JP5519323B2 - Rotation detection device and rotation detection system - Google Patents

Description

  The present invention relates to a rotation detection device that detects a rotation state such as a rotation angle and a rotation direction of a DC motor, and a rotation detection system including the rotation detection device.

  DC motors with brushes (hereinafter simply referred to as “DC motors”) have also been used in vehicles, such as air mix dampers for temperature adjustment and mode dampers for switching air outlets in vehicle air conditioners. It is used to adjust the opening / closing angle. In controlling a DC motor used in such applications, in order to accurately adjust the open / close angle of each damper, the rotation state such as the rotation angle, rotation direction, and rotation speed of the DC motor is detected and detected. Based on the rotation state, the opening / closing angle of each damper is controlled to be a desired angle.

  As a general method for detecting the rotation state of a DC motor, a method of providing a sensor such as a rotary encoder or a potentiometer and detecting based on a detection signal from the sensor is well known. For this reason, a method of detecting the rotational state by providing such a sensor is also adopted in the vehicle.

  However, in the method of detecting the rotational state by providing the sensor in this way, a space for installing the sensor is required for each DC motor, and the detection signal from the sensor is separated from the harness for supplying DC power to the DC motor. Is also required for each DC motor, which increases the weight and cost of the vehicle. Therefore, there is an increasing demand for a sensorless system in order to reduce sensors and associated harnesses.

  Various sensorless methods have been proposed for detecting the rotational state of a DC motor without using a large-scale sensor such as a rotary encoder. For example, detection is performed by detecting and counting surge pulses generated when the commutator and brush are switched. How to do is known. However, with this method, since the electromotive force of the motor is reduced and the surge pulse is reduced at the time of low rotation when the motor is started and stopped, it becomes more difficult to detect the surge pulse as the rotation speed becomes lower. The possibility of erroneous detection increases.

  As another sensorless system, a resistor is provided between two specific segments (that is, in parallel with a phase coil connected between the segments) among a plurality of segments (commutator pieces) formed on the commutator. A method of connecting and detecting a rotation pulse based on the current flowing between the segments has been proposed (see, for example, Patent Document 1).

  In the sensorless system disclosed in Patent Document 1, a resistor is connected in parallel to any one of the phase coils, so that a motor circuit (a circuit on the armature coil side composed of a plurality of phase coils) is provided via a brush. When a direct current is supplied to, the current flowing between the brushes changes so as to be accompanied by periodic fluctuations according to the rotation angle of the motor. By detecting the rotation pulse based on this change in current, the detection accuracy can be improved as compared with the detection method based on the simple surge pulse described above.

JP 2003-111465 A

  However, even in the method disclosed in Patent Document 1, as in the method based on the surge pulse described above, there remains a problem that the lower the rotation speed, the smaller the change in current and the higher the possibility of false detection. Yes.

  The present invention has been made in view of the above problems, and an object thereof is to enable accurate detection of the rotation state of a DC motor regardless of the rotation speed without providing a sensor such as an encoder.

  The invention according to claim 1, which has been made in order to solve the above problem, is a rotation detection device that detects the rotation state of a DC motor that rotates by receiving power supply from a DC power supply, and the DC motor includes the DC motor. An impedance between at least a pair of brushes to which a DC voltage from a DC power supply is applied in the motor is configured to periodically change as the DC motor rotates.

The rotation detection device detects an AC current superimposing unit that superimposes an AC voltage on a DC voltage applied between the pair of brushes, and an AC current or an AC voltage supplied from the AC superimposing unit to the DC motor. and the energization detecting means for detecting a target, on the basis of the detection object detected by the current detecting means, a rotation state detecting means for detecting the rotation angle of the DC motor, at least one of a rotational direction and rotational speed, And a shunt suppression unit that suppresses shunting of the alternating current from the AC superimposing unit to other than the DC motor.

  In the rotation detection system configured as described above, an AC voltage can be applied to a DC motor to be detected by an AC superimposing means separately from a driving DC voltage. As is well known, the driving of a DC motor is performed by DC power from a DC power supply. Therefore, even if an AC voltage is applied from the AC superimposing means, the AC voltage does not affect the torque of the DC motor. .

On the other hand, since the direct current motor is configured such that the impedance changes periodically with rotation, the amplitude of the alternating current component (alternating current) due to the application of the alternating voltage from the alternating current superimposing means out of the current flowing through the direct current motor. Changes periodically with the rotation of the DC motor (ie with periodic changes in impedance). Therefore, if the AC current or AC voltage is detected, the rotational state of the DC motor is determined based on the detected AC current or AC voltage (for example, based on the change in the amplitude of the AC component indicated by the AC current or AC voltage ). Can be detected. In addition, as a detection target , for example, current, voltage, power, or the like can be considered.

  Also, since the AC voltage from the AC superimposing means does not affect the torque of the DC motor, the AC voltage is always constant regardless of the DC motor status (acceleration / deceleration, constant speed, stop, etc.). Can be applied to a DC motor to allow an alternating current to flow.

  Thus, for example, even when the DC voltage to the DC motor is interrupted during braking, the rotation state can be reliably detected even when the vehicle is decelerated to stopped by continuing to apply the AC voltage. In addition, even when the motor is stopped, the rotation state of the DC motor can be detected by continuing to apply the AC voltage. For example, even if the DC motor rotates by a predetermined amount, it can be detected reliably.

By the way, in the rotation detection device of the present invention configured to detect the rotation state based on the AC current or the AC voltage supplied from the AC superimposing means, in order to detect the rotation state with high accuracy, from the AC superimposing means. It is desirable that most of the output AC current (ideally all) flows to the DC motor.

  However, in actuality, the DC motor is configured so that not only the AC voltage from the AC superimposing unit but also at least the DC voltage from the DC power source can be applied. In addition to the path that flows to the DC motor side, there is also a path that goes to the side other than the DC motor side (for example, the DC power supply side). Therefore, all of the alternating current output from the alternating current superimposing unit does not flow to the direct current motor, and a part of the alternating current is shunted to a path other than the direct current motor side.

Therefore, in the present invention, by providing the diversion suppression means, the alternating current from the AC superimposing means is prevented from being diverted to a path other than the DC motor.
Therefore, according to the rotation detection device of the first aspect, even if the DC voltage from the DC power supply becomes 0 at the time of braking, the rotation state is maintained even during the deceleration to the stop by continuously applying the AC voltage. Can be reliably detected. Moreover, since the rotation state is detected based on the alternating current supplied from the alternating current superimposing means and flowing to the direct current motor, the detection is performed without affecting the direct current (that is, without affecting the torque of the motor). be able to.

  Therefore, it is possible to provide a rotation detection device that can accurately detect the rotation state of the DC motor regardless of the rotation speed without providing a sensor such as an encoder and preventing torque fluctuation. Become.

Further, by providing the shunt suppression means, the AC current output from the AC superimposing means is prevented from being shunted to a path other than the DC motor side, and more AC current flows to the DC motor. ing. Therefore, the quality of the detection result ( alternating current or alternating voltage ) detected by the energization detecting means can be maintained at a high quality, and it is possible to provide a rotation detection device with high rotation state detection accuracy.

  Next, the invention according to claim 2 is the rotation detection device according to claim 1, wherein the shunt suppression means is arranged in the energization path from the DC power source to the DC motor, and the AC superimposing means is It is connected between the DC motor and the shunt suppression means in the energization path, and is configured to apply an AC voltage.

  According to the rotation detection device of the second aspect configured as described above, it is possible to suppress an alternating current that is diverted from the application site to other than the direct current motor, and to allow a larger amount of alternating current to flow to the direct current motor. .

  Here, various specific configurations of the shunt suppression means are conceivable. For example, as described in claim 3, it may be configured to be able to block the passage of current in a predetermined stop band. As described in Item 7, an extremely simple configuration in which an inductance element is provided may be employed.

  That is, the invention according to claim 3 is the rotation detection device according to claim 2, wherein the shunt suppression means includes a predetermined part including all or part of the frequency component of the AC voltage applied by the AC superimposing means. The stopband is used as a stopband, and at least the current passing through the stopband can be suppressed. The term “blocking” here does not necessarily mean to completely block the passage of current in the band (stopping band), and of course including that (complete blocking), at least, This means that the passage can be sufficiently reduced as compared with the case where there is no branching suppression means.

  According to the rotation detection device according to claim 3 configured in this way, part or all of the frequency component of the alternating current output from the alternating current superimposing means is shunted to a path other than the direct current motor side. Can be suppressed.

As a more specific configuration example, for example, a parallel resonance circuit according to claim 4 or a band rejection filter circuit according to claim 5 can be considered.
That is, the invention according to claim 4 is the rotation detecting device according to claim 3, wherein the shunt suppression means includes an inductance element having a predetermined inductance value and a capacitance element having a predetermined capacitance value. Are connected in parallel, and are set so that the resonance frequency becomes a frequency within the stop band.

  The invention according to claim 5 is the rotation detecting device according to claim 3, wherein the shunt suppression means is a band rejection filter circuit configured to be able to suppress the passage of current in the stop band.

  By configuring the shunt suppression means with a parallel resonance circuit or a band rejection filter circuit in this way, it is possible to realize the shunt suppression means with a simple circuit configuration and reliably prevent the passage of current in the stop band. it can.

The invention according to claim 6 is the rotation detecting device according to any one of claims 3 to 5, wherein the alternating current superimposing means is configured to be able to apply a sine wave voltage as an alternating voltage. In the shunt suppression means, a predetermined frequency band including the frequency of the sine wave voltage is set as the stop band. Then, the rotation state detection means passes the AC component in the pass band from the detection target (AC current or AC voltage) detected by the energization detection means, with the predetermined frequency band including the frequency of the sine wave voltage as the pass band. And a band-pass filter circuit that blocks the passage of AC components other than the pass band, and a rotation signal that is a signal corresponding to the change in amplitude based on the change in amplitude of the AC component that has passed through the band-pass filter circuit. Rotation signal generation means for generating.

  In general, almost all the frequency components of the sine wave voltage are fundamental frequency components, and the presence of harmonic components is negligible. Therefore, by allowing the frequency of the sine wave voltage (fundamental wave frequency) to be suppressed by the shunt suppression means, it is possible to suppress the shunt of the alternating current (in this case, the sine wave current) output from the AC superimposing means. it can.

  Then, in the rotation state detecting means, the AC component of the frequency of the sine wave voltage (fundamental frequency) is passed using the band pass filter circuit, so that the AC component of the necessary frequency is passed and the unnecessary frequency component is passed. The AC component having a high S / N (signal to noise ratio) can be passed (extracted). Therefore, based on the AC component having a high S / N, the rotation signal can be generated reliably and with high accuracy.

On the other hand, the invention according to claim 7 is the rotation detecting device according to claim 2, wherein the shunt suppression means is an inductance element.
As is well known, the inductance element has a frequency characteristic such that the impedance increases as the frequency increases. Moreover, the larger the inductance value, the larger the impedance. Therefore, the passage of alternating current can be suppressed, and the higher the frequency, the greater the suppression effect.

  For this reason, it is possible to prevent the alternating current from the alternating current superimposing means from being shunted to the side other than the direct current motor, while having a very simple and inexpensive structure including the inductance element.

  And when a shunt suppression means is comprised by an inductance element as mentioned above, it is effective if an alternating current superimposition means and a rotation state detection means are comprised as described in Claim 8, for example.

