JPS6240977Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an electric motor drive device that can accurately control the conveyance speed of a material to be conveyed, such as a steel pipe.

2. Description of the Related Art Conventionally, as an inspection means for products such as steel pipe rolling equipment, for example, X-ray flaw detection equipment or the like has been used to inspect joints of products. In such inspection equipment, it is common to place the steel pipe as a product on a transport roll, and while the transport roll is driven by an electric motor to transport the steel pipe, the steel pipe is detected for flaws using X-ray flaw detection equipment. and in this case,
In order to ensure flaw detection accuracy, it is important to control the conveyance speed of products such as steel pipes to a predetermined value.

FIG. 1 shows the configuration of a conventional motor drive device for controlling conveyance rolls in such equipment.

In the figure, a speed reference signal set in a reference circuit 1 is applied to a signal comparator 2 as a speed control target for a transport roll driving electric motor 10 connected to a transport roll 12. On the other hand, the speed signal obtained from the tachometer generator 11 directly connected to the electric motor 10 is
The signal is applied as a speed feedback signal to the signal comparator 2 and compared with the speed reference signal to determine its deviation;
The deviation signal is amplified by the speed control circuit 3.
The output of this speed control circuit 3 is given to a signal comparator 4 as a current reference signal for current control in the next stage.
Further, the motor current detected by the current transformer 8 provided between the AC power source 9 and the power converter 7 is input as a current feedback signal to the signal comparator 4, and is compared with the current reference signal. The deviation is determined, and the deviation signal is subjected to minor current control in the current control circuit 5. Furthermore, the output signal of this current control circuit 5 is input to the next stage phase control circuit 6, and the firing angle of the power converter 7 composed of a thyristor or the like is controlled in phase according to the input amount. This is to control the speed.

Therefore, in such a configuration, when the steel pipe 13 is placed on the transport roll 12 connected to the electric motor 10 and flaw detection is performed using the X-ray flaw detection equipment 14 while the steel pipe 13 is being transported, the speed of the electric motor 10 is controlled. The transport rolls 12 transport the steel pipe 13 at a predetermined speed.

However, such conventional electric motor drive devices have the following problems. In other words, as shown in FIG. 2, the part where the steel pipe 13 is in contact with the conveyor roll 12 is the slope of the conveyor roll 12. In other words, the transport roll 12
Since the circumferential speed of the transport roll 12 differs from the side with the largest diameter, the transport speed of the steel pipe changes depending on the position where the steel pipe 13 contacts the slope of the transport roll 12. In other words, when the diameter of the steel pipe 13 changes, the conveyance speed of the steel pipe 13 also changes, so the steel pipe 13
Problems arise, such as the need to change the setting of the speed standard each time according to the type, ie, diameter, of the steel pipe 13, and that it is difficult to accurately control the conveyance speed of the steel pipe 13 for the above-mentioned reasons.

This invention was developed to solve the above problems, and its purpose is to directly detect the conveying speed of the steel pipe using a measuring roll or the like that is in contact with the surface of the steel pipe, and use this as a speed feedback signal. Accordingly, it is an object of the present invention to provide an electric motor drive device that can accurately control the conveyance speed of steel pipes.

In order to achieve the above object, the electric motor drive device according to the present invention includes a speed detection means for detecting the conveyance speed of the material to be conveyed, a current detector for detecting the current of the electric motor, and an output signal from the speed detection means. A speed control system that receives a speed feedback signal and a speed reference signal as input and sends out an output signal based on a deviation signal between these two signals, and a speed correction signal and a speed reference signal that are output signals from this speed control system. A voltage control system that receives as input the voltage reference signal obtained by adding the voltage feedback signal of the motor and sends out an output signal based on the deviation signal of these two signals, and a current reference signal that is the output signal from this voltage control system. The present invention is characterized in that it is configured to include a control system that controls the speed of the motor by controlling the current of the motor based on the deviation signal between the signal and the current feedback signal that is the output signal from the current detector.

