Multi-rotation angle detection device

Abstract

The multiple rotation angle detection device includes a segment counter that counts segments obtained by dividing one rotation period of a rotating body into two in an angle range exceeding one rotation to generate a count value, a precision absolute angle detector that generates an absolute angle detection value within one rotation period with high resolution, and a calculation device that integrates the count value and the absolute angle detection value to generate a multiple rotation absolute angle detection value. The segment counter includes a power generation sensor, a magnetic field generation source, a sensor element, and a non-volatile memory that stores the count value and information that can identify pulse information. The pulse information includes the output state of the sensor element and the polarity of the pulse voltage. The magnetic field generation source applies an alternating magnetic field of two periods per rotation in the axial direction of the magnetic wire. When power is supplied from an external source, the calculation device performs calculation for integration using the count value stored in the non-volatile memory and the information that can identify pulse information.

Description

Related Applications

[0001] This application claims priority to Japanese Patent Application No. 2024-060973 filed on April 4, 2024, and International Application No. PCT / JP2024 / 30971 filed on August 29, 2024, the entire contents of which are incorporated herein by reference. [Technical field]

[0002] This invention relates to a multiple rotation angle detection device using a power generation sensor, and more particularly to a device that detects multiple rotation absolute angles exceeding one rotation by combining the count value of a segment counter using a power generation sensor with an angle detection value obtained from an angle detector that precisely detects the absolute angle in one rotation period. [Background technology]

[0003] A magnetic wire with a large Barkhausen effect (large Barkhausen jump) is known as a Wiegand wire or pulse wire. This magnetic wire has a core and a skin surrounding the core. One of the core and skin is a soft (soft magnetic) layer in which the magnetization direction is reversed even in a weak magnetic field, while the other is a hard (hard magnetic) layer in which the magnetization direction does not reverse unless a strong magnetic field is applied. A power generating sensor can be constructed by winding a coil around such a magnetic wire.

[0004] When the hard layer and the soft layer are magnetized in the same direction along the axial direction of the wire, the magnetization direction of the soft layer is reversed when the strength of the external magnetic field in the opposite direction to the magnetization direction increases and reaches a certain magnetic field strength. This reversal of the magnetization direction starts at a certain part of the magnetic wire and propagates throughout the wire, and the magnetization directions of the soft layers are reversed simultaneously. At this time, the large Barkhausen effect is manifested, and a pulse signal is induced in the coil wound around the magnetic wire. When the external magnetic field strength increases further and reaches a certain magnetic field strength, the magnetization direction of the hard layer is reversed.

[0005] In this specification, the magnetic field strength at which the magnetization direction of the soft layer is reversed is called the "operating magnetic field," and the magnetic field strength at which the magnetization direction of the hard layer is reversed is called the "stabilizing magnetic field."

[0006] The output voltage obtained from the coil is constant regardless of the speed at which the input magnetic field (external magnetic field) changes, and since it has hysteresis characteristics with respect to the input magnetic field, it has no chattering. For this reason, the pulse signal generated by the coil is used in position detection devices, etc.

[0007] When an alternating magnetic field is applied to the power generating sensor, two pulse signals are generated per cycle: one positive pulse signal and one negative pulse signal. A magnet is used as the source of the magnetic field, and an alternating magnetic field is applied to the power generating sensor by the relative movement of the magnet and the power generating sensor. The position can be detected by counting the generated pulse signals.

[0008] Because the output from the coil is electric, it is possible to create a power-generating sensor (power-generating sensor) that does not require an external power supply. In other words, the output energy of the coil can also operate peripheral circuits without an external power supply.

[0009] Angle sensors such as absolute encoders are essentially unable to detect angles exceeding one rotation. While power is supplied, angles of more than one rotation can be detected by integrating the amount of movement, but when the power is cut off, information of more than one rotation is lost.

[0010] On the other hand, a segment counter that uses a power generation sensor can continue counting and detect multiple rotations of more than one because it can use the output energy of the coil even when the external power supply is cut off. However, segment counters that use power generation sensors can generally only detect rough angles. Therefore, when precise angle detection is required, such as when used for motor control, the count value of the segment counter and the angle detection value of a separately installed precision absolute angle detector are combined to use the precise angle detection value over multiple rotations (multiple rotation absolute angle detection value).

[0011] Patent Documents 1, 2 and 3 disclose a method and an apparatus for integrating the count value of a segment counter and the angle detection value of a precision absolute angle detector.

[0012] Patent Document 1 uses a segment counter in which three power generation sensors are arranged at positions with a phase difference of 60 degrees each.

[0013] The output of only one power generating sensor cannot identify the direction of movement when the direction of movement changes. Therefore, by using multiple power generating sensors and using the phase difference between the outputs of each power generating sensor, the direction of movement can be identified.

[0014] In order for the power generating sensor to output a pulse voltage, it is necessary for the magnetization direction of only the soft layer to be reversed from a state in which the magnetization directions of the hard layer and soft layer of the magnetic wire are the same. Even if the magnetization direction of only the soft layer is reversed when the magnetization directions of the hard layer and soft layer are not the same, no pulse signal is generated, or even if a pulse signal is generated, it is very small.

[0015] When rotation continues in one direction, after the operating magnetic field is reached and a pulse voltage is output, there is a timing when the stabilizing magnetic field is reached before the operating magnetic field is reached again. Therefore, a pulse voltage is always generated at the angular position where the operating magnetic field is reached.

[0016] However, when rotating in both directions, that is, when the rotation direction is switched, the pulse voltage is not output even when the operating magnetic field is reached, and so-called pulse missing may occur. Specifically, if the rotation direction is reversed before the stabilizing magnetic field is reached after the operating magnetic field is reached and the pulse voltage is output, the magnetization directions of the hard layer and the soft layer are not aligned, so that the pulse voltage is not output even when the operating magnetic field is reached again.

[0017] By arranging multiple power generation sensors at positions with different phase differences and using the phase difference between their output pulses, the direction of rotation can be identified. However, even if two power generation sensors are used, if one of them has a missing pulse, the direction of rotation cannot be identified. Therefore, as disclosed in Patent Document 1, it is necessary to use three power generation sensors. Patent Document 1 further arranges the three power generation sensors at positions with a phase difference of 60 degrees each in order to integrate the count value of the segment counter and the detection value of the precision position detector and to correct the deviation of the origin position.

[0018] However, using multiple power generation sensors increases the size and cost of the position detector.

[0019] Patent Documents 2 and 3 disclose a segment counter that processes the pulse signal of one power generating sensor and the output signal of another sensor element that is not a power generating sensor to determine the direction of rotation and count accordingly. Even in this case, if the above-mentioned missing pulse occurs, there is a problem when integrating the count value of the segment counter and the detection value of the precision position detector. Therefore, Patent Documents 2 and 3 monitor the magnetization state of the magnetic wire of the power generating sensor and correct the value of the segment counter by the amount of the missing pulse voltage according to the magnetization state. As a result, the count value of the segment counter and the detection value of the precision position detector are synchronized and integrated.

[0020] Specifically, the magnetization state monitors disclosed in Patent Documents 2 and 3 apply a gradually increasing current to the coil of the power generation sensor, and apply the magnetic field generated by the coil to the magnetic wire. The voltage generated at both ends of the coil is then observed to monitor whether the magnetization direction of the magnetic wire is reversed. This makes it possible to check the magnetization state of the magnetic wire.

[0021] However, to determine the magnetization direction of the magnetic wire and correct the count value based on that, as in Patent Documents 2 and 3, complex signal processing is required, which makes it difficult to reduce the size and cost of the device. [Prior art documents] [Patent documents]

[0022] [Patent Document 1] Patent No. 6226811 [Patent Document 2] Patent No. 5730809 [Patent Document 3] JP 2024-14598 A Summary of the Invention [Problem to be solved by the invention]

[0023] An embodiment of the present invention provides a multi-rotation angle detection device that is advantageous in terms of device size and cost reduction.

[0024] More specifically, one embodiment of the present invention provides a multi-rotation angle detection device that can combine the count value of a segment counter configured without using multiple power generation sensors and the angle detection value of a precision absolute angle detector to generate a multi-rotation absolute angle detection value without requiring complex signal processing. [Means for solving the problem]

[0025] 1. One embodiment of the present invention provides a multiple rotation angle detection device that generates a multiple rotation absolute angle detection value of a rotating body rotating around a rotation axis. The multiple rotation angle detection device includes a segment counter that counts segments obtained by dividing one rotation period of the rotating body into two (typically equally divided) in an angle range exceeding one rotation of the rotating body in accordance with the rotation of the rotating body to generate a count value. The multiple rotation angle detection device includes a precision absolute angle detector that operates by an external power supply and generates an absolute angle detection value within one rotation period of the rotating body with a higher resolution than the segments. The multiple rotation angle detection device includes a calculation device that operates by an external power supply and combines the count value of the segment counter and the absolute angle detection value of the precision absolute angle detector to generate a multiple rotation absolute angle detection value of the rotating body. The segment counter includes one (only one) power generation sensor, a magnetic field generating source that rotates around the rotation axis together with the rotor, a sensor element (typically a sensor element other than the power generation sensor) that is provided separately from the power generation sensor and that is in either a first output state or a second output state depending on the rotational position of the rotor, and a non-volatile memory that stores the count value. The power generation sensor has a magnetic wire that exhibits the large Barkhausen effect and a coil wound around the magnetic wire. The magnetic field generating source applies an alternating magnetic field of two periods per rotation to the magnetic wire in the axial direction as the rotor rotates, and in response to this, the power generation sensor generates a pulse voltage of four pulses per rotation of the rotor.

[0026] The segment counter can operate by energy of the pulse voltage generated by the power generating sensor without receiving an external power supply. When the power generating sensor generates a pulse voltage, the segment counter identifies the rotation direction and rotation position of the rotating body based on pulse information indicating the output state of the sensor element and the polarity of the pulse voltage generated by the power generating sensor, and stores information capable of identifying the pulse information in the nonvolatile memory. When the power generating sensor generates a pulse voltage, the segment counter updates the count value using the pulse information and information capable of identifying the pulse information at the time of the previous pulse voltage generation, and stores the updated count value in the nonvolatile memory.

[0027] When the power generation sensor generates a pulse voltage of a first polarity while the sensor element is in the first output state, the segment counter increments (counts up) the count value if the pulse information differs from the pulse information when the previous pulse voltage was generated. Also, when the power generation sensor generates a pulse voltage of a second polarity while the sensor element is in the first output state, the segment counter decrements (counts down) the count value to update the count value if the pulse information differs from the pulse information when the previous pulse voltage was generated. In this way, the segment counter performs a counting operation twice per rotation of the rotating body.

[0028] When the sensor element is in the second output state, if a count value update omission occurs in which the count value is not updated due to a lack of pulse voltage caused by a reversal of the rotation direction, the segment counter corrects the count value to compensate for the count value update omission.

[0029] When the arithmetic device receives an external power supply, it uses the count value stored in the non-volatile memory and information capable of identifying the pulse information to integrate the count value of the segment counter and the absolute angle detection value of the precision absolute angle detector to generate a multi-rotation absolute angle detection value of the rotating body.

[0030] During the integration, when the absolute angle detection value belongs to one of two specified angle regions each including a rotational position at which the pulse voltage is generated when the sensor element is in the second output state and the absolute angle detection value and the count value are inconsistent, the calculation device determines a correction direction based on the polarity of the pulse voltage immediately before it is specified from information that can identify the pulse information, and performs correction processing.

[0031] According to this configuration, the magnetic field generating source applies an alternating magnetic field of two periods per rotation in the axial direction of the magnetic wire, so that the power generating sensor generates four pulse voltages per rotation. The segment counter generates a count value by counting two segments that divide one rotation period. Specifically, when the sensor element is in the first output state, a basic counting operation is performed, that is, a counting operation of counting up in response to a pulse voltage of a first polarity and counting down in response to a pulse voltage of a second polarity. Even if a pulse voltage is generated, if the pulse information (polarity of the pulse voltage and the output state of the sensor element) is the same as when the previous pulse voltage was generated, the count value is not updated. When the sensor element is in the second output state, an exceptional counting operation is performed. That is, an operation for correcting the count value is performed only when a pulse voltage loss (missing pulse) occurs due to a reversal of the rotation direction, and the count value is not updated as a result.

