CN117957388A - Gearbox provided with a shift fork having an auxiliary device - Google Patents

Abstract

The invention relates to a gearbox (1) comprising two stationary housings (2, 3) and a shaft (4) connecting the two stationary housings (2, 3), on which shaft at least one single assisted fork group (5, 6) is mounted. According to the invention, a shaft (4) is fixedly mounted in the two housings (2, 3) and a single assisted fork group (5, 6) slides along said shaft (4) when a gear shift command is established.

Description

Gearbox provided with a shift fork having an auxiliary device

Technical Field

The present invention relates to a gearbox provided with an auxiliary device.

Background

Hereinafter, the abbreviation "GB" stands for transmission.

Some gearboxes are equipped with a dog clutch with square engagement surfaces instead of a synchronizer. Such dog clutch systems require a specific angular alignment position in order to engage each other. To achieve this alignment position, one solution is to increase the dynamic characteristics of the dog clutch by equipping the fork with a propulsion device that accumulates energy during the time between the upstream shift command and the downstream dog clutch alignment phase.

However, the GB architecture currently under development is becoming more and more stringent:

Increasing the internal gear volume within GB (higher torque to be transmitted, acoustic limitations, etc.),

Adding new functions (exchangers, oil circuits etc.),

Integrate the traditional GB functions to meet the new limitations of these GB (gear interlock, parking brake, etc.).

Furthermore, the external environment of these GB is also increasingly congested, preventing the size of these gearboxes from being indiscriminately enlarged in order to achieve the desired performance.

In summary, while current assisted shift fork technology perfectly responds to shift restrictions, it has the disadvantage of being rather cumbersome due to the assistance function compared to standard forks.

Disclosure of Invention

The gearbox according to the invention comprises at least one shift fork provided with auxiliary means so as to allow said gearbox to meet all the requirements set forth, while maintaining a compact size compared to the existing GB.

The subject of the invention is a gearbox comprising: two fixed shells; a shaft connecting the two stationary housings, on which shaft at least one single assisted fork group is mounted, said group comprising a dog clutch, an assistance device and a shift fork mounted on said shaft, the dog clutch being mechanically connected to the assistance device in such a way that when a shift command is given, an external element moves the dog clutch, thereby moving the fork via the assistance device in a direction parallel to said shaft.

According to the invention, the shaft is fixedly mounted in both housings and, when a shift command is established, the entire assisted fork group comprising the dog clutch, the auxiliary device and the fork slides along said shaft to allow the fork to be pushed along the shaft under the action of the auxiliary device.

Existing gearboxes use an assisted fork fixed to the shaft and when a shift command is given, the entire shaft carrying the assisted fork must be translated to perform the shift. However, the movable shaft requires a lot of space in the two housings defining the gearbox to ensure such translation. Since in the gearbox according to the present invention the fork moves along the fixed shaft connecting the two housings, it is no longer necessary to enlarge the size of the gearbox in order to ensure such movement. This provides significant space savings compared to existing gearboxes while maintaining the same operating efficiency. The shaft of the gearbox according to the invention may carry one, two, three or more assisted forks, depending on the size and architecture of the gearbox. Thus, unlike existing gearboxes, in which each shaft carries only one assisted fork, the gearbox according to the present invention has a shaft capable of carrying a plurality of assisted forks, allowing to simplify the manufacture of said gearbox and to reduce its size. The gearbox according to the invention may for example be a dog clutch gearbox provided with a dog clutch with square engagement surfaces instead of a synchronizer. Such dog clutch systems require a specific angular alignment in order to engage each other. In order to achieve this alignment, it is necessary to increase the dynamic characteristics of the dog clutch by equipping the fork with auxiliary devices that accumulate energy during the time between the upstream shift command and the downstream dog clutch alignment phase. The auxiliary device allows a certain delay of the movement of the fork with respect to the movement of the dog clutch, which delay is effectively utilized to generate propulsion energy intended to move the fork.

