Automotive side-channel fluid pump

The invention is directed to an automotive side channel fluid pump for providing pressurized fluids within a fluid circuit of an automobile.

A typical side channel pump in particular for the automotive sector comprises a pump housing which defines a pump chamber. A pump wheel is arranged within the pump chamber to define a side channel together with the pump housing. The pump wheel can be co-rotatably connected via a drive shaft to a motor rotor of an electric drive motor, for driving the pump wheel and for thereby accelerating the fluid within the side channel.

Generally, the drive shaft is supported by separate bearings which are arranged in the pump housing or in other structurally suitable components. The pump wheel is typically connected to a drive shaft in a co-rotatable manner, wherein the drive shaft is supported by two separate bearings which are both arranged at the motor-sided end of the pump wheel, each bearing at one axial side of the motor rotor. Thereby, the pump wheel overhangs with respect to the bearings to one axial side at a free axial end of the drive shaft so that massive radial forces resulting from the rotating centrifugal pump wheel mass act remote from the supporting zones via a lever arm onto the drive shaft. This arrangement of the pump wheel can cause the pump wheel to flutter in particular if the pump wheel rotates with high rotational speed. In addition, the bearings need a relatively large space within the pump housing which results in a relatively large side channel pump. It is an object of the present invention to provide a compact automotive side channel fluid pump with a reliable support of the pump wheel within the pump housing.

This object is achieved by an automotive side channel fluid pump with the features of main claim 1.

An automotive side channel fluid pump according to the present invention comprises a pump housing defining a pump chamber, the pump chamber being preferably cylindrical. The automotive side channel fluid pump further comprises a pump wheel which is rotatably arranged within the pump chamber. The pump wheel and the pump housing thereby define a side channel inside the pump chamber in which the fluid is accelerated by a plurality of pump wheel blades.

The pump wheel is provided with an axially protruding integral bearing journal which radially supports the pump wheel in a corresponding bearing shell. The bearing shell is an integral part of the pump housing, i.e., the bearing journal of the pump wheel is directly radially supported within the bearing shell of the pump housing. The bearing shell and the bearing journal thereby preferably define a friction bearing wherein the radial outside surface of the bearing journal is in a frictional contact with the radial inside surface of the bearing shell. Preferably, the bearing journal and/or the bearing shell are made of a material with relatively good sliding properties, for example a plastic material, so that the friction coefficient of the friction pairing is relatively low which is in particular advantageous if the pumped fluid is a gas or another fluid with relatively poor tribological characteristics. For example, a pump wheel made of plastic or aluminium could be supported by a plastic pump housing so that the friction pairing is provided with relatively good sliding properties without using any additional lubricants. The direct supporting of the pump wheel within the pump housing allows a relatively compact design of the automotive side channel fluid pump, because only one additional bearing means is required at the pump wheel or a drive shaft being co-rotatably connected to the pump wheel to define a statically determined support of the pump wheel. As a result, one of the two separate bearings of a conventional side channel pump can be left out. Thereby, the axial length of the automotive side channel fluid pump can be significantly reduced compared to a state-of-the-art side channel pump.

In a preferred embodiment of the present invention the axially protruding bearing journal is cylindrical. Accordingly, the bearing shell within the pump housing is correspondingly shaped. A cylindrical friction bearing which only supports the pump wheel in radial direction defines a relatively costefficient, compact and easily manufacturable type of bearing. In addition, the assembly process is relatively uncomplicated, so that the application of the cylindrical friction bearing results in relatively low manufacturing costs of the automotive side channel fluid pump. Alternatively, other bearing types, for example a conical friction bearing which, additionally to the radial support, supports the pump wheel in one axial direction can be applicated within the automotive side channel fluid pump.

