EP2015953A1

EP2015953A1 - Gearbox with a power take-off axle

Info

Publication number: EP2015953A1
Application number: EP07748458A
Authority: EP
Inventors: Erik GÖRAS
Original assignee: Scania CV AB
Current assignee: Scania CV AB
Priority date: 2006-05-05
Filing date: 2007-05-02
Publication date: 2009-01-21
Also published as: WO2007129977A1; SE529867C2; EP2015953A4; SE0601008L

Abstract

A motor vehicle (101) with a power takeoff (3) and a transmission device (1) with a power takeoff (3) are described, whereby the pto (3) is intended to transfer power from an engine (118) to an external machine. The motor vehicle (101) and the transmission device (1) comprise a first pto wheel (19) adapted to being driven by the output shaft (27), a second pto wheel (20) arranged on the pto shaft (12), and a power transmission means arranged between the first pto wheel (19) and the second pto wheel (20) to transmit power from the first pto wheel (19) to the second pto wheel (20).

Description

Gearbox with a power take-όf f ^~ axle Technical field

The present invention relates to a transmission device for a motor vehicle, which transmission device comprises a power takeoff arranged on a power takeoff shaft. The present invention also relates to a motor vehicle equipped with such a transmission device.

Description of state of the art Motor vehicles have an engine connected to a transmission device for propelling them. Some motor vehicles are provided with a power takeoff (pto) connected to the engine. The pto may be intended for driving some external machine such as a winch, a generator, a sweeping machine or some agricultural equipment. The pto may alternatively be intended for internal use in the vehicle, e.g. for operating a crane, a tilt device or a cooling unit. In some cases it is desired to be able to connect the external machine while the vehicle is in motion, but in other cases it is only desired to engage the pto when the vehicle is stationary. The pto may be arranged to be driven by the engine or via the gearbox.

The pto shaft and the pto are usually arranged on the transmission device so that the same engine can be used for motor vehicles with a pto as for motor vehicles without a pto, but it is also possible to have the pto shaft connected directly to the engine. To be able to engage the pto, some form of connecting device is required between the engine and the pto. Where the pto is driven via a transmission device, it is desirable that the connecting device be so arranged that the main clutch need not be used for engaging the pto.

European patent application EP 1147936 A2 describes a pto drive mechanism of a work vehicle. The work vehicle has a connecting device between the engine and the drive means. It is desirable to be able to use a variety of speed ratios between the engine and the pto shaft. In today's motor vehicles, this usually entails a great deal of work on the motor vehicle or the transmission device.

Another problem with today's transmission devices with a pto is that they entail relatively large transmission losses as compared with transmission devices without a pto.

Summary of the invention An object of the present invention is to provide a motor vehicle which has an engine and a pto shaft whereby the speed ratio between the engine and the pto shaft can in a simpler manner than in today's motor vehicles be varied between different versions of the same kind of motor vehicle.

Another object of the present invention is to provide a transmission device for a motor vehicle, which transmission device comprises a mainshaft and a pto shaft, whereby the speed ratio between the mainshaft and the pto shaft can in a simpler manner than in today's transmission devices be varied between different versions of the same kind of transmission device.

A further object of the present invention is to provide a motor vehicle with has a pto whereby the power losses when the pto is not being used are less than in motor vehicles according to the state of the art.

A yet further object of the present invention is to provide a transmission device which has a pto whereby the power losses when the pto is not being used are less than in motor vehicles according to the state of the art.

At least one of the objects is achieved by a motor vehicle and a transmission device according to the respective attached independent claims. A first aspect of the present invention presents a motor vehicle comprising an engine with an output shaft and a pto shaft which is adapted to being driven by the output shaft and is intended for transfer of power from the engine to an external machine. The motor vehicle is characterised in that it comprises a first pto wheel adapted to being driven by the output shaft, a second pto wheel arranged on the pto shaft, and a power transmission means arranged between the first pto wheel and the second pto wheel to transmit power from the first pto wheel to the second pto wheel.

Having a power transmission means between the pto wheels makes it possible to change the size of either of the power transmission wheels, and hence the speed ratio between the engine and the pto, without having to alter the mutual distance between the second pto wheel and the shaft on which the first pto wheel is arranged. It is thus possible to adapt each separate gearbox with respect to the speed ratio between the engine and the pto without greater modifications than changing the size of one of the pto wheels and changing the size of the power transmission means.

