WO2016099379A1

WO2016099379A1 - A gear shifting device for a range gear in a gearbox

Info

Publication number: WO2016099379A1
Application number: PCT/SE2015/051311
Authority: WO
Inventors: Peer Norberg; Daniel HÄGGSTRÖM; Per ARNELÖF
Original assignee: Scania Cv Ab
Priority date: 2014-12-18
Filing date: 2015-12-07
Publication date: 2016-06-23
Also published as: SE1451586A1; DE112015005175T5; SE539335C2

Abstract

The present invention relates to a gear shifting device (24) for a range gear (22) in a gearbox (2). The range gear comprises a planetary gear (22) arranged between a main shaft (11) and an output shaft (23) in the gearbox (2). The gear shifting device (24) comprises a shift sleeve (31) rotationally fixedly connected to the main shaft (11) and an actuator (26) configured to move the shift sleeve (31) in an axial direction in relation to the main shaft (11) to a low range position in which the planetary gear provides a low gear ratio between the main shaft (11) and the output shaft (23) and a high range position in which the planetary gear (22) provides a high gear ratio between the main shaft (11) and the output shaft (23). The gearbox (2) comprises a stationary contact surface (36) and that the shift sleeve (31) comprises a contact surface (35). The actuator (26) is also able to move the shift sleeve (31) in an axial direction in relation to the main shaft (11) to a third position at which said contact surfaces (35, 36) come in contact with each other.

Description

A gear shifting device for a range gear in a gearbox BAKGROUND OF THE INVENTION AND PRIOR ART

The present invention relates to a gear shifting device for a range gear in a gearbox according to the preamble of claim 1. A conventional gearbox comprises a main shaft, a counter shaft, a plurality of gearwheel pairs each comprising a primary gearwheel fixedly arranged on the counter shaft and a secondary gearwheel rotatably arranged on the main shaft. The primary gearwheel and the secondary gearwheel of the gearwheel pairs are in constant meshing engagement with each other.

Some gearboxes comprises a range gear arranged between the main shaft and an output shaft of the gearbox. The range gear provides the gearbox with twice as many gears. The range gear comprises a planetary gear including a sun wheel, planetary wheels, a ring wheel and a planetary carrier. A gear shifting device shifts the range gear into a low range gear and a high range gear. In the low range gear, the ring wheel is stationary locked and the rotary motion from the main shaft is transmitted, via the including components of the planetary gear, to the output shaft. In this case, the output shaft will rotate with a lower speed than the main shaft. In the high range gear, the gear shifting device provides a rotationally fixed connection between the main shaft and a component of the planetary gear fixedly connected to the output shaft. In this case, the output shaft rotates with the same speed as the main shaft.

During an upshift process from the low range gear to the high range gear, the main shaft need to be decelerated in order to obtain a synchronous speed with the output shaft before it is possible to establish the rotationally fixed connection between the main shaft and said component of the planetary gear fixedly connected to the output shaft. In a gearbox with an unsynchronized range gear, the deceleration of the main shaft is performed by means of a transmission brake. A transmission brake is normally designed as a multi disc brake. A multi disc brake is relative expensive, it requires a relatively large mounting space resulting in a longer gearbox and it causes drag losses in a non-activated state. SUMMARY OF THE INVENTION

The object of the present invention is to provide a main shaft brake for a range gear in a gearbox having a simple design, causing substantially no drag losses in a non- activated state, and requiring a small space in the gearbox.

The above mentioned objects are achieved by the gear shifting device according to the characterised part of claim 1. The gear shifting device comprises an ordinary shift sleeve which is positionable in a low range position and in a high range position by an actuator. According to the invention, the shift sleeve is also positionable in a third braking position by means of the same actuator. The shift sleeve is rotationally fixedly connected to the main shaft. Thus, it is possible to brake the main shaft by means of the shift sleeve. The rotary shift sleeve comprises a contact surface which comes in contact with a stationary contact surface in the third braking position. The friction between the contact surfaces provides a braking action of the shift sleeve and thus of the main shaft. The gear shifting device has an ordinary design except for the contact surface of the shift sleeve and the stationary contact surface in the gearbox.

