JP2011169813A - Magnetic encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic encoder having high accuracy and high resolution by improving detection accuracy of a magnetic encoder. <P>SOLUTION: The magnetic encoder includes: a rotor including a magnet; a plurality of magnetic detection elements arranged in the vicinity of the magnet; and an output part outputting a detection signal detected by the magnetic detection elements sequentially selected from among the plurality of magnetic detection elements to the combining part combining a rotation position of the rotor on the basis of the plurality of detection signals detected by the plurality of magnetic detection elements. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a magnetic encoder.

  There are optical and magnetic encoders as rotational position detection devices for detecting the rotational position. The optical encoder, which is an optical rotational position detection device, uses a photoelectric conversion element such as a photodiode for the detection unit, and can detect the rotational position with high precision. However, the detection unit detects condensation or splashes of oil. It may be difficult to use in an environment that directly takes into account. Magnetic encoders (see, for example, Patent Document 1), which are magnetic rotational position detectors, use magnetic detection elements such as Hall elements and magnetoresistive elements. Although it is difficult, it can be used even in an environment where condensation or oil splash is directly applied to the detection unit.

JP 2004-20548 A

  By the way, in recent years, encoders have been applied to robots, industrial machine tools, and the like, and magnetic encoders that can be used with high accuracy and can be used even in the severe environment described above have been required.

  As the detection element of the magnetic encoder described above, a magnetic detection element such as a Hall element or a magnetoresistive element is used. However, a Hall element is often used because of its small size and low price. However, the Hall element has variations in detection sensitivity, variations in offset voltage variation due to environmental temperature, and the like. As described above, since the output of a magnetic detection element such as a Hall element varies, there is a problem that a highly accurate magnetic encoder may not be obtained.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a magnetic encoder that can improve detection accuracy even when the output of a magnetic detection element varies.

  The present invention has been made to solve the above-described problems, and includes a rotor having a magnet, a plurality of magnetic detection elements arranged in the vicinity of the magnet, and a plurality of detections by the plurality of magnetic detection elements. An output unit for outputting the detection signal detected by the magnetic detection element selected in order from the plurality of magnetic detection elements to a combining unit that combines the rotational positions of the rotor based on the detection signal of And a magnetic encoder.

  According to the present invention, a magnetic encoder that can improve detection accuracy can be provided.

It is a schematic block diagram which shows an example of a structure of the magnetic encoder by 1st Embodiment of this invention. It is a block diagram which shows the structure of the output part with which the magnetic encoder by 1st Embodiment is provided, and a synthetic | combination control part. FIG. 5 is an operation diagram showing an example of the operation of the magnetic encoder according to the first embodiment. It is explanatory drawing for demonstrating the relationship between a some Hall element and a synthetic | combination part about (Formula 5) and (Formula 6) in 1st Embodiment. It is a block diagram which shows the structure of the output part by 2nd Embodiment. In 2nd Embodiment, it is the schematic which shows two connection states of a Hall element. It is an operation | movement diagram which shows an example of operation | movement of the magnetic encoder by 2nd Embodiment. It is a block diagram which shows the structure of the equalization circuit of a Hall element in the 1st connection state by 2nd Embodiment. It is a block diagram which shows the structure of the equalization circuit of a Hall element in the 2nd connection state by 2nd Embodiment. In 2nd Embodiment, when the input terminal and output terminal of a Hall element are replaced periodically, it is an output diagram which illustrates the signal output from a synthetic | combination amplifier circuit. In 2nd Embodiment, it is an output diagram which shows the voltage value before and behind averaging of the signal voltage output from the synthetic | combination amplifier circuit when changing environmental temperature. It is a schematic block diagram which shows an example of a structure of the magnetic encoder by 3rd Embodiment. It is a block diagram which shows the structure of the output part by 3rd Embodiment. It is an operation | movement diagram which shows an example of operation | movement of the magnetic encoder by 3rd Embodiment. In 5th Embodiment, it is a connection diagram which shows the connection between a Hall element, a power supply part, and a differential amplifier part in the case of carrying out the offset removal in the case of one Hall element. In 5th Embodiment, it is a 1st connection diagram which shows the connection between a Hall element, a power supply part, and a differential amplifier part in the case of offset removal in the case of two Hall elements. In 5th Embodiment, it is the 2nd connection diagram which shows the connection between a Hall element, a power supply part, and a differential amplification part in the case of offset removal in the case of two Hall elements. It is an operation | movement diagram which shows an example of operation | movement of the magnetic encoder by 5th Embodiment. It is a block diagram which shows the structure of the output part by 5th Embodiment.

[First Embodiment]
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram showing the configuration of a magnetic encoder 100 which is a rotation angle detection device according to the first embodiment of the present invention.

  As shown in FIG. 1, a magnetic encoder 100 includes a rotor 6 having a magnet 5 and a plurality of magnetic detection elements 1 (MS1), 2 (MS2), 3 (MS3) arranged in the vicinity of the rotor 6. ), 4 (MS3) and the substrate set 9 on which the magnetic detection elements 1, 2, 3, 4 and other control components are mounted. Here, the vicinity of the rotor 6 means, for example, the circumference of the rotor 6 or the circumference of the rotor 6.

  The magnet 5 is a permanent magnet, for example. Each of the magnetic detection elements 1, 2, 3, 4 is, for example, a Hall element. Hereinafter, the magnetic detection elements 1, 2, 3, and 4 will be referred to as Hall elements 1, 2, 3, and 4, respectively.

  In FIG. 1, when the rotor 6 rotates about a rotation axis that is perpendicular to the paper surface, the magnet 5 rotates with the rotation of the rotor 6 and is detected by the Hall elements 1, 2, 3, and 4. The magnetic field from the magnet 5 changes. The magnetic encoder 100 detects the change of the magnetic field by four Hall elements, Hall elements 1, 2, 3, and 4, respectively, and detects the rotational position of the rotor 6 from the detected change amount of the magnetic field.

  Here, the “rotation position” in the present embodiment is a rotation angle, position information indicating the rotation position, or angle information indicating the rotation angle.

  The four Hall elements 1, 2, 3, 4 described with reference to FIG. 1 have, for example, the same detection sensitivity, and each have the same output level. The four Hall elements 1, 2, 3, 4 are arranged on the plane of the substrate set 9, for example, on the plane having the same direction as the rotation axis of the rotor 6 and the normal vector. And arranged on a circumference that is equidistant from the rotation axis of the rotor 6. The Hall elements 1, 2, 3, 4 are arranged at equal intervals (in this case, an equal angle of 90 degrees with the rotation axis of the rotor 6 as the center). The hall elements 1 and 3 and the hall elements 2 and 4 to be paired are arranged so as to face each other with the rotation axis of the rotor 6 as the center, and 180 degrees about the rotation axis of the rotor 6 as a center. They are arranged at an angle.

  The Hall elements 1, 2, 3, and 4 have two output terminals (out + and out−), respectively. These two output terminals are connected to terminals of analog SW (analog switch) 2 and SW3 described later (see FIG. 2). 2 indicates that it is connected to the output terminal out- of the Hall element 1 in FIG.

  Hereinafter, for example, a signal output from the output terminal out + of the Hall element 1 is referred to as “signal MS1out +”, and a signal output from the output terminal out− of the Hall element 1 is referred to as “signal MS1out−”. The signals output from the Hall elements 2, 3, 4 are also referred to in the same manner as the signals output from the Hall element 1.

