JP2008295249A - Drive arrangement of brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive arrangement of a brushless motor capable of smoothly starting without setting a start pattern after preliminary testing of a start condition, nor comprising a memory device for the start pattern although conventionally the start pattern for driving as a synchronous motor is required to be tested in advance for acquiring it. <P>SOLUTION: The voltage acquired by adding up voltage drops from a counter electromotive force, current, and coil resistance is taken as a voltage applied to a non-brush motor so that a current that generates a maximum required torque flows. The rotational speed is increased almost linearly up to such rotational speed as the applied voltage becomes equal to the counter electromotive force not to flow a current. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a drive device for a brushless motor, and more particularly to a drive device for a brushless motor that obtains a rotor position detection signal by using a counter electromotive force generated in a stator winding.

  The drive unit of the brushless motor that detects the rotor position from the counterelectromotive force included in the terminal voltage of the stator winding of the brushless motor is positioned at the position where no counterelectromotive force is generated when starting from a stopped state. A detection signal cannot be obtained. For this reason, the stator winding is forcibly energized and operated as a synchronous motor, and after increasing the rotational speed until the back electromotive force becomes sufficiently large, the rotor position is detected from the back electromotive force. Do the driving.

  Japanese Patent Laid-Open No. 2001-103785 is an example of a drive device for a non-printer motor that detects the position of a rotor by using a counter electromotive force generated in a stator winding.

JP 2001-103785 A

  The drive device of the above-described conventional brushless motor has no description about a specific method for determining a start pattern to operate as a synchronous motor, and obtains a start pattern by previously testing start conditions having a huge number of combinations. There was a need.

  The above problem is that the voltage obtained by adding the back electromotive force, the current, and the voltage drop due to the winding resistance is the applied voltage of the brushless motor so that the current that generates the required maximum torque flows, and the applied voltage is equal to the back electromotive force. This is achieved by increasing the rotational speed substantially linearly to a rotational speed at which no current flows.

  By applying the present invention, a driving device for a brushless motor capable of setting a starting pattern by testing in advance a starting condition having an enormous number of combinations and smoothly starting without having a storing device for the starting pattern Can be provided.

  FIG. 1 is an overall configuration diagram of an embodiment according to the present invention. 1 is an AC power supply, 2 is a rectifying diode, 3 is a smoothing capacitor, 4 is a bridge inverter, 6 is a current detection circuit, 7 is a current limiting circuit, 8 is a position detection circuit, 9 is a start signal generation circuit, 10 Is a switching circuit, 11 is a rotational speed measurement circuit, 12 is a rotational speed command circuit, 13 is a rotational speed comparison circuit, 14 is a voltage control circuit, 15 is a gate control circuit, 16 is a modulation circuit, The drive device is configured. Reference numeral 5 denotes a brushless motor.

  A position detection operation based on a so-called sensorless 120 ° energization method for detecting the rotor position from the back electromotive force included in the terminal voltage of the stator winding of the brushless motor will be described. In the non-printer motor, the back electromotive force is generated in the stator winding only when the rotor is rotating. Therefore, when the rotor is stopped, the back electromotive force is generated from the back electromotive force generated in the stator winding. The rotor position cannot be detected. Conventionally, when a non-printing motor is started by a sensorless 120 ° energization method, a synchronous operation starting method for starting operation as a synchronous motor is adopted. In the synchronous operation, the energized phase of the stator winding is switched by a signal from the start signal generation circuit 9, and the rotational speed is gradually increased. After the rotational speed is increased until the back electromotive force becomes sufficiently large, the switching circuit 10 switches to the position detection operation in which the operation is performed by detecting the rotor position from the back electromotive force. The position detection circuit 8 detects the magnetic pole position of the rotor using the back electromotive force of the non-energized winding. The time corresponding to the commutation delay angle from the reference position to the preset switching of the energized phase of the stator winding, with the position where the counter electromotive force and neutral point potential of the non-energized winding are crossed as the reference position After the elapse of time, a position detection signal for switching the energized phase of the stator winding is generated.

  FIG. 2 shows the operation principle of the digital position detection method. In the 120 ° energization method, the position detection circuit 8 detects the position using the back electromotive force of the non-energized winding. The digital position detection is a position detection signal that directly compares the counter electromotive force of the non-conducting winding and the neutral point potential, and is characterized in that the next phase is commutated. As shown in FIG. 2, when V + → W− is energized, the position is detected by the u-phase voltage, and a W− → u−commutation is performed by delaying an electrical angle set in advance by a microcomputer timer, for example, an electrical angle of 30 °. . V phase and W phase information is not required. In this way, the position is detected using the back electromotive force of the non-energized winding and the operation is performed.

  The drive unit of the brushless motor that detects the rotor position from the counterelectromotive force included in the terminal voltage of the stator winding of the brushless motor is positioned at the position where no counterelectromotive force is generated when starting from a stopped state. A detection signal cannot be obtained. For this reason,. Conventionally, when a brushless motor is started by a 120 ° energization method, a synchronous operation start method that starts operation as a synchronous motor is adopted. Synchronous operation is a method of gradually increasing the rotational speed using a synchronization table.

