JP2012239301A - Motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor controller capable of starting a three-phase motor smoothly and quickly.SOLUTION: The motor controller 100 includes an energization control section 50 that energizes a switching element owned by an inverter and controls the rotation of a three-phase motor 7 on the basis of an operation command and a stop command, and an energization instruction section 10 that instructs the energization control section 50 to energize between preset two ones of three terminals owned by the three-phase motor 7 and to stop the energization on the basis of a stop command regardless of the next operation command.

Description

  The present invention relates to a motor control device that controls rotation of a motor.

  Conventionally, a three-phase motor including a stator having a stator coil and a rotor having a permanent magnet has been used as a power source for electric equipment. Such rotation of the three-phase motor is controlled by attraction and repulsion acting between the magnetic flux generated by energizing the stator coil and the magnetic flux of the permanent magnet. Once the three-phase motor starts rotating, the rotation of the three-phase motor can be appropriately controlled by switching the energization to the stator coil. However, when a sensorless brushless motor is used as the three-phase motor, the above attractive force and repulsive force may not easily act depending on the stop position of the rotor before starting rotation (before starting). In such a case, even if there is an operation command from the control means, as shown in FIG. 6A, the three-phase motor becomes difficult to start and the start-up time becomes long or the start-up fails (not shown). there is a possibility. Therefore, a technique for improving such a problem has been studied (for example, Patent Document 1).

  As shown in FIG. 6B, the compressor driving device described in Patent Document 1 energizes at least one phase for a predetermined time (for example, 3 seconds) to move the rotor to an initial position, and then performs normal energization control. To start the three-phase motor from the initial position.

JP 2005-90466 A

  In the technique described in Patent Document 1, since the rotor is once moved to the initial position, the startup is stable. However, since energization for moving the rotor to the initial position is performed after an operation command is issued from the control means, there is a time loss until the motor performs steady operation.

  In view of the above problems, an object of the present invention is to provide a motor control device that can start a three-phase motor smoothly and quickly.

  The characteristic configuration of the motor control device according to the present invention for achieving the above object includes an energization control unit configured to energize a switching element of an inverter based on an operation command and a stop command to control rotation of a three-phase motor; Based on the stop command, regardless of the next operation command, the power supply control unit is instructed to supply power to two preset terminals among the three terminals of the three-phase motor and to stop the power supply. And an energization instruction unit.

  With such a characteristic configuration, the rotor of the three-phase motor can be moved to a position where it can be easily started based on the magnetic flux generated in the stator coil provided between the two terminals after the stop command for the three-phase motor. Therefore, when there is an instruction to start the three-phase motor, the three-phase motor can be started smoothly. In addition, after the stop command, the rotor can be moved to a position where it can be easily started before the next operation command is issued. Therefore, even if the next operation command is issued, the start-up time of the three-phase motor is delayed. There is no. Therefore, the three-phase motor can be started quickly.

  In addition, it is preferable that an energization duration changing unit that changes an energization duration from energization between the two terminals to a stop of the energization is preferable.

  With such a configuration, the energization continuation time can be changed according to the rotation angle necessary for the rotor to move between two positions where it can be easily started. Therefore, the amount of power required for specific energization control can be reduced as much as possible.

  In addition, it is preferable that a standby time is provided from when the stop command is issued to when an energization instruction is given between the two terminals.

  Here, even when a stop command is issued, the rotor of the three-phase motor rotates by inertia according to the operating condition before the stop command, the weight of the rotor, and the like. With such a configuration, since the specific energization control can be held during inertial rotation, the amount of power required for the specific energization control can be reduced as much as possible.

  Further, it is preferable that a standby time changing unit for changing the standby time is provided.

  With such a configuration, the standby time can be changed according to the operation state before the stop command, the weight of the rotor, and the like. Therefore, the rotor can be reliably and smoothly moved to a position where it can be easily started.

It is a block diagram which shows typically schematic structure of a motor control apparatus. It is a figure shown about the drive pattern of an inverter. It is a time chart which concerns on electricity supply control at the time of moving to an initial position. It is a figure which shows the relationship between a rotor and a stator. It is a figure shown about the drive pattern of the inverter which concerns on other embodiment. It is a time chart which concerns on electricity supply control of a prior art.

