MECHANICAL SWITCHABLE AUTOMOTIVE COOLANT PUMP

Abstract

A coolant pump for providing a coolant to an engine includes a pump frame, a rotatable rotor shaft, a pulley wheel co-rotatably fixed to the rotor shaft, an axially shiftable ferromagnetic rotatable pump wheel, and an electromagnetic wet friction clutch arrangement. The pump wheel is axially shiftable with respect to the rotor shaft and the pump frame. The clutch arrangement comprises a static electromagnet, a clutch disk co-rotatably supported by the rotor shaft, a first clutch friction surface arranged at the clutch disk and a thereto corresponding second clutch friction surface arranged at the pump wheel, and a separate stop friction surface arranged at the pump wheel and a thereto corresponding static stop friction surface arranged at the static pump frame. The electromagnet, when fully energized, axially attracts the pump wheel so that the separate stop friction surface and the static stop friction surface engage to stop the pump wheel.

Description

CROSS REFERENCE TO PRIOR APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2015/069111, filed on Aug. 20, 2015. The International Application was published in English on Feb. 23, 2017 as WO 2017/028921 A1 under PCT Article 21(2).

FIELD

The present invention relates to a mechanical switchable automotive coolant pump for providing a liquid coolant for an automotive engine.

BACKGROUND

A mechanical automotive coolant pump is mechanically driven by an automotive internal combustion engine so that the coolant pump generally rotates with a rotational speed which is proportional to the rotational speed of the engine. No coolant flow is needed in some situations, in particular after starting a cold engine. A switchable automotive coolant pump is provided with a friction clutch so that the rotational connection between the pulley wheel of the pump and the pump wheel can be engaged and disengaged as needed. The friction clutch can generally be provided in a dry zone or in the wet zone of the pump. The disengaged clutch disk of a wet friction clutch still rotates and thereby rotates the coolant liquid which rotates the pump wheel. A significant drag moment is in practice transferred by a wet friction clutch in the disengaged clutch state so that a considerable pump performance is generated even if no pump performance is needed. The friction clutch can be actuated by an electromagnet which attracts at least one clutch element when the electromagnet is electrically energized.

SUMMARY

An aspect of the present invention is to provide a mechanical switchable automotive coolant pump with a reduced pump performance when the wet clutch of the pump is disengaged.

In an embodiment, the present invention provides a mechanical switchable automotive coolant pump for providing a liquid coolant for an automotive engine. The mechanical switchable automotive coolant pump includes a static pump frame, a rotor shaft configured to rotate, the rotor shaft being rotatably supported at the static pump frame, a pulley wheel configured to be co-rotatably fixed to the rotor shaft and to be mechanically driven by the automotive engine, a pump wheel comprising a ferromagnet, and an electromagnetic wet friction clutch arrangement. The pump wheel is configured to rotate and to be axially shiftable, and to be rotatably supported and axially shiftable with respect to each of the rotor shaft and the static pump frame. The electromagnetic wet friction clutch arrangement comprises a static electromagnet configured to be energized, a clutch disk which is co-rotatably supported by the rotor shaft, a first clutch friction surface arranged at the clutch disk, a second clutch friction surface arranged at the pump wheel, a separate stop friction surface arranged at the pump wheel, and a static stop friction surface arranged at the static pump frame. The first clutch friction surface corresponds to the second clutch friction surface. The separate stop friction surface corresponds to the static stop friction surface. The static electromagnet, when fully energized, axially attracts the pump wheel so that the separate stop friction surface and the static stop friction surface engage with each other, thereby stopping the pump wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:

FIG. 1 shows a longitudinal section of a mechanical switchable automotive coolant pump in the with a clutch arrangement in the engaged state;

FIG. 2 shows the enlarged clutch arrangement of FIG. 1;

FIG. 3 shows the clutch arrangement of FIG. 2 in a disengaged state; and

FIG. 4 shows the clutch arrangement of FIG. 2 in an intermediate state.

DETAILED DESCRIPTION

The mechanical switchable automotive coolant pump according to the present invention is provided with a static pump frame which is provided with some kind of device to fix the coolant pump to an automotive engine or to an automotive frame. The pump frame can also be provided with a pump wheel housing comprising a coolant inlet and a coolant outlet.

The coolant pump is provided with a rotatable rotor shaft which is rotatably supported at the pump frame. The rotor shaft is not necessarily directly supported at the pump frame, but can be directly supported at another rotatable part which is itself directly rotatably supported at the static pump frame.

