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Patent Searching and Data


Title:
SYSTEM FOR SHIFTING GEAR WITH DOUBLE-ACTING CYLINDERS
Document Type and Number:
WIPO Patent Application WO/2006/096065
Kind Code:
A1
Abstract:
A system for shifting gear comprising a gear lever (1) which is pivotally connected at its lower end (9). The gear lever's movement is transferred to two master cylinders (2, 3), which are in fluid connection with each side (6a, 6b) of a double-acting cylinder (6). The system is characterised in that a transfer structure (10) is attached to the gear lever and is movably mounted in its axial direction, where the master cylinders' piston rods (2a, 3a) are attached to the transfer structure. The transfer structure is provided with a guide part (12) which interacts with a guide structure (13) arranged in a stationary manner relative to the gear lever when it is moved.

Inventors:
GUNNERUD MORTEN BERGER (NO)
Application Number:
PCT/NO2006/000065
Publication Date:
September 14, 2006
Filing Date:
February 16, 2006
Export Citation:
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Assignee:
KONGSBERG AUTOMOTIVE AS (NO)
GUNNERUD MORTEN BERGER (NO)
International Classes:
F16H61/30; F15B7/00; F15B7/08; F16H59/04
Foreign References:
US3583159A1971-06-08
FR2545160A11984-11-02
US6338286B12002-01-15
US2924943A1960-02-16
US2358887A1944-09-26
GB1436272A1976-05-19
FR872168A1942-06-01
Other References:
None
Attorney, Agent or Firm:
Onsagers AS. (Oslo, NO)
Download PDF:
Claims:
CLAIMS
1. A system for shifting gear comprising a gear lever which is pivotally connected at its lower end, where the gear lever's movement is transferred to two master cylinders, each of which is in fluid connection with a side of a doubleacting cylinder, where the system is characterised in that a transfer structure is attached to the gear lever and is movably arranged in its axial direction, where the master cylinders' piston rods are attached to the transfer structure and the transfer structure is provided with a guide part which interacts with a guide structure arranged in a stationary manner relative to the gear lever when it is moved.
2. A system for shifting gear according to claim 1, characterised in that the guide part and the guide structure are adapted according to the desired transmission ratio between the gear lever movement and the piston's stroke length.
3. A system for shifting gear according to claim 1 or 2, characterised in that the guide part is provided in the form of a guide pin.
4. A system for shift gear according to one of the claims 13, characterised in that the guide structure comprises a guide slot where the guide part or the guide pin is received.
Description:
System for shifting gear with double-acting cylinders

The invention relates to a system for shifting gear.

The system comprises a gear lever which is pivotally connected at its lower end, where movement of the gear lever is transmitted to two master cylinders, which are in fluid connection with each side of a double-acting cylinder.

According to the prior art one master cylinder will be pressurised when the gear lever is moved in one direction and the other master cylinder will be pressurised when the gear lever is moved in the other direction. Pressurisation of one of the master cylinders causes the side of the double-acting cylinder with which the master cylinder is connected to be pressurised. By means of this pressurisation the piston is moved in the double-acting cylinder. The piston is connected with the gear shift mechanism and movement of the piston causes a shift to a new gear ratio depending on the direction in which the gear lever is moved.

A disadvantage with known solutions is that when the gear lever starts its movement from a position where there is no pressure in any of the circuits, this gear lever movement causes the pressure to increase in one master cylinder and thereby also in one circuit, while the pressure is reduced in the other master cylinder and thereby also in the other circuit. Negative pressure is then produced in the other circuit, resulting in the risk of infiltration of air. Attempts have been made to solve the problem of negative pressure in previously known solutions by adapting the individual system so as to cause the pressure increase in one circuit to take place faster than pressure reduction in the other circuit. This is achieved by designing the system's components in such a manner that at the beginning of the gear lever movement, the related master cylinder in the circuit where the pressure increases is given a longer stroke length than the master cylinder in the other circuit. This adaptation, however, requires the stroke lengths and angles of levers and components employed for connecting the gear lever and the master cylinders to be individually designed and dimensioned.

A drawback of this system is that changing the design and dimensions of individual components, such as for example diameters and stroke lengths, results in the need to reconstruct the lever system from gear lever to the master cylinders in order to maintain the desired effect, i.e. avoid negative pressure in the circuits. Thus it can be seen that a simple change such as different diameters on the master pistons makes it necessary to reconstruct the entire gear lever mechanism. It is an object of the present invention to provide a simplified system where the object is achieved that both the master cylinders are pressurised simultaneously in an initial phase of the gear lever movement, and where the drawback is avoided that

simple changes in the system's components result in restructuring of the entire system.

It is a further object of the present invention to provide an alteration in the linkage between gear lever and the master cylinders' pistons, where the gear ratio between the gear lever movement and the pistons' stroke length can be altered.

These objects are achieved with the invention according to claim 1 with embodiments of the invention as specified in the associated dependent patent claims.

According to claim 1 the linkage alteration comprises a transfer structure which is attached to the gear lever and which is movably arranged in the gear lever's axial direction. The master cylinders' piston rods are attached to the transfer structure. The transfer structure is provided with a guide part which interacts with a guide structure which is mounted in a stationary manner relative to the gear lever when it is moved. The interaction between the guide part and the guide structure together with the transfer structure's design and movable attachment to the gear lever permit a simultaneous depression of the master cylinders' pistons in an initial phase of the gear lever's movement from the neutral position.

