Drive units for motor vehicles normally comprise a plurality of elements between the engine and the drive shaft for the wheels. In most cases the drive unit comprises a clutch device and a gear device between the engine and the drive shaft. The clutch device is usually mounted in a clutch housing behind the engine and can be operated by an actuator device, which may be a purely mechanical device or hydraulic, pneumatic or combinations thereof. The moment of force is then further transmitted from the clutch to the gear device and thereafter to the drive shaft. The gear device is also normally mounted in a housing.

Within the prior art there are several ways of arranging control systems for the actuating device for a hydraulically and/or pneumatically operated clutch.

GB 2314137 describes an actuating device for a friction clutch comprising a retractable bearing assembly coupled to a pneumatic cylinder arranged within the clutch housing and a control valve which is partially outside the bell housing so as to be accessible for maintenance and repair. In this solution the control valve is located in a large opening in the bell housing. It is generally desirable to have as sealed a bell housing as possible so as to prevent to the greatest possible extent the penetration of dirt and other elements into the bell housing. By having a large opening for location of the control valve, a large seal is required in the circumference of the opening. Another drawback is that as long as it is located inside or partially inside the clutch housing, the valve housing, and thereby also the valve, is exposed to the environmental stresses that exist inside the clutch housing, i. e. high normal temperature (generally 100-150 degrees C in a lorry, higher in a private car), as well as large amounts of dust.

In SU 1594000 a valve device is described for controlling cylinder devices, which is arranged outside the bell housing. The valve device is engaged with fluid transfer pipes that are inserted through the housing wall to the cylinder device. The penetration of the pipes through the housing wall is a wear point on the pipes while at the same time there are openings in the housing wall. Furthermore, the fluid transfer pipes in themselves may be subject to damage, resulting in leakage.

Assembling this system is also time-consuming with penetration of pipes that have to be mounted both in the cylinder device and the valve device.

The object of the present invention is to reduce or eliminate the disadvantages of the risk of leakage from the fluid transfer pipes. It is also an object to minimise the possibility of penetration of dirt into the clutch housing. Another object is to simplify the assembly and maintenance of the system, thereby achieving economic benefits. It is also an object to achieve a solution that provides a more compact solution with regard to transfer of fluid from the outside of a housing to the inside and vice versa.

These objects are achieved with the present invention as defined in the following claims.

The present invention relates to a drive unit for motor vehicles. The drive unit comprises a clutch in a clutch housing, between an engine and a gear device in a gearbox housing. The clutch has an actuator for activating/deactivating the clutch.

The actuator is mounted inside the clutch housing. The actuator is controlled by a valve block, which receives signals in response to the operator's actions. The signals may be mechanical, hydraulic, pneumatic, electrical or digital or transmitted in another way. The valve block for controlling the actuator is mounted on the outside of the housings. There are fluid transfer lines between the valve block and the actuator for transferring fluid for activating and/or deactivating the actuator.

These fluid transfer lines between the valve block and the actuator are composed of at least one hollow bore in the material forming at least one of the housings.

In an embodiment of the invention the clutch housing and gearbox housing may be in the form of one housing unit and the fluid transfer lines composed of hollow bores in this common housing, or they may be provided in the clutch housing alone or the gearbox housing alone or a combination of hollow bores in both housings. In the latter case it will be natural to employ some kind of seal in the transition between the housings in order to obtain a sealed fluid transfer.

In a preferred embodiment of the invention the valve block is mounted on the housing wall, and the fluid transfer line (s) from the valve block pass directly from the valve block into the hollow bore (s) in the housing, with the result that an opening in the valve block communicates directly with an opening of a hollow bore, and moreover the actuator is mounted on the inner housing wall and a fluid transfer line to the actuator passes directly from a hollow bore in the housing to the actuator, with the result that an opening in the actuator communicates directly with an opening of a hollow bore. Alternative variants are to mount the valve block on the outside of the housing wall in direct communication with hollow bores, the insides of which are in communication with fluid transfer lines leading to the actuator or vice versa where the actuator is mounted on the inside of the housing wall in direct communication with the hollow bores, the outsides of which are connected with fluid transfer lines leading to the valve block. In all of these embodiments fluid transfer from valve block to actuator is composed at least partly of hollow bores in the material forming the housing round the clutch and/or the gear device.

The actuator will normally be located closer to a centre axis for the transmission between clutch and gear than the actual valve block that controls the actuator. In such an embodiment the hollow bore (s) in the housing will comprise a substantially radial bore in a substantially radial wall of a housing. In this case the housing may be the clutch housing and/or the gear housing or a housing in the form of a unit for covering both devices.

In a preferred embodiment of the invention, seals are provided in the transition between the valve block and the housing and/or the housing and the actuator, thus facilitating a sealed connection between the hollow bores and the valve block and/or actuator. This is important in order to avoid leakage in the clutch housing or loss of control fluid for the actuator. In this case simple devices may also be envisaged for locking the valve block and the actuator to the housing wall that simultaneously ensure correct positioning in relation to the hollow bores and sealed transfers.

The invention also comprises a system in connection with a drive unit in a motor vehicle for transferring at least one fluid through at least one fluid transfer line between an element mounted on the inside of a housing and the outside of the housing. The characterising novelty is that the fluid transfer line is substantially composed of a hollow bore in the material forming the housing.

The invention will now be explained in greater detail by an embodiment with reference to the attached drawing illustrating an embodiment of the invention for transfer of fluid between actuator and valve block.

