JP2003315094A - Encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an encoder wherein influence of magnetization distribution, attaching error, gap fluctuation, etc., can be reduced in the case that a plurality of magnetic impedance elements are built in. <P>SOLUTION: In a magnet 1 of a fixed side, multipole magnetization is performed in a relative moving direction to a member of a moving side. In the moving side, thin film yokes 2-5 are arranged facing each other in a comb teeth shape. Block-shaped yokes 6, 7 are arranged so as to be in contact with ends of the thin film yokes 2, 4. An amorphous wire 8 having magnetic impedance effect is arranged between the thin film yokes 2, 4, and an amorphous wire 9 is arranged between the thin film yokes 3, 5. In the amorphous wires 8, 9, a current is made to flow by using a circuit which is not shown in figure, and a magnetic field is detected. Bias coils 10, 11 for applying a bias magnetic field and feedback coils 12, 13 for performing feedback are wound around the amorphous wires 8, 9, respectively. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an encoder for detecting position information by a magnetic field.

[0002]

2. Description of the Related Art An encoder using a magnetic sensitive element has been proposed. For example, JP-A-7-181239
The publication discloses a method of using a magneto-impedance element (MI element) that utilizes a magneto-impedance effect (Magneto-Impedance effect: MI effect) as a magnetically sensitive element. More specifically, a technique is disclosed in which a high-frequency current is passed through a magnetic wire such as an amorphous wire to obtain a high impedance change in a low magnetic field and to realize a small magneto-impedance element with high sensitivity.
A high-resolution encoder can be realized by using such a high-sensitivity magneto-impedance element. However, in the technique of this publication, when using a magnet that is magnetized in multiple poles, it is necessary to use a plurality of magneto-impedance elements in order to eliminate the influence of the magnetization distribution of the magnet.
Therefore, for multiple magneto-impedance elements,
It is necessary to install and position the magnet with high accuracy,
Such highly accurate positioning work is extremely difficult. Therefore, in order to solve the influence of the magnetization distribution in such a magnet, Japanese Unexamined Patent Publication No. 9-113591 discloses a technique using a thin-film type magneto-impedance element. According to this technique, convex magnetic films are formed in a rack shape on a continuous magnetic film at a predetermined pitch, and a magnetizing medium (magnet) is opposed to this at a predetermined pitch and is relatively moved. This makes it possible to detect an average magnetic field without being affected by variations in the arrangement of magnets,
It is possible to realize a highly sensitive and highly accurate encoder.

[0003]

However, the conventional encoder using the magnetic sensitive element has the following problems. First, it is better to arrange a plurality of magnetic detectors in order to average and reduce the influence of the mounting error of the magnetic sensitive element and the uneven distribution of the gap, but in order to realize this, It is necessary to form a plurality of magnetic sensitive elements at the same time. However, when a plurality of magneto-sensitive elements are formed at the same time, in order to improve the characteristics of the encoder, it is necessary to perform a process such as giving magnetic anisotropy to the magneto-sensitive element at the same time.
Further, since it is necessary to form a plurality of layers, as a result, the manufacturing process of the magnetic sensitive element becomes complicated. Especially, in the case of a magnetically sensitive element for a rotary encoder, the manufacturing process becomes more complicated. Thirdly, if a plurality of magnetic sensitive elements are arranged at the same time without manufacturing a plurality of magnetic sensitive elements at the same time, it becomes necessary to perform positioning with high precision, and as a result, manufacturing of an encoder becomes difficult. . Further, the conventional encoder using the thin film type magnetic impedance element as the magnetic sensitive element has the following problems in addition to the above-mentioned problems. Since the bias coil is not used due to the structural limitation due to the thin shape, the nonlinear magnetic characteristic portion of the magneto-impedance element is used, the output signal is distorted, and the sinusoidal output signal cannot be obtained. For this reason, high resolution interpolation cannot be performed, and the resolution of the encoder becomes low, so that it cannot be used for applications such as precision machine tools.

The present invention has been made in view of the above circumstances, and an object thereof is to reduce the influence of magnetization distribution, mounting error, gap variation, etc. even when a plurality of magnetic sensitive elements are incorporated. Another object is to provide an encoder in which magnets can be arranged with high dimensional accuracy and which can be realized with a simple circuit configuration.

[0005]

In order to solve the above-mentioned problems, the encoder of the present invention comprises magnetic field generating means for alternately generating magnetic fields of opposite polarities at a predetermined pitch along one direction, and the magnetic field. An encoder provided with magnetic field detection means for detecting a periodic change in the magnetic field from the magnetic field generation means by a magnetic sensitive element by moving relative to the generation means, and sending position information corresponding to the change in the magnetic field. At
The magnetic field detecting means is provided with a yoke formed of a soft magnetic material of a thin film or a foil body in a comb-shaped pattern, facing the plurality of magnetic poles of the magnetic field generating means, and the magnetic sensitive element between the yokes. , Each comb tooth of the comb tooth-shaped pattern collects magnetic fluxes from a plurality of magnetic poles of the magnetic field generating means, and returns the collected magnetic flux to the magnetic sensitive element section through the yoke, It is characterized in that the element sends position information corresponding to the change of the magnetic field.

