JP2012124368A - Transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transformer which lowers a Q value without making a wire material forming a coil thin and reduces the reverberation period of an ultrasonic sensor.SOLUTION: In a transformer 11, a coil 14 encloses at least a part of a core 13. A conductive shield case 16 houses the core 13 and the coil 14. A conductive magnetic resistance providing member 17 is disposed in the shield case 16 to form a closed circuit.

Description

  The present invention relates to a transformer used in an ultrasonic sensor.

  In general, since the bumper of the vehicle is located outside the driver's field of view, there is a risk that the corner of the bumper collides with an obstacle such as a person or an object when the vehicle is traveling. In order to solve this problem, it has been proposed to install a corner sensor configured to include an ultrasonic sensor in a vehicle bumper or the like (for example, Patent Document 1).

  The ultrasonic sensor emits an ultrasonic wave having a predetermined frequency from a speaker, and receives a reflected wave obtained by reflecting the ultrasonic wave by an obstacle with a microphone. The control unit of the corner sensor mounted on the vehicle and connected to the ultrasonic sensor calculates the distance to the obstacle based on the time difference from transmission to reception and issues an alarm when the distance is shorter than a predetermined value. It is configured as follows. The driver can avoid the collision between the vehicle and the obstacle based on the warning.

  The vibrators constituting the speaker do not stop vibrating immediately after the transmission of ultrasonic waves is stopped. Therefore, in order to prevent the vibration from being erroneously detected as a reflected wave by the microphone, it is necessary to disable reception by the microphone until the vibration is sufficiently attenuated (reverberation time). Specifically, after the transmission signal for driving the speaker is stopped, the reflected wave can be received by the microphone after the standby time corresponding to the reverberation time has elapsed. Therefore, the shorter the reverberation time, the shorter the standby time, and it becomes possible to detect an obstacle at a shorter distance. This means improved corner sensor performance.

JP 2001-59867 A

  Since a certain level of voltage is required to generate ultrasonic waves from the speaker, a transformer having a boosting function is used in the corner sensor. As a result of repeated studies by the present inventors, it has been found that the reverberation time can be shortened by lowering the Q value of the coil in the transformer. The Q value is an index that generally indicates the ease of passing a coil signal. Therefore, in order to reduce the Q value, the wire forming the coil may be thinned to increase the resistance value. However, when the wire is made thin, there is a problem that a short circuit between the lines and a disconnection are likely to occur, and the reliability of the transformer is lowered.

  Accordingly, an object of the present invention is to provide a transformer capable of reducing the Q value without reducing the wire forming the coil and reducing the reverberation time of the ultrasonic sensor.

In order to achieve the above object, the present invention provides the following.
(1): Core and
A coil surrounding at least a portion of the core;
A conductive shield case for housing the core and the coil;
A transformer comprising: a conductive magnetoresistive member disposed in the shield case and forming a closed circuit.
(2): It is further provided with a magnetic body which is arranged in the shield case and surrounds the core and the coil, and the conductive magnetoresistive member is arranged inside the magnetic body. The transformer according to (1).
(3): The transformer according to (1) or (2), wherein the magnetoresistance imparting member surrounds at least a part of the core.
(4): The transformer according to any one of (1) to (3), wherein the magnetoresistance imparting member surrounds at least a part of the coil.
(5) The transformer according to any one of (1) to (4), wherein the magnetoresistive member is made of the same material as the coil.
(6): The transformer according to (5), wherein the magnetic resistance applying member is formed by a part of the coil.

  A part of the magnetic flux generated from the coil as a voltage is applied passes inside the closed circuit formed by the magnetoresistive member, and an eddy current flows on the surface of the conductive magnetoresistive member. This eddy current causes a loss in magnetic flux, so that the resistance value of the coil increases, and as a result, the Q value of the coil decreases. According to said structure, since it is not necessary to make the wire which forms a coil thin, generation | occurrence | production of the situation of insulation between wires or a disconnection can be avoided, and the reliability of a transformer can be maintained.

  The magnetoresistive member is a simple member that can be formed simply by making the copper wire into an annular shape, for example, and the reverberation time of the ultrasonic sensor can be shortened only by adding such a member to a conventional coil. In addition, since it can be manufactured by using a part of the wire forming the coil and a surplus material, it is possible to minimize the increase in component cost.

