The invention refers to an automotive vacuum pump for generating vacuum, namely an absolute pressure of below 600 millibar, for actuating pneumatic automotive devices.

The vacuum pump according to the invention can be driven mechanically, for example by the internal combustion engine, or can be driven electrically by an electric motor. The vacuum pump according to the invention is a vane pump comprising a pump housing defining a pump cavity and comprising a rotatable pump rotor body with at least one vane slit supporting a shiftable vane. The shiftable vane rotating in the pump cavity separates and defines at least two rotating pumping chambers.

Typical examples of automotive vacuum pumps are disclosed in DE 198 44 904 and WO 2014/154239 Al.

It is an object of the invention to provide a simple and cost-effective automotive vacuum vane pump.

This object is achieved with an automotive vacuum vane pump with the features of main claim 1.

The automotive vacuum vane pump according to the invention is provided with a pump housing which defines a pump cavity within the pump housing. A pump rotor body is rotatably arranged within the pump cavity and Is provided with at least one vane slit supporting at least one shiftable vane defining at least two rotating pumping chambers. The pumping chambers are completely defined by the outside circumferential surface of the pump rotor body, the lateral inside housing wall surface, the axial inside housing wall surfaces and by the vane which separates the pump cavity into the at least two rotating pumping chambers. The pump rotor body has two axial ends, namely an axial low-pressure end and an axial high-pressure end. The low-pressure end of the pump rotor body Is axially supported by a closed housing wall, When the vacuum pump Is operating, the pressure at the low-pressure end of the pump rotor body Is equal or close to the vacuum pressure inside the pump cavity and the rotating pumping chambers, At the other axial end of the pump rotor body, namely the high-pressure end, the pump housing is open to atmospheric pressure. As a consequence, when the vacuum pump Is operating, the pump rotor body is axially pushed in the direction of the closed housing wall by the pressure difference between the pressures at the high -pressure end and the low-pressure end.

The vacuum pump is provided with a radial friction bearing which is axialiy arranged between the vane slit and the high-pressure end of the pump rotor body. The radial friction bearing has two functions, namely to provide a radial bearing for rotatably supporting the pump rotor body at the pump housing and to provide a sealing structure pneumatically separating the pump cavity from atmospheric pressure.

A separate axial rotor retaining arrangement is provided at the high- pressure end of the pump rotor body. The rotor retaining arrangement is defined by a retaining sheet body which is preferably a metal sheet body. The retaining sheet body is arranged in a transversal plane which is a plane perpendicular to the rotational axis of the pump rotor body. The retaining sheet body is axially blocking at least partially the high-pressure end of the pump rotor body so that the pump rotor body is blocked from significantly moving axially into the direction of the high-pressure end. The retaining sheet body is not serving as an axial bearing because, under normal operating conditions, the pressure difference between the two axial rotor body ends normally is sufficient to move and push the rotor body into the other direction, namely into the direction of the low-pressure end of the rotor body. The retaining sheet body has the object, to keep the rotor body in an axial operating position if the pressure difference should not be sufficient, and in particular, if the vacuum pump is not operative or is starting.

According to a preferred embodiment, the retaining sheet body defines a retaining ring for blocking the outer ring portion of the high-pressure end of the pump rotor body. Only the outer ring portion of the pump rotor body is axiaily blocked by the retaining sheet body. Preferably, the retaining sheet body defines a center opening so that a coupling structure of the rotor body is axiaily accessible for a corresponding coupling structure of a driving means.

According to a preferred embodiment of the invention, the automotive vacuum pump is of the lubricated type. The friction surfaces of the pump rotor are lubricated. Preferably, a lubrication conduit arrangement is provided for lubricating the radial friction bearing with a lubrication liquid. The lubrication conduit arrangement comprises one or more lubrication conduits in the pump housing and/or the rotor body for providing pressurized lubricant to frictiona! portions of the pump. The lubrication is also a significantly reduces the friction and the wearout, and has also a sealing effect.

