Permanent electromagnet system, control device, and control method

Abstract

A permanent electromagnet system (16) comprises a permanent electromagnet (10) and a control device (14). The permanent electromagnet includes first permanent magnets (20), a second permanent magnet (22) having a variable magnetization direction, and coils (24). The control device includes an energization control unit (50) that brings the permanent electromagnet into a released state by causing a first current (I1) of the first magnitude (Ie) to flow through the coil, and brings the permanent electromagnet into an adsorbed state by causing a second current (I2) of the second magnitude (If) to flow through the coil in a direction opposite to that of the first current.

Description

Permanent Magnet System, Control Device, and Control Method

[0001] The present disclosure relates to a permanent magnet system, a control device, and a control method.

[0002] Japanese Patent Application Laid-Open No. 60-130106 discloses an adsorption device including an alnico magnet, an exciting coil disposed around the alnico magnet, and a ferrite magnet disposed on the outer periphery of the exciting coil. When a direct current is applied to the exciting coil and the magnetization direction of the alnico magnet becomes the same as the magnetization direction of the ferrite magnet, the adsorption device adsorbs a magnetic material even when the energization of the exciting coil is cut off. When a direct current in the reverse direction is applied to the exciting coil and the magnetization direction of the alnico magnet becomes opposite to the magnetization direction of the ferrite magnet, the adsorption force of the adsorption device does not occur even when the energization of the exciting coil is cut off.

[0003] Reduction of power consumption in permanent magnets is eagerly awaited.

[0004] The present disclosure aims to solve the above-described problems.

[0005] A first aspect of the present disclosure is a permanent magnet system including a permanent magnet capable of switching between an adsorption state in which a magnetic material can be adsorbed and a release state in which the adsorption state is released, and a control device that controls the permanent magnet. The permanent magnet includes a first permanent magnet having a fixed magnetization direction, a second permanent magnet whose magnetization direction can change, and a coil wound around the outer periphery of the second permanent magnet. The control device has an energization control unit that makes the magnetization direction of the second permanent magnet face a first magnetization direction by flowing a first current of a first magnitude through the coil, puts the permanent magnet in the release state, and makes the magnetization direction of the second permanent magnet face a second magnetization direction opposite to the first magnetization direction by flowing a second current of a second magnitude in a direction opposite to the first current through the coil, putting the permanent magnet in the adsorption state, and the first magnitude is smaller than the second magnitude.

[0006] A second aspect of the present disclosure is a control device for controlling a permanent electromagnet that has a first permanent magnet with a fixed magnetization direction, a second permanent magnet whose magnetization direction can be changed, and a coil wound around the outer circumference of the second permanent magnet, and which can switch between an adsorption state in which a magnetic material can be attracted and a release state in which the adsorption state is released, wherein the control device includes an energizing control unit that causes the magnetization direction of the second permanent magnet to be directed in the first magnetization direction by passing a first current of a first magnitude through the coil, thereby releasing the permanent electromagnet, and causes the magnetization direction of the second permanent magnet to be directed in the second magnetization direction opposite to the first magnetization direction by passing a second current of a second magnitude in the opposite direction to the first magnetization direction through the coil, thereby releasing the permanent electromagnet, wherein the first magnitude is smaller than the second magnitude.

[0007] A third aspect of the present disclosure is a control method for controlling a permanent electromagnet that has a first permanent magnet with a fixed magnetization direction, a second permanent magnet whose magnetization direction can be changed, and a coil wound around the outer circumference of the second permanent magnet, and which can switch between an adsorption state in which a magnetic material can be adsorbed and a release state in which the adsorption state is released, comprising: a release control step of passing a first current of a first magnitude through the coil to orient the magnetization direction of the second permanent magnet to a first magnetization direction, thereby putting the permanent electromagnet into the release state; and an adsorption control step of passing a second current of a second magnitude in the opposite direction to the first current through the coil to orient the magnetization direction of the second permanent magnet to a second magnetization direction opposite to the first magnetization direction, thereby putting the permanent electromagnet into the adsorption state, wherein the first magnitude is smaller than the second magnitude.

[0008] According to this disclosure, the power consumption of permanent electromagnets can be reduced.

[0009] Figure 1 illustrates a permanent electromagnet system comprising a permanent electromagnet, a connecting circuit, and a control device. Figure 2A illustrates the magnetic flux generated in a permanent electromagnet in a released state, where the adsorption state capable of attracting a magnetic material has been released. Figure 2B illustrates the magnetic flux generated in a permanent electromagnet in an adsorption state. Figure 3 shows an example of the configuration of a connecting circuit. Figure 4 shows an example in which the current flowing through the coil and the adsorption force of the permanent electromagnet change in response to the voltage applied to the coil. Figure 5 is a flowchart illustrating a control processing procedure for controlling a permanent electromagnet. Figure 6 shows an example in which the current flowing through the coil and the adsorption force of the permanent electromagnet change in response to the voltage applied to the coil. Figure 7 shows an example in which the current flowing through the coil and the adsorption force of the permanent electromagnet change in response to the voltage applied to the coil.

[0010] Figure 1 illustrates a permanent electromagnet system 16 having a permanent electromagnet 10, a connection circuit 12, and a control device 14. The control device 14 controls the permanent electromagnet 10. In the permanent electromagnet 10, in response to the control of the permanent electromagnet 10 by the control device 14, the permanent electromagnet 10 can switch between an adsorption state in which it can attract a magnetic material W and a released state in which the adsorption state is released.

[0011] The permanent electromagnet 10 includes a first permanent magnet 20 with a fixed magnetization direction, a second permanent magnet 22 whose magnetization direction can be changed, a coil 24, a yoke 26, and a non-magnetic material 28. The first permanent magnet 20 is a neodymium magnet containing, for example, neodymium in addition to iron. The second permanent magnet 22 is an alnico magnet containing, for example, aluminum, nickel, and cobalt in addition to iron.

