JP2001141410A - Position detecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a detecting apparatus which is capable of detection with high resolution in the case of fine displacement. SOLUTION: A coil part 10 is constituted by arranging a plurality of coil sections LA-LD in order in the direction of displacement which coils are excited in phase. Relative position of a magnetic response member 11 composed of magnetic substance or conductor to the coil part changes in accordance with a detection objective position. Inductance of the coil sections changes corresponding to the relative position. When one end portion 11a of the member 11 moves from one end of a coil section to the other end, a voltage between both ends of the coil section increases or decreases gradually. Analog operation circuits 20, 21 add and/or subtract voltages led out from each coil section, thereby forming two AC output signals showing amplitudes of sine and cosine function characteristics corresponding to the detection objective position. From correlation of amplitude values in the AC output signals, a specified phase value θin the sine and cosine functions regulating the amplitude values is detected, thereby forming position detecting data of an object to be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device including a coil which is excited by an alternating current and a magnetic or conductive material which is displaced relative to the coil, and relates to a linear position within a predetermined range. Or, it is suitable for detecting a rotational position, and in particular, generates an output AC signal showing an amplitude function characteristic of a plurality of phases according to a detection target position using only a primary coil excited by a one-phase AC. About things.

[0002]

2. Description of the Related Art An inductive linear position detector called an LVDT is known. The two-wire type LVDT includes one primary coil and one secondary coil, and the inductive coupling between the primary and secondary coils changes according to the amount of penetration of the movable portion made of a magnetic material into the coil portion. Then, an induced output signal having a voltage level corresponding to the voltage is generated in the secondary coil. 3-wire type L
The VDT has a differential transformer configuration composed of one primary coil and two secondary coils connected in anti-phase series. In this case, a movable portion made of a magnetic material having a predetermined length has a negative-phase secondary. The inductive coupling between the primary and secondary coils changes in a balanced manner according to the amount of penetration into either of the coils, and an induced output signal of a voltage level corresponding to the inductive coupling is generated in the secondary coil. This LVDT
The output signal of the sine characteristic and the output signal of the cosine characteristic according to the position of the movable portion are generated by performing an operation of adding or subtracting the secondary output signal of RD output signal with cosine characteristic
The data is processed by the converter to generate digital data in which the position of the movable part is detected. As another type of position detector, only an excitation coil is provided, and a change in its self-inductance according to the displacement of the movable magnetic core is detected by measuring a phase shift amount by an RL circuit. Things are also known.

[0003]

A conventionally known LVDT
However, since a primary coil and a secondary coil are required, the number of parts is increased, and there is a limit in reducing the manufacturing cost. In addition, there is a limit to downsizing. Further, the usable phase angle range in the output signal of the sine characteristic and the cosine characteristic according to the position of the movable part is a two-wire type LV.
About 45 degrees for DT, 90 for 3-wire LVDT
It is relatively narrow, on the order of degrees, and it has been difficult to expand the detectable phase angle range. Also, in the three-wire type LVDT, there is a problem that the usability is poor in application because the position where the movable part is displaced to the left and right can be detected based on the state where the movable part is located at the center of the coil part. . Further, the detection resolution for the minute displacement of the detection target was poor. On the other hand, with a position detector that measures the self-inductance of the excitation coil, the number of coils can be reduced, but the phase shift amount corresponding to the displacement of the detection target can be obtained only in a narrow range. The measurement of the amount was difficult, and the detection resolution was poor, making it unsuitable for practical use. Further, when the impedance of the coil changes accompanying the change in the ambient temperature, the amount of phase shift also changes, so that the temperature characteristics cannot be compensated.

The present invention has been made in view of the above points, and has a small and simple structure, a wide range of usable phase angles, and a high resolution even when the displacement of a detection target is minute. It is an object of the present invention to provide a position detecting device capable of detecting the temperature characteristic and easily compensating the temperature characteristic.

[0005]

A position detecting device according to the present invention is provided with a coil portion having a plurality of coils excited by an AC signal, and a coil portion arranged to be displaced relative to the coil portion. The relative position between the member and the coil portion changes according to the displacement of the detection target, and the impedance of each coil changes according to the relative position. The voltage generated in each coil changes while the relative position changes over a predetermined range, and the voltage generated in each coil changes in a specific manner for each coil corresponding to the change in the detection target position. At least one having a predetermined periodic function characteristic as an amplitude coefficient is obtained by taking out a pattern indicating and a voltage generated in each of the coils and performing an operation by combining them. Those equipped with an analog operation circuit that generates an AC output signal.

[0006] The magnetic response member typically comprises at least one of a magnetic substance and a conductor. When the magnetic response member is made of a magnetic material, as the degree of proximity of the member to the coil increases, the self-inductance of the coil increases, the electrical impedance of the coil increases, and the voltage generated in the coil, that is, The terminal voltage (or voltage drop) increases. Conversely, as the degree of proximity of the magnetically responsive member to the coil decreases, the inductance of the coil decreases, the electrical impedance of the coil decreases, and the voltage generated at the coil, that is, the voltage between terminals, decreases. I do. Thus, the voltage generated in the coil while the relative position of the magnetic responsive member with respect to the coil changes over a predetermined range with the displacement of the detection target,
That is, the terminal voltage increases or decreases.

For example, typically, while the relative position of the magnetically responsive member with respect to the coil changes over a predetermined range, the voltage between terminals of the coil shows a gradually increasing curve from 0 to 90 degrees in a sine function. Can be compared to a function value change in the range of A plurality of coils are provided, and as the position of the magnetic response member with respect to each of these coils is relatively displaced in accordance with the displacement of the detection target,
The gradual (or gradual) change in the terminal voltage of each coil occurs in different ways. For example, if the output voltage of a certain coil shows a gradually increasing curve characteristic in a certain predetermined section and the output voltage of another coil shows a gradually increasing curve characteristic in another predetermined section that follows, the output of the first coil When the combination operation is performed so that the output voltage of the second coil is subtracted from the voltage, it is possible to obtain a function characteristic in the range of 0 to 180 degrees in the sine function, in which the amplitude voltage gradually increases and then gradually decreases. . In such a combination calculation of the output voltages of the respective coils, temperature drift compensation can be automatically performed by the offset effect of the subtraction calculation, so that accurate position detection can be realized with a simple configuration. .

In this manner, the gradually increasing (or gradually decreasing) change in the voltage (terminal voltage) generated in each coil is regarded as a change in a partial phase range of a predetermined periodic function, and these are appropriately combined to calculate (addition and / or addition). Or subtraction), it is possible to generate a plurality of AC output signals each showing an amplitude according to a predetermined cycle wg function characteristic according to the position to be detected. That is, by taking out the voltage between both ends of each coil section, adding and / or subtracting them, and combining them, one or more AC outputs having an amplitude coefficient according to a predetermined periodic function characteristic according to the position to be detected are obtained. A signal can be generated. The multiple AC output signals generated are
It is preferable that the periodic function characteristic defining the amplitude of each AC output signal is shifted by a predetermined phase. Then, for example, like a resolver, an AC output signal having an amplitude coefficient according to a sine function characteristic and an AC output signal having an amplitude coefficient according to a cosine function characteristic can be generated according to a detection target position.

A position detecting device according to the present invention comprises: a coil section in which a plurality of coil sections excited by a predetermined AC signal are sequentially arranged along a displacement direction of an object to be detected; A magnetic responsive member arranged so as to be displaced in a relative position between the member and the coil portion in accordance with a position to be detected, and changing an inductance of each coil section in accordance with the relative position. The voltage generated in the coil section gradually increases or decreases while the member is displaced from one end to the other end of one coil section, and the voltage of each coil section is taken out,
An analog arithmetic circuit for generating at least one AC output signal having an amplitude according to a predetermined periodic function characteristic in accordance with the position to be detected and performing an arithmetic operation by combining them.

Also in this case, as described above, when the magnetic responsive member is made of a magnetic material, the self-inductance of the coil section increases as the degree of approach or penetration of the coil section with respect to each coil section increases. The end of the member is 1
During the displacement from one end to the other end of one coil section, the voltage (that is, the voltage between both ends or the voltage between terminals) generated in the coil section gradually increases. Since the plurality of coil sections are sequentially arranged along the direction of displacement of the detection target, the position of the magnetic responsive member with respect to each of these coil sections is relatively displaced in accordance with the displacement of the detection target. Gradually (or gradually) changes in the voltage between both ends in turn occur. Therefore, the voltage between the coil terminals gradually increases (or gradually decreases).
By using the change as a change in a partial phase range of a predetermined periodic function and using them in combination, a plurality of AC output signals each representing an amplitude according to a predetermined periodic function characteristic according to the position to be detected are generated. be able to. That is, by taking out the voltages between both ends of each coil section, adding and / or subtracting the voltages and combining them, a plurality of AC output signals each showing an amplitude according to a predetermined periodic function characteristic according to the position to be detected are generated. can do.

