Electric motor with thermal fuse

Abstract

The invention relates to an electric motor (5) for driving a motor vehicle component, with electronics (15) comprising a stamped grid (28) provided with a plastic overmolding (29) and a current path carrying the motor current with two spaced-apart current path ends (30, 31) which form an interruption point (32) bridged by a thermal fuse (24) in the form of a spring-loaded contact bridge (34), wherein the contact bridge (34) is pivotably held about a rotation axis (47) extending perpendicular to the plane of the interruption point (32), wherein a contact contour (51) is provided which limits the pivoting range of the contact breaks (34), against which the contact bridge (34) pivots rotationally in the event of the thermal fuse (24) being triggered as a result of the spring return force of a spring element (38), and wherein the contact bridge (34) is arranged in a circular segment-shaped guide track (33) formed from the plastic overmolding (29). and / or is ledwhich limits the swivel range of the contact bridge (34) at at least one of the circular radii and / or guides the contact bridge (34) along a circular arc-shaped cam wall (52).

Description

The invention relates to an, in particular brushless, electric motor for driving a motor vehicle component, having electronics which have a stamped grid provided with a plastic injection molding with a current path carrying the motor current with two current path ends spaced apart from one another, which form a break point bridged by means of a thermal fuse in the form of a spring-loaded contact bridge. The term motor vehicle component is understood in particular to mean a fan wheel for cooling water.DE 20 2010 002 664 U1 discloses a direct current motor for driving a motor vehicle component, in particular a fan motor for cooling water, having a rotor and having a commutator, on which the carbon brushes bear in a contacting manner. A stamped grid injection-molded with plastic forms a current path which is impressed into an electrical insulation and is electrically conductively connected to one of the carbon brushes. The current path which carries the motor current is interrupted to form two mutually spaced current path ends, and the interruption point is bridged by a contact spring as a thermal fuse.DE 10 2009 036 578 B3 relates to a thermal fuse, in particular for a power module of a motor vehicle, having a conductor track which is arranged on a printed circuit board and is interrupted by an interruption point, and which has a first conductor track section and a second conductor track section in each case adjacent to the interruption point. A contact bridge, which is arranged in the region of the interruption point, has a first contact section and a second contact section opposite one another. The contact sections are fastened in a first position on the conductor track sections by means of solder at soldering points. In the first contact position, the contact bridge is acted upon by spring force in such a way that when the melting point of the solder is reached, the contact sections are separated from the corresponding conductor track sections. Furthermore, the thermal fuse has a spring element which, when the melting point of the solder is reached, brings about a movement of the contact bridge which runs parallel to the printed circuit board. In the second or release position, the contact bridge is held in a cage without contacting the first conductor track section.DE 10 2009 036 578 B3 discloses a thermal fuse having a spring-loaded contact bridge, the triggering movement of which in the case of triggering is oriented parallel to a printed circuit board on which the conductor track section adjacent to a separating point runs, with which the contact bridge is contacted by means of solder melting in the case of triggering.FR 2 972 863 A1 discloses an electric motor with electronics which has a stamped grid provided with a plastic injection molding and having a current path carrying the motor current with two current path ends spaced apart from one another, which form a break point bridged by means of a thermal fuse in the form of a spring-loaded induction coil. One of the coil ends, which is contacted by means of solder melting in the case of release, covers a spring end of a prestressed helical spring, so that the corresponding coil end is lifted from the contact point in the case of release.The invention is based on the object of specifying an, in particular brushless, electric motor for driving a motor vehicle component, in particular a fan wheel for cooling water, with a space-saving and reliably triggering thermal fuse.This object is achieved according to the invention by the features of claim 1.For this purpose, the electric