[0012] In this embodiment, as shown in Figure 1, the first permanent magnet 20 and the second permanent magnet 22 are arranged adjacent to each other. The cylindrical first permanent magnet 20 covers the outer surface of the cylindrical second permanent magnet 22. That is, the second permanent magnet 22 is housed in the hollow part of the first permanent magnet 20. The magnetization direction of the first permanent magnet 20 and the magnetization direction of the second permanent magnet 22 are parallel to each other, as will be described later using Figures 2A and 2B.

[0013] Furthermore, the first permanent magnet 20 and the second permanent magnet 22 do not necessarily have to be placed adjacent to each other. The first permanent magnet 20 and the multiple second permanent magnets 22 included in the permanent electromagnet 10 may be arranged such that the magnetization direction of the first permanent magnet 20 intersects with the respective magnetization directions of the second permanent magnets 22.

[0014] The coil 24 is wound around the outer circumference of the second permanent magnet 22. In this embodiment, as shown in Figure 1, the coil 24 is wound around the outer circumference of the first permanent magnet 20, which is located outside the second permanent magnet 22. The yoke 26 houses the first permanent magnet 20, the second permanent magnet 22, and the coil 24 inside. The yoke 26 is made of ferromagnetic steel and allows magnetic flux corresponding to the magnetic force generated by the permanent electromagnet 10 to pass through it.

[0015] The yoke 26 has a top yoke 26t, a bottom yoke 26b, and an outer yoke 26u. The top yoke 26t and bottom yoke 26b extend in a direction intersecting the magnetization directions of the first permanent magnet 20 and the second permanent magnet 22. The outer yoke 26u is arranged to surround the first permanent magnet 20, the second permanent magnet 22, and the coil 24, and extends in a direction parallel to the magnetization directions of the first permanent magnet 20 and the second permanent magnet 22. The top yoke 26t forms an adsorption surface on which the permanent electromagnet 10 attracts the magnetic material W.

[0016] A non-magnetic material 28 is placed between the top yoke 26t and the outer yoke 26u. The non-magnetic material 28 is made of, for example, stainless steel.

[0017] The coil 24 is electrically connected to the power supply 30 via a connection circuit 12. The connection circuit 12 is a circuit that allows current from the power supply 30 to flow through the coil 24. An example of the configuration of the connection circuit 12 will be described later with reference to Figure 3. The power supply 30 is a DC power supply that supplies current to the coil 24.

[0018] The control device 14 operates the connection circuit 12, applying a voltage from the power supply 30 to the coil 24, causing current to flow through the coil 24. The magnetization direction of the second permanent magnet 22 can change depending on the direction of the current flowing through the coil 24. For example, after a negative voltage, the first voltage V1, is applied to the coil 24 and a negative current flows through the coil 24, the magnetization direction of the second permanent magnet 22 will be in the first magnetization direction D1. Even after the current stops, the magnetization direction of the second permanent magnet 22 will remain in the first magnetization direction D1. The magnetization direction of the first permanent magnet 20 is fixed to be in the second magnetization direction D2. The second magnetization direction D2 is in the opposite direction to the first magnetization direction D1.

[0019] After a second positive voltage V2 is applied to coil 24 and a positive current flows through coil 24, the magnetization direction of the second permanent magnet 22 is oriented towards the second magnetization direction D2. Even after the current stops, the magnetization direction of the second permanent magnet 22 is maintained at the second magnetization direction D2. The magnetization direction of the second permanent magnet 22 will be described later using Figures 2A and 2B.

[0020] The control device 14 includes an arithmetic unit 40 and a storage unit 42. The arithmetic unit 40 includes a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). In other words, the arithmetic unit 40 includes processing circuitry. The storage unit 42 includes volatile memory such as RAM (Random Access Memory) and non-volatile memory such as ROM (Read Only Memory) or flash memory. The volatile memory is used as the working memory of the processor. The non-volatile memory stores programs executed by the processor and other necessary data.

[0021] The calculation unit 40 includes a power supply control unit 50 and a power supply control unit 52. The power supply control unit 50 and the power supply control unit 52 are realized when the calculation unit 40 executes a program stored in the storage unit 42. The power supply control unit 50 and the power supply control unit 52 may be realized by integrated circuits such as ASICs (Application Specific Integrated Circuits) or FPGAs (Field Programmable Gate Arrays), or by electronic circuits including discrete devices.

[0022] The energization control unit 50 can supply a first current I1 of a first magnitude Ie to the coil 24, as will be described later using Figure 4. This allows the magnetization direction of the second permanent magnet 22 to be directed towards the first magnetization direction D1. In this case, the permanent electromagnet 10 is in a deactivated state, as will be described later using Figure 2A. In other words, the energization control unit 50 can deactivate the permanent electromagnet 10.

[0023] The energization control unit 50 can supply a second current I2 with a second magnitude If to the coil 24 in the opposite direction to the first current I1, as will be described later using Figure 4. This allows the magnetization direction of the second permanent magnet 22 to be directed towards the second magnetization direction D2, which is opposite to the first magnetization direction D1. In this case, as will be described later using Figure 2B, the permanent electromagnet 10 is in an attracted state. Note that, as will be described later using Figure 4, the first magnitude Ie of the first current I1 is smaller than the second magnitude If of the second current I2.

[0024] The power control unit 52 can change the applied voltage that the power supply 30 applies to the coil 24. Therefore, in response to the control by the power control unit 52, the power supply 30 can apply a first voltage V1, which will be described later using Figure 4, to the coil 24, and can also apply a second voltage V2, which will be described later using Figure 4, to the coil 24.

[0025] When a first voltage V1 is applied to the coil 24, the power control unit 52 controls the power supply 30 to set the output voltage of the power supply 30 to the first voltage V1. When a second voltage V2 is applied to the coil 24, the power control unit 52 controls the power supply 30 to set the output voltage of the power supply 30 to the second voltage V2. In this embodiment, the power control unit 52 changes the magnetization direction of the second permanent magnet 22 by changing the applied voltage that the power supply 30 applies to the coil 24.