A pulley wheel is co-rotatably and axially fixed at the rotor shaft and is suitable to be mechanically driven by the engine. The pulley wheel can generally be driven by any kind of mechanical transfer element such as a gear wheel, a transmission belt, a friction wheel etc. The term “pulley wheel” as used herein is not limited to a belt-driven wheel. The pulley wheel can, for example, be driven by the engine via a transmission belt. The pulley wheel is fixed to the rotor shaft and is not rotatable nor axially shiftable with respect to the rotor shaft.

The coolant pump is provided with a rotatable and axially shiftable pump wheel which is rotatably supported and which is axially shiftable with respect to the rotor shaft and with respect to the pump frame. The pump wheel can be axially moved and can rotate independently of the dynamic state of the rotor shaft. The pump wheel is provided with a ferromagnet so that an energized electromagnet magnetically attracts and axially pulls the ferromagnetic pump wheel.

The coolant pump is provided with an electromagnetic wet friction clutch arrangement of which the frictional clutch elements are arranged in the wet zone of the coolant pump. The clutch arrangement is provided with a static electromagnet in the dry zone and with a clutch disc which is co-rotatably supported by the rotor shaft. The clutch disk always rotates with the rotational speed of the rotor shaft.

The clutch disk is provided with a clutch friction surface, and the pump wheel is provided with a corresponding clutch friction surface, both of which are arranged in the wet zone. Both clutch friction surfaces are in full frictional contact with each other in the engaged clutch state so that the pump wheel and the clutch disk rotate with the same rotational speed.

The pump wheel is provided with a separate stop friction surface, and the pump frame is provided with a corresponding static stop friction surface. A sufficient braking torque is generated when the stop friction surfaces of the pump wheel and of the pump frame are in frictional contact with each other which completely stops the rotation of the pump wheel when the wet friction clutch is in the fully disengaged state.

The friction clutch is in the engaged state if the electromagnet is not excited so that the pump wheel rotates with the same rotational speed as the rotor shaft. The stop friction surfaces are not in contact.

When the electromagnet is electrically excited, the pump wheel is axially attracted by and in the direction of the electromagnet so that the stop friction surfaces of the pump frame and the pump wheel are axially engaged with the result that the rotation of the pump wheel is completely stopped. The clutch friction surfaces are not in contact.

The coolant pump according to the present invention is provided with a frictional brake arrangement defined by the stop friction surfaces which, in the disengaged state, completely stops any rotation of the pump wheel when the electromagnet is fully energized. A zero-flow of the coolant is realized in the fully disengaged clutch state. The internal combustion engine is therefore no longer cooled by a flowing coolant if no cooling performance is needed or wanted.

In an embodiment of the present invention, the clutch disk can, for example, be provided with a ferromagnet and be supported axially shiftable at the rotor shaft. The rotor shaft supports the pump wheel and the clutch disk. Since the clutch disk is provided with a ferromagnet, the clutch disk is axially attracted by the energized electromagnet. Both the clutch disk and the pump wheel are axially attracted by the energized electromagnet. When the electromagnet is energized, the clutch disk is axially pulled from an engaged position in which the clutch friction surfaces are in frictional engagement with each other into a disengaged position in which the clutch friction surfaces are not in any frictional contact with each other. Since the clutch disk co-rotates with the rotor shaft, however, the rotating clutch disk rotates the liquid coolant which thereby generates a significant drag torque to the pump wheel. The energized electromagnet also axially attracts the pump wheel so that the stop friction surfaces come into and remain in frictional contact with each other so that the pump wheel stops and no longer rotates.

In an embodiment of the present invention, the clutch disk can, for example, be axially preloaded by a preload spring into an engaged clutch position. If the electromagnet is not energized, the preload spring pushes all elements of the clutch disk axially into the engaged clutch position so that the clutch friction surfaces get in frictional contact with each other with the consequence that the pump wheel co-rotates with the rotor shaft. The pump wheel always co-rotates with the rotor shaft if the clutch actuation fails. The clutch arrangement is therefore fail-safe.

In an embodiment of the present invention, the pump wheel can, for example, be provided with a non-ferromagnetic pump wheel body comprising pump blades and with a separate ferromagnetic clutch ring which is fixed to the pump wheel body, for example, by bolts or by gluing. The pump wheel body can be made of plastic which allows the realization of a complex form with good fluidic properties and low weight, whereas the ferromagnetic clutch ring can be provided with good electromagnetic properties and/or with good frictional properties.

In an embodiment of the present invention, the wheel-sided clutch friction surface and the wheel-sided stop friction surface can, for example, be provided at the ferromagnetic clutch ring. Both pump-wheel-sided friction surfaces are provided at the ferromagnetic clutch ring which is part of the pump wheel.

