Patent Description:
Motor vehicle vacuum pumps are typically used in motor vehicles for providing vacuum to a brake booster of a motor vehicle braking system, in particular for providing vacuum to a vacuum chamber of the brake booster. The motor vehicle vacuum pump can be the only vacuum source for the brake booster, or can be used in combination with other vacuum sources as for example an intake system of an internal combustion engine.

The brake booster utilizes the pressure difference between its vacuum chamber pressure and the surrounding atmospheric pressure to enhance a mechanic brake force which is generated by pressing the brake pedal of the motor vehicle and which mechanically actuates the motor vehicle braking system. Providing the brake booster vacuum chamber with an adequate vacuum is therefore crucial to ensure a reliable operation of the brake booster and, as a result, to ensure a reliable and convenient operation of the motor vehicle braking system.

<CIT> discloses, for example, a motor vehicle vacuum pump with a pumping unit with a rotatable pump rotor, wherein the pump rotor is configured to pump fluid from a suction side to a discharge side of the pumping unit during pump operation. The motor vehicle vacuum pump also comprises a pump housing with a housing discharge opening, wherein the housing discharge opening is fluidically connected with the discharge side of the pumping unit. If the motor vehicle vacuum pump is switched off after pump operation, ambient air is sucked into the pump housing via the housing discharge opening because of the pressure difference between the at least partially evacuated pump housing and the ambient atmosphere. The disclosed motor vehicle vacuum pump is provided with a special discharge channel with an abrupt cross section expansion toward the discharge opening to reduce the inflow velocity of the ambient air at the discharge opening during the pump venting and thus to reduce humidity and particle entry into the pump housing. This provides a relatively durable motor vehicle vacuum pump.

However, the motor vehicle vacuum pump of <CIT> has to be installed in the motor vehicle in a defined orientation in which the discharge opening is oriented downwardly to prevent liquid, e.g. condensation water, from accumulating in the discharge channel. This prescribed installation orientation significantly restricts the installation possibilities and thus the application possibilities of the disclosed motor vehicle vacuum pump.

<CIT> discloses a vacuum pump comprising a separate deflection element which is attached to a pump housing and which defines a deflection channel, wherein the deflection channel is fluidically connected with a housing discharge opening and is configured to deflect the fluid flow discharged out of the housing discharge opening during pump operation.

<CIT> discloses a vacuum pump comprising a deflection element which is formed integrally with a cover element of a pump housing and which defines a deflection channel, wherein the deflection channel is fluidically connected with a housing discharge opening and is configured to deflect the fluid flow discharged out of the housing discharge opening during pump operation.

<CIT> discloses a vacuum pump comprising a check valve which is attached to a pump housing and which defines a straight discharge channel that is fluidically connected with a housing discharge opening.

An object of the present invention is therefore to provide a durable and versatile motor vehicle vacuum pump.

This object is achieved with a motor vehicle vacuum pump with the features of claim <NUM>.

The motor vehicle vacuum pump according to the present invention is provided with a pumping unit with a rotatable pump rotor. The pump rotor is arranged in a pumping chamber and is configured to pump fluid from a suction side of the pumping unit to a discharge side of the pumping unit if the pump rotor is driven during pump operation. The pumping chamber is preferably substantially cylindrical and the pump rotor preferably comprises a rotor body which is eccentrically arranged in the pumping chamber and which comprises several radially slidable rotor vanes. During pump operation, the rotor vanes are in touching radial contact with a pumping chamber sidewall and define several rotating, fluidically separated pumping-chamber compartments which convey fluid from the suction side of the pumping unit to the discharge side of the pumping unit. The pumping unit is configured in that way that the volume of a pumping compartment varies during its movement from the suction side to the discharge side so that the conveyed fluid is compressed.

The motor vehicle vacuum pump according to the present invention is also provided with a pump housing which comprises a housing discharge opening. The pump housing is typically composed of a plurality of housing parts which define a plurality of housing chambers. The pump housing typically defines at least the pumping chamber and a motor chamber. The housing discharge opening is fluidically connected with the discharge side of the pumping unit so that fluid is discharged to the ambient atmosphere via the housing discharge opening during pump operation. The housing discharge opening can be a simple opening within a housing sidewall or can be defined by a housing discharge tube/nozzle which protrudes from the housing sidewall. The housing discharge opening is typically provided with a substantially circular opening cross-section.

