Rotation detector

Abstract

Detecting coils (112 to 114) generate a positive or negative voltage pulse. Each time a voltage pulse is generated, a controller (125) receives electric power of the voltage pulse, and operates to acquire states of the detecting coils, information relating to the detecting coil that generated the voltage pulse, and a rotational speed of a rotating shaft (115), and updates a non-volatile memory (127). During the update, the controller (125) detects a pulse omission with reference to information relating to the current voltage pulse, a history of the states of the detecting coils when the last voltage pulse and the last-but-one voltage pulse were generated, and a history of information relating to the detecting coil that generated the last-but-one voltage pulse, said histories being held in the non-volatile memory (127), and corrects the states of the detecting coils and the rotational speed, held in the non-volatile memory (127).

Description

[Technical Field]

[0001] The present disclosure relates to a rotation detector. [Background technology]

[0002] International Publication No. 2013 / 157279 (Patent Document 1) discloses a battery-less rotation detector that detects and holds the rotation direction and rotation speed of a rotating shaft without receiving power from an external source.

[0003] The rotation detector described in Patent Document 1 includes a magnet that rotates in synchronization with the rotating shaft, multiple detection coils that each receive a magnetic field from the magnet and generate a voltage pulse, and a signal processing circuit that operates by receiving power from the voltage pulse. In Patent Document 1, each time one of the multiple detection coils generates a voltage pulse, the rotation position of the magnet estimated from the voltage pulse is stored in non-volatile memory. By storing not only the current rotation position of the magnet but also the previous rotation position in non-volatile memory, the signal processing circuit can detect the occurrence of a "pulse missing" - a missing voltage pulse immediately after the rotation direction of the rotating shaft is reversed - and estimate the correct rotation position taking this into account. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2013 / 157279 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the rotation detector described in Patent Document 1 can deal with pulse missing immediately after the rotation direction of the rotating shaft is reversed, but has the problem of not being able to deal with pulse missing caused by other factors. For example, a voltage pulse may not be generated or the voltage level of the voltage pulse may drop significantly due to a quality problem in a component that generates the voltage pulse, such as a detection coil. Alternatively, a circuit that detects the voltage pulse may fail.

[0006] When such a situation occurs, the rotation detector described in Patent Document 1 is unable to estimate the rotation position due to unexpected operation, and as a result outputs an error. Once an error occurs, the device incorporating the encoder cannot continue to operate, and the device must be stopped and restored. This raises concerns about damage caused by the device being unable to operate.

[0007] The present disclosure has been made to solve such problems, and an object of the present disclosure is to improve the accuracy of correction of the rotation speed for missing detection of voltage pulses in a rotation detector that detects the rotation speed of a rotating shaft based on voltage pulses generated from a detection coil. [Means for solving the problem]

[0008] A rotation detector according to the present disclosure detects the rotation direction and rotation speed of a rotating shaft. The rotation detector includes a rotation detection mechanism attached to the rotating shaft to detect the rotation of the rotating shaft, and a signal processing circuit electrically connected to the rotation detection mechanism. The rotation detection mechanism includes a magnet and L detection coils (L is a natural number greater than or equal to 3). The magnet is configured to rotate synchronously with the rotating shaft and has N magnetic poles (N is a natural number greater than or equal to 2) arranged in the rotation direction. The L detection coils are arranged at positions offset from each other by a predetermined phase along the rotation direction of the magnet. Each of the L detection coils is configured to receive a magnetic field from the magnet and generate a voltage pulse of positive or negative polarity every half cycle of the magnet's rotation period. The signal processing circuit includes a constant voltage circuit that generates a power supply voltage from the power of the voltage pulse each time a voltage pulse is generated, a controller that operates by receiving the power supply voltage, and a nonvolatile memory. The nonvolatile memory is configured to store the states of the L detection coils when the voltage pulse is generated, the rotation speed of the rotating shaft, and history information about the detection coil that generated the voltage pulse. The controller is configured to execute a process of acquiring the states of the L detector coils, information about the detector coil that generated the voltage pulse, and the rotation speed of the rotating shaft each time a voltage pulse is generated, and updating the nonvolatile memory. In the updating process, the controller detects a missing voltage pulse by referencing the information about the current voltage pulse and the history of information about the L detector coils when the previous voltage pulse was generated, the L detector coils when the voltage pulse before last was generated, and the detector coils that generated the voltage pulse before last, which are stored in the nonvolatile memory, and corrects the states of the L detector coils and the rotation speed of the rotating shaft stored in the nonvolatile memory. [Effects of the Invention]

[0009] According to the present disclosure, in a rotation detector that detects the rotation speed of a rotating shaft based on voltage pulses generated from a detection coil, it is possible to improve the accuracy of correcting the rotation speed in response to missing voltage pulses. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing an overall configuration of a rotation detector according to a first embodiment. [Figure 2] FIG. 2 is a diagram illustrating a configuration example of a rotation detection mechanism. [Figure 3] 1 is a diagram schematically showing the relationship between the magnetization of a magnetic wire and an external magnetic field. FIG. [Figure 4] 10 is a diagram showing the relationship between an external magnetic field applied to a detection coil from a rotating magnet and a voltage pulse output from the detection coil. FIG. [Figure 5] FIG. 4 is a waveform diagram of a voltage pulse generated from a detection coil. [Figure 6] 10 is a diagram showing changes in the state signals of the A-phase detection coil, the B-phase detection coil, and the C-phase detection coil when the magnet is rotating. FIG. [Figure 7] FIG. 2 is a diagram illustrating a hardware configuration of a signal processing circuit. [Figure 8] FIG. 10 shows a conversion table used in the update process according to the first embodiment. [Figure 9] FIG. 10 shows a conversion table used in the update process according to the first embodiment. [Figure 10] FIG. 10 is a diagram illustrating an example of a pattern in which a missing pulse occurs. [Figure 11] FIG. 10 is a diagram showing an overall configuration of a rotation detector according to a second embodiment. [Figure 12] FIG. 10 shows a conversion table used in the update process according to the second embodiment. [Figure 13] FIG. 10 shows a conversion table used in the update process according to the second embodiment. [Figure 14] FIG. 10 is a diagram showing an overall configuration of a rotation detector according to a third embodiment. [Figure 15] FIG. 10 is a diagram showing an overall configuration of a rotation detector according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0012] Embodiment 1 (Overall configuration of rotation detector) 1 is a diagram showing the overall configuration of a rotation detector according to embodiment 1. Rotation detector 101 according to embodiment 1 is a battery-less rotation detector, and is configured to detect and hold the rotation direction and rotation speed of a rotating body without receiving power from an external source.

[0013] 1, the rotation detector 101 includes a rotation detection mechanism 110 and a signal processing circuit 120. The signal processing circuit 120 is electrically connected to the rotation detection mechanism 110.

[0014] The rotation detection mechanism 110 is attached to a rotating shaft 115 and is configured to detect the rotation of the rotating shaft 115. The rotating shaft 115 is, for example, the output shaft of a motor. Note that the rotation detection mechanism 110 is not limited to the rotating shaft 115, and can be applied to any rotating body that can rotate around an axis.

[0015] The rotation detection mechanism 110 has a magnet 111 and detection coils 112, 113, and 114. The magnet 111 has a disk shape and is attached concentrically to a rotating shaft 115. The magnet 111 has two magnetic poles (N pole and S pole) on each half circumference. The magnet 111 rotates together with the rotating shaft 115 in a CW (clockwise) direction or a CCW (counterclockwise) direction. The CW (clockwise) direction is the right rotation direction (forward rotation) when viewed from the rotating shaft 115, and the CCW (counterclockwise) direction is the left rotation direction (reverse rotation) when viewed from the rotating shaft 115.

[0016] 1, the rotating shaft 115 and the magnet 111 are arranged concentrically, but it is sufficient that the magnet 111 rotates in synchronization with the rotation of the rotating shaft 115. Furthermore, the number of magnetic poles of the magnet 111 may be two or more.

[0017] The detection coils 112, 113, and 114 are arranged at intervals in the rotation direction of the magnet 111 so as to surround the outer periphery of the magnet 111. Each of the detection coils 112, 113, and 114 is formed of a magnetic wire that exhibits the large Barkhausen effect. The magnetic wire is configured using a hard magnetic material inside the wire and a soft magnetic material outside the wire. In the following description, the detection coil 112 will also be referred to as the "A-phase detection coil," the detection coil 113 will also be referred to as the "B-phase detection coil," and the detection coil 114 will also be referred to as the "C-phase detection coil." Note that the number of detection coils is not limited to three, and may be three or more.

[0018] (Configuration of rotation detection mechanism) Next, the configuration and operation of the rotation detection mechanism 110 shown in FIG. 1 will be described.