It is a 4th page figure which shows the appearance of the transformer concerning a 1st embodiment of the present invention, (A) is a top view, (B) is a front view, (C) is a bottom view, (D) is a right side view. is there. It is sectional drawing of the trans | transformer along line II-II in (A) of FIG. It is sectional drawing along line II-II in (A) of Drawing 1 showing a transformer concerning a 2nd embodiment of the present invention. It is sectional drawing which followed the line II-II in (A) of FIG. 1 which shows the trans | transformer which concerns on the 3rd Embodiment of this invention. It is sectional drawing along line II-II in (A) of Drawing 1 showing a transformer concerning a 4th embodiment of the present invention. It is sectional drawing along line II-II in (A) of Drawing 1 showing a transformer concerning a 5th embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Elements having the same, equivalent or similar functions between the respective embodiments are given the same reference numerals, and redundant descriptions are omitted.

  An example in which the coil according to the first embodiment of the present invention is applied to a corner sensor transformer is shown in FIGS. The transformer 11 includes an insulating base 12, a first core 13, a coil 14, a second core 15, a shield case 16, a short ring 17, and a lead terminal 18.

  The base 12 is made of a thermoplastic insulating resin such as a liquid crystal polymer and is integrally formed with the four lead terminals 18. Each lead terminal 18 is made of copper phosphate, and includes a terminal portion 18 a and a coil connection portion 18 b that protrude in the horizontal direction from the side surface of the base 12.

  The terminal part 18a and the coil connection part 18b are connected inside the base 12 and are electrically continuous. When the transformer 11 is mounted on a circuit board (not shown), the terminal portion 18a is disposed on a predetermined contact provided on the circuit board and is used for soldering. Accordingly, the terminal portion 18a is electrically connected to a predetermined circuit formed on the circuit board and is fixed on the circuit board.

  The first core 13 is a cylindrical nickel-based ferrite core, and its bottom is fixed to the base 12. A copper wire is wound around the outer peripheral surface of the first core 13 to form a coil 14. Four lead parts (not shown) (terminals of the primary side coil and terminals of the secondary side coil) drawn from the coil 14 are respectively connected to the coil connection parts 18b of the corresponding lead terminals 18 and fixed and conductive by soldering. Is done. An appropriate material can be selected as long as the wire forming the coil 14 has conductivity.

  The second core 15 is a nickel-based ferrite core, and is a cylindrical body whose upper surface is closed and whose lower surface is opened. The cylindrical body has a size capable of accommodating the coil 14 together with the first core 13 therein. As shown in FIG. 1A and FIG. 2, a screw 21 is formed on the outer peripheral surface of the second core 15, and a cross groove 22 is formed on the upper surface.

  By arranging the second core 15 surrounding the first core 13 and the coil 14 in the shield case 16, magnetic flux leakage to the outside can be reduced. An appropriate material can be selected for the second core 15 as long as it is a magnetic material such as ferrite.

  The shield case 16 is made of a copper alloy, and has a dimension capable of accommodating the second core 15 therein, and is a cylindrical body having an open bottom surface. As shown in FIGS. 1A and 2, a round hole 23 for exposing the cross groove 22 of the second core 15 is formed on the upper surface of the cylindrical body. The shield case 16 has a function of preventing magnetic flux generated when a voltage is applied to the coil 14 from leaking to the outside and blocking disturbing magnetic flux coming from the outside.

  Any suitable conductive material such as a metal having a shielding function can be selected for the shield case 16.

  As shown in FIG. 2, the shield case 16 has a double structure comprising an inner case 16a and an outer case 16b. The inner case 16 a is formed with a screw 24 that is screwed with the screw 21 of the second core 15.

  When the transformer 11 configured in this way inserts a tool such as a Phillips screwdriver from the round hole 23 of the shield case 16 and engages the tip of the tool with the cross groove 22 of the second core 15 and rotates it, the second The core 15 moves inside the shield case 16 along the central axis direction of the coil 14 via the screw 21 and the screw 24, and a desired inductance is obtained.

  The short ring 17 is a ring-shaped member produced by winding a copper wire surplus material forming the coil 14 several times (in this embodiment, twice) so as to cover a part of the outer peripheral surface of the coil 14. Is arranged. Note that the short ring 17 may be formed by drawing out a part of the wire that is wound around the first core 13 and forming the coil 14 instead of the independent member produced by using the remainder of the copper wire. Is possible.

