JP2017142200A - Position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position detector that can ensure the accuracy of position detection.SOLUTION: A position detector 1 includes a first detection coil 5 near a detection target 3 and a second detection coil 6 (reference coil) distant from the detection target 3. Outputs (detection voltages) of the first and second detection coils 5 and 6 vary according to the distance to the detection target 3. A position calculation part 8 determines the position of the detection target 3 (detection target part 2) based on outputs (detection voltages) of the first and second detection coils 5 and 6. The second detection coil 6 has a smaller coil diameter than the first detection coil 5 has. This makes the maximum values of the outputs of the first and second detection coils 5 and 6 equal to each other.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a position detection device that detects the position of a detection target.

  Conventionally, the position of the detection target is used as a detection position detection device, and the metal part as the detection target is disposed opposite to the detection coil, and the change in the inductance of the detection coil when the metal part moves is detected. A technique for detecting the position is well known (see, for example, Patent Document 1).

Special table 2007-505534

In this type of position detection device, there has been a need to accurately position the detection target.
The objective of this invention is providing the position detection apparatus which can ensure the precision of a position detection.

  A position detection device that solves the above problem applies an AC voltage from a power source to a detection coil, and based on an output signal of the detection coil that changes according to a distance from the detection target, a position calculation unit performs detection of the detection target. In the configuration for detecting a position, the detection coil includes a first detection coil located on a side closer to the detection target, and a second detection coil located on a side far from the detection target, and the first detection coil The coil and the second detection coil are formed in different shapes so that the waveform of the output of the first detection coil and the waveform of the output of the second detection coil intersect in the position detection range of the detection target, The position calculation unit calculates the position of the detection target based on the output signals of the first detection coil and the second detection coil.

  According to this configuration, the shapes of these coils are set so that the waveform of the output of the first detection coil is equal to the waveform of the output of the second detection coil. For this reason, it becomes possible to make the dynamic range of the detection circuit which detects the output of a 1st detection coil and a 2nd detection coil low. Therefore, when the outputs of the first detection coil and the second detection coil are detected by the detection circuit, it is possible to suppress an error in the value to be detected, so that the accuracy of position detection can be improved.

  In the position detection device, the first detection coil and the second detection coil have the same maximum output value of the first detection coil and the maximum output value of the second detection coil in the position detection range of the detection target. The shape is preferably formed so that According to this configuration, the shapes of these coils are set so that the maximum value of the output of the first detection coil is equal to the maximum value of the output of the second detection coil. For this reason, the dynamic range of the detection circuit that detects the outputs of the first detection coil and the second detection coil can be made as low as possible, which is further advantageous in improving the position detection accuracy.

  In the position detection device, it is preferable that the first detection coil and the second detection coil are arranged side by side along a moving direction of the detection target. According to this configuration, since the first detection coil and the second detection coil are arranged in a balanced manner, the maximum value of the output of the first detection coil and the maximum value of the output of the second detection coil can be easily matched. Is possible.

  In the position detection device, it is preferable that the first detection coil and the second detection coil have opposite winding directions so that directions of flowing currents are opposite to each other. According to this configuration, when the detection target approaches or separates from the first detection coil, the inductances of the first detection coil and the second detection coil change in opposite directions. For this reason, when calculating the position of the detection target, it is possible to increase the fluctuation range of the calculation result. Therefore, it is advantageous to more accurately detect the position of the detection target.

  In the position detection device, it is preferable that the second detection coil is formed to have a winding diameter smaller than that of the first detection coil. According to this configuration, the maximum value of the output of the first detection coil and the maximum value of the output of the second detection coil can be obtained by a simple configuration in which the winding diameter of the second detection coil is reduced with respect to the first detection coil. Can be set identically.

  In the position detection device, it is preferable that the second detection coil is formed with a smaller number of turns than the first detection coil. According to this configuration, the maximum value of the output of the first detection coil is equal to the maximum value of the output of the second detection coil by a simple configuration in which the number of turns of the second detection coil is reduced with respect to the first detection coil. It becomes possible to set to.

