WO2006022577A1

WO2006022577A1 - Device for servo-assisted gear shifting, and use thereof

Info

Publication number: WO2006022577A1
Application number: PCT/SE2005/001023
Authority: WO
Inventors: Hilding Nilsson; Torbjörn JANSSON
Original assignee: Scania CV AB
Current assignee: Scania CV AB
Priority date: 2004-08-23
Filing date: 2005-06-29
Publication date: 2006-03-02
Anticipated expiration: 2007-02-23
Also published as: DE112005001947T5; SE0402057L; SE0402057D0; SE526265C2

Abstract

A device for servo-assisted gear changing in a motor vehicle manual gearbox comprises a selector shaft (1) adapted to being rotated in order to effect gear change, a gear lever (2) connected thereto and adapted to responding to manual movement away from an unengaged position by causing the selector shaft to rotate for gear changing, and a servo arrangement with at least one pressure medium source, a power means capable of being acted upon by the latter, and two valves (6, 7) adapted to opening a connection between a pressure medium source and a power means in order to act in support of gear changing in response to rotation of the selector shaft via the gear lever in one direction from the unengaged position, and the other for such action in response to rotation of the selector shaft via the gear lever in the opposite direction.

Description

Device for servo-assisted gear shifting and use thereof

FIELD OF THE INVENTION AND STATE OF THE ART

The present invention relates to a device for servo-assisted gear changing in a motor vehicle manual gearbox comprising a selector shaft adapted to being rotated in order to effect gear change, a gear lever connected to the latter, and a servo arrangement assisting the gear changing movement according to the preamble of the attached claim 1 , and use thereof.

The motor vehicle may be of any desired kind, but the provision of such a servo arrangement to facilitate gear changing is particularly relevant in heavy motor vehicles, such as trucks and buses, at which the invention is particularly, but not exclusively, directed as regards the area of use.

Said gear lever need not at all be, and is most likely not to be, the lever which the driver of the motor vehicle handles in order to effect a gear change from an unengaged position of the gear lever. The lever which the driver handles may be connected to said gear lever in various ways, e.g. via a wire control.

In such a device it is important that there is so-called "servo play", whereby the servo arrangement does not begin to assist the gear changing movement until the gear lever has moved somewhat away from the unengaged position, since otherwise the unengaged position could not be maintained, because the servo arrangement would urge the gear lever and the selector shaft away from that position. In a device of this kind, gear changing may be effected by movement of the gear lever in opposite directions in order to rotate the selector shaft in opposite directions from said unengaged position. Applying the action of the servo arrangement to assisting the gear changing movement in both directions from the unengaged position entails special adaptation of the servo arrangement.

DE 3339591 A1 describes a device of the kind mentioned in the introduction. In that device, the gear lever and the selector shaft in said unengaged position are already connected together for joint rotation so that the selector shaft rotates immediately when the gear lever moves away from the unengaged position. The movement of the gear lever acts upon a leaf spring which, when the gear lever moves said distance away from the unengaged position, connects the servo arrangement by effecting contact to a contact means for connection of a pressure medium source. The leaf spring contacts one of two said contact means, depending on which direction the gear lever moves from the unengaged position. This involves a valve being caused, via the pressure medium source, to act upon a power means coordinated with the respective direction. Such a valve is both complicated and expensive while at the same time being relatively sensitive, entailing risk of failure and/or requiring excessive maintenance.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a device of the kind defined in the introduction which overcomes the disadvantages of the device described above. This object is achieved according to the invention by the servo arrangement being provided with two said valves, one of them adapted to being opened, for action to assist gear changing via a said power means in response to rotation of the selector shaft via the gear lever in a direction from the unengaged position, and the other arranged for such action in response to rotation of the selector shaft via the gear lever in the opposite direction, and by a connection between the gear lever and the selector shaft being arranged to allow the gear lever to move said distance in each direction from the unengaged position before the gear lever and the selector shaft become locked together for joint rotation, and to ensure that the respective valve opens after this movement to a distance from the unengaged position.

