This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2009-201717, filed on Sep. 1, 2009, the entire contents of which are incorporated herein by reference.
The present invention relates to a current sensor for detecting the magnitude of current flowing through a conductor.
A known current sensor uses magnetic detection elements such as Hall elements or magnetoresistance effect elements. The current detection performed by a current sensor that uses Hall elements will now be described.
When current flows through a current path such as a wire, the current forms a magnetic field near the current path. The strength of the magnetic field is proportional to the magnitude of the current. When a Hall element is arranged in the magnetic field formed near the current path, the Hall element generates a Hall voltage that is proportional to the current flowing through the current path. A current sensor that uses the Hall element detects the current flowing through the current path based on the Hall voltage.
However, when the strength of the magnetic field acting on the Hall element is small, the proportional relationship of the magnetic field strength and the Hall voltage becomes difficult to maintain. Further, the strength of the magnetic field generated by the current flowing through the current path is low in the first place. To increase the current detection sensitivity of the current sensor, Japanese Laid-Open Patent Publication No. 2002-303642 describes a magnetic core that concentrates the magnetic flux generated by the current flowing through a current path and amplifies the magnetic flux acting on the Hall element. A prior art current sensor including a magnetic core will now be described with reference to
The current sensor of
The current sensor of the prior art requires the relatively large printed circuit board 103, the area of which must be sufficient for the mounting of the Hall element 102 and the electronic components. The relatively large printed circuit board 103 occupies space in the case 104 and imposes great restrictions on the degree of design freedom for the current sensor.
The present invention provides a current sensor having a high degree of design freedom.
One aspect of the present invention is a current sensor for outputting a detection signal corresponding to a current flowing through a bus bar. The current sensor includes a magnetic core that concentrates and amplifies magnetic flux generated by the current near a detection portion of the bus bar. A magnetic detection element detects the magnetic flux concentrated by the magnetic core and outputs an electrical signal corresponding to the detected magnetic flux. A signal processing circuit includes electronic components and processes the electrical signal output from the magnetic detection element to generate the detection signal. The magnetic detection element and the electronic components are mounted on a lead frame. The magnetic detection element, the electronic components, and the lead frame are combined to form a single sensor module. The current sensor detects the current flowing through the bus bar with the sensor module and outputs the detection signal.
Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:
A current sensor according to a first embodiment of the present invention will now be discussed with reference to
As shown in
As shown in
A planar tongue 23 projects from the upper surface of the lower case 20. A sensor module 30 is mounted on the tongue 23. In the example of
Referring to
The lead frame 40 is a conductive component or metal component including a plurality of leads 42a to 42e. A resin mold 33 seals the Hall IC 31, the electronic components 32, and part or all of each of the leads 42a to 42e. The lead 42b has a planar basal portion defining an element mounting portion 41. The Hall IC 31 is mounted on the element mounting portion 41. The Hall IC 31 has terminals coupled to basal portions of the leads 42a to 42e. This electrically connects the Hall IC 31 to the lead frame 40. The electronic components 32 and the leads 42a to 42e form a signal processing circuit for processing voltage signals output from the Hall IC 31.
The leads 42a to 42d each have a distal portion extending from a bottom surface of the resin mold 33. The distal portions of the leads 42a to 42c function as a power supply terminal and an output terminal of the sensor module 30. The sensor module 30 is manufactured by mounting the Hall IC 31 and the electronic components 32 on the lead frame 40 and then sealing the lead frame 40, the Hall IC 31, and the electronic components 32 with a resin material. Molding, such as insert molding, may be performed for the sealing with resin material. The resin material is the material forming the resin mold 33 and may be, for example, thermoset resin. In this manner, the Hall IC 31, the electronic components 32, and the leads 42a to 42e are combined and integrated through resin molding in the single sensor module 30. This increases the coupling reliability of the Hall IC 31, the electronic components 32, and the lead frame 40 as compared to a prior art current sensor that solders a Hall element and electronic components to a printed circuit board.
The tongue 23 has a front portion from which basal portions of metal pins T1 to T4 extend, as viewed in
As shown in
With reference to
As shown in
Due to such a structure, the magnetic core 12 concentrates and amplifies the magnetic flux generated by the current flowing through the bus bar 11 in the current sensor. The leakage flux in the clearance CT acts on the Hall IC 31 of the sensor module 30. In this state, the Hall IC 31 outputs a voltage signal in correspondence with the current flowing through the bus bar 11. The detection signal is output to an external device via the connector 21.
The current sensor of the first embodiment does not use a printed circuit board for the mounting of the Hall element (Hall IC 31). This accordingly reduces design correction work for changing the location and direction of the Hal element (Hall IC 31). More specifically, when changing the direction of the Hall element by “90°”, the direction of the printed circuit board would have to be changed together with the Hall element. This results in drastic design changes of the current sensor. In contrast, with the first embodiment, the direction of the Hall element (Hall IC 31) may easily be changed by “90°” just by changing, for example, the direction of the sensor module 30 by “90°” as shown in
The elimination of the printed circuit board from the current sensor of the first embodiment allows for size reduction and lower manufacturing costs.
