WO2017009918A1

WO2017009918A1 - Braking device for elevator hoisting machine

Info

Publication number: WO2017009918A1
Application number: PCT/JP2015/069998
Authority: WO
Inventors: 喜也鈴木
Original assignee: 三菱電機株式会社
Priority date: 2015-07-13
Filing date: 2015-07-13
Publication date: 2017-01-19

Abstract

The purpose of the present invention is to reduce collision noise by, when a brake lining (131) hits a brake drum (10), dividing the braking force and shifting the timing at which the braking force is applied. This braking device for an elevator hoisting machine according to the present invention is provided with: the brake drum (10) linked to the elevator hoisting machine; a brake part (13) that applies a brake on the brake drum (10); a first movable iron core (14) that is linked to the brake part (13) and that is moved in directions for making contact with and separating from the brake drum (10); a first urging part that restricts movement of the first movable iron core (14) in a direction for pressing the brake part (13) against the brake drum (10); a second movable iron core (18) that urges the first movable iron core (14) in a direction for pressing the brake part (13) against the brake drum (10); and a second urging part that restricts movement of the second movable iron core (18) in a direction for pressing the brake part (13) against the brake drum (10). The timing at which the movement of the second movable iron core (18) is restricted by the second urging part is set so as to be after the timing at which the movement of the first movable iron core (14) is restricted by the first urging part.

Description

Braking device for elevator hoisting machine

This invention relates to a technique for reducing collision noise when a braking device provided in an elevator hoisting machine brakes the movement of a brake drum.

In a conventional braking system for an elevator hoisting machine, a brake drum connected to the hoisting machine, a brake part that applies a braking force to the brake drum, a movable iron core to which the brake part is fixed, and a contact of the brake drum A core that moves the movable iron core so as to be positioned at a position or a non-contact position, a floating spring that supports the core, a first coil that generates a suction force between the core and the movable iron core, and the core and the movable iron core And a stroke adjusting bolt for adjusting the distance between the two.

Also, a second coil that generates a suction force that attracts the core to the body side between the body fixed to the hoist and the core is provided in the core. The number of turns of the second coil is less than that of the first coil, and the brake drum non-contact position of the brake portion is displaced in two steps when the first coil and the second coil are de-energized. With such a configuration, the collision noise when the brake drum and the brake lining collide is reduced. As described above, the elevator hoisting machine braking device is disclosed as a prior art.

JP 2013-18646 A

In the prior art, when the brake lining hits the braking surface of the brake drum, the braking force is at its maximum value, and therefore, there is a problem in that the collision sound when the brake lining hits the braking surface of the brake drum is loud, which makes passengers uncomfortable.

The present invention has been made to solve such a problem. When the brake lining hits the braking surface of the brake drum, the braking lining and the braking surface collide by dividing the braking force and shifting the timing of the operation. It aims at suppressing the collision sound of time.

A brake device for an elevator hoisting machine according to the present invention includes a brake drum connected to the elevator hoisting machine, a brake part for braking the brake drum, a brake part connected to the brake part, and moved in a direction to contact and separate from the brake drum. A movable iron core, a first urging portion for restricting the first movable iron core in a direction in which the brake portion is pressed against the brake drum, and a first urging iron core in a direction in which the brake portion is pressed against the brake drum. A second movable iron core, and a second urging portion that restricts the movement of the second movable iron core in a direction in which the brake portion is pressed against the brake drum. The second movable iron core is provided by the second urging portion. The timing at which the movement of the first movable iron core is regulated is delayed from the timing at which the movement of the first movable iron core is regulated by the first urging unit.

According to this invention, it is possible to suppress a collision sound when the lining and the braking surface of the brake drum collide.

It is a figure showing the whole elevator drive device concerning this invention. It is sectional drawing which shows the elevator hoisting machine of Embodiment 1 which concerns on this invention. It is sectional drawing which shows the one side of the brake device for elevator hoists of Embodiment 1 which concerns on this invention. It is a figure which shows control of the elevator hoisting machine of Embodiment 1 which concerns on this invention. It is sectional drawing which shows the one side of the braking device for elevator hoists of Embodiment 4 which concerns on this invention. It is a figure which shows control of the elevator hoisting machine of Embodiment 4 which concerns on this invention.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below. The present invention is not limited to the first embodiment. In Embodiment 1 of the present invention, the braking force is divided and the operation timing is shifted, so that the collision sound when the lining and the braking surface of the brake drum collide is reduced compared to the conventional apparatus.

