JP2005201657A - Rotation angle detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive small-sized rotation angle detection device capable of measuring the rotation angle in the range of 360 degrees. <P>SOLUTION: A permanent magnet 2 is mounted on a rotating shaft 3, and generates a main magnetic field MF. A coil 5 generates an auxiliary magnetic field SF. The main magnetic field MF is rotated relative to the auxiliary magnetic field SF following rotation of the rotating shaft 3. Two magnetic resistance sensors are arranged in a sensor unit 4 so as to output electric signals having the phase difference of 45 degrees mutually. The main magnetic field operates both magnetic resistance sensors of the sensor unit 4 in a saturated region regardless of the rotation angle of the rotating shaft 3. Each magnetic resistance sensor outputs an electric signal of a level corresponding to the direction of the magnetic field regardless of the intensity of the magnetic field in the saturated region. A composite magnetic field formed by the main magnetic field and the auxiliary magnetic field forms the saturated region at the angle at which one magnetic resistance sensor outputs the maximum level, and forms an unsaturated region at the opposite angle by 180 degrees. The level of an electric signal outputted from each magnetic resistance sensor in the unsaturated region is lower than the level outputted in the saturated region. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rotation angle detection device.

  Conventionally, a magnet arranged on a rotation axis of a measurement object, two magnetoresistive sensors that output an electric signal corresponding to the magnetic field (main magnetic field) of the magnet, and the rotation angle of the measurement object from the outputs of the two magnetoresistive sensors 2. Description of the Related Art A rotation angle detection device including a control unit that identifies a rotation angle is known. However, since the rotation angle detection device using the magnetoresistive sensor cannot determine the direction of the main magnetic field, the measurement range is limited to 180 degrees at the maximum.

Patent Document 1 discloses a rotation angle detection device that includes a coil that generates an auxiliary magnetic field and that can measure a rotation angle of 180 degrees or more by determining the direction of the main magnetic field.
Patent Document 2 discloses a rotation angle detection device that can measure a rotation angle of 180 degrees or more by providing a measuring element for determining the direction of the main magnetic field.

Japanese translation of PCT publication No. 2002-525588 JP-A-11-94512

However, in the rotation angle detection device described in Patent Document 1, it is necessary to apply auxiliary magnetic fields in different directions to the two magnetoresistive sensors, so that the arrangement of the magnetoresistive sensor and the shape of the coil are complicated. Therefore, a large space is required for mounting the magnetoresistive sensor and the coil, and there is a problem that the rotation angle detection device is enlarged.
Further, the rotation angle detection device described in Patent Document 2 requires a measuring element for determining the direction of the main magnetic field, and thus has a problem that the manufacturing cost increases and a rotation angle device is enlarged.
The present invention has been made to solve the above problems, and an object of the present invention is to provide a small and inexpensive rotation angle detection device by measuring a rotation angle in a range of 360 degrees.

According to the invention described in claims 1 to 9, from the electrical signal having the phase difference output from the first magnetoresistive sensor and the second magnetoresistive sensor that operate only in the main magnetic field excluding the auxiliary magnetic field, Candidate rotation angles to be measured can be selected within a rotation angle range of 360 degrees.
In order to identify the rotation angle of the measurement object from the selected rotation angle candidates, it is only necessary to know the direction of the measurement object, that is, the direction of the main magnetic field. First, the direction of the main magnetic field is different from the direction of the combined magnetic field formed by the main magnetic field and the auxiliary magnetic field, except for the rotation angle of the measurement object in which the direction of the main magnetic field and the direction of the auxiliary magnetic field are parallel. Therefore, the electrical signals output from the first magnetoresistive sensor and the second magnetoresistive sensor differ depending on only the main magnetic field and the combined magnetic field. The direction of the main magnetic field can be determined by the control means evaluating the difference between the different electric signals.

  On the other hand, when the main magnetic field and the auxiliary magnetic field are in the same direction, the first magnetoresistive sensor and the second magnetoresistive sensor operate with the combined magnetic field in the saturation region, and when the main magnetic field and the auxiliary magnetic field are in the opposite direction, The magnetoresistive sensor and the second magnetoresistive sensor operate with a combined magnetic field in a non-saturated region. The first magnetoresistive sensor and the second magnetoresistive sensor operating with the combined magnetic field in the saturation region each output an electrical signal corresponding to the direction of the combined magnetic field. On the other hand, the first magnetoresistive sensor and the second magnetoresistive sensor operating with the combined magnetic field in the non-saturated region region are smaller in electrical signal than when operating with the combined magnetic field in the saturated region in the same direction. Is output. For this reason, the first magnetic field when the combined magnetic field is formed by the electric signal of the first magnetoresistive sensor or the second magnetoresistive sensor when only the main magnetic field excluding the auxiliary magnetic field, and the auxiliary magnetic field is formed. By evaluating the level difference from the electrical signal of the magnetoresistive sensor or the second magnetoresistive sensor, it is possible to determine whether the directions of the main magnetic field and the auxiliary magnetic field are the same or opposite. Therefore, the rotation angle of the measurement target can be specified from the rotation angle candidates selected in the range of 360 degrees.

