WO2015038053A1

WO2015038053A1 - Synchromesh unit in a gearbox

Info

Publication number: WO2015038053A1
Application number: PCT/SE2014/051039
Authority: WO
Inventors: Jonas Lundin
Original assignee: Scania Cv Ab
Priority date: 2013-09-11
Filing date: 2014-09-10
Publication date: 2015-03-19
Also published as: SE537524C2; SE1351046A1

Abstract

The present invention pertains to a synchromesh device for a gearbox. The synchromesh device comprises an annular coupling element (5, 14), a latch cone (6, 9) and a coupling cone (7, 10). The coupling element (5, 14) is shiftably arranged in an axial direction between a first end position, in which the coupling element (5, 14) is freely rotatable in relation to the coupling cone (7, 10), and a second end position, in which the coupling element's cogs (5a, 14a) engage with the coupling cone's cogs (7a, 10a). The synchromesh device comprises a slot-shaped space between a radially external control surface (5c, 14c) of the coupling element (5, 14) and a radially internal control surface (6c, 9c) of the latch cone (6, 9), and a lock element (8, 11) arranged inside said space. Said control surfaces (6c, 9c) are designed in such a way, that the lock element (8, 11) establishes a connection between the coupling element (5, 14) and the latch cone (6, 9) in a connecting position, located at a distance from the first end position, so that the latch cone (6, 9) is moved along by the coupling element (5, 14) during a continued movement towards the first end position, up to a position in which the latch cone's conically shaped friction surface (6a, 9a) is located at a distance from the coupling cone's conically shaped friction surface (7a, 10a).

Description

Synchromesh unit in a gearbox BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention pertains to a synchromesh device in a gearbox according to the preamble of claim 1. Many heavy goods vehicles often have a gearbox comprising a range gear. A range gear usually consists of a planetary gear that may provide every primary gear in the gearbox with a high and a low gear ratio. In order to manoeuvre the range gear, a driver may shift a manoeuvring element, which may be fixed around a gear lever, to a position indicating a desired gear in the range gear. When the manoeuvring device is manoeuvred, a pneumatically driven cylinder is usually activated, shifting a ring wheel in the planetary gear between a high and a low gear ratio position. Alternatively, the gearing may be indicated by an automatic system. Since the ring wheel in the low gear ratio position is connected with a stationary coupling cone, and in the high gear ratio position is connected with a rotating coupling cone, the ring wheel's engine speed must be synchronised before it may engage with the respective coupling cones. The range gear comprises synchromesh devices in the form of latch cones, moved along by the ring wheel when this is shifted towards a coupling cone. The latch cone has a conically shaped friction surface, which is brought to engage with a correspondingly shaped conical friction surface of the coupling cone. When the conical friction surfaces engage with each other, the latch cone and the coupling cone relatively soon obtain a synchronised speed. When this happens, the ring wheel may be shifted a final distance to an end position, in which it engages with the coupling cone.

When the ring wheel is shifted in an opposite direction to an opposite end position, it disengages from the coupling cone. The latch cone, however, is generally not actively removed from the coupling cone during this movement, which entails that the latch cone may move freely within the axial space created between the ring wheel and the coupling cone. This space is generally relatively small, and as a result the latch cone's conical friction surface is often located at a very small distance from the coupling cone's friction surface, when the ring wheel is in this end position. In this end position, the conical friction surfaces rotate in relation to each other. Thus a braking torque is created in the oil-filled space between the latch cone's and the coupling cone's friction surfaces. The magnitude of this braking torque depends on several factors, such as the transmission oil's viscosity, the temperature of the oil, the distance between the conical surfaces and the relative speed between the conical surfaces. This braking torque through the shaft's rotation movement may be designated as a drag loss, which leads to a reduced efficiency of the gearbox and an increased fuel consumption of the combustion engine connected to the gearbox.

Synchromesh devices are also used to synchronise the speed of cogwheels and shafts in gearboxes in connection with engagement of gears. A shiftably arranged coupling sleeve may in this case be releasably connected with two alternative cogwheels on a shaft in the gearbox. The coupling sleeve is shiftably arranged in axial directions for engaging with the respective cogwheels, with the help of a latch cone having a conically shaped friction surface, and a coupling cone with a correspondingly shaped conical friction surface. Drag losses arise here as well, when the coupling sleeve is in an end position in which the latch cone and the coupling cone rotate in relation to each other.

