Dog clutch device, transmission unit for a motorcycle with the dog clutch device and motorcycle
The invention relates to a dog clutch device. More specifically, the invention relates to a dog clutch device comprising a dog gear comprising a plurality of lugs, whereby the lugs extend in a axial direction, a receiving gear comprising a plurality of receiving sections for receiving the plurality of the lugs, whereby the dog clutch is in a closed state, when the plurality of the lugs are engaged in the plurality of the receiving sections, and is in an open state, when the plurality of the lugs are disengaged from the plurality of the receiving sections. The invention further relates to a transmission unit for a motorcycle with the dog clutch device and a motorcycle with the transmission unit and/or the dog clutch device.

Transmission systems for vehicles enable a driver to change the transmission ratio between the motor of the vehicle and the driven wheels of the vehicle. During the change of the transmission ratio, the connection between the motor and the driven wheels must be opened. Usually clutches of a friction type are used to open and to close the connection between the motor and the driven wheels. Further usually one or more clutches of an interference type are used to couple rotating parts in the transmission system.

A dog clutch is an example for a clutch of the interference type. The document GB968,289 representing the closest prior art, discloses such a dog clutch for a motorcycle. The dog clutch comprises two drive sprockets rotatably mounted on a shaft and a ring disposed between the two drive sprockets and non-rotatably mounted on the said shaft. The sprockets comprise recesses extending in an axial direction of the shaft. The ring comprises so-called "dogs", which extend from the ring in both axial directions and are complementary to the recesses of the sprockets. The ring can be displaced in the axial direction of the shaft, so that the dogs can be inserted in to the recesses of one of the sprockets in order to enable a positive locking between the sprocket and the ring in the direction of rotation around the shaft and/or in circumferential direction.

It is an object of the present invention to provide a dog clutch device with an improved operating behavior. This and further objects are achieved by a dog clutch device with the features of claim 1, a transmission unit with the features of claim 9 and a motorcycle with the features of claim 10. Preferred or advantageous embodiments are disclosed by the dependent claims, the description as following and the figures.

Subject-matter of the invention is a dog clutch device, which is suitable and/or adapted for a transmission unit. The transmission unit is part of a vehicle, for example an automobile or in a preferred embodiment a motorcycle. The transmission is for example realized as a change speed gearbox and/or provides different transmission ratios for the transmission of a drive torque between the motor of the vehicle and the driven wheels of the vehicle. The transmission unit may provide more than two, preferably more than three, more than four or more than five different transmission ratios as gears. In an alternative embodiment it is possible that the transmission unit is realized as an automatic gearbox.

The dog clutch device is operable to couple two clutch partners in a rotatably fixed manner, when the dog clutch device is in a closed state, and to decouple the two clutch partners, when the dog clutch device is in an open state. In the closed state the two clutch partners are connected with each other in a positive locking and/or form-locking manner, especially with respect to the direction of rotation of the dog clutch device and/or the two clutch partners. In the open state, the two clutch partners can rotate independently from each other.

The dog clutch device comprises a dog gear, which is preferably circular in shape and extends perpendicular to an axis of rotation of the dog clutch device. The dog gear comprises a plurality, for example three, four or five, lugs, which are sometimes also called dogs in this technical connection. The lugs extend in an axial direction with respect to the axis of rotation. The lugs may only extend in one axial direction, in other embodiments two sets of lugs are provided, whereby one set of lugs extends in one axial direction and the other set of lugs extends in the other axial direction. The lugs are preferably formed integrally with a body of the dog gear. The lugs are preferably realized as protrusions, studs or stems. It is especially preferred that the dog gear is made of metal, especially steel.

The dog clutch device further comprises a receiving gear, which is preferably circular in shape and extends perpendicular to the axis of rotation of the dog clutch device. The receiving gear comprises a plurality of receiving sections for receiving the plurality of the lugs extending in one axial direction from the dog gear. The receiving sections may be realized as recesses in the receiving gear. Preferably, the receiving sections are realized as passages or through-holes extending through the receiving gear in the axial direction. Simplified, the receiving sections are holes in the receiving gear.

