SE539335C2

SE539335C2 - A gear shifting device for a range gear in a gearbox

Info

Publication number: SE539335C2
Application number: SE1451586A
Authority: SE
Inventors: Norberg Peer; Häggström Daniel; Arnelöf Per
Original assignee: Scania Cv Ab
Priority date: 2014-12-18
Filing date: 2014-12-18
Publication date: 2017-07-04
Also published as: WO2016099379A1; DE112015005175T5; SE1451586A1

Abstract

11 Abstract The present invention re1ates to a gear shifting device (24) for a range gear (22) in agearbox (2). The range gear comprises a planetary gear (22) arranged between a mainshaft (11) and an output shaft (23) in the gearbox (2). The gear shifting device (24)comprises a shift s1eeve (31) rotationa11y fixedly connected to the main shaft (11) andan actuator (26) conf1gured to move the shift s1eeve (31) in an axia1 direction inre1ation to the main shaft (11) to a low range position in which the planetary gearprovides a low gear ratio between the main shaft (11) and the output shaft (23) and ahigh range position in which the planetary gear (22) provides a high gear ratio betweenthe main shaft (11) and the output shaft (23). The gearbox (2) comprises a stationarycontact surface (36) and that the shift s1eeve (31) comprises a contact surface (35). Theactuator (26) is a1so ab1e to move the shift s1eeve (31) in an axial direction in re1ationto the main shaft (11) to a third position at which said contact surfaces (35, 36) come in contact with each other. (Pig. 2)

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 l.

A conventional gearbox comprises a main shaft, a counter shaft, a plurality ofgearwheel pairs each comprising a primary gearwheel ﬁxedly arranged on the countershaft and a secondary gearwheel rotatably arranged on the main shaft. The primarygearwheel 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 outputshaft 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, aring wheel and a planetary carrier. A gear shifting device shifts the range gear into alow range gear and a high range gear. In the low range gear, the ring wheel isstationary looked and the rotary motion from the main shaft is transmitted, via theincluding components of the planetary gear, to the output shaft. In this case, the outputshaft will rotate with a lower speed than the main shaft. In the high range gear, the gearshifting device provides a rotationally fixed connection between the main shaft and acomponent 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 mainshaft need to be decelerated in order to obtain a synchronous speed with the outputshaft before it is possible to establish the rotationally fixed connection between themain shaft and said component of the planetary gear fixedly connected to the outputshaft. In a gearbox with an unsynchronized range gear, the deceleration of the mainshaft is performed by means of a transmission brake. A transmission brake is norrnallydesigned as a multi disc brake. A multi disc brake is relative expensive, it requires arelatively 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 ina 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 thecharacterised part of claim l. The gear shifting device comprises an ordinary shiftsleeve which is positionable in a low range position and in a high range position by anactuator. According to the invention, the shift sleeve is also positionable in a thirdbraking position by means of the same actuator. The shift sleeve is rotationally fixedlyconnected to the main shaft. Thus, it is possible to brake the main shaft by means ofthe shift sleeve. The rotary shift sleeve comprises a contact surface which comes incontact with a stationary contact surface in the third braking position. The frictionbetween the contact surfaces provides a braking action of the shift sleeve and thus ofthe main shaft. The gear shifting device has an ordinary design except for the contactsurface of the shift sleeve and the stationary contact surface in the gearbox.Consequently, the gear shifting device comprises a main shaft brake having a verysimple design and which can be manufactured to a low cost. In the low range positionand the high range position, the contact surface of the shift sleeve is situated at adistance from the stationary contact surface. Thus, the main shaft brake causessubstantially no drag losses in a non-activated state. Furtherrnore, the gear shiftingdevice 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 movingthe shift sleeve in a parallel direction to a rotary axis of the main shaft, wherein thecontact surface of the shift sleeve forms an angle less than 90° to the rotary axis of themain 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 forrning a suitable angle in relationto the direction of the force from the actuator, it is possible to obtain an increased forceratio 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 surfacescomprises a friction lining. Thereby, it is possible to achieve a high friction betweenthe contact surfaces and an effective braking action of the main shaft. The frictionlining may constitute the contact surface of the shift sleeve. The friction lining may bean integrated part of the shift sleeve or a releasable part of it. Altematively or in combination, the friction lining constitutes the stationary contact surface.