In an embodiment of the present invention, an axial stop surface can, for example, be provided to axially stop the clutch disk in the disengaged position. The stop surface can, for example, be provided to co-rotate with the rotor shaft but to be axially fixed. The rotor-shaft-sided axial stop surface defines the axial disengagement position of the clutch disk in the disengaged state, namely, when the electromagnet is energized and thereby attracts the clutch disk into the disengaged clutch disk position. The axial clutch disk stop limits the axial movement path of the clutch disk so that the clutch disk is not in frictional contact with the pump wheel even if the pump wheel is also axially attracted and pulled by the energized electromagnet into its axial disengagement position.

The clutch arrangement must not get jammed in the disengaged state. The stop surface can, for example, lie in a transversal plane with respect to the longitudinal rotational axis of the rotor shaft and the pump wheel. The stop surface does not generate any frictional force in an axial direction so that the clutch arrangement always reliably returns into the preloaded engaged position if the electromagnet is not energized.

In an embodiment of the present invention, the axial electromagnetic gap between the ferromagnetic clutch ring and the ferromagnetic clutch disk can, in any clutch state, be at least two times larger than the axial electromagnetic gap between the clutch ring and the electromagnet and between the clutch disk and the electromagnet. In other words, no relevant axial electromagnetic force is generated between the ferromagnetic clutch ring and the ferromagnetic clutch disk. Relevant magnetic forces in the axial direction are only directly generated between the electromagnet and the ferromagnetic clutch ring, and between the electromagnet and the ferromagnetic clutch disk. Another result of this arrangement is that no relevant eddy currents can appear between the ferromagnetic clutch disk and the ferromagnetic clutch ring so that no relevant electromagnetic drag torque exists.

In an embodiment of the present invention, the axial electromagnetic gap between the ferromagnetic clutch ring and the ferromagnetic clutch disk can, for example, be at least 1.0 mm, for example, at least 2.0 mm.

In an embodiment of the present invention, the pump wheel can, for example, be provided with a separate non-ferromagnetic friction ring arranged in the axial electromagnetic gap between the ferromagnetic clutch ring and the ferromagnetic clutch disk. The friction ring has a double-function, namely, providing good friction quality as the antagonist of the friction disc and also defining a sufficiently large axial electromagnetic gap between the ferromagnetic clutch ring and the ferromagnetic clutch disk. The friction ring provides that the axial electromagnetic gap between the ferromagnetic clutch ring and the ferromagnetic clutch disk always remains above a minimum value even in the engaged clutch state so that no relevant magnetic field and eddy currents appear in this area.

In an embodiment of the present invention, an electronic clutch control can, for example, be provided to energize the electromagnet in a full-disengagement state. The clutch control is provided with an intermediate-engagement-state in which the clutch control provides the electromagnet with less electric energy than in the full-disengagement state. In the intermediate clutch-engagement-state, the electric energy can be on a level which puts the clutch wheel into a disengaged position but does not pull the pump wheel completely into its disengagement position so that the stop friction surfaces of the pump wheel and the pump frame do not come into a full frictional contact. The pump wheel can therefore still rotate and is rotated by the fluidic drag moment generated by the rotating clutch disk. With the third switching state of the clutch arrangement, a third rotational speed of the pump wheel can be realized, namely, an immediate pump wheel speed which can, for example, be in the range of 20% to 50% of the rotational speed of the rotating clutch disk. The intermediate clutch state thereby allows the pump performance of the coolant pump to be more accurately adapted to the cooling performance requirement.

An embodiment of the present invention is explained below under reference to the drawings.

The drawings show a mechanical switchable automotive coolant pump 10 for providing a liquid coolant for an automotive engine 12. The coolant pump 10 is mechanically driven by a rotating drive of the engine 12 which drives a transmission belt 13. The transmission belt 13 drives a pulley wheel 22 of the coolant pump 10. The coolant pump 10 of this embodiment is not provided with its own pump wheel housing, but is adapted to be mounted directly to an engine body 11 of the engine 12. The engine body 11 defines an axial pump inlet channel 17 and an outlet volute 18 which radially surrounds a pump wheel 60.

The coolant pump 10 is provided with a static pump frame 30 which is fixed to the engine body 11 by a suitable fixation element, namely by screws and/or bolts. The pump frame 30 rotatably supports a rotatable rotor shaft 20 which is supported at the pump frame 30 by a shaft bearing 26, which is a roller bearing in the shown embodiment. The pump frame 30 also supports a static electromagnet 32 which is provided as a ring-shaped electromagnetic coil which, if energized with electric energy, generates a toroidal electromagnetic field.

