Transformer and manufacturing method thereof, charging device, and power supply unit

Abstract

To provide a transformer capable of avoiding core cracking even when temperature changes, a charging device using the transformer, and a power supply unit.SOLUTION: The transformer includes an upper core 303 and a lower core 302, each inserting a primary winding 401 and a secondary winding 402 therethrough, and which are arranged opposite each other. The lower core includes a single core part, and the upper core includes multiple core parts. The upper core and lower core are arranged facing each other being interposed by a gap 405, and are secured together by adhesive tape in a state of being bonded together and placed opposite each other or arranged so that they face each other. Below the lower core, a cooling device is provided.SELECTED DRAWING: Figure 4A

Description

Technical Field

[0001] The present disclosure relates to a transformer, a charging device using the transformer, a power supply device using the transformer, and a method for manufacturing the transformer, which are used in a power conversion circuit such as a DC-DC converter, for example.

Background Art

[0002] Conventionally, electric vehicles and plug-in hybrid vehicles are equipped with in-vehicle charging devices for charging rechargeable batteries from a commercial AC power supply. For example, they are disclosed in Patent Document 1 and Patent Document 2. Here, Patent Document 1 discloses a transformer in which E-cores are combined vertically. Further, Patent Document 2 discloses a transformer in an outer iron type transformer, in which inner legs are divided from the center and a heat dissipation plate is interposed therebetween.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the transformers of Patent Documents 1 and 2 have a problem that core cracking occurs due to temperature changes.

[0005] An object of the present disclosure is to provide a transformer that can avoid core cracking even when a temperature change occurs, a charging device using the transformer, and a power supply device using the transformer.

Means for Solving the Problems

[0006] The transformer according to the present disclosure includes a primary winding and a secondary winding, and includes a first core and a second core that are inserted through the primary winding and the secondary winding and are arranged to face each other. The first core includes one first core portion. The second core includes a plurality of second core portions. It is characterized by this.

Advantages of the Invention

[0007] According to the transformer according to the present disclosure, even when a temperature change occurs, core cracking can be avoided, and the reliability of the transformer can be improved.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 5

Figure 6

Figure 7A

Figure 7B

Figure 7C

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12A

Figure 12B

Figure 12C

Figure 12D

Figure 12E

Figure 13A

Figure 13B

Figure 13C

Figure 13D

Figure 13E

Figure 14

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0010] (Problems of Comparative Examples) Hereinafter, the transformer disclosed in Patent Document 1 is referred to as Comparative Example 1, and the transformer disclosed in Patent Document 2 is referred to as Comparative Example 2, and these problems will be described.

[0011] In a transformer in which E-shaped cores are combined vertically as in Comparative Example 1, due to a rapid temperature change such as a heat cycle test, the core in the longitudinal direction of the E-shaped core is arranged on the outermost side, and it expands or contracts according to the coefficient of thermal expansion of the core following the temperature change. Here, the inner legs located inside the core have a large volume and are located inside, so the temperature change is delayed, and due to the delay from the expansion or contraction in the longitudinal direction of the E-shaped core, core cracking occurs at the center of the core, and the reliability decreases.

[0012] Further, when a transformer in which the inner legs are divided from the center as in Comparative Example 2 is applied to a leakage-built-in transformer in which a gap is provided in the inner legs, the manufacturability deteriorates, and the balance of the lower surface, which mainly serves as a cooling surface, and furthermore, the adhesion of the connection between the cores of the outer legs cannot be maintained, the stability of the inductance value and the coolability of the core are impaired, and the reliability of the transformer operation decreases.

[0013] (Embodiment) Embodiments according to the present disclosure for solving the above problems will be described below. However, the configurations described below are merely examples of the present disclosure, and the present disclosure is not limited to the following embodiments. Even outside these embodiments, various modifications can be made according to the design and the like as long as the technical idea according to the present disclosure is not deviated from.