In a particularly preferred embodiment of the present invention, the pump housing comprises a pump cover which is preferably covering the pump chamber at that axial side where the side channel is arranged, i.e., the friction bearing is at the axial end of the pump wheel that faces the side channel. Accordingly, the pump cover and the pump wheel define the side channel. As the pump cover is, with respect to the electric drive motor, arranged at the opposite axial end of the automotive side channel fluid pump, the pump wheel is radially supported at its both axial sides, i.e., the bearing journal is arranged at that side of the pump wheel opposite to the motor rotor. The bilateral support of the pump wheel, wherein the pump wheel is arranged between the two supporting zones results in an excellent absorption of the radial forces resulting from the rotating centrifugal mass of the pump wheel and from the pressure forces within the side channel so that, compared to the state-of-the-art, the force does not act via a lever arm at the free axial end of the drive shaft. Thereby, the pump wheel runs smooth and precisely within the pump chamber so that the sealing gap between the pump wheel and the pump housing is very constant even at a higher rotational speed of the pump wheel. This flutter-free rotation of the pump wheel allows the application of a very small sealing gap resulting in a high sealing quality of the side channel.

An axial extension of the bearing journal is preferably at least 50% of an axial height of a disc-shaped part of the pump wheel. The disc-shaped part of the pump wheel is substantially the part that comprises the pump wheel blades that accelerate the fluid within the side channel. As a result, the dimensions of the bearing journal depend substantially on the dimensions of the pump wheel and of the side channel so that a reliable support of the pump wheel is guaranteed.

Preferably, the pump wheel is axially supported within the pump housing by an axial end surface of the protruding integral bearing journal. This distal axial end surface is in a frictional and force transferring contact with an opposite and corresponding axial support surface at the axial inside of the pump housing or the pump cover so that the sealing gap between the pump wheel and the pump housing or the pump cover is exactly defined and remains relatively constant.

An embodiment of the present invention is described with reference to the enclosed figure showing a schematic longitudinal cross-sectional view of an automotive side channel fluid pump according to the present invention. The enclosed figure shows an electrically driven automotive side channel fluid pump 10 for providing pressurized oil within an oil circuit of an automobile. The automotive side channel fluid pump 10 comprises a multipiece pump housing 12 comprising a pump cover 17 which is made of a Teflon-based plastic material with relatively good sliding properties. The pump housing 12 further comprises a pump housing body 18 which together with the pump cover 17 defines a cylindrical pump chamber 15.

A substantially disc-shaped pump wheel 20 being made of an aluminium- based material is rotatably arranged within the pump chamber 15, the pump wheel 20 being provided with a plurality of radially oriented pump wheel blades 25 which are equiangularly arranged over the circumference of the pump wheel 20. The pump wheel 20 covers a side channel 14 which is defined within the pump cover 17 by a U-shaped groove which extends circularly over the circumference of the pump cover 17 between a pump chamber inlet 13 and a pump chamber outlet (not shown). The pump cover 17 additionally defines a pump inlet duct 171 which extends from the pump chamber inlet 13 axially outwards. Furthermore, the pump cover 17 defines a pump outlet duct 172 which extends from the pump chamber outlet tangentially outwards with respect to the side channel 14, wherein the pump outlet duct 172 extends in the tangential direction that corresponds to the rotational direction of the pump wheel 20 and thereby corresponds to the flow direction of the oil within the side channel 14.

Due to the rotation of the pump wheel 20, the oil is sucked in through the inlet duct 171 and through the pump chamber inlet 13 into the pump chamber 15. After that, the fluid is accelerated by the pump wheel blades 25 within the side channel 14 and is accelerated substantially in rotational direction of the pump wheel 20. Thereby the oil is pressurized and is pumped through the side channel 14 towards the pump chamber outlet, through which the oil is discharged from the pump chamber 15 through the outlet duct 172 into the oil circuit of the automobile.

