Patent Description:
A motor vehicle electronic coolant pump is typically provided to circulate a coolant of a motor vehicle cooling circuit, primarily for cooling an internal combustion engine of the motor vehicle. To avoid damage of the internal combustion engine, the electronic coolant pump has to be reliable and failsafe. Since the available space in a motor vehicle engine compartment is limited, electronic coolant pumps are typically designed very compact. Electronic coolant pumps can be, for example, provided with an electric motor with a compact stator coil arrangement requiring only a small space for the motor stator. However, the compact stator coil arrangement hast to be driven with a high drive energy density to allow a high mechanical pump performance. The high energy density in the stator coil arrangement generates significant heat caused by resistive heating. The generated heat has to be efficiently dissipated to avoid an overheating of the electric motor, in particular of a heat sensitive motor electronics, and to allow a high motor efficiency.

An electronic coolant pump for a motor vehicle is disclosed, for example, in <CIT>. The coolant pump is provided with a pump housing which defines a pumping chamber and a motor chamber. The pumping chamber is filled with the coolant and comprises a radially inner pump inlet, a radially outer pump outlet and a pump volute extending from downstream of the pump inlet to the pump outlet. The motor chamber is fluidically separated from the pumping chamber by a separation sidewall extending substantially in a radial plane. The coolant pump is provided with an electric motor with a rotatable motor rotor, a motor stator with a compact stator coil arrangement and a motor electronics for energizing the stator coil arrangement. The stator coil arrangement is defined by a single stator coil being arranged laterally with respect to the motor rotor. The motor stator and the motor electronics are arranged in the dry motor chamber. The coolant pump comprises a pump wheel which is arranged in the pumping chamber and which is co-rotatably connected with the motor rotor by an axially extending rotor shaft so that the pump wheel is driven by the electric motor.

The stator coil arrangement is provided axially adjacent to a volute cooling sector of the pump volute. The stator coil arrangement is in thermal contact with the separation sidewall, in particular with a cooling section of the separation sidewall being defined by the volute cooling sector, so that the stator coil arrangement is cooled by the coolant being pumped through the pump volute and flowing along the sidewall cooling section. However, the sidewall cooling section area is relatively small. As a result, at least parts of the stator coil arrangement being located radially further outside with respect to the volute cooling sector are not cooled efficiently so that this stator coil arrangement heats up relatively fast. The higher the temperature of the stator coil arrangement is, the lower is its electromagnetic efficiency. As a result, the stator coil arrangement has to be driven with higher drive energy to achieve a predefined motor performance, which in turn increases the heat being generated in the stator coil arrangement. In addition, the higher drive energy causes additional heating of the motor electronics providing the drive energy to the stator coil arrangement. As a result, the electric motor and, in particular, the motor electronics can overheat which can cause a malfunction or even a failure of the electronic coolant pump.

<CIT> discloses an electric coolant pump comprising a motor chamber, in which a motor stator and a motor electronics are arranged, and a pumping chamber, in which a pump wheel is arranged. The motor chamber is defined at a pumping-chamber-sided axial side by a transversal housing wall, and the pumping chamber is defined at a motor-chamber-sided axial side by a rotor sleeve cover.

<CIT> and <CIT> each disclose an electric coolant pump which has no motor electronics and therefore does not fall within the scope of protection of the present patent application. The stator coil arrangement of these electric coolant pumps is arranged axially adjacent to an outlet of the pump volute and in thermal contact with the separation sidewall which fluidically separates the motor chamber from the pumping chamber.

It is an object of the invention to provide a compact and reliable electronic coolant pump with a high pump performance.

This object is achieved with an electronic coolant pump with the features of claim <NUM>.

The electronic coolant pump according to the invention is provided with a pump housing which defines a pumping chamber and a motor chamber, both being fluidically separated from each other by a separation sidewall extending substantially in a radial plane. The pumping chamber is filled with a liquid coolant during pump operation and comprises a radially inner pump inlet and a radially outer pump outlet. Preferably, the pump inlet substantially extends in an axial motor direction and the pump outlet substantially extends in a radial plane so that the pump inlet extends substantially perpendicular with respect to the pump outlet. The pump inlet and the pump outlet are fluidically connected by a pump volute extending from downstream of the pump inlet to the pump outlet in a radial plane. The flow cross section of the pump volute increases from the pump inlet to the pump outlet to provide an efficient coolant discharge.