  FIG. 3 is an explanatory diagram of a synchronization table according to the present invention. Since the backless electromotive force is not generated in the non-printer motor in the stopped state, an excessive current flows when a normal voltage is applied to the stator winding. Therefore, at the start of the synchronous operation, the voltage control circuit 14 performs voltage control that suppresses the current to a current value in consideration of the allowable value of the current capacity of the bridge inverter 4, the demagnetization start current of the non-printing motor 5, vibration, and the like. . As the time advances, the rotational speed increases. A non-brush motor generates back electromotive force when the rotor rotates. For this reason, when the applied voltage is constant, the current flowing through the stator winding decreases. As a result, the motor torque commensurate with the load torque during the synchronous operation cannot be generated and the step-out is stopped. For this reason, the voltage control circuit 14 operates so that the current flowing through the stator winding does not decrease due to the counter electromotive force during the period t2 during which the position detection is permitted after the operation start t0.

If the motor torque generated by the current flowing through the stator winding at t2 at which position detection is permitted is smaller than the load torque, the step-out will stop before switching to the position detection operation. The voltage control of the voltage control circuit 14 at the start of the synchronous operation is a value taking this point into consideration.
After time t2, the voltage control circuit 14 performs constant voltage control. As the time advances, the rotational speed further increases and the back electromotive force also increases. As a result, the current flowing through the stator windings decreases, and the rotor phase approaches the applied voltage in order to generate a motor torque commensurate with the load torque. When the phases are matched, the switching circuit 10 operates to switch from synchronous operation to position detection operation. Only the rotational speed is increased by constant voltage control, and there is no item to be obtained in advance by a special experiment or the like.

  Since the voltage control circuit 14 performs constant voltage control after the time t2, the rotational speed further increases as the time advances, the counter electromotive force increases, and no current flows through the stator winding at the applied voltage. If it is not possible to switch to the position detection operation even at this stage, it is determined that the operation has not been started due to some trouble, and the operation is stopped. This is time t3.

  As described above, the drive device for a brushless motor according to the present invention has the basic features such as the rotation speed of the brushless motor, the applied voltage, the counter electromotive force, the current flowing through the stator winding, and the phase of the applied voltage and the counter electromotive force. Since it depends on the item, it is not necessary to previously test activation conditions having a huge number of combinations to obtain activation patterns.

  Further, the rotation speed command circuit 12 generates a rotation speed command, the measurement result of the rotation speed measurement circuit 11 is compared with the rotation speed comparison circuit, and the voltage control circuit 14 and the modulation circuit 16 act to obtain a predetermined rotation speed. Realize. The current detection circuit 6 and the current limit circuit 7 detect and control an excessive current at the time of abnormal start-up, and these are the same as the drive device for the non-printing motor according to the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS The whole block diagram of the drive device of the brushless motor by this invention. FIG. 3 is an explanatory diagram of an operation principle of a digital position detection method. Explanatory drawing of the synchronization table by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... AC power supply, 2 ... Rectifier diode, 3 ... Smoothing capacitor, 4 ... Bridge inverter, 5 ... Non-printing motor, 6 ... Current detection circuit, 7 ... Current limiting circuit, 8 ... Position detection circuit, 9 ... Start signal generation circuit, 10 ... switching circuit, 11 ... rotational speed measuring circuit, 12 ... rotational speed command circuit, 13 ... rotational speed comparison circuit, 14 ... voltage control circuit, 15 ... gate control circuit, 16 ... modulation circuit.

Claims (4)

Driving of a brushless motor for detecting a rotor magnetic pole position from a back electromotive force included in a terminal voltage of a stator winding of a brushless motor having a rotor having a permanent magnet and a three-phase stator winding When starting up the machine, the stator winding is forcibly energized to operate as a synchronous motor, and the energization period is gradually shortened until the counter electromotive force becomes sufficiently large, and the rotational speed is increased. After the power becomes sufficiently large, the commutation delay angle from the reference position to the switching of the energized phase of the stator winding is made with the position where the counter electromotive force and the neutral point voltage are compared and crossed as the reference position. In the drive device of the brushless motor that switches the energized phase of the stator winding after a lapse of time corresponding to the commutation delay angle from the reference position,
The counter electromotive force and the neutral point voltage after the first rotation speed at which the counter electromotive force is generated so that the position detection circuit can operate, or at a rotation speed higher by a predetermined value than the first rotation speed. In the second rotational speed, the position detection to be compared is permitted, and a current that generates the necessary maximum torque flows at the first rotational speed or the second rotational speed that is higher than the first rotational speed by a predetermined value. The voltage obtained by adding the back electromotive force, the current, and the voltage drop due to the winding resistance is the applied voltage of the brushless motor, and the rotation speed at which the applied voltage and the back electromotive force are equal and the current does not flow, or a predetermined value from it. A drive device for a brushless motor, wherein the third rotation speed, which is a high rotation speed, is set as an upper limit rotation speed for synchronous operation.   2. The drive device for a brushless motor according to claim 1, wherein the rotational speed is increased substantially linearly during a period from the start of energization to the third rotational speed.   2. The drive device for a brushless motor according to claim 1, wherein the applied voltage is gradually increased in a period from the start of energization to the second rotation speed.   The drive device for a brushless motor according to claim 1, wherein the operation is stopped when the position detection operation is not switched at the third rotational speed.

Images