Technical field

The present invention relates to a motor vehicle with an engine and a power take-off from the engine. The present invention also relates to a method for connecting the power take-off and a programme for controlling the connection process.

State of the art

Motor vehicles have an engine connected to a gearbox for their propulsion. Some motor vehicles are provided with a power take-off which is connected to the engine. The power take-off may be intended to drive an external machine such as a winch, a generator, a sweeping machine or an agricultural implement. The power take-off 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 may be desired to connect the external machine while the vehicle is in motion, as well as in other cases it may only be desired to connect the power take-off when the vehicle is standing still. The power take-off may be adapted to being driven directly by the engine or via the gearbox.

Engaging the power take-off involves some form of connecting device between the engine and the power take-off. In cases where the power take-off is driven via the gearbox, it is desirable that the connecting device be so arranged that engaging the power take-off does not involve using the main connection. European patent application EP 1147936 A2 describes a method for controlling a power take-off drive mechanism of a work vehicle. The work vehicle has a connecting device between the engine and the drive means. The connecting device is a disc clutch of dry or wet type. Disc clutches have the advantage that they can slip while in operation. However, the greater the difference in speed between the engine and the power take-off at the time of engaging the power take-off, Hie quicker disc clutches become worn. According to EP 1147936 A2, this problem is minimised by the speed of the engine being reduced to

the lowest possible speed before Hie power take-off is engaged. Reducing the engine's speed minimises the difference in speed and hence the wear on the disc clutch.

A problem with disc clutches is that they are relatively expensive to make, with consequent adverse effects on the motor vehicle's production cost. An alternative to using disc clutches is using connecting devices based on two means connected together without the possibility of slipping. One type of such a connecting device is a so-called claw connection. A claw connection usually takes the form of a rotatable first means with splines arranged along an outer circumference, a rotatable second means with splines arranged along an outer circumference and a third means with a hole running through it which has splines in the hole. The third means is adapted to being movable between a first position in engagement with both the first splined surface and the second splined surface and a second position in engagement with either or neither of Hie splined surfaces. To this end, the third means is most commonly adapted to being movable in an axial direction. Corresponding functions can be performed by gearwheels.

A problem with claw connections and other connections based on two gearwheels which have to come into mutual engagement is that they have hitherto involved stationary gearwheels. This has meant the engine having to be switched off before the gearwheels can be connected together.

Description of the invention

An object of the present invention is to provide a motor vehicle with a disc-free connecting device and a method and a computer programme for such a connecting device which make it possible for power from the engine to be connected to a power take-off without the engine having to be stopped.

This object is achieved with a motor vehicle, a method and a memory medium according to the attached claims.

Further advantages of the invention are achieved by the features defined in the dependent claims.

A first aspect of the present invention takes the form of a motor vehicle comprising an engine, a power take-off for driving an external machine, and a connecting device arranged between the engine and the power take-off. The connecting device comprises a first means which is adapted to being driven by the engine and which has a first axis of rotation, a second means which is connected to the power take-off and has a second axis of rotation, a movable third means for connecting together the first means and the second means, and a movement means for movement of the third means.

The third means is movable between a first position and a second position, whereby only in the first position is the third means in engagement with both the first means and the second means so that power can be transmitted from the engine to the power take- off. The motor vehicle is characterised by comprising a control unit for controlling the movement means and the engine, which control unit is so arranged that, upon receiving a control signal requiring power to be transmitted from the engine to the power take-off, the control unit controls the engine in such a way as to reduce the engine's speed to a certain speed and thereafter controls the movement means in such a way that the movement means moves the third means to the first position.

Reducing the engine's speed makes it possible for the third means to be moved without the engine being stopped. The result is a saving of time for the user of the motor vehicle.

The first means may either be adapted to being driven directly by the engine or be adapted to being driven by the engine via a gearbox and/or a main connection. In the latter case, the gearbox is usually arranged between the powered wheels and the engine, with the main connection arranged between the gearbox and the engine, hi the motor vehicle according to the invention, the connecting device is used for engaging and disengaging the power take-off.

The third means is in engagement with the first means and the second means in different ways depending on their configuration. The third means may be a means adapted to being locked firmly to the first means and the second means in order to transmit power from the first means to the second means. Alternatively, the third means may be a means which rotates relative to both the first means and the second means when transmitting power between the first means and the second means. In the latter case the third means may for example be a gearwheel.

