GB2200968A - A clutch shift mechanism - Google Patents

Abstract

A shift mechanism for engaging and disengaging clutches comprises an axially movable clutch sleeve (1) which is positively connected to at least one of the two halves thereof. The motion for engaging and disengaging the clutch is imparted to the sleeve (1) by way of a shift fork (16) whose two arms engage around the sleeve (1). A rolling bearing (21, 35, 37) between the shift fork (16) and the sleeve (1) provides a rotary connection between the two fork arms (16a, 16b) and the sleeve (1). The rolling bearing (21) is so preloaded that both its races are loaded continuously by way of its rolling members, to obviate sliding between the latter races and the rolling members upon engagement of the clutch - i.e., during the initial movement of the sleeve (1). <IMAGE>

Description

"A Clutch Shift Mechanism" The invention relates to a clutch shift mechanism comprising an axially movable sleeve, the engaging and disengaging movement of the sleeve being produced by means of a shift fork whose two arms or limbs engage a rolling bearing surrounding the sleeve, the rolling bearing producing a rotatable connection between the sleeve and the fork. Normally the sleeve will be positively connected to at least one of the two halves of the clutch.

In known clutch shift mechanisms of this kind slide blocks are provided to connect the shift fork to the rotating clutch sleeve. The slide blocks, which are positioned diametrically opposite one another, engage in a groove in the outer periphery of the sleeve, the groove width corresponding closely to the slide block width such that the-blocks can slide on the rotating sleeve and transfer thereto the movement emanating from the shift fork. The continuous relative movement between the rotating sleeve and the nonrotating slide blocks can cause rapid wear thereof and is therefore a cause of disturbances in operation.

It has already been suggested that the shift fork arms be connected to the rotatably mounted clutch sleeve by way of a rolling bearing. In this arrangement the rolling bearing is in the unloaded state whether the clutch is engaged or disengaged. Consequently, when a transmission or driving motor starts up, it is impossible to prevent sliding occurring between the two races of the rolling bearing and the rolling members included between them. The sliding movement may cause damage to the rolling bearing after a short period of operation and therefore the clutch is liable to fail.

It is an object of the invention to provide an improved shift mechanism which will at least partly remedy this situation and obviate this disadvantage.

Broadly statedthe invention consists in a clutch shift mechanism comprising an axially movable sleeve, the engaging and disengaging movement of the sleeve being produced by means of a shift fork whose two arms or prongs engage around a rolling bearing extending around the sleeve, the rolling bearing producing a rotatable connection between the sleeve and the fork, the rolling bearing being so preloaded that both races of the bearing are loaded continuously by way of its rolling members.

Thus it will be seen that the invention proposes so to preload the rolling bearing that both of its races are loaded continuously by way of its rolling members. With a rolling bearing thus preloaded, operative movements of the shift fork can readily be transmitted to the clutch sleeve without any risk of sliding occurring between the rolling members and one or both races during start-up. This step greatly reduces the risk of damage to the being, even though shifting is frequent, and reduces the likelihood of disturbances in clutches of this kind.

Conveniently, the rolling bearing transmitting the shift movement of the shift fork to the coupling sleeve is a deep groove ball bearing. In a preferred construction it has an outer race formed in two halves divided around the race periphery1 the two halves being clamped together axially of the bearing. Bearings of this kind are particularly suitable for the proposed purpose since they can be loaded in both axial directions and can transmit clutch-engaging and clutch-disengaging forces to and from the shift fork. -Alternatively, a deep groove ball bearing can be used to transmit the shift movement, the bearing having a wavy cage which clamps all the balls axially and presses consecutive balls alternately on to one or the other shoulder of the bearing.

In another possible arrangement according to the invention, in order to avoid the use of special bearings as just described, two skew ball bearings, preferably r positioned with the thrust shoulder on the inside, may be used to provide the connection between the shift fork and the sleeve. In such case their inner races may be spaced apart from one another by a spacer ring and their outer races clamped together axially.