For example, typically, a gradually increasing curve of the voltage between both ends of a coil section generated while the end of the magnetic response member is displaced from one end to the other end of one coil section is, for example, a zero curve in a sine function. It can be compared to a function value change in the range from degrees to 90 degrees. Further, this gradually increasing curve can be converted into a gradually decreasing curve which gradually decreases from the predetermined level by inverting the amplitude of the curve negatively and performing a voltage shift for adding a predetermined level (offset level). Such a gradual change curve can be compared to, for example, a function value change in a range from 90 degrees to 180 degrees in the sine function. Thus, 4 arranged in order
In the two coil sections, the gradually increasing change in the voltage between both ends of the coil section is changed by a proper addition and / or subtraction as necessary, so that a function value change in the range of 0 to 90 degrees in the sine function is performed. , A function value change in a range from 90 degrees to 180 degrees, a function value change in a range from 180 degrees to 270 degrees, and a function value change in a range from 270 degrees to 360 degrees. The inclination direction of the curve and the offset level of the voltage shift in each range can be appropriately controlled by appropriate analog calculation. Thus, it is possible to generate a first AC output signal indicating an amplitude according to a sine function characteristic according to the position to be detected.
It is also possible to generate a second AC output signal indicating an amplitude according to a periodic function having the same characteristic, that is, a cosine function having a phase shift.

Thus, as a preferred embodiment,
It is possible to generate two AC output signals each showing an amplitude according to the sine and cosine function characteristics according to the position to be detected. For example, if the position to be detected is represented by an angle θ, an AC output signal having an amplitude showing a sine function characteristic can be generally expressed by sin θ sinωt, and an AC output signal having an amplitude showing a cosine function characteristic. Can be represented by cos θ sin ωt. This is similar to the form of an output signal of a position detector called a resolver, and is extremely useful. For example, the 2 generated by the analog arithmetic circuit
The two AC output signals are input, the phase value in the sine and cosine functions that defines the amplitude value is detected from the correlation between the amplitude values in the two AC output signals, and the position of the detection target is detected based on the detected phase value. It is preferable to include an amplitude / phase converter that generates detection data.

When a good conductor such as copper is used as the magnetic response member, the self-inductance of the coil decreases due to eddy current loss, and the end of the magnetic response member moves from one end of one coil section to the other end. During the displacement to the end, the voltage across the coil section will gradually decrease. Again,
Detection can be performed in the same manner as described above. As the magnetic response member, a hybrid type in which a magnetic body and a conductor are combined may be used. As another embodiment, a permanent magnet may be included as the magnetic response member, and the coil unit may include a magnetic core. In this case, the corresponding portion of the magnetic core on the side of the coil portion corresponding to the approach of the permanent magnet becomes magnetically saturated or supersaturated, and the magnetically responsive member, that is, the permanent magnet is displaced from one end to the other end of one coil section. The voltage between both ends of the coil section gradually decreases.

Thus, according to the present invention, only the primary coil needs to be provided, and the secondary coil is not required. Therefore, it is possible to provide a position detecting device having a small and simple structure. Further, a plurality of coils are sequentially arranged along the displacement direction of the detection target, and the voltage between both ends of the coil section gradually increases while the end of the magnetic response member is displaced from one end to the other end of one coil section. Since the characteristic change (or gradual decrease) occurs sequentially between the coils, the voltages of the coil sections are respectively taken out and added and / or subtracted and combined to obtain a predetermined value according to the position to be detected. A plurality of AC output signals each representing an amplitude according to a periodic function characteristic (for example, two AC output signals each representing an amplitude according to a sine and cosine function characteristic) can be easily generated, and a wide usable phase angle range can be obtained. Can be.
For example, as described above, detection can be performed in a full phase angle range from 0 degrees to 360 degrees. Since output voltages of a plurality of coil sections exhibiting the same temperature characteristic are added or subtracted and combined to generate a plurality of AC output signals each exhibiting an amplitude according to a predetermined periodic function characteristic, the temperature characteristic is automatically compensated. As a result, it is possible to easily perform the position detection excluding the influence of the temperature change. Further, by detecting a phase value in a predetermined periodic function (for example, a sine and cosine function) that defines the amplitude value from the correlation between the amplitude values of the plurality of AC output signals, even if the displacement of the detection target is minute, high resolution is obtained. Can be detected.

According to another aspect of the present invention, the apparatus further comprises means for generating a predetermined reference voltage, wherein the analog operation circuit performs an operation by combining the voltage from each coil or each coil section with the reference voltage. You may do so.
When the number of coils or coil sections is small, there is only a small change curve of the voltage between both ends of the coil section during the displacement of the end of the magnetic response member from one end of the coil section to the other end. Not generated. Therefore, a plurality of AC output signals each showing an amplitude according to a predetermined periodic function characteristic according to the detection target position by performing a calculation by combining the separately generated reference voltage and the output voltage of each coil,
Typically, two AC output signals each representing an amplitude according to the sine and cosine function characteristics according to the detection target position can be generated. As a means for generating the reference voltage, a dummy impedance element having an arbitrary configuration may be used. For example, it may be a resistance element or an inductance means such as a coil.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows an embodiment in which an amplitude change in a full range of electrical angles from 0 to 360 degrees can be obtained in two AC output signals each having an amplitude indicating a sine and a cosine function characteristic. FIG. 1A shows an example of a physical arrangement relationship between a coil unit 10 and a magnetic response member 11 in a position detecting device according to this embodiment by a schematic external view, and FIG. The schematic diagram (C) shows the coil unit 1.
It is a figure which shows an example of an electric circuit of 0. The position detecting device shown in FIG. 1 detects a linear position to be detected.
For example, the coil unit 10 is relatively fixed, and the magnetic response member 11 relatively linearly displaces according to the displacement of the detection target. Conversely, the magnetic response member 11 may be relatively fixed, and the coil unit 10 may be relatively displaced in accordance with the displacement of the detection target. The coil unit 10 includes a plurality of coil sections (six coil sections Lα, LA, LB, and L in the illustrated example) that are excited by a predetermined one-phase AC signal.
C, LD, and Lβ) are sequentially arranged along the displacement direction of the detection target. For example, each coil section Lα, LA, L
B, LC, LD, and Lβ are assumed to have the same properties such as the number of turns and the coil length. The magnetic response member 11 is made of a magnetic material such as a bar-shaped iron, for example, and enters the coil space of the coil unit 10. As an example, the magnetic response member 1
When 1 advances, the tip 11a of the magnetic response member 11
First, the coil section Lα is entered, and then the coil section L
A, LB, LC, and LD enter in this order, and finally enter the coil section Lβ. A two-dot chain line 11 ′ indicates the magnetic response member 11 that has penetrated to the last coil section Lβ.

The four middle coil sections LA, LB, L
The range corresponding to C and LD is the effective detection range. Assuming that the length of one coil section is K, a length 4K that is four times the length is the effective detection range. The coil sections Lα and Lβ provided one before and after the effective detection range are auxiliary coils. The auxiliary coils Lα and Lβ are provided so that the cosine function characteristic can be obtained faithfully, and can be omitted if accuracy is not so much pursued.

As shown in FIG. 1C, each coil section L
α, LA, LB, LC, LD, and Lβ are excited with a constant voltage or constant current by a predetermined one-phase AC signal (tentatively indicated by sinωt) generated from the AC power supply 12. When voltages between both ends of each coil section Lα, LA, LB, LC, LD, Lβ are indicated by Vα, VA, VB, VC, VD, Vβ, respectively, these voltages Vα, VA, VB, VC, V
Terminals 13 to 19 are provided for extracting D and Vβ. As can be easily understood, each coil section Lα,
LA, LB, LC, LD, and Lβ need not be separate coils that are physically separated, and only terminals 13 to 19 need to be provided at positions that divide the total length of a series of coils into six. That is, the coil portion between the terminals 13 and 14 is a coil section Lα, the coil section between the terminals 14 and 15 is the coil section LA, the coil section between the terminals 15 and 16 is the coil section LB, and the coil section between the terminals 16 and 17. Is the coil section L
C, a coil portion between terminals 17 and 18 is a coil section LD,
A coil portion between the terminals 18 and 19 becomes a coil section Lβ. The output voltages Vα, VA, VB, VC,
VD and Vβ are input to analog arithmetic circuits 20 and 21 in a predetermined combination, and are added or subtracted according to a predetermined arithmetic expression, so that sine and cosine functions corresponding to the detection target position from each analog arithmetic circuit 20 and 21 are obtained. Two AC output signals each having an amplitude indicating the characteristic (that is, two AC output signals having amplitude function characteristics shifted by 90 degrees from each other) are generated. Exemplarily, the analog operation circuit 2
The output signal of 0 is represented by sinθsinωt, and the output signal of the analog operation circuit 21 is represented by cosθsinωt. The analog operation circuits 20 and 21 include operational amplifiers OP1 and OP
It is configured to include P2 and resistance circuit groups RS1 and RS2.

Of course, not limited to the above, each coil section Lα,
Physically separate coils are used as LA to LD and Lβ, which are connected in series and are collectively excited by a predetermined one-phase AC signal, or by separate predetermined excitation signals by a predetermined one-phase AC signal. In-phase excitation may be used. However, the simplest embodiment in which one coil as described above is used at a plurality of intermediate positions corresponding to a plurality of required coil sections is used. Hereinafter, each coil section Lα, LA to LD, Lβ is simply referred to as “coil”.