motor has, in addition to a rotor mounted rotatably with respect to a stator, an electronic system with a stamped grid provided with a plastic injection molding and having a current path carrying the motor current, having two current path ends spaced apart from one another and forming an interruption point, and a thermal fuse with a spring-loaded contact bridge for the interruption point. The contact bridge, which has contact surfaces corresponding to the current path ends, is held pivotably about an axis which runs perpendicular to the plane in which the interruption point lies. A contact contour limiting the pivot range of the contract breaks serves as a stop for the contact bridge in the case of the thermal fuse being triggered.In the case of triggering, the contact bridge pivots in the plane of the interruption point. This allows a space-saving arrangement possibility of the thermal fuse including the contact bridge and the spring element.The contact contour serving as an end stop for the contact bridge in the case of the release of the thermal fuse is suitably formed from the plastic injection molding. Advantageously, the contact bridge is furthermore arranged overall in a circular-segment-like guide slot formed from the plastic injection molding. The interruption point is arranged along one of the circle radii and the contact contour in the region of the other circle radius of the circle segment-like guide link.The circular segment shape of the guide link makes it possible in a simple and reliable manner to delimit the pivot range of the contact bridge on at least one of the circular radii and to guide the contact bridge expediently also along a circular arc-shaped web contour of the guide link. For this purpose, the contact bridge, suitably designed as or in the manner of a stamped and bent part, has a number of crimped portions, which form a raised bridge section between the contact surfaces. As a result, the desired mechanical and / or electrical properties of the contact bridge can be easily adjusted. In particular, the contact bridge can be adapted to different current intensities.The contact bridge has a bridge free end and a holding end opposite it. With this, the contact bridge is seated on a pivot pin, suitably formed from the plastic injection molding and forming the axis of rotation, which pivot pin passes through a corresponding opening in the holding end of the contact bridge. In the region of the bridge free end there is a first contact surface which, in the normal state, is soldered to one of the current path ends when the thermal fuse is not triggered. A second contact surface, which is in contact with the other current path end and can likewise be soldered to the latter, is advantageously located between the first contact surface and the axis of rotation on the side of the interruption point facing the latter.The spring element is particularly preferably designed as a leg spring with a spring eye and two spring legs. In the assembled state, the spring eye coaxially surrounds the axis of rotation, in particular the pivot pin. This provides a common pivoting of the spring element or its spring leg interacting with the contact bridge and the contact bridge about the same rotational or pivot axis in a simple and reliable manner.One of the spring legs of the leg spring is held on a cantilever arm on the stop side and there suitably on an undercut contour, while the other spring leg rests under spring prestress on the contact bridge on its bridge longitudinal side facing away from the stop contour. There, the contact bridge expediently has protrusions extending in the pivoting direction, which are overlapped and / or undercut by the bridge-side spring leg.In the case of the thermal fuse being triggered, the spring element continues to exert a spring force on the contact bridge in the direction of the contact contour. This ensures in a particularly reliable manner that neither the contact bridge nor the spring element is detached from its fixing point in the region of the axis of rotation. For this purpose, the spring legs of the spring element extend in the initial state at a suitable angle to each other in such a manner that both in the bridged installation state and in the released state of the contact bridge, the spring legs preferably extend at an acute angle to each other and thus always a sufficient spring force acts on the contact bridge. Suitably, the spring element is made of round wire. This provides a cost-effective possibility for producing the spring element.The contact bridge, which is suitably designed as or in the manner of a stamped and bent part with a number of crimped portions, forms a raised bridge section in the region of the axis of rotation and between the contact surfaces. In