JP2008271614A - Control method for rotational speed of driven device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely control the rotational speed of a driven device in a power transmission device using a magnetic joint. <P>SOLUTION: In the power transmission device using a magnetic joint, the following correlations are determined: correlation A between the rotational speed of the driven device obtained when the rotational speed is increased and the distance D between the rotating plate and the magnet plate of the magnetic joint; and correlation B between the rotational speed obtained when the rotational speed is reduced and the distance D between the rotating plate and the magnet plate. The distance D is set based on these correlations A, B. The distance D is differently set when the rotational speed of the driven device is increased to target rotational speed E and when the rotational speed of the driven device is reduced to the target rotational speed E. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for controlling the rotational speed of a driven device such as a pump or a fan using a magnetic coupling.

  For example, equipment for rolling steel materials is provided with a blower fan that supplies air mixed with combustion gas to a burner of a heating furnace, for example. Conventionally, the amount of air blown to the burner has been adjusted by a flow rate adjusting valve provided in a flow path between the burner and a blower fan rotated at a maximum speed by a motor. In this case, even when the supply amount of air is small, since the blower fan is rotated at the maximum speed, wasteful power is consumed and the running cost is increased. Therefore, it is desirable to control the rotational speed of the blower fan in accordance with the amount of air supplied to save power in the blower fan. Therefore, for example, it can be proposed to connect a magnetic coupling capable of controlling the rotational speed of the blower fan between the blower fan and the motor.

  The magnetic coupling includes, for example, a rotating plate made of a nonmagnetic conductor plate and a magnetic plate, and a magnet plate, and the magnet plate and the rotating plate are arranged to face each other without contact. Then, for example, the rotating plate is rotated by a magnetic action by the rotation of the magnet plate, so that power can be transmitted. This magnetic coupling is more energy efficient than a normal mechanical coupling. In addition, since power is transmitted in a non-contact manner, vibration is not transmitted to the load side and the life is long. The magnetic coupling adjusts the distance between the rotating plate and the magnet plate to change the transmitted power and control the rotational speed on the load side (see Patent Document 1).

JP-A-5-252800

  However, when the magnetic coupling is used as described above, even if the distance between the rotating plate and the magnet plate is set to a predetermined distance, the actual rotational speed may not be exactly the target rotational speed and may vary. . This is due to the magnetic or mechanical factors of the magnetic coupling, when the rotational speed is increased to the target rotational speed and when the rotational speed is decreased to the target rotational speed. This is probably because a so-called hysteresis phenomenon occurs in which the relationship between the distance and the rotational speed is different. When the inventor actually conducted an operation test of the magnetic coupling and examined it, the hysteresis as shown in FIG. 6 was confirmed.

  For this reason, if the magnetic coupling is simply used to control the rotational speed of a blower fan or the like, the rotational speed of the blower fan cannot be strictly controlled. As a result, for example, the heating temperature in the heating furnace is not strictly controlled, and the steel material varies.

  The present invention has been made in view of this point, and an object thereof is to strictly control the rotational speed of a driven device such as a blower fan in a power transmission device using a magnetic coupling.

  According to the present invention for achieving the above object, a magnet having a rotatable magnet plate and a rotating plate that is disposed so as to face the magnet plate in a non-contact manner and is rotatable by the magnetic action between the magnet plate and the magnet plate. It has a joint, and one of the magnet plate and rotary plate of the magnetic joint is connected to the drive source, and the other is connected to the driven device, and the rotational power of the drive source is transmitted to the driven device via the magnetic joint. In the power transmission device, the method of controlling the rotational speed of the driven device by adjusting the distance between the rotating plate and the magnet plate of the magnetic coupling, the rotation when the rotational speed of the driven device is increased Correlation between the speed and the distance between the rotating plate and the magnet plate, the rotational speed when the rotational speed of the driven device is lowered, and the correlation between the distance between the rotating plate and the magnet plate, respectively. Based on the correlation, rotation of the driven device The distance between the rotating plate and the magnet plate is set individually for increasing the degree to the target rotational speed and for decreasing the rotational speed of the driven device to the target rotational speed. .

  According to the present invention, the rotational speed of the driven device is strictly controlled even when there is hysteresis in the relationship between the rotational speed and the distance between the rotating plate and the magnet plate when the rotational speed of the driven device is increased and decreased. Can be controlled.

  In the method for controlling the rotational speed of the driven device, the distance between the rotating plate and the magnet plate when the rotational speed of the driven device is increased and the rotation when the rotational speed is decreased at the same target rotational speed. When the difference between the distance between the plate and the magnet plate is obtained and the rotational speed of the driven device is lowered to the target rotational speed, the rotational plate and the magnet plate when the rotational speed of the driven device is increased The distance between the rotating plate and the magnet plate may be obtained by correcting the difference in the set distance.

