JP5573042B2 - Magnetic encoder - Google Patents

Description

The present invention relates to a magnetic encoder that detects a rotational position and a rotational speed of a rotating body such as a motor.

Since the detection unit of the conventional angle detection device or magnetic encoder is in the rotating magnetic field to be detected, the induced voltage generated by the circuit loop from the lead wire of the detection unit to the signal processing unit is superimposed on the detection signal to detect the angle. There was a problem of becoming an error. As countermeasures, as shown in FIG. 15, magnetic detection elements 130 and 131 fixed to the base 180, a cylindrical rotating body 120 on the outer periphery of the base 180, and a permanent magnet 122 fixed to the rotating body 120, 124, the phase of the induced voltage generated in the circuit loop formed between the conductors of the magnetic detection elements 130 and 131 for detecting the angle of the rotating body and the control means ECU 182 is respectively determined. From the lead-out portion and the wiring portion so that the induced signals superimposed on the A-phase signal and B-phase signal, which are 90 degrees out of phase, become the same phase as the detection signal of the magnetic detection element. There has been disclosed a rotation angle detection device in which the influence of the induced voltage is reduced and the accuracy is improved by devising the wiring of the conductive wire (see, for example, Patent Document 1).

JP 2007-218592 A (page 10, FIG. 1)

  However, in the conventional example, in order for the detection signal and the induced voltage to have exactly the same phase, it is necessary to accurately align the magnetic sensing surface of the magnetic detection element and the surface of the wiring portion in parallel. There is a phase shift of the induced voltage with respect to the detection signal. When induced voltages having different phases are superimposed on the detection signal, there is a problem that an error is caused in the angle calculation process because a change in the phase together with the amplitude appears in the detection signal.

The present invention has been made in view of such problems, and is not affected by the induced voltage superimposed on the detection signal even when the wiring conductor from the magnetic detection unit to the signal processing unit is in the magnetic flux. An object of the present invention is to provide a highly accurate magnetic encoder that does not cause an angular error.

To solve the above SL problem, the present invention is constructed as follows.
The present invention is a disk-shaped or ring-shaped permanent magnet attached to a rotating shaft and magnetized in one direction perpendicular to the axial direction, a ring-shaped fixed body provided through the permanent magnet and a gap, A plurality of magnetic field detection elements disposed inside the fixed body, and a circuit board that transmits signals of the plurality of magnetic field detection elements and performs rotation angle calculation processing, wherein the circuit board is fixedly disposed above the fixed body In the encoder, the plurality of magnetic field detection elements are arranged in order at intervals of 90 degrees in mechanical angle. It comprises third and fourth magnetic field detection elements, and the magnetic field detection element has a linear terminal lead portion extending in a plane parallel to the magnetosensitive surface, and is connected to the circuit board via the terminal lead portion. The pair of magnetic field detection elements attached to the position opposed to the rotation axis connect the output positive terminals and the output negative terminals, and connect one power positive terminal and the other power negative terminal that form a pair. It is characterized by connecting.
Further, the present invention provides a power supply positive terminal of the first magnetic field detection element, a power supply negative terminal of the third magnetic field detection element, a power supply positive terminal of the second magnetic field detection element, and a power supply negative terminal of the fourth magnetic field detection element. And connecting a power supply negative terminal of the first magnetic field detection element and a power supply positive terminal of the third magnetic field detection element, and a power supply negative terminal of the second magnetic field detection element and a power supply positive terminal of the fourth magnetic field detection element. ,
An output positive terminal of the first magnetic field detection element and an output positive terminal of the third magnetic field detection element are connected, connected to one input terminal of the first differential amplifier, and an output negative terminal of the first magnetic field detection element An output negative terminal of the third magnetic field detection element is connected, connected to the other input terminal of the first differential amplifier, and an output positive terminal of the second magnetic field detection element and an output positive terminal of the fourth magnetic field detection element. A second terminal connected to one input terminal of the second differential amplifier, an output negative terminal of the second magnetic field detecting element and an output negative terminal of the fourth magnetic field detecting element, and a second differential amplifier; And the rotation angle is calculated from the output signals of the first and second differential amplifiers.
The present invention also provides a disk-shaped or ring-shaped permanent magnet attached to a rotating shaft and magnetized in one direction perpendicular to the axial direction, and a ring-shaped fixed body provided via the permanent magnet and a gap. A plurality of magnetic field detection elements arranged inside the fixed body, a circuit board provided above the fixed body and having a plurality of layers of conductive patterns for transmitting detection signals of the plurality of magnetic detection elements; In the magnetic encoder for detecting the rotational angle position from the detection signal of the magnetic detection element, the plurality of magnetic field detection elements are arranged in order at every 90 degrees in mechanical angle. A conductive wire pattern of the circuit board comprising the third and fourth magnetic field detecting elements, the output positive terminals of the opposing magnetic detecting elements forming a pair, and the output negative terminals being concentrically formed around the rotation axis. It is characterized by being connected.
Further, the present invention is characterized in that the conductive wire patterns that form a pair of the circuit boards are formed in separate layers of the circuit board so as to be concentrically overlapped with the same diameter around the rotation axis. .
Further, the present invention, the magnetic field detection element is characterized in that a Hall element.