According to the present invention, the motor vehicle vacuum pump comprises a separate deflection element which is attached to the pump housing. The deflection element defines a deflection channel which is fluidically connected with the housing discharge opening so that fluid is discharged via the deflection channel to the ambient atmosphere during pump operation. The deflection channel preferably discharges directly into the ambient atmosphere so that the deflection channel defines the final section of the discharge flow path. The deflection channel is configured to deflect the fluid flow which is discharged out of the housing discharge opening during pump operation, i.e. the deflection channel is designed in that way that the flow direction of the fluid is changed during the passage of the fluid through the deflection channel. The discharge channel can, for example, be designed curved or angled. The discharge channel can also be designed straight but inclined with respect to the discharge direction of the housing discharge opening. In any case, the deflection channel is designed in that way that the flow direction of the fluid which flows through the discharge channel is deflected with respect to the flow direction of the fluid at the housing discharge opening.

The separate deflection element according to the invention can be easily adapted for different installation orientations of the motor vehicle vacuum pump. The deflection element can in particular be easily designed in that way that the ambient-atmosphere-sided end of the deflection channel is oriented downwardly if the motor vehicle vacuum pump is installed. The downward-oriented deflection channel allows liquid, e.g. condensation water, to drain out of the deflection channel and also minimizes humidity and particle entry into the pump housing during the pump venting. The separate deflection element allows the motor vehicle vacuum pump to be easily adapted to different installation orientations and thus to different installation sites without requiring a redesign of the (complete) pump housing. The separate deflection element according to the present invention thus provides a durable and versatile motor vehicle vacuum pump.

According to the present invention, the deflection element and/or the pump housing are designed in that way that the deflection element is attachable to the pump housing with different orientations with respect to the pump housing. This allows to realize different spatial orientations of the deflection element and, in particular, of the ambient-atmosphere-sided end of the deflection channel with the same deflection element. This allows the motor vehicle vacuum pump to be adapted to different installation sites by simply attaching the deflection element to the pump housing with a different spatial orientation and thus provides a versatile motor vehicle vacuum pump.

Preferably, the deflection element is provided with a fastening receptacle and the pump housing is provided with a protruding housing discharge tube which defines the housing discharge opening and which is inserted into the fastening receptacle so as to fasten the deflection element at the pump housing. This allows for a simple attachment of the deflection element to the pump housing by "plugging" the housing discharge tube into the fastening receptacle of the deflection element. Preferably, the fastening receptacle and/or the housing discharge tube are designed in that way that the deflection element is attachable to the pump housing with different spatial orientations. More preferably, the fastening receptacle is provided with a substantially cylindrical opening and the housing discharge tube is provided with a corresponding, substantially cylindrical outside surface so that the deflection element can be attached with different rotational orientations with respect to the housing discharge tube. Typically, the inside surface of the fastening receptacle and the outside surface of the housing discharge tube are designed to provide a force fit or a form fit in the circumferential direction so as to prevent an unintentional rotation of the deflection element on the housing discharge tube. This provides a versatile motor vehicle vacuum pump.

In a preferred embodiment of the present invention, a housing-discharge-opening-remote outlet channel section of the deflection channel is provided angled with respect to a housing-discharge-opening-adjoining inlet channel section of the deflection channel, preferably the outlet channel section is provided substantially perpendicular to the inlet channel section. The inlet channel section is typically provided center justified with the housing discharge opening. The angled deflection allows the spatial orientation of the ambient-atmosphere-sided end of the deflection channel and thus the discharge direction of the deflection element to be simply varied by rotating the deflection element around the axis of extension of the inlet channel section and thus by rotating the deflection element around the center of the discharge opening. This allows the motor vehicle vacuum pump to be easily adapted to different installation sites by rotating the deflection element and thus provides a versatile motor vehicle vacuum pump.

Preferably, the housing-discharge-opening-adjoining inlet channel section of the deflection channel is provided with a smaller flow cross-section area compared to a flow cross-section area of the housing-discharge-opening-remote outlet channel section of the deflection channel. The larger flow cross-section area of the outlet channel section reduces the flow velocity at the ambient-atmosphere-sided outlet opening of the deflection channel with respect to the flow velocity at the housing-discharge-opening-sided inlet opening of the deflection channel. This reduces the ambient air inflow velocity at the deflection channel outlet opening during the venting of the vacuum pump and thus significantly reduces the humidity and particle entry into the pump housing.