[0019] Fig. 2 is a diagram showing an example of the configuration of the rotation detection mechanism 110. The positional relationship between the magnet 111 and the detection coils 112, 113, and 114 will be described using Fig. 2. Furthermore, the detection logic for the number of rotations of the rotating shaft 115 using the rotation detection mechanism 110 will be described.

[0020] 2, the detection coils 112, 113, and 114 are arranged to extend in the radial direction of the magnet 111, at positions that are shifted from one another by a predetermined phase in the rotational direction of the magnet 111. In the example of FIG. 2, at the central angle of the magnet 111, the A-phase detection coil 112 is arranged at a position 60° in the CW direction from the B-phase detection coil 113, and the C-phase detection coil 114 is arranged at a position 60° in the CCW direction from the B-phase detection coil 113. However, the arrangement positions of the detection coils 112, 113, and 114 are not limited to this.

[0021] Then, six angular regions are formed around the magnet 111, based on the "origin position (0°)" according to the arrangement of the detection coils 112, 113, and 114. Specifically, the arrangement position of the B-phase detection coil 113 is set as the "origin position," and "region 1" to "region 6" are formed every 60° in the clockwise direction. Also, the angular position where the magnet 111 changes from south pole to north pole in the clockwise direction is set as the "magnet reference."

[0022] In the magnetic wire constituting each of the detection coils 112, 113, and 114, the soft magnetic material has magnetization characteristics as shown in FIG. 3. FIG. 3 is a diagram schematically illustrating the relationship between the magnetization M of the magnetic wire and the external magnetic field H. As shown in FIG. 3, the magnetic wire exhibits a behavior in which the magnetization M suddenly reverses when the strength of the external magnetic field H exceeds a certain value (the Great Barkhausen effect). The reversal speed of the magnetization M at this time is always constant, regardless of how the external magnetic field H is applied. Therefore, in this embodiment, by utilizing this magnetization characteristic, a detection coil made of magnetic wire is disposed on the outer periphery of the magnet 111 that rotates together with the rotating shaft 115, so that a constant voltage pulse can be generated from the detection coil at all times, regardless of the rotation speed of the rotating shaft 115 (i.e., the magnet 111).

[0023] Figure 4 shows the relationship between the external magnetic field applied to the detection coil from the rotating magnet 111 and the voltage pulse output from the detection coil. The upper part of Figure 4 shows the relationship between the external magnetic field (dashed line) and the voltage pulse (solid line) when the magnet 111 is rotating in the CW direction. The lower part of Figure 4 shows the relationship between the external magnetic field (dashed line) and the voltage pulse (solid line) when the magnet 111 is rotating in the CCW direction.

[0024] As shown in FIG. 4, when magnet 111 rotates at a constant speed together with rotating shaft 115, the external magnetic field applied to the detection coil has a sinusoidal waveform with one cycle being the time it takes magnet 111 to rotate once.

[0025] The detection coil generates one voltage pulse for each half cycle of the external magnetic field. The detection coil generates a positive voltage pulse during the positive half cycle of the external magnetic field and a negative voltage pulse during the negative half cycle of the external magnetic field. Therefore, by detecting these voltage pulses, the rotation detector 101 can count the number of rotations of the rotating shaft 115. Furthermore, by utilizing the power of these voltage pulses, a battery-less rotation detector 101 can be realized.

[0026] The timing at which positive and negative voltage pulses are generated differs depending on the rotation direction of magnet 111. In Fig. 4, the position at which the voltage pulse is generated in the CW direction is shifted by an angle φ from the position at which the voltage pulse is generated in the CCW direction.

[0027] Returning to FIG. 2, each of the detection coils 112, 113, and 114 arranged around the outer periphery of the magnet 111 generates positive and negative voltage pulses in response to the rotation of the magnet 111 (rotation shaft 115). FIG. 5 is a waveform diagram of the voltage pulses generated by the detection coils 112, 113, and 114. FIG. 5(a) is a waveform diagram of the voltage pulses generated by the detection coils 112, 113, and 114 when the magnet 111 rotates in the CW direction. FIG. 5(b) is a waveform diagram of the voltage pulses generated by the detection coils 112, 113, and 114 when the magnet 111 rotates in the CCW direction. Note that in each diagram, "A-phase pulse" indicates the voltage pulse of the A-phase detection coil 112, "B-phase pulse" indicates the voltage pulse of the B-phase detection coil 113, and "C-phase pulse" indicates the voltage pulse of the C-phase detection coil 114.

[0028] 5(a) shows the waveforms of the A-phase pulse, B-phase pulse, and C-phase pulse when the magnet 111 rotates once in the CW direction, i.e., when the magnet reference position changes from 0° (origin position) to 360°. In the example of FIG. 2, the A-phase detection coil 112 is placed at a position of 60°, the B-phase detection coil 113 is placed at the origin position (0°), and the C-phase detection coil 114 is placed at a position of 300°.

[0029] As described with reference to FIG. 4, each of the detection coils 112, 113, and 114 generates a positive or negative voltage pulse every half rotation period of the magnet 111. However, the generation position of each voltage pulse is not the arrangement position of the corresponding detection coil, but a position shifted by an angle φ / 2 from the arrangement position. For example, the generation position of a positive A-phase pulse is shifted by φ / 2 in the CW direction from the arrangement position of the A-phase detection coil 112 at 60°. Furthermore, the generation position of a negative A-phase pulse is shifted by φ / 2 in the CW direction from the position 240°, which is symmetrical to the arrangement position of the A-phase detection coil 112 at 60°. This is because, as shown in FIG. 3, after the external magnetic field generated by the magnet 111 is reversed, the magnetization M of the magnetic wire does not reverse unless the external magnetic field reaches a certain strength (hereinafter also referred to as a threshold). In this way, when the rotation direction of the magnet 111 is the CW direction, the generation position of each voltage pulse is shifted in the CW direction from the arrangement position of the corresponding detection coil.

[0030] Figure 5(b) shows the waveforms of the A-phase pulse, B-phase pulse, and C-phase pulse when the magnet 111 rotates once in the CCW direction, i.e., when the magnet reference position changes from 360° to 0° (origin position).

[0031] 5(b), similarly to FIG. 5(a), the generation positions of the A-phase pulse, B-phase pulse, and C-phase pulse are not the same as the arrangement positions of the corresponding detection coils, but are positions shifted by an angle φ / 2 from the arrangement positions. However, when the rotation direction of magnet 111 is the CCW direction, the generation positions of the voltage pulses are positions shifted in the CCW direction from the arrangement positions of the corresponding detection coils.

[0032] As described above, each of the A-phase detection coil 112, the B-phase detection coil 113, and the C-phase detection coil 114 generates positive and negative voltage pulses in response to the rotation of the magnet 111. The rotation detection mechanism 110 transmits the voltage pulses output from the phase detection coils to the signal processing circuit 120. The signal processing circuit 120 generates its power supply voltage using the power of the voltage pulses transmitted from the rotation detection mechanism 110. The signal processing circuit 120 also detects the rotation direction and rotation speed of the rotating shaft 115 based on the voltage pulses.

[0033] To detect the rotation speed of the rotating shaft 115, it is first necessary to generate status signals indicating the status of the A-phase detection coil 112, the B-phase detection coil 113, and the C-phase detection coil 114. The status signals for each phase detection coil can be generated based on the voltage pulses generated by the phase detection coil.

[0034] Specifically, the status signal of each phase detection coil can be generated so that it rises from L (logic low) level to H (logic high) level when a positive voltage pulse is generated, and falls from H level to L level when a negative voltage pulse is generated. That is, the status signal of each phase detection coil is held at H level from the time the corresponding detection coil generates a positive voltage pulse until it generates a negative voltage pulse, and is held at L level from the time the corresponding detection coil generates a negative voltage pulse until it generates a positive voltage pulse. In this way, the status signal of each phase detection coil is a signal that indicates the polarity of the last voltage pulse generated by the corresponding detection coil.

[0035] 6A and 6B are diagrams showing changes in the status signals of the A-phase detection coil 112, the B-phase detection coil 113, and the C-phase detection coil 114 when the magnet 111 is rotating. Fig. 6A shows changes in the status signals of the detection coils of each phase when the magnet 111 is rotating in the CW direction, and Fig. 6B shows changes in the status signals of the detection coils of each phase when the magnet 111 is rotating in the CCW direction. As shown in Figs. 6A and 6B, each status signal alternates between H level and L level every 180° (half cycle).

[0036] Here, consider the case where the rotation count data is changed near the "origin position" shown in Figure 2 (i.e., the case where the rotation count is counted). Specifically, when the magnet 111 rotates in the CW direction from the state where the magnet reference is at the origin position (Figure 2), and the magnet reference passes the origin position again, the rotation count (count value) is increased by +1 (count up). Also, when the magnet 111 rotates in the CCW direction from the state where the magnet reference is at the origin position, and the magnet reference passes the origin position again, the rotation count (count value) is decreased by -1 (count down).

