JP2007074834A - Starter for sensorless motors - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid zero-crossing potential detection from being influenced by increase in a kickback current when a sensorless motor is started under overload, and stably start the motor. <P>SOLUTION: A position detection circuit 4 detects the position of the sensorless motor based on comparison of the following: the terminal voltages Vu, Vv, Vw of stator windings U, V, W in multiple phases with a reference voltage Vst generated by a reference voltage generation circuit 6 that generates the predetermined constant reference voltage Vst. At this time, a control circuit 5 operates as follows: at starting rotation, it generates energization phase signals Pu, Pv, Pw based on only the rising of the terminal voltages Vu, Vv, Vw of the stator windings U, V, W at the position detection circuit 4; at a predetermined number of rotations or higher, it generates energization phase signals Pu, Pv, Pw based on position detection from the rising side and the falling side of the terminals voltages Vu, Vv, Vw of the stator windings U, V, W. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a starter for a sensorless motor such as a DC brushless motor driven by an inverter.

As a conventional example of this type of brushless motor, there is a technique described in Patent Document 1.
That is, the technique disclosed in Patent Document 1 is a brushless motor including a rotor having a permanent magnet and a stator having a multi-phase stator winding for applying a magnetic field to apply a rotational force to the rotor. And detecting a position based on a comparison between a terminal voltage of the plurality of phase stator windings and a reference voltage, and detecting the presence or absence of a counter electromotive voltage induced in the stator winding from the terminal voltage. A back electromotive voltage detecting means for outputting a detection signal is provided, a power supply timing signal forming means for outputting a power supply timing signal based on a position detection signal from the back electromotive voltage detection means is provided, and power supply from the power supply timing signal forming means is provided. Provide output means for controlling the energization of the stator winding based on the timing signal, determine the normal or abnormal rotation of the rotor by the state detection signal from the back electromotive voltage detection means, When it is determined that the normal is intended to provide an abnormality detecting means for outputting an abnormality detection signal.
In the position sensorless system that obtains the position detection signal based on the back electromotive voltage induced in the stator winding of each phase of the above configuration, when noise is superimposed on the terminal voltage of the stator winding, or the load of the rotor When the rotation unevenness due to torque fluctuation becomes large, the back electromotive voltage cannot be detected normally, and the state of the state detection signal from the back electromotive voltage detection means changes from the normal state. Thus, the abnormality detection means can determine whether the rotation of the rotor is normal or abnormal by detecting the change state of the state detection signal, and outputs an abnormality detection signal when it is determined as abnormal. Therefore, based on the abnormality detection signal from the abnormality detection means, for example, countermeasures for abnormality such as stopping operation of the energization timing signal forming means to stop energization of the stator winding or operating an alarm device are taken. Can be taken.

The technique disclosed in Patent Document 2 uses a position sensor that detects a rotor position of a motor by selecting one of a 180-degree energization drive and an intermittent energization drive for a motor that drives a load. When the sensorless operation is performed, intermittent energization driving is performed at the time of start-up and at a low speed, and the operation is switched to 180-degree energization driving as the motor speed increases.
In this way, when performing motor drive without a sensor, intermittent energization drive is performed at the start, and then the motor is reliably activated in a short time by performing 180-degree energization drive, and high efficiency and low vibration are achieved. You can drive. For this reason, since the starting current can be reduced, it is possible to prevent the drive elements of the inverter circuit that are likely to occur at the time of starting, and to realize a highly reliable control device.

In the brushless motor device whose rotation is controlled by an inverter, the technology disclosed in Patent Document 3 includes an inverter that energizes each phase in the brushless motor based on a control signal, a back electromotive voltage and a reference voltage of the brushless motor. Position detection means for detecting the rotational position of the brushless motor using either the rising timing or the falling timing among the timings at which the comparison result of the logic is inverted, and outputting the position information, and this position detecting means outputs Position speed calculation means for calculating the rotation position and rotation speed from the position information, and output the PWM duty ratio of the inverter and the amount of change of the reference voltage based on the rotation speed information, the speed command, and the DC voltage of the DC power supply, When the PWM duty ratio is saturated, an operation for changing the amount of change in the reference voltage is performed. A reference voltage value is calculated on the basis of the newly calculated reference voltage change amount, and when the position detection means uses the rising timing, the reference voltage is made lower than the reference value, Reference voltage generating means for making the reference voltage higher than a reference value when using a falling timing, and drive control generating means for generating a control signal for the inverter based on the output phase of the advance phase output by the position speed calculating means. By providing, the advance angle of the applied voltage phase with respect to the counter electromotive voltage phase can be made larger.
JP-A-5-227785 JP 2003-111483 A Japanese Patent No. 3515047