More preferably, the deflection channel comprises an intermediate channel section which fluidically connects the outlet channel section with the inlet channel section, wherein the intermediate channel section is provided with a flow cross-section area which is smaller than the flow cross-section area of the outlet channel section, preferably smaller than or equal to the flow cross-section area of the inlet channel section. This further reduces humidity and particle entry into the pump housing.

In a preferred embodiment of the present invention, the deflection element is made of an elastic plastic, preferably made of rubber. The elastic deflection element allows a simple press-fitting attachment of the deflection element to the pump housing. This provides a reliable attachment of the deflection element without requiring any additional fixation means.

An embodiment of the present invention is described with reference to the enclosed drawings, wherein.

<FIG> shows a motor vehicle vacuum pump <NUM> which is used in a motor vehicle braking system for providing a vacuum to a vacuum chamber of a motor vehicle brake booster <NUM>.

The motor vehicle vacuum pump <NUM> comprises a substantially cylindrical pump housing <NUM> with a pot-shaped housing main body <NUM> and a housing cover element <NUM> which is attached to the housing main body <NUM>. The pump housing <NUM> is provided with a housing discharge tube <NUM> which radially protrudes from a housing sidewall <NUM> of the housing main body <NUM>. The housing discharge tube <NUM> is provided cylindrical and integral with the housing sidewall <NUM>. The housing discharge tube <NUM> defines a circular housing discharge opening <NUM> at its housing-sidewall-remote end.

The motor vehicle vacuum pump <NUM> comprises a pumping unit <NUM> which is arranged in the pump housing <NUM>. The pumping unit <NUM> comprises a rotatable pump rotor <NUM> which is configured to pump fluid, in particular gas, from a suction side <NUM> of the pumping unit <NUM> to a discharge side <NUM> of the pumping unit <NUM> during pump operation. In the present embodiment, the motor vehicle vacuum pump <NUM> is a rotary vane pump wherein the pump rotor <NUM> comprises a plurality of rotor vanes which are configured to be radially slidable and to rotate within a substantially cylindrical pumping chamber.

The suction side <NUM> of the pumping unit <NUM> is fluidically connected to the motor vehicle brake booster <NUM>, in particular to the vacuum chamber of the motor vehicle brake booster <NUM>, via a check valve <NUM>. The check valve <NUM> allows a fluid flow from the motor vehicle brake booster <NUM> toward the pumping unit <NUM> during pump operation and prevents a backward fluid flow from the pumping unit <NUM> toward the motor vehicle brake booster <NUM> if the motor vehicle vacuum pump <NUM> is switched off.

The discharge side <NUM> of the pumping unit <NUM> is fluidically connected with the housing discharge opening <NUM> of the housing discharge tube <NUM> via a housing-internal discharge channel <NUM>.

The motor vehicle vacuum pump <NUM> also comprises an electric motor <NUM> which is arranged in the pump housing <NUM>. The electric motor <NUM> is configured to drive the pump rotor <NUM> via a rotor shaft <NUM> which is co-rotatably connected with the pump rotor <NUM>. In the present embodiment, the electric motor <NUM> is electronically commutated and is configure to be operated with a variable rotational motor speed.

The motor vehicle vacuum pump <NUM> also comprises a pump control unit <NUM> which is configured to control the electric motor <NUM>. In the present embodiment, the pump control unit <NUM> is configured to provide a closed-loop control of the variable rotational motor speed of the electric motor <NUM>.

The motor vehicle vacuum pump <NUM> also comprises a separate, substantially L-shaped deflection element <NUM> which is attached to the pump housing <NUM>. In the present embodiment, the deflection element <NUM> is made of rubber and is provided with a substantially cylindrical fastening receptacle <NUM>. The deflection element <NUM> is fastened at the pump housing <NUM> by a press-fit-connection formed by pressing the housing discharge tube <NUM> of the pump housing <NUM> into the fastening receptacle <NUM> of the deflection element <NUM>.

