GB2354558A

GB2354558A - Thrust bearing arrangement for a motor

Info

Publication number: GB2354558A
Application number: GB9922422A
Authority: GB
Inventors: Michael Shaun Cullen
Original assignee: Trico Products Corp
Current assignee: Trico Products Corp
Priority date: 1999-09-23
Filing date: 1999-09-23
Publication date: 2001-03-28
Anticipated expiration: 2019-09-23
Also published as: GB9922422D0; GB2354558B

Abstract

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 load-carrying components of the bearing into constant running contact with each other. Said thrust element comprises a resiliently urged or urgeable thrust pad 53 and may further comprise a spring element 54. Preferably, the thrust pad 53 comprises a domed head 60 and axial spigot 61. Preferably also, the spring 54 and thrust pad 53 are housed in a removeable cap 5 at one end of the motor assembly. The cap 5 preferably comprises an end cap section 51 and a removeable plug section 52, which further comprises at least one leg 55 having a saw-tooth formation in mating arrangement with a correspondingly formed component 57 on the end cap section 51. Preferably, said thrust element is mounted in an electric motor (1, Fig. 1) for use in a vehicle windscreen wiper system.

Description

2354558 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 io 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.

We have proposed a solution to the above-identified problem in our British Patent Application No. 9619598.7. However, we are now proposing a solution whereby the components thereof are readily accessible for fitting and are accurately engaged with one another.

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 thereot to exert such axial thrust on the spindle as to bias load carrying components of the bearing into substantially ponstant running contact with each other, wherein the thrust element comprises a resiliently urged, or urgeable thrust pad.

The thrust pad may be resiliently urged or urgeable into contact with the lo spindle by a spring, such as a compression spring acting along the axis of the spindle. The spring and thrust pad may be housed in a removable cap. The cap may be attached to the housing of the motor at one end thereot with such attachment preferably being afforded by means on one or both of the housing and/or end cap.

Furthermore, the cap may comprise a plug section and end cap section, the thrust pad and spring being preferably housed in the plug section, Preferably, the plug section and end cap section are resiliently attached by second attachment means formed on one or both of the plug section and/or end cap section. Such attachment means may comprise at least one peripheral axial leg attached to the plug section, the at least one leg preferably having a saw-tooth formation in mating arrangement with a correspondingly formed component on the end cap section. In a preferred embodiment, the plug section comprises six of such legs, each of which mate with respective formations formed on inner circumferential surfaces of the end cap section. Each of the circumferential surfaces may be resiliently urged into mating relationship with a corresponding leg. The formations on adjacent legs may be out-of-phase, preferably 180' out-of-phase, such that an effective ratchet length, as defined herein, is half the wavelength of the formation.

Preferably, the thrust pad 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 pad, 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 pad comprises a domed thrust surface for engagement with the end of the spindle which may be io correspondingly-shaped, whereby a positive self-centering action affords relative positive location between the bearing portion of the thrust pad and the end of the spindle.

Preferably, the thrust pad comprises an axial spigot. The axial spigot may be of a size such that it engages a central aperture defined by the spring. The thrust cap may comprise a planar surface which acts as a bearing surface for the spring in order that the spring may resiliently urge the thrust pad to act on 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 inventive 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 may 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 resides in a motor comprising a spindle supported for rotation about its longitudinal axis by a bearing, and a resiliently urged, or urgeable thrust element acting or arranged to act on the spindle 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 is located in a housing which has a leg attached thereto, the housing being attached to a motor casing by virtue of formations on the leg.

The housing may comprise a plurality of attached legs, preferably six, each of which may comprise formations to facilitate attachment of the housing to the casing. The formations may have a regular profile, such as a saw-tooth profile. The profile of the formations on adjacent legs may be out-of-phase, preferably 180' out-of-phase such that a ratchet length, as defined herein, is half the wavelength of the formation.

A third 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 load-carrying components of the bearing into constant running contact with each other, the thrust element comprising a resiliently urged or urgeable thrust pad.