With the above configuration, the self-inductance of the coil increases as the degree of approach or penetration of the magnetic response member 11 with respect to each coil increases, and the end of the member is displaced from one end of one coil to the other end. The voltage between both ends of the coil gradually increases. A plurality of coils Lα, LA, LB,
Since the LC, LD, and Lβ are sequentially arranged along the displacement direction of the detection target, as the position of the magnetic responsive member with respect to these coils is relatively displaced in accordance with the displacement of the detection target, FIG. ), The voltages Vα, VA, VB, VC, VD, and Vβ between both ends of each coil gradually change. In FIG. 2A, in a section where the output voltage of a certain coil is inclined, the end of the magnetic response member 11 is displaced from one end of the coil to the other end. Typically, while the end of the magnetically responsive member 11 is displaced from one end of one coil to the other end, a gradually increasing curve of the voltage across the coil has a range of 90 degrees in a sine or cosine function. Can be compared to the function value change of Therefore, by adding and / or subtracting the output voltages Vα, VA, VB, VC, VD, and Vβ of each coil in an appropriate combination,
Two AC output signals sinθsi each having an amplitude indicating a sine and cosine function characteristic according to the position to be detected
nωt and cosθsinωt can be generated.

That is, in the analog arithmetic circuit 20, the output voltages VA, VB, V of the coils LA, LB, LC, LD are output.
By calculating C and VD as in the following equation (1), FIG.
An AC output signal showing an amplitude curve of a sine function characteristic as shown in (B) can be obtained, which is equivalent to "s
in θ sinωt ”. (VA−VB) + (VD−VC) Equation (1)

In the analog arithmetic circuit 21, the output voltages Vα, Vα of the coils Lα, LA, LB, LC, LD, Lβ
By calculating VA, VB, VC, VD, and Vβ as in the following equation (2), an AC output signal showing an amplitude curve of a cosine function characteristic as shown in FIG. 2B can be obtained. It should be noted that the amplitude curve of the cosine function characteristic shown in FIG.
cos θ sin ωt ”, which corresponds to a cosine function characteristic because it shows a deviation of 90 degrees from the sine function characteristic. Therefore, this is called an AC output signal having a cosine function characteristic, and hereinafter, equivalently, “cos θs
inωt ”. (VA−Vα) + (VB−VC) + (Vβ−VD) Expression (2) Instead of the operation of the expression (2), the operation of the following expression (2 ′) may be performed. (VA−Vα) + (VB−VC) −VD Equation (2 ′)

The AC output signal "-cos θ sin ωt" having the negative cosine function characteristic obtained by the equation (2) is electrically subjected to 180-degree phase inversion processing, whereby c
A signal represented by osθsinωt may be generated and used as an AC output signal having a cosine function characteristic. However, in the subsequent phase detection circuit (amplitude / phase conversion circuit) 22, for example, the AC output signal having the cosine function characteristic is converted into “−cos θs
inωt ”, the AC output signal“ −cos θ ”having a negative cosine function characteristic is used.
sin ωt ”. Equation (2)
By performing the operation of the following equation (2 ″) instead of the operation of
Actually, the AC output signal “cosθsi
nωt ”can be generated. (Vα−VA) + (VC−VB) + (VD−Vβ) Equation (2 ″)

The phase angle θ in the sine and cosine functions, which is the amplitude component of each AC output signal, corresponds to the position to be detected. Yes, it is. Accordingly, the effective detection range having a length of 4K corresponds to the range of 0 to 360 degrees of the phase angle θ. Therefore, by detecting the phase angle θ, the detection target position in the range of the length of 4K can be absolutely detected.

Here, the compensation of the temperature characteristic will be described. The impedance of each coil changes according to the temperature.
The output voltages Vα, VA, VB, VC, VD, and Vβ also fluctuate. For example, each voltage increases or decreases in one direction as shown by a broken line with respect to a solid curve in FIG. However, the AC output signals sinθsinωt and co
In FIG. 2B, sθ sinωt appears as a change in amplitude in both positive and negative directions as indicated by a broken line with respect to a solid curve. If this is shown using the amplitude coefficient A, Asin θ
sin ωt and Acos θ sin ωt, and the amplitude coefficient A changes according to the ambient temperature, and this change appears in the two AC output signals in the same manner. As is clear from this, the amplitude coefficient A indicating the temperature characteristic does not affect the phase angle θ in the respective sine and cosine functions. Therefore, in this embodiment, the temperature characteristics are automatically compensated, and accurate position detection can be expected.

The phase detection circuit (or amplitude phase conversion means) 22 measures the phase components θ of the amplitude functions sin θ and cos θ in the AC output signals sin θ sin ωt and cos θ sin ωt having sine and cosine function characteristics, so that the position to be detected is absolute. Can be detected. The phase detection circuit 22 may be configured using, for example, a technique disclosed in Japanese Patent Application Laid-Open No. 9-126809 filed by the present applicant. For example, the first AC output signal sinθsinωt is electrically shifted by 90 degrees to generate the AC signal sinθcosωt, and the second AC output signal cosθsinωt is added / subtracted and combined to obtain sin (ωt + θ) and sin (ωt + θ). ωt-
θ), two AC signals (signals obtained by converting the phase component θ into an AC phase shift) that are phase-shifted in the leading and lagging directions according to θ, and measuring the phase θ,
Stroke position detection data can be obtained. Alternatively, R used to process the known resolver output
A -D converter may be used as the phase detection circuit 22.

As shown in FIG. 2B, an AC output signal sinθsinωt having sine and cosine function characteristics is provided.
And the amplitude characteristic at cos θ sinωt does not show true sine and cosine function characteristics, assuming that the correspondence between the angle θ and the detection target position x has linearity.
However, the phase detection circuit 22 apparently performs the phase detection processing on the AC output signals sinθsinωt and cosθsinωt as those having amplitude characteristics of sine and cosine functions, respectively. As a result, the detected phase angle θ
Does not show linearity with respect to the detection target position x. However, in the position detection, the non-linearity between the detection output data (the detected phase angle θ) and the actual detection target position is not a very important problem. In other words, it suffices if the position can be detected with a predetermined reproducibility. If necessary, the output data of the phase detection circuit 22 is subjected to data conversion using an appropriate data conversion table so that accurate linearity is obtained between the detected output data and the actual detection target position. Can be easily performed. Therefore, the AC output signal sin θ sin having the amplitude characteristics of the sine and cosine functions referred to in the present invention.
ωt and cosθsinωt do not have to show true sine and cosine function characteristics, but may actually be something like a triangular wave shape as shown in FIG. 2 (B). What is necessary is just to show such a tendency. That is, any periodic function similar to a trigonometric function such as a sine may be used. Note that FIG.
In the example of (B), changing the viewpoint, the scale on the horizontal axis is assumed to be θ and the scale is formed of a required non-linear scale. If the scale on the horizontal axis is assumed to be x, the scale is apparent. Even if it looks like an upper triangular wave, it can be said that θ is a sine function or a cosine function.

The change range of the phase component θ of the amplitude functions sin θ and cos θ in the AC output signals sin θ sinωt and cos θ sinωt having the sine and cosine function characteristics is limited to the change in the full range from 0 ° to 360 ° as in the above embodiment. Instead, the change may be in a narrower limited angle range. In that case, the configuration of the coil can be simplified. The effective detection range may be narrow when the purpose is to detect a minute displacement, and in such a case, the detectable phase range may be an appropriate range of less than 360 degrees. In addition, there are various cases where the detectable phase range may be an appropriate range of less than 360 degrees depending on the purpose of detection, and the present invention can be appropriately applied to such a case.
Hereinafter, these modifications will be described.

FIG. 3 shows an embodiment capable of producing a phase change in the range from 0 degrees to 180 degrees. In this case, the coil unit 10 includes two coils LA and LB corresponding to the effective detection range and auxiliary coils Lα and Lβ provided one before and after the other. In the analog operation circuit 23, the voltages Vα, VA, VB,
By inputting Vβ and calculating as in the following equation (3), for example, an AC output signal sinθsinωt showing an amplitude curve of a sine function characteristic is generated, and calculating as in the following equation (4) to obtain a cosine function characteristic. To generate an AC output signal cos θ sinωt indicating the amplitude curve of VA-VB: Equation (3) (VA-Vα) + (VB-Vβ): Equation (4)

As can be easily understood by referring to FIG. 2 described above, the AC output signal showing the amplitude curve of the sine function characteristic in the range of 0 to 180 degrees by the calculation of the equation (3). sin θ sin ωt can be generated. In addition, by the calculation of Expression (4), -90 degrees to 0 degrees to 9
AC output signal cosθsi indicating the amplitude curve of the cosine function characteristic in the range of 0 ° to 180 ° to 270 °
nωt can be generated. As described above, the auxiliary coil Lβ can be omitted. In this case, by detecting the phase angle component θ of the amplitude function, the two coils LA,
The detection target position in the range of the length corresponding to the coil length 2K of the LB can be absolutely detected. The arithmetic expression is not limited to the above, and can be set as appropriate. That is, the arithmetic expression can be appropriately changed depending on in which angle range a phase change having a width of 180 degrees is caused.
For example, to generate an effective phase change corresponding to an angle range of 180 degrees to 360 degrees, “(Vα−VA) +
(Vβ−VB) ”, an AC output signal sinθsinωt having a sine function characteristic is generated, and“ VB−V
An AC output signal cos θ sinωt having a cosine function characteristic can be generated by the arithmetic expression of “A”.

