JP2008035690A - Drive system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive system which does not easily cause out-of-step, and is inexpensively constituted, and to provide the drive system which drives a plurality of motors synchronously. <P>SOLUTION: In the drive system 1 of a mechanism in which synchronous drive by a plurality of the motors 3 is required, the motor includes a stator with a polyphase coil wound around a pole tooth, and a magnet rotor which is rotatably supported inside the stator. A skew amount of the magnet rotor is set to a range up to one pole tooth pitch angle of the stator from such an angle as obtained by dividing 360 degrees by a least common multiple of the number of the pole teeth of the stator, and the number of magnetic poles of magnets, when the displacement of a radial direction at each of both end faces of the outer periphery of the magnet is represented by a mechanical angle. A plurality of the motors 3 are driven synchronously by one inverter 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a drive system of a mechanism that mainly requires synchronous drive by a plurality of motors.

  In recent years, motors used as drive sources for industrial equipment are often used from inexpensive induction motors to achieve multiple functions, and synchronous motors that emphasize superior controllability and motor efficiency are often used. A conveyance system has been proposed in which a plurality of synchronous motors are connected to a plurality of control devices and driven synchronously.

On the other hand, a method for controlling the rotation of a synchronous motor using an inverter has been proposed, and a stator having a plurality of teeth on the surface of a pole tooth and a plurality of rotors using permanent magnets in the direction of the rotation axis are also provided. Synchronous motor including a rotor having teeth and a synchronous motor that hardly causes a step-out phenomenon even when operated by an inverter, and does not easily cause a step-out phenomenon even during sudden acceleration / deceleration, a rotation control method, and an inverter (For example, refer to Patent Document 1).
JP 2005-143178 A

  The problem to be solved is that the synchronous motor of Patent Document 1 described above cannot be obtained at low cost because it is a hybrid type with a complicated rotor structure.

  Further, for control for preventing step-out during acceleration / deceleration by the inverter (adding ΔV to the output voltage V), ΔV is obtained by using a function generator having the frequency as an input, and the detected current value exceeds a predetermined value. This ΔV is added to the output voltage and stored as a function table in a memory such as a ROM.

  In this case, since ΔV is constant, it cannot be handled when the acceleration / deceleration changes or when the load inertia is different from the initial operating condition, and there is a risk of stepping out.

  In general, a synchronous motor is operated at a stable constant rotational speed after synchronous pull-in, but it is difficult to pull back to the synchronous speed again when stepping out due to overload. For this reason, a dedicated control device or special control is required to pull back to the synchronous speed again, and some operation or some additional device is required to restart the synchronous motor that has stepped out and stopped. In many cases, an expensive circuit is required to take advantage of the excellent characteristics. Further, there is a possibility that the primary winding may burn out due to an excessive increase in current.

  In addition, when a general synchronous motor is started up with a constant frequency power source, significant vibration occurs even when there is no load, and it is difficult to start up in a loaded state.

  The conventional transport system has a problem in that a pulley is attached to a rotation shaft of a drive motor and rotational force is transmitted to a plurality of roller shafts via belts, and the mechanism is complicated and dust and the like are easily attached.

  On the other hand, when a plurality of synchronous motors are driven synchronously, the plurality of synchronous motors are connected to a plurality of control devices, and synchronous operation is possible by receiving a synchronization signal from a host controller or the like. It had become something.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object of the present invention is to provide a drive system that is difficult to step out and can be configured at low cost, and a drive system that can drive a plurality of motors synchronously.

  The drive system of the present invention includes a motor in which a magnet of a magnet rotor is skewed and an inverter that drives the motor, and the plurality of motors are synchronously driven by a single inverter.

  Further, the motor includes a stator having a multi-phase winding wound around pole teeth, and a magnet rotor rotatably supported inside thereof, and the magnet rotor has a magnetic pole (N pole, S poles) are alternately arranged and skewed in the axial direction on both end faces of the magnet.