[0026] Specifically, when the energization control unit 50 directs the magnetization direction of the second permanent magnet 22 towards the first magnetization direction D1, it operates the connection circuit 12 to apply a first voltage V1 to the coil 24 for a first time T1. As a result, a first current I1 of a first magnitude Ie flows through the coil 24. In this case, the permanent electromagnet 10 is in a deactivated state.

[0027] After the first voltage V1 is applied to the coil 24 for a first time T1, the energizing control unit 50 operates the connection circuit 12 to stop the application of the first voltage V1 to the coil 24. In other words, the energizing control unit 50 stops the energizing of the coil 24. In this case, the first current I1 no longer flows through the coil 24. Even after the energizing of the coil 24 is stopped, the magnetization direction of the second permanent magnet 22 is maintained in the first magnetization direction D1. Therefore, the disengaged state of the permanent electromagnet 10 is maintained.

[0028] When the energization control unit 50 directs the magnetization direction of the second permanent magnet 22 to the second magnetization direction D2, it operates the connection circuit 12 to apply a second voltage V2 to the coil 24 for a second time T2. As a result, a second current I2 of second magnitude If flows through the coil 24. In this case, the permanent electromagnet 10 is in an attracted state.

[0029] After the second voltage V2 is applied to the coil 24 for a second time T2, the energization control unit 50 operates the connection circuit 12 to stop the application of the second voltage V2 to the coil 24. In other words, the energization control unit 50 stops the energization of the coil 24. In this case, the second current I2 no longer flows through the coil 24. Even after the energization of the coil 24 is stopped, the magnetization direction of the second permanent magnet 22 is maintained in the second magnetization direction D2. Therefore, the attractive state of the permanent electromagnet 10 is maintained.

[0030] Figure 2A illustrates the magnetic flux B generated in a permanent electromagnet 10 that is in a released state, meaning it is no longer able to attract the magnetic material W. As described above, the magnetization direction of the first permanent magnet 20 is fixed to the second magnetization direction D2. When a negative voltage, the first voltage V1, is applied to the coil 24, the magnetization direction of the second permanent magnet 22 becomes the first magnetization direction D1. The second magnetization direction D2 is in the opposite direction to the first magnetization direction D1. In this case, the permanent electromagnet 10 is in a released state. The principle of why the permanent electromagnet 10 is in a released state when the magnetization direction of the second permanent magnet 22 is the first magnetization direction D1 will be explained below.

[0031] When the magnetization direction of the second permanent magnet 22 is oriented in the first magnetization direction D1, the north pole of the first permanent magnet 20 and the south pole of the second permanent magnet 22 are in close proximity to each other. Also, the south pole of the first permanent magnet 20 and the north pole of the second permanent magnet 22 are in close proximity to each other. Because the first permanent magnet 20 and the second permanent magnet 22 attract each other, the permanent electromagnet 10 is in a stable state.

[0032] The magnetic flux B entering from the south pole and exiting from the north pole of the first permanent magnet 20 passes through the top yoke 26t and enters the south pole of the second permanent magnet 22. The magnetic flux B entering from the south pole and exiting from the north pole of the second permanent magnet 22 passes through the bottom yoke 26b and enters the south pole of the first permanent magnet 20. In other words, all of the magnetic flux B passing through the first permanent magnet 20 and the second permanent magnet 22 is confined within the permanent electromagnet 10. Since the magnetic flux B does not escape outside the top yoke 26t, the magnetic force of the permanent electromagnet 10 does not extend outside the permanent electromagnet 10. In this case, the permanent electromagnet 10 does not possess an attractive force and therefore does not attract the magnetic material W. Consequently, the permanent electromagnet 10 is in a released state.

[0033] Figure 2B illustrates the magnetic flux B generated in the permanent electromagnet 10 when it is in an attracted state. As described above, the magnetization direction of the first permanent magnet 20 is fixed to the second magnetization direction D2. When a second voltage V2, which is a positive voltage, is applied to the coil 24, the magnetization direction of the second permanent magnet 22 becomes the same as the magnetization direction of the first permanent magnet 20, which is the second magnetization direction D2. In that case, the permanent electromagnet 10 is in an attracted state. The principle of why the permanent electromagnet 10 is in an attracted state when the magnetization direction of the second permanent magnet 22 is facing the second magnetization direction D2 will be explained below.

[0034] When the magnetization direction of the second permanent magnet 22 is oriented in the second magnetization direction D2, the north pole of the first permanent magnet 20 and the north pole of the second permanent magnet 22 are in close proximity to each other. Also, the south pole of the first permanent magnet 20 and the south pole of the second permanent magnet 22 are in close proximity to each other. Because the first permanent magnet 20 and the second permanent magnet 22 repel each other, the permanent electromagnet 10 is in an unstable state.

[0035] The magnetic flux B entering from the south pole and exiting from the north pole of the first permanent magnet 20 passes through the top yoke 26t and enters the magnetic material W, moving away from the north pole of the adjacent second permanent magnet 22. The magnetic flux B that has passed through the magnetic material W further passes through the outer yoke 26u and bottom yoke 26b and enters the south pole of the first permanent magnet 20. The magnetic flux B entering from the south pole and exiting from the north pole of the second permanent magnet 22 passes through the top yoke 26t and enters the magnetic material W, moving away from the north pole of the adjacent first permanent magnet 20. The magnetic flux B that has passed through the magnetic material W further passes through the outer yoke 26u and bottom yoke 26b and enters the south pole of the second permanent magnet 22.

[0036] In other words, all the magnetic flux B passing through the first permanent magnet 20 and all the magnetic flux B passing through the second permanent magnet 22 exit the top yoke 26t. Therefore, the magnetic force of the permanent electromagnet 10 extends outside the permanent electromagnet 10. In this case, the permanent electromagnet 10 possesses an attractive force and attracts the magnetic material W. Thus, the permanent electromagnet 10 is in an attracted state.