SUMMARY OF THE INVENTION

The objective of the present invention is to provide a synchromesh device comprising an axially shiftable coupling element, a latch cone with a conical friction surface and a coupling cone with a conical friction surface, wherein the drag losses in the oil-filled space between said friction surfaces may substantially always be kept at a low level when the coupling element has been shifted to an end position, in which it is disengaged from the coupling cone.

This objective is achieved with a synchromesh device of the type mentioned above, which is characterised by the features specified in the characterising portion of claim 1. The lock element thus establishes a connection between the coupling element and the latch cone in a connecting position, which the coupling element passes before it reaches the end position in which the coupling element is disengaged from the coupling cone. Thus, the latch cone is shifted from the coupling cone over a distance corresponding to the distance of the coupling element' s movement between the connecting position and the end position. If the components comprised are suitably dimensioned, the coupling element may reach the connecting position at a relatively large distance from the end position. Therefore, the latch cone may be shifted a relatively long distance from the coupling cone, so that the oil-filled space between the latch cone's conical friction surface and the coupling cone's conical friction surface becomes relatively large. Thus, relatively small drag losses are obtained and as a result the gearbox may achieve a high efficiency, and the combustion engine connected with the gearbox achieves reduced fuel consumption.

According to one embodiment of the present invention, the lock element is

substantially annular and assembled in a biased state in said space, so that it strives to expand radially outwards or radially inwards. A lock element striving to expand radially outwards obtains a radial position, which is defined by the radially external control surface. As a rule, the radial external control surface is defined by the coupling element. Alternatively, a lock element, which strives to be compressed radially inwards may be used. The annular lock element may comprise an elongated body with a substantially circular curvature between two free ends. Such a lock element may easily be applied in a biased state in said radial space. The lock element may consist of a metal material with suitable resilient properties.

According to one embodiment of the present invention, the coupling element' s control surface comprises a first stop surface, limiting the movement of the lock element in an axial direction, and the latch cone's control surface comprises a first stop surface, limiting the lock element's movement in an opposite axial direction, and said connection is established by way of said stop surfaces coming into contact with opposite sides of the lock element in the connecting position. During the coupling element's shifting movement in a direction towards the first end position, the coupling element's stop surface will first come into contact with the lock element. Thus, the lock element is initially moved along by the coupling element. When the lock element comes into contact with the latch cone's stop surface in the connecting position, the coupling element may move both the lock element and the latch cone with it from the coupling cone. When the coupling element reaches the first end position, the latch cone will be at a predetermined axial distance from the coupling cone. According to one embodiment of the present invention, the coupling element' s control surface comprises a second stop surface, limiting the movement of the lock element in an axial direction, and the latch cone's control surface comprises a second stop surface, limiting the movement of the lock element in an opposite axial direction, and said second stop surfaces come into contact with the opposite sides of the lock element when the coupling element reaches a second end position. When the coupling element is moved in an axial direction towards the second end position, it initially moves the lock element along with it. When the lock element comes into contact with the latch cone's second stop surface, both the lock element and the latch cone are moved along by it. Subsequently, the latch cone's conical friction surface comes into contact with the coupling cone's conical friction surface. Since the coupling cone is not shiftable, it stops the latch cone's and the lock element's shifting movement. The coupling element is substantially stationary while the rotation speeds of the latch cone and the coupling cone are substantially synchronised by way of the conical friction surfaces coming into contact with each other. When the latch cone and the coupling cone have achieved the same speed, the coupling element may be shifted a final distance in which it engages with the coupling cone's cogs. The movement of the coupling element may be stopped in the second end position by way of interference between the coupling element and the coupling cone.

According to one embodiment of the present invention, the coupling element is arranged around a central shaft, and the coupling element' s control surface has a breaking point which is located between said stop surfaces, and which is located at the control surface's smallest radial distance from the central shaft. A lock element striving to be shifted radially outwards is here lead towards one of the respective stop surfaces, depending on which side of the breaking point it is in contact with the contact surface. The part of the control surface located between the breaking point and the second stop surface presses the lock element radially inwards, when the coupling element reaches a pre- synchronisation state. In the pre- synchronisation state, an oil film between the conical surfaces is forced away, following which the conical surfaces are pressed against each other.

