WO2014120068A1

WO2014120068A1 - Steering spindle arrangement

Info

Publication number: WO2014120068A1
Application number: PCT/SE2014/050104
Authority: WO
Inventors: Martin STJERNLING
Original assignee: Scania Cv Ab
Priority date: 2013-01-31
Filing date: 2014-01-28
Publication date: 2014-08-07
Also published as: DE112014000374B4; DE112014000374T5; SE1350108A1; SE536870C2

Abstract

The present invention concerns a steering spindle arrangement that comprises a spindle bolt (2), an axle beam (1) that is fixed attached at a central part (2b) of the spindle bolt (2), and a stub axle (3) that has a first arm (4) that is arranged such that it can rotate around a first part (2a) of the spindle bolt (2) through a first roller bearing (8) and a second arm (6) that is arranged such that it can be rotated around a second part (2c) of the spindle bolt (2) through a second roller bearing (13). The steering spindle arrangement comprises a friction element (21) that is connected in a manner that does not allow rotation to the stub axle (3) and a force-exerting arrangement (10, 22) with which it is possible to press the friction element (21) against a surface (2a₁) at the spindle bolt (2) with an adjustable force such that the stub axle (3) experiences a desired resistance to rotation when it is rotated around the spindle bolt (2).

Description

Steering spindle arrangement

BACKGROUND AND PRIOR ART

The present invention relates to a steering spindle arrangement according to the preamble to claim 1.

A steering spindle arrangement for a steerable wheel in a vehicle generally comprises a spindle bolt that has a conical part for the attachment of an axle beam. A stub axle that supports the wheel is mounted to pivot on the steering spindle bolt with the aid of an upper bearing that may be a sliding bearing and a lower bearing that may be a conical roller bearing. The lower bearing in this case absorbs both axial and radial forces, while the upper bearing absorbs radial forces. The coefficient of friction of the glide bearing is not negligible. This results in the sliding bearing experiencing a varying resistance to rotation when the stub axle is pivoted relative to the axle beam, depending on the load on the sliding bearing. For a truck, in particular, the load at a steering spindle arrangement can differ considerably between operating conditions in which the vehicle is loaded and conditions in which it is not loaded.

Steerable vehicle wheels that are arranged on a pivotable stub axle experience a resistance to rotation when they are rotated relative to a spindle bolt in a steering spindle arrangement. If the resistance to rotation is too low, there is a risk that vibration arises in the transmission that transfers steering motions from the steering wheel of the vehicle to the steerable wheels. If the resistance to rotation is too high, an unnecessarily large force is required to turn the wheels. It is, therefore, important that the stub axle experiences a resistance to rotation that has a suitable magnitude when it is rotated around the spindle bolt. It is important also that the resistance to rotation does not vary as the load of the vehicle is changed.

WO 97/13674 reveals a spindle bolt that is threaded at both an upper end and at a lower end. An upper nut is mounted at the upper thread and a lower nut is mounted at the lower thread. An inner ring on an upper conical roller bearing can be locked against a surface of the axle beam with the aid of the upper nut. The upper conical roller bearing and a lower conical roller bearing can be pre-tensioned by means of the lower nut. Roller bearings are in this case used as bearings at both ends of the spindle bolt relative to the stub axle.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a steering spindle arrangement for which it is possible to set a required constant resistance to rotation for a stub axle that rotates around a spindle bolt, which resistance is essentially independent of the load on the steering spindle arrangement.

This object is achieved with a steering spindle arrangement of the type described in the introduction that is characterised by the distinctive features that are specified in the characterising part of claim 1. When a vehicle turns, steerable wheels and stub axles rotate relative to the spindle bolt and the axle beam. According to the invention, a friction element is used that is connected to the stub axle such that it cannot rotate and that makes contact with a surface of the spindle bolt. A force of friction in this way arises between the friction element and the spindle bolt when the stub axle is rotated relative to the spindle bolt. This force of friction results in the stub axle experiencing a resistance to rotation when it is rotated around and the spindle bolt. The magnitudes of the force of friction and the resistance to rotation are determined by the force with which the friction elements are pressed against the spindle bolt by a force-exerting the arrangement. The force-exerting arrangement can press the friction elements against the spindle bolt with an adjustable force. A suitable force can be applied with the aid of such a force-exerting arrangement onto the friction element such that a desired resistance to rotation is obtained. The steering spindle arrangement does not comprise any sliding bearing: it comprises only roller bearings for the mounting in bearings of the stub axle relative to the spindle bolt. Roller bearings have very low friction, and a friction that is essentially independent of the load on the roller bearing. This means that the stub axle can experience a set resistance to rotation that is defined by the force arrangement when this is rotated relative to the spindle bolt, independent of the load.