Consequently, the gear shifting device comprises a main shaft brake having a very simple design and which can be manufactured to a low cost. In the low range position and the high range position, the contact surface of the shift sleeve is situated at a distance from the stationary contact surface. Thus, the main shaft brake causes substantially no drag losses in a non-activated state. Furthermore, the gear shifting device requires substantially no more space than an ordinary gear shifting device without main shaft brake.

According to an embodiment of the invention, said actuator provides a force moving the shift sleeve in a parallel direction to a rotary axis of the main shaft, wherein the contact surface of the shift sleeve forms an angle less than 90° to the rotary axis of the main shaft. An actuator shifting gear in a range gear provides in a non-synchronized position a considerably smaller force than the force required to brake the main shaft. By designing the shift sleeve with a contact surface forming a suitable angle in relation to the direction of the force from the actuator, it is possible to obtain an increased force ratio from the actuator. Preferably, the angle is in the range of 6-10 ° to the rotary axis of the main shaft. In this case, it is possible to increase the force ratio from the actuator up to about ten times. According to an embodiment of the invention, at least one of said contact surfaces comprises a friction lining. Thereby, it is possible to achieve a high friction between the contact surfaces and an effective braking action of the main shaft. The friction lining may constitute the contact surface of the shift sleeve. The friction lining may be an integrated part of the shift sleeve or a releasable part of it. Alternatively or in combination, the friction lining constitutes the stationary contact surface. According to an embodiment of the invention, the first contact surface comprises a part of a stationary wall in the gearbox. The stationary wall may comprise a conical protruding part provided with the first contact surface. The stationary contact surface may provide a corresponding angle in relation to the rotary axis of the main shaft as the contact surface of the shift sleeve.

According to an embodiment of the invention, the shift sleeve comprises a connection portion by which it is rotationally fixedly connected to a driver on the main shaft. The connection portion may be a teeth portion to be in constant engagement with a corresponding teeth portion of the driver. The driver may be a disk shaped member fixedly arranged on the main shaft. When the contact surface of the shift sleeve comes in contact with the stationary contact surface, the braking action on the shift sleeve will be transmitted to the main shaft via the driver.

According to an embodiment of the invention, the range gear comprises a sun wheel rotationally fixedly connected to a main shaft in the gearbox, planetary wheels, and a planetary wheel carrier rotationally fixedly connected to an output shaft of the gearbox. When the shift sleeve is, in a low range position, the rotary movement of the main shaft may be transmitted, via the sun wheel, the planetary wheels and the planetary wheel carrier to the output shaft. In this case, the output shaft obtains a lower speed than the main shaft. In the high range position, the shift sleeve provides a rotationally fixedly connection between the shift sleeve and a coupling member fixedly arranged on a planetary wheel carrier of the planetary gear such that the rotational speed of the main shaft is transmitted unchanged to the output shaft. According to an embodiment of the invention, the shift sleeve, in the high range position, is configured to provide a rotationally fixed connection between the shift sleeve and a coupling member fixedly arranged on the planetary wheel carrier such that the rotary speed of the main shaft is transmitted to the same rotary speed of the output shaft. The shift sleeve may comprise a connection portion in the form of a teeth portion comprising axial teeth being configured to come in engagement with a teeth portion of the coupling member on a planetary wheel carrier. In this case, the shift sleeve and the coupling member on the planetary wheel carrier have corresponding teeth portions arranged on a corresponding distance from the main shaft.

According to an embodiment of the invention, the gear change mechanism comprises a control unit configured to control the actuator. The control unit may receive

information from a plurality of operational parameters and select a suitable gear in the gearbox in view of received parameter values. The control unit activates the actuator such that it moves the shift sleeve to the selected range position. According to an embodiment of the invention, the control unit is configured to control the actuator such that it moves the shift sleeve to the third position in order to brake the rotary movement of the main shaft to a synchronous speed with the output shaft before it initiates a movement of the shift sleeve to the high range position. When the gear is to be shifted from the low range gear to the high range gear, the rotary movement of the main shaft is to be decelerated to a synchronous speed with the output shaft. The control unit activates the actuator such it moves the shift sleeve from the low range position to the third position in which the contact surface of the shift sleeve comes in contact with the stationary contact surface. The force from the actuator and the friction between the contact surfaces provide a braking action on the shift sleeve and the main shaft. As soon as the main shaft has been decelerated to a synchronous speed with the output shaft, the control unit activates the actuator such it moves the shift sleeve to the high range position. As soon as a synchronous speed has been reached, the actuator moves the shift sleeve to the high range position in which the teeth portion of the shift sleeve is moved into engagement with the teeth portion of the connection member on the planetary carrier.