The electronic coolant pump comprises an electric motor with a rotatable motor rotor, a static motor stator and a motor electronics for energizing the stator coil arrangement. The rotatable motor rotor is magnetically driven by the motor stator. Preferably, the motor rotor is permanent-magnetic so that no wear-prone sliding contacts are required to electromagnetically magnetize the motor rotor. The electric components, i.e. the motor electronics and the electromagnetic motor stator, are sensitive to the coolant and, as a result, are arranged in the dry motor chamber.

The motor stator is provided with a single compact stator coil arrangement which can be defined by a single stator coil or can comprise several stator coils. In any case, all stator coils of the stator coil arrangement are arranged concentrated in a compact cluster, i.e. all stator coils are arranged in direct vicinity to each other. The stator coil arrangement is arranged laterally with respect to the motor rotor so that all stator coils of the stator coil arrangement are arranged on the same side of the motor rotor. The stator coils are not distributed along the circumference of the motor rotor. As a result, only a small space is required for the stator coil arrangement.

The electronic coolant pump is provided with a pump wheel being co-rotatably connected with the motor rotor so that the pump wheel is driven by the electric motor. The pump wheel can be provided integrally with the motor rotor or, alternatively, can be co-rotatably connected with the motor rotor, for example, by a rotor shaft. The pump wheel is arranged in the pumping chamber for pumping the coolant from the pump inlet through the pump volute to the pump outlet. Preferably, the pump wheel is located in the radial center of the pump volute so that the coolant entering the pumping chamber via the preferably axial pump inlet flows substantially axially against the pump wheel and is accelerated radially outwardly by the rotating pump wheel.

According to the invention, the stator coil arrangement is located axially adjacent to a volute cooling sector of the pump volute. The volute cooling sector defines a sidewall cooling section which axially separates the volute cooling sector from the motor chamber. The sidewall cooling section is cooled by the coolant flowing through the volute cooling sector. The stator coil arrangement is in thermal contact with the sidewall cooling section, i.e. there is no air gap between the stator coil arrangement and the sidewall cooling section. The cooling section of the separation sidewall is made of a material with a high thermal conductivity, for example made of aluminum. According to the invention, the thermal conductivity of the sidewall cooling section material is higher than <NUM> W/(m·K). This allows an efficient heat transfer from the stator coil arrangement via the sidewall cooling section into the coolant. As a result, the stator coil arrangement can be cooled by the coolant being pumped through the pump volute.

The volute cooling sector starts at the pump outlet and ends at a volute angle of <NUM>° starting at the pump outlet and running in a pump-inlet-facing circumferential direction of the pump volute, i.e. the volute cooling sector is located at the pump outlet. As a result, the volute cooling sector defines a relatively large sidewall cooling section area because the flow cross section of the pump volute increases from the pump inlet to the pump outlet. This allows an efficient cooling of the entire stator coil arrangement which reduces the temperature of stator coil arrangement and the heat being dissipated by the stator coil arrangement into the motor chamber.

The reduced stator coil arrangement temperature improves the electric conductivity and, as a result, the electromagnetic efficiency of the stator coil arrangement so that lower driving energy is required to achieve a predetermined pump performance. This reduces the waste heat generation in the motor electronics. The reduced waste heat generation in the motor electronics and the reduced heat dissipation of the stator coil arrangement into the motor chamber avoid an overheating of the motor electronics. In addition, the improved electromagnetic efficiency allows a higher pump performance for predetermined driving energy. As a result, the electronic coolant pump according to the invention can reliably provide a high mechanical pump performance.

Beside of the higher electric conductivity of the stator coil arrangement, the efficient cooling of the stator coil arrangement also allows dissipating more heat via the sidewall cooling section into the coolant so that more heat can be generated in the stator coil arrangement without overheating the stator coil arrangement. As a result, the efficient cooling of the stator coil arrangement allows reducing the coil wire cross section of the stator coil arrangement without losing motor efficiency and without overheating the stator coil arrangement. This allows a more compact stator coil arrangement and, as a result, a compact electric motor.

