Patent Publication Number: US-9431722-B2

Title: Electrical contact system for contacting a coil

Description:
FIELD OF THE INVENTION 
     The present invention relates to an electrical contact system for contacting a coil, in particular a coil of a rotational speed sensor, and to the use of an electrical contact system in a rotational speed sensor for acquiring the rotational speed in an exhaust gas turbocharger. 
     BACKGROUND INFORMATION 
     Electrical coils are used in many industrial products. One possible application is for example the use of an electrical coil as a rotational speed sensor. In industrial applications, the available space for the installation of such electrical coils, in particular rotational speed sensors, is often small. It is therefore a technical challenge to accommodate the electrical coil, together with its electrical contacting, in the smallest constructive space and to ensure, over the lifespan of its use, a reliable electrical contact between the electrical terminals and the coil. 
     As a rule, electrical coils are made up of a defined number of windings of a wire around a holding body. As an electrical wire, frequently a thin metal wire is used, and particularly often so-called enameled copper wire is used. This electrical wire is surrounded by an electrically insulating layer of enamel, also referred to hereinafter as an insulating layer, in such a way that no electrical short-circuit arises between the wire windings that contact each other. The insulating layer used is often made up of a protective enamel that in many cases has a thickness of from 1 to 5 μm. In order to enable operation of the finished wound coil, the wire ends of the coil must be reliably electrically contacted, and for this purpose in particular the insulating layer has to be reliably penetrated. For this purpose, in many cases thermal contacting methods are used, such as welding or soldering. 
     Such thermal contacting methods require an additional working process that entails increased installation costs and process costs. 
     In addition, it is often difficult in the available narrow constructive space to ensure a reliable electrical contacting using the known thermal contacting methods. 
     German Published Patent Application No. 10 2004 002 935 describes an electrical connection system for producing an ignition coil that is intended to replace currently used contacting methods for connecting thin enameled wires in ignition coils with a so-called “cold” contacting. However, such an electrical connection system is preferably suitable for an end-face contacting. 
     SUMMARY 
     In comparison with the existing art, the electrical contact system for contacting a coil has the advantages that the contacting requires very little constructive space, and that it is also possible to reliably produce a plurality of different electrical contactings in different contact regions that are not situated at an end face of the holding body. In addition, equipment for thermal contacting processes can be done without. This yields significant cost advantages and space advantages in the design of the contacting of a coil. 
     According to the present invention, an electrical contact system is proposed for contacting a coil, in particular a coil of a rotational speed sensor, having the following components: a holding body, the holding body being electrically insulating, a line segment of at least one electrical line, the electrical line being surrounded by an electrical insulating layer, at least one spring element, the at least one spring element being electrically conductive, the spring element having at least one opening, the at least one opening forming a cutting edge in at least some regions of its edge. The at least one spring element is pressed with the at least one cutting edge against the line segment in such a way that the at least one cutting edge pierces through the electrical insulating layer, and an electrical contact is produced between the at least one spring element and the at least one line segment. According to the present invention, at least one bus bar is provided, the at least one bus bar being electrically conductive and the holding body and/or the at least one bus bar being provided with a clamping means, the bus bar being fixedly clamped on the holding body by the clamping means, and in this way the spring element being tensioned between the bus bar and a contact region of the holding body, and in this way the at least one line segment is electrically contacted with the at least one bus bar by the at least one spring element. 
     Particularly advantageous here is the possibility of fixedly clamping the bus bar on the holding body, using the clamping means, and in this way tensioning the spring element between the bus bar and the contact region of the holding body reliably over the entire lifespan of the system, and in this way producing a reliable electrical contact between the line segment and the bus bar. In addition, the clamping means advantageously make it possible for the bus bar also to be routed laterally along the holding body, so that it is also possible to produce a non-end-face cold contacting in a plurality of contact regions of the holding body, using a plurality of bus bars. In this way, such an electrical contact system can be produced in a particularly small constructive space. 
