magnetic field generator

Abstract

Provided is a magnetic field generating device that is capable of generating a strong magnetic field that is stable over a long period of time due to a stable switching element action and a useful cooling method that makes the temperature of a condenser constant.　This magnetic field generating device comprises a compressor (21), a condenser (22), an expansion valve (23), and an evaporator that are connected so that a cooling liquid circulates therethrough, wherein: the evaporator is formed from a coil (16) that is formed with a plurality of micropores (32) through which the cooling liquid flows and is wound in a solenoid state; a resonance circuit (15) that has a condenser (33) and causes the coil (16) to resonate is connected to the coil (16); and the coil (16) and the condenser (33) are cooled with the cooling liquid. Consequently, the magnetic field generating device achieves a stable operation of a switching element (30) and is capable of generating a strong magnetic field that is stable over a long period of time with superior cooling that makes the temperature of the condenser (33) constant.

Description

[Technical Field]

[0001] The present invention relates to a magnetic field generating device that can generate a magnetic field stably for a long period of time. [Background technology]

[0002] Alternating magnetic field therapy, which uses heating by an alternating magnetic field to kill tumor cells, has been known. For example, Patent Document 1 discloses an alternating magnetic field (AMF) head including an electric coil and a ferromagnetic core. An AMF generator coupled to the AMF head is configured to generate an alternating current (AC) signal and transmit the AC signal to the electric coil of the AMF head. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Table 2018-510700 Summary of the Invention [Problem to be solved by the invention]

[0004] Devices that have a coil that generates an induction magnetic field, such as an induction heater, are provided with a resonant circuit, and a large current is passed through the coil to generate a strong magnetic field. A resonant circuit is an LC circuit in which a capacitor (C) is connected in series or parallel to a coil (L). The capacitance of the capacitor C [F] of the resonant circuit is designed so that it resonates at the target frequency f0 [Hz]. In the case of a series resonant circuit, the capacitance of the capacitor C [F] is determined so that the following equation is satisfied:

[0005]

number

[0006] The value of L [H] represents the inductance of the coil. In actual use, large currents flow through capacitors and coils, causing the capacitors and coils themselves to heat up. This causes the values ​​of inductance L and capacitance C to change, resulting in deviations from the intended frequency f0 [Hz]. Generally, the Q value (quality factor) is used to represent the sharpness of the resonance peak. For example, in the case of a series resonant circuit, the quality factor, or Q value, is expressed by the following formula: where f is the frequency and R is the resistance value.

[0007]

number

[0008] This Q value is 1 / 2 the peak current value at the resonance point. 0.5 Using the values ​​of frequencies f1 and f2, this can be expressed as follows: For example, in the case of an LCR series resonant circuit configuration with a frequency f0 of 220 kHz and a sharp peak value with a Q value of 1000, f2-f1=220000 / 1000=220 Hz.

[0009]

number

[0010] Therefore, in order to maintain the resonance peak, in this example, a mechanism is required to adjust the temperature-induced resonance frequency deviation with an accuracy of 220 Hz or less.

[0011] As mentioned above, heat generation in the capacitor and coil changes the capacitor capacitance C and the coil inductance L, causing the resonance point of the resonant circuit to shift, which creates the problem of not being able to generate a strong current at the target frequency.

[0012] In order to solve the above-mentioned problems, the present invention aims to provide a magnetic field generator that can provide stable operation of switching elements and a useful cooling method for keeping the temperature of a capacitor constant, and can generate a strong magnetic field stably for a long period of time. [Means for solving the problem]

[0013] The magnetic field generating device of the present invention comprises a compressor, a condenser, an expansion valve, and an evaporator, which are connected so that a cooling liquid circulates therethrough, and the evaporator has a plurality of through holes through which the cooling liquid flows. The coil substrate is a cylindrical spiral a resonant circuit having a capacitor that resonates the coil is connected to the coil, the condenser is provided with a cooling plate having a plurality of micropores formed therein through which the cooling liquid flows; The coil and the condenser are cooled by the coolant. [Effects of the Invention]

[0014] The magnetic field generator of the present invention includes a compressor, a condenser, an expansion valve, and an evaporator, all connected to allow a coolant to circulate. The evaporator is formed of a solenoid-wound coil with multiple through-holes for the coolant to flow through. Thus, the magnetic field generator of the present invention is provided with a structure for cooling the coil that generates the magnetic field by appropriately flowing coolant through it. The coil is connected to a resonant circuit having a capacitor that resonates the coil, and the capacitor is cooled by the coolant that cools the coil. Therefore, a strong magnetic field can be generated stably for a long period of time.