According to a possible feature of the invention, the fork comprises a base with two parallel first arms crossed by the shaft and the dog clutch comprises two parallel second arms crossed by the shaft, wherein the two second arms surround the first arms along the shaft, the two main rings each having a body and an enlarged collar, placed around the shaft and passing through the two first arms in such a way that the enlarged collars face each other inside the first arms and are pushed away from each other by an auxiliary spring wound around the shaft and against said enlarged collar in such a way that the bodies of the two main rings pass through the first arms to abut against the two second arms of the dog clutch. For this particular configuration, the auxiliary means of the fork comprise an auxiliary spring which allows the enlarged collars of the two main rings to be held against the walls of the first arm facing each other. At the same time, the body of the main ring passes through the walls of the two first arms facing each other, each in contact with the second arm of the dog clutch. When a shift command is given, an external control element connected to the dog clutch moves the dog clutch in a given direction along the shaft. Initially, movement of the dog clutch will move one of the two primary rings in contact with the dog clutch in the same direction along the shaft. During this initial phase, the auxiliary spring is folded on itself without being compressed, so that no pressure is applied to the other main ring. In the second phase, the movement of the dog clutch always continues in the same direction along the shaft, which causes the compression of the auxiliary spring, eventually moving the other main ring in the same direction, so that the fork always moves in the same direction. Thus, there is a time interval between the movement of the dog clutch and the movement of the fork, which is effectively utilized to accumulate energy by compressing the auxiliary spring and then to advance the fork along the shaft in the same direction as the movement of the dog clutch by suddenly releasing the energy.

According to a possible feature of the invention, the body of each main ring is cylindrical and hollow, the enlarged collar being formed by an annular flange extending said body along the axis of rotation of the main ring, each main ring defining an internal passage of constant section extending along the body and the enlarged collar. The diameter of the internal passage is larger than the diameter of the shaft, although two main rings may be screwed around the shaft. The two main rings pass through the two first arms of the fork and can move along the shaft with respect to the two first arms under the action of the dog clutch movement. When no shift command is given, the two rings are locked on the two first arms of the fork under the action of an auxiliary spring which keeps the enlarged collar against the facing walls of the first arms, while the body of the main ring passes through said walls, each against the second arm of the dog clutch.

According to a possible feature of the invention, a cylindrical bearing ring is interposed in the internal passage of each main ring, said bearing ring having an internal diameter greater than the diameter of the shaft and being interposed between the shaft and said main rings.

According to a possible feature of the invention, each bearing ring is made of polytetrafluoroethylene.

According to a possible feature of the invention, the two second arms of the dog clutch are connected by an elongated wall, wherein the dog clutch has a curved protrusion originating from said elongated wall and provided with a recess intended to receive a control element capable of moving said dog clutch after establishment of a shift command. The projection is preferably perpendicular to the elongated wall connecting the two second arms.

According to a possible feature of the invention, the gearbox comprises at least two single assisted fork sets placed side by side on the shaft. The two groups are independent such that movement of the assisted fork of one of the two groups along the shaft does not affect movement or other aspects of the assisted fork of the other group.

According to a possible feature of the invention, the shaft comprises two retention clips between which the set of auxiliary forks is placed, said two clips being intended to lock said set of auxiliary forks on the shaft during the transit phase. The two clamps have a temporary function that is separate from the operation of the gearbox. These two clamps are intended to prevent the set of assisted forks from inadvertently sliding along the shaft, while the shaft on which these sets are provided is not yet installed in the gearbox. For example, the two clamps may be active during a transport or maintenance phase of the shaft on which the assisted fork group is provided.

According to a possible feature of the invention, the gearbox is a dog clutch gearbox equipped with a dog clutch with a square front.

Another subject of the invention is a method of operating a gearbox according to the invention.

According to the invention, the method comprises the following stages:

A phase of issuing a shift command,

A phase of moving the dog clutch along the shaft in a given direction by means of an external control element connected to said dog clutch and actuated by a signal corresponding to said command, wherein during this phase the fork remains fixed along the shaft, said movement moving one of the two main rings,

-A phase of extension of the movement of the dog clutch in the same direction, said phase moving the fork along the shaft in the same direction as the movement of the dog clutch under the action of the spring which has been compressed and which causes the movement of the other main ring.

For this type of method, the various phases are performed by means of main rings which allow the dog clutch to move with respect to the fork. During the movement phase, although the dog clutch is moving, the fork has not moved, since the auxiliary spring simply folds on itself due to the movement of one main ring, has not been put in compression. During the extension phase of movement, which occurs in the succession of the movement phases, the spring is compressed and then, under the action of the movement of the other main ring, the fork is pushed along the shaft in the same direction as the movement of the dog clutch.

