Coupling mechanism with magnetic blocking gap and parameter design method thereof

Abstract

This invention discloses a coupling mechanism with magnetically blocking gaps and its parameter design method, belonging to the field of magnetic coupling transmission technology. It includes a transmitting coil and a magnetic core. The main body of the transmitting coil is flat against the upper surface of the magnetic core. The transmitting coil is integrally wound from a single Litz wire in a combination of a Q-type coil and a DD-type coil. Through-holes are formed on the magnetic core, allowing the main body of the transmitting coil to fit against the magnetic core without increasing the overall thickness of the transmitting coil. Magnetic blocking gaps are formed along the wall of each through-hole in the magnetic core, penetrating both the upper and lower surfaces of the magnetic core. These gaps block the circulating magnetic flux generated by the coil within the through-hole in the magnetic core, thus preventing the formation of eddy currents and the resulting heat generation. This significantly improves the local problems of the magnetic core in the coupling mechanism without affecting the system's coupling coefficient and transmission performance.

Description

Technical Field

[0001] This invention belongs to the field of magnetic coupling transmission technology, and more specifically, relates to a coupling mechanism with a magnetically resistive gap and its parameter design method. Background Technology

[0002] A magnetic core is a sintered magnetic metal oxide composed of various iron oxide mixtures. Placing a magnetically conductive material (magnetic core) in the magnetic circuit of an inductor coil can increase the magnetic induction intensity of the electromagnet.

[0003] In some coupling mechanisms where coils and magnetic cores work together, such as Figure 1 As shown, for structural or volume considerations, the coil needs to pass through the magnetic core. Because the magnetic element generates alternating magnetic flux through the core under the influence of a changing magnetic field, an induced current is produced. This current flows in a vortex pattern, hence the name eddy current. Furthermore, since the resistivity of the magnetic element is not infinite, and the magnetic conductor has a certain resistance value, the eddy current flowing through the core generates heat, i.e., eddy current loss. In other words, the eddy current effect causes the core to heat up. If these temperatures are ignored, the safety of the coupling mechanism will inevitably be affected. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a coupling mechanism with a magnetically resistive gap and its parameter design method to solve the technical problems in the background art.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: a coupling mechanism with a magnetically resistive gap and its parameter design method, including a transmitting coil and a magnetic core, the key being: the main body plane of the transmitting coil is attached to the upper surface of the magnetic core, and the transmitting coil is integrally wound from a Litz wire in the form of a combination of a Q-type coil and a DD coil;

[0006] A through hole is formed on the magnetic core. One end of the transmitting coil passes through the first through hole from the lower surface of the magnetic core to the upper surface and is wound turn by turn from the outside to the inside to form the Q-type coil. The end of the Q-type coil passes through the second through hole to the lower surface of the magnetic core and returns to the upper surface of the magnetic core from the third through hole. Then, it is wound turn by turn from the inside to the outside according to the first winding direction to form the first D-type sub-coil. The end of the first D-type sub-coil extends outward and is wound turn by turn from the outside to the inside according to the second winding direction to form the second D-type sub-coil. The end of the second D-type sub-coil passes through the magnetic core from the fourth through hole and forms the other end of the transmitting coil on the lower surface of the magnetic core.

[0007] A magnetic blocking slit is formed along the hole wall in each through hole of the magnetic core, and the magnetic blocking slit extends through the upper and lower surfaces of the magnetic core.

[0008] As a preferred embodiment of the present invention, the magnetically resistive gap is cross-shaped.

[0009] As a preferred embodiment of the present invention, the width of the magnetically resistive gap is 8 mm.

[0010] As a preferred embodiment of the present invention, the length of the magnetically resistive gap is 32cm.

[0011] As a preferred embodiment of the present invention, an aluminum plate is also attached to the lower surface of the magnetic core.

[0012] As a preferred embodiment of the present invention, the aluminum plate is provided with heat dissipation channels.

[0013] As a preferred embodiment of the present invention, a cooling fan is provided on the heat dissipation channel.

[0014] As a preferred embodiment of the present invention, heat dissipation fins are provided on the aluminum plate.

[0015] As a preferred embodiment of the present invention, an inverter compensation layer is provided at the bottom of the aluminum plate.