[0015] Furthermore, according to the magnetic field generator of the present invention, the coolant may be a hydrofluorocarbon refrigerant, a hydrofluoroolefin refrigerant, or a carbon dioxide refrigerant alone or in combination. This allows the coil and condenser to be cooled efficiently by utilizing the evaporation of the refrigerant in the evaporator, thereby generating a strong magnetic field with high performance.

[0016] Furthermore, the magnetic field generator of the present invention may have a circulation circuit that allows the coolant to flow in parallel through the cooling sections of the coil and the condenser, respectively. With this configuration, the coil and the condenser can be cooled appropriately.

[0017] Furthermore, according to the magnetic field generator of the present invention, a control valve whose opening degree is controlled independently of the expansion valve may be provided in the path through which the coolant flows to the condenser. This allows the flow of coolant that cools the condenser to be controlled separately from the flow of coolant that cools the coil, thereby enabling the temperature of the condenser to be controlled appropriately. As a result, the coil and the condenser can each be cooled appropriately.

[0018] Furthermore, the magnetic field generator of the present invention may further include a control device that controls the opening of the control valve so that the capacitor reaches a predetermined temperature. This allows the control device to optimally control the temperature of the capacitor. As a result, the coil and capacitor are optimally cooled, and the magnetic field generator can stably generate a strong magnetic field for a long period of time. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a block diagram of a control system of a magnetic field generating device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing a circuit of a refrigerant circulation system of a magnetic field generating device according to an embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing a coil of a refrigeration circuit according to an embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing an example of a cooling structure for a switching circuit of a magnetic field generating device according to an embodiment of the present invention. [Figure 5] FIG. 5 is a diagram showing an example of capacitor connections in the magnetic field generating device according to the embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing an example of a cooling structure for a capacitor of a magnetic field generating device according to an embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing an end portion of a cooling plate of a magnetic field generating device according to an embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing a circuit of a refrigerant circulation system of a magnetic field generating device according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, a magnetic field generating device according to an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. Note that the illustrated aspects do not limit the present invention, but merely exemplify the embodiment of the present invention.

[0021] 1 is a block diagram showing an outline of a control system of a magnetic field generator 1 according to an embodiment of the present invention. Referring to Fig. 1, the magnetic field generator 1 has a power supply circuit 10, a main control circuit 11, a refrigerator control circuit 12, a driver circuit 13, a switching circuit 14, a resonance circuit 15, a coil 16 that generates a magnetic field, and a feedback control circuit 17.

[0022] The magnetic field generator 1 has a coil 16 and generates a magnetic field with a target magnetic flux density by passing an alternating current of a predetermined frequency through the coil 16. The coil 16 is compact, for example, about the size of a human head. The magnetic field generator 1 is particularly useful when a strong magnetic field is to be generated by passing a large current through the coil 16. The magnetic field generator 1 is suitable for treating areas where conventional surgery is difficult or impossible, such as brain tumors and breast cancer.

[0023] The power supply circuit 10 is a circuit that supplies power and is connected to a main control circuit 11, a refrigerator control circuit 12, a driver circuit 13, and a switching circuit 14. The main control circuit 11 is a circuit that controls the generation of a magnetic field by a coil 16. Specifically, the main control circuit 11 controls the alternating current that flows through the coil 16 via power supply circuits such as a driver circuit 13 having a driver, a switching circuit 14 having a switching element 30 (see FIG. 4), and a resonance circuit 15.

[0024] Resonant circuit 15 is connected to coil 16 and constitutes a power supply circuit that generates a magnetic field in coil 16. Specifically, resonant circuit 15 has a capacitor 33 (see FIG. 5) that causes coil 16 to resonate. The feedback control circuit 17 is connected to the resonance circuit 15 and transmits the state of resonance caused by the resonance circuit 15 to the refrigerator control circuit 12 .

[0025] The refrigerator control circuit 12 is a control device that controls the cooling of the coil 16 and the condenser 33. The refrigerator control circuit 12 controls the operation of the compressor 21, expansion valves 23 and 24, the blower fan of the condenser 22, etc., shown in FIG.

[0026] When the temperature of the coil 16 and capacitor 33 that make up the resonant circuit 15 changes, the resonant frequency deviates from the target frequency, making it impossible to obtain the target current. The magnetic field generator 1 according to this embodiment has a mechanism for cooling the coil 16 and capacitor 33, and solves the above problem by maintaining the temperatures of the coil 16 and capacitor 33 appropriately.

[0027] Fig. 2 is a diagram showing a circuit of a circulation system for a refrigerant as a coolant for the magnetic field generator 1. Referring to Fig. 2, the magnetic field generator 1 has a coil 16 that generates a magnetic field, and also has a basic circuit configuration that cools the coil 16 with a refrigerant as a coolant.

