SURGE SUPPRESSION DEVICE

A surge suppression device has a resistive element, a capacitor electrically connected to the resistive element, a terminal electrically connected to the opposite side of the resistive element to the side connected to the capacitor, a fixing metal bracket to be fixed to a fixing target, and a mold resin to mold the resistive element, the terminal and the fixing metal bracket. The capacitor is located away from the mold resin.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application claims the priority of Japanese patent application No. 2022-025901 filed on Feb. 22, 2022, and the priority of Japanese patent application No. 2022-157380 filed on Sep. 30, 2022, and the entire contents thereof are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a surge suppression device.

BACKGROUND OF THE INVENTION

Patent Literature 1 discloses a surge suppression unit for suppressing the generation of surge voltage in the wiring of three-phase alternating current from an inverter to a motor. The surge suppression unit described in Patent Literature 1 has three series circuits each with a resistor and a capacitor, and the ends of the three series circuits on the capacitor side are connected to each other.

Citation List Patent Literature 1: JP2014-132811A

SUMMARY OF THE INVENTION

Here, in a series circuit in which a resistor and a capacitor are connected, unless special efforts are made, the capacitor may receive heat from the resistor, causing an excessive temperature rise, which may lead to a decrease in the life of the capacitor. However, in Patent Literature 1, there is no detailed description of the structure of a series circuit in which a resistor and a capacitor are connected.

The present invention was made in view of the aforementioned circumstances, and it is an object to provide a surge suppression device capable of suppressing a temperature rise of a capacitor.

So as to achieve the above-mentioned object, one aspect of the present invention provides a surge suppression device, comprising: a resistive element;

a capacitor electrically connected to the resistive element;

a terminal electrically connected to an opposite side of the resistive element to a side connected to the capacitor;

a fixing metal bracket to be fixed to a fixing target; and

a mold resin to mold the resistive element, the terminal, and the fixing metal bracket,

wherein the capacitor is located away from the mold resin.

ADVANTAGEOUS EFFECTS OF THE INVENTION

According to the present invention, it is possible to provide the surge suppression device that can suppress the temperature rise of the capacitor.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

The first embodiment of the present invention will be described with reference toFIGS.1to5. The embodiments described below is shown as a suitable concrete example for implementing the invention, and although there are parts that specifically illustrate various technically preferred technical matters, the technical scope of the invention is not limited thereto concrete embodiment.

FIG.1is a circuit diagram showing a surge suppression device1in use. The surge suppression device1of this embodiment is used, for example, by being connected to each of a U-phase wiring13u,a V-phase wiring13v,and a W-phase wiring13wbetween a motor11and an inverter12. In this case, the surge suppression device1suppresses the application of surge voltage to the motor11. The surge suppression device1has three series circuits2, in which a resistive element21and a capacitor22are connected in series. The three series circuits2are connected to the U-phase wiring13u, V-phase wiring13v,or W-phase wiring13w,respectively, on a resistive element21-side. The three series circuits2are star-connected by connecting the respective capacitor22-sides to each other. The surge suppression device1of this embodiment will be described in detail hereinafter.

FIG.2is a perspective view of the surge suppression device1.FIG.3is a front view of the surge suppression device1. In addition to the surge suppression device1, the motor case111and bolts b, which are to be fixed to the surge suppression device1, are shown inFIG.3.FIG.4is a IV-IV line arrowhead cross-portion ofFIG.3.

The surge suppression device1has three series circuits2, three terminals3, a fixing metal bracket4, a mold resin5, an interconnecting portion6, a second fixing metal bracket7, a second mold resin8, and a flat plate portion9. The series circuit2is composed of a resistive element21and a capacitor22connected in series via a connecting portion23. The three terminals3are connected to the opposite side of the connecting portion23in the three resistive elements21respectively. As shown inFIG.3, the fixing metal bracket4is fitted, for example, to the motor case111as a fixing target. The mold resin5molds the three resistive elements21, the three terminals3, and the fixing metal bracket4. The interconnecting portions6electrically connect the opposite sides of the connecting portions23in the three capacitors22. The second fixing metal bracket7is fitted to a fixation object, such as, for example, the motor case111. The second mold resin8molds the three capacitors22, the interconnecting portions6, the connecting portions23, and the second fixing metal bracket7. The second mold resin8is an example of capacitor embedded resin in which the capacitors22are embedded. The flat plate portion9is provided to overlap the second fixing metal bracket7.

The resistive elements21are formed lengthy in one direction; the three resistive elements21are arranged in parallel with each other. Hereafter, the longitudinal direction of the resistive element21is referred to as the X-direction. The direction at right angles to the X-direction in which the three resistive elements21are aligned is referred to as the Y-direction. Furthermore, the direction at right angles to both the X and Y-directions is referred to as the Z-direction.

The resistive element21includes a long resistive element211in the X-direction and two cap electrodes212fitted to both ends of the resistive element211. The resistive element211can be, for example, a wire wound resistive element or a ceramic resistive element, although there is no particular limitation. The cap electrodes212are made of conductive metal in the form of caps. As shown inFIG.4, the cap electrode212has a disc-shaped bottom portion212afacing the resistive element211in the X-direction and a circular cylindrical side portion212bextending from the periphery edge of the bottom portion212ato a resistive element211-side in the X-direction. The resistive element21has two resistive element terminals213connected to each cap electrode212. The resistive element terminals213are formed as plates opposite the bottom portion212aand are joined to the bottom portion212a.The two resistive element terminals213of the resistive elements21are formed to protrude from the joined cap electrode212to the same side of each other. The one-sided resistive terminal213of each of the three resistive elements21is connected to the terminal3, and the other resistive terminal213of each is connected to the connecting portion23. Hereinafter, the side with the two resistive element terminals213protruding in the resistive element21may be referred to as the lower side and the opposite side as the upper side, but the expressions upper and lower are for convenience and do not limit the orientation of the surge suppression device1with respect to the vertical direction in the state of use, for example.

The terminal3has a thickness in the Z-direction and a plate shape that is long in the X-direction. The terminal3is made of metal, such as pure copper, for example. As shown inFIG.4, the terminal3has a through hole31into which the resistive element terminal213is inserted. The resistive element terminal213may not only be inserted into the through hole31, but may also be joined to the terminal3using solder or the like. One end of one side in the X-direction in the terminal3faces the resistive element21in the Z-direction through the mold resin5. Specifically, the terminal3faces the cap electrode212on the terminal3side in the resistive element21and the portion between the two cap electrodes212in the resistive element211in the Z-direction through the mold resin5. A bolt insertion hole32is formed at the end opposite to the resistive element21in the terminal3. The end of the terminal3is electrically connected to the U-phase wiring (see reference character13uinFIG.1), V-phase wiring (see reference character13vinFIG.1), or W-phase wiring (see reference character13winFIG.1).

The connecting portion23has the shape of a long plate-shaped metal material bent into a U-shape. In this embodiment, the connecting portion23is made of a metallic material having lower thermal conductivity than the terminal3. Specifically, the connecting portion23is made of phosphor bronze, which has a lower thermal conductivity than pure copper, the metal material constituting the terminal3. This increases the thermal resistance in the thermal path from the resistive element21to the capacitor22through the connecting portion23and reduces the heat transferred to the capacitor22. The connecting portion23has a first portion231, a second portion232, and a third portion233. The first portion231is connected to the resistive element terminal213on the opposite side of the terminal3in the resistive element21and extends in the X-direction. The first portion231is connected to the resistive element terminal213by solder or the like at the end in the X-direction. The second portion232extends downward from the end of the first portion231opposite the resistive element terminal213. The third portion233is extended in the X-direction from the lower end of the second portion232and is connected to the capacitor22. The cross-sectional area of the connecting portion23is smaller than the area of the cross-sectional area perpendicular to the X-direction of the terminal3. The cross-sectional area of the connecting portion23is the area of the cross-portion perpendicular to the heat path from the resistive element21through the connecting portion23to the capacitor22. In other words, the heat of the resistive element21is transferred to the capacitor22by traveling in the X-direction through the first portion231, in the Z-direction through the second portion232, and in the X-direction through the third portion233, and the cross-sectional area of the connecting portion23means the area of the cross portion perpendicular to the X-direction of the first portion231, the area of the cross portion perpendicular to the Z-direction of the second portion232, or the area of the cross portion perpendicular to the X-direction of the third portion233. The width of the connecting portion23is smaller than the width of the terminal3. The width of the connecting portion23may be smaller than the diameter of the cap electrode212of the resistive element21. Furthermore, the thickness of the connecting portion23is smaller than the thickness of the terminal3. These allow the thermal resistance at the connecting portion23to be greater than the thermal resistance of the terminal3, reducing the heat transferred from the resistive element21to the capacitor22through the connecting portion23.

As shown inFIG.3, the fixing metal bracket4is made of a crank-shaped metal having thermal conductivity, such as aluminum. The fixing metal bracket4has a base41extending in the Y-direction and two extending portions42extending downward from both ends of the base41in the Y-direction. As shown inFIGS.3and4, the base41faces the three resistive elements21and the three connecting portions23in the Z-direction via the mold resin5. Specifically, the base41faces in the Z-direction via the mold resin5to the part between the two cap electrodes212in the resistive elements21, the cap electrode212on the connecting portion23side, and the first portion231in the connecting portion23.

As shown inFIG.3, the extending portion42has a vertical extending portion421extending downward from both ends of the base41and a transverse extending portion422extending outward in the Y-direction from the lower end of the vertical extending portion421. The transverse extending portion422has a bolt insertion hole422athat penetrates in the Z-direction. In the bolt insertion hole422a,a bolt b is inserted to fix the fixing metal bracket4to the motor case111as a fixing target. Then, the three resistive elements21, the three terminals3, the three connecting portions23, and the fixing metal bracket4are molded with the mold resin5.

As shown inFIG.2, the mold resin5has a rectangular shape with thickness in the

Z-direction. The mold resin5is formed by placing the three terminals3, the three resistive elements21, the three connecting portions23, and the fixing metal bracket4in the mold and injecting resin into the mold to cure it. The mold resin5molds the entire three resistive elements21. The mold resin5also covers a portion of each of the terminal3, the connecting portion23, and the fixing metal bracket4. The terminal3is exposed from the mold resin5on the side of the bolt insertion hole32, and the part opposite to the bolt insertion hole32is covered by the mold resin5. The connecting portion23is covered with the mold resin5except for the end of the second portion232-side in the first portion231. In the fixing metal bracket4, the upper ends of the base41and each of the two extending portions42are covered by the mold resin5.