According to one embodiment of the present invention, the latch cone's radially outward-facing sections have a surface forming the first stop surface in the latch cone's control surface. Thus, these radially outward-facing sections have, in addition to the function of creating a rotationally fixed connection between the coupling element and the latch cone, the task of creating a stop surface guaranteeing that the latch cone is separated from the coupling cone on occasions when the coupling element is moved towards the first end position.

According to one embodiment of the present invention, the latch cone's radially outward-facing sections have a surface forming the second stop surface of the latch cone's control surface. Thus, these radially outward-facing sections also have, in addition to the function of creating a rotationally fixed connection between the coupling element and the latch cone, the function of defining a stop position for the lock element on occasions when the coupling element is moved towards the second end position.

According to one embodiment of the present invention, the coupling element is a ring wheel in a planetary gear that constitutes a range gear in the gearbox. A range gear may provide every primary gear in the gearbox with a high and low gear ratio. The ring wheel is connected with a stationary coupling cone in the low gear ratio position and with a rotating coupling cone in the high gear ratio position. The speed of the ring wheel must thus be synchronised before it may be brought into engagement with the respective coupling cones. In the low gear ratio position, the ring wheel is shifted to an axial end position, in which it engages with the stationary coupling cone. In the high gear ratio position, the ring wheel is shifted to an opposite end position, in which it engages with the rotating coupling cone.

According to one embodiment of the present invention, the coupling element is a coupling sleeve, arranged around a shaft in the gearbox, wherein the coupling sleeve is shiftably arranged between a second end position in which it engages with a cogwheel defining a gear in the gearbox, and a first end position in which it may rotate freely in relation to the cogwheel. Suitably, the coupling sleeve is arranged between two cogwheels, so that it may alternatively be connected with one of the cogwheels, while it may simultaneously rotate freely in relation to the other cogwheel. BRIEF DESCRIPTION OF THE DRAWINGS

Below is a description, as an example, of preferred embodiments of the invention with reference to the enclosed drawings, in which:

Fig. 1 shows an exploded view of a range gear comprising synchromesh

devices according to the present invention,

Fig. 2 shows the range gear in an assembled state,

Figs. 3a-d show one of the synchromesh devices in Fig. 2, with the ring wheel in four different positions and

Fig. 4 shows the synchromesh devices for connection of gears in a gearbox.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Fig. 1 shows an exploded view of the components in a range gear. Range gears are arranged in gearboxes in vehicles to provide each primary gear in the gearbox with a high and a low gear ratio. The range gear is connected with a main shaft 1 in the gearbox. The main shaft 1 comprises a section, equipped with splines la. The range gear comprises a sun wheel 2 with an internal section equipped with splines 2a, having a shape corresponding to the shaft 1. The sun wheel 2 is thereby rotatably connected with the main shaft 1. The sun wheel 2 thus rotates with the same speed as the main shaft 1. The sun wheel 2 has an external section, equipped with cogs 2b. A planet carrier 4, equipped with a number of planet wheels 3, is arranged radially externally of the sun wheel 2. The planet wheels 3 are designed with cogs 3a, rotating in

engagement with the sun wheel's cogs 2b. The planet carrier 4 comprises a shaft lb, which constitutes the gearbox's output shaft. A ring wheel 5 is mounted radially outward of the planet carrier 4. The ring wheel 5 comprises an internal section with cogs 5a, engaging with the plant wheels' cogs 3a. The ring wheel 5 comprises an external peripheral recess 5b for receipt of a manoeuvring element, which may be a pneumatically driven manoeuvring cylinder shifting the ring wheel 5 in an axial direction.

