JP2008286667A - Electromagnetic induction type position sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an absolute encoder that outputs a displacement signal of low distortion, in a position sensor using an electromagnetic induction action for detecting a change of a reluctance as an amplitude change of an alternating current magnetic flux, using coils, by forming the plurality of coils with a conductor pattern using a printed board technique or the like. <P>SOLUTION: An electromagnetic induction type position sensor includes the coils 6 for receiving the alternating current magnetic flux of repeating high intensity and low intensity at substantial wavelength λ along a relative moving direction of a position detecting object, and for outputting an electromagnetic induced voltage varied accompanying a relative motion of the position detecting object. The coil 6 is constituted by connecting even number of same-shaped conductor patterns 11, 12, 13, 14 and 21, 22, 23, 24 of wavelength λ. The even number of same-shaped conductor patterns are arranged in positions where a phase difference between the first set of conductor patterns 11, 12, 13, 14 and the second set of conductor patterns 21, 22, 23, 24 is brought into λ/2 when conductor patterns are divided evenly into the two sets. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electromagnetic induction type position sensor that detects the position of a member that rotates or linearly moves relative to each other by electromagnetic induction.

  Conventionally, on a spindle of a machine tool, etc., a scale with a gear-like unevenness formed by hobbing etc. on a cylindrical outer periphery made of soft magnetic material is fixed to a rotating shaft, and the change in reluctance of the outer periphery of the scale is converted into an electrical signal. A position sensor is used. Since such a position sensor uses magnetism for position detection, it has excellent environmental resistance against water and oil. In addition, since such a position sensor can easily produce scales of various diameter sizes by machining, for example, it requires a large number of external sizes such as a spindle of a machine tool. Suitable for applications that require different types of through holes.

  As the above position sensor, a plurality of coils are formed by a conductor pattern using printed circuit board technology described in Patent Document 1 below, and the change in reluctance is detected using these coils to determine the amplitude of the alternating magnetic flux. There is a position sensor using an electromagnetic induction effect detected as a change.

  The technique described in Patent Document 1 will be described with reference to FIG. On the first and second layers of the sensor substrate 60, which is a printed circuit board on which a conductor pattern is formed, sinusoidal conductor patterns 41 and 51, 42 and 52, 43 and 53, 44 having eight pairs of λ wavelengths, 54, 45 and 55, 46 and 56, 47 and 57, 48 and 58 are spaced apart in a direction orthogonal to the scale movement direction (not shown) and have a constant phase difference π / in the scale movement direction. 4 (λ / 8) are shifted in order.

  Connection of each pattern will be described. Assuming that the pair of sinusoidal conductor patterns of the first and second layers of the sensor substrate 60 is one set, and the first to eighth sets in order from top to bottom, the patterns of the first and sixth sets ( 41, 46, 56, 51), the first set of sinusoidal conductor patterns 41 is connected to the sixth set of sinusoidal conductor patterns 46 on the left side of the substrate, and the sixth set of sinusoidal conductor patterns 46 is connected. Are connected to the second-layer sinusoidal conductor pattern 56 by the interlayer connection on the right side of the substrate. The second-layer sinusoidal conductor pattern 56 is connected to the sinusoidal conductor pattern 51 by a second-layer substrate left-side pattern that is not visible in FIG.

  The connection of the second set and the fifth set (42, 45, 55, 52) is substantially the same connection configuration as the first set and the sixth set (41, 46, 56, 51). Further, the first set of sine wave conductor patterns 51 are connected to the second set of sine wave conductor patterns 42 by interlayer connection on the right side of the substrate, so that the first group, the sixth group, the second group, the fifth group, and the like. Are all connected in series to form a coil 65.

  In addition, in the first and sixth sets of sinusoidal conductor patterns, the direction of the current flowing in the conductor pattern is reversed in the first and sixth sets of sinusoidal conductor patterns, and the electromagnetically induced signals are reversed. In order to perform the series connection shown in FIG. 4, signals generated in each pattern are added. In a similar manner, the third and fourth sets, and the seventh and eighth sets of sinusoidal conductor patterns are also connected in series to form the coil 66.

  With the above configuration, an output signal corresponding to the rotational position of the scale can be obtained from the coils 65 and 66.