However, the technique disclosed in Patent Document 1 is a back electromotive force detection means for detecting the presence or absence of the back electromotive voltage and outputting a state detection signal when operating at a speed lower than the no-load speed. Since the back electromotive voltage (potential difference) is proportional to the rotation speed, the signal processing is easily affected by noise and load fluctuation, and the state detection signal operation becomes difficult. For example, when the hydraulic pump is driven by a motor, when the oil temperature decreases and the viscosity increases, the load torque necessary for the rotation of the pump increases, so that the rotational speed decreases under a constant input voltage. In the case of an automobile of the ATF, the kinematic viscosity of 1000 mm ² / sec about versus about 10 mm ² / sec of the normal use region, the load torque becomes 10 times or more, sometimes speed becomes 1/10 . At such a low rotational speed, it is difficult to specify the position of the rotor by the above method, and stable starting is difficult.
Furthermore, when the pump is driven by a motor, the drive current is large during low-temperature operation, and the coil resistance of the motor and the resistance of the motor drive circuit are reduced, resulting in low impedance. Increases and affects the zero-cross potential. For example, when switching the low voltage side of the energized phase, the kickback current flows on the high voltage side of the circuit, and conversely when switching the high voltage side, it flows on the low voltage side of the circuit, but on the low voltage side. If it flows, it will affect the ground potential of the circuit, the potential at the middle point of the winding will fall below the reference voltage, and the zero cross point will not be recognized. As described above, when it becomes difficult to detect the position of the stator, stable starting becomes difficult.

  The technique disclosed in Patent Document 2 performs intermittent energization driving at a low speed of less than 3000 rpm of the first rotation speed, and 180-degree energization driving at a medium speed driving of 3000 rpm or more and less than 6000 rpm of the second rotation speed. At high speeds of 6000 rpm or higher, the intermittent energization drive is restored. However, when intermittent energization drive is performed at a low speed of less than 3000 rpm of the first rotation speed, the same problem as in Patent Document 1 occurs. However, Patent Document 2 does not have the awareness of the problem and does not describe the solution.

  Regarding Patent Document 3, as in Patent Document 1, when operating at a lower rotational speed than the no-load rotational speed, signal processing is easily affected by noise and load fluctuations, and operation becomes difficult. There is no disclosure about the point where stable starting becomes difficult.

  Therefore, in order to solve these problems, the present invention avoids affecting the detection of the zero cross potential due to the increase of the kickback current at the time of start-up under an overload condition, and performs sensor-less start-up. An object of the present invention is to provide a motor starting device.

In the sensorless motor starting device according to claim 1, a rotor having a plurality of permanent magnets, a stator having a plurality of stator windings for applying an alternating magnetic field for applying a rotational force to the rotor, and a predetermined A reference voltage generation circuit that generates a constant voltage reference voltage, and a comparison between a terminal voltage of the plurality of stator windings and a reference voltage generated by the reference voltage generation circuit, from the terminal voltage to the stator A position detection circuit that detects a position by detecting a counter electromotive voltage induced in the winding, and a starting rotation generates an energization phase signal based only on the rise of the terminal voltage of the stator winding of the position detection circuit. And a control circuit that generates an energization phase signal based on the position detection from the rising side and the falling side of the terminal voltage of the stator winding of the position detection circuit at a predetermined rotational speed or higher.
Here, the alternating magnetic field that gives a rotational force to the rotor does not mean a circular rotating magnetic field by sinusoidal alternating current, but is generated by sequentially changing the direction of the magnetic field by 120 degrees or more. It means a rotating magnetic field.
The reference voltage generation circuit may be a constant voltage generation circuit, and the position detection circuit only needs to be able to detect the zero cross point together with the comparison circuit.
The starting rotation recognized by the control circuit can be a predetermined number of rotations or a predetermined time after starting driving.
Further, the energization phase signal generated by the control circuit generates an energization phase signal having a predetermined pulse width based only on the rise of the position detection of the terminal voltage of the stator winding, and at a predetermined rotation speed or higher. Any energization phase signal may be generated based on the pulse width obtained from the position detection from the rising side and the falling side of the position detection of the terminal voltage of the stator winding.