  According to the present invention, position detection accuracy can be ensured in the position detection device.

The block diagram of the position detection apparatus of one Embodiment. The side view of the board | substrate of a position detection apparatus. The characteristic view of the coil output with respect to the distance change of a detection target. The block diagram of the conventional position detection apparatus. The characteristic view of the coil output with respect to the distance change of a detection target. Schematic which shows the shape of the 2nd detection coil of another example. Schematic which shows the shape of the 2nd detection coil of another example.

Hereinafter, an embodiment of the position detection device will be described with reference to FIGS.
As shown in FIG. 1, the position detection device 1 is a type of eddy current sensor that detects the position of the detected portion 2 (the distance to the detected portion 2). The eddy current sensor is a sensor that detects the position of the detected portion 2 based on a change in eddy current generated in metal (in this example, the detection target 3). The position detection device 1 according to the present example corresponds to the power source 4 of the position detection device 1, the first detection coil 5 and the second detection coil 6 to which the AC voltage Vc is applied from the power source 4, and the movement of the detected portion 2. And a detection target 3 that changes a magnetic field generated in the first detection coil 5 and the second detection coil 6.

  The detection target 3 is composed of, for example, a plate-like member (conductor plate) made of metal. The detection target 3 in this example is interlocked with the detected portion 2 by being attached and fixed to the detected portion 2. The detection target 3 moves along the axial direction (coil axis direction: arrow Z direction in FIG. 1) of the coil axis La of the first detection coil 5 (second detection coil 6) in accordance with the movement of the detected portion 2. 1 The linear reciprocation which approaches or separates from the detection coil 5 is possible.

  The first detection coil 5 and the second detection coil 6 are arranged side by side along the moving direction of the detection target 3 (the axial direction of the coil axis La). In the case of this example, the first detection coil 5 is arranged on the side closer to the detection target 3, and the second detection coil 6 is arranged on the side far from the detection target 3. This is because the output voltage (inductance) of the first detection coil 5 is used as a signal for position detection, and the second detection coil 6 is used as a reference coil (reference coil) of the first detection coil 5.

  The first detection coil 5 and the second detection coil 6 are connected in series to the power supply 4. The winding directions of the first detection coil 5 and the second detection coil 6 are reversed so that the directions of the flowing currents are opposite to each other. That is, the first detection coil 5 and the second detection coil 6 are configured to generate magnetic fields in opposite directions when the winding directions are opposite to each other.

  The first detection coil 5 and the second detection coil 6 have a maximum value V1max (illustrated in FIG. 2) of the output (output signal V1) of the first detection coil 5 in the position detection range K (illustrated in FIG. 2) of the detection target 3. ) And the maximum value V2max (shown in FIG. 2) of the output of the second detection coil 6 (output signal V2) (shown in FIG. 2) are both formed to have different shapes. . In the case of this example, the second detection coil 6 is formed smaller than the first detection coil 5. The small size means that the winding diameter of the first detection coil 5 is X1 and the winding diameter of the second detection coil 6 is X2, and the winding diameter (coil size) is small (X1> X2). . The number of turns of the first detection coil 5 and the second detection coil 6 may be the same or different.

  The first detection coil 5 and the second detection coil 6 are connected to a detection circuit 7 that detects voltages (output signals V1, V2) generated in the first detection coil 5 and the second detection coil 6. The detection circuit 7 of this example includes a voltage detection unit 7 a that detects the voltage of the first detection coil 5 and a voltage detection unit 7 b that detects the voltage of the second detection coil 6. The voltage detector 7 a is connected between the input and output ends of the first detection coil 5, and the voltage detector 7 b is connected between the input and output ends of the second detection coil 6.