The gearbox according to the invention has the advantage of having a shaft capable of receiving a plurality of assisted shift forks, whereas in existing gearboxes the shaft can only carry a single fork. This simplifies the manufacture of the gearbox and significantly reduces the size of the gearbox.

Drawings

A detailed description of a preferred embodiment of a gearbox according to the present invention is provided below with reference to the following drawings:

Figure 1 shows a partial perspective view of a gearbox according to the invention,

Figure 2 shows an exploded perspective view of a single assisted fork group of a gearbox according to the invention,

Figure 3 shows a perspective view of the group in figure 2,

Figure 4 shows a perspective view of the shaft of the gearbox and two single assisted shift fork sets according to the present invention,

Figure 5 shows another angular perspective view of the shaft and two single assisted fork sets of figure 4,

Figure 6 shows a cross-sectional view of the shaft and two single assisted shift fork sets of figures 4 and 5,

Fig. 7 shows a cross-sectional view of an assisted fork group of a gearbox according to the invention, illustrating a first stage of movement of the group after a gear shift command,

Fig. 8 shows a cross-sectional view of the set of fig. 7, illustrating a second stage of movement of the set after a shift command,

Fig. 9 shows a cross-sectional view of the set of fig. 7 and 8, illustrating a third stage of movement of the set after a shift command.

Detailed Description

The following detailed description is based on specific examples of gearboxes and is in no way limiting to the scope of the invention.

The gearbox according to the invention comprises at least one single assisted shift fork group provided with an assistance device. Such gearboxes are equipped with dog clutches with square fronts, rather than synchronizers. Such dog clutch systems require a specific angular alignment position in order to engage each other. In order to achieve such an aligned position, it is necessary to increase the dynamic characteristics of the dog clutch by equipping the fork with auxiliary means that accumulate energy during the time interval between the upstream shift command and the downstream dog clutch alignment phase.

With reference to fig. 1, 4 and 6, a gearbox 1 according to the present invention is delimited by two housings 2, 3 and comprises a shaft 4 connecting said two housings 2, 3, on which two single assisted fork sets 5, 6 are mounted. A particular feature of the gearbox 1 according to the invention is that the shaft 4 is fixedly mounted in the two housings 2, 3, but cannot move relative to these two housings. The shaft 4 resembles a cylindrical elongated metal rod, the two ends of which (considered along the longitudinal axis of the rod) are each inserted in suitable receptacles in the housings 2, 3.

Referring to fig. 2 and 3, the two single assisted shift fork sets 5, 6 are identical and each consist of a shift fork 7, an assist device 8 and a dog clutch 9. The fork 7 conventionally comprises a functional portion 10, which is arc-shaped, preferably semicircular, and a support base 11, by means of which the fork is mounted on the shaft 4. The support base 11 illustratively includes: two flat, parallel first arms 12, 13, each provided with a circular opening 14; and a flat connecting wall 15 connecting the two first arms 12, 13 and perpendicular thereto. The functional part 10 extends on one side of the connecting wall 15 and the two first arms 12, 13 extend on the other side of the connecting wall 15, which is opposite to the side on which the functional part 10 extends. The dog clutch 9 schematically comprises: two flat, parallel second arms 16, 17, each provided with a circular opening 18; and a flat connecting wall 19 connecting the two second arms 16, 17 and perpendicular thereto. The dog clutch 9 likewise comprises a projection 20 having two flat and vertical sections 21, 22, a first section 21 of which originates from the edge of the connecting wall 19 and a second section 22 of which extends said first section 21. The first segment 21 starts from a central region of the edge of the connecting wall 19 and extends in the same plane as said connecting wall 19, while the second segment 22 extends perpendicular to the plane of said connecting wall 19. The second section 22 comprises an elongated recess 23 extending along said second section 22 and leading to an edge 24 of said second section 22 representing its distal end. The recess 23 serves as an anchor point for an external control element whose function is to initiate movement of the dog clutch 9 in a given direction along the shaft 4 upon issuing a shift command in the gearbox 1.

It should be noted that the spacing between the two second arms 16, 17 of the dog clutch 9 is greater than the spacing between the two first arms 12, 13 of the fork 7.

