Patent Description:
Mechanical motor vehicle coolant pumps are mechanically driven by a crank shaft of the internal combustion engine, for example via a belt drive, a chain drive or a gearing. The rotational speed of a coolant pump wheel of mechanical motor vehicle coolant pumps is therefore always proportional to the rotational speed of the crank shaft of the internal combustion engine. The cooling demand of the internal combustion engine however is typically not proportional to the rotational speed of the crank shaft. Controllable mechanical motor vehicle coolant pumps are therefore provided with an arrangement which allows to control the coolant discharge flow without controlling the rotational speed of the coolant pump wheel. One concept to realize the control of the discharge flow is to provide a control slider which is configured to be axially shiftable with respect to the coolant pump wheel in order to control an effective discharge flow cross-section of the coolant pump wheel by partially or completely covering the radial outside of the coolant pump wheel with a cylindrical side wall of the control slider.

Such a controllable mechanical motor vehicle coolant pump is disclosed in <CIT>. The disclosed coolant pump comprises a push-out pressure chamber which is configured to be hydraulically pressurized in order to generate a hydraulic push-out push force axially pushing the control slider in the axial pump direction over the coolant pump wheel. The push-out pressure chamber is defined axially by a slider bottom wall of the control slider as well as by a transverse housing surface, and is defined radially inwardly by an inner slider support surface which shiftably supports a radially inner bottom wall surface of the slider bottom wall.

The transverse housing surface is defined by a first housing element and the inner slider support surface is defined by a separate second housing element which axially abuts the transverse housing surface of the first housing element. The unsealed contact interface between the second housing element and the transverse housing surface, however, allows pressurized liquid to leak into the push-out pressure chamber from a fluid channel located radially inward of the inner slider support surface within the second housing element. This leakage can lead to an unintentional increase of the hydraulic pressure of the push-out pressure chamber, which in turn can cause an unintentional shifting of the control slider toward the coolant pump wheel and thus an unintentional reduction of the effective discharge flow cross section of the coolant pump wheel by the control slider. Insufficient discharge flow of the coolant pump, however, can cause severe damage to the internal combustion engine of a motor vehicle.

<CIT> discloses a controllable motor vehicle coolant pump comprising a cylindrical slider element and a ring-disc-shaped piston device, which is attached to an end face of the slider element facing away from the coolant pump wheel. The piston device has an inside diameter matching that of the slider element, and an outside diameter larger than that of the slider element. The piston device is arranged axially between the coolant pump wheel and a transverse housing surface. A radially inner surface of the slider element and of the piston device are shiftably supported by an inner cylindrical surface defined by a housing element, and a radially outer surface of the piston device is shiftably supported by an outer cylindrical surface defined by the same housing element.

An object of the present invention is therefore to provide a controllable mechanical motor vehicle coolant pump which allows reliable control of the coolant discharge flow.

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

The controllable mechanical motor vehicle coolant pump according to the present invention is a flow pump, preferably a centrifugal pump, which is configured to pump a liquid coolant, such as water, from a pump inlet to a pump outlet. The controllable mechanical motor vehicle coolant pump according to the present invention is preferably configured to pump liquid coolant through a cooling circuit of an internal combustion engine.

The controllable mechanical motor vehicle coolant pump according to the present invention is provided with a rotatable drive shaft which extends in an axial pump direction. The drive shaft is configured to be mechanically driven by an engine of a motor vehicle, for example via a gearing, a belt drive or a chain drive.

The controllable mechanical motor vehicle coolant pump according to the present invention is also provided with a coolant pump wheel which is co-rotatably connected with the drive shaft and which is configured to pump the liquid coolant from the pump inlet to the pump outlet. Preferably, the coolant pump wheel is arranged at an axial end of the drive shaft and the pump inlet is arranged coaxial to the coolant pump wheel so that the liquid coolant flows axially against a central part of the coolant pump wheel. The pump outlet is preferably arranged radially outward of the coolant pump wheel so that the liquid lubricant is accelerated toward the pump outlet by the centrifugal force generated by the rotating coolant pump wheel.

