Rotation detecting device

Abstract

A rotation detecting device (101) comprises a rotation detecting mechanism (110) that includes N magnets (111) disposed in the rotation direction of a rotating body (115) and L detection coils (112, 113) disposed in the rotation direction of the magnets, a voltage pulse detecting circuit (124) that detects voltage pulses generated by the detection coils and outputs a detection signal, a constant voltage circuit (122) that generates a power supply voltage from the voltage pulses, a controller (125) that executes detection processing for detecting the rotation state of the rotating body (115) on the basis of the detection signal from the voltage pulse detecting circuit (124), and a non-volatile memory (126) that stores information acquired in the detection processing, wherein: the detection processing includes read processing, update processing, and write processing; and when a second voltage pulse is detected before the detection processing based on a first voltage pulse is completed, the read processing of the detection processing based on the second voltage pulse is omitted.

Description

Rotation detection device

[0001] The present disclosure relates to a rotation detection device that detects the rotation of a rotating body.

[0002] In recent years, from the standpoint of energy conservation and maintenance efficiency, there has been a demand for rotation detection devices to obtain electrical energy by utilizing ambient light or magnetic fields, pressure changes, vibrations, etc., rather than relying on power supply from a backup battery or external power source, and to perform detection processing using the obtained electrical energy.

[0003] For example, Japanese Patent Application Laid-Open Publication No. 2008-14799 (Patent Document 1) discloses an absolute value encoder equipped with an absolute position detector that detects the absolute position within one rotation of a rotating shaft and a multi-rotation detector that detects multiple rotations. The multi-rotation detector includes a permanent magnet attached to the tip of the rotating shaft and a power generator composed of a magnetic wire and coil that exhibits the large Barkhausen effect. The magnetic wire and coil are positioned so that they can detect the magnetic field of the permanent magnet. When the external power supply is interrupted, the power supply for the multi-rotation detector is backed up by voltage generated by the power generator, allowing the amount of multiple rotations to continue to be detected even when the main power supply is cut off.

[0004] International Publication No. 2013 / 157279 (Patent Document 2) and International Publication No. 2023 / 140000 (Patent Document 3) disclose rotation detection devices that include a magnet that rotates in synchronization with a 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. The rotation detection device can detect and maintain the rotation direction and rotation speed of the rotating shaft without receiving power from an external source.

[0005] JP 2008-14799 A International Publication No. 2013 / 157279 International Publication No. 2023 / 140000

[0006] In the battery-less rotation detection device described above, as the number of detection coils (power generating elements) is increased to improve the accuracy and reliability of rotation detection, the phase difference between the detection coils becomes narrower, and therefore the interval between voltage pulses becomes shorter.

[0007] On the other hand, when detecting the rotation of a rotating body, since the rotating shaft does not necessarily rotate continuously, it is necessary to complete the entire detection process based on one voltage pulse using the power from that voltage pulse, assuming that the next voltage pulse will not be generated, and therefore it is necessary to operate the signal processing circuit that performs the detection process with low power consumption.

[0008] However, as described above, if the number of detection coils is increased to improve the accuracy of rotation detection, the interval between voltage pulses will become shorter even at the same rotation speed. This means that while the signal processing circuit is performing detection processing based on one voltage pulse, the next voltage pulse may occur. In such a case, the signal processing circuit may not be able to correctly perform detection processing based on one of the voltage pulses. As a result, there is a concern that the rotation speed at which the rotation detection device can guarantee detection accuracy may decrease.

[0009] The present disclosure has been made to solve such problems, and the purpose of the present disclosure is to provide a technology for accurately and stably detecting the rotation state of a rotating body in a rotation detection device that detects the rotation of a rotating body based on voltage pulses generated by multiple detection coils, even when the intervals between generation of voltage pulses by the multiple detection coils become short.

[0010] A rotation detection device according to one aspect of the present disclosure detects the rotation of a rotating body. The rotation detection device includes a rotation detection mechanism attached to the rotating body and detecting the rotation of the rotating body, and a signal processing circuit electrically connected to the rotation detection mechanism. The rotation detection mechanism is configured to rotate in synchronization with the rotating body and includes a magnet having N magnetic poles arranged in the rotational direction, and L detection coils arranged at positions shifted from each other by a predetermined phase along the rotational direction of the magnet. L and N are natural numbers greater than or equal to 2. 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 includes a voltage pulse detection circuit, a constant voltage circuit, a nonvolatile memory, and a controller. The voltage pulse detection circuit detects voltage pulses generated by each of the L detection coils and outputs a detection signal indicating the polarity of the detected voltage pulse and the detection coil that generated the voltage pulse. Each time a voltage pulse is generated, the constant voltage circuit generates a power supply voltage from the power of the voltage pulse. The nonvolatile memory and the controller operate by receiving the power supply voltage from the constant voltage circuit. The controller is configured to start operation upon receiving a power supply voltage from the constant voltage circuit and to execute a detection process to detect the rotational state of the rotating body based on a detection signal from the voltage pulse detection circuit each time a voltage pulse is generated. The nonvolatile memory is configured to store information acquired in the detection process regarding the states of the L detection coils and the rotation speed of the rotating body when the voltage pulse is generated. The detection process includes a read process for reading information stored in the nonvolatile memory to the controller, an update process for updating the information based on the information read by the read process and the voltage pulse detection signal, and a write process for writing the information updated by the update process to the nonvolatile memory. If the voltage pulse detection circuit has detected a second voltage pulse by the time the detection process based on the first voltage pulse is completed, the controller omits at least the read process of the detection process based on the second voltage pulse.

[0011] According to the present disclosure, in a rotation detection device that detects the rotation of a rotating body based on voltage pulses generated by multiple detection coils, the rotation state of the rotating body can be detected accurately and stably even when the interval between generation of voltage pulses by the multiple detection coils becomes short.

[0012] FIG. 1 is a diagram illustrating an overall configuration of a rotation detection device according to a first embodiment. FIG. 2 is a diagram illustrating a first configuration example of a rotation detection mechanism. FIG. 3 is a diagram illustrating a second configuration example of a rotation detection mechanism. FIG. 4 is a diagram schematically illustrating a relationship between magnetization of a magnetic wire and an external magnetic field. FIG. 5 is a diagram illustrating a 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. 6 is a diagram illustrating a voltage pulse output by the detection coil and the magnetization direction of the detection coil. FIG. 7 is a diagram illustrating a hardware configuration of a signal processing circuit. FIG. 8 is a diagram illustrating a selection condition for a power supply switching circuit to select a full-wave rectifier circuit. FIG. 9 is a diagram illustrating a selection condition for a power supply switching circuit to select an external main power supply. FIG. 10 is a diagram illustrating a first example of operation of the power supply switching circuit. FIG. 11 is a diagram illustrating a second example of operation of the power supply switching circuit. FIG. 12 is a diagram illustrating a third example of operation of the power supply switching circuit. FIG. 13 is a diagram illustrating an operation of a voltage pulse detection circuit. FIG. 14 is a flowchart illustrating a processing flow from when a controller starts operation to when it ends operation. FIG. 15 is a diagram illustrating an example of a conversion table. FIG. 16 is a diagram illustrating an overall configuration of a rotation detection device according to a second embodiment. FIG. 17 is a flowchart illustrating a processing flow from when a controller starts operation to when it ends operation. 10 is a flowchart illustrating a processing flow from when a controller starts operating until it ends the operation. FIG. 11 is a diagram illustrating an overall configuration of a rotation detection device according to a fourth embodiment. FIG. 12 is a circuit diagram illustrating an example configuration of a half-wave rectifier circuit. FIG. 13 is a diagram illustrating a smoothing capacitor in a full-wave rectifier circuit that stores electric charges of positive and negative voltage pulses output from a detection coil. FIG. 14 is a diagram illustrating a smoothing capacitor in a half-wave rectifier circuit that stores electric charges of positive and negative voltage pulses output from a detection coil. FIG. 15 is a flowchart illustrating a processing flow from when a controller starts operating until it ends the operation. FIG. 16 is a block diagram illustrating an example configuration of a batteryless multi-rotation encoder according to a fifth embodiment. FIG. 17 is a block diagram illustrating an example configuration of a flow meter according to a fifth embodiment. FIG. 18 is a block diagram illustrating an example configuration of a steering device according to a fifth embodiment.

[0013] 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.

[0014] Embodiment 1. <Overall Configuration of Rotation Detection Device> Fig. 1 is a diagram showing the overall configuration of a rotation detection device 101 according to Embodiment 1. Rotation detection device 101 according to Embodiment 1 is configured to be able to detect and hold the rotation direction and rotation speed of a rotating body even when not receiving an external power supply. As shown in Fig. 1, rotation detection device 101 includes a rotation detection mechanism 110 and a signal processing circuit 120. Signal processing circuit 120 is electrically connected to rotation detection mechanism 110.

[0015] 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 or an engine. 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.

[0016] The rotation detection mechanism 110 includes a magnet 111 and detection coils 112 and 113. The magnet 111 has a disk shape and is attached concentrically to a rotating shaft 115. The magnet 111 has two magnetic poles (North and South poles) 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 direction is the clockwise rotation direction (forward rotation) as viewed from the rotating shaft 115, and the CCW direction is the counterclockwise rotation direction (reverse rotation) as viewed from the rotating shaft 115.

[0017] 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. The number of magnetic poles of the magnet 111 may be two or more.

[0018] The detection coils 112 and 113 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 and 113 is formed of a magnetic wire that exhibits the large Barkhausen effect. In the following description, the detection coil 112 is also referred to as the "A-phase detection coil," and the detection coil 113 is also referred to as the "B-phase detection coil." The number of detection coils is not limited to two, and may be three or more.