Preferably, the thrust pad comprises a domed head and axial spigot. The axial spigot may be of a size such that it is engagable with a central aperture defined by a spring. The thrust cap may comprise a planar surface which acts as a bearing surface, in use, for the spring in order that the spring may resiliently urge the thrust pad to act, in use, on the spindle. The domed head may be so shaped to be engageable with a correspondingly shaped end surface of the spindle.

The present invention will now be described in detail by way of example io only and with reference to a currently preferred embodiment and to the accompanying drawings in which:

Figure I is an exploded view of an electric motor according to the present invention; Figure 2 is an exploded view of the cap shown in Figure 1; Figures 3A and 3B respectively show side views of the cap whilst not engaged and engaged with the spindle of the motor shown in Figure 1; and Figures 4A, 4B and 4C respectively show a plan view, a view through section A-A of Figure 4A and a side elevation of a plug section of the motor.

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

The motor I 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 and is mounted within the housing 3 by a suitable end bearing (not shown). A main bearing 6, for example, 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. 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, housed in an assembly 8, rotatable about an axis which is generally orthogonal to the longitudinal axis of the spindle 4.

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

The vehicle windscreen wiper system may be of the type in which the toothed element aff-ords a generally planar end wfface formed with a plurality of electrically conductive tracks on which respective electrical contact fmgers 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 cap 5 is provided which is attached to the housing 3 by mutually co-operating, or mating, components 10, I I fon-ned respectively on the cap and the housing. One or each of the components 10, 11 may deform upon attachment such that a substantially permanent connection is formed therebetween.

Referring now to Figure 2, an exploded view of the cap 5 is shown, wherein the cap 5 comprises an end cap section 51 and a plug section 52. The cap 5 further comprises a thrust pad 53 and spring 54.

The plug section 52 comprises six axial legs 55 formed at the periphery thereof each of which has a saw-tooth formation thereon. The end cap section 51 is provided with a generally circular aperture 56 provided with, at distinct locations about its circumference, resilient members 57 which are so located that when the end cap section 51 and plug section 52 are forced together the members io 5 7 engage the saw-tooth formation on a corresponding leg 5 5.

Referring now to Figures 3A and 3B there is shown the cap 5 of the invention with the thrust pad 53 in a position where it is respectively non engaged and engaged with the spindle 4 of the motor 1.

The thrust pad 53 is disposed to act between the spring 54 and an adjacent end of the spindle 4 for the purpose of exerting such axial thrust on the spindle 4, along its longitudinal axis, as to bias load carrying components of the ball bearing 6 into constant running contact with each other. Without such a thrust pad 53, 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.

The thrust pad 53 comprises a domed head 60 and axial spigot 61. The axial spigot 61 is of a size such that it is engaged by the spring 54. A planar surface 62 of the domed head 60 acts as a bearing surface for the spring 54 in order that the spring 54 may resiliently urge the thrust pad 53 away from the plug section 52 of the cap 5. The domed head 60 is so shaped to engage a corTespondingly shaped end surface of the spindle 4.

When the head 60 is not engaging the spindle 4 it stands proud of a notional plane, represented by A-A, and when it engages the spindle 4 it is forced toward the plug section 52, against the urging of the spring 54.

Referring now to Figures 4A, 4B and 4C, the plug section 52 is shown in various views. As stated above, the legs 55 are formed with a saw-tooth profile which, in use, engages a correspondingly shaped mating component 57 on the cap section 5 1. The legs 55 may be separated into two distinct types 550 and 55 1.

Each of the legs 550 has a matched pitch such that the teeth of the sawtooth io formations on these legs 550 are at equal displacements from the top 58 of the plug section 52. The legs 551 also have a matched pitch such that the teeth on the of the saw-tooth formation on these legs 5 5 1 are at equal displacements from the top 58 of the plug section 52.