In a preferred embodiment the transfer structure will be provided with a bore in which the gear lever's rod portion is received. The piston rods may be attached at each end of the plate body's lower lateral edge. As a skilled person will appreciate, the transfer structure may be composed of different components where the shape of the body together with its connection to the gear lever can be varied according to current design conditions and the effects that require to be achieved. The guide part and the guide structure may also be composed of different types of components, the crucial factor being that the right conditions are produced for controlled movement of the gear lever and the transfer structure in order to obtain simultaneous initial pressurisation of both circuits.

The guide part and the guide structure will preferably be able to be adapted according to the desired transmission ratio between the gear lever movement and the piston's stroke length. If some of the system's components are altered, interaction between the guide part and the guide structure can be easily adapted to the new conditions in the system. If it is desirable to introduce a non-linearity in the system, this can be accomplished by adapting the guide part or the guide structure or both.

The guide part will preferably be in the form of a guide pin and the guide structure may preferably be comprised of a guide slot in which the guide pin is located. As a

person skilled in the art will appreciate, this arrangement may also be provided conversely, where the guide part is composed of a guide slot and the guide structure of a guide pin. If it is desirable to change the transmission ratio, this can easily be done by changing the shape of the guide slot, with the master cylinders' stroke length being changed without the need to make other constructive changes.

The guide structure has to be arranged in a stationary manner and this can be solved in various ways. One embodiment may be mentioned here where the guide structure is a guide slot provided in a plate body which is attached to the vehicle and in relation to which the gear lever and the transfer structure are moved. The invention will now be described by means of an example as illustrated in the figures;

Figure 1 illustrates a gear shift system according to the prior art. Figure 2 illustrates a first embodiment of the invention. Figure 3 illustrates a second embodiment of the invention. In figure 1 a gear lever 1 is illustrated which is pivotally attached to the vehicle at its lower end. The gear lever 1 is provided with rods Ia and Ib which are connected at each end to the piston rods 2a, 3a belonging to the first and second hydraulic master cylinders 2 and 3 respectively. The gear lever can be moved in the direction illustrated by the arrows A and B. When the gear lever 1 is moved in the direction illustrated by the arrow A, this causes the piston rod 2a to be pushed downwards and the fluid in the master cylinder 2 to be pressurised. Fluid is then transferred from the master cylinder 2 through pipe 4 to the double-acting cylinder's 6 side 6a and the piston 7 is moved in a direction corresponding to direction A'. Correspondingly, movement of the gear lever in direction B causes the piston 7 to be moved in direction B'. The piston 7 is connected to a gear shift mechanism 8 by a transfer device 7a, and movement of the piston 7 therefore results in a shift of gear by the gear shift mechanism 8 changing position and thereby engagement with a second gear wheel combination. When the gear lever is moved in direction A from a position where there is no pressure in any of the circuits to a position where the hydraulic piston 2 and pipe 4 as well as the double-acting cylinder's 6 side 6a are pressurised, the pressure will be reduced in the second circuit. This is because the piston rod 3 a is pulled upwards when the gear lever 1 is moved in direction A, thereby producing a negative pressure in the circuit. Negative pressure is undesirable in the circuit since it produces the right conditions for infiltration of air into the circuit.

The problems that arise when using the system in figure 1 are solved by the invention as it is illustrated in a first embodiment in figure 2. In figure 2 it can be seen that the gear lever 1 is mounted at its lower end in pivot bearing 9. The gear

lever's 1 directions of travel are illustrated by the arrows A and B. A transfer structure 10 is attached to the gear lever 1 by the gear lever 1 being passed through a bore provided in the transfer structure 10. The transfer structure 10 is so arranged that it can be moved in the gear lever's axial direction. The transfer structure 10 is provided with a guide part 12 in the form of a guide pin which is located in an interacting guide structure 13, provided here in the form of a guide slot. In figure 2 the guide slot is depicted in the form of a plate body 14. The plate body 14 may be designed as an approximately triangular body slanting outwards from the gear lever. Furthermore, the piston rods 2a, 3 a belonging to the master cylinders 2, 3 are attached to the transfer structure 10. The master cylinders 2 and 3 are connected to a double-acting cylinder 6 corresponding to that illustrated in figure 1.

The transfer structure 10 acts as a lever for transferring the gear lever movement to the master cylinders' piston rods 2a and 3a. When the gear lever movement starts from a neutral initial position like that illustrated in figure 2, and is moved in direction A or B, interaction between guide part 12 and guide structure 13 together with the design of the transfer structure will cause both the piston rods 2a and 3 a to be pushed downwards and both the circuits to be pressurised in the gear lever movement's initial phase. The problems associated with formation of negative pressure in one circuit are thereby avoided. On further movement of the gear lever a greater pressure is exerted against the piston in the cylinder 2 than against the piston in the cylinder 3, thereby achieving a movement of the piston in the double- acting cylinder for shifting gear according to the direction of the gear lever movement.

In the embodiment illustrated in figure 2, alteration of the shape of the slot can be employed to change the transmission ratio between the gear lever movement and the piston's 2b, 3b stroke length. It is therefore possible to achieve a non- linear transmission ratio between the gear lever movement and the piston's 2b, 3b stroke length by adapting the shape of the slot.

An example of a second slot shape is illustrated in a second embodiment of the invention in figure 3. The rest of the invention's components are the same and are illustrated by the same reference numerals in figure 3.