Further, according to the first to ninth aspects of the present invention, without providing a plurality of auxiliary magnetic field generating means for generating auxiliary magnetic fields in different directions or separately providing means for determining the direction of the main magnetic field, By controlling the auxiliary magnetic field in a certain direction with respect to the one magnetoresistive sensor and the second magnetoresistive sensor by the control means, the rotation angle of the measurement object can be specified. Therefore, the auxiliary magnetic field generating means can be reduced in size and the manufacturing cost can be reduced.
Further, according to the invention described in claims 1 to 9, the auxiliary magnetic field generating means sets the first magnetoresistive sensor and the second magnetoresistive sensor in the non-saturated region when the main magnetic field and the auxiliary magnetic field are in opposite directions. It is only necessary to generate an auxiliary magnetic field with the strength to be operated at. Since the strength of the auxiliary magnetic field can be reduced compared to the main magnetic field, the auxiliary magnetic field generating means can be reduced in size.

  According to the second aspect of the present invention, the auxiliary magnetic field generating means includes the auxiliary magnetic field parallel to the direction of the magnetic field at which the first magnetoresistive sensor or the second magnetoresistive sensor outputs the electric signal having the maximum level or the minimum level. It is characterized by generating. In the direction of the magnetic field, the output of the magnetoresistive sensor operating in the non-saturated region changes relatively greatly with changes in the magnetic field strength. For example, as shown in FIG. 5, with respect to the direction of the magnetic field, an electric signal for a magnetic field (P1) having a strength for operating the magnetoresistive sensor in the saturation region and a magnetic field having a strength for operating the magnetoresistive sensor in the non-saturated region ( Comparing the level differences L1, L2, and L3 with respect to the electric signal for P3), the level difference L1 in the direction of the magnetic field that outputs the electric signal of the maximum level is larger than the level differences L2 and L3 in the directions of the other magnetic fields. I understand. That is, even if the strength of the auxiliary magnetic field is relatively small, the first magnetoresistive sensor or the second magnetoresistive sensor has a large level difference between when operating in the saturation region and when operating in the non-saturation region. Outputs electrical signals. Therefore, since the strength of the auxiliary magnetic field can be reduced, the auxiliary magnetic field generating means can be reduced in size.

According to claims 3 to 5, the auxiliary magnetic field generating means is a coil. Since the auxiliary magnetic field generating means can be realized with a simple circuit, the auxiliary magnetic field generating means can be reduced in size and the manufacturing cost can be reduced.
According to claims 3 to 5, the coil of the auxiliary magnetic field generating means is wound in a single direction. Since the number of turns can be easily increased as compared with the case of winding in multiple directions, the current supplied to the coil can be reduced.
Further, according to claims 3 to 5, the control means includes a circuit for controlling a current supplied to the coil. Since the circuit for controlling the current can be realized with a simple circuit, the control means can be reduced in size and the manufacturing cost can be reduced.

According to the fourth aspect of the invention, the space for mounting the auxiliary magnetic field generating means can be reduced by winding the coil so as to cover the first magnetoresistive sensor and the second magnetoresistive sensor. In addition, since the auxiliary magnetic field can be efficiently influenced on the first magnetoresistive sensor and the second magnetoresistance by winding the coil three-dimensionally, the number of turns of the coil can be reduced or the coil can be passed through the coil. The current can be reduced.
According to the fifth aspect of the present invention, the mounting space of the auxiliary magnetic field generating means can be reduced by stacking the coils in the vicinity of the upper part or the lower part of the first magnetoresistive sensor and the second magnetoresistive sensor. Further, since the coil can be formed by a semiconductor lamination technique, the manufacturing cost of the auxiliary magnetic field generating means can be reduced.

In the invention according to claim 6, since the first magnetoresistive sensor and the second magnetoresistive sensor are arranged so that the electrical signals to be output have a phase difference of 45 degrees, the auxiliary magnetic field is eliminated. The outputs of the first magnetoresistive sensor and the second magnetoresistive sensor in the state of only the main magnetic field have a relationship between a sine wave and a cosine wave with respect to the rotation angle. Therefore, the control means can easily select the rotation angle candidate by the arctangent calculation.
According to the seventh aspect, since the magnetoresistive element of the first magnetoresistive sensor and the magnetoresistive element of the second magnetoresistive sensor are arranged concentrically, the magnetoresistive elements can be arranged compactly. Therefore, the first magnetoresistive sensor and the second magnetoresistive sensor can be reduced in size.