     In comparison with the existing art, the use of an electrical contact system in a rotational speed sensor for acquiring the rotational speed in an exhaust gas turbocharger has the advantage that, due to the particularly small design of the coil and of the electrical contact system, a rotational speed sensor can be produced that can be used even in the limited constructive space of an exhaust gas turbocharger housing, and that has a particularly good signal-noise ratio due to its compact design. In addition, the contact system according to the present invention is particularly suitable for ensuring, at low contacting costs, a reliable contacting of the rotational speed sensor in the exhaust gas turbocharger over its entire lifespan, and in all operating states of the exhaust gas turbocharger. In this way, there result significant cost advantages, while the lifespan of the rotational speed sensor remains at least the same. 
     Due to the fact that the at least one spring element is made, as a flexible spring, from a metal strip, and that the at least one spring element immediately electrically contacts at least one bus bar, it is advantageously achieved that the spring element has a particularly flat construction and, in the mounted state, comes to be seated in a plane between the bus bar and the holding body that is substantially parallel to the plane of the bus bar and to the plane of the holding body. In addition, the use of a flexible spring ensures a reliable contacting, due to the spacing tolerance compensation brought about by the spring element, even when there are changes in the spacing between the bus bar and the holding body, for example as a result of thermal or mechanical stress. 
     An advantageous development of the electrical contact system provides that the at least one bus bar is detachably connected to the holding body. In this way it is advantageously brought about that the bus bar can be mounted particularly easily, and that the bus bar can be exchanged particularly easily during maintenance work. 
     An advantageous development of the electrical contact system provides that the contacting region has a snap indentation opening having at least one snap indentation, and that the at least one spring element has a spring element snap nose, and that the at least one spring element engages, via the at least one spring element snap nose, in the snap indentation opening, and grasps the at least one snap indentation. This advantageously brings it about that the spring element is fastened on the holding body in a captive manner secure against slippage, and that the mounting process can in this way advantageously be simplified. 
     Due to the fact that the at least one bus bar engages at the end in a recess of the at least one spring element, forming a pivot bearing for the at least one bus bar, it is advantageously achieved that the bus bar can be mounted and fixed on the holding body particularly simply. In addition, it is advantageously achieved that the connection between the spring element and the bus bar is permanently ensured over the lifetime of the electrical contact system, and is substantially not impaired by aging processes of the material. 
     An advantageous development of the electrical contact system provides that the clamping means on the holding body is fashioned as at least one pin, there being fashioned in the at least one bus bar at least one socket-type opening such that the at least one pin is accommodated in the at least one socket-type opening, forming a non-positive connection between the at least one pin and the at least one socket-type opening. The realization of the clamping means as a pin and socket-type opening advantageously brings about a particularly simple and secure mounting of the bus bar on the holding body. In addition, if more than one pin and more than one socket-type opening are used, a precise positioning and orientation of the bus bar relative to the holding body is advantageously brought about. 
     Due to the fact that the at least one spring element has at least one flexible clip, the at least one flexible clip being bent around the at least one bus bar in such a way that the at least one spring element is fastened on the at least one bus bar, it is advantageously brought about that the bus bar and the spring element form a mounting unit, making the mounting of the electrical contact system particularly simple. Moreover, in this way it is advantageously brought about that the electrical contact between the spring element and the bus bar is permanently ensured. Finally, in this way it is advantageously brought about that the winding process during the production of the coil on the holding body can be carried out easily, because, other than the holding body and the enameled copper wire for the coil, no moving parts are present that could become detached during the winding process or that could cause an imbalance during the winding process. 
     A further exemplary embodiment of the electrical contact system provides that the at least one spring element has two clamping arms at a distance from the holding body that at least in some regions surround the holding body in the contact region, the clamping arms having spring clips on their ends, and the at least one bus bar having two clamping jaws extending toward the holding body, and that the at least one bus bar is pushed, with its clamping jaws, over the clamping arms of the at least one spring element in such a way that the spring clips are tensioned between the clamping jaws and the holding body. This development advantageously brings about a particularly simple mounting and particularly reliable contacting of the coil. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1 a    shows an exploded view of an electrical contact system according to the present invention for contacting a coil, according to a first exemplary embodiment. 
         FIG. 1 b    shows a detail of the electrical contact system of  FIG. 1   a.    
         FIG. 1 c    shows a perspective view of the electrical contact system for contacting a coil in the mounted state according to  FIG. 1   a.    
         FIG. 2 a    shows an exploded view of an electrical contact system according to the present invention for contacting a coil according to a second exemplary embodiment. 