  The Hall elements 1, 2, 3, 4 each have two input terminals (in + and in−) to which a current or voltage is applied. These two input terminals are connected to analog SW1 and SW4 terminals described later (see FIG. 2). 2 indicates that it is connected to the input terminal in− of the Hall element 1 in FIG. 1.

  Hereinafter, for example, a signal output from the input terminal in + of the Hall element 1 is referred to as “signal MS1in +”, and a signal output from the input terminal in− of the Hall element 1 is referred to as “signal MS1in−”. The signals output from the Hall elements 2, 3, 4 are also referred to in the same manner as the signals output from the Hall element 1.

  Next, the configuration of the magnetic encoder 100 that detects the rotational position of the rotor 6 from the amount of change in the magnetic field detected by the four Hall elements described above will be described with reference to FIG. For example, the configuration of the magnetic encoder 100 that detects the rotational position of the rotor 6 includes, as an example, an output unit 200 that sequentially outputs detection signals detected by the Hall elements 1, 2, 3, and 4, and synthesis control. The unit 300 is provided.

  First, the configuration of the output unit 200 will be described. The output unit 200 includes analog SW 1, SW 2, SW 3, and SW 4, a power supply unit 210, a differential amplification unit 220, and an A / D conversion unit (A / D converter) 230.

  Here, as described above, each of the Hall elements 1, 2, 3, and 4 includes a total of four terminals, that is, two input terminals (in + and in−) and two output terminals (out + and out−). ing. These terminals of the Hall element are connected to corresponding analog SWs 1, 2, 3, 4 respectively. Hereinafter, one of the Hall elements 1, 2, 3, and 4 will be described as a Hall element.

  Each of the analog switches SW1, SW2, SW3, and SW4 includes four first terminals and one second terminal. The four first terminals of the analog SW1 are connected to the input terminals in + of the Hall elements 1, 2, 3, and 4, respectively. A power supply unit 210 is connected to one second terminal of the analog SW1.

  Further, address select signals S0 and S1 are input to the analog SW1. In the analog SW1, one of the four first terminals is selected by a combination of the address select signals S0 and S1, and the selected first terminal, second terminal, Is connected. The address select signals S0 and S1 are selection signals supplied from, for example, the synthesis control unit 300 (the control unit 320 included in the synthesis control unit 300), and any one of the four first terminals. Is a selection signal for selecting.

  With such a configuration, based on the combination of the address select signals S0 and S1, the input terminal in + of any one of the hall elements 1, 2, 3, and 4 is connected via the analog SW1. And connected to the power supply unit 210.

  Similar to the analog SW1, the output terminal out + of any one of the hall elements 1, 2, 3, and 4 selected based on the combination of the address select signals S0 and S1 passes through the analog SW2. And connected to the input terminal + of the differential amplifier 220.

  Similarly, based on the combination of the address select signals S0 and S1, the output terminal out− of any one Hall element selected from the Hall elements 1, 2, 3 and 4 passes through the analog SW3. And connected to the input terminal − of the differential amplifier 220.

  Similarly, based on the combination of the address select signals S0 and S1, the input terminal in− of any one Hall element selected from the Hall elements 1, 2, 3, 4 is connected via the analog SW4. Grounded. Note that the second terminal of the analog SW4 may be grounded via the resistor R1.

  Based on the combination of the address select signals S0 and S1, the power supply unit 210 applies analog SW1 and analog SW4 to any one of the Hall elements 1, 2, 3, and 4 as described above. And current or voltage is supplied through.

  The differential amplifying unit 220 outputs the output terminal out + and the output terminal out− of any one of the Hall elements 1, 2, 3, and 4 selected based on the combination of the address select signals S0 and S1. Are input via the analog SW2 and the analog SW3 described above. Then, the differential amplifier 220 differentially amplifies the input output terminal out + and output terminal out− of the Hall element and outputs the result to the A / D converter 230.

  The A / D conversion unit 230 performs A / D conversion on the output from the differential amplification unit 220 and outputs the result to the synthesis control unit 300. The A / D conversion unit 230 performs A / D conversion on the output from the differential amplification unit 220 at a timing based on the supplied A / D control signal, and outputs the result to the synthesis control unit 300. This A / D control signal is a control signal supplied from the control unit 320, for example, and is a control signal indicating the timing of A / D conversion.

  As described above, the power supply unit 210 sequentially supplies power to the Hall elements 1, 2, 3, and 4 based on the combination of the address select signals S0 and S1. In addition, the differential amplifier 220 and the A / D converter 230 differentially amplify detection signals detected by the Hall elements sequentially supplied by the power supply unit 210 and sequentially output the detection signals.

  In this embodiment, “in order” means “in time series” or “selectively one by one from a plurality”.

  That is, the output unit 200 supplies a current or voltage to any one of the hall elements selected from the hall elements 1, 2, 3, and 4 based on the combination of the address select signals S0 and S1. The output from one Hall element selected and supplied with current or voltage is differentially amplified and output.

  In the present embodiment, the address select signals S0 and S1 are signals that sequentially select one Hall element from the Hall elements 1, 2, 3, and 4. Therefore, the output unit 200 passes the analog SW1 to any one Hall element selected in order from the Hall elements 1, 2, 3, 4 based on the combination of the address select signals S0 and S1. Current or voltage is supplied, and the output from the selected one Hall element is differentially amplified and output as a detection signal.

  Further, in this way, the switching unit 260 (first switching unit) composed of the analog SW1, SW2, SW3, and SW4 is connected between the Hall elements 1, 2, 3, 4 and the power supply unit 210. , And the connection between the Hall elements 1, 2, 3, 4 and the differential amplifier 220 is sequentially switched with respect to the Hall elements 1, 2, 3, 4.

  Next, the configuration of the composition control unit 300 will be described. The composition control unit 300 includes a composition unit 310 and a control unit 320.

  The synthesizing unit 310 is a detection signal output from the differential amplification unit 220 of the output unit 200 and corresponds to an output from the Hall element selected in order from the Hall elements 1, 2, 3, and 4. And the rotational position of the rotor 6 is synthesized based on the stored detection signal.

  The synthesis control unit 300 is, for example, a detection signal output from the differential amplification unit 220 of the output unit 200, and is output from the Hall elements selected in order from the Hall elements 1, 2, 3, and 4. There may be provided a detection signal storage unit for storing a detection signal corresponding to.

  The control unit 320 outputs the above-described address select signals S0 and S1 to the analog SW1, SW2, SW3, and SW4, and outputs the above-described A / D control signal to the A / D conversion unit 230. SW2, SW3 and SW4 and A / D converter 230 are controlled. As an example, the control unit 320 generates the address select signals S0 and S1 and the A / D control signal described above based on a predetermined cycle.

  In addition, the control unit 320 causes the combining unit 310 of the rotor 6 to store the detection signal output from the differential amplification unit 220 of the output unit 200 in the detection signal storage unit and the stored detection signal. Controls the timing of combining the rotational positions.

  Next, an example of the operation of the magnetic encoder 100 described with reference to FIGS. 1 and 2 will be described with reference to FIG.

