GB2280232A

GB2280232A - Selector rod interlocking mechanism that reduces dragging movements

Info

Publication number: GB2280232A
Application number: GB9414309A
Authority: GB
Inventors: Vinzenz Schmidt; Gerd Wollschlaeger
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1993-07-15
Filing date: 1994-07-15
Publication date: 1995-01-25
Anticipated expiration: 2014-07-15
Also published as: GB9414309D0; GB2280232B; DE4323648C1

Abstract

An interlocking mechanism for gearbox selector rods 2, 3 and 4 comprises two detent elements 11, 12 with pin ends 15, 16 which engage in bore 10 so as to reduce dragging or parasitic movement. The pin ends 15, 16 have flat end faces which cooperate with flat end faces on locking pin 23 located in bore 10. Head ends 13, 14 of the detent elements 11, 12 have raised hemispherical portions 17, 18 that engage locating grooves 19, 20 in selector rods 2,4. The detent elements 11,12 are urged towards the selector rods 2, 4 by springs 21, 22 which sit on the shoulder of stepped bores 8, 9. If merely the locking of adjacent selector rods is required the bore 10 and locking pin 23 may he replaced by an annular U-shaped groove (27, fig 5). To accommodate selector rods that do not lie in the same plane a further detent element (28, fig 6) may be provided. To ensure mutual locking the detent elements 11, 12 must be furnished with stud extensions (30, 31 fig 6). <IMAGE>

Description

"Interlock mechanism for selector rods in motor vehicle change-speed gear boxes." The invention relates to an interlock mechanism for selector rods in motor vehicle change-speed gear boxes having three or more selector rods.

From DE-OS 21 32 736 an interlock mechanism for selector rods in motor vehicle change-speed gear boxes is known comprising at least three mutually lockable selector rods which preferably lie in a plane and have locking members arranged between the selector rods, the locking members comprising detent elements held in their locked position on the outer selector rods by compression springs and a locking pin displaceable in a transverse bore in the middle selector rod and engaging with the ends of the detent elements.

Such known interlock mechanisms are used to prevent selector rods being displaced if one of the selector rods has already been shifted or is in the course of being shifted. Such an interlock mechanism is also intended to ensure that only one selector rod can ever be moved at a time.

The possibility or probability that several selector rods might be moved at the same time arises from the fact that the selector forks fixed to the selector rods include so-called selector arms with a groove to receive the selector fingers of the gear-changing mechanism, which are situated very close together in one region of the changespeed gear box so that in a selection movement of the selector finger one of the various selector arms, and with it its corresponding selector fork and selector rod, can be selectively moved a short distance. As a result of manufacturing tolerances in the manufacture of the selector forks with their selector arms and of the selector rod guides it may happen that adjacent selector arms bear against one another and rub against one another in the immediate neighbourhood of the selection finger. As a result, in a subsequent engaging movement of one of the selector arms the other selector arm may be dragged along with it to some extent.

It is likewise possible for a free selector rod to be set in motion independently as a result of vibrations of the motor vehicle if it is not positively locked.

In the known interlock mechanism the spring-loaded detent elements have hemispherical ends which cooperate with corresponding catches in the outer selector rods, while their ends facing the middle selector rod are likewise hemispherical in shape and cooperate with the locking pin in the transverse bore in the middle selector rod. By simple consideration of tolerances during corresponding gear-changing movements of the selector rods, preferably using computer aided design programs, it is quickly seen that in a transition region initial dragging movements of the selector rods are possible before compulsory interlocking occurs.

Such initial dragging movements of adjacent selector rods can lead to undesirable difficulties in gear selection.

The object of the present invention is to provide an improved interlock mechanism in which the possibility of such a malfunction is reduced.

To this end, according to the invention an interlock mechanism for selector rods in motor vehicle change-speed gear boxes having three or more selector rods comprises two opposed locking members each associated with a respective outer selector rod, said locking members comprising detent elements displaceable in stepped bores between said outer rods and being urged towards their respective associated rods by compression springs, each detent element comprising a head end adapted to engage in a locating groove in its associated selector rod and a pin end having a cylindrical end part with a flat end face that cooperates with an inner selector rod lying between said two outer selector rods or with a third locking member associated with the inner selector rod.

In an embodiment of the invention wherein the said outer and inner selector rods are arranged in one plane the third locking member is a locking pin displaceable in a transverse bore in the inner selector rod.

By providing the detent elements with a cylindrical end part with a flat surface, the possibility of initial dragging movement of adjacent selector rods is reduced to a minimum.

Further details of the invention are explained in claims 2 to 4.

The invention will now be explained in more detail with reference to three exemplary embodiments illustrated in the accompanying drawings, in which: Figs. 1 to 4 are diagrammatic sections through three selector rods lying in a plane in the region of the interlock mechanism with the selector rods in different gear selection positions; Fig. 5 is a simplified embodiment of an interlock mechanism according to Figs.

1 to 4; and Fig. 6 is an embodiment of the interlock mechanism as it could be used in the case of selector rods not lying exactly in the same plane.

In Figures 1 to 4 three selector rods 2, 3 and 4 are arranged to slide axially in corresponding guide bores 5, 6 and 7 in a gearbox housing 1 (only shown in section).

Between the adjacent selector rods 2 & 3 and 3 & 4 there are transverse bores 8 and 9, in the present embodiment in the form of stepped bores.