According to an embodiment of the invention, the gear shifting device comprises a shift fork transmitting the movements from the actuator to the shift sleeve. Such a shift fork may have a forked portion arranged in a circular recess of the rotating shift sleeve. Thereby, it is possible to transmit the movements of the actuator to corresponding movements of the shift sleeve to the three different position. BRIEF DESCRIPTION OF THE DRAWINGS

In the following a preferred embodiment of the invention is described, as an example, with reference to the attached drawings, on which: Fig. 1 shows a gearbox with a range gear and

Fig. 2 shows a gear shifting device of a range gear according to the invention in a low range position,

Fig. 3 shows the gear shifting device in Fig. 2 in a braking position and

Fig. 4 shows the gear shifting device in Fig. 2 in a high range position.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Fig. 1 shows a schematically indicated vehicle 1 provided with a gearbox 2. The vehicle 1 can be a heavy vehicle. The gearbox 2 comprises a housing and an input shaft 3 driven by a not shown engine. The gearbox comprises further a counter shaft 4 provided with a plurality of gearwheels 5-10 of different sizes. The gearwheels 5-10 are separate units fixedly mounted on the counter shaft 4 or formed as a homogeneous part of the counter shaft 4. The gearbox 2 comprises a main shaft 11 provided with a plurality of gearwheels 12- 17 of different sizes. Each gearwheel 5-10 on the counter shaft 4 is in constant engagement with a gearwheel 12-17 on the main shaft 11 such they form a number of gearwheel pairs in the gearbox 2. Each gearwheel pair includes a primary gearwheel 5-10 fixedly attached on the counter shaft 4 and secondary gear wheel 12-17 rotatably arranged on the main shaft 11 or the input shaft 3.

The gearbox 2 is equipped with a split gear which in a first split position connects the input shaft 3 with the counter shaft 4 via a first gearwheel pair 5, 12 and which in a second split position connects the input shaft 3 with the counter shaft 4 via a second gearwheel pair 6, 13. The second gearwheel pair 6, 13 provides a ratio that defines a third gear in the gearbox 2. The gearbox 2 further includes a third gearwheel pair 7, 14 which defines a second gear in the gearbox 2, a fourth gearwheel pair 8, 15 which defines a first gear in the gearbox 2, a fourth gearwheel pair 9, 16 which defines a creep gear and a fifth gearwheel pair 10, 17 which defines a reverse gear. The fifth gearwheel pair 10, 17 includes an intermediate gearwheel which provides a reverse rotation of the main shaft 11.

The input shaft 3 is rotatably arranged in the gearbox 2 by means of a roller bearing 18a. The secondary gearwheels 12-17 are rotatably arranged on the main shaft 11 by means of roller bearings 18b that can be needle bearings. The main shaft 11 is rotatably arranged by means of two roller bearings 18c. Synchronizing units 19-21 are disposed adjacent to the secondary gear wheels 12-15 of the main shaft 11. Each synchronizing unit 19-21 is configured to synchronize and lock at least one of the secondary gear wheels 12-15 on the main shaft 11. A first synchronizing unit 19 has the task to establish the different split positions. The first synchronizing unit 19 is able to connect the input shaft 3 to the counter shaft 4 in the gearbox 2, via the first gearwheels pair 5, 12 in a first split position and, via the second gearwheels pair 6, 13in a second split position. A second synchronization unit 20 is configured to synchronize and lock the secondary gearwheels 13, 14 on the main shaft 11. A third synchronizing unit 21 is adapted to synchronize and lock the secondary gearwheel 15 on the main shaft 11. Furthermore, it is possible, by the first synchronizing unit 19 and the second synchronizing unit 20, to provide a direct connection between the input shaft 3 and the main shaft 11 and provide a direct-drive gear in the gearbox 2.

The gearbox also includes a range gear 22 which is arranged between the main shaft 11 and an output shaft 23 of the gearbox 2. The range gear 22 comprises a sun wheel 22a fixedly arranged on the main shaft 11, planetary wheels 22b and a planetary wheel carrier 22c fixedly connected to the output shaft 23. By means of the range gear 22, all ordinary gears in the gearbox 2 can be provided with a high range gear or a low range gear. Thus, the range gear 22 provides the gearbox 2 with twice as many gears. A schematically indicated gear shifting device 24 is configured to shift gears in the range gear 22.