That is, the invention according to claim 8 is the rotation detection device according to claim 7, wherein the alternating current superimposing means uses, as an alternating current voltage, a fundamental wave component of a predetermined frequency and at least one harmonic with respect to the fundamental wave component. A distortion wave voltage having a wave component can be applied. Then, the rotation state detection means uses a predetermined frequency below the frequency of the fundamental wave component of the distorted wave voltage as a cutoff frequency, and detects from the detection target (alternating current or AC voltage) detected by the energization detection means above the cutoff frequency. A high-pass filter circuit that passes an AC component, and a rotation signal generation unit that generates a rotation signal that is a signal corresponding to the change in amplitude based on a change in amplitude of the AC component that has passed through the high-pass filter circuit; It is equipped with.

  The distorted wave voltage has a harmonic component in addition to the fundamental wave component, and its energy (frequency spectrum) as a whole is distributed over a wide band above the fundamental frequency. On the other hand, as described above, the inductance element that constitutes the shunt suppression means has a higher impedance and is less likely to pass as the frequency increases. Therefore, it is possible to effectively suppress the alternating current (current including harmonics) output from the alternating current superimposing means from being shunted to a path other than the motor side.

  Then, in the rotation state detecting means, it is possible to extract an alternating current component having a larger energy by passing an alternating current component equal to or higher than the fundamental frequency of the distorted wave voltage using a high-pass filter circuit. Therefore, it is possible to generate the rotation signal reliably and with high accuracy based on the AC component having a large energy.

  Next, a ninth aspect of the present invention is a rotation detection system including a DC motor that rotates by receiving power supplied from a DC power source, and a rotation detection device that detects a rotation state of the DC motor.

  The DC motor is configured such that the impedance between at least a pair of brushes to which a DC voltage from a DC power source is applied in the DC motor periodically changes as the DC motor rotates.

The rotation detection device includes an AC superimposing unit that superimposes an AC voltage on a DC voltage applied between a pair of brushes, and an energization that detects an AC current or an AC voltage supplied from the AC superimposing unit to a DC motor as a detection target. Detection means, rotation state detection means for detecting at least one of the rotation angle, rotation direction, and rotation speed of the DC motor based on the detection target detected by the energization detection means, and AC from the AC superimposing means And a shunt suppression unit that suppresses shunting of the current other than the DC motor.

  According to this rotation detection system, since the rotation detection device for detecting the rotation state of the DC motor includes the configuration according to any one of claims 1 to 8 described above, The same effects as those of claims 1 to 8 can be obtained.

  Various specific configurations of the DC motor in which the impedance between the pair of brushes periodically changes with rotation are conceivable, for example, configurations according to claims 10 and 11.

  That is, the invention according to claim 10 is the rotation detection system according to claim 9, wherein the DC motor includes an armature coil composed of at least three-phase coils and a plurality of armature coils connected to the armature coil. And at least a pair of brushes for supplying current to each phase coil through the commutator. Then, any two commutator pieces among a plurality of commutator pieces are set as one set, and at least one set of commutator pieces has a capacitance value different from that between other sets of commutator pieces. It is configured as follows.

  An eleventh aspect of the present invention is the rotation detection system according to the ninth aspect, wherein the DC motor includes a housing in which a plurality of field generating magnets are fixed in the circumferential direction on the inner circumferential surface. A rotor core having an armature coil made of a plurality of phase coils, a commutator having a plurality of commutator pieces connected to the armature coil, and at least a pair of brushes slidably contacting the commutator And have. And it is comprised so that the inductance between a pair of said brush may change periodically with rotation.

  The DC motor in the rotation detection system according to claim 10 is configured such that a periodic change in impedance caused by rotation occurs by providing a difference in capacitance value between commutator pieces. The DC motor in the rotation detection system according to claim 11 is configured such that the inductance periodically changes with the rotation, and thereby the impedance changes periodically with the rotation. ing.

It is a figure showing the schematic structure of the rotation detection system of 1st Embodiment. It is a figure showing the waveform of the voltage (AC superposition voltage) applied to the motor of a 1st embodiment. It is explanatory drawing for demonstrating three types of states (motor circuit) which arise while the motor of 1st Embodiment rotates 180 degrees. It is a figure showing an example of the motor current waveform which flows during rotation of the motor of a 1st embodiment. It is a block diagram showing the structure of the rotation signal detection part of 1st Embodiment. It is explanatory drawing showing the frequency spectrum of the alternating current output from the superimposition part of 1st Embodiment. It is a circuit diagram showing the alternating current equivalent circuit of the rotation detection system of 1st Embodiment. It is explanatory drawing showing the frequency characteristic of the impedance of LC parallel resonant circuit. It is explanatory drawing showing an example of the motor current waveform at the time of stop control. It is explanatory drawing showing an example of the rotation pulse produced | generated in a signal processing part. It is a figure showing schematic structure of the rotation detection system of 2nd Embodiment. It is explanatory drawing showing the alternating current (square wave) voltage produced | generated in the superimposition part of 2nd Embodiment, and the alternating current output from a superimposition part. It is a block diagram showing the structure of the rotation signal detection part of 2nd Embodiment. It is explanatory drawing showing the frequency spectrum of the alternating current output from the superimposition part of 2nd Embodiment. It is a figure showing schematic structure of the rotation detection system of 3rd Embodiment. It is a circuit diagram showing the alternating current equivalent circuit of the rotation detection system of 3rd Embodiment. It is explanatory drawing for demonstrating the structure of a band rejection filter (BRF). It is explanatory drawing showing the other Example of the motor of a detection target. It is explanatory drawing showing the other Example of the motor of a detection target. It is explanatory drawing showing the other Example of the motor of a detection target. It is explanatory drawing showing the other Example of the motor of a detection target. It is explanatory drawing showing the other Example of the motor of a detection target. It is explanatory drawing showing the other Example of a rotation detection system.

Preferred embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 shows a schematic configuration of a rotation detection system according to an embodiment to which the present invention is applied. As shown in FIG. 1, the rotation detection system 1 of the present embodiment is a device for detecting the rotation angle of a DC motor (hereinafter simply referred to as “motor”) 2 and rotationally drives the motor 2 (torque is applied). A DC power source 3 that outputs a DC voltage for generating the motor 2, a superposition unit 5 that outputs an AC voltage for detecting the rotation angle of the motor 2, and a current (motor current) flowing through the motor 2. A rotation signal detector 6 that generates and outputs a signal (rotation pulse Sp) according to the rotation angle, and a rotation angle detection that detects the rotation angle of the motor 2 based on the rotation pulse Sp output from the rotation signal detector 6. And an LC parallel resonance circuit 8 for suppressing the alternating current output from the superimposing unit 5 from being shunted to the DC power supply 3 side.

  The DC power source 3 outputs a DC voltage having a predetermined voltage value Vb, and the DC voltage is applied to the motor 2 (specifically, applied between the brushes 16 and 17). An LC parallel resonance circuit 8 which is one of the most characteristic configurations in the rotation detection system 1 of the present embodiment is provided in a DC energization path from the positive electrode side of the DC power supply 3 through the motor 2 to the ground line (ground potential). Although provided, the LC parallel resonance circuit 8 will be described later.

  The superimposing unit 5 superimposes the AC voltage generated by the AC power source 4 on the DC voltage output from the DC power source 3 and the AC power source 4 that generates the AC voltage of the predetermined frequency f1 and applies it to the motor 2. Coupling capacitor C10.

  The AC voltage generated by the AC power supply 4 is a sine wave voltage in this embodiment. Therefore, the voltage output from the superimposing unit 5 is a sine wave voltage, and a sinusoidal alternating current is also output for the current.

Therefore, the AC superimposed voltage obtained by superimposing the AC voltage from the superimposing unit 5 on the DC voltage from the DC power supply 3 is superimposed on the DC voltage (Vb) with the AC voltage having the amplitude Vs and the frequency f1 as shown in FIG. It becomes the voltage of AC / DC mixing (a kind of pulsating flow). Therefore, the current flowing through the motor 2 when the AC superimposed voltage is applied to the motor 2 also becomes a current (AC superimposed current) in which the AC current is superimposed on the DC current (see FIG. 4, details will be described later).
However, since the motor 2 is a DC motor, the component that contributes to the rotation of the motor 2 (provides torque to be driven to rotate) in the AC superimposed current is a DC component by a DC voltage applied by the DC power supply 3. In addition, the AC component due to the AC voltage applied from the superimposing unit 5 does not participate in the rotation itself and does not affect the torque.

  The AC voltage from the superimposing unit 5 is applied to the motor 2 in order to detect the rotation state (rotation angle in the present embodiment) of the motor 2, and the rotation signal detection unit 6 is connected to the motor 2 as will be described later. The rotation pulse Sp is generated based on the alternating current component of the current flowing through. That is, the superimposing unit 5 is provided not for the power source for rotating the motor 2 but for the purpose of detecting the rotation state (rotation angle in the present embodiment) of the motor 2.

  The AC voltage output from the superimposing unit 5 is a path from the positive electrode side of the DC power source 3 to the motor 2 through the motor 2 to the ground line. It is applied to the application site P of the path between the LC parallel resonance circuit 8 and the motor 2 provided in the path. Therefore, the alternating current output from the superimposing unit 5 flows to the motor 2 side through the application site P.

  A part of the alternating current output from the superimposing unit 5 is also shunted from the application site P to the direct current power source 3 side. However, in the present embodiment, the LC parallel resonance circuit 8 is provided as a diversion suppressing means for suppressing the diversion, and thereby the diversion to the DC power supply 3 side is minimized.

  In addition, the output of the DC voltage from the DC power supply 3 and the output of the AC voltage from the superposition unit 5 can be controlled independently of each other. In the present embodiment, when the motor 2 is rotated (from startup to steady rotation), the DC voltage from the DC power source 3 is applied and the AC voltage from the superimposing unit 5 is also applied in a superimposed manner. On the other hand, when stopping (braking) the rotating motor 2, the DC voltage from the DC power supply 3 to the motor 2 is interrupted, and the application of the AC voltage from the superimposing unit 5 is continued. That is, the AC voltage from the superimposing unit 5 is continuously applied to the motor 2 at least while the motor 2 is rotating.

  The motor 2 is a three-phase DC motor with a brush that includes a pair of brushes 16 and 17 disposed opposite to each other (that is, 180 ° apart in the rotational direction) and has a three-phase coil as an armature coil. The commutator 10 includes three commutator pieces 11, 12, and 13 that are in contact with the brushes 16 and 17. Each of the three (three-phase) phase coils L1, L2, L3 constituting the armature coil is Δ-connected as shown in the figure.

  That is, the first phase coil L1 is connected between the third commutator piece 13 and the first commutator piece 11, and the second phase coil L2 is connected between the first commutator piece 11 and the second commutator piece 12. Is connected, and the third phase coil L3 is connected between the second commutator piece 12 and the third commutator piece 13. The armature is constituted by the armature coil and the commutator 10 including these three phase coils L1, L2, and L3. In addition, the inductance of each phase coil L1, L2, L3 is the same value (L1 = L2 = L3). Further, the phase coils L1, L2, L3 are arranged so as to be separated from each other by 2 / 3π in electrical angle.

