JP2000116097A - Electric motor device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] In a motor device in which load driving is shared by a plurality of motors to reduce an inertia coefficient, operation of a plurality of motors can be stably obtained by a common power supply. To provide a motor device as described above. SOLUTION: In a motor device in which the shafts of two electric motors 1 and 2 are connected to drive the same load, respective phase windings U1, V1 and W1 of a stator of one electric motor 1 are Y-connected. , Each phase winding U2, V2, W of the stator of the other electric motor 2
2 is connected in series with each of the phase windings U1, V1, and W1 of the stator of the motor 1 to form a vertical joint connection, and the phase windings U2, V2, and the other terminal U2 ₁ of W2, V2 _1, W2 AC voltage of ₁ to 3-phase that so as to drive the electric motors 1, 2 of the two supplies. Since the winding current of each phase of the two electric motors 1 and 2 is completely the same, stable operation can be obtained even if power is supplied from a common power supply.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor device using a three-phase AC motor, and more particularly to a motor device using a plurality of motors to drive a load.

[0002]

2. Description of the Related Art Electric motors are widely used as actuators (drive sources) for machine tools, manufacturing apparatuses, industrial robots, and the like. One type of motor for the actuator is a permanent magnet field type servo motor having a three-phase AC armature winding, which is frequently used because it excels in cost performance.

By the way, a kind of performance required of such an electric motor for an actuator has responsiveness. For example, a press machine or a semiconductor bonding apparatus which requires a high tact operation requires a particularly high responsiveness. However, the responsiveness of this motor is mainly determined by the inertia ratio MD ² (also referred to as GD ² ) in the rotating part. From the viewpoint of high responsiveness, a motor with a small inertia ratio MD ² is used as much as possible. Is desirable.

[0004] Here, in the symbols representing the moment of inertia MD ^2, the symbol M, that of the figures for the mass of the rotating part, because the symbol D is also that of the figures for the diameter, for the same torque The diameter (diameter) of the rotor may be reduced, and the length may be increased accordingly. Thus, the electric motor having a small moment of inertia MD ² in this way is made to special specifications, be quite expensive compared to general-purpose motor.

[0005] Therefore, with respect to the motor requiring capacity (output), a plurality of small motors having rated capacity, for example by sharing the volume with two, thereby while using a general-purpose motor, inertia efficiency MD ² Conventionally, a method for reducing the value has been proposed.

[0006] Here, The reason for reduction of the moment of inertia MD ² can be obtained by sharing the capacity required by a plurality of motors, when divided, as described below, rotary This is because the diameter of the child can be reduced.

[0007] Assuming that the diameter of the rotor is D and the length is L, the volume V and the mass M of the rotor are as follows. V = (π / 4) D ² L M = βV β: Equivalent Specific Gravity If the magnitude of the inertia coefficient MD ² is defined as an inertia value (inertia) J, this is as follows. J = K ₁ MD ² = K ₂ D ⁴ L K ₁ , K ₂ : constant

Next, assuming that the electromagnetic force between the stator and the rotor of the electric motor is F, the electromagnetic force F is substantially proportional to the facing area between the stator and the rotor. Therefore, F = K ₃ DL K ₃ : constant. Torque T of the motor is substantially proportional to the electromagnetic force _{F, T = K 4 FD =} K 5 D 2 L K 4, K 5: is a constant.

Here, if the capacity of the motor is divided into two units, the torque per unit can be reduced to half. Therefore, assuming that the torque of the divided motor is T _D , T _D = (１ ／) T = (１ ／) K ₅ D ² L.

Next, assuming that the ratio between the diameter D and the length L of the rotor is designed to be substantially the same, L = K ₆ D K ₆ : a constant (≒ 1), and the rotor of the divided motor is Is the diameter of D _D and the length is L _D
When, the ^{_{(1/2) K 5 D 2 K}} 6 D = K 5 D D 2 K 6 D D.

[0011] ^{Therefore, (1/2) D 3 = D} D 2 , and the thus becomes _{D = 1.26D D D D = 0.76D} . That is, if the motor is divided into two motors, a rotor having a diameter of about 80% of the diameter of the original motor is sufficient.

Here, since the original inertia value J is J = K ₂ D ⁴ L as described above, from the above relation, J = K ₂ D ⁴ L = K ₂ D ⁴ · K the _{6 D = K 2 K 6 D} 5. Therefore, when this put the relationship _{D = 1.26D D, J = K} 2 K 6 (1.26D D) 5 = K 2 K 6 (1.26) 5 D D 5 ∴ J = (1.26 ) the ^{_{5 · J D J = 3.18J D}} .