  The motor includes a stator having a multi-phase winding wound around pole teeth, and a magnet rotor rotatably supported inside the stator, and the multi-phase winding of the stator has an impedance protection function. .

  Further, the skew amount of the magnet rotor is fixed from an angle obtained by dividing 360 ° by the least common multiple of the number of pole teeth of the stator and the number of magnet magnetic poles when the radial deviation at both end surfaces of the magnet outer periphery is represented by a mechanical angle. This is set to a range up to the single pole tooth pitch angle of the child.

  The inverter that synchronously drives the motor automatically controls the output voltage by performing a feedforward calculation according to the inertia and acceleration / deceleration of the load when the acceleration / deceleration operation is performed by changing the output frequency. .

  Furthermore, it is a conveying apparatus using the drive system according to any one of claims 1 to 6 and having a motor directly connected to a rotating shaft of a conveying roller.

  According to the drive system of the present invention, since a magnet rotor in which the magnet of the motor is skew-magnetized is used, even if there is no CS sensor, the inverter can be started and operated at a synchronous speed, and the drive system can be inexpensive. In addition, smooth start characteristics can be obtained simply by connecting a plurality of motors to one inverter, and the motors can be driven synchronously.

  Moreover, since an increase in current due to overload can be suppressed by providing an impedance protection function for the multipolar winding to prevent burnout, there is an advantage that control tolerance for the escape torque is increased and step-out can be prevented.

  In addition, the amount of skew of the magnet rotor is calculated by dividing 360 ° by the least common multiple of the number of pole teeth of the stator and the number of magnet magnetic poles when the radial deviation at both end surfaces of the magnet outer periphery is represented by a mechanical angle. By setting to a range up to 1 pole tooth pitch angle, the inverter can be reliably started without using a CS sensor. Moreover, vibration can be suppressed by applying a skew.

  Also, when accelerating / decelerating operation by changing the output frequency with the inverter, the output voltage is automatically controlled by the feedforward calculation according to the load inertia and acceleration / deceleration, so the step-out phenomenon is unlikely to occur. , Stable synchronous driving is possible.

Also, by performing a soft start at the start (acceleration) or a soft stop at the stop (deceleration), a sudden current change at the start / stop can be suppressed to prevent step-out.

  Furthermore, if the drive system described above is used in a conveyance device in which a motor is directly connected to the rotation shaft of the conveyance roller, transmission means (such as a belt and a chain) for driving the rotation shaft of the conveyance roller as in the past becomes unnecessary. The structure of the mechanism can be simplified. Since no belt or chain is used, there is no adhesion of oil or dust, resulting in a clean drive system.

  In a drive system having a mechanism that requires synchronous drive by a plurality of motors, the system includes a motor having a magnet rotor skewed and an inverter that drives the motor, and the plurality of motors are synchronously driven by a single inverter. . The motor includes a stator having a multi-phase winding wound around pole teeth, and a magnet rotor rotatably supported inside thereof, and the skew amount of the magnet rotor is determined in a radial direction at both end surfaces of the magnet outer periphery. When the misalignment of the stator is represented by a mechanical angle, a range from 360 ° divided by the least common multiple of the number of pole teeth of the stator and the number of magnet poles to the one pole tooth pitch angle of the stator is used. The winding has an impedance protection function, and when the inverter performs acceleration / deceleration operation by changing the output frequency, it automatically calculates by feedforward calculation according to the operation speed, load inertia and acceleration / deceleration Control the output voltage. Also, soft start is performed at startup (acceleration) and soft stop is performed at stop (deceleration). Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  In the first embodiment, a driving system that enables synchronous driving by a plurality of motors, which is an overall feature of the present invention, will be described with reference to the drawings of a linear transfer type conveying device in which a motor is directly connected to a driving roller.