As shown inFIG.3, the length of the base41in the Y-direction is approximately the same as the length of the mold resin5in the Y-direction. And, as shown inFIG.2, the main surface40of the fixing metal bracket4when viewed from the Y-direction is exposed from the mold resin5and is flush with the surface of the mold resin5. As shown inFIGS.3and4, the bottom surface411of the base41is located above the bottom surface5aof the mold resin5and is covered by the mold resin5.

FIG.5shows an enlarged schematic diagram of a portion of the cross portion of the mold resin5. The mold resin5is composed of a base resin501having electrical insulation properties and a filler502having a higher thermal conductivity than the base resin501. The base resin501is made of an electrically insulating resin, such as PPS (polyphenylene sulfide) resin or epoxy resin. The filler502can be composed of, for example, metal or ceramic powder, specifically aluminum oxide, boron nitride, aluminum nitride, or the like. InFIG.5, the filler502is represented as a circular shape for convenience, but the shape of the filler502is not limited thereto. The thermal conductivity of mold resin5should be 3 W/(m·K) or more. The thermal conductivity of mold resin5can also be 10 W/(m·K) or less. As shown inFIGS.2to4, three capacitors22are placed on the underside of the mold resin5.

The capacitors22can be ceramic capacitors, for example, having a capacitor body221in which a capacitor element is coated with resin, and two capacitor terminals222protruding from the capacitor body221. One of the capacitor terminals222is connected to the third portion233of the connecting portion23. The ends opposite to the connecting portion23in the three capacitors22are connected to each other at the interconnecting portion6. The interconnecting portion6is a bus bar that is long in the Y-direction and thick in the Z-direction.

As shown inFIG.3, the second fixing metal bracket7is made of a crank-shaped metal having thermal conductivity, such as aluminum. The second fixing metal bracket7has a second base71extending in the Y-direction and two second extending portions72extending downward from both ends of the second base71in the Y-direction. The second extending portion72has a second longitudinal extending portion721extending from the second base71in the Z-direction and a second transverse extending portion722extending from the lower ends of the second longitudinal extending portion721to the outside in the Y-direction. The three capacitors22and the interconnecting portions6are arranged in the recess70formed by the second base71and the second longitudinal extending portion721. The second transverse extending portion722is located below the transverse extending portion422of the fixing metal bracket4and overlaps said transverse extending portion422in the Z-direction. The second transverse extending portion722has a bolt insertion hole722athat is connected to the bolt insertion hole422aof the transverse extending portion422. As shown inFIG.4, the width of the second fixing metal bracket7in the X-direction is equal to the width of the fixing metal bracket4in the X-direction, and in the X-direction, the second fixing metal bracket7is formed in the same area as the fixing metal bracket4. The three capacitors22, the interconnecting portion6, and the second fixing metal bracket7are molded with the second mold resin8.

The second mold resin8is formed to fill the recess70of the second fixing metal bracket7. The second mold resin8is formed by placing the three capacitors22, the interconnecting portions6, the connecting portions23, and the second fixing metal bracket7in the mold and injecting resin into the mold to cure. The second mold resin8covers the entirety of the three capacitors22and the interconnecting portions6, and covers the third portion233of the connecting portion23. The second mold resin8also covers the inner surface of the recess70in the second fixing metal bracket7.

The second mold resin8is formed at a distance from the mold resin5. Then, a space exists between the mold resin5and the second mold resin8. When viewed from the Z-direction, the entire second mold resin8fits into the formed area of the mold resin5. The second mold resin8is located between the two extending portions42of the fixing metal bracket4.

In this embodiment, the second mold resin8is made of the same material as the mold resin5. That is, the second mold resin8comprises a base resin having electrical insulation properties and a filler having a higher thermal conductivity than the base resin. The thermal conductivity of the second mold resin8should be 3 W/(m·K) or more. The thermal conductivity of the mold resin5can be 10 W/(m·K) or less. A flat plate portion9is arranged on the underside of the second mold resin8.

The flat plate portion9is formed as a plate having a thickness in the Z-direction and a length in the Y-direction. The flat plate portion9is made of a thermally conductive metal such as aluminum. The flat plate portion9is superimposed on the bottom surface of the transverse extending portion422and the bottom surface of the second mold resin8in the second fixing metal bracket7. The flat plate portion9is not molded into the second mold resin8. As shown inFIG.3, the flat plate portion9has bolt insertion holes91that are connected to the bolt insertion holes422aof the fixing metal bracket4and the bolt insertion holes722aof the second fixing metal bracket7. The fixing metal bracket4, the second fixing metal bracket7, and the flat plate portion9are co-tightened to the motor case111by inserting the bolts b through the bolt insertion holes422a,bolt insertion holes722a,and bolt insertion holes91and by screwing them to the motor case111. The flat plate portion9allows more portions of the surface of the second mold resin8to be covered by metal members (i.e., the second fixing metal bracket7and the flat plate portion9), which facilitates heat dissipation from the second mold resin8to the metal members. The flat plate portion9can be omitted.

Functions and effects of the first embodiment

The surge suppression device1of this embodiment is equipped with the mold resin5that molds the resistive element21, the terminal3, and the fixing metal bracket4. Therefore, the heat generated in the resistive element21is transferred to the terminal3and fixing metal bracket4via the mold resin5, and is dissipated to the mating member connected to the terminal3and the object to which the fixing metal bracket44is fixed. This prevents the heat generated in the resistive element21from being transferred to the capacitor22and causing the capacitor22to become hot. Since the capacitor22is located at a distance from the mold resin5, the heat transfer from the mold resin5to the capacitor22is suppressed and the capacitor22temperature rise is suppressed. As a result, the capacitor22can be prolonged in life as a result of the suppression of the capacitor22temperature rise.