Since the capacity of the electric motor is divided into two, the original capacity is obtained for two motors. That is, J = 1.59 · (2J _D ) 2J _D = 0.63 J Therefore, by dividing the motor into two, the original motor is reduced to about 6
It can be seen that the same capacity can be obtained with a relatively low inertia value.

When a load of a certain capacity is shared and driven by a plurality of motors, the following two types of driving methods are mainly used in the prior art. Common power supply method A method of driving multiple motors with a common power supply. For example, when there are two motors, these two motors are connected in parallel and operated by one power supply such as a power amplifier. Independent drive method A method of operating with an independent power supply for each motor.

[0015]

In the above prior art, it cannot be said that consideration is given to the control of each motor when a common load is shared and driven by a plurality of motors, and the following problems arise. there were. First, in the common power supply system, there is no problem if the characteristics (for example, induced voltage constants) of the motors are completely the same.

However, in practice, it is unavoidable that the characteristics of the motors are irregular. Therefore, in the method described above, a circulating current Ig appears between the two motors M1 and M2, for example, as shown in FIG. Due to the loss due to the circulating current Ig, the efficiency is reduced and extra heat is generated.

In the following method, if the control is performed only by looking at the speed of the motor, interference appears in the operation state of the motor and hunting occurs. Therefore, the speed fluctuation rate is intentionally increased, thereby increasing the load. A scheme is taken to ensure that an appropriate share is given naturally.

Although this method is generally stable when operating at a constant speed, hunting also occurs when a load change or a speed change occurs. Therefore, in the method, the speed of one motor is controlled,
A method of controlling the torque of the other electric motor has also been proposed.
In the case of this method, the control is generally successful, but the control method is difficult and is not easily generalized.

An object of the present invention is to provide a motor device in which a plurality of motors share the drive of a load to reduce the inertia coefficient, whereby the operation of the plurality of motors can be stably performed by a common power supply. An object of the present invention is to provide an electric motor device as described above.

[0020]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a motor apparatus using a three-phase AC motor, in which the three-phase AC motor has a stator connection in which the windings of each phase of the stator windings are vertically connected by star connection. This is achieved by using a plurality of three-phase AC motors and driving the plurality of three-phase AC motors by a single control circuit.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a motor device according to the present invention will be described in detail with reference to the illustrated embodiments. FIG.
Is an embodiment in which the electric motor device according to the present invention is applied to a servo motor system. This embodiment includes two electric motors 1 and 2 and connects their shafts 3 and 4 with a shaft joint 5, Then, it is connected to the input shaft 7 of the speed reduction mechanism 6 by a joint 8, and power is taken out from the output shaft 9 of the speed reduction mechanism 6 to control a machine tool (not shown) or the like.

The driving and control of the two motors 1 and 2 are performed by a control circuit 10. For this reason, the control circuit 10 is supplied with a control command C given from the outside and an encoder 11 provided in the motor 2. The servo amplifier is configured to input a rotation signal R and perform feedback control in accordance with the rotation signal R.

The electric motor 1 is a general permanent magnet field type servo motor having three-phase stator (armature) windings. The stator windings are as shown in FIG. , _One terminal U1 ₁ , V1 of one of the windings U1, V1, W1 of each phase.
And 1 _1, W1 _1, the other terminal U1 _2, V1 _2, W1 ₂ are taken out all independently outside, but that is a so-called six lead-out scheme.

The electric motor 2 is also a permanent magnet field type servo motor having three-phase stator windings, but is not of a single axis type but of a double axis type. Similarly, as shown in FIG. , One terminal U of the windings U2, V2, W2 of each phase of the stator
2 _1, V2 _1, W2 ₁ and the other terminal U2 _2, V2 _2, W2
₂ is a 6-hole outlet system in which all of them are taken out independently.

At this time, the stator windings of the motors 1 and 2 have the same phase rotation direction and the same winding direction for the U, V and W phase windings. Shall be Next, the electric motor 1 and the electric motor 2 have their stator windings so-called vertically connected as follows.
(Cascade) and then to the control circuit 10.

First, the stator windings U1, V1, W of the motor 1
Of the one terminal, the other terminals U1 ₂ , V1 ₂ , and W1 ₂ are commonly connected by a terminal plate 13. At this time, the terminal plate 13
The not used, terminals U1 _2, V1 _2, W1 ₂ and may be connected directly together. Next, the stator windings U1, V1, terminal U1 ₁ of W1, V1 _1, W1 ₁ is a stator winding motor 2 U
2, V2, the other terminal U2 ₂ of W2, V2 _2, W2 ₂ to connect respectively.

The three-phase output terminal U of the control circuit 10
V and W have stator windings U2, V2 and W of the electric motor 2, respectively.
The two terminals U2 ₁ , V2 ₁ and W2 ₁ are connected.

