A high-humidity and high-current resistant film capacitor

Abstract

The present invention relates to a high-humidity and high-current resistant film capacitor, comprising a capacitor housing, a film capacitor core, a capacitor end cap, and a pin. The capacitor end cap has a resin injection hole in its center. The interior of the capacitor housing is filled with a dense epoxy resin layer that completely encapsulates the film capacitor core. An epoxy resin layer is also filled between the capacitor end cap and the dense epoxy resin layer. During the process of curing the liquid epoxy resin adhesive to a solid epoxy resin adhesive, the dense epoxy resin layer is subjected to megasonic vibration and negative pressure extraction. The high-humidity and high-current resistant film capacitor of the present invention still has excellent high-current resistance even in a high-humidity environment. The dense epoxy resin layer used for encapsulation has a dense structure, a low internal bubble content, good insulation, and high compressive strength.

Description

Technical Field

[0001] The invention relates to a high-humidity and high-current resistant film capacitor, belonging to the technical field of capacitors. Background Art

[0002] Film capacitors, also known as plastic film capacitors, use plastic film as the dielectric.

[0003] The structure of an existing film capacitor generally includes a capacitor housing, a film capacitor core located inside the capacitor housing, a capacitor end cover used to encapsulate the capacitor housing, and pins installed on the capacitor end cover. One end of the capacitor housing is open and the other end is closed. The pins are electrically connected to the film capacitor core. A resin injection hole is provided in the center of the capacitor end cover. Liquid epoxy resin adhesive is filled into the interior of the capacitor housing through the resin injection hole to completely encapsulate the film capacitor core. After the liquid epoxy resin adhesive is cured, an insulating encapsulation layer is formed that completely encapsulates the film capacitor core.

[0004] However, as the capacity requirements of film capacitors used for energy storage become increasingly larger, especially in the field of new energy vehicles, film capacitors that are resistant to high humidity and high current are needed; and the curing of epoxy resin adhesives used in existing capacitors is room temperature curing. After curing, epoxy resin is not absolutely waterproof and has certain water absorption and permeability; in addition, the liquid epoxy resin adhesive that completely wraps the film capacitor core will inevitably produce bubbles. Even if it is left to stand for 1-2 days, the bubbles cannot be emptied at all due to the certain viscosity of the epoxy resin. These all lead to the limited resistance of the cured insulation layer to high humidity and high current, which significantly affects the service life of the film capacitor.

[0005] Based on this, the present invention is proposed. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention provides a high-humidity and high-current resistant film capacitor. The specific technical solution is as follows:

[0007] A high-humidity and high-current resistant film capacitor, comprising a capacitor housing, a film capacitor core located within the capacitor housing, a capacitor end cap for encapsulating the capacitor housing, and pins mounted on the capacitor end caps. The capacitor housing is open at one end and closed at the other end. The pins are electrically connected to the film capacitor core. A resin injection hole is provided in the center of the capacitor end cap. The interior of the capacitor housing is filled with a dense epoxy resin layer that completely encapsulates the film capacitor core. An epoxy resin layer is further filled between the capacitor end cap and the dense epoxy resin layer. Both the dense epoxy resin layer and the epoxy resin layer are made of cured epoxy resin adhesive.

[0008] During the process of curing the liquid epoxy resin adhesive into a solid epoxy resin adhesive, the dense epoxy resin layer applies megasonic vibration to the liquid epoxy resin adhesive and performs negative pressure extraction.

[0009] As a further improvement, a first threaded column is fixedly connected to the outside of the bottom of the capacitor housing.

[0010] A further improvement is that a megasonic vibration table is used to apply megasonic vibration to the liquid epoxy resin adhesive. The megasonic vibration table includes a metal table top, the surface of the metal table top is provided with a plurality of mounting holes adapted to the first threaded column, the capacitor housing is located above the metal table top, and a locking nut matching the first threaded column is provided below the metal table top; a plurality of megasonic vibrators distributed in an array are fixedly mounted on the lower surface of the metal table top.

[0011] As a further improvement, a hot melt adhesive layer is provided between the film capacitor core and the bottom of the capacitor shell, and the hot melt adhesive layer is made of hot melt adhesive.

[0012] A further improvement is that a negative pressure exhaust sleeve is used to perform negative pressure exhaust on the liquid epoxy resin adhesive. The negative pressure exhaust sleeve includes a sleeve that is mounted on the outside of the open end of the capacitor housing. One end of the sleeve is open and the other end is closed. The open end of the sleeve is sealed to the open end of the capacitor housing, and a one-way valve connected to the inner cavity of the sleeve is embedded in the center of the closed end of the sleeve.