An embodiment of the present invention will be described below with reference to the drawings. Fig. 3 shows an example of the configuration of the motor drive device according to the present invention. In the figure, the minor current control system is the same as that in Fig. 1, so its explanation is omitted, and here the newly configured voltage control The system and speed control system are described below. In the figure, a speed reference signal from a reference circuit 1 for setting the transport speed of a steel pipe 13 is inputted as a reference signal to a speed control circuit 3 and a voltage control circuit 19 via signal comparators 16 and 17, respectively. That is, in the signal comparator 16, the tachometer generator 11 is connected to the measuring roll 15 which is in direct contact with the steel pipe 13.
The feedback signal of the transport speed detected by the above-mentioned speed reference signal is compared with the speed reference signal to find the deviation thereof, and the deviation signal is controlled by the speed control circuit 3. Further, in the signal comparator 17, the speed reference signal and the output signal from the speed control circuit 3 are added, and the added signal becomes a voltage reference signal for the voltage control circuit 19 at the next stage, and a feedback signal of this signal and the motor voltage is 20 by the signal comparator 18 to find the deviation, and the deviation signal is controlled by the voltage control circuit 19. In other words, the signal comparator 1
The speed control circuit 3
The output signal is given to the signal comparator 17 as a speed correction signal limited to a value that corrects the change in conveyance speed.

With this configuration, even if the diameter of the steel tube 13 changes and the conveyance speed of the steel tube 13 changes, the speed change is given to the voltage control circuit 19 as a speed correction signal, so that the conveyance speed of the steel tube 13 is always maintained at a predetermined level. The speed can be controlled to the value of . In addition, by configuring the control system as described above,
Even when there is no steel pipe 13 on the conveyor roll 12, that is, when the measuring roll 15 in contact with the steel pipe 13 floats and the speed detection signal is lost, the voltage control of the minor control system can control the electric motor 1.
0 is controlled, and the operation can be continued without any problems.

Hereinafter, the specific effect of this point will be explained in detail using FIG. 4.

As long as the speed of the electric motor 10 is kept constant, the conveyance speed of the steel pipe 13 changes depending on the diameter of the steel pipe 13. That is, as shown in FIG. 4, the point where the steel pipe 13 contacts the conveyor roll 12 when it is at its minimum diameter is A,
If the point where the steel pipe 13 with the largest diameter contacts the transport roll 12 is B, and if the rotation speed of the transport roll 12 is the same, then the transport speed of the steel pipe 13 that contacts at point B and the steel pipe 13 that contacts at point A are When comparing the transport speed at point B, point B is faster than point A. In other words, since the conveyance speed is the same as the circumferential speed of the conveyor roll 12, the closer the conveyor roll 12 comes into contact with the thicker diameter portion, the more
The circumferential speed, that is, the conveyance speed is high. Therefore, the reference circuit 1 sets the speed of the electric motor 10 that can obtain the conveying speed at point C, which is the midpoint between points A and B. In this case, the speed reference signal from the reference circuit 1 is a voltage reference signal for the electric motor 10, and the conveyance speed at point C is obtained as the speed of the electric motor 10 when this signal is input.

For example, first, when the steel pipe 13 moves from point C to point B and comes into contact with the conveyance roll 12, the conveyance speed becomes faster than the speed of the speed reference signal from the reference circuit 1 (peripheral speed at point C). The transport speed of the steel pipe 13 at this time is
Measuring roll 15 and tachometer generator 11
The signal detected through the speed control circuit 3 and the speed reference signal from the reference circuit 1 are compared by the signal comparator 16 to find the deviation, and then the signal is sent to the reference circuit 1 again via the speed control circuit 3.
The signal comparator 17 compares it with the speed reference signal from. In this case, the detection signal for the transport speed of the steel pipe 13 is input as a negative polarity signal (-), and the speed reference signal from the reference circuit 1 is input as a positive polarity signal (+). On the other hand, the speed control circuit 3 has an input signal and an output signal.
Since they are configured to have the same polarity, the deviation signal obtained by the signal comparator 16 becomes a negative polarity signal (- ), and a negative polarity signal (-) is input to the signal comparator 17 via the speed control circuit 3. The speed reference signal from the reference circuit 1 is input to the signal comparator 17 as a positive polarity signal (+), and the voltage reference signal to the signal comparator 18 is output from the speed control circuit 3 rather than the original reference. It will be reduced by the negative polarity signal (-). In other words, the speed of the electric motor 10 is reduced,
A predetermined conveyance speed can be obtained.

On the other hand, when the steel pipe 13 moves closer to point A than point C and contacts the transport roll 12, the transport speed becomes slower than the speed of the speed reference signal from the reference circuit 1 (peripheral speed at point C). In this case, the output of the signal comparator 16 becomes a positive polarity signal (+), and the output of the speed control circuit 3 also becomes a positive polarity signal (+). That is, in the signal comparator 17, the speed reference signal (+) from the reference circuit 1 and the deviation signal (+) between the detection signal of the conveying speed of the steel pipe 13 are added to obtain a voltage reference signal. Therefore, the speed of the electric motor 10 will be increased, and a predetermined conveyance speed will be obtained.