The range gear comprises a first latch cone 6, arranged at a first side of the ring wheel 5. The first latch cone 6 is adapted with a radially inward-facing, conically shaped friction surface 6a. The first latch cone 6 comprises first radially outwardly protruding sections 6b and second radially outwardly protruding sections 6d, engaging with the internal cogs 5a of the ring wheel 5. The first latch cone 6 is thus rotatably connected with the ring wheel 5, so that they rotate at the same speed. Since the ring wheel's cogs 5a and the latch cone's protruding sections 6b, 6d have an axial extension, the latch cone 6 may be shifted in an axial direction in relation to the ring wheel 5. The first latch cone 6 comprises a radially external surface 6c, which has an axial extension between the protruding sections 6b, 6d. The first latch cone 6 also comprises cogs 6e, adapted to engage with the cogged section 5a of the ring wheel 5. A first coupling cone 7 is arranged in connection with the first latch cone 6. The first coupling cone 7 is arranged to be stationary and may e.g. be attached to a wall element in the gearbox. The coupling cone 7 comprises a radially outward-facing, conically shaped friction surface 7a, which is adapted to come into contact with the latch cone's conically shaped friction surface 6a. The first coupling cone 7 comprises radially outward-facing cogs 7b, adapted to engage with the internal cogs 5a of the ring wheel 5. A first annular lock element 8 is adapted to be assembled inside a slot-shaped space between the ring wheel 5 and the first latch cone 6. The annular first lock element 8 does not have a fully circular shape, but is equipped with two free end sections 8a, which are arranged at a distance from each other. The first lock element 8 may thus easily be compressed and mounted in a biased state, in which it tends to expand in a radial direction outwards.

The range gear comprises, at an opposite side of the ring wheel 5, a second latch cone 9. The second latch cone 9 is arranged with a radially inward-facing, conically shaped friction surface 9a. The second latch cone 9 comprises first radially outward- protruding sections 9b, and second radially protruding sections 9d, which engage with the cogs 5a of the ring wheel 5. The second latch cone 9 is thus rotatably connected with the ring wheel 5, so that they rotate with the same speed. Since the ring wheel's cogs 5a and the second latch cone's protruding sections 9b, 9d have an axial extension, the second latch cone 9 may be shifted in an axial direction in relation to the ring wheel 5. The second latch cone 9 comprises a radially external surface 9c, located between the protruding sections 9b, 9d. The second latch cone 9 also comprises cogs 9e, adapted to engage with the cogged section 5a of the ring wheel 5. A second coupling cone 10 is arranged in connection with the second latch cone 9. The second coupling cone 10 comprises a radially outward-facing, conically shaped friction surface 10a, which is adapted to come into contact with the second latch cone's 9 conically shaped friction surface 9a. The second coupling cone 10 comprises radially outward-facing cogs 10b, adapted to engage with the ring wheel's cogs 5a. The second coupling cone 10 comprises a radial internal section equipped with splines 10c, so that the coupling cone is rotatably connected with the main shaft section comprising splines la. The second coupling cone 10 therefore rotates with the same speed as the main shaft 1. The second coupling cone 10 is mounted on the shaft 1 in a non-shiftable position. A second annular lock element 11 is arranged in a slot-shaped space between the ring wheel 5 and the second latch cone 9. The second annular lock element 11 does not have a fully circular shape, but comprises two free end sections 11a, which are arranged at a distance from each other. The second lock element 11 may thus easily be compressed and mounted in a biased state, in which it tends to expand in a radial direction outwards. A central shaft 12 extends through the main shaft 1.

Fig. 2 shows the range gear's components in an assembled state. In order to provide a shifting by the range gear, the ring wheel 5 is shifted by a non-displayed actuator in an axial direction between two end positions. The ring wheel 5 is here displayed in an end position, in which it engages with the first coupling cone 7. The movement of the main shaft 1 is transferred, in this case via the sun wheel 2, the planet wheels 3 and the planet carrier 4, to the output shaft lb of the gearbox. The speed of the main shaft 1 is transferred, in this case, to the output shaft lb with a down shift. The range gear in this case provides a low gear ratio. When the ring wheel 5 is shifted in an opposite axial direction to an opposite end position, the ring wheel's cogs 5a are connected with the second coupling cone's cogs 10b. The movement of the main shaft 1 is transferred, in this case via the second coupling cone 10, the ring wheel 5, the planet wheels 3 and the planet carrier 4, to the output shaft lb of the gearbox. The entire planetary gear, including the ring wheel 5, here rotates as one unit, so that the speed of the main shaft 1 is transferred unchanged to the output shaft lb. The range gear provides in this case a high gear ratio.

