JP2007304072A - Position detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position detector improved in detection responsiveness and further in toughness to disturbance such as temperature through a simple structure. <P>SOLUTION: This position detector comprises two conductive plates 12 and 14 fixed to a fixed side 10a; a displacement-side conductive plate 16 fixed to a displacement side 10b and disposed in a position opposed to a plurality of conductors; power sources 18 and 20 supplying power to the fixed-side conductive plates in different phases; a phase detection circuit 30 detecting a capacitance ratio caused between each of the fixed-side conductive plate and the displacement-side conductive plate as a phase of potential difference; and an arithmetic circuit 32 computing a displacement quantity or an absolute angle from the detected phases. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a position detection device, and more particularly to a position detection device having a structure similar to a resolver.

As this type of position detection device, for example, a technique described in Patent Document 1 is known. In that technology, a resonance circuit is configured with a coil and a capacitor, and the self-inductance of the coil or the capacitance of the capacitor is changed with respect to the displacement, and the change in the resonance frequency of the resonance circuit is detected by the displacement. The detection accuracy of the displacement amount is improved.
JP 2002-206948

  In the prior art, the amount of displacement is detected based on the electrostatic capacity. However, since the electrostatic capacity changes even if the interval slightly deviates from the intended one, it is troublesome to prepare the detection conditions. There was an inconvenience. Further, in order to obtain the displacement from the capacitance, it is necessary to detect the resonance frequency. However, since feedback is used to detect the resonance frequency, there is a limit to the response of detection. In addition, the resonance frequency is susceptible to not only displacement but also disturbances such as temperature.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a position detection device that solves the above-described problems, is simple in configuration, improves detection response, and further improves toughness against disturbances such as temperature. .

  In order to achieve the above object, in the position detecting device according to claim 1, a plurality of fixed-side conductors fixed to the fixed side, a plurality of conductors fixed to the displacement side, and the plurality of conductors A displacement-side conductor disposed at a position opposite to the first and second power supply means for supplying power to the plurality of fixed-side conductors in different phases, and the plurality of fixed-side conductors. And a phase detecting means for detecting a capacitance ratio generated between the displacement-side conductor and a phase of potential change, and a calculating means for calculating a displacement amount or an absolute angle from the detected phase. .

  In the position detection device according to claim 2, the fixed-side conductor and the displacement-side conductor are relatively moved with a certain separation distance, and the arithmetic means is configured to move from the detected phase to a displacement amount. It was comprised so that it might calculate.

  In the position detection device according to claim 3, the fixed-side conductor and the displacement-side conductor are relatively rotated with a constant separation distance, and the calculation means is configured to calculate an absolute angle from the detected phase. It was comprised so that it might calculate.

  In the position detection device according to claim 1, the capacitance ratio generated between each of the plurality of fixed-side conductors and the displacement-side conductor is detected as a phase of potential change, and a displacement amount is detected from the detected phase. Alternatively, the absolute angle is calculated so that the above-mentioned drawbacks of the prior art can be solved, the configuration is simple, the detection response can be improved, and the toughness against disturbances such as temperature is improved. Can be made.

  In the position detection device according to claim 2, the fixed-side conductor and the displacement-side conductor move relative to each other with a constant separation distance, and the displacement amount is calculated from the detected phase. In addition to the effects described above, it is possible to accurately detect a change in the displacement amount on the displacement side with respect to the fixed side.

  In the position detection device according to claim 3, the fixed-side conductor and the displacement-side conductor are configured to relatively rotate with a constant separation distance and calculate the absolute angle from the detected phase. In addition to the effects described above, it is possible to accurately detect a change in the absolute angle on the displacement side with respect to the fixed side.

  The best mode for carrying out the position detection apparatus according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is an explanatory sectional view schematically showing a position detection apparatus according to a first embodiment of the present invention.

  In FIG. 1, the code | symbol 10 shows a position detection apparatus. The position detection device 10 includes a plurality (specifically) two conductive plates (conductors) 12 and 14 fixed (arranged) on the fixed side 10a and one fixed (arranged) on the displacement side 10b. A conductive plate (conductor) 16 is provided. The conductive plates 12 and 14 are spaced apart from each other so as not to be electrically connected.

  The conductive plate 16 is configured to change the overlapping (overlapping) area in accordance with the displacement while moving parallel to the conductive plates 12 and 14 (without changing the distance). For convenience of understanding, a portion of the conductive plate 16 that overlaps with the conductive plate 12 is denoted as 16a, and a portion that overlaps with the conductive plate 14 is denoted as 16b.