The configuration of the elevator drive device will be described with reference to FIGS. 1 and 2.

FIG. 1 is a diagram showing an entire elevator driving apparatus according to the present invention. In FIG. 1, each structure of an elevator drive device is demonstrated. The elevator control device 1 issues a control command for moving the elevator safely and comfortably. The hoisting machine 2 is a driving machine that raises and lowers the car 3 according to a control command output by the elevator control device 1. The car 3 is for passengers to ride. The counterweight 4 is provided at a position facing the car 3 in order to balance the weight of the car 3. The hoisting rope 5 suspends and supports the counterweight 4 with the car 3 and guides the lifting and lowering of the counterweight 4 with the car 3 by driving the hoisting machine 2. The baffle wheel 6 is disposed below the hoisting machine 2 and used in an auxiliary manner in order to keep the distance between the car 3 and the counterweight 4 constant. The speed detection unit 7 detects the operation speed of the car 3 during elevator operation. Further, the speed detected by the speed detector 7 is output to the elevator control device 1. The load detection unit 8 detects the load of the car 3. The load of the car 3 detected by the load detector 8 is output to the elevator control device 1.

In the basic operation of the elevator, the speed information of the car 3 detected by the speed detector 7 and the load information of the car 3 detected by the load detector 8 are output to the elevator control device 1, and the speed information of the car 3 and the car 3 are output. The elevator control device 1 that has received the load information issues a control command to the hoist 2. When operating the elevator, the elevator control device 1 outputs an operation command to the hoisting machine 2, and the hoisting machine 2 moves up and down the counterweight 4 with the car 3 via the hoisting rope 5. When braking the elevator, the elevator control device 1 outputs a braking command to the hoisting machine 2 to stop the lifting and lowering of the car 3 and the counterweight 4.

FIG. 2 is a cross-sectional view of the elevator hoisting machine according to the present invention in a strange story on a plane perpendicular to the drive shaft. FIG. 3 is a view showing one elevator hoisting brake device in FIG. As shown in FIG. 2, the housing 9 is an outer shell. The brake drum 10 is connected to the housing 9 and rotates by receiving an external force. The braking surface 11 is provided on the brake drum 10. The braking device 12 is disposed so as to be pressed against the braking surface 11 of the brake drum 10. Further, the braking device 12 brakes the brake drum 10.

The braking device 12 will be described with reference to FIGS. The braking device 12 includes a brake unit 13, a first first movable iron core 14, a first spring 15, a first electromagnetic magnet 16, a first coil 17, a second movable iron core 18, and a second spring 19. , The second electromagnetic magnet 20, the second coil 21, and the elastic member 22.

The brake unit 13 presses against the braking surface 11 of the brake drum 10 and applies braking. The brake unit 13 includes a lining 131 and a brake shoe 132. The lining 131 is fixed to the brake shoe 132 and presses against the braking surface 11 of the brake drum 10 during braking. The brake shoe 132 is a component that stops movement by being pressed against the braking surface 11 of the rotating brake drum 10 during braking. The brake shoe 132 is mounted on the first movable iron core 14 via a connecting member, and is moved in a direction in which the brake shoe 132 is in contact with and separated from the brake drum 10 integrally with the first movable iron core 14.

The first movable iron core 14 is connected to the brake unit 13. In addition, the first movable iron core 14 is moved integrally with the brake unit 13 in a direction in which the first movable iron core 14 contacts and separates from the brake drum 10. The first spring 15 biases the first movable iron core 14 in the direction in which the brake portion 13 is pressed against the braking surface 11 of the brake drum 10 during braking. The first electromagnetic magnet 16 and the first coil 17 generate an electromagnetic force that attracts the first movable iron core 14.

The first urging unit includes a first spring 15, a first electromagnetic magnet 16, and a first coil 17. The first urging unit restricts the movement of the first movable iron core 14 in the direction in which the brake unit 13 is pressed against the brake drum 10.

