JP2008026217A - Proximity sensor and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable assembly using a reflow furnace by lessening a magnetic influence to the outside. <P>SOLUTION: An excitation part 5 mounts an excitation coil 9 stored in a case 12 comprising a magnetic body and wound around a core 8 and a high-frequency power supply 10 for supplying a high frequency current to the excitation coil 9 on a PC plate 13 by soldering. In addition, A detection part 6 mounts a detection coil 11 stored in a case 17 comprising a magnetic body and wound around a core 14, an amplifier 15 for performing amplification or the like of an induction voltage induced in the detection coil 11 and a capacitor 16 for forming a resonant circuit together with the detection coil 11 on the PC plate 18 by soldering. A proximity sensor 7 is composed by having the excitation part 5 and the detection part 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a proximity sensor that detects an approaching state between objects, and an electronic device including the proximity sensor.

An electronic device having a structure in which a housing having a display unit and a housing having an operation unit can be folded, for example, a foldable mobile phone, detects an approaching state between these housings, that is, an open / closed state of the mobile phone. Thus, predetermined control is performed. In order to detect such an approaching state, for example, there is one provided with an open / close sensor composed of a permanent magnet and a magnetic sensor using a Hall element or an MR (Magneto Resistance) element (for example, Patent Document 1). reference).
JP 2005-303688 A

However, the magnetism of the permanent magnet used in the above configuration always acts to the outside, and may adversely affect, for example, a magnetic card. In addition, an electronic device on which this open / close sensor is mounted is usually configured to have a large number of electronic components, and these electronic components are attached to a printed wiring board (hereinafter simply referred to as a PC board) by soldering. It is done.
At the time of this soldering, the electronic component passes through a high-temperature reflow furnace together with the PC plate. However, since the permanent magnet has the property of demagnetizing at high temperatures, it cannot be passed through a reflow furnace, and is manually soldered separately from other electronic components and attached to the PC board. . For this reason, there existed a problem that an assembly man-hour increased or the error of the attachment position of a permanent magnet produced.

  The present invention has been made in view of the above circumstances, and an object thereof is to mount a proximity sensor that can reduce the magnetic influence on the outside and can be assembled using a reflow furnace, and the proximity sensor. To provide electronic equipment.

  In order to achieve the above-described object, the proximity sensor according to the present invention includes a primary coil, current supply means for supplying a current that changes in magnitude to the primary coil over time, and relative to the primary coil. And a secondary coil arranged so that its position can be changed, and the distance between the primary coil and the secondary coil is detected based on the magnitude of the induced electromotive force of the secondary coil.

  According to this configuration, when a current whose magnitude changes with time passes from the current supply means to the primary coil, a magnetic field whose strength changes in the vicinity is generated. In this state, when the relative position of the secondary coil to the primary coil is changed and both coils approach each other, a voltage corresponding to the distance between the coils is induced in the secondary coil. On the other hand, when the relative position of the secondary coil with respect to the primary coil is changed and the two coils are separated, no voltage is induced in the secondary coil. Thus, the distance between the primary coil and the secondary coil is detected based on the voltage induced in the secondary coil, that is, the magnitude of the induced voltage.

  According to the present invention, for example, only when the current supply means needs to detect the approaching state of each coil, a magnetic field whose strength changes in magnitude by supplying a current whose magnitude changes with time to the primary coil. If the supply of this current is stopped when it is not necessary to detect this, the magnetic influence on the outside can be reduced. Further, since no permanent magnet is used, assembly using a reflow furnace can be performed in the same manner as other electronic components, so that the number of assembling steps can be reduced and the mounting position accuracy can be improved.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 2 is a perspective view showing an appearance of a foldable mobile phone including the proximity sensor of the present invention. A cellular phone 1 (corresponding to an electronic device) includes a display housing 2 (corresponding to a first airframe) having a display panel portion 2a, and an operating housing 3 (corresponding to a second airframe) having an operation panel portion 3a. The housings 2 and 3 are connected to each other so as to be foldable. As a result, the mobile phone 1 can open the display panel unit 2a with respect to the operation panel unit 3a and develop the operation panel unit 3a into an open state in which the operation panel unit 3a can be operated. It can be folded into a combined closed state.