[0028] The magnetic field generating device 1 comprises a compressor 21, a condenser 22, an expansion valve 23, and a coil 16 as an evaporator, which are connected via refrigerant piping, and forms a vapor compression refrigeration cycle circuit that cools the coil 16 by evaporation of the refrigerant.

[0029] The compressor 21 is a device that compresses the refrigerant and sends it to the condenser 22. As the compressor 21, various types of compression devices such as rotary type, scroll type, reciprocating type, screw type, and the like can be used.

[0030] In particular, the rotary compressor 21 is suitable for configuring a compact magnetic field generator 1 with a small cooling capacity. The compressor 21 may also be a two-stage compression type. The use of a two-stage compression type as the compressor 21 is suitable for compressing a high-pressure carbon dioxide refrigerant.

[0031] The condenser 22 is, for example, an air-cooled heat exchanger in which air that exchanges heat with the refrigerant is blown by a blower fan. For example, the condenser 22 may be a fin-and-tube heat exchanger (not shown).

[0032] The condenser 22 may also be a water-cooled heat exchanger. Various types of heat exchangers, such as plate type, shell-and-tube type, and double-tube type, can be used as the condenser 22. In particular, a plate type heat exchanger is preferable because it has high heat exchange efficiency and allows the condenser 22 to be made compact.

[0033] The expansion valve 23 reduces the pressure of the refrigerant liquid that has passed through the condenser 22. The expansion valve 23 also has the function of adjusting the flow of the refrigerant. As the expansion valve 23, various types of valves can be used, including an electronic expansion valve, a thermostatic expansion valve, and a capillary tube. For automatic control, the expansion valve 23 is preferably an electronic expansion valve whose opening can be adjusted by a stepping motor. By using an electronic expansion valve as the expansion valve 23, the cooling of the coil 16 can be controlled with high efficiency, and magnetic field generation performance can be improved.

[0034] The coil 16 is a component for generating an alternating magnetic field, and also functions as an evaporator in the refrigeration cycle circuit. As an evaporator, the coil 16 is cooled by the refrigerant. This prevents the coil 16 from becoming too hot even when a high current flows through it, and allows it to stably generate a strong magnetic field for a long period of time.

[0035] The magnetic field generator 1 also has a refrigerant circulation circuit for cooling the power supply circuit. Specifically, the refrigerant pipe that carries the refrigerant that has passed through the condenser 22 branches into a path 27 that carries the refrigerant that cools the coil 16 and a path 28 that carries the refrigerant that cools the switching circuit 14 and the resonant circuit 15 of the power supply circuit.

[0036] An expansion valve 24 is provided in path 28 via a refrigerant pipe, and the switching circuit 14 and the resonant circuit 15 of the power supply circuit are arranged so as to be able to be cooled. Path 28, which passes through switching circuit 14 and resonant circuit 15, merges with path 27, which passes through coil 16, to form path 26 which is connected to compressor 21.

[0037] The expansion valve 24 provided in the path 28 reduces the pressure of the refrigerant liquid that has passed through the condenser 22. The expansion valve 24 also has the function of adjusting the flow of the refrigerant in the path 28. The expansion valve 24 may be an electronic expansion valve, a thermostatic expansion valve, a capillary tube, or any other type of valve.

[0038] For automatic control, an electronic expansion valve whose opening can be adjusted by a stepping motor is preferable as the expansion valve 24. By employing an electronic expansion valve as the expansion valve 24, it is possible to highly efficiently control the cooling of the switching circuit 14 and the resonant circuit 15, and improve the magnetic field generation performance.

[0039] Cooling plates 31 and 35 serving as evaporators are provided in a path 28 for the refrigerant that cools the switching circuit 14 and the resonant circuit 15. Details will be described later.

[0040] Resonant circuit 15, which constitutes a power supply circuit, is connected to the inlet and outlet sides of coil 16 via wiring 18, and passes an alternating current through coil 16. That is, a current is passed from cooled resonant circuit 15 to cooled coil 16, and a magnetic field can be generated with high efficiency.

[0041] The magnetic field generator 1 is also provided with temperature sensors 41, 42, 43, and 44 for measuring temperature. The temperature sensor 41 is provided near the coil 16 and measures the temperature of the coil 16 and the like. The temperature sensor 42 is provided in the resonant circuit 15 and measures the temperature near the capacitor 33 (see FIG. 5). The temperature sensors 43 and 44 are sensors for measuring the temperature of the refrigerant, with the temperature sensor 43 being provided in the refrigerant piping or the like on the outlet side of the coil 16, and the temperature sensor 44 being provided in the refrigerant piping or the like on the outlet sides of the switching circuit 14 and the resonant circuit 15.