JP 2006-17533 A

  Since the position sensor using a plurality of coils like the sensor substrate 60 in FIG. 4 described above has arranged sinusoidal conductor patterns having a phase difference in the moving direction of the scale, the electromagnetic induction generated by each conductor pattern is arranged. A signal obtained by combining the voltages is obtained. For this reason, the distortion of the amplitude change with respect to the position change can be reduced by the averaging effect, and highly accurate position detection can be performed. Even with this conventional position detection method, sufficient accuracy is obtained. When a signal having a signal period λ is divided approximately by 10,000, this error only appears as an error of about 10 when converted to a position detection error. .

  However, if more precise position detection is desired, the synthesized signal of the actual electromagnetic induction voltage contains third-order, fifth-order, and seventh-order harmonic components. It was difficult to convert.

  The present invention has been made under the circumstances as described above, and an object of the present invention is to provide a signal with a synthesized electromagnetic induction voltage that does not contain third-order, fifth-order, and seventh-order harmonic components, and has higher accuracy. An electromagnetic induction type position sensor is provided.

  The electromagnetic induction type position sensor of the present invention receives an alternating magnetic flux that repeatedly repeats the intensity at a wavelength λ in the relative movement direction of the position detection object, and generates an electromagnetic induction voltage that changes with the relative movement of the position detection object. An electromagnetic induction type position sensor including a coil for outputting, wherein the coil is configured by connecting an even number of conductor patterns having the same shape and a wavelength λ in series, and the even number of conductor patterns are the even number of conductor patterns. When the conductor pattern is equally divided into two sets, the phase difference between the first set and the second set of conductor patterns is λ / 6, λ / 10, or λ / 14. Features.

  Another electromagnetic induction type position sensor according to the present invention receives an alternating magnetic flux that repeats strong and weak at a wavelength λ in the relative movement direction of the position detection object, and changes in accordance with the relative movement of the position detection object. An electromagnetic induction type position sensor including a coil for outputting an induced voltage, wherein the coil is configured by connecting conductor patterns having the same shape and multiples of 4 of a wavelength λ in series, and multiples of the 4 conductors In the pattern, when the multiple conductor patterns of 4 are equally divided into four sets, the phase difference between the first set and the second set of conductor patterns and the phase difference between the third set and the fourth set of conductor patterns are λ / 10 and is characterized in that the phase difference between the first set and the third set and the phase difference between the second set and the fourth set of conductor patterns are arranged at positions where λ / 6. In this case, it is desirable that the four sets of conductor patterns from the first set to the fourth set are arranged side by side in a direction orthogonal to the relative movement direction.

  In the electromagnetic induction type position sensor of the present invention, the phase of the sinusoidal conductor pattern is shifted by λ / 6, λ / 10, or λ / 14, and the third, fifth, and seventh orders of the signal by connecting them in series. Therefore, it is possible to obtain a substantially sinusoidal signal amplitude change with high accuracy with respect to the displacement of the position. As a result, an error included in the position obtained by the division calculation can be reduced, and a highly accurate position sensor can be realized. In addition, by arranging the positions shifted in the vertical direction with respect to the moving direction, sinusoidal conductor patterns per unit area can be arranged with high density, and the electromotive voltage due to the electromagnetic induction voltage can be increased.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of an electromagnetic induction type position sensor. FIG. 2 is a diagram showing a coil shape of the sensor substrate 8 of FIG. FIG. 3 is a block diagram showing an example of a signal processing circuit for processing a signal from the electromagnetic induction type position sensor of FIG.

  The scale 2 is made of an iron material or the like that is a cylindrical soft magnetic material, and is fixed to the rotating shaft 1. In addition, the scale 2 has 36 concavo-convex portions of a gear-like shape with a substantially λ pitch on the outer peripheral portion thereof. The electromagnet 5 around which the coil 4 is wound is made of a soft magnetic material having a high frequency characteristic such as ferrite. The coil 4 is shaped into a sine wave excitation signal VEX via a waveform shaping circuit 36 based on the excitation pulse signal EX generated by the timer 38 shown in FIG. Further, the sine wave excitation signal VEX is input to the current amplifier 32. The current amplifier 32 amplifies the sine wave excitation signal VEX and passes a sine wave AC excitation current I · SIN (ωt) to the coil 4. As a result, the electromagnet 5 generates an alternating magnetic flux toward the uneven surface of the scale 2. At this time, in the vicinity of the surface of the scale 2, an alternating magnetic flux that repeats strength with a pitch of a wavelength λ is generated in the rotation direction of the scale 2 in accordance with the reluctance change due to the unevenness of the surface. That is, the electromagnet 5 and the scale 2 function as AC magnetic flux generating means for generating AC magnetic flux that repeats the intensity of the wavelength λ in the moving direction of the position detection target (rotating shaft 1).