  In the invention described in claim 8, since the process of selecting the candidate for the rotation angle of the measurement object and the process of determining the direction of the main magnetic field are alternately performed, for example, even when the measurement object rotates at high speed, it is selected immediately before If the control means determines the direction of the main magnetic field based on the rotation angle candidates, the main direction determined in the process of determining the actual main magnetic field direction and the main magnetic field direction in the process of selecting the rotation angle candidates is determined. The direction of the magnetic field can be matched. Therefore, an accurate rotation angle can be measured.

  According to the ninth aspect of the present invention, the process of selecting the rotation angle candidate to be measured is executed a plurality of times for each process of determining the direction of the main magnetic field. The number of processes for determining the direction of the magnetic field can be reduced. Therefore, it is possible to shorten the effective processing time of the processing for specifying the rotation angle.

Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a schematic diagram showing a rotation angle detection device 1 according to a first embodiment of the present invention. The permanent magnet 2 as the main magnetic field generating means described in the claims is attached to a rotating shaft 3 to be measured such as a steering wheel, and generates a main magnetic field MF in the vicinity of the sensor unit 4.
The coil 5 as the auxiliary magnetic field generating means described in the claims generates an auxiliary magnetic field SF in the vicinity of the sensor unit 4 by a current supplied from an ASIC (Application Specific Integrated Circuit) 6 for detecting the rotation angle. Specifically, for example, the coil 5 is laminated on a printed circuit board 18 on which the sensor unit 4 is mounted (see FIG. 2). The printed circuit board 18 is fixed to the main body of the rotation angle detection device 1.

  The sensor unit 4 includes a magnetoresistive sensor 100 and a magnetoresistive sensor 200 as shown in FIG. One of the magnetoresistive sensor 100 and the magnetoresistive sensor 200 is a first magnetoresistive sensor, and the other is a second magnetoresistive sensor. The magnetoresistive sensor 100 and the magnetoresistive sensor 200 are bridge circuits of the magnetoresistive elements 101 to 104 and the magnetoresistive elements 201 to 204, respectively.

  When a predetermined voltage is supplied between the power supply terminal 120 and the GND terminal 122, the magnetoresistive sensor 100 outputs a voltage corresponding to the direction of the combined magnetic field CF formed by the main magnetic field MF and the auxiliary magnetic field SF to the output terminal 124. And output terminal 126. Hereinafter, the voltage output between the output terminal 124 and the output terminal 126 is referred to as an electric signal 130. The magnetoresistive sensor 200 outputs an electrical signal 230 in the same manner as the magnetoresistive sensor 100.

  The magnetoresistive sensor 100 and the magnetoresistive sensor 200 are arranged so as to output an electric signal 130 and an electric signal 230 having a phase difference of 45 degrees with respect to a magnetic field in the same direction. Specifically, the angle formed by the direction of the magnetic field (arrow C) from which the magnetoresistive sensor 100 outputs an electric signal at the maximum level and the direction of the magnetic field (arrow D) from which the magnetoresistive sensor 200 outputs an electric signal at the maximum level is set. It is arranged to be 45 degrees. In addition, the magnetoresistive elements 101 to 104 and the magnetoresistive elements 201 to 204 are alternately arranged on a concentric circle.

As shown in FIG. 1, the rotation angle detection ASIC 6 as a control unit described in the claims includes a CPU 8, a ROM 10, a RAM 12, an A / D conversion circuit 13, an arithmetic circuit 14, and a power supply circuit 16. The CPU 8 executes a predetermined process based on a program stored in the ROM 10.
The A / D conversion circuit 13 digitizes the electrical signal 130 and the electrical signal 230. The arithmetic circuit 14 performs a predetermined calculation. For example, the arithmetic circuit 14 performs an arc tangent calculation in a process of selecting a rotation angle candidate to be described later. The power supply circuit 16 supplies a predetermined current to the coil 5 at a predetermined timing under the control of the CPU 8. The power supply circuit 16 corresponds to a circuit for controlling a current flowing in the coil described in the claims. The RAM 12 is a memory that temporarily stores calculation results and the like in the arithmetic circuit 14.

Hereinafter, the relationship among the main magnetic field MF, the auxiliary magnetic field SF, and the composite magnetic field CF will be described with reference to FIG.
Since the permanent magnet 2 is attached to the rotating shaft 3, the main magnetic field MF rotates with the rotating shaft 3. The direction of the auxiliary magnetic field SF is the same as the arrow C. That is, the coil 5 is wired to the printed circuit board 18 in the vicinity of the sensor unit 4 so as to be orthogonal to the arrow C (see FIG. 2).
Hereinafter, it is assumed that the rotation angle when the main magnetic field MF and the arrow C are in the same direction is 0 degree, and the direction of the main magnetic field that rotates together with the rotary shaft 3 increases counterclockwise.