[0042] Next, cooling of the coil 16 by the refrigeration cycle circuit will be described in detail. The refrigerant, which is a cooling liquid, flows and circulates through paths 26, 27, and 28 of the refrigerant piping in the direction A. Specifically, the refrigerant is sucked into compressor 21, where it is pressurized and reaches a high temperature. The refrigerant compressed by compressor 21 is sent to condenser 22 via the refrigerant piping, and is cooled by condenser 22.

[0043] A portion of the refrigerant cooled in the condenser 22 flows through the refrigerant piping path 27 to the expansion valve 23. The refrigerant is then decompressed by the expansion valve 23 to become a low-temperature gas-liquid mixed fluid, which is then introduced into the coil 16.

[0044] The refrigerant sent to the coil 16 vaporizes by utilizing the heat generated by the current in the coil 16 as latent heat of vaporization. The refrigerant evaporates inside the coil 16 and removes heat from the coil 16. During this time, the refrigerant reaches a saturation temperature corresponding to the pressure of the refrigerant flowing through the coil 16, forming a uniform temperature distribution.

[0045] The refrigerant evaporated in coil 16 is combined with the refrigerant in path 28 and returns to compressor 21 where it is compressed again. The above-described process is then repeated. That is, a circulating flow of refrigerant is formed that cools coil 16 by passing through compressor 21, condenser 22, expansion valve 23, and coil 16 as an evaporator in this order.

[0046] Furthermore, a portion of the refrigerant cooled by condenser 22 flows through refrigerant piping path 28 to expansion valve 24, which serves as a control valve whose opening is controlled independently of expansion valve 23. The refrigerant is then decompressed by expansion valve 24 to become a low-pressure, low-temperature gas-liquid mixed fluid, which is introduced into cooling plates 31 and 35.

[0047] The refrigerant sent to the cooling plates 31 and 35 is vaporized by utilizing the heat generated by the currents in the switching circuit 14 and the resonant circuit 15 as latent heat of evaporation. That is, the refrigerant evaporates inside the cooling plates 31 and 35, removing the heat generated from the switching circuit 14 and the resonant circuit 15.

[0048] The refrigerant evaporated by the cooling plates 31 and 35 is combined with the refrigerant in the path 27 and returned to the compressor 21 to be compressed again. Then, the above-mentioned process is repeated. That is, the compressor 21, the condenser 22, the expansion valve 24 and a cooling plate as an evaporator 31 A circulating flow of the coolant is formed which cools the switching circuit 14 and the resonant circuit 15 by passing through the cooling plate 35 in this order.

[0049] In this way, the magnetic field generator 1 can maintain the temperatures of the cooling plates 31, 35 at a uniform, constant temperature using the refrigerant in the refrigeration cycle circuit, and as a result, the switching element 30 and the capacitor 33 in contact with the cooling plates 31, 35 can be maintained at a constant temperature.

[0050] The action of this refrigerant keeps the coil 16 and the capacitor 33 of the resonant circuit 15, which determine the resonant frequency, at a constant temperature, so that an alternating current of a predetermined frequency can be passed through stable resonance.

[0051] As described above, the opening degree of expansion valve 24 is controlled independently of expansion valve 23 provided in path 27. This allows the flow of coolant that cools switching element 30 and capacitor 33 to be controlled separately from the flow of refrigerant that cools coil 16. This allows coil 16, switching element 30, and capacitor 33 to be cooled to their respective appropriate temperatures.

[0052] The refrigerant used in the magnetic field generator 1 is, for example, hydrofluorocarbon, hydrofluoroolefin, carbon dioxide, or a mixture thereof. This allows the coil 16 and cooling plates 31 and 35 to be cooled efficiently by utilizing the latent heat of evaporation of the refrigerant, and a strong magnetic field can be generated stably for a long period of time.

[0053] The condenser 22 may be a gas cooler in which the condensation of the refrigerant is not clear. That is, fluorocarbon refrigerants such as typical refrigerants HFC-32 and HFC-404A are condensable in the normal operating environment of the condenser 22, which is about -20°C to 42°C. However, in the case of carbon dioxide refrigerant, the condenser 22 operates in the supercritical region, so the condenser 22 is called a gas cooler. Even if the condenser 22 is a gas cooler, it is still a mechanism for cooling the refrigerant.

[0054] Fig. 3 is a diagram showing a schematic configuration of the coil 16 of the magnetic field generator 1. Referring to Fig. 3, the coil 16 is a member that generates a magnetic field by the flow of current, and is wound in a solenoid shape. As described above, the coil 16 constitutes an evaporator of the refrigeration cycle circuit.