Preferably, the stator coil arrangement is defined by a single stator coil being arranged laterally and satellite-like with respect to the motor rotor. The single stator coil allows a very compact realization of the stator coil arrangement and, as a result, of the electronic coolant pump. In addition, the single stator coil can be easily arranged axially adjacent to and in thermal contact with the sidewall cooling section.

In a preferred embodiment of the invention, the thermal contact between the stator coil arrangement and the sidewall cooling section is provided by a heat transfer element being arranged axially between and in direct contact with the sidewall cooling section and the stator coil arrangement. The heat transfer element is provided with a high thermal conductivity of at least <NUM> W/(m·K). Preferably, the heat transfer element is relatively flexible so that the heat transfer element can be adapted to the contour of the stator coil arrangement. This allows a large contact area between the heat transfer element and the stator coil arrangement and, as a result, allows very efficient heat dissipation from the stator coil arrangement via the heat transfer element and the sidewall cooling section into the coolant and, as a result, an efficient cooling of the stator coil arrangement.

Since significant heat is generated in the motor electronics during the motor operation, sufficient cooling of the motor electronics is required to avoid a malfunction or damage of the motor electronics and, as a result, to avoid a failure of the electronic coolant pump. In a preferred embodiment of the invention, the motor electronics is provided in thermal contact with the separation sidewall so that the motor electronics is cooled by the coolant being pumped through the coolant pump. This provides a reliable electric motor and, as a result, a reliable electronic coolant pump. Preferably, the geometry of the motor electronics is adapted to the geometry of the pump volute so that the entire motor electronics can be provided in thermal contact with the separation sidewall.

Preferably, the motor rotor is arranged in a rotor chamber being fluidically separated from the motor chamber by a separation can. The separation can extends through the air gap between the motor rotor and the motor stator and is made of a material which is permeable for the magnetic field generated by the motor stator. Since the rotor chamber is fluidically separated from the motor chamber, the rotor chamber does not have to be sealed against the pumping chamber. This allows a simple co-rotatable connection of the motor rotor with the pump wheel not requiring any complex sealing elements which are expensive and liable to wear.

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

The electronic coolant pump <NUM> comprises a multi-part pump housing <NUM> with a pumping chamber cover element <NUM>, a motor chamber cover element <NUM> and a separation sidewall <NUM> substantially extending in a radial plane. In the present embodiment of the invention, the separation sidewall <NUM> is made of a material with a high thermal conductivity, for example made of aluminum. The pumping chamber cover element <NUM> and the separation sidewall <NUM> define a pumping chamber <NUM> being filled with a coolant during pump operation. The pumping chamber <NUM> comprises a radially inner pump inlet <NUM>, a radially outer pump outlet <NUM> and a pump volute <NUM> extending from downstream of the pump inlet <NUM> to the pump outlet <NUM> in a radial plane. The pump inlet <NUM> extends substantially in an axial motor direction and the pump outlet <NUM> extends substantially in a radial plane so that the pump inlet <NUM> is arranged substantially perpendicular with respect to the pump outlet <NUM>. The flow cross section of the pump volute <NUM> increases from the pump inlet <NUM> to the pump outlet <NUM>. The motor chamber cover element <NUM> and the separation sidewall <NUM> define a motor chamber <NUM> being fluidically separated from the pumping chamber <NUM> by the separation sidewall <NUM>.

The coolant pump <NUM> comprises an electric motor <NUM> with a rotatable permanent-magnetic motor rotor <NUM>, a static electromagnetic motor stator <NUM> and a motor electronics <NUM> for energizing the motor stator <NUM>. The motor rotor <NUM> is located in a rotor chamber <NUM> being fluidically separated from the motor chamber <NUM> by a separation can <NUM>. The motor stator <NUM> and the motor electronics <NUM> are arranged in the dry motor chamber <NUM>.

The motor rotor <NUM> is co-rotatably fixed to a rotor shaft <NUM> being rotatable about an axis of rotation R. The rotor shaft <NUM> is rotatably supported in the separation can <NUM> and in the separation sidewall <NUM> by two suitable shaft bearings <NUM>,<NUM>. The rotor shaft <NUM> axially extends from the rotor chamber <NUM> into the pumping chamber <NUM>.