[0014] FIG. 1 is a block diagram showing a configuration example of an in-vehicle charger 101 according to an embodiment of the present disclosure. The in-vehicle charger 101 in FIG. 1 is characterized by converting AC power from a commercial AC power supply 102 into DC power and outputting it to a rechargeable battery 106, and insulating before and after the conversion by a transformer 206 built in a DC-DC converter 105.

[0015] In FIG. 1, the in-vehicle charger 101 includes a rectifying and smoothing circuit 103, a power factor correction circuit (PFC circuit) 104, and a DC-DC converter 105. In an electric vehicle or a plug-in hybrid vehicle, AC power from a 100V or 200V commercial AC power supply 102 is rectified and smoothed by the rectifying and smoothing circuit 103. Next, the PFC circuit 104 performs power factor correction on the input rectified and smoothed voltage and suppresses harmonics, and then outputs it to the DC-DC converter 105. The DC-DC converter 105 converts the input DC voltage into a DC output voltage corresponding to the battery voltage of the subsequent rechargeable battery 106.

[0016] FIG. 2 is a circuit diagram showing a configuration example of the DC-DC converter 105 in FIG. 1. In the present embodiment, as an example, an LLC resonant type DC-DC converter 105 widely used in high-efficiency power supplies such as industrial switching power supplies, in-vehicle chargers, and further power converters is used as the DC-DC converter.

[0017] In FIG. 2, an LLC resonant DC-DC converter 105 includes an inverter circuit 201, a resonant capacitor 209, a transformer 206, a rectifier circuit 210, a smoothing capacitor 211, and a control circuit 220 that generates gate signals Sg1 to Sg4 for controlling the operation of the inverter circuit 201, between input terminals T1 and T2 and output terminals T3 and T4. Here, the inverter circuit 201 is configured by connecting, in a bridge form, switching elements such as N-channel MOS transistors 202 to 205, and the MOS transistors 202 to 205 are turned on or off according to the gate signals Sg1 to Sg4, thereby converting a DC voltage into an AC voltage. The transformer 206 includes a leakage inductance 207, an exciting inductance 208 of the primary winding, and an inductance 212 of the secondary winding.

[0018] In the DC-DC converter 105, the inverter circuit 201 converts the input voltage into an AC voltage by switching, and outputs it to the rectifier circuit 210 via the resonant capacitor 209 and the transformer 206. Here, by utilizing the resonance of the two inductances of the leakage inductance 207 and the exciting inductance 208 of the transformer 206 and the resonant capacitor 209 and one capacitor, the output voltage is changed using a frequency modulation method that changes the switching frequency of the four MOS transistors 202 to 205. Next, the output voltage from the transformer 206 is rectified by the rectifier circuit 210, smoothed by the smoothing capacitor 211, and then a DC voltage is output.

[0019] With the DC-DC converter 105 configured as described above, the switching loss can be reduced by zero voltage switching, and the surge current and voltage can be reduced by a switching current close to a sine wave, and the noise can be reduced.

[0020] FIG. 3 is a perspective view showing the appearance of the transformer 206 in FIG. 2, FIG. 4A is a longitudinal sectional view taken along the line A-A' of FIG. 3, and FIG. 4B is a cross-sectional view taken along the line B-B' of FIG. 3. The up, down, left, and right directions in FIGS. 3, 4A, and 4B are described as the up, down, left, and right directions, but this is not intended to limit the usage form of the transformer 206. As shown in FIG. 3, the manufactured transformer 206 is placed on an air-cooled or water-cooled cooling device 305.

[0021] In FIGS. 3 and 4A, the transformer 206 includes a lower core 302 that is an E-shaped core and constitutes one core part, two core parts 303a and 303b of upper cores 303 that are each U-shaped cores, and a bobbin 301 that is formed between the lower core 302 and the upper core 303 and is inserted into a closed magnetic path region 403 formed by the lower core 302 and the upper core 303. Here, in each groove of the bobbin 301, a primary winding 401 and a secondary winding 402 are wound such that the central axis of the closed magnetic path region 403 becomes the winding axis. In this embodiment, each of the cores 302 and 303 is composed of, for example, a ferrite core. The bobbin 301 is made of an insulating material such as polyphenylene sulfide resin.

