WO2015072908A1

WO2015072908A1 - Compact vehicle transmission

Info

Publication number: WO2015072908A1
Application number: PCT/SE2014/051312
Authority: WO
Inventors: Jörgen FORSBERG
Original assignee: Scania Cv Ab
Priority date: 2013-11-18
Filing date: 2014-11-06
Publication date: 2015-05-21
Also published as: SE1351359A1; DE112014004825B4; DE112014004825T5; SE538083C2

Abstract

The invention pertains to a transmission, comprising: - an input shaft (14), on which a first cogwheel (20) is rotatably arranged; - a main shaft (18) arranged in line with the input shaft (14), on which main shaft (18) a second cogwheel (22) is rotatably arranged; - a layshaft (32), on which a first and a second gear (36) are attached, which first gear (34) is in engagement with the first cogwheel (20) and which second gear (36) is in engagement with the second cogwheel (22); - a first coupling sleeve (46) which is arranged with splines (48) on the input shaft (14), and which is axially shiftable along the input shaft (14), which first coupling sleeve (46) in a first position is arranged to, with internal teeth (49), engage with the first cogwheel (20) in order to connect the first cogwheel (20) with the input shaft (14), and which first coupling sleeve (46) in a second position is arranged to disconnect the first cogwheel (20) on the input shaft (14); and - a second coupling sleeve (50) which through internal teeth (52) is in engagement with and shiftably arranged on the second cogwheel (22), which second coupling sleeve (50) in a first position is arranged to disconnect the second cogwheel (22) from the input shaft (14), and which second coupling sleeve (50) in a second position is arranged to engage with the input shaft (14), in order to connect the second cogwheel (22) with the input shaft (14). The first and second coupling sleeves (46, 50) are arranged between the first and second cogwheels (20, 22). The invention also pertains to a gearbox comprising such a transmission, a vehicle comprising such a gearbox and a method to control a transmission.

Description

Compact vehicle transmission

BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention pertains to a transmission according to the preamble of claim 1 , a gearbox, which comprises such a transmission according to the preamble of claim 9, a vehicle, which comprises such a gearbox according to the preamble of claim 10, and a method to control a transmission according to the preamble of claim 1 1 .

Vehicles, and in particular heavy goods vehicles, e.g. trucks, are usually equipped with a gearbox, which may be automatic, manual or a combination thereof, connected to the combustion engine. In an automated manual transmission, a so-called AMT gearbox, the gearbox is controlled by an electronic control device. Such a gearbox may be equipped with a transmission, comprising an input shaft, a main shaft and a layshaft parallel to the input shaft and main shaft. It is also possible to equip the transmission with double layshafts. The gearbox may also be equipped with a range gearbox, which may constitute a separate device or be integrated in the gearbox.

The main shaft is connectible with cogwheels to an input shaft via the layshaft, and to an output shaft in the gearbox via the range gearbox, if this is integrated in the gearbox. The main shaft may also be connected directly with the input shaft via a clutch device, in order to thus establish a direct gear through the transmission and the gearbox. The transmission may also be equipped with a split gear unit, through which the layshaft is connectible to the input shaft via two different cogwheels. A brake mechanism may be arranged to retard the layshaft in connection with change of gears, in order to achieve a substantially synchronous rotation speed in the layshaft and the main shaft with one gearing in between, so that the new gear may be engaged without any substantial torque existing between the relevant transmission parts, which are brought to engage with each other at the moment the new gear is engaged.

Transmissions of this type may have synchronisation devices comprising conical synchronisation rings and coupling rings. Synchronisation devices may, however, be combined with or replaced by toothed coupling sleeves, which are displaced axially with manoeuvring forks, in order to engage with cogwheels mounted on the input shaft and the main shaft. Each cogwheel mounted on the input shaft and the main shaft is engaged with corresponding cogwheel elements, which are rotationally connected with the layshaft. On shifting, the coupling sleeve is displaced axially in order to engage with coupling teeth arranged on a selectable cogwheel in order to connect, and to rotationally lock, the cogwheel to the input shaft and the main shaft.