That is, according to the encoder of the present invention, a magnetic field generating means (for example, a magnet) for generating a magnetic field of opposite polarity at a predetermined pitch, and a comb-shaped pattern arranged to face each magnetic pole of the magnetic field generating means. When a magnetic field detecting means (for example, a magnetic detecting section) having a magnetic field is moved relative to the magnetic sensitive element (that is, a magneto-impedance element such as an amorphous wire) interposed in the magnetic path of the yoke forming the magnetic detecting section. Due to the effect, the change in the magnetic field caused by the relative movement is detected as a voltage value. As a result, the encoder can detect the relative position information. With such a configuration, it is possible to reduce the influence of variations in the magnetization distribution, mounting errors of each component, fluctuations in the magnetic gap, and the like, so that an encoder with high detection accuracy can be realized. .

Further, the encoder of the present invention is characterized in that, in the above-mentioned invention, the magnetic sensing element detects a change of a magnetic field by a magnetic impedance effect. Further, the encoder of the present invention is characterized in that, in the above-mentioned invention, a plurality of the magnetic field detecting means for detecting magnetic fields of the same phase are provided, and each of the magnetic field detecting means includes a plurality of the magnetic sensitive elements in series. And That is, with such a configuration, the sum of the signals transmitted from the plurality of magnetic field detection means (magnetic detection units) can be output, so that a large magnetic detection signal can be output and the dispersion of the magnetic flux distribution can be increased. The effect of can be reduced.

Further, in the encoder of the present invention according to the above-mentioned invention, the magnetic field detecting means has a step angle of 1 pitch of 360.
When the angle is °, the phase of the magnetic field is 0 °, 90 °, 180
It is characterized in that they are arranged for each phase so as to have a relationship of 270 °. That is, according to this configuration,
Waveforms that change into four sine waves that are 90 ° out of phase are obtained.

In the encoder of the present invention according to the above-mentioned invention, the magnetic field detecting means has magnetic field phases of 0 ° and 180 °.
And the components of 90 ° and 270 ° are output as differential components (as sin θ and cos θ), respectively. That is, by detecting such a differential component, the influence of the disturbance magnetic field can be eliminated, so that the encoder can perform highly accurate position detection.

Also, in the encoder of the present invention according to the above-mentioned invention, the magnetic field detecting means includes a differential component having a magnetic field phase of 0 ° and a differential component of 180 °, and a magnetic field phase having a magnetic field phase of 90 ° and 270. It is characterized in that it is divided by a differential component of °, the arctangent thereof is obtained, and the angle information within one pitch is output. According to this configuration, for example, sin θ is divided by the component of cos θ, and arc tangent (θ = tan ⁻¹ (sin θ / cos
θ)) is obtained and the angle information within one pitch is output. That is, the number of sine waves is counted along with the relative movement, and
The angular position within this one pitch is calculated. As a result, the position in the whole can be obtained.

Further, in the encoder of the present invention, in each of the above inventions, the magnetic field detecting means may include a bias coil for biasing the level of the magnetic field detected by the magnetic sensitive element. That is, by biasing the magnetically sensitive element (magnetic impedance element) with the bias coil, the magnetic impedance element can use only a portion having good linearity in the detected magnetic characteristics. This increases the detection accuracy of the encoder.

Further, in the encoder of the present invention, in each of the above inventions, the magnetic field detecting means may be provided with a feedback coil for feeding back information on the magnetic field detected by the magnetic sensitive element, and further provided for each magnetic sensitive element. Each of the separated feedback coils may be connected in series. That is, if a feedback coil is provided to form a feedback system, various characteristics such as linearity, temperature characteristics, and frequency response are improved. Therefore, a highly accurate encoder used for position control of a precision machine tool can be realized. Further, in the present invention according to each of the above-mentioned inventions, the magnetic field generating means may be composed of a coil formed in a zigzag shape.

In the encoder of the present invention, the first magnetic circuit element in which the soft magnetic material of the thin film or foil is formed in a comb-tooth pattern, the coil or the magnet, and the soft magnetic material of the thin film or foil is comb-shaped. A second magnetic circuit element including a yoke formed in a pattern and a magnetic sensitive element provided between the yokes, wherein the first magnetic circuit element and the second magnetic circuit element are A magnetic field generated by a coil or a magnet of the second magnetic circuit element is configured to flow back to the first magnetic circuit element and the second magnetic circuit element, and the first magnetic circuit element has the second magnetic circuit element. By moving relative to the element, the magnetic resistance of the magnetic circuit in which the first magnetic circuit element is composed of the second magnetic circuit element periodically changes, and the change in the magnetic resistance causes the first magnetic circuit element and Second Magnetic field refluxing the magnetic circuit is configured to vary periodically, and wherein the sending the location information the sensitive magnetic element in response to changes in the magnetic field.