[0022] The lower core 302 is composed of an E-shaped core including two outer legs 302a and 302b, one inner leg 302c, and a bottom surface portion 302d for supporting these. Here, the inner leg 302c is arranged to be inserted into the closed magnetic path region 403. The closed magnetic path region 403 penetrates in a horizontal direction parallel to the core end face.

[0023] The upper core 303 is composed of a core part 303a of a U-shaped core and a core part 303b of a U-shaped core. The core part 303a includes an outer leg 303aa, an inner leg 303ab, and a bottom surface portion 303ac for supporting these. The core part 303b includes an outer leg 303ba, an inner leg 303bb, and a bottom surface portion 303bc for supporting these.

[0024] Each of the core parts 303a and 303b of the upper core 303 is arranged to face the lower core 302 as follows. (1) The end face of the outer leg 303aa of the core portion 303a faces the end face of the outer leg 302a of the lower core 302 and is adhesively bonded to each other with an adhesive. (2) The end face of the outer leg 303ba of the core portion 303b faces the end face of the outer leg 302b of the lower core 302 and is adhesively bonded to each other with an adhesive. (3) The end faces of the inner leg 303ab of the core portion 303a and the inner leg 303bb of the core portion 303b are separated via a predetermined gap 405 and are arranged to face the end face of the inner leg 302c of the lower core 302. (4) Note that the two core portions 303a and 303b are separated from each other via a predetermined gap 406 and are arranged to face each other in the lateral direction.

[0025] Here, the inner leg 302c of the lower core 302 inserted into the closed magnetic path region 403 and the inner legs 303ab and 303bb of the two core portions 303a and 303b inserted into the closed magnetic path region 403 of the upper core 303 are separated and arranged to face each other with the gap 405 therebetween as described above. By adjusting the interval of this gap 405, the exciting inductance 208 that constitutes the resonance frequency of the LLC resonant type DC-DC converter 105 can be adjusted. Further, the leakage inductance 207 is adjusted by the distance between the primary winding 401 and the secondary winding 402. Here, it is adjusted by the thickness of the bobbin between the primary winding 401 and the secondary winding 402, the difference in the number of turns wound around the upper and lower grooves of the primary winding 401 composed of two stages, and similarly the difference in the number of turns wound around the upper and lower grooves of the secondary winding 402 composed of two stages.

[0026] Furthermore, in the cross section viewed from above in FIG. 4B, the outer legs 303aa and 303ba and the inner legs 303ab and 303bb respectively protrude downward from the bottom portions 303ac and 303bc, and it can be understood that closed magnetic path regions 403 are formed between the outer leg 303aa and the inner leg 303ab and between the outer leg 303ba and the inner leg 303bb. Note that the closed magnetic path region 403 is filled with a filler 403A made of an insulating material such as a silicone filler at the end of the manufacturing process of the entire core. At that time, the filler 403A may also enter the gap 405 and the gap 406.

[0027] Note that although the lead wires arranged in a normal transformer, the bobbin cover for ensuring the insulation distance between the core and the winding, and further the mechanism for positioning the bobbin and the core are not shown in the drawings, they may be added as appropriate.

[0028] Also, in the in-vehicle charging device 101, heat dissipation and cooling of each component are carried out by providing a cooling device 305 (Fig. 3) such as a water cooling device or an air cooling device. The cooling device 305 is arranged below the transformer 206 to dissipate the heat generated by the transformer 206. At this time, the flatness with the bottom surface of the lower core 302 greatly affects the heat dissipation performance. Here, when each core 302, 303 normally generates heat, the lower core 302 is cooled by the cooling device 305, the upper core 303 is less likely to dissipate heat than the lower core 302, the upper core 303 is hotter than the lower core 302, and a temperature difference occurs between the upper and lower cores 302, 303.

