JP5897923B2 - Rotation detector - 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 plurality of DC motors.

  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.

  In order to meet such a demand for the sensorless system, the applicant of the present application has proposed the following sensorless technology in Patent Document 1. That is, the DC motor is configured such that the impedance between the pair of brushes periodically changes with rotation. Furthermore, an AC superimposing means for superimposing an AC voltage (AC current) on a DC current supplied from the DC power source to the DC motor is provided. And an alternating current component is extracted from the electric current which flows into a direct-current motor, and a rotation state is detected based on the change (periodic change which arises by the change of the said impedance) of the alternating current component.

JP 2010-63347 A

  However, in the sensorless technology described in Patent Document 1, one AC superimposing unit for superimposing an AC current is required for one DC motor. Therefore, as the number of DC motors increases, the corresponding amount increases. The AC superimposing means necessary for detecting the rotation state of each DC motor also increases. That is, the same number of AC superimposing means as the number of DC motors whose rotation state should be detected is required.

Therefore, as the number of DC motors increases, the number of AC superimposing means must be increased by the same number, which leads to an increase in size and cost of the apparatus.
The present invention has been made in view of the above problems, and in a rotation detection device configured to detect a rotation state of a DC motor based on a change in an AC component to be energized, a plurality of DC motors to detect the rotation state are provided. Even if it exists, it aims at the cost reduction and size reduction of the whole apparatus by suppressing the use number of an alternating current superimposition means.

The present invention made to solve the above problems is provided individually for each of a plurality of DC motors, a motor drive circuit for driving a plurality of DC motors, an AC superimposing means for applying an AC voltage to the plurality of DC motors. A rotation signal generating means for detecting an electric quantity related to an alternating current among currents flowing through the DC motor and generating a rotation signal indicating a rotation state of the DC motor based on the detected electric quantity; and a DC motor based on the rotation signal A rotation state detection unit that detects at least one of the rotation angle, rotation direction, and rotation speed (that is, the rotation state).

  And the rotation detection apparatus of this invention is comprised so that an alternating current superimposition means may apply a common alternating voltage to several direct-current motors. Further, the common AC voltage is superimposed on the DC voltage applied to the plurality of DC motors.

  Therefore, according to the rotation detection device of the present invention, the AC superimposing means applies a common AC voltage to a plurality of DC motors, and the AC voltage is applied to each DC motor while being superimposed on the DC voltage. Even if there are a plurality of DC motors that should detect this, the number of AC superimposing means used can be suppressed, thereby realizing a reduction in cost and size of the entire apparatus.

The common AC voltage means an AC voltage applied in parallel from one AC superimposing means to each DC motor (that is, the same AC voltage supply source is the same).
DC motor multiple is at least one motor-side impedance element may be connected to a specific two commutator segments of the plurality of commutator segments provided in the DC motor.

  In the rotation detection device configured as described above, the impedance between the brushes of each of the plurality of DC motors changes periodically with rotation, and thereby the voltage between the brushes of each DC motor changes periodically. For this reason, the rotation signal generated by the rotation signal generating means is a signal reflecting the periodic change, and thus the rotation state of each DC motor can be reliably detected.

Because as the motor-side impedance element, various elements having a predetermined impedance is conceivable, that the is For example capacitor, it is possible to increase the periodic variation width of the AC voltage caused by the rotation, each The rotation state of the DC motor can be detected more reliably.

Ac superimposing means, the plurality of DC motor, and is configured to apply a simultaneous alternating voltage between the negative electrode of the DC power source for supplying one DC voltage of a pair of brushes with the respective DC motor Also good .

  According to the rotation detection device having the above configuration, an AC voltage can be applied to each of a plurality of DC motors from a single AC superimposing means, and an AC voltage can be reliably applied to each DC motor with a simple configuration. it can.

Motor drive circuit, for each of a plurality of DC motors, corresponding the brushes are connected to both of a pair of brushes DC motor has to selectively to one of the positive electrode side and negative electrode side of the respective DC power supply A half-bridge circuit for connection is provided, and at least two of the plurality of DC motors are connected to one another of a pair of brushes that each has, and for each brush connected to each other, it may be configured so that an AC voltage is applied by a single half-bridge circuits alternating superimposing means is connected to be shared by the motors.

  In the rotation detection device having the above-described configuration, each of the plurality of DC motors has a configuration in which a half-bridge circuit is connected to each of a pair of brushes, and a single half-bridge is common to the brushes connected to each other. The circuit is connected. The alternating current superimposing means applies an alternating voltage to the brushes connected to each other.

  Therefore, according to the rotation detection device having the above-described configuration, the same half-bridge circuit is connected to the plurality of brushes connected to each other, and the plurality of brushes connected to each other is used. Since an AC voltage can be applied by the same AC superimposing means, the number of AC superimposing means used can be more efficiently suppressed with a simple configuration.

A pair of brushes with the direct current motor multiple, at least, the brush an AC voltage is applied by the AC superposing section may be provided with a circuit side impedance element between its brush and the motor drive circuit .

  According to the rotation detection device having the above-described configuration, at least the energization path between the brush to which the AC voltage is applied by the AC superimposing means and the motor drive circuit (specifically, between the brush and the DC power source and between them, the DC By providing impedance to the current-carrying path that does not include the motor, the component that does not flow to the DC motor but flows to the DC power source side out of the AC current from the AC superimposing means is reduced, and the component that flows to the DC motor side is increased. As a result, the rotation signal generating means can detect the amount of electricity (and thus generate the rotation signal) more easily and with high accuracy.

The circuit side impedance element can suppress the alternating current from the alternating current superimposing means from flowing to the direct current power source without passing through the direct current motor, and can appropriately supply power from the direct current power source to the direct current motor (direct current energization). As long as the level can be maintained, various types of elements can be used.