Fig. 2 shows a gear shifting device 24 according to the invention. The gear shifting device comprises a control unit 25 configured to activate an actuator 26. The actuator 26 may be pneumatic actuator. The actuator 26 comprises an extensible arm 27 connected to a shift fork 28. The shift fork 28 has a contact portion 29 to be arranged in a circular recess 30 of an annular shift sleeve 31. A radial inner surface of the annular shift sleeve 31 is provided with a teeth portion 32 having teeth extending in an axial direction in relation to the main shaft 11. The teeth portion 32 is in constant engagement with a teeth portion 33 on the outer periphery of a disc-shaped driver 34. The teeth portion 32 of the shift sleeve 31 has a width making it possible to move the shift sleeve 31 in an axial direction without going out of engagement with the teeth portion 33 of driver 34. The driver 34 is fixedly attached on the main shaft 11. Thus, the shift sleeve 31 and the driver 34 rotate with the same speed as the main shaft 11.

The shift sleeve 31 comprises a contact surface 35 comprises a friction lining. The contact surface 35 forms an angle of about 5-10° to the rotational axis 1 la of the man shaft 11. A complimentary contact surface 36 is arranged on a stationary wall 37 in the gearbox 2. The main shaft 11 extends through an opening in the stationary wall 37 and it is rotatably arranged in relation to the stationary wall 37 by means of a roller bearing 38. The planet carrier 22c are rotatably connected to the main shaft 11 via a roller bearing 39 and fixedly connected to the output shaft 23 on an opposite side of the planetary wheels 22b. Thus, the planet carrier 22c rotates with the same speed as the output shaft 23. The planet carrier 22c comprises a connection member 40 with a teeth portion 41 having axial teeth. The teeth portion 41 is arranged at the same radial distance from the rotational axis 1 la of the main shaft 11 as the teeth portion 33 of the driver 34. The control unit 25 receives information from a number of operation parameters 42. The control unit 25 also receives information from a first sensor 43 about the speed of the main shaft 11 and from a second sensor 44 about the speed of the output shaft 23. Fig. 2 shows the shift sleeve 31 in a low range position. In the low range position, the shift sleeve 31 is out of engagement with the teeth portion 41 of the connection member 40 on the planetary wheel carrier 22c. The rotary movement of the main shaft 11 is transmitted via the sun wheel 22a, the planetary wheels 22b and the planetary wheel carrier 22c, to the output shaft 23. In this case, the output shaft 23 obtains a lower speed than the main shaft 11. In the low range position, the contact surface 35 of the shift sleeve 31 is located at a well-defined axial distance from the contact surface 36 of the stationary wall 37. Thereby, the contact surfaces 35, 36 do not substantially cause any drag losses when the shift sleeve 31 is in the low range position. In view of received operation parameters 42, the control unit 25 determines to shift gear from the low range gear to the high range gear in the range gear 22. However, it is not possible to move the shift sleeve 31 direct to the high range position due to the different speeds between the main shaft 11 and the output shaft 23. Thus, the actuator 26 moves the shift fork 28 and the shift sleeve 31 in an axial direction towards the stationary wall 37 and the third position, which is shown on Fig. 3. When the contact surface 35 of the shift sleeve 31 comes in contact with the contact surface 36 of the stationary wall 37, the force from the actuator and the friction between the contact surfaces 35, 36 provide a braking action of the shift sleeve 31, the driver 34 and the main shaft 11. Fig. 3 shows the shift sleeve 31 in the third position. The control unit 25 receives substantially continuously information from a first sensor 43 about the speed of the main shaft 11 and from the second sensor 44 about the speed of the output shaft 23. As soon as the main shaft 11 has been decelerated to a synchronous speed with the output shaft 23, the control unit 25 activates the actuator 26 such that it moves the shift sleeve 31 in a direction towards the planetary wheel carrier 22c and the high range position. Since the main shaft 11 and the output shaft 23 has a synchronous speed, it is possible to move the shift sleeve 31 to the high range position in which the teeth portion 32 of shift sleeve 31 comes in engagement with the teeth portion 41 of the connection member 40 which is shown in Fig. 4. In the high range position, the shift sleeve 31 provides a rotationally fixed connection between the main shaft 11 and the output shaft 23 via the driver 34, the shift sleeve 31 and the planetary wheel carrier 22c. Consequently, the main shaft 11 and the output shaft 23 rotates with the same speed in the high range position.