[0029] Fig. 5 is a longitudinal sectional view showing an enlarged view of the distortion generated in each of the cores 302, 303 when a temperature difference occurs between the upper and lower cores 302, 303 of a transformer in which the upper core 303 is not divided into two parts according to the conventional example. Fig. 5 shows the result of enlarging and displaying the analysis result of the distortion generated in the cores 302, 303 when such a temperature difference occurs between the upper and lower cores 302, 303 in the E-shaped core of the conventional example. Here, the bobbin 301, the primary winding 401, and the secondary winding 402 are not shown.

[0030] As is clear from Fig. 5, it can be seen that the upper core 303 is deformed convex upward due to the coefficient of thermal expansion of the core 303, and a tensile stress is applied outward. This can also be understood from the fact that the thickness of the inner leg of the upper core 303, which was the same size at the same temperature, is thicker than the thickness of the inner leg of the lower core 302 as indicated by the reference numeral 303p. When such a stress is applied, core cracking may occur in the E-shaped core of the conventional example, but by separating the core part 303a of the U-shaped core and the core part 303b of the U-shaped core as in the configuration of the present embodiment, the stress is released, and it becomes possible to reduce core cracking.

[0031] In many in-vehicle passive components, it is necessary to comply with the tests defined by the Automotive Electronics Council (AEC). One of these tests is the heat cycle test, and resistance to rapid temperature changes is also required. In the conventional upper and lower E-shaped cores, the inner legs located inside the core have a large volume and are located inside, so the temperature change is delayed. Due to the delay from the expansion or contraction in the longitudinal direction of the E-shaped core located outside, core cracking may occur at the center of the core. However, like the configuration of the present embodiment, by dividing the upper core 303 into two core portions 303a and 303b of the U-shaped core, the volume of the inner leg is reduced. In addition, the heat from the surroundings is easily transmitted to the inner leg due to the gap between the U-shaped cores, making it difficult for core cracking to occur. Also, even if stress is generated, since it is divided at the center, the stress is reduced, making it difficult for core cracking to occur.

[0032] In the present embodiment, as the transformer 206 of the LLC resonant type DC-DC converter 105 having a gap 405 (FIG. 4A), the actual manufacturing method requires ingenuity. In particular, when adhering the outer legs of the upper core 303 and the lower core 302, as shown in FIG. 4A, for example, when trying to adhere with an epoxy-based adhesive 404, the adhesive 404 peels off due to the gap 405, or an unintended gap is formed between the outer legs (303aa, 302a) (303ba, 302b) of the upper core 303 and the lower core 302, which may cause a decrease from the desired inductance.

[0033] FIG. 6 is a longitudinal sectional view when the transformer 206 of FIG. 1 is fixed with the adhesive 404.

[0034] To solve the above problems, as shown in FIG. 6, when adhering, the upper and lower sides of the transformer 206 are reversed, and the upper core 303 composed of the two core portions 303a and 303b of the U-shaped core is arranged on the upper side, while the lower core 302 is arranged on the lower side. By fixing the space between the outer legs (303aa, 302a) (303ba, 302b) of the upper core 303 and the lower core 302 with the adhesive 404, the desired configuration can be realized.

[0035] Also, since the inner legs of the upper core 303 and the lower core 302 in FIG. 5 are separated by a gap, there are differences in the deformation of the inner leg thickness between the upper and lower parts. If these are fixed, stress will be generated in the cores 302 and 303 in a form that resists deformation so as not to follow each other between the two. That is, if the outer legs of the upper core 303 and the lower core 302 are not fixed with the adhesive 404, the stress in the core can be further relaxed. Therefore, a method of fixing with an adhesive tape can be considered, but if there is a gap 405, it may be difficult to wind the adhesive tape in the form of FIG. 4A etc.