The first pto wheel may be arranged on the output shaft, in which case the pto is with advantage arranged directly on the engine.

The motor vehicle may also have a transmission device which comprises a casing, a mainshaft supported in the casing, a first primary gearwheel arranged on the mainshaft, a countershaft supported in the casing, and a first countershaft gearwheel which is arranged on the countershaft and in engagement with the first primary gearwheel, whereby the engine's output shaft is adapted to driving the mainshaft and the first pto wheel is arranged on either the mainshaft or the countershaft. Transmission devices with a mainshaft and a countershaft are usually applicable in motor vehicles for changing the speed ratio between the engine and powered wheels during operation. Engine manufacture is facilitated by having the pto driven by a shaft in the transmission device instead of by the output shaft from the engine.

The transmission device may also comprise a second primary gearwheel arranged on the mainshaft, and a second countershaft gearwheel which is arranged on the countershaft and in engagement with the second primary gearwheel, whereby each of the primary gearwheels is lockable relative to the mainshaft for choice of speed ratio between the mainshaft and the countershaft. Transmission devices in motor vehicles are usually arranged in this way in order to provide more than one speed ratio between the engine and powered wheels.

The first pto wheel and the second pto wheel may be gearwheels. Having pto wheels in the form of gearwheels makes assured engagement possible between pto wheels and the power transmission means.

Where the pto wheels are gearwheels, the power transmission means is with advantage either a chain or a toothed belt.

Alternatively, the first pto wheel and the second pto wheel may be pulleys, in which case the power transmission means will be a belt. The belt may for example be a V- belt.

Motor vehicles may also comprise a pto clutch for engaging and disengaging the pto. This is advantageous in that the pto can then be disengaged without using a clutch between the engine and any transmission device and without switching off the engine. A pto clutch thus makes it possible, for example, for the pto to be disconnected while the vehicle is in motion. There may be a plurality of reasons for disengaging the pto. One reason may be wishing to change the external machine which is connected to the pto.

The pto clutch may be adapted to locking and freeing the first pto wheel relative to the shaft on which the first pto wheel is arranged. Arranging the pto clutch in this manner minimises the mechanical parts which have to be driven by the engine when the pto is disengaged.

The pto clutch may take the form of a pto locking means arranged for movement on the shaft on which the first pto wheel is arranged, between first and second positions in which the first pto wheel is respectively locked to and free from the shaft on which the first pto wheel is arranged. This is a relatively simple and robust solution used for the locking of gearwheels in transmission devices between the engine and powered wheels of motor vehicles according to the state of the art.

The pto locking device may be provided with a synchronising device such as those used in transmission devices arranged between the engine and powered wheels in motor vehicles according to the state of the art.

A second aspect of the present invention presents a transmission device for a motor vehicle, which transmission device comprises a casing, a mainshaft supported in the casing, a first primary gearwheel arranged on the mainshaft, a countershaft supported in the casing, a first countershaft pto wheel arranged on the countershaft and in engagement with the first primary gearwheel, and a pto shaft intended to draw power from the engine and adapted to being driven by either the mainshaft or the countershaft.

The transmission device is characterised in that it comprises a first pto wheel arranged on either the mainshaft or the countershaft, a second pto wheel arranged on the pto shaft, and a power transmission means arranged between the first pto wheel and the second pto wheel to transmit power between the first pto wheel and the second pto wheel.

A transmission device according to the second aspect of the present invention affords the same advantages as described above in connection with the first aspect of the present invention.

Preferred embodiments of the invention are described below with reference to the attached drawings. Brief description of the drawings

Fig. 1 depicts a motor vehicle with a transmission device according to an embodiment of the present invention.

Fig. 2 depicts in cross-section a transmission device according to a first embodiment of the invention.

Fig. 3 depicts part of a motor vehicle according to an alternative embodiment of the present invention.

Description of preferred embodiments

In the following description of preferred embodiments of the invention, similar features in the various drawings are given the same reference notations.

Fig. 1 depicts a motor vehicle 101 according to an embodiment of the present invention. The motor vehicle 101 comprises a first powered wheel 103 and a second powered wheel 104 which are adapted to being driven by a differential gear 102. The motor vehicle 101 further comprises an engine 118, a transmission device 1 connected to the engine 118, and a universal shaft 106 arranged between the transmission device 1 and the differential gear 102. A pto 3 is arranged from the transmission device 1. The motor vehicle 101 also comprises a driving cab 107 inside which there is an operating device 108 for engaging and disengaging the pto 3.