[0016] To achieve this objective, the present invention also provides a method for designing parameters of a coupling mechanism with a magnetically resistive gap, characterized by comprising the following steps:

[0017] S1: Determine the excitation current of the transmitting coil and select the type of magnetically resistive gap based on the maximum coupling coefficient of the coupling mechanism;

[0018] S2: Gradually increase the width of the magnetic deflection gap, observe the change in the average magnetic flux of the magnetic core through simulation, and select the width of the magnetic deflection gap based on the change in the average magnetic flux of the magnetic core.

[0019] S3: Gradually increase the length of the magnetic reluctance gap, observe the change in the average magnetic flux of the core through simulation, and select the length of the magnetic reluctance gap based on the change in the average magnetic flux of the core.

[0020] This invention provides a coupling mechanism with a magnetically resistive gap and its parameter design method, which has the following beneficial effects:

[0021] In the coupling mechanism where the coil passes through the magnetic core, a magnetic blocking gap is opened along the hole wall on each through hole of the magnetic core. By setting the magnetic blocking gap, the circulating magnetic flux generated by the coil in the through hole in the magnetic core can be blocked, thereby avoiding the formation of eddy currents and the generation of heat. This can significantly improve the local problems of the magnetic core in the coupling mechanism without affecting the system coupling coefficient and transmission performance. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure when the coil passes through the magnetic core, which is provided for the purpose of this background technology.

[0023] Figure 2 This is a schematic diagram of the coupling mechanism with a magnetically resistive gap provided in this embodiment;

[0024] Figure 3 This is a schematic diagram illustrating the variation of the average magnetic flux density of the magnetic core under different gap widths in the simulation experiment provided in this embodiment;

[0025] Figure 4 This is a schematic diagram of the cross-shaped magnetic resistive gap structure provided in this embodiment;

[0026] Figure 5 This is a schematic diagram showing the relationship between the length and width of the magnetically resistive gap and the magnetic induction intensity B in the simulation experiment provided in this embodiment;

[0027] Figure 6 This is a simulation diagram of the magnetic field of the 30cm magnetically resistive gap in the simulation experiment provided in this embodiment;

[0028] Figure 7 This is a simulation diagram of the magnetic field of the 32cm magnetically resistive gap in the simulation experiment provided in this embodiment;

[0029] Figure 8 This is a simulation diagram of the eddy current heating of the magnetic core before optimization in the COMSOL software provided in this embodiment;

[0030] Figure 9 This is a simulation diagram of the optimized eddy current heating of the magnetic core in the COMSOL software provided in this embodiment.

[0031] In the diagram: 1. Transmitting coil; 2. Magnetic core; 3. Aluminum plate; 4. Inverter compensation layer; 5. Magnetic blocking gap. Detailed Implementation

[0032] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0033] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0035] Please see Figure 2 As shown, the present invention provides the following technical solution: a coupling mechanism with a magnetically resistive gap, including a transmitting coil 1 and a magnetic core 2, wherein the main body plane of the transmitting coil 1 is attached to the upper surface of the magnetic core 2, and the transmitting coil 1 is integrally wound from a Litz wire in the form of a combination of a Q-type coil and a DD coil;

[0036] A through hole is made on the magnetic core 2. One end of the transmitting coil 1 passes through the first through hole from the lower surface to the upper surface of the magnetic core 2 and is wound from the outside to the inside to form a Q-type coil. The end of the Q-type coil passes through the second through hole to the lower surface of the magnetic core 2 and returns to the upper surface of the magnetic core 2 from the third through hole. Then, it is wound from the inside to the outside according to the first winding direction to form a first D-type sub-coil. The end of the first D-type sub-coil extends outward and is wound from the outside to the inside according to the second winding direction to form a second D-type sub-coil. The end of the second D-type sub-coil passes through the fourth through hole and forms the other end of the transmitting coil 1 on the lower surface of the magnetic core 2.

[0037] A magnetic blocking slit 5 is provided along the hole wall on each through hole of the magnetic core 2, and the magnetic blocking slit 5 extends through the upper and lower surfaces of the magnetic core 2.

[0038] Furthermore, such as Figure 4 As shown, in order to achieve better and more uniform magnetic blocking, the magnetic blocking gap 5 is cross-shaped, with a width of 8mm and a length of 32cm.

[0039] The above design was verified based on the following experiments:

[0040] Simulation experiments were conducted with different magnetically resistive gap widths, and the results were as follows: Figure 3 The experimental results show that the average magnetic induction intensity B of the magnetic core 2 drops rapidly as the width of the magnetic reluctance gap 5 increases, then drops to a lower value at around 4-8 mm, and then increases again at a very slow pace.

