# Patent

## Title
Power conversion apparatus

## Abstract

A power conversion apparatus includes a casing and an inverter unit housed in the casing. The inverter unit includes a unit case, a capacitor block removably provided at a position on an inner side of a detachable side plate of the unit case, and a fan block placed in the unit case in such a manner as to be removable from a front side. The capacitor block includes a capacitor case having a plurality of capacitor insertion holes, a plurality of electrolytic capacitors placed in the capacitor insertion holes, respectively, and a laminated bus bar connected to the electrolytic capacitors. The fan block includes a fan case and a cooling fan provided in the fan case.

## Background
CROSS-REFERENCE TO RELATED APPLICATION
The present application claims priority under 35 U.S.C. §119 to Japanese Patent Applications No. 2009-181802 filed Aug. 4, 2009 and No. 2010-142726 filed Jun. 23, 2010. The contents of the applications are incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power conversion apparatus.
2. Discussion of the Background
A power conversion apparatus includes various units such as an inverter unit. Such units are housed in a casing.
The units basically include, for example, as disclosed in Japanese Unexamined Patent Application Publication No. 2002-354839 published on Dec. 6, 2002, electrical components such as electrolytic capacitors included in circuits, conductors connecting the electrical components to each other, casings securing and protecting the electrical components and the conductors, and cooling fans that cool the electrical components.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, a power conversion apparatus includes a casing and an inverter unit housed in the casing. The inverter unit includes a unit case, a capacitor block removably provided on an inner side of a detachable side plate of the unit case, and a fan block placed in the unit case in such a manner as to be removable from a front side. The capacitor block includes a capacitor case having a plurality of capacitor insertion holes, a plurality of electrolytic capacitors placed in the capacitor insertion holes, respectively, and a laminated bus bar connected to the electrolytic capacitors. The fan block includes a fan case and a cooling fan provided in the fan case.



BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be described in further detail with reference to the accompanying drawings, wherein:
FIG. 1 is a front view of a power conversion apparatus according to a first embodiment of the present invention;
FIG. 2 is a perspective view of an inverter unit according to the first embodiment of the present invention, part of which is disassembled for easier recognition;
FIG. 3 is an exploded perspective view of the inverter unit shown in FIG. 2;
FIG. 4 is a cross-sectional view showing a mechanism of supporting a capacitor block of the inverter unit shown in FIG. 2;
FIG. 5 is a perspective view of a fan block shown in FIG. 2; and
FIG. 6 is a perspective view of a capacitor block according to a second embodiment of the present invention, part of which is disassembled for easier recognition.