When no current is supplied to the coil 5 by the power supply circuit 16, the auxiliary magnetic field SF is not generated, and therefore the composite magnetic field CF and the main magnetic field MF are the same magnetic field (see FIG. 4A).
When the main magnetic field MF and the auxiliary magnetic field SF are in the same direction, the combined magnetic field CF and the main magnetic field MF are in the same direction, and the strength of the combined magnetic field CF is larger than the main magnetic field MF (see FIG. 4B).
When the main magnetic field MF and the auxiliary magnetic field SF are in opposite directions and the strength of the auxiliary magnetic field SF is smaller than the strength of the main magnetic field MF, the combined magnetic field CF and the main magnetic field MF are in the same direction, and the strength of the combined magnetic field CF is It becomes smaller than the main magnetic field MF (see FIG. 4D).
In the range where the angle θ formed by the main magnetic field MF and the arrow C is greater than 0 ° and smaller than 180 °, the angle φ formed by the combined magnetic field CF and the arrow C is smaller than the angle θ formed by the main magnetic field MF and the arrow C (FIG. 4). (See (c)).
In the range where the angle θ formed by the main magnetic field MF and the arrow C is greater than 180 degrees and smaller than 360 degrees, the angle φ formed by the composite magnetic field CF and the arrow C is larger than the angle θ formed by the main magnetic field MF and the arrow C (FIG. 4). (See (e)).

In the state where the auxiliary magnetic field SF is not generated, the strength of the main magnetic field MF is as follows: the magnetoresistive sensor 100 (resistive magnetoresistive elements 101 to 104) and the magnetoresistive sensor 200 (magnetoresistive elements 201 to 204) of the sensor unit 4. Is a magnetic field having a magnitude that causes the axis to operate in the saturation region regardless of the rotation angle of the rotary shaft 3, for example, a magnitude indicated by P1 in FIG.
Since the permanent magnet 2 is disposed on the rotation shaft 3 to be measured, the rotation angle of the rotation shaft 3 can be specified from the angle formed by the direction of the main magnetic field MF and the arrow C. Hereinafter, the angle θ formed by the direction of the main magnetic field MF and the arrow C is referred to as a rotation angle. The strength of the auxiliary magnetic field SF varies depending on the magnitude of the current supplied to the coil 5.

  Hereinafter, the state in which the CPU 8 of the ASIC 6 stops the power supply circuit 16 from supplying current to the coil 5 (hereinafter referred to as current supply stop state), and the magnetoresistive sensor 100 and the magnetoresistive sensor 200 regardless of the rotation angle of the rotary shaft 3. When the ASIC 6 supplies the coil 5 with a current that is large enough to generate the combined magnetic field CF that operates in the saturation region (hereinafter referred to as a saturation current supply state), and when the rotation angle of the rotary shaft 3 is 0 degree. When the magnetoresistive sensor 100 and the magnetoresistive sensor 200 are operated in the saturation region, and the rotation angle of the rotary shaft 3 is 180 degrees, the combined magnetic field CF having a strength that operates the magnetoresistive sensor 100 and the magnetoresistive sensor 200 in the non-saturated region is obtained. The electric signal 130 and the electric current in a state where the ASIC 6 supplies a current of a magnitude that is generated to the coil 5 (hereinafter, a non-saturated current supply state) Issue 230 will be described.

First, the electric signal 130 and the electric signal 230 in the current supply stop state will be described.
In the current supply stop state, since the auxiliary magnetic field SF is not generated, the composite magnetic field CF and the main magnetic field MF are in the same direction. Further, since the magnetoresistive sensor 100 and the magnetoresistive sensor 200 are arranged so as to output electrical signals having a phase difference of 45 degrees, the electrical signal 130 and the electrical signal 230 are as shown in FIG. The cosine waveform and sine waveform are doubled with respect to the rotation angle. Therefore, when the arc tangent calculation is performed based on the electric signal 130 and the electric signal 230, two rotation angles (for example, 45 degrees and 225 degrees) can be easily selected as rotation angle candidates (FIG. 6B). reference).

Next, the electric signal 130 and the electric signal 230 in the saturated current supply state will be described.
As shown in FIG. 7, in the saturation current supply state, due to the influence of the auxiliary magnetic field SF, the rotation angle is larger than 0 degree and smaller than 180 degrees compared to the current supply stop state (see FIG. 6A). The phase advances in the range where the rotation angle is larger than 180 degrees and smaller than 360 degrees. That is, the levels of the electric signal 130 and the electric signal 230 in the current supply stop state and the saturation current supply state at an arbitrary rotation angle other than 0 degrees and 180 degrees in which the direction of the main magnetic field MF and the direction of the auxiliary magnetic field SF are parallel. Is different.