  When a voltage is applied to the coil 14, a magnetic flux is generated. A part thereof passes through the inside of the short ring 17 forming a closed circuit, and an eddy current flows on the surface of the short ring 17. This eddy current causes a loss in magnetic flux, so that the resistance value of the coil 14 increases, and the short ring 17 functions as a magnetoresistance applying member of the present invention. As a result, the Q value of the coil 14 decreases, and the reverberation time of the ultrasonic sensor can be shortened.

  According to said structure, since it is not necessary to make the wire which forms the coil 14 thin, generation | occurrence | production of situations, such as insulation between wires and a disconnection, can be avoided, and the reliability of the transformer 11 can be maintained. Further, the performance of the ultrasonic sensor can be improved only by adding a simple part called a short ring 17 to the coil 14 of the conventional specification. Further, since the short ring 17 can be manufactured by using a surplus material of the wire forming the coil 14, it is possible to minimize an increase in component cost.

Table 1 shows the test results showing the fact that the performance of the ultrasonic sensor has been improved by the effect of providing the magnetoresistance of the short ring 17. The Q value and the reverberation time are measured by changing the number of turns of the wire forming the short ring 17, and the Q value reduction rate and the reverberation time reduction rate are compared with the same measurement conditions as the configuration without the short ring 17. Asked. From this result, it can be seen that the provision of the short ring 17 reduces the Q value of the coil 14 and shortens the reverberation time of the ultrasonic sensor. It can also be seen that the effect of imparting magnetoresistance is increased by increasing the number of turns of the wire forming the short ring 17.

  The requirements for the magnetoresistive member are only required to be conductive, to form a closed circuit, and to be disposed at a position where the magnetic flux generated from the coil 14 passes through the inside of the closed circuit. If these are satisfied, any material, shape and arrangement can be adopted. For example, the shape of the short ring 17 is not limited to the above annular shape, and may be a frame having a rectangular shape or an arbitrary polygonal shape.

  FIG. 3 shows a transformer 11A according to the second embodiment of the present invention. In the present embodiment, the shield ring 17 </ b> A, which is a copper ring-shaped member, is fixedly arranged in an appropriate method in the space defined by the second core 15. When a voltage is applied to the coil 14, a magnetic flux is generated. A part thereof passes inside the short ring 17A forming a closed circuit, and an eddy current flows on the surface of the short ring 17A. Since the eddy current causes a loss in the magnetic flux, the resistance value of the coil 14 increases, and as a result, the Q value of the coil 14 decreases.

  Note that the short ring 17 </ b> A may be manufactured by using a part of the wire material forming the coil 14 or a surplus material like the short ring 17.

  The shape and arrangement of the short ring are appropriately determined according to the density of magnetic flux generated from the coil. It does not matter whether it is concentric or eccentric with respect to the central axis of the coil. In general, when a shield ring is disposed at a location where the magnetic flux density is low, it is necessary to increase the area of the location where the magnetic flux passes in order to obtain a desired magnetoresistance imparting effect. In the case of the short ring 17 using a copper wire, the passage length of the magnetic flux may be increased by increasing the diameter of the ring or increasing the number of turns of the copper wire. In the case of the short ring 17A, the passage length of the magnetic flux may be increased by increasing the diameter of the ring or increasing the dimension along the central axis of the coil 14. Such a short ring can be produced by processing a copper plate into a cylindrical shape or a rectangular tube shape.

  FIG. 4 shows a transformer 11B according to a third embodiment of the present invention. In the present embodiment, the shield ring 17 </ b> B, which is a copper cylindrical member, is arranged so as to surround substantially the entire outer peripheral surface of the coil 14. When a voltage is applied to the coil 14, a magnetic flux is generated. A part thereof passes through the inside of the short ring 17B forming a closed circuit, and an eddy current flows on the surface of the short ring 17B. Since the eddy current causes a loss in the magnetic flux, the resistance value of the coil 14 increases, and as a result, the Q value of the coil 14 decreases.

  In the present embodiment, since the short ring 17B is provided on the outer peripheral surface of the coil 14, the width and position of the short ring 17B can be easily adjusted in order to obtain a desired magnetic resistance imparting effect.

  The length dimension of the short ring 17 </ b> B in the direction along the central axis of the coil 14 is appropriately determined according to the desired magnetoresistance imparting effect, and may be any configuration that surrounds at least a part of the outer peripheral surface of the coil 14.

