GB2317504A

GB2317504A - Motor bearing thrust arrangement

Info

Publication number: GB2317504A
Application number: GB9619598A
Authority: GB
Inventors: Roy Edward Hopkins
Original assignee: ACDTRIDON EUROP Ltd
Current assignee: ACDTRIDON EUROP Ltd
Priority date: 1996-09-19
Filing date: 1996-09-19
Publication date: 1998-03-25
Anticipated expiration: 2016-09-19
Also published as: GB9619598D0; GB2317504B

Abstract

A motor 1 for example and electric motor adapted for use in a vehicle windscreen wiper system, comprises an armature spindle 4 supported for rotation about its longitudinal axis A-A by a bearing 6, and includes a thrust spring 13 disposed between facing portions of the mounting housing 3 and adjacent end of the spindle 4, and arranged to exert such axial thrust on the spindle 4 and to bias load carrying components of the main bearing 6 into constant running contact. The spring 13 may comprise a generally flat spring leaf 17 having a portion 17'' affording a bearing surface which preferably includes a dished thrust surface 19 in which the adjacent rounded end of the spindle 4 locates.

Description

MOTOR DESCRIPTION The present invention relates to a motor particularly, though not exclusively, an electric motor intended for use in a vehicle windscreen wiper system.

In operation of a vehicle windscreen wiper system, the forward and reverse traverses of the windscreen wiper blade(s) across the vehicle windscreen give rise to cyclical loading forces on components of the system. These cyclical loading forces can give rise to the generation of substantial amounts of noise, especially in a system where there is any free play and/or backlash between components of the system, particularly the motor.

It is an object of the present invention to provide a motor, for example, an electric motor suitable, say, for a vehicle windscreen wiper system, which is more positive and, hence, quieter in operation than hitherto known motors and is better able to cope with the cyclically variant loading forces to which it may be subjected during operation of any system with which it is associated.

It is another object of the invention to provide a thrust element for use in a motor, such as an electric motor which can be used in a vehicle windscreen wiper system, which element renders the associated motor more positive and, hence, quieter in operation than known motors.

Thus, and according to a first aspect of the present invention, there is provided a motor comprising a spindle supported for rotation about its longitudinal axis by a bearing, and a thrust element acting or arranged to act on the spindle, preferably an end thereof, to exert such axial thrust on the spindle as to bias load carrying components of the bearing into substantially constant running contact with each other, wherein the thrust element comprises a generally flat spring.

Preferably, the generally flat thrust spring comprises a bearing portion which extends substantially normally to the rotational axis of the spindle. In this arrangement, the thrust exerted on the spindle by the spring, can be set very accurately and maintained in the longitudinal direction along the axis of the rotatable motor spindle.

Preferably, the bearing portion of the spring comprises a dish-shaped thrust surface for engagement with the end of the spindle which may be correspondingly-shaped, whereby a positive selfcentering action affords relative positive location between the bearing portion of the generally flat thrust spring and the end of the spindle.

Preferably also, the motor is an electric motor and the spindle may constitute part, or an extension, of an armature of the motor.

The bearing which supports the spindle for rotation may comprise rolling elements which constitute at least some of the load carrying components of the bearing.

In a preferred embodiment of the invention motor,the bearing is a ball bearing and the rolling elements comprise a plurality of bearing balls.

Preferably, the motor is adapted for use in a vehicle windscreen wiper system in which it will be subjected to cyclically varying loading forces arising, in operation of the system, from the alternating forward and reverse traverses of the windscreen wiper(s).

An end portion of the spindle may be formed with a helical extension forming a rotatable worm engageable with a toothed element having an axis of rotation which is orthogonal to that of the rotational axis of the spindle. The toothed element may be a part of the transmission drive to the windscreen wipers of a vehicle windscreen wiper(s) system with which the motor may be associated.

A second aspect of the invention provides a thrust element arranged to act on a bearing-supported, axially rotatable spindle of a motor to exert, in use, such axial thrust on the spindle as to bias loadcarrying components of the bearing into constant running contact with each other, the thrust element comprising a generally flat spring.

The present invention will now be described in detail by way of example only and with reference to a currently preferred embodiment and to the accompanying drawings in which: Figure 1 is a partially cut-away side view of an electric motor according to the present invention in association with elements of a vehicle windscreen wiper system; Figure 2 is a partially cut-away end view of the electric motor shown in Figure 1; Figure 3 is a simplified detailed view of a portion of the motor shown in Figures 1 and 2; Figures 4A and 4B respectively show side and front views of a thrust spring used in the motor shown in Figures 1 to 3; and Figure 4C shows a detail of the spring of Figures 4A and 4B.