[0037] The control that changes the state of the permanent electromagnet 10 from a released state to an attracted state by applying a second voltage V2 to the coil 24 for a second time T2 is, as described above, a control that changes the state of the permanent electromagnet 10 from a stable state to an unstable state. In response to the second voltage V2 applied to the coil 24 for a second time T2, a second current I2 of second magnitude If flows through the coil 24.

[0038] The control that changes the state of the permanent electromagnet 10 from an attracted state to a released state by applying a first voltage V1 to the coil 24 for a first time T1 is, as described above, a control that changes the state of the permanent electromagnet 10 from an unstable state to a stable state. In response to the first voltage V1 applied to the coil 24 for a first time T1, a first current I1 of first magnitude Ie flows through the coil 24.

[0039] Therefore, the first magnitude Ie of the first current I1 that flows through the coil 24 to stabilize the permanent electromagnet 10 can be smaller than the second magnitude If of the second current I2 that flows through the coil 24 to destabilize the permanent electromagnet 10. An example in which the first magnitude Ie of the first current I1 is smaller than the second magnitude If of the second current I2 will be described later using Figure 4.

[0040] Figure 3 shows an example of the configuration of the connection circuit 12. The connection circuit 12 is composed of an H-bridge that includes multiple switches. The multiple switches included in the connection circuit 12 are the first switch SW1, the second switch SW2, the third switch SW3, and the fourth switch SW4 shown in Figure 3.

[0041] The first switch SW1 and the second switch SW2 are connected in series from the positive terminal to the negative terminal of the power supply 30. The third switch SW3 and the fourth switch SW4 are connected in series from the positive terminal to the negative terminal of the power supply 30. One end Pa of the coil 24 is electrically connected between the first switch SW1 and the second switch SW2. The other end Pb of the coil 24 is electrically connected between the third switch SW3 and the fourth switch SW4.

[0042] In other words, a first switch SW1 is interposed between the positive terminal of the power supply 30 and one end Pa of the coil 24. A second switch SW2 is interposed between the negative terminal of the power supply 30 and one end Pa of the coil 24. A third switch SW3 is interposed between the positive terminal of the power supply 30 and the other end Pb of the coil 24. A fourth switch SW4 is interposed between the negative terminal of the power supply 30 and the other end Pb of the coil 24.

[0043] When the energization control unit 50 of the control device 14 operates the connection circuit 12 to apply a voltage from the power supply 30 to the coil 24, a current flows through the coil 24. In the present embodiment, the direction in which the current flows from one end Pa to the other end Pb of the coil 24 is defined as the positive direction. In that case, the second voltage V2, which is a positive voltage, is applied to the coil 24, and one end Pa of the coil 24 is at a higher potential than the other end Pb. The direction in which the current flows from the other end Pb to one end Pa of the coil 24 is defined as the negative direction. In that case, the first voltage V1, which is a negative voltage, is applied to the coil 24, and the other end Pb of the coil 24 is at a higher potential than one end Pa.

[0044] Suppose that the energization control unit 50 operates the connection circuit 12 to turn on the first switch SW1 and the fourth switch SW4 and turn off the second switch SW2 and the third switch SW3. In that case, the second voltage V2, which is a positive voltage, is applied to the coil 24, and a current in the positive direction flows through the coil 24. When the second voltage V2 is applied to the coil 24 for the second time period T2, the magnetization direction of the second permanent magnet 22 faces the second magnetization direction D2. The permanent magnet 10 is in the attracted state.

[0045] After the second time period T2 has elapsed, the energization control unit 50 turns off the first switch SW1 and the fourth switch SW4. Although the current no longer flows through the coil 24, the magnetization direction of the second permanent magnet 22 maintains the second magnetization direction D2, and the attracted state of the permanent magnet 10 is maintained.

[0046] Suppose that the energization control unit 50 operates the connection circuit 12 to turn on the second switch SW2 and the third switch SW3 and turn off the first switch SW1 and the fourth switch SW4. In that case, the first voltage V1, which is a negative voltage, is applied to the coil 24, and a current in the negative direction flows through the coil 24. When the first voltage V1 is applied to the coil 24 for the first time period T1, the magnetization direction of the second permanent magnet 22 faces the first magnetization direction D1. The permanent magnet 10 is in the released state. By operating the connection circuit 12, the attracted state and the released state of the permanent magnet 10 can be easily switched.

[0047] After the first time T1 has elapsed, the energization control unit 50 turns off the second switch SW2 and the third switch SW3. Although the current no longer flows through the coil 24, the magnetization direction of the second permanent magnet 22 maintains the first magnetization direction D1, and the released state of the permanent electromagnet 10 is maintained.

[0048] FIG. 4 is a diagram showing an example in which the current flowing through the coil 24 and the attracting force of the permanent electromagnet 10 change according to the voltage applied to the coil 24. In the permanent electromagnet 10 in the released state, at time zero, the power supply control unit 52 of the control device 14 controls the power supply 30 to set the output voltage of the power supply 30 to the second voltage V2. The energization control unit 50 operates the connection circuit 12 to continuously apply the second voltage V2 to the coil 24 for the second time T2. The value of the second voltage V2, which is a positive voltage, is Vf.

[0049] During the second time T2 from time zero, the magnitude of the current flowing through the coil 24 increases from zero in the positive direction. As a result, by flowing a second current I2 of a second magnitude If through the coil 24, the magnetization direction of the second permanent magnet 22 can be directed to the second magnetization direction D2. Therefore, the permanent electromagnet 10 has an attracting force. The value of the attracting force of the permanent electromagnet 10 due to this is Fo. Furthermore, by flowing a second current I2 (I2 = If) of a second magnitude If in the positive direction through the coil 24, a magnetic force is generated in the coil 24. By adding the accompanying attracting force, the value of the attracting force of the permanent electromagnet 10 reaches Fp. The permanent electromagnet 10 is in an attracted state.