[0036] FIG. 7A is a longitudinal sectional view when the transformer 206 in FIG. 2 is fixed with an adhesive tape 701. Further, FIG. 7B is a longitudinal sectional view when the entire circumference of the transformer 206 in FIG. 2 is fixed with the adhesive tape 701, and FIG. 7C is a perspective view showing the appearance when the entire circumference of the transformer 206 in FIG. 2 is fixed with the adhesive tape 701. Here, the adhesive tape 701 is an insulating fixing tape for fixing electrical components, such as a Kapton (registered trademark) tape made by DuPont.

[0037] To solve the above problems, when fixing with the adhesive tape 701, as shown in FIG. 7A, the adhesive tape 701 is arranged on the flat surface 601a of the mounting table 601, the top and bottom of the transformer 206 are reversed, and the core parts 303a and 303b of the upper core 303 composed of two U-shaped cores are arranged downward and fixed on the adhesive tape 701. Next, the bobbin 301 around which the primary winding 401 and the secondary winding 402 are wound is inserted and arranged in the closed magnetic circuit region 403 of the upper core 303. Finally, the lower core 302 is covered, and finally, the entire core is wound around with the adhesive tape 701 to fix it, so that the desired configurations of FIGS. 7B and 7C can be realized.

[0038] FIG. 8 is a longitudinal sectional view when a heat-resistant elastic body 801 is interposed between the core parts 303a and 303b of the two U-shaped cores of the transformer 206 in FIG. 2 and fixed with an adhesive tape 701.

[0039] A gap 405 is interposed between the core portions 303a and 303b of the two U-shaped cores. However, as shown in FIG. 8, a heat-resistant elastic body 801 having a heat-insulating effect may be interposed in the gap 405. Similar to FIG. 7, the top and bottom of the transformer 206 may be reversed and fixed with an adhesive tape 701. Thereby, the stress caused by the temperature difference between the upper core 303 and the lower core 302 can be absorbed by the heat-resistant elastic body 801, and a stable transformer structure can be constructed. Note that the heat-resistant elastic body 801 is, for example, a so-called gap filler having a sheet shape and is made of an insulating resin such as a silicone resin.

[0040] FIG. 9 is a longitudinal sectional view when a heat-resistant elastic body 901 is interposed between the core portions 303a and 303b of the two U-shaped cores of the transformer 206 in FIG. 2 and the lower core 302 of the E-shaped core and fixed with an adhesive tape 701.

[0041] Furthermore, as shown in FIG. 9, by interposing a heat-resistant elastic body 901 having a heat-insulating effect in the gap 405, reversing the top and bottom of the transformer 206 as in FIG. 7, and fixing with an adhesive tape 701, a stable transformer structure can be constructed. Note that the heat-resistant elastic body 901 is, for example, a so-called gap filler having a sheet shape and is made of an insulating resin such as a silicone resin. Note that the heat-resistant elastic body 801 in FIG. 8 and the heat-resistant elastic body 901 in FIG. 9 may be formed together.

[0042] As described above, the transformer 206 according to the present embodiment divides the upper core 303 into two parts and configures the lower core 302 with an E-shaped core, thereby reducing the stress on the upper core 303. Thereby, even in the case of a rapid temperature change, the delay in the temperature change of the inner legs is reduced between the U-shaped cores to prevent core cracking. Even when a gap 406 is arranged between the inner legs, the flatness of the core bottom surface is maintained, the heat dissipation from the core bottom surface is enhanced, the adhesion between the cores of the outer legs is enhanced, and the electrical stability such as inductance and the manufacturability of the transformer can be enhanced. Thereby, the reliability can be enhanced.

[0043] (Modification 1) FIG. 10 is a longitudinal sectional view showing a configuration example of a transformer 206A according to Modification 1, which is composed of one I-shaped core 302A and two U-shaped cores 303Aa and 303Ab.