  First, the control unit 320 of the synthesis control unit 300 outputs address select signals S0 and S1. For example, when the output of the address select signals S0 and S1 is the same as the output of the 2-bitUP counter, the hall elements are selected one by one in the order of the hall elements 1 to 4 via the analog SW1, SW2, SW3, and SW4. (See FIG. 3). Thus, the power supply unit 210 always drives one Hall element, and the differential amplifier 220 outputs detection signals in the order of the Hall elements 1 to 4.

  In addition, the control unit 320 of the synthesis control unit 300 outputs the A / D control signal to the A / D conversion unit 230 according to the timing of switching the address select signals S0 and S1, and the differential amplification unit of the output unit 200 The timing at which the detection signal output from 220 is stored in the detection signal storage unit, and the timing at which the synthesis unit 310 synthesizes the rotational position of the rotor 6 is controlled based on the stored detection signal.

  Thereby, the synthesis unit 310 can synthesize the rotational position of the rotor 6 at an appropriate timing. The appropriate timing here is the following timing. For example, immediately after switching the address select signals S0 and S1, noise or the like may be superimposed on the detection signals output from the Hall elements 1 to 4. In such a case, if the combining unit 310 combines the rotational positions of the rotor 6, there is a possibility that the combining cannot be performed appropriately.

  The appropriate timing described above means that there is no possibility that noise or the like is superimposed on the detection signals output from the Hall elements 1 to 4 just after switching the address select signals S0 and S1, and the rotation of the rotor 6 is performed. This is the timing at which the positions can be appropriately combined. For example, the appropriate timing is a timing at which a predetermined time has elapsed since switching of the address select signals S0 and S1 and no noise is generated in the detection signals output from the Hall elements 1 to 4. .

  Next, an example of a synthesis method by the synthesis unit 310 will be described. The synthesizer 310 synthesizes the rotational position of the rotor 6 by the following formulas 1 and 2, for example.

First composite output: [(Vms1 + Vofft1) − (Vms3 + Vofft3)] (Formula 1)
Second composite output: [(Vms2 + Vofft2) − (Vms4 + Vofft4)] (Expression 2)

here,
Vms1: Hall element 1 output, Vofft1: Offset voltage associated with Hall element 1 circuit,
Vms2: Hall element 2 output, Vofft2: Offset voltage associated with the Hall element 2 circuit,
Vms3: Hall element 3 output, Vofft3: Offset voltage associated with the Hall element 3 circuit,
Vms4: Hall element 4 output, Vofft4: Offset voltage associated with the Hall element 4 circuit.

  In (Expression 1), the signal Vms1 + Vofft1 is a detection signal by the Hall element 1, and the signal Vms3 + Vofft3 is a detection signal by the Hall element 3. In (Expression 2), the signal Vms2 + Vofft2 is a detection signal by the Hall element 2, and the signal Vms4 + Vofft4 is a detection signal by the Hall element 4.

  As shown in (Expression 1) and (Expression 2), the combining unit 310 outputs a plurality of Hall elements from two Hall elements facing each other around the rotation center axis of the rotor 6. The detected signals are synthesized.

  Here, when an amplification circuit such as the differential amplification unit 220 is provided for each of the plurality of Hall elements and the output of the Hall element is simply amplified by the corresponding amplification circuit, the amplification circuit is different for each Hall element. It will be. Therefore, in this case, the offset voltage included in the output from each Hall element may vary depending on the temperature. Therefore, an output error may occur in the amplified output.

  On the other hand, when the differential amplifier 220 is common to each Hall element as in the present embodiment, the offset voltage term in the above equation is canceled and substantially eliminated, and the following simple equation: It becomes.

First composite output: [Vms1-Vms3] (Equation 3)
Second composite output: [Vms2-Vms4] (Equation 4)

  As a result, the magnetic encoder 100 according to the present embodiment is not affected by the fluctuation of the offset voltage of the circuit (offset voltage fluctuation), and therefore the detection accuracy can be made high.

  In the case of the configuration shown in FIG. 2 of the present embodiment, analog SW1, SW2, SW3, and SW4 that are inexpensive standard logic ICs are required. However, compared to the case where the analog SW1, SW2, SW3, and SW4 are not used and the power supply unit 210 and the differential amplification unit 220 are provided for the respective Hall elements, in the present embodiment, for example, the differential amplification unit 220 and one power supply unit 210 that is a circuit for driving the Hall element may be provided. Therefore, as a whole, the configuration can be made inexpensive. Moreover, these circuit systems become one system, and the power consumption by the Hall element in a standby state is unnecessary. Therefore, the entire circuit has an effect of reducing power consumption.

  Note that the combining unit 310 may combine the rotational position of the rotor 6 using, for example, the following Expression 5 and Expression 6.

First composite output: [Vms1 + Vms2-Vms3-Vms4] (Equation 5)
Second composite output: [Vms1-Vms2-Vms3 + Vms4] (Equation 6)

  Note that the first combined output calculated by (Expression 1), (Expression 3), or (Expression 5) and the second combined output calculated by (Expression 2), (Expression 4), or (Expression 6). Corresponds to the two-phase signal of the encoder. Here, the first combined output is the A-phase signal output, and the second combined output is the B-phase signal output. In addition, due to the arrangement relationship of the Hall elements, the A and B phase signal outputs have a phase difference of 90 °. The rotational position of the encoder in this case is calculated by (Equation 7).

Encoder output (angle): tan ⁻¹ (A phase signal output / B phase signal output) (Expression 7)

  Here, for example, it is assumed that the synthesis unit 310 includes a synthesis unit A, a synthesis unit B, and a synthesis unit C. The synthesizer A synthesizes the A-phase signal output that is the first synthesized output based on (Equation 1), (Equation 3), or (Equation 5). The synthesizer B synthesizes the B-phase signal output that is the second synthesized output based on (Equation 2), (Equation 4), or (Equation 6). The synthesizing unit C calculates the rotational position of the encoder based on (Equation 7) using the A-phase signal output synthesized by the synthesizing unit A and the B-phase signal output synthesized by the synthesizing unit B. The calculated rotation position of the encoder is output.

  Here, with reference to FIG. 4, in the case of (Expression 5) and (Expression 6), the relationship between the plurality of Hall elements 1, 2, 3, 4 described in FIG. Will be described.

  Among the plurality of Hall elements 1, 2, 3, and 4, a Hall element included in a first region divided by a first plane including the rotation center axis of the rotor 6 is defined as a first Hall element group. A Hall element included in the second region divided by one plane is defined as a second Hall element group. In addition, among the plurality of Hall elements 1, 2, 3, and 4, the second plane that includes the center axis of rotation and is divided by a second plane that forms a predetermined angle with the first plane. Hall elements included in the third region are defined as a third Hall element group, and Hall elements included in the fourth region divided by the second plane are defined as a fourth Hall element group. This predetermined angle is, for example, 90 degrees.

  As shown in FIG. 4, an axis that is the rotation center axis of the rotor 6 and is perpendicular to the paper surface is defined as a Z axis. Two axes that are perpendicular to the Z-axis and that are horizontal and perpendicular to the paper surface are defined as an X-axis and a Y-axis. Here, for the sake of explanation, the angular position of the Hall element 1 is set to 0 degree, the angular position of the Hall element 2 is set to 90 degrees, the angular position of the Hall element 3 is set to 180 degrees, and the Hall element 1 is set to 180 degrees. The angular position of the element 4 is 270 degrees.