The fixing metal bracket4faces the resistive element21via the mold resin5.

Therefore, the heat transfer from the resistive element21to the fixing metal bracket4through the mold resin5can be promoted, and the heat dissipation of the resistive element21can be improved. As a result, the heat transfer from the resistive element21to the capacitor22is suppressed.

The terminal3faces the resistive element21through the mold resin5. Therefore, the heat transfer from the resistive element21to the terminal3through the mold resin5can be promoted, and as a result, the heat transfer of the resistive element21to the capacitor22is suppressed.

The connecting portion23is molded by the mold resin5, and the connecting portion23faces the fixing metal bracket4through the mold resin5. Hence, the heat of the connecting portion23is easily transferred to the fixing metal bracket4via the mold resin5, and the connecting portion23can be prevented from becoming hotter. As a result, the temperature rise of the capacitor22connected to the connecting portion23is suppressed.

The cross-sectional area of the connecting portion23is smaller than the cross-sectional area of the terminal3. In other words, the thermal resistance of the connecting portion23is greater than that of the terminal3. Therefore, heat generated in the resistive element21is more easily transferred to the terminal3than to the connecting portion23, and the heat transfer to the connecting portion23connected to the capacitor22is suppressed. Furthermore, the connecting portion23is made of a metallic material with lower thermal conductivity than the terminal3. Specifically, the connecting portion23is made of phosphor bronze, which has a lower thermal conductivity than pure copper, the metal material comprising the terminal3. Therefore, the thermal resistance in the thermal path from the resistive element21to the capacitor22through the connecting portion23can be increased. As a result, less heat is transferred from the resistive element21to the capacitor22through the connecting portion23, and more heat is dissipated directly from the resistive element21to the terminal3and from the resistive element21to the terminal3and the fixing metal bracket4through the mold resin5. As a result, the high temperature of the capacitor22is further suppressed.

The surge suppression device1is also equipped with the second mold resin8that molds the connecting portion23, the capacitor22, and the second fixing metal bracket7. Therefore, some of the heat emitted from the resistive element21goes through the connecting portion23to the capacitor22, but the heat in the connecting portion23is diffused into the second mold resin8before reaching the capacitor22. Hence, the heat transferred from the resistive element21to the capacitor22through the connecting portion23can be reduced. The heat generated in the capacitor22due to energizing the capacitor22, etc. is diffused into the second mold resin8. The heat diffused into the second mold resin8is then dissipated through the second fixing metal bracket7to the object to which the second fixing metal bracket7is fixed. Furthermore, the second mold resin8is located away from the mold resin5. Hence, the heat from the mold resin5covering the resistive element21can be suppressed from being transferred to the second mold resin8, and as a result, the temperature rise of the capacitor22in the second mold resin8is suppressed.

The base41of the fixing metal bracket4is molded by the mold resin5, and the second mold resin8is arranged between the two extending portions42. Hence, the space between the two extending portions42can be effectively utilized and the surge suppression device1as a whole can be downsized.

The mold resin5also molds the plurality of resistive elements21. Therefore, the heat of the plurality of resistive elements21can be transferred to the fixing metal bracket4and the terminal3via one mold resin5, and the surge suppression device1as a whole can be downsized and the number of parts can be reduced.

The mold resin5has the base resin501, and the filler502that has a higher thermal conductivity than the base resin501. Therefore, the thermal conductivity of the mold resin5can be made higher, increasing the heat transferred from the resistive element21through the mold resin5to the terminal3and the fixing metal bracket4, thereby reducing the heat transferred from the resistive element21to the capacitor22.

The thermal conductivity of the mold resin5is 3 W/(m·K) or more and 10 W/(m·K) or less. By setting the thermal conductivity of the mold resin5to 3 W/(m·K) or more, the heat transferred from the resistive element21through the mold resin5to the terminal3and fixing metal bracket4can be increased and the heat transferred from the resistive element21to the capacitor22can be reduced. In addition, by setting the thermal conductivity of the mold resin5to 10 W/(m·K) or less, the cost of the mold resin5can be reduced and its moldability can be improved. To increase the thermal conductivity of the mold resin5, it is necessary to include more filler502. However, the more filler502is added, the higher the cost of the mold resin5becomes, and the flowability of the raw material in a molten state, which becomes the mold resin5, becomes poor, and the moldability of the mold resin5tends to deteriorate. Therefore, by setting the thermal conductivity of the mold resin5to 10 W/(m·K) or less, the cost of the mold resin5can be reduced and the moldability of the mold resin5can be improved.

As described above, according to the present embodiment, it is possible to provide the surge suppression device that can suppress the temperature rise of the capacitor.

Second Embodiment

FIG.6is a perspective view of the surge suppression device1in this embodiment.FIG.7is a front view of the surge suppression device1.FIG.8is the VII-VII arrowhead cross-portion ofFIG.7.

This embodiment is an embodiment in which the position of the fixing metal bracket4and the shape of the second fixing metal bracket7, etc., are modified from the first embodiment.

As shown inFIG.8, the base41of the bracket4faces in the Z-direction through the mold resin5to the portion between the two cap electrodes212in the resistive element211, while it does not face the two cap electrodes212in the Z-direction. The base41partly faces the central region of the resistive element21in the X-direction in the Z-direction. Here, the central region of the resistive element21in the X-direction can be, for example, the central portion when the resistive element21is divided into five equal parts in the X-direction.