DETAILED DESCRIPTION OF THE EMBODIMENTS
Embodiments of the present invention will now be described with reference to the drawings. Herein, like elements are denoted by like reference numerals, whereby redundant descriptions are omitted.
First Embodiment
Referring to FIGS. 1 to 5, the configuration of a power conversion apparatus according to a first embodiment of the present invention will now be described.
As shown in FIG. 1, a power conversion apparatus 1, such as an inversion apparatus, according to the first embodiment includes, in a casing 2, various units such as a control unit 3, a converter unit 4, inverter units 5, and a power unit 6. The control unit 3 is operable from outside of the casing 2.
Among the units 3, 4, 5, and 6, the inverter units 5 each include, as shown in FIGS. 2 and 3, a unit case 7 that includes a circuit-side case 8 and a wind-tunnel-side case 9.
The circuit-side case 8 includes a front plate 8a provided on the front, a left side plate 8b and a right side plate 8c provided on the left and right sides, respectively, a top plate 8d provided at the top, a bottom plate 8e provided at the bottom, and a partition plate 8f defining the boundary between the circuit-side case 8 and the wind-tunnel-side case 9. All of the foregoing plates are detachably assembled together. The front plate 8a includes three parts, i.e., a top front plate 8aa, a middle front plate 8ab, and a bottom front plate 8ac, so as to be disassembled partially. The bottom front plate 8ac is provided with a handle 8ad so that cooling fans 13b and/or electrolytic capacitors 12b described below can be removed safely, if necessary, for inspection and/or replacement. Furthermore, the bottom front plate 8ac is recessed with respect to the top front plate 8aa and the middle front plate 8ab so that the handle 8ad does not protrude from the front plate 8a. 
The front plate 8a, the left side plate 8b, the right side plate 8c, the top plate 8d, the bottom plate 8e, and the partition plate 8f defining the boundary between the circuit-side case 8 and the wind-tunnel-side case 9 all have substantially flat plate-like shapes. The top plate 8d and the bottom plate 8e have ventilating holes 8da and 8ea, respectively, intended for cooling and provided by making holes and/or cuts. The partition plate 8f has a switching-device insertion hole 8fa and a fan-block through hole 8fb, described below, provided side by side.
The wind-tunnel-side case 9 includes a left side face 9a, a right side face 9b, and a rear face 9c. The wind-tunnel-side case 9 is detachably attached to a base 11aa of a heat sink 11a, described below, from the rear side of the inverter unit 5. The wind-tunnel-side case 9 attached to the heat sink 11a provides a wind tunnel forming a passageway allowing cooling air for cooling the heat sink 11a to pass therethrough.
The inverter unit 5 includes, in the circuit-side case 8, various blocks such as a terminal block 10, a device block 11, a capacitor block 12, and a fan block 13.
The terminal block 10 is provided at a position behind the front plate 8a and includes a positive input terminal 10a, a negative input terminal 10b, and so forth affixed to the left side plate 8b. The positive input terminal 10a and the negative input terminal 10b are connected to relay conductors 10aa and 10ba, respectively.
The device block 11 includes the heat sink 11a, a plurality of switching devices 11b, and relay conductors 11ba connected to the switching devices 11b. The heat sink 11a includes the base 11aa and a fin 11ab. The switching devices 11b are tightly mounted on the rear face of the base 11aa at regular intervals.
The heat sink 11a is attached to the partition plate 8f. With the switching devices 11b placed in the switching-device insertion hole 8fa of the partition plate 8f, the base 11aa is fastened to the partition plate 8f with, for example, bolts. By fastening the base 11aa to the partition plate 8f, the part of the partition plate 8f having the switching-device insertion hole 8fa between the circuit-side case 8 and the wind-tunnel-side case 9 provides a dust- and waterproof structure. If a sealing member, such as a gasket or a packing, is interposed between the base 11aa and the partition plate 8f, dust- and waterproofness is further enhanced.
The capacitor block 12 includes a capacitor case 12a, a plurality of, for example, eight electrolytic capacitors 12b, a laminated bus bar 12c, and so forth.
The capacitor block 12 is provided between the terminal block 10 and the device block 11.
The capacitor case 12a has a configuration allowing a plurality of, for example, eight electrolytic capacitors 12b to be arranged in a line. That is, the capacitor case 12a has eight capacitor insertion holes 12aa arranged in a line. The eight electrolytic capacitors 12b are inserted into the eight capacitor insertion holes 12aa and are fastened with fastening bands 12ab, thereby being secured to the capacitor case 12a. The capacitor case 12a has, in the longitudinal direction in which the cooling air flows, a first end plate 12ac and a second end plate 12ad having a first airhole 12ae and a second airhole 12af, respectively. As shown in FIGS. 3 and 4, the capacitor case 12a is placed on an upper case support 12d and a lower case support 12e affixed to the left side plate 8b and is fastened thereto with screws or the like.
In addition, a space in which the fan block 13, described below, is placed is provided between the capacitor case 12a and the bottom plate 8e. 
The eight electrolytic capacitors 12b that have been placed in and fastened to the eight capacitor insertion holes 12aa are connected at upper terminals 12ba thereof to the laminated bus bar 12c. The laminated bus bar 12c includes a plurality of bus bars with insulating members interposed therebetween.
The electrolytic capacitors 12b are arranged linearly in the vertical direction of the power conversion apparatus 1, and the width of the laminated bus bar 12c connecting the electrolytic capacitors 12b to each other is set to be equal to the width of the row of the electrolytic capacitors 12b. Thus, the area of the laminated bus bar 12c is minimized.