  The sensor substrate 8 is disposed so as to be sandwiched between the electromagnet 5 and the outer peripheral surface of the scale 2, and is fixed to the electromagnet 5 side with a certain gap from the scale 2. The sensor substrate 8 is made of a printed circuit board having a two-layer structure, and a first-layer conductor pattern and a second-layer conductor pattern (illustrated by broken lines in FIG. 2), which are surface layers, are interposed via a sheet-like insulating material. Two types of coils, that is, a coil 6 and a coil 7 are formed by connecting these conductor patterns between layers.

  The coil 6 is composed of eight conductor patterns (11, 12, 13, 14, 21, 22, 23, 24, and the like) illustrated in the upper half in FIG. 2, and the coil 7 is illustrated in the lower half in FIG. 8 conductor patterns (15, 16, 17, 18, 25, 26, 27, 28).

  Each conductor pattern has a sine wave shape. Further, the sinusoidal conductor patterns formed at the same position on the first layer and the second layer have shapes of opposite phases. In other words, the first and second layers of the sensor substrate 8 are paired sinusoidal conductor patterns (11 and 21, 12 and 22, 13 and 23, 14 and 24, 15 and 25, 16 in opposite phases to each other. 26, 17 and 27, 18 and 28) are arranged.

  The eight sets of conductor patterns formed on the sensor substrate 8 are arranged at a predetermined interval in a direction orthogonal to the moving direction of the scale 2. A pair of sinusoidal conductor patterns having opposite phases are connected to each other on the left side of the substrate in the case of the coil 6 and on the right side of the substrate in the case of the coil 7 by a conductor pattern other than the sinusoidal shape and interlayer connection. A pattern is formed.

  Next, connection of four sets of conductor patterns constituting one coil will be described. The coil 6 is configured by connecting four sets of conductor patterns (11 and 21, 12 and 22, 13 and 23, and 14 and 24) formed on the upper half of the sensor substrate 8. That is, the first set of conductor patterns composed of the conductor patterns 11 and 21 is connected to the conductor patterns 21 and 12 on the right side of the substrate, and is connected in series to the second set of conductor patterns. Further, the second set of conductor patterns is connected to the conductor patterns 22 and 13 and is connected in series to the third set of conductor patterns. Further, the third set of conductor patterns is connected to the conductor patterns 23 and 14 and is connected to the fourth set of conductor patterns. As described above, four sets of sinusoidal conductor patterns formed on the upper half of the sensor substrate 8 are connected in series to form the coil 6.

  The coil 7 is configured by connecting four sets of conductor patterns (15 and 25, 16 and 26, 17 and 27, and 18 and 28) formed in the lower half of the sensor substrate 8. That is, as in the case of the coil 6, the coil 7 is formed by connecting four sets of sinusoidal conductor patterns of the conductor patterns 15 and 25, 16 and 26, 17 and 27, and 18 and 28 in series on the left side of the substrate. Composed.

  Here, the sinusoidal conductor patterns 11 and 12, 13 and 14, 15 and 16, and 17 and 18 are sinusoidal conductor patterns having phases different from each other by λ / 10. The sinusoidal conductor patterns 11 and 13, 12 and 14, 15 and 17, and 16 and 18 are sinusoidal conductor patterns having phases different from each other by λ / 6. In other words, each sinusoidal conductor pattern has one other sinusoidal conductor pattern having a phase difference of λ / 10 and another sinusoidal conductor pattern having a phase difference of λ / 6. For example, in the case of the sine wave conductor pattern 11, the sine wave conductor pattern 12 is another sine wave conductor pattern having a phase difference of λ / 10, and the sine wave conductor is another sine wave conductor pattern having a phase difference of λ / 6. Each pattern 13 exists. In the case of the sine wave conductor pattern 12, the sine wave conductor pattern 11 is another sine wave conductor pattern having a phase difference of λ / 10, and the sine wave conductor is another sine wave conductor pattern having a phase difference of λ / 6. Each pattern 14 exists.