The starting rotation for generating the energization phase signal based only on the rising side of the terminal voltage of the stator winding of the position detection circuit of the starter of the sensorless motor according to claim 2 refers to the stator winding of the position detection circuit. This is the number of rotations at which the position detection from the rising side of the terminal voltage is performed a predetermined number of times.
Here, the starting rotation is a rotation number obtained by performing position detection from the rising side of the terminal voltage of the stator winding of the position detection circuit a predetermined number of times, and does not ask for a lack of rising signal. .

In the sensorless motor starter according to claim 1, the position detection circuit compares the terminal voltage of the stator windings of a plurality of phases with a reference voltage generated by a reference voltage generation circuit that generates a predetermined constant voltage reference voltage. Based on the terminal voltage, a back electromotive voltage induced in the stator winding is detected to detect the position. At this time, the control circuit generates an energization phase signal based only on the rise of the terminal voltage of the stator winding of the position detection circuit at the start rotation, and the stator winding of the position detection circuit exceeds a predetermined rotation speed. The energization phase signal is generated based on the position detection from the rising side and the falling side of the terminal voltage.
Therefore, even when the sensorless motor is driven in an overload state, even if the kickback current increases and affects the zero-cross potential, the increase in the kickback current avoids affecting the detection of the zero-cross potential. In addition, stable starting can be performed using a signal only on the rising side of the terminal voltage of the stator winding of the position detection circuit.

  The sensorless motor starter according to claim 2 detects the position of the starting rotation for generating the energization phase signal based only on the rising side of the terminal voltage of the position detection circuit from the rising side of the terminal voltage of the position detection circuit. Therefore, in addition to the effect of the first aspect, it is not necessary to use a sensor such as a rotational speed sensor or a speed sensor, so that the control circuit configuration can be simplified.

Next, a starter for a sensorless motor according to an embodiment of the present invention will be described with reference to the drawings.
[Embodiment 1]

  FIG. 1 is a circuit configuration diagram showing an overall configuration of a sensorless motor starter according to an embodiment of the present invention. FIG. 2 is a relationship diagram between the electrical phase angle of the sensorless motor starter according to the embodiment of the present invention and the control signal of the inverter, and FIG. 3 is a normal rotation of the sensorless motor starter according to the embodiment of the present invention. FIG. 4 is a waveform diagram of the U-layer terminal voltage, the comparison signal, and the energization phase signal during rotation and overload rotation, and FIG. 4 is a flowchart of the drive program of the starter for the sensorless motor according to the embodiment of the present invention.

  In FIG. 1, a DC power source 1 is a circuit in which a battery or an AC power source is converted to a DC power source. The inverter 2 sequentially turns on and off the plurality of switch elements UP, VP, WP and switch elements UN, VN, WN based on the control signal, and converts the direct current from the direct current power source 1 into an alternating magnetic field, which will be described later. Current is sequentially supplied to a plurality of stator windings U, V, W of the stator 3a of the motor 3. The DC brushless motor 3 includes a stator 3 a having a plurality of windings and a rotor 3 b having a permanent magnet, and rotates by electric power supplied from the inverter 2. The reference voltage generation circuit 6 is a circuit that generates a reference voltage composed of a constant voltage circuit or the like.