The current sensor of the first embodiment has the advantages described below.
(1) The Hall IC 31, the electronic components 32, and the lead frame 40 are combined to form the single sensor module 30. The current sensor detects the current flowing through the bus bar 11 with the sensor module 30 and outputs the detection signal. This allows for the elimination of the printed circuit board, which is one of the elements forming the prior art current sensor, and thereby improves the degree of design freedom for the current sensor. Further, each element is coupled with a higher reliability. Moreover, in comparison with the prior art current sensor that mounts the Hall element on the printed circuit board, due to the elimination of the printed circuit board, the current sensor of the first embodiment allows for size reduction and lower manufacturing costs.
(2) The case 1 is formed by the upper case 10, which integrates the detection portion of the bus bar 11 and the magnetic core 12, and the lower case 20, which integrates the metal pins T1 to T4. The coupling of the sensor module 30 to the metal pins T1 to T4 attaches the sensor module 30 to the lower case 20. Thus, the current sensor is completed just by coupling the upper and lower cases 10 and 20 to each other. This facilitates the assembling of the current sensor.
The sensor module is manufactured by mounting a magnetic detection element and electronic components on a lead frame and sealing the magnetic detection element, the electronic components, and the lead frame in a resin mold. This manufacturing process increases the reliability for coupling the elements and facilitates the manufacturing of the sensor module.
The first embodiment may be modified as described below.
A hybrid vehicle generally includes an inverter that converts DC power, which is supplied from the vehicle battery, into three-phase AC power. The three-phase AC power converted by the inverter is supplied via three bus bars to each phase (U phase, V phase, and W phase) of an in-vehicle motor. In the hybrid vehicle, a current sensor normally detects the current flowing through the three bus bars and controls the power that the motor should be supplied with based on the detected current. Such a hybrid vehicle may use a current sensor that detects the current flowing through each of the three bus bars. This current sensor would have three sets of the magnetic core 12 and Hall IC 31. In such a current sensor, in comparison with a sensor that detects current flowing through only one bus bar, the shape and arrangement of the printed circuit board would impose great restrictions on the degree of design freedom. The structure of the current sensor illustrated in
In the first embodiment, the power supply and output terminals of the sensor module 30 are arranged on the bottom surface of the resin mold 33. However, the terminal layout is not limited in such a manner. For example, as shown in
In the first embodiment, the Hall IC 31 and the electronic components 32 are mounted on the lead frame 40, which includes the element mounting portion 41 and the leads 42a to 42e. Then, these parts are sealed in a resin material when molding the resin mold 33 to manufacture the sensor module 30.
In a further manufacturing process, for example, after mounting the Hall IC 31 and the electronic components 32 on the lead frame 40, the sensor module 30 may be molded with the Hall IC 31, the electronic components 32, and the lead frame 40 being accommodated in a suitable case.
In the current sensor of the first embodiment, the detection portion of the bus bar 11 and the magnetic core 12 are integrally molded (embedded) with each other. Alternatively, the bus bar 11 and the magnetic core 12 may be discrete from each other. For example, the bus bar 11 may be separable from the case 1 (particularly, the upper case 10). For example, the sensor module 30 may be used in lieu of the Hall element 102 and the printed circuit board 103 of
When the metal pins T1 to T4 have sufficient strength for supporting the sensor module 30, the tongue 23 may be eliminated. This simplifies the structure of the lower case 20 and consequently simplifies the structure of the current sensor.
In the first embodiment, the leakage flux generated in the clearance CT of the magnetic core 12 is detected by a Hall element. Instead, a magnetoresistance effect element of which resistance varies in accordance with the magnetic flux due to the magnetoresistance effect may be used to detect the leakage flux. As long as the magnetic flux concentrated by the magnetic core 12 is detected and an electrical signal corresponding to the detected magnetic flux is output, any magnetic detection element may be used.
It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the scope of the invention. Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.
Number | Date | Country | Kind |
---|---|---|---|
2009-201717 | Sep 2009 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
5523677 | Kawakami et al. | Jun 1996 | A |
7501808 | Ishihara et al. | Mar 2009 | B2 |
7679357 | Aratani et al. | Mar 2010 | B2 |
20080030190 | Ishihara et al. | Feb 2008 | A1 |
20080048642 | Aratani et al. | Feb 2008 | A1 |
Number | Date | Country |
---|---|---|
1109974 | Oct 1995 | CN |
4-131776 | Dec 1992 | JP |
2002-303642 | Oct 2002 | JP |
2003-043074 | Feb 2003 | JP |
2004-257953 | Sep 2004 | JP |
2007-171156 | Jul 2007 | JP |
2008-051704 | Mar 2008 | JP |
Entry |
---|
English translation of 2009-201717, Japanese office action dated Nov. 25, 2012, 2 pages. |
Office Action for corresponding CN application No. 201010269190.9 dated Nov. 15, 2012; 6 pages. |
Japanese Office Action dated Nov. 25, 2012. No English translation. 2009-201717. |
Number | Date | Country | |
---|---|---|---|
20110050222 A1 | Mar 2011 | US |