[0055] Specifically, the coil 16 is formed by winding a long flat plate or the like made of a good conductor such as silver, aluminum, copper, or any of various alloys into a coil shape. More specifically, the coil 16 is made of a substantially flat plate-shaped material having a substantially rectangular cross section, and is wound in a substantially spiral shape such that the long side of the cross section corresponds to the radial direction of the coil 16 and the short side corresponds to the winding axis direction of the coil 16. In other words, the coil 16 is wound so that the short side of the substantially rectangular cross section follows the shape of a substantially cylinder.

[0056] Coil 16 has a structure in which a large number of micropores 19, which are minute through-holes, i.e., microchannels, are formed, and a refrigerant can flow through the micropores 19. Specifically, a flat plate that is the material for coil 16 has a plurality of micropores 19 formed therethrough in the longitudinal direction of the flat plate. That is, coil 16 has a plurality of micropores 19 formed therein that serve as flow paths through which the refrigerant flows. Note that coil 16 may be an induction coil.

[0057] The cross-sectional shape of the micropores 19 may be a substantially circular shape as shown in Fig. 3, or may be a polygonal shape such as a triangle, a rectangle, a pentagon, or an ellipse. The micropores 19 may be formed so as to be aligned in a single row in the winding diameter direction of the coil 16, or may be formed in multiple rows.

[0058] Next, the cooling structure of the switching element 30 that generates an alternating current will be described in detail. 4 is a diagram showing an example of a cooling structure for the switching circuit 14. Referring to FIG. 4, the switching circuit 14 is provided with a cooling plate 31 that comes into contact with the switching element 30.

[0059] The cooling plate 31 is an evaporator that cools the switching element 30 that generates an alternating current. The cooling plate 31 is connected to the refrigerant pipe of the path 28 (see FIG. 2) so that the refrigerant decompressed by the expansion valve 24 (see FIG. 2) can flow through the cooling plate 31.

[0060] Specifically, the cooling plate 31 is a substantially flat member made of a good conductor such as aluminum, copper, silver, iron, or various alloys, and inside the cooling plate 31 are formed a plurality of micropores 32, i.e., microchannels, through which a refrigerant can flow.

[0061] More specifically, the cooling plate 31 has a large number of micropores 32 formed therein, penetrating from one end face to the other end face along the main surface that contacts the switching elements 30. The cross-sectional shape of the micropores 32 may be circular, elliptical, triangular, rectangular, pentagonal, or other polygonal shape, or any other shape.

[0062] When carbon dioxide is used as the refrigerant, the micropores 32 preferably have a substantially circular cross section in order to withstand the high pressure of the refrigerant and improve heat conduction by shortening the heat conduction distance. The micropores 32 may also be arranged in a plurality of rows, thereby ensuring a large heat exchange area with the refrigerant.

[0063] As described above, the cooling plate 31 has micropores 32 inside it that serve as refrigerant flow paths, and the refrigerant passing through the micropores 32 evaporates at a constant temperature. That is, the cooling plate 31 acts as an evaporator, and the refrigerant evaporates at the saturation temperature of the fluid pressure. This allows the cooling plate 31 to maintain a uniform temperature. This allows the switching element 30, which generates an alternating current of a predetermined frequency, to operate stably.

[0064] Next, the cooling structure of the capacitor 33 of the resonant circuit 15 will be described in detail with reference to FIGS. Fig. 5 is a diagram showing an example of connection of capacitors 33. As shown in Fig. 5, resonant circuit 15 is composed of a plurality of capacitors 33. The capacitors 33 are connected by conductive connecting members 34 such as copper bars, and form a predetermined capacitor capacitance C.

[0065] Capacitor 33 generates heat when a large current flows through it. In the prior art, it was considered to place an external fan to air-cool capacitor 33. However, with this conventional cooling method, the temperature of the cooling air changes with changes in the installation environment, making it impossible to maintain the designed value of capacitor capacitance C.

[0066] Fig. 6 is a diagram showing an example of a cooling structure for the capacitor 33 according to this embodiment. As shown in Fig. 6, the resonant circuit 15 is provided with a cooling plate 35 that contacts the surface of the capacitor 33. The capacitor 33 is directly cooled by the cooling plate 35 that contacts the surface of the capacitor 33.

[0067] Fig. 7 is an enlarged view of part B shown in Fig. 6, showing an end portion of cooling plate 35. Referring to Figs. 6 and 7, cooling plate 35 is formed from a substantially plate-shaped member in which a plurality of micropores 36 through which a refrigerant flows are formed. Micropores 36 are microchannels that penetrate from one end face to the other end face of the substantially plate-shaped member that is the raw material for cooling plate 35, along the main surface of the substantially plate-shaped member, similar to micropores 32 of cooling plate 31 shown in Fig. 4.