It is a block diagram showing schematic structure of the motor drive system of 1st Embodiment. It is explanatory drawing showing the operation example (9 types of drive states) of the motor drive system of 1st Embodiment. It is a block diagram showing schematic structure of a motor. It is explanatory drawing for demonstrating three types of states (motor circuit) which arise while a motor rotates 180 degrees. It is explanatory drawing for demonstrating that the rotation pulse SP is produced | generated by applying alternating current from an alternating current superimposition part, (a) is an output waveform example of the alternating voltage and electric current from an alternating current superimposition part, (b) is An example of a waveform of a voltage detected by the AC detector, (c) is an example of a waveform of a rotation pulse SP generated based on the detected voltage. It is a circuit diagram showing the structure of an alternating current detection part. It is a time chart for demonstrating the production | generation of the rotation pulse SP for every drive state in the motor drive system of 1st Embodiment. It is a block diagram showing schematic structure of the motor drive system of 2nd Embodiment. It is explanatory drawing showing the operation example (27 types of drive states) of the motor drive system of 2nd Embodiment. It is a block diagram showing the other Example of a motor drive system.

Preferred embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
As shown in FIG. 1, the motor drive system 1 of the present embodiment controls the drive of two motors M1 and M2, and mainly includes a DC power supply 2 and three half-bridge circuits B1, B2, and B3. A control unit 3, an AC superposition unit 4, a first AC detection unit 6, and a second AC detection unit 7. The DC power source 2 outputs a DC voltage Vcc. Also, each of the three half bridge circuits B1, B2, and B3 has a well-known configuration including two transistors.

  The first half-bridge circuit B1 is configured by connecting a first transistor Tr1 and a second transistor Tr2 in series. Specifically, the emitter of the first transistor Tr1 and the collector of the second transistor Tr2 are connected to each other, and the connection point is connected to one end of the first inductor L01. The collector of the first transistor Tr1 is connected to the positive electrode of the DC power supply 2, and the emitter of the second transistor Tr2 is connected to the negative electrode of the DC power supply 2 (which is also the ground potential of the motor drive system 1). The first control signal ST1 from the control unit 3 is input to the base of the first transistor Tr1, and the second control signal ST2 from the control unit 3 is input to the base of the second transistor Tr2.

  The second half bridge circuit B2 is configured by connecting a third transistor Tr3 and a fourth transistor Tr4 in series. Specifically, the emitter of the third transistor Tr3 and the collector of the fourth transistor Tr4 are connected to each other, and the connection point is connected to one end of the second inductor L02. The collector of the third transistor Tr3 is connected to the positive electrode of the DC power supply 2, and the emitter of the fourth transistor Tr4 is connected to the negative electrode of the DC power supply 2. The third control signal ST3 from the control unit 3 is input to the base of the third transistor Tr3, and the fourth control signal ST4 from the control unit 3 is input to the base of the fourth transistor Tr4.

  The third half-bridge circuit B3 is configured by connecting a fifth transistor Tr5 and a sixth transistor Tr6 in series. Specifically, the emitter of the fifth transistor Tr5 and the collector of the sixth transistor Tr6 are connected to each other, and the connection point is connected to one end of the third inductor L03. The collector of the fifth transistor Tr5 is connected to the positive electrode of the DC power supply 2, and the emitter of the sixth transistor Tr6 is connected to the negative electrode of the DC power supply 2. The fifth control signal ST5 from the control unit 3 is input to the base of the fifth transistor Tr5, and the sixth control signal ST6 from the control unit 3 is input to the base of the sixth transistor Tr6.

  Each of the transistors Tr1 to Tr6 is an NPN bipolar transistor in this embodiment, but this is only an example, and other switching elements such as MOSFETs may be used.

  These three half-bridge circuits B1, B2, B3 drive the motors M1, M2 by controlling the energization from the DC power supply 2 to the motors M1, M2 in accordance with the control signals ST1-ST6 from the control unit 3. Is.

  Each of the two motors M1 and M2 is a DC motor with a brush having a pair of brushes, as will be described in detail later. Of these, the first motor M1 has one brush (first brush) 16 connected to the other end of the first inductor L01 and the other brush (second brush) 17 connected to the other end of the second inductor L02. And is connected to one brush (first brush) 41 of the second motor M2. The second motor M2 has its first brush 41 connected to the other end of the second inductor L02 and to the second brush 17 of the first motor M1, and the other brush (second brush) 42 is The other end of the third inductor L03 is connected. The two motors M1 and M2 have the same specifications in this embodiment.

  In the motor drive system 1 of the present embodiment, nine types of drive states are realized by the control signals ST1 to ST6 from the control unit 3 as shown in FIG. FIG. 2 shows the rotation states of the motors M1 and M2 and the ON / OFF states of the transistors Tr1 to Tr6 for each driving state. As shown in FIG. 2, for example, in the driving state A in which only the first motor M1 is rotated forward (rotated in the forward direction), the fourth transistor in the first transistor Tr1 and the second half bridge circuit B2 in the first half bridge circuit B1. The transistor Tr4 is turned on.

  As shown in FIG. 1, the forward rotation direction is a rotation direction when a direct current is passed from the first brush 16 to the second brush 17 in the first motor M1, and the second direction. In the motor M <b> 2, the rotation direction is when a direct current is passed from the first brush 41 to the second brush 42. As shown in FIG. 1, the reverse rotation direction is the rotation direction when power is supplied in the opposite direction to the normal rotation direction.

  The control unit 3 controls each of the motors M1 and M2 so that each of the motors M1 and M2 operates in any one of the nine types of driving states shown in FIG. 2 by controlling the control signals ST1 to ST6. To do.

  The AC superimposing unit 4 is connected to the common connection node N0 in the energization path from the second brush 17 of the first motor M1 to the first brush 41 of the second motor M2. An AC voltage is applied to connection node N0.

  The AC superimposing unit 4 superimposes the AC voltage generated by the AC power source 5 on the AC voltage 5 generated by the AC power source 5 and the DC voltage Vcc output from the DC power source 2. And a coupling capacitor C0 for application to the capacitor. In this embodiment, the AC voltage generated by the AC power supply 5 is a square wave voltage as shown in the upper part of FIG. Therefore, the alternating current output via the coupling capacitor C0 has a substantially impulse waveform as shown in the lower part of FIG.

