Method of controlling a coupling arrangement in a gearbox

Abstract

A method of controlling the coupling arrangement in a gearbox, comprising: displacing the coupling sleeve to the second position by applying a first force on the coupling sleeve in the direction from the first position to the second position, overcoming a spring force acting on the coupling sleeve in the direction from the second position to the first position; relieving the first force on the coupling sleeve when the coupling sleeve is in the second position, and when a reaction force acting on the coupling sleeve overcomes the spring force, which reaction force is a result of torque transferred by the third engagement means on the coupling sleeve; applying the first force on the coupling sleeve in the direction from the first position to the second position, if the coupling sleeve is leaving the second position; and reducing the torque transferred by the coupling sleeve using the second power source.

Claims

1. A method of controlling a coupling arrangement in a gearbox, comprising: a coupling sleeve, which is axially displaceable between a first and second position; a first and second rotatable element, which are connectable to and disconnectable from each other by means of the coupling sleeve; a first power source connected to the first rotatable element; a second power source connected to the second rotatable element; a first engagement means arranged on the first rotatable element; a second engagement means arranged on the second rotatable element a third engagement means arranged on the coupling sleeve; the first and second engagement means are configured to transfer torque between the first and second rotatable element via the third engagement means arranged on the coupling sleeve, and the first and second engagement means are configured to allow an axial displacement of the third engagement means along the first and second engagement means, said method comprising: a) displacing the coupling sleeve to the second position by applying a first force on the coupling sleeve in a direction from the first position to the second position, which overcomes a spring force acting on the coupling sleeve in a direction from the second position to the first position; b) relieving the first force on the coupling sleeve when the coupling sleeve is in the second position, and when a reaction force acting on the coupling sleeve overcomes the spring force acting on the coupling sleeve, which reaction force is a result of the torque transferred by the third engagement means arranged on the coupling sleeve; c) applying the first force on the coupling sleeve in the direction from the first position to the second position if the coupling sleeve is leaving the second position; and d) reducing the torque transferred by the coupling sleeve by means of the second power source.

2. The method according to claim 1, further comprising: e) increasing a torque transferred by the coupling sleeve by means of the first and/or second power source.

3. The method according to claim 2, further comprising: f) returning to step b) when the coupling sleeve is in the second position.

4. The method according to claim 1, further comprising before step b): g) detecting the axial position of the coupling sleeve by means of a position detector element.

5. The method according to claim 1, wherein step d) is performed only if the coupling sleeve will not reach the second position, when the first force is applied on the coupling sleeve.

6. The method according to claim 1, wherein the first, second and third engagement means are splines elements forming a splines connection between the coupling sleeve and the first and second rotatable element.

7. A coupling arrangement comprising: a coupling sleeve, which is axially displaceable between a first and second position; a first and second rotatable element, which are connectable to and disconnectable from each other by means of the coupling sleeve; a first power source connected to the first rotatable element; a second power source connected to the second rotatable element; a first engagement means arranged on the first rotatable element; a second engagement means arranged on the second rotatable element; a third engagement means arranged on the coupling sleeve; the first and second engagement means are configured to transfer torque between the first and second rotatable element via the third engagement means arranged on the coupling sleeve, and the first and second engagement means are configured to allow an axial displacement of the third engagement means along the first and second engagement means, wherein the coupling arrangement is controlled by: a) displacing the coupling sleeve to the second position by applying a first force on the coupling sleeve in a direction from the first position to the second position, which overcomes a spring force acting on the coupling sleeve in a direction from the second position to the first position; b) relieving the first force on the coupling sleeve when the coupling sleeve is in the second position, and when a reaction force acting on the coupling sleeve overcomes the spring force acting on the coupling sleeve, which reaction force is a result of the torque transferred by the third engagement means arranged on the coupling sleeve; c) applying the first force on the coupling sleeve in the direction from the first position to the second position if the coupling sleeve is leaving the second position; and d) reducing the torque transferred by the coupling sleeve by means of the second power source.