The laminated bus bar 12c connected to the electrolytic capacitors 12b is also connected to the relay conductors 11ba connected to the switching devices 11b, and to the relay conductors 10aa and 10ba connected to the positive input terminal 10a and the negative input terminal 10b. 
In the capacitor block 12, all of the electrolytic capacitors 12b are fastened to the capacitor case 12a. Therefore, when the electrolytic capacitors 12b are removed from the circuit-side case 8, the eight electrolytic capacitors 12b and the capacitor case 12a can all be removed at a time, providing good working efficiency.
The terminal block 10 and the capacitor block 12 may alternatively be provided on the right side plate 8c, not on the left side plate 8b. 
As shown in FIGS. 3 and 5, the fan block 13 includes a fan case 13a and cooling fans 13b provided in the fan case 13a. 
Cooling air produced by the cooling fans 13b is made to flow from the lower side toward the upper side in the inverter unit 5.
The fan case 13a includes a first fan case 13aa positioned in the circuit-side case 8 and a second fan case 13ab positioned in the wind-tunnel-side case 9. The first fan case 13aa and the second fan case 13ab are provided as an integral body. The first fan case 13aa is larger than the second fan case 13ab. Therefore, a step 13ac is formed at the boundary between the first fan case 13aa and the second fan case 13ab. When the fan block 13 is inserted into and placed in the unit case 7, the second fan case 13ab passes through the fan-block through hole 8fb of the partition plate 8f, and the step 13ac of the fan case 13a is pressed against the periphery of the fan-block through hole 8fb. Thus, the part of the partition plate 8f having the fan-block through hole 8fb between the circuit-side case 8 and the wind-tunnel-side case 9 provides a dust- and waterproof structure. If a sealing member, such as a gasket or a packing, is interposed between the step 13ac and the partition plate 8f, dust- and waterproofness is further enhanced.
The cooling fans 13b include a first cooling fan 13ba provided in the first fan case 13aa and a second cooling fan 13bb provided in the second fan case 13ab. The first cooling fan 13ba and the second cooling fan 13bb are provided with finger guards 13c (13ca and 13cb, respectively).
The fan block 13 is inserted into the space in the inverter unit 5 between the first end plate 12ac of the capacitor case 12a and the bottom plate 8e from the lowest position on the front side, i.e., from the position where the bottom front plate 8ac is provided, thereby being removably placed in the space.
The fan block 13 placed in the space between the first end plate 12ac of the capacitor case 12a and the bottom plate 8e is pressed at the leading end thereof, i.e., the rear face thereof, against the wind-tunnel-side case 9 with leaf springs 9ca and 9cb, functioning as elastic members and provided on the left and right sides of the rear face 9c of the wind-tunnel-side case 9, interposed therebetween, thereby being supported. The leaf springs 9ca and 9cb have at the tips thereof angled portions, respectively, that are bent upward.
At the trailing end, i.e., the front face, of the fan block 13, the right side (the upper side in the drawings) is fastened with screws to the first end plate 12ac provided at the bottom of the capacitor case 12a, and the left side (the lower side in the drawings) is fastened with screws to the lower case support 12e, whereby the trailing end of the fan block 13 is supported. The fan block 13 has at the central portion on the front face thereof a handle 13ad so that the fan block 13 can be inserted into and removed from the inverter unit 5.
The first and second cooling fans 13ba and 13bb placed in the unit case 7 are driven to rotate when the power conversion apparatus 1 is driven.
The first cooling fan 13ba positioned in the circuit-side case 8 cools the terminal block 10 and the capacitor block 12 by feeding cooling air toward the blocks 10 and 12. The electrolytic capacitors 12b provided in the capacitor case 12a are also cooled by the cooling air from the first cooling fan 13ba because the cooling air flows through the first airhole 12ae and the second airhole 12af provided in the first end plate 12ac and the second end plate 12ad of the capacitor case 12a. 
The second cooling fan 13bb positioned in the wind-tunnel-side case 9 cools the switching devices 11b through the heat sink 11a by feeding cooling air toward the fin 11ab of the heat sink 11a. 
In such a configuration, the cooling fans 13b and the electrolytic capacitors 12b, which are service parts, are replaced in the following manner.
To replace the first cooling fan 13ba and the second cooling fan 13bb with new ones, the fan block 13 is pulled out of the circuit-side case 8.
First, the bottom front plate 8ac is detached from the circuit-side case 8. The bottom front plate 8ac is fastened to the left side plate 8b, the right side plate 8c, and the bottom plate 8e with, for example, screws. Therefore, the screws are removed, whereby the bottom front plate 8ac is detached.
Subsequently, the fan block 13 is removed from the circuit-side case 8 and the wind-tunnel-side case 9.
The first fan case 13aa provided on the front side of the fan block 13 has the right side face thereof fastened with screws to and supported by the first end plate 12ac of the capacitor case 12a, and the left side face thereof fastened with screws to and supported by the lower case support 12e. Therefore, the screws are removed. The rear face of the fan block 13, i.e., the second fan case 13ab, is not screwed to but is only supported by being pressed against the wind-tunnel-side case 9 with the leaf springs 9ca and 9cb provided on the left and right sides of the rear face 9c of the wind-tunnel-side case 9. Therefore, only the removal of the screws on the first fan case 13aa makes the fan block 13 being able to be pulled out of the unit case 7. In this state, the fan block 13 is pulled out of the unit case 7. Subsequently, the first cooling fan 13ba and the second cooling fan 13bb are replaced with new cooling fans or the like.