  For example, as indicated by reference numeral 301, the first plane is assumed to be a plane perpendicular to the paper surface at angular positions of 135 degrees and 315 degrees with respect to the rotation center axis of the rotor 6. In this case, the first Hall element group is Hall elements 1 and 2, and the second Hall element group is Hall elements 3 and 4. Further, as indicated by reference numeral 302, the second plane is assumed to be a plane perpendicular to the paper surface at angular positions of 45 degrees and 225 degrees with respect to the rotation center axis of the rotor 6. In this case, the third Hall element group is Hall elements 2 and 3, and the fourth Hall element group is Hall elements 4 and 1.

  Here, the term of (Equation 5) is regarded as (Vms1 + Vms2) − (Vms3 + Vms4), and among these, a configuration for synthesizing Vms1 + Vms2 is referred to as a synthesis unit A1, and a configuration for synthesizing Vms3 + Vms4 is described as a synthesis unit A2. The synthesizing unit A calculates the difference between the outputs of the synthesizing unit A1 and the synthesizing unit A2, that is, (Vms1 + Vms2) − (Vms3 + Vms4). Output) is synthesized. Similarly to (Formula 5), (Formula 6) is synthesized with (Vms1 + Vms4) and (Vms2 + Vms3) by the synthesis unit B1 and the synthesis unit B2. The combining unit B calculates (Vms1 + Vms4) − (Vms2 + Vms3), and the second combined output (B-phase signal output) is combined.

  A hall element obtained by synthesizing the hall elements 1 and 2 included in the first hall element group described above by the synthesis unit A1 is an intermediate position between the hall elements 1 and 2, for example, a position indicated by reference numeral A1 in FIG. This corresponds to a synthetic Hall element located at a position of 45 degrees around the rotation center axis of the rotor 6.

  Similarly, the Hall element obtained by combining the Hall elements 3 and 4 included in the above-described second Hall element group by the combining unit A2 is located at a position intermediate between the Hall elements 3 and 4, for example, the symbol A2 in FIG. Corresponding to a synthetic Hall element at a position of 225 degrees around the rotation center axis of the rotor 6.

  The synthesizer A synthesizes the Hall element synthesized by the synthesizer A1 for the first Hall element group and the Hall element synthesized by the synthesizer A2 for the second Hall element group with the signs reversed. is doing. Here, the Hall element synthesized by the synthesis unit A1 for the first Hall element group and the Hall element synthesized by the synthesis unit A2 for the second Hall element group are centered on the rotation center axis of the rotor 6. The N pole and the S pole of the magnet 5 of the rotor 6 are 180 degrees with the rotation center axis of the rotor 6 as the center. Therefore, for example, when the Hall element synthesized by the synthesis unit A1 for the first Hall element group described above detects the N pole, the Hall element synthesized by the synthesis unit A2 for the second Hall element group This is because the S pole is detected and the sign of the detected signal is reversed.

  In this way, the combining unit A1 combines the detection values from the plurality of Hall elements included in the first Hall element group to increase the output value of the combining unit A1. The combining unit A2 combines the detection values from the plurality of Hall elements included in the second Hall element group to increase the output value of the combining unit A2.

  Further, the combining unit A includes an output value from the combining unit A1 that combines detection values from a plurality of Hall elements included in the first Hall element group, and a plurality of elements included in the second Hall element group. The output value of the combining unit A2 is further increased by combining the output value from the combining unit A2 that combines the detection values from the Hall elements with the signs reversed.

  For example, the combining unit A indicates the rotational position of the rotor 6 detected by the combined Hall element at a position indicated by reference numeral A1 in FIG. 4 and at a position of 45 degrees about the rotation center axis of the rotor 6. This is equivalent to or equivalent to outputting the indicated signal. In addition, since this synthetic Hall element outputs an output value obtained by synthesizing four Hall elements 1, 2, 3, and 4, the synthesizing unit A outputs a single Hall element. In contrast, a large signal (detection signal) can be output.

  As in the case of the first Hall element group and the second Hall element group described above, the synthesis unit B is, for example, shown in FIG. 4 by the third Hall element group and the fourth Hall element group. This is equivalent to or equivalent to outputting a signal indicating the rotational position of the rotor 6 detected by the synthetic Hall element at the position indicated by B1 and at a position of 135 degrees around the rotational center axis of the rotor 6. . Moreover, since this synthetic Hall element outputs an output value obtained by synthesizing four Hall elements 1, 2, 3, and 4, the synthesis unit B outputs the output by one Hall element. In contrast, a large signal (detection signal) can be output.

  Further, as described above, the combining unit A is, for example, the rotation detected by the combined Hall element at the position indicated by the reference symbol A1 in FIG. 4 and at a position of 45 degrees around the rotation center axis of the rotor 6. A signal indicating the rotation position of the child 6 is output, and the combining unit B is, for example, a combined hole at a position indicated by reference numeral B1 in FIG. 4 and at a position of 135 degrees around the rotation center axis of the rotor 6. A signal indicating the rotational position of the rotor 6 detected by the element is output. That is, the combined Hall element of the combining unit A and the combining unit B has a positional relationship of 90 degrees around the rotation center axis. Therefore, the synthesizing unit A and the synthesizing unit B can output an A-channel approximate sine wave detection signal and a B-channel approximate sine wave detection signal that are 90 degrees out of phase, respectively.

  In this way, the combining unit A combines the detection signals detected by the plurality of Hall elements 1, 2, 3, and 4 so as to be the first combined magnetic detection element that detects the rotational position of the rotor 6. An approximate sine wave detection signal of A channel is output. The combining unit B is a second combined magnetic detection element that detects the rotational position of the rotor 6 and is at a predetermined angular position (for example, 90 degrees) with respect to the combining unit A around the rotation center axis. The detection signals detected by the plurality of Hall elements 1, 2, 3, and 4 are combined to output a B channel approximate sine wave detection signal so as to be a second combined magnetic detection element.

  As described above using (Equation 1) and (Equation 2), the encoder 100 according to the present embodiment has four Hall element signals that are simply opposed to the Hall elements (Hall element 1 and Hall element 3, Hall In the case of (Equation 5) and (Equation 6), not all the detection signals of the Hall element 1 to the Hall element 4 are used. It is possible to average variations in sensitivity of Hall elements and variations in offset voltage due to changes in environmental temperature.

  The signals of the Hall elements 1, 2, 3, 4 are input to the synthesis amplifier circuit so as to add / subtract the signals of the opposing Hall elements having an angle of 180 degrees with the rotation center axis of the rotor 6 as the center. Yes. Therefore, even if the rotor 6 is eccentric, the rotational position error due to this eccentricity can be canceled.

  By adopting such a method, the detection signal of the approximate sine wave generated by synthesis is increased, and as a result, the offset voltage fluctuation value is apparently decreased (relative to the detection signal). effective. For example, a detection value is output from each of the hall elements 1, 2, 3, and 4. The detection value is a predetermined output level, and variations with respect to the output level cannot be ignored. However, as described above, the variation is relative to the value obtained by combining the detection values output from the plurality of Hall elements 1, 2, 3, and 4, that is, the output level of the detection value output from the combined Hall element. Therefore, the variation can be ignored. Therefore, the magnetic encoder 100 according to the present embodiment can improve detection accuracy and achieve high accuracy and high resolution even when the outputs of the plurality of Hall elements vary.