8. A gearbox comprising a coupling arrangement comprising: a coupling sleeve, which is axially displaceable between a first and second position; a first and second rotatable element, which are connectable to and disconnectable from each other by means of the coupling sleeve; a first power source connected to the first rotatable element; a second power source connected to the second rotatable element; a first engagement means arranged on the first rotatable element; a second engagement means arranged on the second rotatable element; a third engagement means arranged on the coupling sleeve; the first and second engagement means are configured to transfer torque between the first and second rotatable element via the third engagement means arranged on the coupling sleeve, and the first and second engagement means are configured to allow an axial displacement of the third engagement means along the first and second engagement means, wherein the coupling arrangement is controlled by: a) displacing the coupling sleeve to the second position by applying a first force on the coupling sleeve in a direction from the first position to the second position, which overcomes a spring force acting on the coupling sleeve in a direction from the second position to the first position; b) relieving the first force on the coupling sleeve when the coupling sleeve is in the second position, and when a reaction force acting on the coupling sleeve overcomes the spring force acting on the coupling sleeve, which reaction force is a result of the torque transferred by the third engagement means arranged on the coupling sleeve; c) applying the first force on the coupling sleeve in the direction from the first position to the second position if the coupling sleeve is leaving the second position; and d) reducing the torque transferred by the coupling sleeve by means of the second power source.

9. A vehicle comprising a gearbox having a coupling arrangement comprising: a coupling sleeve, which is axially displaceable between a first and second position; a first and second rotatable element, which are connectable to and disconnectable from each other by means of the coupling sleeve; a first power source connected to the first rotatable element; a second power source connected to the second rotatable element; a first engagement means arranged on the first rotatable element; a second engagement means arranged on the second rotatable element; a third engagement means arranged on the coupling sleeve; the first and second engagement means are configured to transfer torque between the first and second rotatable element via the third engagement means arranged on the coupling sleeve, and the first and second engagement means are configured to allow an axial displacement of the third engagement means along the first and second engagement means, wherein the coupling arrangement is controlled by: a) displacing the coupling sleeve to the second position by applying a first force on the coupling sleeve in a direction from the first position to the second position, which overcomes a spring force acting on the coupling sleeve in a direction from the second position to the first position; b) relieving the first force on the coupling sleeve when the coupling sleeve is in the second position, and when a reaction force acting on the coupling sleeve overcomes the spring force acting on the coupling sleeve, which reaction force is a result of the torque transferred by the third engagement means arranged on the coupling sleeve; c) applying the first force on the coupling sleeve in the direction from the first position to the second position if the coupling sleeve is leaving the second position; and d) reducing the torque transferred by the coupling sleeve by means of the second power source.

10. A computer program product comprising program code stored on a non-transitory computer-readable medium, said computer program product for controlling a coupling arrangement in a gearbox, comprising: a coupling sleeve, which is axially displaceable between a first and second position; a first and second rotatable element, which are connectable to and disconnectable from each other by means of the coupling sleeve; a first power source connected to the first rotatable element; a second power source connected to the second rotatable element; a first engagement means arranged on the first rotatable element; a second engagement means arranged on the second rotatable element; a third engagement means arranged on the coupling sleeve; the first and second engagement means are configured to transfer torque between the first and second rotatable element via the third engagement means arranged on the coupling sleeve, and the first and second engagement means are configured to allow an axial displacement of the third engagement means along the first and second engagement means wherein said computer program code comprises computer instructions to cause said at least one control unit to cause components of the coupling arrangement to perform the following operations: a) displacing the coupling sleeve to the second position by applying a first force on the coupling sleeve in a direction from the first position to the second position, which overcomes a spring force acting on the coupling sleeve in a direction from the second position to the first position; b) relieving the first force on the coupling sleeve when the coupling sleeve is in the second position, and when a reaction force acting on the coupling sleeve overcomes the spring force acting on the coupling sleeve, which reaction force is a result of the torque transferred by the third engagement means arranged on the coupling sleeve; c) applying the first force on the coupling sleeve in the direction from the first position to the second position if the coupling sleeve is leaving the second position; and d) reducing the torque transferred by the coupling sleeve by means of the second power source.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Below is a description of, as examples, preferred embodiments of the invention with reference to the enclosed drawings, in which:

(2) FIG. 1 schematically illustrates a vehicle provided with a coupling arrangement according to the invention,

(3) FIG. 2 shows a sectional view of a gearbox provided with a coupling arrangement according to the invention,