[0041] As shown in the equation, the eddy current heating power within the magnetic core 2 is negatively correlated with the square of the magnetic diameter length, which is also negatively correlated with the square of the distance from the eddy current heating point to the lead wire. Therefore, the eddy current heating power generated by the magnetic core 2 is smaller at distances from the lead wire. Thus, to further reduce the impact of the optimized design of the magnetic core 2 on the performance of the coupling mechanism, the magnetic resistance gap 5 is set as follows... Figure 4The cross-shaped slot shown is centered around the through hole;

[0042] To investigate the relationship between the length and width of the magnetically resistive gap 5, simulation experiments were conducted with magnetically resistive gaps 5 of different lengths and widths, and the results were as follows: Figure 5 The experimental results, as shown in the figure, indicate that the width of the magnetically resistive gap 5 varies from 4 to 12 mm, which has little effect on the average magnetic flux density B of the magnetic core 2. However, the length of the magnetically resistive gap 5 has a significant impact on the average magnetic flux density B of the magnetic core 2. When the length of the magnetically resistive gap 5 is between 0 and 30 cm, the average magnetic flux density B of the magnetic core 2 decreases with the increase of the length of the magnetically resistive gap 5, and decreases sharply to the minimum at 30-32 cm. Above 32 cm, the length of the magnetically resistive gap 5 has little effect on the magnetic flux density, and the average magnetic flux density B of the magnetic core 2 increases slightly with the increase of the length of the magnetically resistive gap 5.

[0043] Taking an 8mm wide magnetically resistive gap 5 as an example, the magnetic field was simulated for gap lengths of 30cm and 32cm. The results are as follows. Figure 6 , Figure 7 As shown, it can be seen that when the length of the magnetic reluctance gap 5 is 30cm, some magnetic circuits still have relatively small magnetic reluctance, and the magnetic circuits are not blocked by the air magnetic reluctance gap 5. The average magnetic induction intensity B of the magnetic core 2 is relatively large. However, when the length of the magnetic reluctance gap 5 of the magnetic core 2 increases to 32cm, the magnetic circuits are all blocked by the air magnetic reluctance gap 5, and the overall average magnetic induction intensity B of the magnetic core 2 is relatively low.

[0044] COMSOL software has multiphysics simulation capabilities, which can be used to study the electromagnetic heat generated in the magnetic core 2 by the magnetic field of the magnetically resistive gap 5. The optimization results are simulated, and the simulation results are as follows: Figure 8 Figure 9 The figure shows the temperature change of core 2 after ten minutes of system operation under a 200A current excitation. As can be seen from the figure, the eddy current heating of core 2 before optimization is basically consistent with the heating location measured in the actual experiment, with the temperature near the hot spot exceeding 100℃. However, after adding a 32cm long and 0.8cm wide cross-shaped magnetically resistive gap 5, the eddy current heating of core 2 is significantly improved. Furthermore, the magnetic field simulation results show that the self-inductance of the optimized power transmitting coil 1 of core 2 is 33.3uH and the mutual inductance is 9.8uH. After optimization, the self-inductance of the power transmitting coil 1 becomes 33.1uH and the mutual inductance becomes 9.66uH. Its coupling coefficient k only changes from 0.294 to 0.292. The impact on the self-inductance and mutual inductance of the power transmitting coil 1 is less than 3%, and the impact on the coupling coefficient is less than 1%. Therefore, this optimization process has a small impact on the system's power transmission performance.

[0045] The simulation results above demonstrate that the proposed optimization method for hotspots in core 2, which is less affected by coupling coefficients, is effective. It significantly improves the local hotspot problem in core 2 of the coupling mechanism without affecting the system's coupling coefficient or transmission performance. Subsequent sections will conduct physical experiments on a prototype system to verify the practicality of this method.

[0046] To better dissipate heat, an aluminum plate 3 is attached to the lower surface of the magnetic core 2. The aluminum plate 3 is provided with heat dissipation channels, and preferably, heat dissipation fins are provided on the aluminum plate 3.

[0047] To further improve heat dissipation, and considering factors such as size, cost, and ease of installation, cooling fans are installed on the heat dissipation channel. Preferably, cooling fans are installed at the edge of aluminum plate 3, so that air flows through the interior of aluminum plate 3, forming forced air cooling.

