WO2012070939A2

WO2012070939A2 - Driving mechanism as well as method for driving a vehicle

Info

Publication number: WO2012070939A2
Application number: PCT/NL2011/050801
Authority: WO
Inventors: Roëll Marie van Druten; Alexander Franciscus Anita Serrarens; Bas Gerard Vroemen
Original assignee: Dti Group B.V.
Priority date: 2010-11-24
Filing date: 2011-11-24
Publication date: 2012-05-31
Also published as: WO2012070939A3

Abstract

A driving mechanism for a vehicle, comprises: - a drive source, - a launching module having an input which is connected to the drive source and an output, which module comprises a brake as well as a planetary gear set having at least three rotational members, of which a first rotational member is connected to the input, a second rotational member is connected to the output and a third rotational member is connected to the brake, - a transmission provided with a transmission housing, which transmission comprises an input shaft which is connected to the output of the launching module, and an output shaft, as well as at least one switchable or controllable speed transforming gear, and - an end drive having an input which is connected to the output shaft of the transmission, and an output. The brake concerned is a dry plate friction brake.

Description

Driving mechanism as well as method for driving a vehicle

DESCRIPTION: Field of the invention.

The invention relates to a driving mechanism for a vehicle, comprising

- a drive source,

- a launching module having an input which is connected to the drive source and an output, which module comprises a brake as well as a planetary gear set having at least three rotational members, of which a first rotational member is connected to the input, a second rotational member is connected to the output and a third rotational member is connected to the brake,

- a transmission provided with a transmission housing, which transmission comprises an input shaft which is connected to the output of the launching module, and an output shaft, as well as at least one switchable or controllable speed transforming gear , and

- an end drive having an input which is connected to the output shaft of the transmission, and an output.

The transmission ratio between the input and output shafts of the transmission can preferably adopt two different values. Furthermore, the drive source may here be for example a combustion engine and or electromotor and the end drive may for example be a fixed reduction and/or a differential.

State of the art A driving mechanism of this type is generally known. When the known driving mechanism is used in a vehicle, relatively much energy is lost on cooling the brake of the launching module when the vehicle is being launched and if the transmission is arranged as a CVT (Continuous Variable Transmission) variator on the operation of this variator. Summary of the invention It is an object of the invention to provide a driving mechanism of the type defined in the opening paragraph in which less energy is needed for cooling the brake and optionally for the operation of the variator. For this purpose the driving mechanism according to the invention is characterised in that the brake is a dry-plate friction brake. As a result, no cooling is needed (which is usually oil cooling) for launching the vehicle from a halted position. By arranging the launching module and end drive in such a way that they have large transmission ratios, the transmission can be arranged as a relatively small CVT variator which has a higher efficiency than a large CVT variator and, in addition, requires less oil flow for it to be operated. Since no cooling is needed for launching the vehicle and less oil flow for the operation of the variator, it will furthermore be sufficient to install a relatively small oil pump.

The brake is preferably located in a dry space, so that fewer liquid sealings are necessary than if the brake were accommodated in a wet space of, for example, the transmission. This dry space may be, for example, a space between the transmission housing and a housing section fitted against this housing.

The brake preferably comprises two brake plates, as well as a brake disc which is positioned between the brake plates and is covered with friction material, the brake disc being connected to the third rotational member of the planetary gear set and the brake plates being connected to the transmission housing. This provides that the heat that is developed during the braking action is properly dissipated to the transmission housing.

The driving mechanism preferably includes cooling means which actively cool the brake plates with cooling agent from the drive source or with oil from the transmission.

The planetary gear set may also be located in the dry space which does away with the need for a sealing means between the brake and the planetary gear set. In that case the planetary gear set is preferably grease-lubricated.

Furthermore, the driving mechanism preferably includes a short-circuit clutch which can connect together two of the rotational members of the planetary gear set.