According to the present invention, the output signals of the paired magnetic field detection elements attached at positions facing the rotation axis are in phase, and the induced voltages generated in the lead portions of the magnetic field detection elements are in reverse phase. An amplitude change and a phase change due to superposition of an induced voltage of the detection signal can be eliminated, and a highly accurate rotation angle can be obtained from the detection signal.
Further , according to the present invention, by forming the conductor pattern of the circuit board concentrically around the rotation axis, the induced voltage superimposed on the conductor pattern of the detection signal due to the leakage magnetic flux from the disk-shaped permanent magnet is canceled out. Therefore, a highly accurate rotation angle can be obtained.
In addition, according to the present invention, the signal lines forming a pair of magnetic detection elements are formed in separate layers of the circuit board so as to overlap in a circular shape with the same diameter around the rotation axis, so that the rotation axis direction of the external magnetic field Since the induced voltage superimposed on the conductor pattern of the detection signal can be canceled by the component, a highly accurate rotation angle can be obtained.
In addition, according to the present invention, since the Hall element is used as the magnetic detection element, it can be easily configured at a relatively low cost.

The front view which shows the structure of 1st Example of this invention. The side view which shows the structure of 1st Example of this invention. Shape of Hall element forming a pair of the first embodiment of the present invention Connection diagram of the first embodiment of the present invention The front view which shows the magnetic field direction of 1st Example of this invention. The side view which shows the magnetic field direction of 1st Example of this invention The schematic diagram which shows the magnetic field direction and signal direction of 1st Example of this invention. The perspective view which shows the structure of 2nd Example of this invention. The perspective view which shows the conducting wire pattern of the circuit board of 2nd Example of this invention. The figure which shows the detection signal connection of the magnetic detection element of 2nd Example of this invention. Schematic diagram showing the operation of the second embodiment of the present invention. The perspective view which shows the conducting wire pattern of the circuit board of 3rd Example of this invention. Schematic diagram showing the operation of the third embodiment of the present invention. Schematic diagram showing the magnetic flux leakage of the magnetic encoder board Diagram showing conventional magnetic encoder configuration

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a front view showing the configuration of the first embodiment of the present invention, and FIG. 2 is a side view showing the configuration of the first embodiment of the present invention. In the figure, the rotating shaft 11 is attached to a shaft such as a motor and rotates together with the motor. The permanent magnet 12 is fixed to the rotating shaft 11. There is a ring-shaped fixed body 13 on the outer periphery from the permanent magnet 12 through a gap. The fixed body 13 may be either a magnetic body or a non-magnetic body, but a magnetic body is preferable because a detection signal of the Hall element is increased. Hall elements 41, 42, 43, and 44, which are magnetic field detection elements for detecting the magnetic field generated by the permanent magnet 12, are arranged inside the fixed body 13 that is a magnetic body. Hall elements 41 and 43 and 42 and 44 are opposed to the rotation axis, respectively, and the pair of Hall elements 41 and 43 are arranged with a mechanical angle of 90 ° shifted from the pair of Hall elements 42 and 44 around the rotation axis. Yes. The circuit board 15 is fixed above the fixed body 13 by a support body (not shown), and the power supply terminals and output terminals of the Hall elements 41, 42, 43, and 44 are connected. Signal processing for rotation angle detection is performed.
FIG. 3 shows the shapes of the Hall elements 42 and 44 arranged at the opposing positions. There are magnetic sensing portions 90 and 91 for detecting a magnetic field in the vertical direction at the center of the package, the terminal (1) is a power supply positive terminal, the terminal (3) is a power supply negative terminal, the terminal (2) is an output positive terminal, and a terminal ( 4) is an output negative terminal. There are lead-out portions 81 to 84 and 85 to 88 for drawing out signals from the respective terminals in a direction parallel to the package.
The hall elements 41, 42, 43, and 44 are connected to the circuit board 15 through the lead-out portion.