[0050] At time Ta when the second time T2 has elapsed from time zero, the energization control unit 50 operates the connection circuit 12 to stop the energization of the coil 24. As a result, the value of the voltage applied to the coil 24 becomes zero. The value of the current flowing through the coil 24 also becomes zero. Although the magnetic force of the coil 24 is lost, since the magnetization direction of the second permanent magnet 22 maintains the second magnetization direction D2, the value of the attracting force of the permanent electromagnet 10 becomes Fo. The permanent electromagnet 10 maintains the attracted state.

[0051] Subsequently, in the permanent electromagnet 10 which is in the adsorption state, at time Tb, the power supply control unit 52 controls the power supply 30 to set the output voltage of the power supply 30 to a first voltage V1. The energization control unit 50 operates the connection circuit 12 to continuously apply the first voltage V1 to the coil 24 for a first time T1. The value of the first voltage V1, which is a negative voltage, is -Ve.

[0052] The magnitude Ve of the first voltage V1 is smaller than the magnitude Vf of the second voltage V2. In this embodiment, the length of the first time T1 is equal to the length of the second time T2. This makes it possible to make the first magnitude Ie of the first current I1 smaller than the second magnitude If of the second current I2. Therefore, the power consumption when the permanent electromagnet 10 is released can be reduced. In other words, the power consumption in the permanent electromagnet 10 can be reduced.

[0053] Furthermore, by adjusting the first voltage V1, the first magnitude Ie of the first current I1 can be suppressed. Therefore, the first magnitude Ie of the first current I1 can be easily adjusted.

[0054] During the first hour T1 from time Tb, the magnitude of the current flowing through coil 24 increases from 0 in the negative direction. As a result, a first current I1 of magnitude Ie flows through coil 24, which causes the magnetization direction of the second permanent magnet 22 to be directed towards the first magnetization direction D1. Therefore, the permanent electromagnet 10 does not possess any attractive force. The value of the attractive force of the permanent electromagnet 10 approaches zero. However, a magnetic force is generated in coil 24 due to the flow of a first current I1 (I1 = -Ie) of magnitude Ie in the negative direction. Because an attractive force is generated as a result, the value of the attractive force of the permanent electromagnet 10 does not coincide with zero. However, since the permanent electromagnet 10 cannot attract the magnetic material W, the permanent electromagnet 10 is in a released state.

[0055] At time Tc, which is one hour T1 after time Tb, the energization control unit 50 operates the connection circuit 12 to stop the energization of coil 24. As a result, the voltage applied to coil 24 becomes zero. The current flowing through coil 24 also becomes zero. Because the magnetic force of coil 24 is lost, the attractive force of the permanent electromagnet 10 becomes zero. The magnetization direction of the second permanent magnet 22 maintains the first magnetization direction D1. The permanent electromagnet 10 remains in the released state.

[0056] Figure 5 is a flowchart illustrating the control procedure for controlling the permanent electromagnet 10. This procedure is performed by the calculation unit 40 of the control device 14 executing a program stored in the storage unit 42.

[0057] When this processing procedure is started, in step S1, the energization control unit 50 determines whether or not to release the permanent electromagnet 10. If the answer in step S1 is YES, the processing procedure proceeds to step S2. If the answer in step S1 is NO, the processing procedure proceeds to step S5. In step S2, the power supply control unit 52 controls the power supply 30 to set the output voltage of the power supply 30 to the first voltage V1.

[0058] In step S3, the power supply control unit 50 operates the connection circuit 12 to turn on the second switch SW2 and the third switch SW3, and to turn off the first switch SW1 and the fourth switch SW4. In this way, the power supply control unit 50 applies a first voltage V1 to the coil 24 for a first time T1. This allows a first current I1 of a first magnitude Ie to flow through the coil 24. The power supply control unit 50 turns the magnetization direction of the second permanent magnet 22 toward the first magnetization direction D1, thereby releasing the permanent electromagnet 10.

[0059] In step S4, the power supply control unit 50 operates the connection circuit 12 to turn off the second switch SW2 and the third switch SW3. In this way, the power supply control unit 50 stops supplying power to the coil 24.

[0060] In step S5, the power supply control unit 50 determines whether or not to put the permanent electromagnet 10 into an attracted state. If the answer in step S5 is YES, the process proceeds to step S6. If the answer in step S5 is NO, the process proceeds to step S9. In step S6, the power supply control unit 52 controls the power supply 30 to set the output voltage of the power supply 30 to the second voltage V2.

[0061] In step S7, the power supply control unit 50 operates the connection circuit 12 to turn on the first switch SW1 and the fourth switch SW4, and to turn off the second switch SW2 and the third switch SW3. In this way, the power supply control unit 50 applies a second voltage V2 to the coil 24 for a second time T2. This allows a second current I2 of second magnitude If to flow through the coil 24. The power supply control unit 50 directs the magnetization direction of the second permanent magnet 22 to the second magnetization direction D2, thereby attracting the permanent electromagnet 10.

[0062] In step S8, the power supply control unit 50 operates the connection circuit 12 to turn off the first switch SW1 and the fourth switch SW4. In this way, the power supply control unit 50 stops supplying power to the coil 24.

[0063] In step S9, the energization control unit 50 determines whether or not to terminate control of the permanent electromagnet 10. For example, if the control device 14 has received a control termination instruction from an operator using the control device 14, the result in step S9 is YES. If the result in step S9 is YES, this processing procedure ends. If the result in step S9 is NO, this processing procedure returns to step S1.

[0064] The embodiments described above may be modified as follows. In the following modifications, explanations that overlap with those in the embodiments will be omitted. Also, in the figures used in the following modifications, components identical to those described in the embodiments will be denoted by the same reference numerals.