  In the present embodiment, only one AC superimposing unit 4 is provided for the two motors M1 and M2, and the AC voltage from the AC superimposing unit 4 is connected to the two motors M1 and M2. Applied to the common connection node N0. That is, one AC superimposing unit 4 is shared for detecting the rotation angles of the two motors M1 and M2. Therefore, when either one of the two transistors Tr1 and Tr2 constituting the first half-bridge circuit B1 is turned on, an alternating current from the alternating current superimposing unit 4 flows through the first motor M1. Further, when any one of the two transistors Tr5 and Tr6 constituting the third half bridge circuit B3 is turned on, an alternating current from the alternating current superimposing unit 4 flows through the second motor M2. Furthermore, when any one of the transistors Tr1 and Tr2 constituting the first half-bridge circuit B1 and any one of the transistors Tr5 and Tr6 constituting the third half-bridge circuit B3 are turned ON, The alternating current from the alternating current superimposing unit 4 flows through both the first motor M1 and the second motor M2 simultaneously.

  With this configuration, the motors M1 and M2 are not only applied with the DC voltage Vcc from the DC power supply 2, but also the AC voltage output from the AC superimposing unit 4 to the DC voltage Vcc from the DC power supply 2. An alternating current superimposed voltage is applied. Therefore, each motor M1, M2 has an AC / DC mixed (a kind of pulsating current) current (AC superposition) in which an AC current from the AC superimposing unit 4 is superimposed on a DC current from the DC voltage from the DC power supply 2. Current) flows.

  However, since each of the motors M1 and M2 is a DC motor, a component that contributes to rotation of the motors M1 and M2 (provides torque to be driven to rotate) in the AC superimposed current is applied by the DC power supply 2. It is a direct current component due to the direct current voltage Vcc, and the alternating current component due to the alternating current voltage applied from the alternating current superimposing unit 4 does not participate in the rotation itself and does not affect the torque. The AC voltage from the AC superimposing unit 4 is applied to the motors M1 and M2 in order to detect the rotation state of the motors M1 and M2.

  That is, as will be described later, the first AC detection unit 6 performs the first rotation based on the AC component of the current flowing through the first motor M1 (specifically, based on the AC component of the voltage of the first node N1). A pulse SP1 is generated. Further, the second AC detection unit 7 generates the second rotation pulse SP2 based on the AC component (specifically, based on the AC component of the voltage at the second node N2) of the current flowing through the second motor M2. . That is, the AC superimposing unit 4 is provided not for a power source for rotating the motors M1 and M2, but for the purpose of detecting the rotation state of the motors M1 and M2.

  Note that the output of the DC voltage Vcc from the DC power supply 2 and the output of the AC voltage from the AC superposition unit 4 can be controlled independently. Depending on the operating state (ie, driving state) of each half-bridge circuit B1, B2, B3, the motor is energized downstream from the DC current energizing direction of the motor, that is, from one of the motor brushes to the ground. The AC voltage from the AC superposition unit 4 may be applied to the path. However, even if an AC voltage is applied to the motor on either the upstream side or the downstream side, an AC current can flow through the motor (the AC current can be superimposed on the DC current).

  As shown in FIG. 3, each of the motors M1 and M2 has a housing 60 formed of a yoke (yoke) made of soft magnetic material, and various configurations such as an armature coil and a rotor core (not shown) are provided in the housing 60. Contains parts. The housing 60 has a substantially cylindrical shape, and two magnets 61 and 62 for generating a magnetic field are fixed to the inner peripheral surface thereof so as to face each other in the radial direction. Each of the magnets 61 and 62 is a permanent magnet, and one of the polarities on the side facing the armature coil is an N pole and the other is an S pole. Each of the motors M1 and M2 includes a pair of brushes 16 and 17 (41 and 42) arranged opposite to each other (that is, 180 ° apart in the rotation direction), and a three-phase coil is used as an armature coil. Have. That is, each of the motors M1 and M2 of the present embodiment is configured as a brushed three-phase DC motor having a field pole of two poles.

Since the first motor M1 and the second motor M2 have the same configuration, the description of FIG. 3 will be continued with the first motor M1 as an object.
The first motor M <b> 1 includes a commutator 10 including 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, 13 are in contact with the brushes 16, 17, and each brush is rotated along with the rotation of the commutator 10 by the rotation of the motors M 1, M 2. The two commutator pieces in contact with 16 and 17 are switched.

Further, in the present embodiment, a capacitor C1 is connected in parallel with the first phase coil L1 in the first motor M1.
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 2, the capacitor C1 can be handled as not equivalently present, and therefore the DC current from the DC power source 2 flows only through the phase coils L1, L2, and L3.

  On the other hand, if the circuit (motor circuit) in the first motor M1 between the brushes 16 and 17 is viewed as an AC circuit, each phase coil L1, L2, L3 has a high impedance, whereas the capacitor C1 has a low impedance. The difference between the two is great. Therefore, for example, when the first motor M1 rotates clockwise from the state shown in FIG. 3 (that is, the commutator 10 rotates clockwise) and the first commutator piece 11 comes into contact with the second brush 17, Between each brush 16 and 17, the parallel circuit (parallel resonant circuit) of the 1st phase coil L1 and the capacitor | condenser C1 is formed. 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.

  That is, from the viewpoint of direct current, the motor circuit can be regarded as a circuit composed of only three phase coils L1, L2, and L3. The presence of is not affected.

  On the other hand, in terms of alternating current, the motor circuit formed between the brushes changes each time the two commutator pieces in contact with the brushes 16 and 17 are switched according to the rotation angle of the first motor M1. Therefore, 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 switching of the commutator piece occurs three times while the first motor M1 rotates 180 °. Change is a two-step process.

  FIG. 4A shows a change in the connection state inside the first motor M1, that is, a change in the motor circuit formed between the brushes 16 and 17, while the first motor M1 rotates 180 °. As shown in FIG. 4A, the motor circuit of the first motor M1 according to the present embodiment mainly includes three rotation states Ma, rotation state Mb, and rotation state Mc while the first motor M1 rotates 180 °. Change to type.

  The rotation state Ma is a state in which the first commutator piece 11 is in contact with the first brush 16 and the second commutator piece 12 is in contact with the second brush 17 as shown in the drawing. An equivalent circuit of the first motor M1 in this rotational state Ma, 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 rotational state Ma, 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, 17, and Any phase coil always exists in the path from the brush 16 to the other brush 17. Therefore, in this rotational state Ma, the inductance of each phase coil L1, L2, L3 is dominant, and the impedance of the entire motor circuit is increased.