The controllable mechanical motor vehicle coolant pump according to the present invention is also provided with a transverse housing surface which extends substantially transversely with respect to the drive shaft and radially surrounds the drive shaft. The transverse housing surface is preferably substantially perpendicular to the drive shaft. The transverse housing surface does not have to be completely flat, but can also have axially protruding and/or axially recessed surface sections.

The controllable mechanical motor vehicle coolant pump according to the present invention is also provided with a cylindrical inner slider support surface which radially surrounds the drive shaft and is coaxial to the drive shaft. The cylindrical inner slider support surface is typically circular-cylindrical, i.e., provided with a circular radial cross section, but can generally be provided with any radial cross-sectional shape, e.g., elliptical or polygonal.

The controllable mechanical motor vehicle coolant pump according to the present invention is also provided with a substantially pot-shaped control slider which is arranged coaxially with respect to the drive shaft and the coolant pump wheel, and which radially surrounds the drive shaft. The control slider is preferably designed as a single piece. The control slider comprises a substantially cylindrical slider side wall which is configured to radially surround the coolant pump wheel, i.e., the slider side wall is provided with an inner diameter which is slightly larger than the outer diameter of the coolant pump wheel. The slider side wall is typically circular-cylindrical. The control slider also comprises a slider bottom wall which extends substantially transversely with respect to the drive shaft and is arranged axially between the coolant pump wheel and the transverse housing surface. A radially inner bottom wall surface of the slider bottom wall is shiftably supported by the inner slider support surface in all possible shifting positions of the control slider.

The control slider is configured to be axially shiftable with respect to the coolant pump wheel between a maximum-discharge-flow position and a minimum-discharge-flow position in order to control an effective discharge cross section and thus a discharge flow out of the coolant pump wheel by partially or completely covering the radially outward discharge flow cross section of the coolant pump wheel with the cylindrical slider side wall. The control slider is preferably configured to completely cover the discharge cross section of the coolant pump wheel if positioned in the minimum-discharge-flow position, and to completely uncover the discharge cross section of the coolant pump wheel if positioned in the maximum-discharge-flow position. In any case, the effective discharge cross section of the coolant pump wheel, i.e., the part of the discharge cross section which is not covered by the slider side wall of the control slider, is smaller if the control slider is positioned in the minimum-discharge-flow position than if the control slider is positioned in the maximum-discharge-flow position.

The controllable mechanical motor vehicle coolant pump according to the present invention is also provided with a push-out pressure chamber which is located between the slider bottom wall and the transverse housing surface. The push-out pressure chamber is defined at one axial side by the transverse housing wall and radially inwardly by the inner slider support surface. The push-out pressure chamber is configured to be hydraulically pressurized in order to generate a hydraulic push-out push force which pushes the slider bottom wall away from the transverse housing surface and toward the coolant pump wheel and thus pushes the control slider toward the minimum-discharge-flow position. The push-out pressure chamber is typically annular and radially surrounds the drive shaft. The push-out pressure chamber is preferably configured to be hydraulically pressurized by being filled with pressurized coolant.

According to the present invention, the transverse housing surface and the inner slider support surface are both defined by a first housing element. As a result, there is no contact interface between separate housing elements at the radially inner side of the push-out pressure chamber via which liquid could leak into the push-out pressure chamber. This avoids unintentional pressurization of the push-out pressure chamber and therefore provides reliable control of the control slider position and thus of the discharge flow of the coolant pump. The inner slider support surface is in particular defined by a cylindrical protrusion of the first housing element which axially protrudes from the transverse housing surface. The transverse housing surface and the inner slider support surface are preferably both defined by a main housing body which supports the drive shaft.

In a preferred embodiment of the present invention, the first housing element also defines a cylindrical outer slider support surface which shiftably supports a radially outer side wall surface of the cylindrical slider side wall so that the control slider is supported on its radial inside and on its radial outside by the same housing element. This allows the radial distance between the inner slider support surface and the outer slider support surface to be defined very accurately because manufacturing tolerances need to be considered only for a single housing element. The accurate manufacturing of the slider support surfaces ensures reliable sealing of the radial gap between the control slider and the surrounding housing element by a sealing ring, which avoids or at least minimizes liquid leakage out of the push-out control chamber. The accurate manufacturing of the control slider chamber also ensures reliable and smooth shiftable support of the control slider within the surrounding housing element. This ensures a reliable control of the control slider position and therefore of the discharge flow of the coolant pump.