  The conductive plates 12 and 14 are connected to power sources 18 and 20, respectively. The power supplies 18 and 20 generate voltages (AC voltages) that change with known different phases and supply them to the conductive plates 12 and 14. Similarly, the conductive plate 16 is electrically connected to a conductive plate 22 fixed to the displacement side 10b via an electric wire 24. The conductive plate 22 is arranged so as to always have a certain overlapping area while moving in parallel with respect to the conductive plate 26 on the fixed side 10a arranged to face each other.

  The conductive plate 26 is connected to a phase detection circuit 30 where the phase of the potential or current change due to the change in capacitance ratio is detected. The phase detection circuit 30 is connected to an arithmetic circuit 32, and its output, that is, the detected phase is input to the arithmetic circuit 32, and the displacement amount is calculated from the detected phase. The conductive plates 12, 14, and 16 have a rectangular shape and are made of a conductive material such as copper foil. Specifically, the phase detection circuit 30 and the arithmetic circuit 32 are formed of a microcomputer.

  FIG. 2 is a schematic diagram illustrating an application example of the position detection device 10. The displacement detection device 10 according to this embodiment is applicable to, for example, detection of displacement of a vehicle suspension. In this case, the fixed side 10a includes a cylinder 100 connected to a vehicle body (not shown), and the displacement Side 10b consists of a piston 102 connected to an axle (not shown).

  Conductive plates 22 and 26 are connected to them as output side couplings, and the phase is detected. Based on the output of the displacement detection device 10, for example, a feedback signal in the active suspension is generated.

Returning to the description of FIG. 1, in the illustrated configuration, the conductive plates 12, 14, and 16 have a length in the depth direction of L, a length in the horizontal direction of W, and the conductive plate 16 from the left end of the conductive plate 12 (in FIG. 1). If the distance to the left end of x is x, the area S16a of the portion 16a and the area S16b of the portion 16b are as follows.
S16a = L × (W−x)
S16b = L × x
The conductive plates 12 and 14 and the conductive plate 16 relatively move (translate) while keeping the distance between them constant d.

The potentials V generated on the conductive plates 12 and 14 by the power sources 18 and 20 are as follows.
V12 = V0 × cos (ωt), V14 = V0 × sin (ωt)
In the above, V0 and ω are appropriate constants, and t is a variable representing time.

The capacitances of the portions 16a and 16b are as follows.
C16a = εL (W−x) / d
C16b = εLx / d
Where ε represents the dielectric constant in air.

Therefore, the charge Q generated in the conductive plate 16 is as follows.
Q = εV0 / d × ((W−x) cos (ωt) + xsin (ωt))
= ΕV0 / d × √ (W ² −2Wx + 2x ² ) cos (ωt−φ) Equation 1
However, tan φ = x / (W−x).

  On the other hand, the capacitance determined by the conductive plates 22 and 26 is always constant because the overlap area and the distance between the conductive plates are constant, so the phase detection circuit 30 reflects the phase of Q described above. Voltage is input. Therefore, the phase detection circuit 30 derives tan φ from the expression 1 and outputs it to the arithmetic circuit 32. The arithmetic circuit 32 calculates the displacement x from the inputted tan φ.

  If the explanation of the principle of this detection is supplemented slightly, the electric charge Q generated in the conductive plate 26 is as shown in the above equation 1, and the output current I is as shown in the equation 2 at the bottom of FIG. . That is, since it is assumed that the AC frequency output from the power supplies 18 and 20 is high, in other words, ω is large, ∂x / ∂t≈0, that is, the displacement x is regarded as a constant. The current I is converted into a voltage by a current sensor (not shown), the potential V 'shown in Equation 3 is obtained, the capacitance ratio is obtained from φ therein, and the displacement x is calculated therefrom.

  In the position detecting device 10 according to the first embodiment, the capacitance on the conductive plate 16 side is changed by changing the capacitance ratio of the capacitor formed between the conductive plates 12 and 14 and the conductive plate 16 due to the displacement. The phase of the change changes between the phases of the power supplies 18 and 20, and the potential change on the conductive plate 16 side is input to the phase detection circuit 30 via the capacitor constituted by the conductive plates 22 and 26, and the phase detection circuit The phase of the potential change to which 30 is input is output to the arithmetic circuit 32. As a result, the displacement can be detected quickly and accurately without using a time-consuming process such as feedback as in the prior art, with a simple configuration.

  In addition, since the phase change due to the displacement is the capacitance ratio of the two capacitors constituted by the conductive plates 12 and 16 and the conductive plates 14 and 16, the static change due to the change in the distance between the fixed side and the displacement side or the temperature. The change in capacitance is canceled out, and the displacement can be detected with high accuracy without being affected by disturbance.