[0065] (Modification 1) In the embodiment described above, the magnitude of the first voltage V1 is smaller than the magnitude of the second voltage V2, and the length of the first time T1 is equal to the length of the second time T2. This makes it possible to make the first magnitude Ie of the first current I1 smaller than the second magnitude If of the second current I2. However, it is not limited to this.

[0066] Figure 6 shows an example where the current flowing through the coil 24 and the attractive force of the permanent electromagnet 10 change in response to the voltage applied to the coil 24. From time zero to time Tb, when the permanent electromagnet 10 changes from the released state to the attracted state and maintains that attracted state, the graph shown in Figure 6 is the same as the graph shown in Figure 4. After time Tb, when the permanent electromagnet 10 changes from the attracted state to the released state, the graph shown in Figure 6 differs from the graph shown in Figure 4.

[0067] In the permanent electromagnet 10, which is in an adsorbed state, at time Tb, the power supply control unit 52 controls the power supply 30 to set the output voltage of the power supply 30 to a first voltage V1. The energization control unit 50 operates the connection circuit 12 to continuously apply the first voltage V1 to the coil 24 for a first time T1. The value of the first voltage V1, which is a negative voltage, is -Vf. That is, the magnitude Vf of the first voltage V1, which is a negative voltage, is equal to the magnitude Vf of the second voltage V2, which is a positive voltage.

[0068] In this modified example 1, the length of the first time T1 is shorter than the length of the second time T2. This makes it possible to make the first magnitude Ie of the first current I1 smaller than the second magnitude If of the second current I2. Therefore, the power consumption when releasing the permanent electromagnet 10 can be reduced. In other words, the power consumption in the permanent electromagnet 10 can be reduced. Furthermore, by adjusting the first time T1, the first magnitude Ie of the first current I1 can be suppressed. Therefore, the first magnitude Ie of the first current I1 can be easily adjusted.

[0069] During the first hour T1 from time Tb, the magnitude of the current flowing through coil 24 increases from 0 in the negative direction. As a result, a first current I1 of magnitude Ie flows through coil 24, which causes the magnetization direction of the second permanent magnet 22 to be directed towards the first magnetization direction D1. Therefore, the permanent electromagnet 10 does not possess any attractive force. The value of the attractive force of the permanent electromagnet 10 approaches zero. However, a magnetic force is generated in coil 24 due to the flow of a first current I1 (I1 = -Ie) of magnitude Ie in the negative direction. Because an attractive force is generated as a result, the value of the attractive force of the permanent electromagnet 10 does not coincide with zero. However, since the permanent electromagnet 10 cannot attract the magnetic material W, the permanent electromagnet 10 is in a released state.

[0070] At time Tc, which is the time T1 after time Tb, the energization control unit 50 operates the connection circuit 12 to stop the application of the first voltage V1 to the coil 24. As a result, the voltage applied to the coil 24 becomes zero. The current flowing through the coil 24 also becomes zero. Because the magnetic force of the coil 24 is lost, the attractive force of the permanent electromagnet 10 becomes zero. The magnetization direction of the second permanent magnet 22 maintains the first magnetization direction D1. The permanent electromagnet 10 remains in the released state.

[0071] (Modification 2) In the above-described embodiment, when the magnetization direction of the second permanent magnet 22 is directed toward the first magnetization direction D1, a first voltage V1 smaller than the second voltage V2 is continuously applied to the coil 24 for a first time T1. This makes the first magnitude Ie of the first current I1 smaller than the second magnitude If of the second current I2. However, it is not limited to this.

[0072] Figure 7 shows an example where the current flowing through the coil 24 and the attractive force of the permanent electromagnet 10 change in response to the voltage applied to the coil 24. From time zero to time Tb, when the permanent electromagnet 10 changes from the released state to the attracted state and maintains that attracted state, the graph shown in Figure 7 is the same as the graph shown in Figure 4. After time Tb, when the permanent electromagnet 10 changes from the attracted state to the released state, the graph shown in Figure 7 differs from the graph shown in Figure 4.

[0073] In the permanent electromagnet 10, which is in an adsorbed state, at time Tb, the power supply control unit 52 controls the power supply 30 to set the output voltage of the power supply 30 to a first voltage V1. The energization control unit 50 operates the connection circuit 12 to intermittently apply the first voltage V1 to the coil 24 for a first time T1. The value of the first voltage V1, which is a negative voltage, is -Vf. That is, the magnitude Vf of the first voltage V1, which is a negative voltage, is equal to the magnitude Vf of the second voltage V2, which is a positive voltage.

[0074] In this modified example 2, a first voltage V1 is intermittently applied to the coil 24 using PWM (Pulse Width Modulation) control. The effective application time of the first voltage V1 is obtained by multiplying the length of the first time T1 by the duty cycle. The duty cycle is greater than 0 and less than 1. The length of the first time T1 is equal to the length of the second time T2. Therefore, the effective application time of the first voltage V1 is less than the length of the second time T2.

[0075] This makes the first magnitude Ie of the first current I1 smaller than the second magnitude If of the second current I2. Therefore, the power consumption when releasing the permanent electromagnet 10 can be reduced. In other words, the power consumption in the permanent electromagnet 10 can be reduced. Furthermore, by adjusting the duty cycle, the effective application time of the first voltage V1 can be easily adjusted. In other words, by adjusting the duty cycle, the first magnitude Ie of the first current I1 can be suppressed. Therefore, the first magnitude Ie of the first current I1 can be easily adjusted.

[0076] During the first hour T1 from time Tb, the magnitude of the current flowing through coil 24 increases from 0 in the negative direction. As a result, a first current I1 of magnitude Ie flows through coil 24, which causes the magnetization direction of the second permanent magnet 22 to be directed towards the first magnetization direction D1. Therefore, the permanent electromagnet 10 does not possess any attractive force. The value of the attractive force of the permanent electromagnet 10 approaches zero. However, a magnetic force is generated in coil 24 due to the flow of a first current I1 (I1 = -Ie) of magnitude Ie in the negative direction. Because an attractive force is generated as a result, the value of the attractive force of the permanent electromagnet 10 does not coincide with zero. However, since the permanent electromagnet 10 cannot attract the magnetic material W, the permanent electromagnet 10 is in a released state.