Referring to fig. 2 and 3, each group 5,6 likewise comprises two main rings 25, two bearing rings 26 and an auxiliary spring 27, said elements constituting auxiliary means. Each main ring 25 comprises a hollow cylindrical body 28 and an enlarged collar 29 which lengthens the cylindrical body 28 along its axis of rotation. The enlarged collar 29 resembles an annular flange having an outer diameter larger than the outer diameter of the hollow cylindrical body 28, said collar 29 being defined by two flat annular faces. Each main ring 25 defines an internal cylindrical passage, the diameter of which is constant along the entire length of said main ring 25 (including the main body 25 and the collar 29), wherein said diameter is greater than the diameter of the shaft 4. Each bearing ring 26 is constituted by a hollow cylindrical wall, the outer diameter of which is smaller than the diameter of the internal passage of the main ring 25 and the inner diameter of which is greater than the diameter of the shaft 4. The auxiliary springs 27 are coil springs in which the inner diameter of each coil is larger than the diameter of the shaft 4.

Referring to fig. 4 to 9, each assisted fork group 5, 6 is mounted on the shaft 4 while following rules are followed:

the fork 7 is mounted on the shaft 4 in such a way that said shaft 4 passes through the openings 14 in the two first arms 12, 13,

The dog clutch 9 is mounted on the shaft 4 in such a way that the shaft 4 passes through the openings 18 of the two second arms 16, 17 and that the second arms 16, 17 enclose the first arms 12, 13 of the fork 7. In other words, the first arms 12, 13 are interposed between the second arms 16, 17 around the shaft 4,

Each bearing ring 26 is placed in the internal passage of the main ring 25 and the two groups of these two rings 25, 26 are placed around the shaft 4 in such a way that the body 28 of the main ring 25 passes through the two first arms 12, 13 and that the enlarged collar 29 is located in the space defined by said two first arms 12, 13,

An auxiliary spring 27 is screwed around the shaft 4 between the two first arms 12, 13 of the fork 7 in such a way that it comes into contact with the two enlarged collars 29 and tends to push said collars 29 against the walls of the first arms 12, 13 facing each other. In this configuration, the main body 28 of the main ring 25 is exposed from the first arms 12, 13 toward the outside thereof, abutting against the second arms 16, 17 of the dog clutch 9, respectively.

Referring to fig. 1, 4, 5 and 6, two single fork sets 5, 6 of a gearbox 1 according to the present invention are independently mounted side by side on a fixed shaft 4 joining two housings 2, 3. In fact, the activation of one of the two single fork groups 5, 6 has no effect on the activation or other aspects of the other group 5, 6. The two groups 5, 6 are slidably mounted on a shaft 4 which itself remains fixed, whether or not the fork 7 is activated. Two clips 30, 31 are each inserted in a groove of the shaft 4, one on each side of the two single fork sets 5, 6, to prevent said sets 5, 6 from inadvertently sliding along the shaft 4 during the transport or maintenance phases. These clips 30, 31 have no specific function during operation of the gearbox 1. Depending on the characteristics and geometry of the gearbox 1, the two single fork sets 5, 6 may be offset relative to each other with respect to the fixed shaft 4.

Referring to fig. 7, 8 and 9, a method of operating a gearbox according to the invention comprises the following stages:

a phase of issuing a shift command, while the single fork group 5, 6 in question is balanced on the shaft 4, as shown in figure 7,

A phase of moving the dog clutch 9 of the single fork group 5, 6 along the shaft 4 in a given direction (as indicated by arrow 32) during which the fork 7 remains fixed along the shaft 4, by means of an external control element connected to said dog clutch 9 and actuated by a signal corresponding to a shift command. In fact, during this phase of movement, the dog clutch 9 has moved the main ring 25 with respect to the fork 7, said ring 25 having begun to fold the auxiliary spring 27 itself between the two first arms 12, 13, but without compressing it,

A phase of extension of the movement of the dog clutch 9 in the same direction, said extension of movement causing, under the action of the auxiliary spring 27, which has been compressed and causes the movement of the other main ring, a sudden movement of the fork 7 along the shaft 4 in the same direction as the movement of the dog clutch 9, as indicated by the arrow 33.