addition, the contact bridge preferably has a bending sink which is directed towards the contact surface facing the axis of rotation. Since this contact surface is radially upstream of the axis of rotation in the direction of the interruption point, only a correspondingly shortened radial bridge section of the contact bridge is carrying current.In the case of triggering the thermal fuse, i.e. in the case of overheating, the solder melts in the region of the or each current path end, so that the contact bridge can swivel unimpeded about the axis of rotation and in the plane of the interruption point in the case of triggering. The melted solder connections are practically secured, which ensures a reliable interruption of the interruption or contact point bridged by means of the thermal fuse or its contact bridge.The advantages associated with the invention consist in particular in the fact that by triggering the thermal fuse in the plane of the interruption point, a simple, favorable and space-saving possibility for integrating the thermal fuse into an electric motor which is desirably of space-saving design is provided.An exemplary embodiment of the invention is explained in more detail below with reference to a drawing. Shown therein are: FIG. 1 is an exploded view of a radiator fan for a motor vehicle with a brushless inner rotor motor with integrated converter electronics, FIG. 2 shows an electronics compartment with electronics of the electric motor, with a printed circuit board equipped with electrical or electronic components, and with a stamped grid provided with a plastic injection molding, and with a thermal fuse, FIG. 3 shows the stamped grid with plastic injection molding including a break point to be bridged with the thermal fuse in a perspective illustration, FIG. 4 shows a detail in a perspective illustration of the thermal fuse with a spring-loaded contact bridge in the contact position within a guide slot with a contact contour as an end stop for the contact bridge in the event of the thermal fuse being triggered.Corresponding parts are provided with the same reference numerals in all figures.FIG. 1 shows an exploded view of a fan 1 for the radiator of a motor vehicle. The fan 1 comprises a fan wheel 2 with a central cap 3, around whose outer periphery air guide blades 4 (shown only in some cases) are arranged in a uniformly distributed manner. The fan 1 furthermore comprises an electric motor 5, also referred to as a fan motor, by means of which the fan wheel 2 is driven in rotation.The electric motor 5 is substantially formed by a stator 6, which is wound with a three-phase rotating field winding 7 in the form of coils. The motor 5 further comprises a permanently excited rotor 8, which is mounted in the interior of the stator 6 such that it can rotate about a motor axis 9. For supporting the rotor 8, the motor 5 comprises two rolling bearings 10 and 11 which engage the rotor 8 from axially opposite sides. The axial play of the rotor 8 between the two rolling bearings 10 and 11 is sprung in this case by a spring ring 12.The motor 5 furthermore comprises an approximately disk-shaped or half-shell-shaped motor carrier 13. On an end face facing away from the fan wheel 2, an electronics compartment 14 is introduced into the motor carrier 13, into which an inverter electronics 15 is inserted. For the sealed closure of the electronics compartment 14, the motor 5 comprises an electronics compartment cover 16, also referred to below as housing cover.The rotor 8 is formed (in a manner not shown in more detail) by a laminated core into which permanent magnets are inserted in order to generate an excitation field, wherein the laminated core together with the permanent magnets inserted is encapsulated by injection molding with a plastic casing. Similarly, the stator 6 also consists of a laminated core which is injection-molded with a plastic casing.The motor support 13 is formed in particular by a one-piece die-casting made of aluminum. The electronics compartment cover 16 is preferably an injection-molded part made of plastic.On its front side, the rotor 8 is provided with four screw domes 18, by means of which the rotor 8 is screwed to the fan wheel 2 in the mounted state. The motor 5 and thus the entire fan 1 are fastened to the vehicle via the motor carrier 13, which for this purpose is provided with three screw lugs 19 protruding from its outer periphery. The motor 5 is a brushless, self-cooled inner rotor motor or inner rotor motor.FIG. 2 shows a perspective illustration of a slightly modified motor carrier 13 with electronics 15 inserted into the corresponding electronics compartment 14, which, in contrast to the embodiment according to FIG. 1, are assigned, for example, only three capacitors. The electronics 15 comprise a stamped grid 20 injection-molded with plastic and a printed circuit board or printed circuit board 21 equipped with electrical components. The electric motor 5 is operated by a bridge circuit (B6 circuit) which is implemented in the stamped grid 20 injection-molded. For this purpose, the injection-molded stamped grid 20 has a number of switchable semiconductor components 22, by means of which three phase windings of the field winding 7 of the electric motor 5 are energized alternately. The electric current used for this purpose is provided by a direct current source in a manner not shown in more detail.The three phase windings of the field winding 7 of the electric motor 5 are connected in a delta connection, for example, via the capacitors 23. In other words, in each case two electrically adjacent phase windings are electrically connected to one another at a motor-side contact point, which in turn are electrically contacted via a bridge-side contact point to in each case one bridge branch of the bridge circuit. The windings are made of a painted copper wire and wound centrally into a coil.In FIG. 2, a thermal fuse 24 can be seen in addition to the injection-molded stamped grid 20 and the semiconductor components 22 and the capacitors 23. The thermal fuse 24 protects the electric motor 5 from overheating and the risk of fire. If the motor 5 overheats, the thermal fuse 24 trips and current can no longer flow to or from the motor 5. Terminals 25, 26, and 27 form an input terminal and an output terminal for the motor current and two sensor signal outputs, respectively, e.g. for the measurements of the rotational speed (rotational speed), the rotational direction and / or the position of the motor 5.As is comparatively clearly evident from FIG. 3, the stamped grid 28 which realizes conductor tracks and the conductor tracks of which carry the motor current is provided by means of a plastic injection molding 29 and is electrically insulated. In the region of the thermal fuse removed here, current path ends 30, 31 carrying the motor current can be seen, between which a break point 32 is formed in the stamped grid 28. The current path ends 30, 31 and the interruption point 32 are located in a guide slot 33 formed from the plastic injection molding 29 and configured at least on the inside in the shape of a segment of a circle.As is comparatively clearly evident from FIG. 4, the thermal fuse 24 is formed from a contact bridge 34 which, in the bridged state, connects the current path ends 30 and 31 of the stamped grid 28 to one another. The contact bridge 34 has contact surfaces 35 and 36, at least the contact surface 36 assigned to a bridge free end 37 of the contact bridge 34 being connected by means of a soldered connection to the corresponding (corresponding) current path end 31 of the stamped grid 28. The or each solder joint makes electrical contact between the current path ends 30 and 31 via the contact bridge 34 and mechanically connects the contact bridge 34 to the respective current path end 30, 31 of the stamped grid 28 to form a mechanically fixed connection.For the realization of the function of the thermal fuse 24, a separate spring element 38 in the form of a leg spring is provided, which is held by a first spring leg 39 on a cantilever 40 formed from the plastic injection molding 29 and there in an undercut contour 42 that is the rear in the pivoting direction 41 of the contact bridge 34. The second spring leg 43 rests on the front side of the contact bridge 34 in the pivoting direction 41 under spring prestress. The spring legs 42, 43 of the spring element 38 are at an acute angle to one another and are connected to one another via a spring or leg eye 45 which forms a spring eye 44 and has a plurality of spring windings. With this spring eye 44, the spring element 38 is seated on a pivot pin 46, which is advantageously likewise formed from the plastic injection molding 29 and forms the axis of rotation 47 for the contact bridge 34.The contact bridge 33 is mounted rotatably about the axis of rotation 47, with its holding end 48 facing away from the bridge free end 37, into which a bore, not visible, is made for receiving the pivot pin 46, which axis of rotation is perpendicular to the plane in which the interruption point 32 lies. The spring eye 45 of the spring element 38 and thus its spring eye 44 is arranged coaxially with respect to the pin 46 and thus with respect to the axis of rotation 47.The contact bridge 34 is designed in the manner of a stamped and bent part with a number of crimped portions, which form a central, raised bridge section 34 a. The second contact surface 35 of the contract fractures 34 provided between the axis of rotation 47 at the holding end 48 and the interruption point 32 is located on the underside of a bending sink 34 bfacing the stamped grid 28 and the plastic injection molding 29, with respect to which sink both the central bridge section 34 aand the holding end 48 of the contact bridge 34 are raised. In contrast, both contact surfaces 35 and 36 of the contact bridge 34 are at the same height level with respect to the plane of the interruption point 32. In this case, the contact surface 36 assigned to the bridge free end 37 is located on the underside of a bridge portion 34 cthat is correspondingly lowered with respect to the raised bridge portion 34 aThe contact bridge-side spring leg 43 of the spring element 38 suitably made of round wire is held by means of two add-on portions 49, 50, which are integrally formed on the contact bridge 34 and extend in the opposite direction to the pivot direction 41 shown. In this case, this spring leg 43 engages under the formation 49 provided on the central, raised bridge section 34 aand engages over the formation 50 provided on the bridge free end 37.The circular segment-like guide link 33 forms a contact contour 51 in the region of its circle radius facing away from the interruption point 32 in the pivoting direction 41. This contact or stop contour 51 serves as a stop for the contact bridge 34 in the event of the thermal fuse 24 being triggered and thus as an end stop for the pivoting movement of the contact bridge 34 about the axis of rotation 47.A link wall 52 following the circular arc of the circular segment-like guide link 33 is likewise formed from the plastic injection molding 29 and delimits there the partial surface of a circular surface formed by the guide link 33, in the center of which the axis of rotation 47 is located. Inside the guide slot 33, slots 53, 54 in the shape of a circular arc are introduced into the plastic injection molding 29 and into the stamped grid 28 lying underneath. On the inner side of the circular-arc-shaped slot 54 facing the axis of rotation 57, a circular-arc-shaped guide contour 55 is formed from the plastic injection molding 29 within the guide slot 33. This is located in the transition region between the central, raised bridge section 34 aand the bending depression 34 b. This guide contour 54 serves for additionally pivoting or sliding guidance of the contact bridge 34 in the event of the thermal fuse 24 being triggered.In the event of a release after the solder of the solder joints has melted, the contact bridge 34 and the bridge-side spring leg 43 of the spring element 38 will pivot about the pin 46 and thus about the axis 47. The contact surface 35 of the contract fractures 34 is located in the vicinity of the axis of rotation 47, but is intentionally arranged at a distance from it. The thermal fuse 24 triggers in particular in the event of an overtemperature, in that the solder melts and the contact bridge 34 pivots as a result of the spring force of the spring element 38 by a combined rotational and shearing movement, so that the interruption point 32 bridged by the prestressed contact bridge 34 is interrupted. In the case of triggering, the contact bridge 34 pivots from a first position (contact position) into a second position (triggering position), wherein the pivoting movement takes place about the axis of rotation 47 and in the plane of the interruption point 32. The pivoting movement of the contract fractures 34 in the pivoting direction 41 is limited by the contact contour 51 in that the contract fractures 34 strike there and advantageously continue to be under spring prestress by means of the spring element 38. As a result, the contact bridge 34 and in particular the spring element 38 are held captive in both positions (contact and release position). During the pivoting, the contact spring 34 is securely guided within the guide slot 33 even without a guide contour 55, since the contact spring 34 can slide with its contact surfaces 35, 36 along the corresponding circular segment-like surface section (surface region) of the plastic injection molding 29.The invention is not limited to the above-described embodiments. Rather, other variants of the invention can also be derived from this by the person skilled in the art without departing from the subject matter of the invention. In particular, all the individual features described in connection with the individual exemplary embodiments can also be combined with one another in another manner without departing from the subject matter of the invention.List of reference characters1 Fan 2 Fan wheel 3 Cap 4 Air guide vane 5 Fan / electric motor 6 Stator 7 Rotating field winding 8 Rotor 9 Motor axis 10 Rolling bearing 11 Rolling bearing 12 Spring ring 13 Motor carrier 14 Electronics compartment 15 Converter / electronics 16 Electronics