The three capacitors22, the interconnecting portions6, and the second fixing metal bracket7, which are molded by the second mold resin8, are arranged on opposite sides of the terminals3across the fixing metal bracket4in the X-direction. The three capacitors22, the interconnecting portions6, and the second fixing metal bracket7molded by the second mold resin8are located away from the fixing metal bracket4.

The second fixing metal bracket7has a box-shaped portion73opening toward the opposite side of the terminal3in the X-direction and a flange portion74extending outward from the bottom end of the box-shaped portion73to both sides in the Y-direction. The box-shaped portion73has a rectangular plate-like bottom plate731, which is thick in the X-direction and long in the Y-direction, and a rectangular cylindrical side plate732, which is extended in the X-direction from the periphery of the bottom plate731and is open on the side opposite the bottom plate731. Bolt insertion holes741are formed in the flange portion74, and the second fixing metal bracket7is bolted to the motor case at the flange portion74. In this embodiment, the fixing target of the second fixing metal bracket7is the motor case similar to the fixing target of the fixing metal bracket4, but it may be a different member from the fixing target of the fixing metal bracket4. The three capacitors22and the interconnecting portions6are received inside the box-shaped portion73of the second fixing metal bracket7, and the second mold resin8is filled. The inside of the box-shaped portion73may be filled with resin by potting instead of the second mold resin8. In this case, the load on the joints between the three capacitors22and the interconnecting portion6and the connecting portion23is easily reduced.

As shown inFIG.8, the end face5bof the side from which the connecting portion23protrudes in the mold resin5is located near the end face81of the side from which the connecting portion23protrudes in the second mold resin8. The length L1in the X-direction from the end face5bof the mold resin5to the resistive element21is three times longer than the length L2in the X-direction from the end face5con the side where the terminal3protrudes in the mold resin5to the resistive element21. The length in the X-direction (i.e., L1) of the portion distributed in the mold resin5in the connecting portion23is three or more times longer than the length in the X-direction L2from the end face5cof the mold resin5to the resistive element21. In this embodiment, the flat plate portion (see reference character9inFIGS.2to4) is not arranged on the lower side of the second fixing metal bracket7.

The other configuration of this embodiment is the same as that of the first embodiment. The same reference characters used in the second and subsequent embodiments as those used in the previous embodiments represent the same components, etc. as those in the previous embodiments, unless otherwise indicated.

Functions and Effects of the Second Embodiment

In this embodiment, the fixing metal bracket4has the base41facing the central region of the resistive element21in the Z-direction through the mold resin5. Heat of the resistive element21tends to be dissipated to the terminal3and the connecting portion23, which are metal parts in contact with the resistive element21, and thus tends to stay in the center region of the resistive element21rather than both ends of the resistive element21. Therefore, the heat in the center of the resistive element21can be dissipated to the fixing metal bracket4through the mold resin5by facing the fixing metal bracket4to the center of the resistive element21. As a result, the temperature rise of the resistive element21can be suppressed and the heat transferred from the resistive element21to the capacitor22can be reduced.

The second mold resin8is filled inside the box-shaped portion73of the second fixing metal bracket7. This allows a larger area of the second mold resin8to be enclosed by the second fixing metal bracket7. As a result, the heat from the capacitor22is more easily dissipated through the second mold resin8to the second fixing metal bracket7.

The length L1in the X-direction of the portion distributed in the mold resin5in the connecting portion23is three times longer than the length L2in the X-direction from the end face of the side from which the terminal3protrudes to the resistive element21in the mold resin5. As a result, the heat transferred from the resistive element21to the connecting portion23is easily diffused into the mold resin5, and the temperature rise of the connecting portion23is suppressed. Therefore, the heat transfer from the connecting portion23to the capacitor22is suppressed. Other functions and effects are the same as those of the first embodiment.

Third Embodiment

FIG.9is a perspective view of the surge suppression device1.FIG.10is a front view of the surge suppression device1.FIG.11is a cross-sectional view of the XI-XI line arrow inFIG.10.

This embodiment is an embodiment in which the shape of the mold resin5, the position of the fixing metal bracket4, the position of the capacitor22with respect to the second mold resin8, etc., have been modified with respect to the first embodiment.

The shape of the mold resin5has been devised to reduce the amount of resin used, to reduce size, and to reduce weight. The mold resin5has four first recesses51in which the surface opposite the second mold resin8in the Z-direction is recessed, and two second recesses52in which the surface on the side from which the terminal3protrudes in the X-direction is recessed. The four first recesses51are two first recesses51formed in the range between adjacent resistive elements21in the Y-direction and two first recesses51formed on the outer side in the Y-direction of the two resistive elements21located at both ends of the three resistive elements21. The first recesses51are formed from one end of the mold resin5in the X-direction to the other end, and are open on both sides in the X-direction. As shown inFIG.10, the formation range of the first recess51in the Z-direction overlaps the formation range of the resistive element21in the Z-direction. The second recess52is formed in the range between adjacent resistive elements21in the Y-direction. The second recess52is connected to the first recess51.

As shown inFIG.11, the end face of the second recess52in the X-direction is located between the terminal3and the base41of the fixing metal bracket4in the X-direction.