  Embodiments of the present invention will be described below with reference to the drawings. The motor control device 100 according to the present invention has a function of controlling the rotation of the three-phase motor and facilitating starting of the stopped three-phase motor. In particular, the motor control device 100 according to the present embodiment moves the rotor to a preset initial position until the next operation command is issued after the stop command for the three-phase motor, and according to the subsequent operation command. Makes it easy to start a three-phase motor. In the present embodiment, a sensorless brushless three-phase motor in which a permanent magnet is provided in the rotor and a stator coil is provided in the stator will be described as an example.

  FIG. 1 is a schematic diagram showing a configuration of a motor control device 100 according to the present invention. The motor control device 100 includes a control unit 1, an inverter 6, a three-phase motor 7, and a rotor position detection unit 8.

  Although not shown, the three-phase motor 7 includes a rotor including a permanent magnet and a stator that generates a magnetic flux for applying a rotational force to the rotor. This stator includes U-phase, V-phase, and W-phase three-phase stator coils 7U, 7V, and 7W. Each stator coil is connected by Δ connection and connected to the inverter 6.

  The inverter 6 controls the three-phase motor 7 and converts a DC voltage into an AC voltage. For this reason, the inverter 6 functions as a frequency converter. The DC voltage is supplied from a power source 20 connected to the inverter 6. The inverter 6 includes a total of six transistors Q1, including high-side transistors Q1, Q3, and Q5 connected to the positive terminal side of the power source 20 and low-side transistors Q2, Q4, and Q6 connected to the negative terminal side of the power source 20. -It consists of Q6.

  For example, when only the transistor Q1 and the transistor Q4 are turned on at the same time, energization between two terminals among the three terminals of the three-phase motor 7 is performed. The three terminals are a U-phase terminal 41, a V-phase terminal 42, and a W-phase terminal 43. The two terminals when only the transistor Q1 and the transistor Q4 are simultaneously turned on are the V-phase terminal 42 and the W-phase terminal 43. Therefore, when only the transistor Q1 and the transistor Q4 are turned on at the same time, current is supplied between the V-phase terminal 42 and the W-phase terminal 43. By this energization, current flows from the power source 20 to the second power source line 22 via the first power source line 21, the transistor Q1, the stator coil 7V, and the transistor Q4, and from the power source 20 to the first power source line 21, the transistor Q1, and the stator coil. A current flows through the second power supply line 22 via 7U, the stator coil 7W, and the transistor Q4.

  On the other hand, when only the transistor Q3 and the transistor Q2 are turned on at the same time, current is supplied between the V-phase terminal 42 and the W-phase terminal 43. This energization causes a current to flow from the power source 20 to the second power source line 22 via the first power source line 21, the transistor Q3, the stator coil 7V, and the transistor Q2, and from the power source 20 to the first power source line 21, the transistor Q3, and the stator coil. A current flows through the second power supply line 22 via 7W, the stator coil 7U, and the transistor Q2.

  Here, the direction of the current flowing through each stator coil differs between when only the transistor Q1 and the transistor Q4 are turned on and when only the transistor Q3 and the transistor Q2 are turned on. Therefore, a magnetic flux corresponding to the direction of current flow is generated in each stator coil, and an attractive force and a repulsive force are generated between the magnetic flux and a permanent magnet provided in the rotor. Therefore, the rotor can obtain a rotational force by sequentially turning on the upper and lower pair transistors formed by the high-side transistor and the low-side transistor selected from the transistors Q1 to Q6.