FIG. 4 shows an embodiment capable of producing a phase change in the range of 0 to 90 degrees. In this case, the coil unit 10 includes one coil LA corresponding to the effective detection range and one auxiliary coil L provided before and after the coil LA.
α, Lβ. Analog operation circuit 24
In this case, the voltage Vα, VA, Vβ between terminals of each coil is input, and the AC output signal sinθs showing the amplitude curve of the sine function characteristic is calculated by, for example, the following equation (5).
inωt is generated and calculated as in the following equation (6) to obtain an AC output signal c indicating an amplitude curve of a cosine function characteristic.
osθ sinωt is generated. VA-Vβ: Equation (5) VA-Vα: Equation (6)

This can also be easily understood by referring also to FIG.
An AC output signal sinθsinωt showing an amplitude curve of a sine function characteristic in a range of 90 degrees to 180 degrees can be generated. Also, by the calculation of the expression (6), −
AC output signal cos θ sin ω indicating the amplitude curve of the cosine function characteristic in the range of 90 degrees to 0 degrees to 90 degrees
t can be generated. Therefore, a range of 0 to 90 degrees can be secured as the effective detection range. Also in this case, the arithmetic expression is not limited to the above expression, and can be set as appropriate. That is, the arithmetic expression can be appropriately changed depending on in which angle range a phase change having a width of 90 degrees occurs.

In the above embodiment, the auxiliary coils Lα and Lβ are provided before and after the effective detection range, however, these auxiliary coils Lα and Lβ can be omitted. FIG.
Shows an example, and shows an embodiment capable of causing a phase change in a range from 0 degrees to 180 degrees. In this case, the coil unit 10 includes two coils LA and LB corresponding to the effective detection range. As described above, since the coils LA and LB are sequentially arranged along the displacement direction of the detection target, the position of the magnetic response member 11 with respect to these coils is relatively displaced in accordance with the displacement of the detection target. As illustrated in FIG. 5B,
Gradual changes in the voltages VA, VB across the coils occur sequentially. Here, it is assumed that the voltage obtained when the magnetic response member 11 does not enter the coil at all is Vo (minimum voltage), and the voltage obtained when the magnetic response member 11 fully enters the coil is VN ( Assuming that the maximum voltage is the maximum voltage, the constant voltage generation circuit 27 generates an AC (sin ωt) constant voltage corresponding to the added value “VN + Vo” of the voltages Vo and VN as a reference voltage. Output voltage VA of each coil
When the constant voltage “VN + Vo” is subtracted from the sum of VB and VB, the resulting voltage “VA + VB−VN−Vo” is
As shown in (B), a cosine function characteristic (or a minus cosine function characteristic) in a range of 0 to 180 degrees is shown. On the other hand, when VB is subtracted from voltage VA, the obtained voltage "VA-VB" shows a sine function characteristic in a range of 0 to 180 degrees as shown in FIG. 5B.

Therefore, in FIG.
By subtracting the voltages VA and VB between both ends of A and LB by the subtraction circuit 25, the subtraction result “VA−VB” is obtained as
An AC output signal sinθsinωt having a sine function characteristic can be generated. The output voltages VA and VB of the coils LA and LB are added by the arithmetic circuit 26, and the addition result V
By subtracting the reference voltage “VN + Vo” generated from the constant voltage generation circuit 27 from A + VB by the subtraction circuit 28,
As a result of the subtraction, “VA + VB− (VN + Vo)” (that is, “VA + VB−VN−Vo”), an AC output signal cosθsinωt having a cosine function characteristic can be generated. Here, it is assumed that the reference voltage “VN + Vo” generated from the constant voltage generation circuit 27 changes with the temperature characteristics in the same manner as the temperature characteristics of the coils LA and LB. Therefore, the constant voltage generation circuit 27 may be configured using a dummy coil having the same characteristics as the coil LA or LB, and may be excited by the same excitation AC signal. For example, if a magnetic core having the same characteristics as the magnetic response member 11 is always inserted into such a dummy coil, the same voltage as the maximum voltage VN obtained when the magnetic response member 11 fully enters the coil. The constant voltage VN can be constantly generated while having a temperature characteristic. Also,
If a magnetic core is not inserted into such a dummy coil, a constant voltage Vo similar to the minimum voltage Vo can be obtained.

The constant voltage generating circuit 27 as described above is not limited to the case where the number of coils is two, but can be applied to a case where an appropriate number of coils are used. For example, when three coils LA, LB, and LC are sequentially connected in cascade so that a phase change in a range of 0 to 270 degrees can be generated in a 3K effective detection range, a constant value is set. The voltage generation circuit 27 generates the constant voltages VN and Vo as separate reference voltages, and outputs the output voltages VA, VB,
Using VC and the reference voltages VN and Vo from the constant voltage generating circuit 27, an AC output signal sinθsinωt having a sine function characteristic can be generated by an operation “VA−VB−VC + Vo”, and “VA + VB−VC” -V
N ”can generate an AC output signal cos θ sinωt having a cosine function characteristic.

As another embodiment, only one coil may be provided corresponding to the effective detection range. In that case, the phase change width of the effective detection range corresponding to the coil length K of one coil is less than 90 degrees. FIG. 6 shows an example of this, and as shown in FIG.
A is provided, and a resistance element R1 is connected in series with the coil LA. As a result, the amplitude component of the voltage VA between the terminals of the coil LA changes according to the displacement of the magnetic response member 11 as shown in FIG.
6B, the amplitude component of the voltage drop VR between the terminals of the resistance element R1 changes accordingly.
It gradually decreases as shown in FIG. The voltage VR between the terminals of the resistance element R1 is converted to an AC output signal sin θs
If the voltage VA between the terminals of the coil LA is regarded as an AC output signal cos θ sinωt having a cosine function characteristic, as shown in FIG. 6 (C), the width between the sine function and the cosine function is less than 90 degrees. It can correspond to the characteristics in the angle range. Therefore, by inputting these AC output signals to the phase detection circuit 22,
The phase angle θ in the corresponding angle range having a width of less than 90 degrees can be absolutely detected.

FIG. 7 shows a modification of FIG.
1 is provided with a dummy coil LN. The dummy coil LN is connected in series to the detection coil LA affected by the displacement of the magnetic response member 11, but is not affected by the displacement of the magnetic response member 11. A constant voltage VN, which is the same as the maximum voltage VN obtained when the magnetic response member 11 fully enters
It can be generated at all times while having a temperature characteristic. Therefore, the terminal voltage VA of the coil LA and the terminal voltage VN of the dummy coil LN according to the displacement of the magnetic response member 11 are generated as shown in FIG. 7B. The arithmetic circuit 29 calculates these voltages VA and VN in accordance with a predetermined arithmetic expression. For example, as shown in FIG.
VN ”generates an AC output signal sinθsinωt having a sine function characteristic, and“ VA−VN ”generates an AC output signal cosθsi having a cosine function characteristic.
Generate nωt. This can be associated with characteristics in an angular range having a width of less than a certain 90 degrees as shown in FIG. Therefore, by inputting these AC output signals to the phase detection circuit 22, the phase angle θ in the corresponding angle range having a width of less than 90 degrees can be absolutely detected. Note that the dummy coil LN is not limited to the series connection as shown in FIG. 7A, and may be connected in parallel with the detection coil LA as shown in FIG. 7E.

In each of the above embodiments, the coil section 10 is arranged so that the axes of the respective coils substantially coincide with each other, and the magnetic responsive member 11 enters the center space of the coil. However, the arrangement relationship between the coil unit 10 and the magnetic response member 11 is not limited to this, and may be any. For example, as illustrated in FIG. 8, a configuration in which the axes of the coils Lα, LA to LD, and Lβ are arranged side by side in the coil unit 10 and the magnetic responsive member 11 passes near the end of the coil. It may consist of. In this case, the coils Lα, LA to LD, Lβ may be wound around an iron core.

Even in the case where the axes of the coils in the coil section 10 are substantially aligned as in the example of FIG. 1, the magnetic responsive member 11 does not enter the center space of the coil. It may be configured. FIG. 9A shows an example of such a structure, in which the magnetic responsive member 11 passes in the vicinity of the coil portion 10 in parallel with the axial direction thereof. In that case, it is preferable to insert the iron core 30 in the axial space of each of the coils Lα, LA to LD, Lβ. As a result, the way of generating the magnetic flux to the outer periphery of the coil is improved, the sensitivity to the magnetic response member 11 near the outer periphery is improved, and the detection accuracy is improved. FIG. 9B shows another example in which the magnetic responsive member 11 has a hollow cylindrical shape, and the coil portion 10 enters the hollow cylindrical space of the magnetic responsive member 11. I have. In this case as well, it is preferable to insert the iron core 30 in the axial space of each of the coils Lα, LA to LD, Lβ to improve the way the magnetic flux flows to the outer periphery of the coil.

FIG. 10 is a side view and a sectional view showing another example of the configuration of the coil section 10 and the magnetic response member 11. In this case, the mutual arrangement interval of the coils Lα, LA to LD, Lβ is K as in the example of FIG. 1, but the length of each coil is short. That is, each adjacent coil Lα, L
A to LD and Lβ do not need to be close to each other as shown in FIG. 1 and may be appropriately separated. The tip 11a of the magnetic response member 11 has a pointed, tapered shape. For example, a tip portion having a length of about K has a tapered shape. Thereby, the inductance change of the coil due to the movement of the tip 11a of the magnetic response member 11 can have a smooth gradually increasing (or gradually decreasing) change characteristic. Needless to say, even when the coils Lα, LA to LD, Lβ are closely arranged as shown in FIG. 1, the tip 11a of the magnetic response member 11 may be appropriately tapered.