  FIG. 4 is an explanatory sectional view schematically showing a position detection apparatus according to the second embodiment of the present invention.

  In the second embodiment, the position detection device 10 is configured as an absolute angle detector, has a cylindrical shape with a radius r and a depth L, and has a displacement side 10b that freely rotates around the axis of the cylinder, and a displacement side 10b. It is constituted by a fixed side 10a having a cylindrical hollow with a radius r + d and a depth L and having a coincident central axis. However, d is a sufficiently short distance with respect to r.

  For example, as shown in FIG. 5, the position detection apparatus 10 according to the second embodiment is configured to be fixed to one end of a crankshaft 106 of the internal combustion engine 104 and detect a crank angle. The detected angle thus obtained is used for controlling the timing of the supply / exhaust valve.

  In the second embodiment, conductive plates (conductors) 42 and 44 are disposed on the fixed side 10a, and a conductive plate (conductor) 46 is disposed on the displacement side 10b so as to face the conductive plate. By changing the absolute angle of 10b, the area 46a overlapping the conductive plate 42 and the area 46b overlapping the conductive plate 44 out of the area of the conductive plate 46 are changed.

  The conductive plate 46 is electrically connected to a conductive plate (conductor) 48 disposed on the displacement side 10 b via an electric wire 50, and is disposed on the fixed side 10 a so as to face the conductive plate 48. 52, and the overlapping area and interval (separation distance) between the conductive plate 48 and the conductive plate 52 are constant regardless of the absolute angle.

The conductive plates 42 and 44 are connected to power sources 54 and 56, respectively. The power sources 54 and 56 generate the following potentials and supply them to the conductive plates 42 and 44, respectively.
V42 = V0 × cos (ωt)
V44 = V0 × sin (ωt)

  The conductive plates 42, 44, 46 have a shape such that a rectangle having a length L in the depth direction and a length W in the circumferential direction is attached to a cylinder, and the distance between the conductive plates 42, 44 and the conductive plate 46 (separation). The distance) is kept at a constant distance d sufficiently small with respect to L and W.

Assuming that the length from the upper end of the conductive plate 42 to the upper end of the conductive plate 46 is x as shown in FIG. 4, the areas of the 46a portion and the 46b portion are as follows.
S46a = L × (W−x)
S46b = L × x
As in the first embodiment, V0 and ω are appropriate constants, and t is a variable representing time.

In the configuration described above, the phase detection circuit 30 and the arithmetic circuit 32 perform the same processing as in the first embodiment, thereby detecting the displacement x and then detecting the absolute angle θ as follows.
θ = x / r [rad]

  Even in the position detection device 10 according to the second embodiment, the capacitance ratio of the capacitor formed between the conductive plates 42 and 44 and the conductive plate 46 changes due to the displacement, whereby the potential on the conductive plate 46 side. The phase of the change changes between the phases of the power sources 54 and 56, and the potential change on the conductive plate 46 side is input to the phase detection circuit 30 via the capacitor constituted by the conductive plates 48 and 50, and the phase detection circuit Since the phase of the potential change when 30 is input is output to the arithmetic circuit 32, the absolute angle can be quickly obtained without using a time-consuming process such as feedback as in the prior art while having a simple configuration. And it can detect with high precision.

  FIG. 6 is an explanatory sectional view schematically showing a position detection apparatus according to the third embodiment of the present invention.

  The position detection device 10 according to the third embodiment is also configured as an absolute angle detector, has a disk shape with a radius r, a displacement side 10b that freely rotates around the central axis of the disk, and a center that coincides with the displacement side 10b It is constituted by a fixed side 10a having an axis and having a disk shape as well as a radius r. However, the fixed-side disk and the displacement-side disk are kept parallel (relatively rotated) with a sufficiently small distance d to r.

  Conductive plates (conductors) 62 and 64 are disposed on the fixed side 10a, and a conductive plate (conductor) 66 is disposed on the displacement side 10b so as to face the conductive plate. By changing the absolute angle of the displacement side 10b, Of the area of the conductive plate 66, the area 66a overlapping the conductive plate 62 and the area 66b overlapping the conductive plate 64 are changed.

  The conductive plate 66 is electrically connected to a conductive plate (conductor) 68 disposed on the displacement side 10 b via an electric wire 70, and is disposed on the fixed side 10 a so as to face the conductive plate 68. 72 is arranged. The overlapping area and interval (separation distance) between the conductive plate 68 and the conductive plate 72 are constant regardless of the absolute angle.