When the control unit 25 determines to shift gear from the high range gear to the low range gear in the range gear, it activates the engine connected to the input shaft 3 of the gearbox 2 in order to create a torque free state between the main shaft 11 and the output shaft 23 in the gearbox 2. When such a torque-free state is created, the control unit 25 activates the actuator 26 such it moves the shift sleeve 31 from the high range position to the low range position. The invention is not restricted to the described embodiment but may be varied freely within the scope of the claims.

Claims

1. A gear shifting device (24) for a range gear (22) in a gearbox (2), wherein the range gear comprises a planetary gear (22) arranged between a main shaft (11) and an output shaft (23) in the gearbox (2) and wherein the gear shifting device (24) comprises a shift sleeve (31) rotationally fixedly connected to the main shaft (11) and an actuator (26) configured to move the shift sleeve (31) in an axial direction in relation to the main shaft (11) to a low range position in which the planetary gear provides a low gear ratio between the main shaft (11) and the output shaft (23) and a high range position in which the planetary gear (22) provides a high gear ratio between the main shaft (11) and the output shaft (23), characterised in that the gearbox (2) comprises a stationary arranged contact surface (36) and that the shift sleeve (31) comprises a contact surface (35), and that the actuator (26) is also able to move the shift sleeve (31) in an axial direction in relation to the main shaft (11) to a third position at which said contact surfaces (35, 36) come in contact with each other.

2. A gear shifting device according to claim 1, characterised in that said actuator (26) provides a force moving the shift sleeve (31) in a parallel direction to a rotary axis (42) of the main shaft (11), wherein the contact surface of the shift sleeve (35) forms an angle less than 90° to the rotary axis (42) of the main shaft (11).

3. A gear shifting device according to claim 1 or 2, characterised in that at least one of said contact surfaces comprises a friction lining (35).

4. A gear shifting device according to any one of the preceding claims, characterised in that the first contact surface (36) comprises a part of a stationary wall (37) in the gearbox (2).

5. A gear shifting device according to any one of the preceding claims, characterised in that the shift sleeve (31) comprises a connection portion (32) by which it is rotationally fixedly connected to a driver (34) on the main shaft (11).

6. A gear shifting device according to any one of the preceding claims, characterised in that the range gear (22) comprises a sun wheel (22a) rotationally fixedly connected to a main shaft (11) in the gearbox (2), planetary wheels (22b), and a planetary wheel carrier (22c) rotationally fixedly connected to an output shaft (23) of the gearbox (2).

7. A gear shifting device according to claim 6, characterised in that rotary movement of the main shaft (11) is transmitted, in the low gear position, via the sun wheel (22a), the planetary wheels (22b) and the planetary wheel carrier (22c) to the output shaft (23).

8. A gear shifting device according to claim 6 or 7, characterised in that the shift sleeve (31), in the high range position, is configured to provide a rotationally fixed connection between the driver (34) and a coupling member (40) fixedly arranged on the planetary wheel carrier (22c) such that the speed of the main shaft (11) is transmitted unchanged to the output shaft (23)..

9. A gear shifting device according to claim 8, characterised in that the shift sleeve (31) comprises a connection portion in the form of a teeth portion (32) comprising axial teeth configured to come in engagement with a teeth portion (41) of the coupling member (40) on a planetary wheel carrier (22c).

10. A gear shifting device according to any one of the preceding claims, characterised in that the gear change mechanism comprises a control unit (25) configured to control the actuator (26).

11. A gear shifting device according to claim 10, characterised in that the control unit (25) is configured to control the actuator (26) such that it moves the shift sleeve (31) to the third position in order to brake the rotary movement of the main shaft (11) to a synchronous speed with the output shaft (23) before it initiates a movement of the shift level (31) to the high range position.

12. A gear shifting device according to any one of the preceding claims, characterised in that the gear shifting device comprises a shift fork transmitting the movements from the actuator (26) to the shift sleeve (31).

13. A gearbox comprising a gear shift device according to any one of the claims 1-12.

14. A vehicle comprising a gear box according to claim 13.