As still another example, each coil of the coil unit 10 may be composed of a plurality of coil portions separately arranged. FIG. 11 shows one example of one coil LA.
Is shown as an example of the separation arrangement. In FIG. 11, four coil portions LA1 and LA are separately arranged.
2, cover the range of K by LA3, LA4
The coils LA are configured. Each coil part LA
1, LA2, LA3, LA4 are connected in series, and the coil L
The voltage VA between the terminals A is output. In this case, the number of turns of each coil part LA1, LA2, LA3, LA4 may be common or may be different as appropriate. Further, the separation intervals of the arrangement of the coil portions LA1, LA2, LA3, LA4 may be equal or may be different as appropriate. By making the number of coil turns, the separation interval, and the like non-uniform (non-linear), it is possible to cause a change in self-impedance having characteristics closer to a curve of a sine function or a cosine function. Then, the non-linearity of the relationship between the detection phase angle θ and the actual detection target distance (position) can be improved. Similarly, when the adjacent coils Lα, LA to LD, Lβ are closely arranged as shown in FIG. 1, the number of turns may not be uniform in the range of the entire length K of one coil, but may be uneven. . This can also cause a change in the self-impedance having characteristics closer to the curve of the sine function or the cosine function, and can improve the nonlinearity of the relationship between the detection phase angle θ and the actual detection target distance (position). it can.

Further, the position detecting device according to the present invention is not limited to the detection of a perfectly straight line position, but can also be applied to the detection of the position of a detection target which is displaced in an arc or a curve within a predetermined range. . FIG. 12 shows an example thereof.
Each of the coils LA to LD of the coil unit 10 has a predetermined angle range ψ
Are sequentially arranged in an arc shape, and the magnetic responsive member 1
1 is arranged to swing about the axis C over the angular range ψ. Further, the position detecting device of the present invention can be configured as a detecting device for detecting an angle in a predetermined range in rotation.

In each of the above embodiments, the magnetic responsive member 11 is not limited to a magnetic material, but may be a non-magnetic good conductor such as copper or aluminum. In that case,
As the magnetic response member 11 approaches, the voltage between the coil terminals gradually decreases due to the eddy current loss. Also, a hybrid type combining a magnetic body and a conductor may be used.
In this case, for example, as shown in FIG.
Non-magnetic good conductor 1 formed by tapering
It is preferable to arrange the magnetic body 11c so as to compensate for the decrease of 1b.

As another embodiment, the magnetic response member 11 may include a permanent magnet, and each coil of the coil unit 10 may include an iron core. FIG. 14 shows an example of the permanent magnet 1 functioning as the magnetic response member 11.
1M has, for example, a hollow ring shape, and the coil portion 10 enters into this ring space. An iron core 31 is inserted into the axial space of each of the coils Lα, LA to LD, Lβ of the coil unit 10. Permanent magnet 11M
However, when approaching any of the coils, the iron core 31 corresponding to the adjacent portion is partially in a magnetically saturated or supersaturated state, and the voltage between terminals of the coil is reduced. Permanent magnet 1
1M is displaced from one end of the coil to the other end, so that the voltage between both ends of the coil is gradually reduced.
The length of M has at least a length corresponding to the coil length K. Thus, the permanent magnet 11 is used as the magnetic response member 11.
When the M is used, similarly to the case where the nonmagnetic good conductor 11b is used, the magnetic response member 11, that is, the permanent magnet 11 is used.
While M is displaced from one end of one coil to the other, a gradual change in the voltage across the coil can be caused. However, in the example of FIG. 14, when the permanent magnet 11M passes by a certain coil, the state returns to the non-saturation state. What is necessary is just to be able to obtain a change in the amplitude level. Alternatively, the magnetic response member 1
By arranging a plurality of permanent magnets 11M continuously as 1, the magnetically saturated or supersaturated state may be maintained. The permanent magnet 11M is not limited to a ring shape, and may have another shape such as a rod shape. In that case, FIG.
In the same manner as in the example of FIG.
It has an arrangement configuration through which the magnetically responsive member 11 of 1M passes. The iron core 31 may have a relatively thin shape or the like so as to easily cause magnetic saturation.

FIG. 15 shows the coil section 1 in FIG.
This is a modification of the arrangement of each coil of No. 0, in which crosstalk between adjacent coils can be prevented to improve detection accuracy. In FIG. 15A, a magnetic spacer 3 is interposed between the coils Lα, LA to LD, Lβ.
2 are arranged. As a result, the path of the magnetic flux generated in each coil is not diffused but passes from the inside of each coil to the nearest end (the location of the magnetic spacer 32), to the outer periphery, and to the nearest end (the magnetic spacer 32). ) And return to the inside, that is, a route indicated by Φ in the drawing. Therefore, crosstalk can be prevented, the response (impedance change) of each coil to the presence of the magnetically responsive substance 11 close to the outer periphery of each coil can be extremely improved, and the detection accuracy can be improved. In FIG. 15A, a magnetic spacer 3 provided between adjacent coils is used.
Although 2 is one, as shown in FIG. 15B, two magnetic spacers 32a and 32b may be arranged between the adjacent coils with some separation. In this case, a non-magnetic material may be used instead of the iron core 30 as the bobbin of the coil. As in the modification shown in FIG.
The partitioning of each coil by 2, 32a and 32b is also applicable in the embodiment of FIG.

FIG. 16 is a sectional view showing another embodiment of the position detecting device according to the present invention. As the magnetic response member 11 penetrates into the coil section 10, the inductance of the coil gradually decreases. FIG. 17A shows FIG.
6 is a schematic perspective view of the outer appearance of the arrangement of the coil unit 10 and the magnetically responsive substance 11, (B) is a schematic sectional view in the axial direction of the coil, and (C) is a diagram showing an example of an electric circuit of the coil unit 10. . The configuration shown in FIG.
4, the magnetic response member 11 has a hollow cylindrical shape, and the coil portion 10 enters the hollow cylindrical space of the magnetic response member 11.

In FIG. 16, a coil unit 10 includes a plurality of coils (four coils LA,
LB, LC, LD) are sequentially wound, and the outer periphery is covered with a non-magnetic and non-conductive protective tube (or coating or mold) 41. As the protective tube 41, any material may be used. For example, a heat-shrinkable tube made of an insulating resin is inexpensive.

The bobbin 40 is formed of a non-magnetic hollow cylinder, and houses one or a plurality of magnetic rods 42 therein. The magnetic rod 42 extends over the entire length of the coil unit 10 and sets an inductance value, that is, an impedance value, over the entire length of the coil unit 10. By appropriately adjusting the thickness or the number of the magnetic rods 42 housed in the bobbin section 40, the setting of the inductance value over the entire length of the coil section 10 can be changed. It is preferable to use a magnetic rod 42 having a conductive coating formed by applying copper plating or the like around the magnetic rod 42. This helps to compensate for temperature drift characteristics. The bobbin part 40 may be made of non-magnetic material, and may be made of metal or resin. When a device to which this position detecting device is applied is used for an application to which a large load is applied, such as a large construction machine, it is preferable to use a metal in order to secure sufficient strength. For example,
The bobbin part 40 is formed using non-magnetic stainless steel or the like. In the case of a small device that is not so, the use of resin is inexpensive and lightweight.

With the position detecting operation according to the embodiment of FIG.
This will be described with reference to FIG. In FIG. 17, only one magnetic rod 42 is shown for convenience of illustration, and the bobbin 40
Are not shown. The coil unit 10 includes four coils LA, LB, LC, and LD having the same properties such as the number of turns and the coil length.
They are arranged sequentially along the direction of linear displacement. The change in the relative positional relationship between the coil unit 10 and the magnetic response member 11 according to the displacement of the detection target is the same as in the embodiment of FIG. That is, when the magnetic response member 11 advances to the right in the drawing according to the displacement of the detection target, the tip 11 of the magnetic response member 11
a first penetrates the magnetic field of the coil LA, and then penetrates the magnetic field in the order of the coils LB, LC, and LD. A two-dot chain line 11 'indicates the magnetic response member 11 that has penetrated to the last coil LD. Four coils LA, LB, L
The range 4K corresponding to C and LD is the effective detection range,
Actually, since the accuracy is lowered at both ends of the range 4K, that portion is not used, and the actual effective detection range is slightly narrower than 4K. Of course, in order to enable full detection in the effective detection range 4K, auxiliary coils Lα and Lβ may be provided before and after as in the previous embodiment.

Each of the coils LA, LB, LC, and LD has one or several magnetic rods 42 inserted into its core over its entire length. The inductance value is maximum. The self-inductance of the coil decreases as the degree of approach or penetration of each coil of the magnetic response member 11 with respect to the magnetic field increases. The voltage across the coil gradually decreases. That is, when the magnetic response member 11 is a magnetic material, the magnetic material covers the outer periphery of the coil. 11 and the self-inductance of the coil decreases. Also,
When the magnetic response member 11 is a conductor, the conductor covers the outer periphery of the coil, causing eddy current loss due to a magnetic field, and reducing the self-inductance of the coil. As described above, in the embodiment of FIG. 16, the self-inductance of the coil decreases in accordance with the proximity of the magnetic response member 11 to the coil unit 10 regardless of whether the magnetic response member 11 is made of a magnetic material or a conductor. Since the inductance reduction rate due to the eddy current loss of the outer conductor is greater than the inductance reduction rate due to magnetic flux leakage due to the outer magnetic body, a more preferred embodiment uses a conductor as the magnetic response member 11. It is. The conductor as the magnetic response member 11 may be a thin layer, as long as it has a skin effect. In that case, for example, the magnetic responsive member 11 may be formed by disposing a conductor on the peripheral wall of the cylindrical space of an appropriate hollow cylindrical base member (movable body) (may be copper plating or the like). .