The dog gear represents or is connected to one of the clutch partners, the receiving gear represents or is connected to the other of the clutch partners. The dog clutch device is in the closed state, when the lugs are engaged, especially inserted in the receiving section. The dog clutch device is in the open state, when the lugs are disengaged or outside from the receiving sections.

According to the invention it is proposed that the dog clutch device comprises plastic plugs, which are arranged on the lugs and/or which are arranged in the receiving section, whereby the plastic plugs provide sliding and/or contact surfaces between the lugs and the receiving sections. It is preferred that the plastic plugs mechanically separate the lugs from the receiving sections.

The advantages of the invention is that noisy gear shifting (clashing) due to metal contacts during the gear shifting as well as sudden jerks and vibrations can be reduced by the solution according to the invention. Furthermore excessive wear of contact points between engaging gears due system rigidity can also be reduced.

In a preferred embodiment of the invention, the plugs are made of polyamide. This material has the advantage of commercially available in a suitable grade and withstands high temperature and wear with assurance of prolonged life.

It is preferred that the receiving sections, especially in a plan view or in a cross section perpendicular to the rotation axis, extend in a circle around the axis of rotation. The receiving sections are especially kidney-shaped and/or extend as a slot around the rotation axis. The receiving sections have in the axial direction a constant or nearly constant free cross section. Each receiving section may be constructed by two curved side walls, which are formed coaxial to the axis of rotation and concentric to each other. Each receiving sections provides two straight side walls, which extend in a radial direction with respect to the axis of rotation.

It is furthermore preferred that the plastic plugs for the receiving sections are receiving plugs, which extend over the circumferential walls of the respective receiving section. It is especially preferred that the receiving plugs cover the said four walls especially the surface of the said four walls in their entirety. The receiving plugs have at least a front opening for receiving the lugs and preferably a back opening. The receiving plugs form a reception for the lugs. The receiving plugs may be realized as a sleeve covering the inner surface of the receiving section.

The lugs are preferably formed as segments of a circular ring around the axis of rotation and/or as a segment of a doughnut around the axis of rotation. It is preferred that each lug provides two curved walls, which extend concentric to the axis of rotation and concentric to each other. The lug furthermore provides two straight walls, which extend in a radial direction with respect to the axis of rotation.

The plugs for the lugs are preferably realized as slip-on plugs, which form outer sleeves for the lugs. The slip-on plugs preferably cover all walls of the lugs, but can provide an open end, so that the axially orientated face of the lugs are free from the slip-on plugs.

It is especially preferred that the dog clutch device provides plugs for the lugs and plugs for the receiving sections. It is especially preferred that the receiving plugs are complementary to the slip-on plugs. In this preferred embodiment, the material between the lugs and the receiving sections are double-walled, so that noise and vibrations are effectively damped.

The dog clutch device may comprise a shaft, especially a rotating shaft. The dog gear and the receiving gear are arranged on the shaft. The dog gear is non-rotatably mounted on the shaft, so that the dog gear rotates together with the shaft. On the contrary, the receiving gear is mounted rotatably on the shaft, so that the receiving gear may rotate freely around the shaft, as long as the dog clutch device is in the open state. The dog gear is displaceably mounted on the shaft in an axial direction, so that the dog gear may be shifted from axial position on the shaft to another axial position on the shaft. In order to allow the dog gear these functions, the shaft may have external teeth extending in an axial direction and the dog gear may have internal teeth also extending in the axial direction and being engaged with the external teeth of the shaft. In order to transfer the dog clutch device from the open state in the closed state, the dog gear is moved in the axial direction towards the receiving gear. With this movement, the lugs are inserted in the receiving sections.

It is especially preferred that at least one of the gears or both gears are realized as sprockets and/or have external teeth for transferring torque.