  The position detection device 1 includes a position calculation unit 8 that calculates the position of the detection target 3 based on the outputs of the first detection coil 5 and the second detection coil 6. The position calculation unit 8 is based on an output signal (output voltage) V1 input from the voltage detection unit 7a and an output signal (output voltage) V2 input from the voltage detection unit 7b. The position of is calculated. Specifically, the position calculation unit 8 obtains a value (V1 / V2) obtained by dividing the output signal V1 of the voltage detection unit 7a by the output signal V2 of the voltage detection unit 7b, and from this value, the first detection coil 5 is obtained. And the position of the detection target 3, that is, the position of the detected portion 2 is calculated.

  As shown in FIG. 2, in the first detection coil 5 and the second detection coil 6 of this example, the first detection coil 5 is provided on the first layer 10 a (for example, the surface) of the substrate 10, and the second detection coil 6 is By being provided on the second layer 10 b (for example, the back surface) of the substrate 10, they are arranged on the same substrate. The first detection coil 5 is formed only on the first layer 10 a of the substrate 10, and the second detection coil 6 is formed only on the second layer 10 b of the substrate 10.

Next, the operation and effect of the position detection device 1 will be described with reference to FIGS.
As shown in FIG. 3, in the position detection range K of the position detection device 1, the detection target 3 moves linearly from a point P 1 closest to the first detection coil 5 to a point P 2 farthest from the first detection coil 5. And At this time, as the detection object 3 moves away, the inductance of the first detection coil 5 gradually increases, and the output signal V1 of the first detection coil 5 changes in a curved manner from V1min to V1max. Take the waveform. On the other hand, the inductance of the second detection coil 6 gradually decreases, and the output signal V2 of the second detection coil 6 changes in a curved manner from V2max to V2min. That is, the output of the first detection coil 5 and the output of the second detection coil 6 take a change waveform in which the maximum values V1max and V2max are the same.

  FIG. 4 shows a configuration of a conventional position detection device 31. The position detection device 31 illustrated in FIG. 4 has a configuration in which the second detection coil 6 has the same size as the first detection coil 5 with respect to the configuration of the position detection device 1 of this example. That is, the first detection coil 5 and the second detection coil 6 have the same winding diameter and number of coil turns.

  As shown in FIG. 5, in the case of the conventional position detection device 31, when the detected portion 2 moves from the point P <b> 1 to the point P <b> 2 in the position detection range K, the detection target 3 moves away from the first detection coil 5. Accordingly, the output signal V1 takes a change waveform that rises in a curved shape from V1min ′ to V1max ′. That is, the voltage of the first detection coil 5 changes so as to increase from V1min 'to V1max'. On the other hand, the output signal V2 of the second detection coil 6 takes a change waveform that descends in a curve from a high value V2max 'to V2min'. That is, the output voltage of the second detection coil 6 falls from a high maximum value V2max ′ to a voltage V2min ′ that is slightly higher than the maximum value of the first detection coil 5.

  Incidentally, the detection circuit 7 has a predetermined input voltage range (dynamic range of detection voltage), and is set to the maximum value of the output of the detection coil (the first detection coil 5 or the second detection coil 6). For example, in the case of the position sensor 31 of the conventional positioning, since the maximum value V2max ′ of the second detection coil 6 is higher than the maximum value V1max ′ of the first detection coil 5, the dynamic range (full scale) of the detection circuit 7 is the first. 2 The maximum value V2max ′ of the detection coil 6 is set.

  In general, a detection error occurs in the detection circuit 7, and the error occurs at what percentage of the dynamic range of the detection circuit 7. Therefore, if the dynamic range of the detection circuit 7 is high, the position detection error increases accordingly. In the conventional position detection device 31, the dynamic range of the detection circuit 7 is set to “V2max ′” which is the maximum value of the second detection coil 6. That is, in the case of the conventional position detection device 1, since the dynamic range is as large as “V2max ′”, the detection error generated in the detection circuit 7 increases accordingly.