Providing so-called "servo play" in the manner of the invention by a said connection between the gear lever and the selector shaft makes it possible for two simple and robust standard valves available "off the shelf from suppliers to be used in the servo arrangement. The result is that the servo arrangement is not only simpler and less expensive but also more reliable than in the case of previously known devices of this kind.

According to an embodiment of the invention, said connection comprises a part which on one side is rigidly connected to the gear lever and on the other side is connected in the manner of a ball joint to the selector shaft in order to allow oblique movement of said part relative to the selector shaft in response to movement of the gear lever from said unengaged position in order to act, after the gear lever has moved said distance, upon the valve which is associated with the intended direction of rotation of the selector shaft. Arranging such a part in the connection is an easy and reliable way of providing the desired so-called "servo play" in both directions so that the respective valve can be safely acted upon and provide assistance for the gear changing movement. It also makes it easy to ensure that the action of the servo arrangement ceases upon cessation of the manual movement of the gear lever, since it is easy to arrange that in such a situation the part reverts to a neutral position of rest.

According to another embodiment of the invention, said part is a sleeve which substantially concentrically surrounds the selector shaft in the unengaged position, has a larger inside diameter than the outside diameter of the selector shaft and is connected to the selector shaft by said balljoint-type connection, and the sleeve is adapted to performing, when the gear lever moves away from said unengaged position, an oblique movement relative to the selector shaft before, via the balljoint- type connection, it transfers force applied to it to the selector shaft. Using such a sleeve makes it easy to implement the device according to the invention involving the action of two different valves in response to a gear lever moving said certain distance from an unengaged position.

According to an embodiment of the invention, the balljoint-type connection takes the form of a splined connection between the sleeve and the selector shaft, said splined connection being short relative to the length of the sleeve. Such a short splined connection, which in the case of a gearbox of, for example, a truck may have a length of the order of 2- 10 mm, acts like a balljoint as regards the possibility of oblique positioning of the sleeve relative to the selector shaft, and can at the same time lock the gear lever and the selector shaft for joint rotation when the gear lever has moved said distance from the unengaged position.

According to another embodiment of the invention, the selector shaft is hollow and one end of the sleeve is firmly connected to a rod which in the sleeve's longitudinal direction extends into the selector shaft from one end of the latter. The rod may help to hold the sleeve in position relative to the selector shaft, but what above all can be provided by this arrangement is suitable resistance to the manual movement of the gear lever involved in change in gear, by the thickness of the rod being adapted to the transverse dimensions of the hollow space in the selector shaft in order to provide a driver of the vehicle with convenient lever sensation when changing gear.

According to another embodiment of the invention, each of the two valves has movable valve means adapted to defining an intermediate space for accommodating said part between them, and the intermediate space is so dimensioned that the respective valve means are arranged at small distances from the part when the gear lever is in the unengaged position. This means that oblique positioning of the part in one direction will result in the one movable valve means being acted upon and the respective valve thereby being opened, while the conditions are the same for the other movable valve means in the case of movement in the opposite direction.

According to an embodiment of the invention, the pressure medium source incorporated in the device is a compressed air source. Although this is advantageous, some other pressure medium, such as hydraulic fluid, is also conceivable. The invention also relates to a use of a device as above for servo- assisted gear changing in a manual gearbox in a motor vehicle, particularly in a heavy vehicle such as a truck or bus. What such a use entails and what advantages are associated with it are indicated by the description above of the various embodiments of the device according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention, cited by way of example, is described below with reference to the attached drawings, in which:

Fig. 1 is a partly cutaway view in the direction of the selector shaft of a device according to an embodiment of the invention in an unengaged position,

Fig. 2 is a partly cutaway sideview of the device according to Fig. 1 , turned through 90° relative to Fig. 1 , with a splined connection between a sleeve and the selector shaft shown magnified,

Fig. 3 is a view corresponding to Fig. 1 of the device with the gear lever moved a said distance from the unengaged position,