[Second Embodiment]
Next, a second embodiment will be described. Here, a configuration different from the first embodiment will be described.

  In general, the Hall element has an unbalanced voltage (offset voltage) due to the asymmetry of the output terminal, and there is a problem in that this may cause a variation with temperature. In the second embodiment, a configuration in which the offset of the Hall element can be canceled by the method of compensating for this unbalanced voltage in the configuration of the first embodiment will be described.

  FIG. 5 is a configuration diagram showing a configuration of the output unit 200 when canceling the offset of the Hall element in the case where the number of Hall elements is four as in the first embodiment of FIG. In FIG. 5, in the configuration of the output unit 200, the configuration from a plurality of analog SWs to the differential amplification unit 220 is illustrated.

  The output unit 200 shown in FIG. 5 is different in that the analog SW1, SW2, SW3, and SW4 of the output unit 200 of FIG. 2 become analog SW10, SW20, SW30, and SW40.

  Each of the analog switches SW10, SW20, SW30, and SW40 includes eight first terminals and one second terminal. The eight first terminals of the analog SW 10 are connected to the input terminals in + of the Hall elements 1, 2, 3, and 4 and the output terminals out− of the Hall elements 1, 2, 3, and 4, respectively. ing. A power supply unit 210 is connected to one second terminal of the analog SW 10.

  In FIG. 5, the Hall element 1 is indicated as MS1, the Hall element 2 is indicated as MS2, the Hall element 3 is indicated as MS3, and the Hall element 4 is indicated as MS4. In FIG. 5, the input terminal in + of each of the Hall elements 1, 2, 3 and 4 is the terminal 1, the output terminal out + is the terminal 2, the input terminal in− is the terminal 3, and the output terminal out−. Is shown as a terminal 4.

  In FIG. 5, the analog SW 10 includes a connection between one of the eight first terminals included in the analog SW 10 and the input terminal in + (terminal 1) of the Hall element 1. The position of one of the eight first terminals is indicated by the symbol “MS1-1”.

  Further, the address select signals S0, S1, and S2 are input to the analog SW10. In the analog SW 10, any one of the eight first terminals is selected by the combination of the address select signals S 0, S 1, and S 3, and the selected first terminal and the second terminal are selected. Terminal is connected.

  As in the case of FIG. 2, the address select signals S0, S1, and S2 are selection signals supplied from the control unit 320 included in the synthesis control unit 300, and any one of the eight first terminals is selected. A selection signal for selecting a terminal.

  With this configuration, as in the case of FIG. 2, any one Hall element selected from the Hall elements 1, 2, 3, 4 based on the combination of the address select signals S0, S1, and S2 is used. The input terminal in + (terminal 1) is connected to the power supply unit 210 via the analog SW10.

  Furthermore, based on the combination of the address select signals S0, S1, and S2, the output terminal out- (terminal 4) of any one of the hall elements 1, 2, 3, 4 is analog The power supply unit 210 is connected via the SW10.

  That is, the analog SW 10 allows not only the power supply unit 210 to be connected to the input terminal of the Hall element but also the power supply unit 210 to be connected to the output terminal of the Hall element.

  Similarly to the analog SW 10, the analog SWs 20, 30, and 40 can be connected in the case of FIG. 2, and further, the connection of the Hall element output terminal and the output terminal can be reversed as in the case of FIG. .

  That is, with the configuration in FIG. 5, in addition to the connection in the configuration in FIG. 2 as shown in FIG. 6A, the connection in FIG. 6B is also possible.

  That is, as shown in FIG. 5, the switching unit 261 (third switching unit) composed of the analog SWs 10, 20, 30, and 40 outputs a detection signal from the input terminal to which power is supplied and the Hall element. The output terminal to be switched is switched for each Hall element.

  Next, FIG. 7 shows an operation diagram showing the operation of the second embodiment. Here, the case where the Hall element 1 is in the connection state as shown in FIG. 6A is referred to as “Hall element 1a”, and the case where the Hall element 1 is in the connection state as shown in FIG. 6B is referred to as “Hall element 1b”. To do.

  Assume that an address select signal (S0, S1, S2) is output from the control unit 320 of the synthesis control unit 300, and the output is the same as the output of the 3-bit UP counter. In this case, the Hall elements are selected in the order of the Hall elements 1a, 1b, 2a, 2b,... 4b. The current or voltage supplied from the power supply unit 210 always drives one Hall element. The differential amplifier 220 differentially amplifies and outputs the output of the Hall elements in the order of the Hall elements 1 to 4.

  Thereafter, the synthesizer 310 stores the detection signal output from the differential amplifier 220 in the state of the Hall element 1a and the detection signal output from the differential amplifier 220 in the state of the Hall element 1b, and averages them. Is calculated. Then, the synthesis unit 310 uses the calculated average as the detection signal of the Hall element 1.

  Similarly to the case of the Hall element 1, the combining unit 310 uses the averaged detection signal for the Hall elements 2, 3, and 4 as the detection signal for the Hall elements 2, 3, and 4. Thereafter, as in the case of the first embodiment, the combining unit 310 combines the rotational positions of the rotor 6 based on the detection signals of the Hall elements 1, 2, 3, 4 calculated by averaging.

  As described above, in the second embodiment, by increasing the number of selected analog SWs to 8, the same effects as in the first embodiment can be obtained, and further, the unbalanced voltage of the Hall element can be compensated (offset cancellation). There is an effect that can be done.

  For example, the average calculation of the detection signal output from the differential amplifier 220 in the state of the Hall element 1a and the detection signal output from the differential amplifier 220 in the state of the Hall element 1b is performed by the combining unit 310. It is possible to calculate within the logic IC. This calculation can cancel the offset of the Hall element.

  Thus, in contrast to the case of the first embodiment, in the second embodiment, the number of analog SW selections is increased, the number of address select signals is increased, and the calculation method in the synthesis unit 310 is changed. Although there is no increase in the number of components. Therefore, the magnetic encoder 100 according to the second embodiment has the effects of high accuracy, low cost, and low power consumption, and the effect of being able to cancel offset.

  Also in the case of the second embodiment, similarly to the case of the first embodiment, the synthesis unit 310 performs (Expression 1) and (Expression 2) (or (Expression 3) and (Expression 4). ), The first and second combined outputs may be output based on some detection signals from the Hall elements. Also in the case of the second embodiment, as in the case of the first embodiment, the synthesizing unit 310 performs all detection signals from the Hall elements as in (Equation 5) and (Equation 6). Based on the above, the first and second combined outputs may be configured.

  Next, a method for canceling the offset of the Hall element will be described in detail. An equivalent circuit of the Hall element is shown in the bridge circuit shown in FIG. In this equivalent circuit, the voltage at the input terminal is defined as voltage Vi (+) and voltage Vi (−), and the voltage at the output terminal is defined as voltage Vo (+) and voltage Vo (−). Here, when the magnetic field is zero, the voltage Vu generated at the output terminal in FIG. 8 and the voltage Vu generated at the output terminal when the input / output terminal and the output terminal are switched as shown in FIG. When calculating the sum with ', it is almost zero.

  The voltages Vu and Vu ′ used in the description of FIGS. 8 and 9 described above correspond to the voltages V1 and V2 described above. When the change due to the change in the magnetic field is “proportional to magnetic strength” and the change due to the offset is “X (offset)”, the voltages V1 and V2 are expressed by the following equations 8 and 9. .