[0019] <Rotation Detection Mechanism 110> Next, an example of the configuration and operation of the rotation detection mechanism 110 shown in FIG. 1 will be described.

[0020] Fig. 2 is a diagram showing a first configuration example of the rotation detection mechanism 110. The positional relationship between the magnet 111 and the detection coils 112 and 113 will be described using Fig. 2. Furthermore, the principle of detecting the number of rotations of the rotating shaft 115 using the rotation detection mechanism 110 shown in Fig. 2 will be described.

[0021] As shown in Fig. 2, the detection coils 112, 113 are arranged to extend in the radial direction of the magnet 111, at positions that are shifted from each other 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 B-phase detection coil 113 is arranged at a reference position, and the A-phase detection coil 112 is arranged at a position 90° clockwise from the reference position. The A-phase detection coil 112 is arranged rotated 90° relative to the B-phase detection coil 113.

[0022] Then, six angular regions are formed around the magnet 111, with the "origin position (0°)" as the reference, according to the arrangement of the detection coils 112 and 113. Specifically, the arrangement position of the B-phase detection coil 113 is set as the "origin position," and "region 1" to "region 4" are formed every 90° 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."

[0023] The arrangement of the detection coils 112 and 113 is not limited to that shown in FIG. 2 . As long as the relationship between the direction of the external magnetic field H applied from the magnet 111 to the detection coils 112 and 113 and the direction of the magnetic wires of the detection coils 112 and 113 remains the same, the detection coils 112 and 113 may be moved from the positions shown in FIG. 2 . FIG. 3 is a diagram showing a second configuration example of the rotation detection mechanism 110. As shown in FIG. 3 , the positions of the detection coils 112 and 113 may be shifted in the vertical direction of the page while maintaining the orientation of the magnetic wires. This allows the arrangement of the detection coils to be optimized and the size of the detection coils to be increased, thereby increasing the power generation capacity of the detection coils.

[0024] The magnetic wire constituting each of the detection coils 112 and 113 has magnetization characteristics as shown in FIG. 4 . FIG. 4 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. 4 , 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. 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 rotational speed of the rotating shaft 115 (i.e., the magnet 111).

[0025] Figure 5 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 5 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 5 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.

[0026] As shown in Figure 5, when magnet 111 rotates at a constant speed together with rotating shaft 115, an external magnetic field having a sinusoidal waveform, with one cycle corresponding to the time it takes for magnet 111 to rotate once, is applied to each of detection coils 112 and 113.

[0027] When the applied external magnetic field varies sinusoidally, one voltage pulse is generated across both ends of the detection coil for each half cycle of the external magnetic field. Specifically, as shown in Figure 5, when the magnet is magnetized in the reverse direction (hereinafter also referred to as the "negative direction") and an external magnetic field is applied in the forward direction (hereinafter also referred to as the "positive direction"), the detection coil generates a positive voltage pulse. When the magnet is magnetized in the positive direction and an external magnetic field is applied in the negative direction, the detection coil generates a negative voltage pulse. Note that the timing of the voltage pulse generation differs depending on the direction of rotation of the magnet 111.

[0028] Returning to Fig. 2, each of the detection coils 112, 113 arranged around the outer periphery of the magnet 111 alternately generates positive and negative voltage pulses in accordance with the rotation of the magnet 111 (rotation shaft 115). Figs. 6 and 7 are diagrams showing the voltage pulses output by the detection coils 112, 113 and the magnetization directions of the detection coils 112, 113. In the example of Fig. 2, the A-phase detection coil 112 is arranged at a 90° position, and the B-phase detection coil 113 is arranged at the origin position (0°).

[0029] Fig. 6 shows the waveforms of the A-phase pulse and the B-phase pulse when the magnet 111 rotates once in the CW direction, i.e., when the magnet reference position changes from 0° to 360°. Fig. 7 shows the waveforms of the A-phase pulse and the B-phase pulse when the magnet 111 rotates once in the CCW direction, i.e., when the magnet reference position changes from 360° to 0°.

[0030] In each figure, "A-phase pulse" indicates the voltage pulse of the A-phase detection coil 112, and "B-phase pulse" indicates the voltage pulse of the B-phase detection coil 113. "A-phase magnetization state" indicates the magnetization direction of the A-phase detection coil 112, and "B-phase magnetization state" indicates the magnetization direction of the B-phase detection coil 113. The magnetization directions of the detection coils 112 and 113 are "H (logical high)" when they are in the positive direction, and "L (logical low)" when they are in the negative direction.

[0031] As described with reference to FIG. 5 , a positive or negative external magnetic field is applied to each of the detection coils 112 and 113 every half cycle. Each of the detection coils 112 and 113 outputs a voltage pulse every time the magnetization direction of the detection coil reverses. Specifically, as shown in FIGS. 6 and 7 , when the magnetization direction of the detection coil reverses from the negative direction (L) to the positive direction (H), the detection coil outputs a positive voltage pulse. Furthermore, when the magnetization direction of the detection coil reverses from the positive direction (H) to the negative direction (L), the detection coil outputs a negative voltage pulse. Note that the magnetization direction of the detection coil is maintained until the magnetization direction is reversed, so the magnetization direction of the detection coil can be detected by detecting the direction of the voltage pulse output from the detection coil.

[0032] 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 clockwise 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 counterclockwise 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).

[0033] In this case, as shown in FIG. 6, when the magnetization direction of the A-phase detection coil 112 is positive (H) and it is detected that the magnetization direction of the B-phase detection coil 113 has changed from positive (H) to negative (L) (i.e., when a negative voltage pulse is detected from the B-phase detection coil 113), it is determined that the magnet reference has passed the origin position in the clockwise direction, and the number of rotations is increased by +1.

[0034] Also, according to FIG. 7, when the magnetization direction of the A-phase detection coil 112 is positive (H) and it is detected that the magnetization direction of the B-phase detection coil 113 has changed from negative (L) to positive (H) (i.e., when a positive voltage pulse is detected from the B-phase detection coil 113), 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.

[0035] Furthermore, it is possible to estimate in which region the magnet reference is located, i.e., the rotational position of the magnet 111, from the magnetization directions of the detection coils 112 and 113. For example, when the magnetization direction of the A-phase detection coil 112 is the positive direction (H) and the magnetization direction of the B-phase detection coil 113 is the negative direction (L), it can be estimated that the magnet reference is located in region 1. According to this, when the magnet reference moves from region 4 to region 1, it can be determined that the magnet 111 has made one rotation in the clockwise direction, and the number of rotations can be increased by +1, and when the magnet reference moves from region 1 to region 4, it can be determined that the magnet 111 has made one rotation in the counterclockwise direction, and the number of rotations can be decreased by -1.

[0036] Note that the generation position of each voltage pulse is not the same as the arrangement position of the corresponding detection coil, but is a position offset by an angle φ° from that arrangement position. For example, when the magnet 111 rotates in the clockwise direction, the generation position of the negative A-phase pulse is offset by φ° in the clockwise direction from the arrangement position of the A-phase detection coil 112 at 90°. Furthermore, the generation position of the positive A-phase pulse is offset by φ° in the clockwise direction from the arrangement position of the A-phase detection coil 112 at 270°, which is a half rotation (180°) from the arrangement position of the A-phase detection coil 112 at 90°. This is because, as shown in FIG. 5 , after the external magnetic field generated by the magnet 111 reverses, 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 clockwise direction, the generation position of each voltage pulse is offset in the clockwise direction from the arrangement position of the corresponding detection coil.

[0037] 7, similarly to Fig. 6, the generation positions of the A-phase pulse and B-phase pulse are not the same as the arrangement positions of the corresponding detection coils, but are shifted by an angle φ° from the arrangement positions. However, when the rotation direction of magnet 111 is the CCW direction, the generation positions of the voltage pulses are shifted in the CCW direction from the arrangement positions of the corresponding detection coils.

[0038] In this way, whether the magnet 111 is rotated in the clockwise or counterclockwise direction, hysteresis with an angular difference of φ° occurs. This hysteresis differs for each detection coil due to variations in the characteristics of the detection coils 112, 113 and the magnet 111, as well as variations in the distance between the detection coils 112, 113 and the magnet 111. Therefore, if the detection coils 112, 113 are arranged within the range of the angular difference of φ°, the order of the voltage pulses output by each detection coil may be reversed. In this case, it becomes difficult to accurately detect the rotation direction of the magnet 111. Therefore, it is desirable to arrange the detection coils 112, 113 at a spacing greater than the angular difference φ° of the hysteresis.

[0039] <Signal Processing Circuit 120> Next, an example of the configuration and operation of the signal processing circuit 120 shown in FIG. 1 will be described.

[0040] Fig. 8 is a diagram showing the hardware configuration of the signal processing circuit 120. As shown in Fig. 8, 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.

[0041] 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 processes to be executed by the signal processing circuit 120.

[0042] 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 from the detection coils 112 and 113 from the rotation detection mechanism 110.

[0043] 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.

[0044] Note that 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 application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a complex programmable logic device (CPLD).

[0045] 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 121A and 121B, a constant voltage circuit 122, a power supply switching circuit 123, a voltage pulse detection circuit 124, a controller 125, a nonvolatile memory 126, an external circuit I / F 127, and an oscillator circuit 128. Of these, at least the controller 125 may be implemented by the CPU 10 shown in FIG. 8 executing a program. Alternatively, these circuits may be implemented as a single integrated circuit. Alternatively, these circuits may be divided into multiple integrated circuits, and each integrated circuit may be manufactured using a semiconductor process rule suitable for that circuit.