When the transmission is arranged in a gearbox of a vehicle, the direct gear mode is preferred in the operating conditions at substantially constant speed, which is com- mon in commercial vehicles such as trucks. The gearing ratio then becomes 1 :1 through the transmission and losses in the gearbox are thus reduced. In order to further reduce the fuel consumption, it is desirable to disconnect the cogwheels from the input shaft and the layshaft, entailing that the layshaft or layshafts are at a standstill. As a consequence, the gears fixedly attached to the layshafts will not exert any brak- ing torque on the vehicle's power source, entailing reduced fuel consumption. When the layshafts rotate, the fixedly attached gears will move in the gearbox's transmission oil, creating losses and a torque counteracting the power source.

The transmission of a vehicle, and especially a truck, comprises a large number of gear steps, entailing that the transmission and the gearbox will be of considerable length and weight, which in turn results in an increased weight and increased fuel consumption of the vehicle and that the gearbox will require a larger installation space in the vehicle. Document US 7798937, B2 shows a transmission with one layshaft, which may be moved to a standstill position at direct gear. Two cogwheels are arranged on the input shaft, each of which engages with the respective gears on the layshaft. Gear elements on each side of one of the cogwheels may move the cogwheels into en- gagement with the input shaft. One of the gear elements is also arranged to connect the input shaft with a main shaft to achieve a direct gear position.

Document US 201 10259147, A1 shows a transmission that comprises two parallel layshafts. One input shaft may, through a coupling element, be connected with a main shaft, so that a direct gear position is obtained.

SUMMARY OF THE INVENTION Despite prior art solutions, there is a need to further develop a transmission, which requires a limited installation space and which does not substantially encumber a power source when a direct gear position is connected through the transmission.

The objective of the present invention is thus to provide a transmission with a com- pact construction.

Another objective of the invention is to provide a transmission which reduces a vehicle's fuel consumption. These objectives are achieved with a transmission of the type specified at the beginning, characterised by the features specified in claim 1 .

Such a transmission requires a limited installation space. The first and second coupling sleeves are shiftably arranged inside the axial compartment formed between the first and the second cogwheels. Thus, the length of the transmission will be limited, leading to a compact transmission. The manoeuvring forks with associated control equipment, connected to the first and the second coupling sleeves, may also be assembled compactly in relation to each other, which reduces the transmission's size and the requirements for installation space.

When the cogwheels are disconnected from the input shaft and the main shaft, the layshaft(s) will be at a standstill. As a consequence, the gears fixedly attached to the layshafts will not exert any braking torque on the vehicle's power source, entailing reduced fuel consumption. The objectives specified above are achieved also with a gearbox of the type mentioned above, which is characterised by the features specified in claim 8. The objectives specified above are achieved also with a vehicle of the type mentioned above, which is characterised by the features specified in claim 9.

The above objectives are achieved also with a method to control a transmission of the type specified at the beginning, characterised by the features specified in claim 10.

Other advantages of the invention are set out in the detailed description below. BRIEF DESCRIPTION OF THE DRAWINGS

Below is a description, as an example, of preferred embodiments of the invention with reference to the enclosed drawings, in which:

Fig. 1 shows, in a schematic side view, a vehicle with a gearbox and transmission according to the present invention,

Fig. 2 shows a cross-sectional view of a transmission according to the present invention, Fig. 3 shows a detailed cross-sectional view of a transmission according to the present invention in a first position,

Fig. 4 shows a side view of an input shaft in the transmission, seen in the direction A in Fig. 3,

Fig. 5 shows a detailed cross-sectional view of a transmission according to the present invention in a second position,

Fig. 6 shows a first coupling sleeve in a perspective view, Fig. 7 shows a third coupling disc in a perspective view,

Fig. 8 shows a detailed cross-sectional view of a transmission according to the present invention in a third position, and

Fig. 9 shows a flow chart of a method to control the transmission according to the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Fig. 1 shows a vehicle 1 in a schematic side view, the vehicle 1 being equipped with a transmission 2 according to the present invention. The transmission 2 is placed in a gearbox 6, which is connected to a driving engine, such as a combustion engine 8 and/or an electric engine, which operates the driving wheels 10 of the vehicle 1 via the gearbox 6 and a propeller shaft 12.