The first axis of rotation may be parallel with the second axis of rotation and the third axis of rotation. Having the first axis of rotation parallel with the second axis of rotation avoids the use of a bevel gear between the first axis of rotation and the second axis of rotation. Power losses can be minimised by also arranging the third axis of rotation parallel with the first axis of rotation.

The first axis of rotation may be common with the second axis of rotation. Arranging the first axis of rotation and the second axis of rotation in this way makes it possible to configure the connecting device more compactly. At the same time it becomes possible to make use of a third means which is locked to the rotation of the first means upon engagement with the first means.

The first means may take the form of a hub and the second means may take the form of a shaft, whereby the second means is supported in the first means. Such a construction of the connecting device is possible if the first axis of rotation is common with the second axis of rotation. Such a construction also makes it possible to configure the third means in a large number of different ways. Having the second means supported in the first means results in compact construction.

The third means may be adapted to being movable in an axial direction along the third axis of rotation. Arranging the third means in such a way makes it possible to achieve robust construction, since it then becomes easier to achieve in a short time a large engagement surface between the third means or the first means and the second means. A large engagement surface is desirable for reducing the stresses on the respective

means and the time of engagement, since the stresses may be extremely large as a result of the rotation of the first means at the time of engagement of the power takeoff. Alternatively, the third means may be movable perpendicularly to the third axis of rotation. For the third means to be movable radially relative to the third axis of rotation, the third means needs to be a gearwheel in order to be able to come into engagement with the first means and/or the second means by radial movement relative to the third axis of rotation.

The third axis of rotation may be common with the first axis of rotation. This is necessary if the third means is to be capable of being locked to both the first means and the second means upon the connecting together of the first means and the second means.

In cases where the first means can be locked to both the first means and the second means, the first means may comprise a first splined surface which surrounds the common axis of rotation and constitutes an internal portion of a splined connection. The second means may correspondingly comprise a second splined surface which is of substantially the same form as the first splined surface and surrounds the common axis of rotation. The third means men comprises an external surface and has running through it a hole with an internal splined surface adapted to engagement with the first splined surface and the second splined surface, whereby only when the third means is in the first position is the internal splined surface of the third means in engagement with both the first splined surface and the second splined surface. Such a configuration of the third means is advantageous in that a large engagement surface between the third means and the first means or the second means can be achieved in a short time by movement of the third means to the first position. Axial movement of the third means will thus put the third means into engagement with the first means or the second means.

The third means may be supported in the movement means. The third means can thereby always be in contact with the movement means while at the same time the friction between the movement means and the third means can be minimised.

The first means may comprise a first gearwheel portion substantially in the form of a gearwheel, whereby the second means comprises a second gearwheel portion substantially of the same form as the first gearwheel portion, and whereby the third means comprises a gearwheel which is only in contact with the gearwheel portions when the third means is in the first position.

The movement means may comprise a piston unit. A piston unit effects movement of the third means in an uncomplicated way. It is possible to effect the movement of the third means in other ways than by using a piston unit. It is possible, for example, to use a rotating machine connected to a gearbox for converting the rotary motion to a linear motion.

The piston unit may be adapted to being powered by compressed air. It is of course possible alternatively to power the piston unit hydraulically by a hydraulic fluid. The hydraulic fluid would be pumped into the piston unit by a pump.

The speed to which the engine's speed is reduced is with advantage lower than the engine's idling speed and preferably less than 200 revolutions per minute and most preferably below 100 revolutions per minute. Reducing the engine's speed to such a level makes it possible to move the third means to the first position without the engine being stopped.

A second aspect of the present invention takes the form of a method for engaging a power take-off, in order to drive an external machine, via a connecting device arranged between the engine and the power take-off. The connecting device comprises a first means which is connected to the engine and which has a first axis of rotation, a second means which is connected to the power take-off and has a second axis of rotation, a movable third means for connecting together the first means and the second means, and a movement means for movement of the third means. The third means is movable between a first position and a second position, whereby only in the first position is the third means in engagement with both the first means and the second means so mat

power can be transmitted from the engine to the power take-off. The method is characterised in that it comprises the steps of reducing the engine's speed to a certain speed and thereafter controlling the movement means so that the movement means moves the third means to the first position.