[0046] Signal processing circuit 120 is configured to execute a "detection process" that detects the rotational state of rotating shaft 115, such as the rotation speed, direction of rotation, and rotation angle of rotating shaft 115, based on the voltage pulse each time either of detection coils 112, 113 in rotation detection mechanism 110 generates the voltage pulse. As will be described later, this detection process includes a "read process" that reads information such as the state of each phase detection coil and the rotation speed of rotating shaft 115 stored in nonvolatile memory 126, an "update process" that updates the information such as the state of each phase detection coil and the rotation speed of rotating shaft 115 based on the information read by the read process and the information of the detection coil that generated the current voltage pulse, and a "write process" that writes the information updated by the update process to nonvolatile memory 126.

[0047] The signal processing circuit 120 is normally configured to execute the above detection process using the power of one voltage pulse input from the rotation detection mechanism 110. However, if one of the detection coils 112, 113 generates a voltage pulse and the other detection coil generates another voltage pulse between the time the other detection coil generates a voltage pulse and the time the other detection coil finishes the detection process based on the voltage pulse, the signal processing circuit 120 is configured to perform exclusive control using the power supply switching circuit 123 and to change part of the detection process based on the other voltage pulse.

[0048] In one aspect, signal processing circuit 120 is configured to omit at least the readout process of the detection process based on the different voltage pulses, so that signal processing circuit 120 can accurately and stably perform the detection process on rotating shaft 115 even when the output interval of the voltage pulses becomes shorter as the rotation speed of rotating shaft 115 increases.

[0049] (Full-wave rectifier circuits 121A, 121B) The full-wave rectifier circuit 121A is electrically connected to the A-phase detection coil 112 and full-wave rectifies the voltage pulse (A-phase pulse) output from the A-phase detection coil 112. The full-wave rectifier circuit 121A includes, for example, a diode bridge and a capacitor connected to the output side of the diode bridge. The capacitor stores the rectified voltage pulse output from the diode bridge. The power stored in the capacitor is supplied to the constant voltage circuit 122 in response to selection by the power supply switching circuit 123.

[0050] The full-wave rectifier circuit 121B is electrically connected to the B-phase detection coil 113 and full-wave rectifies the voltage pulse (B-phase pulse) output from the B-phase detection coil 113. The full-wave rectifier circuit 121B includes, for example, a diode bridge and a capacitor connected to the output side of the diode bridge. The capacitor stores the rectified voltage pulse output from the diode bridge. The power stored in the capacitor is supplied to the constant voltage circuit 122 in response to selection by the power supply switching circuit 123.

[0051] (Constant voltage circuit 122) The constant voltage circuit 122 receives a voltage selected by the power supply switching circuit 123 from the voltage pulse output from the full-wave rectifier circuit 121A, the voltage pulse output from the full-wave rectifier circuit 121B, and the output voltage of the external main power supply, and generates a constant voltage from the selected voltage.

[0052] The constant voltage circuit 122 drives the controller 125, the oscillator circuit 128, and the nonvolatile memory 126 by supplying the generated constant voltage to these circuits. The external main power supply is a main power supply provided outside the rotation detection device 101 and is mainly used to drive the rotating body. The constant voltage circuit 122 can continue to supply voltage to the controller 125, the oscillator circuit 128, and the nonvolatile memory 126 even when the rotating shaft 115 is stopped.

[0053] (Power Supply Switching Circuit 123) The power supply switching circuit 123 is electrically connected to the full-wave rectifier circuits 121A and 121B and the external main power supply. The power supply switching circuit 123 is configured to be able to switch the voltage source for the controller 125, the oscillator circuit 128, and the non-volatile memory 126 between the full-wave rectifier circuits 121A and 121B and the external main power supply. Specifically, the power supply switching circuit 123 selects one of these circuits and connects it to the constant voltage circuit 122 depending on the voltages input from the full-wave rectifier circuits 121A and 121B and the external main power supply. The power supply switching circuit 123 further outputs to the controller 125 a signal indicating the selected circuit and a signal indicating a circuit whose input voltage has reached the selection start voltage.

[0054] 9 and 10 are diagrams illustrating the conditions for selecting a voltage source in power supply switching circuit 123. Fig. 9 is a diagram illustrating the conditions for selecting full-wave rectifier circuits 121A and 121B. Fig. 9 shows the waveforms of voltage pulses input from each of full-wave rectifier circuits 121A and 121B.

[0055] When the voltage pulse rises to a predetermined selection start voltage, the power supply switching circuit 123 selects the full-wave rectifier circuit that outputs the voltage pulse and connects it to the constant voltage circuit 122 .

[0056] The output voltage of the selected full-wave rectifier circuit gradually decreases as the power stored in the selected full-wave rectifier circuit is consumed to drive the controller 125 and the nonvolatile memory 126. When the voltage pulse decreases to a predetermined deselection voltage, the power supply switching circuit 123 cuts off the connection between the selected full-wave rectifier circuit and the constant voltage circuit 122, thereby deselecting the selected full-wave rectifier circuit.

[0057] 10 is a diagram illustrating selection conditions for selecting an external main power supply, showing the waveform of a voltage input from the external main power supply (hereinafter also referred to as "external power supply voltage").

[0058] When the external power supply voltage rises to a predetermined selection start voltage, the power supply switching circuit 123 selects the external main power supply and connects it to the constant voltage circuit 122. When the voltage supply from the external main power supply stops and the external power supply voltage drops to a predetermined selection release voltage, the power supply switching circuit 123 cuts off the connection between the selected external main power supply and the constant voltage circuit 122, thereby deselecting the external main power supply.

[0059] Generally, the external power supply voltage is more stable than the output voltage of the full-wave rectifier circuits 121A and 121B. Therefore, after the external main power supply is selected, even if the voltage pulse output from either of the full-wave rectifier circuits 121A and 121B rises to the selection start voltage, that full-wave rectifier circuit is prevented from being selected and connected to the constant voltage circuit 122 until the external power supply voltage drops to the selection release voltage.

[0060] The selection start voltage and deselection voltage shown in Figures 9 and 10 are set to threshold values ​​that allow the controller 125 and non-volatile memory 126 to reliably complete processing after the full-wave rectifier circuits 121A, 121B or the external main power supply are selected and the controller 125 and non-volatile memory 126 are driven.

[0061] 11 is a diagram illustrating a first example of the operation of the power supply switching circuit 123. Fig. 11 shows the waveforms of the voltage pulse input from the full-wave rectifier circuit 121A and the external power supply voltage input from the external main power supply, as well as the operations of the power supply switching circuit 123 and the controller 125.

[0062] As shown in FIG. 11, at time t0, no voltage pulse is input and the external power supply voltage is less than the selection start voltage, so the power supply switching circuit 123 does not select either the full-wave rectifier circuits 121A, 121B or the external main power supply.

[0063] In this state, a voltage pulse is input from the full-wave rectifier circuit 121A, and when the voltage pulse rises to the selection start voltage (time t1), the power supply switching circuit 123 selects the full-wave rectifier circuit 121A and connects the full-wave rectifier circuit 121A to the constant voltage circuit 122.

[0064] The controller 125 operates by receiving a power supply voltage from the constant voltage circuit 122. The controller 125 executes a detection process based on the voltage pulse.

[0065] The power supply switching circuit 123 is configured not to switch the voltage source during execution of the detection process using the voltage pulse from the full-wave rectifier circuit 121A as the voltage source. In the example of FIG. 11 , at time t2 during execution of the detection process, the external power supply voltage rises to the selection start voltage. However, at time t2, the power supply switching circuit 123 does not deselect the full-wave rectifier circuit 121A and select the external main power supply. In other words, the power supply switching circuit 123 performs exclusive control to prevent the external main power supply from being connected to the constant voltage circuit 122.

[0066] Then, if the external power supply voltage exceeds the selection start voltage at time t3 when the detection process is completed, power supply switching circuit 123 selects the external main power supply and connects it to constant voltage circuit 122. As a result, the connection between full-wave rectifier circuit 121A and constant voltage circuit 122 is cut off and the external main power supply and constant voltage circuit 122 are connected before time t4 when the voltage pulse input from full-wave rectifier circuit 121A drops to the selection release voltage.

[0067] 12 is a diagram illustrating a second example of the operation of the power supply switching circuit 123. In FIG. 12, the waveforms of the voltage pulse input from the full-wave rectifier circuit 121A and the external power supply voltage input from the external main power supply are shown, and the operations of the power supply switching circuit 123 and the controller 125 are also shown.

[0068] 12, at time t0, no voltage pulse is input. Because the external power supply voltage is equal to or higher than the selection start voltage, the power supply switching circuit 123 selects the external main power supply and connects it to the constant voltage circuit 122. Therefore, the controller 125 receives a voltage supply from the external main power supply and performs the write process.

[0069] In this state, when a voltage pulse is input from the full-wave rectifier circuit 121A, the power supply switching circuit 123 does not switch the voltage source during the write process using the external main power supply as the voltage source. In the example of FIG. 12 , at time t1 during the write process, the external power supply voltage drops to the deselection voltage, while at time t2, after time t1, the voltage pulse rises to the selection start voltage. However, the power supply switching circuit 123 does not deselect the external main power supply at time t1. In other words, the power supply switching circuit 123 performs exclusive control to prevent the full-wave rectifier circuit 121A from being connected to the constant voltage circuit 122.

[0070] Then, if the voltage pulse exceeds the selection start voltage at time t3 when the write process is completed, the power supply switching circuit 123 selects the full-wave rectifier circuit 121A and connects it to the constant voltage circuit 122. At time t4 when the voltage pulse input from the full-wave rectifier circuit 121A drops to the selection release voltage, the power supply switching circuit 123 cuts off the connection between the full-wave rectifier circuit 121A and the constant voltage circuit 122.

