JPWO2007055135A1 - Magnetic encoder device - Google Patents

Abstract

Provided is a magnetic encoder having a low number of power supply lines and output signal lines for driving a magnetic field detecting element, a low cost, and a high degree of freedom in installation. The disc-shaped permanent magnet (2) constituting the magnet generator is magnetized perpendicularly and parallel to one direction with respect to the rotating shaft (11) of the rotating body (1). The magnetic field detector (6) is installed on the rotation center axis (10) of the rotating body (1) on the processing circuit board (4). The magnetic field detection unit (6) includes two magnetic field detection elements (not shown) arranged to detect magnetic fields in different directions in a plane perpendicular to the rotation axis, and is perpendicular to the rotation axis (11). A magnetic field in the biaxial directions of X and Y on the XY plane is detected.

Description

  The present invention relates to a magnetic encoder device that detects a rotational position of a rotating body.

(Conventional example 1)
Conventionally, as a magnetic encoder that obtains highly accurate position information, a magnetic type that detects a magnetic field generated by a disk-like permanent magnet magnetized in parallel with two poles in a plane and detects an absolute value of the position of a rotating body An encoder is disclosed (for example, see Patent Document 1).
FIG. 22 is a perspective view showing the configuration of the magnetic encoder in the first prior art.
In the figure, 1 is a rotating body, 2 is a permanent magnet fixed to the rotating body 1 via a rotating shaft 11, and is magnetized in one direction perpendicular to the rotating shaft 11.
Reference numerals 611 to 614 denote magnetic field detection elements, which are arranged on the permanent magnet 2 via a gap in the axial direction and fixed on the fixed body 7. The magnetic field detection elements 611 to 614 are arranged at a mechanical angle of 90 degrees in the circumferential direction and detect changes in the magnetic field generated by the permanent magnet 2 in accordance with the rotation of the rotating body 1. This detection signal is converted into a rotation angle by the signal processing circuit 5 to detect the absolute value position of the rotating body 1.

(Conventional example 2)
In addition, a magnetic field generated by a permanent magnet magnetized in parallel to two poles in a plane attached to the rotating body is detected by six magnetic field detecting elements arranged at equal intervals in the axial direction through gaps, and rotated. An apparatus that detects the absolute value of the position of the body is disclosed (for example, see Patent Document 2).
FIG. 23 is a perspective view showing a configuration of a magnetic encoder in the second prior art.
In the figure, 1 is a rotating body, 2 is a permanent magnet fixed to the rotating body 1 via a rotating shaft 11, and is magnetized in one direction perpendicular to the rotating shaft 11.
Reference numerals 621 to 626 denote magnetic field detection elements. The magnetic field detection elements 621 to 626 are a pair of two A1 phase detection elements 621, A2 phase detection elements 622, and B1 phase detection provided at positions that are 180 degrees out of phase with mechanical angles. The element 623 and the B2 phase detection element 624, and the C1 phase detection element 625 and the C2 phase detection element 626 are composed of a total of three pairs, and are arranged on the fixed body 7.

FIG. 24 is a block diagram of a signal processing circuit.
The signal processing circuit includes a first difference between the A1 phase detection element 621 and the A2 phase detection element 622, the B1 phase detection element 623 and the B2 phase detection element 624, and the C1 phase detection element 625 and the C2 phase detection element 626, respectively. Dynamic amplifiers 81, 82, and 83 are provided. The first differential amplifiers 81 to 83 are configured to remove even-order harmonic components by taking a difference between output signals of a pair of magnetic field detection elements.
Further, second differential amplifiers 84 and 85 are provided at the subsequent stage of the first differential amplifiers 81 and 82 and the first differential amplifiers 82 and 83, respectively.
The second differential amplifiers 84 and 85 combine two differential output signals after removing even-order harmonic components by the first differential amplifiers 81 and 82 and the first differential amplifiers 82 and 83, respectively. By taking the sum, the third-order harmonic component contained in the differential output signal is removed, and the encoder is highly accurate.

(Conventional example 3)
In addition, an N pole is formed at one end on the circumference of a disk-shaped permanent magnet fixed to the rotating shaft, and an S pole is formed at the other end. Has been disclosed (see, for example, Patent Document 3).
FIG. 25 is a perspective view of the angle sensor in the third conventional example, and FIG. 26 is a graph showing the relationship between the rotation angle of the angle sensor and the output voltage.
When the disk-shaped permanent magnet 12 rotates, the strength of the magnetic field acting on the magnetoresistive element 13 changes according to the rotation angle, thereby changing the resistance of the magnetoresistive element 13. When the resistance change of the magnetoresistive element 13 is detected as a voltage change, an output signal corresponding to the rotational angle position of the shaft 11 as shown in FIG. 26 is obtained. The output voltage of the magnetoresistive element 13 alternately repeats increasing and decreasing linearly every time the shaft 11 rotates 90 degrees in one direction. Then, the fact that the linear portion of the output voltage waveform is proportional to the rotation angle is utilized.