  FIG. 5 shows a transformer 11C according to a fourth embodiment of the present invention. In the present embodiment, the shield ring 17 </ b> C, which is a copper cylindrical member, is disposed along the inner peripheral surface of the second core 15. When a voltage is applied to the coil 14, a magnetic flux is generated. A part thereof passes inside the short ring 17C forming a closed circuit, and an eddy current flows on the surface of the short ring 17C. Since the eddy current causes a loss in the magnetic flux, the resistance value of the coil 14 increases, and as a result, the Q value of the coil 14 decreases.

  According to the configuration of the present embodiment, the short ring 17C can be provided in advance on the inner peripheral surface of the second core 15, and the assembly workability of the transformer is improved.

  The length dimension of the short ring 17 </ b> C in the direction along the central axis of the coil 14 is appropriately determined according to the desired magnetoresistive effect, and may be any configuration that surrounds at least a part of the outer peripheral surface of the coil 14. Further, the short ring 17 </ b> C may be manufactured by using a part of a wire material forming the coil 14 or a surplus material like the short ring 17.

  FIG. 6 shows a transformer 11D according to a fifth embodiment of the present invention. In the present embodiment, the shield ring 17 </ b> D, which is a copper cylindrical member, is arranged so as to surround substantially the entire outer peripheral surface of the first core 13 inside the coil 14. When a voltage is applied to the coil 14, a magnetic flux is generated. A part thereof passes inside the short ring 17D forming a closed circuit, and an eddy current flows on the surface of the short ring 17D. Since the eddy current causes a loss in the magnetic flux, the resistance value of the coil 14 increases, and as a result, the Q value of the coil 14 decreases.

  According to the configuration of the present embodiment, the short ring 17D can be provided in advance on the outer peripheral surface of the first core 13, and the assembly workability of the transformer is improved.

  The length dimension of the short ring 17 </ b> D in the direction along the central axis of the coil 14 is appropriately determined according to the desired magnetoresistance imparting effect, and may be any configuration that surrounds at least a part of the outer peripheral surface of the first core 13. . Further, the short ring 17 </ b> D may be manufactured by using a part of a wire material forming the coil 14 or a surplus material like the short ring 17.

  The above embodiment is an example for facilitating understanding of the present invention, and does not limit the present invention. It goes without saying that the present invention can be modified without departing from the gist thereof, and the present invention can include equivalents thereof.

  In the above embodiment, the cylindrical first core 13 is provided, but a core having an arbitrary cross-sectional shape such as a prismatic shape can be used. The first core 13 may be an air core, a laminated core, or a toroidal core. The coil 14 may be formed so as to surround at least a part of the first core 13.

  Although the shield case 16 having a double structure is provided in the above embodiment, a single structure having only one shield plate may be used.

  In the above embodiment, the screws 21 and 24 that are screwed together are formed on the outer peripheral surface of the second core 15 and the inner peripheral surface of the inner shield 16 a, and the second core 15 extends inside the shield case 16 in the axial direction of the coil 14. It is supposed to be movable along. However, the second core 15 may be fixedly arranged inside the shield case 16.

  The application of the ultrasonic sensor using the transformer according to the present invention is not limited to a corner sensor attached to a bumper or the like of a vehicle, but to an ultrasonic sensor used for an inter-vehicle distance sensor attached to a front part or a rear part of a vehicle. You may apply. Further, it can be used for an ultrasonic sensor used not only for mounting on a vehicle but also for an appropriate use in which a reduction in reverberation time is expected.

11 Transformer 12 Base 13 First core (core)
14 Coil 15 Second core (magnetic material)
16 Shield Case 17 Short Ring (Magnetic Resistance Giving Member)
18 Lead terminal

Claims (6)

The core,
A coil surrounding at least a portion of the core;
A conductive shield case for housing the core and the coil;
A transformer comprising: a conductive magnetoresistive member disposed in the shield case and forming a closed circuit. A magnetic body disposed in the shield case and surrounding the core and the coil;
The transformer according to claim 1, wherein the conductive magnetoresistive member is disposed inside the magnetic body.   The transformer according to claim 1, wherein the magnetic resistance applying member surrounds at least a part of the core.   The transformer according to any one of claims 1 to 3, wherein the magnetoresistive member surrounds at least a part of the coil.   The transformer according to any one of claims 1 to 4, wherein the magnetoresistive member is made of the same material as the coil.   The transformer according to claim 5, wherein the magnetic resistance applying member is formed by a part of the coil.

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