The second movable iron core 18 is provided at opposing positions on both sides of the first spring 15 with the first spring 15 as a reference, and is moved in a direction in which the second movable iron core 18 contacts and separates from the brake drum 10. Further, the second movable iron core 18 biases the first movable iron core 14 in a direction in which the brake portion 13 is pressed against the braking surface 11 of the brake drum 10. The second spring 19 biases the second movable iron core 18 in a direction in which the brake portion 13 is pressed against the braking surface 11 of the brake drum 10. Due to the magnetic field generated from the second coil 21 when energized, the second movable iron core 18 resists the force of the second spring 19 and moves away from the braking surface 11 of the brake drum 10 in the second electromagnetic magnet 20. Aspirate. Further, the second spring 19, the second electromagnetic magnet 20, and the second coil 21 constitute a second urging unit. The second urging unit restricts the movement of the second movable iron core 18 in the direction in which the brake unit 13 is pressed against the brake drum 10.

The elastic member 22 is provided between the first movable iron core 14 and the second movable iron core 18. The elastic member 22 prevents the second electromagnetic magnet 20 from attracting the first movable iron core 14 via the second movable iron core 18 and also causes the second movable iron core 18 to be in the first state when energization is interrupted. The impact sound and impact that collide with the movable iron core 14 are reduced. The elastic member 22 may be a nonconductive elastic body. The elastic member 22 of the present invention uses a rubber member.

Next, the operation of the braking device for the elevator hoist will be described.

When the current flowing in the coil is interrupted (such as during a power failure), when the excitation of the coil is released, the brake portion 13 is pressed against the braking surface 11 of the brake drum 10 by the force of the spring. On the other hand, when a current is passed through the coil, the movable iron core is attracted in a direction away from the braking surface 11 of the brake drum 10 against the force of the spring by the magnetic field generated from the coil. In this manner, a braking state / non-braking state can be created by controlling current interruption / energization in the coil.

In Embodiment 1 of the present invention, when the elevator normally operates, the first coil 15 and the second coil 21 are excited to resist the force of the first spring 15 and the second spring 19. The first movable iron core 14 is attracted to the first electromagnetic magnet 16, and the second movable iron core 18 is attracted to the second electromagnetic magnet 20. In this case, the brake unit 13 is separated from the brake drum 10 and enters a non-braking state.

When the elevator is braked (eg, during a power failure), the first coil 15 and the second movable core 18 are moved by the spring force by cutting off the energization of the first coil 15 and the second coil 21. The brake unit 13 is moved in a direction in which the brake unit 13 is pressed against the braking surface 11 of the brake drum 10. In this case, a braking force is applied to the brake drum 10, the rotation of the brake drum 10 is braked, and a braking state is established.

In the first embodiment, at the time of braking, the elevator control device 1 controls the first electromagnetic magnet 16 so as to cut off the current earlier than the second electromagnetic magnet 20. For this reason, the energization interruption timing of the first electromagnetic magnet 16 and the second electromagnetic magnet 20 is shifted. Thereby, the lining 131 collides with the braking surface 11 of the brake drum 10 with a force smaller than the necessary braking force. Since the second movable iron core 18 hits the first movable iron core 14 via the elastic member 22 with the remaining force necessary to reach the necessary braking force, the impact and the collision sound are reduced.

Here, in the operation process in which the elevator is braked, the braking force applied to the brake drum 10 is divided into two times, and the elevator control device 1 controls the braking device 12. The elevator control device 1 outputs a cutoff signal to the first coil 15 and then outputs a cutoff signal to the second coil 19. The first spring 15 is actuated before the second spring 19 due to the time difference between the cutoff signals output from the elevator control device 1. As a result, the brake unit 13 gently collides with the braking surface 11 of the brake drum 10. Further, by providing the elastic member 22 between the first movable iron core 14 and the second movable iron core 18, the impact and the collision sound are reduced. For example, when the speed and weight of the car 3 are large, the inertial force generated in the car 3 is large when the elevator is suddenly stopped, and the shut-off timing of the first coil 15 and the second coil 21 is shifted. It is smaller than the inertial force generated when the car is suddenly stopped, and the impact on the car 3 can be reduced.

In the first embodiment, with the first coil 15 as a reference, the second movable iron core 18 and the second urging portion are provided at opposing positions on both sides of the first coil. An example in which the braking force to be applied is divided into two times has been described. However, the configuration and arrangement described above are not limited. For example, when a pair or more of the second movable iron core 18 and the second urging portion are provided at opposite positions on both sides of the first coil with the first coil 15 as a reference, the second movable iron core 18 and the second biasing portion are applied to the brake drum 10. The braking force can be divided into multiple times.