[0037] 6(a), when the status signal of the A-phase detection coil 112 is at H level and it is detected that the status signal of the B-phase detection coil 113 has fallen from H level to L level, it is determined that the magnet reference has passed the origin position in the CW direction, and the number of rotations is increased by +1.Also, when the status signal of the A-phase detection coil 112 is at H level and it is detected that the status signal of the B-phase detection coil 113 has risen from L level to H level, it is determined that the magnet reference has passed the origin position in the CCW direction, and the number of rotations is decreased by -1.

[0038] Alternatively, the rotation speed can be increased by +1 when the status signal of the C-phase detection coil 114 is at L level and a falling edge of the status signal of the B-phase detection coil 113 is detected, and decreased by -1 when the status signal of the C-phase detection coil 114 is at L level and a rising edge of the status signal of the B-phase detection coil 113 is detected.

[0039] Alternatively, the rotation speed can be increased by +1 when the status signal of the A-phase detection coil 112 is at H level, the status signal of the C-phase detection coil 114 is at L level, and a falling edge of the status signal of the B-phase detection coil 113 is detected, and the rotation speed can be decreased by -1 when the status signal of the A-phase detection coil 112 is at H level, the status signal of the C-phase detection coil 114 is at L level, and a rising edge of the status signal of the B-phase detection coil 113 is detected.

[0040] Furthermore, by looking at the status signals of the detection coils of each phase, it is possible to estimate in which region the magnet reference is located, i.e., the rotational position of the magnet 111. For example, when the status signal of the A-phase detection coil 112 is at H level, the status signal of the B-phase detection coil 113 is at L level, and the status signal of the C-phase detection coil 114 is at L level, it can be estimated that the magnet reference is located in region 1. According to this, when the magnet reference moves from region 6 to region 1, it can be determined that the magnet 111 has made one rotation in the CW direction, and the number of rotations can be increased by +1, and when the magnet reference moves from region 1 to region 6, it can be determined that the magnet 111 has made one rotation in the CCW direction, and the number of rotations can be decreased by -1.

[0041] (Configuration of signal processing circuit) Next, the configuration and operation of the signal processing circuit 120 shown in FIG. 1 will be described.

[0042] Fig. 7 is a diagram showing the hardware configuration of the signal processing circuit 120. As shown in Fig. 7, the signal processing circuit 120 includes a CPU (Central Processing Unit) 10, a RAM (Random Access Memory) 11, a ROM (Read Only Memory) 12, an I / F (Interface) device 13, and a storage device 14. The CPU 10, RAM 11, ROM 12, I / F device 13, and storage device 14 exchange various data via a communication bus 15.

[0043] The CPU 10 loads a program stored in the ROM 12 into the RAM 11 and executes it. The program stored in the ROM 12 describes the processing to be executed by the signal processing circuit 120.

[0044] The I / F device 13 is an input / output device for exchanging signals and data with the rotation detection mechanism 110 and external devices. The I / F device 13 receives voltage pulses output by the detection coils 112, 113, and 114 from the rotation detection mechanism 110.

[0045] The memory device 14 is a storage for storing various types of information, such as information about the rotation detection mechanism 110 and information about the rotating body. The memory device 14 also has an updatable nonvolatile memory for storing information (such as the state of the detection coil and the number of rotations of the rotating shaft 115) obtained from the voltage pulse received from the rotation detection mechanism 110. The nonvolatile memory will be described in detail later.

[0046] All or part of the functions realized by the CPU 10 executing the programs may be realized using a hard-wired circuit such as an integrated circuit, for example, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a CPLD (Complex Programmable Logic Device).

[0047] Returning to Fig. 1, the functional configuration of the signal processing circuit 120 will be described. The signal processing circuit 120 includes full-wave rectifier circuits 121_A, 121_B, and 121_C, a constant voltage circuit 122, an enable circuit 123, a pulse waveform code determination circuit 124, a controller 125, an adder 126, a nonvolatile memory 127, an external circuit I / F 128, and a power supply switching circuit 129. Of these, at least the controller 125 and the adder 126 are realized by the CPU 10 shown in Fig. 7 (see Fig. 7) executing a program.

[0048] The signal processing circuit 120 executes a series of operations described below every time any of the detection coils 112, 113, and 114 in the rotation detection mechanism 110 outputs a voltage pulse.

[0049] The full-wave rectifier circuit 121_A is electrically connected to the A-phase detection coil 112, full-wave rectifies the voltage pulse (A-phase pulse) output from the A-phase detection coil 112, and outputs the rectified voltage pulse to the constant voltage circuit 122.

[0050] The full-wave rectifier circuit 121_B is electrically connected to the B-phase detection coil 113, full-wave rectifies the voltage pulse (B-phase pulse) output from the B-phase detection coil 113, and outputs the rectified voltage pulse to the constant voltage circuit 122.

[0051] The full-wave rectifier circuit 121_C is electrically connected to the C-phase detection coil 114, full-wave rectifies the voltage pulse (C-phase pulse) output from the C-phase detection coil 114, and outputs the rectified voltage pulse to the constant voltage circuit 122.

[0052] The constant voltage circuit 122 generates a constant voltage from a voltage pulse provided from one of the full-wave rectifier circuits 121_A, 121_B, and 121_C, and supplies the generated constant voltage as a power supply voltage to the enable circuit 123, the pulse waveform code determination circuit 124, the controller 125, the adder 126, and the non-volatile memory 127.

[0053] The power supply switching circuit 129 is configured to be able to switch the power supply source for the controller 125 and the nonvolatile memory 127 between the constant voltage circuit 122 and an external power supply (not shown) provided outside the rotation detector 101. The external power supply is the main power supply for driving the rotating body. This allows power to continue to be supplied to the controller 125 and the nonvolatile memory 127 even when the rotating shaft 115 is stopped.

[0054] Nonvolatile memory 127 stores the state of the detection coil for each phase when a voltage pulse is generated, the number of rotations of rotating shaft 115, and information about the detection coil that generated the voltage pulse (detection coil number). This information is acquired each time any of detection coils 112, 113, and 114 generates a voltage pulse and stored in nonvolatile memory 127. Nonvolatile memory 127 also stores conversion tables (see FIGS. 8 and 9) described below.

[0055] The nonvolatile memory 127 is configured to store, with regard to the state of the detector coils of each phase and the information on the detector coils that generated the voltage pulses, at least information on the state of the detector coils of each phase when the previous voltage pulse was generated and the detector coil that generated the previous voltage pulse, as well as information on the state of the detector coils of each phase when the voltage pulse before last was generated and the detector coil that output the voltage pulse before last. This information is updated by the controller 125 every time a voltage pulse is generated.

[0056] When the enable circuit 123 confirms that the voltage supplied from the constant voltage circuit 122 has stabilized, it sends a trigger signal to the pulse waveform code determination circuit 124, the controller 125, the adder 126, and the non-volatile memory 127 to start their operation.

[0057] The pulse waveform code determination circuit 124 starts operating upon receiving a trigger signal from the enable circuit 123. The pulse waveform code determination circuit 124 generates a detection signal for the A-phase detection coil 112 based on the voltage pulse (A-phase pulse) output from the A-phase detection coil 112, generates a detection signal for the B-phase detection coil 113 based on the voltage pulse (B-phase pulse) output from the B-phase detection coil 113, and generates a detection signal for the C-phase detection coil 114 based on the voltage pulse (C-phase pulse) output from the C-phase detection coil 114.

[0058] The detection signal of each phase detection coil indicates whether a voltage pulse is generated from the corresponding phase detection coil and the polarity of the generated voltage pulse. The detection signal goes high when the corresponding detection coil generates a positive voltage pulse, low when the corresponding detection coil generates a negative voltage pulse, and zero when the corresponding detection coil does not generate a voltage pulse. In other words, the detection signal records information about the voltage pulse generated by each phase detection coil as a history. The pulse waveform sign determination circuit 124 transmits the generated detection signal to the controller 125.

[0059] The controller 125 transmits the detection signals of the detection coils of each phase received from the pulse waveform code determination circuit 124 to the adder 126. The controller 125 further accesses the nonvolatile memory 127 to read from the nonvolatile memory 127 the number of rotations of the rotating shaft 115 when the previous voltage pulse was generated, the state of the detection coils of each phase when the previous voltage pulse was generated and information about the detection coil that generated that voltage pulse, and the state of the detection coils of each phase when the voltage pulse before last was generated and information about the detection coil that output that voltage pulse. The controller 125 transmits this read information to the adder 126.

[0060] The adder 126 updates the state and rotation speed of each phase detection coil to the latest state and rotation speed of each phase detection coil using a conversion table (see FIGS. 8 and 9) described later based on the information received from the controller 125 (the state signal of each phase detection coil when the current voltage pulse was generated and the information read from the nonvolatile memory 127). The adder 126 transmits the updated latest state and rotation speed of each phase detection coil to the controller 125.