A further subject-matter of the invention is a transmission unit for a motorcycle with the features of claim 9. Motorcycle transmission is an important aggregate for changing the speed and power in the motorcycle driveline. It provides means for changing the ratio between the engine speed and the driving wheel to best meet each particular driving situation. The transmission unit is primarily responsible for transmitting engine torque to wheels based on load conditions. The motorcycle has to switch gears in order to move at a wide range of speeds.

The transmission unit comprises a gear lever, which is preferably foot controlled, and a gear cam, which is operatively connected with the gear lever. The gear cam is pivotable, whereby the pivoting of the gear cam is controlled by the gear lever. At least one gear fork is operatively connected with the gear cam. More precisely, the gear fork can be shifted along a shifter rail, whereby the shift position is controlled by the gear cam. Furthermore the transmission unit comprises a dog clutch device as described above. The dog clutch device is operatively connected with the gear fork. The gear fork shifts the dog gear in axial direction on the shaft in order to change the state of the dog clutch device from the open state into the closed state and/or from the closed state in the open state. In other words, the gear switching in the transmission unit is preferably achieved by using a shift mechanism comprising a shift drum cam as the gear cam, the shift forks guided on the shifter rails. The drum is operated through the linkage with the gear shifting pedal as the gear lever resulting in a rotation of the cam. Then shift forks has to follow the route of the drum cam profile, The rotating motion of the drum cam results into a linear gear shift between the dog gear and the receiving gear, so that the lugs of the dog gear enter into the receiving sections of the receiving gear. Such engagement of lug and receiving section results into the required torque transfer.

A further subject-matter of the invention is a motorcycle with the features of claim 10 comprising a transmission unit as described and/or a dog clutch device as described.

Further features, advantages and effects are disclosed by the description of a preferred embodiment of the invention and the figures as attached. The figures show:

Figure 1a,b a schematic illustration of a dog clutch device as an embodiment of the invention in an open and in a closed state;

Figure 2 a dog gear of the dog clutch device in figure 1 in a schematic three-dimensional view;

Figure 3 a receiving gear of the dog clutch device in figure 1 in a schematic three-dimensional view;

Figures 1 a, b show a schematic illustration of a dog clutch device 1 as an embodiment of the invention. The dog clutch device is a component of a transmission unit of a motorcycle for transmitting torque from an engine of the motorcycle to a wheel of the motorcycle. The dog clutch device is a positive locking clutch for transmitting rotation.

The dog clutch device 1 comprises a shaft 2, which can be an input shaft or an output shaft of the transmission unit. The shaft 2 rotates during operation of the transmission unit to transmit the torque. The shaft 2 defines an axis of rotation R. The dog clutch device 1 comprises two sprockets, namely a dog gear 3 and a receiving gear 4, which are arranged on the shaft 2. Each of the gears 3, 4 has external teeth, which are not shown in the figures. It is also possible that the dog gear 3 does not have external teeth, as it is driven by the shaft 2. The dog gear 3 is non-rotatably, but axial displacably arranged on the shaft 2. With respect to a circumferential direction, the dog gear 2 is positively locked on the shaft 2. The receiving gear 4 is freely rotatably arranged on the shaft 2, but cannot be displaced in the axial direction.

The dog gear 3 comprises lugs 5, which extend from one side of the dog gear 3 in an axial direction. As it can be seen in figure 2, the dog gear 3 comprises four lugs, which are arranged in a circle around the axis of rotation R. The receiving gear 4 comprises receiving sections 6 realized as through holes or slots for receiving the lugs 4. Therefore, the receiving sections 6 are adapted in their position and dimension to accommodate the lugs 4.

The figure 1a shows the dog clutch device 1 in an open state, whereby the dog gear 3 and the receiving gear 4 are spaced apart from each other. In the open state, the receiving ear 4 can rotate independently from the dog gear 3. Figure 1b shows the dog clutch device 1 in the closed state, whereby the dog gear 3 is displaced in the direction towards the receiving gear 4, so that the lugs 5 are inserted in the receiving sections 6. In the closed state, the dog gear 3 and the receiving gear are positively locked with each other. In the closed state, a torque can be transmitted from the shaft 2 and the dog gear 3 to the receiving gear 4 or in the opposite direction.