[0071] 13 is a diagram illustrating a third example of the operation of the power supply switching circuit 123. Fig. 13 shows the waveforms of the voltage pulse (A-phase pulse) input from the full-wave rectifier circuit 121A and the voltage pulse (B-phase pulse) input from the full-wave rectifier circuit 121B, and the operations of the power supply switching circuit 123 and the controller 125.

[0072] 13, at time t0, no A-phase pulses or B-phase pulses are input. In addition, because the external power supply voltage (not shown) is lower than the selection start voltage, the power supply switching circuit 123 does not select any of the full-wave rectifier circuits 121A and 121B or the external main power supply.

[0073] In this state, when a B-phase pulse is input from the full-wave rectifier circuit 121B, the power supply switching circuit 123 selects the full-wave rectifier circuit 121B and connects it to the constant voltage circuit 122 in response to the B-phase pulse rising to the selection start voltage at time t1. The controller 125 receives a supply of voltage from the full-wave rectifier circuit 121B and executes a detection process based on the B-phase pulse.

[0074] The power supply switching circuit 123 is configured not to switch the voltage source during execution of the detection process using the B-phase pulse from the full-wave rectifier circuit 121B as the voltage source. In the example of FIG. 13 , at time t2 during execution of the detection process, the A-phase pulse rises to the selection start voltage. However, the power supply switching circuit 123 does not cancel the selection of the full-wave rectifier circuit 121B at time t2. In other words, the power supply switching circuit 123 performs exclusive control to prevent the full-wave rectifier circuit 121A from being connected to the constant voltage circuit 122.

[0075] Then, if the A-phase pulse exceeds the selection start voltage at time t3 when the detection process is completed, the power supply switching circuit 123 selects the full-wave rectifier circuit 121A and connects it to the constant voltage circuit 122. At time t5 when the voltage pulse input from the full-wave rectifier circuit 121A drops to the selection release voltage, the power supply switching circuit 123 cuts off the connection between the full-wave rectifier circuit 121A and the constant voltage circuit 122.

[0076] During execution of the detection process based on the B-phase pulse, the power supply switching circuit 123 executes exclusive control to prevent the full-wave rectifier circuit 121A from being connected to the constant voltage circuit 122, thereby preventing consumption of the power stored in the capacitor in the full-wave rectifier circuit 121A before the start of the detection process based on the A-phase pulse. This makes it possible to prevent the controller 125 from running out of power during execution of the detection process based on the A-phase pulse.

[0077] (Voltage Pulse Detection Circuit 124) The voltage pulse detection circuit 124 receives voltage pulses (A-phase pulse, B-phase pulse) output from the A-phase detection coil 112 and the B-phase detection coil 113, and detects the voltage pulses of each phase. FIG. 14 is a diagram illustrating the operation of the voltage pulse detection circuit 124. FIG. 14 shows the waveforms of voltage pulses input from the detection coils. The voltage pulse detection circuit 124 generates a positive-going pulse detection signal when the voltage pulse reaches a positive-going pulse detection voltage. The voltage pulse detection circuit 124 generates a negative-going pulse detection signal when the voltage pulse reaches a negative-going pulse detection voltage. The voltage pulse detection circuit 124 outputs the generated detection signal (hereinafter also referred to as a "voltage pulse detection signal") to the controller 125.

[0078] The detection signal of each phase detection coil may be implemented in any manner as long as it indicates the polarity (positive direction / negative direction) and phase (A phase / B phase) of the detected voltage pulse.

[0079] (Non-volatile memory 126) The non-volatile memory 126 stores the state of the detection coil for each phase when a voltage pulse is generated, the number of rotations of the rotating shaft 115, and information about the detection coil that generated the voltage pulse (detection coil number). This information is acquired by the controller 125 each time either of the detection coils 112 and 113 generates a voltage pulse. The controller 125 processes the acquired information and stores the processing results in the non-volatile memory 126. The non-volatile memory 126 also stores a conversion table (see FIG. 16 ), which will be described later.

[0080] The nonvolatile memory 126 is configured to store information about the state of each phase detection coil and the detection coil that generated the voltage pulse, at least the state of each phase detection coil when the previous voltage pulse was generated and the detection coil that generated the previous voltage pulse. This information is updated by the controller 125 every time a voltage pulse is generated.

[0081] Furthermore, by adding a parity code, a cyclic redundancy check (CRC) code, or a Hamming code to the data stored in the nonvolatile memory 126, the reliability of the stored data can be improved.

[0082] (Oscillator Circuit 128) The oscillator circuit 128 is configured to supply a clock that serves as a reference for the operation of the controller 125 and the nonvolatile memory 126. Specifically, the oscillator circuit 128 outputs an internally generated clock to the controller 125. The controller 125 uses the received clock and outputs the clock to the nonvolatile memory 126.

[0083] For example, the controller 125 outputs a clock to the nonvolatile memory 126 only when access to the nonvolatile memory 126 is required. This reduces power consumption when the nonvolatile memory 126 is not being accessed. Alternatively, the controller 125 can reduce the speed at which the nonvolatile memory 126 is accessed by dividing the frequency of the received clock and outputting the divided clock to the nonvolatile memory 126, thereby reducing power consumption during access. This reduces the load on the constant voltage circuit 122, thereby stabilizing the operation of the constant voltage circuit 122.

[0084] The oscillator circuit 128 outputs a clock enable signal indicating that the voltage, period, duty ratio, etc. of the internally generated clock are stable to the controller 125. The controller 125 starts operating in response to the clock enable signal becoming valid, thereby improving the reliability of the operation of the controller 125.

[0085] (Controller 125) The controller 125 is driven by the voltage supplied from the constant voltage circuit 122 and operates in synchronization with the clock supplied from the oscillation circuit 128. The controller 125 maintains its initial state and does not operate from the time when the voltage is supplied from the constant voltage circuit 122 and the clock is supplied from the oscillation circuit 128 until the clock enable signal becomes valid. The controller 125 then starts operating at the time when the clock enable signal becomes valid.

[0086] FIG. 15 is a flowchart illustrating the flow of processing from when the controller 125 starts to when it finishes its operation.

[0087] 15 , when controller 125 starts operation, it first executes a “read process” in step (hereinafter, step will be abbreviated as “S”) 101. In the read process (S101), controller 125 reads information stored in nonvolatile memory 126 regarding the state of the detection coil for each phase when a voltage pulse was generated, the number of rotations of rotating shaft 115, and the detection coil (detection coil number) that generated the voltage pulse, and stores the read information inside controller 125.

[0088] It should be noted that if the supply of voltage from the constant voltage circuit 122 to the controller 125 is interrupted, the information held within the controller 125 will be lost. Therefore, when the voltage supply from the constant voltage circuit 122 is interrupted and then resumed, the controller 125 reads out the information from the nonvolatile memory 126 and holds it within the controller 125.

[0089] At this time, the clock may be supplied to the nonvolatile memory 126 only while the controller 125 is executing the read process (S101), or the clock may be continuously supplied to the nonvolatile memory 126 from when the controller 125 starts operation until when the controller 125 ends operation. However, since power consumption increases while the clock is being supplied, power consumption can be reduced by supplying the clock to the nonvolatile memory 126 only while the read process (S101) is being executed.

[0090] Next, in S102, the controller 125 determines whether a voltage pulse has been detected based on the voltage pulse detection signal provided by the voltage pulse detection circuit 124. If it is determined that a voltage pulse has been detected (YES in S102), the controller 125 proceeds to S103 and executes an "update process." In the update process (S103), the controller 125 calculates the latest state of the detection coils for each phase and the rotation speed of the rotating shaft 115, etc., using the conversion table shown in FIG. 16 based on information stored internally and the voltage pulse detection signal input from the voltage pulse detection circuit 124. The controller 125 uses the calculation results to update and store the internal information.

[0091] Fig. 16 is a diagram showing an example of a conversion table. As shown in Fig. 16, the conversion table shows the transition of the state of each phase detection coil and the region in which the magnet reference is located as the magnet 111 rotates. In the conversion table, "before update" means the state before the current voltage pulse updated, and "after update" means the state after the current voltage pulse updated. An "H" in the voltage pulse detection signal indicates a state in which a positive voltage pulse is detected in each phase detection coil, and an "L" indicates a state in which a negative voltage pulse is detected in each phase detection coil.

[0092] The updated information includes the "area" and "magnetization state," as well as the updated count value (multi-rotation counter value) of the number of rotations of the rotating shaft 115. "No change" indicates that the number of rotations will not be updated, "Increase (+1)" indicates that the number of rotations will be increased by +1, and "Decrease (-1)" indicates that the number of rotations will be decreased by -1.

[0093] 16, the controller 125 may determine that an abnormality has occurred and execute a process other than the process of updating the count value of the number of rotations of the rotating shaft 115. For example, information notifying the occurrence of an abnormality may be stored in advance in the controller 125 or the nonvolatile memory 126, and the information notifying the occurrence of an abnormality may be updated instead of updating the count value of the number of rotations of the rotating shaft 115. In this way, it is possible to prevent an incorrect number of rotations of the rotating shaft 115 from being read out to the outside of the rotation detection device 101.

[0094] Furthermore, in order to analyze the cause of the abnormality, a voltage pulse detection signal indicating the polarity and phase number of the voltage pulse obtained from the voltage pulse detection circuit 124 when the abnormality occurs may be included in the information notifying the occurrence of the abnormality.

[0095] If no voltage pulse is detected in S102 (NO in S102), or if the update process (S103) has ended, the controller 125 determines in S104 whether the external main power supply is in a selected state and the external power supply voltage exceeds the deselection voltage based on a signal from the power supply switching circuit 123. If the external main power supply is in a selected state and the external power supply voltage exceeds the deselection voltage, a YES determination is made in S104. If the external main power supply is not in a selected state, a NO determination is made in S104.