The short-circuit clutch may be positioned between the input and the output or between the rotational members of the launching module which are connected to the input and the output, but as conditions dictate, it may be more advantageous for the short-circuit clutch to be positioned between the brake or the third rotational member connected to it, on the one hand, and the input or output of the launching module or the first or second rotational member connected to it, on the other. The short-circuit clutch is preferably positioned in a wet space of the driving mechanism, for example, inside the transmission housing, and is preferably operated by means of a plunger which is located in the transmission housing, a spline bearing being present between the plunger and the short-circuit clutch.

The rotational members of the planetary gear set are preferably formed by a sun gear, a planet carrier and a ring gear, while the brake is preferably connected to the sun gear. The planetary gear set is preferably a retarding gear set if the latter is braked.

For mounting the launching module in a simple fashion, its input and output are connected to the drive source and the input shaft of the transmission preferably by means of spline connections.

The driving mechanism preferably comprises an oil pump which is connected to the input of the launching module and/or to an electromotor and can be driven by the drive source and/or the electromotor. Preferably a freewheel bearing/freewheel bearing clutch is positioned between the drive source and the oil pump and/or between the electromotor and the oil pump.

The driving mechanism furthermore preferably comprises a hydraulic system the oil pump forms part of, as well as a main conduit connected to the output of the oil pump and in which there is a conduit pressure regulated by the oil pump, and an oil tank connected to the input of the oil pump, which hydraulic system further includes control valves for operating hydraulically controlled components, such as the brake and the CVT variator, as well as an accumulator which is connected to the main conduit. The control valves may then control the pressure on the primary pulley and the pressure on the secondary pulley of the variator preferably independently of each other, and, preferably, the electromotor drives the oil pump in an intermittent fashion to keep the accumulator at the proper pressure level.

The hydraulic system furthermore preferably includes an open/close valve which is positioned between the oil pump and the accumulator and preferably a non-return valve which is positioned between the oil pump and the main conduit.

In addition, the hydraulic system preferably includes a further open/close valve which is positioned between the output of the oil pump and the oil tank and by which the conduit pressure produced by the oil pump can be lowered in an intermittent fashion. The low-pressure oil may then be used for lubrication of transmission components.

The hydraulic system further preferably includes an overpressure valve which is positioned between the output of the oil pump and the oil tank or is integrated with the further open/close valve. This overpressure valve determines the lubricating pressure in the hydraulic system.

The turning directions of the input and output of the launching module are preferably equal to each other.

An end clutch for selecting the forward gear is preferably positioned between the output shaft of the transmission and the end drive. This end drive preferably comprises two gear trains.

An additional speed transforming gear forming the reverse transmission is preferably positioned between the variator and the output of the end drive. Preferably one of the gear wheels of the end drive forms part of the additional speed transforming gear.

Between the output shaft of the transmission and the additional speed transforming gear there is preferably positioned a reverse clutch by means of which the reverse gear can be selected.

The reverse clutch and the end clutch are preferably operated by a single actuation element which can adopt three positions, which are: reverse clutch closed, end clutch closed and both clutches open. This reverse clutch and end clutch are preferably arranged as claw clutches and/or synchronizers.

A highly advantageous embodiment of the driving mechanism according to the invention is characterised in that the drive mechanism does not include a cooler. Thanks to the dry launching module no large cool flow is needed and, in consequence, no cooler either (this may be a heat exchange that may be either air-cooled or water-cooled (preferably coupled to the cooling circuit of the drive source)). Owing to the lack of a torque converter as a launching module there is no need for a large oil flow either. Since a cooler and a torque converter are usually the dominant users of the oil flow, the oil pump may have a much smaller design. Since the launching module comprises a dry brake which can dissipate its heat to the transmission housing, a proper cooling without oil is guaranteed.

The invention likewise relates to a method for driving a vehicle that is provided with a driving mechanism according to the invention, which vehicle further includes wheels that are connected to the output of the end drive. With regard to the method the invention is characterised in that by actuating the brake the vehicle is accelerated from a halted position. Preferably, after the brake has been actuated, the short-circuit clutch is energized and the brake is opened to further accelerate the vehicle. The latter operation is preferably carried out when the highest speed in the variator is reached and it is desired to further reduce the number of revolutions of the combustion engine. In an advantageous embodiment of the method according to the invention the number of revolutions of the engine is lowered when a change is made from brake to short- circuit clutch.