Preferably, the controllable mechanical motor vehicle coolant pump is provided with an auxiliary pumping unit which is configured to hydraulically pressurize the push-out pressure chamber. The auxiliary pumping unit according to the present invention is a so-called side channel pump and comprises an auxiliary pumping unit side channel and an auxiliary pumping unit pump wheel. The auxiliary pumping unit side channel is defined by a separate second housing element which is arranged between the coolant pump wheel and the transverse housing surface of the first housing element. The auxiliary pumping unit pump wheel is provided integrally with the coolant pump wheel on a back side of the coolant pump wheel which faces the second housing element. The auxiliary pumping unit allows to hydraulically actuate the control slider without requiring an external hydraulic pressure source, wherein the auxiliary pumping unit is very compact and therefore does not require significant additional installation space.

In a preferred embodiment of the present invention, the controllable mechanical motor vehicle coolant pump is provided with a push-out pressure chamber feed channel which is configured to fluidically connect the push-out pressure chamber with a discharge side of the auxiliary pumping unit side channel, wherein a section of the push-out pressure chamber feed channel extends between the drive shaft and the inner slider support surface. The push-out pressure chamber feed channel, in particular, extends axially from the second housing element, which defines the auxiliary pumping unit side channel, into the axially protruding part of the first housing element which defines the inner slider support surface and axially through the complete axial extent of the protruding part to behind the transverse housing surface. Typically, a control valve is provided within the first housing element for controlling the liquid flow from the push-out pressure chamber feed channel into the push-out pressure chamber. The particular design of the push-out pressure chamber feed channel provides a reliable fluidic connection between the auxiliary pumping unit and the push-out pressure chamber which does not require any complex sealing or significant additional installation space.

Preferably, the controllable mechanical motor vehicle coolant pump is provided with a push-in pressure chamber which is located between the coolant pump wheel and the slider bottom wall, and is configured to be hydraulically pressurized in order to generate a hydraulic push-in push force which pushes the slider bottom wall away from the coolant pump wheel. The push-in pressure chamber is preferably permanently pressurized during pump operation. The push-in pressure chamber can be, for example, in fluidic communication with the discharge flow cross section of the (main) coolant pump wheel so that the push-in pressure chamber is permanently filled with pressurized coolant with the pump discharge pressure during pump operation. In this case, the present pressure provided by the auxiliary pumping unit must always be higher than the present pressure provided by the coolant pump wheel in order to allow the control slider position to be controlled via controlling the hydraulic pressure of the push-out pressure chamber. The push-in pressure chamber can be, alternatively, fluidically connected to the discharge side of the auxiliary pumping unit pump wheel, wherein a ratio between the hydraulic pressures of the push-in pressure chamber and of the push-out pressure chamber and thereby the control slider position is controlled by at least one control valve. It is also possible that the auxiliary pumping unit is configured to provide two different hydraulic pressure levels, wherein the push-in pressure chamber is permanently fluidically connected to a lower hydraulic pressure level of the auxiliary pumping unit and the push-out pressure chamber is selectively fluidically connectable to a higher hydraulic pressure level of the auxiliary pumping unit in order to control the hydraulic pressure of the push-out pressure chamber. The push-in pressure chamber allows the control slider to be moved completely hydraulically without requiring any mechanical actuation means such as a preload spring or the like.

An embodiment of the present invention is described with reference to the enclosed figure, which shows a sectional view of a controllable mechanical motor vehicle coolant pump according to the present invention.

The figure shows a controllable mechanical motor vehicle coolant pump <NUM> which is configured to pump a liquid coolant through a cooling circuit of an internal combustion engine of a motor vehicle. The controllable mechanical motor vehicle coolant pump <NUM> comprises a drive shaft <NUM> which is rotatably supported within and by first housing element <NUM> and which extends in an axial pump direction. The drive shaft <NUM> is configured to be mechanically driven by the internal combustion engine of the motor vehicle. The drive shaft <NUM> can, for example, be co-rotatably connected with a drive wheel which is driven by a crank shaft of the internal combustion engine via a belt drive.