[0032] Because a two-segment segment counter counts every 0.5 rotation, the multi-rotation angle value equivalent to the count value contains an error (quantization error) of up to 0.25 rotations in the rotation angle. Furthermore, if a pulse drop occurs, an error of 0.25 rotations is added before the error is corrected. Therefore, the multi-rotation angle value equivalent to the count value contains an error of up to ±0.5 rotations. When the phase difference of the pulse voltage generation position relative to the segment boundary is added to this, the overall error can exceed ±0.5 rotations, so if the count value is used as is and integrated with the absolute angle detection value, an error of up to ±1 rotation can occur.

[0033] Therefore, in this embodiment, when the count value and the absolute angle detection value are integrated, a correction process is performed under a predetermined condition. Specifically, when the integration is performed when power is supplied from an external source, it is checked whether the absolute angle detection value belongs to either of two predetermined angle regions that each include a rotation position at which a pulse voltage is generated when the sensor element is in the second output state. If the judgment is positive, it is further checked whether the absolute angle detection value and the count value are inconsistent. Typically, it is checked whether the even / odd of the absolute angle detection value and the count value are inconsistent. If there is a mismatch, the arithmetic device performs a correction process by determining a correction direction based on the polarity of the immediately preceding pulse voltage, which is specified from information that can identify the pulse information acquired from the non-volatile memory of the segment counter. In this way, by performing a simple correction process as necessary, it is possible to integrate the count value of the segment counter and the angle detection value of the precision absolute angle detector to obtain a precise multi-rotation absolute angle detection value.

[0034] In this way, a precise multi-rotation absolute angle detection value can be generated by combining the count value of the segment counter and the angle detection value of the precision absolute angle detector using only a single power generating sensor, without the need for determining the magnetization direction of the magnetic wire or performing correction / synchronization processing based on that.

[0035] 2. The segment counter may decrement the count value when the power generation sensor generates a pulse voltage of the first polarity while the sensor element is in the second output state and the pulse information at the time of the previous pulse voltage generation indicates the first output state and the first polarity. The segment counter may increment the count value when the power generation sensor generates a pulse voltage of the second polarity while the sensor element is in the second output state and the pulse information at the time of the previous pulse voltage generation indicates the first output state and the second polarity. This allows the segment counter to correct the count value so as to compensate for the missed update of the count value due to the effect of a missing pulse voltage caused by the reversal of the rotation direction.

[0036] 3. The information that can identify the pulse information preferably includes, for example, any two or more pieces of information among the output state of the sensor element, the polarity of the pulse voltage, and the rotation direction identified by them. These three pieces of information are in a relationship in which if two of them are specified, the remaining one can be identified. More specifically, the information that can identify the pulse information may be the pulse information itself (i.e., the output state of the sensor element and the polarity of the pulse voltage). The information that can identify the pulse information may also include one of the output state of the sensor element and the polarity of the pulse voltage included in the pulse information, and the rotation direction identified by the pulse information. Of course, the information that can identify the pulse information may include all (three) pieces of information, namely, the output state of the sensor element, the polarity of the pulse voltage, and the rotation direction identified by them.

[0037] 4. The sensor element preferably includes a magnetic sensor responsive to a magnetic field generated by the magnetic field source.

[0038] Since the magnetic field generating source rotates together with the rotating body, the output of the magnetic sensor becomes a first output state or a second output state depending on the rotational position of the rotating body, i.e., the rotational position of the magnetic field generating source.

[0039] 5. It is preferable that the multi-rotation angle detection device performs signal processing using an intermediate position between the position where the pulse voltage of the first polarity is generated and the position where the pulse voltage of the second polarity is generated when the sensor element is in the second output state as the origin of angle detection.

[0040] This configuration makes it possible to make the phase difference of the pulse voltage generation position with respect to the segment boundary equal in either direction of rotation. For example, the intermediate position between the pulse voltage generation position during rotation in one direction of rotation and the pulse generation position during rotation in the other direction of rotation may be treated as the origin of angle detection (origin for calculation processing). In this case, the pulse voltage generation positions in both directions of rotation, i.e., the count positions of the segment counter, are symmetrical in positive and negative, so signal processing can be simplified.

[0041] 6. The computing device a first step of subtracting the absolute angle detection value from the count value read from the non-volatile memory after combining them in unit amounts and converting the subtraction result into an integer in units of rotation speed to obtain a rotation speed; It is preferable to execute a second step of calculating a multiple rotation absolute angle detection value by adding up the rotation speed calculated in the first step and the absolute angle detection value after combining them in unit amounts.

[0042] For example, when matching the unit of the absolute angle detection value, the subtraction in the first step can be expressed as nU / 2-θs using the angle detection amount U of the absolute angle detection value per rotation, the count value n of the segment counter, and the absolute angle detection value θs. The calculation in the first step to obtain the rotation speed N using this is expressed by the following formula (1) using an integer conversion operator INT (an operator that rounds down to an integer by discarding the decimal point). 0.5 is a constant that is added for rounding off. Next, the calculation in the second step to obtain the multiple rotation absolute angle detection value θm is expressed by the following formula (2) when matching the unit of the absolute angle detection value θs.

[0043]

number

[0044] 7. It is preferable that the calculation device performs the correction process on the target value for integer conversion in the first step or the rotation speed obtained by the integer conversion in the first step based on the determined correction direction.

[0045] The correction process for the target value for integerization may be performed on any of the following in equation (1): the count value n, the rotation number conversion value n / 2 of the count value n, the multiple rotation angle value nU / 2 corresponding to the count value n, the difference nU / 2-θs between the multiple rotation angle value and the absolute angle detection value θs, the value (nU / 2-θs) / U obtained by dividing the difference by the angle detection amount U, and a constant 0.5 for rounding. Specifically, the correction process may be a process of adding or subtracting a fixed correction amount (>0) according to the correction direction determined based on the polarity of the pulse voltage. The process for the rotation number may be a process of adding or subtracting a fixed correction amount (>0) according to the correction direction determined based on the polarity of the pulse voltage to the rotation number N obtained by equation (2).

[0046] 8. The power generation sensor preferably includes a pair of magnetic flux conducting pieces made of soft magnetic bodies symmetrical to each other with respect to a symmetry plane set at the center position of the magnetic wire in the axial direction. The pair of magnetic flux conducting pieces preferably includes a pair of axis-orthogonal portions extending parallel to each other in an axis-orthogonal direction perpendicular to the axial direction from both ends of the magnetic wire, and a pair of axis-parallel portions extending in a direction approaching each other along the axial direction from the tips of the pair of axis-orthogonal portions, with the proximal ends facing each other with a gap in the axial direction. The pair of magnetic flux conducting pieces preferably includes the axis-orthogonal portions and a wire placement portion consisting of a hole or groove penetrating in the axial direction to which both ends of the magnetic wire are fixed. The power generation sensor is preferably configured so that the opposite side of the axis-parallel portions to the magnetic wire is a detection area.

[0047] It is preferable that the magnetic field generating source has four magnetic poles fixed to the rotating body so that, when the rotating body rotates, the magnetic field generating source sequentially enters the detection area through an orbit having a portion along the axial direction of the magnetic wire (more specifically, a circumferential orbit having a tangent parallel to the axial direction), and magnetic poles of different polarities alternately face the power generating sensor via a gap. It is preferable that the direction of the magnetic flux of each magnetic pole is perpendicular to the direction of movement of the magnetic pole, and intersects with the magnetic wire when facing the power generating sensor. It is preferable that the arrangement interval of the four magnetic poles on the orbit is longer than the total length of the magnetic wire. It is preferable that the length of the magnetic poles on the orbit is shorter than the total length of the magnetic wire and is 50% or less of the arrangement interval.

[0048] With this configuration, when the magnetic pole passes through the detection area of ​​the power generation sensor, the magnetic flux density passing through the magnetic wire changes abruptly from a stabilized magnetic field in one direction to a stabilized magnetic field in the other direction, and during this change, no plateau occurs where the change in magnetic flux density stagnates. This reduces the variation in the pulse generation position and the difference in the pulse generation position depending on the direction of rotation, making it possible to narrow the two predetermined angle regions where correction processing is required.

[0049] Also, a magnetic field generating source having four magnetic poles that generate a magnetic flux perpendicular to the moving direction of the magnetic poles and in a direction (gap direction) that intersects with the magnetic wire when facing the power generation sensor can be constructed using four individual magnets magnetized in the gap direction. Such individual magnets may be, for example, general-purpose two-pole magnets that can be magnetized by an air-core coil, so magnet costs can be reduced. In addition, since the magnetization direction is the gap direction, there is no need to strictly adjust the direction of the individual magnets (for example, the angle with respect to the radial direction) when fixing the individual magnets to the second support, so assembly costs can be reduced.

[0050] The length of the magnetic pole on the track is preferably equal to or less than half the total length of the magnetic wire, which allows the change in magnetic flux density when the magnetic pole passes through the detection area to be more abrupt.

[0051] In addition, it is preferable that the arrangement interval of the magnetic poles on the track is 1.5 times or more the total length of the magnetic wire, so that when a magnetic pole passes through the detection area, the influence of the magnetic field from other magnetic poles can be suppressed, and the change in magnetic flux density can be made even sharper.

[0052] The sensor element is preferably a magnetic sensor that distinguishes the polarity of the magnetic pole located at the center of the power generation sensor in the axial direction. With this configuration, it is possible to detect the direction of rotation in addition to detecting the position. [Brief description of the drawings]

[0053] [Figure 1] FIG. 1 is a block diagram for explaining an example of the configuration of a multiple rotation angle detection device according to an embodiment of the present invention. [Figure 2A-2C] Fig. 2A is a perspective view for explaining a structural example of a segment counter, Fig. 2B is a plan view thereof, and Fig. 2C is a front view seen in the direction of arrow IIC in Fig. 2B. [Figure 3A] FIG. 3A is a simplified plan view of the power generation sensor, showing the initial state where the rotation angle is 0 degrees. [Figure 3B] FIG. 3B shows the change in magnetic flux relative to the rotation angle and the operation of the power generation sensor. [Figure 4] FIG. 4 is a diagram for explaining an example of the counting operation of the segment counter. [Diagram 5] FIG. 5 is a table for explaining an example of a more detailed counting operation of the segment counter. [Figure 6] FIG. 6 is a diagram for explaining the effect of a missing pulse on the count value. [Figure 7] FIG. 7 shows the relationship between the count value of the segment counter and the angle detection value (precise angle detection value) of the precision absolute angle detector. [Figure 8] FIG. 8 shows a precision multi-rotation absolute angle detection value (precise angle detection value) obtained by integrating the count value of the segment counter and the angle detection value of the precision absolute angle detector. [Figure 9]FIG. 9 shows the calculation result obtained by subtracting the precise angle detection value (line 81 in FIG. 7) from the multi-rotation angle equivalent value of the segment counter (lines 82, 82-, 82+ in FIG. 7) and then adding 0.5 (rotations). [Figure 10] FIG. 10 shows the calculation results obtained by processing the calculation results of FIG. 9 using the integer operator INT (an operator that rounds down to the nearest integer). [Figure 11] FIG. 11 is a flowchart illustrating an example of processing by the arithmetic device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0055] 1 is a block diagram for explaining a configuration example of a multiple-rotation angle detection device according to an embodiment of the present invention. The multiple-rotation angle detection device 100 is a device that detects a multiple-rotation absolute angle of a rotating shaft 30 (one example of a rotating body) rotating around a rotation axis 33, and generates a multiple-rotation absolute angle detection value that is the detected value. The multiple-rotation absolute angle refers to an absolute angle within an angle range that exceeds one rotation, i.e., spans multiple rotations. The multiple-rotation angle detection device 100 includes a precision absolute angle detector 1, a segment counter 2, and a calculation device 4.