Further, the input comparison circuit 7 inputs the output voltage of the inverter 2 and the electromotive force of the stator windings U, V, W of the stator 3 a of the DC brushless motor 3 as terminal voltages of the stator 3 a of the DC brushless motor 3. The voltage is detected by dividing with the resistor r ₁ / (r ₁ + r ₂ ), and is compared with the reference voltage Vst of the reference voltage generation circuit 6. The reference voltage Vst is set to ½ of the supply voltage E from the DC power supply 1. The reference voltage generation circuit 6 that outputs the reference voltage Vst and the input comparison circuit 7 that detects the terminal voltage of the stator 3 a of the DC brushless motor 3 constitute a position detection circuit 4. The control circuit 5 is a microcomputer that outputs to the inverter 2 an energization phase signal for on / off control of a plurality of switch elements UP, VP, WP and switch elements UN, VN, WN of the inverter 2.

Next, the basic operation of rotation of the sensorless motor of the present embodiment will be described.
The activation and rotation of the rotor 3b of the DC brushless motor 3 is caused by the switching element UP as shown in the relationship diagram between the electrical phase angle of FIG. 2 and the control signal of the inverter at the terminals of the stator windings U, V and W. , VP, WP and switch elements UN, VN, WN are sequentially turned on / off, and terminal voltages Vu, Vv, Vw are detected. The position detection circuit 4 compares the terminal voltages Vu, Vv, and Vw with the reference voltage Vst of the reference voltage generation circuit 6. Then, the comparison signals Ue, Ve, We and energization phase signals Pu, Pv, Pw are detected from the result of comparing the terminal voltages Vu, Vv, Vw and the reference voltage Vst.

  The position detection circuit 4 including the reference voltage generation circuit 6 that outputs the reference voltage Vst and the input comparison circuit 7 that detects the terminal voltage of the stator 3a, as shown in FIG. A comparison signal Ue shown in FIG. 3C is obtained by comparing the terminal voltage Vu with the reference voltage Vst (= E / 2). Similarly, comparison signals Ve and We (not shown) for V phase and W phase are obtained. Further, by detecting the zero cross point of the counter electromotive force induced in the stator windings U, V, W, the energization phase signal Pu is obtained as shown in FIG. Similarly, energized phase signals Pv and Pw (not shown) of V phase and W phase are obtained. Further, the control circuit 5 logically converts the energization phase signals Pu, Pv, and Pw to generate six base signals, and supplies them to the switch elements UP, VP, WP and the switch elements UN, VN, WN of the inverter 2. Then, the switch elements UP, VP, WP and the switch elements UN, VN, WN are sequentially turned on and off, and the stator windings U, V, W are energized to rotate the rotor 3b. Note that the shaded portion of the comparison signal Ue shown in FIG.

Further, the basic operation of the sensorless motor starting device of the present embodiment will be described.
The reference voltage generation circuit 6 outputs a reference voltage Vst. The input comparison circuit 7 detects the terminal voltages Vu, Vv, Vw of the stator windings U, V, W. The position detection circuit 4 including the reference voltage generation circuit 6 and the input comparison circuit 7 has a zero crossing that rises and falls depending on the terminal voltage Vu and the reference voltage Vst, as shown in FIG. The point is detected, and the comparison signal Ue is obtained in FIG. Similarly, phase signals Ve and We (not shown) are also obtained by comparing the terminal voltages Vv and Vw with the reference voltage Vst, and the energization phase signals are detected by detecting the rising and falling zero cross points of the counter electromotive force. Pu, Pv, and Pw are obtained.
The control circuit 5 sequentially applies the energization phase signals Pu, Pv, Pw to the switch elements UP, VP, WP and the switch elements UN, VN, WN of the inverter 2, which are six energization timing signals, and turns them on and off. The stator windings U, V, and W are energized, and the rotor 3b is rotated by the alternating magnetic field.
Under normal rotation of the DC brushless motor 3, when the comparison signals Ue, Ve, We are obtained based on the terminal voltages Vu, Vv, Vw induced in the stator windings U, V, W of each phase, the DC brushless motor Since the third rotor 3b rotates at a substantially constant speed, the terminal voltages Vu, Vv, Vw induced in the stator windings U, V, W also rise and the falling signal waveforms substantially coincide.