According to one embodiment of the present invention, the force-exerting arrangement comprises a spring means that is adapted to be brought into contact with the friction element and a spring tensioning element with which it is possible to provide tension at the spring means such that it presses the friction element against the spindle bolt. The spring means is here arranged in a position between the spring tensioning element and the friction element. The spring tensioning element exerts a force at the spring means such that it is compressed. The spring means thus exerts a spring force that presses the friction element against the steering spindle. A variable force that presses the friction element against the steering spindle can be created with the aid of the spring tensioning element, which force depends on the compression of the spring means.

According to one embodiment of the present invention, the friction element is connected to the stub axle such that it cannot rotate. The friction element is in this way prevented from rotating. The friction element may be connected to the stub axle such that it cannot rotate by at least one radially protruding part that is arranged in an indentation in the stub axle. The indentation has a form and a position such that it prevents the friction element rotating relative to the stub axle. It is appropriate that the friction element comprise at least two such radially protruding parts, and it is an advantage if these are arranged symmetrically.

According to one embodiment of the present invention, the friction elements are a friction disk that comprises a plane surface that is adapted to be in contact with the said surface of the spindle bolt and a plane surface on an opposing side that is adapted to be in contact with the spring means. The spring means in this case exerts a spring force onto one plane surface of the friction disk such that the opposing plane surface of the friction disk is pressed against the said surface at the spindle bolt. Such a friction disk may have a simple design and a reliable function.

According to one embodiment of the present invention, the spring means is a cup spring. Cup springs have a small extension in an axial direction and they may also provide a relatively large spring force at a relatively small compression. Thus, cup springs are extremely suitable to be used in this context. It is, however, possible to use other types of spring means. According to one embodiment of the present invention, the spring tensioning element comprises a component with a threaded part that is arranged such that it can be rotated on a threaded part of the stub axle. Such a threaded component can compress the spring means and create a spring force with a very high precision through the component being screwed to a suitable position relative to the stub axle. It is an advantage if the threaded component is a bearing cover. A bearing cover is required in all circumstances in order to seal one end of the spindle bolt and one of the roller bearings. It is therefore suitable appropriate that the bearing cover for this purpose. Alternatively, a separate component can be used for this purpose. Also such a component may be threaded and may consist of a suitably designed nut, screw or similar component that is used to tighten the spring means.

According to one embodiment of the present invention, the friction element is adapted to be brought into contact with an end surface of the spindle bolt. The spindle bolt has an essentially plane end surface that is very suitable to be used as contact surface in this context. It is an advantage if the friction element in this case is brought into contact such that it is in contact with a relatively large fraction of the end surface of the spindle bolt.

According to one embodiment of the present invention, the first bearing is a needle roller bearing. A needle roller bearing is a roller bearing that can absorb radial forces. Also other types of roller bearing can be used as first and second bearings, such as conical roller bearings and spherical roller bearings. Conical roller bearings and spherical roller bearings can absorb both axial and radial forces. Thus, both the first bearing and the second bearing are roller bearings. In this way, the load on the steering spindle arrangement essentially does not affect the friction or resistance to turning of the bearings. It is appropriate that the bearings be surrounded by suitable seals and bearing covers that protect from the entry of dirt. The bearings can in this way achieve a very low friction during a long period of operation.

According to one embodiment of the present invention, it comprises an axial bearing that is arranged in an axial position between a surface of the stub axle and a surface of the axle beam.

It is an advantage if the axial bearing has a plane first surface that is in contact with a plane contact surface of the stub axle and a plane second surface that is in contact with a plane contact surface of the axle beam. It is an advantage if the said plane surfaces have an extent in a plane that is perpendicular relative to a longitudinal axis through the spindle bolt. The axial bearing may be an axial sliding bearing. Alternatively, the axial bearing may be a needle roller bearing. BRIEF DESCRIPTION OF THE DRAWING

One preferred embodiment of the invention will be described below with reference to the attached drawing, of which:

Figure 1 shows a steering spindle arrangement according to present invention and Figure 2 shows a cross-sectional view of the steering spindle arrangement in the plane A-A in Figure 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Figure 1 shows a section through one end of an axle beam 1 in a vehicle. The axle beam 1 is provided with a conical hole 1 a for the attachment of a spindle bolt 2. The spindle bolt 2 has a corresponding conical central part 2b that comprises the hole la with which the spindle bolt 2 is attached at the axle beam 1. The spindle bolt 2 has an upper part 2a with a cylindrical form and a lower part 2c with a cylindrical form. A steerable and non-driving wheel at the vehicle is adapted to be attached at a stub axle 3 that is arranged such that it can rotate around the spindle bolt 2. The stub axle 3 has an upper arm 4 with a first penetrating hole 5 for the reception of the upper part 2a of the spindle bolt and a lower arm 6 with a second penetrating hole 7 for the reception of the lower part 2c of the spindle bolt. The upper part 2a of the spindle bolt is fixed into a first penetrating hole at the of the arm 4 with the aid of a needle roller bearing 8. A first elastic seal 9 is arranged at a lower opening at the first penetrating hole 5 in a position below the needle roller bearing 8. The first elastic seal 9 prevents dirt from entering the needle roller bearing 8 through a lower opening at the first penetrating hole 5. A first bearing cover 10 closes an upper opening at the first penetrating hole 5. The bearing cover 10 comprises a threaded part threads that are adapted to be fixed by screwing into a threaded part 11 that is peripherally arranged in the upper opening at the first penetrating hole 5. A sliding bearing in the form of an axially arranged glide ring 12 of a rigid metal material, such as a steel material, is arranged around the spindle bolt 2 in a position below the first elastic seal 9. The glide ring 12 is arranged in a transition region between the central part 2b of the spindle bolt and the upper part 2a of the spindle bolt. The glide ring 12 is designed as a disk and comprises a first plane upper glide surface 12a that is in contact with a plane contact surface at the stub axle 3 and a second plane lower glide surface 12b that is in contact with a plane contact surface at the axle beam 1.

The lower arm 6 of the stub axle 3 comprises a second penetrating hole 7. A conical roller bearing 13 is arranged in the second penetrating hole 7. The conical roller bearing 13 comprises an inner ring 14 that is fixed attached around the lower part 2c of the spindle bolt and an outer ring 15 that is fixed against an outer wall surface of the hole 7. A second elastic seal 16 is arranged at a position above the conical roller bearing 13 in connection with an upper opening to the second penetrating hole 7. A second bearing cover 17 closes a lower opening at the second penetrating hole 7. The bearing cover 17 is screwed in place with screws 18. An O-ring 19 guarantees that the second bearing cover 17 provides a closed seal at the lower opening at the second penetrating hole 7. The second bearing cover 17 and the second elastic seal 16 provide a closed interior seal that prevents dirt entering the conical roller bearing 13. The bearing cover 17 comprises a lower support surface for the conical roller bearing 13. The conical roller bearing 13 is mounted with the aid of shims 20 at the said support surface such that the bearing 13 acquires a suitable level of pre-tension.

The first part 2a of the spindle bolt has a first end surface 2a._\. A friction disk 21 is arranged in connection with the first end surface 2a_\. The friction disk 21 has a plane lower surface 21a that is in contact with the first end surface 2&i of the spindle bolt and a plane upper surface 21b. Figure 2 shows a sectional view through a part of the upper arm 4 of the stub axle where the friction disk 21 can be seen from above. It can here be seen that the friction disk 21 has protruding radial parts 21c that extend each into an indentation 4a in the upper arm 4 in connection with the threaded part 11. The indentation 4 may have an essentially vertical extension in the vertical part of the thread and an opening. The friction disk 21 and the protruding parts 21c can in this way be inserted into the relevant vertical indentations 4a to the position at which the friction disk 21 comes into contact with the first end surface 2ai. The indentations 4a prevent the protruding parts 21c and thus the friction disk 21 rotating within the first penetrating hole. Thus the friction disk is prevented from rotating relative to the upper arm 4 of the stub axle 3. The number of protruding parts 21c and indentations 4a is here three, but the number may, of course, be varied. After the friction disk 21 has been applied at its location in contact with the first end surface 2a_l5 a cup spring 22 is arranged at the friction disk. The cup spring 22 in this case has such a form that a lower internal surface 22 a comes into contact with the upper surface 21b of the friction disk. Finally, the bearing cover 10 is applied at its location and screwed into the threaded part 11. The bearing cover 10 comprises an indentation 10a for a tool at an external surface, with which tool the bearing cover is screwed into the threaded part 11 at the upper arm 4 of the stub axle 3. When the bearing cover 10 is screwed into the said threads 11, a plane internal surface 10b of the bearing cover 10 comes into contact with the upper surface 22b of the cup spring 22. As screwing of the bearing cover 10 into the threaded part 11 continues, the internal surface 10b of the bearing cover exerts a force onto the cup spring 22 such that it is compressed in the axial direction. The cup spring 22 thus exerts a corresponding spring force onto the spring disk 21. The spring disk 21 thus pressure with a corresponding force against the first side surface 2aj of the spindle bolt 2. The force with which the friction disk 21 is pressed against the first side surface 2ai can be adjusted to a desired value with the aid of the screw position of the bearing cover 10 in the threaded part 11. The threads of the bearing cover 10 and the threads of the threaded part 11 are self-locking such that they are held in place in a screw position when the tool is removed, since they have a rise and a friction such that they are not unscrewed when the bearing cover 10 is subject to the said force from the cup spring 22.