FIG. 8A shows the level difference 150 of the electrical signal 130 shown in FIG. 6A and FIG. 7 in the range 151 and in the range of 180 degrees to less than 360 degrees. It is a graph in which graphs 152 are superimposed.
FIG. 8B shows a graph 251 showing the level difference 250 of the electric signal 230 in the range of 0 degree or more and less than 180 degrees and a graph showing the range of 180 degree or more and less than 360 degree as in FIG. 8A. 252 is a graph in which 252 are superimposed.
Here, if the reference for evaluating the level difference between the magnetoresistive sensor employed when determining the direction of the main magnetic field and the selected magnetoresistive sensor is determined according to the rotation angle candidates, for example, according to the table shown in FIG. If the processing is performed, the direction of the main magnetic field MF can be determined from the level difference 150 or the level difference 250.

  For example, when the rotation angle candidates are 45 degrees and 225 degrees, the rotation angle candidates are larger than 0 degrees (or 180 degrees) and smaller than 65 degrees (or 245 degrees), so the magnetoresistive sensor 100 is selected. . If the level difference 150 of the electric signal 130 output from the magnetoresistive sensor 100 is a positive value, it can be seen that the direction of the main magnetic field MF is in a range larger than 0 degree and smaller than 65 degrees. Can be identified. If the level difference 150 is a negative value, it can be seen that the direction of the main magnetic field MF is in a range larger than 180 degrees and smaller than 245 degrees, so that the rotation angle can be specified as 225 degrees. However, when the rotation angle candidates are 0 degrees and 180 degrees, the level difference 150 is 0, and thus the rotation angle cannot be specified.

Next, the electric signal 130 and the electric signal 230 in the non-saturated current supply state will be described.
In the non-saturated current supply state, the levels of the electrical signals 130 and 230 near the rotation angle of 0 degrees operate in the saturation region, and the levels of the electrical signals 130 and 230 near the rotation angle of 180 degrees are non-level. Operates in the saturation region. Therefore, as shown in FIG. 10, the levels of the electric signal 130 and the electric signal 230 do not change in the vicinity of the rotation angle of 0 degrees compared to the saturation current supply state. On the other hand, the levels of the electric signal 130 and the electric signal 230 in the vicinity of the rotation angle of 180 degrees are smaller than in the saturated current supply state.

  FIG. 11A shows the level difference 160 of the electric signal 130 shown in FIG. 6A and FIG. 10 in the range 161 and less than 180 degrees and the range 161 to less than 360 degrees. It is a graph in which the graph 162 is superimposed. 11B, similarly to FIG. 11A, the graph 261 showing the level difference 260 of the electric signal 230 in a range of 0 degrees or more and less than 180 degrees and the graph 262 showing a range of 180 degrees or more and less than 360 degrees. It is the graph which piled up.

  When the rotation angle candidates are 0 degrees and 180 degrees, it can be seen that the direction of the main magnetic field MF is 0 degrees if the level difference 160 is 0, and the direction of the main magnetic field MF if the level difference 160 is a negative value. Is 180 degrees (see FIG. 11A). For the rotation angles other than 0 degrees and 180 degrees, the direction of the main magnetic field MF can be determined by the same processing as in the saturated current supply state. Therefore, for example, by performing processing according to the table shown in FIG. 12, the direction of the main magnetic field MF can be determined in the range of 0 to 360 degrees.

  That is, when the rotation angle candidates are not 0 degrees and 180 degrees, the direction of the main magnetic field is determined based on the level difference 160 or the level difference 260 accompanying the phase difference between the combined magnetic field and the main magnetic field, and the combined magnetic field and the main magnetic field are determined. When the rotation angle candidates that cause no phase difference are 0 degree and 180 degrees, the direction of the main magnetic field can be determined based on the level difference 160 caused by the saturated magnetic field and the unsaturated magnetic field.

FIG. 13 is a flowchart showing the operation of the rotation angle detection device 1 that selects a rotation angle candidate in the current supply stop state, determines the direction of the main magnetic field MF in the unsaturated current supply state, and identifies the rotation angle.
Hereinafter, the operation of the rotation angle detection device 1 will be described.
When the CPU 8 of the ASIC 6 receives the rotation angle detection start request, the power supply circuit 16 stops the current supply to the coil 5 and controls the current supply stop state (S1).