The pump wheel 20 comprises a cylindrical and axially protruding bearing journal 24 which extends axially from an axial end surface 21 which is facing the pump cover 17. The axial extension h2 of the bearing journal 24 is about 80% of the axial height hl on a disc-shaped part 22 of the pump wheel 20 in that section where the pump wheel blades 25 are arranged. The bearing journal 24 extends into a correspondingly shaped cylindrical recess 35 defining a bearing shell 30 within the pump cover 17. Thereby, the radial outer surface of the bearing journal 24 is in a frictional direct contact with the radial inner surface of the bearing shell 30 so that the bearing journal 24 and the bearing shell 30 define a friction bearing 26 which radially supports the pump wheel 20 within the pump cover 17. Due to the pairing of a plastic pump cover 17 and an aluminium pump wheel 20, the corresponding sliding surfaces of the bearing journal 24 and the bearing shell 30 define a friction pairing with an extremely low friction coefficient resulting in an extremely wear-resistant friction bearing 26.

The bearing journal comprises an axial end surface 241 which is in a direct contact with a facing axial pump cover surface 175 so that a first axial stop 245 is defined that axially supports the pump wheel 20 from moving towards the pump cover 17. Thereby, a relatively constant sealing gap 38 is defined between the axial end surface 21 of the pump wheel 20 and the facing axial end surface 178 of the pump cover 17 which defines a dynamic and contact-free sealing of the side channel with relatively high and constant sealing quality.

The pump wheel comprises an axial bore hole 28 which extends axially through the centre axis of the pump wheel 20. The pump wheel 20 is mounted to a steel drive shaft 11 which is inserted into the axial bore hole 28 such that the pump wheel 20 and the drive shaft 11 are co-rotatably connected to each other. The drive shaft 11 protrudes from the pump wheel 20 at an axial end that is arranged opposite to the side channel 14. Furthermore, the drive shaft 11 is not completely extending through the axial bore hole 28 of the pump wheel 20 so that the axial end surface 111 of the drive shaft 11 is countersunk with respect to the axial end surface 241 of the bearing journal 24. Thereby, a direct contact between the axial end surface 111 of the drive shaft 11 and the pump cover 17 is avoided so that the plastic pump cover 17 is not subjected to any mechanical wear by the drive shaft 11.

The protruding part of the drive shaft 11 is co-rotatably connected to a motor rotor 51 of a brushless electric drive motor 50 that rotates the pump wheel 20 within the pump chamber 15. The electric drive motor 50 further comprises a motor stator 52 which is circumferentially surrounding the motor rotor 51, wherein the motor rotor 51 and the motor stator 52 are fluid ically separated from each other by a hollow cylindrical separating tube 181 which is an integral part of the plastic pump housing body 18. The separating tube 181 is axially closed by a plastic rotor chamber cover 16 that hermetically seals the rotor chamber 40 which is housing the motor rotor 51.

The disc-shaped rotor chamber cover 16 comprises a protruding collar 161 which defines a bearing shell, wherein the drive shaft 11 is inserted into the collar 161 and is therefore in a direct frictional contact with the bearing shell collar 161 so that a second motor-sided friction bearing 162 is provided that radially supports the drive shaft 11. The pump wheel 20 is thereby provided with a bilateral support supporting the pump wheel 20 at both axial sides resulting in a smooth and precise rotation of the pump wheel 20 even at relatively high rotational speed. In addition, an axial end surface 112 of the drive shaft 11 at that axial end which is remote from the pump wheel 20 is in a direct contact with a corresponding facing axial end surface 165 of the rotor chamber cover 16. Thereby, the drive shaft 11 and the pump wheel 20 are axially supported from moving axially away from the pump cover 17 so that, compared to the first axial stop 245 of the pump wheel 20 and the pump cover 17, this second axial stop 168 axially supports the pump wheel 20 and the drive shaft 11 in the opposite axial direction. The second axial stop 168 collaborates with the first axial stop 245 such that the pump wheel 20 is axially fixed in both axial directions against any relative movement referring to the pump cover 17 or the pump housing body 18 so that the sealing gap 38 between the pump wheel 20 and the pump cover 17 remains constant. Furthermore, a stator chamber 41 which houses the motor stator 52 of the electric drive motor 50 and which surrounds the rotor chamber 40 is axially closed by a plastic stator chamber cover 19 which hermetically seals the stator chamber 41 against the environment.