         FIG. 2 b    shows a perspective view of the electrical contact system of  FIG. 2 a    during a mounting step. 
         FIG. 2 c    shows the electrical contact system for contacting a coil of  FIG. 2 a   , in the finally mounted state. 
         FIG. 2 d    shows a perspective view of a cross-section through the holding body of  FIGS. 2 a  to 2 c   , in the region of the snap indentation opening. 
         FIG. 3 a    shows a perspective exploded view of a contact system according to the present invention for contacting an electrical coil according to a third exemplary embodiment. 
         FIG. 3 b    shows a perspective view of a cross-section through an electrical contact system according to  FIG. 3 a   , in the region of the contact region. 
         FIG. 3 c    shows a perspective representation of a contact system for contacting an electrical coil according to  FIGS. 3 a  and 3 b   , in the mounted state. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1 a    shows an electrical contact system  100  for contacting a coil  120 , in particular a coil  120  of a rotational speed sensor. Electrical coil  120  is formed by windings of an electrical line  140  around a holding body  200 . Electrical line  140  is preferably made of enameled copper wire, i.e. thin copper wire surrounded by an electrically insulating layer of insulation. The layer of insulation is preferably made of a thin layer of enamel having a thickness of 1 to 5 μm. The insulating layer is necessary in order to prevent electrical short circuits within the wound coil body, thus enabling a tight winding of coil  120 . Coil  120  is electrically contacted via two wire ends that protrude from the coil body. In the depicted exemplary embodiment, electrical coil  120  is wound onto a winding segment  210  of holding body  200  situated at the end of holding body  200 , and is preferably used as a rotational speed sensor for an exhaust gas turbocharger. 
     Holding body  200  is made up of an electrically insulating material, preferably plastic. Holding body  200  has, seen from winding region  210  of coil  120 , first a substantially round or elliptical cross-section along an end region  214  that is particularly suitable for winding on coil  120 . As it continues further, at the end of end region  214  a first collar  230  is formed. Along the longitudinal axis, behind first collar  230  there follows a contact segment  218 . In this exemplary embodiment, in contact segment  218  the cross-section of holding body  200  is substantially rectangular, the surface of holding body  200  in contact segment  218  having two planar surfaces situated on opposite sides, each forming a contact region  220 . As holding body  200  continues, there follows a second collar  232  that runs around holding body  200 , coinciding approximately with the end of contact region  220  and having, in a prolongation of contact region  220 , a collar opening  234  that can also act as clamping means  240 . Behind this second collar  232 , pins  242 , acting as clamping means  240 , are fashioned on holding body  200 , two pins  242  being fashioned on each side of holding body  200  on which a contact region  220  is situated. In other specific embodiments, however, only one pin  242  may be fashioned, or more than two pins  242  may be fashioned on each side of a contact region  220 . 
     Electrical line  140  that is to be contacted is guided from winding region  210  of coil  120  along end region  214  of holding body  200  in contact region  220  of holding body  200 . 
     Electrical contacting device  100  additionally has a spring element  300  that has a T-shaped design, the three T ends of spring element  300  being fashioned as flexible clips  340 . In the depicted exemplary embodiment, three openings  320  are situated in spring element  300 . Openings  320  are fashioned substantially orthogonal to the longitudinal axis of spring element  300 . Edges  320  are each fashioned as cutting edge  322 . Line segment  142  provided with the insulating layer here stands in mechanical contact to openings  320 , with their cutting edges  322 . When spring element  300  is loaded with a mechanical pressure, at least one cutting edge  322  breaks through the insulating layer of electrical line  140 . This forms a mechanical and electrical contact between electrical line  140 , preferably fashioned as an enameled copper wire, and electrically conductive spring element  300 . 
     In addition, the electrical contact system has a bus bar  400  that has an oblong basic body running in a direction of longitudinal extension, the basic body having a substantially rectangular cross-section and being provided with socket-type openings  440 , the socket-type openings  440  being fashioned so that they can be fitted onto pins  242  of the holding body with a press fit. Bus bar  400  is particularly preferably made of an electrically conductive material, particularly preferably a metal. Bus bar  400  is constructively designed such that, in the mounted state, it has adequate bending rigidity to be able to permanently hold spring element  300  against holding body  200  with tension. 