The conductive plates 62 and 64 are connected to power sources 74 and 76, respectively. The power sources 74 and 76 generate the following potentials and supply them to the conductive plates 62 and 64, respectively.
V62 = V0 × cos (ωt)
V64 = V0 × sin (ωt)

  The conductive plates 62, 64, 66 have a fan shape with an outer peripheral radius r, an inner peripheral radius r ′, and a circumferential length of λ, and an interval (separation distance) between the conductive plates 62, 64 and the conductive plate 66. Is kept at a constant distance d sufficiently small with respect to r, r ′ and λ.

When the length from the upper end of the conductive plate 62 to the upper end of the conductive plate 64 is x as shown in FIG. 6, the areas of the 66a portion and the 66b portion are as follows.
S66a = (λ−x) × (r−r ′) / 2
S66b = xx (r−r ′) / 2
As in the previous embodiment, V0 and ω are appropriate constants, and t is a variable representing time.

By performing the same processing as in the first embodiment in the above configuration, the displacement x can be detected, and then the absolute angle θ can be detected as follows.
θ = x / r [rad]

  Even in the position detection device 10 according to the third embodiment, the capacitance ratio of the capacitor formed between the conductive plates 62 and 64 and the conductive plate 66 changes due to the displacement, so that the potential on the conductive plate 66 side. The phase of the change changes between the phases of the power supplies 74 and 76, and the potential change on the conductive plate 66 side is input to the phase detection circuit 30 via the capacitor constituted by the conductive plates 68 and 72, and the phase detection circuit Since the phase of the potential change when 30 is input is output to the arithmetic circuit 32, the absolute angle can be quickly obtained without using a time-consuming process such as feedback as in the prior art while having a simple configuration. And it can detect with high precision.

  In the position detection device 10 according to the first to third embodiments, as described above, a plurality of, more specifically, two fixed-side conductors (conductive plates 12, 14, conductive plates 42 and 44, conductive plates 62 and 64) and a displacement side conductor (conductive plate 16, conductive plate) fixed to the displacement side 10b and disposed at a position facing the plurality of conductors. 46, conductive plate 66) and first and second power supply means (power supplies 18, 20, power supplies 54, 56, power supplies 74, 76) for supplying electric power to the plurality of fixed-side conductors in different phases. A phase detection means (phase detection circuit 30) for detecting a capacitance ratio generated between the plurality of fixed-side conductors and the displacement-side conductors as a phase of potential change, and from the detected phases Arithmetic means for calculating the displacement amount or absolute angle (arithmetic circuit 32 It was as configuration provided with a door.

  The fixed-side conductor and the displacement-side conductor (conductive plates 12, 14, 16) move relative to each other with a constant separation distance, and the calculation means calculates the displacement amount x from the detected phase. It was configured to calculate.

  Further, the fixed-side conductor and the displacement-side conductor (conductive plates 42, 44, 46, 62, 64, 66) rotate relatively with a constant separation distance, and the calculation means detects the detection The absolute angle θ is calculated from the phase.

It is explanatory drawing which shows typically the position detection apparatus based on 1st Example of this invention. It is explanatory drawing which shows the example of application of the position detection apparatus shown in FIG. It is explanatory drawing which shows the detection principle of the position detection apparatus shown in FIG. It is explanatory drawing which shows typically the position detection apparatus based on 2nd Example of this invention. It is explanatory drawing which shows the example of application of the position detection apparatus shown in FIG. It is explanatory drawing which shows typically the position detection apparatus which concerns on 3rd Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Position detection apparatus, 10a Fixed side, 10b Displacement side, 12, 42, 62 Fixed side conductive plate (conductor), 14, 44, 64 Fixed side conductive plate (conductor), 16, 46, 66 Displacement side Conductive plate (conductor), 18, 20, 54, 56, 74, 76 Power source (first and second power supply means), 22, 48, 68 Displacement side conductive plate (conductor), 26, 52 , 72 Fixed side conductive plate (conductor), 30 phase detection circuit, 32 arithmetic circuit

Claims (3)

  A plurality of fixed-side conductors fixed to the fixed side, a displacement-side conductor fixed to the displacement side and disposed at a position facing the plurality of conductors, and the plurality of fixed-side conductors First and second power supply means for supplying electric power to the body in mutually different phases, and capacitance ratios generated between the plurality of fixed-side conductors and the displacement-side conductors as potential change phases A position detection apparatus comprising: phase detection means for detecting; and calculation means for calculating a displacement amount or an absolute angle from the detected phase.   2. The fixed-side conductor and the displacement-side conductor move relative to each other with a constant separation distance, and the calculation means calculates a displacement amount from the detected phase. Position detection device.   2. The fixed-side conductor and the displacement-side conductor are relatively rotated with a constant separation distance, and the calculation means calculates an absolute angle from the detected phase. Position detection device.

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