  Any two of the three commutator pieces 11, 12, and 13 are in contact with the brushes 16 and 17, respectively, and the brushes 16 and 17 are rotated as the commutator 10 is rotated by the rotation of the motor 2. The two commutator pieces that come into contact with are switched.

  Although not shown in the drawings, the motor 2 of the present embodiment has a yoke housing, a field made of a permanent magnet is provided on the inner wall side of the yoke housing, and an armature is disposed so as to face the field. ing.

  Further, in the present embodiment, in the motor 2, a capacitor C1 is connected in parallel with the first phase coil L1. Therefore, the DC voltage from the DC power source 3, the AC voltage from the superimposing unit 5, and the AC superimposed voltage in which both are superimposed are the brushes 16 and 17 and any two commutator pieces in contact with them. Is applied to a circuit (motor circuit) composed of the phase coils L1, L2, L3 and the capacitor C1 inside the motor 2.

  When the AC voltage or the AC superimposed voltage is applied between the brushes of the motor 2, an AC current or an AC superimposed current in which an AC current is superimposed on a DC current (current including an AC component) flows through the motor circuit. .

  As is well known, the capacitor C1 functions as a very high resistance in which a current hardly flows in a direct current, and has a low impedance characteristic that a current easily flows as the frequency increases in an alternating current. For this reason, when viewed from the DC power source 3, the capacitor C1 can be treated as not equivalently present, so that the DC current from the DC power source 3 flows only through the phase coils L1, L2, and L3.

  On the other hand, when viewed from the superimposing unit 5, each phase coil L1, L2, L3 has a high impedance, whereas the capacitor C1 has a low impedance, and the difference between the two is large. Therefore, for example, the motor 2 rotates clockwise from the state shown in FIG. 1 (that is, the commutator 10 rotates clockwise), and the first commutator piece 11 is applied to the brush 17 on the downstream side (ground potential side) of the energization path. Comes into contact with each other, a parallel circuit of the first phase coil L1 and the capacitor C1 is formed between the brushes 16 and 17. That is, a current-carrying path of only the capacitor C1 is formed between the brushes 16 and 17, and a parallel resonance circuit of the capacitor C1 and the combined inductance of the phase coils L1, L2, and L3 is formed as a whole motor circuit. . Therefore, in this state, the impedance of the motor circuit between the brushes 16 and 17 has parallel resonance characteristics, and the impedance becomes lower as the frequency becomes higher in the frequency band higher than the resonance frequency.

  In other words, from a direct current perspective, the motor circuit can be regarded as a circuit composed of only three phase coils L1, L2, and L3. Will not be affected.

  On the other hand, in terms of alternating current, each time the two commutator pieces in contact with the brushes 16 and 17 are switched according to the rotation angle of the motor 2, the motor circuit formed between the brushes also changes. The impedance of the motor circuit also changes. However, in this embodiment, since one capacitor C1 is connected only to the first phase coil L1, the commutator piece is switched three times while the motor 2 rotates 180 °, but the impedance change is There are two stages.

  FIG. 3A shows a change in the connection state inside the motor 2 during the rotation of the motor 2 by 180 °, that is, a change in the motor circuit formed between the brushes 16 and 17. As shown in FIG. 3A, the motor circuit of the motor 2 of the present embodiment changes mainly into three types of state A, state B, and state C while the motor 2 rotates 180 °.

  In the state A, as shown in the figure, the first commutator piece 11 is in contact with the brush 16 on the positive electrode side (hereinafter also referred to as “Vb side”) of the DC power supply 3 and the ground potential side (hereinafter also referred to as “GND side”). The second commutator piece 12 is in contact with the brush 17. An equivalent circuit of the motor 2 in this state A, that is, a motor circuit formed between the brushes 16 and 17 is a circuit shown on the right side in the drawing.

  In this state A, since the capacitor C1 and the third phase coil L3 are connected in series, there is no current path of only the capacitor C1 between the brushes 16 and 17, and one of the brushes One phase coil always exists in the path from 16 to the other brush 17. Therefore, in this state A, the inductances of the phase coils L1, L2, and L3 are dominant, and the impedance of the entire motor circuit is increased. Therefore, the AC component (AC current component) included in the current flowing through the motor 2 is increased. The amplitude is small.

  The state B is a state rotated about 50 ° clockwise from the state A, and the commutator piece contacting the brush 16 on the Vb side is changed from the first commutator piece 11 to the third commutator piece 13 in the state A. It is switched to. The second commutator piece 12 is in contact with the brush 17 on the GND side.

  Even in this state B, since the capacitor C1 and the second phase coil L2 are connected in series, there is no current path of only the capacitor C1 between the brushes 16 and 17, and one of the brushes One phase coil always exists in the path from 16 to the other brush 17. Therefore, even in this state B, the impedance of the entire motor circuit is high, and therefore the amplitude of the alternating current component is small. Note that, in this state B and the state A, the impedance of the entire circuit is the same, as is clear by comparing the equivalent circuits in the figure. Therefore, the amplitude of the alternating current component is also the same size.

  The state C is a state further rotated by about 50 ° clockwise from the state B, and the commutator piece contacting the GND-side brush 17 is changed from the second commutator piece 12 in the state A and B to the first rectification. It has switched to the child piece 11. The third commutator piece 13 is in contact with the brush 16 on the Vb side.

  In this state C, the series circuit of the second phase coil L2 and the third phase coil L3, the first phase coil L1, and the capacitor C1 are connected in parallel. Therefore, between the brushes 16 and 17, there is an energization path only for the capacitor C1. Thereby, the impedance of the motor circuit is lowered.

  In particular, in the present embodiment, a parallel resonance circuit is formed as the entire motor circuit, and its impedance has parallel resonance characteristics. Therefore, in a frequency band higher than the resonance frequency, the higher the frequency, the more dominant the capacitor C1 and the lower the impedance. For this reason, the amplitude of the alternating current component is increased.

  Thus, while the motor 2 rotates 180 °, the commutator piece that contacts the brushes 16 and 17 is switched three times, and accordingly, the motor circuit between the brushes 16 and 17 is in the state A, There are three types, B and C. However, since the impedance of the entire circuit is the same in the state A and the state B as described above, the impedance change that occurs during the 180 ° rotation is a two-stage.

  In the process of rotation of the motor 2, there is a switching period in which one brush simultaneously contacts two adjacent commutator pieces, and the impedance between the brushes also changes during this switching period. 2 only occurs instantaneously during one rotation, and the accompanying impedance change is instantaneous. Therefore, in this embodiment, this switching period is not considered.

  When the rotation further proceeds from the state C, the commutator piece in contact with the brush 16 on the Vb side is switched from the third commutator piece 13 in the state C to the second commutator piece 12. The first commutator piece 11 is in contact with the brush 17 on the GND side. This state is a state in which the Vb-side brush 16 and the GND-side brush 17 are interchanged in the state A described above, and the impedance of the entire motor circuit is the same as in the state A. Therefore, this state is referred to as a state A ′ in the following description.

  When the rotation further proceeds from this state A ′, the commutator piece that contacts the GND-side brush 17 is switched from the first commutator piece 11 to the third commutator piece 13 in the state A ′. The second commutator piece 12 is in contact with the brush 16 on the Vb side. This state is a state in which the Vb-side brush 16 and the GND-side brush 17 are interchanged in the state B described above, and the impedance of the entire motor circuit is the same as in the state B. Therefore, in the following description, this state is referred to as state B ′.

  When the rotation further proceeds from the state B ′, the commutator piece that contacts the brush 16 on the Vb side is switched from the second commutator piece 12 in the state B ′ to the first commutator piece 11. The third commutator piece 13 is in contact with the brush 17 on the GND side. This state is a state in which the Vb-side brush 16 and the GND-side brush 17 are interchanged in the state C described above, and the impedance of the entire motor circuit is the same as in the state C. Therefore, this state is referred to as a state C ′ in the following description.

  Then, when the rotation further proceeds from the state C ′, the state is switched again to the state A. Hereinafter, as the rotation proceeds, the state B → the state C → the state A ′ → the state B ′ → the state C ′ → the state A → Switch.

  That is, while the motor 2 makes one rotation, the motor circuit is sequentially switched to six types of states A, B, C, A ′, B ′, and C ′ according to the rotation angle. Will be switched. Among these, the states A, B, A ′, and B ′ all have the same impedance (high impedance). Further, the states C and C ′ have the same impedance, and the value thereof is much lower than the impedance of the state A or the like.

  FIG. 3B shows the frequency characteristics of the impedance of the motor circuit in each state. As described above, the impedances of the motor circuits in the states A, B, A ′, and B ′ are the same. In this state A, B, A ′, B ′, there is almost no influence of the capacitor C1, and although a small peak value (small resonance point) occurs at the frequency fa, the characteristic that the impedance increases as the frequency increases as a whole. It becomes.

  On the other hand, in the states C and C ′, the impedance characteristics change greatly due to the resonance between the phase coils L1, L2, and L3 and the capacitor C1, and the impedance becomes small with the resonance frequency fb as the center (maximum value). For this reason, the states A, B, A ′, B ′ and the states C, C ′ have different impedances except for the frequency fc where the impedances match (characteristics intersect). In particular, the impedance ratio increases in a frequency band higher than the frequency fc to a certain degree.

Therefore, in the present embodiment, the frequency f1 of the alternating current output from the superimposing unit 5 is set to be a predetermined frequency higher than the frequency fc.
The change in the impedance of the motor circuit described above is caused by a change in the AC component (AC current component) included in the motor current flowing through the motor 2 or an AC component (AC voltage component) included in the voltage of the energization path through which the motor current flows. It appears directly as a change.

  FIG. 4 is a diagram illustrating an example of a rotating motor current. As shown in FIG. 4, the motor current has a waveform in which an alternating current component is superimposed on a direct current component. Focusing on the alternating current component, the amplitude of the alternating current component is small in the states A, B, A ′, and B ′, and the amplitude of the alternating current component is large in the states C and C ′. That is, while the motor 2 rotates 180 °, the amplitude of the alternating current component changes into two types (two steps).

  Therefore, in the present embodiment, the rotation signal detection unit 6 generates the rotation pulse Sp based on the change in the amplitude of the AC current component of the motor current caused by the change in the impedance due to the rotation of the motor 2. Then, based on the rotation pulse Sp, the rotation angle detector 7 detects the rotation angle of the motor 2.

  FIG. 5 shows a specific configuration of the rotation signal detection unit 6. The rotation signal detection unit 6 generates a rotation pulse Sp by performing various signal processing based on the alternating current detected by the current detection unit 21 and the alternating current detected by the current detection unit 21. And a signal processing unit 22.

The current detection unit 21 includes a current detection resistor R1 disposed in an energization path (more specifically, an energization path from the brush 17 on the ground potential side to the ground line) through which the motor current flows, and the voltage at both ends of the current detection resistor R1 is , incorporated as a detection signal corresponding to the motor current to the signal processing section 22.

  The signal processing unit 22 includes a band pass filter (BPF) 23, an amplification unit 24, an envelope detection unit 25, a low pass filter (LPF) 26, a threshold setting unit 27, and a comparison unit 28. .

  The BPF 23 has a general configuration as shown in the figure, and includes an operational amplifier 30, a parallel circuit including a resistor R <b> 2 and a capacitor C <b> 11 connected between the output terminal and the inverting input terminal of the operational amplifier 30, and the operational amplifier 30. A series circuit including a resistor R3 and a capacitor C12 connected between the inverting input terminal and the ground line.