In the first embodiment, the timing at which the movement of the second movable iron core 18 is regulated by the second urging unit is delayed from the timing at which the movement of the first movable iron core is regulated by the first urging unit. Thereby, the collision sound when the brake part 13 collides with the brake drum 10 can be reduced from the conventional one.

Embodiment 2. FIG.
The second embodiment of the present invention will be described below with reference to FIGS. Constituent elements common to the first embodiment are denoted by the same reference numerals and description thereof is omitted. In the second embodiment, the resistance values of the discharge resistances of the first coil 15 and the second coil 19 are different.

FIG. 4 is a diagram showing control of the elevator hoist apparatus according to the first embodiment of the present invention. As shown in FIG. 4, the control circuit of the hoisting machine 2 includes an elevator control device 1, a power supply unit 23, a power cutoff circuit 24, a first discharge resistor 25, and a second discharge resistor 26. .

The power supply unit 23 supplies a predetermined current. The power cutoff circuit 24 receives the power cutoff command from the elevator control device 1 and shuts off the power circuit. The first discharge resistor 25 is a discharge resistor connected in parallel to both ends of the first coil 17. The first discharge resistor 25 is connected in parallel with the first coil 17 after being connected in series with the diode. Those connected in parallel are connected in series with the power cutoff circuit 24. The second discharge resistor 26 is connected in series with the diode and then connected in parallel with the second coil 21. Those connected in parallel are connected in series with the power cutoff circuit 24. The first discharge resistor 25 is connected in parallel with the second discharge resistor 26, and the resistance value of the first discharge resistor 25 is set larger than the resistance value of the second discharge resistor 26.

Next, the operation of the braking device of the elevator hoisting machine will be described with reference to FIG.

When the elevator is abnormal, the elevator control device 1 outputs a braking command to the hoisting machine 2. Thereby, the braking device 12 operates and the power supply to the first coil 17 and the second coil 21 is interrupted. As a result, the electric power accumulated in the first coil 17 is consumed by the first discharge resistor 25, and the electric power accumulated in the second coil 21 is consumed by the second discharge resistor 26. Since the resistance value of the first discharge resistor 25 is set to be larger than the resistance value of the second discharge resistor 26, the power of the first electromagnetic magnet 16 disappears earlier than the power of the second electromagnetic magnet 20 when the energization is cut off. . As a result, the first electromagnetic magnet 16 is cut off earlier than the second electromagnetic magnet 20.

By the above operation, the lining 131 collides with the braking surface 11 with a force smaller than the required braking force. Since the second movable iron core 18 hits the first movable iron core 14 via the elastic member 22 with the remaining force necessary to reach the necessary braking force, the impact and the collision sound are reduced.

In the second embodiment, similar to the first embodiment, the collision sound when the lining 131 collides with the braking surface 11 can be reduced as compared with the conventional one. Also, the impact on the braking surface 11 and the car 3 can be reduced as compared with the conventional one.

Embodiment 3 FIG.
The third embodiment of the present invention will be described below with reference to FIGS. Constituent elements common to the first embodiment are denoted by the same reference numerals and description thereof is omitted. In the third embodiment, the operation of the braking device is controlled by supplying electric power to the second coil.

In FIG. 1, the speed detector 7 is provided directly or in the vicinity of the hoisting machine 2. The speed detector 7 uses a speed governor, a speed governor encoder (not shown), and the like, and acquires the speed signal of the car 3 from the speed governor encoder according to the movement of the car 3. The load detection unit 8 is provided in the car 3 and acquires the load of the car 3.

Next, the operation of the braking device 12 of the elevator hoist 2 will be described with reference to FIG.

When the elevator is operated, the elevator controller 1 outputs signals of the car load detected by the load detector 8 and the car speed detected by the speed detector 7 to the elevator controller 1. The elevator control device 1 controls selection of ON or OFF of the power supply to the second coil 21 according to the received load of the car 3 and the speed of the car 3. When the load and speed of the car 3 are large, the power supply to the second coil 21 is turned off. When the load and speed of the car 3 are small, the power supply to the second coil 21 is turned on.