Given knowledge of the particular vehicle and the steering spindle arrangement as described above, it is possible to estimate a suitable value for the resistance to rotation that the stub axle 3 is to experience when it is rotated around the spindle bolt 2. The suitable value of the resistance to rotation is corresponded to by a certain compression of the cup spring 22 and a certain position of the bearing cover 10. The bearing cover 10 is thus screwed to the position at which the desired resistance to rotation is obtained. Since the bearings are constituted by only roller bearings 8, 13, they demonstrate a very low friction that is essentially independent of the load on the steering spindle arrangement. The stub axle in this way experiences an essentially constant resistance to rotation that is defined by the position of the bearing cover 10 and that is essentially independent of the load on the steering spindle arrangement. If it is necessary to change the resistance to rotation, this can be done by a rotation movement of the bearing cover 10 to a new position. The position of the bearing cover 10 can be defined by how many revolutions or degrees it has been turned from an initial position. It is thus very easy to change the resistance to rotation if it is necessary to adjust this.

The invention is not in any way limited to the embodiment that has been described in the drawing: it can be freely varied within the scope of the patent claims. It is obvious that the steering spindle arrangement can be mounted such that the upper end and the lower end exchange positions.

Claims

1. A steering spindle arrangement that comprises a spindle bolt (2), an axle beam (1) that is fixed attached at a central part (2b) of the spindle bolt (2), and a stub axle (3) that comprises a first penetrating hole (5) with a first roller bearing (8) for the reception of a first part (2a) of the spindle bolt (2) and a second penetrating hole (7) with a second roller bearing (13) for the reception of a second part (2c) of the spindle bolt (2), characterised in that the steering spindle arrangement comprises a friction element (21) that is connected to the stub axle (3) in a manner that does not allow it to rotate and a force-exerting arrangement (10, 22) with which it is possible to press the friction element (21) against a surface (2a at the spindle bolt (2) with an adjustable force such that the stub axle (3) experiences a desired resistance to rotation when it is rotated around the spindle bolt (2).

2. The steering spindle arrangement according to claim 1 , characterised in that the force-exerting arrangement comprises a spring means (22) that is adapted to be brought into contact with the friction element (21) and a spring tensioning element (10) with which it is possible to provide a tension of the spring means (22) such that it presses the friction element (21) against the said surface (2aj) of the spindle bolt (2).

3. The steering spindle arrangement according to claim 1 or 2, characterised in that the friction element (21) is connected to the stub axle (3) in a manner that does not allow rotation through at least one radially protruding part (21c) that is arranged in an indentation (4a) in the stub axle (3).

4. The steering spindle arrangement according to any one of the preceding claims, characterised in that the friction element is a friction disk (21) that comprises a plane surface (21a) that is adapted to be in contact with the said surface (2a of the spindle bolt (2) and a plane surface (21b) at an opposing side that is adapted to be in contact with the spring means (22).

5. The steering spindle arrangement according to any one of claims 2 to 4,

characterised in that the spring means is a cup spring (22).

6. The steering spindle arrangement according to any one of claims 2 to 5,

characterised in that the spring tensioning element is constituted by a threaded component (10) that is arranged such that it can be rotated at a threaded part (11) of the stub axle (3).

7. The steering spindle arrangement according to claim 6, characterised in that the threaded component is a bearing cover (10).

8. The steering spindle arrangement according to any one of the preceding claims, characterised in that the friction element (21) is adapted to be arranged in contact with an end surface (2aj) of the spindle bolt (2).

9. The steering spindle arrangement according to any one of the preceding claims, characterised in that the first bearing is a needle roller bearing (8).

10. The steering spindle arrangement according to any one of the preceding claims, characterised in that it comprises an axial bearing (12) that is arranged in an axial position between a surface of the stub axle (3) and a surface of the axle beam (1).