  The directions of the currents flowing through the four sine wave conductor patterns 11, 12, 13, and 14 in the first layer of the coil 6 all flow in the same direction, and the four sine wave conductor patterns 21, 22, and 23 in the second layer. , 24 are all in the same direction, and a current that is opposite to the pair of sinusoidal conductor patterns (11, 12, 13, 14) flows. The coil 7 is also set in the same current direction. As a result, an output signal corresponding to the rotational position of the scale can be obtained from the coils 65 and 66.

  Next, the principle of removing the third harmonic by shifting the phase of the sinusoidal conductor pattern by λ / 6 will be described. The third harmonic is a signal component having three periods in the electromagnetically induced signal λ, in other words, a signal component having λ / 3 as one period, and its phase is determined by the conductor pattern. For this reason, the third harmonic signal generated by electromagnetic induction in the reference conductor pattern and the third harmonic signal generated in the conductor pattern in which the phase of the conductor pattern is shifted by λ / 6 are a signal whose phase is shifted by λ / 6. Become. Here, since one cycle of the third harmonic is λ / 3, the fact that the phase of the third harmonic is shifted by λ / 6 means that the phase is opposite. That is, the third harmonic signal generated in the reference conductor pattern and the third harmonic signal generated in the conductor pattern whose phase is shifted by λ / 6 have the same amplitude and opposite phase signal components. In addition, by connecting the reference conductor pattern and the conductor pattern whose phase is shifted by λ / 6 in series, the electromagnetically induced signals are added, so that the third harmonic signal component is canceled.

  Similarly, the fifth harmonic is a signal component having λ / 5 as one cycle. Therefore, the fifth-order harmonic signal generated by electromagnetic induction in the reference conductor pattern and the fifth-order harmonic generated in the conductor pattern in which the phase of the conductor pattern is shifted by λ / 10 are opposite in phase to each other by λ / 10. Signal. The reference conductor pattern and the conductor pattern whose phase is shifted by λ / 10 are connected in series, and electromagnetically induced signals are added, so that the signal component of the fifth harmonic is canceled.

  As described above, according to the inductive position sensor of the present embodiment, a sine wave closer to ideal can be obtained by removing the third and fifth harmonics, and the position calculated by dividing this signal is calculated. The interpolation error can be improved to about 3 when dividing 10,000, and a highly accurate electromagnetic induction type position sensor can be realized. Each sinusoidal conductor pattern can be arranged at a higher density in the direction orthogonal to the scale movement direction by shifting the phase shown in this embodiment, and the electromotive voltage due to the electromagnetic induction voltage per unit area is increased. can do.

  In the above-described embodiment, the arrangement pattern of the conductor pattern for canceling the third harmonic and the fifth harmonic is described. However, it is not always necessary to cancel both the third and fifth harmonic components. A pattern arrangement that cancels only one of the harmonic components may be adopted. Conversely, in addition to the third and fifth harmonics, the pattern arrangement may be such that the seventh harmonic is canceled. In the case of canceling the seventh harmonic, the patterns may be arranged so that each sinusoidal conductor pattern has another sinusoidal conductor pattern having a phase difference λ / 14.

  Specifically, one set of coils is formed with eight sets of sinusoidal conductor patterns, and the first set and the second set, the third set and the fourth set, the fifth set and the sixth set, the seventh set and the eighth set. The eyes are arranged with a phase shift of λ / 14 from each other. The first group, the third group, the second group, the fourth group, the fifth group, the seventh group, the sixth group, and the eighth group are arranged with phases shifted by λ / 10. Further, the first group, the fifth group, the second group, the sixth group, the third group, the seventh group, the fourth group, and the eighth group are arranged with a phase shift of λ / 6. Thereby, the third, fifth and seventh harmonics can be removed. However, since the 7th harmonic component itself has a signal level that is a fraction of that of the 3rd and 5th order and has little influence on the error, the pattern arrangement is such that the 7th harmonic is not necessarily canceled. It does not have to be.