The primary gears in a gearbox may thus provide a low gear ratio or a high gear ratio in the range gear. With the help of a range gear, a gearbox provides twice as many gears. Since the ring wheel 5 in the low gear ratio position is connected with the first coupling cone 7 which is stationary, and in the high gear ratio position is connected with the second coupling cone 10 which rotates with the speed of the main shaft 1, a torque interruption must be made during a shifting process in the range gear, in order to synchronise the speed of the ring wheel 5 with the speed of the respective coupling cones 7, 10. A first synchromesh device is used to synchronise the speed of the ring wheel 5 with the first coupling cone 7, and a second synchromesh device is used to synchronise the speed of the ring wheel 5 with the second coupling cone 10.

Figs. 3a-d show one of the right sides of the ring wheel 5 in four different axial positions during a shifting movement between the two end positions. This right side of the ring wheel 5 comprises the first synchromesh device. The first synchromesh device comprises the ring wheel 5, the first latch cone 6, the first coupling cone 7 and the first lock element 8. The first lock element 8 is arranged in a slot- shaped space, defined by an internal radial control surface 5c of the coupling sleeve 5, and an external radial control surface 6c of the first latch cone 6. The first lock element 8 is assembled in a biased state in said space, so that it strives to expand radially outwards. The control surface 5c of the ring wheel extends between a first stop surface 5c_1; defining an end position for the lock element 8 in relation to the ring wheel 5, and a second stop surface 5c_2, defining a second end position for the lock element 8 in relation to the ring wheel 5. The control surface 5c of the ring wheel has a gradient, so that the radial distance to the central shaft 12 decreases from the first stop surface 5ci to a breaking point 5c₃. Similarly, the distance of the control surface 5c decreases from the second stop surface 5c₂ to the breaking point 5c₃. The control surface 5c of the ring wheel is located at a greater radial distance from the central shaft 12 in connection with the second stop surface 5c₂ , than what the control surface 5c is, in connection with the first stop surface 5ci. The first latch cone 6 has a control surface 6c, with a first stop surface 6ci defining a first end position

for the lock element 8 in relation to the latch cone 6, and a second stop surface 6c₂ defining a second end position for the lock element 8 in relation to the latch cone 6.

Fig. 3a shows the ring wheel 5 in an end position, in which the cogs 5a of the ring wheel engage with the first coupling cone's cogs 7b. Since the first coupling cone 7 is stationary, the ring wheel 5 is stationary. The movement of the main shaft 1 is transferred, in this case via the sun wheel 2, the planet wheels 3 and the planet carrier 4, to the output shaft lb of the gearbox. The speed of the main shaft 1 is transferred here, via the range gear, to the output shaft lb with a down shift. The first lock element 8 is arranged between the first stop surface 5ci of the ring wheel and the latch cone's first stop surface 6ci. On occasions when the range gear is shifted to the end position with a high gear ratio, the non-displayed actuator is activated and provides a shifting movement of the ring wheel 5 in an axial direction to the left. Since the first lock element 8 strives to expand radially outwards, it is continuously in contact with the ring wheel's control surface 5c. Given that the control surface 5c has a gradient in the contact area with the lock element 8, the control surface 5c initially moves the lock element 8 along with it, until the latch cone 6 is stopped by the planet wheels 3. When the latch cone 6 is stopped, it may resist, so that the first lock element 8 is pressed radially inwards by the control surface 5c. The first lock element 8 may thus pass by the local minimum point 5c₃ of the control surface 5c. After the first lock element 8 has passed by the minimum point 5c₃, it may expand radially outwards again, in contact with the control surface 5c, until it comes into contact with the control surface's second stop surface 5c₂, as displayed in Fig. 3b. During the continued shifting movement of the ring wheel 5, this moves the first lock element 8 along with it, via the second stop surface 5c₂. This movement continues until the lock element 8 comes into contact with the first latch cone's second stop surface 6c_2i as displayed in Fig. 3c. The coupling element's second stop surface 5c₂ limits the movement of the first lock element 8 in an axial direction, and the first latch cone's second stop surface 6c₂ limits the movement of the lock element 8 in an opposite axial direction. The ring wheel 5 has now reached a connecting state with the latch cone 6. During a final part of the shifting movement, with the help of the other stop surfaces 5c₂, 6c₂, the first lock element 8 and the first latch cone 6 are moved along by the ring wheel 5. Thus, the lock element 8 and the first latch cone 6 are shifted as one unit by the ring wheel 5. The shifting movement ceases when the ring wheel 5 reaches the end position as displayed in Fig. 3d. The ring wheel 5 may now rotate freely in relation to the first coupling cone 7. The ring wheel's cogs 5a on the opposite, non-displayed left side have now been connected with the cogs 9b of the second latch cone 9. Therefore, the ring wheel 5 and the second latch cone 9 rotate with the same speed as the second coupling cone 10. The movement of the main shaft 1 is transferred, in this case via the second coupling cone 10, the ring wheel 5, the planet wheels 3 and the planet carrier 4, to the output shaft lb. The range gear provides, in this case, a high gear ratio.