  On the other hand, in the case of the position detection device 1 of this example, the waveform of the output of the first detection coil 5 at a predetermined point in the position detection range K (see FIG. 5) by making the second detection coil 6 smaller than the first detection coil 5. 3) and the waveform of the output of the second detection coil 6 (downward curve in FIG. 3) are set to intersect each other. That is, the first detection coil 5 and the second detection coil 6 have different shapes so that the output waveform of the first detection coil 5 and the output waveform of the second detection coil 6 intersect within the position detection range K. Is formed. For this reason, the maximum value of the detection voltage in the detection circuit 7 can be reduced, and as a result, the dynamic range of the detection circuit 7 can be reduced, so that the error generated in the detection circuit 7 can be reduced accordingly. Therefore, it is advantageous to ensure the position detection accuracy of the position detection device 1.

  In the case of this example, the first detection coil 5 and the second detection coil 6 make the second detection coil 6 smaller than the first detection coil 5, so that the maximum value V1max of the output of the first detection coil 5 2 The maximum value V2max of the output of the detection coil 6 is made equal. Therefore, the dynamic range of the detection circuit 7 can be reduced as much as possible, which is further advantageous for improving the position accuracy of the position detection device 1.

  The 1st detection coil 5 and the 2nd detection coil 6 are arrange | positioned along with the moving direction (arrow Z direction of FIG. 1) of the detection target 3. As shown in FIG. Thus, since the first detection coil 5 and the second detection coil 6 are arranged in a balanced manner, the maximum value V1max of the output of the first detection coil 5 and the maximum value V2max of the output of the second detection coil 6 are the same. It can be made easier to match.

  The winding directions of the first detection coil 5 and the second detection coil 6 are reversed so that the directions of the flowing currents are opposite to each other. Thereby, when the detection target 3 approaches or separates from the first detection coil 5, the inductances of the first detection coil 5 and the second detection coil 6 change in opposite directions. That is, if the inductance of the first detection coil 5 increases, the inductance of the second detection coil 6 decreases. Conversely, if the inductance of the first detection coil 5 decreases, the inductance of the second detection coil 6 increases. . For this reason, when calculating the position of the detection target 3, it is possible to increase the fluctuation range of the calculation result. Therefore, it is advantageous to more accurately detect the position of the detection target 3 (detected portion 2).

  When the maximum value V1max of the output of the first detection coil 5 and the maximum value V2max of the output of the second detection coil 6 are set equal, the second detection coil 6 has a smaller winding diameter than the first detection coil 5. It is formed as follows. Therefore, the maximum value V1max of the output of the first detection coil 5 and the maximum value V2max of the output of the second detection coil 6 are set to be the same with a simple configuration in which the winding diameter of the second detection coil 6 is reduced. Can do. In addition, since the size of the second detection coil 6 can be reduced, it contributes to a reduction in the size of the position detection device 1.

Note that the embodiment is not limited to the configuration described so far, and may be modified as follows.
As shown in FIG. 6, in setting the maximum value V1max of the output of the first detection coil 5 and the maximum value V2max of the output of the second detection coil 6, for example, the first detection coil 5 and the second detection coil Instead of changing the size of 6, for example, the second detection coil 6 may be formed by forming fewer turns than the first detection coil 5. In this case, the outputs of the first detection coil 5 and the second detection coil can be made the same with a simple configuration in which the number of turns of the second detection coil 6 is reduced.

As shown in FIG. 7, the second detection coil 6 may have a coil shape in which the coil diameter decreases (stepwise decreases) toward the inner diameter direction of the coil.
The arrangement pattern in which the first detection coil 5 and the second detection coil 6 are not arranged on the same axis may be used.

-The coil shape (winding shape) of the 1st detection coil 5 and the 2nd detection coil 6 is not restricted to square shape, For example, it can change into other shapes, such as circular shape.
The first detection coil 5 and the second detection coil 6 may have the same direction of flowing current.