  In the drive system 1 of FIG. 1, motors 3 are directly connected to the rotation shafts of the plurality of drive rollers 2. For example, at least three drive rollers 2 that are directly connected to the motor 3 may be disposed within the L dimension of the workpiece 5 to be transferred, and the plurality of motors 3 are connected to one inverter 4 and driven synchronously. The inverter 4 may be a general one that drives an induction motor with a sinusoidal voltage.

  In order to start and synchronize the plurality of motors 3 with one inverter 4, it is necessary to apply skew magnetization to the rotor magnet of the motor 3 of the present invention. As will be described later, the motor 3 can be started up by a sine wave voltage by the inverter 4 without requiring a CS sensor due to this skew amount.

  Here, the amount of skew magnetization will be described with reference to the drawings. The motor 3 is composed of a stator in which three-phase windings are successively wound around pole teeth having 12 slots and Y-connected (not shown), and a rotor magnet whose outer periphery is alternately magnetized with eight poles. FIG. 2 is a developed plan view showing this relationship. One pole tooth pitch of the stator is 30 degrees, and the magnetization angle per magnetic pole of the rotor magnet is 45 degrees in mechanical angle.

  When the amount of skew of the rotor magnet is expressed in terms of mechanical angle as the radial deviation at both end faces of the magnet outer circumference, 360 ° is the least common multiple of the number of stator pole teeth (12) and the number of magnet poles (8) (24) If the angle is divided by (15 degrees), the cogging torque can be minimized with no loss. Further, the skew amount may be set in a range up to a single pole tooth pitch angle (30 degrees) of the stator. In addition, since motor efficiency will deteriorate rapidly when it exceeds 1 pole tooth pitch angle (30 degree | times), it is unpreferable.

  Thus, when the stator is 12 slots and the rotor magnet is 8-pole magnetized, by setting the skew amount in the range of 15 degrees to 30 degrees, the magnetic flux generated by one N pole (or S pole) is generated. Since it is always linked with two or more stator pole teeth (windings), one magnetic pole of the magnet rotor is affected not only by one pole and one phase, but also by the electromagnetic force of the other phase, so that the sine wave power supply Can be activated without a CS sensor, and synchronous pull-in can be realized.

  Even if an overload stop occurs due to driving with a constant frequency power supply, restarting and synchronous pull-in can be realized without removing any operation on the inverter and the motor body simply by removing the overload factor.

  In order to prevent burnout due to overload stop, the three-phase winding is wound with a thin coil so as to have an impedance protection function to ensure safety during overload. As a result, the increase in current during overload is reduced, so that the control tolerance for the escape torque is increased, and there is an advantage that step-out can be prevented.

  Thus, it can start reliably by the one inverter 4, and the several motor 3 can be driven synchronously even if there is no synchronizing signal from a high-order controller. Even if there is only one motor 3, it can be reliably started by the inverter 4 and operated at a synchronous speed.

  In the drive system of the second embodiment, the configuration of the motor is the same as that of the first embodiment, and only the control method of the inverter is different. FIG. 3 is an explanatory diagram of the V / F output characteristics of the inverter.

  When the motor is started and stopped at a constant frequency in the drive system of the first embodiment, vibration is caused. For this reason, the soft start is performed at the start (acceleration) or the soft stop is performed at the stop (deceleration).

  This soft start and soft stop are generally performed in the motor control by the inverter, and the output voltage is controlled during normal operation from the starting excitation frequency fs based on the normal constant V / F control during acceleration / deceleration in FIG. The V / F characteristic up to the excitation frequency fr becomes point abc.

  On the other hand, increasing the output voltage in advance at the time of startup is usually performed as a boost of the output voltage in the inverter. Thereby, the workpiece | work on a conveying apparatus can be transferred smoothly.

  The inverter according to the second embodiment controls the output voltage according to the inertia and acceleration / deceleration of the load when the acceleration / deceleration operation is performed by changing the output frequency.

  Here, when the voltage applied to the motor when driving at a constant rotational speed is V, and the output voltage during acceleration / deceleration is Vs, it can be expressed as Vs = V + ΔV. The value of ΔV is calculated in a feed-forward manner according to the excitation frequency, acceleration, and load inertia.

