Electric motor-pump assembly

Abstract

In an electric motor-pump assembly, two working diaphragms, each delimiting a working chamber, are cyclically driven by a crank drive via connecting rods. The crank drive includes eccentrics for each connecting rod, which are placed on an axial bearing journal in the extension of an output shaft of an electric motor. In order to ensure a rotationally fixed connection between the eccentrics and the bearing journal to be produced and in order to ensure an angularly precise position of the two eccentrics, each of the eccentrics is connected to the bearing journal by a positively locking engagement.

Claims

1. An electric motor-pump assembly, for providing pressure for a brake actuation device of a motor vehicle brake system, having a pneumatic brake booster, comprising: a vacuum pump; and an electric motor driving the vacuum pump, wherein the vacuum pump comprises at least two working chambers, each defined by a working element, wherein each working element is connected to a connecting rod, which is supported by a crank drive, which comprises a bearing journal, which is driven by the electric motor and onto which a first eccentric for one connecting rod and a second eccentric for another connecting rod are rotationally locked, for which purpose each eccentric has an opening, through which the bearing journal projects, wherein the first eccentric bears against the second eccentric, and wherein the rotationally locked connection between the bearing journal and the first and second eccentrics is produced by a positive interlock, for which purpose the bearing journal and the opening of each eccentric each have a cross section deviating from a circular shape, the cross section of the bearing journal having a different shape than the cross section of the opening of each eccentric, such that the first eccentric is fitted onto the bearing journal at precisely 180 relative to the second eccentric.

2. The electric motor-pump assembly as claimed in claim 1, wherein the bearing journal has at least two opposing flats, and wherein a circumferential surface of each opening through which the bearing journal passes has two parallel boundary surfaces, wherein a distance between the two opposing flats of the bearing journal corresponds to a distance between the two parallel boundary surfaces of the opening, so that each of the two parallel boundary surfaces is set against a respective one of the two opposing flats to form a positive interlock.

3. The electric motor-pump assembly as claimed in claim 1, wherein the bearing journal is provided with a plurality of longitudinal channels.

4. The electric motor-pump assembly as claimed in claim 3, wherein a free end of the bearing journal comprises a head tapering conically towards the free end of the bearing journal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be explained in more detail below with reference to an exemplary embodiment. In the drawing:

(2) FIG. 1 shows an embodiment according to the state of the art,

(3) FIG. 2 shows a side view of a bearing journal as output shaft of an electric motor,

(4) FIG. 3 shows a side view of an eccentric, matching the bearing journal according to FIG. 2,

(5) FIG. 4 shows a crank drive, which is connected to the output shaft by means of a clamping sleeve,

(6) FIG. 5 shows a side view and a cross sectional view of the clamping sleeve and FIG. 6 shows a further embodiment of the bearing journal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) Referring first of all to FIG. 1:

(8) The vacuum pump 1 is a double-diaphragm pump having two opposing working diaphragms 2, which are each clamped between a pump housing 3 and a working chamber cover 4 and thereby define a working chamber 5. The working diaphragms 2 can be moved in opposite directions by means of a crank drive 6, wherein the crank drive 6 has an eccentric 7 for each working diaphragm 2, on which the eye of a connecting rod 8, connected to the respective working diaphragm 2, is supported. The reciprocating movement of the working diaphragms 2, which in this exemplary embodiment form the working elements of the vacuum pump 1, causes air to be drawn into the working chamber from the unit to be exhausted, before it is expelled into the atmosphere.

(9) A discharge valvenot shown herevia which the air expelled from the working chamber is fed, in each case via a discharge port in the working chamber cover, to a discharge port in the pump housing 3, is provided in each of the working chamber covers 4. The two discharge ports in the pump housing open into an internal chamber 9 of the pump housing 3, the so-called crank chamber, which encloses the crank drive 6. An air outlet 10 provided in the pump housing allows the air to be quietly discharged from the internal chamber 9.

(10) Eccentrics 7, 7 are press-fitted onto a bearing journal 11 of circular cross section, which extends the output shaft 12 of an electric motor 13, externally fitted to the pump housing 3, in an axial direction, and the axis of which lies in the axis of the output shaft 12.

(11) By contrast, an aspect of the invention, as represented in FIGS. 2 and 3, provides for a bearing journal 11 having an angular cross section with multiple lateral flats 14, which each run parallel to the axis of the bearing journal 11, and at least two of which are situated opposite one another and run parallel.

(12) Each eccentric 7 according to FIG. 3 comprises a disk, which has an off-center opening 15, which has a rectangular cross section. A balance weight 16, which extends in a radial direction, can also be seen, integrally formed with the disk.

(13) The distance between the two long sides of the opening 7, which each form a boundary surface 17, is equal to the distance between the two aforementioned flats 14. The distance between the short sides of the opening 15 is equal to the diameter of the bearing journal 11, relative to a plane, parallel to the flats 14 and running through the axis of the bearing journal. In this way a positive interlock is obtained between the bearing journal and the eccentric 7.

(14) The disks are of a certain thickness, so that the opening 15 has a certain depth, allowing the flats 14 to bear against the long boundary surfaces of the rectangular opening 15 over a sufficiently large contact area. This ensures that a sufficiently large torque can be transmitted.

(15) In addition, this allows a second eccentric 7, which is of similar construction to the first eccentric 7 represented, to be fitted onto the bearing journal at precisely 180 to the first eccentric 7.

(16) FIG. 4 shows the cross section through a further invention. An axial blind hole 18 is made in the end face of the output shaft 12. Holes 19 in the eccentrics 7 for receiving the bearing journal 11 are circular.

(17) For a rotationally locked connection of the eccentrics 7 to the output shaft 12, a clamping sleeve 20 is provided. This is a hollow cylinder having a longitudinal slot 21 and made from a spring steel. The longitudinal slot 21 allows the clamping sleeve 20 to be radially compressed when it is fed through the holes. The resilient characteristics then cause the clamping sleeve 20 to expand and create a secure positive interlock in the openings of the eccentric disks and in the blind hole.

(18) FIG. 6 shows a further embodiment of the bearing journal 11. The bearing journal 11 has a knurled surface, which comprises a plurality of longitudinal channels 22, which allows a positively interlocking connection to an eccentric, which has a corresponding, mating knurled surface.

(19) At its free end the bearing journal has a conical head 23, which facilitates the fitting of the eccentrics. A groove 24, running around the bearing journal runs between the knurled surface and the head.

REFERENCE NUMERALS

(20) 1 vacuum pump 2 working diaphragms 3 pump housing 4 working chamber cover 5 working chamber 6 crank drive 7 eccentric 8 connecting rod 9 internal chamber 10 air outlet 11 bearing journal 12 output shaft 13 electric motor 14 flats 15 opening 16 balance weight 17 boundary surface 18 blind hole 19 hole 20 clamping sleeve 21 longitudinal slot 22 longitudinal channels 23 head 24 groove