Preferably, the retaining sheet body defines a spring stopper of a fluidic pump outlet valve. The spring stopper is an integral part of the retaining sheet body. The vacuum pump is provided with at least one outlet valve through which the pumped gas/air and, if given, the liquid lubricant exit the vacuum pump. The pump outlet is provided with the fluidic one-way pump outlet valve which preferably also comprises a spring sheet valve body which is arranged between the retaining sheet body and the pump housing. Preferably, the pump outlet valve is a spring sheet valve. The maximum opening position of the valve body, which is a spring sheet, is limited by the spring stopper defined by the retaining sheet body. The retaining sheet body has two functions, namely keeping the rotor body at its correct axial position and also defining a spring stopper. Preferably, two separate pump outlet valves are provided at the high- pressure end of the pump housing. Providing two different pump outlets with a separate outlet valve, respectively, allows to completely discharge the rotating pumping chamber especially in the final compression phase if both outlet valves are provided in the section defining the final compression phase. Alternatively one of the two outlet valves is provided at the section defining the suction phase to allow the pump to be driven also in reverse direction. The discharge of the liquid lubricant in the final compression phase of the rotating pumping chamber is improved significantly by providing two separate outlets with separate outlet valves. The retaining sheet body defines the respective spring stoppers of both outlet valves. Both spring stoppers are an integral part of the retaining sheet body.

According to a preferred embodiment of the invention, the retaining sheet body integrally defines an elastic rotor biasing element for axiaiiy pushing the pump rotor body away from the sheet body. The pump housing and the pump rotor body can be made of different materials with different coefficients of thermal expansion. As a typical example, the pump housing can be made out of metal and the pump rotor body can be made out of plastic. The elastic rotor biasing element guarantees that the low-pressure end surface of the pump rotor is axiaiiy always in touch with and supported by the corresponding closed housing wall. Preferably, the axial friction bearing is defined by the front end surface at the low-pressure end of the pump rotor and by a corresponding housing cover defining the closed housing wall.

The vacuum pump is provided with only one axial friction bearing because, when operated, the pump rotor is axiaiiy pushed by the axial pressure difference against the single axial friction bearing.

Preferably, the lateral outside of the pump rotor body is completely stepless and cylindrical in shape over its entire axial extend. The pump rotor body is completely cylindrical. As a consequence, the pump rotor body is not provided with any circumferential step which could serve as a retaining means, A cylindrical pump rotor body is simple and cost- effectively producible.

According to a preferred embodiment of the invention, the pump rotor body is provided with one single continuous vane slit supporting one single vane separating the pump cavity into two rotating pumping chambers.

One embodiment of the invention is described with reference to the enclosed drawings, wherein figure 1 shows a longitudinal section of an automotive vacuum vane pump according to the invention, figure 2 shows a perspective view of the pump rotor body and the retaining sheet body of the pump of figure 1, figure 3 shows another perspective view of the retaining sheet body of figure 2, and figure 4 shows a cross section IV-IV of the pump of figure 1.

The figures show an automotive vacuum pump 10 for generating a vacuum of an absolute pressure of below 600 mbar. The vacuum pump 10 generates the vacuum for automotive devices which are pneumatically actuated, for example brake servo units, flaps, switches etc. The vacuum pump 10 comprises a massive metal pump housing 12 of two separate housing parts, namely a housing main body 21 and a housing cover 14 at one axial end of the pump housing 12. The pump housing 12 surrounds and defines a pump cavity 11. The pump housing 12 supports a rotatabie plastic pump rotor body 16 of which the lateral outside surface is completely cylindrlcai and stepiess in shape. The pump rotor body 16 is provided with a single continuous radial vane slit 18 supporting a single shiftab!e vane 20 which separates the pump cavity 11 into two rotating pumping chambers. The pump housing 12 and the rotor body 16 together define two separate radial friction bearings 80,81, namely one radial friction bearing 81 at the low-pressure end 15 of the rotor body 16 and another radial friction bearing 18 at the high-pressure end 17 of the rotor body 16. At the low- pressure end 15, the radial bearing 81 is defined by a cylindrical bearing ring surface of the housing cover 14 and the corresponding cylindrical outside surface of an end portion of the rotor body 16. The housing cover 14 is also provided with a housing wall 13 lying in a transversal plane with respect to the rotation axis of the pump rotor body 16. The inside surface 47 of the housing cover wall 13 and the low-pressure sided front end surface 49 of the rotor body 16 together define an axial friction bearing 48.

The pump housing 12 is pneumatically closed at the low-pressure end 15 of the pump rotor 16 so that, when the vacuum pump 10 is operating, the low pressure generated within the pump cavity 11 is also present at the axial friction bearing 48. The pump housing 12 is pneumatically open at the other axial end, namely at the high pressure end 17 of the rotor body 16. As a consequence, the complete axial end surface of the rotor body 16 at Its high pressure end 17 is always under atmospheric pressure which is, when the pump 10 is operating, higher than the vacuum pressure at the other axial end 15 of the pump rotor body 16.

The high-pressure sided radial bearing 80 is defined by a cylindrical outside ring surface portion of the rotor body 16 and a corresponding cylindrical inside ring surface portion of the housing main body 21.