In particular preferred constructions two collars extend around the deep groove ball bearing or skew ball bearings and both have a shoulder positioned against the outer end face of one half. of the race or of the outer raceof the skew ball bearings; one of the two collars engages completely over one half of the race or one of the outer races and only partly over the other half of the race or the other outer race and both collars are formed around their periphery with bores which extend parallel to the clutch axis and are designed to receive clamping screws.The halves forming the outer race for the two outer races can be pressed together by means of the two collars and the clamping screws, the latter being aligned in the direction of the axis of the rolling bearing so that in the case of a deep groove ball bearing all the balls are pressed on to the groove base of the inner race, while if skew ball bearings are used, the balls are pressed on to the inwardly positioned shoulders of the inner races. Consequently, axial shifting forces in either direction are transmitted to the sleeve either by the deep groove ball bearing or by the two skew ball bearings which keep the inner race of the rolling bearing immobile, and move the sleeve into the required position.

In the preferred construction the longer of the two collars has two pins arranged diametrically opposite one another at its periphery. The pins provide the required connection between the collar and the two arms of the shift fork positioned below or beside the clutch sleeve, and initiate the axial movement thereof.

Preferably, the clamping screws are arranged to provide resilient retention of the two collars axially. The preloading force acting on the race halves or on the outer races thus remains substantially constant and is unaffected by temperature increases which occur when the transmission-is in use and may cause substantial thermal expansion of the clamping screws. This resilient mounting of the two collars may be achieved by a spring positioned in a widened bore in one of the collars, the spring surrounding the shank of the clamping screw and being preloaded between the head of the screw and the end face of the collar bounding the widened bore.

The invention may be performed in various ways and one specific embodiment, with some possible modifications, will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 is an end view of a clutch shift mechanism according to the invention, looking along the clutch axis, the view being in section on the line A-B of Figure 2, Figure 2 is a side elevation in section on the line C-D of Figure 1, Figure 3 is a detail section on the line E-E of Figure 1, and Figures 4 and 5 are side elevations on an enlarged scale showing alternative kinds of rolling bearings which may be used in shift mechanisms according to the invention.

In the example illustrated in Figures 1-3, clutch sleeve 1 is arranged to selectively interconnect two shaft ends 4,5 carrying gears 2,3 so that the shaft ends co-rotate. The sleeve 1 is arranged for axial movement on the two gears 2,3 and its internal toothing engages with the external toothing of the gears.

The axial shifting movement is applied to the sleeve 1 by means of a handle 6 positioned outside the transmission casing 7 at the end of a shift shaft 8 which is pivotally mounted in the casing walls transversely to the rotational axis 9 of the sleeve 1 (see Figure 1). A pinion 10 on the shift shaft 8 transmits the shift movements to a two-armed lever 11 positioned below the shaft 8 and arranged to be pivotable about a transverse axis 12, the lever being located by a casing pin 13 whose axis 12 extends parallel with the shaft 8 in a plane through the rotational axis 9 of the sleeve 1. Each of the two arms of the lever 11 has a toothed segment 14, the upper segment meshing with the teeth of the pinion 10 while the bottom segment 14 meshes with a toothed part 15 of a shift fork 16 and, on rotation of the pinion 10, produces a corresponding pivotal movement of the shift fork 16.The fork 16 positioned below the sleeve 1, is pivotable about a transverse casing axis 17 which extends parallel with the shaft 8. The fork 16 engages around the bottom half of the periphery of the sleeve 1 by means of two arms 16a,16b, one of which carries the toothed part 15 providing the connection with the two-armed lever 11. The ends of the fork arms are U-shaped (Figure 2) and each extend around one of a pair of pins 18 which are positioned coaxially of one another on the axis 12, and on diametrically opposite sides of the sleeve 1.

The pins 18 are positioned on the periphery of a collar 19 which extends around the sleeve 1 and which, as shown in Figure 2; locates and surrounds two skew ball bearings 21 spaced apart from one another by means of a spacer ring 20. Referring to Figure 3, the two outer races 22 of the bearings 21 are located between a shoulder 23 of the collar 19 and a shoulder 23 of a second collar 24, the two collars being spring-biased towards one another axially of the sleeve 1.The clamping force on the two collars 19,24 thus acts by way of the two outside, or more remote shoulders of the two outer races 22, and the balls, on the inside or adjacent shoulders of the two inner races 25, and presses these races 25 against the spacer ring 20 Consequently, with the skew ball bearings 21 thus clamped or loaded, the forces initiated by the shift fork 16 can be transmitted in both directions of clutch sleeve movement.