  In addition, an excitation unit 5 (details will be described later) is embedded in the center of the end portion far from the connecting portion 4 of the display housing 2 among the housings 2 and 3. On the other hand, a detection unit 6 (details will be described later) is embedded in the center of the end portion of the operation casing 3 far from the connecting portion 4. Therefore, in the closed state described above, the excitation unit 5 and the detection unit 6 are positioned to face each other. In the present embodiment, the excitation unit 5 and the detection unit 6 constitute an proximity sensor (shown with reference numeral 7 in FIG. 1).

  FIG. 1 is a diagram showing a principle configuration of the proximity sensor 7, schematically showing an excitation unit 5 and a detection unit 6 embedded in the display housing 2 and the operation housing 3 of the mobile phone 1, respectively. . As shown in FIG. 1, the excitation unit 5 includes an excitation coil 9 (corresponding to a primary coil) wound around a shaft-shaped core 8 formed of a magnetic material such as iron, and the excitation coil. 9 includes a high frequency power source 10 (corresponding to a current supply means) for supplying a high frequency current of several tens kHz to several hundred kHz, for example.

  In addition, the exciting coil 9 is a case 12 (a container 12 formed of a magnetic material such as iron, with a surface facing a detection coil 11 (corresponding to a secondary coil) on the detection unit 6 side, which will be described later, being opened. (Corresponding to the core). And these are attached by soldering on the PC board 13 fixed inside the display housing | casing 2, and are electrically connected.

  On the other hand, the detection unit 6 includes a detection coil 11 wound around a shaft-shaped core 14 formed in the same manner as the core 8, and an amplifier 15 (amplification circuit) that performs amplification of an induced voltage induced in the detection coil 11 and the like. And a capacitor 16 that forms a resonance circuit together with the detection coil 11. Similarly to the exciting coil 9, the detection coil 11 is also housed in a case 17 (corresponding to a core) formed in the same manner as the case 12. And these are attached by soldering on the PC board 18 fixed inside the operation housing | casing 3, and are electrically connected.

  Each coil 9, 11 is attached to each case 2, 3 so that when the mobile phone 1 is in the closed state described above, the cores 8, 14 located at the respective winding centers are in an approaching state facing each other. Has been placed.

FIG. 3 is a diagram illustrating an electrical configuration of the proximity sensor 7. As shown in FIG. 3, output terminals of the high frequency power supply 10 are connected to both ends of the exciting coil 9. The high-frequency power supply 10 is configured to include, for example, an inverter circuit that converts a DC voltage supplied from a battery (not shown) of the mobile phone 1 into a high-frequency voltage. Therefore, a high frequency voltage output from the high frequency power supply 10 is applied to both ends of the exciting coil 9 so that a high frequency current is supplied to the exciting coil 9.
When a high frequency current is supplied to the excitation coil 9, an alternating magnetic field is generated around the excitation coil 9, and when the detection coil 11 is moved to a position where it is exposed to the alternating magnetic field, the excitation coil 9 and the detection coil 11 are moved. Are electromagnetically coupled, and an induced voltage is induced in the detection coil 11.

  The high frequency power supply 10 is controlled by a control circuit (control means) (not shown) of the mobile phone 1 so as to repeat energization and disconnection at predetermined intervals, for example, every several tens of milliseconds to several hundreds of milliseconds. In other words, the high frequency power supply 10 intermittently supplies a high frequency current to the exciting coil 9.

  On the other hand, both ends of the capacitor 16 are connected to both ends of the detection coil 11, and a resonance circuit is formed by the detection coil 11 and the capacitor 16. When the resonance frequency of the resonance circuit and the frequency on the high-frequency power supply 10 side substantially coincide, an induced voltage is efficiently induced in the detection coil 11 at a so-called resonance point.

  FIG. 4 shows an induced voltage induced in the detection coil 11 when the capacitance value of the capacitor 16 of the resonance circuit is changed. In FIG. 4, the place where the induced voltage is maximum is the resonance point described above, and the capacitance value of the capacitor 16 in this embodiment is set to C0 which is the value at this time.

Further, both ends of the detection coil 11 are connected to input terminals of the amplifier 15, respectively. The amplifier 15 rectifies and smoothes the high-frequency induced voltage induced in the detection coil 11, and then amplifies the amplified DC voltage Vo from the output terminal. The voltage Vo is input to the control circuit of the mobile phone 1.
Therefore, the control circuit detects the approaching state of the excitation unit 5 and the detection unit 6 embedded in the mobile phone 1 by monitoring the voltage Vo. The control circuit monitors the voltage Vo almost in synchronization with the timing when the high frequency power supply 10 energizes the exciting coil 9 described above.