[0056] The precision absolute angle detector 1 is an angle sensor that generates a precise absolute angle detection value within one rotation period of the rotating shaft 30, i.e., from 0 degrees to 360 degrees, with a higher resolution than the segment counter 2, which will be described next. The precision absolute angle detector 1 is, for example, configured as an optical absolute encoder. The precision absolute angle detector 1 is configured to generate an absolute angle detection value of an angle region within one rotation period (0 degrees to 360 degrees) with a resolution of 16 bits (65,536 steps).

[0057] The precision absolute angle detector 1 typically operates by receiving power supply from an external power source. Specifically, the multi-rotation angle detection device 100 includes a power supply circuit 3 that can be connected to an external power source. When connected to the external power source, the power supply circuit 3 supplies power to the precision absolute angle detector 1, and the precision absolute angle detector 1 operates by receiving that power. The precision absolute angle detector 1 inputs a 16-bit absolute angle detection value to the arithmetic unit 4, for example, by serial communication.

[0058] The segment counter 2 counts the segments obtained by dividing (dividing equally) one rotation period of the rotating shaft 30 in accordance with the rotation of the rotating shaft 30, and generates a count value that indicates an angle value for each segment in an angle range spanning multiple rotations (more than one rotation) of the rotating shaft 30. In this embodiment, the segment counter 2 counts the segments obtained by dividing (typically dividing equally) one rotation period of the rotating shaft 30 into two. In other words, the basic count number per rotation of the rotating shaft 30 is 2.

[0059] The segment counter 2 includes one (only one) power generation sensor 20, a magnetic field generating source 50 that rotates around the rotation axis 33 together with the rotating shaft 30, a sensor element SE (not a power generation sensor) separate from the power generation sensor 20, a counter circuit 8, and a non-volatile memory 9 that stores the count value. The non-volatile memory 9 may be composed of FeRAM (ferroelectric random access memory). In this embodiment, the counter circuit 8 and the non-volatile memory 9 are incorporated into one counter memory IC (integrated circuit) 10. The segment counter 2 further includes a signal evaluation circuit 5, a rectification / power supply circuit 6, and a signal processing circuit 7.

[0060] The power generation sensor 20 generates a pulse voltage in response to a change in the magnetic field caused by the rotation of the magnetic field generating source 50. The sensor state SS, which is the output state of the sensor element SE, is either a first output state or a second output state in response to the rotation position of the rotating shaft 30. This sensor state SS is supplied to the signal processing circuit 7. In this embodiment, the sensor element SE is a magnetic sensor that detects the magnetic field of the magnetic field generating source 50 in response to the rotation of the magnetic field generating source 50, and is in the first output state or the second output state in response to the magnetic field generated by the magnetic field generating source 50. An example of a magnetic sensor is a Hall IC. The signal evaluation circuit 5 determines the polarity of the pulse voltage generated by the power generation sensor 20, and supplies a signal representing the result of the polarity determination (pulse polarity PP) to the signal processing circuit 7. The signal processing circuit 7 converts the signal representing the result of the polarity determination (pulse polarity PP) received from the signal evaluation circuit 5 and the signal representing the output state of the sensor element SE (sensor state SS) into digital data (serial signal), and supplies it to the counter memory IC10 as pulse information (PP, SS). The pulse information includes the pulse polarity PP and the sensor state SS.

[0061] The rectifier / power supply circuit 6 rectifies the pulse voltage generated by the power generation sensor 20, converts it into an appropriate voltage, and supplies it to the sensor element SE, the signal evaluation circuit 5, the signal processing circuit 7, and the counter memory IC10 (the counter circuit 8 and the non-volatile memory 9). Therefore, the sensor element SE, the signal evaluation circuit 5, the signal processing circuit 7, and the counter memory IC10 (the counter circuit 8 and the non-volatile memory 9) can operate without receiving power from an external power source. In other words, the segment counter 2 operates with power generated by self-power generation even when there is no external power supply. The counter memory IC10 can operate with power supplied from the power supply circuit 3 when the power supply circuit 3 is connected to an external power source.

[0062] The counter circuit 8 built into the counter memory IC10 executes a counting operation according to a predetermined counter logic based on the pulse information (pulse polarity PP and sensor state SS) supplied from the signal processing circuit 7 and the previous pulse information stored in the nonvolatile memory 9. This counting operation is executed regardless of whether or not external power is supplied from the power supply circuit 3. The count value obtained by the counting operation is stored in the nonvolatile memory 9. This count value is saved even when there is no power supply (nonvolatile storage). When an external power supply is being supplied, the counter memory IC10 can supply the count value and pulse information (PP, SS) stored in the nonvolatile memory 9 to the arithmetic unit 4 by serial communication.

[0063] The arithmetic device 4 operates by receiving power supply from the power supply circuit 3 when the power supply circuit 3 is connected to an external power supply. When the external power supply is turned on, the arithmetic device 4 requests a precision absolute angle detection value from the precision absolute angle detector 1, and also requests a count value and pulse information (PP, SS) from the non-volatile memory 9. The precision absolute angle detector 1 supplies the precision absolute angle detection value to the arithmetic device 4 by serial communication. The non-volatile memory 9 supplies the count value and pulse information (PP, SS) to the arithmetic device 4 by serial communication. The arithmetic device 4 integrates the precision absolute angle detection value and the count value to generate and output a multi-rotation absolute angle detection value. The multi-rotation absolute angle detection value output by the arithmetic device 4 is supplied to, for example, a higher-level controller (not shown) and used for controlling the rotation of an electric motor, etc.

[0064] The arithmetic unit 4 integrates the precision absolute angle detection value using the count value supplied from the non-volatile memory 9. When integrating, the arithmetic unit 4 executes a correction process, which will be described later, as necessary.

[0065] Fig. 2A is a perspective view for explaining a structural example of the segment counter 2, and Fig. 2B is a plan view thereof. Fig. 2C is a front view seen in the direction of the arrow IIC in Fig. 2B. The segment counter 2 includes a power generation sensor 20, a magnetic field generation source 50, and a sensor element SE (e.g., a magnetic sensor).

[0066] The power generation sensor 20 is disposed on a first support 31 and supported by the first support 31. In this embodiment, the first support 31 also has a sensor element SE mounted thereon.

[0067] The magnetic field generating source 50 is fixed to the second support 32. The second support 32 moves relative to the first support 31. Specifically, the second support 32 is coupled (fixed) to the rotating shaft 30 and rotates together with the rotating shaft 30 around the rotation axis 33. Therefore, the second support 32 can be a part of a rotating body. In contrast, the first support 31 is fixedly disposed and held in a non-rotating state. As a result, the magnetic field generating source 50 rotates together with the second support 32 around the rotation axis 33 and moves relative to the first support 31.

[0068] The rotating shaft 30 is typically rotated by a driving force from a drive shaft of an electric motor (not shown). When the electric motor is driven in both directions, the rotating shaft 30 rotates in both the counterclockwise direction CCW and the clockwise direction CW accordingly. The first support 31 may be a printed wiring board arranged along a plane perpendicular to the rotation axis 33.

[0069] The magnetic field generating source 50 includes four magnets M1, M2, M3, M4 (individual magnets) arranged at a position away from the rotation axis 33. The magnets M1, M2, M3, M4 are fixed to the second support 32 so as to sequentially enter the detection region SR of the power generation sensor 20 by the rotational motion of the second support 32 about the rotation axis 33. The magnets M1, M2, M3, M4 are magnetized in a direction parallel to the rotation axis 33 and arranged at equal angular intervals around the rotation axis 33. In this example, the magnets M1, M2, M3, M4 are plate-shaped (more specifically, disk-shaped) magnetized in the thickness direction, but the shape of the magnets M1, M2, ... is not limited to this. For example, they may be rectangular or rectangular plate-shaped, and individual magnets may be used that are arc-shaped in plan view (specifically, sector-shaped with the radially inner part cut off).

[0070] The magnets M1, M2, M3, M4 are magnetized so that N poles n1, n2, ... and S poles s1, s2, ... are alternately arranged in the circumferential direction in a plan view (see FIG. 2B) seen from a direction parallel to the rotation axis 33. As a result, when the second support 32 rotates in one direction around the rotation axis 33, the N poles and S poles of different polarities alternately enter the detection region SR (see FIG. 2C) of the power generation sensor 20, generating an alternating magnetic field in the vicinity of the power generation sensor 20. The magnetic poles n1, s1, n2, s2 move along a circumferential orbit 51 around the rotation axis 33. The arrangement of the power generation sensor 20 and the magnetic field source 50 is determined so that the orbit 51 passes through the detection region SR. The magnetic poles n1, s1, n2, s2 are arranged at equal intervals on the orbit 51.

[0071] The power generation sensor 20 is mounted on one main surface of a first support 31 (printed wiring board). The power generation sensor 20 includes a magnetic wire FE and a pair of first and second magnetic flux conducting pieces FL1 and FL2 having soft magnetic material parts magnetically coupled to both ends of the magnetic wire FE. A coil SP (induction coil) is wound around the magnetic wire FE between the first and second magnetic flux conducting pieces FL1 and FL2. The first and second magnetic flux conducting pieces FL1 and FL2 are made of soft magnetic material parts of substantially the same shape and size. More specifically, the first and second magnetic flux conducting pieces FL1 and FL2 are configured symmetrically with each other with respect to a symmetry plane 27 (a virtual plane for explaining the geometric arrangement) perpendicular to the axial direction x at an axial center position 25 (hereinafter referred to as the "axial center position 25") of the magnetic wire FE.

[0072] The magnetic wire FE is configured to exhibit the large Barkhausen effect. Specifically, the magnetic wire FE has a core and a skin covering it. One of the core and the skin is a soft layer (soft magnetic layer) whose magnetization direction is reversed even in a weak magnetic field, and the other is a hard layer (hard magnetic layer) whose magnetization direction is not reversed unless a strong magnetic field is applied.

[0073] Each of the magnetic flux conducting pieces FL1, FL2 has a magnetic flux conducting end 21, 22 facing the detection region SR. The magnetic wire FE is arranged such that an axial direction x is set parallel to a tangent at a point (contact point) on the track 51 between the pair of magnetic flux conducting ends 21, 22, and a central position 25 in the axial direction x (hereinafter referred to as "axial central position 25") is set on a perpendicular line to the tangent at the contact point.

[0074] In this embodiment, the first magnetic flux conducting piece FL1 and the second magnetic flux conducting piece FL2 include an axis-orthogonal portion 41 extending parallel to each other from both ends of the magnetic wire FE in an axis-orthogonal direction perpendicular to the axial direction x, and an axis-parallel portion 42 extending from a tip of the axis-orthogonal portion 41 in a direction approaching each other along the axial direction x. Both ends of the magnetic wire FE are fixed to the base ends of the axis-orthogonal portions 41 of the first magnetic flux conducting piece FL1 and the second magnetic flux conducting piece FL2. More specifically, the base end of the axis-orthogonal portion 41 is provided with a wire arrangement portion 23 having a hole or groove formed therein penetrating in the axial direction x. Both ends of the magnetic wire FE are fixed to the axis-orthogonal portions 41 in the wire arrangement portion 23, penetrating the axis-orthogonal portions 41 of the first magnetic flux conducting piece FL1 and the second magnetic flux conducting piece FL2, respectively. For example, the magnetic wire FE and the first and second magnetic flux conducting pieces FL1 and FL2 are coupled and fixed to each other by a resin (not shown) disposed in a hole or groove constituting the wire placement portion 23. As a result, both ends of the magnetic wire FE are magnetically coupled to the first and second magnetic flux conducting pieces FL1 and FL2, respectively.

[0075] The power generation sensor 20 is configured so that the side opposite the magnetic wire FE with respect to the axially parallel portion 42 is a detection region SR for detecting a magnetic field.