[0096] If the external main power supply is selected and the external power supply voltage exceeds the deselection voltage (YES in S104), the controller 125 returns to S102 and executes the processes of S102 and S103 again. That is, the controller 125 determines whether the next voltage pulse has been detected in S102, and if the next voltage pulse has been detected (YES in S102), the controller 125 calculates the latest state of the detection coils for each phase and the rotation speed of the rotating shaft 115, etc., using the conversion table shown in FIG. 16 based on the information stored internally and the voltage pulse detection signal input from the voltage pulse detection circuit 124. The controller 125 uses this calculation result to update and store the internal information.

[0097] While the external main power supply remains selected (YES in S104), a stable voltage is supplied from the external main power supply to the constant voltage circuit 122 even if no new voltage pulses are supplied from the detection coil, so the controller 125 can continue to stably store information internally. Therefore, the controller 125 returns to S102 while retaining the information.

[0098] On the other hand, if the external main power supply is not selected (NO in S104), the controller 125 proceeds to S105 and executes a "write process." In the write process (S105), the controller 125 writes to the non-volatile memory 126 the information stored internally, including the state of the detection coil for each phase when the voltage pulse was generated, the number of rotations of the rotating shaft 115, and the detection coil that generated the voltage pulse.

[0099] If the external main power supply is not selected (NO in S104), the constant voltage circuit 122 cannot receive a voltage supply from the external main power supply, and as the voltage pulses output by the full-wave rectifier circuit connected to the constant voltage circuit 122 gradually decrease, the constant voltage circuit 122 is no longer able to supply a constant voltage to the controller 125. This causes the information held within the controller 125 to be erased. Therefore, before the output voltage of the constant voltage circuit 122 decreases, the controller 125 executes a write process (S105) to store the information held within the controller 125 in the nonvolatile memory 126.

[0100] When the writing process (S105) is completed, in S106, the controller 125 determines, based on the voltage pulse detection signal provided from the voltage pulse detection circuit 124, whether or not a voltage pulse different from the voltage pulse used to calculate the latest state of each phase detection coil and the rotation speed of the rotating shaft 115 has been detected.

[0101] If it is determined that a voltage pulse has been detected (YES in S106), the controller 125 acquires the time point at which the full-wave rectifier circuit connected to the constant voltage circuit 122 was switched to another full-wave rectifier circuit based on a signal from the power supply switching circuit 123. The controller 125 then executes a "standby process" for a predetermined time from the time point at which the voltage source was switched. The standby process is a process in which the controller waits for operation after the voltage source is switched until the voltage stabilizes.

[0102] Generally, immediately after switching the voltage source, the voltage fluctuates without stabilizing, and gradually converges to a constant voltage level. Therefore, if a large load is applied immediately after switching the voltage source, the voltage level drops significantly, which may result in the loss of information held by the controller 125. In particular, when access to the nonvolatile memory 126 occurs in the write process (S105), a large amount of power is consumed, increasing the possibility that the controller 125 will lose information. Therefore, by providing a standby process (S107) immediately after switching the voltage source, the voltage drop can be avoided.

[0103] After the standby process (S107) is completed, the controller 125 executes the update process (S103). Based on the voltage pulse detected in S106 and the information stored internally, the controller 125 uses a conversion table (FIG. 16) to calculate the latest state of the detection coils for each phase and the rotation speed of the rotating shaft 115. The controller 125 uses the calculation results to update and store the internal information.

[0104] On the other hand, if it is determined in S106 that a voltage pulse has not been detected (NO in S106), the controller 125 determines in S108 whether or not the external main power supply is in a selectable state based on the signal from the power supply switching circuit 123. If the output voltage of the external main power supply has reached the selection start voltage, a YES determination is made in S108.

[0105] If it is determined that the external main power supply is selectable (YES in S108), the controller 125 returns to S102 and executes the processes of S102 and S103 again. That is, the controller 125 determines whether the next voltage pulse has been detected in S102, and if the next voltage pulse has been detected (YES in S102), executes the update process (S103). The controller 125 uses a conversion table based on the voltage pulse detected in S102 and information stored internally to calculate the latest state of the detection coils for each phase and the rotation speed of the rotating shaft 115. The controller 125 uses the calculation results to update and store the internal information.

[0106] On the other hand, if it is determined that the external main power supply is not selectable (NO in S108), the controller 125 stops the voltage supply from the constant voltage circuit 122 and therefore ends the operation.

[0107] 15 , let us consider a case where the controller 125 terminates operation after executing the write process (S105) without executing the processes of S106 and S108. In this case, even though the controller 125 receives a voltage supply from either the external main power supply or the full-wave rectifier circuits 121A and 121B and the information stored therein has not been lost, the controller 125 will execute the read process (S101) in response to the restart of operation. In other words, the controller 125 will perform an unnecessary operation.

[0108] In contrast, in the first embodiment, if a voltage can be supplied from either the external main power supply or full-wave rectifier circuits 121A, 121B between the read process (S101) and the write process (S105) (YES determinations in S102, S104, and S106), the controller 125 is configured to omit the read process (S101) and execute the write process (S105). This allows the controller 125 to correctly detect the state of the detection coils for each phase and the rotation speed of the rotating shaft 115, even if the output intervals of the voltage pulses become shorter as the rotation speed of the rotating shaft 115 increases.

[0109] For example, even in a situation where the current voltage pulse attenuates while waiting for the completion of the write process (S105) for the previous voltage pulse after it exceeds the detection voltage, power consumption is reduced due to the effect of omitting the read process (S101), so the update process (S103) and write process (S105) can be performed correctly for the current voltage pulse.

[0110] This allows the controller 125 to execute the update process (S103) and the write process (S105) using only the voltage generated from the voltage pulse each time either of the detection coils 112 and 113 outputs the voltage pulse, thereby making it possible to detect the rotation state of the rotating shaft 115 without receiving a voltage supply from an external main power supply.

[0111] (External circuit I / F 127) When reading the rotation speed of the rotating shaft 115 from outside the rotation detection device 101, the rotation speed can be read by accessing the non-volatile memory 126 via the external circuit I / F 127 and the controller 125.

[0112] Furthermore, if the rotation number is updated during the rotation number reading operation, the controller 125 creates the read data so that the read data is not split.

[0113] The external circuit I / F 127 may be configured by a parallel communication I / F including a clock signal, an address signal, a data signal, and a data valid signal, or may be configured by a serial communication I / F such as a UART (Universal Asynchronous Receiver Transmitter), an SPI (Serial Peripheral Interface), an I2C (Inter-Integrated Circuit), or a USB (Universal Serial Bus).

[0114] When the nonvolatile memory 126 is accessed from the outside, a power supply voltage is supplied from the external main power supply to the power supply switching circuit 123 through the external circuit I / F 127. This makes it possible to read the rotation speed without relying on the power of the voltage pulse.

[0115] When a voltage is supplied from an external main power supply via external circuit I / F 127, power supply switching circuit 123 connects the external main power supply to constant voltage circuit 122, and voltage is supplied to controller 125. When controller 125 receives voltage from constant voltage circuit 122 and starts operating, it first executes a read process (S101). In the read process (S101), controller 125 reads information stored in nonvolatile memory 126 about the state of the detection coils for each phase when a voltage pulse was generated, the number of rotations of rotating shaft 115, and the detection coil that generated the voltage pulse, and stores the read information inside controller 125.

[0116] Thereafter, when the voltage supply from the external main power supply is cut off (YES in S104 ), the controller 125 proceeds to a write process ( S105 ) and writes the information held within the controller 125 to the non-volatile memory 126 .

[0117] In this way, voltage is supplied from the external main power supply, and the controller 125 reads the number of rotations of the rotating shaft 115 after completing the read process (S101), thereby eliminating the need to access the nonvolatile memory 126 to read the number of rotations. This makes it possible to avoid conflict between the above-mentioned detection process and the operation of reading the number of rotations from the outside.

[0118] When assembling the rotation detection device 101, or when reassembling the rotation detection device 101 that has been disassembled, the positional relationship between the magnet 111 and the detection coils 112, 113 estimated from the information stored in the non-volatile memory 126, such as the state of the detection coils of each phase when a previous voltage pulse was generated, the number of rotations of the rotating shaft 115, and the detection coil that generated the voltage pulse, does not necessarily match the actual positional relationship between the magnet 111 and the detection coils 112, 113.

[0119] Therefore, when assembling the rotation detection device 101, or when reassembling the rotation detection device 101 that has been disassembled, the controller 125 initializes the non-volatile memory 126 by updating only the state of the detection coils of each phase when a voltage pulse was generated and the information about the detection coil that generated the voltage pulse, without updating the number of rotations of the rotating shaft 115, until the state reflects the actual positional relationship between the magnet 111 and the detection coils 112 and 113 (for example, until at least two voltage pulses have been generated). This allows the estimated positional relationship to match the actual positional relationship.

[0120] As described above, in the rotation detection device 101 according to the first embodiment, if the voltage pulse detection circuit 124 detects the second voltage pulse before completing the detection process based on the first voltage pulse (YES determination in S106), the controller 125 is configured to omit at least the read process (S101) of the detection process based on the second voltage pulse.

[0121] Specifically, when the write process (S105) based on the first voltage pulse is completed, if the voltage pulse detection circuit 124 detects the second voltage pulse (YES in S106), the controller 125 omits the read process (S101) and executes the update process (S103) based on the second voltage pulse.

[0122] Furthermore, if the external main power supply is in a selected state at the time when the update process based on the first voltage pulse (S103) is completed and the external power supply voltage exceeds the deselection voltage (YES determination in S104), the controller 125 omits the write process based on the first voltage pulse (S105) and the read process (S101), and executes the update process based on the second voltage pulse (S103).