[0061] When the controller 125 receives the information from the adder 126, it again accesses the nonvolatile memory 127 and writes into the nonvolatile memory 127 the latest state and rotation speed of each phase detection coil, as well as information about the detection coil that generated the current voltage pulse.

[0062] The signal processing circuit 120 performs the above-mentioned series of operations using the power supply voltage generated from the voltage pulse each time one of the detection coils 112, 113, and 114 outputs a voltage pulse, thereby enabling the signal processing circuit 120 to detect the rotation speed of the rotating shaft 115 without a battery.

[0063] When reading the rotation count of the rotating shaft 115 from outside the rotation detector 101, the rotation count can be read by accessing the nonvolatile memory 127 via the external circuit I / F 128 and the controller 125. At this time, the controller 125 is configured to restrict access to the nonvolatile memory 127 from outside so that the above-mentioned series of operations for updating the rotation count do not conflict with the operation of reading the rotation count from outside.

[0064] Furthermore, when nonvolatile memory 127 is accessed from the outside, power supply switching circuit 129 supplies power supply voltage from an external power supply (main power supply) to controller 125 and nonvolatile memory 127. Furthermore, power supply voltage is supplied directly from the external power supply to external circuit I / F 128. Therefore, the rotation speed can be read without depending on the power of the voltage pulse.

[0065] As a result, when power is supplied from an external power source, the information stored in nonvolatile memory 127 is called up into a register (not shown) built into signal processing circuit 120, and when it is detected that the power supply has ended, the information is stored from the register into nonvolatile memory 127, thereby making it possible to avoid conflicting accesses to nonvolatile memory 127.

[0066] (Update process) As described above, adder 126 executes a process of updating the states of the detection coils of each phase and the rotation speed of rotating shaft 115 stored in nonvolatile memory 127 based on the voltage pulses output from each of detection coils 112, 113, and 114 in response to the rotation of magnet 111. However, if a phenomenon occurs in which a voltage pulse is missing in at least one detection coil during the rotation of magnet 111 (hereinafter also referred to as "pulse missing"), adder 126 is configured to execute a correction process to compensate for the missing voltage pulse during the update process. The update process including this correction is executed in accordance with the conversion tables shown in FIGS. 8 and 9.

[0067] 8 and 9 show the transition of the state of each phase detection coil and the area where the magnet reference is located as the magnet 111 rotates. In this conversion table, the "current status" shows the state of each phase detection coil from the time when the previous voltage pulse is generated until the time when the current voltage pulse is generated, and the area where the magnet reference is located, estimated from the state of each phase detection coil.

[0068] The "previous status" indicates the state of each phase detection coil from the generation of the voltage pulse before last to the generation of the previous voltage pulse, and the area in which the magnet reference is located, estimated from the state of each phase detection coil. Note that the current status and the previous status are each updated in response to the generation of the current voltage pulse.

[0069] In the conversion table, "before update" means before the status was updated by the current voltage pulse, and "after update" means after the status was updated by the current voltage pulse. In addition to the "current status" and "previous status," the information before update includes information about the detection coil that generated the voltage pulse two times before last (referred to as the "second-to-last detection coil number").

[0070] In addition to the "current status" and "previous status," the updated information includes the correction amount (denoted as "count") for the count value of the number of rotations of the rotating shaft 115. Note that a value of "0" indicates that the number of rotations is not to be corrected, a value of "1" indicates that the number of rotations is to be increased by +1, and a value of "-1" indicates that the number of rotations is to be decreased by -1.

[0071] The conversion table further shows the detection signals (labeled "power generating element input") of each of the detection coils 112, 113, and 114. These detection signals are signals generated by the pulse waveform code determination circuit 124 (FIG. 1) described above. "H" indicates that the detection coil has generated a positive voltage pulse, "L" indicates that the detection coil has generated a negative voltage pulse, and "0" indicates that the detection coil has not generated a voltage pulse. When the detection signals are stored in nonvolatile memory 127, the information may be compressed by encoding the detection signals instead of using "0," "H," or "L."

[0072] When a state transition not shown in the conversion table appears, the signal processing circuit 120 determines that a phenomenon other than the expected missing pulse has occurred, and outputs an error.

[0073] The update process including the correction process executed by the adder 126 will be described below. Here, there are two types of "missing pulses": a missing pulse that occurs immediately after the rotation direction of the magnet 111 is reversed, and a missing pulse that occurs at a timing other than the above timing. The adder 126 performs correction processing for each of these two types of missing pulses.

[0074] First, a correction process for a missing pulse that occurs immediately after the rotation direction of the rotary shaft 115 is reversed will be described.

[0075] If the rotation direction of the magnet 111 reverses immediately after the detection coil generates a voltage pulse, a magnetic field of opposite polarity to the magnetic field that generated the voltage pulse due to the reversal of the magnet 111 is applied to the detection coil. Even if the strength of this applied magnetic field exceeds a threshold, the voltage level of the voltage pulse generated by the detection coil may decrease. If the voltage level of the voltage pulse decreases significantly, the signal processing circuit 120 cannot receive the power of the voltage pulse and operates, resulting in a missing pulse. As a result, a discrepancy occurs between the actual magnet reference position and the magnet reference position estimated from the state of the detection coils for each phase stored in the nonvolatile memory 127.

[0076] Here, as a "first example," let us assume that, starting from a situation in which the B-phase detection coil 113 is placed at the origin position and the magnet reference is at the origin position (see FIG. 2), the magnet reference moves in the CW direction from region 6 to region 1, causing the strength of the magnetic field applied to the B-phase detection coil 112 to exceed the threshold. As a result, a voltage pulse is generated from the B-phase detection coil 112. Thereafter, immediately after the generation of the voltage pulse, the rotation of the magnet 111 is reversed in the CCW direction, causing the magnet reference to return from region 1 to region 6.

[0077] At this time, in the rotation detector 101, as the magnet 111 rotates in the CCW direction, the strength of the magnetic field of the opposite polarity applied to the B-phase detection coil 113 exceeds the threshold. However, the voltage level of the voltage pulse generated by the B-phase detection coil 113 is small, and the signal processing circuit 120 does not operate, resulting in a "missing pulse." As a result, the controller 125 retains the state of each phase detection coil indicating that the magnet reference is located in region 1, without updating the state of each phase detection coil and the position of the magnet reference stored in the nonvolatile memory 127.

[0078] As the magnet 111 continues to rotate in the CCW direction, the strength of the magnetic field applied to the phase-C detection coil 114 exceeds the threshold, causing the phase-C detection coil 114 to generate a voltage pulse. However, as described above, the nonvolatile memory 127 retains the state of each phase detection coil when the magnet reference is located in region 1. On the other hand, when the magnet reference moves from region 1 to region 6 or region 2, only the phase-B detection coil 113 or the phase-A detection coil 112 generates a voltage pulse, but not the phase-C detection coil 114. Therefore, the adder 126 can detect that a missing pulse has occurred.

[0079] As in the first example above, the situation in which the C-phase detection coil 114 generates a voltage pulse while the state of each phase detection coil is held when the magnet reference is located in region 1 can also occur when the magnet reference moves in the CCW direction from region 2 to region 1 and then the rotation direction of the magnet 111 is reversed immediately thereafter. This case is referred to as the "second example."

[0080] In the second example, when the magnet reference returns from region 1 to region 2, a pulse drop occurs in the A-phase detection coil 112, and as the magnet 111 continues to rotate in the CW direction, the magnet reference moves to region 3, causing the C-phase detection coil 114 to generate a voltage pulse. In the second example, as in the first example, the magnet reference does not move from a state in which it is located in region 1 to a region in which the C-phase detection coil 114 generates a voltage pulse, so the adder 126 can detect that a pulse drop has occurred.

[0081] Here, in both the first and second examples, the magnet reference position estimated from the state of the detection coils for each phase when the previous voltage pulse was generated is in region 1, so it is not possible to distinguish between the first and second examples. Therefore, even if a missing pulse can be detected, it is not possible to correct the magnet reference position or the rotation speed.

[0082] On the other hand, the position of the magnet reference, estimated from the state of each phase detection coil when the voltage pulse two pulses ago was generated and stored in nonvolatile memory 127, is different: in the first example, it is region 6, while in the second example, it is region 2. Therefore, the first and second examples can be distinguished. Specifically, in the first example, a pulse drop occurred when the magnet reference moved from region 1 to region 6, and it can be estimated that the C-phase detection coil 114 generated a voltage pulse when the magnet reference moved from region 6 to region 5. Therefore, the state of each phase detection coil when the previous voltage pulse was generated, stored in nonvolatile memory 127, (current status) can be corrected to the state of each phase detection coil when the magnet reference was located in region 5, one region away from region 1 in the CCW direction, and the rotation speed can be reduced by -1. In the conversion table of FIG. 8, this correction process is shown as "first example."