[0013] As a further improvement, the initial air pressure in the sleeve is 70,000-80,000 Pa.

[0014] As a further improvement, the megasonic vibrator vibrates intermittently, with a vibration time of 5 to 10 minutes per hour; and the megasonic frequency of the megasonic vibrator is 0.87 MHz.

[0015] As a further improvement, the power of the megasonic vibrator varies every minute and changes in a sharp pulse shape within the range of 20 to 50 W.

[0016] As a further improvement, table legs are respectively installed on both sides of the metal table top.

[0017] As a further improvement, a plurality of reinforcing ribs are provided on the outer side of the capacitor end cover, and the intersection of the reinforcing ribs is located at the resin injection hole.

[0018] Beneficial effects of the present invention:

[0019] The high-humidity and high-current resistant film capacitor of the present invention still has excellent high-current resistance even in a high-humidity environment. The dense epoxy resin layer used for packaging has a dense structure, low internal bubble content, good insulation and high compressive strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic structural diagram of the high-humidity and high-current resistant film capacitor of the present invention;

[0021] Figure 2 A schematic top view of the capacitor end cover of the present invention;

[0022] Figure 3 is a schematic diagram of the interior of the capacitor housing of the present invention;

[0023] Figure 4 This is a schematic diagram of the connection between the megasonic vibration table, capacitor housing, and negative pressure exhaust sleeve of the present invention;

[0024] Figure 5 This is a photo of the packaging of the high-humidity and high-current resistant film capacitors described in the present invention;

[0025] Figure 6 This is a real photo of the high-humidity and high-current resistant film capacitor described in the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Example 1

[0027] like Figures 1-3 As shown, the high-humidity and high-current resistant film capacitor includes a capacitor housing 10, a film capacitor core 30 located inside the capacitor housing 10, a capacitor end cover 20 for encapsulating the capacitor housing 10, and a pin 40 installed on the capacitor end cover 20. One end of the capacitor housing 10 is open and the other end is closed. The pin 40 is electrically connected to the film capacitor core 30. A resin injection hole 21 is provided in the center of the capacitor end cover 20. A first threaded column 11 is fixedly connected to the outside of the shell bottom of the capacitor housing 10.

[0028] The capacitor housing 10 is filled with a dense epoxy resin layer 50 that completely wraps the film capacitor core 30. An epoxy resin layer 51 is also filled between the capacitor end cover 20 and the dense epoxy resin layer 50. Both the dense epoxy resin layer 50 and the epoxy resin layer 51 are made of cured epoxy resin adhesive.

[0029] During the process of curing the liquid epoxy resin adhesive into a solid epoxy resin adhesive, the dense epoxy resin layer 50 applies megasonic vibration to the liquid epoxy resin adhesive and performs negative pressure extraction.

[0030] That is, by first injecting the existing ordinary liquid epoxy resin adhesive into the capacitor housing 10, then applying megasonic vibration to the liquid epoxy resin adhesive and performing negative pressure extraction, and finally obtaining the dense epoxy resin layer 50 after solidification; finally, installing the capacitor end cover 20, and then injecting the existing ordinary liquid epoxy resin adhesive through the resin injection hole 21. At this time, it is no longer necessary to apply megasonic vibration to the liquid epoxy resin adhesive and perform negative pressure extraction. It can be left to stand for 1 day in the existing manner. After solidification, the existing conventional epoxy resin layer 51 is obtained.

[0031] The final product can be seen in the photo Figure 5 、 6 . Example 2

[0032] like Figure 4 As shown, a megasonic vibration table is used to apply megasonic vibration to the liquid epoxy resin adhesive. The megasonic vibration table includes a metal table plate 70. The plate surface of the metal table plate 70 is provided with multiple mounting holes adapted to the first threaded column 11. The capacitor housing 10 is located above the metal table plate 70. A locking nut 12 adapted to the first threaded column 11 is provided below the metal table plate 70. A plurality of megasonic vibrators 72 distributed in an array are fixedly mounted on the lower surface of the metal table plate 70.

[0033] The megasonic vibrator 72 vibrates intermittently, vibrating for 5 to 10 minutes per hour. The megasonic frequency of the megasonic vibrator 72 is 0.87 MHz. The power of the megasonic vibrator 72 varies every minute, varying in a sharp pulse pattern within the range of 20 to 50 W. For example, within a 5-minute vibration cycle, the power of the megasonic vibrator 72 is 20 W in the first minute, 50 W in the second minute, 35 W in the third minute, 27 W in the fourth minute, and 20 W in the fifth minute.