The change from brake to the short-circuit clutch is preferably made without the CVT variator significantly changing its gear setting, or if the variator changes its gear ratio retarding towards the output, or if the desired power drops below a certain limit value.

Brief description of the drawings. The invention will be described below in more detail based on an example of embodiment of the driving mechanism according to the invention represented in the drawing figures, in which:

Fig. 1 shows a lay-out of an embodiment of the driving mechanism according to the invention;

Fig. 2 gives a diagrammatic representation of the driving mechanism shown in

Fig. 1; and

Fig. 3 shows the hydraulic system of the driving mechanism shown in Figs. 1 and 2. Detailed description of the drawings

Fig. 1 shows a lay-out of an embodiment of the driving mechanism according to the invention. The driving mechanism 1 is present in a vehicle of which only the differential 3 and the drive shafts 5 to the wheels are shown. The driving mechanism comprises a drive source 7 which is formed in this embodiment by a combustion engine, but which may also be formed, for example, by an electromotor. On the output shaft 9 of the drive shaft is positioned a flywheel 11 which is connected to the input 15 of a launching module 17 via torsion dampers 13. The output 19 of the launching module is connected to the input shaft 21 of a transmission forming part of the driving mechanism. In this embodiment this transmission is formed by a CVT variator 23 whose output shaft 25 is connected to the input 27 of an end drive 29 forming part of the driving mechanism. The output 31 of the end drive is connected to the differential 3 of the vehicle. This end drive 29 is formed by two gear trains 33 and 35. An additional speed transforming gear 37 fonning the reverse transmission is positioned between the variator 23 and the output 31 of the end drive. One of the gears 35 of the end drive forms part of this additional speed transforming gear 37.

Between the output shaft 25 of the transmission and the end drive 29 is positioned an end clutch D and between the output shaft 25 of the transmission and the additional speed transforming gear 37 is positioned a reverse clutch R. By means of these two clutches a selection may be made between driving forward and reversing. Both clutches D and R are arranged as claw clutches and or synchronizers and are operated by a single actuation body that may adopt three positions which are: reverse clutch R closed, end clutch D closed and both clutches open.

The launching module 17 is formed by a planerary gear set 39 comprising three rotational members of which a first rotational member 41 is connected to the input 15, a second rotational member 43 is connected to the output 19 and a third rotational member 45 is connected to a brake 47. The turning directions of the input 15 and output 19 of the launching module 17 are equal to each other.

Between the first and the second rotational member 41 and 43 respectively of the planetary gear set is positioned a short-circuit clutch 49 by means of which these two rotational members can be connected to each other. Alternatively, it is possible for the short- circuit clutch to be positioned between, on the one hand, the third rotational member and, on the other hand, the first or second rotational member, which is indicated by means of dotted lines.

Fig. 2 diagrammatically shows the driving mechanism 1. The variator 23, end drive 29 with additional speed transforming gear 37 and the differential 3 are located inside the transmission housing 51. A housing part 53, which accommodates the planetary gear set 39 of the launching module and the short-circuit clutch 49, is fitted against this transmission housing. The space in the transmission housing 51 as well as the space between the housing part 53 and the transmission housing are wet spaces. This short-circuit clutch 49 is formed by a multiple wet-plate clutch and is operated by means of a plunger 55 which is located in the transmission housing 51. A spline bearing 57 is positioned between the plunger 55 and the short-circuit clutch 49.