[0044] In the core configuration of the embodiment, it has been composed of one E-shaped core and two U-shaped cores facing it. However, as in Modification 1 of FIG. 10, it may be composed of one I-shaped core 302A and U-shaped cores 303Aa and 303Ab that constitute two core portions facing it. Here, the U-shaped core 303Aa is configured to include an outer leg 303Aaa, an inner leg 303Aab, and a bottom surface portion 303Aac that supports them. Further, the U-shaped core 303Ab is configured to include an outer leg 303Aba, an inner leg 303Abb, and a bottom surface portion 303Abc that supports them.

[0045] In Modification 1 configured as above, similar to the embodiment, heat dissipation and stress relaxation of the core can be realized. Furthermore, since the gap 405 is located at the bottom end surfaces of the inner legs 303Aab and 303Abb, the leakage magnetic flux 1001 generated in the gap 405 is far from the primary winding 401 and the secondary winding 402, and the leakage magnetic flux 1001 does not interlink with the primary winding 401 and the secondary winding 402, and the eddy current loss generated can also be reduced.

[0046] (Modification 2) FIG. 11 is a longitudinal sectional view showing a configuration example of a transformer 206B according to Modification 2, which is composed of one T-shaped core 302B and two L-shaped cores 303Ba and 303Bb.

[0047] In Modification 2 of FIG. 11, the core configuration may be composed of one T-shaped core 302B and two L-shaped cores 303Ba and 303Bb facing it. Here, the T-shaped core 302B is configured to include an inner leg 302Bb and a bottom surface portion 302Ba that supports it. Further, the L-shaped core 303Ba is configured to include an outer leg 303Bab and a bottom surface portion 303Baa that supports it. Furthermore, the L-shaped core 303Bb is configured to include an outer leg 303Bbb and a bottom surface portion 303Bba that supports it.

[0048] In Modification 2 configured as described above, it has the same operational effects as Modification 1.

[0049] Next, the process of the manufacturing method of the transformer 206 in FIGS. 6 and 7C will be described below.

[0050] (Process Example 1 of the Manufacturing Method) FIGS. 12A to 12E are longitudinal sectional views showing each process of the manufacturing process of the transformer 206 in FIG. 6.

[0051] As shown in FIG. 12A, the core portions 303a and 303b of the upper core 303 composed of two U-shaped cores are arranged and fixed downward on the flat surface 601a of the mounting table 601. Next, as shown in FIG. 12B, the bobbin 301 around which the primary winding 401 and the secondary winding 402 are wound is inserted and arranged in the closed magnetic path region 403 of the upper core 303. Further, as shown in FIG. 12C, an adhesive 404 is applied to the end faces of the outer legs 303aa and 303ba of the core portions 303a and 303b. Next, as shown in FIG. 12D, the lower core 302 is placed so as to cover the lower core 302 with the end faces of the outer legs 302a and 302b of the lower core 302 facing the end faces of the outer legs 303aa and 303ba of the core portions 303a and 303b respectively, thereby adhering and fixing the lower core 302 and the upper core 303. Finally, as shown in FIG. 12E, after inverting the transformer, which is an assembly of the lower core 302 and the upper core 303, upside down, the transformer 206 is installed in a predetermined case (not shown), the filling agent 403A is poured and cured, and the filling material 403A is filled into the closed magnetic path region 403 to fix the bobbin 301, thereby obtaining the transformer 206 for the manufacturing purpose. Here, since not only the upper and lower cores 302 and 303 but also the windings 401 and 402 of the transformer 206 generate heat, the entire transformer 206 is housed in a predetermined case and filled with potting made of silicone resin or the like in the case, so that the windings 401 and 402 and the upper and lower cores 302 and 303 dissipate heat to the lower cooling device 305 or the like through the potting.