  Specifically, the transistors Q1-Q6 are driven with the pattern shown in FIG. In FIG. 2, “O” is attached to the transistor to be turned on. First, only the transistors Q2 and Q5 are turned on (step # 01). As a result, current is passed between the U-phase terminal 41 and the V-phase terminal 42, and current flows through the stator coil 7 U from the U point toward the V point, and the stator coil 7 W and the stator coil 7 V have the U point, the W point, Current flows through point V. Here, assuming that all the stator coils have the same impedance and the same number of turns, a larger current flows in the stator coil 7U than in the stator coil 7W and the stator coil 7V. For this reason, the magnetic flux density of the magnetic flux generated in the stator coil 7U is larger than the magnetic flux density of the magnetic flux generated in the stator coil 7W and the stator coil 7V. Accordingly, in step # 01, the magnetic flux of the stator coil 7U is more dominant than the magnetic fluxes of the stator coil 7W and the stator coil 7V. Therefore, the stator coil 7U and the permanent magnet are changed according to the magnetic flux generated in the stator coil 7U. The rotor rotates so as to face each other. In FIG. 2, it is assumed that an “N pole” is generated at one end of the stator coil 7 </ b> U due to the energization, and since it becomes dominant as described above, it is hatched for easy understanding.

  Next, only the transistors Q2 and Q3 are turned on (step # 02). As a result, current is passed between the W-phase terminal 43 and the V-phase terminal 42, and a current flows through the stator coil 7 </ b> V from the W point toward the V point, while the W point, the U point, Current flows through point V. In this case, since the magnetic flux of the stator coil 7V is more dominant than the magnetic flux of the stator coil 7W and the stator coil 7U, the stator coil 7V and the permanent magnet are opposed to each other according to the magnetic flux generated in the stator coil 7V. The rotor rotates.

  Then, only the transistors Q3 and Q6 are turned on (step # 03). As a result, current is passed between the W-phase terminal 43 and the U-phase terminal 41, and a current flows through the stator coil 7W from the W point toward the U point, while the stator coil 7V and the stator coil 7U have the W point, the V point, Current flows through point U. In this case, since the magnetic flux of the stator coil 7W is more dominant than the magnetic flux of the stator coil 7V and the stator coil 7U, the stator coil 7W and the permanent magnet face each other according to the magnetic flux generated in the stator coil 7W. The rotor rotates.

  Thereafter, only the transistors Q1 and Q6 are turned on (step # 04). As a result, current is passed between the V-phase terminal 42 and the U-phase terminal 41, and a current flows through the stator coil 7 U from the V point toward the U point, while the stator coil 7 W and the stator coil 7 V have the V point, the W point, Current flows through point U. In this case, since the magnetic flux of the stator coil 7U is more dominant than the magnetic flux of the stator coil 7W and the stator coil 7V, the stator coil 7U and the permanent magnet are opposed to each other according to the magnetic flux generated in the stator coil 7U. The rotor rotates.

  Next, only the transistors Q1 and Q4 are turned on (step # 05). As a result, current is passed between the V-phase terminal 42 and the W-phase terminal 43, and current flows through the stator coil 7V from the V point toward the W point, while the stator coil 7U and the stator coil 7W have the V point, the U point, A current flows through the W point. In this case, since the magnetic flux of the stator coil 7V is more dominant than the magnetic flux of the stator coil 7U and the stator coil 7W, the stator coil 7V and the permanent magnet are opposed to each other according to the magnetic flux generated in the stator coil 7V. The rotor rotates.

  Then, only the transistor Q4 and the transistor Q5 are turned on (step # 06). As a result, current is passed between the U-phase terminal 41 and the W-phase terminal 43, and a current flows through the stator coil 7W from the U point toward the W point, and at the U, V point, the stator coil 7U and the stator coil 7V, A current flows through the W point. In this case, since the magnetic flux of the stator coil 7W is more dominant than the magnetic flux of the stator coil 7U and the stator coil 7V, the stator coil 7W and the permanent magnet are opposed to each other according to the magnetic flux generated in the stator coil 7W. The rotor rotates.

  As shown in FIG. 1, the transistors Q1-Q6 are provided with diodes D1-D6 so that the cathode terminal is connected to the collector terminal and the anode terminal is connected to the emitter terminal. Here, energy is stored in each stator coil during energization, but these diodes D1-D6 are applied to peripheral components by back electromotive force generated due to the energy when each stator coil is de-energized. It is arranged to prevent adverse effects.