Further, the present invention, in the invention including the first and second magnetic circuit elements, is provided with a plurality of magnetic field detecting means for detecting magnetic fields having the same phase, and each of the magnetic field detecting means is provided with a plurality of magnetic field detecting means. The magnetically sensitive element of 1 is provided in series. The present invention also provides the first and second
In each invention including the magnetic circuit element, when the magnetic field detecting means sets the step angle of one pitch to 360 °, the phases of the magnetic fields are 0 °, 90 °, 180 ° and 270 °. As described above, each phase is arranged. In the invention including the first and second magnetic circuit elements, the magnetic field detecting means may have a magnetic field phase component of 0 ° and 180 ° and 90 ° and 270.
Each of the ° components is output as a differential component. Further, in the present invention according to each invention including the first and second magnetic circuit elements, the magnetic field detecting means includes a differential component of a magnetic field phase component of 0 ° and a differential component of 180 ° phase of the magnetic field. It is characterized in that it is divided by a component having a phase of 90 ° and a differential component of 270 °, the arctangent thereof is obtained, and angle information within one pitch is output. Moreover, the present invention is the invention including the first and second magnetic circuit elements,
The magnetic field detecting means includes a bias coil for biasing the level of the magnetic field detected by the magnetic sensitive element. Further, in the present invention according to each invention including the first and second magnetic circuit elements, the magnetic field detecting means includes a feedback coil for feeding back information on a magnetic field detected by the magnetic sensitive element. Characterize. In the invention including the first and second magnetic circuit elements, the magnetic field generated by the coil and the magnet of the second magnetic circuit element is replaced by the magnetic field generated by the bias coil. It is characterized by having done.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an encoder according to the present invention will be described in detail below with reference to the drawings. Figure 1
[Fig. 3] is an external view of the encoder according to the first embodiment of the present invention, where (a) is a top view and (b) is a side view.
That is, this figure shows one magnetic detection unit of the encoder using the magnet. First of all, using this figure,
The encoder of the embodiment will be described. In the figure, on the fixed side, as shown in the figure, the magnet 1 forming the magnetic field generating means is arranged so as to face the member on the moving pole side, and is arranged in a multi-pole magnetized direction in the relative moving direction. Has become.
The members on the moving side that constitute the magnetic field detection means are thin film yokes 2, 3, 4, 5 of magnetic material, and block-shaped yokes 6.
7, amorphous wires 8 and 9 made of a material having a magnetic impedance effect, and bias coils 10 and 11
And the feed back coils 12 and 13 are arranged as shown in the figure.

The magnet 1 is arranged on a non-magnetic substrate (not shown) on the fixed side, and is multi-polarized in the direction of relative movement with the member on the moving side. On the moving side, a thin film yoke 2, a thin film yoke 3, and a thin film yoke 4 and a thin film yoke 5 are arranged facing each other in a comb shape on a non-magnetic substrate (not shown). The block-shaped yokes 6 and 7 are arranged in contact with the ends of the thin film yokes 2 and 4. still,
The block-shaped yokes arranged so as to contact the ends of the thin film yokes 3 and 5 are not shown. The substrate supporting the magnet and the substrate supporting each member such as the moving side thin film yoke have a relative magnetic permeability of 10 or less and a resistivity of 1 or less.
It can be formed of a metal, glass, ceramics, plastic material or the like having a thickness of 0 μΩ · m or less.

Between the two block-shaped yokes 6 and 7,
An amorphous wire 8 which is a magnetically sensitive element having a magneto-impedance effect is arranged. Similarly, the amorphous wire 9 is also arranged between the block-shaped yokes (not shown) arranged so as to contact the ends of the thin film yokes 3, 5. The amorphous wires 8 and 9 may be made of other materials as long as they have a magnetic impedance effect. Since the amorphous wires 8 and 9 of such a magnetic sensitive element are generally called a magnetic impedance element (MI element), the amorphous wire is hereinafter referred to as a magnetic impedance element or MI element, if necessary. Sometimes. A current is applied to the amorphous wires 8 and 9 by a circuit (not shown) to detect a magnetic field. A bias coil 1 for applying a bias magnetic field is provided around the amorphous wires 8 and 9, respectively.
Two coils 0, 11 and feedback coils 12, 13 for feedback are wound. Note that the configuration of FIG. 1 is drawn as a linear type encoder, but a rotary type encoder has the same configuration.

In FIG. 1, the ends of the comb teeth extending from the thin film yokes 2, 3, 4, 5 and the ends of the magnet 1 in the width direction are drawn so as to coincide with each other. However, if the comb teeth are made longer, or conversely, the width of each of the magnets 1 is made wider, even if the alignment is somewhat unsuccessful due to an attachment error between the fixed side member and the moving side member. ,
It is possible to reduce the influence of the magnetization distribution, mounting error, gap variation, and the like.

Next, the operation of the detector in the encoder shown in FIG. 1 will be described. The magnetic flux flowing from the magnet 1 is
It flows from the comb teeth of the thin film yokes 2, 3, 4, and 5 as shown in the figure, and reaches the portions of the amorphous wires 8 and 9 which are the magnetic impedance elements. For example, when the magnetic flux flows as shown by the arrow in FIG. 1, the maximum magnetic flux flows clockwise as a whole. Therefore, when the fixed-side magnet 1 and the moving-side members relatively move from the positional relationship as shown in FIG. 1, the magnetic flux flowing as shown by the arrow in the figure changes in a sine wave shape, and the amorphous wire 8 , 9 detect the change in the magnetic flux.

FIG. 2 is a diagram showing the characteristics of the impedance change of a magneto-impedance element such as an amorphous wire with respect to the change of the magnetic field. In FIG. 2, the horizontal axis represents the change in magnetic field and the vertical axis represents the change in impedance (Z). As shown in FIG. 2, since the impedance characteristic of the magneto-impedance element has a curved portion, a bias magnetic field is applied by the bias coils 10 and 11 or a magnet (not shown) to utilize the characteristic of a portion having good linearity. I am trying. Therefore, as shown in FIG. 2, even when the magnetic field generated by the magnet 1 is zero, the detected impedance is shifted to a value higher than zero due to the bias magnetic field component. That is, a sine wave characteristic centered on the bias magnetic field component can be obtained. It is generally known that a sinusoidal wave can be obtained by setting the gap length between the magnetic field generating means and the detector to be equal to or greater than the magnetizing pitch.