[0076] Each of the magnetic flux conducting pieces FL1 and FL2 made of a soft magnetic material part has an axis-orthogonal portion 41 having a substantially rectangular parallelepiped shape and an axis-parallel portion 42 having a substantially rectangular parallelepiped shape connected to the tip portion, which is the end portion of the axis-orthogonal portion 41 on the detection region SR side, and has an L-shape bent at a right angle at the joint between the axis-orthogonal portion 41 and the axis-parallel portion 42. The axis-parallel portion 42 extends along the axial direction x so as to cover the magnetic wire FE, i.e., to shield between the magnetic wire FE and the detection region SR. The first magnetic flux conducting piece FL1 and the second magnetic flux conducting piece FL2, which have mutually symmetrical shapes, extend toward the axial center side of the magnetic wire FE, and their proximal ends 42a face each other with a gap therebetween near the axial center position 25 of the magnetic wire FE. The intermediate position of this gap in the axial direction x corresponds to the axial center position 25 in the axial direction, and therefore the distances in the axial direction x from the proximal ends 42a of the pair of axis-parallel portions 42 to the symmetry plane 27 are equal. The distance L of the interval in the axial direction x is set to 5% to 50% of the distance D between the pair of axis-orthogonal portions 41 at the joining position between the magnetic wire FE and the axis-orthogonal portions 41, and more preferably 20% to 40%. More specifically, the distance D is the distance in the axial direction x between the inner surfaces (the inner surfaces of the axis-orthogonal portions 41) of the pair of magnetic flux conduction pieces FL1, FL2 that face each other in the axial direction x at the joining position with the magnetic wire FE. The proximal end 42a forms a plane perpendicular to the axial direction x, and the two planes that form the two proximal ends 42a are parallel to each other and face each other in the axial direction x.

[0077] The soft magnetic parts constituting the magnetic flux conducting pieces FL1 and FL2 are preferably made of a material whose coercive force is equal to or less than that of the magnetic wire FE and whose relative permeability is 500 or more. Such materials have properties such as low magnetic resistance, low hysteresis, and low self-dielectric. As a result, even when a high-frequency alternating magnetic field generated when the magnetic field generating source 50 moves at high speed is applied, the output characteristics of the power generation sensor 20 are less affected. Specifically, the soft magnetic parts are preferably made of Ni-based ferrite or Mn-based ferrite.

[0078] The axially parallel portions 42 of the first and second magnetic flux conducting pieces FL1 and FL2 form magnetic flux conducting ends 21 and 22 that form detection area facing surfaces that face the detection area SR. The magnetic flux conducting ends 21 and 22 (detection area facing surfaces) are flat surfaces that are parallel to the axial direction x. When a magnetic pole is disposed in the detection area SR, the magnetic flux conducting ends 21 and 22 (detection area facing surfaces) guide magnetic flux from the magnetic pole into the first and second magnetic flux conducting pieces FL1 and FL2.

[0079] The axially parallel portions 42 of the first magnetic flux conducting piece FL1 and the second magnetic flux conducting piece FL2 are joined to a wiring pattern (not shown) formed on one main surface of the first support 31 (printed wiring board), thereby surface-mounting the power generating sensor 20 on the first support 31 (printed wiring board). The power generating sensor 20 is disposed so that the axial direction x of the magnetic wire FE is aligned with a tangent at one point (contact point) on a circumference whose central axis is the rotation axis 33, and the axial center position 25 of the magnetic wire FE coincides with the contact point. The detection region SR of the power generating sensor 20 is on the opposite side of the axially parallel portions 42 to the magnetic wire FE, and in this example, is an area on the other main surface side of the first support 31 (printed wiring board).

[0080] In the power generation sensor 20 configured as described above, the magnetic field of the detection region SR is guided to both ends of the magnetic wire FE by the magnetic flux conducting pieces FL1 and FL2 having soft magnetic parts. In addition, since the axial parallel portion 42 parallel to the axial direction x of the magnetic wire FE is located between the detection region SR and the magnetic wire FE, the magnetic flux moving from the detection region SR to the axial intermediate portion (midway position in the axial direction) of the magnetic wire FE is shielded by the axial parallel portion 42. In particular, when the distance L in the axial direction x between the adjacent ends 42a of the axial parallel portions 42 of the pair of magnetic flux conducting pieces FL1 and FL2 is set to 5% to 50% of the distance D between the axially orthogonal portions 41 at the joining position with the magnetic wire FE, an excellent magnetic shielding effect can be obtained. Therefore, since the magnetic field in the axial direction x can be applied over a wide range of the axial direction x of the magnetic wire FE, the large Barkhausen effect can be sufficiently induced, and a high-output signal can be obtained.

[0081] Moreover, since the power generation sensor 20 includes the magnetic flux conducting pieces FL1 and FL2, which are fixedly connected to the magnetic wire FE, the magnetic field generating source 50 (magnets M1, M2, M3, M4) as a detection medium may be disposed in the detection region SR. This makes it easy to combine magnetic field generating sources 50 with different shapes and / or polarities.

[0082] The four magnets M1, M2, M3, and M4 constituting the magnetic field generating source 50 are arranged with their magnetic poles n1, s1, n2, and s2 facing the first support 31 (printed wiring board), respectively. In this example, the second support 32 is configured in an annular shape surrounding the rotation axis 33. More specifically, the second support 32 is configured as an annular plate-like body, is arranged along a plane perpendicular to the rotation axis 33, and is parallel to the first support 31 (printed wiring board). In the second support 32, the magnets M1, M2, M3, and M4 are fixed to a surface facing the other main surface of the first support 31 (printed wiring board). The magnets M1, M2, M3, and M4 are arranged at equal intervals in the circumferential direction around the rotation axis 33, that is, at angular intervals of 90 degrees around the rotation axis 33. The magnetization direction of each of the magnets M1, M2, M3, and M4 is parallel to the rotation axis 33. The magnets M1, M2, M3, and M4 are fixed to the second support 32 so that the magnetic poles n1, s1, n2, and s2 of different polarities alternately face the first support 31 (printed wiring board) when the rotation axis 30 rotates in one direction. The distance from the rotation axis 33 to the magnets M1, M2, M3, and M4 (more specifically, the centers of the magnetic poles n1, s1, n2, and s2 facing the first support 31) is equal to the distance from the rotation axis 33 to the axial center position 25 of the magnetic wire FE. That is, in a plan view along the rotation axis 33, the magnetic wire FE and the magnets M1, M2, M3, and M4 are located on circumferences of equal radii with the rotation axis 33 as the central axis, and are thus positioned so as to be able to face each other in a direction parallel to the rotation axis 33. The second support 32 is preferably a yoke made of a soft magnetic material.

[0083] Since magnets M1, M2, M3, and M4 are magnetized in a direction parallel to the rotation axis 33, the direction of the magnetic flux of each magnetic pole n1, s1, n2, and s2 is perpendicular to the direction of movement of the magnetic pole n1, s1, n2, and s2, and is a direction that intersects with the magnetic wire FE when facing the power generation sensor 20, i.e., the direction in which the gap 35 between the magnetic poles n1, s1, n2, and s2 and the power generation sensor 20 opens (gap direction).

[0084] The arrangement interval λ of the four magnetic poles n1, s1, n2, s2 on the track 51, i.e., the interval between adjacent magnetic poles n1, s1, n2, s2 in the circumferential direction, is longer than the total length Lw of the magnetic wire FE (see FIG. 2C). More specifically, in this example, the arrangement interval λ is 1.5 times or more the total length Lw of the magnetic wire FE. In addition, the length α (length along the track 51) of the magnetic poles n1, s1, n2, s2 on the track 51 is shorter than the total length Lw of the magnetic wire FE and is 50% or less of the magnetic pole arrangement interval λ. In this example, the length α of the magnetic poles n1, s1, n2, s2 on the track 51 is half or less of the total length Lw of the magnetic wire FE.

[0085] In the printed wiring board constituting the first support 31, a sensor element SE, for example a magnetic sensor, is further mounted on the main surface on which the power generation sensor 20 is mounted. In this example, the sensor element SE is disposed at a position substantially opposite to the center position of the axial direction x of the magnetic wire FE. As a result, when the magnetic poles n1, s1, n2, s2 face the power generation sensor 20 on the track 51 between the first magnetic flux conducting piece FL1 and the second magnetic flux conducting piece FL2, the sensor element SE detects the magnetic field from the magnetic poles n1, s1, n2, s2 and outputs an identification signal. As a result, when the magnetic poles n1, s1, n2, s2 are present at a position opposite to the center of the power generation sensor 20, the sensor element SE is in a first output state in which it outputs an identification signal indicating that it detects an N pole, or in a second output state indicating that it detects an S pole. The sensor element SE may be disposed in a different manner. Specifically, the sensor element SE may be disposed at a position where it can detect a magnetic field from any one of the magnetic poles n1, s1, n2, and s2 when that magnetic pole faces the center of the power generation sensor 20. More specifically, based on the arrangement in FIG. 2B, the sensor element SE may be disposed at any one of a plurality of positions at angular intervals of 360 degrees / 4 (=90 degrees) around the rotation axis 33.

[0086] Fig. 3A is a simplified plan view of the segment counter 2, and Fig. 3B shows the change in magnetic flux relative to the rotation angle and the operation of the power generation sensor 20. In Fig. 3A, one S pole s2 faces the center of the power generation sensor 20, and one N pole n1 is located at a position 90 degrees away in the clockwise direction CW. This state is set as the origin (0 degrees) of the rotation angle, and Fig. 3B shows the change in magnetic flux density with the rotation of the second support 32, with the angle value increasing in the counterclockwise direction CCW. The magnetic flux density here refers to the density of the magnetic flux component passing through the magnetic wire FE.

[0087] The magnetic field generation source 50 (magnets M1, M2, M3, M4) generates two periods of an alternating magnetic field while the rotating shaft 30 rotates once around the rotation axis 33.

[0088] When the four magnets M1, M2, M3, and M4 rotate in the counterclockwise direction CCW together with the second support 32, if the magnetic flux density falls below the negative stabilizing magnetic field, a positive pulse ready state SET_P (positive set state) is entered, and if the magnetic flux density then exceeds the positive operating magnetic field, a positive pulse "P" is generated. Also, when the four magnets M1, M2, M3, and M4 rotate in the counterclockwise direction CCW together with the second support 32, if the magnetic flux density exceeds the positive stabilizing magnetic field, a negative pulse ready state SET_N (negative set state) is entered, and if the magnetic flux density then falls below the negative operating magnetic field, a negative pulse "N" is generated. Therefore, as shown in FIG. 3B, a negative pulse "N" is generated near 0 degrees and 180 degrees, and a positive pulse "P" is generated near 90 degrees and 270 degrees.

[0089] Similarly, when the four magnets M1, M2, M3, and M4 rotate in the clockwise direction CW together with the second support 32, the positive pulse ready state SET_P (positive set state) is entered when the magnetic flux density falls below the negative stabilizing magnetic field, and then a positive pulse "P" is generated when the magnetic flux density exceeds the positive operating magnetic field. Also, when the four magnets M1, M2, M3, and M4 rotate in the clockwise direction CW together with the second support 32, the negative pulse ready state SET_N (negative set state) is entered when the magnetic flux density exceeds the positive stabilizing magnetic field, and then a negative pulse "N" is generated when the magnetic flux density falls below the negative operating magnetic field. Therefore, as shown in FIG. 3B, a positive pulse "P" is generated near 0 degrees (360 degrees) and 180 degrees, and a negative pulse "N" is generated near 90 degrees and 270 degrees.

[0090] On the other hand, near 90 degrees and 270 degrees, the N poles n1 and n2 face the power generation sensor 20, so the sensor element SE is in the first output state "H". On the other hand, near 0 degrees and 180 degrees, the S poles s1 and s2 face the power generation sensor 20, so the sensor element SE is in the second output state "L". As shown in FIG. 3B, the pulse information representing the state when a positive pulse "P" occurs near 90 degrees and 270 degrees is represented as "HP", and the pulse information representing the state when a negative pulse "N" occurs near 90 degrees and 270 degrees is represented as "HN". Also, the pulse information representing the state when a positive pulse "P" occurs near 0 degrees and 180 degrees is represented as "LP", and the pulse information representing the state when a negative pulse "N" occurs near 0 degrees and 180 degrees is represented as "LN".

[0091] 3B, if the rotation direction is counterclockwise CCW, the pulse information is HP or LN, and if the rotation direction is clockwise CW, the pulse information is HN or LP. That is, if the pulse information is HP or LN, the counter memory IC10 can identify that the rotation direction is counterclockwise CCW, and if the pulse information is HN or LP, the counter memory IC10 can identify that the rotation direction is clockwise CW.