In the foregoing method, the fork 7 has been moved in the same direction as the moving direction of the dog clutch 9, but with a time delay during which drive energy has been generated by the compression of the assist spring 27. Once the threshold compression of the spring 27 is reached, said spring advances the fork 7 via the main ring for shifting.

Claims (10)

1. A gearbox (1) comprising: two fixed housings (2, 3); -a shaft (4) connecting the two stationary housings (2, 3), on which shaft at least one single assisted fork group (5, 6) is mounted, said group (5, 6) comprising a claw clutch (9), an assistance device (25, 26, 27) and a shift fork (7) mounted on said shaft (4), the claw clutch (9) being mechanically connected to the assistance device (25, 26, 27) in such a way that when a shift command is given an external element moves the claw clutch (9) such that the fork (7) is moved via the assistance device (25, 26, 27) in a direction parallel to said shaft (4), characterized in that the shaft (4) is fixedly mounted in the two housings (2, 3), and in that the entire assisted fork group (5, 6) comprising the claw clutch (9), the assistance device (25, 26, 27) and the fork (7) is slid along said shaft (4) to allow the assistance device (7) to be pushed down along the shaft (25, 27) when a shift command is established.

2. Gearbox according to claim 1, characterized in that the fork (7) comprises a base with two parallel first arms (12, 13) traversed by the shaft (4) and the dog clutch (9) comprises two parallel second arms (16, 17) traversed by the shaft (4), and in that the two second arms (16, 17) enclose the first arms (12, 13) along the shaft (4), the two main rings (25) each having a body (28) and an enlarged collar (29), placed around the shaft (4) and traversing the two first arms (12, 13) in such a way that the enlarged collars (29) face each other inside the first arms (12, 13) and are pushed away from each other by an auxiliary spring (27) wound around the shaft (4) and abutting against said enlarged collars (29) in such a way that the bodies (28) of the two main rings (25) traverse the first arms (12, 13) to abut against the two second arms (17) of the dog clutch (9).

3. Gearbox according to claim 2, wherein the main body (28) of each main ring (25) is cylindrical and hollow, and wherein the enlarged collar (29) is formed by an annular flange extending said main body (28) along the rotation axis of the main ring (25), each main ring (25) defining an internal passage of constant section extending along the main body (28) and the enlarged collar (29).

4. A gearbox according to claim 3, characterised in that a cylindrical bearing ring (26) is interposed in the internal passage of each main ring (25), and in that said bearing ring (26) has an internal diameter greater than the diameter of the shaft (4) and is interposed between the shaft (4) and said main rings (25).

5. Gearbox according to claim 4, characterised in that each bearing ring (26) is made of polytetrafluoroethylene.

6. Gearbox according to any one of claims 2 to 5, characterised in that the two second arms (16, 17) of the dog clutch (9) are connected by an elongate wall (19), and in that the dog clutch (9) has a curved protrusion (20),

The curved protrusion originates from the elongated wall (19) and is provided with a recess (23),

The recess is intended to receive a control element which is able to move the dog clutch (9) after a gear shift command has been established.

7. Gearbox according to any of the claims 2 to 6, characterised in that it comprises at least two single assisted fork groups (5, 6) placed side by side on the shaft (4).

8. Gearbox according to claim 7, characterized in that the shaft (4) comprises two retention clips (30, 31) between which the assisted fork groups (5, 6) are placed, and in that said two clips (30, 31) are intended to lock said assisted fork groups (5, 6) on the shaft (4) during the transport phase.

9. Gearbox according to any of the claims 2 to 8, characterized in that the gearbox (1) is a dog clutch gearbox equipped with a dog clutch with a square front.

10. A method of operating a gearbox according to any one of claims 2 to 9, characterised in that the method comprises the following stages:

A phase of issuing a shift command,

-A phase of movement of the dog clutch (9) along the shaft (4) in a given direction by means of an external control element connected to said dog clutch (9) and actuated by a signal corresponding to said command, wherein during this phase the fork (7) remains fixed along the shaft (4), said movement moving one of the two main rings (25),

-A phase of extension of the movement of the dog clutch (9) in the same direction, said phase moving the fork (7) along the shaft (4) in the same direction as the movement of the dog clutch (9) under the action of the spring (27) which has been compressed and which causes the movement of the other main ring (25).