GB2153022A

GB2153022A - Gear shift mechanism for gear boxes

Info

Publication number: GB2153022A
Application number: GB08431339A
Authority: GB
Inventors: Jiri Frydrych; Bohuslav Urvalek; Antonin Pan
Original assignee: Ustav Pro Vyzkum Motorovych Vozidel
Current assignee: Ustav Pro Vyzkum Motorovych Vozidel
Priority date: 1983-12-12
Filing date: 1984-12-12
Publication date: 1985-08-14
Also published as: CS933683A1; FR2556292B1; GB2153022B; GB8431339D0; FR2556292A1; DE3445175A1; CS240189B1

Abstract

A gear box wherein reverse gear and a forward gear are engaged by a common shift rail 2, carrying a swinging lever, meshing by the end 8a of the first arm 8 in a groove of reverse gear and by a fork 12 with a forward gear is characterized by two radial projections, 4 and 5 on the gear shift bar mutually spaced in the direction of its axis one behind the other, the mutually facing parts of which form sliding surfaces for an end 9a of the other arm 9 of the swinging lever, and the said end lies behind the first projection and over the level of the upper part of the other projection. In engaging reverse the end 9a moves between the projections 4 and 5 (as shown in phantom) but when the rod 2 is moved to engage the forward gear by fork 12 no movement of the reverse engaging lever occurs. The invention is especially applicable to five-speed-gear gear boxes of motor vehicles, where the reverse gear and the fifth speed gear are shifted by means of a common gear shift bar. <IMAGE>

Description

SPECIFICATION Gear shift mechanism for gear boxes The invention relates to a gear shift mechanism for gear boxes, including a shiftable gear shift bar, which controls a swinging lever meshing by an end of the first arm in a groove of an inserted gear of the back motion and carries a gear shift element of the next speed gear.

As to gear boxes, one speed gear of which and a back motion are shifted by means of a common shiftable gear shift bar, it is desirable that, when shifting the gear shift bar in the sense of shifting the speed gear, the swinging lever meshing a groove of an inserted gear of the back motion may be not simultaneously turned a little. In this way even the inserted gear of the back motion would be shifted, and this useless, non-functional shift would require a free space in the gear box. This fact would result in increasing dimensions of the gear box, what is undesirable. In hitherto known embodiments the said problem is solved so that on a shiftable gear shift bar, carrying a shifting fork for the fifth speed gear is formed a pin meshing in a groove of an L-shape in a swinging lever for shifting the inserted gear of the back motion.At shifting the gear shift bar in the sense of shifting of the fifth speed gear, the pin moves in a part of the L-groove, which is in fact parallel with the axis of the gear shift bar; in this way the swinging lever is not turned and the inserted gear of the back motion is not shifted.

There is a drawback in this known solution, viz.

that, because of pressing the groove of an L-shape in the swinging lever; a radius is created, which lies close to the flat of the pin, what requires an increased clearance between the pin and surface of the L-groove, being in fact rectangular to the axis of the gear shift bar. This clearance, at keeping the gearing of the swinging lever, decreases the shift of the inserted gear of the back motion at its shifting. This undesirable diminishing of the shift of the inserted gear may be obviated by increasing the gearing on the swinging lever, but it results in increasing the shifting force and in a bigger difference in an axial shift of the inserted gear of the back motion, determined by production tolerances.

But such results are undesirable. Because of the said clearance, a free axial shift of the inserted gear of the back motion takes place, and in this way its undesirable contact to the toothed shifting sleeve of the first speed gear at its shifting may come in question.

The invention aims to omit the said drawbacks in a considerable way. This aim is achieved by means of a gear shift mechanism for gear boxes, including a shiftable gear shift bar, which controls a swinging lever, meshing by the end of the first arm in the groove of an inserted gear of the back motion and carries a gear shift element of a next speed gear, according to the invention so that two, in fact radial, projections are arranged on the gear shift bar in the direction of its axis one behind the other, the nearer parts of which form sliding surfaces for an end of the other arm of the swinging lever, and the said end lies behind the first projection and over the level of the upper part of the other projection. The swinging lever is located on a pin, and this pin, as well as ends of arms of the swinging lever, lies in tops of a triangle.Between the end of the other arm of the swinging lever and the sliding surface of the first projection a gap takes place, and the said end partially protrudes over the other projection. The ends of arms of the swinging lever are bent and provided with curved contact surfaces. The projections together with a finger, meshing in a choosing and shifting slide block, are a part of a gate fixly connected to the gear shift bar.

By means of this gear shift mechanism one achieves an accurate and reliable back motion shifting as well as of the next speed gear by a single gear shift bar; even at shifting the back motion there is kept the same lift of the shifting and choosing slide block as for other speed gears. A self shift of the inserted gear of the back motion in the basic position and at shifting the speed gear shifted by the same gear shift bar is removed.

In order that the invention may be clearly understood and readily carried into effect, a preferred embodiment thereof is, by way of example, hereinafter more fully described and illustrated in the accompanying drawings, in which: Figure 1 shows a mechanism in a view in the direction of the axis of the gear shift bar.

Figure 2 shows a view to a mechanism perpendicularly to the axis of the gear shift bar; dash-dot lines show also a position at shifted back motion.

Figure 3 shows a basic position of projections and the end of the other arm of the swinging lever.

Figure 4 shows a position at shifted back motion parts in this position are marked with position numbers provided with an apostrophel.

