The present invention refers to a mechanical switchable automotive cooiant pump for pumping a coolant to an automotive combustion engine.

A mechanical coolant pump is mechanically driven by the combustion engine so that the pumping rate is proportional to the rotational speed of the engine. Right after a cold start of the engine, no relevant coolant fiow is needed. A switchable coolant pump which is provided with a ciutch for engaging or disengaging the pump rotor allows to disengage the pump rotor as long as the engine is cold and does not need a relevant coolant flow. One type of clutch actuation is the electromagnetic clutch which is provided with an electromagnetic actuator which engages or disengages the clutch disc which is axiaify movable, A mechanical switchable coolant pump with electromagnetic clutch actuation is provided with two roller bearings and electromagnetic means which makes the cooiant pump capacious.

It is an object of the invention to provide a compact mechanical and e!ectromagnetica!ly switchable automotive coolant pump.

This object is solved with a coolant pump with the features of claim 1.

The coolant pump according to the invention is provided with a stationary pump frame which is mountable to an engine block of the combustion engine. The stationary pump frame comprises a cylindrical support body which is arranged coaxiaily with other rotating parts of the pump.

The pump comprises a rota table pump rotor which is provided with a pump wheel for pumping the coolant, with a pump rotor shaft and with a pump rotor clutch disc. The pump rotor shaft connects the pump wheel with the pump rotor dutch disc stiffly so that the pump rotor is rotating as one part. The pump rotor shaft is directly supported by a first roller bearing at the inside of the cylindrical support body. The rotatable pump rotor forms a first rotating unit,

A second rotating unit is formed by the rotatable driving rotor which is provided with a radial driving rotor clutch disc and with a cylindrical pulley wheel which is driven by the engine, The driving rotor is directly supported by a separate second roller bearing at the support body.

One of the two clutch disks is ferromagnetic and is axia!ly movable. An electromagnetic stationary clutch actuator is provided to switch or to axia!!y move the movable clutch disk between an engaged and a disengaged position. When the electromagnetic actuator is energized the ferromagnetic movable clutch disk is attracted. If the ferromagnetic clutch disc is permanently magnetized, the clutch disk even can be pushed away by the electromagnetic actuator depending on the polarity of the energized actuator. The stationary clutch actuator is preferably directly mounted at the support body. The two clutch disks and the electromagnetic actuator together define an electromagnetic friction clutch unit.

The outer ring of the pump rotor bearing is defined by the inside of the support body, i.e. is an integral part of the support body, and the inner ring of the pulley wheel bearing is directly press fitted onto the outside of the support body. The two roller bearings are radially a very compact so that the radial extension of the coolant pump is compact as well. A compact coolant pump is important because the installation space for the coolant pump is generally small.

According to another preferred embodiment of the invention, the outside of the support body is provided with an axial cable slit which is radially covered by the inner ring of the driving rotor bearing. An electrical cable for electrically supplying the coil ring is provided in the cable slit. The term "axial" in the present context does not mean that the slit has to be orientated strictly axially but that the slits orientation generally has an axial component to make it possible to transport electric energy from the proximal pump rotor side of the pump frame to the distal side of the pump frame where the electromagnetic actuator is located.

According to a preferred embodiment of the invention, the inner ring of 5 the pump rotor bearing is defined by the pump rotor shaft. This means that the outer and the inner ring of the pump rotor bearing are not realized as separate ring parts but are integral parts of other parts, i.e. are integral parts of the support body and the pump rotor shaft. This allows a very compact construction of the coolant pump.

10 According to a preferred embodiment of the invention, a cylindricai spacer of non-ferromagnetic material is radially provided between the ring coil and the pump rotor shaft. The spacer is directly mounted to the outside of the support body and the ring coil is mounted to the outside of the spacer. Providing a non-ferromagnetic spacer radially between the ring coil and the support body makes the electromagnetic actuator more efficient in axia! direction.

According to a preferred embodiment of the invention the pump rotor clutch disc is the one which is axialiy movable.

Preferably, the axialiy movable clutch disk is pretensioned into the engaged position by a pretension element. The pretension element can be one or more separate coil spring(s). Alternatively, the pretension element can be realized as a part of the movable clutch disc which is formed as a cup spring, whereby a ringlike part of the cup spring is defining a clutch ring.

One embodiment of the invention is described with reference to the drawing, wherein

figure 1 shows the longitudinal cross section of a mechanical switchable automotive coolant pump mounted to an engine block.

The figure shows a longitudinal cross-section of the coolant pump 10 which is mounted to the block 15 of an internal combustion engine 14. The coolant pump 10 is a mechanical coolant pump which is driven by a pulley belt 60 which is driven by the engine 14. The coolant pump 10 is switchable which means that the permanent rotation transmitted by the pulley belt 60 can be transmitted or non-transmitted to a pump wheel 20 pumping the coolant by switching the electrical clutch unit 62.

The coolant pump 10 comprises a stationary pump frame 12 with a flange 13 and a support body 28. The flange 13 is directly mounted to the corresponding opening flange of the engine block 15. The pump frame support body 28 is generally cylindrical and Is supporting all rotating units, as will be described.

A rotatabie pump rotor 16 comprises the pump wheel 20 for pumping the coolant, a pump rotor shaft 22 and a pump rotor clutch disc 38 with a ferromagnetic clutch ring 39, A circular sealing 58 is provided to seal the gap between the pump frame 12 and the rotor shaft 22 water-tight.

The pump rotor clutch disk 38 is realized as a disk spring, so that the clutch ring 39 of the clutch disk 38 is axially movable. The disk spring pushes the clutch ring 39 in distal direction into an engaged position. The pump rotor 16 is rotatabiy supported at the support body 28 by a rotor bearing 30. The inner ring and the outer ring of the rotor bearing 30 are integral parts of the pump rotor shaft 22 and of the cylindrical pump frame support body 28, and therefore are defined by the outside 24 of the pump rotor shaft 22 and by the inside 26 of the cylindrical support body 28.

A rotatabie driving rotor 18 is defined by a cylindrical pulley wheel 34, which is driven by the pulley belt 60, and a ringlike radial clutch disc 36. The driving rotor 18 is rotatabiy supported at the outside of the pump frame support body 28 by means of a driving rotor roller bearing 32 which is a conventional roller bearing with a separate outer ring 44 and a separate inner ring 46. The inner ring 46 of the roller bearing 32 is press fitted to the outside of the support body 28. The pulley wheel 34 is provided with a support structure 48 which is T-shaped in cross section whereby the cylindrical cross bar is press fitted to the outside of the outside ring 44 of the driving rotor roller bearing 32.

A stationary clutch actuator 40 is defined by a circular coil ring 41 which is directly fixed at the support body 28, whereby a non-ferromagnetic spacer 42 made out of plastic, aluminum or copper is arranged radially between the coil ring 41 and the support body 28, The coil ring 41 is electrically connected to the pump control 50 via an electrical cable 54 which is placed in an axial cable slit 52 which is provided at the outside surface of the cylindrical support body 28. The cable slit can alternatively be provided at the inner ring 46 of the driving rotor roller bearing 32. The clutch actuator 40, the driving rotor clutch disc 36 and the pump rotor clutch disc 38 together define a clutch unit 62.

When the coil ring 41 is energized by the pump control 50, the axialiy movable pump rotor clutch ring 39 is moved in proximal direction into a disengaged position. When the coil ring 41 is not energized, the clutch ring 39 is moved in distal direction into an engaged position so that the clutch is engaged and the rotation of the driving rotor 18 is transmitted to the pump rotor 16, so that the pump wheel 20 is rotating.