(Conventional example 4)
In addition, a rotation is detected by attaching a magnet on the rotating shaft of the rotating body and installing a magnetic sensor having a plurality of magnetoresistive elements arranged in different detection directions perpendicularly to the direction in which the magnet rotates. A detector is disclosed (for example, see Patent Document 4).
FIG. 27 is a perspective view showing a configuration of a rotation detector in the fourth prior art.
In the figure, reference numeral 22 denotes a cylindrical outer shape, a permanent magnet magnetized on two poles of N pole and S pole on the upper surface, and 37 a magnetic sensor, which is installed at a position away from the upper surface of the permanent magnet 22 and is permanent. A magnetoresistive pattern for detecting a magnetic field in the vertical direction and a magnetoresistive pattern for detecting a magnetic field in the direction of the magnetic detection surface are formed on the magnet 22.
When the permanent magnet 22 rotates, the magnetic sensor 37 detects the rotation of the magnetic field and outputs a signal of one waveform per rotation. The rotation of the rotating body is detected from the change in output. Furthermore, when two magnetic sensors 37 are installed, the rotational direction can also be detected.
JP 2000-65596 A JP 2001-33277 A Japanese Patent Publication No.7-119619 JP 7-27776 A

  In the magnetic encoder disclosed in the first prior art, since the magnetic field generated by the permanent magnet attached to the rotating body is a sine wave with a small distortion, a highly accurate encoder can be obtained. However, since four or more magnetic field detection elements are required, the number of power supply lines and output signal lines for driving the magnetic field detection elements increases. Accordingly, there is a problem that the installation of wiring and magnetic field detection elements becomes complicated and the cost is increased. Further, it is necessary to install the magnetic field detection elements at equal intervals, but there is a problem that the installation accuracy greatly affects the encoder accuracy. Furthermore, since there are many wirings, there was a problem that it was easy to pick up noise and low reliability.

  In addition, since the magnetic encoder device disclosed in the second prior art has a large size of the magnetic field detection element, it is necessary to install each magnetic field detection element away from the center of the rotation axis, and the size of the magnetic field detection unit is large. There was a problem. In addition, since it is difficult to dispose at equal intervals with high accuracy, there has been a problem that detection accuracy deteriorates due to eccentricity of the permanent magnets and shake of the rotating shaft. Furthermore, there is a variation in the characteristics of each magnetic field detection element, and there is a problem that it is impossible to completely remove the second and third order harmonic components. In addition, only the magnetic field detection element is mounted near the permanent magnet, and the drive circuit and signal amplification circuit for driving the magnetic field detection element are installed away from the permanent magnet, which increases the number of power lines and output signal lines. In addition, there is a problem that noise resistance decreases.

  In addition, the magnetic encoder disclosed in the third prior art is limited to a range in which the angle detection range has linearity of the output voltage, and has low accuracy. Therefore, there is a problem that it cannot be applied to a servo motor or the like that is required to detect the rotation angle with high accuracy over the entire circumference of the 360 degree range.

  Further, the rotation detection device disclosed in the fourth prior art can detect a rough position, but has a problem that it cannot be applied to a servo motor or the like that is required to detect a rotation angle with high accuracy.

  The present invention has been made in view of such problems, and has a simple structure, can be reduced in size, is low in cost, and is resistant to eccentricity of a permanent magnet and shake of a rotating shaft, and has high reliability and high accuracy. An object of the present invention is to provide an encoder device.

In order to solve the above problems, the present invention is configured as follows.
The invention according to claim 1 is a disk-shaped or ring-shaped permanent magnet fixed to a rotating body and magnetized in two poles, a magnetic field detecting unit for detecting a magnetic field generated by the permanent magnet, and the magnetic field detecting unit And a signal processing circuit for processing a signal from the magnetic encoder device that detects the absolute position of the rotating body. And a magnetic field detection element section for detecting a magnetic field in a plurality of axial directions in a plane perpendicular to the rotation axis on an extension of the rotation center axis of the permanent magnet.
The invention according to claim 2 is characterized in that the plurality of axial directions are biaxial directions.
The invention according to claim 3 is characterized in that the plurality of axial directions are three axial directions.
According to a fourth aspect of the present invention, the magnetic field detection element section is formed by forming magnetic field detection elements for detecting magnetic fields in the respective axial directions closer to each other by a semiconductor technology.
The invention described in claim 5 is characterized in that the magnetic field detection element portion is arranged close to a magnetic field detection element package for detecting a magnetic field in each axial direction.
According to a sixth aspect of the present invention, the magnetic field detection unit includes the magnetic field detection element unit, a drive circuit that drives the magnetic field detection element unit, and a signal processing unit that processes an output signal of the magnetic field detection element unit. It is characterized by being integrated in one package.
The invention according to claim 7 is characterized in that the permanent magnet is magnetized in parallel in a plane perpendicular to the rotation axis.
The invention according to claim 8 is characterized in that the permanent magnet comprises a permanent magnet having parallel anisotropy.