[0092] In the vicinity of 0 degrees (360 degrees), 90 degrees, 180 degrees, and 270 degrees, the change in magnetic flux density with respect to the rotation angle is very steep. Therefore, there is little variation in the pulse generation position (angle at which the pulse is generated), and the deviation in the pulse generation position that depends on the direction of rotation, i.e., the phase difference ±PS, is extremely small. In addition, because the angle difference from the operating magnetization to the stabilizing magnetic field is very small, the range (reversal range) in which so-called pulse missing occurs when the movement direction (rotation direction) is reversed is narrow.

[0093] Also, since the long axis direction of the power generation sensor 20 is the circumferential tangent direction, the external dimensions of the segment counter 2 can be made smaller. From another perspective, the diameter of the hollow portion of the second support 32 can be made larger. In addition, since general-purpose individual magnets that can be manufactured by magnetizing the thickness direction with an air-core coil can be used as the magnets M1, M2, M3, and M4, the magnet costs can be reduced. Of course, since individual magnets of the same design can be used for general-purpose rotation detection devices of different sizes, no special magnets with a dedicated design are required. Moreover, since the N poles and S poles of the magnets M1, M2, M3, and M4, which are individual magnets magnetized in the thickness direction, can be fixed to the second support 32 by alternately orienting them in one direction, the assembly work is simple, and the assembly costs can be reduced accordingly.

[0094] As described above, the arrangement interval λ of the four magnetic poles n1, s1, n2, s2 on the orbit 51 is longer than the total length Lw of the magnetic wire FE (preferably 1.5 times or more), so that a flat portion where the magnetic flux density is 0 appears in the intermediate region between 0 degrees (360 degrees), 90 degrees, 180 degrees, and 270 degrees where the pulse is generated, as shown in Fig. 3B. This makes it possible to separate the influence of the magnetic field from the adjacent magnetic poles n1, s1, n2, s2 on the orbit 51, and to make the change in the magnetic flux density in the vicinity of 0 degrees (360 degrees), 90 degrees, 180 degrees, and 270 degrees steep. This tendency is further strengthened by setting the length α of the magnetic poles n1, s1, n2, s2 on the orbit 51 to 50% or less of the arrangement interval λ of the magnetic poles.

[0095] As described above, the length α of the magnetic poles n1, s1, n2, and s2 on the track 51 is shorter than the total length Lw of the magnetic wire FE. This ensures a steep change in magnetic flux density without causing a flat portion in the change in magnetic flux density in the vicinity of 0 degrees (360 degrees), 90 degrees, 180 degrees, and 270 degrees. It is preferable to set the length α of the magnetic poles n1, s1, n2, and s2 to half or less of the total length Lw of the magnetic wire FE, since this makes the change in magnetic flux density steeper.

[0096] With this configuration, a pulse is generated each time the magnetic poles n1, s1, n2, s2 of one of the magnets M1, M2, M3, M4 pass the detection area SR along the track 51 by the counterclockwise CCW rotation about the rotation axis 33, generating a pulse voltage of four pulses per rotation. Similarly, a pulse is generated each time the magnetic poles n1, s1, n2, s2 of one of the magnets M1, M2, M3, M4 pass the detection area SR along the track 51 by the clockwise CW rotation about the rotation axis 33, generating a pulse voltage of four pulses per rotation. The rotation position and the rotation direction can be identified by the polarity of these pulses and the sensor element SE which is in the first output state "H" or the second output state "L" when the magnets M1, M2, M3, M4 are on the track 51 between the first magnetic flux conducting piece FL1 and the second magnetic flux conducting piece FL2.

[0097] FIG. 4 is a diagram for explaining an example of the operation of the segment counter 2. In this embodiment, the segment counter 2 counts segments obtained by dividing an angular region around the rotation axis 33 into two (typically equal parts), and generates a count value representing the counting result. The two segments are defined by two boundaries a and b set at 180-degree intervals around the rotation axis 33. The boundaries a and b are boundaries at which the count value of the segment counter 2 switches in response to a voltage pulse generated by the power generation sensor 20. In other words, the segment counter 2 performs two counting operations per rotation. Specifically, the boundary a corresponds to the position (90 degrees) where the N pole n1 faces the center of the power generation sensor 20, and the boundary b corresponds to the position (270 degrees) where the N pole n2 faces the center of the power generation sensor 20. When each of the N poles n1, n2 moves across a position facing the center of the power generation sensor 20 in a counterclockwise direction CCW, it counts up (the count value is incremented), and when it moves in a clockwise direction CW, it counts down (the count value is decremented).

[0098] The meanings of the symbols in the figure are the same as those in FIG. 3B, and are as follows: "H" is a state value representing that the sensor element SE has detected either of the N poles n1, n2 and is in the first output state. "L" is a state value representing that the sensor element SE has detected either of the S poles s1, s2 and is in the second output state. These state values ​​correspond to the magnetic detection data generated by the signal processing circuit 7 based on the output of the sensor element SE. "P" is a pulse polarity value representing the generation of a positive pulse of the power generation sensor 20. "N" is a pulse polarity value representing the generation of a negative pulse of the power generation sensor 20. These pulse polarity values ​​correspond to the polarity discrimination data generated by the signal processing circuit 7 based on the output of the signal evaluation circuit 5.

[0099] The pulse information supplied from the signal processing circuit 7 to the counter circuit 8 is represented by a combination of these, is updated every time the power generation sensor 20 generates a pulse, and is stored in the non-volatile memory 9 as identifiable information. "HP" is pulse information representing a positive pulse generation when any of the N poles n1, n2 face the center of the power generation sensor 20. "LN" is pulse information representing a negative pulse generation when any of the S poles s1, s2 face the center of the power generation sensor 20. "HN" is pulse information representing a negative pulse generation when any of the N poles face the center of the power generation sensor 20. "LP" is pulse information representing a positive pulse generation when any of the S poles s1, s2 face the center of the power generation sensor 20. In FIG. 4, the arrows attached to the positions (pulse generation positions) where each pulse information is generated indicate the rotation direction (counterclockwise direction CCW or clockwise direction CW) when a pulse voltage is generated. The same applies to FIG. 6 described later.

[0100] As in the case of Fig. 3B, "SET_P" represents the angle range in which the device is in a preparation state for generating a positive pulse (positive set state), and "SET_N" represents the angle range in which the device is in a preparation state for generating a negative pulse (negative set state).

[0101] The basic operation of the segment counter 2 is as follows.

[0102] When the rotating shaft 30 rotates in the counterclockwise direction CCW, a positive pulse is generated near the boundaries a and b corresponding to the rotation angles of 90 degrees and 270 degrees, respectively. At this time, pulse information HP is generated. The segment counter 2 counts up by one (increments the count value) in response to the pulse information HP. That is, it counts up when the rotation angle increases by passing through 90 degrees (boundary a) and 270 degrees (boundary b), respectively. As shown in FIG. 3B, since the change in magnetic flux density with respect to the rotation angle has a finite slope, the position where the pulse information HP is generated during rotation in the counterclockwise direction CCW (pulse generation position) has a positive phase difference +PS (for example, +2 degrees) with respect to 90 degrees (boundary a) and 270 degrees (boundary b).

[0103] When the rotating shaft 30 rotates in the clockwise direction CW, a negative pulse is generated near the boundaries a and b corresponding to the rotation angles of 90 degrees and 270 degrees, respectively. At this time, pulse information HN is generated. The segment counter 2 counts down (decrements the count value) in response to the pulse information HN. That is, it counts down when the rotation angle passes through 90 degrees (boundary a) and 270 degrees (boundary b) and decreases. As shown in FIG. 3B, since the change in magnetic flux density with respect to the rotation angle has a finite slope, the position where the pulse information HN is generated during rotation in the clockwise direction CW (pulse generation position) has a negative phase difference -PS (for example, -2 degrees) with respect to 90 degrees (boundary a) and 270 degrees (boundary b).

[0104] FIG. 5 is a table for explaining an example of a more detailed counting operation of the segment counter 2. The counter circuit 8 built in the counter memory IC 10 executes the counting operation by logic according to this table. When the power generation sensor 20 generates a pulse, the pulse information input from the signal processing circuit 7 to the counter circuit 8 is updated. The counting operation (Counter Operation) is determined by a combination of the updated pulse information (NEW) and the immediately previous pulse information (OLD). The counter circuit 8 reads the immediately previous pulse information (OLD) from the non-volatile memory 9 and executes the counting operation using it. As described above, the rotation direction (counterclockwise direction CCW or clockwise direction CW) of the rotating shaft 30 can be identified by the pulse information. FIG. 5 also shows the rotation direction identified from the pulse information.

[0105] When the updated pulse information is HP, if the previous state value is any of HN, LP, or LN (i.e., other than HP), a +1 count-up operation is performed. When the updated pulse information is HN, if the previous pulse information is any of HP, LP, or LN (i.e., other than HN), a -1 count-down operation is performed. In other words, when a pulse voltage is generated when the output state of the sensor element SE is the first output state "H" (N pole detection state), if the pulse information is different from the previous value, a count-up or count-down is performed depending on the polarity "P" or "N" of the pulse voltage.

[0106] When the updated pulse information is LP, a count-down operation of -1 is performed only when the immediately preceding pulse information is HP. That is, when a pulse voltage with polarity "P" occurs when the sensor element SE is in the second output state "L", the count value is decremented when the immediately preceding pulse information indicates the first output state "H" and polarity "P". When the updated pulse information is LN, a count-up operation of +1 is performed only when the immediately preceding pulse information is HN. That is, when a pulse voltage with polarity "N" occurs when the sensor element SE is in the second output state "L", the count value is incremented when the immediately preceding pulse information indicates the first output state "H" and polarity "N". These are exceptional count operations performed when the output state of the sensor element SE is in the second output state "L" (S pole detection state), and are correction operations to compensate for missed count value updates due to the effect of pulse missing (missing pulse voltage due to reversal of the rotation direction) described later.

[0107] For other changes in pulse information, the count value remains unchanged (the count value changes to "0"). That is, if the current and previous pulse information are equal, if the current pulse information is LP and the previous pulse information is HN or LN, and if the current pulse information is LN and the previous pulse information is HP or LP, the count value remains unchanged.

[0108] In this way, the counter circuit 8 operates to identify the rotation direction and rotation position of the rotating shaft 30 according to the latest and previous pulse information, i.e., using the output state of the sensor element SE and the polarity of the pulse voltage generated by the power generation sensor 20, update the count value, and write the count value to the non-volatile memory 9.

[0109] FIG. 6 is a diagram for explaining the effect of a missing pulse on the count value.

[0110] Consider a case where the rotation angle changes along the trajectory T1. That is, the rotation angle increases across the boundary a due to the rotation in the counterclockwise direction CCW, so that a positive pulse is generated at the position 61, and the pulse information HP is generated. If the rotation direction is reversed to the clockwise direction CW before the rotation angle reaches the position where the stabilizing magnetic field is applied to the magnetic wire FE of the power generation sensor 20, the rotation angle decreases beyond the boundary a without the magnetic wire FE being in a negative pulse generation preparation state (SET_N), and the magnetic wire FE reaches the position 62 where the pulse information HN should be generated. At this time, the negative pulse that should be generated at the position 62 is not generated (pulse missing), so the pulse information is not updated. After that, when the rotation angle decreases due to further rotation in the clockwise direction CW, the magnetic wire FE is in a positive pulse generation preparation state (SET_P). Then, when the rotation direction is reversed again to the counterclockwise direction CCW, the rotation angle increases across the boundary a, a positive pulse is generated again at the position 61, and the pulse information HP is generated. Therefore, if the pulse information changes from HP to HN, a basic countdown operation of -1 should occur, but in reality, the pulse information changes from HP to HP, so the count value remains unchanged ("others" in FIG. 5). That is, the pulse information changes from HP to HP, but since it is the same position, it is not counted. In the locus T1, when the reversal position from the rotation in the clockwise direction CW to the rotation in the counterclockwise direction CCW is a position (position on the counterclockwise CCW side) before reaching the generation position of the pulse information LP near the rotation angle = 0 degrees, a similar scenario occurs. Therefore, in the case of the scenario of the locus T1, the count value of the segment counter 2 may include an error of one pulse (+0.25 rotations) until the second pulse information HP is generated and the count is ignored. The behavior is also the same when the rotation direction is reversed (see locus T3), and the state value changes from HN to HN, and the count value remains unchanged (see FIG. 5). In this case, the count value may include an error of one pulse (-0.25 rotations). Therefore, until an exceptional counting operation is performed, the count value may include an error of ±0.25 rotations. More strictly, the count value may further include an error of the phase difference ±PS.