Next, the CPU 8 of the ASIC 6 stores the electrical signal 130 and the electrical signal 230 for an arbitrary rotation angle digitized by the A / D conversion circuit 13 in the RAM 12 as digital data 132 and digital data 232, respectively (S2).
Next, the CPU 8 of the ASIC 6 causes the arithmetic circuit 14 to execute an arc tangent calculation based on the digital data 132 and the digital data 232 stored in the RAM 12, and uses two rotation angles (for example, 45 degrees and 225 degrees) as rotation angle candidates. ) Is selected (S3). The CPU 8 of the ASIC 6 stores the selected rotation angle candidate in the RAM 12.

Next, the CPU 8 of the ASIC 6 causes the power supply circuit 16 to start supplying current to the coil 5 and controls it to the aforementioned unsaturated current supply state (S4).
Next, the CPU 8 of the ASIC 6 stores the electrical signal 130 and the electrical signal 230 for an arbitrary rotation angle digitized by the A / D conversion circuit 13 in the RAM 12 as digital data 133 and digital data 233, respectively (S5).

In step S6, the CPU 8 of the ASIC 6 determines whether or not the rotation angle candidates stored in the RAM 12 are included in the range of 65 degrees (or 245 degrees) or more and less than 115 degrees (or 295 degrees). If the angle candidate is not included in the range, step S7 is executed, and if included, step S8 is executed.
In step 7, the CPU 8 of the ASIC 6 causes the arithmetic circuit 14 to calculate the difference between the digital data 132 stored in the RAM 12 and the digital data 133, and determines the direction of the main magnetic field MF based on the sign of the difference (see FIG. 12). ), The determined orientation of the main magnetic field MF is stored in the RAM 12.

In step S8, the CPU 8 of the ASIC 6 causes the arithmetic circuit 14 to calculate the difference between the digital data 232 stored in the RAM 12 and the digital data 233, and determines the direction of the main magnetic field MF based on the sign of the difference (see FIG. 12). ), The determined orientation of the main magnetic field MF is stored in the RAM 12.
After execution of step S7 or step S8, the CPU 8 of the ASIC 6 specifies the rotation angle based on the rotation angle candidates stored in the RAM 12 and the direction of the main magnetic field MF (S9).
The CPU 8 of the ASIC 6 repeatedly executes the processing from step S1 to step S9 until it receives a rotation angle detection end request (S10).

  In the rotation angle detection device that detects the rotation angle of the measurement object that rotates at a low speed, the process of selecting a rotation angle candidate may be executed a plurality of times for each execution of the process of determining the direction of the main magnetic field MF. Good. Specifically, for example, as shown in FIG. 14, a first rotation angle candidate is selected (S12), a second rotation angle candidate is selected (S14), and the direction of the main magnetic field MF is determined (S18). Alternatively, the first rotation angle and the second rotation angle may be specified (S20 and S21).

(Second Embodiment)
A second embodiment of the present invention is shown in FIG. In the second embodiment, the coil 5 is wound so as to cover the sensor unit 4. Other configurations are substantially the same as those in the first embodiment.
In the second embodiment, since the coil 5 is wound three-dimensionally so as to cover the sensor unit 4, the auxiliary magnetic field can be efficiently influenced on the magnetoresistive sensor 100 and the magnetoresistive sensor 200. The number of windings can be reduced, or the current flowing through the coil 5 can be reduced. Further, by winding the coil 5 in close contact with the sensor unit 4, the mounting space of the coil 5 can be reduced.

  According to the above-described plurality of embodiments of the present invention, the CPU 8 of the ASIC 6 controls the power supply circuit 16 to control the current supply stop state and the non-saturated current supply state. Candidates are selected, the direction of the main magnetic field is determined in the unsaturated current supply state, and the rotation angle is specified. Thereby, the rotation angle from 0 degree to 360 degrees can be specified.

  Further, paying attention to the output characteristics of the magnetoresistive sensor 100 and the magnetoresistive sensor 200, the magnetoresistive sensor 100 that operates in the saturation region and the magnetoresistive sensor 100 that operates in the non-saturation region are used to determine the rotation angle of 0 degrees and 180 degrees Therefore, if one coil 5 wound in a single direction is provided, a rotation angle from 0 degrees to 360 degrees can be specified. Since a plurality of coils are not necessary, the rotation angle detection device 1 can be reduced in size. Further, since the winding may be performed in a single direction, the number of windings of the coil 5 can be easily increased. That is, since the current flowing through the coil 5 can be reduced, the power consumption of the rotation angle detection device 1 can be reduced.

(Other embodiments)
In the above embodiments, the permanent magnet 2 is arranged on the rotating shaft 3 to be measured, and the sensor unit 4 and the coil 5 are mounted on the printed circuit board 18 fixed to the main body. However, the permanent magnet 2 is arranged on the main body. The sensor unit 4 and the coil 5 may be disposed on the rotating shaft 3. Further, although the permanent magnet 2 is arranged as the main magnetic field generating means on the rotating shaft 3 to be measured, an electromagnet may be installed on the rotating shaft 3 as the main magnetic field generating means.