The pump frame 30 also fixedly supports a shaft sealing 34 which surrounds and seals the rotor shaft 20 and thereby fluidically separates the wet zone of the coolant pump 10 from the dry zone. The electromagnet 32, the shaft bearing 26, the pulley wheel 22 and a part of the rotor shaft 20 are provided in the dry zone. The other rotating elements of the coolant pump 10 are provided and located in the wet zone.

The rotor shaft 20 co-rotatably supports a ferromagnetic clutch disk 51 which is axially shiftable with respect to the rotor shaft 20 but which co-rotates with the rotor shaft 20. The rotor shaft 20 is provided with an axial transmission groove 27, and the clutch disk 51 is provided with a corresponding transmission nose 52 protruding radially into the axial transmission groove 27.

The rotor shaft 20 is also provided with a support structure 40 which is fixed to the rotor shaft 20 and which axially supports an axial preload spring 28 which pushes the clutch disk 51 in axial distal direction away from the support structure 40. The support structure 40 is provided with an axial stop surface 56 to axially stop the clutch disk 51 in the disengaged position as is shown in FIG. 3.

The rotor shaft 20 rotatably supports a pump wheel 60 which is rotatable as well as axially shiftable with respect to the rotor shaft 20. The pump wheel 60 is provided with a plastic pump wheel body 67 which is not ferromagnetic, with a ferromagnetic clutch ring 66, and with a separate non-ferromagnetic friction ring 70. The pump wheel body 67 is rotatably and axially shiftably supported by a sliding bearing at the rotor shaft 20. The sliding bearing is defined by a separate sliding bearing sleeve 24 which is axially fixed by a fixation ring 23 at the rotor shaft 20.

The pump wheel body 67 comprises numerous pump blades 65 axially protruding from the distal side of a pump wheel body base disk 74 of the pump wheel body 67. The ferromagnetic clutch ring 66 is fixed to the pump wheel body 67 at the proximal side of the pump wheel body base disk 74 at the outer circumference thereof. The ferromagnetic clutch ring 66 is provided with an axial clutch ring leg and with a radial clutch ring leg, as seen in cross-section. A stop friction surface 64 is provided at the proximal end of the axial clutch ring leg which is in frictional contact with a corresponding stop friction surface 36 of the pump frame 30 in the disengaged state of the friction clutch arrangement 50, as is shown in FIG. 3. Both clutch friction surfaces 62 and stop friction surface 64 lie in a transversal plane which is rectangular to the rotational axis 21 of the rotor shaft 20.

The pump wheel 60 is also provided with a separate non-ferromagnetic friction ring 70 at the proximal surface of the radial clutch ring leg of the ferromagnetic clutch ring 66. The proximal side of the friction ring 70 serves as a clutch friction surface 62 of the pump wheel 60. The clutch disk 51 is provided with a ring-like clutch friction surface 54 which corresponds with the clutch friction surface 62 at the pump wheel 60. If the clutch friction surfaces 54, 62 are in full frictional contact with each other, the pump wheel 60 co-rotates with the clutch disk 51 and the rotor shaft 20.

The electromagnet 32, the clutch disk 51, and the ferromagnetic clutch ring 66 together define an electromagnetic wet friction clutch arrangement 50.

An electronic clutch control 14 is provided which controls and energizes the electromagnet 32. In the engaged clutch state of the friction clutch arrangement 50, as is shown in FIGS. 1 and 2, the clutch control 14 does not energize the electromagnet 32 at all so that the axial preload spring 28 axially pushes the clutch disk 51 into its engaged position and so that the clutch friction surfaces 54, 62 are in full frictional contact with each other. The pump wheel 60 rotates with the rotational speed of the rotor shaft 20.

In the fully disengaged clutch state as is shown in FIG. 3, the clutch control 14 fully energizes the electromagnet 32 so that the clutch disk 51 is axially attracted with a relatively high axial attraction force and the ferromagnetic clutch ring 66 of the pump wheel 60 is axially attracted with a relatively low axial attraction force. The clutch disk 51 therefore first axially contacts the axial stop surface 56 and, thereafter, the stop friction surface 64 of the pump wheel 60 contacts the corresponding stop friction surface 36 of the pump frame 30.

In the intermediate clutch state as is shown in FIG. 4, the electromagnet 32 is moderately energized by the clutch control 14 so that the clutch disk 51 is fully retracted into its disengaged position, but the pump wheel 60 is not substantially attracted. The stop friction surfaces 64, 36 therefore do not get into relevant frictional contact. As a result, the pump wheel 60 is rotated with about 20% of the rotational speed of the clutch disk 51 because of the fluidic drag torque transmitted by the liquid coolant which fills the wet zone.