The controllable mechanical motor vehicle coolant pump <NUM> comprises a coolant pump wheel <NUM> which is attached to an axial end of the drive shaft <NUM> so that the coolant pump wheel <NUM> rotates together with the drive shaft <NUM>. The coolant pump wheel <NUM> is configured to pump the liquid coolant from an suction chamber <NUM>, which is axially adjacent to the coolant pump wheel <NUM> and fluidically connected with a pump inlet, into a discharge chamber <NUM>, which radially surrounds the coolant pump wheel <NUM> and is fluidically connected with a pump outlet.

The controllable mechanical motor vehicle coolant pump <NUM> comprises a substantially pot-shaped control slider <NUM> with a substantially circular-cylindrical slider side wall <NUM> and a slider bottom wall <NUM>. The slider side wall <NUM> is provided with an inner diameter which is slightly larger than an outer diameter of the coolant pump wheel <NUM> so that the slider side wall <NUM> can radially surround the coolant pump wheel <NUM>. The slider bottom wall <NUM> extends substantially transversely with respect to the drive shaft <NUM> and is located axially between the coolant pump wheel <NUM> and a transverse housing surface <NUM> of the first housing element <NUM>, which transverse housing surface <NUM> extends substantially transversely with respect to the drive shaft <NUM> and radially surrounds the drive shaft <NUM>.

The control slider <NUM> is shiftably supported within and by the first housing element <NUM>, wherein a radially inner bottom wall surface <NUM> of the slider bottom wall <NUM> is supported by a circular-cylindrical inner slider support surface <NUM> of the first housing element <NUM>, and a radially outer side wall surface <NUM> of the slider side wall <NUM> is supported by a circular-cylindrical outer slider support surface <NUM> of the first housing element <NUM>. The inner slider support surface <NUM> and the outer slider support surface <NUM> each radially surround the drive shaft <NUM> and are each coaxial to the drive shaft <NUM>. The inner slider support surface <NUM> is defined by a cylindrical protrusion <NUM> of the first housing element <NUM>, which cylindrical protrusion <NUM> axially protrudes from the transverse housing surface <NUM> toward the coolant pump wheel <NUM>. The control slider <NUM> can be axially shifted with respect to the coolant pump wheel <NUM> thereby partially or completely covering a radially outward discharge flow cross section D of the coolant pump wheel <NUM> with the slider sidewall <NUM>, as visible in the figure, in order to control an effective discharge flow cross section D-eff of the coolant pump wheel <NUM> which is the uncovered part of the discharge flow cross section D.

The controllable mechanical motor vehicle coolant pump <NUM> comprises a push-out pressure chamber <NUM> which is defined axially by the slider bottom wall <NUM> as well as the transverse housing surface <NUM>, and is defined radially by the inner slider support surface <NUM> and the outer slider support surface <NUM>. The push-out pressure chamber <NUM> generates a hydraulic push-out push force which pushes the slider bottom wall <NUM> away from the transverse housing surface <NUM> and toward the coolant pump wheel <NUM> if the push-out pressure chamber <NUM> is hydraulically pressurized.

The controllable mechanical motor vehicle coolant pump <NUM> comprises an auxiliary pumping unit <NUM> with an auxiliary pumping unit pump wheel <NUM> and an auxiliary pumping unit side channel <NUM>. The auxiliary pumping unit side channel <NUM> is defined by a separate second housing element <NUM> which is arranged axially between the coolant pump wheel <NUM> and the transverse housing surface <NUM> and axially abuts the cylindrical protrusion <NUM> of the first housing element <NUM>. The auxiliary pumping unit pump wheel <NUM> is provided integrally with the coolant pump wheel <NUM>, and is defined on a back side of the coolant pump wheel <NUM> which faces the second housing element <NUM>. The auxiliary pumping unit <NUM> is configured to hydraulically pressurize the push-out pressure chamber <NUM> via a push-out pressure chamber feed channel <NUM>.