The brake 47 is a dry-plate friction brake and is located in a dry space between the flywheel 11 and the housing part 53. Sealing rings 59 are positioned between the dry and wet spaces. The brake 47 comprises two brake plates 61 and a brake disc 63 positioned in between and which is covered with friction material. The brake plates 61 are connected to the transmission housing 51 and are actively cooled with cooling agent from the drive source or with oil from the transmission. The brake plate 63 is connected to the third rotational member 45 of the planetary gear set which is formed by the sun gear of the planetary gear set. The ring gear 41 of the planetary gear set is connected to the input 15 and the planet carrier 43 is connected to the output 19 of the launching module. The planetary gear set 39 is a speed retarding gear set if the brake 47 is closed.

The input and output 15 and 19 respectively of the launching module 17 are connected by means of spline connections 65 to the drive source 7 and the input shaft 21 of the transmission.

The drive mechanism comprises a hydraulic system for operating the brake and clutches and the variator. The hydraulic system 1 comprises an oil pump 67 (cf. Fig. 1) which is connected to the input 15 of the launching module 17.

Fig. 3 shows the hydraulic system 71 of the driving mechanism. The hydraulic system comprises a main conduit 73 connected to the oil pump 67 in which main conduit there is a conduit pressure that is maintained by the oil pump. The input 68 of the oil pump 67 is connected to an oil tank 75. The hydraulic system 71 further includes a plurality of control valves 77 for operating the hydraulically controlled parts such as the brake 47, the CVT variator 21 , the end clutch D, the reverse clutch R and the short-circuit clutch 49, as well as an accumulator 79 which is connected to the main conduit 73. These control valves 77 are capable of controlling the pressure on the primary pulley 81 and the pressure on the secondary pulley 83 of the variator 23 independently of each other.

The oil pump 67 is connected to an electromotor 85 and to the drive source 7 and can be driven by both these driving devices. Between the drive source 7 and the oil pump

67 and between the electromotor 85 and the oil pump 67 are positioned freewheel bearings / freewheel bearing clutches 87. The electromotor 85 can drive the oil pump 67 in an intermittent fashion to keep the accumulator 79 at the proper pressure level. Between the oil pump 67 and the accumulator 79 is positioned an open/close valve 89 and between the output

68 of the oil pump 67 and the oil tank 75 is positioned a further open/close valve 91, by means of which the conduit pressure produced by the oil pump can be lowered in an intermittent fashion. Between the output 69 of the oil pump 67 and the oil tank 75 is positioned an overpressure valve 93 and between the oil pump 67 and the main conduit 73 is positioned a non-return valve 95.

The open/close valve 89 between the hydraulic accumulator and conduit pressure is closed when the drive source 7 is stopped and, when an increased conduit pressure is desired, the further open/close valve 91 is closed to increase the oil pump pressure. When a very rapid increase of the conduit pressure is desired, the further open/close valve 91 is closed to increase the oil pump pressure and simultaenously, or shortly afterwards, the open/close valve 89 between the hydraulic accumulator and the main conduit is closed.

Albeit the invention has been described in the foregoing based on the drawings, it should be observed that the invention is not by any manner or means restricted to the embodiment shown in the drawings. The invention also extends to all embodiments deviating from the embodiment shown in the drawings within the spirit and scope defined by the claims. For example, an electromotor/generator or a flywheel may be coupled to one of the shafts of the driving mechanism. In the situation where a flywheel is coupled to one of the shafts of the driving mechanism, a clutch may be positioned between the flywheel and this shaft.

Claims

CLAIMS:

1. A driving mechanism (1) for a vehicle, comprising

- a drive source (7),

- a launching module (17) having an input (15) which is connected to the drive source and an output (19), which module comprises a brake (47) as well as a planetary gear set (39) having at least three rotational members, of which a first rotational member (41) is connected to the input, a second rotational member (43) is connected to the output and a third rotational member (45) is connected to the brake,

- a transmission (23) provided with a transmission housing (51), which transmission comprises an input shaft (21) which is connected to the output of the launching module, and an output shaft (25), as well as at least one switchable or controllable speed transforming gear, and

- an end drive (29) having an input (27) which is connected to the output shaft of the transmission, and an output (31),

characterised in that the brake (47) is a dry-plate friction brake.