  As shown in the frequency spectrum of FIG. 6, the frequency component of the alternating current output from the superimposing unit 5 is basically only the frequency (fundamental wave frequency) f1 of the sine wave voltage generated by the AC power supply 4. is there. Strictly speaking, harmonic components other than the fundamental frequency f1 are included, but the level is negligible compared to the fundamental frequency f1, and is not considered in this embodiment.

  Therefore, as shown by the broken line in FIG. 6, the BPF 23 passes a signal having a predetermined bandwidth (pass band) centered on the frequency f1 of the alternating current output from the superimposing unit 5 and signals in other bands. Is configured to be blocked. That is, among the detection signals detected by the current detection unit 21, a signal in a predetermined pass band centered on the frequency f 1 is extracted by the BPF 23 and input to the subsequent amplification unit 24.

  Note that the pass band of the BPF 23 does not necessarily need to have its center frequency matched with the frequency f1 of the alternating current, and may have some deviation. However, it is desirable that at least the frequency f1 of the alternating current is included in the passband.

The amplifying unit 24 includes an operational amplifier 31, a resistor R4 connected between the output terminal and the inverting input terminal of the operational amplifier 31, and a resistor R5 connected between the inverting input terminal of the operational amplifier 31 and the ground line. The signal input to the non-inverting input terminal (detection signal from the BPF 23) is amplified at a predetermined amplification factor.
The detection signal amplified by the amplification unit 24 is envelope-detected by the envelope detection unit 25. The envelope detector 25 includes a rectifying diode D1, a resistor R6 having one end connected to the cathode of the diode D1 and the other end connected to the ground potential, and one end connected to the cathode of the diode D1. A capacitor C13 having an end connected to the ground potential is provided, and a detection signal from the amplifying unit 24 is input to the anode of the diode D1.

The envelope detection unit 25 performs envelope detection on the detection signal input from the amplification unit 24 and generates a constant signal (hereinafter referred to as “detection signal”) corresponding to the amplitude.
The generated detection signal is input to the comparison unit 28 after the high frequency component is cut by the LPF 26. The LPF 26 has a known configuration including a resistor R7 and a capacitor C14. A diode D2 is connected in parallel to the resistor R7. The connection direction of the diode D2 is opposite to the direction in which the detection signal is input.

  The comparator 28 includes a comparator 32, a resistor R10 connected between the output terminal and the inverting input terminal of the comparator 32, one end connected to the non-inverting input terminal of the comparator 32, and the other end connected to the LPF 26. The resistor R8 includes a resistor R9 having one end connected to the inverting input terminal of the comparator 32 and the other end connected to the threshold setting unit 27.

  The detection signal output from the envelope detection unit 25 is input to the comparison unit 28 via the LPF 26, and is input to the non-inverting input terminal of the comparator 32 via the resistor R8 in the comparison unit 28. On the other hand, the threshold value from the threshold setting unit 27 is input to the inverting input terminal of the comparator 32 via the resistor R9. Thereby, the comparator 32 compares the detection signal with the threshold value, and outputs the comparison result.

  In the present embodiment, the threshold value set by the threshold value setting unit 27 and input to the comparison unit 28 is a period in which the amplitude of the motor current waveform shown in FIG. 4 is small (that is, states A, B, A ′, B ′). A predetermined value that is larger than the detection signal in the period (period) and smaller than the detection signal in the period in which the amplitude is large (that is, the period of states C and C ′) is set.

  Therefore, in a period with a small amplitude, the detection signal input from the envelope detection unit 25 to the comparison unit 28 is 0 V and is smaller than the threshold value from the threshold setting unit 27, so that a low level signal is output from the comparator 32. Is done. On the other hand, in a period in which the amplitude is large, the detection signal input from the envelope detection unit 25 to the comparison unit 28 is larger than the threshold value, so that a high level signal is output from the comparator 32.

Then, the low-level and high-level signals output from the comparator 32 are output to the rotation angle detection unit 7 as the rotation pulse Sp corresponding to the rotation angle of the motor 2.
As described above, the signal processing unit 22 performs various signal processing on the motor current (detection signal) detected by the current detection resistor R1 and generates the rotation pulse Sp, thereby reducing disturbance and noise. The generated accurate rotation pulse Sp is generated.

  The rotation angle detection unit 7 detects the rotation angle of the motor 2 based on the rotation pulse Sp input from the signal processing unit 22 by, for example, a method of detecting and counting the rising edge of the rotation pulse Sp. The detected rotation angle is used as a feedback signal in a control circuit of the motor 2 (not shown).

  By the way, in the rotation detection system 1 of the present embodiment, apart from the application of the DC voltage from the DC power source 3 to the motor 2, the superimposing unit 5 is provided for detecting the rotation angle, and the AC voltage from the superimposing unit 5 is added to the DC voltage. Are superimposed on each other (or AC voltage alone) and applied to the motor 2. Specifically, as shown in FIG. 1, an alternating voltage is superimposed and applied to the application site P in the direct current energizing path.

  Therefore, as described above, a part of the alternating current output from the superimposing unit 5 is also diverted from the application site P to the direct current power source 3 side. The diversion to the DC power source 3 side and the influence thereof will be described more specifically with reference to FIG.

  FIG. 7 is an AC equivalent circuit of the rotation detection system 1 as viewed from the superimposing unit 5. As shown in FIG. 7, the rotation detection system 1 is a circuit in which the series circuit of the motor 2 and the rotation signal detection unit 6 and the DC power supply 3 are connected in parallel when viewed from the superposition unit 5.

  In the rotation detection system 1 of the present embodiment in which the rotation angle is detected based on the amplitude change of the alternating current from the superimposing unit 5, ideally, in order to detect the rotation with high accuracy, the superimposing unit 5 is ideal. It is desirable that all the alternating current i output from the motor 2 flows through the motor 2.

  However, in practice, the AC equivalent circuit viewed from the superimposing unit 5 is in a state where the DC power source 3 is connected in parallel to the motor 2 as shown in FIG. Instead of flowing only to the motor 2 side, the current is also shunted to the DC power supply 3 side.

  In order to detect the rotation angle of the motor 2 with high accuracy, the smaller the AC current iv that is shunted to the DC power supply 3 side, the better. The larger the AC current im that flows to the motor 2 side is, the better. However, in general, the impedance Zv of the DC power supply 3 is smaller than the impedance on the motor 2 side (the sum of the impedance Zm of the motor 2 and the impedance Zs of the rotation signal detector 6). Therefore, most of the AC current i output from the superimposing unit 5 is shunted to the DC current 3 side, and the AC current im to the motor 2 side that is originally required becomes small. That is, a sufficient alternating current cannot be supplied to the motor 2.

  For this reason, the amplitude of the alternating current component (alternating current component) in the current detected by the current detector 21 is reduced, and only a detection signal with poor quality and accuracy can be detected, and the rotational angle detection accuracy is reduced. In order to increase the alternating current im to the motor 2 side, for example, it is conceivable to increase the capacity of the coupling capacitor C10 constituting the superimposing unit 5 and supply a larger alternating current i. This is not preferable in terms of both system configuration and cost.

  Therefore, in the rotation detection system 1 of the present embodiment, the AC current from the superimposing unit 5 is shunted to the DC power supply 3 side in the DC power supply path from the DC power supply 3 to the motor 2 to the DC power supply 3 side path. An LC parallel resonant circuit 8 is provided to suppress the occurrence (to keep it as low as possible). The LC parallel resonance circuit 8 is formed by connecting a capacitor C5 having a predetermined capacitance value and a coil L5 having a predetermined inductance value in parallel, and the impedance has a frequency characteristic as shown in FIG. Have. That is, it has a well-known parallel resonance characteristic having a peak value at the resonance frequency.

  In the present embodiment, the resonance frequency of the LC parallel resonance circuit 8 is set to the frequency of the alternating voltage (alternating current) output from the superimposing unit 5, that is, the frequency f1 of the alternating voltage generated by the alternating current power source 4. In addition, element values of the capacitor C5 and the coil L5 constituting the LC parallel resonance circuit 8 are set.

  Therefore, the LC parallel resonant circuit 8 is a circuit having a very large impedance when viewed from the superimposing unit 5, and the passage of a current in a predetermined band (stop band) including the resonance frequency is blocked. The term “blocking” as used herein does not only mean that no current passes, but much of the alternating current from the superimposing unit 5 flows to the motor 2 side, and the detection signal from the current detecting unit 21 is increased. It also includes suppressing the shunting to the DC power source 3 to the extent that quality can be maintained.

  With this LC parallel resonance circuit 8, the current iv that is shunted to the DC power supply 3 side becomes very small, and most of the AC current i from the superimposing unit 5 flows to the motor 2 side. As a result, a sufficient amount of alternating current flows on the motor 2 side, and the quality of the detection signal detected by the current detection unit 21 is greatly improved.

  The resonance frequency of the LC parallel resonance circuit 8 is preferably matched with the frequency f1 of the AC voltage as described above, but the frequency f1 of the AC voltage is sufficient as long as the diversion to the DC power supply 3 side can be sufficiently reduced. There may be a gap.

  Next, an example of a motor current waveform when the rotating motor 2 stops is shown in FIG. In FIG. 9, the waveform of the alternating current component is very small during the period in which the impedance of the motor circuit is large and the amplitude of the alternating current component is small (period in which states A, B, and A′B ′). doing. The same applies to FIG. 10 described later.

  When performing stop control (brake control) in which the rotating motor 2 is braked and stopped, application of a DC voltage (supply of DC current) from the DC power source 3 to the motor 2 is stopped. On the other hand, the alternating voltage (alternating current) from the superimposing unit 5 is not involved in driving the motor 2 but is applied (supplied) for the purpose of detecting the rotation angle of the motor 2 only. It can be applied continuously after the start of stop control as well as during steady rotation, and can also be applied after stop of rotation. Therefore, in this embodiment, even after the stop control is started, the application of the AC voltage from the superimposing unit 5 is continuously performed at least until the motor 2 is completely stopped.

  As a result, the motor current after the start of the stop control (after the application of the DC voltage from the DC power supply 3 is stopped) is changed to the current generated by the induced electromotive force of the motor 2 itself as shown in FIG. Is superimposed. Among these, the magnitude of the current due to the induced electromotive force gradually decreases as the rotation speed of the motor 2 decreases, and becomes zero when the motor 2 stops.

  On the other hand, since the alternating current is continuously supplied from the superimposing unit 5 at least until the motor 2 is completely stopped for detecting the rotation angle as described above, as shown in FIG. Regardless of the rotation speed, an alternating current having an amplitude corresponding to the rotation angle (according to a change in impedance of the motor circuit) flows. Therefore, the rotation angle of the motor 2 can be detected regardless of the rotation speed.

  An example of the rotation pulse Sp generated by the signal processing unit 22 during the stop control shown in FIG. 9 is shown in FIG. The waveform on the upper side in FIG. 10 is the waveform of the detection signal output from the amplification unit 24 in the signal processing unit 22. This detection signal is a signal in a predetermined pass band (output signal from the BPF 23) centered on the frequency f1 among the detection signals detected by the current detection unit 21 (that is, the voltage across the current detection resistor R1). It is amplified by the amplifying unit 24.