According to the first aspect of the present invention, since the magnetic field detection unit includes the magnetic field detection element unit that detects magnetic fields in a plurality of axial directions in a plane perpendicular to the rotation axis, the magnetic field detection unit has a simple configuration. The rotation angle can be detected. Therefore, the number of leads can be reduced, and the production / assembly cost can be reduced.
In addition, since the magnetic field detection unit is disposed on the extension of the rotation center axis of the permanent magnet, fluctuations in the detected magnetic field due to eccentricity or shaking of the rotation axis are reduced, and a highly accurate encoder can be realized.
Further, if the permanent magnet is formed in a ring shape with a hollow inside, the permanent magnet can be mounted on a rotation shaft to be detected such as a motor. Therefore, the encoder and the detection target can be integrated, the structure is simple, the vibration resistance is improved, and the size can be reduced.

  Further, according to the invention of claim 2, if the magnetic field detection unit includes a magnetic field detection element unit that detects a magnetic field in a biaxial direction in a plane perpendicular to the rotation axis, the size of the magnetic field detection unit can be reduced, The rotation angle can be detected with a simple configuration.

  According to the invention described in claim 3, if the magnetic field detection unit includes a magnetic field detection element unit that detects a magnetic field in three axial directions in a plane perpendicular to the rotation axis, the size of the magnetic field detection unit can be reduced. Further, it is possible to output a signal with extremely small waveform distortion in which the harmonic components of the second and third multiples are canceled.

  According to the invention described in claim 4, if the magnetic field detection elements of the magnetic field detection element portion are formed close to each other by semiconductor technology, variation in characteristics between the elements can be reduced and an accurate detection signal can be obtained. It is done.

  According to the fifth aspect of the present invention, if the magnetic field detection element unit is configured in the vicinity of the magnetic field detection element package, the detection magnetic field variation due to the eccentricity or shake of the rotating shaft can be reduced with high accuracy with a simple configuration. An encoder can be realized.

  According to the invention described in claim 6, if the magnetic field detection element unit, the drive circuit, and the signal processing unit are integrated in one package to form the magnetic field detection unit, it is possible to reduce the size and the number of leads. Manufacturing and assembly costs can be reduced. Furthermore, since the angle information can be communicated to the host controller using a digital signal, noise resistance is improved and the output signal line can be lengthened.

  According to the seventh aspect of the present invention, if the permanent magnet is magnetized in parallel in a plane perpendicular to the rotation axis, the magnetic field generated by the permanent magnet becomes a sine wave with little distortion, and a highly accurate encoder can be provided. .

  According to the eighth aspect of the present invention, if the permanent magnet has parallel anisotropy, the permanent magnet can be easily magnetized in parallel in the plane without requiring a special magnetizing device.