  However, for example, in the case of the DC brushless motor 3 that drives the pump, the drive current increases during low temperature operation, and the resistance of the stator windings U, V, and W of the DC brushless motor 3 and the resistance of the motor drive circuit. Becomes smaller, and the overall impedance is low. At this time, the rising and falling signals of the terminal voltages Vu, Vv, Vw of the stator windings U, V, W are in particular only that the rotor 3b of the DC brushless motor 3 is stopped or rotated at a substantially low speed. Is not enough back electromotive force. In this state, when the input is switched by the energization phase signals Pu, Pv, Pw, the kickback current increases in the falling signals of the terminal voltages Vu, Vv, Vw of the stator windings U, V, W. However, this will affect the zero-cross potential. In the example of FIG. 3D, the kickback current increases in an overload state at a low temperature, which affects the ground potential, the potential at the neutral point of the stator windings U, V, and W decreases, and the reference voltage It becomes Vst or less, and the zero cross point cannot be detected. Thus, if it becomes difficult to detect the position of the rotor 3b, stable start-up becomes difficult.

Therefore, at the start of such activation, as shown in the case of the U phase in the position detection circuit 4 in FIG. 3D, the zero crossing of the rising of the terminal voltage Vu by the terminal voltage Vu and the reference voltage Vst (= E / 2). By detecting only the point, the comparison signal Ue indicating the U-phase case is obtained in FIG. Similarly, comparison signals Ve and We (not shown) can be obtained by comparing the terminal voltages Vv and Vw with the reference voltage Vst.
Here, the energization phase signals Pu (FIG. 3 (e)), Pv, and Pw are given by the control circuit 5 to the switch elements UP, VP, WP and the switch elements UN, VN, WN which are the six base signals of the inverter 2. The switch elements UP, VP, and WP and the switch elements UN, VN, and WN are sequentially turned on and off to energize the stator windings U, V, and W, thereby rotating the rotor 3b.

As a result, when the DC brushless motor 3 for driving a pump or the like is driven at a low temperature and in an overload state, the kickback current increases even if the kickback current increases and affects the zero cross potential. It is possible to avoid the influence of the increase on the detection of the zero-cross potential and to perform stable start-up.
Also, the back electromotive voltage is normal even when noise is superimposed on the terminal voltages Vu, Vv, Vw of the stator windings U, V, W, or when the rotation unevenness due to load torque fluctuation of the rotor 3b becomes large. Can never be detected.

In order to control the program using the microcomputer of the control circuit 5, the program shown in FIG.
First, when the driving power of the DC brushless motor 3 is turned on, the counter n is cleared in step S1, and it is determined in step S2 whether the value of the counter n is 5 or more. When the counter n ≧ 5, normal in step S8. The operation control by PWM control is entered, and this routine is exited. However, when the counter n <5, it means the start-up initial stage, so that the fixed rotation speed control is entered in step S3. Here, “fixed” means that the pulse width X of the energization phase signals Pu, Pv, Pw is set to a specific value. In step S4, the output of the position detection circuit 4 is seen to detect a rising zero cross point. This detection may be performed for each phase, but it is not always necessary, and only one phase or two phases can be used. In step S5, it is determined whether or not the rising zero cross point has been detected. When the zero cross point has been detected in step S5, the counter n is incremented by "+1" in step S6, and the zero cross point is detected in step S5. If not, the counter n is kept cleared in step S7, and the routine from step S2 to step S7 is repeatedly executed. When it is determined in step S2 that the value of the counter n is 5 or more, normal rotation control is entered.
The pulse width X of the energization phase signals Pu, Pv, and Pw changes every time the rising zero cross point is detected so as to gradually approach the pulse width X of the energization phase signals Pu, Pv, and Pw in normal rotation. You may let them.

  Thus, in the said embodiment, it has the rotor 3b which has a some permanent magnet, and the multiphase stator windings U, V, and W which act the alternating magnetic field which gives a rotational force to the rotor 3b. In a sensorless motor starting device having a stator 3a, a reference voltage generating circuit 6 for generating a reference voltage having a predetermined constant voltage, and terminal voltages Vu, Vv, Based on a comparison between Vw and the reference voltage Vst generated by the reference voltage generation circuit 6, a position detection circuit 4 for detecting counter electromotive voltages induced in the stator windings U, V, W from the terminal voltages Vu, Vv, Vw. In starting rotation, the energization phase signals Pu, Pv, Pw are generated based only on the rise of the terminal voltages Vu, Vv, Vw of the stator windings U, V, W, and the stator is rotated at a predetermined rotational speed or more. Terminal voltages Vu, Vv of windings U, V, W Energizing phase signal Pu based on the detected position from the rising side and the falling side of the Vw, Pv, those having a control circuit 5 for generating Pw.

