WO2017028914A1

WO2017028914A1 - Lubricated automotive vacuum pump

Info

Publication number: WO2017028914A1
Application number: PCT/EP2015/069022
Authority: WO
Inventors: Giorgio Peroni; Raffaele Squarcini
Original assignee: Pierburg Pump Technology Gmbh
Priority date: 2015-08-19
Filing date: 2015-08-19
Publication date: 2017-02-23
Also published as: CN107923400A; EP3337980A1; US20180245592A1

Abstract

The invention refers to a lubricated automotive vacuum pump (10) for providing low-pressure for an automotive actuator, comprising a pump housing (12) housing a pump chamber (16) which is radially defined by a circumferential chamber surface (22), a pump rotor (30) rotating around an axial rotation axis (13), the pump rotor (30) being provided with a rotor body (32) with a vane slit (34) wherein a shiftable vane (36) is shiftably supported which separates the pump chamber (16) into rotating compartments (161, 162), a friction bearing (50) for rotatably supporting the pump rotor (30) at the static pump housing (12), the friction bearing (50) being defined by a cylindrical stator friction bearing surface (52) of the pump housing (12) and a corresponding cylindrical rotor bearing surface (51) of the rotor (30), a pump gas inlet (15) and a separate pump gas outlet (38), an oil inlet channel (60) for providing lubrication oil to the pump rotor (30), and a separate oil outlet opening (411, 412) at the rotor body (32) and an automatic mechanical switchover valve (40) for temporarily connecting the oil outlet opening (411, 412) with an oil drain (70).

Description

Lubricated automotive vacuum pump

The invention refers to a lubricated automotive vacuum pump for providing low-pressure to an automotive actuator.

An automotive vacuum pump provides low-pressure of less than absolute 500 mbar for one or more automotive actuators, for example for a pneumatic brake power assist unit. The vacuum pump is lubricated with oil for reducing mechanical wear, improving the pneumatic efficiency and dissipating heat.

The liquid lubricant flows into the pump chamber where at least one rotating vane separates the pump chamber into several rotating compartments. The pump chamber of conventional vacuum pumps is provided with a gas outlet opening which is fluidically connected to a pump gas outlet. If the pump chamber is not provided with a separate oil outlet opening, the liquid lubricant is pumped out of the pump chamber together with the compressed air. Alternatively, the vacuum pump can be provided with a separate static oil outlet opening at the chamber housing. The oil outlet opening is located in the final compression sector. The oil outlet channel can be provided with a check valve so that the oil outlet channel is only open if the fluidic pressure is above a particular threshold pressure and the oil outlet channel only opens in the final compression phase.

The pressure situation and the pressure level in the pump chamber can be very different and depends in particular on the total pressure at the pump gas inlet which can be in a range of 1000 mbar to 100 mbar. But the check valve generally opens at the same pressure difference so that an optimized opening moment of the check valve cannot be realized for all pressure situations. The mechanical check valve causes noise and generally can be damaged.

It is an object of the invention to provide a lubricated automotive vacuum pump with improved lubrication oil removal means.

This object is solved with a lubricated automotive vacuum pump with the features of claim 1.

The lubricated automotive vacuum pump comprises a pump housing housing a pump chamber which is radially defined by a circumferential chamber surface. The vacuum pump also is provided with a pump rotor rotating around an axial rotation axis. The pump rotor Is provided with a rotatable rotor body supporting at least one shiftable vane in a corresponding vane slit. The vane or the vanes separate the pump chamber into several rotating pump compartments. The vacuum pump is provided with a friction bearing for rotatably supporting the pump rotor at the static pump housing. The friction bearing is preferably provided at one ax!al end portion of the rotor body of the pump rotor. The friction bearing is defined by a hollow cylindrical stator friction bearing surface of the pump housing and a corresponding cylindrical rotor bearing surface of the pump rotor.