[0083] In the second example, as in the first example, the state (current status) of each phase detection coil when the previous voltage pulse was generated and the rotation speed, which are stored in the nonvolatile memory 127, can be corrected. Specifically, in the second example, it can be estimated that a pulse drop occurred when the magnet reference moved from region 1 to region 2, and then the C-phase detection coil 114 generated a voltage pulse when the magnet reference moved from region 2 to region 3. Therefore, the state (current status) of each phase detection coil when the previous voltage pulse was generated and stored in the nonvolatile memory 127 can be corrected to the state of each phase detection coil when the magnet reference was located in region 3, which is one region jump in the clockwise direction from region 1. However, in the second example, the rotation speed is not corrected. In the conversion table of FIG. 8, this correction process is shown as "Second Example."

[0084] In this way, by referring to the state of the detection coils of each phase when the previous voltage pulse was generated, the state of the detection coils of each phase when the voltage pulse before that was generated, and the current voltage pulse (polarity and detection coil), it is possible to estimate the transition of the magnet-based position. As a result, it is possible to correct the state of the detection coils of each phase and the number of rotations stored in nonvolatile memory 127.

[0085] Next, a correction process for pulse dropouts occurring at timings other than the timing immediately after the rotation direction of the rotary shaft 115 is reversed will be described with reference to FIG.

[0086] Unlike the first and second examples described above, even in situations where the magnet 111 continues to rotate without reversing its rotation direction immediately after the detection coil generates a voltage pulse, or where a pulse drop occurs immediately after the magnet 111 reverses its rotation direction and continues to rotate, a pulse drop may occur due to quality issues or noise in the power generating and detection components. Even in these cases, the signal processing circuit 120 cannot operate with the power of the voltage pulse, resulting in a pulse drop. As a result, a discrepancy may occur between the actual magnet reference position and the magnet reference position estimated from the state of the detection coils for each phase stored in the nonvolatile memory 127.

[0087] 10, a case will be considered as a "third example" in which the B-phase detection coil 113 is placed at the origin position, and the magnet reference is at the origin position, and then the magnet reference moves in the CW direction from region 6 to region 1, region 2, region 3, and region 4 in that order. The solid arrows in the figure indicate the actual rotational movement of the magnet 111, and the dashed arrows indicate the rotational movement of the magnet 111 recognized by the signal processing circuit 120.

[0088] First, when the magnet reference moves in the CW direction from region 6 to region 1, a negative voltage pulse is generated from the B-phase detection coil 113. Accordingly, the adder 126 increases the number of rotations by +1.

[0089] Next, when the magnet reference moves from region 1 to region 2, it is assumed that even if the magnetic field strength exceeds the threshold in the A-phase detection coil 112, no voltage pulse is generated due to quality problems, noise, or the like.

[0090] Furthermore, when the magnet reference moves from region 2 to region 3, the phase C detection coil 114 generates a positive voltage pulse.

[0091] The generation pattern of this series of voltage pulses is the same as the generation pattern of voltage pulses in the first example. Therefore, following the first example, the adder 126 estimates that a missing pulse occurred immediately after the rotation direction of the rotating shaft 115 reversed to the CCW direction, and corrects the state of each phase detection coil when the previous voltage pulse was generated (current status), which is stored in the nonvolatile memory 127, to the state of each phase detection coil when the magnet reference was located in region 5, and corrects the state of each phase detection coil when the voltage pulse before last was generated (previous status) to the state of each phase detection coil when the magnet reference was located in region 6. Furthermore, the adder 126 makes a correction to decrease the number of rotations by -1. However, as is clear from FIG. 10, this estimation and correction differ from the actual rotational movement of the magnet 111.

[0092] Subsequently, when the magnet reference moves in the CW direction from region 3 to region 4, the B-phase detection coil 113 generates a positive voltage pulse. This voltage pulse generation pattern is not normally generated when the magnet reference is located in region 5. Furthermore, this generation pattern is not generated when a pulse missing occurs in the CW direction, or when a pulse missing occurs immediately after a pulse missing occurs immediately after reversing to the CCW direction.

[0093] Therefore, the adder 126 refers to the state of each phase detection coil when the previous voltage pulse was generated, the state of each phase detection coil when the voltage pulse before last was generated, and also the history of information (detection coil numbers) of the detection coils that generated the previous and previous-previous voltage pulses, which are stored in the nonvolatile memory 127.

[0094] Specifically, if the voltage pulse before last was generated from the B-phase detection coil 113 and the previous voltage pulse was generated from the C-phase detection coil 114, the adder 126 estimates that the magnet 111 is rotating in the CW direction and that a pulse missing occurred when the previous voltage pulse was generated. The adder 126 then estimates that the position of the magnet reference when the previous voltage pulse was generated was in Region 3, not Region 5, and updates the position of the magnet reference when the previous voltage pulse was generated to Region 4. Specifically, the adder 126 corrects the state of each phase detection coil when the previous voltage pulse was generated (current status), which is stored in the nonvolatile memory 127, to the state of each phase detection coil when the magnet reference was located in Region 4, and corrects the state of each phase detection coil when the voltage pulse before last was generated (previous status), to the state of each phase detection coil when the magnet reference was located in Region 3. Furthermore, the adder 126 increases the number of rotations by +1 and stores the result in the nonvolatile memory 127. In the conversion table of FIG. 9, this correction process is shown as "third example."

[0095] In the above pattern, if the voltage pulse two pulses ago was generated from a coil other than the B-phase detection coil 113, it is determined that this is not the estimated movement, so the adder 126 does not make any correction and outputs an error.

[0096] Next, as a "fourth example," consider a case where a pulse missing occurs immediately after the rotation direction of the magnet 111 is reversed, followed by another pulse missing. For example, consider a case where the B-phase detection coil 113 is placed at the origin position, the magnet reference is at the origin position, and the magnet reference moves in the clockwise direction from region 6 to region 1, and then, due to a reversal of the rotation direction, the magnet reference moves in the counterclockwise direction to region 6, region 5, and region 4 in that order.

[0097] First, when the magnet reference moves in the CW direction from region 6 to region 1, a negative voltage pulse is generated from the B-phase detection coil 113. Accordingly, the adder 126 increases the number of rotations by +1.

[0098] Subsequently, when the rotation direction of the magnet 111 reverses and the magnet reference moves CCW from region 1 to region 6, if a missing pulse occurs in the B-phase detection coil 113, the nonvolatile memory 127 retains the state of each phase detection coil when the magnet reference was located in region 1.

[0099] Next, when the magnet reference moves in the CCW direction from region 6 to region 5, even if the magnetic field strength exceeds the threshold in the C-phase detection coil 114, no voltage pulse is generated due to quality problems, noise, etc.

[0100] Furthermore, when the magnet reference moves in the CCW direction from region 5 to region 4, the A-phase detection coil 112 generates a negative voltage pulse. The generation pattern of this voltage pulse is the same as when the magnet reference moves in the CW direction from region 1 to region 2. Therefore, the adder 126 estimates that the magnet reference is located in region 2, and stores in the nonvolatile memory 127 the state of each phase detection coil when the magnet reference is located in region 2 as the current status.

[0101] Furthermore, when the magnet reference moves CCW from region 4 to region 3, the B-phase detection coil 113 generates a negative voltage pulse. This voltage pulse generation pattern is not normally generated when the magnet reference is located in region 2. Therefore, the adder 126 references the state of each phase detection coil when the previous voltage pulse was generated and the state of each phase detection coil when the voltage pulse two times previous was generated, which are stored in the nonvolatile memory 127, as well as the history of the detection coils (detection coil numbers) that generated the previous and two times previous voltage pulses.

[0102] Specifically, if the voltage pulse two pulses ago was generated from the B-phase detection coil 113, the adder 126 estimates that the magnet 111 was actually rotating in the CCW direction and that a missing pulse occurred when the previous voltage pulse was generated. In this case, the adder 126 estimates that the position of the magnet reference when the voltage pulse two pulses ago was generated was in Region 4, not Region 2, and updates the position of the magnet reference when the previous voltage pulse was generated to Region 3. Specifically, the adder 126 corrects the state of each phase detection coil when the previous voltage pulse was generated (current status), which is stored in the nonvolatile memory 127, to the state of each phase detection coil when the magnet reference was located in Region 3, and corrects the state of each phase detection coil when the voltage pulse two pulses ago was generated (previous status) to the state of each phase detection coil when the magnet reference was located in Region 4. Furthermore, the adder 126 performs a correction to decrease the rotation speed by 1, and stores the result in the nonvolatile memory 127. In the conversion table of FIG. 8, this correction process is shown as "Fourth Example."