  The rotation state Mb is a state rotated about 50 ° clockwise from the rotation state Ma, and the commutator piece contacting the first brush 16 is changed from the first commutator piece 11 to the third commutator in the rotation state Ma. It has switched to the piece 13. The second commutator piece 12 is in contact with the second brush 17.

  Even in this rotational state Mb, 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 the first Any phase coil always exists in the path from the brush 16 to the second brush 17. Therefore, the impedance of the entire motor circuit is high even in this rotational state Mb. It should be noted that the rotational state Mb and the rotational state Ma have the same impedance as the whole circuit, as is clear by comparing the equivalent circuits shown in the figure.

  The rotation state Mc is a state in which the rotation state Mc is further rotated by about 50 ° clockwise from the rotation state Mb, and the commutator piece contacting the second brush 17 is the second commutator piece 12 in the rotation state Ma, Mb from the second commutator piece 12. 1 commutator piece 11 is switched to. The third commutator piece 13 is in contact with the first brush 16.

  In this rotation state Mc, 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 respectively connected in parallel. Therefore, between the brushes 16 and 17, there is an energization path only for the capacitor C1. That is, a parallel resonant circuit is connected between the brushes. As a result, in a region where the impedance of the motor circuit is higher than the resonance frequency of the parallel resonance circuit, the capacitor C1 becomes dominant as the frequency becomes higher, and the impedance becomes lower.

  As described above, while the first motor M1 rotates 180 °, the commutator piece that contacts the brushes 16 and 17 is switched three times, and the motor circuit between the brushes 16 and 17 rotates accordingly. There are three types of states Ma, Mb, and Mc. However, since the rotation state Ma and the rotation state Mb have the same impedance as the entire circuit as described above, the change in impedance that occurs during the 180 ° rotation is in two stages.

  In the process of rotation of the first motor M1, there is a switching period in which one brush is in contact with two adjacent commutator pieces at the same time, and the impedance between the brushes changes during this switching period. Is only instantaneously generated during one rotation of the first motor M1, and the accompanying change in impedance is instantaneous. Therefore, in this embodiment, this switching period is not considered.

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

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

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

  Then, when the rotation further proceeds from the rotation state Mc ′, the rotation state is switched to the rotation state Ma again. Hereinafter, as the rotation proceeds, the rotation state Mb → the rotation state Mc → the rotation state Ma ′ → the rotation state Mb ′ → the rotation state Mc ′ → The rotation state is switched from Ma to.

  That is, the first motor M1 is rotated by 60 ° in accordance with the rotation angle of the first motor M1 in accordance with the rotation angle of the first motor M1 in six rotation states Ma, Mb, Mc, Ma ′, Mb ′, and Mc ′. This means that the state changes every time. Among these, the rotation states Ma, Mb, Ma ′, and Mb ′ all have the same impedance (high impedance). Further, the rotational states Mc and Mc 'have the same impedance, and the value is much lower than the impedance of the rotational state Ma and the like. With such a configuration, the impedance between the brushes 16 and 17 (impedance of the motor circuit) periodically changes as the first motor M1 rotates.

  FIG. 4B 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 rotation states Ma, Mb, Ma ′, and Mb ′ are the same. In this rotation state Ma, Mb, Ma ′, Mb ′, there is almost no influence of the capacitor C1, and although a small peak value (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 case of the rotational states Mc and Mc ', the impedance characteristics change greatly due to resonance between the phase coils L1, L2, and L3 and the capacitor C1, and the impedance becomes small around the resonance frequency fb (maximum value). Therefore, the rotational states Ma, Mb, Ma ′, Mb ′ and the rotational states Mc, Mc ′ 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 of the fundamental wave component of the alternating current output from the alternating current superimposing unit 4 (hereinafter referred to as “alternating current fundamental frequency”) is set to be a predetermined frequency f1 higher than the frequency fc. ing.

  The change in the impedance of the motor circuit described above is caused by the change in the AC component (AC motor current) included in the motor current flowing through the first motor M1, or the AC component (AC) included in the voltage of the energization path through which the motor current flows. It appears directly as a change in voltage component.

  Therefore, as shown in FIG. 1, the first AC detection unit 6 detects the voltage of the energization path of the first motor M1, and based on the AC component included in the detected voltage, determines the rotation state of the first motor M1. The first rotation pulse SP1 shown is generated.

  FIG. 5B is an example of the voltage at the first node N1 detected by the first AC detector 6 when the first motor M1 rotates in the forward direction. As shown in FIG. 5B, the detection voltage of the first node N1 has a waveform in which an AC component is superimposed on a DC component. When attention is paid to the AC component, the rotation state Ma (Ma ′) and the rotation state Mb (Mb ′) have a large amplitude during the rotation state Mc (Mc ′) where the impedance with respect to the AC fundamental frequency f1 is small and conversely the impedance is large. During this period, the amplitude decreases. That is, while the first motor M1 rotates 180 °, the amplitude of the AC component changes into two types (two steps).

  Therefore, in the present embodiment, the first AC detection unit 6 rotates the first motor M1 based on the amplitude change of the AC voltage component of the first node N1 caused by the change in impedance with the rotation of the first motor M1. A first rotation pulse SP1 indicating the state is generated. As shown in FIG. 5C, the first rotation pulse SP1 generated by the first AC detection unit 6 is at a high level and has a low amplitude rotation state Ma during the period of the high amplitude rotation state Mc (Mc ′). The pulse signal becomes a low level during the period of (Ma ′), rotation state Mb (Mb ′).

  FIG. 6 shows a specific configuration of the first AC detection unit 6. The first AC detection unit 6 includes a detection resistor R1 that detects the voltage of the first node N1, a high-pass filter (HPF) 21, a level shift circuit 22, an envelope detection unit 23, and a low-pass filter (LPF) 24. The comparison unit 25 and the threshold setting unit 26 are provided.