[0068] cooling plate 35 The cooling plate is formed of a substantially plate-shaped member made of a good conductor such as aluminum, copper, silver, iron, or various alloys. 35 is bent so as to cover the group of aligned condensers 33 and is in contact with the outer surfaces of the condensers 33. This configuration allows the heat generated by the condensers 33 to be absorbed as the latent heat of evaporation of the refrigerant without leaking to the outside.

[0069] The cross-sectional shape of the micropores 36 may be circular, elliptical, triangular, rectangular, pentagonal, or other polygonal shapes, or various other shapes. When carbon dioxide refrigerant is used, micropores 36 having a substantially cylindrical inner shape with high pressure resistance are desirable. The micropores 36 may also be arranged in a plurality of rows, thereby ensuring a large heat exchange area with the refrigerant.

[0070] In this way, micropores 36 that serve as refrigerant flow paths are formed inside the cooling plate 35, and the refrigerant passing through the micropores 36 evaporates at a constant temperature. In other words, the cooling plate 35 acts as an evaporator, and the refrigerant evaporates at the saturation temperature of the fluid pressure. This allows the cooling plate 31 to have a uniform temperature. This makes it possible to uniformize the temperature of the capacitor 33 and pass an alternating current of a predetermined frequency through stable resonance.

[0071] As an example, if the capacitance C of capacitor 33 in resonant circuit 15 is 0.00118 μF and the Q value is 1000, a temperature change of +2°C to +3°C will cause a 0.1% change in capacitance C. As a result, a shift of 110 Hz will occur in the resonance point.

[0072] As mentioned above, the ±2°C conversion is 2°C relative to the resonance peak. -0.5 The temperature is reduced by 2 times, but air cooling using a fan, as in the prior art, cannot adequately address this. In other words, a ±2°C change is a temperature fluctuation level that is easily affected by the ambient temperature sucked in by the fan of the fan. Therefore, air cooling using a fan cannot prevent the phenomenon in which the effect of the resonant circuit 15 is reduced by about 30%.

[0073] In contrast, in the magnetic field generator 1 according to this embodiment, the condenser 33 is cooled by a cooling plate 35 through which a refrigerant flows. The method of cooling the condenser 33 by the cooling plate 35 utilizes the latent heat of evaporation of the refrigerant, so it is easy to make the surface temperature of the cooling plate 35 uniform within ±0.1°C. Therefore, for example, if the design temperature is set to room temperature, 25°C, and the capacitance C of the condenser 33 is designed and the components are selected, the cooling plate 35 can be controlled to always maintain 25°C.

[0074] A specific method for controlling the magnetic field generating device 1 will be described in detail below with reference to FIGS. 1 and 2, this embodiment employs a method of directly cooling the coil 16 by flowing a refrigerant through the inside of the coil 16. The coil 16 is controlled so as to maintain a constant surface temperature of, for example, the insulating material or case that houses the coil 16.

[0075] The temperature of the coil 16 can be controlled by, for example, PID control (Proportional-Integral-Derivative Control).

[0076] Specifically, the temperature of the coil 16 is measured by a temperature sensor 41 that is appropriately installed in the coil 16. The temperature sensor 41 is installed, for example, on the surface of the coil 16, on the surface of a coil case (not shown) that houses the coil 16, or on the refrigerant piping on the inlet side of the coil 16. That is, the temperature sensor 41 obtains temperature data that corresponds to the evaporation temperature of the refrigerant flowing through the coil 16.

[0077] The opening of the expansion valve 23 is controlled by the refrigerator control circuit 12 constituting the control device so that the temperature of the coil 16 measured by the temperature sensor 41 becomes a target temperature, for example, 25°C. Furthermore, the refrigerator control circuit 12 may control the rotation speed of the compressor 21 so that the temperature of the coil 16 measured by the temperature sensor 41 reaches a predetermined target temperature, for example, 25°C.

[0078] Furthermore, the temperature of the refrigerant piping, i.e., a temperature corresponding to the temperature of the refrigerant, is measured by a temperature sensor 43 provided at an appropriate position, such as in the refrigerant piping on the outlet side of the coil 16. The opening of the expansion valve 23 may be controlled based on the temperature on the outlet side of the coil 16 measured by the temperature sensor 43. For example, the opening of the expansion valve 24 may be controlled by the refrigerator control circuit 12 so that the temperature measured by the temperature sensor 43 becomes a predetermined target temperature.

[0079] For example, superheat control may be performed to control the expansion valve 23 based on the difference between the temperature of the refrigerant in the coil 16 measured by the temperature sensor 41 and the temperature of the refrigerant that has passed through the coil 16 measured by the temperature sensor 43.