[0111] Next, consider the case where the rotation angle changes along the trajectory T2. When the rotation angle increases across the boundary a due to the rotation in the counterclockwise direction CCW, and a positive pulse is generated at position 71, the pulse information HP is generated. If the rotation direction is reversed to the clockwise direction CW before the rotation angle reaches a position where the stabilizing magnetic field is applied to the magnetic wire FE of the power generation sensor 20, the rotation angle decreases beyond the boundary a without the magnetic wire FE being in a negative pulse generation preparation state (SET_N), and the position 72 where the pulse information HN should be generated is reached. At this time, the negative pulse that should be generated at position 72 is not generated (pulse missing), so the pulse information is not updated. After that, the magnetic wire FE is further rotated in the clockwise direction CW to be in a positive pulse generation preparation state (SET_P), and when the rotation angle reaches position 73, a negative pulse is generated and the pulse information LP is generated. Therefore, if the pulse information changes from HP to HN, a basic -1 countdown operation should be performed, but in reality, the pulse information changes from HP to LP, so an exceptional -1 countdown operation is performed (see FIG. 5). This compensates for the effects of missing pulses. When the rotation direction is reversed (trajectory T4), the behavior is similar, with the pulse information changing from HN to LN and an exceptional countdown operation of +1 being performed (see Figure 5). Until this exceptional counting operation is performed, the count value may contain an error of ±0.25 rotations. More strictly speaking, the count value may further contain an error equivalent to the phase difference ±PS.

[0112] If the initial count value is "0" (even), the correct count value for the angle range of one rotation (360 degrees) is an even number in the angle range of -90 degrees (+270 degrees) to +90 degrees (the right half of boundaries a and b in Figure 5), and an odd number in the angle range of +90 degrees to +270 degrees (the left half of boundaries a and b in Figure 5).

[0113] 7 shows the relationship between the count value of the segment counter 2 and the angle detection value of the precision absolute angle detector 1 with respect to the rotation angle of the rotating shaft 30 in the positive rotation angle range. The horizontal axis represents the rotation angle of the rotating shaft 30, with one rotation (360 degrees) represented as 1. The vertical axis represents the multi-rotation absolute angle value, with one rotation (360 degrees) represented as 1. In the internal processing of the calculation device 4, for example, the range of one rotation is represented with a resolution of 16 bits (65,536 steps).

[0114] As the rotating shaft 30 rotates, the angle detection value θs of the precision absolute angle detector 1 (hereinafter simply referred to as the “absolute angle detection value θs”) changes in a sawtooth wave shape between 0 and 1, as indicated by line 81.

[0115] On the other hand, the value 0.5n obtained by converting the count value n (n is an integer) of the segment counter 2 into the number of rotations ideally shows a step-like change as shown by line 82 with the rotation of the rotary shaft 30. For example, the count values ​​in an angle section of 0.5 rotation (180 degrees) with a median value at intervals of 0.5 rotation (180 degrees) from 0 degree as the base are ideally 0, 1, 2, 3, ..., and the corresponding number of rotations is 0, 0.5, 1.0, 1.5, ...). Since the count of the segment counter 2 is 2 counts per rotation, the height of the step per count is 0.5 rotation. The quantization error in this case is at most half that, 0.25 rotations.

[0116] When the aforementioned missing pulse occurs, an error of ±0.25 rotations is added to the count value n of the segment counter 2. Line 82- in Fig. 7 represents the rotation speed converted value when the count value n of the segment counter 2 includes an error of -0.25 rotations with respect to the case of line 82. Similarly, line 82+ in Fig. 7 represents the rotation speed converted value when the count value n of the segment counter 2 includes an error of +0.25 rotations with respect to the case of line 82.

[0117] Line 82- in Fig. 7 is represented by taking into account a phase difference -PS (for example, -2 degrees) in the pulse generation position in addition to an error of -0.25 rotations caused by a missing pulse. Similarly, line 82+ in Fig. 7 is represented by taking into account a phase difference +PS (for example, +2 degrees) in the pulse generation position in addition to an error of +0.25 rotations caused by a missing pulse.

[0118] The calculation device 4 uses the count value n of the segment counter 2 and the absolute angle detection value θs to perform calculations, for example, in a first step represented by the following equation (1) and a second step represented by the following equation (2), and integrates them to calculate a multi-rotation absolute angle detection value θm. In the following equations (1) and (2), N represents the number of rotations (amount of rotation) from the reference point (origin of rotation position) of the rotating shaft 30. U represents the amount of angle detection per rotation (for example, U=65536 (16 bits)), which corresponds to the resolution of the precision absolute angle detector 1.

[0119]

number

[0120] First step In formula (1), the count value n is multiplied by the amount of detected angle U per rotation, and then divided by the number of segments "2" to obtain a conversion value nU / 2. This conversion value nU / 2 is a numerical value obtained by converting the count value n into the unit of the detected absolute angle value θs. The detected absolute angle value θs is subtracted from the conversion value nU / 2 to obtain nU / 2-θs, which is then divided by the detected angle amount U to convert to the number of rotations. This is rounded off by adding 0.5 and processing with the integer conversion function INT (a function that rounds down the decimal part to an integer). This gives the number of rotations N.

[0121] Second step The multiple rotation absolute angle detection value θm for the count value n of the segment counter 2 can be obtained by multiplying the number of rotations N obtained in the first step by the angle detection amount U per rotation. By adding the absolute angle detection value θs, which is a precise angle detection value within one rotation, to this, the multiple rotation absolute angle detection value θm representing the precise multiple rotation absolute angle can be obtained as shown in formula (2).

[0122] An example of the calculation result to be obtained is shown in Fig. 8. In order to execute a part or all of the above-mentioned calculations in the calculation device 4, a table prepared in advance may be used as necessary.

[0123] In the actual calculation of the rotation speed N, it is convenient to use the following equation (3), which is equivalent to the above equation (1), in order to avoid handling decimal values.

[0124]

number

[0125] FIG. 9 shows the calculation result (0.5n-θ+0.5) obtained by subtracting the absolute angle detection value θs (line 81 in FIG. 7) from the rotation number conversion value (value equivalent to a multi-rotation angle) of the count value n of the segment counter 2 (lines 82, 82-, 82+ in FIG. 7) and then adding 0.5 rotations. This corresponds to the object to be processed by the integer conversion function INT in the above equation (1). The calculation results corresponding to lines 82, 82-, 82+ in FIG. 7 are represented by lines 92, 92-, 92+, respectively. It can be seen that stepped lines showing sawtooth changes are obtained in each section of one rotation.

[0126] FIG. 10 shows the calculation results obtained by processing the calculation results in FIG. 9 using the integer operator INT (an operator that discards decimal points). This corresponds to the processing result of the above equation (1). The calculation results corresponding to lines 92, 92-, and 92+ in FIG. 8 are represented by lines 102, 102-, and 102+, respectively. The ideal calculation result is represented by line 102. On the other hand, the calculation results of lines 102- and 102+ mean that an error of ±1 rotation occurs in the number of rotations N every 0.5 rotation, i.e., every 180 degrees, due to the phase difference ±PS in the pulse generation positions.

[0127] In other words, when the target of the integer conversion process has an error of 0.5 rotations or more, the rotation number N obtained by the integer conversion process may have an error of ±1.

[0128] Therefore, in this embodiment, the calculation device 4 performs a correction process as necessary when integrating the count value n of the segment counter 2 and the absolute angle detection value θs to obtain the multiple rotation absolute angle detection value θm. An example of correcting the count value n will be described below.

[0129] 9 and 10, an error occurs in the rotation count N when the rotation angle (value converted into the rotation count) is near 0, 0.5, 1.0, 1.5, ..., that is, near rotation angles of 0 degrees, 180 degrees, 360 degrees, 450 degrees, ... in increments of 180 degrees. That is, an error may occur in the rotation count N when the rotation angle belongs to the angle region A1 of 0 degrees ±PS and the angle region A2 of 180 degrees ±PS shown in FIG. 6. That is, an error may occur in the rotation count N when the absolute angle detection value θs belongs to either of the two angle regions A1 and A2 that respectively include the rotation positions at which a pulse voltage is generated when the sensor element SE is in the second output state (S pole detection state).

[0130] Therefore, when the absolute angle detection value θs output by the precision absolute angle detector 1 immediately after the power is turned on belongs to either of the angle regions A1 or A2, the arithmetic unit 4 determines whether the absolute angle detection value θs and the count value n obtained from the segment counter 2 immediately after the power is turned on are consistent. Specifically, it determines whether the parity of the count value n and the absolute angle detection value θs are consistent. Since the angle region A1 belongs to the angle range of -90 degrees (+270 degrees) to +90 degrees, the correct count value n is an even number. Since the angle region A2 belongs to the angle range of +90 degrees (+270 degrees), the correct count value n is an odd number. In other cases, the count value n and the absolute angle detection value θs are inconsistent.

[0131] When the count value n and the absolute angle detection value θs are inconsistent, the arithmetic unit 4 determines the correction direction based on the polarity of the immediately preceding pulse voltage included in the pulse information read from the non-volatile memory 9 (the polarity of the immediately preceding pulse voltage specified from the information read from the non-volatile memory 9), and corrects the count value n according to the determined correction direction. When the polarity of the pulse voltage is positive (P), the arithmetic unit 4 performs a correction of subtracting 1, which is a predetermined correction amount, from the count value n. When the polarity of the pulse voltage is negative (N), the arithmetic unit 4 performs a correction of adding 1, which is a predetermined correction amount, to the count value n. That is, the correction direction (whether to add or subtract) is determined based on the polarity of the immediately preceding pulse voltage, and according to this determination, "1" as the correction amount (>0) is added or subtracted.

[0132] In this example, the correction amount for the count value n is set to "1". However, since it is only necessary that the rotation speed N obtained through the integerization process becomes the correct value, the correction amount for the count value n does not have to be 1. If a correction amount including a fractional part is allowed, for example, the correction amount may be selected in the range of 0.5 < correction amount < 1.5. More precisely, the correction amount can be selected in the range of PS < correction amount < PS + 2.

[0133] Specifically, the mismatch between the count value n and the absolute angle detection value θs occurs when a pulse drop occurs and the exceptional counting operation (columns of pulse information LP and LN in FIG. 5) to compensate for it is not performed. For example, in the case of trajectories T2 and T4 in FIG. 6, this corresponds to the case where positions 73 and 74 are not reached within angle region A1 when power is turned on. Therefore, the case where the polarity of the immediately preceding pulse voltage is positive (P) is the case of pulse information HP, and the case where the polarity of the immediately preceding pulse voltage is negative (N) is the case of pulse information HN.

[0134] Even in the case of loci T1 and T3, there may be cases where the count value n and the absolute angle detection value θs are inconsistent when the power is turned on, but since no error occurs in the number of rotations N obtained by processing using formula (1), correction of the count value n is not necessary. However, since the above-mentioned correction process may be performed in the case of loci T1 and T3 as well, the angle region A1 may be made wider than 0 degrees ±PS, and similarly, the angle region A2 may be made wider than 180 degrees ±PS.

[0135] Specifically, the angle region A1 can be set in a range greater than -90 degrees (+270 degrees) + PS and smaller than 90 degrees - PS so as to include the section of 0 degrees ± PS. The angle region A2 can be set in a range greater than 90 degrees + PS and smaller than +270 degrees - PS so as to include the section of 180 degrees ± PS. For example, when the phase difference PS = 2 degrees, a margin β (e.g. β = 1 degree) is provided for the phase difference, and the angle region A1 is set to a section of -3 degrees (+357 degrees) or more and +3 degrees or less (0 degrees ± (PS + β)), and the angle region A2 is set to a section of 177 degrees or more and 183 degrees or less (180 degrees ± (PS + β)), so that the correction process can be reliably performed within a necessary and sufficient range to obtain an accurate rotation speed N.