[0052] (Process Example 2 of the Manufacturing Method) Figs. 13A to 13E are longitudinal sectional views showing each process of the manufacturing process of the transformer 206 in Fig. 7C.

[0053] As shown in Fig. 13A, after fixing the adhesive tape 701 on the flat surface 601a of the mounting table 601, as shown in Fig. 13B, the core portions 303a and 303b of the upper core 303 composed of two U-shaped cores are arranged and fixed on the adhesive tape 701 with the bottom sides facing down. Next, as shown in Fig. 13C, after inserting and arranging the bobbin 301 around which the primary winding 401 and the secondary winding 402 are wound into the closed magnetic path region 403 of the upper core 303, the lower core 302 is placed so that the end faces of the outer legs 302a and 302b of the lower core 302 face the end faces of the outer legs 303aa and 303ba of the core portions 303a and 303b, respectively. Finally, as shown in Fig. 13D, after fixing the outer periphery of the outer legs and the bottom surface portion of the combined body of the lower core 302 and the upper core 303 using the adhesive tape 701, the transformer, which is the combined body, is turned upside down, and then the transformer 206 is installed in a predetermined case (not shown), and the filling agent 403A is poured and cured, and the filling material 403A is filled into the closed magnetic path region 403 to fix the bobbin 301, thereby obtaining the transformer 206 for manufacturing purposes. Here, since the transformer 206 generates heat not only in the upper and lower cores 302 and 303 but also in the windings 401 and 402, the entire transformer 206 is housed in a predetermined case and filled with potting made of silicone resin or the like in the case, so that the windings 401 and 402 and the upper and lower cores 302 and 303 dissipate heat to the lower cooling device 305 or the like through the potting.

[0054] (Modification Example 3) Fig. 14 is a perspective view showing the appearance of a configuration example of a transformer 206C according to Modification Example 3, which is composed of a lower core 302 of one U-shaped core and an upper core 303 composed of core portions 303a, 303b, 303c, and 303d of an E-shaped core in which the upper core 303 is divided into four parts.

[0055] In FIG. 14, the upper core 303 is configured to be divided into four core portions 303a, 303b, 303c, and 303d each having a rectangular end face shape. Here, gaps 406 and 406 are respectively interposed between the core portion 303a and the core portion 303b, and between the core portion 303c and the core portion 303d. Further, gaps 407 and 407 are respectively interposed between the core portion 303a and the core portion 303c, and between the core portion 303b and the core portion 303d.

[0056] In the embodiment of FIG. 3, the stress in the direction of line A - A' is relaxed by the gap 406. In contrast, in Modification 3, not only is the stress in the direction of line A - A' relaxed by the gaps 406 and 406, but also the stress in the direction orthogonal to the direction of line A - A' can be relaxed by the gaps 407 and 407, which has a unique effect.

[0057] In Modification 3, although the upper core 303 is divided into four parts, for example, the upper core 303 may be divided into three parts at intervals of 120 degrees around the center of the transformer 206. Similarly, the upper core 303 may be divided into five or more parts around the center of the transformer 206.

[0058] (Other Modifications) In the above embodiments, the primary winding 401 is the upper winding and the secondary winding 402 is the lower winding, but the present disclosure is not limited to this. These can be interchanged, or the primary winding 401 and the secondary winding 402 can be arranged inside and outside or vice versa with respect to the inner legs, and the same effects can be obtained.

[0059] The primary winding 401 and the secondary winding 402 may be made of copper wire, Litz wire, or triple insulated winding wire (TIW).

Industrial Applicability

[0060] The transformers 206, 206A, 206B, 206C according to the present disclosure can be used not only in the DC-DC converter 105 of the charging device 101 in FIG. 1 that supplies a charging voltage to the rechargeable battery 106, but also in various power supply devices that supply a predetermined power supply voltage to a load.