[0034] A negative pressure exhaust sleeve is used to vacuum the liquid epoxy resin adhesive. The negative pressure exhaust sleeve includes a sleeve 80 that is sleeved on the outside of the open end of the capacitor housing 10. One end of the sleeve 80 is open and the other end is closed. The open end of the sleeve 80 is sealed to the open end of the capacitor housing 10, such as by using hot melt adhesive for sealing. After the sealing is completed, it is cut open with a knife; a one-way valve 60 connected to the inner cavity of the sleeve 80 is embedded in the center of the closed end of the sleeve 80.

[0035] The initial pressure in the sleeve 80 is 70,000-80,000 Pa. Atmospheric pressure is 101,325 Pa, and the sleeve 80 is under negative pressure. A vacuum pump is used to evacuate the inner cavity of the sleeve 80 through the one-way valve 60. After the evacuation is completed, the one-way valve 60 maintains the negative pressure in the inner cavity of the sleeve 80.

[0036] In this embodiment, due to the megasonic vibration + negative pressure adsorption, the bubbles in the liquid epoxy resin adhesive can be directedly discharged into the sleeve 80; in addition, the megasonic vibration can also improve the curing effect of the liquid epoxy resin adhesive, and the structure after curing is denser and the compressive strength is further improved.

[0037] Comparative Example 1

[0038] In this example, during the process of curing the dense epoxy resin layer 50 from liquid epoxy resin adhesive to solid epoxy resin adhesive, only megasonic vibration is applied to the liquid epoxy resin adhesive without negative pressure exhaust; the rest is the same as in Example 2.

[0039] Comparative Example 2

[0040] In this example, during the process of curing the liquid epoxy resin adhesive into a solid epoxy resin adhesive, the dense epoxy resin layer 50 is not subjected to megasonic vibration, but only subjected to negative pressure pumping; the rest is the same as in Example 2.

[0041] Comparative Example 3

[0042] In this example, the megasonic vibrator 72 is replaced by an ultrasonic vibrator, and the ultrasonic frequency is 20 kHz; the rest is the same as in Example 2.

[0043] Comparative Example 4

[0044] In this example, the megasonic frequency is 0.85 MHz, and the rest is the same as in Example 2.

[0045] Comparative Example 5

[0046] In this example, the megasonic frequency is 0.9 MHz, and the rest is the same as in Example 2.

[0047] Comparative Example 6

[0048] In this example, the megasonic frequency is 1 MHz, and the rest is the same as in Example 2.

[0049] Comparative Example 7

[0050] In this example, the power of the megasonic vibrator 72 varies every minute and changes in a triangular wave shape within the range of 20 to 50 W. The rest is the same as in Example 2.

[0051] Comparative Example 8

[0052] In this example, the power of the megasonic vibrator 72 varies every minute, and changes in a sawtooth wave shape within the range of 20 to 50 W. The rest is the same as in Example 2.

[0053] Reference ratio

[0054] The film capacitor in this example is an existing film capacitor, which does not have a dense epoxy resin layer 50 , but only a conventional epoxy resin layer 51 that completely wraps the film capacitor core 30 .

[0055] Film capacitor high humidity and high current resistance test

[0056] 1. Place the film capacitor in a water tank, pour distilled water into the water tank to completely submerge the film capacitor, cover the tank and seal it, and inject compressed air into the water tank until the air pressure in the water tank is 0.2Mpa; let it stand for 1 day, open the tank cover, take out the film capacitor, and put it into an oven to dry at 60°C for 30 minutes (at this time, if in a high-pressure water environment, water enters the capacitor housing 10 through the epoxy resin layer 51 at the resin injection hole 21 in the film capacitor. If the density of the dense epoxy resin layer 50 is insufficient, the dense epoxy resin layer 50 will also absorb a small amount of moisture, resulting in a decrease in the insulation of the device. At this time, relying solely on low-temperature baking at 60°C cannot dry out the moisture in the dense epoxy resin layer 50. It must be baked for at least more than 12 hours to be effective). Afterwards, take it out and test whether it breaks down at different current values.

[0057] 2. After the test is completed, the capacitor housing 10 is peeled off, the dense epoxy resin layer 50 is taken out, and its compressive strength is measured.

[0058] The test results of Example 2, Comparative Examples 1-8, and Reference Examples are shown in Table 1:

[0059] Table 1

[0060]

[0061] In Comparative Examples 7 and 8, the different degrees of power change are mainly due to the influence of the megasonic vibration time. In Comparative Examples 7 and 8, the vibration time needs to reach more than 20 minutes per hour to increase the breakdown current value to close to 610 mA. In Comparative Examples 3 to 6, even if the vibration time reaches 60 minutes per hour, the breakdown current value will not increase.