  The detection signal from the amplification unit 24 passes through the envelope detection unit 25, the LPF 26, and the comparison unit 28, thereby generating a rotation pulse Sp as shown on the lower side of FIG. In this example, a rotation pulse Sp having a predetermined time width is generated every time the amplitude of the alternating current component changes from a small amplitude to a large amplitude.

  In this embodiment, the rotation pulse Sp is generated every time the motor 2 rotates 180 °. Therefore, the rotation angle of the motor 2 can be detected on the assumption that the motor 2 has rotated 180 ° each time the rotation pulse Sp is generated.

  The rotation detection system 1 of the present embodiment is configured to detect the rotation angle of the motor 2 based on the rotation pulse Sp, but based on the interval (for example, the rising edge interval) of the rotation pulse Sp. You may comprise so that the rotational speed of the motor 2 can also be detected.

  As described above, in the rotation detection system 1 of the present embodiment, the superimposing unit 5 is provided for detecting the rotation angle separately from the DC power source 3 as a drive source for driving the motor 2. When rotating, an AC superimposed voltage obtained by superimposing the AC voltage from the superimposing unit 5 on the DC voltage from the DC power source 3 is applied to the motor 2, whereby an AC superimposed current containing an AC component flows through the motor 2. .

  Further, in the motor 2, a rotation angle detection capacitor C1 is connected in parallel with the first phase coil L1 among the three-phase coils L1, L2, and L3. Then, the signal processing unit 22 generates a rotation pulse Sp corresponding to the change in the amplitude of the motor current (alternating current) detected by the current detection unit 21. Since the capacitor C1 is connected, the impedance of the motor circuit between the brushes 16 and 17 changes according to the rotation angle of the motor 2, and the change appears as an amplitude change of the alternating current. Therefore, the rotation pulse Sp can be generated and the rotation angle can be detected based on the change in the amplitude of the alternating current.

  Therefore, according to the rotation detection system 1 of the present embodiment, even if the application of the DC voltage from the DC power supply 3 (supply of DC current) is stopped when the motor 2 is stopped (braking), the AC voltage is applied (AC By continuing the supply of electric current, the rotation angle can be reliably detected until it stops completely (and even after it stops completely). Moreover, the rotation angle is detected based on the alternating current output from the superimposing unit 5 and is detected without affecting the motor drive. Therefore, it is possible to accurately detect the rotation angle without depending on the rotation speed without providing a large-scale sensor such as a rotary encoder and preventing torque fluctuation.

  In addition, an LC parallel resonance circuit 8 is provided in a path from the application site P to the DC power supply 3 side, whereby the AC current output from the superimposing unit 5 is routed to a path other than the motor 2 side (DC power supply in this embodiment). 3, and a larger amount of alternating current flows to the motor 2. Therefore, the quality of the detection signal detected by the current detection unit 21 can be maintained at a high quality, and furthermore, a high-quality rotation pulse Sp can be generated based on the detection signal, so that the rotation with high accuracy can be performed. Corner detection is possible.

  In particular, in the present embodiment, the alternating current output from the superimposing unit 5 is a sine wave, and the frequency component thereof is only the frequency f1 as described with reference to FIG. Therefore, by making the resonant frequency of the LC parallel resonant circuit 8 coincide with the wave frequency f1, it is possible to more reliably suppress the alternating current from the superimposing unit 5 from being shunted to the direct current power source 3 side.

  Further, the signal processing unit 22 is provided with a BPF 23 at its input stage, and its pass band is set to a predetermined bandwidth centered on the fundamental frequency f1. Therefore, the alternating current component of the frequency f1 can be reliably extracted from the current flowing through the current detector 21. On the other hand, since signals of frequencies other than the passband are blocked by the BPF 23, a detection signal with a very high S / N can be output to the amplification unit 24 at the subsequent stage.

  In the present embodiment, the superimposing unit 5 corresponds to the AC superimposing unit of the present invention, the current detection unit 21 (current detection resistor R1) corresponds to the energization detecting unit of the present invention, and the BPF 23 is the bandpass filter of the present invention. The comparison unit 28 corresponds to the rotation signal generation means of the present invention. The signal processing unit 22 and the rotation angle detection unit 7 constitute a rotation state detection unit of the present invention.

[Second Embodiment]
FIG. 11 shows a schematic configuration of the rotation detection system 40 of the present embodiment. Similar to the rotation detection system 1 of the first embodiment shown in FIG. 1, the rotation detection system 40 of the present embodiment is a system for detecting the rotation angle of the motor 2. A drive DC voltage is applied to the motor 2. A point having a DC power source 3 for applying, a point having a superimposing unit 41 for applying (superimposing) an AC voltage for rotation angle detection to the motor 2, and a current in a path from the motor 2 to the ground line The point that the detection unit 21 is provided and the point that the signal processing unit 47 generates the rotation pulse Sp based on the detection signal detected by the current detection unit 21 are the same as in the first embodiment. .

  Therefore, the same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof is omitted. In the following description, the configuration different from the rotation detection system 1 of the first embodiment will be mainly described.

  In the rotation detection system 40 of the present embodiment, the alternating voltage generated by the alternating current power supply 46 in the superimposing unit 41 is a square wave voltage (a kind of distorted wave voltage) as shown in the upper part of FIG. The alternating current output via the coupling capacitor C10 has a substantially impulse waveform as shown in the lower part of FIG.

  Therefore, the alternating current output from the superimposing unit 41 includes higher-order harmonic components in addition to the fundamental wave frequency f <b> 1 that is the frequency of the square wave voltage generated by the AC power supply 46. Specifically, as shown in the frequency spectrum of FIG. 14, in addition to the fundamental frequency f1, an nth harmonic (second harmonic) having a frequency fn that is n times (n is a natural number of 2 or more) the fundamental frequency f1. 3rd harmonic, 4th harmonic, etc.). Among them, the currents of the fundamental wave component (f1) and the odd harmonic components (f3, f5, f7...) Are particularly increased.

  Note that the alternating current output from the superimposing unit 41 does not always have a substantially impulse current waveform as shown in FIG. 12, and the circuit constants such as the rotation angle of the motor 2 and other circuits other than the motor 2. It changes by things. However, including the harmonic component is the same.

  Further, in the rotation detection system 1 of the first embodiment, the LC parallel resonance circuit 8 is provided in order to prevent the alternating current from the superimposing unit 5 from being shunted to the DC power supply 3 side. In the embodiment, instead of the LC parallel resonance circuit 8, a choke coil L7 is provided for the same purpose. That is, the choke coil L7 prevents the alternating current from the superimposing unit 41 from being shunted to the direct current power source 3 side.

  The choke coil L7 is a kind of inductance element, and has a frequency characteristic that the impedance increases as the frequency increases, as is well known. Moreover, the larger the inductance value, the larger the impedance. Therefore, the passage of alternating current can be suppressed, and the higher the frequency, the greater the suppression effect.

  Therefore, in the present embodiment, the choke coil L7 is used as a shunt suppression unit in order to effectively suppress the shunting of the alternating current including the higher-order harmonic components as described above to the DC power supply 3 side. It is used. Thereby, also in this embodiment, much of the alternating current output from the superimposing unit 41 flows to the motor 2 side.

  Further, the signal processing unit 47 in the rotation signal detection unit 42 has the same configuration as the signal processing unit 22 of the first embodiment except for the input stage filter. That is, in the signal processing unit 22 of the first embodiment, the detection signal from the current detection unit 21 is input to the amplification unit 24 via the BPF 23. However, in the signal processing unit 47 of the present embodiment, FIG. As shown in FIG. 13, the detection signal from the current detection unit 21 is input to the amplification unit 24 via the HPF 48.

  The HPF 48 is a well-known high-pass filter circuit including a capacitor C15 and a resistor R11. The signal detected by the current detection resistor R1 taken into the signal processing unit 47 is cut by the HPF 48 in a band lower than a predetermined cut-off frequency, and a signal in a band higher than the cut-off frequency passes.

  This cut-off frequency is set to a frequency lower than the fundamental wave frequency f1 of the alternating current output from the superposition unit 41, as indicated by a broken line in FIG. Therefore, all the frequency components of the alternating current output from the superimposing unit 41 pass through the HPF 48.

  Also in the rotation detection system 40 configured as described above, the amplitude of the alternating current component (including even higher-order harmonic components in this example) flowing through the motor 2 changes as the motor 2 rotates. Therefore, the rotation pulse Sp can be generated by the signal processing unit 47 based on the change in the amplitude. Then, the rotation angle of the motor 2 can be detected based on the rotation pulse Sp.

  According to the rotation detection system 40 of the present embodiment described above, as in the rotation detection system 1 of the first embodiment, rotation is performed without providing a large-scale sensor such as a rotary encoder and without causing torque fluctuations. The rotation angle can be accurately detected regardless of the speed.

  Further, a choke coil L7 is provided on the path from the application site P to the DC power supply 3 side, whereby the AC current output from the superimposing unit 5 is a path other than the motor 2 side (positive side of the DC power supply 3). And a larger amount of alternating current flows to the motor 2. Therefore, the quality of the detection signal detected by the current detection unit 21 can be maintained at a high quality, and furthermore, a high-quality rotation pulse Sp can be generated based on the detection signal, so that the rotation with high accuracy can be performed. Corner detection is possible.

  Moreover, since the shunting of the alternating current to the DC power supply 3 side is realized by the choke coil L7, the LC parallel resonant circuit 8 of the first embodiment and the band reject filter 64 (third embodiment described later) Compared to FIG. 15), the diversion can be suppressed with a very simple configuration and at a low cost.

  In particular, in the present embodiment, the alternating current output from the superimposing unit 5 is a current including up to higher harmonic components in addition to the fundamental frequency f1, as described with reference to FIG. Therefore, by using the choke coil L7, whose impedance increases as the frequency increases, as the shunt suppression means, it is possible to more reliably suppress the alternating current from the superimposing unit 5 from being shunted to the DC power supply 3 side.

  Further, the signal processing unit 22 is provided with an HPF 48 at its input stage, and its pass band is set to a predetermined cutoff frequency that is lower than the fundamental frequency f1. Therefore, the AC component including the fundamental frequency f1 and its harmonic component can be reliably extracted from the current flowing through the current detector 21 without loss.

For example, in a motor (medium / large motor) having a rated power of several watts or more, a choke coil is often arranged in series with the motor 2 in order to prevent surge noise. In that case, the choke coil for preventing surge noise is used in combination as the choke coil L7 of the present embodiment, that is, as a means for suppressing the alternating current from the superimposing portion 41 from being shunted to the direct current power source 3 side. [Third Embodiment]
FIG. 15 shows a schematic configuration of the rotation detection system 60 of the present embodiment. Similarly to the rotation detection system 1 of the first embodiment shown in FIG. 1, the rotation detection system 60 of this embodiment is a system for detecting the rotation angle of the motor 2, and a driving DC voltage is applied to the motor 2. A pulse that is provided with a DC power source 3 for application, a point that a motor 5 is provided with a superposition unit 5 for applying (superimposing) an AC voltage for detecting a rotation angle, and a rotation pulse based on the current flowing through the motor 2. About the point provided with the rotation signal detection part 6 which produces | generates Sp, it is the same as 1st Embodiment.

  Therefore, the same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof is omitted. In the following description, the configuration different from the rotation detection system 1 of the first embodiment will be mainly described.