FIG. 4 is a connection diagram of the Hall elements 42 and 44 according to the first embodiment of the present invention. The terminal (1) of the Hall element 42 is connected to the + power supply, and the terminal (3) is connected to the −power supply. Considering the relationship between the position of the permanent magnet 12 in FIG. 2 and the Hall elements 42 and 44, the output positive terminal (2) of the Hall element 42 on the N-pole side of the permanent magnet 12 becomes + output, and the circuit is connected via the lead-out portion 82. It is connected to the conductive wire 61 on the substrate 15. Further, the negative output terminal (4) of the Hall element 42 becomes a negative output, and is connected to the conductive wire 62 on the circuit board 15 through the lead-out portion 84. The conducting wires 61 and 62 are connected to the first differential amplifier 100 on the circuit board 15.
Next, the power source negative terminal (3) of the Hall element 44 facing the Hall element 42 and the rotating shaft 11 is connected to a positive power source, and the power source positive terminal (1) is connected to a negative power source. The negative output terminal (4) of the Hall element 44 on the N-pole side of the permanent magnet 12 becomes a negative output and is connected to the conductive wire 64 on the circuit board 15 via the lead-out portion 88. Further, the positive output terminal (2) of the Hall element 44 becomes a positive output and is connected to the conductive wire 63 on the circuit board via the lead-out portion 86. The conductive wires 64 and 63 are connected to the first differential amplifier 100 on the circuit board 15. The positive output terminals (2) and the negative output terminals (4) of the Hall element 42 and the Hall element 44 are connected to each other and connected to the first differential amplifier, and output to the first differential amplifier. A sine wave signal is obtained with respect to the rotation angle. The pair of Hall elements 41 and 43 is configured and connected in the same manner as the Hall elements 42 and 44 and connected to the second differential amplifier to obtain an output signal of a cosine wave function.

Next, the principle of canceling the induced voltage superimposed on the detection signal of the Hall element of the present invention will be described.
When the rotating shaft 11 rotates, a signal corresponding to the rotational angle position is detected in each Hall element in response to a change in the radial magnetic field of the permanent magnet 12.
FIG. 5 is a front view showing the magnetic field direction at a certain rotation angle according to the first embodiment of the present invention.
FIG. 6 is a side view showing the magnetic field direction at a certain rotation angle according to the first embodiment of the present invention.
FIG. 7 is a schematic diagram showing a magnetic field direction and a signal direction at a certain rotation angle according to the first embodiment of the present invention, and the magnetic sensitive directions of the Hall elements 42 and 44 are all upward in the drawing.
According to FIG. 7, the magnetic field direction in the vicinity of the magnetic sensitive part of the Hall element 42 is an upward direction on the paper surface, and the magnetic field direction in the vicinity of the magnetic sensitive part of the Hall element 44 is a downward direction on the paper surface. At this time, the output negative terminal (4) of the Hall element 42 is -potential, the output positive terminal (2) is + potential, the output negative terminal (4) of the Hall element 44 is -potential, and the output positive terminal (2) is + potential. It becomes.

However, according to FIG. 6, the magnetic circuit composed of the permanent magnet 12 and the fixed body 13 that is a magnetic body includes not only the Hall elements 42 and 44 but also the lead portions 81 to 84 and 85 to 88, and the lead portion An induced voltage is generated in a circuit loop composed of a conducting wire part. Here, the power supply terminals 81, 83, 85, 87 are not shown. In particular, the magnetic flux interlinked with the lead-out portion is as large as the magnetic flux density detected by the Hall element, so the induced voltage represented by the time change of the magnetic flux interlinked with the circuit is superimposed on the detection signal from Faraday's law. Resulting in.
According to FIGS. 6 and 7 of the configuration of the present invention, the induced voltage of the circuit loop composed of the lead portion to the lead wire portion of the Hall element 42 becomes a positive potential on the lead portion 84 side, and the lead voltage to the lead portion of the Hall element 44 is composed of The induced voltage of the circuit loop is a positive potential on the lead-out portion 86 side.