  FIG. 7 shows an example of the detection voltage detected by the detection resistor R1. FIG. 7 schematically illustrates an example of the internal operation of each of the AC detection units 6 and 7, particularly the first AC detection unit 6, for each driving state. Specifically, for each of the driving states A to G, the ON / OFF states of the transistors Tr1 to Tr6 are shown, the detected voltage waveform of the first motor M1 (that is, the voltage at the first node N1), the first AC detection The output waveform of the HPF 21 in the unit 6, the output waveform of the level shift circuit 22, the output waveform of the envelope detector 23, and the waveform of the first rotation pulse SP1 are illustrated. About the 2nd alternating current detection part 7, only 2nd rotation pulse SP2 finally output is illustrated by the lowest stage of FIG.

  As shown in FIG. 7, the detection voltage detected by the detection resistor R1 is a positive voltage when the first motor M1 is energized in the forward rotation direction as in the driving state B or the driving state F. When the first motor M1 is energized in the reverse direction as in the driving state C or the driving state G, the voltage becomes negative. The reason why the amplitudes of these detection voltages periodically increase or decrease (change in two stages) is as already described with reference to FIG.

  The HPF 21 has a known configuration including a capacitor C11 and a resistor R2. The detection voltage by the detection resistor R1 is cut by the HPF 21 in the band of the predetermined cutoff frequency or less. This cutoff frequency is set to a frequency lower than the AC basic frequency f1. Therefore, all the frequency components of the alternating current output from the alternating current superimposing unit 4 (the component of the alternating current basic frequency f1 and its harmonic components) pass through the HPF 21. The detection voltage detected by the detection resistor R1 is cut in the low frequency region by the HPF 21, and has a waveform that swings around 0V as shown in FIG.

The signal extracted by the HPF 21 is level shifted and amplified by the level shift circuit 22.
The level shift circuit 22 includes an operational amplifier 27, a resistor R5 connected between the output terminal and the inverting input terminal of the operational amplifier 27, one end connected to the non-inverting input terminal of the operational amplifier 27, and the other end connected to the ground line. Corresponding to the amount of level shift, the resistor R6 connected to the resistor R4, one end connected to the inverting input terminal of the operational amplifier 27, and the resistor R3 connected to the non-inverting input terminal of the operational amplifier 27. A reference voltage generation unit 29 that generates a predetermined reference voltage and an operational amplifier 28 are provided. The operational amplifier 28 is configured as a so-called voltage follower in which the inverting input terminal and the output terminal are short-circuited, and the reference voltage from the reference voltage generation unit 29 input to the non-inverting input terminal is input as it is. . The output terminal of the operational amplifier 28 is connected to the other end of the resistor R4, and the output voltage (that is, the reference voltage) from the operational amplifier 28 is input to the inverting input terminal of the operational amplifier 27 via the resistor R4.

  On the other hand, the operational amplifier 27 constitutes a non-inverting amplifier circuit as a whole together with the resistors R3, R4, R5 connected thereto. The detection signal from the HPF 21 is input to the non-inverting input terminal of the operational amplifier 27 through the resistor R3.

  Therefore, the detection signal from the HPF 21 is level-shifted (level down) by the reference voltage generated by the reference voltage generation unit 29 and amplified by the non-inverting amplifier circuit. That is, as shown in FIG. 7, a DC offset is added to the output signal from the HPF 21 by the reference voltage, further amplified, and a voltage of 0 V or higher is output to the envelope detector 23.

  The signal level-shifted and amplified by the level shift circuit 22 is envelope-detected by the envelope detector 23. The envelope detector 23 includes a rectifying diode D1, a resistor R7 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 C12 having an end connected to the ground potential is provided, and a signal from the level shift circuit 22 is input to the anode of the diode D1.

  The envelope detection unit 23 envelope-detects the signal input from the level shift circuit 22 and generates a constant signal (hereinafter referred to as “detection signal”) corresponding to the amplitude of the alternating current as shown in FIG. Is done.

  The generated detection signal is input to the comparison unit 25 after the high frequency component is cut by the LPF 24. The LPF 24 has a known configuration including a resistor R8 and a capacitor C13. A diode D2 is connected in parallel to the resistor R8. The connection direction of the diode D2 is opposite to the direction in which the detection signal is input.

  The comparator 25 includes a comparator 30, a resistor R 11 connected between the output terminal and the inverting input terminal of the comparator 30, one end connected to the non-inverting input terminal of the comparator 30, and the other end connected to the LPF 24. The resistor R9 and the resistor R10 having one end connected to the inverting input terminal of the comparator 30 and the other end connected to the threshold setting unit 26 are provided.

  The detection signal output from the envelope detection unit 23 is input to the comparison unit 25 via the LPF 24, and is input to the non-inverting input terminal of the comparator 30 via the resistor R9 in the comparison unit 25. On the other hand, the threshold value from the threshold value setting unit 26 is input to the inverting input terminal of the comparator 30 via the resistor R10. As a result, the comparator 30 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 26 and input to the comparison unit 25 is a period in which the amplitude is small (that is, the rotation states Ma, Mb, Ma ′, A predetermined value that is larger than the detection signal in the period Mb ′) and smaller than the detection signal in the period in which the amplitude is large (that is, the period of the rotation states Mc and Mc ′) is set.

  Therefore, in a period with a small amplitude, the detection signal input from the envelope detection unit 23 to the comparison unit 25 is 0 V and is smaller than the threshold value from the threshold setting unit 26, so that a low level signal is output from the comparator 30. Is done. On the other hand, in a period in which the amplitude is large, the detection signal input from the envelope detection unit 23 to the comparison unit 25 is larger than the threshold value, so that a high level signal is output from the comparator 30.

  Then, the low level and high level signals output from the comparator 30 are output to the control unit 3 as the first rotation pulse SP1 corresponding to the rotation angle of the first motor M1, as shown in FIG.

  The configuration of the second AC detection unit 7 that generates the second rotation pulse SP2 for the second motor M2 is exactly the same as the configuration of the first AC detection unit 6 described above. That is, the second AC detection unit 7 detects the voltage of the second node N2 in the energization path between the second brush 42 of the second motor M2 and the other end of the third inductor L03, and based on the detected voltage. Through the same signal processing as the first rotation pulse SP1 described above, the second rotation pulse SP2 is generated and output to the control unit 3.