The figure illustrates a schematic section of the drive device for a motor vehicle comprising an engine (not shown), which via a clutch device 1 (schematically illustrated) transmits a moment of force on a shaft (not shown) to a gear device 2 (schematically illustrated), which at the rear transmits the moment to a drive shaft (not shown) for the motor vehicle. The moment of force is transmitted from the clutch 1 via a shaft mounted in a shaft tube 3 to the gear device 2. The clutch device 1 and the gear device 2 are mounted in a surrounding housing 4. The housing in this embodiment comprises a gear housing portion 5 and a clutch-housing portion 6, each of which encloses the gear device 2 and the clutch device 1 respectively.

Between these two housing portions, the housing comprises a substantially radial partition 7. In a second embodiment of the invention the gear housing portion and the clutch housing portion may each be composed of an independent housing and the partition is composed of a part of one or the other independent housing.

Inside the housing 4 the shaft mounted in the shaft tube 3 transmits the moment of force from the clutch device 1 to the gear device 2. The shaft extends through the radial partition 7 of the housing 4 and the shaft tube 3 is provided with a flange portion 31 in abutment against the radial partition 7.

Inside the clutch-housing portion 6 between the clutch device 1 and the radial partition 7 there is mounted an annular actuator 8, located concentrically around the shaft tube 3. The actuator 8 comprises a piston unit 9. The piston unit 9 is designed with a substantially radially extending piston portion 10. A guide-bushing portion 11 of the piston unit 9 abuts against the shaft tube 3 radially inside the piston portion 10. The guide-bushing portion 11 has an axial extension along the shaft tube 3. At the other end of the guide-bushing portion 11 relative to the piston portion 10, the piston unit 9 comprises an annular bearing support portion 12, which is U- shaped in cross section and holds an annular ball bearing 13 whose other part is in abutment with the clutch device 1.

The piston portion 10 of the piston unit is inserted axially into the interior of a cylinder portion 32. The cylinder portion 32 is a portion of the shaft tube 3, which portion 32 extends from the shaft tube's flange portion 31 in a substantially axial direction at a greater radial distance from the centre axis than the shaft tube's 3 main portion 30, for a length backwards over the shaft tube's main portion 30. The shaft tube with the main portion 30, flange portion 31 and the cylinder portion 32 is fixed relative to the radial partition 7 of the housing 4.

A part of the shaft tube's 3 main portion 30, the flange portion 31 and the cylinder portion 32 together with the piston portion 10 of the piston unit 9 form a working chamber 14 for an annular piston cylinder representing the actuator 8. The working chamber 14 is provided with a seal 15 between the piston portion 10 and the cylinder portion 32 and a seal 16 between the piston portion 10 and the main portion 30. On the opposite side of the piston portion 10 there is a free-wheel chamber 17 which is separated from the rest of the interior of the clutch housing by a bellows 18, which is mounted at an outer end of the cylinder portion 32 and an outer end of the bearing support portion 12.

In the embodiment the valve block 20 which controls the activation/deactivation of the actuator 8 is illustrated mounted directly on the outside of the housing 4. This means that the valve block 20 is attached directly to the housing 4 and an outlet for a control fluid from the valve block communicates directly with a control fluid hollow bore 21 in the material forming the housing 4. The hollow bore 21 extends from the valve block 20 in a radial hollow bore 22 into the radial partition 7 and on into an axial hollow bore 23 at the inner end of the radial bore and directly to the working chamber 14 of the actuator 8. From the valve block 20, therefore, a direct fluid transfer passes through the control fluid hollow bore 21 to the actuator's working chamber 14. By providing seals in the transition between valve block 20 and the housing 4 and the actuator 8, a sealed and reliable fluid transfer is obtained between these parts, without making unnecessary holes in the housing. This also makes for easy assembly since it enables mounting devices to be provided for both valve block 20 and actuator 8 which also create a sealed connection to the hollow bores 21. It also helps to avoid having exposed fluid transfer lines and penetrations thereof through the housing wall.

In an embodiment of the invention, in addition to the control fluid hollow bore 21 there is also provided a venting bore 24 extending from the free-wheel chamber 17 through the cylinder portion 32 of the shaft tube and through the housing to a venting valve/outlet arranged on the outside of the housing 4, usually as a part of the valve housing 20, for discharge and admission of air from the outside of the housing to the free-wheel chamber 17 on movement of the piston unit for operation of the clutch device. This is an extra feature of the invention.

When the actuator is pressurised and the piston moves to the left, the air inside the venting chamber will be discharged, which is not a problem. However, when the actuator piston moves to the right, the venting chamber will suck in air. If this is air from the inside of the clutch housing, this air will contain a great deal of dust particles, which in turn will cause increased wear on the actuator. It is therefore desirable for the venting chamber also to have the opportunity of breathing in clean air. This may be air from the outside-or preferably from a clean air source (filtered and/or dried air).

The invention has now been described by an embodiment where the actuator is employed for a pressure-operated clutch, but an actuator for a traction-operated clutch may equally well be envisaged. It is also possible to envisage other forms of actuator to be operated by a control fluid where it is desirable to have the actuator mounted inside the housing surrounding clutch or gear, and the valve block for controlling this actuator located outside the housing. It is also conceivable that there may be more radial supply hollow bores for operation of the same actuator or for transferring different control fluids to the interior of the housing. A number of variations may therefore be envisaged in relation to the described embodiment, which are within the scope of the invention as defined in the following patent claims.