2. A driving mechanism as claimed in claim 1, characterised in that the brake (47) is located in a dry space.

3. A driving mechanism as claimed in claim 1 or 2, characterised in that the brake (47) comprises two brake plates (61), as well as a brake disc (63) which is positioned in between the brake plates and is covered with friction material, the brake disc being connected to the third rotational member (45) of the planetary gear set and the brake plates being connected to the transmission housing ( 1 )

4. A driving mechanism as claimed in claim 3, characterised in that the driving mechanism comprises cooling means which actively cool the brake plates (61) with cooling agent coming from the drive source (7) or with oil from the transmission (23).

5. A driving mechanism as claimed in any one of the previous claims, characterised in that the planetary gear set (39) is located in the dry space.

6. A driving mechanism as claimed in claim 5, characterised in that the planetary gear set (39) is grease-lubricated.

7. A driving mechanism as claimed in any one of the previous claims, characterised in that the driving mechanism comprises a short-circuit clutch (49) which can connect together two of the rotational members of the planetary gear set (39).

8. A driving mechanism as claimed in claim 7, characterised in that the short- circuit clutch (49) is positioned between the brake (47) or the third rotational member (45) connected to the brake, on the one hand, and the input (15) or output (19) of the launching mopdule (17) or the first or second rotational member (41, 43) connected to it, on the other.

9. A driving mechanism as claimed in claim 7 or 8, characterised in that the short-circuit clutch (49) is located in a wet space of the driving mechanism.

10. A driving mechanism as claimed in claim 7, 8 or 9, characterised in that the short-circuit clutch (49) is operated by means of a plunger (55) which is located in the transmission housing (51), a spline bearing (57) being present between the plunger and the short-circuit clutch.

11. A driving mechanism as claimed in any one of the previous claims, characterised in that the rotational members (41, 43, 45) are formed by a sun gear, a planet carrier and a ring gear while the brake (47) is connected to the sun gear.

12. A driving mechanism as claimed in any one of the previous claims, characterised in that the planetary gear set (39) is a speed retarding gear set if the latter is braked.

13. A driving mechanism as claimed in any one of the previous claims, characterised in that the input and output (15, 19) respectively, of the launching module (17) are connected by means of spline connections (65) to the drive source (7) and the input shaft (21) of the transmission (23).

14. A driving mechanism as claimed in any one of the previous claims, characterised in that the transmission (23) comprises a CVT variator having at least a single controllable, variable transmission.

15. A driving mechanism as claimed in any one of the previous claims, characterised in that the driving mechanism comprises an oil pump (67) which is connected to one of the parts of the driving mechanism.

16. A driving mechanism as claimed in claim 15, characterised in that the oil pump (67) is connected to the input (15) of the launching module (17).

17. A driving mechanism as claimed in claim 16, characterised in that a freewheel bearing/freewheel clutch bearing (87) is positioned between the drive source (7) and the oil pump (67).

18. A driving mechanism as claimed in claim 15, 16 or 17, characterised in that the driving mechanism comprises an electromotor (85) which is connected to the oil pump (67).

19. A driving mechanism as claimed in claim 18, characterised in that a further freewheel bearing/freewheel clutch bearing (87) is positioned between the electromotor (85) and the oil pump (67).

20. A driving mechanism as claimed in any one of the previous claims 15 to 19, characterised in that the driving mechanism comprises a hydraulic system (71) the oil pump

(67) forms part of, as well as a main conduit (73) connected to the output (69) of the oil pump and in which there is a conduit pressure regulated by the oil pump, and an oil tank (75) connected to the input (68) of the oil pump, which hydraulic system further includes control valves (77) for operating hydraulically controlled components, such as the brake (47) and the CVT variator (23), as well as an accumulator (79) which is connected to the main conduit.

21. A driving mechanism as claimed in claims 18 and 20, characterised in that the electromotor (85) drives the oil pump (67) in an intermittent fashion to keep the accumulator (79) at the proper pressure level.