Fig. 2 shows a cross-sectional view of a transmission 2 according to the present invention. The transmission 2 comprises an input shaft 14, at which a first cogwheel 20 is rotatably arranged. The input shaft 14 may at a first end 16 be adapted to be con- nected to the combustion engine 8 (Fig. 1 ) via a manoeuvrable friction clutch (not displayed). The transmission 2 also comprises a main shaft 18, arranged in line with the input shaft 14, at which main shaft 18 a second cogwheel 22 is rotatably arranged. With a second end 24 facing away from the first end 16, the input shaft 14 is placed on the main shaft 18 with a rolling bearing 26. The main shaft 18 is preferably designed to be connected to the propeller shaft 12 of the vehicle 1 with an end 28, facing away from the input shaft 14. On the main shaft 18, additional cogwheels 30 are arranged, in order to achieve several different gearings through the transmission 2. A layshaft 32, on which a first and a second gear 34, 36 are fixedly attached, extends in parallel with the input shaft 14 and the main shaft 18. The first gear 34 is in engagement with the first cogwheel 20 and the second gear 36 is in engagement with the second cogwheel 22. It is also possible to equip the transmission 2 with an additional, second layshaft 38, so that the transmission 2 comprises double layshafts 32, 38. Fig. 2 shows the second layshaft 38 schematically, with dashed lines. On the second layshaft 38, a third and a fourth gear 40, 42 are attached, which third gear 40 is in engagement with the first cogwheel 20 and which fourth gear 42 is in engagement with the second cogwheel 22. On the layshafts 32, 38, additional gears 44 may be arranged, which are in engagement with the additional cogwheels 30 arranged on the main shaft 18. The first and the second cogwheels 20, 22 and the additional cogwheels 30 are mounted on the input shaft 14 and the main shaft 18, respectively. If double layshafts 32, 38 are used, however, it is possible to arrange the first and the second cogwheels 20, 22 and the additional cogwheels 30 without bearings, which entails that they will have a radially contactless relationship to the input shaft 14 and the main shaft 18. The gears on the layshaft may be driven as well as be driving. Accordingly, they may drive the cogwheels 20, 22 and the additional cogwheels 30 in one operating mode. In another operating mode they may be driven by the cogwheels 20, 22 and the additional cogwheels 30.

Fig. 3 shows a detailed cross-sectional view of the transmission 2, according to the present invention, in a first position in the area where the input shaft 14 is placed on the main shaft 18. A first coupling sleeve 46 is, by way of splines 48, arranged on the input shaft 14 and axially shiftable along the input shaft 14. The first coupling sleeve 46 is, in the first position, arranged by way of internal teeth 49 to engage with the first cogwheel 20, in order to connect the first cogwheel 20 on the input shaft 14. A second coupling sleeve 50 is, by way of internal teeth 52, in engagement with and shiftably arranged on the second cogwheel 22, whose second coupling sleeve 50, shown in a first position in Fig. 3, is arranged to disconnect the second cogwheel 22 from the input shaft 14 and the main shaft 18. A first coupling disc 54, with peripherally arranged teeth 56, is connected with the first cogwheel 20. When the first coupling sleeve 46 is shifted to the first position, the teeth 49 of the first coupling sleeve 46 engage with the teeth 56, arranged peripherally on the first coupling disc 54. A second coupling disc 58, with peripherally arranged teeth 60, is connected with the first cogwheel 22. When the first coupling sleeve 50 is shifted to the first position, the internal teeth 52 of the second coupling sleeve 50 engage with the teeth 60, arranged peripherally on the second coupling disc 58. A third coupling disc 62, with peripherally arranged teeth 64, is arranged on the input shaft 14 between the first and the second coupling sleeve 50. The function of the third coupling disc 62 is described in further detail below.