[0080] Specifically, the opening degree of the expansion valve 23 may be controlled by the refrigerator control circuit 12 so that the difference between the temperature of the refrigerant in the coil 16 measured by the temperature sensor 41 and the temperature of the refrigerant that has passed through the coil 16 measured by the temperature sensor 43 becomes a predetermined target temperature.

[0081] This allows the refrigerant to be maintained in a gas-liquid two-phase state at a predetermined pressure throughout almost the entire area of ​​the coil 16. Therefore, the refrigerant absorbs heat equally throughout almost the entire area of ​​the coil 16, making the temperature distribution within the coil 16 uniform.

[0082] 1, 2 and 6, in the temperature control of the condenser 33, the temperature of the condenser 33 and the like is measured by a temperature sensor 42 installed at an appropriate position on the cooling plate 35 of the condenser 33. That is, temperature data corresponding to the temperature of the refrigerant flowing through the cooling plate 35 and the like is obtained. Based on the temperature of the condenser 33 measured by the temperature sensor 42, the refrigerator control circuit 12 performs, for example, PID control to control the opening of the expansion valve 24.

[0083] The cooling plate 35 that cools the resonant circuit 15 may be controlled in a manner similar to that of the cooling plate 31 that cools the coil 16. That is, the refrigerator control circuit 12 may control the opening of the expansion valve 24 so that the temperature of the cooling plate 35 measured by the temperature sensor 42 becomes a predetermined target temperature.

[0084] In addition, a temperature sensor 44 may be installed in the refrigerant piping on the outlet side of the cooling plate 35, and the opening of the expansion valve 24 may be controlled by the refrigerator control circuit 12 so that the temperature measured by the temperature sensor 44 becomes a predetermined target temperature.

[0085] Alternatively, the opening of expansion valve 24 may be controlled using the difference between the measurement value of temperature sensor 42 installed at an appropriate position such as the surface of cooling plate 35 and the measurement value of temperature sensor 44 installed on the refrigerant outlet pipe. This makes the temperature of cooling plate 35 uniform, and as a result, condenser 33 can be maintained at the designed temperature.

[0086] As already explained, the refrigerant that cools the power supply circuit of the magnetic field generating device 1 may be a hydrofluorocarbon refrigerant such as R32, R410A, or R404A, or a hydrofluoroolefin such as R1234yf, or a carbon dioxide refrigerant that is a natural refrigerant, or a mixture of these refrigerants.

[0087] Regardless of the refrigerant, the refrigerant's latent heat can be utilized by evaporating inside the coil 16 and inside the cooling plate 35 of the condenser 33. This allows a large amount of heat to be removed from the objects to be cooled, such as the coil 16 and the condenser 33, and the objects to be cooled can be controlled to a uniform temperature. Note that any refrigerant that can form a vapor compression refrigeration cycle can be expected to have the same effect. Carbon dioxide refrigerant is particularly preferred because it can significantly reduce flow resistance.

[0088] Next, as a modified example of the embodiment, a magnetic field generating device 101 shown in FIG. 8 will be described in detail. 8 is a diagram showing a circuit of a refrigerant circulation system of a magnetic field generating device 101 according to another embodiment of the present invention. Note that components that have the same or similar functions and effects as those in the already described embodiments are given the same reference numerals, and their description will be omitted.

[0089] 8, magnetic field generating device 101 is provided with expansion valve 25 as a control valve capable of controlling the flow of refrigerant, downstream of switching circuit 14 and resonance circuit 15 in path 28 of the refrigerant piping.

[0090] The expansion valve 25 is, for example, an electronic expansion valve, a thermostatic expansion valve, a capillary tube, or the like, and has a structure that generates an appropriate pressure loss in the flow of the refrigerant. For automatic control, the expansion valve 23 is preferably an electronic expansion valve whose opening can be adjusted by a stepping motor.

[0091] 6 and 8, the amount of heat generated by the coil 16 is much larger than the amount of heat generated by the capacitor 33 and the like of the resonant circuit 15. In other words, the amount of heat generated by the capacitor 33 and the like is much larger than the amount of heat generated by the coil 16. heat Small compared to the quantity.

[0092] 4, 6 and 8, as described above, the expansion valve 25 is provided in the refrigerant piping downstream of the cooling plates 31 and 35 that cool the switching circuit 14 and the resonant circuit 15. This makes it possible to adjust the evaporation pressure of the refrigerant in the cooling plates 31 and 35 to be high.

[0093] That is, the evaporation pressure of the refrigerant flowing through the coil 16 in the path 27 to cool the coil 16 can be set to a different value from the evaporation pressure of the refrigerant flowing through the cooling plates 31, 35 in the path 28 to cool the switching element 30 and the capacitor 33. This allows the coil 16 and the capacitor 33 to be efficiently cooled at different evaporation temperatures suited to their respective heat values.