22. A driving mechanism as claimed in claim 20 or 21, characterised in that the hydraulic system (71) further includes an open/close valve (89) which is positioned between the oil pump (67) and the accumulator (79).

23. A driving mechanism as claimed in claim 20, 21 or 22, characterised in that the control valves (77) can control the pressure on the primary pulley (81) and the pressure on the secondary pulley (83) of the variator (23) independently of each other.

24. A driving mechanism as claimed in any one of the previous claims 20 to 23, characterised in that the hydraulic system (71) further comprises a non-return valve (95) which is positioned between the oil pump (67) and the main conduit (73).

25. A driving mechanism as claimed in any one of the previous claims 20 to 24, characterised in that the hydraulic system (71) further includes a further non-return valve (91) which is positioned between the output (69) of the oil pump (67) and the oil tank (75) and by which the conduit pressure produced by the oil pump can be lowered in an intermittent fashion.

26. A driving mechanism as claimed in claim 25, characterised in that the hydraulic system (71) further includes an overpressure valve (93) which is positioned between the output (69) of the oil pump (67) and the oil tank (75) or is integrated with the further open close valve (91).

27. A driving mechanism as claimed in any one of the previous claims, characterised in that the turning directions of the input (15) and output (19) of the launching module (17) are equal to each other.

28. A driving mechanism as claimed in any one of the previous claims, characterised in that an end clutch (D) is positioned between the output shaft (25) of the transmission (23) and the end drive (29).

29. A driving mechanism as claimed in any one of the previous claims, characterised in that an end drive comprises two gear trains (33, 35).

30. A driving mechanism as claimed in any one of the previous claims, characterised in that an additional speed transforming gear (37) forming the reverse transmission is positioned between the variator (23) and the output (31) of the end drive (29).

31. A driving mechanism as claimed in claim 30, characterised in that at least one of the gears (33, 35) of the end drive (29) forms part of the additional speed transforming gear (37).

32. A driving mechanism as claimed in claim 30 or 31, characterised in that a reverse clutch (R) is positioned between the output shaft (25) of the transmission (23) and the additional speed transforming gear (37).

33. A driving mechanism as claimed in claims 28 and 32, characterised in that the reverse clutch (R) and the end clutch (D) are operated by a single actuation element which can adopt three positions, which are: reverse clutch (R) closed, end clutch (D) closed and both clutches open.

34. A driving mechanism as claimed in any one of the previous claims 28 to 33, characterised in that the reverse clutch (R) and/or the end clutch (D) are arranged as claw clutches and/or synchronizers.

35. A driving mechanism as claimed in any one of the previous claims, characterised in that the driving mechanism does not comprise a cooler.

36. A method for driving a vehicle that is provided with a driving mechanism as claimed in any one of the previous claims, which vehicle further includes wheels that are connected to the output (31) of the end drive (29), characterised in that by actuating the brake (47) the vehicle is accelerated from a halted position.

37. A method as claimed in claim 36, characterised in that after the brake (47) has been actuated, the short-circuit clutch (49) is energized and the brake is opened to further accelerate the vehicle.

38. A method as claimed in claim 37, characterised in that this operation is carried out when the highest speed in the variator (23) is reached and it is desired to further reduce the number of revolutions of the drive source (7).

39. A method as claimed in claim 37 or 38, characterised in that the number of revolutions of the engine is lowered when a change is made from brake (47) to short-circuit clutch (49).

40. A method as claimed in claim 37, 38 or 39, characterised in that the change from brake (47) to the short-circuit clutch (49) takes place without the CVT variator (23) significantly changing its transmission.

41. A method as claimed in claim 37, 38 or 39, characterised in that the change from brake (47) to the short-circuit clutch (49) takes place when the CVT variator (23) shows a gear ratio retarding towards the output (31).

42. A method as claimed in any one of the previous claims 37 to 41, characterised in that the change from the brake (47) to the short-circuit clutch (49) does not take place until the desired power drops below a certain limit value.