The base41of the fixing metal bracket4faces the portion between the two cap electrodes212in the resistive element211in the Z-direction via the mold resin5, while it does not face the two cap electrodes212in the Z-direction. The base41partly faces the central region of the resistive element21in the X-direction in the Z-direction. In the present embodiment, the base41partly faces the center of the resistive element21in the X-direction in the Z-direction. The bottom surface411of the base41is exposed from the mold resin5and is flush with the bottom surface5aof the mold resin5.

The capacitor22is eccentrically disposed in the X-direction with respect to the second mold resin8. Here, one side in the X-direction, which is the direction in which the end of the capacitor22-side (i.e., the third portion233) in the connecting portion23extends, and the side where the capacitor22is positioned with respect to the third portion233is the tip side. As shown inFIG.11, the center position Cl of the capacitor body221in the X-direction is located on the tip side of the second mold resin8than the center position C2in the X-direction. The entire capacitor body221may be located on the tip side of the second mold resin8than the center position C2in the X-direction of the second mold resin8. Otherwise, the same as in the first embodiment.

Functions and Effects of the Third Embodiment

In this embodiment, the center position Cl of the capacitor body221in the X-direction is located at the tip side of the second mold resin8than the center position C2in the X-direction. Hence, the length of the connecting portion23covered by the second mold resin8can be extended. A part of the heat of the resistive element21goes to the capacitor22through the connecting portion23. In this embodiment, by increasing the length of the connecting portion23covered by the second mold resin8, it is easier to diffuse the heat to the second mold resin8. Therefore, the heat transfer of the resistive element21to the capacitor22is suppressed.

In addition, the recesses (i.e., the first recess51and the second recess52) are formed in the mold resin5in the range between adjacent resistive elements21in the Y-direction. Therefore, the amount of mold resin5used can be reduced, the size can be made smaller, and the weight can be made lighter. In addition, since the surface of the mold resin5is formed unevenly by providing recesses in the mold resin5, the surface area of the mold resin5can be ensured, and the heat dissipation from the mold resin5to the surrounding space can be improved. Other functions and effects are the same as those of the first embodiment.

Fourth Embodiment

FIG.12is a perspective view of the surge suppression device1in this embodiment.FIG.13is a plan view of the surge suppression device1.FIG.14is a front view of the surge suppression device1.FIG.15is a cross-sectional view of the XV-XV line inFIG.14.

This embodiment is an embodiment in which the shape of the mold resin5, the shape of the connecting portion23, and the sealing structure of the capacitor22are changed mainly with respect to the first embodiment.

As shown inFIGS.12and13, a recess53is formed in the mold resin5in the range between adjacent resistive elements21in the Y-direction. The recess53is formed so that the surface of the terminal3side of the mold resin5in the X-direction is recessed in the X-direction in the entire Z-direction. The recess53serves to reduce the amount of resin used in the mold resin5, reduce the weight of the mold resin5, and ensure the creepage distance between adjacent resistive elements21.

The mold resin5has a first exposed recess54for exposing the resistive element terminals213aof the three resistive elements21connected to the three terminals3and a second exposed recess55for exposing the resistive element terminals213bof the three resistive elements21connected to the three connecting portions23.

In this embodiment, the first exposed recess54is formed at three locations in the mold resin5to expose each of the three resistive element terminals213a.The first exposed recess54is formed at an end of the mold resin5on the terminal3-side in the X-direction and on the opposite side of the second mold resin8in the Z-direction. In this embodiment, the entire resistive element terminal213aand a portion of the cap electrode212connected to said resistive element terminal213aare exposed from the first exposed recess54. By exposing the resistive element terminal213afrom the mold resin5, the injection pressure exerted during molding of the mold resin5on the junction portion of the resistive element terminal213aand the terminal3can be suppressed and the connectivity between the resistive element terminal213aand the terminal3can be ensured.

The second exposed recesses55are formed at three locations in the mold resin5so as to expose each of the three resistive element terminals213b.The second exposed recess55is formed at the end of the mold resin5on the side of the connecting portion23in the X-direction and opposite the second mold resin8in the Z-direction. In this embodiment, the entire resistive element terminal213band a portion of the cap electrode212connected to the resistive element terminal213bare exposed from the second exposed recess55. By exposing the resistive element terminal213bfrom the mold resin5, the injection pressure during molding of the mold resin5can be prevented from acting on the junction portion between the resistive element terminal213band the connecting portion23, and the connectivity between the resistive element terminal213band the connecting portion23can be ensured.

The second exposed recesses55are recesses closed on both sides in the Y-direction, and a portion of the mold resin5is present between adjacent second exposed recesses55. This facilitates ensuring the insulation distance between adjacent resistive elements21, and as a result of suppressing the decrease in the volume of the mold resin5, the decrease in the heat dissipation of the resistive elements21through the mold resin5is suppressed. For example, it is also possible to adopt a configuration in which three resistive element terminals213bare exposed in one wide second exposed recess. This configuration is particularly effective when it is desired to reduce the amount of mold resin5used, reduce weight, etc.

The pair of resistive element terminals213a,213bof the resistive element21comprise conductors of circular cross portion. In particular, when the pair of resistive terminals213a,213bof the resistive element21are made of conductive wires, if the resistive terminals213a,213bare embedded in the mold resin5, unlike the present embodiment, there is a concern that injection pressure acts on the resistive terminals213a,213bduring molding of the mold resin5and the load on the resistive terminals213a,213bIn this case, there is a concern that the load on the resistive element terminals213a,213bmay increase. Therefore, in this embodiment, the resistive element terminals213a,213bare exposed from the first exposed recess54and the second exposed recess55.