As shown in FIG. 17C, each coil L
A, LB, LC, and LD are excited at a constant voltage or a constant current by a predetermined one-phase AC signal (tentatively indicated by sinωt) generated from the AC power supply 12. Each coil LA, L
V, VB, V
When expressed by C and VD, the respective voltages VA, VB and V
Terminals 14 to 18 are provided for extracting C and VD. As can be easily understood, each coil LA, L
B, LC, and LD need not be separate coils physically separated from each other, but only need to provide the intermediate terminals 14 to 18 at positions where the total length of a series of coils is divided into four. That is, the coil portion between the terminals 14 and 15 becomes the coil LA, the coil portion between the terminals 15 and 16 becomes the coil LB, the coil portion between the terminals 16 and 17 becomes the coil LC, and the terminals 17 and 1
The coil portion between 8 becomes the coil LD. The output voltage VA, VB, VC, VD of each coil is calculated by the analog operation circuit 2
0 and 21 are input in a predetermined combination and added or subtracted in accordance with a predetermined arithmetic expression, so that each of the analog arithmetic circuits 20 and 21 has an amplitude indicating a sine and cosine function characteristic according to the detection target position. The two AC output signals sinθsinωt and cosθsinωt are generated.

As described above, as the degree of approach or penetration of each coil of the magnetic response member 11 with respect to the magnetic field increases, the self-inductance of the coil decreases.
While one end 11a is displaced from one end to the other end of one coil, the voltage between both ends of the coil gradually decreases. Here, since the plurality of coils LA, LB, LC, and LD are sequentially arranged along the displacement direction of the detection target, the position of the magnetic response member with respect to these coils is relatively determined according to the displacement of the detection target. As illustrated in FIG. 18A, the voltages VA, VB, VC, and VD across the coils are changed as the displacement occurs.
Gradually decrease in order. In FIG. 18A, in a section where the output voltage of a certain coil is inclined, the end 11a of the magnetic response member 11 is displaced from one end of the coil toward the other end. Typically, the gradual change curve of the voltage across the coil that occurs while the end 11a of the magnetically responsive member 11 is displaced from one end of the coil to the other end is represented by 9 in the sine or cosine function.
It can be compared to a function value change in the range of 0 degrees. Therefore, by adding and / or subtracting the output voltages VA, VB, VC, and VD of each coil in an appropriate combination, two AC outputs each having an amplitude indicating a sine and cosine function characteristic according to the position to be detected. Signal si
nθ sinωt and cos θ sinωt can be generated.

That is, in the analog operation circuit 20, the output voltages VA, VB, V of the coils LA, LB, LC, LD are output.
By calculating C and VD as shown in the following equation (7), FIG.
An AC output signal showing an amplitude curve of a sine function characteristic as shown in FIG. 8B can be obtained, which can be equivalently represented by “sin θ sin ωt”. (VB-VA)-(VD-VC) -Vo Expression (7) where Vo is the minimum inductance value (magnetic response member 11).
Is a reference voltage corresponding to the inductance value when one coil is entirely covered, and is for offsetting to zero level.

In the analog operation circuit 21, the output voltages VA, VB, VC, VC of the coils LA, LB, LC, LD are output.
By calculating VD as in the following equation (8),
An AC output signal showing an amplitude curve of a cosine function characteristic as shown in (B) can be obtained. This can be equivalently represented by “cos θ sin ωt”. VA + (VB−VC) + (Vp−VD) −Vo Equation (8) Vp is a reference voltage corresponding to the maximum inductance value (the inductance value when the magnetic response member 11 is not very close to one coil). Yes, to offset the output voltage VD. In consideration of the temperature drift, in order to generate each of the reference voltages Vo and Vp with the same temperature drift characteristics as the temperature drift of each of the coils LA to LD, each of the reference voltages Vo and Vp is interposed with an appropriate dummy coil. Vo and Vp are preferably generated. Of course, other temperature compensation means may be used.

The phase angle θ in the sine and cosine functions, which is the amplitude component of each AC output signal, corresponds to the position to be detected, and the phase angle θ in the range of 90 degrees corresponds to the length K of one coil. Yes, it is. Accordingly, the effective detection range having a length of 4K corresponds to the range of 0 to 360 degrees of the phase angle θ. Therefore, by detecting the phase angle θ, the detection target position in the range of the length of 4K can be absolutely detected. AC output signals sinθsinωt and cosθ of sine and cosine function characteristics
By measuring the phase components θ of the amplitude functions sin θ and cos θ in sin ωt by the phase detection circuit (or amplitude phase conversion means) 22 in the same manner as described above, the detection target position can be absolutely detected.

Here, the compensation of the temperature characteristic in the embodiment of FIG. 16 will be described. The impedance of each coil changes according to the temperature, and the output voltages VA, VB, V
C and VD also fluctuate. For example, similarly to the case of FIG. 2, each voltage increases or decreases in one direction as shown by a broken line with respect to a solid curve in FIG. 18A, but the sine and cosine function characteristics obtained by adding and subtracting these voltages are combined. Since the AC output signals sinθsinωt and cosθsinωt of FIG. 18 show as amplitude changes in both positive and negative directions as shown by a broken line with respect to a solid curve in FIG. And the temperature drift characteristic is compensated for, and accurate position detection can be expected. further,
As described above, by performing copper plating or the like on the outer periphery of the magnetic rod 42 corresponding to the magnetic core of the coil section 10 to form a conductor coating, temperature compensation can be performed. That is, the conductive coating on the surface of the magnetic rod 42 reduces the inductance of the magnetic circuit due to the eddy current loss generated therein. For example, when the temperature of the coil rises when the impedance of each coil increases (this is originally Although the self-inductance decreases, the eddy current loss of the conductive film decreases, thereby relatively increasing the inductance of the magnetic circuit and compensating for the temperature drift of the inductance of the coil. For the same reason, the same temperature drift compensation effect can be expected by using a nonmagnetic metal having some degree of conductivity as the nonmagnetic metal of the bobbin portion 40.

Further, in each of the above embodiments, two output AC signals s having amplitude characteristics of sine and cosine functions are provided.
An example of generating inθsinωt and cosθsinωt (in other words, an example of generating a resolver-type two-phase output) has been described. However, the present invention is not limited to this, and three or more output AC signals having three or more trigonometric amplitude characteristics indicating a predetermined phase shift. (For example, sin θ · sin ωt, sin (θ−120
°) · sinωt and sin (θ-240 °) · sin
ωt) may be output. The number of coils LA to LD to be arranged may be four or more.

As shown in FIG. 19, the coils Lα,
A group of LA to LD, Lβ and another coil Lα ′, L
The groups A ′ to LD ′ and Lβ ′ (there may be more coil groups) are arranged side by side by shifting by a predetermined distance d, and the magnetic responsive member 11 has a width that covers both groups. May be configured. The coils in each group are all in-phase AC signals (eg, sinω
Excited by t). This shift d corresponds to an appropriate phase difference of less than 90 degrees, and by appropriately adding and / or subtracting the output voltages of these coils and combining them, for example, sin θ · sin ωt and sin (θ−
120 °) sin ωt and sin (θ-240 °)
As in the case of sinωt, it is possible to generate a plurality of AC output signals indicating amplitudes according to a plurality of trigonometric functions having a phase difference other than 90 degrees (trigonometric functions having a relationship other than sine and cosine).

In each of the above embodiments, the magnetic responsive member
It may be formed in a predetermined pattern on the surface of a substrate such as a rod or a plate by a surface processing technique such as plating. FIGS. 20A and 20B schematically show an example, in which FIG. 20A is a schematic perspective view, FIG. 20B is a diagram showing a rod base and a coil in a cross section, and FIG. 20C is formed on the surface of the rod base. FIG. 4 is a development view showing an example of a pattern of a magnetic response member. For example, two different magnetically responsive members 11a and 11b are formed and arranged in a predetermined shape pattern such as a triangle gradually increasing or decreasing on the surface of a rod-shaped substrate 66 such as a cylinder piston rod. Magnetic response members 11a and 11b and base material 6
The materials 6 have different magnetic properties. For example, when the base material 66 is a magnetic material such as iron, the magnetic response members 11a and 11b are made of a nonmagnetic good conductor such as copper. Alternatively, when the magnetic response members 11a and 11b are made of a magnetic material such as iron, the base material 66 is made of a non-magnetic material, or even if it is a magnetic material, the base material 66 is formed as a convex portion. , Formed as recesses.

In the coil section 10, coils L1 and L2 are individually provided corresponding to each pattern. The coil unit 10
It is a ring as a whole, and a rod-shaped substrate 66 is inserted into the ring so as to be linearly movable in the axial direction. The first coil L1 is disposed in a semicircular portion of the ring in the coil portion 10, and the second coil L1 is disposed in the other semicircular portion.
2 are arranged. The magnetic response members 11a and 11b are composed of two patterns, the first pattern 11a has a triangular shape that gradually increases from left to right in the figure, and the second pattern 11b has the opposite shape. It has an inverted triangular shape that gradually decreases from left to right. The first coil L1 covers the arrangement area of the pattern 11a, and the second coil L2 covers the arrangement area of the pattern 11b. Magnetic response members 11a, 11 provided on the base material 66
The range K of the pattern of gradually increasing or decreasing b is the detectable range K
Corresponding to That is, when the rod-shaped substrate 66 is displaced in accordance with the displacement of the detection target, the positions of the magnetic responsive members 11a and 11b corresponding to the coils L1 and L2 change, and correspond to the coils L1 and L2. The magnetic response members 11a,
11b, self-inductance, that is, impedance is generated in each coil L1, L2, and output voltages Va, Vb corresponding to the detection target position are obtained from each coil L1, L2.

