic shaft comprises a low number of balls. This because the ball tracks provide large contact surfaces for the balls.

Furthermore, a telescopic shaft is provided having conditions and/or characteristics for a low number of components and a reduced weight. In addition, due to the short dead length of the telescope shaft, more room can be provided for additional components at an end of the telescopic shaft, such as a torque sensor, and the like.

Furthermore, due to these features, a telescopic shaft is provided having conditions and/or characteristics suitable for being manufactured and assembled in a cost-efficient manner.

Accordingly, a telescopic shaft is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.

Optionally, each ball track encloses more than 95 % of the circumference of each ball.

Thereby, a high torsional rigidity of the telescopic shaft is provided despite the fact that each ball track of the telescopic shaft comprises a low number of balls.

Optionally, each ball track comprises a first and a second axial stop each configured to retain the balls, or the ball, in the ball track, by abutting against one of the balls, or the ball.

Thereby, the balls of the telescopic shaft are retained in their respective ball track in a simple and efficient manner.

Optionally, each ball is configured to roll directly against the inner ball track portion and directly against the outer ball track portion upon an axial movement of the inner shaft relative the outer shaft. Thereby, a high torsional rigidity of the telescopic shaft is provided despite the fact that each ball track of the telescopic shaft comprises a low number of balls.

Optionally, the diameter of each ball is within the range of 8 - 20 mm, such as within the range of 9 - 13 mm. Thereby, due to the relatively large diameter of each ball, a high torsional rigidity of the telescopic shaft is provided despite the fact that each ball track of the telescopic shaft comprises a low number of balls.

Optionally, the telescopic shaft comprises one ball only arranged in each ball track. Thereby, a short dead length is provided, which provides conditions for a longer stroke length of the telescopic shaft. Furthermore, a telescopic shaft is provided having conditions and/or characteristics for a low number of components and a reduced weight. In addition, due to the short dead length of the telescope shaft, more room can be provided for additional components at an end of the telescopic shaft, such as a torque sensor, and the like.

Still further, because the telescopic shaft comprises one ball only arranged in each ball track, the need for a ball cage arranged in each ball track is circumvented, which further shortens the dead length of the telescopic shaft and provides conditions for an even longer stroke length of the telescopic shaft. This because, in addition to the balls, such ball gages contribute to the building length of the turning joint of the telescopic shaft, which puts limitations on the stroke length of the telescopic shaft. As a further result thereof, a telescopic shaft is provided having conditions and/or characteristics for a lower number of components and a further reduced weight. In addition, due to the short dead length of the telescope shaft, even more room can be provided for additional components at an end of the telescopic shaft, such as a torque sensor, and the like. In addition, due to these features, a telescopic shaft is provided having conditions and/or characteristics suitable for being manufactured and assembled in a cost-efficient manner. Furthermore, since each ball track encloses more than 90 % of a circumference of each ball, a high torsional rigidity of the telescopic shaft is provided despite the fact that each ball track of the telescopic shaft comprises one ball only.

In addition, since the need for a ball cage arranged in each ball track is circumvented, a safer and more reliable telescopic shaft may be provided. This because usually ball cages are provided in a polymeric material which risks melting or burning in case the telescopic shaft is subjected to high temperatures.

Optionally, the telescopic shaft is a steering shaft configured to transfer torque between a steering wheel of a vehicle and a steering gear of the vehicle. Thereby, a steering shaft is provided having conditions for a longer stroke length and a high torsional rigidity, despite the fact that each ball track of the steering shaft comprises a low number of balls. In addition, due to the short dead length of the steering shaft, more room can be provided for additional components at an end of the steering shaft, such as a torque sensor between the steering gear and the steering shaft. Furthermore, a steering shaft is provided having conditions and/or characteristics suitable for being manufactured and assembled in a cost-efficient manner.

According to a second aspect of the invention, the object is achieved by a vehicle comprising a telescopic shaft according to some embodiments. Since the vehicle comprises a telescopic shaft according to some embodiments, a vehicle is provided comprising a torsional rigid telescopic shaft having conditions for a long stroke length of the telescopic shaft, and conditions and/or characteristics suitable for being manufactured and assembled in a costefficient manner. Accordingly, a vehicle is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the abovementioned object is achieved.

