GB2256900A

GB2256900A - Sealing an i.c.engine starter mechanism.

Info

Publication number: GB2256900A
Application number: GB9212550A
Authority: GB
Inventors: Andre Glerean; Hugues Pawlik; Gerard Vilou
Original assignee: Valeo Equipements Electriques Moteur SAS
Current assignee: Valeo Equipements Electriques Moteur SAS
Priority date: 1991-06-13
Filing date: 1992-06-12
Publication date: 1992-12-23
Anticipated expiration: 2012-06-12
Also published as: GB9212550D0; GB2256900B; FR2677710B1; FR2677710A1; DE4218625A1

Description

22 -, o p, 1 1 A STARTER MECHANISM FOR AN INTERNAL COMBUSTION ENGINE,

HAVING SEALING MEANS This invention relates to a starter mechanism for an internal combustion engine, in particular for a motor vehicle, the mechanism having sealing means to provide protection against ingress of dust.

Such a starter mechanism comprises a motor shaft coupled to the electric starter motor, with a starter pinion mounted on the shaft for rotation with it and being arranged to be displaced axially until it comes into engagement with a toothed crown carried by the engine flywheel. The axial displacement of the starter pinion is limited by a starter head or end stop member which is fixed to the motor shaft.

The starter, and particularly the starter mechanism itself which forms part of the starter assembly, are susceptible to various mechanical influences arising in the environment in which it has to operate. In particular, dust generated by wear in the clutch lining when the vehicle is operating tends to penetrate into the interior of the components of the starter. This effect is increased when the friction liner of the clutch is of an asbestos-free material. In practice, this dust not only settles, but also has certain natural adhesive qualities: over a period of time the dust will build up in the form of a significant coating, which can be hightly detrimental to the operation of the starter assembly.

Although there are some components, for example the contacter assembly or the electric motor, that are able to be protected sealingly at a reasonable cost, this has not hitherto been the case as far as the starter mechanism is concerned, and in particular as regards that portion of the 2 motor shaft that lies between the starter pinion in its rest position and the starter head.

This problem is made even more difficult to resolve when the starter mechanism is of the extending-pinion type, in which the starter pinion is displaced out of the casing of the starter mechanism into its meshing position with the flywheel crown.

In order to avoid a reduction in the overall power output of the starter, the protective means which are used must not generate resistive forces during the displacement of the starter pinion. In addition, during operation of the starter, the protective means must retain their effectiveness and not be subject to wear that would be detrimental to their function over the whole working life of the starter.

According to the invention, there is provided a starter mechanism for an internal combustion engine, comprising a starter pinion which is displaceable axially on a motor shaft between a rest position and a meshing position in which the start pinion is in contact with a starter head, the said starter pinion having a toothed crown extended by a cylindrical portion having an outer surface in contact with a bearing fitted in a support portion of the casing of the starter mechanism, the support portion having at one of its ends a housing which defines a gap between itself and the outer surface of the said cylindrical portion of the pinion, wherein the mechanism further includes a lip seal carried by the pinion for protecting the said outer surface of its cylindrical portion, the lip seal having a lip the length of which is smaller than the width of the said gap and such that in the rest position the lip is inclined, with its free end engaging on a radial wall.

3 The said radial wall may take a number of different forms. For example it may comprise: a shoulder of the bearing, formed integrally in the support portion of the casing; or a deflector with which the bearing is provided; or the inner ring of the bearing; or a ring located in front of the bearing. In all cases, the lip of the lip seal is preferably tapered.

According to a preferred feature of the invention, the starter pinion has a shouldered bore receiving bearing sleeves which cooperate with at least one guide surface formed on the motor shaft, the latter having adjacent to its free end a cylindrical surface having a diameter smaller than the diameter of the guide surface or surfaces, the mechanism having a further seal fixed to the starter pinion and disposed in the said bore between the motor shaft and the pinion, the said further seal having an Lshaped cross section defining an axial end in contact with a said guide surface when the starter mechanism is in its rest position.

A starter mechanism for an engine of a motor vehicle, incorporating the invention in a preferred form, will now be described by way of example only and with reference to the accompanying drawings, in which:- Figure 1 is a view in cross section of part of the starter mechanism incorporating features of the invention; and Figures 2, 3 and 4 are scrap views on a larger scale, each showing a respective modification.

Referring first to Figure 1, this shows a starter mechanism the main components of which are a motor shaft 10 having a threaded end 11 carrying a starter head 12. The motor shaft 10 has a first cylindrical surface 13 extending from 4 its threaded end 11, and at least one further cylindrical surface 14, 141 acting as a guide surface and of larger diameter than the surface 13. The purpose of the guide surface or surfaces will be explained below. The starter head 12 is retained in engagement against the radial shoulder defined at the free end of the first cylindrical surface 13 of the shaft 10 by means of a nut 15, so as to be immobilised against axial movement.

The starter mechanism also includes a starter pinion 16, which is displaceable axially from a rest position shown in the upper part of Figure 1 to a meshing position shown in the lower part of the Figure. In the lower position, the pinion 16 meshes with a conventional toothed crown (not shown) on the engine flywheel. In the meshing position, the starter pinion 16 is in contact with the starter head 12.

The starter pinion 16 includes at one of its ends a toothed crown 17 which is extended in a cylindrical portion 18, having an end portion 20, remote from the crown 17, which constitutes the inner ring of a free wheel 21. The latter also includes rollers 40, riding on the inner ring 20 and surrounded by a protective shroud 41. In the usual way, the starter pinion 16 and the free wheel 21 are made to be rotatable with the motor shaft 10, for example by means of splines which are not shown (not being part of the present invention).