When the respective members are arranged as shown in FIG. 1, two magneto-impedance elements, that is, the amorphous wires 8 and 9 are connected in series by an electric circuit (not shown) and the effective magnetic field components are added. And the component of the disturbance magnetic field can be configured to be subtracted. As an example, in FIG. 1, the bias coils 10 and 11 are applied so that the bias magnetic field rotates in the same direction on the magnetic circuit loop. That is, the amorphous wire 9 on the upper side of FIG. 1 is arranged so that the magnetic field is applied to the right side (or the left side) so that the amorphous wire 8 on the lower side of FIG.
Applies a bias magnetic field by the bias coils 10 and 11 so that the magnetic field is applied in the left direction (right direction). As a result, the effective magnetic field components are added and the disturbance magnetic field components are canceled.

FIG. 3 is a vector diagram of the effective magnetic field and the disturbance magnetic field when a current is passed through the two magneto-impedance elements. In FIG. 3, when two bias magnetic fields are applied to the two magneto-impedance elements by two bias coils (not shown), the vector components of the two bias magnetic fields have the same direction, and the vector components of the effective magnetic field direction are added. On the other hand, the vector components of the disturbance magnetic field in the two magneto-impedance elements are subtracted and canceled.
As a result, the magneto-impedance element is hardly affected by the magnetic field due to the disturbance.

Next, an encoder according to the second embodiment of the present invention will be described. In the second embodiment,
A case where the encoder shown in FIG. 1 is applied to a rotary encoder and a plurality of encoders are arranged will be described. However, the case where there is one magneto-impedance element (amorphous wire) will be mentioned. FIG. 4 is a schematic sectional view of the rotary encoder in the present invention. As shown in FIG. 4, a multi-pole magnetized magnet 23 is attached to a non-magnetic rotating side disc 22 attached to a motor rotating shaft 21. At this time, the magnetizing direction of the magnet 23 is the circumferential direction of the rotating disk 22. Further, a thin film yoke 25, a block-shaped yoke 26, and a magnetic impedance element (amorphous wire) not shown are arranged on a non-magnetic fixed side disk 24 attached to a fixed side such as a motor casing not shown.

Next, in the rotary encoder shown in FIG. 4, the arrangement of the magnetic detecting portion (that is, the magnetic impedance element) on the fixed side disk 24 will be described. Figure 5
It is a figure which shows arrangement | positioning of the magnetic detection part to the fixed side disc of the rotary encoder in FIG. As shown in FIG. 5, on the fixed side disk 24, for example, four magnetic detection units are arranged at equal angles on the circumference so as to have the same phase relationship, and this is referred to as an A phase. Specifically, assuming that the number of multi-pole magnetizations is N, the pitch angle θp = 360 / N, and the arrangement angle interval of the in-phase detector (A phase) is an integral multiple of θp. For example, assuming that N = 5000, the arrangement angle interval of the in-phase detection unit (A phase) is 90 ° (= (360/500
0) × 1250 (a positive multiple)). When the arrangement angle is 90 °, four in-phase detectors are arranged on the circumference.

Next, the magnetic detection part whose phase is shifted by 180 ° from the A phase is defined as the A'phase, and the arrangement angle interval between the A'phase and the A phase is
θa '= (integer multiple of pitch angle + pitch angle x 1/2)
So that the A′-phase magnetic detector is divided into four equal parts for one round. For example, if N = 5000, for example, θ
a ′ = 22.5 ° (= (360/5000) × 312 +
It can be set to (360/5000) × (1/2)) (integral multiple at 312). That is, the pitch angle between the A phase and the A ′ phase can be set to θa ′ = 22.5 °. Similarly, the magnetic detectors whose phases are deviated by 90 ° and 270 ° from the A-phase are referred to as the B-phase and the B′-phase, respectively, and the interval of the arrangement angle of the detector center from the A-phase is θb = (Integer multiple of pitch angle + pitch angle × 1/4), B ′ phase is θb ′ = (integer multiple of pitch angle + pitch angle × 3 /
4), the B-phase and B′-phase detectors are arranged in four equal parts in each round. For example, if N = 5000,
θb = 45.018 ° (= (360/5000) × 62
5+ (360/5000) × (1/4)), θb ′ = 6
7.518 ° (= (360/5000) × 937 + (3
60/5000) × (3/4)).
The above-mentioned arrangement angles are not limited to the above-mentioned values, and it is sufficient that each magnetic detection unit is approximately equally distributed and the phase angle of each magnetic detection unit is satisfied.

4 of each phase (A phase, A'phase, B phase, B'phase)
The two magneto-impedance elements may each independently constitute a magnetic detection circuit, and their output voltages may be added, but the magneto-impedance elements for each phase are connected in series,
If these are connected to the detection circuit like one magneto-impedance element, the circuit can be further simplified. The configuration of the detection circuit that handles the magneto-impedance elements connected in series as if they were one element uses, for example, the CMOS-MI magnetic field sensor circuit disclosed in Japanese Patent Laid-Open No. 9-329655 as shown in FIG. be able to. Since the details of the CMOS-MI magnetic field sensor circuit shown in FIG. 6 are disclosed in the publication, description thereof will be omitted.
According to this CMOS-MI magnetic field sensor circuit, the CMOS
The magneto-impedance elements 33 and 34 such as amorphous wires connected in series are excited by the sharp pulse current in the excessive state of the multi-vibrators 31 and 32, and the current is interrupted by the CMOS multi-vibrators 31 and 32 in the steady state. By doing so, the magneto-impedance elements 33 and 34 can detect the external magnetic field with high accuracy and low power consumption.