     In the perspective view, shown in  FIG. 1 a   , of contact system  100 , on the underside two pins  242  acting as clamping means  240  are visible. These pins are used to attach a further bus bar  400  (not shown in the Figure) that is suitable for contacting another wire end, of a further line segment  142 , of coil  120  using a second spring element  300  (also not shown here). 
     In  FIG. 1 b   , bus bar  400  is shown with spring element  300  fastened thereto by flexible clips  340 . Flexible clips  340  are bent around bus bar  400  in such a way that spring element  300  is fixedly connected mechanically and electrically to bus bar  400 . As is shown in  FIG. 1 b   , in the region of openings  320  spring element  300  has the shape of a plate spring. The region in which openings  320  are situated protrudes from the plane of bus bar  400 , so that when pressure is applied to the region having openings  320 , spring element  300  is pressed in the direction of bus bar  400 , and in this way is tensioned. 
       FIG. 1 c    shows electrical contact system  100  of  FIG. 1 a    in the finally mounted state. Here, pins  242 , fashioned as clamping means  240 , of holding body  200  are guided through socket-type openings  440  of bus bar  400 . Pins  242  are made in such a way that a non-positive connection exists between at least one of the two pins  242  and one of the socket-type openings  440 , through which connection bus bar  400  is fixedly connected to holding body  200 . In order to enable the non-positive connection between a pin  242  and a socket-type opening  440 , pin  242  can have a stelliform cross-section in which the distance from the pin center to the vertices is preferably somewhat greater than the distance between the center of socket-type opening  440  and the edge of second-type opening  440 , so that the bus bar has to be pressed onto pins  242 . However, other cross-sectional shapes of pin  242  are conceivable that ensure a reliable non-positive connection between pin  242  and socket-type opening  440  of bus bar  400 . 
     Through the clamping of bus bar  400  on holding body  200 , spring element  300  is tensioned between bus bar  400  and holding body  200  in the region of its openings  320 . Spring element  300  here operates in the manner of a plate spring. In the depicted exemplary embodiment, line segment  142  comes to be seated between holding body  200  and spring element  300 . Openings  320  of spring element  300  are here situated over line segment  142 . When bus bar  400  is fixed on holding body  200 , the insulating layer of line segment  142  is penetrated at least in the region of cutting edges  322  of spring element  300 , by cutting edges  322  on the edges of openings  320 , causing the spring element to come into direct mechanical and electrical contact with line segment  142 . The electrical contact produced in this way between bus bar  400  via spring element  300  and line segment  142  and conducting wire  140  to coil  120  can thus be produced by a simple mechanical mounting process, without thermal action. The electrical contact between spring element  300  and line segment  142  is moreover also permanently ensured, because bus bar  400  is securely fixed on pin  242  by socket-type openings  440 , and, through its spring force, spring element  300  tensioned between bus bar  400  and holding body  200  compensates differences in spacing, resulting from production, between bus bar  400  and holding body  200 . Such differences in spacing can be caused by aging effects of the materials, or can be caused by mechanical and/or thermal stress. 
     The specific embodiment shown in  FIGS. 1 a  through 1 c    enables a particularly secure and reliable winding of coil  120  on winding segment  210  of holding body  200 , because during the winding process, apart from electrical line  140  fashioned as coil wire and holding body  200 , no further mechanical parts are involved, and in this way mechanical imbalances during the winding process can be avoided to the greatest possible extent. 
     Holding body  200  shown in  FIGS. 1 a  and 1 c    has, along its longitudinal direction, two collars  230 ,  232 , i.e. elements that are shield-shaped and that in the exemplary embodiment are situated at a distance from one another, protruding past the normal diameter of holding body  200 . The two collars  230 ,  232  are fashioned such that when holding body  200 , preferably acting as a rotational speed sensor, is inserted into a rotational speed sensor sleeve, they act as a radial guide for holding body  200 , which extends in oblong fashion. In this way they perform a plurality of functions: on the one hand, they counteract tilting of holding body  200  in the sleeve during insertion, thereby achieving in a reliable and secure manner that coil  120 , acting as rotational speed sensor element or detector coil, can be brought to a stop at the front end of the sleeve, and can thus be brought to be situated at a well-defined distance from the at least one rotating element whose rotational speed is to be acquired. On the other hand, collars  230 ,  232  ensure that holding body  200 , while being mounted, before installation or during insertion into the sleeve of a rotational speed sensor, does not come to lie directly on electrical line  140  or on line segment  142 , undesirably cutting through the insulating layer. Collars  230 ,  232  thus act as handling protection against mechanical defects at the conducting wire and/or at holding body  200 , and/or at bus bar  400 . In the region of bus bar  400 , second collar  232  has an opening that can act as an introduction guide during mounting of bus bar  400  onto pins  242 , and as a clamping means relative to bus bar  400 . 
