Abstract:
An assembling structure is provided which is capable of greatly reducing the material cost, is easy-to-assemble, and can be made smaller. The sensor body is provided on a lower face with a protrusion, which comes into contact with an upper face of the busbar when the sensor body is mounted on the busbar. The busbar is provided with a through-hole passing through the busbar in a vertical direction. A leading end of the protrusion, which passes through the through-hole when the sensor body is mounted on the busbar, is heat-fused and adheres to the circumference of the through-hole.

Description:
TECHNICAL FIELD 
     The present invention relates to an assembly structure of a current detection device which is attachable to a busbar without deteriorating the detecting precision, is low-priced, and is capable of being mass-produced. 
     BACKGROUND ART 
     Conventionally, a current detection device has been known which detects a value of current flowing between a battery and vehicle electric equipment by detecting magnetic flux that is generated from current that flows through a harness connected to a terminal of the battery. The current detection device is attached to part of a vehicle by means of a component such as a bracket or the like. Detection of magnetic flux is carried out in a detecting hole of the current detection device after the harness is inserted into the detecting hole. 
     However, in the conventional current detection device, it is needed to use a separate component such as a bracket in order to attach the current detection device to a vehicle, so that the number of the parts increases and the construction becomes complicated. Further, since the harness that is flexible should be inserted into the detecting hole to perform the current detection, the detecting hole is needed to enlarge, which makes it difficult for an operator to do his detecting work. This restricts the current detection device from being made smaller. 
     Thus, disclosed was a current detection device for a vehicle which can be made smaller, can be easily assembled, and is of a simple construction (e.g. Patent Literature). The current detection device, as shown in  FIG. 8 , is configured so that an end  201  of a busbar  200  is connected to a terminal  101  of a battery  100  by means of a screw  102 , and a current detector  300  is supported by the busbar  200 . Further, another end  202  of the busbar  200  is connected to a terminal  401  of the harness  400  which bites an end of the harness which is connected to vehicle electric equipment. 
     As shown in  FIG. 9 , the current detector  300  includes a detector body  301  in which a core  302  is fixed thereto to surround a detecting hole  304 , through which the busbar  200  passes, and a hall device  303  is mounted between opposite ends of the core  302 , whereby the current detection device is simplified in construction and can be made smaller, thereby improving the assemblability furthermore. 
     BACKGROUND ART 
     Patent Literature 
     
         
         Patent Literature 1: JP-A-2001-272422 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     However, a conventional current detection device has problems as follows: 
     (1) As described above, since a certain magnetic structure is needed to collect magnetic flux, a magnetic core having a hole should be provided, and a busbar passes through the hole. 
     (2) Since if the shape of the busbar is complex, the busbar is difficult to be inserted into the hole, the hole needs to be enlarged, which makes the magnetic core larger. 
     (3) If the shape of the busbar is complex, the amount of cutting scrap increases, resulting in an increase in material loss, and the manufacturing cost also rises due to an increase in the number of processes, which includes e.g. a bending process. 
     The present invention has been made in view of the above problems, and a purpose of the present invention is to provide an assembly structure of a current detection device which considerably reduce the material cost, is easily assembled, and is amenable to miniaturization. 
     Solution to Problem 
     In order to achieve the above object, an assembly structure of a current detection device according to the present invention includes following features. 
     (1) An assembly structure of a current detection device, comprises: 
     a busbar; 
     a sensor body comprised of a heat-fusible resin material; and 
     a magnetic detection element provided on the sensor body to detect magnetism generated from the busbar, 
     wherein a protrusion is provided on a lower face of the sensor body and the lower face of the sensor body comes into contact with an upper face of the busbar when the sensor body is mounted on the busbar; 
     wherein the busbar has a through-hole; and 
     wherein a leading end of the protrusion, which passes through the through-hole of the busbar when the sensor body is mounted on the busbar, is heat-fused and adheres to a circumference of the through-hole. 