FIG. 21A shows each coil L in FIG.
FIGS. 1B and 1C are electric circuit diagrams relating to L2, and FIGS. The characteristics of the output voltages Va and Vb of the coils L1 and L2 are inverse characteristics as shown in FIG. Therefore, these changes in the output voltages Va and Vb are
It can be compared to a function value change in an appropriate range of less than 90 degrees in the sine function or the cosine function. Therefore, by taking out these output voltages Va and Vb through an appropriate analog buffer circuit 100, as shown in FIG. AC output signals (typically sin θ sin ωt and cos θ sin ω
t) can be generated.

FIG. 22 shows a modified example of the coil configuration. FIG. 3A is a perspective view, and FIG. 3B is a developed view showing a correspondence relationship between each coil and a magnetic response member pattern. In this case, the rod-shaped base material 66 in which the magnetic response members 11a and 11b are arranged penetrates into the center space of the coil, and the direction of the internal magnetic flux of the coil is the axial direction of the rod, that is, the straight line to be detected. It is oriented in the direction of displacement. Coil L1 corresponding to pattern 11a and coil L corresponding to pattern 11b
No. 2 is obtained by arranging two coils having the same properties such as the number of turns and the coil length adjacently. Masking MA, MB is performed on a half surface (in the range of approximately 180 degrees) of the inner circumference of each coil with a good conductor such as copper. As a result, an output voltage is generated from each of the coils L1 and L2 in accordance with the corresponding area of the magnetic response units 11a and 11b corresponding only to the half surface that is not masked. The masking MA in the coil L1 is applied to the half surface corresponding to the pattern 11b, and the coil L1 does not respond to the pattern 11b,
Responds only to pattern 11a. The masking MB in the coil L2 is applied to the half surface corresponding to the pattern 11a, and the coil L2 does not respond to the pattern 11a, but responds only to the pattern 11b. Therefore, the output voltage from the coil L1 gradually increases in accordance with the gradual decrease in the coil-corresponding area of the pattern 11a, and the output voltage from the coil L2 gradually decreases in accordance with the gradual increase in the coil-corresponding area in the pattern 11b. The detection operation can be performed as shown in FIG.

FIG. 23 shows an embodiment capable of causing a phase change from 0 degrees to 180 degrees. FIG.
(A) is a development view showing a pattern arrangement example of the magnetic response members 11a to 11f on the surface of the rod-shaped substrate 66.
The magnetic response member has six patterns 11a, 11b, 11
c, 11d, 11e, and 11f, which are arranged in parallel corresponding to a range obtained by dividing the side surface of the piston rod 4 into six in the circumferential direction. The patterns 11a, 11c and 11e are patterns common to each other.
b, 11d and 11f are also common patterns.
In the pattern 11a, 11c and 11e, the area of the magnetic responsive member gradually decreases from left to right in the left half of the length of the rod-shaped base material 66 in FIG. Is a pattern having no magnetic response member.
In the pattern 11b, 11d and 11f, the area of the magnetic response part gradually decreases from left to right in the right half section in the length direction of the rod-shaped base material 66 in FIG. In the figure, the entire surface is a pattern made of a magnetic response member. The ring-shaped coil portion 10 as a whole is
Coils L1, L2, L3, L4, L5, L corresponding to 1a, 11b, 11c, 11d, 11e, 11f, respectively.
6, each of which is obtained by dividing the circumferential direction of the ring into six.
They are arranged so as to correspond to the range of 0 degrees.

When the rod-shaped base material 66 is displaced in the direction of the arrow x, the patterns 11b, 11d, 11f and the coils
2, L4, L6, the corresponding area gradually increases, and each coil L2,
The output voltages V2, V4, V6 of L4, L6 gradually decrease. In this first half section, the other patterns 11a, 11c,
Output voltage V of coils L1, L3, L5 corresponding to 11e
1, V3 and V5 maintain the maximum level because there is no magnetic response member (for example, a conductor). When the output voltages V1, V3, and V5, each of which has a common gradual change pattern, are further displaced, the pattern 11a, 11c, 11e and the coil L1, L3, L5 corresponding to the pattern 11a, 11c, 11e are substantially displaced in the latter half of the stroke. The corresponding area gradually increases,
The output voltages V1, V3, V5 of the coils L1, L3, L5
Changes gradually. In this latter half section, other patterns 11
coils L2, L4, L6 corresponding to b, 11d, 11f
Output voltages V2, V4, and V6 maintain a minimum level because a magnetically responsive member (for example, a conductor) is always present.
Output voltages V1 and V3 each having a common change pattern
And V5 are added and synthesized by the averaging circuit 102 in FIG. 23B to obtain an output VA. The output voltages V2 and V4
And V6 are also added and synthesized by the averaging circuit 102, and the output VB
Get. FIG. 24A shows an example of the combined outputs VA and VB. Thus, the first common patterns 11a, 11c,
The reason why 11e and the second common patterns 11b, 11d, and 11f are alternately arranged and their outputs are added and synthesized is to prevent the adverse effects of the rotation of the rod-shaped base material 66 and the axial misalignment. is there.

As in the example of FIG. 5, assuming that the minimum voltage of the coil output voltage is Vo and the maximum voltage is VN, the constant voltage VN + Vo corresponding to this is supplied from the constant voltage generation circuit 27 to the FIG.
As shown in FIG. Output voltage VA and VB
When the constant voltage VN + Vo is subtracted from the sum of the above, the obtained voltage “VA + VB−VN−Vo” has a cosine function characteristic in a range of approximately 0 ° to 180 ° as shown in FIG. Can be compared. on the other hand,
When VB is subtracted from voltage VA, the resulting voltage “VA−
VB ”, as shown in FIG.
It can be compared to a sine function characteristic within the range of 0 degrees. Each of the arithmetic circuits 25 and 26 in FIG.
28 performs the same arithmetic function as the circuit of the same reference numeral in FIG. Therefore, the same detection operation as in the example of FIG. 5 can be performed.

FIG. 25 shows an example in which a full phase change from approximately 0 degrees to 360 degrees can be realized. FIG. 25A is a developed view showing four different patterns 11a, 11b, 11c, and 11d formed on the base material 66 by the magnetic response member 11. FIG. Each of the patterns 11a to 11d is arranged corresponding to a range obtained by dividing the side surface of the rod-shaped base material 66 into four parts in the circumferential direction. For convenience of explanation, in the same drawing, the rod-shaped base material 66 is divided into four in the length direction, and each quarter section is referred to as P1, P2, P3, and P4, respectively. For example, the pattern 11a is P1 from left to right in the figure.
Form a triangular pattern in which the area gradually increases in the section, P4
The area has a triangular pattern in which the area gradually decreases, and P2
In the section P3 and P3, the entire area is made up of the magnetic response member 11. Other patterns are different sequentially as shown.

FIG. 25B shows the gradual increase and decrease of the output voltages V1 to V4 of the coils L1 to L4 with respect to the position to be detected in the horizontal axis direction. FIG. 25D shows each of the coils L1 to L
4 is an electric circuit diagram related to FIG.
In step 1, the calculation “V1-V3” and the calculation “V2-V4” are performed. FIG. 25C is a graph showing an output signal obtained as a calculation result. The voltage “V1−V3” obtained by subtracting V3 from the output voltage V1 is approximately 0 ° to 360 °.
It can be compared to the cosine function characteristic within the range of degrees. On the other hand, the voltage “V2−V4” obtained by subtracting V4 from voltage V2 can be compared to a sine function characteristic within a range of approximately 0 ° to 360 °. Therefore, as shown in FIG.
AC output signals of sine and cosine function characteristics over a range of degrees (typically sin θ sin ωt and cos θs
inωt).

In each of the above embodiments, the base material 66 is not limited to the rod shape but may be a flat shape. In that case, the magnetic responsive members 11a, 11b,
Are arranged so as to face each other.

Further, as a modified example of the present invention, for example, in FIG. 1C, only one of the analog operation circuits 20 may be used to generate only one AC output signal sinθ · sinωt. In that case, one AC output signal sinθ · sin is used without using the phase detection circuit 22.
The configuration is such that the position detection data is obtained from the amplitude voltage level of ωt. Even in this case, it is possible to provide a simple position detecting device in which the secondary coil is omitted.

When two position detecting devices for generating only one AC output signal sinθ · sinωt as in the above-described modified example are provided side by side as shown in FIG. It can also be configured. That is, in a detection device according to a known phase shift type position detection principle, a two-phase AC signal (for example, sinωt and co
sωt) to excite the primary coils of a plurality of phases, and as a combined output signal of the secondary coils of each phase, an output AC signal (for example, sin
(Ωt + θ)). The idea of the present invention may be applied to a detection device employing such a phase shift type position detection principle. For that, Figure 1
As in the example of 4, two coil groups are arranged in parallel,
AC signals having different phases for each group (for example, sinω
t and cosωt) to excite the coils in each group in common, and in one coil group cos θs
inωt, and sin θc
osωt is formed, and both outputs may be added or subtracted.

In each of the above embodiments, the magnetic responsive member 11
Of course, may be fixed, and the coil unit 10 may be moved in accordance with the displacement of the detection target. In the present invention, the voltage generated in the coil or the voltage between the terminals of the coil is not necessarily limited to the voltage detection type circuit configuration, and should be interpreted in a broad sense. What is adopted is also included in the scope. In short, any circuit configuration that can generate an analog voltage or current according to a change in coil impedance and detect the analog voltage or current can be used.