[0062] In addition, the breakdown current value of the film capacitor in Example 1 in the initial state (not immersed in the water tank) is 650 mA, while the breakdown current value of the film capacitor in the reference example in the initial state (not immersed in the water tank) is 600 mA. Example 3

[0063] In Example 2, to ensure that the film capacitor core 30 always maintains a central position during vibration, a hot melt adhesive layer 31 is provided between the film capacitor core 30 and the bottom of the capacitor housing 10 , and the hot melt adhesive layer 31 is made of hot melt adhesive.

[0064] First, the hot melt adhesive layer 31 is used to fix and position the components, and then the liquid epoxy resin adhesive is filled in. Example 4

[0065] For easy installation, table legs 71 are respectively installed on both sides of the metal table top 70. Example 5

[0066] In order to improve the strength of the capacitor end cover 20 itself, in some embodiments, in order to ensure the connection strength between the epoxy resin layer 51 and the capacitor end cover 20, a plurality of reinforcing ribs 22 are provided on the outside of the capacitor end cover 20, and the intersection of the reinforcing ribs 22 is located at the resin injection hole 21.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high-humidity and high-current resistant film capacitor, comprising a capacitor housing (10), a film capacitor core (30) located inside the capacitor housing (10), a capacitor end cap (20) for encapsulating the capacitor housing (10), and a pin (40) mounted on the capacitor end cap (20), wherein one end of the capacitor housing (10) is open and the other end is closed, the pin (40) is electrically connected to the film capacitor core (30), and a resin injection hole (21) is provided in the center of the capacitor end cap (20), characterized in that: The capacitor housing (10) is filled with a dense epoxy resin layer (50) that completely wraps the film capacitor core (30), and an epoxy resin layer (51) is further filled between the capacitor end cover (20) and the dense epoxy resin layer (50), and both the dense epoxy resin layer (50) and the epoxy resin layer (51) are made of cured epoxy resin adhesive; During the process of curing the liquid epoxy resin adhesive into a solid epoxy resin adhesive, the dense epoxy resin layer (50) applies megasonic vibration to the liquid epoxy resin adhesive and performs negative pressure extraction.

2. The high-humidity and high-current resistant film capacitor according to claim 1, characterized in that: A first threaded column (11) is fixedly connected to the outside of the bottom of the capacitor housing (10).

3. The high-humidity and high-current resistant film capacitor according to claim 2, characterized in that: A megasonic vibration table is used to apply megasonic vibration to liquid epoxy resin adhesive. The megasonic vibration table includes a metal table plate (70). The plate surface of the metal table plate (70) is provided with a plurality of mounting holes adapted to the first threaded column (11). The capacitor housing (10) is located above the metal table plate (70). A locking nut (12) adapted to the first threaded column (11) is provided below the metal table plate (70). A plurality of megasonic vibrators (72) distributed in an array are fixedly mounted on the lower surface of the metal table plate (70).

4. The high-humidity and high-current resistant film capacitor according to claim 1, characterized in that: A hot melt adhesive layer (31) is provided between the film capacitor core (30) and the bottom of the capacitor housing (10), and the hot melt adhesive layer (31) is made of hot melt adhesive.

5. The high-humidity and high-current resistant film capacitor according to claim 1, characterized in that: A negative pressure exhaust sleeve is used to vacuum the liquid epoxy resin adhesive. The negative pressure exhaust sleeve comprises a sleeve (80) sleeved on the outside of the open end of the capacitor housing (10). One end of the sleeve (80) is open and the other end is closed. The open end of the sleeve (80) is sealed to the open end of the capacitor housing (10). A one-way valve (60) communicating with the inner cavity of the sleeve (80) is embedded in the center of the closed end of the sleeve (80).

6. The high-humidity and high-current resistant film capacitor according to claim 5, characterized in that: The initial air pressure in the sleeve (80) is 70,000-80,000 Pa.

7. The high-humidity and high-current resistant film capacitor according to claim 3, characterized in that: The megasonic vibrator (72) vibrates intermittently, with a vibration time of 5 to 10 minutes per hour; the megasonic frequency of the megasonic vibrator (72) is 0.87 MHz.

8. The high-humidity and high-current resistant film capacitor according to claim 7, characterized in that: The power of the megasonic vibrator (72) varies every minute and changes in a sharp pulse shape within the range of 20 to 50 W.

9. The high-humidity and high-current resistant film capacitor according to claim 3, characterized in that: Table legs (71) are respectively installed on both sides of the metal table top (70).

10. The high-humidity and high-current resistant film capacitor according to claim 1, characterized in that: A plurality of reinforcing ribs (22) are provided on the outer side of the capacitor end cover (20), and the intersection of the reinforcing ribs (22) is located at the resin injection hole (21).

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