As a result, as shown in FIG. 4, the stator windings of these two motors 1 and 2 are such that the windings of the respective phases are connected in series, and are connected in a vertical connection state. Connection)
In this way, the three-phase AC outputs U, V, and W of the control circuit 10 are connected.

Further, the electric motors 1, 2 have their shafts 3,
After the shafts 4 are connected to each other, the shaft 4 of the electric motor 2 is connected to the input shaft 7 of the speed reduction mechanism 6. That is, first, the shaft 3 of the electric motor 1 and the portion of the shaft 4 of the motor 2 protruding on the non-load side (encoder side) of the motor 4 are connected by the shaft coupling 5, and the portion of the shaft 4 protruding on the load side is connected to the shaft coupling. 8, the input shaft 7 of the speed reduction mechanism 6
It is combined with.

For this reason, the motor 2 is of the double-shaft type. Thus, the electric motors 1 and 2 share the torque that needs to be given to the input shaft 7 in order to generate a load driving torque on the output shaft 9 of the speed reduction mechanism 6.

The control circuit 10 converts the three-phase rectangular wave voltages EU, EV, EW shown in FIG. 5 into three phases according to a drive command signal C supplied from a higher-level control system (not shown). The electric power is generated from the output terminals U, V, and W and supplied to the stator winding of the electric motor 2 and further to the stator winding of the electric motor 1 via the stator winding of the electric motor 2. At this time, the control circuit 10
Is a rotary encoder 11 attached to the electric motor 1
From the drive command signal C
Is configured so that feedback control works.

In this embodiment, the electric motor 2 is also provided with a rotary encoder 12.
, And is used only when the system is installed, as described later.

Next, the operation of this embodiment will be described. First, assuming that the power required for driving the load is P, the motors 1 and 2 each have a rated output of P / 2. And these electric motors 1,
2 is E / 2, the control circuit 10
Is configured such that three-phase rectangular wave voltages EU, EV, EW of voltage E can be generated from three-phase output terminals U, V, W.

Therefore, as shown in FIG. 5, a three-phase rectangular wave voltage EU, EV,
Assuming that EW is generated from the three-phase output terminals U, V, W of the control circuit 10, the EW is supplied to the motors 1, 2 which are vertically connected. A voltage of E / 2, which is a rated voltage, is applied to each of the motors. Accordingly, torques corresponding to the respective rated outputs P / 2 are generated from the electric motors 1 and 2, and these are combined to reduce the speed. 6 to the input shaft 7.

As a result, the load coupled to the output shaft 9 of the speed reduction mechanism 6 can be operated at the output P. At this time, two motors 1 and 2 are used to obtain the required output P. Therefore, as described above, the inertia value can be set to about 60% as compared with the case where one motor generates the output P, and the responsiveness can be greatly improved.

At this time, the two motors 1, 2
As shown in FIG. 4, since the windings of each phase are connected in series, the same current flows in the motor 1 and the motor 2 in any of the U-phase, V-phase, and W-phase windings. Therefore, despite the fact that power is supplied from one control circuit 10, there is no possibility that hunting will occur, and stable operation can always be obtained.

Also, since there is no parallel connection in the connection path between the two motors 1 and 2, there is no danger that a circulating current is generated. , And a sufficiently high responsiveness can be provided for control.

Furthermore, as a result of the two motors 1 and 2 being connected vertically, there is no danger that the current will be unbalanced even if the characteristics of the motors are slightly different, and stable operation is ensured. Therefore, it is not necessary to strictly adjust the servo constants such as the induced voltage constant, and the system can be easily configured.

Next, in the embodiment of FIG.
The role of the rotary encoder 12 provided in the above will be described. Since the two electric motors 1 and 2 are operated by the same electric current by the same three-phase rectangular wave voltages EU, EV and EW, the magnetic pole positions of the stator and the rotor become And the motor 2 must be connected in the same manner.

Therefore, when the electric motor 1 and the electric motor 2 are installed and the shafts 3 and 4 are connected by the shaft coupling 5, the rotary encoder 12 is used. As shown in FIG. Is input to the oscilloscope 13, and as shown in FIG. 6 (b), the magnetic pole position waveform M
U1 and the magnetic pole position waveform MU2 of the motor 2 are compared, and the shaft position of the motor 1 and the shaft position of the motor 2 are adjusted so that the difference δ between the two becomes substantially zero, and then the shaft joint 5 is connected. I will do it. Here, the oscilloscope 13 is of a trigger sweep type known as a product name synchroscope.

In this embodiment, after the magnetic poles of the electric motors 1 and 2 are aligned and connected by the shaft coupling 5 in this manner, feedback is performed by only one of the two rotary encoders 11 and 12. Since control can be performed, the other rotary encoder can be left as a spare.