Figure 5 shows a position at a shifted speed gear, which is shifted by means of the same gear shift bar as the back motion/parts in this position are marked with position numbers provided with two apostrophesi.

The gear shift mechanism in Fig. 1 and 2 comprises a choosing and shifting slide block 1, which is swivelling and shiftable. In one of the swivelling positions it meshes with a finger 3a made on a gate 3, which is fixly connected to a shiftable and non-revolving gear shift bar 2 of the back motion and other speed gear, for the shifting of which it is provided with a fork 12. A swinging lever 6, seated on a pin 7 and provided with two arms 8, 9 is designed for shifting the back motion. The first arm 8 meshes by its bent end 8a in a groove of an inserted gear 11 of the back motion. A bent end 9a of another arm 9 lies behind the first projection 4 and over the level of the upper surface of the other projection 5. These projections 4 and 5 are formed on the gate 3 and they lie in the direction of its axis one behind the other, and they are, with respect to it, in fact radial.The other projection 5 is ended in the vertical direction by an upper surface being parallel to the axis of the gear shift bar 2, and it must be lower than the first projection 4.

The upper surface prevents for the swinging lever 6, in the basic position and at a shifted speed gear by a fork 12, to move undesirably, viz. in the way that the end 9a of the other arm 9 of the swinging lever 6 is provided with a parallel surface. These surfaces are mutually overlapping in the initial position. The mutually opposite parts of the projections 4 and 5 form sliding surfaces for the end 9a of the other arm 9 of the swinging lever 6. The bent ends 8a, 9a of the arms 8, 9 are made as ball surfaces or cylindrical ones, which may be a part of pins revolvingly assembled on the arms 8, 9.

The swinging lever 6 is a sheet pressing, but it may be manufactured as a casting as well.

If there is not shifted a back motion or the speed gear shifted by the fork 12, the end 9a of the other arm 9 takes place in the position shown in Fig. 3.

The end 9a of the other arm 9 is remote from the sliding surface of the first projection 4 by a clearance B, that an overlapping of the surface on the end 9a of the other arm 9 and the upper surface of the other projection 5 may be achieved. At a movement of the swinging lever 6 of a clearance A between the said surfaces, the surface of the end 9a of the other arm 9 bears on the upper surface of the other projection 5. The inserted gear 11 of the back motion is shifted, but the shift, limited by the clearance A, is only of such a value, that no contact of the inserted gear 11 with other gears of the gear box comes in question. This is also valid for shifting the speed gear by means of the fork 12 after an axial movement of the gear shift bar 2 in the respective direction. This position is shown in Figure 5 and the parts are marked by position numbers with two apostrophes.Clearance A" = A.

If one shifts the back motion, the gate 3 is shifted axially in reverse direction. The sliding surface of the first projection 4 leans at first against the end 9a of the other arm. During the next axial movement of the gate 3 into the position shown in Fig. 4 the parts are marked with an apostrophe,', the sliding surface of the first projection 4' carries away the end 9a' of the other arm 9, which moves along a circle having its centre in the axis of the pin 7 of seating of the swinging lever 6, and it is shifted between the sliding surfaces of the projections 4', 5'. In the limit position, the inserted gear 11 is in engagement with the respective gears of the back motion.

If the inserted gear 11 of the back motion is put out of operation, the gate 3' performs a reverse axial movement. The sliding surface of the other projection 5' carries away the end 9a' of the other arm 9 so long, till the said end 9a' comes into the position shown in Fig. 3. In this way, by means of the swinging lever 6, the inserted gear of the back motion is shifted out of engagement with the respective gears of the back motion.

The gear shift mechanism according to the invention may be applied in fact for all gear boxes, in which the back motion and next speed gear is shifted by means of a single gear shift bar. It is suitable especially for gear boxes of motor vehicles, which are so arranged that opposite the back motion there takes place, on the gear shift lever, a position for another speed gear - usually the fifth speed gear.

Although the invention is illustrated and described with reference to one preferred embodiment thereof, it is to be expressly understood that it is in no way limited to the disclosure of such a preferred embodiment, but it is capable of numerous modifications within the scope of the ap

Claims

pended claims. CLAIMS

1. A gear shift mechanism for gear boxes including a shiftable gear shift bar, which controls a swinging lever, meshing by the end of the first arm in the groove of an inserted gear of the back motion and carries a gear shift element of another speed gear, comprising two, in fact radial, projections being arranged on the gear shift bar in the direction of its axis one behind the other, the mutually nearer parts of which form sliding surfaces for an end of the other arm of the swinging lever, and the said end lies behind the first projection and over the level of the upper part of the other projection.

2. A gear shift mechanism as in claim 1 wherein the swinging lever is located on a pin, and this pin as well as ends of arms of the swinging lever lie in tops of a triangle.

3. A gear shift mechanism as in claim 1, wherein between the end of the other arm of the swinging lever and the sliding surface of the first projection a gap takes place, and the said end partially protrudes over the other projection.

4. A gear shift mechanism as in claim 1, wherein the ends of arms of the swinging lever are bent and provided with curved contact surfaces;

5. A gear shift mechanism as in claim 1, wherein the projections together with a finger, meshing in a choosing and shifting slide block, are a part of a gate fixly connected to the gear shift bar.

6. A gear shift mechanism for gear boxes substantially as herein described with reference to the accompanying drawings.