When the first coupling sleeve 46 is shifted to the first position, the first cogwheel 20 will thus be driven by the input shaft 14. Since the first cogwheel 20 is in engagement with the first gear 34 on the layshaft 32, the layshaft 32 will be driven with a speed corresponding to the gearing between the first cogwheel 20 and the first gear 34. By connecting selected additional cogwheels 30 on the main shaft 18, the main shaft 18 will be operated by the layshaft 32. Depending on the gearing between the addition- ally connected cogwheels 30 and the gears 44, the main shaft 18 will be driven with a specific speed. The shifting of the first and second coupling sleeves 46, 50 is carried out by pneumatically, hydraulically or electrically controlled manoeuvring forks 66, which are shown schematically in Fig. 3. There are additional manoeuvring forks and coupling sleeves (not displayed) to connect and disconnect the additional cogwheels 30 to the main shaft 18.

As also shown in Fig. 3, the first and second coupling sleeves 46, 50 are shiftably arranged inside the axial compartment, formed between the first and the second cogwheel 20, 22. Thus, the length of the transmission 2 will be limited, leading to a compact transmission 2. The manoeuvring forks 66 with associated control equipment, connected to the first and the second coupling sleeves 46, 50 may also be assembled compactly in relation to each other, which reduces the size of the transmission 2 and the requirement of installation space. Fig. 4 shows a side view of the input shaft 14, seen in the direction A of the arrow in Fig. 3. It also shows how a section B-B in Fig. 4 corresponds to the section view in Fig. 3. The first cogwheel 20 is equipped, on its periphery, with cogs 68. The first coupling disc 54 is also connected with the first cogwheel 20, whose first coupling disc 54 is equipped with teeth 56 on its periphery, designed to engage and interact with internal teeth 49 arranged on the first coupling sleeve 46, when the first coupling sleeve 46 is shifted to its first position. The input shaft 14 is equipped at its first end 16 with splines 70. Fig. 5 shows a detailed cross-sectional view of the transmission 2, according to the present invention, when the first coupling sleeve 46 has been shifted to a second position. In the second position, the first coupling sleeve 46 is arranged to disconnect the first cogwheel 20 on the input shaft 14, and in the second position the first cou- pling sleeve 46 is arranged to engage, via the splines 72, with the main shaft 18, in which second position the first coupling sleeve 46 connects the input shaft 14 and the main shaft 18 with each other in a direct gear position. In the direct gear position, both the first and the second cogwheels 20, 22 are disconnected from the input shaft 14 and the main shaft 18, entailing that the layshaft 32 will not be driven by the input shaft 14 or the main shaft 18. The additional cogwheels 30 on the main shaft 18 are disconnected from the main shaft 18, entailing that they rotate freely in relation to the main shaft 18. Thus, the layshafts 32, 38 will not rotate in the direct gear position, resulting in the positive effects described above. As shown in Fig. 5, the first coupling sleeve 46 is equipped with at least one axially protruding section 74, on which splines 72 are arranged for engagement with the main shaft 18. The main shaft 18 is equipped with a radially protruding ring 76, with splines 78 arranged on its periphery. The ring 76 may be a separate entity on the main shaft 18 or integrated with the same. Accordingly, a rotation-locked connection between the first coupling sleeve's 46 axially protruding section 74 and the main shaft 18 is facilitated. In order to facilitate the shift of the first coupling sleeve 46 into the second position, the third coupling disc 62 is equipped with at least one recess 80, which is designed so that the recess allows for a passage of the first coupling sleeve's 46 axially protruding section 74. The second coupling sleeve 50 is, in Fig. 5, shifted into the first position and engages with the peripheral teeth 60 arranged on the second coupling disc 58.