The speed to which the engine's speed is reduced is with advantage below the idling speed of the engine, preferably below 200 revolutions per minute and most preferably below 100 revolutions per minute.

A method according to the second aspect of the present invention has advantages corresponding to those mentioned in connection with the first aspect of the present invention.

A third aspect of the present invention takes the form of a computer-readable memory medium on which a computer programme is stored for controlling a control unit which controls a connecting device between an engine and a power take-off. The connecting device comprises a first means which is connected to the engine and which has a first axis of rotation, a second means which is connected to the power take-off and has a second axis of rotation, a movable third means for connecting together the first means and the second means, and a movement means for movement of the third means. The third means is movable between a first position and a second position, whereby only in the first position is the third means in engagement with both the first means and the second means so that power can be transmitted from the engine to the power take-off. The computer-readable memory medium is characterised in that the computer programme comprises instructions so that when it is run in the control unit the control unit is able, upon receiving a control signal requiring the power take-off to be engaged, to send to the engine a signal which lowers the engine's speed to a certain speed and thereafter to send to the movement means a signal which causes the movement means to move the third means to the first position.

The computer-readable memory medium according to the third aspect of the present invention has the same advantages as mentioned 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 schematically a motor vehicle according to an embodiment of the present invention comprising a connecting device.

Fig. 2 depicts in more detail a connecting device in a motor vehicle according to a first embodiment of the present invention.

Fig. 3 depicts in more detail a connecting device in a motor vehicle according to a second embodiment of the present invention.

Description of preferred embodiments of the invention

In the following description of embodiments of the invention, similar items in the various embodiments are denoted by the same reference notation.

Fig. 1 depicts schematically a motor vehicle 1 according to an embodiment of the present invention comprising a connecting device 2. The motor vehicle also comprises an engine 3 and a power take-off 4. The connecting device 2 is arranged between the engine and the power take-off 4. A driveshaft 5 connects the power take-off 4 to the connecting device 2. The engine 3 is arranged for propulsion of the motor vehicle 1 via a driveshaft 30. The motor vehicle 1 also comprises a control unit 6 adapted to controlling the engine 3 and the connecting device 2. The control unit 6 comprises a memory 18 or is at least connected to a memory unit, e.g. via a CAN bus, in which memory a programme which controls the control unit is stored. A control 19 is for

example arranged in the driver's cab 20 for activating engagement of the power takeoff^ The connecting device 2 will be described in more detail below. The motor vehicle also comprises a gearbox 28 connected to the driveshaft 30 and to the engine 3 via a main connection 29.

The memory may be any desired type of memory known to a specialist within the field such as ROM (read-only memory), PROM (programmable ROM), EPROM (erasable PROM), EEPROM (electrically erasable PROM), flash memory, RAM (random access memory), SRAM (static RAM) or DRAM (dynamic RAM).

Fig. 2 depicts in more detail a connecting device 2 in a motor vehicle 1 according to a first embodiment of the present invention. The connecting device 2 comprises a first means 7 in the form of a hub which is rotatable about a first axis of rotation 8. The first means 7 comprises a driving gearwheel portion 9. The engine 3 is adapted to driving the rotation of the first means 7 by engagement in the driving gearwheel portion 9 of an undepicted engine gearwheel connected to the engine 3. The first means 7 also comprises a first splined surface 10 at one end of the first means 7. The connecting device 2 also comprises a second means 11 in the form of a shaft rotatable about a second axis of rotation 12 which is common with the first axis of rotation 8. The second means 11 is connected to a carrier 13. The power take-off 4 is adapted to being connected to the carrier 13 via the driveshaft 5. The second means 11 comprises a second splined surface 14. The first means 7 and the second means 11 are so arranged that the first splined surface 10 is arranged close to the second splined surface 14. The connecting device 2 also comprises a third means 15 rotatable about a third axis of rotation 16 which is common with the first axis of rotation 8 and the second axis of rotation 12. The third means is partly cut away in Fig. 2 to render the first means and the second means visible. The third means 15 has running through it a hole with an internal splined surface 17 adapted to engagement with the first splined surface 10 and the second splined surface 14. The third means 15 is adapted to being axially movable along the third axis of rotation 16 between a first position and a second position. In the first position the internal splined surface 17 is in engagement with both the first splined surface 10 and the second splined surface 14. In the second

position the internal splined surface 17 is only in engagement with the second splined surface 14. The drawing shows the third means 15 in the first position. A movement means comprising a piston unit 22 is arranged for movement of the third means 15. The movement means comprises a fork 23 with a bearing 24 in which the third means 15 is supported.