Optionally, the vehicle comprises a steering wheel and a steering gear, and wherein the telescopic shaft is configured to transfer torque between the steering wheel and the steering gear. Thereby, a vehicle is provided comprising a steering shaft having conditions for a longer stroke length and a high torsional rigidity. In addition, due to the short dead length of the telescopic shaft, more room can be provided for additional components at an end of the telescopic shaft, such as a torque sensor between the steering gear and the telescopic shaft.

Optionally, the vehicle comprises a chassis and a cab, wherein the steering wheel is arranged in the cab and the steering gear is attached to the chassis, and wherein the cab is resiliently suspended to the chassis. Thereby, a vehicle is provided capable of transferring torque between the steering wheel and the steering gear in a safe and reliable manner, also during movement of the cab relative the chassis.

Optionally, the vehicle comprises a chassis and a cab, wherein the steering wheel is arranged in the cab and the steering gear is attached to the chassis, and wherein the cab is tiltable relative the chassis. Since the telescopic shaft is provided with a short dead length, conditions are provided for a tilting of the cab relative the chassis to a large tilting angle, while more room is provided for additional components at an end of the steering shaft, for example a torque sensor between the steering gear and the steering shaft.

Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS Various aspects of the invention, including its particular features and advantages, will be readily understood from the example embodiments discussed in the following detailed description and the accompanying drawings, in which: Fig. 1 illustrates a telescopic shaft, according to some embodiments, Fig. 2 illustrates a cross section of the telescopic shaft illustrated in Fig. 1, Fig. 3 schematically illustrates a cross section of a ball track of the telescopic shaft illustrated in Fig. 1, Fig. 4 illustrates a portion of the telescopic shaft, illustrated in Fig. 1, in an unassembled state, Fig. 5 illustrates a vehicle comprising a telescopic shaft according to the embodiments illustrated in Fig. 1, and Fig. 6 illustrates the vehicle illustrated in Fig. 5 with a cab of the vehicle in a tilted position.

DETAILED DESCRIPTION Aspects of the present invention will now be described more fully. Like numbers refer to like elements throughout. Well-known functions or constructions will not necessarily be described in detail for brevity and/or clarity.

Fig. 1 illustrates a telescopic shaft 1 for a vehicle, according to some embodiments. The telescopic shaft 1 comprises an outer shaft 5 and an inner shaft 7. The inner shaft 7 is axially movable in the outer shaft 5 in an axial direction ad of the telescopic shaft 1. The telescopic shaft 1 comprises a sealing 8 attached to an end of the outer shaft 5. The sealing 8 is arranged to seal the compartment between the outer shaft 5 and the inner shaft 7. The sealing 8 may be pressed into the end of the outer shaft 5 and may support the inner shaft 7 relative the outer shaft 5 in radial directions of the telescopic shaft 1. The sealing 8 may comprise one or more sealing lips, and/or one or more brushing units, abutting against the inner shaft 7. As is further explained herein, according to the illustrated embodiments, the telescopic shaft 1 is a steering shaft, also referred to as a steering column, configured to transfer torque between a steering wheel of a vehicle and a steering gear of the vehicle.

According to the illustrated embodiments, the telescopic shaft 1 comprises three ball tracks 9, of which only two are indicated in Fig. 1. Each ball track 9 extends in the axial direction ad of the telescopic shaft 1. The telescopic shaft 1 may comprise another number of ball tracks 9, such as two, four, five or six ball tracks 9. According to the present disclosure, the telescopic shaft 1 comprises a maximum of two balls 11 arranged in each ball track 9, i.e. comprises one ball 11 only, or two balls 11 only, arranged in each ball track 9. According to the illustrated embodiments, the telescopic shaft 1 comprises one ball 11 only arranged in each ball track 9. In this manner, as is further explained herein, the need for ball cages arranged in the ball tracks 9 of the telescopic shaft 1 is circumvented, and the building length of the steering column 1 in the axial direction ad thereof is minimized. Furthermore, a long stroke length of the steering column 1 is allowed for and more room is provided for additional components, such as a steering sensor, between the steering column 1 and a further component, such as a steering gear.