  In the method for controlling the rotational speed of the driven device, the distance between the rotating plate and the magnet plate when the rotational speed of the driven device is increased and the rotation when the rotational speed is decreased at the same target rotational speed. When the difference between the distance between the plate and the magnet plate is obtained and the rotation speed of the driven device is increased to the target rotation speed, the rotation plate and the magnet plate when the rotation speed of the driven device is decreased The distance between the rotating plate and the magnet plate may be obtained by correcting the difference in the set distance.

  In the method for controlling the rotational speed of the driven device, when the rotational speed of the driven device is increased to the target rotational speed, the rotational speed is temporarily set higher than the target rotational speed and then set to the target rotational speed. When the rotational speed of the driven device is lowered to the target rotational speed, the rotational speed may be temporarily set lower than the target rotational speed and then set to the target rotational speed.

  According to the present invention, since the rotational speed of the driven device can be strictly controlled in the power transmission device using the magnetic coupling, for example, the heat treatment of the steel material using the rotation of the driven device can be appropriately performed. .

  Hereinafter, preferred embodiments of the present invention will be described. FIG. 1 is a schematic diagram showing an outline of the configuration of a power transmission device 1 in which the rotational speed of a driven device according to the present embodiment is controlled.

  The power transmission device 1 includes, for example, a motor 10 as a drive source, a blower fan 11 as a driven device (load body), and a magnetic coupling 12 that connects the motor 10 and the blower fan 11.

  The blower fan 11 is used for supplying air to a burner of a heating furnace in, for example, a steel rolling facility. In addition, the use of the ventilation fan 11 is not limited to this.

  The magnetic coupling 12 includes a rotating plate 22 made of, for example, a copper disk 20 that is a nonmagnetic conductor and an iron disk 21 that is a magnetic body, and a permanent magnet plate 23. The copper disk 20 and the iron disk 21 of the rotating plate 22 are overlapped and integrated. The permanent magnet plate 23 is disposed opposite to the copper disk 20 of the rotating plate 22, and a space of a distance D is formed between the permanent magnet plate 23 and the rotating plate 22. By rotating the rotating plate 22, an eddy current is generated in the copper disk 20 of the rotating plate 22 by the action of magnetism, and the permanent magnet plate 23 can be rotated by electromagnetic force. Then, by changing the distance D between the permanent magnet plate 23 and the rotating plate 22, for example, the rotating speed of the permanent magnet plate 23 on the driven side can be changed with respect to the rotating speed of the rotating plate 22 on the driving side.

  For example, the rotating plate 22 is connected to the motor 10 by a shaft 30, and the permanent magnet plate 23 is connected to the blower fan 11 by a shaft 31.

  For example, the shaft 31 is provided with a drive unit 40 such as an actuator for moving the permanent magnet plate 23 in the axial direction. Thereby, the distance D between the permanent magnet plate 23 and the rotating plate 22 can be adjusted.

  The operation of the drive unit 40 is controlled by the control unit 50. The control unit 50 is configured by a computer including a CPU, a memory, and the like, for example, and controls the operation of the driving unit 40 by executing a program stored in the memory, for example, so that the rotation speed of the blower fan 11 is the target rotation. The distance D can be adjusted to achieve speed.

  Next, control of the rotational speed of the blower fan 11 performed by the power transmission device 1 configured as described above will be described.

  First, the correlation between the rotational speed and the distance D when the rotational speed of the blower fan 11 is increased, and the correlation between the rotational speed and the distance D when the rotational speed of the blower fan 11 is decreased. Ask for. This is obtained in advance, for example, during an operation test of the power transmission device 1. As a result, for example, as shown in FIG. 2, correlation curves A and B between the rotational speed and the distance D that are different at the time of ascent and descent are obtained.

  Next, based on the correlation curves A and B, for example, the difference C between the rising distance D and the falling distance D at the same rotational speed is obtained. The difference C may be obtained for a plurality of rotational speeds that can be the target rotational speed, or may be obtained for all rotational speeds from the correlation curve A and the correlation curve B. For example, each data of the correlation curves A and B and the difference C is input and stored in the control unit 50, for example.