However, the displacement of the teeth 550 and the displacement of the teeth 551 are such that the profiles are out-of-phase by, for example 1800. With such a configuration, as seen in Figure 4C, the teeth of one leg for example 550, are at a displacement from the top 58 equal to the displacement from the top 58 of the mid-point between the teeth of the other leg, for example 55 1.

This configuration of out-of-phase saw-tooth formations on adjacent legs 550, 551 affords a much finer connection, or "ratchet length7' between the plug section 52 and cap section 51 without the costs associated with machining a saw tooth formation of half the pitch as that on any one of the legs 55. Thus, if the wavelength, that is to say the distance between adjacent teeth on any leg is, for example, I mm, then the effective "ratchet length" for the plug section 52 is 0.5 mm. Therefore, the tolerance of each of the teeth, on each leg, can be much greater than would be necessary were the actual wavelength half of that which is shown in the Figures. This reduces the associated machining costs, providing a much cheaper unit.

The fine "ratchet length" affords the connection an accuracy not available with a set of legs 55 all with "in-phase" identical saw-tooth profiles, and this allows the axial thrust applied to the end of the spindle 4 to be set very accurately.

The domed head 60 of the thrust pad 53 affords accurate relative location between th. e pad 53 and the end of the spindle 4. In the compressed state of the spring 54, the axial thrust exerted thereby upon the pad 53 and hence the spindle 4 is accurately axially directed along the longitudinal axis of the spindle 4. By io 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, vibration-free and noise-free running of the motor and its associated components of the vehicle windscreen wiper system during operation thereof The inventive thrust pad 53 and cap 5 employed in the motor of the present invention is of simple form and, preferably, is manufactured of a suitable plastics or metal material so that it is easy and cheap to manufacture and, by vir-tue of its structure as described herein above, may readily be installed and accurately located relative both to the housing 3 and the adjacent end of the spindle 4.

The solution afforded by the present invention is both elegant and inexpensive to implement and, although it has been described herein above in relation to its particular application to an electric motor for a vehicle windscreen wiper system, it may find equal application in other forms of motor and/or in other applications. The invention is, therefore, not limited in scope by the foregoing detailed description, but is to extend to all such variants as fall within the scope of the broadest statement of claims contained herein of the present invention.