A motor according to the present invention is indicated generally at 1 in Figure 1 and is described herein in the context of a vehicle windscreen wiper system to be described in greater detail below.

The motor 1 is an electric motor having an armature indicated generally at 2 and an enclosed housing 3. A spindle 4 which constitutes part or an extension of the armature 2, has a longitudinal axis A-A and is mounted within the housing 3 by a suitable end bearing 5. A main bearing 6, here shown as a ball bearing including a plurality of bearing balls running in a bearing cage as is well known, supports the spindle 4 within the housing 3 so that it is freely rotatable about its longitudinal axis A-A. Beyond the main bearing 6, and remote from the wound core of the armature 2, the spindle 4 is formed with a helical extension forming a worm 7 the turns of which are engaged with teeth of a toothed element 8 rotatable about an axis B-B which is generally orthogonal to the longitudinal axis A-A of the spindle 4.

The toothed element 8 comprises a generally disclike structure whose teeth are provided by notching on the circumferential edge of the element 8. The association of the rotatable worm 7 and toothed element 8 forms a worm drive of generally known form by which rotation of the spindle 4 about its longitudinal axis A-A is translated into rotation of the toothed element 8 about the orthogonal axis B-B.

The toothed element 8 is secured to a rotatable spindle 11 having an output drive portion 11' for connection to further elements (not shown) of the transmission drive of the vehicle windscreen wiper system. The toothed element 8 and spindle 11 are substantially enclosed within a housing 12.

The vehicle windscreen wiper system may be of the type in which the toothed element 8 affords a generally planar end surface 8' formed with a plurality, here shown as three, of electrically conductive tracks 9 on which respective electrical contact fingers 10 ride for the purpose of deriving electrical control voltage signals which may be used, for example, to regulate and/or switch operation of the electric motor 1. Such a system is already known in the prior art and will not be described herein in any further detail.

In accordance with the present invention a thrust element 13 is disposed to act between an inner end wall portion of the housing 3 and an adjacent end of the spindle 4 for the purpose of exerting such axial thrust on the spindle 4, along its longitudinal axis A-A, as to bias load carrying components of the ball bearing 6 into constant running contact with each other. Without such a thrust element 13, any free play, or backlash, existing within the system is likely to lead to the generation of noise through the cyclically varying loading forces of the windscreen wiper system, when in operation, and too results in excessive wear at various contact surfaces throughout the system.

As can be seen best from the detailed views of Figures 3 and 4, the thrust element 13 comprises a generally flat spring having a pair of generally flat spring leaves 15, 17 integrally joined by a curved spring portion 16. The first spring leaf 15 has, at its end remote from the curved spring portion 16, a foot 20 which, in the assembled state of the spring within the motor housing 3, rests against an adjacent portion 21 of a closure lid for the housing 12 of the toothed element 8, this contact between the foot 20 and portion 21 serving to locate the spring 13 in position within the assembled motor.

The second spring leaf, generally indicated at 17, comprises a first portion 17' and, extending at a slight angle thereto, a second bearing portion 17'' which forms a bearing surface contacting the adjacent end of the spindle 4. In greater detail, this bearing portion 17'' is formed with a dish-shaped or domed thrust surface 19 of such shape, size and disposition to engage a protruding, rounded end surface 14' of a button member 14 at that end of the spindle 4 which is adjacent the internal surface 3' of the housing 3.

The thrust spring 13 is shown in its free, unassembled state in Figure 4A, and in this state it will be seen that the first portion 17' of the second spring leaf 17 lies generally parallel with the first spring leaf 15. The first spring leaf 15 is flat and, in the assembled state within the motor housing 3, rests firmly against the adjacent flat internal surface 3' of the housing 3. During assembly of the armature 2 within the housing 3, the button end 14 of the spindle 4 presses against the bearing surface portion 17'' of the spring leaf 17 in order to compress the spring 13 so that the second spring leaf 17 adopts the state shown in chained lines in Figure 4A, in which the bearing surface 17'' lies at the position indicated 18'' in which it is approximately parallel with the first spring leaf 15. Assembly in this manner leads to compression of the spring 13 to a predetermined load automatically during assembly of the motor. The dish-shaped or domed thrust surface 19 affords accurate relative location between the spring 13 and the button end 14 of the spindle 4 and the compressed state of the spring, in which the bearing surface 17'' lies substantially parallel with the first spring leaf 15 and, hence, the surface of the interior wall 3' of the housing 3, ensures that the axial thrust exerted by the spring 13 upon the spindle 4 is accurately axially directed along the longitudinal axis A-A of the spindle 4. By this means the load carrying components of the ball bearing 6 are biassed into constant running contact, such that any free play, or backlash, which might otherwise exist within the system is taken up, or substantially eliminated, in order to provide for smooth, vibrationfree and noise-free running of the motor and its associated components of the vehicle windscreen wiper system during operation thereof.