[0136] As described above, the power generation sensor 20 has a structure that makes the phase difference PS very small, so that the angle regions A1 and A2 where correction processing is required can be narrowed, and correction processing is not required in most regions.

[0137] In addition, the segment counter 2 and the calculation device 4 perform signal processing with the intermediate position between the position where a positive pulse voltage is generated (position of pulse information LP) and the position where a negative pulse voltage is generated (position of pulse information LN) when the sensor element SE is in the second output state "L" as the origin (0 degrees) of angle detection (see FIG. 6). Therefore, the absolute value of the phase difference PS of the pulse voltage generation position with respect to the segment boundaries a, b is equal in either rotation direction, so that the two angle regions A1, A2 requiring correction processing can be narrowed.

[0138] As can be seen from equation (1), rather than correcting the count value n, the same results can be obtained by performing appropriate correction processing on any of the following: the rotation speed conversion value of the count value n (n / 2), the multi-rotation angle value corresponding to the count value n (nU / 2), the difference between the multi-rotation angle value and the absolute angle detection value θs (nU / 2-θs), the value (nU / 2-θs) obtained by dividing this by the angle detection amount U (nU / 2-θs) / U, and then adding a constant 0.5 for rounding off to this.

[0139] Furthermore, instead of the correction before the integer processing, a correction based on pulse information can be applied to the rotation speed N obtained by the integer processing. That is, when the absolute angle detection value θs belongs to either the angle region A1 or A2 and there is a mismatch between the even or odd of the rotation speed N and the absolute angle detection value θs, the correction direction (addition or subtraction) can be determined based on the pulse polarity included in the immediately preceding pulse information, and a correction amount (typically 1) can be added or subtracted from the rotation speed N according to the determination.

[0140] FIG. 11 is a flowchart showing an example of the processing of the arithmetic device 4.

[0141] When the external power supply is turned on and power supply from the power supply circuit 3 starts, the arithmetic unit 4 reads and acquires the count value n and pulse information from the nonvolatile memory 9 of the segment counter 2 (steps S1, S2). When the external power supply is turned on, the precision absolute angle detector 1 also starts operating, so the arithmetic unit 4 acquires the absolute angle detection value θs output by the precision absolute angle detector 1 (step S3).

[0142] The calculation device 4 judges whether the absolute angle detection value θs belongs to either the angle region A1 or A2 (step S4). If the judgment is positive, the calculation device 4 further judges whether the even / odd of the count value n matches the angle region A1 or A2 (step S5). That is, if the absolute angle detection value θs belongs to the angle region A1 and the count value n is an even number, or if the absolute angle detection value θs belongs to the angle region A2 and the count value n is an odd number, it is judged as "matching", otherwise it is judged as "mismatching". If it is judged as "mismatching" (step S5: NO), the calculation device 4 executes the above-mentioned correction process. That is, based on the pulse information (more specifically, based on the polarity of the immediately preceding pulse voltage included in the pulse information), the direction of correction (whether to add or subtract the correction amount) is determined, and the correction process is executed according to the determination (step S6). That is, if the pulse polarity PP included in the pulse information is positive (P), the correction amount "1" is subtracted from the count value n, and if the pulse polarity PP is negative (N), the correction amount "1" is added to the count value n. Then, based on the result of the correction, the calculation device 4 integrates the count value n of the segment counter 2 and the absolute angle detection value θs output by the precision absolute angle detector 1 to calculate the multiple rotation absolute angle detection value θm (step S7). When the absolute angle detection value θs does not belong to either of the angle regions A1 and A2 (step S4: NO), the correction process (step S6) is omitted. Also, when the angle regions A1 and A2 and the count value n are consistent (step S5: YES), the correction process (step S6) is omitted. In these cases, the count value n is used as it is (without correction process) to calculate the multiple rotation absolute angle detection value θm (step S7).

[0143] The multiple-rotation absolute angle detection value θm thus obtained is used as an initial value, and the multiple-rotation absolute angle detection value θm is updated at a predetermined control period based on the absolute angle detection value θs output thereafter by the precision absolute angle detector 1 (step S8). This operation continues until the external power supply is cut off.

[0144] As described above, in this embodiment, the segment counter 2 has only one power generation sensor 20 and sensor element SE, and is configured such that two periods of an alternating magnetic field are applied per rotation to the magnetic wire FE of the power generation sensor 20. The count value of the segment counter 2 configured in this way and the absolute angle detection value θs generated by the precision absolute angle detector 1 can be appropriately integrated, thereby obtaining a precise multi-rotation absolute angle detection value θm. Therefore, there is no need to use multiple power generation sensors 20.

[0145] As described above, the calculation device 4 executes a correction process as necessary when integrating the count value n and the absolute angle detection value θs. However, this correction process is a simple process in which the correction direction is determined using pulse information (more specifically, the polarity of the immediately preceding pulse voltage) and a correction amount is added or subtracted.

[0146] In Patent Documents 2 and 3, magnetic discrimination is performed when an external power source is turned on, the count value of the segment counter is corrected, and synchronization is achieved with the angle detection value of the precision absolute angle detector. Magnetic discrimination is particularly complicated, and a gradually increasing current is passed through the coil of the power generation sensor to apply the magnetic field generated by the coil to the magnetic wire, and the voltage generated at both ends of the coil is observed to monitor whether the magnetization direction of the magnetic wire is reversed.

[0147] In this embodiment, the count value of the segment counter 2 and the absolute angle detection value θs can be appropriately integrated by a simple calculation using pulse information, without the need for complicated magnetic discrimination as in Patent Documents 2 and 3. This simplifies the configuration and processing, making it possible to provide a small, low-cost, yet high-resolution multi-rotation precision absolute angle detection device.

[0148] Table 1 shows the expected error of the segment counter when the number of periods of the alternating magnetic field per revolution, the number of pulse voltages per revolution, and the number of segments per revolution are variously set.

[0149] [Table 1]

[0150] In Example 1, an alternating magnetic field of one cycle per rotation is applied to the magnetic wire, and the power generating sensor generates two pulse voltages in response to this, and performs one count for the two pulse voltages (i.e., the number of segments is 1). The angle per segment (per count) is 360 degrees, and the step angle converted into the number of rotations is 1 (revolution). The unit of angle in Table 1 is based on the number of rotations. The step error (quantization error) that occurs in the count value due to the step angle is 0.5 (revolutions), which is half the step angle. Furthermore, since the alternating magnetic field per rotation is one cycle, an error of 0.5 (revolutions) occurs due to missing pulses. In addition, the phase difference PS (see Figure 3B) is also an error element. This results in a total error of ±(1.0+PS) rotations.

[0151] In example 2, an alternating magnetic field with one cycle per rotation is applied to the magnetic wire, and in response the power generating sensor generates two pulse voltages and counts the two pulse voltages twice (i.e., the number of segments is 2). The angle per segment (per count) is 180 degrees, and the step angle converted into the number of rotations is 0.5 (revolutions). Therefore, the step error (quantization error) is half that, or 0.25 (revolutions). The error due to missing pulses is 0.5 (revolutions). Therefore, the total error including the phase difference PS is ±(0.75+PS) rotations.

[0152] In Example 3, an alternating magnetic field of two periods per rotation is applied to the magnetic wire, and the power generating sensor generates four pulse voltages in response to the alternating magnetic field, and counts the four pulse voltages twice (i.e., the number of segments is two). This Example 3 corresponds to the above-mentioned embodiment. The angle per segment (per count) is 180 degrees, and the step angle converted into the number of rotations is 0.5 (revolutions). Therefore, the step error (quantization error) is half that, or 0.25 (revolutions). Since the alternating magnetic field per rotation is two periods, the error due to missing pulses is 0.25 (revolutions). Therefore, the total error including the phase difference PS is ±(0.5+PS) rotations (see FIG. 7).

[0153] In Example 4, an alternating magnetic field with two periods per rotation is applied to the magnetic wire, the power generating sensor generates four pulse voltages in response, and counts four times for the four pulse voltages (i.e., the number of segments is four). The angle per segment (per count) is 90 degrees, and the step angle converted into the number of rotations is 0.25 (revolutions). Therefore, the step error (quantization error) is half that, or 0.125 (revolutions). As the alternating magnetic field has two periods per rotation, the error due to missing pulses is 0.25 (revolutions). Therefore, the total error including the phase difference PS is ±(0.375+PS) rotations.

[0154] In Example 5, an alternating magnetic field with three periods per rotation is applied to the magnetic wire, and the power generating sensor generates six pulse voltages in response, and counts three times for the six pulse voltages (i.e., the number of segments is three). The angle per segment (per count) is 120 degrees, and the step angle converted into the number of rotations is 0.333 (revolutions). Therefore, the step error (quantization error) is half that, or 0.167 (revolutions). As the alternating magnetic field has three periods per rotation, the error due to missing pulses is 0.167 (revolutions). Therefore, the total error including the phase difference PS is ±(0.333 + PS) rotations.

[0155] In Example 6, an alternating magnetic field with three periods per rotation is applied to the magnetic wire, and the power generating sensor generates six pulse voltages in response, and counts six times for those six pulse voltages (i.e., the number of segments is six). The angle per segment (per count) is 60 degrees, and the step angle converted into the number of rotations is 0.167 (revolutions). Therefore, the step error (quantization error) is half that, or 0.083 (revolutions). As the alternating magnetic field has three periods per rotation, the error due to missing pulses is 0.167 (revolutions). Therefore, the total error including the phase difference PS is ±(0.250+PS) rotations.

[0156] The power generation sensor outputs one positive and one negative pulse for one period of the alternating magnetic field, for a total of two pulses. The segment counter can be configured to count only positive or negative pulses, making the number of segments half the number of pulses (Example 1, Example 3, Example 5), or to count all pulses, making the number of segments the same as the number of pulses (Example 2, Example 4, Example 6). In order to increase the number of segments, in addition to counting both positive and negative pulses, it is possible to increase the period of the alternating magnetic field per rotation.

[0157] When integrating the highly accurate one-revolution absolute angle detection value (θs) and the segment counter count value (n), the number of rotations per rotation (N) is calculated from the two values, and the one-revolution absolute angle detection value (θs) is added to it. The accuracy required for the calculated number of rotations (N) is less than ±0.5 rotations. Of the two values ​​used to calculate the number of rotations (N), the error of the one-revolution absolute angle detection value (θs) is small and can be ignored. Therefore, the allowable error of the segment counter count value (n) is less than ±0.5 rotations. In other words, in Table 1, the total error must be less than ±0.5 rotations.

[0158] In the cases of Examples 1, 2, and 3, the total error exceeds ±0.5 rotations, so if the count value (n) of the segment counter is used as is, the number of rotations (N) will contain an error of ±1 rotation. In the cases of Examples 1 and 2, where the number of periods is 1, a method can be used in which the counter segments are divided into finer segments and signal processing is performed by obtaining information on the magnetization state of the magnetic wire of the power generation sensor (magnetization direction discrimination) (see Patent Documents 2 and 3). However, an additional circuit is required for magnetization direction discrimination, and the process of magnetization direction discrimination is also complicated, resulting in increased costs. Moreover, rotation must be stopped during processing such as magnetization direction discrimination.

[0159] As shown in Examples 4, 5, and 6, if the number of segments per revolution is 3 or more, the accuracy of the segment counter can be improved and the allowable error can be reduced to less than 0.5 revolutions. Therefore, the number of revolutions can be calculated by directly using the count value (n) of the segment counter.

[0160] However, the number of bits in the non-volatile memory that stores the count value (n) of the segment counter is finite. Therefore, the more segments there are, the smaller the maximum number of rotations (N) that can be counted. Also, since calculations are performed using binary numbers in signal processing, it is convenient for the number of segments to be 2 or a power of 2, and it is most convenient for the number of segments to be 2. Example 5 and Example 6, in which the number of segments includes the prime factor "3", make signal processing somewhat complicated.