  As shown in FIG. 1, the control unit 3 includes a first rotation detection unit 31 and a second rotation detection unit 32. The first rotation detection unit 31 receives the first rotation pulse SP1 output from the first AC detection unit 6, and detects, for example, a rising edge of the first rotation pulse SP1 based on the first rotation pulse SP1. The rotation angle of the first motor M1 is detected by a method such as counting. The detected rotation angle is fed back to a control circuit of the first motor M1 (not shown) in the control unit 3 and used for controlling the first motor M1.

  The second rotation detector 32 receives the second rotation pulse SP2 output from the second AC detector 7, and detects, for example, the rising edge of the second rotation pulse SP2 based on the second rotation pulse SP2. The rotation angle of the second motor M2 is detected by a method such as counting. The detected rotation angle is fed back to a control circuit for a second motor M2 (not shown) in the control unit 3 and used for controlling the second motor M2.

  In addition, although the motor drive system 1 of this embodiment is configured to detect the rotation angle of each motor M1, M2 based on each rotation pulse SP1, SP2, the interval (for example, rising edge) between each rotation pulse SP1, SP2 is configured. The rotational speeds of the motors M1 and M2 (or only the rotational speed) may be detected based on the edge interval.

  In the present embodiment, the first inductor L01 is disposed between the first half bridge circuit B1 and the first node N1, and the second inductor L02 is disposed between the second half bridge circuit B2 and the common connection node N0. The third inductor L03 is disposed between the third half bridge circuit B3 and the second node N2. Among these inductors, the first inductor L01 is for separating the first node N1 from the ground, the second inductor L02 is for separating the common connection node N0 from the ground, The inductor L03 is for separating the second node N2 from the ground.

  The AC equivalent circuit viewed from the AC superimposing unit 4 includes a circuit (first circuit) extending from the common connection node N0 to the ground through the first motor M1, the first inductor L01, and the first half-bridge circuit B1, and the common connection node N0. To the ground via the second inductor L02 and the second half bridge circuit B2 (second circuit), and the ground from the common connection node N0 to the second motor M2, the third inductor L03, and the third half bridge circuit B3. And the circuit (third circuit) leading to are connected in parallel.

  If the second inductor L02 is not provided, the impedance of the second circuit is substantially equivalent to the impedance of the transistors Tr3 and Tr4 of the second half-bridge circuit B2, and one of these two transistors is selected. When is turned on, the impedance of the second circuit becomes the ON resistance (usually a very small value) of the turned-on transistor. Therefore, most of the alternating current from the alternating current superimposing unit 4 is shunted to the second circuit, and the amount of current flowing to the originally required first circuit and third circuit (that is, the motors M1 and M2 side) is reduced. End up. If the amount of alternating current supplied to the motors M1 and M2 is reduced in this way, the change in the amplitude of the alternating voltage detected by the alternating current detectors 6 and 7 becomes dull, and the generation accuracy of the rotation pulses SP1 and SP2 is reduced. May decrease.

  Therefore, in the present embodiment, the second inductor L02 is arranged in the second circuit to increase the impedance of the second circuit, so that most of the AC current from the AC superimposing unit 4 is shunted to the motors M1 and M2 side. Like to do.

  If the first inductor L01 is not provided in the first circuit, when one of the transistors Tr1 and Tr2 constituting the first half-bridge circuit B1 is turned on, the potential of the first node N1 Becomes very close to the ground potential, and hence the amplitude change of the AC voltage at the first node N1 becomes dull. Therefore, in the present embodiment, the first inductor L01 is arranged in the first circuit to electrically isolate the first node N1 and the ground, so that the amplitude of the voltage fluctuation at the first node N1 is increased. . The reason why the third inductor L03 is provided in the third circuit is also the same as that of the first inductor L01, and the second node N2 and the ground are electrically separated to increase the amplitude of voltage fluctuation at the second node N2. This is to ensure that

  As described above, the motor drive system 1 of the present embodiment is configured so that the two motors M1, M2 can be individually driven and controlled using the three half-bridge circuits B1, B2, B3. Then, by applying (superimposing) the AC voltage from one AC superimposing unit 4 to the common connection node N0 to which the motors M1 and M2 are connected to each other, the motors M1 and M2 from the one AC superimposing unit 4 are applied. An alternating voltage can be applied to either or both of the above. That is, a common AC voltage is applied to each of the motors M1 and M2 from one AC superimposing unit 4 and is superimposed on the DC voltage while the DC voltage is applied. For this reason, the number of AC superposition units 4 used can be reduced with respect to the number of motors (two in this example), which makes it possible to reduce the size and cost of the entire system.

  In particular, since the AC superimposing unit 4 of the present embodiment is composed of the AC power source 5 and the coupling capacitor C0, the effect of reducing the number of AC power sources 5 used by suppressing the number of AC superimposing units 4 used is great. Further, since it is desirable in principle that the coupling capacitor C0 has a large capacitance, for example, a capacitor is not integrated in an IC (integrated circuit) but is provided externally separately from the IC. Is. Therefore, the fact that the number of coupling capacitors C0 used can be reduced by applying the present invention greatly contributes to downsizing and cost reduction of the entire system.

  In addition, although there is one AC superimposing unit 4, the AC detecting unit is individually provided for each motor M1, M2, and each rotation pulse SP1, SP2 is generated independently for each motor M1, M2. Is done. Therefore, the rotation angles of the motors M1 and M2 can be detected independently regardless of the driving state of the system.

  In the present embodiment, the first inductor L01, the second inductor L02, and the third inductor LO3 are disposed between the half bridge circuits B1, B2, and B3 and the nodes N1, N0, and N2, respectively. The nodes N1, N0, and N2 are separated from the ground. Therefore, the AC voltage amplitude can be sufficiently generated in each of the AC detection units N1 and N2, and the detection of the AC voltage, and hence the rotation pulses SP1 and SP2, can be performed with high accuracy.

In the present embodiment, the capacitor C1 included in each motor M1, M2 corresponds to the motor side impedance element of the present invention, the three half bridge circuits B1, B2, B3 correspond to the motor drive circuit of the present invention, and the AC The superimposing unit 4 corresponds to the AC superimposing unit of the present invention, the two AC detecting units 6 and 7 correspond to the rotation signal generating unit of the present invention, and the two rotation detecting units 31 and 32 are the rotational state detecting unit of the present invention. The second inductor L02 corresponds to the circuit side impedance element of the present invention.