Fig. 2 illustrates a cross section of the telescopic shaft 1 illustrated in Fig. 1. The cross section of Fig. 2 is straight through the telescopic shaft 1, i.e. the cross section is made in a plane perpendicular to the axial direction ad of the telescopic shaft 1 indicated in Fig. 1. As can be seen in Fig. 2, each ball track 9 comprises an inner ball track portion 9’ at the inner shaft 7 and an outer ball track portion 9” at the outer shaft 5. The balls 11 of the telescopic shaft 1 are configured to roll directly against an inner ball track portion 9’ and directly against an outer ball track portion 9” upon an axial movement of the inner shaft 7 relative the outer shaft 5. In this manner, the inner shaft 7 can be displaced relative the outer shaft 5 in the axial direction with low frictional losses and a low amount of wear of components of the telescopic shaft 1.

Fig. 3 schematically illustrates a cross section of a ball track 9 of the telescopic shaft 1 illustrated in Fig. 1. As can be seen in Fig. 2 and Fig. 3, each ball track 9 encloses more than 90 % of a circumference of each ball 11. Thereby, a high torsional rigidity of the telescopic shaft 1 is provided despite the fact that each ball track 9 of the telescopic shaft 1 comprises a low number of balls 11 because the ball tracks 9 provide large contact surfaces for the balls 11. Furthermore, as indicated in Fig. 3, the inner ball track portion 9’ and the outer ball track portion 9” of the ball track 9 comprises delimiting surfaces 10, 10’. The delimiting surfaces 10, 10’ are each provided with a radius of curvature slightly larger than a radius of the balls, for example 0.1 - 5 % larger than a radius of the balls. Furthermore, as is indicated in Fig. 3, the telescopic shaft comprises gaps 12 between the inner shaft 7 and the outer shaft 5 adjacent to each ball track 9. The feature that each ball track 9 encloses more than 90 % of a circumference of each ball 11 may encompass that gaps 12 between the inner shaft 7 and the outer shaft 5 adjacent to each ball track 9 face less than 10% of the circumference of each ball 11. According to further embodiments, each ball track 9 may enclose more than 95 % of the circumference of each ball 11. Thus, according to such embodiments, the feature that each ball track 9 encloses more than 95 % of a circumference of each ball 11 may encompass that gaps 12 between the inner shaft 7 and the outer shaft 5 adjacent to each ball track 9 face less than 5% of the circumference of each ball 11.

Fig. 4 illustrates a portion of the telescopic shaft 1, illustrated in Fig. 1, in an unassembled state. As can be seen in Fig. 4, according to the illustrated embodiments, the telescopic shaft 1 comprises one ball 11 only arranged in each ball track. In Fig. 4, the inner ball track portion 9’ and a portion of the outer ball track portion 9” are visible. By using only one ball 11 arranged in each ball track, the need for ball cages arranged in each ball track of the telescopic shaft 1 is circumvented. Thereby, a short dead length in the axial direction ad of the telescopic shaft 1 is provided. As a result, conditions are provided for a longer stroke length of the telescopic shaft 1 in the axial direction ad of the telescopic shaft 1.

Furthermore, as can be seen in Fig. 4, each ball track 9 comprises a first and a second axial stop 13, 15. According to the illustrated embodiments, the first axial stops 13 are formed by a plate attached to an end portion of the inner shaft 7 and the second axial stops 15 are formed by portions of the inner shaft 7. Each of the first and second axial stops 13, 15 are configured retain the ball 11, in the respective ball track, by abutting directly against the ball 11.

According to some embodiments, the diameter d of each ball 11 is within the range of 8 - 20 mm, such as within the range of 9 - 13 mm. Thereby, due to the relatively large diameter d of each ball 11, a high torsional rigidity of the telescopic shaft 1 is provided even though each ball track of the telescopic shaft 1 comprises a low number of balls 11.

According to some embodiments of the present disclosure, one or more of the inner ball track portions 9’ may be spring loaded in a radial direction rd of the telescopic shaft 1. That is, according to such embodiments, the inner shaft 7 of the telescopic shaft 1 may comprise one or more rails each comprising an inner ball track portion 9’, wherein the one or more rails each are biased by one or more springs in the radial direction rd of the telescopic shaft 1. In this manner, the components of the telescopic shaft can be manufactured using lower tolerances and the assembly of the telescopic shaft 1 can be facilitated.