The vacuum pump is provided with a pump gas inlet and a separate pump gas outlet. The pump gas outlet is fluidically connected to a gas outlet opening at the pump chamber. The gas outlet opening is provided in a compression sector of the pump chamber where the rotating compartment volume of the rotating compartment decreases when the pump rotor is rotating.

The vacuum pump is provided with a lubricant oil inlet channel for providing lubrication oil to the pump rotor. Lubrication oil Is provided through the inlet channel to the pump rotor to provide lubrication of the friction bearing and to preferably provide lubrication to the pump chamber to lubricate the clearances between the rotating parts and the non- rotating parts of the pump chamber.

The vacuum pump is provided with a separate oil outlet opening at the rotor body and is also provided with an automatic mechanical switchover valve for temporarily connecting the oil outlet opening with an oil drain. The oil outlet opening opens to the pump chamber. The oil outlet opening is not provided static at the pump housing but is provided co-rotating with the pump rotor. The oil outlet channel leading from the oil outlet opening to the oil drain is not always open but is provided with a switchover valve which temporarily and repetitively opens so that oil only can be dissipated from the pump chamber in particular and defined rotor positions. The switching of the automatic mechanical switchover valve is only caused by the rotor rotation. The switchover mechanism can generally be of any kind which opens and closes the switchover valve dependent on the rotational rotor position. The opening and closing of the oil outlet channel does not depend on the pressure situation anymore. However, an additional check valve can be provided in the oil outlet channel.

The oil outlet opening is co-rotating with the corresponding rotating compartment so that the fluidic dynamics of the outflowing oil is improved. The automatic mechanical switchover valve Is reliable and does not cause mechanical noise. Additionally, an automatic mechanical switchover valve can have a simple structure which can be produced cost-effectively.

According to a preferred embodiment of the invention, one oil outlet opening is provided for each rotating compartment, respectively, so that each rotating compartment is provided with its own corresponding oil outlet opening. If two compartments are provided, two oil outlet openings are provided, one oil outlet opening for each compartment.

Preferably, the switchover valve is defined by a rotor valve opening at the rotor body and a stator valve opening at the pump housing. The rotor valve opening and the stator valve opening are in-line to each other, namely in fluidic connection, when the switchover valve Is open. As long as the rotor valve opening and the stator valve opening are not in fluidic connection with each other, the switchover valve is closed. The switching status of the switchover valve is only defined by the rotational rotor position. The mechanical switchover valve is simple and reliable.

According to a preferred embodiment, the rotor valve opening and the stator valve opening are provided at the cylindrical friction bearing surfaces. The friction bearing surfaces define a very small cylindrical gap between them so that in the closed switching status of the switchover valve the valve's sealing quality is very good so that no relevant fluid flow is possible when the switchover valve is closed.

Preferably, the oil outlet opening is defined by an axial bridge groove at the rotor body. The bridge groove has generally an axial component or is exactly provided in an axial direction. Alternatively or additionally, the rotor valve opening can be defined by the axial bridge groove at the rotor body. For every oil outlet opening a separate axial bridge groove is provided in the rotor body. A groove in the rotor body is a simple means and manufacturing of the bridge groove can be provided cost-effectively.

According to a preferred embodiment, the stator valve opening is defined by one single stator groove. The stator groove is preferably provided with axial orientation. Preferably, the respective end portions of the axial rotor bridge grooves and of the static stator g oove define the respective valve openings being in-line in the open switching status of the switchover valve. In other words, the rotor grooves and the stator groove axially overlap in part when the grooves are rotationally in-line with each other. Preferably, the oil outlet opening Is provided in the lagging third of the respective compartment, more preferably in the lagging fifth of the respective compartment. The lagging third of the respective compartment is the sector of the respective compartment which arrives at the separation section the latest. The separation section of the vacuum pump causes a fluidic separation of the rotating compartment into a compression part and a suction part. In the separation section the rotor body is provided adjacent to the circumferential chamber surface so that no relevant fluid flow in circumferential direction is possible through the separation section. The oil outlet opening is preferably provided, seen in circumferential direction, adjacent to the vane slit, namely in a distance of less than 10 mm seen in circumferential direction from the vane slit.