Therefore, four A-phase magneto-impedance elements in FIG. 5 are connected in series to correspond to one element.
CMOS multivibrator 31 in the circuit of FIG.
Can be connected between 32. At this time, the signal input to the output stage differential amplifier 35 is a sine wave having an offset level corresponding to the bias magnetic field. Similarly, four magnetic impedance elements of A ′ phase in FIG. 5 are connected in series to correspond to one element, and the CMOS multivibrator 3 of the magnetic field sensor circuit having the same circuit configuration as in FIG. 6 is provided.
It can be connected between 1, 32. by this,
The signal input to the differential amplifier 35 is a sine wave signal which is 180 ° out of phase with the A-phase signal and has an offset corresponding to the bias magnetic field. These A-phase and A′-phase differential output signals are output from the respective differential amplifiers 35 as sinusoidal signals sin θ whose amplitude is increased by removing the offset. Further, for the B phase and B ′ phase in FIG. 5, if the same circuit as the CMOS-MI magnetic field sensor circuit shown in FIG. 6 is prepared, the cosine wave signal cos θ is output from each differential amplifier 35.

Then, sin θ and cos θ are A / D converted and taken into the CPU or the like. Furthermore, in the CPU,
Divide sin θ by s θ and calculate the arc tangent θ = tan ⁻¹ (sin
θ / cos θ), one pitch is 36
The angular position when 0 ° can be obtained. That is, the number of sine waves is counted along with the rotation, and the angular position within one pitch can be calculated to obtain the angular position on one circumference. Note that sin θ and cos
By dividing θ, it is possible to reduce the influence of the temperature change on the amplitude of the output signal.

Next, items common to the first and second embodiments will be described. Therefore, the description will be made again with reference to FIG. The bias coils 10 and 11 for applying a bias magnetic field to the magneto-impedance elements (amorphous wires 8 and 9) have the same offset as possible for each output according to the characteristics of the magneto-impedance elements (amorphous wires 8 and 9). It is desirable to adjust the current value so that
When the characteristics of the respective magnetic impedance elements (amorphous wires 8 and 9) are relatively uniform,
Magneto-impedance element (amorphous wires 8 and 9)
It is advisable to apply the same current to each phase or all elements. Further, instead of the bias coils 10 and 11, a magnet may be used to apply a bias magnetic field to the magneto-impedance element (amorphous wires 8 and 9).

Further, the feedback coils 12, 13
May or may not be used, but the use thereof improves linearity in the characteristics of the magneto-impedance element (amorphous wires 8 and 9), various characteristics such as temperature characteristics and frequency response. Further, the magnetic impedance elements (amorphous wires 8 and 9) may be individually fed back, but the magnetic impedance elements (amorphous wires 8 and 9) are connected in series so that feedback is performed for each phase. The circuit can be simplified as it goes.

When the magneto-impedance element (amorphous wires 8 and 9) is attached to the fixed-side disc, the block-shaped yokes 6 and 7 are separated from the disc by the magneto-impedance element (amorphous wires 8 and 9). Used in such cases. In the case where the magneto-impedance element (amorphous wires 8 and 9) is a thin film, it can be arranged close to the thin-film yoke, and even if a sufficient magnetic flux is not generated in the magneto-impedance element (amorphous wires 8 and 9). Good.

Next, a method of manufacturing each part of the encoder will be described. Magneto-impedance elements are disclosed in JP-A-7-181239, JP-A-8-285930, JP-A-9-145808, and JP-A-2000-81471.
JP-A-2000-55995, JP-A-2000-1937
Any element capable of obtaining a so-called magnetic impedance effect as disclosed in each publication such as No. 28 may be used.
Other than that, for example, Japanese Patent Laid-Open No. 2000-30921 proposes a magneto-impedance element having asymmetrical magneto-impedance characteristics using amorphous metal thin wires. I don't mind.

Next, the thin film yoke is made of iron-nickel alloy or
A soft magnetic material such as an iron-based amorphous alloy or a ferrite-based oxide is used to form a film by a film forming method such as vapor deposition, sputtering, plating, or adhesion of a foil, and a pattern is formed by photoetching or the like.

The block-shaped yoke is made of iron-nickel alloy, iron-based amorphous alloy, ferritic stainless steel,
A processed soft magnetic (ferrimagnetic) bulk material such as ferrite can be used. In addition, in order to improve high frequency characteristics, a laminate of foils or plates may be used.

Next, various variations of the magnetic detector in the encoder will be described. The relative movement of the encoder may be linear or rotary. In FIG. 1, two magnetic impedance elements (amorphous wires 8 and 9) are drawn in the magnetic detection portion, but either one may be removed so that the thin film yoke is continuous. Alternatively, a plurality of magneto-impedance elements (amorphous wires) may be inserted in the gap of the block-shaped yoke, and the outputs of the plurality of magneto-impedance elements (amorphous wires) may be connected in series to increase the output signal.