Explanation of Signs

[0061] 101 On-vehicle charging device 102 Commercial AC power supply 103 Rectifying and smoothing circuit 104 Power factor correction circuit (PFC circuit) 105 DC-DC converter 106 Rechargeable battery 201 Inverter circuit 202 - 205 MOS transistors 206, 206A, 206B, 206C Transformers 207 Leakage inductance 208 Magnetizing inductance 209 Resonant capacitor 210 Rectifying circuit 211 Smoothing capacitor 212 Inductance 220 Control circuit 301 Bobbin 302 Lower core (core part) 302a, 302b Outer legs 302c Inner leg 302d Bottom surface part 302A I-shaped core (core part) 302B T-shaped core (core part) 302Ba Bottom surface part 302Bb Inner leg 303 Upper core (core part) 303a, 303b, 303c, 303d U-shaped core (core part) 303aa, 303ba Outer legs 303ab, 303bb Inner legs 303ac, 303bc Bottom surface parts 303Aa, 303Ab U-shaped core (core part) 303Aaa, 303Aba Outer legs Inner legs of 303Aab and 303Abb Bottom surfaces of 303Aac and 303Abc L-shaped cores (core parts) of 303Ba and 303Bb Bottom surfaces of 303Baa and 303Bba Outer legs of 303Bab and 303Bbb Cooling device 305 Primary winding 401 Secondary winding 402 Closed magnetic circuit region 403 Filling material 403A Adhesive 404 Gap 405 Gap 406 Gap 407 Mounting table 601 Flat surface 601a Adhesive tape 701 Heat-resistant elastomer 801 Heat-resistant elastomer 901 Leakage magnetic flux 1001 Terminals T1 to T4

Claims

1. A transformer having a primary winding and a secondary winding, the transformer including a first core and a second core that are disposed to face each other and through which the primary winding and the secondary winding are inserted, the first core includes one first core portion, the second core includes a plurality of second core portions; transformer.

2. the first core is a lower core; The second core is an upper core.

2. The transformer according to claim 1.

3. the first core and the second core are disposed to face each other with a gap therebetween. A transformer according to claim 1 or 2.

4. The first core and the second core include a heat-resistant elastomer in the gap and are disposed to face each other. The transformer according to claim 3.

5. The second core portions are arranged with a heat-resistant elastomer interposed therebetween. A transformer according to any one of claims 1 to 4.

6. The first core and the second core are bonded to each other and disposed so as to face each other. A transformer according to any one of claims 1 to 5.

7. The first core and the second core are fixed to each other by an adhesive tape while being arranged to face each other. A transformer according to any one of claims 1 to 5.

8. Further comprising a cooling device provided below the first core. A transformer according to any one of claims 1 to 7.

9. the first core portion is an E-core, Each of the second core portions is a U-shaped core. A transformer according to any one of claims 1 to 8.

10. the first core portion is an I-core, Each of the second core portions is a U-shaped core. A transformer according to any one of claims 1 to 8.

11. the first core portion is a T-core, Each of the second core portions is an L-shaped core. A transformer according to any one of claims 1 to 8.

12. A charging device that supplies a charging voltage to a rechargeable battery, A transformer according to any one of claims 1 to 11, Charging device.

13. A power supply device that supplies a power supply voltage to a load, A transformer according to any one of claims 1 to 11, power supply.

14. A method for manufacturing a transformer having a primary winding and a secondary winding, and including a first core and a second core, comprising the steps of: inserting the primary winding and the secondary winding into the second core including a plurality of second core portions; and inserting the first core through the primary winding and the secondary winding so that the first core faces the second core. How a transformer is manufactured.

15. The step of disposing the first core opposite to the second core includes: and bonding the first core and the second core to each other and disposing them facing each other. The method for manufacturing a transformer according to claim 14.

16. The step of disposing the first core opposite to the second core includes: and fixing the first core and the second core to each other with an adhesive tape while the first core and the second core are disposed so as to face each other. The method for manufacturing the transformer according to claim 14.

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