In the middle selector rod 3 there is a transverse bore 10, which in the neutral position of the three selector rods 2, 3 and 4 is in alignment with the narrower sections of the stepped bores 8 and 9.

Fitted in the stepped bores 8 and 9 are detent elements 11 and 12, each comprising a respective head end (13 or 14) and a pin end (15 or 16). The head ends 13 and 14 have raised hemispherical portions 17 and 18 which can cooperate with corresponding locating grooves 19 and 20 in the selector rods 2 and 4.

The detent elements 11 and 12 are urged by compression springs 21 and 22 towards the adjacent outer selector rods 2 and 4.

In the transverse bore 10 of the middle selector rod 3 there is a displaceable locking pin 23, each end 24 of which is shaped as a section of a sphere with a flat end face.

The detent elements 11 and 12 are provided at their pin ends 15 and 16 with cylindrical end parts 25 and 26 with flat end faces which cooperate with the flat end faces of the locking pin 23.

In Figures 1 to 4 the selector rods 2 to 4 are shown in different positions, with reference to which the way in which the interlock mechanism of the invention works will now be explained.

In Fig. 1 the upper selector rod 3 is shown displaced into its engaged position. The raised portion 17 of the selector element 11 is hereby moved out of the locating groove 19 and moved downwards, compressing the compression spring 21 and causing the pin end 15 to enter the transverse bore in the selector rod 3. The locking pin 23 is thereby blocked and acts in its turn by way of the pin end 16 of the detent element 12 to hold this element firmly with its raised part 18 in the locating groove 20 in the selector rod 4.

In Fig. 2 the selector rod has returned into its neutral position, and the detent element 11 has gone back into the locating groove 19 on the selector rod 4. All three of the selector rods can now move.

In Fig. 3 the lower selector rod 4 is displaced into its engagement position and correspondingly the detent element 12 is displaced upwards against the force of its compression spring 22 and its pin end 16 enters the transverse bore 10 in the selector rod 3, so that the locking pin 23 blocks possible movement of the detent element 11 of the selector rod 2.

In Fig. 4, starting from the neutral position of all three selector rods shown in Fig. 2, it is assumed that the middle selector rod 3 is moved in the engagement direction, and it is clear that the selector rod 3 directly blocks the two detent elements 11 and 12 at their pin ends 15 and 16 and accordingly makes movement of the other two selector rods 2 and 3 impossible.

In Fig. 5 a simplified embodiment of an interlock mechanism according to the invention is shown which can be used when all that matters is to lock the respective immediately adjacent selector rods.

In this embodiment, instead of a transverse bore in the middle selector rod 3' only a peripheral annular groove 27 of U-shaped cross-section is provided which cooperates with the detent elements 11' and 12' in order to lock together only the selector rods 2' and 3' or 3' and 4' respectively that are directly adjacent to one another in the course of a gear change.

In Fig. 6 is shown an embodiment of how selector rods 2", 3" and 4" that do not necessarily lie in one plane can be used. The detent elements 11", 12" and 28 are essentially similar in form and are spring-loaded towards the locating grooves in their selector rods. The stepped bores 8", 9" and 29 are arranged to intersect one another, so that the pin ends of the detent elements can cooperate with one another with their cylindrical end parts.

In order to ensure mutual locking of the detent elements stud extensions 30 and 31 must be provided on the cylindrical end parts of the two mutually opposed pin ends.

Obviously instead of the helical compression springs shown in the Figures other spring arrangements, for example mutually supporting belleville spring arrangements, can be used. In addition the edges of the cylindrical end parts of the pin ends of the detent elements and of the transverse bores can be slightly rounded off or chamfered in the manner usual in machine design.

Claims

Claims.

1. Interlock mechanism for selector rods in motor vehicle change-speed gear boxes having three or more selector rods, comprising two opposed locking members each associated with a respective outer selector rod, said locking members comprising detent elements displaceable in stepped bores between said outer rods and being urged towards their respective associated rods by compression springs, each detent element comprising a head end adapted to engage in a locating groove in its associated selector rod and a pin end having a cylindrical end part with a flat end face that cooperates with an inner selector rod lying between said two outer selector rods or with a third locking member associated with the inner selector rod.

2. Interlock mechanism according to claim 1 wherein the said outer and inner selector rods are arranged in one plane and the third locking member is a locking pin displaceable in a transverse bore in the inner selector rod.

3. Interlock mechanism according to claim 2 wherein the locking pin is formed with part-spherical ends with flat end faces.

3. Interlock mechanism according to claim 1 wherein said outer and inner selector rods are arranged in one plane and the pin ends of the opposed detent elements cooperate with a peripheral U-section annular groove in the inner selector rod.

5. Interlock mechanism according to claim 1 wherein the inner and outer selector rods do not lie in one plane, the locking member associated with the inner selector rod is a detent element similar to those associated with the two outer selector rods, the stepped bores of the three detent elements intersect one another so that the three detent elements cooperate and the two opposed detent elements are provided with blocking extensions.

6. Interlock mechanism according to claim 1, substantially as herein described with reference to Figs.

1 to 4 of the accompanying drawings.

7. Interlock mechanism according to claim 1, substantially as herein described with reference to Fig. 5 of the accompanying drawings.

8. Interlock mechanism according to claim 1, substantially as herein described with reference to Fig. 6 of the accompanying drawings.