The push-out pressure chamber feed channel <NUM> is defined by the second housing element <NUM> and by the first housing element <NUM>. The push-out pressure chamber feed channel <NUM> extends through the cylindrical protrusion <NUM> of the first housing element <NUM> so that a section of the push-out pressure chamber feed channel <NUM> extends between the drive shaft <NUM> and the inner slider support surface <NUM>. The push-out pressure chamber feed channel <NUM> extends through the complete cylindrical protrusion <NUM> to behind the transverse housing surface <NUM>. The push-out pressure chamber feed channel <NUM> fluidically connects a discharge side of the auxiliary pumping unit side channel <NUM> with a push-out pressure chamber feed opening <NUM> which is provided within the transverse housing surface <NUM>. A fluid flow through the push-out pressure chamber feed channel <NUM> into the push-out pressure chamber <NUM> and thus the hydraulic pressure of the push-out pressure chamber <NUM> can be controlled via a control valve <NUM> which is arranged close to the push-out pressure chamber feed opening <NUM> within the first housing element <NUM>.

The controllable mechanical motor vehicle coolant pump <NUM> comprises a push-in pressure chamber <NUM> which is defined axially by the second housing element <NUM> as well as the slider bottom wall <NUM> of the control slider <NUM>, is defined radially outwards by the slider side wall <NUM> of the control slider <NUM>, and is defined radially inward by the inner slider support surface <NUM> as well as the second housing element <NUM>. The push-in pressure chamber <NUM> is in direct fluidic communication with the discharge flow cross section D of the coolant pump wheel <NUM>, and is thus, independent of the present shifting position of the control slider <NUM>, always hydraulically pressurized by the pressurized coolant discharged from the coolant pump wheel <NUM> during pump operation. The push-in pressure chamber <NUM> thus always generate a hydraulic push-in push force during pump operation, which push-in push force pushes the slider bottom wall <NUM> away from the second housing element <NUM> and toward the transverse housing surface <NUM>.

Claim 1:
A controllable mechanical motor vehicle coolant pump (<NUM>) comprising
- a rotatable drive shaft (<NUM>) which extends in an axial pump direction and is configured to be mechanically driven by an engine of a motor vehicle,
- a coolant pump wheel (<NUM>) which is co-rotatably connected with the drive shaft (<NUM>) and is configured to pump a liquid coolant,
- a transverse housing surface (<NUM>) which extends substantially transversely with respect to the drive shaft (<NUM>) and radially surrounds the drive shaft (<NUM>),
- a cylindrical inner slider support surface (<NUM>) which radially surrounds the drive shaft (<NUM>) and is coaxial to the drive shaft (<NUM>),
characterised in that the coolant pump further comprises:
- a substantially pot-shaped control slider (<NUM>) which is configured to be axially shiftable with respect to the coolant pump wheel (<NUM>) in order to control an effective discharge flow cross-section (D-eff) of the coolant pump wheel (<NUM>), the control slider (<NUM>) comprising
• a substantially cylindrical slider side wall (<NUM>) which is configured to radially surround the coolant pump wheel (<NUM>), and
• a slider bottom wall (<NUM>) which extends substantially transversely with respect to the drive shaft (<NUM>) and is arranged axially between the coolant pump wheel (<NUM>) and the transverse housing surface (<NUM>), wherein a radially inner bottom wall surface (<NUM>) of the slider bottom wall (<NUM>) is shiftably supported by the inner slider support surface (<NUM>), and
- a push-out pressure chamber (<NUM>) which
• is located between the slider bottom wall (<NUM>) and the transverse housing surface (<NUM>),
• is defined at one axial side by the transverse housing surface (<NUM>) and radially inwardly by the inner slider support surface (<NUM>), and
• is configured to be hydraulically pressurized in order to generate a hydraulic push-out push force which pushes the slider bottom wall (<NUM>) toward the coolant pump wheel (<NUM>),
wherein the transverse housing surface (<NUM>) and the inner slider support surface (<NUM>) are both defined by a first housing element (<NUM>).