     According to the assembly structure of the current detection device of the construction (1), the sensor body is composed of fusible resin material, so that when heat is applied from exterior, the sensor body can be fused at a certain heating rate. Thus, the protrusion which is integrally formed on the lower face of the sensor body is inserted into the through-hole of the busbar, that is a rectangular metal plate having no protrusion and recess on the circumference, a leading end of the protrusion, which extended below the busbar, is heat-fused to form an adhering mass larger than a diameter of the through-hole, so that the sensor body can be attached to the busbar at the adhering mass. Thus, the adhering mass allows the sensor body and the busbar to be integrally bonded together in the vicinity of the through-hole. 
     Also, according to the assembly structure of the current detection device of the construction (1), there are the effects of the integration of the sensor body and the busbar being realized in a simple manner, the construction being obtained cost-effectively, the current detection device being easily assembled, and the current detection device being made smaller. 
     Advantageous Effects of Invention 
     According to assembly structure of the current detection device, the busbar is configured to have a shape of a simple rectangle having no irregular portions on the circumference, contributing to reduction in material cost, and to efficient assembly of the sensor body and the busbar. Furthermore, the entire construction is simple, is easy-to-assemble, and is very amenable to miniaturization. 
     The present invention has been set forth briefly. Meanwhile, details of the invention will become apparent through reading the embodiments of the invention with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view showing a configuration of a current detection device according to an embodiment of the invention; 
         FIG. 2(A)  is a side view showing the current detection device of  FIG. 1 . 
         FIG. 2(B)  is a cross-sectional view taken along line I-I of  FIG. 1 . 
         FIG. 3  is a cross-sectional view taken along line II-II of  FIG. 2 . 
         FIG. 4A  is a plan view showing a busbar of the current detection device of  FIG. 1 . 
         FIG. 4B  is a front view showing the busbar of the current detection device of  FIG. 1 . 
         FIG. 5  is an exploded perspective view showing the current detection device of  FIG. 1 . 
         FIG. 6  is a cross-sectional view showing the state of a sensor body and the busbar being welded. 
         FIG. 7  is a flow chart showing a procedure of a method of assembling the current detection device according to the embodiment of the invention. 
         FIG. 8  is a front view showing a conventional current detection device. 
         FIG. 9  is a side view of the conventional current detection device of  FIG. 8 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the invention will now be described with reference to the accompanying drawings. 
     First Embodiment 
       FIG. 1  is a plan view showing a configuration of a current detection device according to an embodiment of the invention.  FIG. 2(A)  is a side view showing the current detection device of  FIG. 1 .  FIG. 2(B)  is a cross-sectional view taken along line I-I of  FIG. 1 .  FIG. 3  is a cross-sectional view taken along line II-II of  FIG. 2 .  FIG. 4A  is a plan view showing a busbar of the current detection device of  FIG. 1 .  FIG. 4B  is a front view showing the busbar of the current detection device of  FIG. 1 .  FIG. 5  is an exploded perspective view showing the current detection device of  FIG. 1 .  FIG. 6  is a cross-sectional view showing the state of a sensor body and the busbar being welded.  FIG. 7  is a flow chart showing a procedure of a method of assembling the current detection device according to the embodiment of the invention. 
       FIG. 1  and  FIGS. 2(A) and 2(B)  show the current detection device  10  which is manufactured by an assembling method according to an embodiment of the present invention. The current detection device  10  is mounted in a vehicle and includes a busbar  20 , a sensor body  30  having a detecting section β, and a magnetic shield member  40 . 
     The busbar  20  has one end (a left end in  FIG. 1 ) which is integrally connected to an end of a harness (not shown) for connecting a vehicle electric equipment to a battery (both are not shown) and has another end (a right end in  FIG. 1 ) which is integrally connected to a terminal of the battery. As shown in  FIG. 1  and  FIG. 4 , the busbar  20  has screw holes  21  and  22  on opposite end sides thereof. For example, the busbar is connected with a terminal (i.e. a negative terminal for prevention of a short circuit, although not shown) of the battery by fastening a bolt or a screw through the hole  21 , and the busbar is connected with an end of the harness by fastening a bolt or a screw through the hole  22 . 