The inventive thrust spring 13 employed in th motor of the present invention is of simple form and preferably, is manufactured of a suitable spring stee: so that it is easy and cheap to manufacture and, bs virtue of its structure as described herein above, ma readily be installed and accurately located relative both to the housing 3 and the adjacent button end 12 of the spindle 4. The solution afforded by th present invention is both elegant and inexpensive te implement and, although it has been described hereii above in relation to its particular application to ai electric motor for a vehicle windscreen wiper system it may find equal application in other forms of motoi and/or in other applications. The invention is, therefore, not limited in scope by the foregoine detailed description, but is to extend to all suci variants as fall within the scope of the broadest statement of claims contained herein of the present invention.

Claims

1. A motor comprising a spindle supported for rotation about its longitudinal axis by a bearing, and a thrust element acting or arranged to act on the spindle, preferably an end thereof, to exert such axial thrust on the spindle as to bias load carrying components of the bearing into substantially constant running contact with each other, wherein the thrust element comprises a generally flat spring.

2. A motor according to claim 1, wherein the generally flat thrust spring comprises a spring leaf having a bearing portion which extends substantially normally to the longitudinal rotational axis of the spindle.

3. A motor according to claim 1 or 2, wherein the thrust spring comprises a dish-shaped or domed bearing surface engaging an end of the spindle, whereby a positive self-centering action provides relative positive location between the spring and the end of the spindle.

4. A motor according to claim 3, wherein the dishshaped or domed bearing surface of the thrust spring and the end of the spindle are correspondingly-shaped.

5. A motor according to any preceding claim, wherein the motor is an electric motor and the spindle constitutes part of or an extension of an armature of the motor.

6. A motor according to any preceding claim, wherein the bearing which supports the spindle for axial rotation thereof comprises rolling elements whicl constitute at least some of the load carrying components of the bearing.

7. A motor according to claim 6, wherein the bearinc is a ball bearing and the rolling elements comprise c plurality of bearing balls.

8. A motor according to any preceding claim, whereir a portion of the spindle is formed with a helical extension forming a rotatable worm engageable with c toothed element having an axis of rotation which is orthogonal to that of the longitudinal axis of the spindle.

9. A motor according to claim 8, wherein the toothec element constitutes part of the transmission drive ol a vehicle windscreen wiper system with which the motoi is associable.

10. A motor according to any preceding claim, whereir the generally flat thrust spring comprises a pair oi generally flat spring leaves extending generall parallel to each other.

11. A motor according to claim 10, wherein the pair of generally flat spring leaves are joined at one enc thereof by a curved spring portion.

12. A motor according to claim 10 or 11, wherein c first one of the pair of spring leaves locates the thrust spring within the motor.

13. A motor according to claims 10, 11 or 12, whereii a second one of the pair of spring leaves engages thf end of the spindle.

14. A motor according to claim 13, wherein the second spring leaf comprises a dish-shaped or domed bearing surface engaging the end of the spindle.

15. An electric motor substantially as hereinbefore described with reference to the accompanying drawings.

16. A thrust element arranged to act on a bearingsupported, axially rotatable spindle of a motor to exert, in use such axial thrust upon the spindle as to bias load-carrying components of the bearing into substantially constant running contact with each other, the thrust element comprising a generally flat spring.

17. A thrust element according to claim 16, wherein the generally flat spring comprises a spring leaf having a bearing portion which, in use, is arranged to engage the end of the associated motor spindle and to extend substantially normally to the rotational axis of the spindle.

18. A thrust element according to claim 16 or 17, wherein the generally flat spring comprises a dishshaped or domed bearing surface arranged to engage, in use, an end of the associated motor spindle.

19. A thrust element according to claim 16, wherein the generally flat spring comprises a pair of generally flat spring leaves extending generally parallel to each other.

20. A thrust element according to claim 19, wherein the pair of generally flat spring leaves are joined at one end thereof by a curved spring portion.

21. A thrust element according to claim 19 or 20, wherein, is use, a first one of the pair of spring leaves is arranged to locate the spring within the associated motor.

22. A thrust element according to claim 19, 20 or 21, wherein, in use, a second one of the pair of spring leaves is arranged to engage the end of the associated motor spindles.

23. A thrust element according to claim 22, wherein the second spring leaf comprises a dish-shaped or domed bearing surface arranged, in use, to engage the end of the associated motor spindle.

24. A thrust element substantially as hereinbefore described with reference to the accompanying drawings.