Fig. 5 illustrates a vehicle 3 comprising a telescopic shaft 1 according to the embodiments illustrated in Fig. 1. The vehicle 3 further comprises a steering wheel 21 and a steering gear 23. The telescopic shaft 1 is configured to transfer torque between the steering wheel 21 and the steering gear 23. Furthermore, the vehicle 3 comprises a chassis 30 and a cab 33, wherein the steering wheel 21 is arranged in the cab 33 and the steering gear 23 is rigidly attached to the chassis 30. The cab 33, as referred to herein, may also be referred to as the cabin. According to the illustrated embodiments, the cab 33 is resiliently suspended to the chassis 30, i.e. may move relatively the chassis 30, for example during travel of the vehicle 3. The telescopic shaft 1 will adapt its length accordingly during movement of the cab 33 relative the chassis 30.

According to the illustrated embodiments, the cab 33 is tiltable relative the chassis 30 in order to gain access to an engine 35 of the vehicle 3. In Fig. 5, the cab 33 is illustrated in an un-tilted position.

Fig. 6 illustrates the vehicle 3 illustrated in Fig. 5 with the cab 33 in a tilted position. During tilting of the cab 33 from the un-tilted position towards the tilted position, the telescopic shaft 1 will adapt its length accordingly, and because the telescopic shaft 1 is provided with a short dead length, the telescopic shaft 1 can adapt its length significantly, thus allowing the cab 33 to be tilted to a great tilting angle. In addition, more room is provided for a torque sensor 37 arranged between the telescopic shaft 1 and the steering gear 23.

It is to be understood that the foregoing is illustrative of various example embodiments and that the invention is defined only by the appended claims. A person skilled in the art will realize that the example embodiments may be modified, and that different features of the example embodiments may be combined to create embodiments other than those described herein, without departing from the scope of the present invention, as defined by the appended claims.

As used herein, the term "comprising" or "comprises" is open-ended, and includes one or more stated features, elements, steps, components or functions but does not preclude the presence or addition of one or more other features, elements, steps, components, functions or groups thereof.

Claims (11)

1. A telescopic shaft (1) for a vehicle (3), wherein the telescopic shaft (1) comprises: - an outer shaft (5), - an inner shaft (7) axially movable in the outer shaft (5), and - at least two ball tracks (9) extending in an axial direction (ad) of the telescopic shaft (1), wherein each ball track (9) comprises an inner ball track portion (9’) at the inner shaft (7) and an outer ball track portion (9”) at the outer shaft (5), characterized in that the telescopic shaft (1) comprises a maximum of two balls (11) arranged in each ball track (9), and wherein each ball track (9) encloses more than 90 % of a circumference of each ball (11).

2. The telescopic shaft (1) according to claim 1, wherein each ball track (9) encloses more than 95 % of the circumference of each ball (11).

3. The telescopic shaft (1) according to claim 1 or 2, wherein each ball track (9) comprises a first and a second axial stop (13, 15) each configured to retain the balls (11), or the ball (11), in the ball track (9), by abutting against one of the balls (11), or the ball (11).

4. The telescopic shaft (1) according to any one of the preceding claims, wherein each ball (11) is configured to roll directly against the inner ball track portion (9’) and directly against the outer ball track portion (9”) upon an axial movement of the inner shaft (7) relative the outer shaft (5).

5. The telescopic shaft (1) according to any one of the preceding claims, wherein the diameter (d) of each ball (11) is within the range of 8 - 20 mm, such as within the range of 9 - 13 mm.

6. The telescopic shaft (1) according to any one of the preceding claims, wherein the telescopic shaft (1) comprises one ball (11) only arranged in each ball track (9).

7. The telescopic shaft (1) according to any one of the preceding claims, wherein the telescopic shaft (1) is a steering shaft configured to transfer torque between a steering wheel (21) of a vehicle (3) and a steering gear (23) of the vehicle (3).

8. A vehicle (3) comprising a telescopic shaft (1) according to any one of the preceding claims.

9. The vehicle (3) according to claim 8, wherein the vehicle (3) comprises a steering wheel (21) and a steering gear (23), and wherein the telescopic shaft (1) is configured to transfer torque between the steering wheel (21) and the steering gear (23).

10. The vehicle (3) according to claim 9, wherein the vehicle (3) comprises a chassis (30) and a cab (33), wherein the steering wheel (21) is arranged in the cab (33) and the steering gear (23) is attached to the chassis (30), and wherein the cab (33) is resiliently suspended to the chassis (30).

11. The vehicle (3) according to claim 9 or 10, wherein the vehicle (3) comprises a chassis (30) and a cab (33), wherein the steering wheel (21) is arranged in the cab (33) and the steering gear (23) is attached to the chassis (30), and wherein the cab (33) is tiltable relative the chassis (30).