     As shown in  FIG. 4 , the busbar  20  is configured so that a pair of through-holes  23 A and  23 B are formed between the screw holes  21  and  22  such that the pair of through-holes  23 A and  23 B pass through the busbar  20  in a vertical direction from an upper face of the busbar  20  to a lower face of the busbar  20 . Each of the through-holes  23 A and  23 B has a diameter smaller than that of the screw holes  21  and  22 . The through-holes  23 A and  23 B have the size and shape (generally a ring type) so as to receive a protrusion of the sensor body. Further, the surrounding area or an inner circumferential face of the through-hole may be roughened. This roughened face may contribute to an increase in the degree of adherence of the protrusion of a fusible resin with respect to the through-holes  23 A and  23 B. 
     The sensor body  30  of the embodiment is configured by non-magnetic, fusible synthetic resin material, and includes a connecting section α, a detecting section β, and a positioning section γ in order as named from an end portion (i.e. right side in  FIG. 1 ) on the side of the battery. The respective opposite side faces of the three sections will be called as first side faces  30 A, second side faces  30 B, and third side faces  30 C, respectively. 
     The connecting section α, is a section for connecting a connector (not shown) connected to a signal line (not shown). In this embodiment, a female-type connector of the connecting section α is formed as a chamber (hereinafter, referred to as a ‘connector chamber’) which is surrounded by four standing walls in four-direction. Meanwhile, the signal line serves to transmit, to a control IC unit or the like (not shown), an electric signal which is induced in response to the strength of magnetic field detected by a magnetic detection element  50  of the detecting section β to be described later. However, the signal line is not an essential element of the present invention. That is, the signal line is a means for transmitting a sensor output from the magnetic detection element  50  to an external circuit element (e.g. the control IC unit in this embodiment). Other elements for transmitting the sensor output, for example, to the outside via direct wired connection using a lead wire, or wireless connection may be configured. 
     In the detecting section β, a substrate  51  is mounted in a magnetic chamber  32  which is surrounded by four circumferential walls, and the magnetic detection element  50  is mounted on the substrate  51 . The magnetic detection element  50  detects the strength of magnetic field that is generated by current I flowing through the busbar  20 . For example, in this embodiment, a hall device using a hall effect is used as the magnetic detection element  50 . The hall device converts the strength of magnetic field into an electric signal and output the electric signal (the magnetic field is variably induced by the varying intensity of current I flowing through the busbar  20 ). Thus, for example, an output voltage proportional to the magnetic flux density is output via respective terminals (hereinafter referred to as ‘input terminals’)  53 . Voltage (electric signal) input to the input terminal  53  is output via respective terminals (hereinafter referred to as ‘output terminals’)  54  which are provided on the connector chamber  31  of the connecting section α. The output terminals  54  constitute terminals of the above-mentioned female connector. 
     The substrate  51 , on which the magnetic detection element  50  is mounted, is entirely covered airtightly and waterproofly with an insulating cover  55  composed of e.g. synthetic resin, together with a leading end of the input terminal  53 . The leading end of the input terminal  53  protrudes from the upper portion of the substrate  51 . Thus, an electric circuit including the magnetic detection element  50  can be prevented from becoming moist or being damaged by interference with external parts or the like. 
     The positioning section γ positions the current detection device  10  in a vehicle. The positioning section γ is not particularly an essential component in the present invention. In this embodiment, the current detection device is precisely positioned and fixed to a certain part of a vehicle by engaging an engaging edge  33  with a positioning protrusion (not shown) or the like. 
     Meanwhile, a pair of protrusions  24 A and  24 B extending downwards are provided on a lower face of the sensor body  30 . The protrusions  24 A and  24 B are respectively provided on positions corresponding to the connecting section α and the positioning section γ, particularly the through-holes  23 A and  23 B of the busbar  20 . The protrusions  24 A and  24 B have the size and length so that the protrusions  24 A and  24 B can be inserted in the through-holes  23 A and  23 B. The size of the protrusions  24 A and  24 B is slightly smaller than that of the through-holes  23 A and  23 B, and the length thereof is greatly larger than the thickness of the busbar  20 , e.g. two to three times the thickness of the busbar. 