Since the first latch cone 6, during the final part of the shifting movement, is moved along by the ring wheel 5 to the end position, in which the ring wheel may rotate freely in relation to the coupling cone 7, the first latch cone 6 assumes a position at a distance from the first coupling cone 7. Since the first latch cone 6 rotates with the speed of the ring wheel in the decoupled state, it carries out a rotation movement in relation to the stationary first coupling cone 7. Thus, inevitably a braking torque is created in the oil- filled space between the first latch cone's conical friction surface 6a and the first coupling cone's conical friction surface 7a. The magnitude of this torque is related to the distance between the conical surfaces 6a, 7a. This is dependent on several factors, however, such as the viscosity of the transmission oil, the temperature of the oil and the relative speed between the conical surfaces. In this case, however, it is guaranteed that a sufficiently large distance is created between the conical friction surfaces 6a, 7a for the braking torque to become relatively small. Thus, only small drag losses are obtained in the gearbox, resulting in a reduced fuel consumption of the combustion engine connected with the gearbox.

On those occasions when the ring wheel 5 is shifted to the end position with a high gear ratio, mutual movements in the second latch cone 9, the second coupling cone 10 and the second lock element 11 are provided, corresponding to the movements of the first latch cone 6, the first coupling cone 7 and the first lock element 8, when the ring wheel 5 is shifted to the end position with the low gear ratio. The second synchronising device comprises a slot-shaped space between a control surface 5c of the ring wheel 5, and a control surface 9c of the second latch cone 9. The second lock element 11 is arranged in said slot-shaped space. The second lock element 11 is mounted in a biased state in said space, where it strives to expand radially outwards. During the final part of the shifting movement to the end position, the second lock element 11 and the second latch cone 9 are moved along by the ring wheel 5 Thus, the second latch cone 9 is shifted in an axial direction away from the second coupling cone 10. By this, a distance between the second latch cone's conical friction surface 9a and the second coupling cone's conical friction surface 10a is guaranteed to be created, when the ring wheel 5 reaches the end position. The second coupling cone's conical friction surface 10a is thus guaranteed to rotate at a relatively large predetermined distance from the second latch cone's stationary conical friction surface 9a. Also in this case, the braking torque in the oil-filled space between the conical friction surfaces 9a, 10a becomes relatively small.

When the ring wheel 5 has been shifted in an axial direction to one of the two end positions, it engages with a coupling cone, at the same time as it may rotate freely in relation to the second coupling cone. The movement of the ring wheel 5 from the end position where it may rotate freely in relation to the first coupling cone, to the end position in which it engages with the first coupling cone 7, happens as follows. The shifting movement starts with the ring wheel 5 in the position shown in Fig. 3d. When the actuator shifts the ring wheel 5 in an axial direction to the right, the first lock element 8 is moved along by the ring wheel 5, via the inclined portion of the control surface 5c, extending between the second stop surface 5c₂ and the local minimum point 5c₃. This movement continues until the first lock element 8 comes into contact with the first latch cone's first stop surface 6ci_. At the continued movement of the ring wheel 5, both the first lock element 8 and the first latch cone 6 are moved along by it, until the latch cone's conically shaped friction surface 6a comes into contact with the first coupling cone's 7 conically shaped friction surface 7a. This position is shown in Fig. 3b and may be designated as a pre-synchronisation position. In this position, oil located between the conical surfaces is forced away. During the continued shifting movement by the ring wheel 5, the sloping control surface 5c tends to press the lock element radially inwards between the second stop surface 5c₂ and the local minimum point 5c₃ . The actuator shifts the ring wheel 5 with a force, so that the lock element 8 is pressed radially inwards until it passes the local minimum point 5c₃. The movement of the ring wheel 5 ceases when it reaches a stop surface in connection with the coupling cone's cogs 7b. The lock element 8 at the same time comes into contact with the first stop surface 5ci, as shown in Fig. 3a. During this movement, the first latch cone's conically shaped friction surface 6a is pressed against the first coupling cone's conically shaped friction surface 7a. Therefore, the speed of the ring wheel 5 is braked down quickly, until it reaches the same speed as the first coupling cone 7, which in this case is zero, since the first coupling cone 7 is a stationary component. The speed of the ring wheel 5 is now zero and it may thus be shifted a final distance up to the end position, in which the cogs 5a of the ring wheel engage with the coupling cone's cogs 7b.