FIG. 7 shows a modification of the encoder of the first embodiment shown in FIG. That is, as shown in FIG. 7, one thin film yoke 41 is deformed into a shape in which an amorphous wire or the like is removed, and the other thin film yoke 42 is configured such that the amorphous wires 43 and 44 are inserted in its magnetic path. Deform. Even with this modification, a magnetic detection signal having exactly the same characteristics as in FIG. 1 can be obtained. The operation of magnetism detection is the same as in the case of FIG. 1, and therefore its explanation is omitted.

Further, in FIG. 1 and FIG. 7, the comb teeth are opposed to each other at two positions for each phase, but the comb teeth may be opposed to each other at one position and one of them may be continuous with a thin film yoke. Good. For example, referring to FIG. 1, the thin film yokes 2 and 3 are made continuous by removing the comb teeth. Even if the thin film yokes 4 and 5 have the comb teeth as shown in FIG. The magnetic flux passing through each of the comb teeth 4 and 5 is continuous as in FIG. The number of teeth of each thin film yoke in FIGS. 1 and 7 can be arbitrarily determined.

Further, in FIG. 1, the magnetizing direction of the magnet 1 magnetized in multiple poles is shown to be magnetized in the relative moving direction, but the present invention is not limited to this, and the magnetizing direction is perpendicular to the plane of the drawing. Therefore, the polarity of the magnetic pole may be in any direction. In this case, the substrate on which the magnet 1 is mounted is made of a soft magnetic material so that the magnetic detection portion side (that is, the comb tooth side of the thin film yoke) is formed.
The magnetic flux of can be further increased. Even when the magnetizing direction is perpendicular to the plane of the drawing, the magnetic flux on the magnetic detecting portion side can be further increased by slightly changing the comb tooth shape.

Next, the differential method of the two-phase magneto-impedance elements will be described. In the above description, the method of performing the differential between the A phase and the A ′ phase (or the B phase and the B ′ phase) by the differential amplifier in FIG. 6 has been described.
The two-phase magneto-impedance element can be connected to a full bridge, or can be connected to a half bridge to take out a differential output. FIG. 8 is an example of a circuit in which two-phase magneto-impedance elements are connected to a full bridge to take out a differential output, and FIG. 9 is a two-phase magneto-impedance element connected to a half bridge to perform differential output. Is an example of a circuit for taking out.

Explaining the full bridge circuit of FIG. 8, two of the four phase A magneto-impedance elements mounted on the fixed side disk 24 of FIG. 5 are connected in series, and their impedances are Z1 and Z2, respectively. And four A '
Two of the phase magneto-impedance elements are connected in series and the impedances of the phase magneto-impedance elements are set to Z3 and Z4, respectively. Then, in this full-bridge circuit, for example, sufficiently faster than the frequency of the change of the periodic magnetic flux caused by the relative moving speed than the CMOS multivibrator 31, 32 of FIG. 6 (for example, 100
AC signal is applied. That is, the AC signal F is applied in the circuit of FIG. Then, if the voltage between X and Y of the bridge circuit is taken out as a differential output and rectified to remove the AC component applied by the low pass filter or the like, the change of the periodic magnetic flux amplified from the differential amplifier 35 as described above. The sine wave signal corresponding to can be taken out.

In the case of the half bridge circuit of FIG.
Mounted on the fixed-side disc 24 of four, and the impedance is Z1 by connecting four A-phase magneto-impedance elements in series, and the impedance is Z2 by connecting four A'-phase magneto-impedance elements in series. Configure a bridge circuit. Then, the voltage at the point X where the impedance Z1 and the impedance Z2 are connected may be extracted, used for differential, rectified, and filtered. The AC signal F applied to the full bridge circuit and the half bridge circuit in FIGS. 8 and 9 may be a sine wave signal, but need not be a sine wave signal.

Next, the multi-pole magnetized magnet 1 shown in FIG.
A modified example of the (magnetic field generating means) will be described. Instead of the multi-pole magnetized magnet 1 shown in FIG. 1, a zigzag coil may be used as the magnetic field generating means. Figure 10
It is a conceptual diagram which shows the meandering coil used for the magnetic detection part of an encoder. That is, a periodic magnetic flux such as a multi-pole magnetized magnet as shown in FIG. 1 can be produced by applying a direct current to the meandering coil as shown in FIG. In FIG. 10, since the polarity of the magnetic flux changes at each turn of the zigzag folded coil, magnetic fluxes of different polarities can be created alternately like the magnet 1 of FIG. Note that, when a zigzag coil is used, the configuration on the fixed side is the same as that of the above-described first embodiment, except for the power supply to the magneto-impedance element. In the case of a rotary encoder, it is desirable to supply power to the magneto-impedance element in a non-contact manner.A sine wave is transmitted by a transformer generally called a rotary transformer, which is rectified and converted to direct current. Power can be supplied to the magneto-impedance element.

Next, the case where the magnet (magnetic field generating means) is a soft magnetic film pattern will be described. FIG. 11 is a perspective view of a magnetic detection unit in the encoder when the magnet has a soft magnetic film pattern. As shown in FIG. 11, even if the moving-side magnet is the soft magnetic thin film pattern 51, the magnetic field of the magneto-impedance element 52 can be changed periodically.
The fixed-side structure is the same as the structure shown in FIG.
The bias coil 53 causes the magneto-impedance element 5 to
When a bias magnetic field is applied to the thin film yoke 5 on the fixed side
4 and the soft magnetic thin film pattern 51 on the moving side, a reflux magnetic flux flows, and the magnetic resistance changes due to the relative movement between the fixed side and the moving side, so that the magnetic field of the magneto-impedance element 52 changes.