  A series of control for such transistors Q1-Q6 is performed by the control unit 1. The control unit 1 includes an energization control unit 50 and an energization instruction unit 10 (see FIG. 1). The energization control unit 50 controls the rotation of the three-phase motor 7 by energizing the switching element of the inverter 6 based on, for example, an operation command and a stop command from the control unit 200 as a host system. In particular, the energization control unit 50 controls the switching element of the inverter 6 by PWM (Pulse Width Modulation) control. In the present embodiment, the switching elements included in the inverter 6 correspond to the transistors Q1 to Q6 described above. Therefore, the energization control unit 50 operates the transistors Q1-Q6 included in the inverter 6 by PWM control.

  The control unit 1 is configured by a microcomputer that operates at a low voltage such as 2.5 V or 3.3 V, for example. Therefore, the PWM signal output from the energization control unit 50 may have insufficient drive capability to turn on the transistors Q1-Q6 depending on the current flowing through the transistors Q1-Q6 and the electrical characteristics of the transistors Q1-Q6. . Therefore, a driver (not shown) that increases the drive capability of the PWM signal can be disposed between the energization control unit 50 and the inverter 6. The driver may be constituted by a driver IC or a push-pull circuit assembled with transistors. Of course, when the drive capability of the PWM signal output from the energization control unit 50 is high, it is naturally possible to configure without a driver.

  The rotor position detection unit 8 detects the position of the rotor based on a comparison result between a counter electromotive voltage generated in each of the stator coils 7U, 7V, and 7W and a preset reference voltage as the three-phase motor 7 rotates. . More specifically, the rotor position detector 8 detects that the rotor has reached a preset position. For this detection, a known technique can be used. Therefore, the description is omitted here. The rotor position detection unit 8 transmits the obtained detection result to the control unit 1. The energization control unit 50 performs PWM control based on the detection result transmitted from the rotor position detection unit 8.

  Here, the motor control device 100 according to the present invention provides a regulation that makes it easy to detect the position of the rotor R after the stop command until the next operation command is issued so that the next start can be performed smoothly after the stop command is issued. Move to the initial position. The next operation command is ignored until the movement to the initial position is completed. The rotor R moved to the initial position is stopped at the initial position until an operation command is issued. Hereinafter, control for moving the rotor R to such an initial position will be described.

  Here, as described above, the energization control unit 50 energizes the transistors Q1-Q6 in the pattern shown in FIG. 2 and controls the rotation of the three-phase motor 7. When an operation command is issued from the control unit 200 (see FIG. 1), the control unit 1 performs control from step # 01 in FIG. Here, for example, when the rotor R is in the position reached when energized in step # 02 (see FIG. 4A), the energization control unit 50 proceeds to step # 01 based on the operation command from the control means 200. Even when such energization is performed, the position of the rotor R cannot be quickly detected and rotated. On the other hand, when the rotor R is in a position reached when the rotor R is energized in, for example, step # 06 (see FIG. 4B), the energization control unit 50 relates to step # 01 based on the operation command from the control means 200. When energized, the position of the rotor R can be quickly detected and rotated. Such a position of the rotor R (the position shown in FIG. 4B) corresponds to the initial position described above.

  The movement of the rotor R to the initial position is performed by energizing between two terminals set in advance among the three terminals of the three-phase motor 7 and stopping the energization. The three terminals are a U-phase terminal 41, a V-phase terminal 42, and a W-phase terminal 43. In the present embodiment, the two terminals that are energized when moving the rotor R to the initial position are preset as the U-phase terminal 41 and the W-phase terminal 43. Therefore, in this embodiment, such energization between the two terminals corresponds to the energization in step # 06 in FIG.

  Such an instruction to move the rotor R to the initial position is given by the energization instruction unit 10 (see FIG. 1). The energization instruction unit 10 is based on a stop command for the three-phase motor 7, and is a U-phase terminal 41 and a W-phase terminal 43 that are two terminals set in advance for the energization control unit 50 regardless of the next operation command. Instructing to energize and stop the energization.