  In the above description, the phase is limited to be shifted by λ / 10 and λ / 6. However, even if the phase is slightly changed, substantially the same effect can be obtained with a slightly inferior performance. Therefore, numerical values such as λ / 10 and λ / 6 do not indicate mathematically strict values, but may include errors that can greatly cancel harmonic components.

  In the above-described embodiment, the first to fourth sets of phase differences are set to λ / 10 for the first set, the second set, the third set, and the fourth set. The second set and the fourth set are set to λ / 6, but the first set, the second set, the third set, and the fourth set are set to λ / 6, and the first set, the third set, the second set, and the fourth set are set. The same effect can be obtained even if the eye is λ / 10.

It is a perspective view showing an embodiment of an electromagnetic induction type position sensor. It is a figure which shows the coil shape of the electromagnetic induction type position sensor of FIG. It is a block diagram which shows an example of the electromagnetic induction type position sensor signal processing circuit of FIG. It is a figure which shows the coil of the conventional electromagnetic induction type position sensor.

Explanation of symbols

  1 rotation axis, 2 scale, 4, 6, 7, 65, 66 coil, 5 electromagnet, 8, 60 sensor board, 30, 31 differential amplifier, 32 current amplifier, 34, 35 AD converter, 36 waveform shaping circuit, 37 microprocessor, 38 timer.

Claims (5)

An electromagnetic induction type position provided with a coil that receives an alternating magnetic flux that repeatedly repeats the intensity at a wavelength λ in the relative movement direction of the position detection object and outputs an electromagnetic induction voltage that changes with the relative movement of the position detection object. A sensor,
The coil is configured by connecting an even number of conductor patterns of the same shape and wavelength λ in series,
The even-numbered conductor patterns are arranged at positions where the phase difference between the first and second sets of conductor patterns is λ / 6 when the even-numbered conductor patterns are equally divided into two sets. An electromagnetic induction type position sensor. An electromagnetic induction type position provided with a coil that receives an alternating magnetic flux that repeatedly repeats the intensity at a wavelength λ in the relative movement direction of the position detection object and outputs an electromagnetic induction voltage that changes with the relative movement of the position detection object. A sensor,
The coil is configured by connecting an even number of conductor patterns of the same shape and wavelength λ in series,
The even-numbered conductor patterns are arranged at positions where the phase difference between the first and second sets of conductor patterns is λ / 10 when the even-numbered conductor patterns are equally divided into two sets. An electromagnetic induction type position sensor. An electromagnetic induction type position provided with a coil that receives an alternating magnetic flux that repeatedly repeats the intensity at a wavelength λ in the relative movement direction of the position detection object and outputs an electromagnetic induction voltage that changes with the relative movement of the position detection object. A sensor,
The coil is configured by connecting an even number of conductor patterns of the same shape and wavelength λ in series,
The even-numbered conductor patterns are arranged at positions where the phase difference between the first and second sets of conductor patterns is λ / 14 when the even-numbered conductor patterns are equally divided into two sets. An electromagnetic induction type position sensor. An electromagnetic induction type position provided with a coil that receives an alternating magnetic flux that repeatedly repeats the intensity at a wavelength λ in the relative movement direction of the position detection object and outputs an electromagnetic induction voltage that changes with the relative movement of the position detection object. A sensor,
The coil is configured by connecting conductor patterns of the same shape and multiples of 4 of the wavelength λ in series,
When the multiple of 4 conductor patterns are obtained by equally dividing the multiple of 4 conductor patterns into four sets, the phase difference between the first and second sets of conductor patterns and the third and fourth sets of conductor patterns are obtained. The phase difference of the pattern is λ / 10, and the phase difference between the first set and the third set and the phase difference between the second set and the fourth set of conductor patterns are arranged at positions where the phase difference is λ / 6. Electromagnetic induction type position sensor. The electromagnetic induction type position sensor according to claim 4,
The electromagnetic induction type position sensor, wherein the four sets of conductor patterns from the first set to the fourth set are arranged side by side in a direction orthogonal to the relative movement direction.

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