[0123] Therefore, according to the rotation detection device 101 according to embodiment 1, even if the output interval of the voltage pulses in the detection coils 112 and 113 becomes shorter as the rotation speed of the rotating shaft 115 increases, the controller 125 can accurately and stably detect the rotation state of the rotating shaft 115.

[0124] Embodiment 2 Fig. 17 is a diagram showing the overall configuration of a rotation detection device 201 according to embodiment 2. As shown in Fig. 17, rotation detection device 201 according to embodiment 2 includes rotation detection mechanism 110 and signal processing circuit 220. Signal processing circuit 220 differs from signal processing circuit 120 shown in Fig. 1 in that it includes controller 225 instead of controller 125.

[0125] Like the controller 125, the controller 225 is driven by the voltage supplied from the constant voltage circuit 122 and operates in synchronization with the clock supplied from the oscillation circuit 128. However, the flow of a series of processes from the start of operation from the initial state to the end of operation is different from that of the controller 125.

[0126] Fig. 18 is a flowchart illustrating the flow of processing from the start to the end of operation of the controller 225. The flowchart shown in Fig. 18 differs from the flowchart shown in Fig. 15 in that it includes S204 instead of S104 and in that S209 has been added.

[0127] As shown in FIG. 18, after completing the update process (S103), in S209 the controller 225 determines, based on the voltage pulse detection signal provided from the voltage pulse detection circuit 124, whether or not a voltage pulse different from the voltage pulse used to calculate the latest state of each phase detection coil and the rotation speed of the rotating shaft 115 has been detected.

[0128] If it is determined that a voltage pulse has been detected (YES in S209), the controller 225 executes standby processing (S107) based on a signal from the power supply switching circuit 123. That is, the controller 225 waits for a predetermined time from the point in time when the full-wave rectifier circuit connected to the constant voltage circuit 122 is switched to another full-wave rectifier circuit.

[0129] After the standby process (S107) is completed, the controller 225 executes the update process (S103). Based on the voltage pulse detected in S209 and the information stored internally, the controller 225 uses a conversion table (FIG. 16) to calculate the latest state of the detection coils for each phase and the rotation speed of the rotating shaft 115. The controller 225 uses the calculation results to update and store the internal information.

[0130] In the second embodiment, by providing the process of S209 immediately after the update process (S103), if another voltage pulse is detected while the update process (S103) based on the voltage pulse detected in S102 is being executed, the update process (S103) based on this other voltage pulse can be executed immediately after the update process (S103) is completed. As a result, even if the output interval of the voltage pulses becomes shorter as the rotation speed of the rotating shaft 115 increases, the state of the detection coils for each phase and the rotation speed of the rotating shaft 115 can be accurately calculated.

[0131] If it is determined in S209 that a voltage pulse has not been detected (NO in S209), or if a voltage pulse has not been detected in S102 (NO in S102), the controller 225 determines in S204, based on the signal from the power supply switching circuit 123, whether or not the external power supply voltage exceeds the deselection voltage when the external main power supply is in a selected state, or whether or not the external power supply voltage has reached the selection start voltage and therefore the external main power supply is in a selectable state.

[0132] If the external main power supply is in a selected state and the external power supply voltage is higher than the selection release voltage, or if the external power supply voltage has reached the selection start voltage and the external main power supply is in a selectable state (YES in S204), the controller 225 returns to S102 and executes the processes of S102 and S103 again. That is, the controller 225 determines whether the next voltage pulse has been detected in S102, and if the next voltage pulse has been detected (YES in S102), executes the update process (S103). On the other hand, if the external main power supply is in a selected state and the external power supply voltage is lower than the selection release voltage, or if the external power supply voltage has not reached the selection start voltage (NO in S204), the controller 225 executes the write process (S105).

[0133] 15 in that the process of S204 only checks the magnitude of the current external power supply voltage, regardless of whether the external main power supply is in a selected state. This makes it possible to skip the write process (S105) and read process (S101) when the activation of the external main power supply is detected in a case where the external main power supply is in a non-selected state and the controller 125 is operating by receiving voltage from the full-wave rectifier circuit 121A or 121B.

[0134] As described above, according to the rotation detection device 201 of the second embodiment, if a state is reached in which the second voltage pulse output by the second detection coil or a voltage supply from the external main power supply can be received between the time when the read process (S101) is performed and the time when the update process (S103) based on the first voltage pulse is completed (YES determinations in S209 and S204), the write process (S105) based on the first voltage pulse and the subsequent read process (S101) are omitted.

[0135] This allows the controller 225 to continue executing the update process based on the second voltage pulse (S103) after completing the update process based on the first voltage pulse (S103).As a result, even if the rotation speed of the rotating shaft 115 further increases and the output interval of the voltage pulses becomes even shorter, it becomes possible to correctly calculate the state of the detection coils for each phase and the rotation speed of the rotating shaft 115.

[0136] Embodiment 3 Fig. 19 is a diagram showing the overall configuration of a rotation detection device 301 according to embodiment 3. As shown in Fig. 19, rotation detection device 301 according to embodiment 3 includes rotation detection mechanism 110 and a signal processing circuit 320. Signal processing circuit 320 differs from signal processing circuit 120 shown in Fig. 1 in that it includes a controller 325 instead of controller 125.

[0137] Like the controller 125, the controller 325 is driven by the voltage supplied from the constant voltage circuit 122 and operates in synchronization with the clock supplied from the oscillation circuit 128. However, the flow of a series of processes from the start of operation from the initial state to the end of operation is different from that of the controller 125.

[0138] Fig. 20 is a flowchart illustrating the flow of processing from the start to the end of operation of the controller 325. The flowchart shown in Fig. 20 differs from the flowchart shown in Fig. 15 in that it includes S307 instead of S107 and in that S310 has been added.

[0139] As shown in Fig. 20, if it is determined that a voltage pulse has been detected after the write process (S105) is completed (YES in S106), the controller 325 executes the update process (S103) without executing the standby process (S107 in Fig. 15). The controller 325 uses a conversion table to calculate the latest state and rotation speed of each phase detection coil based on the voltage pulse detected in S106 and the information stored internally. The controller 325 uses the calculation results to update and store the internal information.

[0140] If no voltage pulse is detected in S102 (NO in S102) or if the update process (S103) is completed and the external main power supply is not selected (NO in S104), the controller 325 determines in S310 whether the immediately preceding update process (S103) was an update process (S103) executed based on another voltage pulse after the write process (S105) was completed.

[0141] If it is determined that the immediately preceding update process (S103) was based on a different voltage pulse (YES in S106), the controller 325 proceeds to S307 and executes standby processing. This is to avoid the write process (S105) to the nonvolatile memory 126 being executed in a state where the power supply voltage is unstable because not much time has passed since the power supply switching circuit 123 switched from one full-wave rectifier circuit to the other full-wave rectifier circuit when the immediately preceding update process (S103) was based on a different voltage pulse.

[0142] As described above, in the rotation detection device 301 according to the third embodiment, when the voltage source is switched to the full-wave rectifier circuit in response to the generation of the second voltage pulse (YES in S106), the update process (S103) based on the second voltage pulse is executed, followed by the standby process (S307). This allows the update process (S103) based on each voltage pulse to be executed quickly without the standby process (S307) when multiple voltage pulses are generated consecutively. Therefore, even if the rotation speed of the rotating shaft 115 further increases and the interval between voltage pulse outputs becomes even shorter, the state of the detection coils for each phase and the rotation speed of the rotating shaft 115 can be accurately calculated.

[0143] Embodiment 4 Fig. 21 is a diagram showing the overall configuration of a rotation detection device 401 according to embodiment 4. As shown in Fig. 21, rotation detection device 401 according to embodiment 4 includes a rotation detection mechanism 410 and a signal processing circuit 420.

[0144] The rotation detection mechanism 410 differs from the rotation detection mechanism 110 shown in Fig. 1 in that it includes half-wave rectifier circuits 421A and 421B. The signal processing circuit 420 differs from the signal processing circuit 120 shown in Fig. 1 in that it does not include full-wave rectifier circuits 121A and 121B, and that it includes a power supply switching circuit 423 and a controller 425 instead of the power supply switching circuit 123 and the controller 125.

[0145] (Half-wave rectifier circuits 421A, 421B) Fig. 22 is a circuit diagram showing an example configuration of the half-wave rectifier circuit 421 A. As shown in Fig. 22, the half-wave rectifier circuit 421 A includes input terminals T1 and T2, output terminals T3 to T6, diodes D1 and D2, and capacitors C1 and C2.

[0146] The detection coil 112 is connected between the input terminal T1 and the input terminal T2. The output terminals T3 to T6 are connected to the power supply switching circuit 423. The anode of the diode D1 is connected to the input terminal T1, and the cathode is connected to the output terminal T3. The capacitor C1 is connected between the cathode of the diode D1 and the input terminal T2. The diode D1 half-wave rectifies the positive voltage pulses among the voltage pulses output by the detection coil 112. The capacitor C1 stores the charge of the voltage pulses half-wave rectified by the diode D1. The stored voltage pulses are output between the output terminals T3 and T4.

[0147] The anode of diode D2 is connected to input terminal T2, and the cathode is connected to output terminal T6. Capacitor C2 is connected between the cathode of diode D2 and input terminal T1. Diode D2 half-wave rectifies negative voltage pulses among the voltage pulses output by detection coil 112. Capacitor C2 stores the charge of the voltage pulses half-wave rectified by diode D2. The stored voltage pulses are output between output terminals T6 and T5.

[0148] The configuration of the half-wave rectifier circuit 421B is the same as the configuration of the half-wave rectifier circuit 421A, except that the detection coil 113 is connected between the input terminal T1 and the input terminal T2.