  When the rotational speed of the blower fan 11 is changed to a desired target rotational speed in the power transmission device 1, the target rotational speed is increased from the current rotational speed as shown in FIG. When the rotational speed E is set, the distance D1 corresponding to the target rotational speed E is obtained from the correlation curve A when the rotational speed is increased. When the rotational speed of the blower fan 11 is decreased from the current rotational speed to the target rotational speed E, the distance D1 is obtained based on the correlation curve A when the rotational speed is increased, and the rotational speed is included in the distance D1. A distance D2 that achieves the target rotational speed E is obtained by adding and correcting the difference C in E. The setting distance D is calculated by the control unit 50, for example.

  Then, when the set distance D is obtained, the permanent magnet plate 23 is moved by the drive unit 40 according to an instruction from the control unit 50, for example, and the distance between the permanent magnet plate 23 and the rotating plate 22 is set to the set distance D. Thus, the rotational speed of the blower fan 11 is set to the target rotational speed E.

  According to the above embodiment, the correlation curve A between the rotational speed and the distance D when the rotational speed of the blower fan 11 is increased, and the rotational speed and the distance D when the rotational speed of the blower fan 11 is decreased. A correlation curve B is obtained in advance, and the rotational speed of the blower fan 11 is increased to the target rotational speed E based on the correlation curves A and B, and the rotational speed of the blower fan 11 is decreased. The distance D between the permanent magnet plate 23 and the rotating plate 22 was set individually for the case of the target rotational speed E. By doing so, the rotational speed of the blower fan 11 can be strictly controlled even when there is hysteresis in the relationship between the rotational speed at the time of ascent and descent and the set distance D. Therefore, for example, the amount of air supplied to the burner of the heating furnace by the blower fan 11 is strictly controlled, and the heating temperature in the heating furnace can be strictly controlled, so that a steel material of a desired material can be manufactured.

  In the above embodiment, the correlation curves A and B are correlations between the rotational speed and the distance D. However, if the correlation curves A and B substantially indicate the distance D, for example, the drive of the drive unit 40 is used instead of the distance D. It may be expressed as a voltage value.

  In the above embodiment, the difference C between the distance D when the rotational speed of the blower fan 11 is increased and the distance D when the rotational speed is lowered at the same rotational speed is obtained. When the rotation speed is decreased to the target rotation speed E, the distance D2 is obtained by adding the difference C to the set distance D1 when the rotation speed of the blower fan 11 is increased. When the rotational speed of the blower fan 11 is increased to the target rotational speed E, the set distance D1 is used as it is. By doing this, for example, when controlling the rotational speed, it is possible to calculate both the distance D1 and the distance D2 with reference to one correlation curve A when increasing the rotational speed, so the distance D is calculated more easily. be able to.

  In the above embodiment, when the rotational speed of the blower fan 11 is decreased to the target rotational speed E, the distance D2 is obtained from the set distance D1 when the rotational speed of the blower fan 11 is increased. However, when the rotational speed of the blower fan 11 is increased to the target rotational speed E, the distance D1 may be obtained from the set distance D2 when the rotational speed of the blower fan 11 is decreased. In this case, the distance D1 is obtained by subtracting the difference C of the same target rotational speed E from the set distance D2. In this example, when the rotational speed of the blower fan 11 is lowered to the target rotational speed E, the set distance D2 is used as it is. Also in this case, when controlling the rotation speed, the distance D1 and the distance D2 can be calculated based on one correlation curve B when the rotation speed is lowered, so that the distance D can be calculated more easily. .

  FIG. 3 shows a rotational speed variation curve when the rotational speed setting of the blower fan 11 is changed from 400 rpm to 700 rpm, for example. As can be seen from this graph, it takes 10 seconds or more for the rotation speed to stabilize at 700 rpm. Thus, if it takes time to change the rotational speed, the blower fan 11 is not rotated at an appropriate rotational speed during that time, and for example, the heat treatment of the steel material in the heating furnace cannot be performed.

  Therefore, in the above embodiment, when the rotational speed of the blower fan 11 is increased to the target rotational speed E, the rotational speed is once set higher than the target rotational speed E, and then set to the target rotational speed E. You may do it. Further, when the rotational speed of the blower fan 11 is decreased to the target rotational speed E, the rotational speed may be temporarily set lower than the target rotational speed E and then set to the target rotational speed E.

  For example, as shown in FIG. 4, when the rotational speed of the blower fan 11 is changed from the current rotational speed F to a higher target rotational speed E, the rotational speed is set to a rotational speed H once higher than the target rotational speed E. To be raised. The rotational speed H is set to a speed higher than the target rotational speed E by 5% to 30% of the difference between the target rotational speed E and the current rotational speed F, for example. For example, when the current rotation speed F is 400 rpm and the target rotation speed E is 700 rpm, the rotation speed H is set to about 715 rpm to 790 rpm of 700 rpm + 300 rpm × (0.05 to 0.30). Thereafter, the setting of the rotational speed H is maintained for a predetermined time, preferably about 2 to 10 seconds, and then the rotational speed setting is returned to the target rotational speed E.