[0161] Therefore, the case where the number of segments is two (Example 2, Example 3) is most preferable and can be used generally. Moreover, the total error is smaller in Example 3 than in Example 2, and the correction process is easier because it is sufficient to correct the error of the phase difference ±PS. That is, Example 3 corresponds to the above-mentioned embodiment, and the rotation speed N without error can be obtained by the above-mentioned simple correction process.

[0162] Although the embodiment of the present invention has been described above, the present invention can be embodied in further other forms, as exemplified below.

[0163] For example, in the above embodiment, the non-volatile memory 9 stores pulse information indicating the output state of the sensor element SE and the polarity of the pulse voltage generated by the power generation sensor 20, and when the power generation sensor 20 generates a pulse voltage, the count value is updated by the pulse information and the previous pulse information. However, the information stored in the non-volatile memory 9 does not necessarily need to be the pulse information itself, that is, a pair of the output state of the sensor element SE and the polarity of the pulse voltage, but may be information that can identify the output state of the sensor element SE and the polarity of the pulse voltage. Specifically, any two of the three pieces of information, the output state of the sensor element SE, the polarity of the pulse voltage, and the rotation direction identified from the two pieces of information, may be stored, or all of them (three pieces of information) may be stored. If there are two pieces of information, the remaining one can be identified. For example, when the output state of the sensor element SE is L and the polarity of the pulse voltage is N, the identified rotation direction is CCW. In this case, the information stored in the non-volatile memory 9 may be a combination of the output state "L" of the sensor element SE and the rotation direction "CCW", or a combination of the pulse voltage polarity "N" and the rotation direction "CCW". In the counting process, the set of (L,N), the set of (L,CCW), and the set of (N,CCW) are mathematically equivalent. If other information capable of identifying pulse information is stored in the non-volatile memory 9, a process substantially similar to that of the above-described embodiment can be realized. In the counting process of the segment counter in the present invention, the conditions related to the output state of the sensor element SE and the pulse voltage polarity include not only conditions directly using the information, but also equivalent conditions that can be mathematically derived using other information.

[0164] The arithmetic unit 4 performs arithmetic processing using information capable of identifying pulse information stored in the nonvolatile memory 9. In the correction processing, the arithmetic unit 4 reads the information capable of identifying pulse information from the nonvolatile memory 9 (step S2 in FIG. 11), identifies the polarity of the immediately preceding pulse voltage from the read information, and determines the correction direction based on the identified polarity (step S6).

[0165] In the above embodiment, an example of a magnetic field source that is composed of four individual magnets and has four magnetic poles has been shown, but the magnetic field source may be composed of a ring-shaped multi-pole magnetized magnet surrounding the rotation axis 33. For example, a ring-shaped hard magnetic body can be used as a magnetic field source by providing local magnetized areas (four magnetized areas) spaced apart in the circumferential direction at positions similar to those of the magnets M1 to M4 to form four magnetic poles. The magnetization direction is parallel to the rotation axis 33. The four-pole magnetized ring magnet thus obtained has a configuration in which, when viewed from one direction of the rotation axis 33, four magnetic poles are arranged on a circumference centered on the rotation axis 33, with N poles and S poles arranged alternately. The arrangement interval λ of the four magnetic poles (magnetized areas) on the track 51 is preferably longer than the total length Lw of the magnetic wire FE, and more preferably is 1.5 times or more the total length Lw of the magnetic wire FE. Moreover, the length α (length along the track 51) of the magnetic pole (magnetized region) on the track 51 is preferably shorter than the total length Lw of the magnetic wire FE and is 50% or less of the magnetic pole arrangement interval λ. The length α of the magnetic pole on the track 51 is preferably half or less of the total length Lw of the magnetic wire FE.

[0166] Furthermore, the magnetic poles do not have to be magnets (magnetized hard magnetic bodies); for example, a soft magnetic body (yoke) that guides magnetic flux from the magnet can be provided, and the surface (typically the end face) of that soft magnetic body can be used as the magnetic pole.

[0167] In addition, in the above-described embodiment, the axially orthogonal portion of the magnetic flux conducting piece has a first portion extending from the magnetic wire FE toward the detection region SR and a second portion extending from the magnetic wire FE toward the opposite side of the detection region SR, but omitting the second portion has no substantial effect on the magnetic flux conducting function (magnetic collecting function).

[0168] In the above embodiment, the power generation sensor 20 has L-shaped magnetic flux conducting pieces FL1 and FL2, but the magnetic flux conducting pieces may have other shapes. For example, an I-shaped magnetic flux conducting piece extending linearly from the magnetic wire FE toward the detection area may be used. Alternatively, the magnetic wire may have cylindrical magnetic flux conducting pieces at both ends, each having a size similar to that of a coil.

[0169] Furthermore, the precision absolute angle detector 1 does not necessarily mean a single detector, but may be any detector that has the function of obtaining the absolute angle within one rotation. For example, the precision absolute angle detector 1 may be configured with multiple detectors with a detection range of one rotation or less. As an example, the angle per one cycle / revolution may be calculated from the detection signal of a detector with 32 cycles / revolution and the detection signal of a detector with 31 cycles / revolution. This calculation may also be performed by the calculation device 4.

[0170] In addition, various design modifications can be made within the scope of the claims. [Explanation of symbols]

[0171] 1: Precision absolute angle detector 2: Segment counter 3: Power supply circuit 4: Arithmetic device 5: Signal evaluation circuit 6: Rectification / power supply circuit 7: Signal processing circuit 8: Counter circuit 9: Non-volatile memory 10: Counter memory IC 20: Power generation sensor 30: Rotation axis 31: First support 32: Second support 33: Rotation axis 50: Magnetic field source 100: Multi-rotation angle detection device FE: Magnetic wire FL1: First magnetic flux conducting piece FL2: Second magnetic flux conducting piece M1,M2,M3,M4: Magnet SE: Sensor element SP: Coil SR: Detection area n1,n2 :N pole s1,s2 :S pole Lw: Total length of magnetic wire x: Axial direction λ: Magnetic pole spacing α: Length of magnetic pole

Claims

1. A multiple rotation angle detection device that generates multiple rotation absolute angle detection values ​​of a rotating body that rotates around a rotation axis, a segment counter that counts segments obtained by dividing one rotation period of the rotating body into two segments in an angle range exceeding one rotation of the rotating body in response to rotation of the rotating body, thereby generating a count value; a precision absolute angle detector that operates by an external power supply and generates an absolute angle detection value within one rotation period of the rotating body with a resolution higher than that of the segment; a calculation unit that operates by an external power supply and that combines the count value of the segment counter and the absolute angle detection value of the precision absolute angle detector to generate a multiple rotation absolute angle detection value of the rotating body, the segment counter includes one power generation sensor, a magnetic field generating source that rotates around the rotation axis together with the rotating body, a sensor element that is provided separately from the power generation sensor and that is in either a first output state or a second output state depending on the rotational position of the rotating body, and a non-volatile memory that stores the count value; The power generation sensor includes a magnetic wire that exhibits the large Barkhausen effect and a coil wound around the magnetic wire, the magnetic field generating source applies an alternating magnetic field of two periods per rotation to the magnetic wire in the axial direction as the rotor rotates, and in response to this, the power generating sensor generates a pulse voltage of four pulses per rotation of the rotor; The segment counter is operable by energy of the pulse voltage generated by the power generating sensor without receiving an external power supply, and when the power generating sensor generates a pulse voltage, identifies the rotation direction and rotation position of the rotating body based on pulse information representing the output state of the sensor element and the polarity of the pulse voltage generated by the power generating sensor, stores information that can identify the pulse information in the nonvolatile memory, updates the count value using the pulse information and information that can identify the pulse information at the time of the previous pulse voltage generation, and stores the updated count value in the nonvolatile memory. the segment counter increments the count value when the power generation sensor generates a pulse voltage of a first polarity while the sensor element is in the first output state and the pulse information differs from the pulse information when the immediately preceding pulse voltage is generated, and decrements the count value to update the count value when the power generation sensor generates a pulse voltage of a second polarity while the sensor element is in the first output state and the pulse information differs from the pulse information when the immediately preceding pulse voltage is generated, thereby performing a counting operation twice per rotation of the rotating body; When the sensor element is in the second output state, if a count value update omission occurs in which the count value is not updated due to an effect of a lack of pulse voltage caused by the reversal of the rotation direction, the segment counter corrects the count value to compensate for the count value update omission, when power is supplied from an external source, the arithmetic unit uses the count value stored in the nonvolatile memory and information capable of identifying the pulse information to integrate the count value of the segment counter and the absolute angle detection value of the precision absolute angle detector, thereby generating a multiple rotation absolute angle detection value of the rotating body; When the absolute angle detection value belongs to one of two predetermined angle regions each including a rotation position at which the pulse voltage is generated when the sensor element is in the second output state and the absolute angle detection value and the count value are inconsistent during the integration, the calculation device determines a correction direction based on the polarity of the pulse voltage immediately before the polarity is specified from information that can identify the pulse information, and performs correction processing.

2. The segment counter is When the power generation sensor generates a pulse voltage of the first polarity while the sensor element is in the second output state, the count value is decremented if the pulse information at the time of the previous pulse voltage generation indicates the first output state and the first polarity; When the power generation sensor generates a pulse voltage of the second polarity while the sensor element is in the second output state, the count value is incremented if the pulse information at the time of the previous pulse voltage generation indicates the first output state and the second polarity.

2. The multiple rotation angle detection device according to claim 1, wherein the count value is corrected so as to compensate for an omission in updating the count value due to an influence of a lack of pulse voltage caused by the reversal of the rotation direction.

3. 2. The multi-rotation angle detection device according to claim 1, wherein the information that can identify the pulse information includes any two or more pieces of information selected from the output state of the sensor element, the polarity of the pulse voltage, and the rotation direction identified by the pulse information.

4. The multi-rotation angle detection device according to claim 1 , wherein the sensor element includes a magnetic sensor that responds to the magnetic field generated by the magnetic field generating source.

5. 2. The multi-rotation angle detection device according to claim 1, wherein signal processing is performed using an intermediate position between a position where the pulse voltage of the first polarity is generated and a position where the pulse voltage of the second polarity is generated when the sensor element is in the second output state as an origin of angle detection.

6. The computing device a first step of calculating a rotation speed by adding the absolute angle detection value and the count value read from the nonvolatile memory to each other, subtracting one from the other after combining them into a unit amount, and converting the result of the subtraction into a rotation speed unit and making it an integer; a second step of calculating a multiple rotation absolute angle detection value by adding together the rotation speeds calculated in the first step and the absolute angle detection value after combining them into unit amounts.

7. 7. The multi-rotation angle detection device according to claim 6, wherein the calculation device performs the correction process on the target value for integer conversion in the first step or the rotation number obtained by the integer conversion in the first step, based on the determined correction direction.

8. The power generation sensor includes a pair of magnetic flux conducting pieces made of soft magnetic materials symmetrical to each other with respect to a symmetry plane set at the center position of the axial direction of the magnetic wire, The pair of magnetic flux conduction pieces include a pair of axis-orthogonal portions extending parallel to each other in an axis-orthogonal direction perpendicular to the axial direction from both end portions of the magnetic wire, and a pair of axis-parallel portions extending in a direction approaching each other along the axial direction from tip ends of the pair of axis-orthogonal portions, with proximal ends facing each other with a gap in the axial direction, and have a wire placement portion consisting of a hole or groove penetrating in the axial direction to which the axis-orthogonal portions and both end portions of the magnetic wire are fixed, the power generation sensor is configured to have a detection area on the side opposite to the magnetic wire with respect to the axially parallel portion, the magnetic field generating source has four magnetic poles fixed to the rotating body such that, when the rotating body rotates, the magnetic poles sequentially enter the detection area through a track having a portion along the axial direction of the magnetic wire, and the magnetic poles of different polarities alternately face the power generating sensor via an air gap; The direction of the magnetic flux of each magnetic pole is perpendicular to the direction of movement of the magnetic pole and intersects with the magnetic wire when facing the power generation sensor, The arrangement interval of the four magnetic poles on the track is longer than the total length of the magnetic wire, 6. The multi-rotation angle detection device according to claim 1, wherein the length of the magnetic poles on the track is shorter than the entire length of the magnetic wire and is 50% or less of the arrangement interval.

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