[0149] 1 , in the configuration including full-wave rectifier circuits 121A and 121B, signal processing circuit 120 cannot determine the polarity of the voltage pulse output by detection coils 112 and 113 from the rectified voltage pulse. In contrast, in embodiment 4, half-wave rectifier circuits 421A and 421B each have output terminals T3 and T4 that half-wave rectify a positive voltage pulse and output the result, and output terminals T5 and T6 that half-wave rectify a negative voltage pulse and output the result, and therefore it is possible to determine the polarity of the voltage pulse output by detection coils 112 and 113.

[0150] When the rotation detection mechanism 110 performs a high-speed reversal operation, the detection coil may receive positive and negative voltage pulses consecutively. Figure 23 schematically illustrates how the capacitor in the full-wave rectifier circuit 121A stores charge from the positive and negative voltage pulses output from the detection coil 112. As shown in Figure 23, if a second negative voltage pulse is received after a charge has been stored in the capacitor by a first positive voltage pulse, the capacitor cannot store all of the charge from the second voltage pulse because a voltage is already applied to the capacitor. Therefore, the controller 125 may experience a power shortage while executing a detection process based on the second voltage pulse.

[0151] 24 is a schematic diagram showing how capacitors C1 and C2 in half-wave rectifier circuit 421A store electric charge corresponding to the positive and negative voltage pulses output from detection coil 112. As shown in FIG. 24, electric charge is stored in capacitor C1 by the first positive voltage pulse, and electric charge is stored in capacitor C2 by the second negative voltage pulse. This allows electric charge from the second voltage pulse to be stored in the same way as the first voltage pulse, thereby preventing controller 125 from running out of power while performing detection processing based on the second voltage pulse.

[0152] (Voltage pulse detection circuit 424) Voltage pulse detection circuit 424 is configured to be able to detect half-wave rectified voltage pulses output from half-wave rectifier circuits 421 A and 421 B. Other functions are similar to those of voltage pulse detection circuit 124 shown in FIG. 1 , and therefore detailed description thereof will not be repeated.

[0153] (Power supply switching circuit 423) The power supply switching circuit 423 is electrically connected to the output terminals T3 to T6 of each of the half-wave rectifier circuits 421 A and 421 B. The power supply switching circuit 423 selectively connects the output terminals T3 and T4 or the output terminals T5 and T6 to the constant voltage circuit 122 depending on the voltage of the voltage pulse output between the output terminals T3 and T4 and the voltage of the voltage pulse output between the output terminals T5 and T6.

[0154] In addition, in embodiment 4, voltage pulse detection circuit 424 detects voltage pulses from half-wave rectified voltage pulses, so if charge is stored in the capacitors in half-wave rectification circuits 421A, 421B by the voltage pulses output from detection coils 112, 113, when detection coil 112 outputs the next voltage pulse, the next voltage pulse will be buried by the voltage stored in the capacitor, and there is a possibility that voltage pulse detection circuit 424 will not be able to detect the voltage pulse.

[0155] Therefore, the power supply switching circuit 423 according to the fourth embodiment is configured to receive a signal from the controller 425 and discharge the charge stored in the capacitors in the half-wave rectifier circuits 421A, 421B connected to the power supply switching circuit 423.

[0156] For example, as shown in FIG. 22 , the power supply switching circuit 423 includes a switch S1 and a discharge resistor R1 connected in series between output terminals T3 and T4 of the half-wave rectifier circuit 421A, and a switch S2 and a discharge resistor R2 connected in series between output terminals T5 and T6. The power supply switching circuit 423 receives a signal from the controller 425 and turns on the switch S1, thereby connecting the discharge resistor R1 to the capacitor C1. This causes the charge stored in the capacitor C1 to be discharged using the discharge resistor R1. The power supply switching circuit 423 also receives a signal from the controller 425 and turns on the switch S2, thereby connecting the discharge resistor R2 to the capacitor C2. This causes the charge stored in the capacitor C2 to be discharged using the discharge resistor R2.

[0157] Although not shown, the power supply switching circuit 123 according to the first embodiment can also be configured to receive a signal from the controller 125 and discharge the charge stored in the capacitors in the full-wave rectifier circuits 121A and 121B connected to the power supply switching circuit 123. For example, a switch and a discharge resistor can be connected in series between the output terminals of each of the full-wave rectifier circuits 121A and 121B, and the switch can be turned on in response to a signal from the controller 125, thereby discharging the charge stored in the capacitor.

[0158] (Controller 425) The controller 425 differs from the controller 125 shown in FIG. 1 in that the controller 425 executes a "capacitor discharge process" that outputs a signal to the power supply switching circuit 423 to discharge the electric charge stored in the capacitors C1 and C2 of the half-wave rectifier circuits 421A and 421B.

[0159] Like the controller 125, the controller 425 is driven by the voltage supplied from the constant voltage circuit 122 and operates in synchronization with the clock supplied from the oscillation circuit 128. However, the flow of a series of processes from the start of operation from the initial state to the end of operation is different from that of the controller 125.

[0160] Fig. 25 is a flowchart illustrating the flow of processing from when the controller 425 starts to when it finishes its operation. The flowchart shown in Fig. 25 differs from the flowchart shown in Fig. 15 in that steps S411 to S413 have been added.

[0161] 25, when the external main power supply is in a selected state and the external power supply voltage is higher than the selection start voltage (YES in S104), or when it is determined that the external main power supply is in a selectable state (YES in S108), the controller 425 executes a capacitor discharge process (S411) to discharge the charge stored in the capacitors C1 and C2 of the half-wave rectifier circuit 421A or 421B. After executing the capacitor discharge process (S411), the controller 425 returns to S102.

[0162] Furthermore, if it is determined that a voltage pulse different from the voltage pulse used to calculate the most recent state of the detection coils for each phase and the rotation speed of the rotating shaft 115 has been detected (YES in S106), the controller 425 executes a capacitor discharge process (S412). After executing the capacitor discharge process (S412), the controller 425 executes a standby process (S107).

[0163] Furthermore, if it is determined that the external main power supply is not selectable (NO in S108), the controller 425 executes a capacitor discharge process (S413). After executing the capacitor discharge process (S413), the controller 425 ends its operation.

[0164] As described above, rotation detection device 401 according to embodiment 4 can obtain the same effects as rotation detection device 101 according to embodiment 1, and can also correctly calculate the state of each phase detection coil and the rotation speed of rotating shaft 115 even when the rotation speed of rotating shaft 115 becomes high and the output interval between voltage pulses becomes short.

[0165] Furthermore, by disposing capacitors C1 and C2 included in half-wave rectifier circuits 421A and 421B outside signal processing circuit 420, when signal processing circuit 420 is manufactured as an IC (integrated circuit), a semiconductor process for forming capacitors C1 and C2 on the IC is not required. As a result, compared to rotation detector 101 according to the first embodiment, the IC manufacturing method is not limited, which reduces the manufacturing cost of the IC and allows an increase in the number of manufacturers that can manufacture the IC. As a result, it is possible to improve the availability and cost of ICs.

[0166] Embodiment 5 In embodiment 5, a device to which the rotation detection device according to embodiments 1 to 4 can be applied will be described. The rotation detection device according to embodiments 1 to 4 can be applied to a device having a rotating shaft 115. Such devices include, for example, a battery-less multi-rotation encoder, a fluid volume sensor, and a steering device.

[0167] (Battery-less multi-rotation encoder) Fig. 26 is a block diagram showing an example of the configuration of a battery-less multi-rotation encoder according to embodiment 5. As shown in Fig. 26, rotation detection device 101 can be applied to a battery-less multi-rotation encoder that uses power generated by the rotational energy of rotating shaft 115 of motor 700 to detect and hold the rotation direction and number of rotations of rotating shaft 115.

[0168] Motor 700 is, for example, a servo motor for an industrial robot or a spindle motor for a machine tool. Rotation detection mechanism 110 of rotation detection device 101 is attached to rotating shaft 115, which is the output shaft of motor 700. Signal processing circuit 120 generates a power supply voltage for signal processing circuit 120 using the power of a voltage pulse provided by rotation detection mechanism 110, and detects the rotation direction and rotation speed of rotating shaft 115 based on the voltage pulse. Driver 710 drives motor 700 based on the output signal of signal processing circuit 120.

[0169] 27 is a block diagram showing an example of the configuration of a flowmeter according to embodiment 5. As shown in FIG. 27 , rotation detection device 101 can be applied to a flow sensor 550 for detecting the discharge flow rate of electric pump 520.

[0170] Water is stored in the water storage tank 500. The upstream end of a water supply pipe 510 is connected to the water storage tank 500, and the downstream end of the water supply pipe 510 is connected to a water distribution pipe (not shown) outside the water storage tank 500. An electric pump 520 is provided in the water supply pipe 510 and supplies the water stored in the water storage tank 500 to the water distribution pipe.

[0171] Flow rate sensor 550 is attached to water supply pipe 510 and outputs a detection signal corresponding to the discharge flow rate of electric pump 520. Specifically, flow rate sensor 550 includes impeller 552, rotating shaft 115, rotation detection device 101, and arithmetic circuit 554.

[0172] Impeller 552 rotates under the dynamic pressure of flowing water (fluid). Rotation detector 101 (rotation detection mechanism 110) is attached to rotary shaft 115 of impeller 552. Rotation detector 101 outputs a signal indicating the rotation speed of rotary shaft 115 of impeller 552 to arithmetic circuit 554.

[0173] The arithmetic circuit 554 calculates the discharge flow rate of the electric pump 520 based on the signal from the rotation detection device 101, and outputs the calculation result to a control circuit 560 of the electric pump 520. The control circuit 560 controls the electric pump 520 so that the discharge flow rate becomes the target flow rate.