Claims

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 5 spindle 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 resiliently urged or urgeable thrust pad. 10
2. A motor according to claim 1, wherein the thrust element exerts or is arranged to exert axial thrust on one end of the spindle.
3. A motor according to claim I or 2, wherein the thrust element is resiliently urged or urgeable into contact with the spindle by a spring. 15
4. A motor according to claim 3, wherein the spring is a compression spring acting or arranged to act along the axis of the spindle.
5. A motor according to claim 3 or 4, wherein the spring and thrust pad are 20 housed in a removable cap.
6. A motor according to claim 5, wherein the cap is attached to the housing of the motor at one end thereof
7. A motor according to claim 6, wherein such attachment is afforded by means on one or both of the housing and/or cap.
8. A motor according to claims 5, 6 or 7, wherein the cap comprises a removable plug section and end cap section.
9. A motor according to claim 8, wherein the thrust pad and spring are housed in the plug section.
10. A motor according to claim 8 or 9, wherein the plug section and end cap 5 section are resiliently attached by second attachment means formed on one or both of the plug section and/or end cap section.
11. A motor according to claim 10, wherein said second attachment means comprises at least one peripheral axial leg attached to the plug section. 10
12. A motor according to claim 11, wherein the at least one leg has a saw-tooth formation in mating arrangement with a correspondingly formed component on the end cap section. 15
13. A motor according to claim I I or 12, wherein the plug section comprises six of such legs, each of which mate with respective formations formed on inner circumferential surfaces of the end cap section.
14. A motor according to claim 13, wherein each of the circumferential surfaces 20 are resiliently urged into mating relationship with a corresponding leg.
15. A motor according to claim 13 or 14, wherein the formations on adjacent legs are out-of-phase.
16. A motor according to claim 15, wherein the formations are 180' out-ofphase such that an effective ratchet length, as defined herein, is half the wavelength of the formation.
17. A motor comprising a spindle supported for rotation about its longitudinal axis by a bearing, and a resiliently urged, or urgeable thrust element acting or arranged to act on the spindle 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 is located in a housing which has a leg attached thereto, the housing being attached to a motor casing by virtue of formations on the leg.
18. A motor according to claim 17, wherein the thrust element is resiliently urged or urgeable into contact with the spindle by a spring.
19. A motor according to claim 17 or 18, wherein the housing comprises a plurality of attached legs.
20. A motor according to claim 19, wherein the housing comprises six legs each of which comprise formations to facilitate attachment of the housing to the casing.
21. A motor according to any of claims 17 to 20, wherein the formations have a regular profile.
22. A motor according to claim 21, wherein the profile is a saw-tooth profile.
23. A motor according to claim 19, 20, or 21 when dependent on either of claims 19 or 20, wherein the profile of the formations on adjacent legs is out-ofphase.
24. A motor according to claim 23, wherein the profile is 180' out-ofphase such that an effective ratchet length, as defined herein, is half the wavelength of the formation.
25. A motor according to any of claims 17 to 24, wherein the thrust element comprises a thrust pad.
26. A motor according to any of claims I to 16 or claim 25, wherein the thrust pad comprises a bearing portion which extends substantially normally to the rotational axis of the spindle.
27. A motor according to claim 26, wherein the bearing portion comprises a domed thrust surface for engagement with the end of the spindle.
28. A motor according to claim 27, wherein the end of the spindle is correspondingly-shaped to mate with the domed thrust surface, in order that a positive self-centring action affords relative positive location between the bearing portion of the thrust pad and the end of the spindle.
29. A motor according to any of claims I to 16 or claims 25 to 28, wherein the thrust pad comprises an axial spigot.
30. A motor according to claim 29, wherein the axial spigot engages a central aperture of the spring.
31. A motor according to any of claims 3 to 16, or claim 29 or 30, wherein the thrust pad comprises a planar surface which acts as a bearing surface for an end of the spring.
32. A motor according to any preceding claim, wherein the motor is an electric motor and the spindle constitutes part, or an extension, of an armature of the motor.
33. A motor according to any preceding claim, wherein the bearing which supports the spindle for rotation comprises rolling elements which constitute at least some of the load carrying components of the bearing.
34. A motor according to any preceding claim, wherein the bearing is a ball bearing and the rolling elements comprise a plurality of bearing balls.
35. A motor according to any preceding claim adapted for use in a vehicle windscreen wiper system in which it is subjected to cyclically varying loading forces arising, in operation of the system, from the alternating forward and reverse traverses of the associated windscreen wiper(s).
36. A motor according to any preceding claim, wherein an end portion of the spindle is 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.
37. A motor according to claim 36, wherein the toothed element is a part of the transmission drive to the windscreen wipers of a vehicle windscreen wiper(s) system with which the motor may be associated.
38. 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 load-carrying components of the bearing into constant running contact with each other, the thrust element comprising a resiliently urged or urgeable thrust pad.
39. An element according to claim 38 further comprising a compression spring.
40. An element. according to claim 38 or 39, wherein the thrust pad comprises a domed head and axial spigot.
41. An element according to claim 40, wherein the axial spigot is of a size such that it is engageable with a central aperture defined by the spring.
42. An element according to claim 39, or claim 40 or 41 when dependent upon claim 39, wherein the thrust pad comprises a planar surface which acts as a bearing surface for the spring in order that the spring resiliently urges the thrust pad to act, in use, on the spindle.
43. An element according to claim 40, 41 or claim 42 when dependent upon claim 40 or 41, wherein the domed head is so shaped to be engageable with a correspondingly shaped end surface of the spindle.

io
44. A motor substantially as hereinbefore described with reference to the accompanying drawings.
45. A thrust element substantially as hereinbefore described with reference to the accompanying drawings.