     Thus, when assembling the busbar  20  to the sensor body  30 , the protrusions  24 A and  24 B of the sensor body can be inserted into the through-holes  23 A and  23 B of the busbar  20 , as shown in  FIGS. 2(A) and 2(B) . 
     The magnetic shield member  40  is made from a proper magnetic material, e.g. in this embodiment, magnetic strips having spring property. The magnetic shield member  40  is attached to the sensor body  30  so that the magnetic shield member  40  surrounds the detecting section β of the sensor body  30  and the busbar  20 , thereby magnetically isolating them. In this embodiment, the magnetic shield member  40  includes a lower face  41  and a pair of sidewalls  42 , which is formed in a lateral direction (a lengthwise direction) of the busbar  20 , in order to fixedly surround the detecting section β of the sensor body  30  from the lower side (outside) of the busbar  20  as shown in  FIG. 3 . Further, the magnetic shield member  40  has standing claws  42 A, which extend above the upper portion of the second side  30 B, at four corners of the sidewalls  42 . The standing claws  42 A come into contact with the upper portion from the upper portion of the second side  30 B. 
     The standing claws  42 A are pre-bent at a certain angle. In this state, when the sensor body  30  is housed in magnetic shield member  40 , the distance between the sidewalls  42  is enlarged by the spring property of the magnetic shield member  40  so that the standing claws  42 A is directed upwards the second side  30 B of the sensor body  30  while passing through the second side  30 B of the sensor body  30 , thereby coming into contact with it from the upper portion of the second side  30 B. Meanwhile, the standing claws  42 A may be bent by an assembling operator after the sensor body  30  is housed in the magnetic shield member  40 . 
     The magnetic detection element  50  detects magnetic flux which is generated around the current I flowing through the busbar  20  as shown in  FIG. 1 . Because of this, the magnetic detection element  50  is arranged in a planar direction (i.e. X-Y plane) that detects the magnetic flux of current I flowing through the busbar  20 , and does not detect magnetic flux in a Z-direction that is perpendicular to the X-Y plane of the busbar  20 . That is, the Z-direction perpendicular to the X-Y plane of the busbar  20  is a direction along which the magnetic detection element (a hall device)  50  does not detect the magnetic flux. Thus, although the magnetic detection element  50  has an opened portion at its upper portion, such configuration has no adverse effect upon precise detection of magnetism. 
     Thus, according to the current detection device  10  for a vehicle of the embodiment, since the magnetic shield member  40  is provided, an external electromagnetic bad influence can be suppressed and the precise current detection can be achieved. 
     For example, according to a vehicle system employing the current detection device  10  of the embodiment, in some cases, magnetic field is often generated around a hall device used as the magnetic detection element  50 , or a relay or a motor is often mounted around the magnetic detection element  50 . In this case, because of the generated magnetic field, precise detection of magnetism may not be carried out. Further, because of an effect of environment during traveling of a vehicle, an effect of earth magnetism, high voltage power line, or the like should also be considered. However, according to the current detection device  10  of the embodiment, since the magnetic shield member  40  is provided, the magnetic shield member  40  effectively prevents the sensor output from greatly varying due to the above effects to be considered. 
     A description will now be made to a method of assembling the current detection device  10  of the embodiment. 
     The assembling method of the current detection device  10  includes a fitting process S 1 , a fusing process S 2 , a housing process S 3 , and a fixing process S 4  of a battery and a harness. Meanwhile, in the assembling method of the current detection device, the fixing process of the battery and the harness may be first implemented so that the busbar  20  is bolt-fastened at opposite end sides thereof to the battery and the harness. 
     In fitting process S 1 , the busbar  20  is fitted into a bar-type recess  34  (see  FIG. 2(B)  and  FIG. 5 ) which is formed at the center portion on the lower face of the sensor body  30 . The bar-type recess  34  is formed with the same plane in the whole lengthwise portion thereof extending between opposite ends. Here, the pair of protrusions  24 A and  24 B that protrude from the lower face of the sensor body  30  are inserted into the through-holes  23 A and  23 B of the busbar  20  respectively (see  FIG. 2(B) ). 