As a result, for example, in the embodiment of FIG.
When the rotary encoder 11 of the electric motor 1 fails, the output signal of the rotary encoder 12 of the electric motor 2 is supplied to the control circuit 10 so that the operation can be continued as it is before the failure.

Here, a general-purpose servomotor is usually provided with a rotary encoder. Therefore, according to this embodiment, the cost is increased only by using a general-purpose product without increasing the cost. Reliability can be easily provided.

Next, another embodiment of the present invention will be described. FIG. 7 shows a second embodiment of the present invention. In this embodiment, a reduction mechanism 16 provided with a double-shaft input shaft 7 is used, and one of the input shafts 7, the right-hand shaft 7R in the figure, has an axis. The motor 1 is connected by a joint 17, and the motor 2 is connected to the other shaft 7 </ b> L by a shaft joint 18. In addition,
Other configurations are the same as those of the embodiment of FIG. 1, and therefore, the control circuit 10 is omitted.

In the embodiment shown in FIG. 1, it is necessary to use, as the electric motor 2, a double-shaft electric motor whose shaft 4 protrudes from the brackets on both sides. Thus, in the embodiment of FIG.
As shown in the figure, since both the electric motor 1 and the electric motor 2 need only be of a single-shaft type in which the shaft extends only on the load side, a general-purpose servomotor can be easily applied, and the cost can be reduced.

On the other hand, in the embodiment shown in FIG.
And the motor 2 are coupled in a face-to-face manner, so that the rotation directions are opposite. Therefore, in this embodiment, it is necessary to connect the motor 1 and the motor 2 so that the phase rotation directions of the stator windings are opposite to each other. Therefore, the stator windings of the motor 1 and the motor 2 are For example, the connection may be made as shown in FIG.

In the above embodiment, the power required to drive the load is shared by two motors in order to reduce the inertia value. However, the number of divided motors is not limited to two. Or three or more. In this case, one stator winding of the plurality of motors is Y-connected, and the phase windings of the remaining motors are sequentially connected in series to the windings of each phase of the stator windings. To be connected vertically.

Also, in any case, according to the present invention, one of the plurality of electric motors has a stator winding connected in a Y-connection. For example, the electric motor 1 in the embodiment of FIG. is not limited to six lead-out scheme, as shown in FIG. 9, which is Y-connection inside the electric motor M ₀ of the so-called three lead-out scheme
May be used.

Furthermore, in the above embodiment, the case where a servo motor, particularly a permanent magnet field type servo motor is used as the electric motor has been described. However, the present invention can be implemented by a general-purpose three-phase AC motor such as an induction motor. Needless to say.

In the above embodiment, the servo system is applied. For this reason, a speed reduction mechanism is used in each case. However, this speed reduction mechanism is not indispensable for implementing the present invention. Needless to say, they are used as needed.

[0051]

According to the present invention, control of a plurality of motors can be easily and stably performed by a common control circuit, so that the inertia value can be easily reduced by increasing the number of motors. be able to. Therefore, according to the present invention, the responsiveness can be sufficiently improved even with a general-purpose motor,
A high-performance motor device can be easily provided at a low price.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a motor device according to the present invention.

FIG. 2 is an explanatory diagram illustrating an example of a stator winding of an electric motor according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating an example of a stator winding of the electric motor according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an example of a connection configuration of a stator winding of a motor according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram illustrating an example of a drive current waveform according to an embodiment of the present invention.

FIG. 6 is an explanatory diagram illustrating an example of a magnetic pole position adjustment operation according to an embodiment of the present invention.

FIG. 7 is a block diagram showing another embodiment of the motor device according to the present invention.

FIG. 8 is an explanatory diagram showing an example of a connection configuration of stator windings of an electric motor according to another embodiment of the present invention.

FIG. 9 is an explanatory diagram illustrating an example of a stator winding of the electric motor according to the embodiment of the present invention.

FIG. 10 is an explanatory diagram of a circulating current in a motor device according to the related art.

[Explanation of symbols]

 1, 2 motor 3 axis of motor 1 4 axis of motor 2 5, 8 shaft coupling 6 reduction mechanism 7 input axis of reduction mechanism 6 output axis of reduction mechanism 6 10 control circuit (servo amplifier) 11, 12 rotary encoder 13 terminal Board

Claims (1)

[Claims] 1. A motor device using a three-phase AC motor, wherein the three-phase AC motor is a plurality of three-phase AC motors in which each phase winding of a stator winding is vertically connected and star-connected. Wherein the plurality of three-phase AC motors are driven and controlled by one control circuit.