       FIG. 2 a    shows an exploded view of a second specific embodiment of a contact system  100  according to the present invention for contacting a coil  120 . In this specific embodiment, holding body  200  has in its contacting region a snap indentation opening  260  in which a snap indentation  262  (shown in detail in  FIG. 2 d   ) is situated. Spring element  300  is fashioned as a metallic stamped flexible part, and has, next to openings  320  situated, in this exemplary embodiment, oblique to the main axis of spring element  300 , with their cutting edges  322 , a spring element locking nose  360  that is suitable for snapping into snap indentation  262  of snap indentation opening  260  of holding body  200 . For this purpose, spring element snap nose  360  is bent downward extending out from spring element  300 . In addition, spring element  300  has, at one of its ends, an upwardly bent region in which there is an opening  380 . In addition to its socket-type openings  440 , bus bar  400  has a pivot bearing end region  480  that is fashioned such that it can engage in opening  380  of the spring element so as to form a pivot bearing  450 . 
       FIG. 2 b    shows the mounting process of the specific embodiment of electrical contact system  100  of  FIG. 2 a   . First, spring element  300  is fixed on snap indentation  262  of snap indentation opening  260  of holding body  200 , using spring element snap nose  360 . Subsequently, coil  120  is wound onto holding body  200  in winding segment  210  of holding body  200 , and the coil wire ends, acting as line segment  142 , are guided into contact region  220  in such a way that they come to lie on spring element  300 , fastened by spring element snap nose  360 , and here they lie at least in some regions over openings  320  with their cutting edges  322 . 
       FIG. 2 c    shows the finally mounted state of the specific embodiment of electrical contact system  100  shown in  FIGS. 2 a  and 2 b   . Here, line segment  142  is situated between bus bar  400  and spring element  300 . Through the clamping of bus bar  400  on holding body  200 , plate spring-type spring element  300  is tensioned, and cutting edges  322  pierce the insulating layer of line segment  142  of the coil wire. In this way, a reliable and secure mechanical and electrical contact is produced between bus bar  400  and line segment  142 , and thus coil  120 . Pivot bearing  450  enables a particularly reliable mounting of bus bar  400  with its socket-type openings  440  onto pins  242 . In addition, the connection of metallic bus bar  400  by its pivot bearer end region  480  in opening  380  of spring element  300  ensures a particularly reliable and permanent contacting between bus bar  400  and line segment  142 . This is because this metal-metal connection between bus bar  400  and spring element  300 , and line segment  142  situated between them, is exposed to fewer mechanical alterations due to age and stress than is for example a plastic-metal connection. 
       FIG. 2 d    shows a cross-section of holding body  200  in the region of snap indentation opening  260  of contact region  220 . Spring element snap nose  360  of spring element  300  grasps snap indentation  262 , whereby spring element  300  is securely and reliably fixed on holding body  200 . Here, spring element snap nose  360  can be fashioned as a hook-shaped element that is pressed into the material of holding body  200  in snap indentation  262 . In  FIG. 2 d    it can also be seen how line segment  142  runs over openings  320  with its cutting edges  322  of spring element  300 , spring element  300  still having, in the depicted detail, the plate spring-type curvature of its untensioned state. Due to the mechanical movement of spring element  300  during the clamping of bus bar  400 , in the region of openings  300  there results a vertical and lateral movement of opening  320  and its cutting edges  322  relative to line segment  142 , whereby the insulating layer of line segment  142  is reliably pierced, and spring element  300  reliably electrically contacts line segment  142 . 
       FIG. 3 a    shows an exploded view of a third exemplary embodiment. Here, line segment  142  is wound in a plurality of windings around holding body  200  in contact region  220  of holding body  200 . Contact region  220  of holding body  200  has a substantially round cross-section. Spring element  300  has two clamping arms  390  that stand out in U-shaped fashion toward holding body  200 , substantially circular round openings  320 , having cutting edges  322  fashioned at the edge, being fashioned in clamping arms  390 . At the end of clamping arms  390  there are situated spring clips  392  that stand out slightly from the plane of clamping arms  390 . Clamping arms  390  are substantially rectangular and have at least partly rounded edges. The spacing of the two clamping arms  390  is made such that spring element  300  can easily be pushed over line segment  142  fashioned as coil element. On bus bar  400 , on its end facing spring element  300  there are fashioned two clamping jaws  490  standing out toward holding body  200 , clamping jaws  490  having a U-shape similar to clamping arms  390  of spring element  300 . Here, together with clamping jaws  490 , clamping arms  390  form the clamping means by which bus bar  400  is fixed on holding body  200 . 
       FIG. 3 b    shows the exemplary embodiment of  FIG. 3 a    during the mounting process. Here, spring element  300  is pushed with its clamping arms  390  and its openings  320 , including their cutting edges  322  in contact region  220 , over line segment  142  fashioned as a coil. The spring element is surrounded by clamping jaws  490  of bus bar  400  and is clamped against line segment  142  on holding body  200 . In the depicted mounted state, clamping jaws  490  are not yet pushed over spring clips  392 . Through a further pushing of bus bar  400  with its clamping jaws  490  over spring clips  392 , spring element  300  is tensioned between clamping jaws  490  and line segment  142  on holding body  200 , cutting edges  322  of openings  320  of spring element  300  piercing the insulating layer of line segment  142  and thus ensuring an electrical and mechanical contact between the electrically conductive wire interiors of line segment  142  and spring element  300 . 
       FIG. 3 c    shows a contact system  100  according to the third exemplary embodiment of the present invention; in the depicted Figure, the two line segments  142  of coil  120  (not shown here) are contacted by two spring elements  300  and two bus bars  400 . The two bus bars  400  and the respectively associated spring elements  300  are clamped on holding body  200  from opposite sides. An electrical contact system  100  produced in this way has a particularly secure contacting, because line segment  142  is wrapped around a holding body  200  in contact region  220  in a plurality of windings, and in this way the contact surface between spring element  300 , its cutting edges  322 , and line segment  142  is ensured over a particularly large surface. In addition, contact system  100  produced in this way can be mounted particularly easily by simply pushing clamping jaws  490  of bus bar  400  over clamping arms  390  of spring element  300  after clamping arms  390  of spring element have been previously pushed over line segment  142  in contact segment  220 . Finally, the winding of electrical coil  120  (not shown here) and of contact regions  320  wound with line segment  142  is particularly easily possible, because during the winding process no imbalance caused by additional detachable mechanical parts can occur. 
     Spring elements  300  for all exemplary embodiments are preferably produced as metallic stamped flexible parts. In this way, in a particularly simple manner there result particularly sharp cutting edges  322 . Cutting edges  322  on opening  320  in spring element  300  preferably have a bending radius RS that is significantly smaller than the radius of insulating layer RI of electrical wire  140 . In this way, it is ensured that when spring element  300  is pressed on, via the bus bar  400 , cutting edge  322  reliably pierces the insulating layer of line segment  142  and in this way ensures a reliable electrical and mechanical contact between spring element  300  and line segment  142 . 
     Holding body  200  is preferably produced by an injection molding process in which thermoplastics and also thermosetting materials may be used. Bus bar  400  is preferably made of metal, particularly preferably of brass, bronze, steel, a steel alloy, copper, or aluminum. Bus bar  400  preferably has a galvanically refined surface, a so-called galvanic surface. The surface refinement of bus bar  400  in particular provides protection against corrosion. However, the bus bar can also be made of a conductive plastic, significantly reducing production costs. 
     Electrical contact system  100  according to the present invention is suitable for the contacting of coils  120 , for example for use in a rotational speed sensor, preferably in an exhaust gas turbocharger. However, applications are also conceivable in the contacting of coils for actuators, such as magnetic valves, injectors, or electrical couplings operated with a coil. Electrical contact system  100  according to the present invention is suitable for use in particular for applications in the automotive field or in technical areas in which only a small constructive space is available.