compartment cover 17 Axle bolt 18 Screw boss 19 End face 20 Injection-molded stamped grid 21 Printed circuit board 22 Semiconductor component 23 Capacitor 24 Thermal fuse 25 Input connection 26 Output connection 27 Sensor signal outputs 28 Stamped grid 29 Plastic injection-molded 30 Current path end 31 Current path end 32 Interruption point 33 Guide slot 34 Contact bridge 34 aBridge portion 34 b Biege sink 34 cBridge portion 35 Contact surface of the contact bridge 36 Contact surface of the contact bridge 37 Bridge-free end 38 Spring element 39 First spring leg 40 Cantilever 41 Pivot direction 42 Undercut contour 43 Second spring leg 44 Spring eye 45 spring / leg eye 46 pivot pin 47 pivot axis 48 retaining end 49 molding 50 molding 51 contact / stop contour 52 link wall 53 slot 54 slot 55 guide contour

Claims

Electric motor (5) for driving a motor vehicle component, in particular a fan wheel (2) for cooling water, having an electronics system (15) which has a stamped grid (28) provided with a plastics encapsulation (29), having a current path carrying the motor current, having two current path ends (30, 31) which are spaced apart from one another and which form an interruption point (32) which is bridged by means of a thermal fuse (24) in the form of a spring-loaded contact bridge (34), - wherein the contact bridge (34) is held pivotably about an axis of rotation (47) running perpendicular to the plane of the interruption point (32), and - wherein the contact bridge (34) is arranged and / or guided in a circular-segment-like guide slot (33) which is formed from the plastics encapsulation (29) and delimits the pivoting range of the contact bridge (34) on at least one of the circle radii and / or guides the contact bridge (34) along a circular-arc-like slot wall (52).Electric motor (5) according to Claim 1, characterized in that a contact contour (51) which delimits the pivot range of the contact bridge (34) is provided, against which the contact bridge (34) pivots rotationally in the event of the thermal fuse (24) being triggered as a result of the spring restoring force of a spring element (38).Electric motor (5) according to one of the preceding claims, characterized in that the contact contour (51) serving as an end stop for the contact bridge (34) in the case of release of the thermal fuse (24) is formed from the plastics injection moulding (29).Electric motor (5) according to one of Claims 1 to 3, characterized in that the interruption point (32) is arranged along one of the circle radii and the contact contour (51) is arranged in the region of the other circle radius of the circular-segment-like guide link (33).Electric motor (5) according to one of the preceding claims, characterized in that the contact bridge (34) has a bridge free end (37) and a retaining end (48) opposite the latter, wherein the contact bridge (34) has, in the region of the bridge free end (37), a first contact surface (36) soldered to one of the current path ends (31) and a second contact surface (35) contacted to the other current path end (30), in particular likewise soldered.Electric motor (5) according to Claim 5, characterized in that the second contact surface (35) of the contact bridge (34) is provided between the first contact surface (36) thereof and the axis of rotation (47) on the side of the interruption point (32) facing the latter.Electric motor (5) according to one of the preceding claims, characterized in that the contact bridge (34) is seated with its holding end (48) on a pivot pin (46) which is formed from the plastics injection moulding (29) and forms the axis of rotation (47).Electric motor (5) according to one of the preceding claims, characterized in that the spring element (38) is designed as a leg spring with a spring eye (44) coaxially surrounding the axis of rotation (47), in particular the pivot pin (46), and with a first spring leg (39) held on a cantilever arm (40) on the stop side and with a second spring leg (43) bearing under spring prestress against the contact bridge (34) on its bridge longitudinal side facing away from the contact contour (51).Electric motor (5) according to one of the preceding claims, characterized in that the contact bridge (34) is designed as or in the manner of a stamped and bent part with a number of bends which form a raised bridge section (34a) in the region of the axis of rotation (47) and / or between the contact surfaces (35, 36), in particular in the region of the arc-shaped link wall (52) of the guide link (33).Electric motor (5) according to one of the preceding claims, characterized in that the contact bridge (34) has a bending sink (34b) directed towards the contact surface (35) facing the axis of rotation (47).

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