[0103] If a voltage pulse is generated from the same detection coil (detection coil number) that generated the previous voltage pulse and the polarities of both voltage pulses are the same, the area in which the updated magnet reference is located will be the same as the area in which the previous magnet reference was located. In this case, the controller 125 updates the history of information (detection coil number) about the detection coil that generated the voltage pulse, and writes the other information read from the nonvolatile memory 127 directly into the nonvolatile memory 127. This is because updating the history of detection coil information (detection coil number) updates the information about the detection coil that detected the voltage pulse two times before last, which is referenced during correction. This means that even if the pattern is correctable, it will no longer match the conversion pattern shown in the conversion table (see FIGS. 8 and 9), and an error will be output.

[0104] Furthermore, during the period from immediately after the occurrence of a missing pulse until the actual execution of correction, the area where the magnet reference is actually located differs from the area where the magnet reference is located in the current status stored in nonvolatile memory 127. Therefore, if the rotation count is read during this period, the read rotation count may not match the actual rotation count.

[0105] However, because the rotation speed is read while power is being supplied from an external power source, the position of the magnet reference can be accurately confirmed using another means using an external power source (e.g., an optical, mechanical, or magnetic encoder). This prevents the pre-correction rotation speed from being read by comparing the area where the magnet reference is located with the area where the magnet reference is located stored in nonvolatile memory 127 and outputting an error if there is a mismatch. When determining whether there is a mismatch, it is desirable to consider pulse skips due to a reversal of the rotation direction and determine whether the area where the current magnet reference is located matches the area where the previous magnet reference was located. Furthermore, it is desirable to determine whether the phases at which voltage pulses are generated match, taking into account the hysteresis characteristics of the detection coil (see Figure 3).

[0106] Although the situations where two consecutive pulse missing events occur without reversing the rotation direction of the magnet 111, and where three consecutive pulse missing events occur after reversing the rotation direction of the magnet 111 are extremely rare, if these situations occur, the detection coil that generated the previous voltage pulse and the detection coil that generated the current voltage pulse are considered to be the same. Meanwhile, the region where the magnet reference is actually located has moved to a region symmetrical to the region where the magnet reference is located, estimated from the state of the detection coils of each phase when the voltage pulse was generated. Therefore, the voltage pulses generated by subsequent movements of the magnet reference will have the opposite polarity to the voltage pulses generated by the estimated movements of the magnet reference. In this case, by referencing the information (detection coil number) of the detection coil that generated the voltage pulse two times before last, it is determined that the result does not fall into any of the conversion patterns listed in the conversion tables of FIGS. 8 and 9, and an error is output. Therefore, the region where the magnet reference is located is not corrected to a region different from the region where the magnet reference is actually located. As a result, it is possible to avoid erroneous detection of the rotation speed due to erroneous correction, and to prevent serious accidents such as overrunning of the rotating shaft 115 past the stopping position and misalignment of the rotating shaft 115.

[0107] The area in which the magnet reference was located when the previous voltage pulse was generated can be uniquely determined by having information on whether the magnet reference moved CW or CCW to its current position. Therefore, by using information indicating the moving direction of the magnet reference, it is possible to reduce the amount of information stored in the nonvolatile memory 127.

[0108] Furthermore, since information about the detection coil that generated the voltage pulse two times before last can be obtained from the difference between the area where the previous magnet reference was located and the area where the magnet reference two times before last was located, information about this difference may also be used.

[0109] Even if an inversion pulse is detected, the controller 125 may not update the information in the nonvolatile memory 127, and may handle the next voltage pulse in the same way as if an inversion pulse had been missing.

[0110] As described above, the rotation detector according to the first embodiment can detect not only pulse missing occurring immediately after the rotation direction of magnet 111 is reversed, but also pulse missing occurring at other times by referring to the current voltage pulse (polarity and detection coil) and the history of the state of the detection coils for each phase when the previous voltage pulse was generated, the state of the detection coils for each phase when the previous voltage pulse was generated, and the information (detection coil numbers) of the detection coils that generated the previous and previous-previous voltage pulses, all of which are stored in nonvolatile memory 127. For any pulse missing, the above information can be used to correct the state of the detection coils for each phase (magnet-based position) and the rotation speed of rotating shaft 115, both of which are stored in nonvolatile memory 127. As a result, it is possible to improve the accuracy of rotation speed correction for pulse missing.

[0111] Embodiment 2 Fig. 11 is a diagram showing the overall configuration of a rotation detector according to embodiment 2. As shown in Fig. 11, rotation detector 101A according to embodiment 2 differs from rotation detector 101 shown in Fig. 1 in that it includes signal processing circuit 120A instead of signal processing circuit 120.

[0112] In the signal processing circuit 120A, the controller 125, the adder 126, and the nonvolatile memory 127 in the signal processing circuit 120 shown in FIG. 1 are replaced with a controller 125A, an adder 126A, and a nonvolatile memory 127A, respectively.

[0113] The nonvolatile memory 127A is configured to store the number of rotations of the rotating shaft 115, the state of the detection coil for each phase when a voltage pulse is generated, and the history of information (detection coil number) of the detection coil that generated the voltage pulse, as well as a "correction execution flag" indicating that correction was executed in the previous update process. The nonvolatile memory 127A further stores the conversion tables shown in FIGS. 12 and 13.

[0114] The correction execution flag is added to the updated information in the conversion tables shown in Figures 12 and 13. The correction execution flag is set to "1" if correction was performed in the previous update process, and is set to "0" if correction was not performed.

[0115] The controller 125A accesses the nonvolatile memory 127A and reads from the nonvolatile memory 127A the number of rotations of the rotating shaft 115 when the previous voltage pulse was generated, the state of the detection coils of each phase when the previous voltage pulse was generated and information about the detection coil that output the voltage pulse, the state of the detection coils of each phase when the voltage pulse before last was generated and information about the detection coil that output the voltage pulse, and a correction execution flag. A Send to.

[0116] The adder 126A executes an update process using a conversion table (see FIGS. 12 and 13) based on the information received from the controller 125A (information on the current voltage pulse and information read from the nonvolatile memory 127A). In this update process, if the adder 126A has performed a process to correct the state of the detection coil for each phase (the magnet-based position) stored in the nonvolatile memory 127A, the adder 126A sets a correction execution flag to 1. In addition, if the correction execution flag read from the nonvolatile memory 127A is 1 in the update process and an update process to correct the magnet-based position has been performed, the adder 126A outputs an error.

[0117] The controller 125A accesses the nonvolatile memory 127A again and writes the information received from the adder 126A and the history of the updated detection coil information into the nonvolatile memory 127A.

[0118] In the second embodiment, if a pattern occurs in which correction is to be performed in the next update process while the correction execution flag is set to 1, an error is output. This makes it impossible to continue operating the device, but it is possible to avoid reading an erroneous rotation count. The update process according to the second embodiment will be described below.

[0119] Here, as a "fifth example," consider a situation in which the B-phase detection coil 113 is placed at the origin position, the magnet reference is in region 5, and the magnet reference moves in the CW direction from region 5 to region 6, region 1, and region 2, and then the rotation direction of the magnet 111 is reversed and the magnet reference moves in the CCW direction from region 2 to region 1.

[0120] First, when the magnet reference moves clockwise from region 5 to region 6, the C-phase detection coil 114 generates a negative voltage pulse. Then, when the magnet reference moves clockwise from region 6 to region 1, the B-phase detection coil 113 generates a negative voltage pulse. Accordingly, the adder 126A increases the number of rotations by +1.

[0121] After that, the magnet reference moves in the CW direction from region 1 to region 2, but a pulse drop occurs in which no voltage pulse is generated in the A-phase detection coil 112 due to a quality problem, noise, or the like. Due to this pulse drop, the nonvolatile memory 127A holds the state of each phase detection coil when the magnet reference position is region 1.

[0122] Thereafter, when the rotation direction of the magnet 111 reverses counterclockwise and the magnet reference returns from region 2 to region 1, the A-phase detection coil 112 generates a positive voltage pulse. This voltage pulse generation pattern is not normally possible when the magnet reference is located in region 1. Therefore, the adder 126A performs correction using information that the voltage pulse two pulses ago was generated by the C-phase detection coil 114, in accordance with the conversion tables of FIGS. 12 and 13. At this time, the adder 126A sets the correction execution flag to 1.

[0123] In this case, the adder 126A estimates that the position of the magnet reference when the voltage pulse two times last was generated was not region 1 but region 4, and updates the position of the magnet reference when the previous voltage pulse was generated to region 5. Specifically, the adder 126A corrects the state of each phase detection coil when the previous voltage pulse was generated (current status), which is stored in the nonvolatile memory 127A, to the state of each phase detection coil when the magnet reference was located in region 5, and corrects the state of each phase detection coil when the voltage pulse two times last was generated (previous status) to the state of each phase detection coil when the magnet reference was located in region 4. Furthermore, the adder 126A performs a correction to decrease the rotation speed by -1, and stores this together with a correction execution flag (=1) in the nonvolatile memory 127A. However, this process is an erroneous correction, as it is not a process of correcting to the actual position of the magnet reference.