In the example shown in Figure 1, the starter is of the extending-pinion type, that is to say the starter head 12 is located outside the casing of the starter mechanism, the end portion 22 of the casing constituting the support for the starter pinion 16. The support 22 includes on the outer side of the starter a housing 23, the inner end 24 of which defines a radial shoulder for abutment with a ball bearing 25. The inner ring of the ball bearing 25 is in contact with the outer surface 19 of the cylindrical portion 18 of the starter pinion 16.

It is necessary to protect this outer surface 19 against any deposit of dust, such that the starter pinion 16 will not thereby encounter any force resisting its axial displacement. For this reason, the starter mechanism includes sealing means.

The outer surface 19 is spaced radially away from the cylindrical bore of the housing 23 by a radial distance d. The sealing means includes a lip seal 26 which is secured to the starter pinion 16. The length of the lip of the seal 26 is less than the distance d.

When the starter is at rest, the lip of the seal 26 occupies an inclined position. It has an end 28 (Figures 2 to 4) which bears against a radial wall. In the example shown in Figure 1, this radial wall is that which defines the inner end 24 of the housing 23, i.e. the wall, formed integrally in the support 22, which defines a shoulder for the ball bearing 25.

When the starter is operating, the lip of the seal 26 takes up a radial position as shown in broken lines in Figure 2, under the effect of centrifugal force. In this configuration, the end 28 of the lip of the seal 26 is spaced away from the bore of the housing 23 by a very small distance e. The seal 26 thus acts like a labyrinth seal and prevents penetration of any dust on to the outer surface 19 of the pinion. It will be appreciated that such a seal 26 offers no resistance to axial movement of the 6 pinion, and that it is not subject to any wear in operation of the starter.

Figures 2 to 4 show modifications, in particular as regards the abutment face, or wall, on which the end 28 of the lip bears when the starter is at rest.

In Figure 2, the end 28 is no longer in engagement (as in Figure 1) against a shoulder 24 formed integrally in the support 22. Instead it bears against a deflector element 30 which is part of the ball bearing 25.

In Figure 3, the end 28 bears against the inner ring 31 of the ball bearing 25, the latter being of the sealed type.

In Figure 4, the end 28 bears against a ring 32 located in front of the ball bearing 25.

In each case, and in order to facilitate its deflection into the radial working position, the lip of the seal 26 is of tapered cross section.

Referring once again to Figure 1, the starter pinion 16 has a shouldered bore 35 at its centre, which enables two bearing sleeves to be interposed between the starter pinion 16 and the shaft 10. These bearing sleeves enable the pinion 16 both to slide on the shaft 10 and to rotate around it. The bearing sleeves 36 and 37 are displaced axially over the guide surfaces 14, 141. It should be noted that these surfaces also require to be protected from ingress of dust. For this reason, the sealing means includes a further seal 38, which is fixed to the starter pinion 16 and which is located in the forward part of its shouldered bore 35. The seal 38 has a generally L-shaped cross section, the end of the radial branch of which 7 defines a clearance with the first cylindrical surface 13 of the shaft 10.

In the rest position, only the end of the axial branch of the seal 38 is in contact with the first guide surface 14 of the shaft 10. The diameter D1 of this surface 14 is greater than the diameter D of the cylindrical first surface 13. Thus, when the starter is at rest, the seal 38 provides effective protection for the guide surfaces 14 and 141, and again offers no mechanical resistance during operation. The axial end of the seal 38 ceases to be in contact with the guide surface 14 once the starter pinion 16 begins its axial displacement, and the radial end of the seal does not rub on the cylindrical surface 13.

It will be appreciated that, during operation of the starter, the first guide surface 14 is protected by the seal 38 due to the fact that the pinion 16 is in contact with the starter head 12, as shown in the lower part of Figure 1.

8

Claims

1. A starter mechanism for an internal combustion engine, comprising a starter pinion which is displaceable axially on a motor shaft between a rest position and a meshing position in which the start pinion is in contact with a starter head, the said starter pinion having a toothed crown extended by a cylindrical portion having an outer surface in contact with a bearing fitted in a support portion of the casing of the starter mechanism, the support portion having at one of its ends a housing which defines a gap between itself and the outer surface of the said cylindrical portion of the pinion, wherein the mechanism further includes a lip seal carried by the pinion for protecting the said outer surface of its cylindrical portion, the lip seal having a lip the length of which is smaller than the width of the said gap and such that in the rest position the lip is inclined, with its free end engaging on a radial wall.

2. A mechanism according to Claim 1, wherein the said radial wall is a shoulder of the said bearing, formed integrally in the support portion of the casing.

3. A mechanism according to Claim 1, wherein the said radial wall is defined by a deflector of the bearing.

4. A mechanism according to Claim 1, wherein the said radial wall is an inner ring of the bearing.

5. A mechanism according to Claim 1, wherein the said vertical wall is defined by a ring located in front of the bearing.

6. A mechanism according to any one of the preceding Claims, wherein the lip of the lip seal is tapered.

9 7. A mechanism according to any one of the preceding Claims, wherein the starter pinion has a shouldered bore receiving bearing sleeves which cooperate with at least one guide surface formed on the motor shaft, the latter having adjacent to its free end a cylindrical surface having a diameter smaller than the diameter of the guide surface or surfaces, the mechanism having a further seal fixed to the starter pinion and disposed in the said bore between the motor shaft and the pinion, the said further seal having an L-shaped cross section defining an axial end in contact with a said guide surface when the starter mechanism is in its rest position.

8. A starter mechanism for an internal combustion engine, substantially as described in the foregoing description with reference to Figure 1 of the accompanying drawings.

9. A mechanism according to Claim 8, modified substantially as described in the foregoing description with reference to any one of Figures 2, 3 and 4 of the accompanying drawings.