  Further, when the rotational speed of the blower fan 11 is changed from the current rotational speed F to a lower target rotational speed E as shown in FIG. 5, the rotational speed L is lower than the target rotational speed E. And then returned to the target rotational speed E. The rotational speed L is set to a speed lower than the target rotational speed E by 5% to 30% of the difference between the target rotational speed E and the current rotational speed F, for example. Further, the set time of the rotation speed L is preferably about 2 to 10 seconds.

  According to this example, since the rotational speed of the blower fan 11 is stabilized at the target rotational speed E earlier, for example, the air supply amount by the blower fan 11 is stabilized early, for example, the heating temperature in the heating furnace can be changed in a short time. It can be carried out.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be made within the scope of the ideas described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs. For example, in the said embodiment, although the motor 10 was connected to the rotating plate 22 of the magnetic coupling 12, and the ventilation fan 11 was connected to the permanent magnet plate 23, conversely, the blowing fan 11 was connected to the rotating plate 22, The motor 10 may be connected to the permanent magnet plate 23. Further, the driven device is not limited to the blower fan, and may be a pump or a dust collector used for cooling the rolling roll.

  The present invention is useful when strictly controlling the rotational speed of a driven device in a power transmission device using a magnetic coupling.

It is a schematic diagram which shows the outline of a structure of a power transmission device. It is a graph which shows the correlation curve of the distance of a rotating plate and a permanent magnet plate, and a rotational speed when raising and lowering a rotational speed. It is a graph which shows the fluctuation | variation of the rotational speed at the time of setting change of rotational speed. It is explanatory drawing which shows the example of a setting of the rotational speed when raising a rotational speed. It is explanatory drawing which shows the example of a setting of the rotational speed when reducing a rotational speed. It is a graph which shows the hysteresis about the relationship between the distance of a rotating plate and a magnet plate, and the rotational speed when raising and lowering the rotational speed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power transmission device 10 Motor 11 Blower fan 12 Magnetic coupling 22 Rotating plate 23 Permanent magnet plate D Distance between rotating plate and permanent magnet plate E Target rotational speed

Claims (4)

A magnetic plate having a rotatable magnetic plate and a magnetic coupling provided with a rotating plate that is arranged to face the magnetic plate in a non-contact manner and is rotatable by the magnetic action between the magnetic plate and the magnetic plate. In a power transmission device in which one of the plates is connected to a driving source and the other is connected to a driven device to transmit the rotational power of the driving source to the driven device via a magnetic coupling, the rotating plate and the magnet of the magnetic coupling A method of controlling the rotational speed of the driven device by adjusting the distance between the plates,
Correlation between the rotational speed when the rotational speed of the driven device is increased, the distance between the rotating plate and the magnet plate, the rotational speed when the rotational speed of the driven device is decreased, and the rotation Find the correlation between the distance between the plate and the magnet plate,
Based on the correlation, when the rotational speed of the driven device is increased to the target rotational speed, and when the rotational speed of the driven device is decreased to the target rotational speed, the rotating plate and the magnet plate A method for controlling the rotational speed of a driven device, characterized in that the distances are individually set. Find the difference between the distance between the rotating plate and the magnet plate when the rotational speed of the driven device is increased at the same target rotational speed and the distance between the rotating plate and the magnet plate when the rotational speed is decreased. Every
When the rotational speed of the driven device is decreased to the target rotational speed, the set distance between the rotary plate and the magnet plate when the rotational speed of the driven device is increased is corrected for the difference, and the rotational plate The method for controlling the rotational speed of the driven device according to claim 1, wherein a distance between the magnet plates is obtained. Find the difference between the distance between the rotating plate and the magnet plate when the rotational speed of the driven device is increased at the same target rotational speed and the distance between the rotating plate and the magnet plate when the rotational speed is decreased. Every
When the rotational speed of the driven device is increased to the target rotational speed, the set distance between the rotary plate and the magnet plate when the rotational speed of the driven device is decreased is corrected for the difference, and the rotational plate The method for controlling the rotational speed of the driven device according to claim 1, wherein a distance between the magnet plates is obtained. When increasing the rotational speed of the driven device to the target rotational speed, set the rotational speed higher than the target rotational speed, then set the target rotational speed,
When the rotational speed of the driven device is lowered to the target rotational speed, the rotational speed is once set lower than the target rotational speed, and then set to the target rotational speed. A method for controlling the rotational speed of the driven device according to any one of the above.

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