[0124] After this, the magnet reference moves further in the CCW direction, and when the magnet reference moves from region 1 to region 6, the B-phase detection coil 113 generates a positive voltage pulse. This voltage pulse generation pattern is not normally possible when the magnet reference is located in region 5. When the conversion tables in FIGS. 12 and 13 are used, it is estimated that the magnet reference is located in region 1 rather than region 5, so the updated region is moved to region 6 and the number of rotations is decreased by -1. However, although the position of the magnet reference ultimately returns to the actual position through the above two correction processes, the number of rotations ends up being one short of the actual number of rotations.

[0125] Therefore, in the second embodiment, when an update process is performed with the correction execution flag set to 1, if a further correction process is to be performed, an error is output. This makes it impossible to continue operating the device, but it is possible to avoid reading an erroneous rotation speed.

[0126] As described above, the rotation detector according to the second embodiment can avoid erroneous detection of the rotation number that occurs when a missing pulse in the detection coil is combined with multiple reversals of the rotation direction by referring to the correction execution flag. As a result, it becomes possible to eliminate restrictions on the rotation direction of the rotating shaft 115.

[0127] Embodiment 3 Fig. 14 is a diagram showing the overall configuration of a rotation detector according to embodiment 3. As shown in Fig. 14, rotation detector 101B according to embodiment 3 differs from rotation detector 101 shown in Fig. 1 in that it includes signal processing circuit 120B instead of signal processing circuit 120.

[0128] In the signal processing circuit 120B, the controller 125 in the signal processing circuit 120 shown in FIG. 1 is replaced with a controller 125B.

[0129] Controller 125B accesses nonvolatile memory 127 and reads from nonvolatile memory 127 the number of rotations of rotating shaft 115 when the previous voltage pulse was generated, the state of the detection coils for each phase when the previous voltage pulse was generated and information about the detection coil that output that voltage pulse (detection coil number), and the state of the detection coils for each phase when the voltage pulse before last was generated and information about the detection coil that output that voltage pulse (detection coil number). Controller 125B transmits the read information to adder 126.

[0130] After the update process is performed by the adder 126, the controller 125B accesses the nonvolatile memory 127 again and writes the information from the adder 126 and the updated detection coil information into the nonvolatile memory 127.

[0131] At this time, the controller 125B determines whether the information about the detection coil that generated the previous voltage pulse is the same as the information about the detection coil that generated the current voltage pulse. If these two pieces of information are the same, the controller 125B writes the information read from the nonvolatile memory 127 as is without updating the information stored in the nonvolatile memory 127. Alternatively, if the nonvolatile memory 127 is a nondestructive read-out memory, the controller 125B retains the previous value without writing any new information. On the other hand, if the two pieces of information are different, the controller 125B performs a normal update process and writes the state of the detection coils for each phase, the rotation speed, and the detection coil information to the nonvolatile memory 127.

[0132] In the third embodiment, it is possible to correct even patterns that could not be corrected in the first and second embodiments, and to continue the operation of the rotation detector 101B. The update process according to the third embodiment will be described below.

[0133] Here, as a "sixth example," consider a situation in which the B-phase detection coil 113 is placed at the origin position, the magnet reference is at the origin position, and the magnet reference moves in the CW direction from region 6 to region 1, region 2, and region 3 in that order, and then the rotation direction of the magnet 111 is reversed and the magnet reference moves in the CCW direction from region 3 to region 2 and region 1 in that order.

[0134] First, when the magnet reference moves in the CW direction from region 6 to region 1, the B-phase detection coil 113 generates a negative voltage pulse. Accordingly, the adder 126 increases the number of rotations by +1.

[0135] Next, the magnet reference moves in the CW direction from region 1 to region 2, but a pulse drop occurs in which no voltage pulse is generated in the A-phase detection coil 112 due to quality, noise, etc. Due to this pulse drop, the nonvolatile memory 127 holds the state of each phase detection coil when the magnet reference position is region 1.

[0136] Subsequently, when the magnet reference moves clockwise from region 2 to region 3, the phase-C detection coil 114 generates a positive voltage pulse. The generation pattern of this voltage pulse is the same as that of the "first example" described in the first embodiment. Therefore, the adder 126 assumes that a missing pulse occurred immediately after the rotation direction was reversed, and corrects the state of each phase detection coil when the previous voltage pulse was generated (current status) to the state of each phase detection coil when the magnet reference was located in region 5, and corrects the state of each phase detection coil when the voltage pulse before last was generated (previous status) to the state of each phase detection coil when the magnet reference was located in region 6. Furthermore, the adder 126 decreases the rotation speed by -1.

[0137] Thereafter, when the rotation direction of the magnet 111 reverses counterclockwise and the magnet reference returns from region 3 to region 2, the C-phase detection coil 114 generates a negative voltage pulse. At this time, the detection coil that generated the previous voltage pulse and the detection coil that generated the current voltage pulse are the same C-phase detection coil 114, so the adder 126 does not update the information about the magnet reference region and detection coil.

[0138] Thereafter, when the magnet 111 rotates in the CCW direction and the magnet reference moves from region 2 to region 1, the A-phase detection coil 112 generates a positive voltage pulse. This voltage pulse generation pattern is not normally possible when the magnet reference is located in region 5. Therefore, the adder 126 refers to the history of information about the detection coil that generated the voltage pulse. If the A-phase detection coil 112 generated a voltage pulse two pulses ago, the adder 126 estimates that a pulse missing different from a reversal missing occurred not at the actual time of generation of the previous voltage pulse but at the time of generation of the previous voltage pulse stored in the non-volatile memory 127, and that the magnet reference actually moved in the CW direction.

[0139] In this case, the adder 126 estimates that the position of the magnet reference when the voltage pulse two pulses ago was generated was in region 3, not region 5, and that a missing pulse occurred immediately after the rotation direction was reversed, causing the magnet reference to move in the CCW direction. Therefore, the adder 126 moves the position of the magnet reference when the previous voltage pulse was generated, which is stored in the nonvolatile memory 127, to region 1 and performs a correction to increase the number of rotations by +1. Specifically, the adder 126 corrects the state of each phase detection coil when the previous voltage pulse was generated (current status) to the state of each phase detection coil when the magnet reference was located in region 1, and corrects the state of each phase detection coil when the voltage pulse two pulses ago was generated (previous status) to the state of each phase detection coil when the magnet reference was located in region 2, and stores these in the nonvolatile memory 127. Furthermore, the adder 126 performs a correction to increase the number of rotations by +1 and stores these in the nonvolatile memory 127.

[0140] Now, consider a case where the update process according to the first embodiment is performed in the sixth example. When the magnet reference moves from region 3 in the CCW direction to region 2, the information stored in nonvolatile memory 127, including the rotation speed of rotating shaft 115, the state of each phase's detection coil when the previous and previous-previous voltage pulses were generated, and the information on the detection coil that output the voltage pulse (detection coil number), is updated. At this time, the position of the magnet reference when the previous voltage pulse was generated is designated region 6, and the position of the magnet reference when the previous-previous voltage pulse was generated is designated region 5. Furthermore, the previous voltage pulse is generated by phase C detection coil 114, and the previous-previous voltage pulse is generated by phase C detection coil 114. Thereafter, when the magnet reference moves from region 2 to region 1 in the CCW direction, the voltage pulse generated is a pattern that does not normally occur when the magnet reference is located in region 6. Because the detection coil that generated the previous-previous voltage pulse does not match, none of the correction patterns apply, and an error is ultimately output.

[0141] On the other hand, in the update process according to the third embodiment, the correction is performed as described above, so that it is possible to continue the operation of the device.

[0142] Embodiment 4 Fig. 15 is a diagram showing the overall configuration of a rotation detector according to embodiment 4. As shown in Fig. 15, rotation detector 101C according to embodiment 4 differs from rotation detector 101 shown in Fig. 1 in that it includes a signal processing circuit 120C instead of signal processing circuit 120.

[0143] In the signal processing circuit 120C, the controller 125, the adder 126, and the nonvolatile memory 127 in the signal processing circuit 120 shown in FIG. 1 are replaced with a controller 125C, an adder 126C, and a nonvolatile memory 127C, respectively.

[0144] Nonvolatile memory 127C is configured to store correction history information in addition to the history of the number of rotations of rotating shaft 115, the state of the detection coil for each phase when a voltage pulse was generated, and information (detection coil number) of the detection coil that generated the voltage pulse. The correction history information includes information about the state of the detection coil for each phase when correction was performed and information about detected pulse dropouts. Each time correction is performed, the correction history is updated.