The connecting portion23connecting the resistive element21and the capacitor22comprises a conductor with a circular cross portion. By configuring the connecting portion23with a conductor, the cross-sectional area of the conductor constituting the connecting portion23can be made smaller than the cross-sectional area of the terminal3, and the heat transfer from the resistive element21to the capacitor22via the connecting portion23is suppressed. In this embodiment, the cross-sectional area of the conductor constituting the connecting portion23is smaller than the cross-sectional area of the terminal3and the resistive element terminals213a,213b,respectively. The connecting portion23may be a single wire or a stranded wire, and the surface of the connecting portion23may have an insulating coating.

As shown inFIGS.12and15, the connecting portion23is formed by bending a conductor and has a first portion231, a second portion232, and a third portion233. The first portion231is connected to the resistive element terminal213bof the resistive element21and extends in the X-direction. The second portion232extends in the Z-direction from the opposite end of the resistive element terminal213bof the first portion231. The third portion233extends from the end of the second portion232opposite the first portion231to the same side of the first portion231in the X-direction and is connected to the capacitor22.

As shown inFIGS.14and15, the encapsulation structure of the capacitor22has a box-shaped second mold resin8that molds the second fixing metal bracket7and has an opening82, and a potting resin10that encapsulates the capacitor22within the second mold resin8. In this embodiment, the potting resin10is an example of a capacitor embedded resin that buries the capacitor22.

The second mold resin8is formed in a rectangular box shape having an opening82on the opposite side of the terminal3in the X-direction, and buries the second base71and the second longitudinal extending portion721of the second fixing metal bracket7. The three capacitors22and the interconnecting portions6are arranged in the second mold resin8, which are sealed with potting resin10.

The potting resin10comprises, for example, a thermosetting resin. The potting resin10should be composed of a resin having high thermal conductivity from the viewpoint of improving the heat dissipation of the capacitor22. For example, the potting resin10comprises a base resin having electrical insulation properties and a filler having a higher thermal conductivity than the base resin. In this embodiment, the flat plate portion (see reference character9inFIGS.2to4) in the first embodiment is not arranged, but may be arranged.

Next, an example of a method of molding the mold resin5so as to expose the pair of resistive element terminals213a,213bwill be described usingFIGS.16to18.FIG.16is a perspective view showing the placement of the three resistive elements21in the primary molding unit100.FIG.17is a perspective view of the three resistive elements21in the primary molding unit100.FIG.18is a perspective view showing the completed state of the mold resin5.

As will be described in detail below, the mold resin5is composed of a primary molding part56that molds the fixing metal bracket4and the three terminals3, and a secondary molding part57that molds the integrated fixing metal bracket4, the three terminals, the primary molding part56, and the three resistive elements21. In other words, the mold resin5of this embodiment is formed through a multi-step resin molding process; the primary molding part56and the secondary molding part57may be made of the same resin or of different resins.

In molding the mold resin5, a primary molding process to form the primary molding part56, a resistive element placement process to place the three resistive elements21in the primary molding part56, and a secondary molding process to form the secondary molding part57are performed in this order.

In the primary molding process, the three terminals3and the fixing metal bracket4are placed in a mold, and resin is injected into the mold and cured to form the primary molding part56, as shown inFIG.16. At this time, the shape of the mold is designed so that three placement recesses561are formed on the surface of the primary molding part56after molding to enable placement of the three resistive elements21. In this embodiment, the placement recesses561are formed so that a portion of each of the resistive element211and the pair of cap electrodes212can be inserted, and the pair of resistive terminals213a,213bare arranged outside the placement recesses561when the resistive elements21are placed in the placement recesses561.

After the primary molding process, the resistive element placement process is performed as shown inFIGS.16and17. In this embodiment, during the resistive element placement process, the joining of the resistive element terminal213ato the terminal3is performed. This joining work may be performed after the entire mold resin5is completed.

Next, a secondary molding process is carried out: in the secondary molding process, the primary molding unit100comprising the primary molding part56, the three resistive elements21, and the fixing metal bracket4is placed in the mold, and resin is injected into said mold to cure, forming the secondary molding part57, as shown inFIG.18. At this time, the entire pair of resistive element terminals213aand213bof the resistive element21is placed outside the cavity of the mold, so that the pair of resistive element terminals213aand213bare exposed outside the mold resin5. As a result of the above, the mold resin5is molded with the primary molding part56and the secondary molding part57integrated together.

Functions and Effects of the Fourth Embodiment

In this embodiment, the second mold resin8is formed in a box shape having an opening82. The surge suppression device1has a potting resin10that encapsulates the capacitor22in the second mold resin8. During the formation of the potting resin10, i.e., during potting, it is relatively difficult for pressure to be generated in the resin, thus preventing a large pressure from acting on the capacitor22when the capacitor22is encapsulated. This prevents, for example, a load from being applied to the junction between the capacitor22and the components connected thereto (e.g., the connecting portion23and the interconnecting portion6), thereby reducing the connectivity of the capacitor22and the components connected to the capacitor22.

The entirety of the pair of resistive element terminals213a,213bis exposed from the mold resin5. Therefore, injection pressure during molding of the mold resin5does not act on the resistive element terminals213a,213b,and the load on the junction between the resistive element terminals213a,213band the components connected thereto (e.g., the terminals3and the connecting portion23) resulting in a degradation of their connectivity can be suppressed.