[0077] At time Tc, which is the time T1 after time Tb, the energization control unit 50 operates the connection circuit 12 to stop the application of the first voltage V1 to the coil 24. As a result, the voltage applied to the coil 24 becomes zero. The current flowing through the coil 24 also becomes zero. Because the magnetic force of the coil 24 is lost, the attractive force of the permanent electromagnet 10 becomes zero. The magnetization direction of the second permanent magnet 22 maintains the first magnetization direction D1. The permanent electromagnet 10 remains in the released state.

[0078] (Modification 3) In the embodiments and modifications described above, the first magnitude Ie of the first current I1 is adjusted by adjusting the first voltage V1 and / or the first time T1. However, the first magnitude Ie of the first current I1 may be adjusted by other means. For example, in the connection circuit 12 shown in Figure 3, a variable resistor may be inserted between the power supply 30 and the coil 24. The first magnitude Ie of the first current I1 can be adjusted by adjusting the resistance value of the variable resistor.

[0079] With regard to the embodiments and modifications described above, the following additional information is disclosed.

[0080] (Note 1) The permanent electromagnet system (16) of the present disclosure is a permanent electromagnet system comprising: a permanent electromagnet (10) that can switch between an adsorption state in which a magnetic material (W) can be adsorbed and a release state in which the adsorption state is released; and a control device (14) that controls the permanent electromagnet, wherein the permanent electromagnet has a first permanent magnet (20) whose magnetization direction is fixed; a second permanent magnet (22) whose magnetization direction can be changed; and a coil (24) wound around the outer circumference of the second permanent magnet, and the control device has a first size (Ie) of the coil The device has an energizing control unit (50) that, by passing a first current (I1) through the coil, directs the magnetization direction of the second permanent magnet to the first magnetization direction (D1), thereby releasing the permanent electromagnet, and by passing a second current (I2) of a second magnitude (If) in the opposite direction to the first current through the coil, directs the magnetization direction of the second permanent magnet to the second magnetization direction (D2) in the opposite direction to the first magnetization direction, thereby putting the permanent electromagnet into the attracted state, wherein the first magnitude is smaller than the second magnitude. With this configuration, the power consumption of the permanent electromagnet can be reduced.

[0081] (Note 2) The permanent electromagnet system described in Note 1 further includes a first switch (SW1) and a second switch (SW2) connected in series from the positive terminal to the negative terminal of a power supply (30), and a third switch (SW3) and a fourth switch (SW4) connected in series from the positive terminal to the negative terminal of the power supply, wherein one end (Pa) of the coil is connected between the first switch and the second switch, and the other end (Pb) of the coil is connected between the third switch and the fourth switch, and the current control unit turns on the second switch and the third switch and turns off the first switch and the fourth switch, thereby causing the first current to flow through the coil, and the current control unit turns on the first switch and the fourth switch and turns off the second switch and the third switch, thereby causing the second current to flow through the coil. With such a configuration, the attracted state and the released state of the permanent electromagnet can be easily switched.

[0082] (Note 3) In the permanent electromagnet system described in Note 1 or 2, the current control unit, when orienting the magnetization direction of the second permanent magnet toward the first magnetization direction, continuously applies a first voltage (V1) to the coil for a first time (T1) to cause a first current of a first magnitude to flow through the coil, and when orienting the magnetization direction of the second permanent magnet toward the second magnetization direction, continuously applies a second voltage (V2) to the coil for a second time (T2) to cause a second current of a second magnitude to flow through the coil, wherein the magnitude of the first voltage is smaller than the magnitude of the second voltage, and the length of the first time is equal to the length of the second time. With such a configuration, the first magnitude of the first current can be easily adjusted.

[0083] (Note 4) In the permanent electromagnet system described in Note 1 or 2, the current control unit, when orienting the magnetization direction of the second permanent magnet toward the first magnetization direction, applies a first voltage to the coil continuously for a first time to cause a first current of a first magnitude to flow through the coil, and when orienting the magnetization direction of the second permanent magnet toward the second magnetization direction, applies a second voltage to the coil continuously for a second time to cause a second current of a second magnitude to flow through the coil, the magnitude of the first voltage may be equal to the magnitude of the second voltage, and the length of the first time may be less than the length of the second time. With such a configuration, the first magnitude of the first current can be easily adjusted.

[0084] (Note 5) In the permanent electromagnet system described in Note 1 or 2, the current control unit may, when orienting the magnetization direction of the second permanent magnet toward the first magnetization direction, apply a first voltage to the coil intermittently for a first time to cause a first current of a first magnitude to flow through the coil, and when orienting the magnetization direction of the second permanent magnet toward the second magnetization direction, apply a second voltage to the coil continuously for a second time to cause a second current of a second magnitude to flow through the coil, the magnitude of the first voltage may be equal to the magnitude of the second voltage, and the length of the first time may be equal to the length of the second time. With such a configuration, the first magnitude of the first current can be easily adjusted.

[0085] (Note 6) The control device of the present disclosure is a control device for controlling a permanent electromagnet that has a first permanent magnet with a fixed magnetization direction, a second permanent magnet whose magnetization direction can be changed, and a coil wound around the outer circumference of the second permanent magnet, and is capable of switching between an adsorption state in which a magnetic material can be attracted and a release state in which the adsorption state is released, and includes an energizing control unit that causes the magnetization direction of the second permanent magnet to be directed in the first magnetization direction by passing a first current of a first magnitude through the coil, thereby putting the permanent electromagnet into the release state, and causes the magnetization direction of the second permanent magnet to be directed in the second magnetization direction opposite to the first magnetization direction by passing a second current of a second magnitude in the opposite direction to the first magnetization direction through the coil, thereby putting the permanent electromagnet into the adsorption state, wherein the first magnitude is smaller than the second magnitude. With such a configuration, the power consumption of the permanent electromagnet can be reduced.