1 is a perspective view of a magnetic encoder showing a first embodiment of the present invention. It is an enlarged view of the magnetic field detection part in 1st Example of this invention. It is a block diagram of the signal processing circuit in 1st Example of this invention. It is a circuit diagram of the waveform shaping circuit in the first embodiment of the present invention. It is an output waveform figure of the magnetic field detection part in 1st Example of this invention. It is a perspective view of the magnetic encoder which shows 2nd Example of this invention. It is a block diagram of the magnetic field detection part which shows 3rd Example of this invention. It is a block diagram of the signal processing circuit in 3rd Example of this invention. It is a block diagram of the magnetic field detection part which shows 4th Example of this invention. It is a block diagram of the magnetic field detection part which shows 5th Example of this invention. It is an enlarged view of the magnetic field detection part in 5th Example of this invention. It is a graph which shows the change of the magnetic field of the magnetic field detection element part in 5th Example of this invention. It is a graph which shows the signal output of the magnetic field detection element part in 5th Example of this invention. It is a graph which shows the relationship between the detection magnetic flux density of a Hall element, and Hall output voltage. It is a circuit diagram of the sensor signal processing part in 5th Example of this invention. It is a graph which shows the relationship between a 2nd harmonic component and the amount of eccentricity. It is a graph which shows the waveform of the output signal of the differential calculating part in 5th Example of this invention. It is the graph which FFT-analyzed the output signal of the differential calculating part in 5th Example of this invention. It is a graph which shows the waveform of the output signal of the 3 phase 2 phase conversion part in 5th Example of this invention. It is the graph which carried out the FFT analysis of the output signal of the 3 phase 2 phase conversion part in 5th Example of this invention. It is a block diagram of the signal processing circuit in 5th Example of this invention. It is a perspective view which shows the structure of the magnetic encoder in a 1st prior art. It is a perspective view which shows the structure of the magnetic encoder in a 2nd prior art. It is a block diagram of the signal processing circuit in the 2nd prior art. It is a perspective view of the angle sensor in a 3rd prior art example. It is a graph which shows the relationship between the rotation angle of the angle sensor in a 3rd prior art example, and an output voltage. It is a perspective view which shows the structure of the rotation detector in a 4th prior art.

Explanation of symbols

1: Rotating body 10: Rotating center shaft 11: Rotating shaft 12: Permanent magnet 13: Magnetoresistive element 2, 2 ': Permanent magnet (magnet generator)
3: Magnetic field detectors 31, 32, 33: Magnetic field detector elements 311 and 312: Magnetic field detector elements (Hall elements)
321, 322: Magnetic field detection element package (Hall element package)
331 to 336: Hall element 34: Hall element drive circuit 35: Amplifier circuit 36: Sensor signal processing circuit 360: Input adjustment unit 361-366: Differential amplifier 370: Differential operation unit 371-373: Differential amplifier 380: 3 Phase-to-phase converters 381, 382: differential amplifier 4: processing circuit board 5: signal processing circuit 51, 52: amplifier 53: waveform shaping circuit 531, 532: amplifier 533: adder 534: subtractor 535, 536: amplifier 54: Angle calculation circuit 611-614: Magnetic field detection element 621-626: Magnetic field detection element 7: Fixed body

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

FIG. 1 is a perspective view of a magnetic encoder showing a first embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes a rotating body, and 2 denotes a permanent magnet constituting a magnet generator fixed to the rotating body 1 via a rotating shaft 11, which is perpendicular to the rotating shaft 11 as indicated by an arrow in the figure. Magnetized parallel to one direction. Reference numeral 3 denotes a magnetic field detection unit, and the magnetic field detection unit 3 is installed on the processing circuit board 4 together with the signal processing circuit 5. Further, the magnetic field detection unit 3 includes a magnetic field detection element unit 31 installed on the rotation center axis 10 of the rotating body 1. The magnetic field detection element unit 31 detects a magnetic field in a biaxial direction on the XY plane perpendicular to the rotation axis 11, and the detection directions of the magnetic fields are different from each other by 90 degrees in mechanical angle.

  In this embodiment, a permanent magnet 2 that is a samarium cobalt magnet having a diameter of 10 mm and a thickness of 2 mm, which is magnetized in parallel in one direction, is used. Further, the magnetic field detector 3 is disposed on the rotation center axis 10 through a gap of 2 mm from the permanent magnet 2.

The difference between this embodiment and the first prior art is the configuration of the magnetic field detector.
In the first prior art, two pairs of magnetic field detecting elements, which are arranged concentrically with respect to the rotation center of the rotating body and are 90 degrees out of phase with each other in the circumferential direction of the permanent magnet, are 180 degrees out of phase with each other. Two pairs are provided at positions shifted from each other. On the other hand, in the present embodiment, a magnetic field detection element unit for detecting a magnetic field in the biaxial direction is arranged on the rotation center axis.

FIG. 2 is an enlarged view of the magnetic field detector in the present embodiment.
In the figure, reference numeral 3 denotes an embodiment of the magnetic field detection unit. The magnetic field detection element unit 31 of the magnetic field detection unit 3 is a magnetic field detection element in which the detection directions of the magnetic field are different from each other by approximately 90 degrees in the plane. Certain Hall elements 311 and 312 are formed using semiconductor technology. The Hall element 311 detects a magnetic field Bx in the X-axis direction, and the Hall element 312 detects a magnetic field By in the Y-axis direction. The drive terminal A and the drive terminal B are connected to a drive circuit (not shown) of the hall elements 311 and 312, and a drive current is passed through the hall elements 311 and 312. When the permanent magnet 2 rotates, the Hall elements 311 and 312 receive magnetic fields Bx and By corresponding to the rotation angles, and output sine wave and cosine wave Hall voltages va and vb from the terminals va and vb, respectively. The diameter of the magnetic field detection element unit 31 is 200 μm, and the distance between the Hall elements 311 and 312 is 20 μm or less. Therefore, when viewed from the permanent magnet 2, the Hall elements 311 and 312 can be regarded as being substantially in the same position.

FIG. 3 is a block diagram of the signal processing circuit in this embodiment.
The signal processing circuit 5 includes an amplifier 51 that amplifies the Hall voltage va that is an output signal of the Hall element 311, an amplifier 52 that amplifies the Hall voltage vb of the Hall element 312, a waveform shaping circuit 53, and an angle for calculating a rotation angle. An arithmetic circuit 54 is provided.

Note that if the amplitude value of the output signal differs due to the difference in sensitivity between the Hall elements 311 and 312, an angular error is caused. Therefore, the waveform shaping circuit 53 is provided with an amplitude adjustment circuit for making the amplitude the same. Furthermore, an offset compensation circuit that cancels the offset of the output signal and a phase adjustment circuit that makes the phase difference of the output signal exactly 90 degrees in electrical angle are provided.
FIG. 4 is a circuit diagram of the waveform shaping circuit.
In the figure, 531 and 532 are operational amplifiers constituting an offset compensation circuit, 533 and 534 are adders 533 and subtracters 534 constituting a phase adjustment circuit, and 535 and 536 are amplitudes of the phase-adjusted signals. This is an operational amplifier (amplitude adjustment circuit) that adjusts. The outputs VA and VB of the operational amplifiers 535 and 536 are input to the angle calculation circuit 54.

Next, the operation will be described.
When the permanent magnet 2 makes one rotation, the magnetic field detector 3 detects the magnetic flux density of the sine wave and cosine wave according to the rotation angle position, and outputs Hall voltages va and vb as shown in FIG. The Hall voltages va and vb are amplified by the amplifiers 51 and 52 of the signal processing circuit 5 and then input to the waveform shaping circuit 53. The waveform shaping circuit 53 adjusts the offset, phase, and amplitude.
That is, the offsets of the two-phase signals Va and Vb amplified by the amplifiers 51 and 52 are removed by the amplifiers 531 and 532 of the waveform shaping circuit shown in FIG. 4 and input to the adder 533 and the subtractor 534, and the phase difference is 90 degrees. The phase is adjusted so that Further, the amplitude of the signals output from the adder 533 and the subtracter 534 is adjusted by the amplifiers 535 and 536. The two-phase output signals VA and VB from the waveform shaping circuit 53 with the amplitude adjusted are input to the angle calculation circuit 54, and an angle signal is generated by tangent calculation.

When the rotating body 1 sometimes rotates eccentrically, the detected magnetic flux density waveform is displaced according to the amount of eccentricity. For this reason, in the first prior art, the output signals of the opposing magnetic field detection elements are differentiated to eliminate the influence of eccentricity. However, in the present invention, since the magnetic field detecting element portions for detecting the magnetic fields Bx and By in the biaxial directions are located at substantially the same position, the rate of change in the amplitude values of the Hall voltages va and vb due to the influence of eccentricity is the same. Since the angle is obtained by the tangent calculation of the outputs VA and VB through the waveform shaping circuits 53 of the hall voltages va and vb, in the present invention, the influence of the eccentricity is canceled and the opposing hall elements as in the second prior art There is no need to take the output differential.
The processing functions of the waveform shaping circuit 53 and the angle calculation circuit 54 may be performed by software processing.

  This encoder was evaluated using an encoder with 1 million divisions per rotation as a reference encoder, but an absolute position signal with extremely high resolution was obtained by dividing 32000 into one revolution.

  In this example, a samarium-cobalt-based magnet whose characteristic change due to temperature is small was used as the permanent magnet, but the same effect can be obtained with other rare-earth magnets, ferrite-based magnets, bonded magnets, and SmFeN-based magnets. .

  In the present embodiment, the case where the Hall element is used as the magnetic field detecting element has been described. However, the same effect can be obtained even when the magnetoresistive element is used.

  Further, in this embodiment, a digital arithmetic processing method using a sine wave or cosine wave is adopted as the absolute angle calculation method. However, the angle may be obtained by a phase tracking method, a multiplication method, a phase modulation method, or the like.

FIG. 6 is a perspective view of a magnetic encoder showing a second embodiment of the present invention.
In the figure, 2 ′ is a ring-shaped permanent magnet.
As the permanent magnet 2 ′, a neodymium bond magnet having an inner diameter of 3 mm, an outer diameter of 10 mm, and a thickness of 2 mm, which is magnetized in parallel in one direction, was used.
Similarly to the first embodiment, the magnetic field detection unit 3 includes a magnetic field detection element unit 31 installed on the rotation center axis 10 of the rotating body 1, and X, X on the XY plane perpendicular to the rotation axis 11, A magnetic field in the biaxial direction of Y is detected.
This embodiment is different from the first embodiment in that a ring-shaped permanent magnet is used as the permanent magnet. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  As described above, since the ring-shaped permanent magnet is used in this embodiment, the permanent magnet can be mounted on the rotation shaft to be detected such as a motor. Therefore, the encoder and the detection target can be integrated, the structure is simple, the vibration resistance is improved, and the size can be reduced.

FIG. 7 is a block diagram of a magnetic field detector showing a third embodiment of the present invention.
In the figure, reference numeral 3 denotes an embodiment of the magnetic field detector.
Reference numerals 321 and 322 denote Hall element packages for detecting a magnetic field in one direction.
The Hall element package has a size of 2 mm square and a thickness of 0.5 mm, and includes two drive terminals (not shown) for supplying a drive current to the Hall element package and two output terminals for outputting a Hall voltage. The Hall element package has a magnetic field detection element (not shown) having an outer diameter of 50 μm disposed in the center, and is connected to the drive terminal and the signal output terminal, and is molded with resin. A magnetic field detection element (not shown) of the Hall element package is formed so as to detect a magnetic field parallel to the package surface.

  The Hall element packages 321 and 322 are arranged on the rotation center axis 10 so as to overlap each other so that the detection directions of the magnetic field are about 90 degrees in terms of mechanical angles with respect to the permanent magnet 3 and the 1 mm gap. Since it is difficult to install the two Hall element packages 321 and 322 so that the magnetic field detection direction is precisely 90 degrees in mechanical angle, the waveform shaping circuit is adjusted so that the phase is 90 degrees.

FIG. 8 is a block diagram of a signal processing circuit in this embodiment.
The Hall voltages Va + and Va− output from the Hall element package 321 and the Hall voltages Vb + and Vb− output from the Hall element package 322 are differentially input to the amplifiers 51 and 52 of the signal processing circuit 5, respectively. Since the subsequent processing of the waveform shaping circuit 53 and the angle calculation circuit 54 is the same as that of the first embodiment, the description thereof is omitted.
Similarly to the first embodiment, this encoder was evaluated using an encoder with one million rotations per rotation as a reference encoder, but an absolute position signal obtained by dividing 16000 was obtained.

FIG. 9 is a block diagram of a magnetic field detector showing a fourth embodiment of the present invention.
In the figure, reference numeral 3 denotes an embodiment of the magnetic field detector.
The magnetic field detection element unit 31 in which two Hall elements 311 and 312 are arranged, the Hall element drive circuit 34 for driving the Hall element, and the amplification circuit for the Hall element output signal are integrated in one package.

  As described above, in this embodiment, the number of parts is reduced by using one package, the number of assembling steps is reduced, and the cost is reduced. Further, since the signal is amplified and output, the SN ratio is increased and the noise resistance is improved. Further, since the signal output is increased, the length of the signal line can be increased to 20 m or more. Further, since the Hall element drive circuit 34 is built in, the number of wirings can be reduced.

FIG. 10 is a block diagram of the magnetic field detector in the magnetic encoder showing the fifth embodiment of the present invention.
In the figure, the magnetic field detection unit 3 processes a signal output from the magnetic field detection element unit 33, a magnetic field detection element unit 33 in which six Hall elements are integrated and arranged, a drive circuit 34 that supplies power to the magnetic field detection element. The sensor signal processing unit 36 is configured.
The magnetic field detection element unit 33 is disposed on the rotation center axis of the rotator 1 and detects a magnetic field in three axial directions on an XY plane perpendicular to the rotation axis.

FIG. 11 is an enlarged view of the magnetic field detection element portion.
The magnetic field detection element unit 33 includes a Hall element 331, 332, 333, 334, 335, and 336 having a plane perpendicular to the rotation axis and a magnetic field detection direction of 90, 150, 210, 270, 330, and 30 degrees, respectively. Are formed using semiconductor technology.
The size of the magnetic field detection element unit 33 is 0.5 mmφ, and the size of the magnetic field detection unit 3 is a square having a side of 5 mm.

This embodiment is different from the first embodiment in that the magnetic field detection element unit 33 detects a magnetic field in the three-axis direction on the XY plane perpendicular to the rotation axis 11 and three-phase 2 It is a point provided with a phase conversion circuit.
That is, in the first embodiment, two pairs of magnetic field detection elements are provided at positions where the phase of the magnetic field detection elements is 180 degrees out of phase with each other. 6 magnetic field detection elements for detecting magnetic fields in 6 directions including the opposite direction of 180 degrees are integrated and arranged, and the three-phase output signals from the magnetic field detection element unit 33 are converted into two phases in the magnetic field detection unit 3. A sensor signal processing unit having a three-phase to two-phase conversion circuit for conversion is provided.

Next, the operation will be described.
First, the operation of the magnetic field detector will be described.
FIG. 12 is a graph showing a change in the magnetic field of the magnetic field detection element unit 33 when the permanent magnet rotates. When the disk-shaped permanent magnet 2 having parallel anisotropy magnetized parallel to the radial direction rotates once. The change of the magnetic field in the vicinity of the center of the magnetic field detecting element unit 33 is shown.
Since the peak value of the magnetic field received by the Hall element is 0.25 (T) and the third harmonic component is 1.0e ⁻⁴ (T), it is about 0.004% of the fundamental wave. This indicates that a disk-like permanent magnet having parallel anisotropy generates a sinusoidal magnetic field with very little harmonic distortion.

The change in the magnetic field is converted into an electric signal by the magnetic field detection element unit 33.
FIG. 13 is a graph showing the signal output of the magnetic field detection element section.
The output waveform is a sinusoidal signal including second and third harmonic components although not shown for the second harmonic.

The second-order harmonic component is generated because the center of the permanent magnet does not completely coincide with the center of the rotation axis and the center of the magnetic field detection element unit 33 due to an assembly error or the like. In other words, this occurs because the relative distance between the Hall elements 331 to 336 and the permanent magnet 2 varies slightly depending on the rotation angle of the permanent magnet 2.
In general, the Hall output voltage of the Hall element is not completely proportional to the detected magnetic field and has a non-linearity of about 1% with respect to the ideal characteristic. Therefore, a third harmonic component is generated in the Hall element signal output. . FIG. 14 shows the relationship between the detected magnetic flux density of the Hall element and the Hall output voltage.
An FFT analysis was performed on the output voltage waveform of the Hall element by applying a sinusoidal magnetic field without distortion, and the third-order harmonic component was 0.6%. This is due to the non-linearity of the detection magnetic field of the Hall element and the output voltage.

Next, the operation of the sensor signal processing unit 36 will be described.
FIG. 15 is a circuit diagram of the sensor signal processing unit.
The sensor signal processing unit includes an input adjustment unit 360, a differential operation unit 370, and a three-phase / two-phase conversion unit 380. First, output signals of the six Hall elements 331 to 336 are respectively differential of the input adjustment unit 360. The amplifiers 361 to 366 cancel the offset of the input signal and adjust the amplitude of each output signal to be constant. Next, Hall elements facing each other in the differential operation unit 370, that is, outputs of 331 and 334, 332 and 335, and 333 and 336 are input to the differential amplifiers 371, 372, and 373, and the second order multiple harmonic component Outputs Va1, Vb1, and Vc1 are canceled. Next, in the three-phase to two-phase conversion unit 380, the obtained Va1, Vb1, and Vc1 are input to the differential amplifiers 381 and 382, and Va and Vb in which the harmonic components of the third multiple are canceled are obtained.
As described above, even if the output signal from the magnetic field detection element unit includes the second and third harmonic components, the sensor signal processing unit can reduce these harmonic components.

FIG. 16 is a graph showing the relationship between the second harmonic component and the amount of eccentricity.
The second harmonic component increases with the difference (eccentricity) between the rotation center of the permanent magnet 2 and the central axis of the magnetic field detection element unit 33, but it can be canceled by taking the differential of the Hall element outputs facing each other. Show.

Next, the measurement results in this example will be described.
FIG. 17 is a graph showing the waveform of the output signal of the differential operation unit 370 of the sensor signal processing unit 36. The output signals Va1, Vb1, Vc1 of the differential amplifiers 371, 372, 373 when the permanent magnet 2 is rotated at 6000 rpm. The waveform is shown.
FIG. 18 is a graph obtained by performing FFT analysis on the output signal of the differential operation unit 370, and is obtained by performing FFT analysis on the output signal Va1 of the differential amplifier 371. It can be seen that the output signal Va1 of the differential amplifier 371 includes 0.7% of the third harmonic component due to the nonlinearity of the Hall output voltage of the Hall element.
FIG. 19 is a graph showing the waveform of the output signal of the sensor signal processing unit 36, and FIG. 20 is a graph of the FFT analysis of the output signal of the three-phase / two-phase conversion unit.
As shown in FIG. 20, it can be seen that the third-order harmonic component is reduced to 0.01% or less by the three-phase to two-phase converter 380.