<FIG> shows an enlarged view of a pump section which comprises the housing discharge tube <NUM> and the deflection element <NUM>.

The deflection element <NUM> defines an angled, in particular a rectangular, deflection channel <NUM>. The deflection channel <NUM> is fluidically connected with the housing discharge opening <NUM> and thus with the discharge side <NUM> of the pumping unit <NUM>. The angled deflection channel <NUM> provides a deflection of the fluid flow which is discharged out of the housing discharge opening <NUM> during operation of the pumping unit <NUM>.

The deflection channel <NUM> in particular comprises three adjoining channel sections, a housing-discharge-opening-adjoining inlet channel section <NUM>, a housing-discharge-opening-remote outlet channel section <NUM>, and an intermediate channel section <NUM> which fluidically connects the outlet channel section <NUM> with the inlet channel section <NUM>.

The inlet channel section <NUM> is provided coaxially to the housing discharge tube <NUM> and (center-)aligned with the housing discharge opening <NUM> so that the housing discharge opening <NUM> fluidically leads into the inlet channel section <NUM>. The inlet channel section <NUM> is provided with an inlet section flow cross-section area A1 which is substantially equal to a discharge opening flow cross-section area A2 of the housing discharge opening <NUM>.

The intermediate channel section <NUM> is provided perpendicular to the inlet channel section <NUM>. The intermediate channel section <NUM> is provided with an intermediate section flow cross-section area A3 which is smaller than the inlet section flow cross-section area A1 of the inlet channel section <NUM>.

The outlet channel section <NUM> is provided coaxially to the intermediate channel section <NUM> and thus perpendicular to the inlet channel section <NUM>.

The outlet channel section <NUM> is provided with an outlet section flow cross-section area A4 which is larger than the inlet section flow cross-section area A1 of the inlet channel section <NUM> and thus larger than the intermediate section flow cross-section area A3 of the intermediate channel section <NUM>. Preferably, the outlet section flow cross-section area A4 is at least twice the intermediate section flow cross-section area A3, more preferably at least four times the intermediate section flow cross-section area A3.

The cylindrical fastening receptacle <NUM> allows the deflection element <NUM> to be mounted on the cylindrical housing discharge tube <NUM> with different rotational orientations with respect to the center axis of the housing discharge tube <NUM>. The separate deflection element <NUM> thus can easily be attached to the pump housing <NUM> with different orientations to thereby vary the discharge direction of the deflection channel <NUM> with respect to the pump housing <NUM>.

In <FIG> the deflection element <NUM> is arranged in a first orientation, wherein the outlet channel section <NUM> is located at a housing-cover-element-sided side of the housing discharge tube <NUM> so that the deflection channel <NUM> deflects the discharge flow toward a housing-cover-element-sided side of the motor vehicle vacuum pump <NUM>.

<FIG> shows a possible second orientation of the deflection element <NUM>, wherein the deflection element <NUM> is rotated by <NUM>° around the center axis of the housing discharge tube <NUM> compared to the first orientation. The outlet channel section <NUM> here is located at a housing-cover-element-remote side of the housing discharge tube <NUM> so that the deflection channel <NUM> deflects the discharge flow away from the housing-cover-element-sided side of the motor vehicle vacuum pump <NUM> and thus in the inverse axial direction compared to the first orientation.

Claim 1:
A motor vehicle vacuum pump (<NUM>) comprising
- a pumping unit (<NUM>) with a rotatable pump rotor (<NUM>), the pump rotor (<NUM>) being configured to pump fluid from a suction side (<NUM>) to a discharge side (<NUM>) of the pumping unit (<NUM>) during pump operation,
- a pump housing (<NUM>) with a housing discharge opening (<NUM>), the housing discharge opening (<NUM>) being fluidically connected with the discharge side (<NUM>) of the pumping unit (<NUM>), and
- a separate deflection element (<NUM>) which is attached to the pump housing (<NUM>) and which defines a deflection channel (<NUM>), the deflection channel (<NUM>) being fluidically connected with the housing discharge opening (<NUM>) and being configured to deflect the fluid flow which is discharged out of the housing discharge opening (<NUM>) during pump operation,
characterized in that
the deflection element (<NUM>) is attachable to the pump housing (<NUM>) with different orientations.