Fig. 2 depicts in cross-section a transmission device 1 according to a first embodiment of the invention, which transmission device 1 comprises a casing 2. A mainshaft 5 is supported in the casing 2. The mainshaft 5 comprises an input shaft 6 and a primary shaft 7 which are rotatable relative to one another. The engine 118 has to be connected to the input shaft 6. On the input shaft 6 there is an input gearwheel 8 in engagement with an input countershaft gearwheel 9. On the primary shaft 7 there are a first primary gearwheel 10 and a second primary gearwheel 11. There is also on the primary shaft 7 a first locking means 14 adapted to locking the first primary gearwheel 10 or the second primary gearwheel 11 relative to the primary shaft 7 by movement of the first locking means 14 between different positions along the primary shaft 7 in order to engage with the first primary gearwheel 10, as depicted in Fig. 1 , or with the second primary gearwheel 11 or with neither of the primary gearwheels 10, 11. The transmission device 1 also comprises a countershaft 16 on which there is a first countershaft gearwheel 17 in engagement with the first primary gearwheel 10, and a second countershaft gearwheel 18 in engagement with the second primary gearwheel 11. The two countershaft gearwheels 17, 18 are locked to the countershaft 16. The speed ratio between the input shaft 6 and the primary shaft 5 depends on which of the primary gearwheels 10, 11 is locked to the primary shaft.

In the transmission device 1 there is also a pto shaft 12 on which is arranged a pto 3 to which an external machine can be connected. The transmission device 1 comprises a first pto wheel 19 arranged on the countershaft 16, and a second pto wheel 20 arranged on the pto shaft 12. A power transmission means 13 in the form of a driving belt is arranged round the first pto wheel 19 and the second pto wheel 20 so that the second pto wheel 20 is adapted to being driven by the first pto wheel 19. The speed ratio between the countershaft 16 and the pto shaft 12 is determined by the proportion between the size of the first pto wheel 19 and the second pto wheel 20. The fact that the first pto wheel 19 and the second pto wheel 20 are arranged at a distance from one another makes it easy for the speed ratio between the countershaft 16 and the pto shaft 12 to be altered by replacing either of the pto wheels 19, 20 by a wheel of a different size. The driving belt may be any desired type of belt and may for example be a V- belt or a toothed belt.

A pto locking means 25 with a groove 26 is arranged on the countershaft 16 in such a way as to be movable between a first position in which the first pto wheel 19 is locked relative to the countershaft 16 and a second position, depicted in Fig. 2 in which the pto wheel 19 is freed from the countershaft and therefore the pto 3 is not driven by the engine 118. The pto locking means 25 may be of the same type as the locking means 14 used for locking the primary gearwheels 10, 11. The transmission device comprises a support shaft 21, and actuating means 23 arranged on the support shaft 21 in such a way as to be movable along the support shaft 21. The actuating means 23 comprises a protrusion 4 in engagement with the groove 26 on the pto locking means. A hydraulic piston 22 is arranged between the casing 2 and the actuating means 23 and is adapted to moving the actuating means 23 along the support shaft 21. The hydraulic piston 22 is adapted to being controlled by the operating device 108.

The function of a motor vehicle 101 and a transmission device 1 according to the invention will now be described. When a driver of the motor vehicle 101 wishes to connect driving power to the pto 3, he/she operates the operating device 108 so that the hydraulic piston 22 moves the actuating means 23 and hence also the pto locking means 25 to the right in Fig. 2. The pto locking means 25 will thus come into engagement with the first pto wheel 19, which will thereby be locked to the countershaft 16 so that the pto shaft 12 and hence the pto 3 become powered. When the driver wishes to remove driving power from the pto 3, he/she will operate the operating device 108 so that the hydraulic piston 22 moves the actuating device 23 and hence also the pto locking means 25 to the right in Fig. 2. The pto locking means 25 will thus be disconnected from the first pto wheel 19, which will thus be freed from the countershaft 16. As compared with a motor vehicle and a transmission device with no pto 3, there are thus no further components other than the pto locking means 25 which have to be powered by the engine 118 when the pto 3 is disengaged.