Preferably, the stator groove is provided within 30° of the separation section,

One embodiment of the invention is described with reference to the enclosed drawings, wherein

figure 1 shows a longitudinal section of a lubricated automotive vacuum pump including two oil outlet openings and a mechanical switchover valve, figure 2 shows enlarged one oil outlet opening and the mechanical switchover valve of the vacuum pump of figure 1,

figure 3 shows a top view of the vacuum pump of figure 1 without a cover lid,

figure 4 a side view of the vacuum pump of figure 1, and

figure 5 a cross section V-V of the vacuum pump of figure 1.

The figures show a lubricated automotive vacuum pump 10 for providing pneumatic low-pressure for an automotive actuator. The vacuum pump 10 is a mechanical vacuum pump which Is mechanically driven by an automotive engine.

The vacuum pump 10 is provided with a metal pump housing 12 which is basically defined by the two housing parts, namely a pot -shaped housing body 20 and a cover lid 14. The pump housing 12 surrounds a pumping chamber 16 and also defines a cylindrical stator friction bearing surface 52 of a rotor friction bearing 50.

The vacuum pump 10 is provided with a pump rotor 30 which rotates around an axial rotation axis 13. The pump rotor 30 Is provided with a cylindrical rotor body 32 which is provided with a radial vane slit 34 which supports a vane 36 which is radially shiftable in the vane slit 34. The rotor body 32 is also provided with a cylindrical rotor friction bearing surface 51 which together with the stator friction bearing surface 52 defines a friction bearing 50 at one axial end of the rotor 30. The same axial end of the rotor 30 is provided with a coupling structure 62 for mechanically coupling a driving means of the automotive engine.

The pump housing 12 and the rotor 30 together define the sickle-shaped pump chamber 16 which is laterally defined by a circumferential chamber surface 22, the proximal cylindrical surface 31 defined by the rotor body 32, by a sickle-shaped chamber bottom surface 23 and by an identical sickle-shaped top surface defined by the inside of the cover lid 14.

The sickle-shaped pump chamber 16 is divided by the vane 36 into two separate rotating compartments 161, 162 which rotate when the rotor 30 is rotating. In a separation section 163 of the pump chamber 16 the rotor body 32 is arranged adjacent to the circumferential chamber surface 22 so that no relevant gas flow in circumferential direction is possible.

The vacuum pump 10 is provided with a gas Inlet 15 which is connectable to an automotive actuator, for example to a pneumatic brake assistance unit, and with a gas outlet 38 which is fluidically connected to the atmospheric pressure of the atmosphere. The gas outlet 38 is defined by a gas outlet opening 37 in the circumferential chamber surface 22 and by a check valve 39 arranged fluidically downstream of the gas outlet opening 37 and provided at the outside of the pump housing body 20. Alternatively, the gas outlet can be provided at another pumping chamber wail, for example at the chamber bottom surface.

As best can be seen in figure 5, the vacuum pump 10 is provided with an oil inlet channel 60 which is connected to an external oil pump 11. The oil pump 11 provides pressurized lubricant oil which is pumped via the oil inlet channel 60 to the friction bearing 50 from where the oil flows axially to the pump chamber 16. The rotor body 32 is provided with two axial bridge grooves 421, 422 at the cylindrical surface of the rotor body 32. The housing body 20 is provided with one single axial stator groove 44 In the cylindrical friction bearing surface 52. The axial extent of the two axial bridge grooves 421, 5 422 goes from the pump chamber 16 into the friction bearing 50. The axial extend of the axial stator groove 44 covers most of the axial length of the friction bearing 50. The bridge grooves 421, 422 and the stator groove 44 axially overlap in part so that the overlapping portions of the bridge grooves 421, 422 and of the stator groove 44 define rotor valveo openings 821, 822 and a stator valve opening 80 which together define an automatic mechanical switchover valve 40, respectively. The upper end portion of the axial bridge grooves 421, 422 define two separate oil outlet openings 411, 412 through which oil in the respective rotating compartment 161 can flow out of the pump chamber 16 if the switchovers valve 40 is open. The switchover valve 40 is open if one of the rotor valve openings 821, 822 stand opposite to or is radially in-line with the stator valve opening 80.