The fan block 13 having the new cooling fans is inserted into and placed in the unit case 7 in the reverse procedure.
The fan block 13 is inserted into the unit case 7 while the second fan case 13ab is introduced into the fan-block through hole 8fb of the partition plate 8f. When the entirety of the second fan case 13ab passes through the fan-block through hole 8fb of the partition plate 8f, the step 13ac of the fan case 13a comes into contact with the periphery of the fan-block through hole 8fb of the partition plate 8f. Thus, the position of the fan block 13 in the direction in which the fan block 13 is inserted is determined.
Before the entirety of the second fan case 13ab passes through the fan-block through hole 8fb, the leading end of the second fan case 13ab comes into contact with the angled portions of the leaf springs 9ca and 9cb. When the fan block 13 is further inserted, the leaf springs 9ca and 9cb ride on the second fan case 13ab, thereby pressing the second fan case 13ab against the bottom of the wind-tunnel-side case 9. Thus, the rear face of the fan block 13 is supported without being screwed.
The right side face of the first fan case 13aa provided on the front side of the fan block 13 is screwed to and supported by the first end plate 12ac of the capacitor case 12a, and the left side face of the first fan case 13aa is screwed to and supported by the lower case support 12e. 
Thus, the replacement of the cooling fans 13b is completed.
To replace the electrolytic capacitors 12b with new ones, the capacitor case 12a is pulled out of the circuit-side case 8.
Attachment and removal of the capacitor case 12a are performed in a state where the right side plate 8c is detached from the circuit-side case 8. Therefore, the right side plate 8c is first detached from the circuit-side case 8.
The right side plate 8c is fastened with screws to the top plate 8d, the bottom plate 8e, and the partition plate 8f. Therefore, the screws are removed, whereby the right side plate 8c is detached from the top plate 8d, the bottom plate 8e, and the partition plate 8f. 
In this step, in the capacitor block 12, the laminated bus bar 12c connected to the electrolytic capacitors 12b is provided over the electrolytic capacitors 12b, and the laminated bus bar 12c is also connected to the relay conductors 11ba connected to the switching devices 11b and to the relay conductors 10aa and 10ba connected to the positive input terminal 10a and the negative input terminal 10b. Therefore, the laminated bus bar 12c is disconnected from the foregoing elements, thereby being removed from the circuit-side case 8.
Subsequently, the capacitor case 12a is removed from the circuit-side case 8. The electrolytic capacitors 12b can be removed from the capacitor case 12a without removing the capacitor case 12a from the circuit-side case 8. However, the electrolytic capacitors 12b can be replaced easier when the capacitor case 12a is removed from the circuit-side case 8.
The capacitor case 12a is fastened with screws to the upper case support 12d and the lower case support 12e affixed to the left side plate 8b of the circuit-side case 8. Therefore, the screws are removed, whereby the capacitor case 12a is removed from the circuit-side case 8. The eight electrolytic capacitors 12b are placed in the eight capacitor insertion holes 12aa of the capacitor case 12a and are fastened with the fastening bands 12ab, thereby being secured to the capacitor case 12a. Therefore, the eight fastening bands 12ab are first loosened, the eight electrolytic capacitors 12b are then removed from the capacitor case 12a, and new electrolytic capacitors are placed into the capacitor case 12a. 
Second Embodiment
FIG. 6 is a perspective view of a capacitor block A12 according to a second embodiment of the present invention. For easier recognition, part of the capacitor block A12 is disassembled.
In the second embodiment, an increased number of electrolytic capacitors 12b are provided for high power. For example, if sixteen electrolytic capacitors 12b, twice the number of electrolytic capacitors 12b in the first embodiment, are provided, a capacitor case A12a is provided with two rows of capacitor insertion holes, each of the row including eight holes. Furthermore, a laminated bus bar A12c for high power is provided, and the sizes of bus bars for individual phases and insulating members increase along with the number of connections to the electrolytic capacitors 12b. 
With such a configuration, the power conversion apparatus can be adapted for higher power without changing the configurations of parts, without significantly increasing the number of parts, and without reducing the working efficiency in replacing the electrolytic capacitors.

## Claims

1. A power conversion apparatus comprising:
an outer casing; and
an inverter unit housed in the outer casing, the inverter unit includes:
a unit case, the unit case includes a circuit-side case and a wind-tunnel-side case, the wind-tunnel-side case attached to the circuit-side case, the circuit-side case including a detachable side plate;
a capacitor block removably provided inside of the circuit-side case, the capacitor block positioned on an inner side of the detachable side plate, the capacitor block includes:
a capacitor case having a plurality of capacitor insertion holes;
a plurality of electrolytic capacitors, each of the plurality of electrolytic capacitors placed in a respective one of the plurality of capacitor insertion holes; and
a laminated bus bar connected to the electrolytic capacitors; and

a fan block placed in the unit case in such a manner as to be removable from a front side of the unit case, the fan block includes:
a fan case; and
a circuit-side cooling fan and a wind-tunnel-side cooling fan provided in the fan case,
wherein the circuit-side cooling fan positioned in the circuit-side case, and wind-tunnel-side cooling fan positioned in the wind-tunnel-side case.

2. The power conversion apparatus according to claim 1, wherein the fan block has a leading end thereof supported by being pressed with an elastic member against the wind-tunnel-side case.