  FIG. 3 is a diagram schematically showing a time chart relating to energization control (hereinafter referred to as “initial energization”) when moving the rotor R to the initial position. FIG. 3A shows an “operation command” and a “stop command” from the control means 200 and an “initial energization command” from the energization instruction unit 10 with the horizontal axis as a time axis. The “initial energization instruction” is an instruction instructed from the energization instruction unit 10 to perform “initial energization”. Based on such “operation command”, “stop command”, and “initial energization command”, the energization control unit 50 controls the rotation of the three-phase motor 7. FIG. 3B is a diagram schematically showing a driving state of the three-phase motor 7.

  As shown in FIG. 3, when a “stop command” is input to the energization control unit 50, energization of the stator coil by the energization control unit 50 is stopped, and after the inertia rotation of the rotor R, the three-phase motor 7 is stopped. To do. In such a case, the energization instruction unit 10 instructs the energization control unit 50 to perform initial energization. Accordingly, the energization control unit 50 performs energization in step # 06 in FIG. 2 for a predetermined time. This energization is performed for several hundred milliseconds, for example. Thereby, the rotor R is rotated toward the initial position. Thereafter, the energization instruction unit 10 instructs to stop the initial energization. As a result, the energization control unit 50 stops the initial energization, and the rotor R is stopped at the initial position. The energization control unit 50 is in a standby state until the next “operation command” is issued. As described above, after the “stop command”, the rotor R can be stopped at a predetermined initial position where the position can be easily detected before the next “motion command” is issued. If there is, the three-phase motor 7 can be smoothly rotated.

  Here, as shown in FIG. 3B, a standby time is provided from when a stop command is issued until the energization instruction between the two terminals (U-phase terminal 41 and W-phase terminal 43). The stop command is a command input from the control unit 200 to the energization control unit 50 in order to stop the three-phase motor 7 that is operating. The initial energization in the present embodiment is performed after a predetermined standby time has elapsed since the stop command was issued. This waiting time is indicated by reference numeral t1 in FIG. The standby time t1 is preferably set in advance, for example, several hundred milliseconds.

  The energization instruction unit 10 designates the energization duration from energization between the two terminals to the stop of the energization and instructs the energization control unit 50. The energization continuation time is a time for performing initial energization, that is, performing step # 06 in FIG. For such a time, the energization continuation time is indicated by reference numeral t2 in FIG. The energization duration t2 is preferably set in advance, for example, several hundred milliseconds.

  FIG. 4 is a schematic diagram showing the relationship between the rotor R and the stator S. When a stop command is issued to the rotating three-phase motor 7, the energization of the stator coil is stopped. Therefore, the attractive force and repulsive force between the stator coil and the permanent magnet PM do not act, so the rotor R rotates with inertia and then stops. This stop position cannot be controlled and is not uniquely determined by the rotating speed and the weight of the rotor R.

  Under such circumstances, for example, when the rotor R stops at a position as shown in FIG. 4A, the energization control according to step # 01 in FIG. In some cases, the attractive force and the repulsive force are difficult to act on each other, and it may take time to start the rotor R according to the next operation command. Therefore, the motor control device 100 performs initial energization (energization according to Step # 06 in FIG. 2) after the standby time t1 elapses after the stop command until the energization duration time t2 elapses. Thereby, the rotor R can be moved to a position (initial position) as shown in FIG. Here, the energization duration t2 is set as a time during which the rotor R can be moved to the initial position regardless of the position of the rotor R after the stop command.

  When the energization continuation time t2 elapses, the energization control unit 50 stops the initial energization. As a result, the rotor R can be stopped at a specified initial position where position detection is easy. In this state, when an operation command is issued from the control means 200 to the energization control unit 50, the energization control unit 50 starts energization control from step # 01 in FIG. Thereby, based on the attractive force and repulsive force between the stator coil and the permanent magnet PM, the rotor R can be smoothly rotated from the position of FIG. 4B through the position of FIG. 4C.