Fig. 4 shows a main shaft 1 in a gearbox. The main shaft 1 comprises a section with splines la. A movement- transferring component in the form of a control sleeve 13 is arranged around the shaft 1. The control sleeve 13 comprises an internal section with correspondingly shaped splines 13a, so that the control sleeve 13 is rotatably arranged on the shaft 1. The control sleeve 13 thus rotates with the same speed as the shaft 1. The control sleeve 13 comprises radially outward-facing cogs 13b that engage with internal cogs 14a of an annular coupling element in the form of a coupling sleeve 14. The coupling sleeve 14 comprises a radial recess 14b which is in contact with a non- displayed actuator, shifting the coupling sleeve 14 in an axial direction between two end positions. When the coupling sleeve 14 is shifted to an end position, the coupling sleeve's cogs 14a are connected with cogs 7b of a first coupling cone. The first coupling cone 7 comprises internal cogs 7c, through which it is connected with cogs 15a of a first cogwheel 15. Thus, the first coupling cone 7 and the first cogwheel 15 therefore rotate at the same speed around the shaft 1, via a needle roller bearing 17a. The coupling sleeve 14 is here in an end position, in which it engages with the first coupling cone 7. The shaft 1 in this case obtains a movement which is transmitted from a cogwheel on a non-displayed lateral shaft in relation to the cog wheel 15, via the first coupling cone 7, the coupling sleeve 14 and the control sleeve 13. The shaft 1 obtains a speed, which is defined by the number of cogs of the first cogwheel 15 and the cogwheel on the lateral shaft.

When the coupling sleeve 14 is shifted in an axial direction to an opposite end position, the coupling sleeve's cogs 14a engage with the second coupling cone's cog elements 10b. The second coupling cone 10b comprises internal cogs 10c, through which it is connected with cogs 16a of a second cogwheel 16. Thus, the second coupling cone 10 and the first cogwheel 15 thus rotate with the same speed around the shaft 1, via a needle roller bearing 17b. The coupling sleeve 14 is here at an end position, in which it engages with the second coupling cone 10. The shaft 1 in this case obtains a movement which is transmitted from a cogwheel on a non-displayed lateral shaft in relation to the cogwheel 16, via the second coupling cone 7, the coupling sleeve 14 and the control sleeve 13. The shaft 1 obtains a speed, which is defined by the number of cogs of the second cogwheel 15 and the cogwheel on the lateral shaft.

A first synchromesh device is used to synchronise the speed of the coupling sleeve 14 with the first coupling cone 7, and a second synchromesh device is used to synchronise the speed of the coupling cone 14 with the second coupling cone 10. The coupling sleeve 14 comprises control surfaces 14c, which interact with control surfaces 6c, 9c of the respective latch cones 6, 9, so that slot-shaped spaces are formed in which a respective lock element 8, 11 is arranged. The function and design of the synchromesh devices corresponds to the function of the synchromesh devices in the first

embodiment described above. Therefore the function of the synchromesh devices is not reviewed further here. However, it may be concluded that the lock elements 8, 11, in the same way as the first embodiment, establish a connection between the coupling sleeve 14 and the respective latch cones 6, 9 when the coupling sleeve 14 is in a connecting position, located at a distance from an end position in which the coupling sleeve may rotate freely in relation to one of the coupling cones 7, 10. Subsequently, the respective latch cones 6, 9 are moved along by the coupling sleeve 14, from the connecting position to the end position, so that, in this case also, the friction surfaces 6a, 9a of the latch cones 6, 9 are moved to a position at a distance from the friction surfaces 7a, 10a of the respective coupling cones 7, 10.

The invention is in no way limited to the embodiments displayed in the drawings, but may be varied freely within the scope of the patent claims.