Next, the operation of the above configuration will be described with reference to FIGS.
FIG. 5 schematically shows a state in which the casings 2 and 3 of the mobile phone 1 are folded, that is, a state of the excitation unit 5 and the detection unit 6 in the closed state described above. 5 except for the excitation coil 9, the detection coil 11, the cores 8 and 14, and the cases 12 and 17 are omitted. In the present embodiment, the distance L between the lower end of the case 12 and the upper end of the case 17 is the relative distance between the coils 9 and 11. FIG. 6 shows the relationship between the relative distance L between the coils 9 and 11 and the induced voltage induced in the detection coil 11.

  As described above, when a high frequency current is supplied from the high frequency power supply 10 to the excitation coil 9, an alternating magnetic field is generated around the excitation coil 9. And when each housing | casing 2 and 3 of the mobile telephone 1 are folded, as shown in FIG. 5, each coil 9 and 11 is the state which the cores 8 and 14 located in each winding center oppose and approached each other Thus, the magnetic flux penetrating the detection coil 11 is the largest. The state in which the coils 9 and 11 are approached in this way is when the relative distance L = Lmin in FIG. 6, and the induced voltage induced in the detection coil 11 at this time becomes maximum. That is, the induced voltage is induced most efficiently in the detection coil 11.

  In contrast, when the casings 2 and 3 of the mobile phone 1 are unfolded and are in the open state described above, although not shown, the coils 9 and 11 are separated from each other, and the magnetic flux penetrating the detection coil 11 is the most. Less. The state in which the coils 9 and 11 are separated from each other is when the relative distance L = Lmax in FIG. 6, and the induced voltage induced in the detection coil 11 at this time is minimized.

  As described above, the induced voltage that changes in accordance with the relative distance L between the coils 9 and 11 is converted into a direct current by the amplifier 15 and then amplified, and is supplied to the control circuit of the mobile phone 1 as the voltage Vo. And a control circuit detects the approach state of each coil 9 and 11 by detecting the change of this voltage Vo. That is, the control circuit detects the closed state or the open state of the mobile phone 1 based on the induced voltage induced in the detection coil 11.

As described above, according to the present embodiment, the following effects can be obtained.
Since the high frequency power supply 10 intermittently applies a high frequency voltage to the excitation coil 9 to supply a high frequency current, an alternating magnetic field is provided around the excitation coil 9 during a period when no high frequency current is supplied to the excitation coil 9. Does not occur. Therefore, the magnetic influence on the outside can be reduced. Furthermore, the power consumption of the entire proximity sensor 7 can be reduced.
Further, since the proximity sensor 7 is configured using the excitation unit 5 and the detection unit 6 that do not use a permanent magnet, it is possible to perform soldering using a reflow furnace, reducing the number of assembly steps, and the excitation unit 5 and the attachment position accuracy of the detection unit 6 can be improved.

Since the amplifier 15 is connected to the detection coil 11 and the induced voltage induced in the detection coil 11 is amplified and output to the control circuit, the induced voltage induced in the detection coil 11 is small. Moreover, the detection accuracy of the approaching state of the excitation unit 5 and the detection unit 6 can be increased.
Further, a resonance circuit is formed by connecting the capacitor 16 to the detection coil 11 and the resonance frequency of the resonance circuit is made to substantially coincide with the frequency on the high frequency power supply 10 side, so that an induction voltage is efficiently induced in the detection coil 11. Can be made.

  The excitation coil 9 and the detection coil 11 are wound around the cores 8 and 14 formed of a magnetic material. That is, since the cores 8 and 14 are arranged inside the coils 9 and 11, the magnetic resistance of the coils 9 and 11 is reduced, and an alternating magnetic field is efficiently generated around the excitation coil 9. The induced voltage can be efficiently induced in the detection coil 11.

  In addition, since the exciting coil 9 and the detection coil 11 are accommodated in cases 12 and 17 formed of container-like magnetic bodies with the surfaces facing each other open, the magnetic resistance of each of the coils 9 and 11 is small. And the alternating magnetic field generated around the exciting coil 9 is concentrated on the portions where the coils 9 and 11 face each other, so that the leakage magnetic flux is reduced. Therefore, the magnetic influence on the outside is reduced and the influence of the electromagnetic wave from the outside becomes difficult. And an alternating voltage can be efficiently induced in the detection coil 11 by concentration of an alternating magnetic field as mentioned above and the magnetic resistance of each coil 9 and 11 becoming small.