Here, if the voltage of the detection signal of the Hall element 42 is + Va1 and the voltage of the detection signal of the Hall element 44 is + Va2, the induced voltage of the circuit loop formed by the lead-out portion of the Hall element 42 is −ve1, and the Hall element The induced voltage of the circuit loop composed of the lead-out portion 44 to the lead wire portion is + ve2.
When the detection signals of the Hall elements 42 and 44 on which the induced voltage is superimposed are considered as signals between the + input and the − input before the input of the first differential amplifier 100, the signal Va before amplification of the differential amplifier 100 is
Va = {(Va1-ve1) + (Va2 + ve2)} / 2
At this time, the absolute values of induced voltages | ve1 | and | ve2 | are equal because the interlinkage areas formed by the lead portions 82 and 84 and the lead portions 86 and 88 of the Hall elements 42 and 44 are the same.
That is, the output signal Vaout of the first differential amplifier 100 is Vaout = (Va1 + Va2) / 2 if the amplification factor is 1.

That is, in the present invention, the absolute values of the induced voltages generated in the pair of Hall element signal paths facing the rotation axis are equal, and the induced voltage superimposed on the detection signal can be canceled.
The pair of Hall elements 41 and 43 located 90 degrees away from the Hall elements 42 and 44 has the same configuration as described above, and the output of the differential amplifier of the detection signal of the Hall elements 42 and 44 is Vaout, and the Hall element 41 , 43, the output of the differential amplifier is Vbout, and the rotation angle θ of the permanent magnet is Vaout = V ₀ cos θ
Vbout = V ₀ sin θ
And does not include the induced voltage component, and therefore θ = arctan (Vbout / Vaout)
By performing this calculation, it is possible to obtain a highly accurate angle θ that eliminates the superposition of the induced voltage generated in the circuit loop of the lead-out portion to the lead wire portion.

In this way, the outputs of the Hall elements facing the rotation axis are wired in parallel, and the lead portions of the Hall elements are parallel to the magnetic sensing surface of the Hall elements, thereby inducing the signal generated in the Hall element signal path. The voltage can be canceled, the signal amplitude and the phase are not changed, and an angle with a small detection error can be obtained by the angle calculation process.

In this embodiment, an example of a hollow cylindrical magnet penetrating the shaft has been shown. However, under the condition that the magnetic flux in the vicinity of the detection portion is in the same direction as the extraction portion, the shape of the magnet is solid. The disc-shaped magnet may be a hollow cylindrical magnet. Also, the shaft for fixing the magnet may be solid or hollow.

In contrast to FIG. 6 described above, as shown in FIG. 14, when a magnetic flux leaks outside the vicinity of the Hall element as the magnetic detection element and these magnetic flux penetrates the circuit board 15, the magnetic detection element and the circuit Similarly, an induced voltage is generated by a circuit loop including a signal processing unit on the substrate, and this induced voltage may be superimposed on the detection signal to cause a detection error. The second embodiment of the present invention is for reducing the influence of the induced voltage generated in such a situation.
FIG. 8 is a perspective view showing the configuration of the second embodiment of the present invention. In the figure, reference numeral 11 denotes a rotating shaft which is attached to a shaft such as a motor (not shown) and rotates together with the shaft such as a motor. A permanent magnet 12 is fixed to the rotating shaft 11. Reference numeral 13 denotes a ring-shaped fixed body that is fixed to a stator such as a motor, and is arranged on the outer periphery from the permanent magnet 12 via a gap. The fixed body 13 may be either a magnetic body or a non-magnetic body. However, in order to obtain a large detection signal, the stationary body 13 is a magnetic body in this embodiment. Inside the fixed body 13, Hall elements 41, 42, 43 and 44 for detecting a magnetic field from the permanent magnet 12 are arranged. Hall elements 41 and 43 and 42 and 44 are opposed to the rotation axis, respectively, and the pair of Hall elements 41 and 43 is disposed with a mechanical angle of 90 ° about the rotation axis with respect to the pair of Hall elements 42 and 44. doing. The above is the same as the configuration of the first embodiment.
Reference numeral 15 denotes a circuit board composed of a plurality of layers made of a glass epoxy substrate material, etc., which is used to supply power to the Hall elements 41, 42, 43, and 44, to transmit a detection signal, and to rotate from the detection signal. A detection signal processing circuit for detecting the position is mounted. The circuit board 15 is disposed above the fixed body 13 and is fixed to the fixed body 13. When the rotating shaft 11 rotates, a signal corresponding to the rotational angle position is detected in the Hall elements 41, 42, 43, 44 in response to a change in the magnetic field of the permanent magnet 12 that rotates together with the rotating shaft 11.