[0094] Specifically, the evaporation temperature of the refrigerant flowing through the cooling plates 31, 35 that cool the condenser 33 and the like of the resonant circuit 15 is controlled by the expansion valve 25 so as to reach a predetermined target temperature, for example, 25°C. The expansion valve 24 on the inlet side of the cooling plates 31, 35 is controlled by checking the difference between the temperature of the condenser 33 and the like measured by the temperature sensor 42 and the temperature of the refrigerant on the outlet side of the cooling plates 31, 35 measured by the temperature sensor 44, so that the refrigerant reaches an appropriate superheat level, for example, 5°C.

[0095] In this way, the flow resistance component of expansion valve 24 allows refrigerant to evaporate in cooling plates 31, 35 at a temperature different from the cooling temperature of coil 16. This allows coil 16 and condenser 33 to be cooled at different temperatures, allowing their respective capacities to be matched.

[0096] Since the heat generation amount of the capacitor 33 of the resonant circuit 15 is smaller than that of the coil 16, in one embodiment, a separate expansion valve 25 or a capillary tube may be provided at the outlet of the cooling plate 35 as shown in Figure 8. This flow resistance component allows the refrigerant to evaporate at a temperature different from the cooling temperature of the coil 16, so the capabilities of the coil 16 and the condenser 33 can be matched.

[0097] As described above, the magnetic field generating devices 1, 101 according to this embodiment have a coil 16 with a cross-sectional shape having multiple micropores 19 that allow coolant to circulate in a narrow area, and a structure that allows current and coolant to flow.

[0098] The magnetic field generators 1 and 101 are provided with a capacitor 33 that resonates the coil 16, and have a refrigeration circuit configuration that includes cooling plates 31 and 35 that can cool the capacitor 33 with a cooling liquid.

[0099] The cooling liquid used in the cooling section of the magnetic field generating device 1, 101 is a hydrofluorocarbon or hydrofluoroolefin refrigerant, or carbon dioxide alone or a mixture thereof. Furthermore, the magnetic field generators 1 and 101 have a circulation circuit through which a refrigerant can flow as a cooling liquid for the coil 16 and the condenser 33, respectively.

[0100] Furthermore, the magnetic field generating devices 1 and 101 are provided with control valves in the paths 27 and 28 through which the coolant flows, respectively, and the temperatures of the devices are controlled independently by a control device. Furthermore, in the control, the control valve is controlled so that the condenser 33 reaches a predetermined temperature as designed.

[0101] This configuration prevents the resonant frequency from deviating from the target frequency due to changes in the temperature of the coil 16 and capacitor 33 that make up the resonant circuit 15, thereby obtaining the target current and realizing stable, highly accurate generation of a magnetic field.

[0102] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. [Explanation of symbols]

[0103] 1. Magnetic field generator 10 Power circuit 11 Main control circuit 12 Refrigerator control circuit 13 Driver circuit 14 Switching Circuits 15 Resonant circuit 16 coils 17 Feedback control circuit 18 Wiring 19 Micropore 21 Compressor 22 Condenser 23 Expansion valve 24 Expansion valve 25 Expansion valve 26 Routes 27 Routes 28 routes 30 Switching element 31 Cooling plate 32 Micropore 33 Capacitor 34 Connecting member 35 Cooling plate 36 Micropore 41 Temperature Sensor 42 Temperature Sensor 43 Temperature Sensor 44 Temperature Sensor

Claims

1. The cooling system includes a compressor, a condenser, an expansion valve, and an evaporator connected to circulate a cooling liquid; the evaporator is formed from a coil in which a coil substrate having a plurality of through holes formed therein for allowing the cooling liquid to flow is wound in a cylindrical spiral shape, a resonant circuit having a capacitor that resonates the coil is connected to the coil; the condenser is provided with a cooling plate having a plurality of micropores formed therein through which the cooling liquid flows; The magnetic field generating device is characterized in that the coil and the capacitor are cooled by the cooling liquid.

2. 2. The magnetic field generating device according to claim 1, wherein the coolant is a hydrofluorocarbon-based refrigerant, a hydrofluoroolefin-based refrigerant, a carbon dioxide refrigerant, or a mixture thereof.

3. 3. The magnetic field generating device according to claim 1, further comprising a circulation circuit that allows the coolant to flow in parallel through the cooling portions of the coil and the condenser.

4. 4. The magnetic field generating device according to claim 1, wherein a control valve whose opening is controlled independently of the expansion valve is provided in a path through which the cooling liquid flows to the cooling plate of the condenser.

5. 5. The magnetic field generating device according to claim 4, further comprising a control device for controlling the opening of the control valve so that the capacitor reaches a predetermined temperature.

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