  With each configuration as described above, an induction voltage is efficiently induced in the detection coil 11, so that the number of turns of each coil 9, 11 can be reduced and each coil 9, 11 can be configured smaller. It is possible to reduce the size. In addition, by efficiently inducing the induced voltage, it is possible to increase the detection accuracy of the approaching state while suppressing the power consumption of the entire proximity sensor 7.

  The excitation unit 5 is embedded in the display housing 2 of the mobile phone 1, and the detection unit 6 is embedded in the operation housing 3. That is, since the proximity sensor 7 is mounted on the mobile phone 1, it is possible to detect the closed state and the open state of the mobile phone 1. Therefore, the control circuit which is the control means of the mobile phone 1 can perform a predetermined process according to each of these states. For example, the control circuit controls to turn off the screen display of the display panel unit 2a that is the control target unit when the mobile phone 1 is in the closed state, and then controls to resume the screen display when the mobile phone 1 is in the open state. Such power saving operation becomes possible.

The present invention is not limited to the embodiment described above and illustrated in the drawings, and the following modifications or expansions are possible.
Only one of the cases 12 and 17 for housing the coils 9 and 11 may be provided, or none of them may be provided. Further, only one of the cores 8 and 14 disposed inside the coils 9 and 11 may be provided, or none of them may be provided. Further, the detection unit 6 may not be provided with the amplifier 15 and the capacitor 16. That is, each of the above-described configurations can be appropriately changed based on various performances of the proximity sensor 7 such as the size of the device, the detection accuracy of the approaching state, and the power consumption.

If there is no problem in the detection accuracy of the approaching state, the capacitor 16 may be arranged in another connection form, for example, connected in series to the detection coil 11.
The interval between intermittent energizations of the high-frequency power supply 10 may be changed within a range where the open state and the closed state can be reliably detected at an appropriate timing in consideration of the normal opening / closing speed of the mobile phone 1.
The frequency of the high frequency power supply 10 may be changed based on the size of the proximity sensor 7 or the target power consumption.
The current supply means may be any means as long as it can supply a current whose magnitude changes with time.

The proximity sensor 7 may detect not only the closed state and the open state of the mobile phone 1 but also several states including the state at the intermediate position. Further, the relative distance between the casings 2 and 3 of the mobile phone 1 may be detected.
The proximity sensor 7 can be applied to all electronic devices configured by connecting two machine bodies so as to be openable and closable. For example, the proximity sensor 7 can be applied to a notebook PC or a foldable portable game machine.

The figure which shows the principle structure of the proximity sensor which shows one Embodiment of this invention. External perspective view of a foldable mobile phone equipped with a proximity sensor Diagram showing the electrical configuration of the proximity sensor Diagram showing the relationship between the capacitor value of the resonant circuit and the induced voltage The figure which shows the proximity sensor in the approach state schematically Diagram showing the relationship between the relative distance of each coil and the induced voltage

Explanation of symbols

  In the drawings, 1 is a mobile phone (electronic device), 2 is a display housing (first airframe), 3 is an operation housing (second airframe), 7 is an proximity sensor, 8 and 14 are cores, and 9 is excitation. A coil (primary coil), 10 is a high-frequency power source (current supply means), 11 is a detection coil (secondary coil), 12 and 17 are cases (cores), 15 is an amplifier (amplifier circuit), and 16 is a capacitor.

Claims (7)

A primary coil;
Current supply means for supplying the primary coil with a current that changes in size over time;
A secondary coil disposed so that its position can be changed relative to the primary coil,
A proximity sensor for detecting the distance between the primary coil and the secondary coil based on the magnitude of the induced electromotive force of the secondary coil.   The proximity sensor according to claim 1, wherein the current supply means is a high-frequency power source.   The proximity sensor according to claim 1, further comprising an amplifier circuit that amplifies the output voltage of the secondary coil.   The proximity sensor according to claim 1, further comprising a capacitor that forms a resonance circuit together with the secondary coil.   5. The proximity sensor according to claim 1, wherein a core made of a magnetic material is disposed inside at least one of the primary coil and the secondary coil.   2. The primary coil and the secondary coil, wherein at least one of the coils is accommodated in a core formed of a container-like magnetic body whose surface facing the counterpart coil is open. Thru | or 5. The proximity sensor in any one of 5. In an electronic apparatus comprising a first airframe and a second airframe connected to the first airframe so as to be openable and closable,
An electronic apparatus comprising the first coil and the second coil of the proximity sensor according to any one of claims 1 to 6 provided in the first machine body and the second machine body, respectively.

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