In the rotation detection system 60 of the present embodiment, power is supplied from the DC power supply 3 to the motor 2 via the motor driver 61.
A DC power switch 63 is provided between the DC power supply 3 and the motor driver 61. The DC power switch 63 is controlled (ON / OFF) by a DC application control signal Sdc from the control unit 62. When the DC power switch 63 is ON, a DC voltage from the DC power supply 3 is input to the motor driver 61 and is turned OFF. Sometimes, the input of DC voltage from the DC power source 3 to the motor driver 61 is cut off.

The motor driver 61 is configured by a known H bridge circuit (so-called full bridge) including four switches.
That is, the motor driver 61 includes a switch MOS1, a switch MOS2, a switch MOS3, and a switch MOS4 that are formed of MOSFETs, and the source of each of the high-side switches MOS1 and MOS2 (all are P-channel MOSFETs) is a DC power switch 63. The source of each of the low-side switches MOS3 and MOS4 (both N-channel MOSFETs) is connected to the ground line. The drain of the high-side switch MOS1 is connected to the drain of the low-side switch MOS3, and the connection point (that is, one midpoint J of the H bridge circuit) is connected to one brush 16 in the motor 2. ing. Similarly, the drain of the other switch MOS2 on the high side is connected to the drain of the other switch MOS4 on the low side, and the connection point (the other midpoint K of the bridge circuit) is the other brush 17 in the motor 2. It is connected to the.

  Then, motor driver control signals SM1 to SM4 are input from the control unit 62 to the gates of the switches MOS1 to MOS4, respectively. The switches MOS1 to MOS4 are turned on by the motor driver control signals input to their bases. -Turned off.

  Thus, by providing the motor driver 61, the motor driver 61 can switch between normal rotation and reverse rotation of the motor 2. That is, when the motor 2 is rotated forward, the DC power switch 63 is turned on, and the switch MOS1 and the switch MOS4 among the four switches MOS1 to MOS4 constituting the motor driver 61 are turned on, and the other two switches MOS2 are turned on. , MOS3 is turned off. Thereby, the DC voltage from the DC power supply 3 is applied to the motor 2 via the motor driver 61, and the motor 2 starts normal rotation. At the time of forward rotation, as indicated by an arrow in FIG. 15, a motor current flows from one brush 16 to the other brush 17 in the motor 2 (however, during startup to steady rotation).

  On the other hand, when the motor 2 is reversely rotated, the switch MOS2 and the switch MOS3 among the four switches MOS1 to MOS4 constituting the motor driver 61 are turned on, and the other two switches MOS1 and MOS4 are turned off. As a result, as indicated by an arrow in FIG. 15, in the motor 2, a motor current flows from the other brush 17 to the one brush 16 (however, during startup to steady rotation).

  When the rotating motor 2 is braked, short-circuit braking is performed. The short-circuit braking means that the two switches MOS3 and MOS4 on the low side among the four switches MOS1 to MOS4 constituting the motor driver 61 are turned on so that the terminals of the motor 2 (between the brushes 16 and 17) The motor 2 is braked by short-circuiting through the switches MOS3 and MOS4. When the brushes 16 and 17 of the rotating motor 2 are short-circuited via the switches MOS3 and MOS4, the energy generated by the back electromotive force of the motor 2 generated at the time of the short-circuit is transferred to the low-side switches MOS3 and MOS4, and Consumed by the motor 2, the motor 2 is braked and eventually stops.

  Therefore, when short-circuit braking is performed on the motor 2 in the normal rotation state, as indicated by an arrow in FIG. 15, the motor 2 has a motor current in the direction opposite to that during normal rotation, that is, from the other brush 17 to one of the motors. A motor current flows to the brush 16. Conversely, when short-circuit braking is performed on the motor 2 in the reverse rotation state, as indicated by an arrow in FIG. 15, the motor 2 has a motor current in the direction opposite to that during reverse rotation, that is, from one brush 16 to the other brush. The motor current will flow to 17.

  When the motor 2 is braked by short-circuit braking, if the superimposing unit 5 is provided, for example, on the upstream side (DC power supply 3 side) of the motor driver 61, the superimposing unit is not included in the motor 2 during the short-circuit braking. No AC voltage from 5 is applied. Therefore, in the present embodiment, among the energization paths from the DC power source 3 to the motor 2, the AC voltage from the superimposing unit 5 is applied to the common current path through which the motor current flows during both start-up and steady rotation and short-circuit braking. They are superimposed.

  More specifically, as shown in FIG. 15, the AC voltage from the superimposing unit 5 is superimposed (applied) on the application site P in the path from one midpoint J of the motor driver 61 to one brush 16 of the motor 2. )

  On the other hand, the rotation signal detection unit 6 is provided in a path from the other midpoint K of the motor driver 61 to the other brush 17 of the motor 2 and is configured to detect a current flowing through this path. The rotation pulse Sp from the rotation signal detection unit 6 is input to the control unit 62.

  The control unit 62 controls the DC power switch 63 described above and the switches MOS1 to MOS4 constituting the motor driver 61, and has the same function as the rotation angle detection unit 7 of the first embodiment, that is, a rotation pulse. A function of detecting the rotation angle based on Sp is also provided. In addition, you may make it control the output of the alternating voltage from the superimposition part 5 by the control part 62, and the threshold value set in the threshold value setting part 27 (refer FIG. 5) in the signal processing part 22 is set. You may enable it to variably set with the control signal from the control part 62. FIG.

  In the present embodiment, a signal in a set frequency band (stop band) is passed through a path from the application site P to which the alternating voltage from the superimposing unit 5 is applied to one midpoint J of the motor driver 61. A band reject filter (BRF) 64 is provided as a shunt suppression means for blocking.

  The rotation detection system 60 of the present embodiment is configured to supply DC power to the motor 2 via the motor driver 61, and forward rotation, reverse rotation, and short circuit by switching the switches MOS1 to MOS4 of the motor driver 61. Since the brake is configured to be performed, the AC equivalent circuit of the rotation detection system 60 viewed from the superimposing unit 5 is different for each of forward rotation, reverse rotation, and short-circuit braking, as shown in FIG.

  Among these, during forward rotation when the switch MOS1 and the switch MOS4 are turned ON, an equivalent circuit as shown in FIG. 16A is obtained, and the alternating current from the superimposing unit 5 flows to the motor 2 side, and also the motor driver 61. The current is also diverted from the middle point J to the DC power supply 3 side via the switch MOS1.

  When the switch MOS2 and the switch MOS3 are turned ON, an equivalent circuit as shown in FIG. 16B is obtained, and the alternating current from the superimposing unit 5 flows to the motor 2 side, and one of the motor drivers 61 The current is diverted from the point J to the ground line side through the switch MOS3.

  In the case of short circuit braking when the switch MOS3 and the switch MOS3 are turned on, an equivalent circuit as shown in FIG. 16C is obtained, and the alternating current from the superimposing unit 5 flows to the motor 2 side, The current is diverted from the middle point J to the ground line side through the switch MOS3.

  As described above, the alternating current from the superimposing unit 5 does not flow only to the motor 2 side during forward rotation, reverse rotation, and short-circuit braking, but instead of the motor 2 side (in this example, the motor driver 61). To the middle point J side).

  Therefore, in order to suppress the diversion to the path other than the motor 2 side, a BRF 64 is provided between the application site P and one midpoint J of the motor driver. As a result, much of the alternating current from the superimposing unit 5 flows to the motor 2 side not only during steady rotation (forward rotation / reverse rotation) but also during short-circuit braking.

  Specifically, the BRF 64 has a circuit configuration as shown in FIG. That is, a resistor R12 is connected in parallel with a series connection body of two capacitors C16 and C17, and signals are input and output at both ends of the parallel circuit. The connection point between the two capacitors C16 and C17 is connected to the ground line via the resistor R13. That is, the BRF 64 is a generally known T-type band reject filter (band rejection filter circuit).

  The frequency characteristic of the BRF 64 is as shown by a broken line in FIG. That is, a signal in a predetermined stop band whose center frequency is the frequency f1 of the alternating current output from the superimposing unit 5 is blocked, and signals in other bands pass.

  As is well known, the band reject filter is sometimes called a band eliminate filter, a notch filter, or the like. The LC parallel resonant circuit 8 of the first embodiment can also be regarded as a kind of band reject filter.

  Also in the rotation detection system 60 configured in this way, the amplitude of the alternating current component flowing through the motor 2 changes with the rotation of the motor 2 at any time during normal rotation, reverse rotation, and short-circuit braking. Therefore, the rotation pulse Sp can be generated by the signal processing unit 22 based on the change in the amplitude. Then, the rotation angle of the motor 2 can be detected based on the rotation pulse Sp.

  Therefore, also with the rotation detection system 60 of the present embodiment, as in the rotation detection system 1 of the first embodiment, the rotation speed can be increased without providing a large-scale sensor such as a rotary encoder and without causing torque fluctuations. Therefore, the rotation angle can be detected with high accuracy.

  In addition, a BRF 64 is provided in the path from the application site P to the motor driver 61 side, whereby the alternating current output from the superposition unit 5 is shunted to a path (motor driver 61 side) other than the motor 2 side. Is suppressed, and more alternating current flows to the motor 2. Therefore, the quality of the detection signal detected by the current detection unit 21 can be maintained at a high quality, and furthermore, a high-quality rotation pulse Sp can be generated based on the detection signal, so that the rotation with high accuracy can be performed. Corner detection is possible.

[Modification]
Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above-described embodiments, and can take various forms as long as they belong to the technical scope of the present invention. Needless to say.

  For example, as the shunt suppression means, the LC parallel resonance circuit 8 is used in the first embodiment, and the BRF 64 is used in the third embodiment, but the choke coil L7 used in the second embodiment may be used instead. good. In the first and third embodiments, the alternating current output from the superimposing unit 5 is a sine wave, and the frequency is basically only the frequency f1. For this reason, the inductance value of the choke coil L7 is preferably set so that the impedance of the choke coil L7 at the frequency f1 is sufficiently higher than the impedance on the motor 2 side.

  Moreover, in the said 1st Embodiment and 3rd Embodiment, BPF23 is provided in the input stage of the signal processing part 22, Thereby, from the detection signal by the electric current detection part 21, it is a predetermined pass band containing the frequency f1 of alternating current. Although the signal is extracted, the BPF 23 is used as an example, and other types of filters may be used as long as the signal of the frequency f1 can be extracted. For example, HPF can be used instead of BPF 23.

  However, when HPF is used, not only the signal of frequency f1 but also all signals in a band higher than frequency f1 are extracted. For example, if a noise component having a high frequency is included in the detection signal, it is affected. Therefore, the S / N of the detection signal may be lowered. Therefore, it is desirable to use BPF in order to further increase the S / N.

  In the second embodiment, the choke coil L7 is used as the current diversion suppressing means. Instead, the LC parallel resonance circuit 8 used in the first embodiment and the BRF 64 used in the third embodiment are used. May be.

  When using the LC parallel resonant circuit 8 or the BRF 64 as such, the stop band is set to, for example, the fundamental frequency f1 or the third harmonic frequency f3 among the frequency components of the alternating current output from the superimposing unit 41. For example, it is desirable to set so that a frequency component having a high signal strength is prevented from passing. It should be noted that a plurality of frequency components can be included in the stop band by appropriately setting each element value of the LC parallel resonance circuit 8 and the BRF 64.

  Moreover, in the said 2nd Embodiment, HPF48 is provided in the input stage of the signal processing part 47, and, thereby, it is a signal more than the predetermined cutoff frequency lower than the fundamental wave frequency f1 of alternating current from the detection signal by the electric current detection part 21. However, the HPF 48 is used as an example, and other types of filters may be used as long as at least one frequency component can be extracted. For example, BPF can be used instead of HPF 48.

  However, when the BPF is used, the frequency components that can be extracted are limited, and the energy loss of the detection signal occurs accordingly. Therefore, if priority is given to suppressing the loss of energy of the detection signal, it is desirable to extract all frequency components up to higher harmonics using the HPF 48. Moreover, since the circuit configuration of the HPF 48 can be simplified as compared with the BPF, the HPF 48 is more preferable in terms of cost.

  On the other hand, extracting all the high-order harmonics using the HPF 48 means that, for example, when the detection signal includes a noise component having a high frequency, the noise component is extracted. There is a risk of lowering.

  Therefore, if priority is given to increasing the S / N of the detection signal, it is desirable to extract only necessary frequency components using BPF or the like. In this case, the frequency component to be extracted can be determined as appropriate, but at least one of the fundamental wave component (f1) and the odd harmonic components (f3, f5, f7. It is desirable to extract.

Moreover, a resistance element can also be used as a shunt suppression means. In that case, the larger the resistance value of the resistance element, the higher the shunt suppression effect.
However, when the resistance element is used, the shunting of the alternating current can be suppressed, while a part of the electric power supplied from the DC power source 3 to the motor 2 is consumed by the resistance element, This results in power loss. Therefore, in the case of a motor in which a relatively large current flows, it is not a resistance element, but the LC parallel resonance circuit 8 (FIG. 1), choke coil L7 (FIG. 11), BRF 64 (FIG. 15) shown in the above embodiments. It is desirable to use one that does not cause a loss of DC power, such as

  Further, in addition to the circuits and elements exemplified above, as long as it is possible to effectively suppress the alternating current output from the superimposition unit from being shunted to a path other than the motor 2 side, the specific configuration of the shunt suppression means Is not limited.

In each of the above embodiments, the current detection resistor R1 is used as the current detection unit 21. However, for example, a coil (inductance element) may be used instead of the current detection resistor R1.
Moreover, it goes without saying that the configuration (FIGS. 5 and 13) of the signal detection unit in each of the above embodiments is merely an example and is not limited to the illustrated configuration. As long as the rotation pulse Sp can be generated based on the detection signal from the current detection unit, various configurations can be adopted.

  Moreover, in the said embodiment, although the case where a square wave voltage (1st, 3rd Embodiment) and a sine wave voltage (2nd Embodiment) were demonstrated as voltage which the alternating current power supply in a superimposition part produces | generates, these are demonstrated. Each voltage is only an example, and other types of AC voltages may be generated.

  In each of the above embodiments, the instantaneous impedance change of the motor circuit that occurs when the commutator piece that contacts the brush is switched during the rotation of the motor 2 has been described as being not considered. Although it is true, it is true that the impedance changes, and the change of the impedance periodically occurs with the rotation. Therefore, it is also possible to detect a rotation state such as a rotation angle based on the instantaneous impedance change (and based on the AC component change caused thereby). In that case, it is not always necessary to provide the capacitor C1 as in the motor 2 of each of the above embodiments.

  In the above embodiments, the rotation detection system that detects the rotation angle of the motor 2 has been described. However, instead of the motor 2, for example, a motor 70 as shown in FIG. Is possible.

  The motor 70 shown in FIG. 18 has a configuration in which a capacitor C2 is connected in parallel to the second phase coil L2 in addition to the motor 2 of each of the above embodiments. The capacitance value of the capacitor C2 is different from the capacitance value of the capacitor C1 connected in parallel to the first phase coil L1.

  Therefore, each time the commutator piece in contact with the brushes 16 and 17 is switched while the motor 70 rotates 180 °, that is, each time the motor circuit between the brushes 16 and 17 changes, the impedance of the motor circuit is Change to a different value. That is, in the first embodiment, as shown in FIG. 3, while the motor circuit changes into three types of states A to C while rotating 180 °, the impedance changes are the high impedance of states A and B and the state C. However, in this embodiment, every time the motor circuit changes to three types, the impedance also has different values (three types of values). That is, the impedance of the motor circuit changes in three stages while rotating 180 °.

Therefore, as long as the motor 70 rotates in the same direction, the amplitude of the motor current detected by the current detection unit 21 changes in three stages of small amplitude, medium amplitude, and large amplitude.
Therefore, in order to detect this three-stage amplitude change, the signal processing unit 22 is provided with two threshold setting units in which different threshold values are set, and two corresponding to each of these threshold setting units. It is preferable to provide a comparison unit and output a rotation pulse from each comparison unit. More specifically, for example, a comparison unit that outputs a rotation pulse that becomes H level when the amplitude of the detection signal is greater than or equal to the medium amplitude, and is set to H level when the amplitude of the detection signal is greater than or equal to the large amplitude. And a comparator for outputting various rotation pulses.

With this configuration, the rotation direction of the motor 70 can be detected based on the change pattern of the rotation pulses output from both comparison units.
In addition to the motor 70 shown in FIG. 18, for example, capacitors having different capacities may be connected to each of the three phase coils. Even in this case, it is possible to detect the rotation angle and the rotation direction with high resolution.

  When a capacitor is connected to each of the three phase coils, any two of the capacitors can have the same capacitance value. However, in that case, the rotation angle and the rotation speed can be detected, but the rotation direction cannot be detected.

  Moreover, in the said 1st Embodiment, although the capacitor | condenser C1 was connected so that it might become completely parallel with respect to the 1st phase coil L1 whole, for example, a middle tap is made in a part of 1st phase coil L1, and there. By connecting one end of the capacitor C1 to the capacitor C1, the capacitor C1 may be connected in parallel to a part of the first phase coil L1. Such a connection method can be similarly applied to the motor 70 shown in FIG. 18 and other motors described later.

  In each of the above-described embodiments, the motor 2 is exemplified by a configuration in which the phase coils L1, L2, and L3 are Δ-connected. A motor composed of three phase coils L11, L12, and L13 connected may be used. In the case of star connection, for example, as shown in FIG. 19, the rotation angle and the rotation direction of the motor 80 can be detected by connecting capacitors C31 and C32 in parallel to both of the two phase coils L11 and L12, respectively. .

  Note that the configuration shown in FIG. 19 is merely an example. For example, a capacitor may be connected in parallel only to any one of the phase coils. Further, for example, capacitors may be connected in parallel to all the phase coils L11, L12, L13. In this case, however, the capacitance value of the capacitor needs to be at least two types. For example, a capacitor may be connected between two commutator pieces.

  In each of the above embodiments, a three-phase DC motor having three phases of armature coils has been described as an example. However, the application of the present invention is not limited to a three-phase motor. Even a motor having a phase or higher can be applied.

  As an application example of the present invention for a motor having four or more phases, FIG. 20 shows a case of a five-phase DC motor. The motor 90 shown in FIG. 20 has a commutator including five commutator pieces 91, 92, 93, 94, and 95, and each phase coil L21, L22 as an armature coil is provided in each adjacent commutator piece. , L23, L24, and L25 are connected (Δ connection). The inductance of each phase coil is the same.

  Capacitors C41 and C42 are connected in parallel to two phase coils (first phase coil L21 and second phase coil L22) among the phase coils L21, L22, L23, L24, and L25, respectively. With such a five-phase motor 90, the rotation angle and the rotation speed can be detected.

  In addition, in a motor having four or more phases, if a capacitor is connected in parallel to only one of the phase coils, at least the rotation angle and the rotation speed can be detected. Also, in a motor having four or more phases, if capacitors having different capacitance values are connected to at least two phase coils, similar to the motor 70 shown in FIG. The rotation direction can also be detected based on (and thus the amplitude change pattern of the alternating current).

  In each of the above embodiments, the periodic change of the impedance of the motor circuit accompanying the rotation is realized by connecting the capacitor C1 to the first phase coil L1 of the motor 2 in parallel. There are various other specific configurations of the motor in which the change occurs periodically.

  For example, the motor 100 shown in FIG. 21 also periodically changes the impedance of the motor circuit as it rotates. The motor 100 in FIG. 21 includes a housing 101 and a rotor core 110 accommodated in the housing 101. The rotor core 110 is fixed to a rotating shaft 106 disposed at the axis of the housing 101 and rotates together with the rotating shaft 106.

  The housing 101 has a substantially cylindrical shape, and two magnets 102 and 103 for generating a field are fixed to an inner peripheral surface thereof so as to face each other in the radial direction. When viewed in the circumferential direction, the two magnets 102 and 103 are fixed at a predetermined interval. Each of the magnets 102 and 103 is a permanent magnet, and one of the polarities on the surface facing the rotor core 110 is an N pole and the other is an S pole. That is, the motor 100 is configured as a DC motor having a field pole of two poles.

  The housing 101 is formed of a yoke (yoke) that is a soft magnetic material, and constitutes a magnetic circuit of the motor 100 together with two magnets 102 and 103 fixed to the inner peripheral surface.

  The rotor core 110 is formed of a soft magnetic material, has three teeth (saliency poles) 111, 112, and 113, and an armature coil 105 is wound thereon. Specifically, the first phase coil L1 is wound around the first tooth 111, the second phase coil L2 is wound around the second tooth 112, and the third phase coil L3 is wound around the third tooth 113. The armature coil 105 is constituted by these three phase coils L1, L2, and L3.

  Further, the commutator 10 is fixed to the rotating shaft 106, and a pair of brushes 16, 17 arranged opposite to each other (that is, 180 ° apart in the rotation direction) are in sliding contact with the commutator 10. Yes. The connection state between the commutator 10 and the phase coils L1, L2, and L3 is the same as that of the motor 2 (see FIG. 1) of the first embodiment.

  Further, the motor 100 is provided with a convex portion 104 between the two magnets 102 and 103 on the inner peripheral surface of the housing 101. Since two magnets 102 and 103 are fixed at a predetermined interval in the circumferential direction on the inner peripheral surface of the housing 101, there are two regions (inter-magnet regions) where the magnets 102 and 103 do not exist in the circumferential direction. Existing. In the motor 100, as shown in FIG. 21, a convex portion 104 is provided in one area between the magnets so as to protrude radially inward from the inner peripheral surface of the housing 101. In addition, the convex portion 104 is provided at a predetermined interval from both the magnets 102 and 103 in the circumferential direction so as not to contact any of the two magnets 102 and 103.

  The convex portion 104 is made of a soft magnetic material, has a predetermined length in the circumferential direction, and has a predetermined thickness in the radial direction. And by providing this convex part 104, the magnetic resistance of the magnetic circuit comprised by the rotor core 110 of the motor 100 and the housing 101 changes with rotation of the rotor core 110. FIG. In the following description, “magnetic resistance” means the magnetic resistance of a magnetic circuit constituted by the rotor core 110 and the housing 101 of the motor 2 unless otherwise specified.