(4) FIGS. 3a and 3b show sectional views of a coupling arrangement in a first and second position according to the invention, and

(5) FIG. 4 shows a flow diagram of a method for controlling the gearbox according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(6) FIG. 1 schematically illustrates a vehicle 1 provided with a coupling arrangement 2 according to the invention. The vehicle 1 includes a powertrain 6, which comprises a power source 14, 16 a gearbox 8 and a propeller shaft 12. The power source 14, 16 is coupled to the gearbox 8, and comprises an internal combustion engine 14 or an electrical machine 16 or a combination thereof. The gearbox 8 is further connected to drive wheels 20 of the vehicle 1 via the propeller shaft 12. The gearbox 8 is surrounded by a gearbox housing 22.

(7) FIG. 2 shows a sectional view of the gearbox 8 provided with a coupling arrangement 2 according to the invention. The internal combustion engine 14 is connected to the gearbox 8 via the coupling arrangement 2, which comprises an axially movable coupling sleeve 24. The axially movable coupling sleeve 24 is displaced axially in order to be brought into engagement with a first rotatable element 26, such as an output shaft 26 of the internal combustion engine 14 and a second rotatable element 28, such as an intermediate shaft 28 in the gearbox 8.

(8) A first engagement means 29 is arranged on the first rotatable element 26, a second engagement means 31 is arranged on the second rotatable element 28 and a third engagement means 33 is arranged on the first coupling sleeve 24. The first and second engagement means 29, 31 are configured to transfer torque T.sub.S between the first and second rotatable element 26, 28 via the third engagement means 33 arranged on the coupling sleeve 24. Also, the first and second engagement means 29, 31 are configured to allow an axially displacement of the third engagement means 33 along the first and second engagement means 29, 31. According to an embodiment of the invention the first, second and third engagement means 29, 31, 33 are splines, so that the axially movable coupling sleeve 24 engages the output shaft 26 of the internal combustion engine 14 and the intermediate shaft 28 in the gearbox 8 by means of a splines connection 34.

(9) In a first axial position of the axially movable coupling sleeve 24, the output shaft 26 of the internal combustion engine 14 is disengaged from the intermediate shaft 28. In this axially disengaged position, the axially movable coupling sleeve 24 is engaged only with the intermediate shaft 28 and will rotate together with the intermediate shaft 28 by means of the splines connection 34 between the axially movable coupling sleeve 24 and the intermediate shaft 28. In a second axial position of the axially movable coupling sleeve 24 the output shaft 26 of the internal combustion engine 14 and the intermediate shaft 28 are engaged by means of the axially movable coupling sleeve 24. This second axial position of the axially movable coupling sleeve 24 is illustrated in FIG. 2.

(10) The intermediate shaft 28 is connected to an input shaft 42 of a main gearbox 43. An output shaft 48 of the main gearbox 43 is connected to an input shaft 50 of a range gearbox 52, which is schematically disclosed in FIG. 2. The range gearbox 52 is connected to the drive wheels 20 of the vehicle 1.

(11) The electrical machine 16 is arranged to add torque to the powertrain 6 but also to brake the powertrain 6. A rotor 64 of the electrical machine 16 is connected to the intermediate shaft 28. The electrical machine 16 may be designed to provide enough power and torque to the driving wheels 8 for propulsion of the vehicle 1 without using the internal combustion engine 14. Power to the electrical machine 16 may be provided from an energy storage 68 such as an electrochemical energy storage arranged in the vehicle 1 or from an external energy storage such as wires or other electrical conducting means (not disclosed) in the environment where the vehicle 1 is used. The energy storage 68 may also receive electrical power from the electrical machine 16 when the electrical machine 16 generates brake torque on the input shaft 42 of the main gearbox 43.