Fig. 6 shows the first coupling sleeve 46 in a perspective view. Preferably, several axially protruding sections 74 are symmetrically arranged in the circumferential direc- tion of the first coupling sleeve 46.

Fig. 7 shows the third coupling disc 62 in a perspective view. Preferably, several recesses 80 are symmetrically arranged in the circumferential direction of the third coupling disc 62, being designed and placed so that the recesses 80 allow for a passage of the axially protruding sections 74 on the first coupling sleeve 46.

Fig. 8 shows a detailed cross-sectional view of the transmission 2, according to the present invention, when the first coupling sleeve 46 has been shifted into a third position and the second coupling sleeve 50 has been shifted into a second position. In the third position, the first coupling sleeve 46 has, assumed a neutral position, in which the first coupling sleeve 46 does not engage with the first coupling disc 54, and does not engage with the main shaft 18. Thus, the first cogwheel 20 will be able to rotate freely in relation to the input shaft 14. The main shaft 18 is also not connected with the input shaft 14. In the second position, the second coupling sleeve 50 is arranged to, with the internal teeth 52, engage with the teeth 64 on the periphery of the third coupling disc 62, at the same time as the teeth 52 of the second coupling sleeve 50 engage with the teeth 60 on the periphery of the second coupling disc 58. Thus, the second cogwheel 22 will be connected with the input shaft 14 via the second coupling sleeve 50. The input shaft 14 thus drives the second cogwheel 22, which in turn drives the layshaft 32 or the layshafts 32, 38 via the second gear 36, with a gearing that depends on the gearing ratio between the second cogwheel 22 and the second gear 36. One of the additional cogwheels 30 on the main shaft 18 is connected, so that the main shaft 18 is driven by the layshafts 32, 38 with the selected gearing. As a result, the first and second cogwheels 20, 22 will function as a split gear device.

The shifting of the first and second coupling sleeves 46, 50 is carried out after a substantially zero torque state has arisen between the first and second coupling sleeves 46, 50, as well as the components with which they engage and will engage. This may be achieved via a braking device 82 (Fig. 2) on the layshafts 32, 38 and/or a synchronisation device arranged on the first and second cogwheels 20, 22 (not displayed). In order to achieve gear-shifting, the braking device 82 is activated in order to decelerate the layshaft 32 at change of gears, and in order thus to achieve a sub- stantially synchronous rotation speed of the layshaft 32 and the main shaft 18 with one gearing in between, so that the new gear may be engaged without any substantial torque existing between the relevant transmission parts, which are brought to engage with each other at the moment the new gear is engaged. The transmission according to the invention is preferably housed inside a gearbox 6 (Fig. 1 ), in which lubricating oil for the transmission 2 is also contained.

The method to control the transmission 2 according to the present invention will be described below jointly with the flow chart in Fig. 9, which method comprises the steps:

a) to shift the second coupling sleeve 50 into the first position, in order to disconnect the second cogwheel 22 from the input shaft 14,

b) to shift the first coupling sleeve 46 to a second position in order to connect the in- put shaft 14 and the main shaft 18 with each other with the first coupling sleeve 46, in a direct gear position.

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

Claims

1 . Transmission, comprising:

- an input shaft (14), on which a first cogwheel (20) is rotatably arranged;

- a main shaft (18) arranged in line with the input shaft (14), on which main shaft (18) a second cogwheel (22) is rotatably arranged;

- a layshaft (32), on which a first and a second gear (36) are attached, which first gear (34) is in engagement with the first cogwheel (20) and which second gear (36) is in engagement with the second cogwheel (22);

- a first coupling sleeve (46) which is arranged with splines (48) on the input shaft (14), and which is axially shiftable along the input shaft (14), which first coupling sleeve (46) in a first position is arranged to, with internal teeth (49), engage with the first cogwheel (20) in order to connect the first cogwheel (20) with the input shaft (14), and which first coupling sleeve (46) in a second position is arranged to disconnect the first cogwheel (20) on the input shaft (14); and