A possible spatial orientation of the vacuum pump 10 is shown in figure 1.

The vacuum pump 10 Is mounted and fixed in the respective automotive with a transversal pump plane inclined with respect to the horizontal plane and with a rotational pump orientation so as to provide the oil outlet opening 411 at the lowest point when the switchover valve 40 is open.

However, the spatial orientation of the vacuum pump may differ significantly among the applications. The orientation with respect to the horizontal plane Is not really significant since the oil drain is ensured by the internal pressure of the pump: Hence the effect of the gravity can be considered as marginal.

The open axial end of the axial stator groove 44 defines an oil drain 70 through which the oil coming from the pump chamber 16 and flowing through the respective rotor bridge groove 421 stator groove 44 dissipates to atmospheric pressure.

Claims

A lubricated automotive vacuum pump (10) for providing low- pressure for an automotive actuator, comprising

a pump housing (12) housing a pump chamber (16) which Is radially defined by a circumferential chamber surface (22),

a pump rotor (30) rotating around an axial rotation axis (13), the pump rotor (30) being provided with a rotor body (32) with a vane slit (34) wherein a shiftable vane (36) is shiftably supported which separates the pump chamber (16) into rotating compartments (161, 162),

a friction bearing (50) for rotatably supporting the pump rotor (30) at the static pump housing (12), the friction bearing (50) being defined by a cylindrical stator friction bearing surface (52) of the pump housing (12) and a corresponding cylindrical rotor bearing surface (51) of the rotor (30),

a pump gas inlet (15) and a separate pump gas outlet (38), an oil inlet channel (60) for providing lubrication oil to the pump rotor (30), and

a separate oil outlet opening (411,412) at the rotor body (32) and an automatic mechanical switchover valve (40) for temporarily connecting the oil outlet opening (411,412) with an oil drain (70).

The lubricated automotive vacuum pump (10) of claim 1, wherein one oil outlet opening (411,412) is provided for every rotating compartment (161,162), respectively.

3. The lubricated automotive vacuum pump (10) of one of the preceding claims, wherein the switchover valve (40) is defined by a rotor valve opening (821, 822) at the rotor body (32) and a stator valve opening (80) at the pump housing (12), the rotor valve opening (821, 822) and the stator valve opening (80) being in-line to each other when the switchover valve (40) is open,

4. The lubricated automotive vacuum pump (10) of claim 3, wherein rotor valve opening (821, 822) and the stator valve opening (80) are provided at the friction bearing surfaces (51,52).

5. The lubricated automotive vacuum pump (10) of one of the preceding claims, wherein the oil outlet opening (411, 412) and/or the rotor valve opening (821, 822) are defined by an axial bridge groove (421,422) at the rotor body (32).

6. The lubricated automotive vacuum pump (10) of one of the preceding claims, wherein the stator valve opening (80) Is defined by one single stator groove (44).

7. The lubricated automotive vacuum pump (10) of one of the preceding claims, wherein the oil outlet opening (411, 412) is provided in the lagging third of the respective compartment (161,

162).

8. The lubricated automotive vacuum pump (10) of one of the preceding claims, wherein a separation section (163) is provided where the circumferential chamber surface (22) and the cylindrical rotor body chamber surface (31) define a fluidic separation in circumferential direction, wherein the stator groove (44) is provided within 30° of the separation section (163).