  As described above, according to the motor control device 100 according to the present invention, the rotor R of the three-phase motor 7 is started based on the magnetic flux generated in the stator coil provided between the two terminals after the stop command for the three-phase motor 7. It can be moved to an easy position. Therefore, when there is a start command for the three-phase motor 7, the three-phase motor 7 can be started smoothly. In addition, after the stop command, the rotor R can be moved to a position where it can be easily started before the next operation command is issued. Therefore, even when the next operation command is issued, the startup time of the three-phase motor 7 is delayed. Never become. Therefore, the three-phase motor 7 can be activated quickly.

[Other Embodiments]
In the above-described embodiment, the case where the stator coil of the three-phase motor 7 is Δ-connected has been described. However, the scope of application of the present invention is not limited to this. Of course, the present invention can be applied even when the stator coils of the three-phase motor 7 are Y-connected. In this case, two stator coils among the Y-connected stator coils are energized by the initial energization. More specifically, the energization pattern in the case of Y connection is shown in FIG. First, the transistors Q2 and Q5 are turned on to energize the stator coil 7U and the stator coil 7V. FIG. 5 shows an example in which the N pole appears at one end of the stator coil 7U and the S pole appears at one end of the stator coil 7V. In this case, although not shown, the rotor R rotates so that the permanent magnet PM is positioned between the stator coil 7U and the stator coil 7W. Thereafter, the same energization is performed. Even in the case of Y connection, the initial energization at step # 06 is performed in response to the initial energization command from the energization instruction unit 10. As a result, the rotor R moves to the initial position and is in a standby state at the initial position until the next operation command is issued. For this reason, even in the case of Y connection, it is possible to start the three-phase motor 7 smoothly and quickly while moving the rotor R to the initial position as in the case of Δ connection.

  In the embodiment described above, the standby time t1 is several hundred milliseconds and the energization duration t2 is several hundred milliseconds. However, the scope of application of the present invention is not limited to this. The several hundred milliseconds is merely an example, and it is naturally possible to set it at another time.

  In the above embodiment, the standby time t1 and the energization duration t2 have been described as being set in advance. However, the scope of application of the present invention is not limited to this. It is also possible to configure the motor control device 100 by including one or both of an energization duration changing unit for changing the energization duration t2 and a standby time changing unit for changing the standby time t1. When the energization duration changing unit is provided, the energization control unit 50 may perform initial energization after an appropriate time has elapsed after the stop command. Further, even when energization of the stator coil is stopped, an excitation current flows through the stator coil as the rotor R rotates. Of course, it is possible to wait until it is detected that the excitation current has become zero, and then perform initial energization.

  Here, when the three-phase motor 7 driven by the motor control device 100 is used as a power source for the pump, the stop time of the rotor R varies depending on the viscosity of the liquid flowing through the pump. For this reason, after the stop command, it is preferable to set the waiting time t1 in consideration of the viscosity of the liquid.

  Furthermore, the viscosity of the liquid circulated by the pump may depend on the temperature of the liquid. In this case, the standby time changing unit obtains the detection result from the temperature sensor that detects the temperature of the liquid, and the standby time t1 is set based on the detection result, or the energization duration changing unit sets the energization duration t2. It is also possible to adopt a configuration for setting.

  The present invention can be used in a motor control device that controls rotation of a motor.

6: Inverter 7: Three-phase motor 10: Energization instruction unit 41: U-phase terminal 42: V-phase terminal 43: W-phase terminal 50: Energization control unit 100: Motor controller Q1-Q6: Transistor (switching element)
t1: Standby time t2: Energization duration

Claims (4)

An energization control unit that controls the rotation of the three-phase motor by energizing the switching element of the inverter based on the operation command and the stop command;
Based on the stop command, the energization control unit is instructed to energize between two preset terminals of the three-phase motor and stop the energization regardless of the next operation command. An energization instruction unit to perform,
A motor control device comprising:   The motor control device according to claim 1, further comprising an energization duration changing unit that changes an energization duration from energization between the two terminals to the stop of the energization.   3. The motor control device according to claim 1, wherein a standby time is provided from when the stop command is issued until an instruction to energize between the two terminals. 4.   The motor control device according to claim 3, further comprising a standby time changing unit that changes the standby time.

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