[Second Embodiment]
Next, the motor drive system 50 of 2nd Embodiment is demonstrated using FIG. As apparent from the comparison with FIG. 1, the motor drive system 50 of the present embodiment is equipped with one more motor than the motor drive system 1 of the first embodiment. Each of the AC detection unit and the rotation detection unit in the control unit is added one by one. Hereinafter, the description will focus on the parts different from the motor drive system 1 of the first embodiment.

  The motor drive system 50 of the present embodiment further includes a third motor M3 in addition to the first motor M1 and the second motor M2. The third motor M3 has the same configuration and specifications as the other motors M1 and M2. One of the brushes 43, 44 included in the third motor M3 is connected to the common connection node N0, and the other second brush 44 is connected to the fourth half via the fourth inductor L04. It is connected to the bridge circuit B4.

  The fourth half-bridge circuit B4 is configured by connecting a seventh transistor Tr7 and an eighth transistor Tr8 in series. Specifically, the emitter of the seventh transistor Tr7 and the collector of the eighth transistor Tr8 are connected to each other, and the connection point is connected to one end of the fourth inductor L04. The collector of the seventh transistor Tr7 is connected to the positive electrode of the DC power supply 2, and the emitter of the eighth transistor Tr8 is connected to the negative electrode of the DC power supply 2. The seventh control signal ST7 from the control unit 51 is input to the base of the seventh transistor Tr7, and the eighth control signal ST8 from the control unit 51 is input to the base of the eighth transistor Tr8.

  Thus, in the motor drive system 50 of the present embodiment, only one AC superimposing unit 4 is provided for the three motors M1, M2, and M3, and this one AC superimposing unit 4 includes three motors M1. , M2 and M3.

  And the 3rd alternating current detection part 8 is connected to the 3rd node N3 in the electricity supply path | route between the other end of the 4th inductor L04, and the 2nd brush 44 of the 3rd motor M3. The third AC detection unit 8 detects the third motor M3 based on the change in the amplitude of the AC voltage component at the third node N3 caused by the change in impedance between the brushes 43 and 44 accompanying the rotation of the third motor M3. The third rotation pulse SP3 indicating the rotation state is generated, and the specific configuration thereof is exactly the same as the configuration of the first AC detection unit 6 shown in FIG.

  On the other hand, the control unit 3 is provided with a third rotation detection unit 33 in addition to the first rotation detection unit 31 and the second rotation detection unit 32. The third rotation detection unit 33 is a third AC detection unit. Based on the third rotation pulse SP3 from 8, the rotation angle of the third motor M3 is detected.

  In the motor drive system 50 of the present embodiment, 27 types of drive states are realized by the control signals ST1 to ST8 from the control unit 51 as shown in FIG. FIG. 9 shows the rotation states of the motors M1, M2, and M3 and the ON / OFF states of the transistors Tr1 to Tr8 for each driving state. As shown in FIG. 9, for example, in the driving state P in which the first motor M1 is rotated forward and the third motor M3 is rotated reversely, the first transistor Tr1 in the first half-bridge circuit B1 and the fourth in the second half-bridge circuit B2. The transistor Tr4 and the seventh transistor Tr7 in the fourth half bridge circuit B4 are turned ON.

  According to the motor drive system 50 of this embodiment configured as described above, the three motors M1, M2, and M3 can be individually driven and controlled using the four half-bridge circuits B1, B2, B3, and B4. Then, by applying (superimposing) an AC voltage from one AC superimposing unit 4 to a common connection node N0 to which the motors M1, M2, M3 are connected to each other, each motor M1 , M2, and M3, an AC voltage can be applied to any one, two, or all of them. For this reason, the number of AC superimposing units 4 used can be suppressed with respect to the number of motors (three in this example), which makes it possible to reduce the size and cost of the entire system.

[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, in the above-described embodiment, the first AC detection unit 6 detects the voltage of the first node N1, and generates the first rotation pulse SP1 based on the AC component included in the detected voltage. Thus, the method of generating the rotation pulse based on the voltage of the node is merely an example (the same applies to the other AC detection units 7 and 8). For example, a current detection resistor is arranged on the energization path, the current flowing through the motor is detected by detecting the voltage across the current detection resistor, and the rotation pulse SP is generated based on the AC component included in the detection current You may make it do. That is, as long as the electric quantity related to the alternating current flowing through the motor (that is, directly or indirectly indicating the alternating current) can be detected and the rotation pulse SP can be generated based on the detected electric quantity, the specific configuration is not limited. There are various possibilities.

  Moreover, although the case where the number of motors was two and three was demonstrated in the said embodiment, the number of the motors which comprise a system is not specifically limited, The motor drive system using four or more motors Similarly, the present invention can be applied. Further, the number of brushes (logarithm) constituting the motor is not limited to a pair of brushes as in the above embodiment, and may be a motor having a plurality of pairs of brushes.

  Moreover, in the said embodiment, although the structure which applies an alternating voltage using one alternating current superimposition part 4 with respect to several motor was illustrated, the number of alternating current superimposition parts is not restricted to one, The number of the motors to be used There is no particular limitation as long as the number is smaller.

  The motor drive device 70 shown in FIG. 10 is configured to apply an AC voltage to the three motors M1, M2, and M3 using the two AC superposition units 71 and 72. The motor driving device 70 is different from the motor driving system 50 of the second embodiment shown in FIG. 8 in that the first brush 43 of the third motor M3 is connected to the second node N2, a common connection node. In addition to the first AC superimposing unit 71 (same as the AC superimposing unit 4 in FIG. 8) connected to N1, a point where another first AC superimposing unit 72 is connected to the second node N2, and the control unit 73 However, it is the same as that of 2nd Embodiment except that it controls these two alternating current superimposition parts 71 and 72. In addition, although the 2nd alternating current superimposition part 72 is a thing of the same structure as the 1st alternating current superimposition part 71 in the example of FIG. 10, the thing of a mutually different structure may be sufficient.