The present vacuum pump 10 is a mechanical pump which is mechanically driven by a driving means 26 which is driven by an internal combustion engine. The high-pressure front end 17 of the rotor body 16 is provided with a coupling structure 28 which is complementary to a corresponding coupling structure 30 of the driving means 26.

The housing main body 21 is also provided with an axial gas inlet channel 24 and two axial outlet channels 22, 23, as also can be seen in figure 4, The gas inlet channel 24 is located at the beginning of the pump cavity 11, seen in the rotational direction, where the local volume of the pump cavity increases starting from zero. The two outlet channels 22, 23 which are outlet channels for air and for a liquid lubricant as well, are located at the end of the pump cavity 11, seen in rotational direction, where the local volume of the pump cavity 11 decreases down to zero. The housing main body 21 comprises a lateral pump inlet opening 32 defining the inlet of the gas inlet channel 24 and two axial valve openings 34 defining the outlet openings of the two axial outlet channels 22, 23.

The radial bearing 80 at the high-pressure end 17 is axially completely open so that the rotor body 16 Is not axially supported directly by the housing main body 21 and can axially be inserted into the housing main body 20 through the radial bearing 80.

As can be seen in figure 4, the housing main body 21 is provided with a lubrication conduit arrangement 95 for lubricating the radial friction bearing 80 and all other friction surfaces with the lubrication liquid. The lubrication conduit arrangement 95 comprises a radial lubrication conduit 90 leading into a lubricant outlet opening 92 and comprises an axial lubrication conduit 91. The lubrication conduit arrangement 95 can comprise other lubrication conduits for directly providing the pressurized lubricant to other friction surfaces.

The high-pressure end of the pump housing 12 is mechanically closed by a rotor retaining arrangement 50 defined by a separate metal retaining sheet body 53 orientated and arranged In a transversal plane with respect to the rotational axis of the rotor body 16. T e retaining sheet body 53 is axially and radially fixed to the housing main body 21 and is arranged within a corresponding recess 63 of the housing main body 21 so that no parts of the retaining sheet body 53 protrudes the silhouette of the pump housing 12.

The retaining sheet body 53 has a complex structure and has several functions as best can be seen in figures 2 and 3. The retaining sheet body 53 is basically a flat sheet metal ring with a center opening 78 so that the coupling structure 28 of the rotor body 16 is axially accessible for the corresponding coupling structure 30 of the driving means 26, as shown in figures 1 and 2. The retaining sheet body 53 defines a ring -like retaining ring 76 for axially blocking the corresponding outer ring portion of the high-pressure end 17 of the pump rotor body 16, as can be seen in figures 1 and 2. The Inner diameter of the retaining ring 76 is smaller than the outer diameter of the pump rotor body 16, and is preferably 5 to 10 mm smaller. The retaining ring 76 stops the pump rotor body 16 to axially move outwardly in the direction of the recess 63.

The retaining sheet body 53 is provided with four integral elastic rotor biasing elements 62, 62' for axially pushing the pump rotor body 16 away from the sheet body 53 so that the low-pressure sided front end rotor surface 49 is always hold adjacent to or even in contact with the corresponding Inside surface 47 of the housing cover 14, even if the vacuum pump 10 is not operating and no axial pressure difference Is present. The elastic rotor biasing elements 62, 62' are provided as two sets of double-tongues which are provided as integral parts of the retaining sheet body 53. The tongues respectively extend in circumferential direction and are minimally bended in axial direction towards the corresponding high pressure front-end 17 of the rotor body 16.

The retaining sheet body 53 Is provided with a half-circular strip-like cutout 52 opposite the outlet valves 70, 71.

The retaining sheet body 53, a separate spring element 54 and the valve openings 34 together define two separate outlet valves 70, 71. The retaining sheet body 53 is provided with and defines two integral and partially cut-out spring stoppers 56 which are provided as one set of two tongues. The spring stoppers are bended in distal direction to allow the underlying spring sheet valve bodies 541, 542 which are defined by the spring element 54 to be axially lifted away from the valve seats defined by the opening edge of the valve openings 34. The outlet valve 70, 71 are so- called check valves which open if the pressure difference inside the pump cavity 11 is sufficiently higher than the atmospheric pressure. The mechanic opening range of the spring sheet valve bodies 541, 542 is limited by the spring stoppers 56, 56'.

The spring element 54 and the retaining sheet body 53 are together fixed at the housing main body 21 by a fixation bolt 60. Additional fixation bolts are provided to fix the retaining sheet body 53 at the housing main body 21 over the entire circumference of the circular retaining sheet body 53.