[0145] The nonvolatile memory 127C has a correction execution counter and a pulse detection counter. The correction execution counter is configured to count and store the number of times correction has been executed. The pulse detection counter is configured to count and store the number of times a voltage pulse has occurred.

[0146] The controller 125C accesses the nonvolatile memory 127C and reads from the nonvolatile memory 127C the number of rotations of the rotating shaft 115 when the previous voltage pulse was generated, the state of the detection coils for each phase when the previous voltage pulse was generated and information about the detection coil that output that voltage pulse, the state of the detection coils for each phase when the voltage pulse before last was generated and information about the detection coil that output that voltage pulse, the count values ​​of the correction execution counter and pulse detection counter, and the correction history. The controller 125C transmits this read information to the adder 126C.

[0147] The adder 126C executes an update process using the conversion tables (FIGS. 12 and 13) based on the information received from the controller 125C (information on the current voltage pulse and information read from the nonvolatile memory 127C). In this update process, the adder 126C increments the count value of the pulse detection counter by 1.

[0148] Furthermore, when the adder 126C performs a process to correct the state (magnet reference position) of each phase detection coil stored in the nonvolatile memory 127C during the update process, it increments the count value of the correction execution counter by 1 and acquires, as correction history, the state of each phase detection coil at the time of correction and information on the detection coil when it is estimated that a pulse drop occurred.

[0149] Next, the adder 126C compares the count value of the pulse detection counter with the count value of the correction execution counter. If the ratio of the count value of the correction execution counter to the count value of the pulse detection counter (count value of the correction execution counter / count value of the pulse detection counter) exceeds a predetermined threshold, there is a concern that an abnormality has occurred in the environment or components, and therefore the adder 126C outputs an error.

[0150] For example, if the count value of each counter is a binary number, the adder 126C outputs an error when the ratio exceeds a threshold value of 1 / 2 to the power of 20. If the count value of the pulse detection counter reaches its upper limit before the ratio reaches the threshold, the pulse detection counter and the correction execution counter each shift their count value one bit to the right, thereby halving the count value and continuing to count up. Note that the method for adjusting the count value is not limited to the right shift described above; other methods such as initializing each counter or adjusting the count value to an arbitrary value can also be applied.

[0151] The controller 125C accesses the nonvolatile memory 127C again and writes the information received from the adder 126C (including the count value and correction history) and the updated history of the detection coil information into the nonvolatile memory 127C.

[0152] As described above, in the fourth embodiment, the adder 126C is configured to output an error even when the corrections described in the first and third embodiments can be performed. This makes it impossible to continue operating the device, but it is possible to safely stop the device before an abnormality that cannot be corrected occurs. Furthermore, by storing information on the correction history in the nonvolatile memory 127C, it is possible to obtain information that can lead to identifying the cause of the error.

[0153] The criteria for determining whether or not adder 126C outputs an error are not limited to the above ratio. For example, a configuration is possible in which no pulse detection counter is implemented in nonvolatile memory 127C, but only a correction execution counter is implemented, and adder 126C outputs an error when the count value of the correction execution counter exceeds a predetermined threshold.

[0154] In addition, instead of being configured to output an error, the adder 126C may be configured to issue a warning via an external device to prompt maintenance and inspection of the device while continuing operation of the device. Furthermore, the adder 126C can also write the information on the correction history to a predetermined address in the nonvolatile memory 127C without reading the information on the correction history from the nonvolatile memory 127C.

[0155] The present disclosure allows for the combination of the embodiments, as well as the appropriate modification or omission of the embodiments, within the scope of the invention. In addition, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriate combinations of the disclosed constituent elements.

[0156] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The technical scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0157] 10 CPU, 11 RAM, 12 ROM, 13 I / F device, 14 storage device, 15 communication bus, 101, 101A, 101B, 101C rotation detector, 110 rotation detection mechanism, 111 magnet, 112 A-phase detection coil, 113 B-phase detection coil, 114 C-phase detection coil, 115 rotating shaft, 120, 120A, 120B, 120C signal processing circuit, 121_A, 121_B, 121_C full-wave rectifier circuit, 122 constant voltage circuit, 123 Enable circuit, 124 pulse waveform code determination circuit, 125, 125A, 125B, 125C controller, 126, 126A, 126C adder, 127, 127A, 127C non-volatile memory, 128 external circuit I / F, 129 power supply switching circuit.

Claims

1. A rotation detector that detects the rotation direction and rotation speed of a rotating shaft, a rotation detection mechanism attached to the rotary shaft and detecting rotation of the rotary shaft; a signal processing circuit electrically connected to the rotation detection mechanism; The rotation detection mechanism includes: a magnet configured to rotate in synchronization with the rotation shaft and having N magnetic poles arranged in the rotation direction; L detection coils arranged at positions shifted from each other by a predetermined phase along the rotation direction of the magnet, where N is a natural number of 2 or more and L is a natural number of 3 or more, each of the L detection coils is configured to generate a voltage pulse of positive or negative polarity in response to a magnetic field applied from the magnet; The signal processing circuit a constant voltage circuit that generates a power supply voltage from the power of a voltage pulse every time the voltage pulse is generated; a controller and a nonvolatile memory that operate by receiving the power supply voltage; the nonvolatile memory is configured to store a state of the L detection coils when a voltage pulse is generated, the number of rotations of the rotation shaft, and a history of information about the detection coils that generated the voltage pulse; the controller is configured to execute a process of acquiring, each time a voltage pulse is generated, information on states of the L detection coils, the number of rotations of the rotation shaft, and the detection coil that generated the voltage pulse, and updating the nonvolatile memory; In the updating process, the controller By referring to the information on the current voltage pulse, the states of the L detection coils when the previous voltage pulse was generated, the states of the L detection coils when the voltage pulse before last was generated, and the history of information on the detection coils that generated the voltage pulse before last, which are stored in the nonvolatile memory, the rotation detector detects a pulse drop in which a voltage pulse is missing, and corrects the states of the L detection coils and the rotation speed of the rotating shaft, which are stored in the nonvolatile memory.

2. the controller is configured to change the state of each of the L detection coils to a first logic level when a voltage pulse of positive polarity is generated and to a second logic level when a voltage pulse of negative polarity is generated, and to estimate a rotational position of the magnet from the states of the L detection coils; In the updating process, the controller detecting the missing pulse and estimating the transition of the rotational position of the magnet by referring to the state of the L detection coils when the previous voltage pulse was generated and the state of the L detection coils when the voltage pulse before last was generated, which are stored in the nonvolatile memory, and a history of information on the detection coil that generated the voltage pulse before last; 2. The rotation detector according to claim 1, wherein the states of the L detection coils and the number of rotations of the rotating shaft stored in the nonvolatile memory are corrected based on the estimated transition of the rotation position of the magnet.

3. 3. The rotation detector according to claim 1, wherein the controller detects the pulse missing that occurred while the rotating shaft is rotating in a first rotation direction by referring to the states of the L detection coils when the previous voltage pulse was generated, the states of the L detection coils when the voltage pulse before last was generated, and history of information about the detection coils that generated the voltage pulse before last, all of which are stored in the nonvolatile memory, and corrects the states of the L detection coils and the rotation speed of the rotating shaft, all of which are stored in the nonvolatile memory.

4. 3. The rotation detector according to claim 1, wherein the controller detects the pulse missing that occurs at least two times consecutively after the rotation shaft is reversed from a first rotation direction to a second rotation direction by referring to the states of the L detection coils when the previous voltage pulse was generated, the states of the L detection coils when the voltage pulse before last was generated, and history of information about the detection coil that generated the voltage pulse before last, which are stored in the nonvolatile memory, and corrects the states of the L detection coils and the rotation speed of the rotation shaft, which are stored in the nonvolatile memory.

5. the nonvolatile memory is further configured to store information indicating whether the correction was performed in the previous update process; 3. The rotation detector according to claim 1, wherein the controller outputs an error when the correction is performed in the current update process and the correction was performed in the previous update process.

6. the signal processing circuit has a counter that counts the number of times the correction has been performed; The rotation detector according to claim 1 or 2, wherein the controller outputs an error when the count value of the counter exceeds a threshold value.

7. the signal processing circuit has a first counter that counts the number of times a voltage pulse is generated and a second counter that counts the number of times the correction is performed; 3. The rotation detector according to claim 1, wherein the controller outputs an error when a ratio of the count value of the second counter to the count value of the first counter exceeds a threshold value.

8. the nonvolatile memory is further configured to store information about states of the L detection coils when the correction is performed and information about the missing pulse; The rotation detector according to claim 1 , wherein the controller updates a correction history when the correction is performed.

9. 3. The rotation detector according to claim 1, wherein the controller does not update the nonvolatile memory if the detection coil that generated the previous voltage pulse is the same as the detection coil that generated the voltage pulse two times before.

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