  In the motor drive device 70 configured as described above, the AC voltage from the first AC superimposing unit 71 is used to detect the rotation state of the first motor M1 and the second motor M2, and the AC voltage from the second AC superimposing unit 72 is used. Is used to detect the rotational state of the third motor M3. Even with such a configuration, the rotational state of each of the motors M1, M2, and M3 can be detected by a smaller number of AC superposition units than the number of motors, so that the entire system can be reduced in size and cost.

  Moreover, in the said embodiment, although the drive circuit which consists of a some half bridge circuit was shown as a drive circuit for driving each motor, application of this invention is limited to the motor drive system provided with the half bridge circuit. It is not a thing.

  Moreover, although the motor of the said embodiment was the structure by which the capacitor | condenser C1 was connected in parallel with the 1st phase coil among each phase coil L1, L2, L3, this structure is an example to the last. For example, capacitors having the same or different capacitance may be connected in parallel to any two phase coils, or a separate coil may be connected in parallel to any one phase coil. Further, for example, other configurations other than the configuration in which impedance elements such as capacitors and coils are connected may be used. As a result, various specific configurations inside the motor are conceivable as long as the impedance between the brushes periodically changes with rotation. . As described above, in the process of rotation of the first motor M1, 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. . In the above embodiment, the change in impedance that occurs instantaneously during this switching period is not taken into account, but the change in impedance that occurs instantaneously is used (that is, the instantaneous change in AC component caused by the change in impedance). The rotation state may be detected.

  Furthermore, the direction of rotation of the motor may be detected by generating impedance changes between the brushes accompanying rotation in more stages. For example, in the motor of the above embodiment, a capacitor is further provided in parallel with the second phase coil L2. However, this capacitor has a different capacitance from the capacitor C1 connected in parallel to the first phase coil L1. By configuring the motor in this way, the impedance between the brushes changes in three stages while the motor rotates 180 degrees, and thereby the amplitude of the AC component also changes in three stages. Therefore, the rotation direction of the motor can be detected based on the change pattern of the amplitude of the AC component.

  In the above-described embodiment, the AC power source 5 constituting the AC superimposing unit 4 generates a square wave voltage as illustrated in FIG. 5A. However, this is only an example, and the AC power source There is no particular limitation as to what AC voltage 5 generates.

  In the above embodiment, the inductors L01, L02, and L03 are arranged between the nodes N1, N0, and N2 and the half bridge circuits B1, B2, and B3. However, for example, resistors are arranged instead of the inductors. Other types of impedance elements may be arranged.

  DESCRIPTION OF SYMBOLS 1,50,70 ... Motor drive system, 2 ... DC power supply, 3, 51, 73 ... Control part, 4 ... AC superimposition part, 5 ... AC power supply, 6 ... 1st AC detection part, 7 ... 2nd AC detection part , 8 ... 3rd AC detection part, 10 ... Commutator, 11 ... 1st commutator piece, 12 ... 2nd commutator piece, 13 ... 3rd commutator piece, 16, 41, 43 ... 1st brush, 17, 42, 44 ... second brush, 21 ... HPF, 22 ... level shift circuit, 23 ... envelope detector, 24 ... LPF, 25 ... comparison unit, 26 ... threshold setting unit, 27, 28 ... operational amplifier, 29 ... reference voltage Generation unit 30... Comparator 31. First rotation detection unit 32. Second rotation detection unit 33. Third rotation detection unit 60. Housing 61. 62. ... 2nd alternating current superposition part, B1 ... 1st half bridge circuit, B2 ... 2nd half bridge Circuit, B3 ... Third half bridge circuit, B4 ... Fourth half bridge circuit, C0 ... Coupling capacitor, C1, C11, C12, C13 ... Capacitor, D1, D2 ... Diode, L01 ... First inductor, L02 ... Second Inductor, L03 ... third inductor, L04 ... fourth inductor, L1 ... first phase coil, L2 ... second phase coil, L3 ... third phase coil, M1 ... first motor, M2 ... second motor, M3 ... first 3 motors, N0 ... common connection node, N1 ... first node, N2 ... second node, N3 ... third node, R1 ... detection resistor, R2-R11 ... resistance, SP ... rotation pulse, Tr1 ... first transistor, Tr2 ... 2nd transistor, Tr3 ... 3rd transistor, Tr4 ... 4th transistor, Tr5 ... 5th transistor, Tr6 ... 6th transistor, Tr7 The seventh transistor, Tr8 ... eighth transistor

Claims (4)

A motor drive circuit for driving a plurality of DC motors;
AC superimposing means for applying an AC voltage to the plurality of DC motors;
Provided individually for each of the plurality of DC motors, detects an electric quantity related to an AC current among currents flowing through the DC motor, and generates a rotation signal indicating a rotation state of the DC motor based on the detected electric quantity. A rotation signal generating means;
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 rotation signal;
In a rotation detection device comprising:
The AC superimposing means is configured to apply a common AC voltage to the plurality of DC motors,
The common AC voltage is superimposed on a DC voltage applied to the plurality of DC motors ,
The AC superimposing means is configured to apply the AC voltage to the plurality of DC motors simultaneously between one of a pair of brushes of each DC motor and a negative electrode of a DC power source that supplies the DC voltage. Has been
Of the pair of brushes provided in the plurality of DC motors, at least the brush to which the AC voltage is applied by the AC superimposing means is provided with a circuit-side impedance element between the brush and the motor drive circuit. rotation detecting apparatus characterized by Tei Ru. The rotation detection device according to claim 1,
The rotation detecting device, wherein the plurality of DC motors include at least one motor side impedance element connected between two specific commutator pieces among the plurality of commutator pieces included in the DC motor. The rotation detection device according to claim 2,
The rotation detecting device, wherein the motor side impedance element is a capacitor. The rotation detection device according to any one of claims 1 to 3 ,
The motor driving circuit is connected to each of the pair of brushes of the corresponding DC motor for each of the plurality of DC motors, and each brush is connected to either the positive electrode side or the negative electrode side of the DC power source. Half-bridge circuit for selective connection to
At least two of the plurality of DC motors are connected to one another of the pair of brushes that each has,
The rotation detecting device, wherein the same one half-bridge circuit is connected to the brushes connected to each other and the AC voltage is applied by the AC superimposing means.