In the engaged state of the clutch as is shown in FIGS. 1 and 2, the electromagnetic gap E between the stop friction surfaces 64, 36 is about 0.2 mm, and the electromagnetic gap F between the clutch disk 51 and the axial stop surface 56 is about 0.4 mm. In the disengaged state of the friction clutch arrangement 50 as shown in FIG. 3, the electromagnetic gap D between the ferromagnetic clutch ring 66 and the wheel-sided clutch friction surface 62 is about 1.5 mm. The axial thickness of the separate non-ferromagnetic friction ring 70 is at least 1.0 mm, for example, much more than 1.0 mm. The relatively large axial electromagnetic gap D provides that no relevant axial magnetic forces are present in this gap D and that relevant eddy currents do not appear in this area.

The present invention is not limited to embodiments described herein; reference should be had to the appended claims.

Claims

1-11. (canceled)

12: A mechanical switchable automotive coolant pump for providing a liquid coolant for an automotive engine, the mechanical switchable automotive coolant pump comprising:

a static pump frame;

a rotor shaft configured to rotate, the rotor shaft being rotatably supported at the static pump frame;

a pulley wheel configured to be co-rotatably fixed to the rotor shaft and to be mechanically driven by the automotive engine;

a pump wheel comprising a ferromagnet, the pump wheel being configured to rotate and to be axially shiftable, and to be rotatably supported and axially shiftable with respect to each of the rotor shaft and the static pump frame; and

an electromagnetic wet friction clutch arrangement comprising, a static electromagnet configured to be energized, a clutch disk which is co-rotatably supported by the rotor shaft, a first clutch friction surface arranged at the clutch disk, a second clutch friction surface arranged at the pump wheel, the first clutch friction surface corresponding to the second clutch friction surface, a separate stop friction surface arranged at the pump wheel, and a static stop friction surface arranged at the static pump frame, the separate stop friction surface corresponding to the static stop friction surface, wherein, the static electromagnet, when fully energized, axially attracts the pump wheel so that the separate stop friction surface and the static stop friction surface engage with each other, thereby stopping the pump wheel.

13: The mechanical switchable automotive coolant pump as recited in claim 12, further comprising:

a preload spring configured to axially preload the clutch disk into an engaged clutch position.

14: The mechanical switchable automotive coolant pump as recited in claim 12, wherein the clutch disk is ferromagnetic and is supported to be axially shiftable at the rotor shaft so that the clutch disk is axially attracted by the electromagnet when energized.

15: The mechanical switchable automotive coolant pump as recited in claim 14, wherein the pump wheel further comprises a non-ferromagnetic pump wheel body which comprises pump blades and with a separate ferromagnetic clutch ring which is fixed to the non-ferromagnetic pump wheel body.

16: The mechanical switchable automotive coolant pump as recited in claim 15, wherein the second clutch friction surface and the separate stop friction surface are arranged at the separate ferromagnetic clutch ring.

17: The mechanical switchable automotive coolant pump as recited in claim 12, further comprising an axial stop surface configured to axially stop the clutch disk in a disengaged clutch position.

18: The mechanical switchable automotive coolant pump as recited in claim 12, wherein the separate stop friction surface and the static stop friction surface are configured to lie in a transversal plane.

19: The mechanical switchable automotive coolant pump as recited in claim 15, further comprising:

a first electromagnetic gap between the separate ferromagnetic clutch ring and the clutch disk,

a second electromagnetic gap between the separate ferromagnetic clutch ring and the static electromagnet, and

a third electromagnetic gap between the clutch disk and the static electromagnet,

wherein,

the first electromagnetic gap is at least two times larger than the second electromagnetic gap and the third electromagnetic gap.

20: The mechanical switchable automotive coolant pump as recited in claim 19, wherein the first electromagnetic gap is at least 1.0 mm.

21: The mechanical switchable automotive coolant pump as recited in claim 19, wherein the pump wheel further comprises a separate non-ferromagnetic friction ring which is arranged in the first electromagnetic gap between the separate ferromagnetic clutch ring and the clutch disk.

22: The mechanical switchable automotive coolant pump as recited in claim 12, further comprising:

an electronic clutch control,

wherein,

the electronic clutch control is configured to fully energize the static electromagnet so as to obtain a full-engagement-state where the pump wheel is stopped, and

the electronic clutch control is configured to partially energize the static electromagnet so as to obtain an intermediate-engagement-state where the pump wheel is not completely stopped.