  V1 = (proportional to magnetic intensity) + X (offset) (Equation 8)

  V2 = (proportional to magnetic intensity) −X (offset) (Equation 9)

  As described above with reference to FIGS. 8 and 9, when the average of the voltage V <b> 1 and the voltage V <b> 2 is taken, “X (offset)” is canceled (see the following Expression 10).

  (V1 + V2) / 2 = (proportional to magnetic intensity) (Equation 10)

  Therefore, for example, the average of the measured values obtained by switching the input terminal and the output terminal of the Hall element, that is, the average of the voltage V1 and the voltage V2, is used as the output from the Hall element. Thereby, the offset of the Hall element can be canceled and the magnetic field can be measured using the Hall element. That is, using the Hall element, the offset of the Hall element can be canceled and the rotational position of the rotor 6 can be detected.

  The offset cancellation of the Hall element described above has been described for the case where the magnetic field has not changed, that is, the rotor 6 has not rotated. However, even when the rotor 6 rotates, there is almost no change in the magnetic field when it can be considered that the rotor 6 is not substantially rotated during the period in which the switching circuits 20-1 to 20-4 are switched. In addition, the offset of the Hall element can be canceled as in the case where the magnetic field has not changed.

  Next, an example of a signal output from the combining unit A or B when the input terminal and the output terminal of the Hall element are periodically exchanged will be described with reference to FIG. In the following, switching between the input terminal and the output terminal of the Hall element will be referred to as switching. Here, description will be made assuming that switching is performed every predetermined period T1.

  In response to switching at intervals of the period T1, the output voltage output from the combining unit A or B repeats the voltage V1 and the voltage V2 alternately in the period T1. Note that when switching is performed at intervals of the period T1, the signal output from the combining unit A or B is output with noise generated by switching. However, noise generated by this switching disappears after a predetermined period (for example, about several tens of ns) has elapsed since switching. Therefore, after switching, data after a predetermined time T2 longer than a period in which noise is generated by switching is measured as an output from the combining unit A or B. Thereafter, when new data is determined by switching, the value is measured as new data.

  In this way, the voltages V1 and V2 can be measured alternately. Furthermore, by taking the average of the measured voltage and the latest measured voltage, that is, the latest voltages V1 and V2, the offset of the Hall element can be canceled and the rotational position of the rotor 6 can be detected.

  The period T1 described above may be longer than the time T2 determined in this way. Therefore, the period T1 can be shortened to a period during which noise due to switching occurs. As described above, the measurement of the voltage V1 and the voltage V2 is desirably performed in a short time so that the rotor 6 can be regarded as not rotating. Therefore, it is preferable that the period T1 corresponding to the measurement time interval between the voltage V1 and the voltage V2 can be shortened to a period during which noise due to switching occurs.

  The time T2 can be shortened to a time until noise generated by switching disappears. The time until the noise caused by switching disappears can be determined in advance by simulation or experiment. Therefore, the time T2 can be shortened based on the resistance value and the like, and the period T1 can be determined based on the time T2 set in advance so as to be short.

  Next, FIG. 11 shows a voltage value of a signal output from the combining unit A or B when the environmental temperature is changed (refer to reference signs V1 and V2) and an average voltage value (reference sign (V1 + V2)). / 2). When the environmental temperature changes, the offset fluctuates as the environmental temperature changes, so that the voltage V1 and the voltage V2 fluctuate as shown in FIG. However, the offset of the average (V1 + V2) / 2 of the voltage V1 and the voltage V2 output according to the switching in the period T1 is canceled as described above. Therefore, even if the environmental temperature changes, the average (V1 + V2) / 2 becomes a constant voltage value.

[Third Embodiment]
Next, a magnetic encoder 100 according to a third embodiment will be described. Here, only differences from the magnetic encoder 100 according to the first embodiment or the second embodiment will be described.

  The configuration of the third embodiment is shown in FIG. The third embodiment has substantially the same configuration as the first embodiment, but the number of Hall elements is eight. Also in this case, the eight Hall elements are arranged at equal intervals on the same circumference. Here, as shown in FIG. 12, description will be made assuming that the Hall elements MS1, MS2, MS3, MS4, MS5, MS6, MS7, and MS8 are arranged at equal intervals on the circumference in this order. Each of the Hall elements MS1, MS2, MS3, MS4, MS5, MS6, MS7, and MS8 will be described as a Hall element.

  FIG. 13 is a block diagram showing an example of the configuration of the output unit 200 when controlling the eight Hall elements according to the third embodiment shown in FIG. In FIG. 12, in the configuration of the output unit 200, the configuration from a plurality of analog SWs to the differential amplification unit 220 is illustrated.

  In the case of the first embodiment, since the number of Hall elements is four, the number of first input terminals of each analog SW is four. On the other hand, in the case of the third embodiment, since the number of Hall elements is 8, the number of first input terminals of each analog SW is 8. Therefore, each of the analog SW15, SW25, SW35, and SW45 includes eight first terminals and one second terminal.

  The four terminals of the Hall element are respectively connected to the corresponding analog SW as in the case of FIG. For example, the input terminals in + of the eight hall elements are connected to the eight first terminals of the analog SW 15. Further, the second terminal of the analog SW 15 is connected to the power supply unit 210 as in the case of FIG. Therefore, a current or voltage source is selectively supplied from the power supply unit 210 to the input terminal in + included in the eight Hall elements.

  Similarly, the second terminal of the analog SW 45 to which the input terminals in− of the eight hall elements are connected is connected (grounded) to GND via the resistor R1. The resistor R1 may not be provided. Further, the second terminal of the analog SW 25 to which the output terminals out + of the eight hall elements are connected is connected to the + terminal of the differential amplifier 220. Further, the second terminal of the analog SW 35 to which the output terminals out− of the eight Hall elements are connected is connected to the − terminal of the differential amplifier 220.

Next, an example of the operation of the magnetic encoder 100 according to the third embodiment will be described with reference to FIG.
Assume that an address select signal (S0, S1, S3) is output from the control unit 320 of the synthesis control unit 300, and the output is the same as the output of the 3-bit UP counter. In this case, the switching unit 262 configured by the analog SWs 15, 25, 35, and 45 selects one Hall element in the order of the Hall elements 1, 2, 3, 4, 5, 6, 7, and 8. For this reason, the power supply unit 210 always drives one Hall element in order. Also, the differential amplifier 220 sequentially amplifies and outputs detection signals output from one Hall element.

  In this case, as in the case of the first embodiment, the combining unit 310 may configure the first and second combined outputs using some signals as described above, or may use all of them. You may comprise the 1st, 2nd synthetic | combination output. However, instead of (Expression 3) and (Expression 4), the following (Expression 11) and (Expression 12) are obtained. Further, instead of (Expression 5) and (Expression 6), the following (Expression 13) and (Expression 14) are obtained.

First composite output: [Vms1 + Vms3-Vms5-Vms7] (Equation 11)
Second composite output: [Vms1-Vms3-Vms5 + Vms7] (Equation 12)

First composite output: [Vms1 + Vms2 + Vms3 + Vms4-Vms5-Vms6-Vms7-Vms8] (Equation 13)
Second composite output: [Vms1 + Vms2-Vms3-Vms4-Vms5-Vms6 + Vms7 + Vms8] (Equation 14)

  According to the third embodiment, since the number of Hall elements is larger than that in the case of the first embodiment, the detection signal is increased as compared with the case of the first embodiment, and the rotational position of the rotor 6 can be determined with higher accuracy. Can be detected.