[0174] (Configuration example of steering device) Fig. 28 is a block diagram showing a configuration example of a steering device according to embodiment 5. In the example of Fig. 28, the steering device is a navigation steering device for steering outboard motor 640. The steering device may also be a vehicle steering device.

[0175] The outboard motor 640 is provided at the rear of the hull 600. The outboard motor 640 is configured by integrating a drive source such as an internal combustion engine, a propeller shaft, a propeller, etc. The outboard motor 640 corresponds to one embodiment of a "steering mechanism" that steers the hull 600.

[0176] A steering wheel (steering member) 610 that can be rotated by the operator is provided at the driver's seat of the hull 600. A rotation detection device 101 (rotation detection mechanism 110) is attached to a rotation shaft 115 of the steering wheel 610. The rotation detection device 101 generates a signal corresponding to the rotation angle or amount of rotation of the steering wheel 610 input by the operator, and outputs the generated signal to a control circuit 620.

[0177] The actuator 630 includes a steering actuator (for example, a steering hydraulic cylinder). The control circuit 620 drives the actuator 630 based on output signals from various sensors including the rotation detection device 101, thereby steering the outboard motor 640.

[0178] 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.

[0179] 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.

[0180] 10 CPU, 11 RAM, 12 ROM, 13 I / F device, 14 storage device, 15 communication bus, 101, 201, 301, 401 rotation detection device, 110, 410 rotation detection mechanism, 111 magnet, 112, 113 detection coil, 115 rotating shaft, 120, 220, 320, 420 signal processing circuit, 121A, 121B full-wave rectifier circuit, 122 constant voltage circuit, 123, 423 power supply switching circuit, 124, 424 voltage pulse detection circuit, 125, 225, 325, 425 controller, 126 non-volatile memory, 127 external circuit I / F, 128 oscillation circuit, 421A, 421B half-wave rectifier circuit, 500 water storage tank, 510 water supply pipe, 520 electric pump, 550 Flow sensor, 552 impeller, 554 arithmetic circuit, 560, 620 control circuit, 600 hull, 610 steering wheel, 630 actuator, 640 outboard motor, 700 motor, 710 driver, C1, C2 capacitors, D1, D2 diodes, R1, R2 discharge resistors, S1, S2 switches, T1, T2 input terminals, T3 to T6 output terminals.

Claims

1. A rotation detection device for detecting the rotation of a rotating body, comprising: a rotation detection mechanism attached to the rotating body for detecting the rotation of the rotating body; a signal processing circuit electrically connected to the rotation detection mechanism; the rotation detection mechanism includes: a magnet configured to rotate synchronously with the rotating body 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 L and N are natural numbers of 2 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 includes: a voltage pulse detection circuit that detects the voltage pulses generated by each of the L detection coils and outputs a detection signal indicating the polarity of the detected voltage pulse and the detection coil that generated the voltage pulse; a constant voltage circuit that generates a power supply voltage from the power of the voltage pulse every time a voltage pulse is generated; a controller and a non-volatile memory that operate by receiving the power supply voltage from the constant voltage circuit; the controller is configured to start operating by receiving the power supply voltage from the constant voltage circuit and, every time a voltage pulse is generated, execute a detection process for detecting the rotation state of the rotating body based on the detection signal from the voltage pulse detection circuit; the non-volatile memory is configured to store information regarding the states of the L detection coils and the rotation speed of the rotating body when the voltage pulses are generated, which is obtained in the detection process; the detection process includes: a read process of reading the information stored in the non-volatile memory to the controller; an update process of updating the information based on the information read in the read process and the detection signal from the voltage pulse detection circuit; a write process of writing the information updated in the update process to the non-volatile memory; when the voltage pulse detection circuit detects a second voltage pulse before the detection process based on the first voltage pulse is completed, the controller omits at least the read process of the detection process based on the second voltage pulse. A rotation detection device.

2. When the voltage pulse detection circuit detects the second voltage pulse at the time when the writing process based on the first voltage pulse is completed, the controller omits the reading process and executes the update process based on the second voltage pulse based on the information updated in the update process based on the first voltage pulse and the detection signal of the second voltage pulse. The rotation detection device according to claim 1.

3. When the voltage pulse detection circuit detects the second voltage pulse at the time when the update process based on the first voltage pulse is completed, the controller omits the writing process based on the first voltage pulse and executes the update process based on the second voltage pulse based on the information updated in the update process based on the first voltage pulse and the detection signal of the second voltage pulse. The rotation detection device according to claim 1.

4. The controller executes a standby process of waiting for an operation before starting the update process based on the second voltage pulse from the time when the voltage source for the constant voltage circuit is switched from the first voltage pulse to the second voltage pulse. The rotation detection device according to claim 2 or 3.

5. The controller executes a standby process of waiting for an operation after executing the update process based on the second voltage pulse in response to the voltage source for the constant voltage circuit being switched from the first voltage pulse to the second voltage pulse. The rotation detection device according to claim 2 or 3.

6. The signal processing circuit further includes a power supply switching circuit that selects either the voltage pulse generated by each of the L detection coils or an external main power supply as a voltage source for the constant voltage circuit. The power supply switching circuit is configured to switch the voltage source from the first voltage pulse to the external main power supply in response to the output voltage of the external main power supply exceeding a selection start voltage during the selection of the first voltage pulse. When the external main power supply is in a selectable state at the time when the writing process based on the first voltage pulse is completed, the controller omits the reading process, and in response to the voltage pulse detection circuit detecting the second voltage pulse, based on the information updated in the update process based on the first voltage pulse and the detection signal of the second voltage pulse, executes the update process based on the second voltage pulse. The rotational detection device according to any one of claims 1 to 3.

7. When the power supply switching circuit switches the voltage source to the external main power supply at the time when the update process based on the first voltage pulse is completed, the controller omits the writing process and the reading process based on the first voltage pulse, and in response to the voltage pulse detection circuit detecting the second voltage pulse, based on the information updated in the update process based on the first voltage pulse and the detection signal of the second voltage pulse, executes the update process based on the second voltage pulse. The rotational detection device according to claim 6.

8. The signal processing circuit further includes a power supply switching circuit that selects either the voltage pulse generated by each of the L detection coils or an external main power supply as the voltage source for the constant voltage circuit. The power supply switching circuit is configured to select the external main power supply as the voltage source in response to the output voltage of the external main power supply exceeding a selection start voltage, and to cancel the selection of the external main power supply in response to the output voltage of the external main power supply falling below a selection cancellation voltage. When the output voltage of the external main power supply exceeds the selection cancellation voltage at the time when the update process based on the first voltage pulse is completed, the controller omits the writing process and the reading process based on the first voltage pulse, and in response to the voltage pulse detection circuit detecting the second voltage pulse, executes the update process based on the second voltage pulse based on the information updated in the update process based on the first voltage pulse and the detection signal of the second voltage pulse. The rotation detection device according to any one of claims 1 to 3.

9. The rotation detection mechanism further includes L half-wave rectification circuits provided corresponding to the L detection coils. Each of the L half-wave rectification circuits includes a first half-wave rectifier that outputs a voltage obtained by rectifying a positive-polarity voltage pulse generated by the corresponding detection coil, and a second half-wave rectifier that outputs a voltage obtained by rectifying a negative-polarity voltage pulse generated by the corresponding detection coil. Each of the first half-wave rectifier and the second half-wave rectifier has a capacitor for storing the charge of the rectified voltage pulse. The rotation detection device according to claim 1.

10. The signal processing circuit further includes a power supply switching circuit that selects either the voltage output from each of the L half-wave rectifying circuits or the external main power supply as the voltage source for the constant voltage circuit. The power supply switching circuit is configured to switch the voltage source from the first half-wave rectifying circuit to the external main power supply in response to the output voltage of the external main power supply exceeding the selection start voltage during the selection of the first half-wave rectifying circuit that outputs the voltage obtained by rectifying the first voltage pulse. When the power supply switching circuit has switched the voltage source to the external main power supply at the time when the update process based on the first voltage pulse is completed, the controller uses the power supply switching circuit to execute a discharging process for discharging the charge stored in the capacitor included in the first half-wave rectifying circuit. The rotation detection device according to claim 9.

11. The signal processing circuit further includes a power supply switching circuit that selects either the voltage output from each of the L half-wave rectifying circuits or the external main power supply as the voltage source for the constant voltage circuit. The power supply switching circuit is configured to switch the voltage source from the first half-wave rectifying circuit to the second half-wave rectifying circuit in response to the output voltage of the second half-wave rectifying circuit that rectifies the second voltage pulse exceeding the selection start voltage during the selection of the first half-wave rectifying circuit that outputs the voltage obtained by rectifying the first voltage pulse. When the voltage pulse detection circuit is detecting the second voltage pulse at the time when the writing process based on the first voltage pulse is completed, the controller uses the power supply switching circuit to execute a discharging process for discharging the charge stored in the capacitor included in the first half-wave rectifying circuit. The rotation detection device according to claim 9.

12. A battery-less multi-rotation encoder that detects and holds the rotation direction and rotation speed of a rotating body without receiving external power supply, comprising the rotation detection mechanism according to claim 1, which is attached to the rotating body and detects the rotation of the rotating body, and the signal processing circuit according to claim 1, which is electrically connected to the rotation detection mechanism.

13. A flow rate sensor comprising a rotating body that rotates by receiving the dynamic pressure of a fluid, the rotation detection device according to claim 1 that detects the rotation speed of the rotating body, and an arithmetic circuit that calculates the flow rate of the fluid from the rotation speed detected by the rotation detection device.

14. A steering device comprising: a steering member that can be freely rotated; a steering mechanism that steers the hull; a steering actuator; a rotation detection device according to claim 1 that outputs a signal corresponding to the rotation state of the steering member; and a control circuit that drives the actuator based on the output signal of the rotation detection device to steer the steering mechanism.

Images