Fig. 4 is a partly cutaway view from above of the device in the position according to Fig. 4 and Fig. 5 is a greatly simplified functional view illustrating the basic function of the device according to the invention.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

Fig. 1 illustrates a device for servo-assisted gear changing in a motor vehicle manual gearbox according to an embodiment of the invention. It is here referred to in conjunction with Fig. 2. The device comprises a selector shaft 1 adapted to being rotated in order to effect a gear change. A gear lever 2 is rigidly connected to a sleeve 3 which has a larger inside diameter than the outside diameter of the selector shaft 1 and which in an unengaged position is arranged concentrically relative to and accommodates the selector shaft. The gear lever 2 is adapted, upon manual movement away from the unengaged position depicted in Fig. 1 , to causing the selector shaft to rotate for gear changing. As previously mentioned, it may be some other lever, handle or the like which the vehicle's driver grasps and moves in order, via a connection between it and the gear lever, to move the gear lever.

A connection is arranged between the sleeve 3 and the selector shaft 2 to enable transmission of moment between the gear lever 2 and the selector shaft 1 via the sleeve 3. This connection takes the form of a short so-called splined connection 4 which extends for a distance which is short, e.g. of the order of 2-10 mm, relative to the length of the sleeve and establishes a balljoint-type connection between the sleeve 3 and the selector shaft 1. The selector shaft 1 is hollow and one end of the sleeve 3 is connected firmly to a rod 5 which in the sleeve's longitudinal direction extends into the selector shaft from one end of the latter. The rod keeps the sleeve centred relative to the selector shaft and at the same time holds the sleeve in position axially. The thickness of the rod 5 is preferably adapted to the transverse dimensions of the hollow space in the selector shaft in order to provide a driver of the vehicle with convenient lever sensation during manual manoeuvring of the gear lever into and out of gear. Increasing the thickness of the rod 5 will increase the resistance to gear changing.

The device further comprises two valves 6, 7 of standard type intended to maintain, in the unengaged position according to Fig. 1 , a connection between a pressure medium source and a power means, such as a servo cylinder, which is itself intended to assist a gear changing movement of the selector shaft. Each of the two valves has movable valve means or so-called plungers 8, 9 adapted to defining an intermediate space for accommodating the sleeve 3 between them. This intermediate space is so dimensioned that the respective valve means are arranged at small distances, e.g. of the order of 1 mm, from the sleeve when the gear lever is in the unengaged position.

The function of the device according to the invention will now be described with reference also to Figs. 3-5. When the gear lever 2 is urged from the unengaged position depicted in Fig. 1 in a direction such as that depicted in Fig. 3, the short splined connection 4 with its ball-joint function and the fact that the inside diameter of the sleeve is larger than the outside diameter of the selector shaft will result firstly in the sleeve rotating relative to the connection 4 and assuming an oblique position relative to the selector shaft so that the sleeve reaches and moves the valve means of one of the valves in order to open the respective valve. Only at this stage will the splined connection 4 lock the sleeve and hence the gear lever for joint rotation with the selector shaft and transmit moment between them. The valve 7 will then open a connection between a pressure medium source in the form of a compressed air source 10 and a power means 11 in the form of a servo cylinder, which will then assist the gear changing movement, i.e. the rotation of the selector shaft 1 , by acting directly on the latter or the gear lever or indirectly on either of them.

Once the manual force on the gear lever ceases, the centring rod 5 will cause the sleeve 3 to revert to the concentric position relative to the selector shaft 1 and hence said valve to close and the function of the servo arrangement to cease.

Movement of the gear lever in the opposite direction will cause the second valve 6 to open after the sleeve has assumed an oblique position in the opposite direction, and the servo arrangement will in a corresponding manner assist the gear changing movement.

Fig. 5 illustrates schematically how two power means 11 are connected to the respective valves, but it is within the scope of the invention for the valves to be connected to a single power means, e.g. each to their respective space on opposite sides of a piston.