(12) An electronic control unit 88 is coupled to the gearbox 8, the internal combustion engine 14, the electrical machine 16 and to a pneumatic element 90. A position detecting element 91 is connected to the control unit 88. The position detecting element 91 shown in FIG. 2 is arranged for detecting the axial position of the coupling sleeve 24. Thus, the first and second position of the coupling sleeve 24 and also any position there between may be detected by means of the position detecting element 91. A number of not shown speed sensors in the gearbox 8, and in the internal combustion engine 14 may be connected to the control unit 88. Another computer 72 may also be connected to the control unit 88. The control unit 88 may be a computer 72 with appropriate software for this purpose. The control unit 88 and/or the computer 72 comprise a computer program P, which can include routines to control the gearbox 8. The program P may be stored in an executable form or compressed form in a memory M and/or in a read/write memory. Preferably there is provided a computer program product comprising a program code stored on a, by a computer readable medium for performing gear shifting in the gearbox 8, when said program is run on the control unit 88 or another computer 72 connected to the control unit 88. Said code may be non-volatile, stored in said computer readable medium.

(13) The pneumatic element 90 is by means of an air pressure arranged to generate a first force F.sub.1 on the coupling sleeve 24 to axially displace the coupling sleeve 24 in the direction from the first position to the second position in order to connect the first and second rotatable element 26, 28. A spring 92 is arranged, by means of its spring force F.sub.S, to axially displace the coupling sleeve 24 in the direction from the second position to the first position in order to disconnect the first and second rotatable element 26, 28. The axial displacement of the axially movable coupling sleeve 24 may also be provided with one or more actuating cylinders (not disclosed), which serves to axially displace the coupling sleeve 24 between the first and second position. Such actuating cylinders may be of pneumatic, hydraulic; or electric type.

(14) FIGS. 3a and 3b show sectional views of the coupling arrangement 2 in a first and second position according to the invention. In FIG. 3a the coupling sleeve 24 is in the first, disengaged position and in FIG. 3b the coupling sleeve 24 is in the second, engaged position.

(15) According to the embodiment shown in FIGS. 3a and 3b the first, second and third engagement means 29, 31, 33 are splines, so that the axially movable coupling sleeve 24 engages the output shaft 26 of the internal combustion engine 14 and the intermediate shaft 28 in the gearbox 8 by means of the splines connection 34.

(16) In the first, axially disengaged position, the axially movable coupling sleeve 24 is engaged only with the intermediate shaft 28 and will rotate together with the intermediate shaft 28 by means of the splines connection 34 between the axially movable coupling sleeve 24 and the intermediate shaft 28. The spring force F.sub.S from the spring 92, acts on the coupling sleeve 24 in the direction from the second position to the first position in order to disconnect the first and second rotatable element 26, 28. The first force F.sub.1 emanating from the air pressure from the pneumatic element 90 which acts on the coupling sleeve 24 is zero or substantially zero when the coupling sleeve 24 is in the first position.

(17) In FIG. 3b the axially movable coupling sleeve 24 has been displaced axially to the second position in order to engage the output shaft 26 of the internal combustion engine 14 with the intermediate shaft 28 in the gearbox 8. The axial displacement of the coupling sleeve 24 has been provided by increasing the first force F.sub.1, so that it overcomes the spring force F.sub.S, so that coupling sleeve 24 is displaced in the direction from the first position to the second position in order to connect the first and second rotatable element 26, 28. Such and axially displacement of the coupling sleeve 24 is possible when the speed of first and second rotatable elements 26, 28 has been substantially synchronized or when the first and second rotatable elements 26, 28 are in a stand still condition.

(18) When the coupling sleeve 24 has been displaced to the second position in order to connect the rotatable elements 26, 28 the coupling sleeve 24 will transfer a torque Ts between the rotatable elements 26, 28. The torque Ts is generated by the internal combustion engine 14 and will generate a reaction force F.sub.R in the splines connection 34, which fixates the coupling sleeve 24 on the rotatable elements 26, 28. If the torque from the internal combustion engine 14 is large enough the force from the pneumatic element 90 may be relieved and the coupling sleeve 24 will be fixed in the axially direction due to the reaction force F.sub.R.

(19) However, the coupling sleeve 24 will move away from the second position if the torque T.sub.S transferred by the coupling sleeve 24 is not large enough to generate a reaction force F.sub.R which is larger than the spring force F.sub.S acting on the coupling sleeve 24. Also, due to vibrations and oscillations in the coupling arrangement 2 and some possible misalignment between the coupling sleeve 24 and the rotatable elements 26, 28 there the spring force F.sub.S may overcome the reaction force F.sub.R and the coupling sleeve 24 will move away from the second position. As a result the coupling sleeve 24 may be displaced axially by the spring force F.sub.S and the rotatable elements 26, 28 will be disconnected.