Therefore, in the sensorless motor starter according to the present embodiment, the position detection circuit 4 generates the terminal voltages Vu, Vv, Vw of the stator windings U, V, W of plural phases and the reference voltage Vst of a predetermined constant voltage. Based on the comparison with the reference voltage Vst generated by the reference voltage generating circuit 6, the back electromotive voltages induced in the stator windings U, V, W are detected from the terminal voltages Vu, Vv, Vw to detect the position. At this time, in the starting rotation, the control circuit 5 outputs the energization phase signals Pu, Pv, Pw based only on the rise of the terminal voltages Vu, Vv, Vw of the stator windings U, V, W in the position detection circuit 4. Generate and generate energized phase signals Pu, Pv, and Pw based on position detection from the rising and falling sides of the terminal voltages Vu, Vv, and Vw of the stator windings U, V, and W at a predetermined rotation speed or higher. To do.
Therefore, even when the DC brushless motor 3 is driven in an overload state, the kickback current increases and affects the zero cross potential, but the increase in the kick back current affects the detection of the zero cross potential. Thus, stable starting can be performed using signals only on the rising sides of the terminal voltages Vu, Vv, Vw of the stator windings U, V, W.

  In the above embodiment, the position detection circuit 4 generates the energization phase signals Pu, Pv, Pw based only on the rising sides of the terminal voltages Vu, Vv, Vw of the stator windings U, V, W. Since the rotation is set to a rotation speed at which the position detection from the rising side of the terminal voltages Vu, Vv, Vw of the stator windings U, V, W is performed a predetermined number of times, it is necessary to use a speed sensor or a rotation speed sensor. Therefore, the configuration of the control circuit 5 can be simplified.

FIG. 1 is a circuit configuration diagram showing an overall configuration of a sensorless motor starter according to an embodiment of the present invention. FIG. 2 is a relationship diagram between the electrical phase angle of the sensorless motor starter according to the embodiment of the present invention and the control signal of the inverter. FIG. 3 is a waveform diagram of the U-layer terminal voltage, the comparison signal, and the energization phase signal during normal rotation and overload rotation of the sensorless motor starter according to the embodiment of the present invention. FIG. 4 is a flowchart of the drive program for the sensorless motor starter according to the embodiment of the present invention.

Explanation of symbols

3 DC brushless motor 3a Stator 3b Rotor 4 Position detection circuit 5 Control circuit 6 Reference voltage generation circuits U, V, W Stator windings Vu, Vv, Vw Terminal voltages Pu, Pv, Pw Energization phase signal Vst Reference voltage

Claims (2)

In a sensorless motor starter comprising: a rotor having a plurality of permanent magnets; and a stator having a plurality of stator windings for applying an alternating magnetic field for applying a rotational force to the rotor.
A reference voltage generating circuit for generating a reference voltage having a predetermined constant voltage;
Based on the comparison between the terminal voltage of the multi-phase stator winding and the reference voltage generated by the reference voltage generation circuit, the position detection is performed by detecting the back electromotive voltage induced in the stator winding from the terminal voltage. A position detection circuit that
In the starting rotation, the position detection circuit generates an energization phase signal based only on the rise of the terminal voltage of the stator winding, and the rising side and the falling of the terminal voltage of the stator winding at a predetermined rotation speed or higher. A sensorless motor starting device comprising: a control circuit that generates an energization phase signal based on a side signal.   The starting rotation that generates the energization phase signal based only on the rising side of the terminal voltage of the stator winding of the position detection circuit is to detect the position from the rising side of the terminal voltage of the stator winding of the position detection circuit. 2. The sensorless motor starting device according to claim 1, wherein the number of rotations is a predetermined number of times.

Images