  The V / F characteristic of the inverter of Example 2 will be described with reference to FIG. The inverter of the present invention controls the output voltage so as to pass through the points ab-d-e-c from the starting excitation frequency fs to the excitation frequency fr during steady operation.

Starting between a and d, accelerating with d and e, ec shows a transition to steady operation, b and d correspond to ΔV at startup, and c and e just before reaching steady rotational speed It corresponds to ΔV. If the steady rotational speed is reached by acceleration, the point is quickly shifted to the point c which is the original output voltage. ΔV in FIG. 3 can be conceptually expressed by Equation 1.

In Equation 1, when the excitation frequency changes from f1 to f2, the square root is calculated by squaring the amount of change to obtain the absolute value of acceleration.

  K1 in Expression 1 is an impedance correction coefficient of the motor, and increases as the excitation frequency, that is, the operation speed increases. K2 is an acceleration correction coefficient, and is set larger as the acceleration increases. K3 is a load inertia coefficient and is changed according to the load inertia.

  As described above, in Patent Document 1 described above (the case where ΔV is constant and acceleration / deceleration changes), the risk of stepping out is high, whereas according to the control method of the present invention, the value of ΔV is high. Is automatically set in real time according to the acceleration / deceleration, so that it is possible to cope with changes in acceleration / deceleration. Further, when the load inertia is different, it can be dealt with by changing the value of K3.

  Thus, by adding the soft start and soft stop functions and the function for automatically setting the motor applied voltage during acceleration / deceleration to the conventional inverter, more reliable synchronous driving can be realized.

  In addition, it cannot be overemphasized that one synchronous motor of Example 1 can be driven with one inverter of Example 2, and it can drive | operate without a step out also in the use which does not require synchronous drive.

  The drive system of the present invention is most suitable for synchronous drive with a constant frequency by an inverter, and is also useful for a transport device or the like in which step-out may occur during acceleration / deceleration.

1 is a configuration diagram of a drive system in Embodiment 1 of the present invention. Explanatory drawing of the skew of the motor in Example 1 of this invention V / F characteristic explanatory diagram of the inverter in Embodiment 2 of the present invention

Explanation of symbols

1 Drive system (conveyor)
2 Driving roller 3 Motor 4 Inverter 5 Work 6 Impedance protector

Claims (7)

In a drive system having a mechanism that requires synchronous drive by a plurality of motors, the system includes a motor having a magnet rotor skewed and an inverter that drives the motor, and the plurality of motors are synchronously driven by a single inverter. A drive system characterized by that. The motor includes a stator having a multi-phase winding wound around pole teeth, and a magnet rotor rotatably supported inside the stator. The magnet rotor has magnetic poles (N pole, S pole) in a circumferential direction. Are alternately arranged and skewed in the axial direction at both end faces of the magnet. The motor includes a stator having a multi-phase winding wound around pole teeth, and a magnet rotor rotatably supported inside the stator, and the multi-phase winding of the stator has an impedance protection function. The drive system according to claim 1 or 2. The skew amount of the magnet rotor is obtained by dividing 360 ° by the least common multiple of the number of pole teeth of the stator and the number of magnet magnetic poles when the radial deviation at both end surfaces of the magnet outer periphery is represented by a mechanical angle. The drive system according to any one of claims 1 to 3, wherein the drive system is set in a range up to one pole tooth pitch angle. The inverter that synchronously drives the motor, when performing an acceleration / deceleration operation by changing an output frequency, performs a feed-forward calculation according to load inertia and acceleration / deceleration to automatically control an output voltage. The drive system according to any one of claims 1 to 4. The drive system according to any one of claims 1 to 5, wherein the inverter performs a soft start when starting (acceleration) or a soft stop when stopping (deceleration). A transport apparatus using the drive system according to any one of claims 1 to 6, wherein a motor is directly connected to a rotation shaft of a transport roller.