The invention is of course in no way limited to the embodiment described above, since a multiplicity of possibilities for modifications thereof are likely to be obvious to a specialist in the field, without thereby having to deviate from the basic idea of the invention as defined in the attached claims.

Theoretically, the gear lever might be connected to a part which extends into a hollow end of the selector shaft or a sleevelike extension of the selector shaft, and a connection of the balljoint type might be formed between said part and the selector shaft within the selector shaft or said extension.

Claims

1. A device for servo-assisted gear changing in a motor vehicle manual gearbox comprising a selector shaft (1 ) adapted to being rotated in order to effect gear change, a gear lever (2) connected thereto and adapted to responding to manual movement away from an unengaged position by causing the selector shaft to rotate for gear changing, and a servo arrangement (6-11) with at least one pressure medium source (10), a power means (11) capable of being acted upon by the latter, and a valve (6, 7) adapted to responding to movement of the gear lever from the unengaged position by opening a connection between the pressure medium source and the power means in order to assist the gear changing movement of the selector shaft, the connection between the valve and the gear lever being such that the valve is acted upon by the gear lever so as to open only after the gear lever has moved a distance from the unengaged position, characterised in that the servo arrangement comprises two said valves (6, 7), one of them adapted to being opened in order to act in support of the gear changing movement via a said power means in response to rotation of the selector shaft via the gear lever in a direction away from the unengaged position, and the other for such action in response to rotation of the selector shaft via the gear lever in the opposite direction, and that it comprises a connection (4) between the gear lever and the selector shaft which is adapted to allowing the gear lever to move said distance in each direction from the unengaged position before it locks the gear lever for joint rotation with the selector shaft, and that it ensures that the respective valve opens after said movement to a distance from the unengaged position.

2. A device according to claim 1 , characterised in that said connection comprises a part (3) which on one side is rigidly connected to the gear lever (2) and on the other side is connected in a balljoint manner to the selector shaft (1) in order to allow said part to assume an oblique position relative to the selector shaft in response to movement of the gear lever from said unengaged position in order to act, when the gear lever has moved said distance, upon the valve (6, 7) which is associated with the intended direction of rotation of the selector shaft.

3. A device according to claim 2, characterised in that said part (3) is a sleeve which in the unengaged position is substantially concentric with the selector shaft (1), has a larger inside diameter than the outside diameter of the selector shaft and is connected to the selector shaft by said connection of the balljoint type, and that the sleeve (3) is adapted to responding to movement of the gear lever (2) from said unengaged position by performing an oblique movement relative to the selector shaft (1) before, via the balljoint-type connection, it transmits force applied to it to the selector shaft.

4. A device according to claim 3, characterised in that the balljoint-type connection take the form of a splined connection (4) between the sleeve and the selector shaft (1), said splined connection being short relative to the length of the sleeve (3).

5. A device according to claim 3 or 4, characterised in that the selector shaft (1 ) is hollow and that one end of the sleeve (3) is connected firmly to a rod (5) which in the longitudinal direction of the sleeve extends into the selector shaft from one end of the latter.

6. A device according to claim 5, characterised in that the thickness of the rod (5) is adapted to the transverse dimensions of the hollow space in the selector shaft (1 ) in order to provide a driver of the vehicle with a convenient lever sensation during manual manoeuvring of the gear lever (2) into and out of gear.

7. A device according to any one of claims 2-6, characterised in that each of the two valves (6, 7) has a movable valve means (8, 9) adapted to defining an intermediate space for accommodating said part (3) between them, and that the intermediate space is so dimensioned that the respective valve means are arranged at small distances from the part when the gear lever is in the unengaged position.

8. A device according to any one of the foregoing claims, characterised in that the pressure medium source (10) is a compressed air source.

9. Use of a device according to any one of the foregoing claims for servo-assisted gear changing in a manual gearbox in a motor vehicle, particularly in a heavy vehicle such as a truck or bus.