(20) This problem may be solved by activating the pneumatic element 90, so that the first force F.sub.1 overcomes the spring force F.sub.S. As a result the coupling sleeve 24 may be displaced in the direction from the first position to the second position and thus be returned to the second position.

(21) However, if the reaction force F.sub.R that fixates the coupling sleeve 24 on the rotatable elements 26, 28, is larger than the first force F.sub.1 generated by the air pressure from the pneumatic element 90 the coupling sleeve 24 will not be axially displaced. According to the invention the torque T.sub.S transferred by the coupling sleeve 24 will be reduced by means of the electrical machine 16 if the coupling sleeve 24 is not axially displaced. Since the electrical machine 16 is arranged to exert torque on the intermediate shaft 28 it is possible to activate the electrical machine 16 and reduce the torque T.sub.S transferred by the coupling sleeve 24. The torque exerted by the electrical machine 16 on the intermediate shaft 28 will thus reduce the influence of the torque generated by means of the internal combustion engine 14. As a result, the reaction force F.sub.R will be reduced which means that the first force F.sub.1 may overcome the spring force F.sub.S. As a result, the coupling sleeve 24 may be displaced in the direction from the first position to the second position and thus be returned to the second position.

(22) The method of controlling the coupling arrangement 2 in the gearbox 8, comprises the steps of:

(23) a. displacing the coupling sleeve 24 to the second position by applying a first force F.sub.1 on the coupling sleeve 24 in the direction from the first position to the second position, which overcomes a spring force F.sub.S acting on the coupling sleeve 24 in the direction from the second position to the first position;

(24) b. relieving the first force F.sub.1 on the coupling sleeve 24 when the coupling sleeve 24 is in the second position, and when a reaction force F.sub.R acting on the coupling sleeve 24 overcomes the spring force F.sub.S acting on the coupling sleeve 24, which reaction force F.sub.R is a result of the torque T.sub.S transferred by the third engagement means 33 arranged on the coupling sleeve 24;

(25) c. applying the first force F.sub.1 on the coupling sleeve 24 in the direction from the first position to the second position if the coupling sleeve 24 is leaving the second position; and

(26) d. reducing the torque T.sub.S transferred by the coupling sleeve 24 by means of the second power source 16.

(27) According to the invention the torque T.sub.S transferred by the coupling sleeve 24 will be reduced by means of the second power source 16 if the coupling sleeve 24 is not axially displaced when applying the first force F.sub.1. The torque exerted by the second power source 16 on the second rotatable element 28 will thus reduce the influence of the torque generated by means of the a first power source 14. As a result, the reaction force F.sub.R will be reduced which means that the first force F.sub.1 may overcome the spring force F.sub.S. As a result, the coupling sleeve 24 may be displaced in the direction from the first position to the second position and thus be returned to the second position.

(28) According to an embodiment, the method comprises the further step of:

(29) e) increasing the torque T.sub.S transferred by the coupling sleeve 24 by means of the first and/or second power source 14, 16.

(30) According to a further embodiment, the method comprises the further step of:

(31) f) returning to step b) when the coupling sleeve 24 is in the second position.

(32) Before step b) an embodiment of the method comprises the further step of:

(33) g) detecting the axial position of the coupling sleeve 24 by means of a position detector element 91. The position detector element 91 will detect when the coupling sleeve 24 is in the second position, and also detect if the coupling sleeve 24 moves away from the second position. Thus, the method steps b)-e) for returning the coupling sleeve 24 to the second position will take effect.

(34) Step d) is according to an embodiment of the method performed only if the coupling sleeve 24 will not reach the second position when the first force F.sub.1 is applied on the coupling sleeve 24.

(35) According to a further embodiment the method the first, second and third engagement means 29, 31, 33 are splines elements forming a splines connection 34 between the coupling sleeve 24 and the first and second rotatable element 26, 28.

(36) According to an embodiment of the invention the first force F.sub.1 may be applied when the torque T.sub.S transferred by the third engagement means 33 is below a predetermined value due to driving characteristics of the vehicle 1.

(37) The components and features specified above may within the framework of the invention be combined between the different embodiments specified.