Next, the configuration and operation of the signal processing circuit 5 will be described.
FIG. 21 is a block diagram of the signal processing circuit 5.
In the figure, 53 is a waveform shaping circuit for adjusting the amplitude and phase of a two-phase signal, and 54 is an angle calculation circuit. Since the configuration of the waveform shaping circuit 53 is the same as that of the first embodiment, its description is omitted. Output signals VA and VB from the waveform shaping circuit are input to the angle calculation circuit 54, and an angle signal is generated by tangent calculation. This angle signal is transmitted to the host controller through communication circuit means (not shown).

  The performance of this encoder was evaluated using an encoder with 1 million rotations per rotation as a reference encoder, but an absolute position signal obtained by dividing 1 rotation into 124000 was obtained. The encoder of the first prior art obtained a resolution obtained by dividing 32,000 revolutions by the same evaluation, but it can be seen that the resolution has been improved by a factor of 4 by the present invention.

As described above, in this embodiment, the magnetic field detection element unit in which six magnetic field detection elements are integrated is arranged on the center of the rotation axis, and the magnetic field on the rotation axis of the disk-shaped permanent magnet magnetized in one direction is applied. Since it is detected, a signal with extremely small distortion can be obtained.
In addition, since the magnetic field detection element unit, the drive circuit, and the sensor signal processing unit are integrated into the magnetic field detection unit and packaged, signals of higher harmonic components can be obtained, and noise resistance against electrostatic noise and electromagnetic noise is outstanding. Improved.
In addition, when the secondary harmonic component which generate | occur | produces an assembly error etc. is small enough, you may comprise a magnetic field detection element part with three magnetic field detection elements.

  In this embodiment, a samarium-cobalt magnet having a small characteristic change due to temperature is used as the permanent magnet. As the permanent magnet, other rare earth magnets, ferrite magnets, bonded magnets, and SmFeN magnets can achieve the same effect.

  In this embodiment, the case where the Hall element is used as the magnetic field detection element has been described. However, the same effect can be obtained even when the magnetoresistive element is used.

  As an absolute angle calculation method, in the embodiment, the angle is obtained by digital calculation from a sine wave and cosine wave, but the angle may be obtained by a phase tracking method, a multiplication method, a phase modulation method, or the like.

  Further, in the present embodiment, it has been shown that the third harmonic can be reduced by detecting the magnetic field in three axes using six magnetic field detecting elements, but using five or ten magnetic field detecting elements. It is clear that the fifth-order harmonic component can be reduced by detecting a magnetic field in the 5-axis direction.

  The present invention can be applied to a magnetic encoder device that detects a rotation angle of a servo motor used as an actuator of a machine tool, a robot, or the like.

Claims (8)

A disk-shaped or ring-shaped permanent magnet fixed to a rotating body and magnetized to two poles, a magnetic field detection unit for detecting a magnetic field generated by the permanent magnet, and a signal processing circuit for processing a signal from the magnetic field detection unit In a magnetic encoder device that detects the absolute position of the rotating body,
The magnetic field detection unit is disposed in the direction of the rotation axis of the rotating body via the permanent magnet and a gap, and a magnetic field in a plurality of axial directions in a plane perpendicular to the rotation axis on an extension of the rotation center axis of the permanent magnet A magnetic encoder device comprising a magnetic field detecting element portion for detecting a magnetic field.   The magnetic encoder device according to claim 1, wherein the plurality of axial directions are biaxial directions.   The magnetic encoder device according to claim 1, wherein the plurality of axial directions are three axial directions.   The magnetic encoder device according to claim 1, wherein the magnetic field detection element unit is formed by forming magnetic field detection elements for detecting magnetic fields in the respective axial directions close to each other by a semiconductor technology.   2. The magnetic encoder device according to claim 1, wherein the magnetic field detection element unit includes magnetic field detection element packages that detect magnetic fields in the respective axial directions in close proximity to each other.   The magnetic field detection unit is characterized in that the magnetic field detection element unit, a drive circuit for driving the magnetic field detection element unit, and a signal processing unit for processing an output signal of the magnetic field detection element unit are integrated in one package. The magnetic encoder device according to claim 1.   The magnetic encoder device according to claim 1, wherein the permanent magnet is magnetized in parallel in a plane perpendicular to the rotation axis.   The magnetic encoder device according to claim 7, wherein the permanent magnet is a permanent magnet having parallel anisotropy.

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