According to an embodiment of the invention, the first contact surface comprises a partof a stationary wall in the gearbox. The stationary wall may comprise a conicalprotruding part provided with the first contact surface. The stationary contact surfacemay 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 connectionportion by which it is rotationally fixedly connected to a driver on the main shaft. Theconnection portion may be a teeth portion to be in constant engagement with acorresponding teeth portion of the driver. The driver may be a disk shaped memberfixedly arranged on the main shaft. When the contact surface of the shift sleeve comesin 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 wheelrotationally fixedly connected to a main shaft in the gearbox, planetary wheels, and aplanetary 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 mainshaft may be transmitted, via the sun wheel, the planetary wheels and the planetarywheel carrier to the output shaft. In this case, the output shaft obtains a lower speedthan the main shaft. In the high range position, the shift sleeve provides a rotationallyfixedly connection between the shift sleeve and a coupling member fixedly arrangedon 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 conf1gured to provide a rotationally fixed connection between the shift sleeve and a coupling member fixedly arranged on the planetary wheel carrier suchthat the rotary speed of the main shaft is transmitted to the same rotary speed of theoutput shaft. The shift sleeve may comprise a connection portion in the forrn of a teethportion comprising axial teeth being conf1gured to come in engagement with a teethportion of the coupling member on a planetary wheel carrier. In this case, the shiftsleeve 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 acontrol unit configured to control the actuator. The control unit may receiveinformation from a plurality of operational parameters and select a suitable gear in thegearbox 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 controlthe actuator such that it moves the shift sleeve to the third position in order to brake therotary movement of the main shaft to a synchronous speed with the output shaft beforeit initiates a movement of the shift sleeve to the high range position. When the gear isto be shifted from the low range gear to the high range gear, the rotary movement ofthe main shaft is to be decelerated to a synchronous speed with the output shaft. Thecontrol unit activates the actuator such it moves the shift sleeve from the low rangeposition to the third position in which the contact surface of the shift sleeve comes incontact with the stationary contact surface. The force from the actuator and the frictionbetween the contact surfaces provide a braking action on the shift sleeve and the mainshaft. As soon as the main shaft has been decelerated to a synchronous speed with theoutput shaft, the control unit activates the actuator such it moves the shift sleeve to thehigh range position. As soon as a synchronous speed has been reached, the actuatormoves the shift sleeve to the high range position in which the teeth portion of the shiftsleeve is moved into engagement with the teeth portion of the connection member onthe planetary carrier.

According to an embodiment of the invention, the gear shifting device comprises ashift fork transmitting the movements from the actuator to the shift sleeve. Such a shiftfork 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 andFig. 2 shows a gear shifting device of a range gear according to the invention ina low range position,Fig. 3 shows the gear shifting device in Fig. 2 in a braking position andFig. 4 shows the gear shifting device in Fig. 2 in a high range position.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THEINVENTION Fig. 1 shows a schematically indicated vehicle 1 provided with a gearbox 2. Thevehicle 1 can be a heavy vehicle. The gearbox 2 comprises a housing and an inputshaft 3 driven by a not shown engine. The gearbox comprises further a counter shaft 4provided with a plurality of gearwheels 5-10 of different sizes. The gearwheels 5-10are separate units fixedly mounted on the counter shaft 4 or forrned as a homogeneouspart of the counter shaft 4. The gearbox 2 comprises a main shaft 11 provided with aplurality of gearwheels 12- 17 of different sizes. Each gearwheel 5-10 on the countershaft 4 is in constant engagement with a gearwheel 12-17 on the main shaft 11 suchthey forrn a number of gearwheel pairs in the gearbox 2. Each gearwheel pair includesa primary gearwheel 5-10 fixedly attached on the counter shaft 4 and secondary gearwheel 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 theinput shaft 3 with the counter shaft 4 via a first gearwheel pair 5, 12 and which in asecond split position connects the input shaft 3 with the counter shaft 4 via a secondgearwheel pair 6, 13. The second gearwheel pair 6, 13 provides a ratio that defines athird gear in the gearbox 2. The gearbox 2 further includes a third gearwheel pair 7, 14 which def1nes 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 acreep gear and a fifth gearwheel pair 10, 17 which defines a reverse gear. The fifthgearwheel pair 10, 17 includes an interrnediate gearwheel which provides a reverse rotation of the niain shaft 11.

The input shaft 3 is rotatably arranged in the gearbox 2 by nieans of a roller bearing18a. The secondary gearwheels 12-17 are rotatably arranged on the niain shaft 11 bynieans of roller bearings 18b that can be needle bearings. The niain shaft 11 isrotatably arranged by nieans of two roller bearings 18c. Synchronizing units 19-21 aredisposed adjacent to the secondary gear wheels 12-15 of the niain shaft 11. Eachsynchronizing unit 19-21 is configured to synchronize and lock at least one of thesecondary gear wheels 12-15 on the niain shaft 11. A first synchronizing unit 19 hasthe task to establish the different split positions. The first synchronizing unit 19 is ableto connect the input shaft 3 to the counter shaft 4 in the gearbox 2, via the firstgearwheels 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 tosynchronize and lock the secondary gearwheels 13, 14 on the niain shaft 11. A thirdsynchronizing unit 21 is adapted to synchronize and lock the secondary gearwheel 15on the niain shaft 11. Furtherrnore, it is possible, by the first synchronizing unit 19 andthe second synchronizing unit 20, to provide a direct connection between the input shaft 3 and the niain 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 niain shaft 11and an output shaft 23 of the gearbox 2. The range gear 22 coniprises a sun wheel 22afixedly arranged on the niain shaft 11, planetary wheels 22b and a planetary wheelcarrier 22c fixedly connected to the output shaft 23. By nieans of the range gear 22, allordinary gears in the gearbox 2 can be provided with a high range gear or a low rangegear. Thus, the range gear 22 provides the gearbox 2 with twice as niany gears. Ascheniatically 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 shiftingdevice coniprises a control unit 25 configured to activate an actuator 26. The actuator26 niay be pneuniatic actuator. The actuator 26 coniprises an extensible arrn 27connected 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 anaxial direction in relation to the main shaft 11. The teeth portion 32 is in constantengagement 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 theshift sleeve 31 in an axial direction without going out of engagement with the teethportion 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. Thecontact surface 35 forrns an angle of about 5-10° to the rotational axis 1 la of the manshaft 11. A complimentary contact surface 36 is arranged on a stationary wall 37 in thegearbox 2. The main shaft 11 extends through an opening in the stationary wall 37 andit is rotatably arranged in relation to the stationary wall 37 by means of a roller bearing38. The planet carrier 22c are rotatably connected to the main shaft 11 via a rollerbearing 39 and fixedly connected to the output shaft 23 on an opposite side of theplanetary wheels 22b. Thus, the planet carrier 22c rotates with the same speed as theoutput shaft 23. The planet carrier 22c comprises a connection member 40 with a teethportion 41 having axial teeth. The teeth portion 41 is arranged at the same radialdistance from the rotational axis 1 la of the main shaft 11 as the teeth portion 33 of thedriver 34. The control unit 25 receives information from a number of operationparameters 42. The control unit 25 also receives information from a first sensor 43about the speed of the main shaft 11 and from a second sensor 44 about the speed ofthe output shaft 23.