In the third embodiment, the brake unit 13 is caused to collide with the brake drum 10 at a stroke with the entire braking force or the brake unit 13 is braked with a part of the braking force based on the detected information on the load and speed of the car 3. The drum 10 can be made to collide and the remaining braking force can be selected to be applied later. For example, when the load and speed of the car 3 are small, the elevator controller 1 turns on the power supply to the second coil 21. When the elevator is braked, the second movable iron core 18 is attracted by the second electromagnetic magnet 20 due to the excitation of the second coil 21, so that energization only to the first coil 15 is cut off. The brake unit 13 is caused to collide with the brake drum 10 with a partial braking force. After that, the energization of the second coil 21 is interrupted, so that the second movable iron core 18 hits the first movable iron core 14 via the elastic member 22, so that the remaining part of the braking force remains. Apply the power of.

When the load and speed of the car 3 are large, the elevator controller 1 turns off the power supply to the second coil 21. When the elevator is braked, the energization of the first coil 15 is cut off, so that the force of the first spring 16 and the second spring 19 causes the brake unit 13 to be moved to the brake drum 10 at a stroke with the full braking force. Collide.

In the case of the conventional invention, at the time of an emergency stop of the elevator, the lining 131 collides with the braking surface 11 at a stroke with all the braking force without depending on the load and speed of the car 3. In the third embodiment, since the power supply of the coil is controlled based on the detected information on the load and speed of the car 3, the braking force can be applied appropriately depending on the driving situation. 13, the braking surface 11, and the impact on the car 3 can be reduced.

Embodiment 4 FIG.
The fourth embodiment of the present invention will be described below with reference to FIGS. Constituent elements common to the first embodiment are denoted by the same reference numerals and description thereof is omitted. In the fourth embodiment, the second movable iron core 18, the second electromagnetic magnet 20, the second coil 21, and the second discharge resistor 26 of the first embodiment are made plural.

FIG. 5 is a diagram showing the entire elevator drive apparatus according to the fourth embodiment of the present invention. As shown in FIG. 5, the braking device 12 includes a first movable iron core 14, a first urging unit, two second movable iron cores a 18, two second urging units a, and two second urging units. It has a movable iron core b27 and two second urging portions b. The first urging unit includes a first spring 15, a first electromagnetic magnet 16, and a first coil 17. The second urging portion a includes a second spring a19, a second electromagnetic magnet a20, and a second coil a21. The second urging portion b includes a second spring b28, a second electromagnetic magnet b29, and a second coil b30.

FIG. 6 is a diagram showing control of the elevator hoist apparatus according to the fourth embodiment of the present invention. The first discharge resistor 25 connected in parallel to both ends of the first coil 17 is connected in series with the diode and then connected in parallel with the first coil 17. The second discharge resistor a26 connected in parallel to both ends of the second coil a21 is connected in series with the diode and then connected in parallel with the second coil a21. The second discharge resistor b31 connected in parallel to both ends of the second coil b30 is connected in series with the diode and then connected in parallel with the second coil b30. The resistance value of the first discharge resistor 25 is set larger than the resistance value of the second discharge resistor a26. The resistance value of the second discharge resistor a26 is set larger than the resistance value of the second discharge resistor b31.

Next, the operation of the braking device for the elevator hoisting machine will be described with reference to FIGS.

Since the resistance values are set in the order of the first discharge resistor 25, the second discharge resistor a26, and the second discharge resistor b31, the electric power of the first electromagnetic magnet 16 is the second electromagnetic magnet a20 when the energization of the elevator is cut off. The power of the second electromagnetic magnet a20 disappears earlier than the power of the second electromagnetic magnet b29. Thereby, the braking force is more finely divided. Thereby, in this Embodiment 4, the impact to the braking surface 11 and the cage | basket | car 3 at the time of an emergency stop can be reduced rather than Embodiment 2. FIG. Here, the configuration and arrangement of the fourth embodiment are not limited. For example, in addition to providing the second movable iron cores a and b and the second urging portions a and b, the second movable iron core c and the second urging portion c may be provided.

Embodiment 5 FIG.
The fifth embodiment of the present invention will be described below with reference to FIGS. Constituent elements common to the fourth embodiment are denoted by the same reference numerals and description thereof is omitted. In the fifth embodiment, the operation of the braking device is controlled by supplying electric power to the second coil.