     In fusing process S 2 , the portions (called leading ends) of the protrusions  24 A and  24 B, which have been inserted into the through-hole  23 A and  23 B of the busbar  20  and extended below the lower face of the busbar  20  in the fitting process S 1 , are heat-fused intensively by heating device using laser. When the protrusions  24 A and  24 B are fused, the fused portions are deformed such that the protrusions  24 A and  24 B are pressed against circumferences of the through-holes  23 A and  23 B of the busbar  20  so as to form an adhering mass. After that, heating is stopped, and then air cooling is implemented. Thus, the leading ends of the protrusions  24 A and  24 B become the adhering masses  24 C and  24 D, which are larger than inner diameters of the through-holes  23 A and  23 B on the lower side of the busbar  20  and adhere to the circumferences of the through-holes  23 A and  23 B. Therefore, the busbar  20  becomes bonded integrally and firmly to the lower face of the sensor body  30 . 
     Unlike the conventional technology, such bonding between the sensor body  30  and the busbar  20  by fusing the protrusions  24 A and  24 B can be performed automatically and rapidly without preparing a separate adhering member. Further, since there is no need to make a claw on the busbar by cutting material, material scraps can be reduced. Furthermore, positioning of the protrusions  23 A and  24 B relative to the through-holes  23 A and  23 B is easily and precisely controlled, so that shaking between two elements is prevented from occurring. 
     In housing process S 3 , the sensor body  30  is housed in the magnetic shield member  40  such that the detecting section β of the sensor body  30  and the busbar  20  are surrounded by the magnetic shield member  40 . Thus, the busbar  20  and the magnetic shield member  40  are integrally fixed to the sensor body  30 . 
     In fixing process S 4  of a battery and a harness, an end of the busbar  20 , to which the sensor body  30  and the magnetic shield member  40  are integrally fixed, is connected to a terminal (particularly a negative terminal) of a battery via a bolt or the like, and another end of the busbar  20  is screw-coupled to an end of a harness. 
     Subsequently, a connector, which is connected to a signal line for transmitting a quantity of current detected by the magnetic detection element  50  to a control IC unit (not shown), is connected to the female connector that is configured by the connector chamber  31  provided in the connecting section a of the sensor body  30 . 
     Thus, according to the assembly structure and method of assembling the current detection device  10  for a vehicle of the embodiment, although the busbar  20  has already been mounted onto other component, it is easy to attach the sensor body  30  and the magnetic shield member  40  to the busbar. 
     Further, if the busbar has a simple shape (e.g. a rectangle) as in the embodiment, the sensor body  30  and the busbar  20  may be integrally fixed to each other using an insert molding method. Further, according to the assembly method of the current detection device  10 , the sensor body  30  and the busbar  20  may be separately molded, so that the current detection device that can be made in a mass-production manner to have a small size is realized. 
     The current detection device of the invention is not limited to the part of a vehicle system as described in the embodiment, but may be adapted to a diversity of current detection device in many fields so long as it includes a busbar. 
     While the present invention has been described in detail with reference to specific embodiments, it is apparent to the person skilled in the art that a variety of modifications and changes may be performed without departing from the spirit and scope of the present invention. 
     This application claims the benefit of Japanese Patent Application (No. 2009-008809) filed on Jan. 19, 2009, the subject matter of which is incorporated herein by reference. 
     REFERENCE SIGNS LIST 
     
         
           10  Current detecting apparatus 
           20  Busbar 
           21 ,  22  Screw hole 
           23 A,  23 B Through-hole 
           24 A,  24 B Protrusion 
           30  Sensor body 
           30 A First side face 
           30 B Second side face 
           30 C Third side face 
           31  Connector chamber (Female connector) 
           34  Bar-type recess 
           40  Magnetic shield member 
           41  Lower face 
           42  Sidewall 
           50  Magnetic detection element (Hall device) 
           51  Substrate 
           53  Input terminal 
           54  Output terminal 
         α Connecting section 
         β Detecting section 
         γ Positioning section