In addition, the connecting portion23comprises a conductor. Hence, the heat transfer from the resistive element21to the capacitor22via the connecting portion23is suppressed. Other functions and effects are similar to those of the first embodiment.

Summary of the Embodiments

Next, the technical concepts that can be grasped from the above-described embodiments are described with the help of the reference characters, etc. in the embodiments. However, each reference character, etc. in the following description is not limited to the members, etc. specifically shown in the embodiment as the components in the scope of claims.

According to the first feature, a surge suppression device includes a resistive element21, a capacitor22electrically connected to the resistive element21, a terminal3electrically connected to an opposite side of the resistive element21to a side connected to the capacitor22, a fixing metal bracket4to be fixed to a fixing target111, and a mold resin5that molds the resistive element21, the terminal3, and the fixing metal bracket4, wherein the capacitor22is located away from the mold resin5.

According to the second feature, in the surge suppression device1as described in the first feature, the fixing metal bracket4faces the resistive element21through the mold resin5.

According to the third feature, in the surge suppression device1as described in the first or second feature, the terminal3faces the resistive element21through the mold resin5.

According to the fourth feature, in the surge suppression device1according to any one of the first to third features, a connecting portion23connecting the resistive element21and the capacitor22is molded by the mold resin5, and the connecting portion23is facing the fixing metal bracket4through the mold resin5.

According to the fifth feature, in the surge suppression device1according to the fourth feature, the cross-sectional area of the connecting portion23is smaller than the cross-sectional area of the terminal3.

According to the sixth feature, the surge suppression device1according to any one of the first to fifth features, further includes a capacitor embedded resin8,10in which the capacitor22is embedded, wherein the capacitor embedded resin8,10is located away from the mold resin5.

According to the seventh feature, in the surge suppression device1according to the sixth feature, the fixing metal bracket4includes a base41extending in one direction Y, and two extending portions42extending on the same side from both ends of the base41, wherein the base41is molded by the mold resin5, and wherein the capacitor embedded resin8,10is disposed between the two extending portions42.

According to the eighth feature, in the surge suppression device1according to the sixth or seventh feature, the capacitor22includes a capacitor body221, and a capacitor terminal222protruding from the capacitor body221, and wherein when a direction of extending an end233on the capacitor22of the connecting portion23connecting the resistive element21and the capacitor22is the extending direction X, and one side in the extending direction X where the capacitor22is located relative to the end233is a tip side, a center position C1of the capacitor body221in the extending direction X is located on the tip side of the capacitor body221than the center position C2of the capacitor embedded resin8,10in the extending direction X.

According to the ninth feature, the surge suppression device1according to any one of the sixth to eighth features, further includes a second fixing metal bracket7to be fixed to a fixing target111, wherein the capacitor embedded resin8,10is a second mold resin8that molds the connecting portion23connecting the resistive element21and the capacitor22, and the second fixing metal bracket7.

According to the tenth feature, the surge suppression device1according to any one of the sixth to eighth features, further includes a second fixing metal bracket7to be fixed to the fixing target111, and a second mold resin8to mold the second fixing metal bracket7, wherein the second mold resin8is formed in a box shape having an opening82, and wherein the capacitor embedded resin8,10is a potting resin10that encapsulates the capacitor22within the second mold resin8.

According to the eleventh feature, the surge suppression device1according to any one of the first to tenth features, includes a plurality of series circuits2in which the resistive elements21and the capacitors22are connected in series, wherein the mold resin5molds a plurality of the resistive elements21.

According to the twelfth feature, in the surge suppression device1according to the eleventh feature, the plurality of resistive elements21are arranged in parallel, and wherein a recess51,52,53is formed in the mold resin5in the range between adjacent resistive elements21in an alignment direction of the plurality of resistive elements21.

According to the thirteenth feature, in the surge suppression device1as described in any one of the first to twelfth features, the mold resin5includes a base resin501and a filler502having a higher thermal conductivity than the base resin501.

According to the fourteenth feature, in the surge suppression device1according to the thirteenth feature, the thermal conductivity of the mold resin5is 3 W/m·K or more and 10 W/m·K or less.

According to the fifteenth feature, in the surge suppression device1according to any one of the first to fourteenth features, the resistive element21includes a pair of resistive element terminals213a,213b,and an entirety of the pair of resistive element terminals213a,213bis exposed from the mold resin5.

According to the sixteenth feature, in the surge suppression device1according to any one of the first to fifteenth features, the connecting portion23connecting the resistive element21and the capacitor22comprises a conductor.

Additional Notes

The above description of the embodiments of the invention is not intended to limit the invention according to the claims. It should also be noted that not all of the combinations of features described in the embodiments are essential for the invention to solve the problems of the invention. In addition, the invention can be implemented with appropriate modifications to the extent that it does not depart from the intent of the invention.

For example, in each of the foregoing embodiments, the fixing metal bracket is embedded in the mold resin, but it is not limited thereto, and it is sufficient if a portion of the surface is adhered to the mold resin. For example, the second fixing metal bracket is not in the form of embedded in the second mold resin, but the fixing metal bracket and the mold resin may also be configured as the second fixing metal bracket and the second mold resin. Conversely, the second fixing metal bracket may be configured to be embedded in the second mold resin.

In each of the foregoing embodiments, an example is shown in which the terminal portion is a straight plate, but the shape of the terminal portion can be changed as needed depending on the location of the connecting portion target of the terminal. For example, the terminal part may be made of a metal plate bent into an L-shape, etc.