FIG. 9 is a perspective view showing a conductor pattern formed on the circuit board 15 of the second embodiment of the present invention.
In the figure, a circuit board 15 is a four-layer board, which is a first layer, a second layer, a third layer, and a fourth layer in order from the surface of the figure. The conductor pattern of the first layer is indicated by a solid line, and the conductor patterns of the second layer, the third layer, and the fourth layer are indicated by a broken line. In this figure, only the conductive pattern of the detection signal of the pair of Hall elements 42 and 44 is shown.
The conductor patterns 61 and 62 and 63 and 64 provided on the circuit board 15 are formed by connecting the (+) signal output terminals of the Hall elements 42 and 44 and the (−) signal output terminals as shown in the connection diagram of FIG. Each is connected, and a conductive wire pattern is formed in the radial direction. Conductive wires 61 and 62 have conductive wire patterns formed on the second and third layers of the substrate, respectively, and are superposed at substantially the same position in the rotation axis direction. Conductive wires 63 and 64 are formed in the third layer and the second layer of the substrate, respectively, and are superposed at substantially the same position in the rotation axis direction.

Further, conductor patterns 65 and 66 having different radii concentrically around the rotation axis are formed. The conductor patterns 65 and 66 are formed on the first layer and the fourth layer of the substrate, respectively. The conductor patterns 61 and 64 are connected to the conductor pattern 65 through holes, and the conductor patterns 62 and 63 are connected to the conductor pattern 66 through holes. Note that the layer for forming the pattern may not be the first layer and the fourth layer. The concentric conductor patterns 65 and 66 are connected as differential inputs of the amplifier of the detection signal processing circuit 18.

Next, an operation in which the induced voltage on the substrate conductive pattern line of the present invention is not superimposed on the detection signal will be described.
FIG. 11 is a schematic view showing the operation of the second embodiment of the present invention. FIG. 11A shows a case where the magnetic pole of the permanent magnet 12 is in the horizontal direction, and FIG. 11B shows the operation of the permanent magnet. The cases where the magnetic poles are in the vertical direction are shown. This figure shows the movement of the rotational flux direction component of the leakage flux that penetrates the circuit board 15 together with the radial magnetic field of the permanent magnet 12. In the figure, reference numeral 501 denotes an upward leakage magnetic flux penetrating the circuit board 15 when the magnetic pole of the magnet is horizontal, and 502 is a downward leakage magnetic flux penetrating the circuit board 15 when the magnetic pole of the magnet is horizontal. , 503 is the upward magnetic flux leakage through the circuit board 15 when the magnetic pole of the magnet is vertical, and 504 is the downward magnetic flux leakage through the circuit board 15 when the magnetic pole of the magnet is vertical. Yes. According to Faraday's law of electromagnetic induction, the induced voltage is generated by the time change of the magnetic flux linked to the surface surrounded by the conductive wire. Therefore, the leakage magnetic fluxes 501 and 502 shown in FIG. The induced voltage is generated. However, since the conducting wire pattern 65 is a concentric conducting wire pattern with the rotation axis as the center, the induced voltage due to the leakage magnetic fluxes 501 and 502 has an opposite sign and can be canceled out. Similarly, the induced voltage caused by the leakage magnetic fluxes 503 and 504 can be canceled out in the same manner.

As described above, in the detection signal in which the induced voltage is not superimposed, if Va is the detection signal of the Hall elements 42 and 44, Vb is the detection signal Vb of the Hall elements 41 and 43, and θ is the rotation angle of the permanent magnet, Va = V _0. cos θ, Vb = V ₀ sin θ, and calculation by the detection signal processing circuit 18 makes it possible to obtain a highly accurate angle θ without superposition of induced voltages.

  It should be noted that the configuration of the circuit board 15 can be used on a double-sided board as long as it satisfies the requirements of the present invention. Although the permanent magnet 12 is solid, it may be hollow using a ring-shaped permanent magnet, and the circuit board 15 may be solid instead of hollow.

The present invention is different from the first embodiment in that the + signal output terminals of the paired magnetic detection elements and the − signal output terminals are connected by the conductor pattern of the circuit board formed concentrically around the rotation axis. It is that. As a result, the influence of the induced voltage generated when the leakage flux of the permanent magnet penetrates the circuit board can be offset, and the accuracy of the magnetic encoder can be improved.