[0048] In addition, such as Figure 2 As shown, an inverter compensation layer 4 is provided at the bottom of the aluminum plate 3. The inverter compensation layer 4 is separated from the magnetic core 2 of the transmitting coil 1 by the aluminum plate 3 layer. While dissipating heat, it can also play an electromagnetic shielding role. The magnetic core layer of the transmitting coil 1 and the inverter compensation layer 4 need to be connected by wires for energy transfer. Considering magnetic leakage and aesthetics, the transmitting coil 1 is led to the inverter compensation layer 4 by drilling a hole in the aluminum plate 3.

[0049] This invention also provides a method for designing parameters of a coupling mechanism with a magnetically resistive gap, comprising the following steps:

[0050] S1: Determine the excitation current of transmitting coil 1, and select the type of magnetically resistive gap 5 based on the maximum coupling coefficient of the coupling mechanism;

[0051] S2: Gradually increase the width of the magnetic deflection gap 5, observe the change in the average magnetic flux of the magnetic core 2 through simulation, and select the width of the magnetic deflection gap 5 based on the change in the average magnetic flux of the magnetic core 2.

[0052] S3: Gradually increase the length of the magnetically resisting gap 5, observe the change in the average magnetic flux of the magnetic core 2 through simulation, and select the length of the magnetically resisting gap 5 based on the change in the average magnetic flux of the magnetic core 2.

[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A coupling mechanism with a magnetically resistive gap, comprising a transmitting coil and a magnetic core, characterized in that: The main body plane of the transmitting coil is attached to the upper surface of the magnetic core. The transmitting coil is integrally wound from a single Litz wire in the form of a combination of a Q-type coil and a DD coil. A through hole is formed on the magnetic core. One end of the transmitting coil passes through the first through hole from the lower surface of the magnetic core to the upper surface and is wound turn by turn from the outside to the inside to form the Q-type coil. The end of the Q-type coil passes through the second through hole to the lower surface of the magnetic core and returns to the upper surface of the magnetic core from the third through hole. Then, it is wound turn by turn from the inside to the outside according to the first winding direction to form the first D-type sub-coil. The end of the first D-type sub-coil extends outward and is wound turn by turn from the outside to the inside according to the second winding direction to form the second D-type sub-coil. The end of the second D-type sub-coil passes through the magnetic core from the fourth through hole and forms the other end of the transmitting coil on the lower surface of the magnetic core. A magnetic blocking slit is formed along the hole wall in each through hole of the magnetic core, and the magnetic blocking slit extends through the upper and lower surfaces of the magnetic core.

2. The coupling mechanism with a magnetically resistive gap according to claim 1, characterized in that: The magnetically blocking gap is cross-shaped.

3. The coupling mechanism with a magnetically resistive gap according to claim 1 or 2, characterized in that: The width of the magnetically resistive gap is 8mm.

4. The coupling mechanism with a magnetically resistive gap according to claim 3, characterized in that: The length of the magnetically resistive gap is 32cm.

5. The coupling mechanism with a magnetically resistive gap according to claim 1, characterized in that: An aluminum plate is also attached to the lower surface of the magnetic core.

6. The coupling mechanism with a magnetically resistive gap according to claim 5, characterized in that: The aluminum plate is provided with heat dissipation channels.

7. The coupling mechanism with a magnetically resistive gap according to claim 6, characterized in that: A cooling fan is installed on the heat dissipation channel.

8. The coupling mechanism with a magnetically resistive gap according to claim 6, characterized in that: The aluminum plate is provided with heat dissipation fins.

9. The coupling mechanism with a magnetically resistive gap according to any one of claims 5-8, characterized in that: An inverter compensation layer is provided at the bottom of the aluminum plate.

10. A parameter design method for a coupling mechanism with a magnetically resistive gap as described in any one of claims 1-9, characterized in that, Includes the following steps: S1: Determine the excitation current of the transmitting coil and select the type of magnetically resistive gap based on the maximum coupling coefficient of the coupling mechanism; S2: Gradually increase the width of the magnetic deflection gap, observe the change in the average magnetic flux of the magnetic core through simulation, and select the width of the magnetic deflection gap based on the change in the average magnetic flux of the magnetic core. S3: Gradually increase the length of the magnetic deflection gap, observe the change in the average magnetic flux of the core through simulation, and select the length of the magnetic deflection gap based on the change in the average magnetic flux of the core.

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