[0086] (Note 7) The control method of the present disclosure is a control method for controlling a permanent electromagnet that has a first permanent magnet with a fixed magnetization direction, a second permanent magnet whose magnetization direction can be changed, and a coil wound around the outer circumference of the second permanent magnet, and which can switch between an adsorption state in which a magnetic material can be adsorbed and a release state in which the adsorption state is released, comprising: a release control step of passing a first current of a first magnitude through the coil to orient the magnetization direction of the second permanent magnet to the first magnetization direction, thereby putting the permanent electromagnet into the release state; and an adsorption control step of passing a second current of a second magnitude in the opposite direction to the first current through the coil to orient the magnetization direction of the second permanent magnet to the second magnetization direction opposite to the first magnetization direction, thereby putting the permanent electromagnet into the adsorption state, wherein the first magnitude is smaller than the second magnitude. With such a configuration, the power consumption of the permanent electromagnet can be reduced.

[0087] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above.

Claims

1. A permanent electromagnet system (16) comprising: a permanent electromagnet (10) capable of switching between an adsorption state in which a magnetic material (W) can be attracted and a release state in which the adsorption state is released; and a control device (14) for controlling the permanent electromagnet, wherein the permanent electromagnet comprises: a first permanent magnet (20) with a fixed magnetization direction; a second permanent magnet (22) whose magnetization direction can be changed; and a coil (24) wound around the outer circumference of the second permanent magnet, and the control device is A permanent electromagnet system having an energizing control unit (50) that, by passing a first current (I1) of a first magnitude (Ie) through the coil, directs the magnetization direction of the second permanent magnet to a first magnetization direction (D1), thereby releasing the permanent electromagnet, and by passing a second current (I2) of a second magnitude (If) in the opposite direction to the first current through the coil, directs the magnetization direction of the second permanent magnet to a second magnetization direction (D2) in the opposite direction to the first magnetization direction, thereby putting the permanent electromagnet into the attracted state, wherein the first magnitude is smaller than the second magnitude.

2. A permanent electromagnet system according to claim 1, further comprising a connection circuit (12) having a first switch (SW1) and a second switch (SW2) connected in series from the positive terminal to the negative terminal of a power supply (30), and a third switch (SW3) and a fourth switch (SW4) connected in series from the positive terminal to the negative terminal of the power supply, wherein one end (Pa) of the coil is connected between the first switch and the second switch, and the other end (Pb) of the coil is connected between the third switch and the fourth switch, wherein the energizing control unit turns on the second switch and the third switch and turns off the first switch and the fourth switch, thereby causing the first current to flow through the coil, and the energizing control unit turns on the first switch and the fourth switch and turns off the second switch and the third switch, thereby causing the second current to flow through the coil.

3. A permanent electromagnet system according to claim 1 or 2, wherein the energizing control unit, when orienting the magnetization direction of the second permanent magnet toward the first magnetization direction, continuously applies a first voltage (V1) to the coil for a first time (T1) to cause a first current of a first magnitude to flow through the coil, and when orienting the magnetization direction of the second permanent magnet toward the second magnetization direction, continuously applies a second voltage (V2) to the coil for a second time (T2) to cause a second current of a second magnitude to flow through the coil, wherein the magnitude of the first voltage is smaller than the magnitude of the second voltage, and the length of the first time is equal to the length of the second time.

4. A permanent electromagnet system according to claim 1 or 2, wherein the energizing control unit, when orienting the magnetization direction of the second permanent magnet toward the first magnetization direction, continuously applies a first voltage to the coil for a first time to cause a first current of a first magnitude to flow through the coil, and when orienting the magnetization direction of the second permanent magnet toward the second magnetization direction, continuously applies a second voltage to the coil for a second time to cause a second current of a second magnitude to flow through the coil, wherein the magnitude of the first voltage is equal to the magnitude of the second voltage, and the length of the first time is less than the length of the second time.

5. A permanent electromagnet system according to claim 1 or 2, wherein the energizing control unit, when orienting the magnetization direction of the second permanent magnet toward the first magnetization direction, intermittently applies a first voltage to the coil for a first time to cause a first current of a first magnitude to flow through the coil, and when orienting the magnetization direction of the second permanent magnet toward the second magnetization direction, continuously applies a second voltage to the coil for a second time to cause a second current of a second magnitude to flow through the coil, the magnitude of the first voltage is equal to the magnitude of the second voltage, and the length of the first time is equal to the length of the second time.

6. A control device for controlling a permanent electromagnet that has a first permanent magnet with a fixed magnetization direction, a second permanent magnet whose magnetization direction can be changed, and a coil wound around the outer circumference of the second permanent magnet, and which can switch between an adsorption state in which a magnetic material can be attracted and a release state in which the adsorption state is released, wherein the control device comprises an energizing control unit that causes the magnetization direction of the second permanent magnet to be directed in the first magnetization direction by passing a first current of a first magnitude through the coil, thereby putting the permanent electromagnet into the release state, and causes the magnetization direction of the second permanent magnet to be directed in the second magnetization direction opposite to the first magnetization direction by passing a second current of a second magnitude in the opposite direction to the first magnetization direction through the coil, and the control device wherein the first magnitude is smaller than the second magnitude.

7. A control method for controlling a permanent electromagnet that can switch between an adsorption state in which a magnetic material can be attracted and a release state in which the adsorption state is released, comprising: a release control step of passing a first current of a first magnitude through the coil to orient the magnetization direction of the second permanent magnet in the first magnetization direction, thereby putting the permanent electromagnet into the release state; and an adsorption control step of passing a second current of a second magnitude in the opposite direction to the first current through the coil to orient the magnetization direction of the second permanent magnet in the opposite direction to the first magnetization direction, thereby putting the permanent electromagnet into the adsorption state, wherein the first magnitude is smaller than the second magnitude.

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