Figure 2 is a three-dimensional view of the dog gear 3 in figures 1a,b. In this figure the internal teeth 7 for meshing with external are clearly visible. On each of the lugs 5 a slip-on plug 8 made of plastic is arranged. The lugs 4 are part of the dog gear 3 and may be made from the same material, especially metal as the remaining sections of the dog gear 3. The slip-on plug 8 surrounds the respective lug 5 and covers all surfaces being orientated in a radial direction like a sleeve. The lugs 4 are kidney-shaped.

Figure 3 is a three-dimensional view of the receiving gear 4 in the figures 1a,b. In each of the receiving sections 6 a receiving plug 9 made of plastic is mounted. The receiving plug 9 covers all surfaces of the receiving section 6 being orientated in a radial direction as a sleeve. The remaining free space in the receiving plugs 9 is adapted to accommodate the lugs 4 with the slip-on plugs 8.

During closing and opening the dog clutch device 1, the slip-on plug 8 and the receiving plug 9 slide along each other, so that an operation with low noise or vibration is possible. In the closed state of the dog clutch device 1, a plastic double-wall formed by the slip-on plug 8 and the receiving plug 9 reduces noise and vibration during the transmission of torque.

Reference list

1 Dog clutch device
2 shaft
3 dog gear
4 receiving gear
5 lugs
6 receiving section
7 internal teeth
8 slip-on plugs
9 receiving plugs
R axis of rotation

We Claim
1. Dog clutch device (1) for a transmission unit, the dog clutch device (1) comprising:

a dog gear (3) comprising a plurality of lugs (5), whereby the lugs (4) extend in an axial direction;

a receiving gear (4) comprising a plurality of receiving sections (6) for receiving the plurality of the lugs (5),

whereby the dog clutch device (1) is in a closed state, when the plurality of the lugs (5) are engaged in the plurality of the receiving sections (6), and is in an open state, when the plurality of the lugs (5) are disengaged from the plurality of the receiving sections (6),

characterized in that

the dog clutch device (1) comprises plastic plugs (8,9), which are arranged on the lugs (5) and/or in the receiving sections (6), whereby the plastic plugs (8,9) provide sliding and/or contact surfaces between the lugs (5) and the receiving sections (6).

2. Dog clutch device (1) according to claim 1, characterized in that the plugs (8,9) are made of polyamide.

3. Dog clutch device (1) according to claim 1 or 2, characterized in that the receiving sections (6) are kidney-shaped and/or extend as a slot around an axis of rotation of the receiving gear (4).

4. Dog clutch device (1) according to one of the preceding claims, characterized in that the plastic plugs (8,9) for the receiving sections (6) are receiving plugs (9), which form inner sleeves for the receiving sections (6).

5. Dog clutch device (1) according to one of the preceding claims, characterized in that the lugs (5) are realized as segments of a circular ring and/or doughnut segments.

6. Dog clutch device (1) according to one of the preceding claims, characterized in that in that the plastic plugs (9) for the lugs are slip-on plugs (9), which form outer sleeves for the lugs (5).

7. Dog clutch device (1) according to one of the preceding claims, the dog clutch further comprising a shaft (2), whereby the dog gear (3) is non-rotatably but axially displaceably mounted on the shaft (2) for engaging and disengaging with the receiving gear (4) and whereby the receiving gear (4) is rotatably mounted on the shaft (2).

8. Dog clutch device (1) according to one of the preceding claims, characterized in that the dog gear (3) and/or the receiving gear (4) is/are realized as a sprocket.

9. Transmission unit for a motorcycle comprising a gear lever, a gear cam being in an operative connection with the gear lever, a gear fork and a shifter rail, whereby the gear fork is displacable along the shifter rail and whereby the position of the gear fork on the shifter rail is controlled by the gear cam, characterized by the dog clutch device (1) according to one of the preceding claims, whereby the axial position of the dog gear (3) is controlled by the gear fork.

10. Motorcycle comprising the transmission system according to claim 9.