Next, the compensation of the disturbance magnetic field and the magnetic shield will be described. As described above with reference to FIG. 3, it is possible to reduce the influence of the disturbance magnetic field by connecting the magneto-impedance elements in series or taking a differential, but the magneto-impedance element has a linear characteristic. When a large disturbance magnetic field that causes a portion with a good magnetic field is applied, the effect of reducing the influence of the disturbance magnetic field cannot be expected by the method described above. In such a case, for example, the magnitude of the disturbance magnetic field can be detected by monitoring the ratio of the voltage at the intermediate position to the voltage of the two magneto-impedance elements connected in series in FIG. Therefore, a coil for compensating the disturbance magnetic field may be separately provided to cancel the disturbance magnetic field.
In addition, when performing magnetic shielding, use a non-magnetic and conductive material, a magnetic and conductive material, a magnetic and non-conductive material, etc., depending on the frequency and strength of the external magnetic field. Alternatively, if used in combination, a corresponding magnetic shield effect can be obtained.

To give a concrete example of obtaining the magnetic shield effect, the relative permeability is 10 or less and the resistivity is 10 μΩ · m.
The following materials, and the relative permeability of 100 or more and the resistivity of 10μ
It is preferable that the magnetic circuit of the entire components constituting the encoder is covered with a material having an Ω · m or less, a material having a relative magnetic permeability of 100 or more and a resistivity of 10 μΩ · m or more. Alternatively, a combination of these materials may cover the magnetic circuit of the entire component. Although an example using a magnetic impedance element as the magnetic sensitive element has been disclosed this time, an element such as a magnetoresistive element or a Hall element may be used as the magnetic sensitive element.

[0046]

As described above, according to the encoder using the magnetic sensitive element of the present invention, the following various effects can be obtained. First, since the magnetic detection unit can obtain an averaged output signal of a plurality of magnetic poles, it is possible to reduce the influence of the mounting error of each component of the encoder and the variation of the magnetic gap. Secondly, as the output signal of the magnetic sensitive element of each phase, the output signal of the sum of the plurality of magnetic detection units is obtained, and further, the averaging of the plurality of magnetic poles and the averaging depending on the magnetic detection location can be performed. It is possible to reduce the influence of mounting error and processing error such as eccentricity, magnetic gap difference due to mounting location, and magnetic fluctuation.

Thirdly, since the magnetic sensitive element can be separately manufactured and attached, the characteristic can be improved by the magnetic sensitive element alone, and it is not necessary to use the magnetic sensitive element dedicated to the encoder. The manufacturing process can be simplified and the cost can be reduced. In addition, even when manufacturing magneto-sensitive elements of multiple phases, it is good to form a plurality of thin-film yokes on one substrate and attach the magneto-sensitive element afterwards. The influence of can be reduced.

Furthermore, it is possible to take measures to reduce the influence of temperature changes while maintaining high dimensional accuracy for each encoder component. When the magnetic sensitive element or the magnetic sensitive element and the feedback coil are connected in series, even if a plurality of magnetic sensitive elements are arranged in one phase or magnetic impedance is arranged in a plurality of phases, The magnetic detection circuit can be realized with a relatively simple circuit configuration. Such various effects synergistically realize high resolution, miniaturization, and cost reduction in the encoder using the magnetically sensitive element.

[Brief description of drawings]

FIG. 1 is an external view of an encoder according to a first embodiment of the present invention, (a) is a top view and (b) is a side view.

FIG. 2 is a diagram showing a characteristic of impedance change of a magneto-impedance element such as an amorphous wire with respect to a change of a magnetic field.

FIG. 3 is a vector diagram of an effective magnetic field and a disturbance magnetic field when a current is applied to two magneto-impedance elements.

FIG. 4 is a schematic sectional view of a rotary encoder according to the present invention.

5 is a diagram showing an arrangement of a magnetic detection unit on a fixed side disc of the rotary encoder in FIG.

FIG. 6 is a CMOS-MI magnetic field sensor circuit diagram disclosed in Japanese Patent Laid-Open No. 9-329655.

FIG. 7 is a modified example of the encoder of the first embodiment shown in FIG.

FIG. 8 is an example of a circuit in which two-phase magneto-impedance elements are connected to a full bridge to take out differential outputs.

FIG. 9 is an example of a circuit in which two-phase magneto-impedance elements are connected to a half bridge to take out differential outputs.

FIG. 10 is a conceptual diagram showing a staggered coil used in a magnetic detection unit of an encoder.

FIG. 11 is a perspective view of a magnetic detection unit in the encoder when the magnet has a soft magnetic film pattern.