  The rotor core 110 and the housing 101 are both made of a soft magnetic material, and the magnetic permeability thereof is much larger than that of air. Therefore, the magnetic resistance of the motor 100 is such that the air gap between the rotor core 110 (specifically, the outer peripheral surfaces of the teeth 111, 112, 113) and the inner peripheral surface of the housing 101 or the magnets 102, 103, and the magnets 102, 103. Depends largely on the sum of the thicknesses. That is, the larger the air gap, the larger the magnetic resistance, and conversely, the smaller the air gap, the smaller the magnetic resistance.

  However, the permeability of each of the magnets 102 and 103 is substantially the same as the permeability of air. Therefore, the magnets 102 and 103 are equivalent to the presence of air when viewed magnetically. That is, when considering the magnetic resistance of the motor 100, the existence of the magnets 102 and 103 having the same permeability as air can be ignored, and each of the magnets 102 and 103 can be treated as an air gap. Therefore, if there is no projection 104, the air gap between the rotor core 110 and the inner peripheral surface of the housing 101 is constant even when the rotor core 110 rotates, and therefore the magnetic resistance does not change with the rotation. .

  However, the motor 100 is provided with a soft magnetic convex portion 104 having substantially the same magnetic permeability as the housing 101 on the inner peripheral surface of the housing 101. Therefore, the magnetic resistance of the motor 100 varies depending on the rotation angle of the motor 100, that is, whether or not the outer peripheral surface of each of the teeth 111, 112, 113 of the rotor core 110 faces the convex portion 104. That is, the magnetic resistance changes as the motor 100 rotates. When the magnetic resistance changes, the inductance of the motor circuit also changes, so that the amplitude of the alternating current output from the superposition unit 5 and flowing through the current detection unit 21 also changes.

  This change in amplitude occurs periodically with the rotation of the motor 100 (specifically, the rotation of the rotor core 110 and the rotation shaft 106). Therefore, the rotation angle of the motor 100 can be detected based on the change in the amplitude of the alternating current, as in the above-described embodiments.

  In addition to the motor 100 shown in FIG. 21, a wide variety of configurations that can periodically change the inductance of the motor circuit by modifying the housing side are conceivable. Specifically, the installation position and the number of projections can be changed as appropriate, and the change pattern of the inductance of the motor circuit accompanying rotation can be characterized by modifying the shape of the projection itself. .

  Moreover, the structure for changing the inductance of a motor circuit periodically is realizable besides the method of adding a device to the housing side like the motor 100 shown in FIG. For example, the motor 120 shown in FIG. 22 has a configuration in which an impedance element 122 other than the capacitor is connected in parallel to the phase coil instead of the capacitor C1 with respect to the motor 2 of the first embodiment.

  For example, the impedance element 122 may be an inductance element (coil) or a resistance. In addition, connecting impedance elements in parallel to only one phase coil is merely an example, and impedance elements may be connected to a plurality of phase coils, or a plurality of impedance elements may be connected to one phase coil. May be. The connection method may be parallel connection or series connection. That is, as a result, as long as the impedance of the motor circuit periodically changes with rotation, it is possible to appropriately determine which element is connected to which phase coil.

  In general, in a DC motor, a ring varistor may be used to absorb surge. In the case of a motor having a ring varistor as described above, this ring varistor can be used to cause a periodic impedance change accompanying rotation.

  For example, you may make it connect a capacitor | condenser, an inductance element, etc. between adjacent electrodes among several electrodes which a ring varistor has. In addition, for example, by adding a device to the structure of the ring varistor itself by making a difference in the area of each electrode without separately connecting a capacitor, an inductance element, or the like as in the above-described various motors, the periodicity accompanying the rotation It is also possible to cause a simple impedance change.

In each of the above embodiments, a motor having a pair of brushes has been described. However, the present invention can also be applied to a motor having a plurality of pairs of brushes.
In general, when a motor is driven, a capacitor is often connected between the brushes outside the motor in order to reduce noise (surge) generated when switching between the brush and the commutator piece. By connecting a capacitor between the brushes, that is, in parallel with the motor, noise generated when switching between the brush and the commutator piece can be reduced.

  However, when the brushes are connected by a capacitor outside the motor, most of the alternating current supplied from the superimposing unit flows to the external capacitor, which may make it difficult to detect the rotation state.

  Therefore, when a capacitor is provided outside the motor for noise reduction, it is desirable that the current detection unit 21 be disposed in a loop formed by the external capacitor and the motor and in a path through which the motor current flows. . A specific example is shown in FIG.

  A rotation detection system 130 shown in FIG. 23 is provided with a noise reduction capacitor C50 with respect to the rotation detection system 1 of FIG. In the rotation detection system 130, a condenser C50 is connected in parallel to the motor 2. More specifically, one end of the capacitor C50 is connected to the brush 16 on the DC power source 3 side in the motor 2, and the other end is connected to a path from the current detection unit 21 to the ground line. Therefore, no current flowing through the external capacitor C50 flows through the current detection unit 21, and the current detection unit 21 can detect only the current flowing through the motor 2.

  DESCRIPTION OF SYMBOLS 1,40,60,130 ... Rotation detection system 2,70,80,90,100,120 ... Motor, 3 ... DC power supply, 4,46 ... AC power supply, 5,41 ... Superimposition part, 6,42 ... Rotation Signal detecting unit 7... Rotation angle detecting unit 8. LC parallel resonant circuit 10... Commutator 11, 91 to 95 commutator piece 11 11 first commutator piece 12 12 second commutator piece 13 ... 3rd commutator piece, 16, 17 ... Brush, 21 ... Current detection part, 22, 47 ... Signal processing part, 23 ... BPF, 24 ... Amplification part, 25 ... Envelope detection part, 26 ... LPF, 27 ... Threshold Setting unit 28 ... Comparison unit 30,31 ... Operational amplifier 32 ... Comparator 48 ... HPF 61 ... Motor driver 62 ... Control unit 63 ... DC power switch 64 ... BRF 101 ... Housing 102, 103 ... Magnet 104 ... convex part 105 ... armature 106 ... rotating shaft 110 ... rotor core 111 ... first tooth 112 ... second tooth 113 ... third tooth 122 ... impedance element C1, C2, C5, C11 to C17, C31, C32, C41, C42, C50 ... capacitor, C10 ... coupling capacitor, D1, D2 ... diode, J, K ... midpoint, L1 ... first phase coil, L2 ... second phase coil, L3 ... third phase coil, L5 ... coil, L7: Choke coil, L11-L13, L21-L25 ... Phase coil, MOS1-MOS4 ... Switch, P ... Application site, R1 ... Current detection resistor, R2-R13 ... Resistance

Claims (11)

A rotation detection device that detects a rotation state of a DC motor that rotates by receiving power supply from a DC power source,
The DC motor is configured such that an impedance between at least a pair of brushes to which a DC voltage from the DC power source is applied in the DC motor periodically changes as the DC motor rotates,
The rotation detector is
AC superimposing means for superimposing an AC voltage on a DC voltage applied between the pair of brushes;
An energization detecting means for detecting an alternating current or an alternating voltage supplied to the direct current motor from the alternating current superimposing means as a detection target ;
A rotation state detection means for detecting at least one of a rotation angle, a rotation direction and a rotation speed of the DC motor based on the detection target detected by the energization detection means;
A diversion suppressing unit for suppressing an alternating current from the AC superimposing unit from diverting to other than the DC motor;
A rotation detection device comprising: The rotation detection device according to claim 1,
The shunt suppression means is arranged in a current path from the DC power source to the DC motor,
The rotation detecting device, wherein the AC superimposing unit is connected between the DC motor and the diversion suppressing unit in the energization path and configured to apply the AC voltage. The rotation detection device according to claim 2,
The shunt suppression means is configured to suppress at least the passage of current in the stop band, with a predetermined frequency band including part or all of the frequency component of the AC voltage applied by the AC superimposing means as a stop band. Rotation detecting device characterized by that. The rotation detection device according to claim 3,
The shunt suppression means is set such that an inductance element having a predetermined inductance value and a capacitance element having a predetermined capacitance value are connected in parallel, and the resonance frequency is a frequency within the stop band. In addition, the rotation detecting device is a parallel resonant circuit. The rotation detection device according to claim 3,
The rotation detecting device, wherein the shunt suppressing means is a band stop filter circuit configured to suppress the passage of current in the stop band. The rotation detection device according to any one of claims 3 to 5,
The AC superimposing means is configured to be able to apply a sine wave voltage as the AC voltage,
In the shunt suppression means, a predetermined frequency band including the frequency of the sine wave voltage is set as the stop band,
The rotation state detecting means includes
With a predetermined frequency band including the frequency of the sine wave voltage as a pass band, an AC component in the pass band is allowed to pass from the detection target detected by the energization detecting unit and an AC component other than the pass band is passed. A bandpass filter circuit to block;
Rotation signal generation means for generating a rotation signal that is a signal corresponding to the change in amplitude based on the change in amplitude of the AC component that has passed through the bandpass filter circuit;
A rotation detection device comprising: The rotation detection device according to claim 2,
The rotation detection device, wherein the shunt suppression means is an inductance element. The rotation detection device according to claim 7,
The alternating current superimposing means is configured to be able to apply a distorted wave voltage having a fundamental wave component of a predetermined frequency and at least one harmonic component with respect to the fundamental wave component as the alternating voltage,
The rotation state detecting means includes
A high-pass filter circuit that allows an AC component that is equal to or higher than the cutoff frequency to pass from the detection target that is detected by the energization detection unit, with a predetermined frequency that is equal to or lower than the frequency of the fundamental wave component of the distortion wave voltage as a cutoff frequency; ,
Rotation signal generating means for generating a rotation signal that is a signal corresponding to the change in amplitude based on the change in amplitude of the AC component that has passed through the high-pass filter circuit;
A rotation detection device comprising: A DC motor that rotates by receiving power from a DC power supply;
A rotation detection device for detecting a rotation state of the DC motor;
A rotation detection system comprising:
The DC motor is configured such that an impedance between at least a pair of brushes to which a DC voltage from the DC power source is applied in the DC motor periodically changes as the DC motor rotates,
The rotation detection device includes:
AC superimposing means for superimposing an AC voltage on a DC voltage applied between the pair of brushes;
An energization detecting means for detecting an alternating current or an alternating voltage supplied to the direct current motor from the alternating current superimposing means as a detection target ;
A rotation state detection means for detecting at least one of a rotation angle, a rotation direction and a rotation speed of the DC motor based on the detection target detected by the energization detection means;
A diversion suppressing unit for suppressing an alternating current from the AC superimposing unit from diverting to other than the DC motor;
A rotation detection system comprising: The rotation detection system according to claim 9,
The DC motor is
An armature coil comprising at least three phase coils;
A commutator having a plurality of commutator pieces to which the armature coil is connected;
At least a pair of brushes for supplying current to each phase coil via the commutator;
Have
Any two commutator pieces of the plurality of commutator pieces are set as a set, and at least one set of the commutator pieces has a capacitance value different from that of the other set of commutator pieces. The rotation detection system is characterized by being configured as follows. The rotation detection system according to claim 9,
The DC motor is
A housing in which a plurality of field generating magnets are fixed in the circumferential direction on the inner peripheral surface;
A rotor core provided in the housing and having an armature coil composed of a plurality of phase coils;
A commutator having a plurality of commutator pieces to which the armature coil is connected;
At least a pair of brushes in sliding contact with the commutator;
Have
A rotation detection system, wherein the inductance between the pair of brushes is periodically changed with rotation.

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