- a second coupling sleeve (50) which, with internal teeth (52), is in engagement with and shiftably arranged on the second cogwheel (22), which second coupling sleeve (50) is arranged in a first position, in order to disconnect the second cogwheel (22) from the input shaft (14), and which second coupling sleeve (50) is arranged in a second position, in order to engage with the input shaft (14), in order to connect the second cogwheel (22) with the input shaft (14);

characterised in that:

in the second position, the first coupling sleeve (46) is arranged to engage, through the splines (70), with the main shaft (18), in which second position the first coupling sleeve (46) connects the input shaft (14) and the main shaft (18) with each other in a direct gear position; and

the first and second coupling sleeves (46, 50) are arranged between the first and second cogwheels (20, 22).

2. Transmission according to claim 1 , characterised in that a coupling disc (62) is connected with the input shaft (14) between the first and second coupling sleeves (46, 50), wherein the second coupling sleeve (50) in the second position is arranged to, with the internal teeth (52), engage with teeth (64) on the periphery of the coupling disc (62).

3. Transmission according to any of claims 1 or 2, characterised in that the first coupling sleeve (46) is equipped with at least one axially protruding section (74) on which splines (72) are arranged for engagement with the main shaft (18).

4. Transmission according to claims 2 and 3, characterised in that the coupling disc (62) comprises at least one recess (80), designed so that the recess (80) allows for a passage of the axially protruding section (74) of the first coupling sleeve (46).

5. Transmission according to any of the previous claims, characterised in that the first and second cogwheels (20, 22) are mounted on the input shaft (14) and the main shaft (18).

6. Transmission according to any of the previous claims, characterised in that the input shaft (14) is placed on the main shaft (18).

7. Transmission according to any of the previous claims, characterised in that the transmission (2) comprises a second layshaft (38), on which a third and a fourth gear

(40, 42) are rotatably attached, which third gear (40) is in engagement with the first cogwheel (20) and which fourth gear (42) is in engagement with the second cogwheel (22).

8. Gearbox (6), characterised in that it comprises a transmission (2) according to any of the claims 1 -7.

9. Vehicle (1 ), characterised in that it comprises a gearbox (6) according to claim 8.

10. Method to control a transmission (2), comprising

- an input shaft (14), on which a first cogwheel (20) is rotatably arranged;

- a main shaft (18) arranged in line with the input shaft (14), on which main shaft (18) a second cogwheel (22) is rotatably arranged; - a layshaft (32), on which a first and a second gear (36) are attached, which first gear (34) is in engagennent with the first cogwheel (20) and which second gear (36) is in engagennent with the second cogwheel (22);

characterised in that the transmission also comprises

- a first coupling sleeve (46) which is arranged with splines (48) on the input shaft (14), and which is axially shiftable along the input shaft (14), which first coupling sleeve (46) in a first position is arranged to, with internal teeth (49), engage with the first cogwheel (20) in order to connect the first cogwheel (20) with the input shaft (14), and which first coupling sleeve (46) in a second position is arranged to discon- nect the first cogwheel (20) on the input shaft (14) and to engage with the main shaft (18) with splines (70), so that the first coupling sleeve (46) connects the input shaft (14) and the main shaft (18) with each other in a direct gear position; and

- a second coupling sleeve (50) which, with internal teeth (52), is in engagement with and shiftably arranged on the second cogwheel (22), which second coupling sleeve (50) in a first position is arranged to disconnect the second cogwheel (22) from the input shaft (14), and which second coupling sleeve (50) in a second position is arranged to engage with the input shaft (14), in order to connect the second cogwheel (22) with the input shaft (14);

wherein the method comprises the steps to:

a) shift the second coupling sleeve (50) into the first position, in order to disconnect the second cogwheel (22) from the input shaft (14), and

b) shift the first coupling sleeve to a second position in order to, with the first coupling sleeve, connect the input shaft (14) and the main shaft (18) with each other in a direct gear position.