  The connection between the first detection coil 5 and the second detection coil 6 and the voltage detection unit (the voltage detection units 7a and 7b in this example) is time-division controlled by a switch so that the first detection coil 5 and the second detection coil are detected. A configuration in which the output of the coil 6 is selectively detected by one voltage detector may be employed. In this way, the voltage detection unit required for the position detection device 1 can be reduced, which is advantageous in reducing the size of the device.

The detection target 3 is not limited to the conductor plate (metal plate) but can be changed to other members such as a coil. That is, any member that can generate an eddy current may be used.
The substrate 10 may be a multilayer substrate, and the first detection coil 5 and the second detection coil 6 may be disposed on a predetermined layer of the multilayer substrate.

The first detection coil 5 and the second detection coil 6 may be formed across a plurality of layers of the substrate 10.
The first detection coil 5 and the second detection coil 6 are not limited to being connected in series. For example, the first detection coil 5 and the second detection coil 6 can be appropriately changed to other configurations such as a circuit in which a dedicated power source is connected to each of the first detection coil 5 and the second detection coil 6.

-While detecting the voltage between the 1st detection coil 5 and the 2nd detection coil 6, the voltage of the 2nd detection coil 6 may be detected, and the position of the detection target 3 may be calculated | required from the result of dividing these.
The calculation performed at the time of detecting the position of the detected part 2 is not limited to division, and may be changed to another calculation method.

The coil output used for the position detection calculation is not limited to the voltage value, and may be another parameter such as a current value.
The small winding diameter of the coil includes a small outer diameter of the winding and a small inner diameter of the winding.

  The detection target 3 is not limited to a linear reciprocating movement in the vertical direction of the first detection coil 5, but may be moved in a direction orthogonal to the vertical direction (coil axis direction) of the first detection coil 5, for example. Good. That is, the position detection device 1 may detect the position of the detection target 3 that reciprocates in a direction orthogonal to the coil axis La.

  -In making the output waveform of the 1st detection coil 5 and the output waveform of the 2nd detection coil 6 cross, this is not limited to implement | achieving by making the maximum value of each coil equal. In short, even if the maximum values do not match, it is sufficient that the coil outputs have a waveform that intersects at a predetermined point in the position detection range K.

  The position detection device 1 can be applied to various devices and apparatuses.

  DESCRIPTION OF SYMBOLS 1 ... Position detection apparatus, 2 ... Detected part, 3 ... Detection object, 4 ... Power supply, 5 ... 1st detection coil, 6 ... 2nd detection coil, 8 ... Position calculating part, Vc ... AC voltage, K ... Position detection Range, V1, V2 ... output signal, V1max, V2max ... maximum value of output, X1, X2 ... winding diameter, Z ... direction of movement of detection target.

Claims (6)

In a position detection device that applies an AC voltage from a power source to the detection coil and detects the position of the detection target by a position calculation unit based on the output signal of the detection coil that changes according to the distance to the detection target.
The detection coil includes a first detection coil located on a side closer to the detection target, and a second detection coil located on a side far from the detection target,
The first detection coil and the second detection coil have different shapes so that the waveform of the output of the first detection coil and the waveform of the output of the second detection coil intersect in the position detection range of the detection target. Formed,
The position calculating unit calculates a position of the detection target based on output signals of the first detection coil and the second detection coil. The first detection coil and the second detection coil are shaped so that the maximum value of the output of the first detection coil and the maximum value of the output of the second detection coil are the same in the position detection range of the detection target. The position detection device according to claim 1, wherein: The position detection device according to claim 1, wherein the first detection coil and the second detection coil are arranged side by side along a moving direction of the detection target. The position detection device according to any one of claims 1 to 3, wherein the first detection coil and the second detection coil are wound in opposite directions so that directions of flowing currents are opposite to each other. The position detection device according to any one of claims 1 to 4, wherein the second detection coil is formed to have a winding diameter smaller than that of the first detection coil. The position detection device according to any one of claims 1 to 4, wherein the second detection coil has a smaller number of turns than the first detection coil.

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