When the driver of the motor vehicle 1 operates the control 19 in order to engage the power take-off 4, a control signal will be sent to the control unit 6 for engagement of the power take-off 4. Upon receiving the control signal, the control unit 6 will send to the engine 3 a signal which reduces the speed of the engine 3 to a certain speed which is preferably lower than the engine's idling speed. For example, the engine's idling speed may be reduced to below 200 revolutions per minute and most preferably to below 100 revolutions per minute. Thereafter the control unit 6 sends to the movement means 22 a signal which causes the movement means to move the third means 15 to the first position, in which the internal splined surface 17 is in contact with both the first splined surface 10 and the second splined surface 14. Thereafter the control unit sends to the engine 3 a signal which increases the engine's speed to the same speed as the engine 3 was at before the reduction of the speed of the engine 3. The power take-off 4 is thus engaged.

Fig. 3 depicts in more detail a connecting device 2 in a motor vehicle 1 according to a second embodiment of the present invention. In the connecting device 2 according to this second embodiment, the hub 7 comprises a driving gearwheel portion 9 for driving by the engine 3. The hub 7 also comprises a first gearwheel portion 25 substantially in the form of a gearwheel. The second means comprises a second gearwheel portion 26 of substantially the same form as the first gearwheel portion 25. The third means 27 comprises a gearwheel which is only in engagement with the gearwheel portions 25, 26 when the third means is in the first position. The third means 27 is movable along the third axis of rotation 16. The power take-off 4 is connected to the carrier 13.

It is of course possible to arrange the third means in such a way that it is movable radially relative to the first axis of rotation 8 and the second axis of rotation 12.

It is possible to modify the connecting device according to the second embodiment of the invention, e.g. by arranging the first axis of rotation 8 at a distance from the second axis of rotation 12.

A disadvantage of the connecting device 2 according to this second embodiment of the present invention is that the power transmission surface between the third means 27 and either of the first means 25 and the second means 26 is smaller than in the connecting device 2 according to the first embodiment of the present invention.

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

Although the connecting device 2 is described above as being connected directly to the engine, it is of course possible for the connecting device 2 to be connected to the engine 3 via the gearbox 28.

It is of course possible to effect the connecting device even if the first axis of rotation and the second axis of rotation are not mutually parallel. In that case the third means will comprise a pinion in a bevel gear.

It is of course possible to use other means than a piston unit for moving the third means.

It is possible within the scope of the invention for the third means to be adapted to rotating with the first means and the second means but only be adapted to engaging with a small portion of the first means and the second means.

All the process stages, as also any subsequences of stages, which are described above with reference to the drawings may be controlled by means of a programmed computer. Although the embodiments of the invention described above with reference

to the drawings comprise a computer device and processes which are executed in computer devices, the invention also extends to computer programmes, particularly computer programmes on or in a support, which are suited to implementing the invention. The programme may be in the form of source code, a code between source and object code as in partially compiled form, or in any other form desired which is suitable for use in implementing the process according to the invention. The support may be any desired unit or device capable of supporting the programme. For example, the support may comprise a storage medium such as a flash memory, an ROM (read-only memory), e.g. a CD (compact disc) or a semiconductor ROM, an EPROM (erasable programmable read-only memory), an EEPROM (electrically erasable programmable read-only memory) or a magnetic recording medium, e.g. a floppy disk or hard disk. The support may also be a transmittable support such as an electrical or optical signal which can be conveyed by electrical or optical cables or by radio or by other means. Where the programme has the form of a signal which can be conveyed directly via a cable or other means or medium, the support may take the form of such a cable, device or means. Alternatively, the support may be an integrated circuit in which the programme is embedded, whereby the integrated circuit is adapted to executing, or being used in the execution of, the relevant processes.