Fig. 3 depicts part of a motor vehicle according to an alternative embodiment of the invention. Here a first pto wheel 19 is arranged on the output shaft 27 from the engine 118. A second pto wheel 20 is arranged on the pto shaft 12. Between the first pto wheel 19 and the second pto wheel 20, a chain 28 is arranged to transmit driving power from the output shaft 27 and the pto.

The embodiments described may be modified in many ways without departing from the spirit and scope of the invention, which is only limited by the claims.

It is possible to replace the chain 28 or the belt 13 by, for example, a universal shaft. Alternatively, there might be a third pto wheel in engagement with the first pto wheel 19 and the second pto wheel 20, all the pto wheels being gearwheels. However, the greatest advantages with the invention are achieved in cases where the power transmission means is a belt or a chain.

In the embodiments described, the first pto wheel 19 and the second pto wheel 20 are arranged within the same casing, but it is possible to arrange the pto wheels 19, 20 within different casings.

Claims

1. A motor vehicle (101) comprising an engine (118) with a output shaft (27) and a pto shaft (12) which is adapted to being driven by the output shaft (27) and is intended to transfer power from the engine (118) to an external machine, characterised in that the motor vehicle (101) comprises a first pto wheel (19) adapted to being driven by the output shaft (27), a second pto wheel (20) arranged on the pto shaft (12) and a power transmission means arranged between the first pto wheel (19) and the second pto wheel (20) to transmit power from the first pto wheel (19) to the second pto wheel (20).

2. A motor vehicle (101) according to claim 1, whereby the first pto wheel (19) is arranged on the output shaft (27).

3. A motor vehicle (101) according to claim 1, comprising a transmission device (1) which itself comprises a casing (2), a mainshaft (5) supported in the casing (2), a first primary gearwheel (10) arranged on the mainshaft (5), a countershaft (16) supported in the casing (2), a first countershaft gearwheel (17) arranged on the countershaft (16) and in engagement with a first primary gearwheel (10), whereby the engine's output shaft (27) is adapted to driving the mainshaft (5) and whereby the first pto wheel (19) is arranged on either the mainshaft (5) or the countershaft (16).

4. A motor vehicle (101) according to claim 3, whereby the transmission device (1) also comprises a second primary gearwheel (11) arranged on the mainshaft (5), and a second countershaft gearwheel (17) arranged on the countershaft (16) and in engagement with the second primary pto wheel (11), whereby each of the primary gearwheels (10, 11) is lockable relative to the mainshaft (5) for choice of speed ratio between the mainshaft (5) and the countershaft (16).

5. A motor vehicle (101) according to any one of the foregoing claims, whereby the first pto wheel (19) and the second pto wheel (20) are gearwheels.

6. A motor vehicle (101) according to claim 5, whereby the power transmission means is a chain (28).

7. A motor vehicle (101) according to claim 5, whereby the power transmission means is a toothed belt (13).

8. A motor vehicle (101) according to any one of claims 1-4 whereby the first pto wheel and the second pto wheel are pulleys.

9. A motor vehicle (101) according to claim 8, whereby the power transmission means is a belt (13).

10. A motor vehicle (101) according to any one of the foregoing claims, comprising a pto clutch for engaging and disengaging the pto (3).

11. A motor vehicle (101) according to claim 10, whereby the pto clutch is adapted to locking and disengaging the first pto wheel (19) relative to the shaft on which the first pto wheel (19) is arranged.

12. A motor vehicle (101) according to claim 11, whereby the pto clutch (3) takes the form of a pto locking means (25) arranged for movement on the shaft on which the first pto wheel (19) is arranged between first and second positions in which the first pto wheel (19) is respectively locked to or freed from the shaft on which the first pto wheel (19) is arranged.

13. A transmission device (1) for a motor vehicle (101), which transmission device comprises a casing (2), a mainshaft (5) supported in the casing (2), a first primary gearwheel (10) arranged on the mainshaft, a countershaft (16) supported in the casing, a first countershaft gearwheel (17) arranged on the countershaft (16) and in engagement with the first primary gearwheel (10), and a pto shaft (12) intended to transfer power from the engine and adapted to being driven by either the mainshaft (5) or the countershaft (16), characterised in that the transmission device (1) comprises a first pto wheel (19) arranged on either the mainshaft (5) or the countershaft (16), a second pto wheel (20) arranged on the pto shaft (12), and a power transmission means arranged between the first pto wheel (19) and the second pto wheel (20) to transmit power from the first pto wheel (19) to the second pto wheel (20).