[0072]

As described above, according to the present invention, only the primary coil needs to be provided, and the secondary coil is not required. Therefore, it is possible to provide a position detecting device having a small and simple structure. Also, a plurality of coil sections are sequentially arranged along the displacement direction of the detection target, and the voltage between both ends of the coil gradually increases (or gradually decreases) while the magnetic response member is displaced from one end to the other end of one coil section. Since the characteristic changes occur sequentially in each coil section, the voltage of each coil section is taken out, added and / or subtracted and combined to obtain a predetermined periodic function according to the position to be detected. A plurality of AC output signals each indicating an amplitude according to the characteristic (for example, two AC output signals each indicating an amplitude according to the sine and cosine function characteristics) can be easily generated, and the usable phase angle range can be widened. . Further, by detecting a phase value in a predetermined periodic function (for example, a sine and cosine function) that defines the amplitude value from the correlation between the amplitude values of the plurality of AC output signals, even if the displacement of the detection target is minute, high resolution is obtained. Can be detected.

[Brief description of the drawings]

FIGS. 1A and 1B show an embodiment of a position detecting device according to the present invention, in which FIG. 1A is a schematic diagram of an external appearance, FIG. 1B is a cross-sectional view in a coil axis direction, and FIG. .

FIG. 2 is an explanatory diagram of a detection operation of the position detection device of FIG.

FIG. 3 is an electric circuit diagram related to a coil unit, showing another embodiment of the position detecting device according to the present invention.

FIG. 4 is an electric circuit diagram related to a coil unit, showing still another embodiment of the position detecting device according to the present invention.

FIGS. 5A and 5B show still another embodiment of the position detecting device according to the present invention, wherein FIG. 5A is an electric circuit diagram relating to a coil unit, FIG. (C) is a diagram showing an example of calculation and synthesis of each coil output.

6A and 6B show another embodiment of the position detecting device according to the present invention, wherein FIG. 6A is an electric circuit diagram relating to a coil unit,
(B) is a diagram showing an example of coil output, and (C) is a diagram for explaining a detection principle based on the coil output.

7A and 7B show still another embodiment of the position detecting device according to the present invention, wherein FIG. 7A is an electric circuit diagram related to a coil unit, FIG. 7B is a diagram showing an output example of each coil, and FIG. FIG. 3D is a diagram showing an example of arithmetic synthesis of coil outputs, FIG. 2D is a diagram for explaining a detection principle based on arithmetically synthesized outputs, and FIG. 2E is a circuit diagram showing a modified example of coil connection.

FIG. 8 is a schematic diagram showing a modification of the coil arrangement in each embodiment of the present invention.

9A is a schematic cross-sectional view showing a modified example of the arrangement of the magnetically responsive member and the coil according to the present invention, and FIG. 9B is a schematic view showing another modified example of the arrangement of the magnetically responsive member and the coil. FIG.

FIG. 10 is a schematic cross-sectional view showing still another modification of the coil arrangement and a modification of the tip shape of the magnetic response member in each embodiment of the present invention.

FIG. 11 is a schematic sectional view showing still another modified example of the coil arrangement in each embodiment of the present invention.

FIG. 12 is a side view schematically illustrating an embodiment of the present invention when applied to detection of a position displaced in an arc shape or a curved shape.

FIG. 13 is a plan view schematically showing an example in which a magnetic response member is hybridly configured by a magnetic body and a conductor in each embodiment of the present invention.

FIG. 14 is a perspective view schematically showing an example in which a permanent magnet is included as a magnetic response member in each embodiment of the present invention.

FIG. 15 is a schematic cross-sectional view showing a modification of the arrangement of the coils in the coil unit in FIG. 9 (B).

FIG. 16 is a schematic axial sectional view showing still another embodiment of the position detecting device according to the present invention.

17A and 17B are diagrams illustrating the principle of detection by the position detection device of FIG. 16, wherein FIG. An axial section schematic diagram, (C) is an electric circuit diagram related to the coil portion.

FIGS. 18A and 18B are explanatory diagrams of the position detection operation in the embodiment of FIGS. 16 and 17, wherein FIG. 18A is a diagram showing an output example of each coil, and FIG.

FIG. 19 is a view schematically showing another embodiment of a coil arrangement according to the present invention.

20A and 20B are diagrams showing still another embodiment of the position detecting device according to the present invention, wherein FIG. 20A is a schematic perspective view, FIG. 20B is a diagram showing a rod base material and a coil in a cross section, and FIG. FIG. 4 is a development view showing an example of a pattern of a magnetic response member formed on a surface of a rod base material.

21 (a) is an electric circuit diagram relating to each coil of FIG. 20, and FIGS. 21 (b) and (c) are explanatory diagrams of the detection operation.

FIG. 22 shows an example of a configuration change of a coil unit.
(A) is a perspective view, (b) is a development view showing a correspondence relationship between each coil and a magnetic response member pattern.

23A and 23B are diagrams showing still another embodiment of the position detecting device according to the present invention, wherein FIG. 23A is a developed view showing an example of a pattern of a magnetic responsive member formed on the surface of a rod base material, and FIG. Is an electric circuit diagram related to each coil.

24 is an explanatory diagram of the detection operation in FIG.

25A and 25B are diagrams showing still another embodiment of the position detecting device according to the present invention, wherein FIG. 25A is a developed schematic diagram showing a relationship between an example of an arrangement pattern of a magnetic response member and a coil, FIG. (C) is an explanatory diagram of the detection operation, and (D) is an electric circuit diagram related to each coil.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Coil part 11 Magnetic response member 11a Tip part 11b Conductor 11M Permanent magnet 12 AC power supply Lα, LA, LB, LC, LD, Lβ Coil section (coil) 20, 21, 23, 24, 25, 26, 28 Analog operation Circuit 22 Phase detection circuit 30, 31 Iron core 40 Hobin 41 Protective tube 42 Magnetic rod

Claims (13)

[Claims] 1. A coil unit having a plurality of coils arranged to be excited by an AC signal, and a magnetic responsive member arranged to be displaced relative to the coil unit, wherein Accordingly, the relative position between the member and the coil portion changes, and the impedance of each coil is changed according to the relative position. While the relative position changes over a predetermined range based on the impedance change, The voltage generated in each coil is changed, and the voltage generated in each coil indicates a change pattern unique to each coil corresponding to the change in the detection target position, and the voltage generated in each coil is An analog operation circuit that generates at least one AC output signal having predetermined periodic function characteristics as an amplitude coefficient Comprising position detecting device. 2. A coil section in which a plurality of coil sections excited by a predetermined AC signal are sequentially arranged along a displacement direction of a detection target; and a coil section is disposed so as to be relatively displaced with respect to the coil section. A magnetic responsive member, wherein the relative position between the member and the coil portion changes according to the position to be detected, and the inductance of each coil section changes according to the relative position; The voltage generated in the coil section gradually increases or decreases during the displacement from one end to the other end of the section, and the voltage of each coil section is taken out, and the voltage is applied to each of the coil sections to calculate the combination. An analog operation circuit for generating at least one AC output signal having an amplitude according to a predetermined periodic function characteristic according to the position. 3. The magnetic responsive member is arranged on a predetermined base material in a predetermined pattern having a section whose area gradually increases or decreases along a displacement direction of a detection target position. 2. The position detecting device according to claim 1, wherein the pattern of the gradual increase or decrease shown for each coil is different for each coil. 4. The apparatus according to claim 1, further comprising means for generating a predetermined reference voltage, wherein said analog operation circuit performs an operation by combining said reference voltage with a voltage from each said coil or each coil section. 3. The position detecting device according to claim 1. 5. The analog operation circuit according to claim 1, wherein the plurality of AC output signals are generated, and the periodic function characteristic defining the amplitude of each AC output signal is shifted by a predetermined phase. The position detecting device according to any one of the above. 6. A method for receiving the plurality of generated AC output signals, detecting a specific phase value in the predetermined periodic function that defines the amplitude value from a correlation between the amplitude values in the AC output signal, and detecting the detected phase value. The position detecting device according to claim 5, further comprising an amplitude / phase conversion unit that generates position detection data of the detection target based on the obtained phase value. 7. The plurality of AC output signals include an AC output signal indicating an amplitude according to a sine function characteristic according to a position to be detected and an AC output signal indicating an amplitude according to a cosine function characteristic according to a position to be detected. The position detecting device according to claim 5. 8. The position detecting device according to claim 1, wherein the magnetic response member includes at least one of a magnetic material and a conductor. 9. The position detecting device according to claim 1, wherein the magnetic response member includes a permanent magnet, and the coil unit includes a magnetic core. 10. The position detecting device according to claim 1, wherein said coil portion is wound around a bobbin portion containing a magnetic material. 11. The position detecting device according to claim 10, wherein the bobbin includes a cylindrical portion made of a non-magnetic material and one or more magnetic rods housed in the cylindrical portion. 12. The position detecting device according to claim 10, wherein the magnetic body or the magnetic rod in the bobbin has a conductive film formed on a surface thereof. 13. The coil unit comprises substantially one coil extending along the direction of displacement of the detection object, and by deriving output terminals from a predetermined intermediate position of the one coil, The position detecting device according to claim 1, wherein the plurality of coil sections are formed by one coil.