During elevator operation, information on the car load detected by the load detection unit 8 and the car speed detected by the speed detection unit 7 is output to the elevator control device 1. The elevator control device 1 controls the selection of ON or OFF of the power supply to the second coil a21 and the second coil b30 according to the received load of the car 3 and the speed of the car 3. When the load and speed of the car 3 are large, the power supply to the second coil a21 and the second coil b30 is turned off. When the load and speed of the car 3 are small, the power supply to the second coil a21 and the second coil b30 is turned ON.

Thereby, in the fifth embodiment, when the elevator stops suddenly, the inertial force and the impact on the braking surface and the car can be reduced by controlling the power supply of the coil. Here, the configuration and arrangement of the fifth embodiment are not limited. For example, in addition to providing the second movable iron cores a and b and the second urging portions a and b, the second movable iron core c and the second urging portion c may be provided.

Further, any embodiment from the above-described Embodiment 1 to Embodiment 5 may be combined.

DESCRIPTION OF SYMBOLS 1 Elevator control device, 2 hoisting machine, 3 cages, 4 balance weight, 5 hoisting rope, 6 sled wheel, 7 speed detection unit, 8 load detection unit, 9 housing, 10 brake drum, 11 braking surface, 12 braking device , 13 brake part, 131 lining, 132 brake shoe, 14 first movable iron core, 15 first spring, 16 first electromagnetic magnet, 17 first coil, 18 second movable iron core, 19 second spring (Second spring a of the fourth and fifth embodiments), 20 second electromagnetic magnet (second electromagnetic magnet a of the fourth and fifth embodiments), 21 second coil (implemented) Second coil a), 22 elastic member, 23 power supply system, 24 power supply cutoff circuit, 25 first discharge resistance, 26 second Discharge resistor, 27 a second moving iron core b, 28 a second spring b, 29 a second electromagnet b, 30 a second coil b, 31 a second discharge resistor b

Claims

A brake drum connected to an elevator hoist,
A brake unit for braking the brake drum;
A first movable iron core connected to the brake portion and moved in a direction of contacting and separating from the brake drum;
A first urging portion for restricting movement of the first movable iron core in a direction in which the brake portion is pressed against the brake drum;
A second movable iron core that urges the first movable iron core in a direction in which the brake portion is pressed against the brake drum;
A second urging portion for restricting movement of the second movable iron core in a direction in which the brake portion is pressed against the brake drum,
The timing at which the movement of the second movable iron core is regulated by the second urging unit is delayed from the timing at which the movement of the first movable iron core is regulated by the first urging unit. A brake device for an elevator hoisting machine.
The first urging portion is separated from the brake drum against the first spring and a first spring that urges the first movable iron core in a direction in which the brake portion is pressed against the brake drum. A first electromagnetic magnet that attracts the first movable iron core in a direction, and a first coil that generates an electromagnetic force that attracts the first movable iron core;
The second urging portion separates the second movable iron core from the brake drum against the second spring, and a second spring that urges the second movable iron core in a direction in which the brake portion is pressed against the brake drum. The elevator according to claim 1, further comprising: a second electromagnetic magnet that attracts the second movable iron core in a direction, and a second coil that generates an electromagnetic force that attracts the second movable iron core. Brake device for hoisting machine.
The elevator hoisting machine braking device according to claim 1 or 2, further comprising an elastic member provided between the first movable iron core and the second movable iron core.
A first discharge resistor connected in parallel to the first coil;
A second discharge resistor connected in parallel to the second coil,
The elevator hoisting machine braking device according to claim 2, wherein a resistance value of the first discharge resistor is larger than a resistance value of the second discharge resistor.
The elevator hoisting machine braking device according to claim 2, wherein the first electromagnetic magnet cuts off electricity earlier than the second electromagnetic magnet.
A speed detector for detecting the speed of the elevator car;
A load detector for detecting the load of the elevator car;
An elevator controller that controls the supply of electric power to the second coil based on the speed detected by the speed detector and the load detected by the load detector;
The elevator hoisting machine braking device according to claim 2, further comprising:
The elevator hoisting machine braking device according to claim 1, wherein there are a plurality of the second urging portions.
The elevator hoisting machine braking device according to claim 1, wherein a plurality of the second movable iron cores are provided.