[Fourth Embodiment]
Next, a fourth embodiment will be described.
In the fourth embodiment, the Hall elements of FIG. 12 in the third embodiment are divided into two groups: a group of Hall elements MS1, MS3, MS5, MS7 and a group of Hall elements MS2, MS4, MS6, MS8. Divide into groups. As a result, a plurality of Hall elements can be used as if there were two encoders. For example, the first to fourth synthesized outputs are generated as follows.

First composite output: [Vms1-Vms5] (Equation 15) Compositing unit A
Second composite output: [Vms3−Vms7] (Equation 16)
Third composite output: [Vms2-Vms6] (Equation 17) Combining unit B
Fourth composite output: [Vms4−Vms8] (Equation 18)

  The synthesis method may be (Equation 5) and (Equation 6) described in the first embodiment. The two encoders described above have an angle offset of 45 ° = π / 4 from each other, but finally output the following equation.

  Output: [output of combining unit A + (output of combining unit B−π / 4)] / 2 = θ (Equation 19)

  By using this method, when there is a low-order error in the output of each encoder, the error can be canceled, so that high accuracy can be realized.

This will be described in detail using the following example.
Hall elements MS1 to MS8 are arranged at equal intervals on the substrate. Therefore, the synthesizer 310 can obtain detection signals from the hall elements at intervals of 45 ° (= π / 4).

  However, in reality, due to the eccentricity of the magnet or the rotor, the synthesizing unit 310 cannot obtain an ideal sin signal as a detection signal from the Hall element, and the normal signal waveform is as shown in (Equation 20). Is represented by the sum of low-order Fourier series.

Vms1: sin (θ) + ε2 · sin (2θ + φ2) + ε3 · sin (3θ + φ3)
+ Ε4 · sin (4θ + φ4) + ε5 · sin (5θ + φ5) + (Equation 20)

Here, θ is the reference angle of the rotor, ε is the amplitude of each order, and φ is the phase of each order.
The output of the Hall element arranged opposite to the Hall element is expressed as (Equation 21) by substituting θ + π into the above equation.

Vms5: −sin (θ) + ε2 · sin (2θ + φ2) −ε3 · sin (3θ + φ3)
+ Ε4 · sin (4θ + φ4) −ε5 · sin (5θ + φ5) + (Formula 21)

As a result, the first combined output [Vms1-Vms5] is (Equation 22).

First composite output: Vms1-Vms5
= 2sin (θ) + 2ε3 · sin (3θ + φ3) + 2ε5 · sin (5θ + φ5) + (Equation 22)

  It is clear from (Equation 22) that the first combined output is composed of sin (θ), which is the fundamental wave component, and its odd-order harmonic components. Similarly, the first combined output is expressed as (Equation 23).

Second composite output: Vms3-Vms7
= 2cos (θ) −2ε3 · cos (3θ + φ3) + 2ε5 · cos (5θ + φ5) + (Equation 23)

  Using the first and second combined outputs, the combining unit C outputs a phase angle (for example, specifically, interpolation processing by arctan).

  The combined output of the combining unit B can be obtained by setting θ in the above first and second combined output expressions to θ + π / 4, and is expressed by the following (Expression 24) and (Expression 25).

Third composite output: Vms2-Vms6
= 2sin (θ + π / 4) + 2ε3 · sin (3θ + 3π / 4 + φ3)
+ 2ε5 · sin (5θ + 5π / 4 + φ5) + (Equation 24)

Fourth composite output: Vms4-Vms8
= 2cos (θ + π / 4) -2ε3 · cos (3θ + 3π / 4 + φ3)
+ 2ε5 · cos (5θ + 5π / 4 + φ5) + (Equation 25)

  As described above, the third-order and fifth-order components found in the synthesized signal give the fourth-order component error of the encoder, but if this method is adopted, it can be removed and a highly accurate encoder can be realized.

[Fifth Embodiment]
Next, a fifth embodiment will be described. In the above-described second embodiment, eight types of signals from the four Hall elements are A / D converted, and the combined output is calculated by the combining unit 310. In the fifth embodiment, the Hall element circuit has a differential configuration in order to reduce the analog SW.

  In the case of a single Hall element, offset removal is performed by connecting the Hall element MS1, the power supply unit 210, and the differential amplification unit 220 with each other as shown in FIG. 15 (a) and FIG. 15 (b) or FIG. ) And FIG. 15C, this can be achieved by switching with the analog SW.

  In the case of the differential circuit having two Hall elements, the connections between the Hall element MS1, the Hall element MS2, the power supply unit 210, and the differential amplifier 220 are shown in FIGS. 16 (a) and 16 (b). Thus, it can be achieved by switching with the analog SW.

  The relationship between input and output in the Hall element at the time of offset cancellation is represented by FIG. 15A or FIG. 16A, and FIG. 15A or FIG. 16A shows the a output state described with reference to FIG. Correspond. Further, FIG. 15B, FIG. 16C, or FIG. 16A becomes the b output state described with reference to FIG.

  In the case of a differential circuit with two Hall elements, there are also connections as shown in FIGS. 17 (a) and 17 (b). In the case of a differential circuit with two Hall elements, there are several connection methods that can obtain the same effect in addition to the connection methods shown in FIGS.

There are the following two conditions as connection conditions in the case of the differential circuit having two Hall elements.
(1) When a potential is generated due to the Hall effect of the Hall element, the connection is such that the potentials of the opposing Hall elements do not cancel each other but strengthen each other so that a differential output is obtained.
(2) Connection that does not change the output polarity of the Hall element before and after switching the connection of the Hall element during offset cancellation.

  There are a plurality of such combinations depending on the substrate arrangement (direction) of the opposing Hall elements. In such a case as well, the above-described condition may be satisfied.

  In the connection described above with reference to FIGS. 15, 16, and 17, the synthesis unit 310 synthesizes the synthesized signal using the following (Equation 26) and (Equation 27).

First composite output: [Vms1-Vms3 + Vofftamp] (Equation 26)
Second combined output: [Vms2-Vms4 + Vofftamp] (Equation 27)

  Here, Vofftamp is an offset voltage caused by the differential amplifier 220 and the like. In order to improve detection accuracy, this offset voltage needs to be removed. Here, a case where ON / OFF of current or voltage supplied from the power supply unit 210 is used will be described. That is, in the time chart shown in FIG. 18, the synthesis unit 310 takes in the detection signal from the Hall element. Thereby, as will be described later, the synthesizer 310 can synthesize the detection signal by removing the above-described offset.

  That is, as shown in FIG. 18, the control unit 320 of the synthesis control unit 300 outputs the current or voltage from the power supply unit 210 while outputting the address select signals S0 and S1 as in the first embodiment. And the timing to not output. In FIG. 18, when the voltage ON-OFF signal is high, current or voltage is supplied from the power supply unit 210, and when it is low, current or voltage is not supplied from the power supply unit 210.