  In the above embodiments, the ASIC 6 as the control means described in the claims controls the current supplied to the coil 5 so that the auxiliary magnetic field forms the main magnetic field and the combined magnetic field, and eliminates the auxiliary magnetic field. Although the magnetic field is electrically controlled so that only the magnetic field is present, the control unit may mechanically control the magnetic field by moving the auxiliary magnetic field generating permanent magnet closer to or away from the sensor unit 4.

In the above-described embodiments, the magnetoresistive sensor 100 and the magnetoresistive sensor 200 are arranged so as to output the electrical signal 130 and the electrical signal 230 having a phase difference of 45 degrees from each other. If the signal 230 does not have the same waveform, another phase difference may be used. In addition, the coil 5 is wired in the vicinity of the sensor unit 4 so as to be orthogonal to the arrow C, and an auxiliary magnetic field in the same direction as the arrow C is generated, but the electric signal 130 and the electric signal 230 are both at a zero level. If it is not a direction, an auxiliary magnetic field may be generated in another direction.
In the above embodiments, the direction of the main magnetic field MF is determined based on the positive / negative of the level difference 160 or the level difference 260 between the electric signal 130 in the current supply stop state and the electric signal 130 or the electric signal 230 in the unsaturated current supply state. However, the direction of the main magnetic field MF may be determined by setting a predetermined threshold value.

  In the above embodiments, for example, as shown in FIG. 12, the rotation angle candidates are in the range of 0 degree (or 180 degrees) to less than 65 degrees (or 245 degrees) and 65 degrees (or 245 degrees). The magnetoresistive sensor employed in the process of determining the direction of the main magnetic field, divided into a range smaller than 115 degrees (or 295 degrees) and a range smaller than 115 degrees (or 295 degrees) and smaller than 180 degrees (360 degrees). And the reference for evaluating the level difference of the electrical signal output by the selected magnetoresistive sensor are set in the respective ranges, but may be divided into three different ranges as long as the direction of the main magnetic field can be discriminated. It may be divided into ranges.

In the above embodiments, the arithmetic circuit 14 is provided in the ASIC 6 and the CPU 8 causes the arithmetic circuit 14 to execute various calculations. However, the arithmetic circuit 14 is not provided in the ASIC 6 and the CPU 8 executes various calculations. Good.
In the first embodiment, the coil 5 is laminated on the printed circuit board 18, but may be incorporated in the sensor unit 4. In the first embodiment, the coil 5 is disposed near the lower part of the sensor unit 4, but may be disposed near the upper part.

It is a schematic block diagram which shows the rotation angle detection apparatus by 1st Embodiment of this invention. It is a schematic diagram which shows the mounting state of ASIC of 1st Embodiment, a coil, and a sensor unit. It is a schematic diagram which shows the sensor unit of 1st Embodiment. It is a schematic diagram which shows the relationship between the magnetic field of 1st Embodiment, an auxiliary magnetic field, and a synthetic magnetic field. It is a characteristic view which shows the output characteristic of the magnetoresistive sensor of 1st Embodiment. (A) is a graph which shows the relationship between the rotation angle in the electric current supply stop state of 1st Embodiment, and the electrical signal which a magnetoresistive sensor outputs, (b) is an arc tangent calculation based on the electrical signal shown to (a). It is a graph which shows the result. It is a graph which shows the relationship between the rotation angle in the saturation current supply state of 1st Embodiment, and the electrical signal which a magnetoresistive sensor outputs. It is a graph which shows the level difference of Fig.6 (a) and the electric signal shown in FIG. In the first embodiment, the reference for evaluating the level difference between the magnetoresistive sensor employed when discriminating the rotation angle candidate and the orientation of the main magnetic field and the electrical signal output by the selected magnetoresistive sensor, and the orientation of the main magnetic field It is a figure which shows the relationship. It is a graph which shows the relationship between the rotation angle in the unsaturated current supply state of 1st Embodiment, and the electrical signal which a magnetoresistive sensor outputs. It is a graph which shows the level difference of the electric signal shown to Fig.6 (a) and FIG. In the first embodiment, the reference for evaluating the level difference between the magnetoresistive sensor employed when discriminating the rotation angle candidate and the orientation of the main magnetic field and the electrical signal output by the selected magnetoresistive sensor, and the orientation of the main magnetic field It is a figure which shows the relationship. It is a flowchart which shows the specific process of the rotation angle of 1st Embodiment. It is a flowchart which shows the specific process of another rotation angle. (A) is a top view which shows how to wind the coil which concerns on 2nd Embodiment of this invention, (b) is a side view of the b direction of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotation angle detection apparatus, 2 Permanent magnet (main magnetic field generating means), 5 Coil (auxiliary magnetic field generating means), 6 ASIC (control means) 100 Magnetoresistive sensor, 200 Magnetoresistive sensor, CF synthetic magnetic field, MF main magnetic field, SF Auxiliary magnetic field

Claims (9)

A rotation angle detection device for detecting a rotation angle of a measurement object,
A main magnetic field generating means for generating a main magnetic field;
An auxiliary magnetic field generating means capable of generating an auxiliary magnetic field and forming the main magnetic field and a composite magnetic field;
A first magnetoresistive sensor having a magnetoresistive element and outputting an electric signal corresponding to the main magnetic field or the combined magnetic field;
A second magnetoresistive sensor having a magnetoresistive element and arranged to output an electrical signal having a predetermined phase difference to the first magnetoresistive sensor in response to the main magnetic field or the combined magnetic field; ,
The auxiliary magnetic field generation means is controlled so as to form the main magnetic field and the combined magnetic field, and the rotation angle of the measurement object is determined based on the electrical signals output from the first magnetoresistive sensor and the second magnetoresistive sensor. Control means to identify,
One of the main magnetic field generating means or the auxiliary magnetic field generating means rotates with the object to be measured with respect to the other,
The strength of the main magnetic field is a size for operating the first magnetoresistive sensor and the second magnetoresistive sensor in a saturation region in a state where the auxiliary magnetic field is excluded.
The auxiliary magnetic field is a magnetic field in a certain direction with respect to the first magnetoresistive sensor and the second magnetoresistive sensor, and the strength of the auxiliary magnetic field is determined when the main magnetic field and the auxiliary magnetic field are in the same direction. The first magnetoresistive sensor and the second magnetoresistive sensor are operated in a saturation region, and when the main magnetic field and the auxiliary magnetic field are in opposite directions, the first magnetoresistive sensor and the second magnetoresistive sensor are not operated. It is the size to operate in the saturation region,
The control means outputs the electric power output from the first magnetoresistive sensor and the second magnetoresistive sensor when the auxiliary magnetic field is excluded from the first magnetoresistive sensor and the second magnetoresistive sensor. A candidate for the rotation angle of the measurement object is selected based on the signal, and either the first magnetoresistive sensor or the second magnetoresistive sensor is selected based on the selected rotation angle candidate. The electrical signal of the selected magnetoresistive sensor when the auxiliary magnetic field is excluded from the first magnetoresistive sensor and the second magnetoresistive sensor, the first magnetoresistive sensor, and the second magnetoresistive sensor. Based on a signal level difference with respect to the electrical signal of the selected magnetoresistive sensor when the auxiliary magnetic field forms the main magnetic field and the combined magnetic field with respect to the magnetoresistive sensor. Determine the direction of the main magnetic field, the rotation angle detection apparatus characterized by specifying the rotation angle of the measurement target from the discriminated said main magnetic field direction as a candidate of the selected the angle of rotation.   The auxiliary magnetic field generation means generates the auxiliary magnetic field parallel to the direction of the magnetic field at which the first magnetoresistive sensor or the second magnetoresistive sensor outputs an electric signal having a maximum level or a minimum level. The rotation angle detection device according to claim 1.   3. The rotation angle detection device according to claim 1, wherein the auxiliary magnetic field generation unit is a coil wound in one direction, and the control unit includes a circuit that controls a current flowing through the coil. .   The rotation angle detection device according to claim 3, wherein the coil is wound so as to cover the first magnetoresistive sensor and the second magnetoresistive sensor.   The rotation angle detecting device according to claim 3, wherein the coil is laminated in the vicinity of the upper or lower portion of the first magnetoresistive sensor and the second magnetoresistive sensor.   The said 1st magnetoresistive sensor and the said 2nd magnetoresistive sensor are arrange | positioned so that the electrical signals to output may have a phase difference of 45 degree | times, The any one of Claim 1 to 5 characterized by the above-mentioned. The rotation angle detection device according to one item. Each of the first magnetoresistive sensor and the second magnetoresistive sensor is a bridge circuit composed of four magnetoresistive elements,
The rotation angle detection device according to any one of claims 1 to 6, wherein the magnetoresistive elements of the first magnetoresistive sensor and the second magnetoresistive sensor are arranged concentrically. .   The said control means implements the process which selects the candidate of the rotation angle candidate of the said measurement object, and the process which discriminate | determines the direction of the said main magnetic field alternately, It is any one of Claim 1 to 7 characterized by the above-mentioned. Rotation angle detector.   The said control means performs the process which selects the candidate of the rotation angle of the said measuring object in multiple times per process which discriminates the direction of the said main magnetic field, It is any one of Claim 1 to 7 characterized by the above-mentioned. The rotation angle detection device according to item.

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