The two collars 19,24 are retained by four clamping screws 26 and are drawn towards one another axially of the sleeve 1 so that their shoulders 23 bear on the outer races 22 of the two bearings 21. To this end, and as Figure 1 shows, the collars 19,24 have on their periphery projecting lugs 27 with boxes 28 which receive the screws 26 extending parallel to the rotational axis 9. A helical spring 30 is located in a groove 29 in the longer collar 19 and fits around the shank of the screw 26. The spring 30 bears at one end on the head 31 of the clamping screw 26, and is received non-rotatably in a recess 32 in the collar 19.

At its other end the spring 30 engages the end face 33 bounding the groove 29 and, as shown, is preloaded or biased by the screw 26, the same being tightened by means of a castellated nut 34 at one end, while the bolt head 31 at the other end has opposing flats. Conseqently, expansion of the screw 26 at high temperatures does not reduce the preloading or biasing force acting on the two collars 19,24.

Instead of the two skew ball bearings 21, a single deep groove ball bearing 35 (as shown in Figure 5) can be used to apply shift forces to the sleeve 1 in both directions of movement. The rolling bearing 35, shown in Figure 5, has a divided outer race 36 comprising two halves divided axially around the periphery of the race. When these halves are clamped together axially in a suitable manner (not shown), a roller bearing 35 of this kind can transmit force to the sleeve 1 in both directions.

Similar considerations apply to the deep groove ball bearing 37 shown in Figure 4, having a unitary outer race 38. If a deep groove ball bearing 37 of this kind has a "wavy cage" 39 which presses consecutive balls 40 alternately in opposite directions as indicated by arrows 41 and 42, a rolling bearing 37 of this kind can be used to transmit adjusting forces to the sleeve 1 in both directions.

Claims (9)

1. A clutch shift mechanism comprising an axially movable sleeve, the engaging and disengaging movement of the sleeve being produced by means of a shift fork whose two arms or prongs engage around a rolling bearing extending around the sleeve, the rolling bearing producing a rotatable connection between the sleeve and the fork, the rolling bearing being so preloaded that both races of the bearing are loaded continuously by way of its rolling members.

2. A shift mechanism according to claim 1, in which the rolling bearing is a deep groove ball bearing whose outer race is in two halves divided around the periphery of the race and clamped together axially of the bearing.

3. A shift mechanism according to claim 1, in which the rolling bearing is a deep groove ball bearing having a wavy cage which acts on all the balls axially and presses alternate balls in opposite directions against one or other shoulder of the bearing.

4. A shift mechanism according to claim 1, in which the rolling bearing consists of two skew ball bearings which provide the connection between the shift fork and the shift sleeve, and the inner races of such bearings are spaced apart by a spacer ring, while the outer races are clamped together axially.

5. A shift mechanism according to claim 2 or 4, including two collars which extend around the deep groove ball bearing or the skew ball bearings respectively, both the collars having a shoulder disposed before the outer end face of one half of a race or of an outer race, one collar engaging completely over one half of a race or over one of the outer races and engaging only partially over the other half of the race or the other outer race, both collars being provided at their periphery with bores which extend parallel to the clutch axis and which are adapted to receive clamping screws.

6. A shift mechanism according to claim 5, in which the longer of the two collars has two pins arranged diametrically opposite one another on its periphery.

7. A shift mechanism according to claim 5, in which the clamping screws provide resilient retention of the two collars axially.

8. A shift mechanism according to claim 7, including a spring located in a widened bore in the collar and extending around the shank of the clamping screw, the spring being preloaded between the head of the screw and the end face of the collar.

9. A clutch shift mechanism substantially as in any of the forms described with reference to the accompanying drawings.