  In the time chart shown in FIG. 18, Hall elements are selected in order, such as Hall elements 1a, 1b, 2a, and 2b, by address select signals S0 and S1. In the first half of the period in which one hall element is selected by the address select signals S0 and S1, the control unit 320 of the synthesis control unit 300 sets the voltage ON-OFF signal to high and supplies the current or voltage from the power supply unit 210. Is supplied. Conversely, in the second half of this period, the control unit 320 of the synthesis control unit 300 sets the voltage ON-OFF signal to low and no current or voltage is supplied from the power supply unit 210.

  The synthesizer 310 synthesizes the detection signal based on the following (Expression 28) and (Expression 29).

First composite output: [Vms1-Vms3 + Vofftamp] -Vofftamp = Vms1-Vms3 (Equation 28)
Second composite output: [Vms2-Vms4 + Vofftamp] -Vofftamp = Vms2-Vms4 (Equation 29)

  FIG. 19 shows an example of the configuration of the output unit 200 in the case of the fifth embodiment. Here, in the configuration of the output unit 200, the configuration from a plurality of analog SWs to the differential amplification unit 220 is illustrated.

  As described above, in the fifth embodiment, at least two predetermined Hall elements among the plurality of Hall elements are defined as Hall element groups. For example, as described above, this Hall element group has two Hall elements facing each other about the rotation center axis of the rotor 6. The differential amplifier 220 differentially amplifies detection signals output from at least two Hall elements of the Hall element group and outputs the detection signals.

  In this case, the switching unit 263 (second switching unit) composed of the analog SW 16, SW 26, SW 36, and SW 46 has at least two holes of the Hall element group when differential amplification is performed by the differential amplification unit 220. The connection between at least two hall elements of the hall element group and the differential amplifier is switched so that the detection signals output from the elements strengthen each other and the output polarities of the respective detection signals coincide with each other. .

  With the configuration described above, the magnetic encoder 100 according to the fifth embodiment is the same as the magnetic encoder 100 according to the second embodiment while reducing the number of analog SWs compared to the magnetic encoder 100 according to the second embodiment. The effect of can be produced.

  Further, the analog SW in the magnetic encoder 100 according to the second embodiment has eight first terminals, whereas the analog SW in the magnetic encoder 100 according to the fifth embodiment is the first. Four terminals are sufficient. Therefore, the analog SW itself can be made small and inexpensive.

An example of the features of the present embodiment described above is as follows.
-Since the encoder 100 in this embodiment is composed of one operational amplifier, there is no variation in offset voltage and temperature drift between the two amplifiers, and high-precision detection can be performed.
-Since the encoder 100 in this embodiment outputs after A / D conversion, it is resistant to noise.
The encoder 100 according to the present embodiment detects the detection signal from the Hall element a plurality of times, averages it, and outputs it, so that noise can be canceled and high-precision detection can be performed.
In the present embodiment, the encoder 100 uses eight Hall elements and can cancel the fourth-order error, so that highly accurate detection can be performed.

  As described above, according to the present embodiment described with reference to FIGS. 1 to 19, the characteristics of the Hall element that affects the detection accuracy (eg, variation in offset voltage variation due to environmental temperature) can be made uniform. Therefore, the value of the magnetic detection signal does not change depending on the environmental temperature, and a high-precision and high-resolution magnetic encoder can be stably provided. In addition, since it does not depend on variations in the Hall elements, a high-precision or / and high-resolution magnetic encoder can be stably mass-produced.

  In addition, the encoder 100 according to the present embodiment obtains a signal (detection signal) by periodically switching the input / output terminals of the Hall element with a switching circuit as a method of reducing the offset voltage fluctuation of the Hall element, so that the position detection accuracy Can be improved.

  In the above embodiment, the case where the number of Hall elements is four or eight has been described, but the number of Hall elements may be arbitrary. Since the Hall elements are grouped and arranged opposite to each other around the rotation axis of the rotor 6, the number of Hall elements is desirably an even number. Further, since it is desirable to arrange the Hall elements so that the angles thereof are equally spaced around the rotation axis of the rotor 6, it is desirable that the number of Hall elements is 4n (n is an arbitrary natural number).

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design and the like within a scope not departing from the gist of the present invention.

  1, 2, 3, 4 ... Hall element, 5 ... Magnet, 6 ... Rotor, 100 ... Magnetic encoder, 200 ... Output unit, 210 ... Power supply unit, 220 ... Differential amplification unit, 310 ... Synthesis unit, 320 ... Control unit, 260, 261, 263 ... switching unit

Claims (10)

A rotor having magnets;
A plurality of magnetic sensing elements disposed in the vicinity of the magnet;
For the combining unit that combines the rotation positions of the rotor based on a plurality of detection signals detected by the plurality of magnetic detection elements, the magnetic detection elements selected in order from the plurality of magnetic detection elements An output unit for outputting the detected detection signal;
A magnetic encoder comprising: The synthesis unit is
Storing the detection signal output from the output unit, and combining the rotational position of the rotor based on the stored detection signal;
The magnetic encoder according to claim 1. The output unit is
A power feeding unit that feeds power to the plurality of magnetic detection elements in order;
A differential amplification unit that differentially amplifies and outputs the detection signal detected by the magnetic detection element fed by the power feeding unit;
The magnetic encoder according to claim 1, further comprising: A first switching unit that sequentially switches the connection between the magnetic detection element and the power feeding unit and the connection between the magnetic detection element and the differential amplification unit with respect to the magnetic detection element;
The magnetic encoder according to claim 3, further comprising: At least two of the plurality of magnetic detection elements that are determined in advance as a magnetic detection element group,
A differential amplifier for differentially amplifying and outputting the detection signals output from the at least two magnetic detection elements of the magnetic detection element group;
When differential amplification is performed by the differential amplification unit, the detection signals output from the at least two magnetic detection elements of the magnetic detection element group mutually strengthen each other, and the output polarities of the respective detection signals A second switching unit that switches a connection between the at least two magnetic detection elements of the magnetic detection element group and the differential amplification unit, so as to match
The magnetic encoder according to claim 1, further comprising: The magnetic detection element group includes two magnetic detection elements facing each other around the rotation center axis of the rotor.
The magnetic encoder according to claim 5, wherein: A third switching unit configured to switch, for each magnetic detection element, an input terminal to which power is supplied and an output terminal that outputs the detection signal from the magnetic detection element;
The magnetic encoder according to any one of claims 1 to 6, further comprising: The combining unit combines the detection signals output from the two magnetic detection elements facing each other around the rotation center axis of the rotor in the plurality of magnetic detection elements;
The magnetic encoder according to claim 1, wherein the magnetic encoder is a magnetic encoder. The synthesis unit is
The detection signal output from the output unit is stored, and based on the stored detection signal,
The detection signals detected by the plurality of magnetic detection elements are combined as a first combined signal so as to be a first combined magnetic detection element that detects the rotational position of the rotor,
A second synthetic magnetic sensing element for detecting a rotational position of the rotor, wherein the second synthetic magnetic sensing element is located at a predetermined angular position with respect to the first synthetic magnetic sensing element about a rotational center axis of the rotor; Combining the detection signals detected by the plurality of magnetic detection elements as a second combined signal so as to be a combined magnetic detection element;
Combining the first combined signal and the second combined signal;
The magnetic encoder according to claim 1, wherein the magnetic encoder is a magnetic encoder. The magnetic detection element is a Hall element.
The magnetic encoder according to any one of claims 1 to 9, wherein:

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