The motor stator <NUM> is provided with a laminated stator body <NUM> and with a single electromagnetic stator coil arrangement <NUM>. In the present embodiment of the invention, the stator coil arrangement <NUM> is defined by a single stator coil <NUM> being arranged laterally and satellite-like with respect to the motor rotor <NUM>. The stator coil arrangement <NUM> is electrically connected with and energized by the motor electronics <NUM>. The stator coil arrangement <NUM> and the motor electronics <NUM> are arranged diametrically opposite with respect to the motor rotor <NUM>.

The motor electronics <NUM> comprises several power semiconductors <NUM> being arranged on a printed circuit board <NUM>. In the present embodiment of the invention, the printed circuit board <NUM> of the motor electronics <NUM> is in direct thermal contact with the separation sidewall <NUM> so that the motor electronics <NUM> is cooled by the coolant being pumped through the pump volute <NUM>.

The coolant pump <NUM> comprises a pump wheel <NUM> being located in the pumping chamber <NUM> for pumping the coolant from the pump inlet <NUM> through the pump volute <NUM> to the pump outlet <NUM>. The pump wheel <NUM> is co-rotatably connected with the rotor shaft <NUM> so that the pump wheel <NUM> is driven by the electric motor <NUM>. The pump wheel <NUM> is arranged within the pumping chamber <NUM> in such a way that the coolant entering the pumping chamber <NUM> via the pump inlet <NUM> flows substantially axially against the pump wheel <NUM> and is accelerated radially outwardly by the rotating pump wheel <NUM>.

The stator coil arrangement <NUM> is located axially adjacent to a volute cooling sector <NUM> of the pump volute <NUM>. The volute cooling sector <NUM> extends over a volute angle A = <NUM>° starting at the pump outlet <NUM> and running in a pump-inlet-facing circumferential direction of the pump volute <NUM>. The volute cooling sector <NUM> defines a sidewall cooling section <NUM> which axially limits the volute cooling sector <NUM> towards the motor chamber <NUM>. The sidewall cooling section <NUM> is cooled by the coolant flowing through the volute cooling sector <NUM>.

Claim 1:
Electronic coolant pump (<NUM>) comprising
a pump housing (<NUM>) defining
a pumping chamber (<NUM>) being filled with a coolant during pump operation, with
a radially inner pump inlet (<NUM>),
a radially outer pump outlet (<NUM>) and
a pump volute (<NUM>) extending from downstream of the pump inlet (<NUM>) to the pump outlet (<NUM>), and
a motor chamber (<NUM>) being fluidically separated from the pumping chamber (<NUM>) by a separation sidewall (<NUM>) extending substantially in a radial plane,
an electric motor (<NUM>) with
a rotatable motor rotor (<NUM>),
a static motor stator (<NUM>) with a single compact stator coil arrangement (<NUM>) being arranged laterally with respect to the motor rotor (<NUM>) in the motor chamber (<NUM>) so that all stator coils (<NUM>) of the stator coil arrangement (<NUM>) are arranged on the same side of the motor rotor (<NUM>) and
a motor electronics (<NUM>) being arranged in the motor chamber (<NUM>) for energizing the stator coil arrangement (<NUM>),
wherein the stator coil arrangement (<NUM>) is arranged axially adjacent to a volute cooling sector (<NUM>) of the pump volute (<NUM>) and is in thermal contact with a cooling section (<NUM>) of the separation sidewall (<NUM>) being defined by the volute cooling sector (<NUM>), and
a pump wheel (<NUM>) being arranged in the pumping chamber (<NUM>) and being co-rotatably connected with the motor rotor (<NUM>),
characterized in that
the cooling section (<NUM>) is made of a material with a thermal conductivity higher than <NUM> W/(m.K), and
the volute cooling sector (<NUM>) of the pump volute starts at the pump outlet (<NUM>) and ends at a volute angle (A) of <NUM>° starting at the pump outlet (<NUM>) and running in a pump-inlet-facing circumferential direction of the pump volute (<NUM>).