FIG. 12 is a perspective view showing a conductor pattern of a circuit board formed on the circuit board 15 of the third embodiment of the present invention. This embodiment is different from the second embodiment in that the conductive wire pattern is concentrically overlapped on different layers of the circuit board with the rotation axis as the center, so that the influence of an asymmetric external magnetic field with respect to the rotation axis is reduced. It is to reduce. In the figure, conductor patterns 65 and 66 are formed concentrically around the rotation axis, and the conductor patterns 65 and 66 are formed in the first and fourth layers of the substrate, respectively, and overlap at the same position with respect to the rotation axis direction. Since the other configurations and the connection of the magnetic detection elements are the same as those of the second embodiment, the description thereof is omitted.

Next, an operation in which the induced voltage generated in the conductor pattern is canceled even if an external magnetic field perpendicular to the circuit board 15 penetrates will be described. FIG. 13 is a schematic diagram showing the operation of the third embodiment of the present invention. In the figure, the conductive pattern 65 and the conductive line 66 of the circuit board 15 are formed in separate layers of the substrate, respectively, and overlap at the same position with respect to the rotation axis direction. When an external magnetic field indicated by a broken line is partially linked in the vertical direction, an induced voltage is generated in each of the conductor patterns 65 and 66. However, each induced voltage is offset because it has an opposite phase of the same amplitude, and the magnetic field The accuracy of the encoder can be further improved.

DESCRIPTION OF SYMBOLS 11 Rotating shaft 12 Permanent magnet 13 Fixed body 15 Circuit board 18 Detection signal processing circuit 41, 42, 43, 44 Hall element (magnetic detection element)
61, 62, 63, 64, 65, 66 Conductive pattern 71, 72, 73, 74, 75, 76 Conductive pattern 81-84, 85-88 Lead part 90, 91 Hall element magnetic sensing part 100 1st (2nd) Differential amplifier 120 Rotating body 122, 124 Permanent magnet 130, 131 Magnetic detection element 180 Base 182 ECU

Claims (6)

A disk-shaped or ring-shaped permanent magnet attached to a rotating shaft and magnetized in one direction perpendicular to the axial direction, a plurality of magnetic field detecting elements provided via the permanent magnet and a gap, and the plurality of magnetic field detections A magnetic circuit board that transmits a detection signal of the element and performs a rotation angle calculation process, and the circuit board is disposed above the magnetic field detection element.
The plurality of magnetic field detection elements are arranged at positions facing each other across the rotation axis,
The magnetic field detecting element has a linear terminal lead portion extending in a plane parallel to the magnetic sensitive surface, and is connected to the circuit board via the terminal lead portion,
A pair of magnetic field detection elements arranged at positions facing each other across the rotation axis are connected between output positive terminals and output negative terminals ,
One of the magnetic encoder and the power supply negative terminal of the power supply positive terminal and the other magnetic field detecting element of the magnetic field detection element is characterized Rukoto connected among the magnetic field detection element forming the pair. The plurality of magnetic field detection elements include a first magnetic field detection element, a second magnetic field detection element, a third magnetic field detection element, and a fourth magnetic field detection element that are arranged in order at every 90 degrees in mechanical angle. The magnetic encoder according to claim 1 . Output positive terminals of the first magnetic field detection element and the third magnetic field detection element are connected to one input terminal of the first differential amplifier,
Output negative terminals of the first magnetic field detection element and the third magnetic field detection element are connected to the other input terminal of the first differential amplifier,
The output positive terminals of the second magnetic field detection element and the fourth magnetic field detection element are connected to one input terminal of a second differential amplifier,
Output negative terminals of the second magnetic field detection element and the fourth magnetic field detection element are connected to the other input terminal of the second differential amplifier,
3. The magnetic encoder according to claim 2, wherein a rotation angle is calculated from output signals of the first differential amplifier and the second differential amplifier. The circuit board has a plurality of layers of conductive patterns that transmit detection signals of the plurality of magnetic field detection elements,
The pair of magnetic field detecting elements are connected by the conductive pattern of the circuit board in which output positive terminals and output negative terminals are concentrically formed around the rotation axis. The magnetic encoder according to any one of claims 1 to 3 . The conductor pattern in which the output positive terminals of the pair of magnetic field detection elements are connected to each other and the conductor pattern in which the output negative terminals of the pair of magnetic field detection elements are connected to each other in the plurality of layers of conductor patterns. 5. The magnetic encoder according to claim 4 , wherein the layers are formed so as to overlap concentrically with the same diameter around the rotation axis. Magnetic encoder according to any one of claims 1 to 5 wherein the magnetic field detection element, characterized in that a Hall element.

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