[Explanation of symbols]

1 ... Magnet, 2, 3, 4, 5 ... Thin film yoke, 6, 7 ... Block-shaped yoke, 8, 9 ... Amorphous wire (magnetic impedance element) 10, 11 ... Bias coil, 1
2, 13 ... Feed back coil, 21 ... Motor rotating shaft,
22 ... Rotating side disc, 23 ... Magnet, 24 ... Fixed side disc, 2
5 ... Thin film yoke, 26 ... Block-shaped yoke, 31, 32
... CMOS multivibrator, 33, 34 ... Magnetic impedance element, 35 ... Differential amplifier, 41, 42 ... Thin film yoke, 43, 44 ... Amorphous wire, 51 ... Soft magnetic thin film pattern, 52 ... Magnetoimpedance element, 53
... bias coil, 54 ... thin film yoke.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2F077 AA13 AA25 AA47 CC02 NN03                       NN05 NN09 NN16 NN17 PP11                       QQ05 UU08 VV02                 2G017 AA01 AC01 AC09 AD51 AD63                       AD65 BA09

Claims (17)

[Claims] 1. A magnetic field generating means for alternately generating magnetic fields of opposite polarities at predetermined pitch intervals along one direction, and a relative movement with respect to the magnetic field generating means to periodically generate magnetic fields from the magnetic field generating means. A magnetic field detecting means for detecting a change in a magnetic field by a magnetic sensitive element and transmitting position information corresponding to the change in the magnetic field, wherein the magnetic field detecting means faces the plurality of magnetic poles of the magnetic field generating means. A thin-film or foil soft magnetic material formed into a comb-tooth pattern and the magnetic sensitive element between the yokes, each comb-tooth of the comb-tooth pattern being the magnetic field generating means. The magnetic flux from the plurality of magnetic poles is collected, and the collected magnetic flux is returned to the magnetic sensitive element section through the yoke, whereby the magnetic sensitive element sends out position information corresponding to a change in magnetic field. The encoder to collect. 2. The encoder according to claim 1, wherein the magnetic sensitive element detects a change in magnetic field by a magnetic impedance effect. 3. The magnetic field detecting means for detecting magnetic fields of the same phase are provided in a plurality, and each magnetic field detecting means is provided with a plurality of the magnetic sensitive elements in series. The encoder described in. 4. The magnetic field detecting means has a magnetic field phase of 0 ° or 90 ° when the step angle of one pitch is 360 °.
The encoder according to claim 3, wherein the encoders are arranged for each phase so as to have a relationship of 180 °, 270 °, and 180 °. 5. The magnetic field detecting means has a magnetic field phase of 0 °.
The encoder according to claim 4, wherein the components of 180 ° and 180 ° and the components of 90 ° and 270 ° are output as differential components, respectively. 6. The magnetic field detection means has a magnetic field phase of 0 °.
And the 180 ° component differential component, the magnetic field phase is 9
The encoder according to claim 4, wherein division is performed by a component of 0 ° and a differential component of 270 °, an arctangent thereof is obtained, and angle information within one pitch is output. 7. The encoder according to claim 1, wherein the magnetic field detecting means includes a bias coil that biases the level of the magnetic field detected by the magnetic sensitive element. 8. The encoder according to claim 1, wherein the magnetic field detecting means includes a feedback coil for feeding back information on the magnetic field detected by the magnetic sensitive element. 9. The encoder according to claim 1, wherein the magnetic field generating means is composed of a coil formed in a zigzag shape. 10. A first magnetic circuit element in which a soft magnetic material of a thin film or a foil is formed in a comb-shaped pattern, a coil or a magnet, and a soft magnetic material of a thin film or a foil is formed in a comb-shaped pattern. A second magnetic circuit element including a yoke and a magnetic sensitive element provided between the yoke, the first magnetic circuit element and the second magnetic circuit element being the second magnetic circuit element. A magnetic field generated by a coil or a magnet of the element is circulated to the first magnetic circuit element and the second magnetic circuit element, and the first magnetic circuit element is provided with respect to the second magnetic circuit element. By the relative movement, the magnetic resistance of the magnetic circuit in which the first magnetic circuit element is composed of the second magnetic circuit element periodically changes, and the change in the magnetic resistance causes the first magnetic circuit element and the second magnetic circuit element to change. In circuit element An encoder characterized in that a magnetic field that circulates is configured to change periodically, and the magnetic sensitive element sends out position information corresponding to a change in magnetic field. 11. The magnetic field detecting means for detecting magnetic fields of the same phase are provided in a plurality, each magnetic field detecting means comprising a plurality of the magnetic sensitive elements in series. Encoder. 12. The magnetic field detecting means has magnetic field phases of 0 ° and 90 ° when a step angle of one pitch is 360 °.
The encoder according to claim 11, wherein the encoders are arranged for each phase so as to have a relationship of °, 180 °, and 270 °. 13. The magnetic field detecting means has a phase of a magnetic field of 0.
The components of ° and 180 °, and the components of 90 ° and 270 °,
The encoder according to claim 12, wherein the encoder outputs each as a differential component. 14. The magnetic field detecting means has a phase of a magnetic field of 0.
Dividing the differential component of the 90 ° component and the 180 ° component by the component of the magnetic field phase of 90 ° and the differential component of 270 °, obtaining the arctangent and outputting the angle information within one pitch. The encoder according to claim 12, wherein: 15. The magnetic field detecting means comprises a bias coil for biasing the level of the magnetic field detected by the magnetic sensitive element.
The encoder according to any one of 1. 16. The magnetic field detecting means includes a feedback coil for feeding back information on the magnetic field detected by the magnetic sensitive element.
The encoder according to claim 15. 17. A magnetic field generated by a coil and a magnet of the second magnetic circuit element is replaced by a magnetic field generated by a bias coil.
~ The encoder according to claim 16.