Fig. 2 shows the shift sleeve 31 in a low range position. In the low range position, theshift sleeve 31 is out of engagement with the teeth portion 41 of the connectionmember 40 on the planetary wheel carrier 22c. The rotary movement of the main shaft11 is transmitted via the sun wheel 22a, the planetary wheels 22b and the planetarywheel carrier 22c, to the output shaft 23. In this case, the output shaft 23 obtains alower speed than the main shaft 11. In the low range position, the contact surface 35 ofthe shift sleeve 31 is located at a well defined axial distance from the contact surface36 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 deterrnines 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 thedifferent speeds between the main shaft 11 and the output shaft 23. Thus, the actuator26 moves the shift fork 28 and the shift sleeve 31 in an axial direction towards thestationary wall 37 and the third position, which is shown on Fig. 3. When the contactsurface 35 of the shift sleeve 31 comes in contact with the contact surface 36 of thestationary wall 37, the force from the actuator and the friction between the contactsurfaces 35, 36 provide a braking action of the shift sleeve 31, the driver 34 and themain shaft 11. Fig. 3 shows the shift sleeve 31 in the third position. The control unit 25receives substantially continuously information from a first sensor 43 about the speedof the main shaft 11 and from the second sensor 44 about the speed of the output shaft23. As soon as the main shaft 11 has been decelerated to a synchronous speed with theoutput shaft 23, the control unit 25 activates the actuator 26 such that it moves the shiftsleeve 31 in a direction towards the planetary wheel carrier 22c and the high rangeposition. Since the main shaft 11 and the output shaft 23 has a synchronous speed, it ispossible to move the shift sleeve 31 to the high range position in which the teethportion 32 of shift sleeve 31 comes in engagement with the teeth portion 41 of theconnection member 40 which is shown in Fig. 4. In the high range position, the shiftsleeve 31 provides a rotationally fixed connection between the main shaft 11 and theoutput shaft 23 via the driver 34, the shift sleeve 31 and the planetary wheel carrier22c. Consequently, the main shaft 11 and the output shaft 23 rotates with the samespeed in the high range position.

When the control unit 25 deterrnines to shift gear from the high range gear to the lowrange gear in the range gear, it activates the engine connected to the input shaft 3 of thegearbox 2 in order to create a torque free state between the main shaft 11 and theoutput shaft 23 in the gearbox 2. When such a torque-free state is created, the controlunit 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 rangegear comprises a planetary gear (22) arranged between a main shaft (11) and an outputshaft (23) in the gearbox (2) and wherein the gear shifting device (24) comprises a shiftsleeve (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 mainshaft (11) to a low range position in which the planetary gear provides a low gear ratiobetween the main shaft (11) and the output shaft (23) and a high range position inwhich 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 stationaryarranged 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 axialdirection 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 anangle 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, characterisedm 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, characterisedm that the shift sleeve (31) comprises a connection portion (32) by which it isrotationally 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 inthat the range gear (22) comprises a sun wheel (22a) rotationally fixedly connected toa main shaft (11) in the gearbox (2), planetary wheels (22b), and a planetary wheelcarrier (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 movementof 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 conf1gured to provide a rotationally fixedconnection between the driver (34) and a coupling member (40) fixedly arranged onthe planetary Wheel carrier (22c) such that the speed of the main shaft (11) istransmitted 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) comprisingaxial teeth conf1gured 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, characterisedm that the gear change mechanism comprises a control unit (25) configured to controlthe 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) tothe third position in order to brake the rotary movement of the main shaft (11) to asynchronous speed With the output shaft (23) before it initiates a movement of the shiftlevel (31) to the high range position.

12. A gear shifting device according to any one of the preceding claims, characterisedm that the gear shifting device comprises a shift fork transmitting the movements fromthe 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.