Claims

1. Synchromesh device for a gearbox, wherein the synchromesh device comprises

- an annular coupling element (5, 14) comprising radially inward-facing cogs (5a, 14a) with an axial extension,

- a latch cone (6, 9) comprising radially outward-facing sections (6b, d, 9b, d), with an axial extension intended to be engaged with the cogs (5a, 14a) of the coupling element and a conically shaped friction surface (6a, 9a), and

- a coupling cone (7, 10) comprising a conically shaped friction surface (7a, 10a), adapted to come into contact with the latch cone's conically shaped friction surface (6a, 9a) and radially outward-facing cogs (7b, 10b),

wherein the coupling element (5, 14) is shiftably arranged in an axial direction between a first end position, in which the coupling element (5, 14) is freely rotatable in relation to the coupling cone (7, 10), and a second end position, in which the cog elements (5a, 14a) of the coupling sleeve are engaged with the coupling cone's cogs (7b, 10b), characterised in that the synchromesh device comprises

- a slot-shaped space between a radially external control surface (5c, 14c) of a coupling element (5, 14), and a radially internal control surface (6c, 9c) of the latch cone (6, 9), and

- a lock element (8, 11) which is arranged in said space,

wherein said control surfaces (5c, 6c, 9c, 10c) are designed in such a way, that the lock element (8, 11) establishes a connection between the coupling element (5, 14) and the latch cone (6, 9) in a connecting position, located at a distance from the first end position, so that the latch cone (6, 9) is moved along by the coupling element (5, 14) during a continued movement towards the first end position, up to a position in which the latch cone's conically shaped friction surface (6a, 9a) is located at a distance from the coupling cone's conically shaped friction surface (7a, 10a).

2. Synchromesh device according to claim 1, characterised in that the lock element (8, 11) is substantially annular and mounted in a biased state in said space, so that it strives to expand radially outwards.

3. Synchromesh device according to claim 2, characterised in that the annular lock element (8, 11) comprises an elongated body with a substantially circular curvature between two free ends (8a, 1 la).

4. Synchromesh device according to any of the previous claims, characterised in that the coupling element's control surface (5c, 14c) comprises a first stop surface (5ci), limiting the movement of the lock element (8, 11) in an axial direction, and that the latch cone's control surface (6c, 9c) comprises a first stop surface (6ci) limiting the movement of the lock element (8, 11) in an opposite axial direction, and that said connection is established by way of said stop surfaces (5ci, 6ci) coming into contact with the opposite sides of the lock element (8, 11) in the connecting position.

5. Synchromesh device according to claim 4, characterised in that the control surface (5c, 14c) of the coupling element comprises a second stop surface (5c₂) limiting the movement of the lock element (8, 11) in an axial direction, and that the latch cone's control surface (6c, 9c) comprises a second stop surface (6c₂) limiting the movement of the lock element (8, 11) in an opposite axial direction, and that said second stop surfaces (5c₂, 6c₂) come into contact with the opposite sides of the lock element (8, 11) when the coupling element (5, 14) reaches the second end position.

6. Synchromesh device according to claim 5, characterised in that the coupling element (5, 14) is arranged around a central shaft (12) and that the control surface (5c, 14c) of the coupling element has a breaking point (5c₃) located between said stop surfaces (5ci, 5c₂) and arranged at the smallest radial distance of the control surface (5c, 14c) from the central shaft (12).

7. Synchromesh device according to any of claims 4 to 6, characterised in that the latch cone's radially outward-facing sections (6d, 9d) have a surface that forms the first stop surface (6ci) of the latch cone's control surface (6c, 9c).

8. Synchromesh device according to any of claims 5 to 7, characterised in that the latch cone's radially outward-facing sections (6b, 9b) have a surface that forms the second stop surface (6c₂) of the latch cone's control surface (6c, 9c).

9. Synchromesh device according to any of the previous claims, characterised in that the coupling element is a ring wheel (5) in a planetary gear, which constitutes a range gear in the gearbox.

10. Synchromesh device according to any of the previous claims, characterised in that the coupling element is a coupling sleeve (14), arranged around a shaft (1) in the gearbox, wherein the coupling sleeve (14) is shiftably arranged between an end position in which it engages with a cogwheel (15, 16) that defines a gear in the gearbox, and an opposite end position in which it may rotate freely in relation to the cogwheel (15, 16).