As described above, in this embodiment, the driving device for the electric motor 10 for driving the conveyance roll 12 that conveys the steel pipe 13 as the material to be conveyed is replaced by a measuring roll serving as a speed detection means for detecting the conveyance speed of the steel pipe 13. 15, a tachometer generator 11, a current transformer 8 as a current detector that detects the current of the motor 10, a speed feedback signal that is an output signal from the tachometer generator 11, and a speed reference signal from the reference circuit 1. A speed control system that takes as input and sends out an output signal based on the deviation signal of these two signals, and a voltage standard that is obtained by adding the speed correction signal that is the output signal from this speed control system and the speed reference signal. A voltage control system that receives the signal and the voltage feedback signal of the motor 10 as input and sends out an output signal based on a deviation signal between these two signals, a current reference signal that is an output signal from this voltage control system, and a current transformer 8. The control system includes a control system that controls the motor speed by controlling the current of the motor 10 based on the deviation signal from the current feedback signal that is the output signal from the motor.

Therefore, with this configuration, the conveyance speed of the steel pipe 13 is directly detected by the measuring roll 15 that is in direct contact with the steel pipe 13, and this is given as a speed feedback signal to the speed control system configured at the front stage of the voltage minor loop. Since the conveyance speed of the steel pipe 13 is always controlled to a predetermined value, the conveyance speed of the steel pipe 13 is always controlled to a predetermined value.
Type 3 eliminates the need to change the speed standard setting each time, and has the advantage that the electric motor 10 can be controlled by a minor voltage control system even without the steel pipe 13 on the conveyor roll 12. It is.

It should be noted that the present invention is not limited to the above embodiments, but can be implemented with various modifications without changing the gist thereof.

As explained above, according to the present invention, a speed detection means for detecting the conveyance speed of the material to be conveyed, a current detector for detecting the current of the electric motor, a speed feedback signal which is an output signal from the speed detection means, and a speed A speed control system that receives a reference signal as input and sends out an output signal based on a deviation signal between these two signals, and a speed correction signal that is an output signal from this speed control system is obtained by adding the speed reference signal. A voltage control system that receives a voltage reference signal and a motor voltage feedback signal as input and sends out an output signal based on a deviation signal between these two signals, and a current reference signal that is an output signal from this voltage control system and a current detector. The system is equipped with a control system that controls the motor speed by controlling the motor current based on the deviation signal from the current feedback signal, which is the output signal from the It is possible to provide an extremely reliable electric motor drive device that can perform the following steps.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional electric motor drive device, Fig. 2 is an explanatory drawing showing the contact portion between the conveying roll and the steel pipe, Fig. 3 is a block diagram showing an embodiment of the present invention, and Fig. 4 is It is a figure for explaining the effect|action in the same Example. 1...Reference circuit, 2, 4, 16, 17, 18...
... Signal comparator, 3 ... Speed control circuit, 5 ... Current control circuit, 6 ... Phase control circuit, 7 ... Power converter, 8 ... Current transformer, 9 ... AC power supply, 10 ... Electric motor , 11...Tachometer generator, 12...Transport roll, 13...Steel pipe, 14...X-ray flaw detection equipment, 15
... Measuring roll, 19 ... Voltage control circuit, 20 ... Voltage feedback signal.

Claims (1)

[Scope of utility model registration request] A drive device for an electric motor that drives a transport roll that transports a material to be transported, such as a steel pipe, includes a speed detection means for detecting the transport speed of the material to be transported, a current detector for detecting a current of the motor, and the speed detection unit. A speed control system that receives a speed feedback signal and a speed reference signal that are output signals from the means, and sends out an output signal based on a deviation signal between these two signals, and a speed correction system that is an output signal from this speed control system. A voltage control system that receives as input a voltage reference signal obtained by adding a signal and the speed reference signal and a voltage feedback signal of the motor, and sends out an output signal based on a deviation signal between these two signals, and this voltage control system. a control system that controls the motor speed by controlling the current of the motor based on a deviation signal between a current reference signal that is an output signal from the system and a current feedback signal that is an output signal from the current detector; An electric motor drive device comprising: