EP2573477A2

EP2573477A2 - Air conditioner

Info

Publication number: EP2573477A2
Application number: EP12183798A
Authority: EP
Inventors: Hiroto Uejima; Hiroki Hasegawa; Satoshi Kida
Original assignee: Panasonic Corp
Current assignee: Panasonic Corp
Priority date: 2011-09-20
Filing date: 2012-09-11
Publication date: 2013-03-27
Anticipated expiration: 2032-09-11
Also published as: EP2573477B1; EP2573477A3; CN103017261A; JP2013064564A

Abstract

An air conditioner includes an indoor unit (1) and an electrical unit (8) placed on a side of a front wall (1b) of the indoor unit (1). The electrical unit (8) accommodates a substrate (8c) therein, on which an alternating-current circuit block (132), a high-voltage direct-current circuit block (133) and a low-voltage direct-current circuit block (134) are arrayed in order from a side of an alternating-current power cord connected to an alternating-current power source (131). The alternating-current circuit block (132) includes a noise filter (139) to restrain unnecessary radiation noise from leaking to a primary side. A ground pattern (140) of the low-voltage direct-current circuit block (134) and a pattern (141) of the alternating-current circuit block (132) positioned on the primary side of the noise filter (139) are placed adjacent to each other to form a stray capacitance (143) between those patterns (140, 141). The ground pattern (140) of the low-voltage direct-current circuit block (134) is connected at an end portion thereof to the earth.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an arrangement of an electrical unit mounted in an indoor unit of an air conditioner.

Description of the Related Art

A conventional air conditioner includes an electrical unit accommodating electrical components therein and disposed on a front side of an indoor unit to increase a lateral size of an indoor heat exchanger to thereby increase the amount of heat exchange (see, for example, Patent Document 1).
In general, an alternating-current power cord for connection to an external alternating-current power source extends from a right or left side portion of the air conditioner. In applications where the electrical unit is disposed in front of the heat exchanger, the alternating-current power cord is connected to a right or left end surface of the electrical unit. The electrical unit also accommodates an alternating-current circuit block, a high-voltage direct-current circuit block and a low-voltage direct-current circuit block in order from the side to which the alternating-current power cord is connected.

Prior Art Document(s)

Patent Document 1: Japanese Laid-Open Patent Publication No. 8-110085

SUMMARY OF THE INVENTION

The electrical components generate unnecessary radiation noise, which is generally caused by a switching operation of a switching element such as, for example, a transistor or an FET employed in a switching power source or a high-voltage power source. Because a circuit block for generating the unnecessary radiation noise is present on a side of the direct-current circuits, it is difficult to reduce the noise to zero. It is accordingly necessary to place a noise filter, for example, between the direct-current circuit block and the alternating-current circuit block to thereby prevent the unnecessary radiation noise from leaking to the alternating-current circuit block on a primary side and further from the alternating-current block to the primary side.
However, the noise filter merely acts to attenuate the unnecessary radiation noise to some extent by virtue of an attenuation performance that is determined by frequency characteristics of its impedance.
It is accordingly an objective of the present invention to provide an air conditioner capable of effectively attenuating unnecessary radiation noise that cannot be attenuated by the noise filter.
In accomplishing the above and other objectives, the air conditioner according to the present invention includes an indoor unit, an electrical unit placed on a front side of the indoor unit, an alternating-current power cord connected to the electrical unit and to an external alternating-current power source, and a substrate accommodated within the electrical unit. The substrate includes an alternating-current circuit block, a high-voltage direct-current circuit block and a low-voltage direct-current circuit block, all arrayed thereon in order from a side of the alternating-current power cord. The alternating-current circuit block includes a noise filter to restrain unnecessary radiation noise from leaking to a primary side. A ground pattern of the low-voltage direct-current circuit block and a pattern of the alternating-current circuit block positioned on the primary side of the noise filter are placed adjacent to each other to form a stray capacitance between the ground pattern of the low-voltage direct-current circuit block and the pattern of the alternating-current circuit block. The ground pattern of the low-voltage direct-current circuit block is connected at an end portion thereof to the earth.
The air conditioner according to the present invention can effectively attenuate unnecessary radiation noise that cannot be attenuated by the noise filter.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objectives and features of the present invention will become more apparent from the following description of a preferred embodiment thereof with reference to the accompanying drawings, throughout which like parts are designated by like reference numerals, and wherein:

Fig. 1 is a perspective view of an indoor unit of an air conditioner embodying the present invention;
Fig. 2A is a front view of the indoor unit of Fig. 1;
Fig. 2B is a front view of the indoor unit of Fig. 1 with a front panel removed;
Fig. 3A is a cross-sectional view taken along line A-A in Fig. 2A when the indoor unit is not in operation;
Fig. 3B is a cross-sectional view taken along line A-A in Fig. 2A when the indoor unit is in operation;
Fig. 4 is a perspective view of an electrical unit mounted in the indoor unit of Fig. 1;
Fig. 5 is an exploded perspective view of the electrical unit of Fig. 4;
Fig. 6 is an exploded perspective view of the indoor unit of Fig. 1, particularly depicting a positional relationship between the electrical unit and a filter frame;
Fig. 7 is a cross-sectional view taken along line B-B in Fig. 4;
Fig. 8 is an enlarged cross-sectional view of a mating portion between a base and a cover of the electrical unit of Fig. 4;
Fig. 9A is an enlarged perspective view of a portion C of the electrical unit encircled by a dotted line in Fig. 4;
Fig. 9B is a front view of the portion C as viewed from a direction indicated by D in Fig. 9A;
Fig. 10 is a perspective view of a connecting region between the base and the cover;
Fig. 11A is an exploded perspective view of one of a plurality of connections between the base and the cover;
Fig. 11B is a perspective view of the connection of Fig. 11A after assemblage;
Fig. 12A is a front view of a stopper mounted to the connection of Fig. 11A;
Fig. 12B is a view similar to Fig. 12A, but depicting a modification thereof; and
Fig. 13 is a block diagram of a substrate mounted in the electrical unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

An air conditioner according to the present invention includes an indoor unit, an electrical unit placed on a front side of the indoor unit, an alternating-current power cord connected to the electrical unit and to an external alternating-current power source, and a substrate accommodated within the electrical unit. The substrate includes an alternating-current circuit block, a high-voltage direct-current circuit block and a low-voltage direct-current circuit block, all arrayed thereon in order from a side of the alternating-current power cord. The alternating-current circuit block includes a noise filter to restrain unnecessary radiation noise from leaking to a primary side. A ground pattern of the low-voltage direct-current circuit block and a pattern of the alternating-current circuit block positioned on the primary side of the noise filter are placed adjacent to each other to form a stray capacitance between the ground pattern of the low-voltage direct-current circuit block and the pattern of the alternating-current circuit block. The ground pattern of the low-voltage direct-current circuit block is connected at an end portion thereof to the earth.
The air conditioner of the above-described construction can effectively attenuate unnecessary radiation noise that cannot be attenuated by the noise filter.
The electrical unit also includes a base for placing the substrate thereon and a cover mounted on the base to cover the substrate. The base may have a groove portion defined therein so as to extend along an outer periphery thereof and the cover may have a protrusion formed therewith so as to be fitted into the groove portion in the base, thereby making it possible to restrain foreign substances from entering the electrical unit.
A flame-retardant member may be placed in a space between the base and the cover to enhance safety of the air conditioner.
It is preferred that the flame-retardant member be flexible. The flexible flame-retardant member acts to fill the space between the base and the cover.
Advantageously, the base has an inner side wall and an outer side wall confronting each other, between which the groove portion is formed, and the inner side wall is higher than the outer side wall. This configuration further restrains foreign substances from entering the electrical unit.
The cover may be covered with a metal cover, which acts to restrain fire, which may occur inside the electrical unit, from spreading outside.
An outer surface of the metal cover is preferably coated or painted to thereby restrain a worker from being injured by edges or burrs of the metal during maintenance, thus enhancing safety.
The cover may have a groove portion defined therein, in which an end portion of the metal cover is inserted. This configuration allows the end portion of the metal cover to be covered with the groove portion in the cover, thus enhancing safety during maintenance.
A preferred embodiment of the present invention is explained hereinafter with reference to the drawings, but the present invention is not limited thereto.
Fig. 1 is a perspective view of an indoor unit of an air conditioner embodying the present invention. Fig. 2A is a front view of the indoor unit with a front panel installed, while Fig. 2B is a front view of the indoor unit with the front panel removed. Fig. 3A is a cross-sectional view taken along line A-A in Fig. 2A when the indoor unit is not in operation, while Fig. 3B is a cross-sectional view taken along line A-A in Fig. 2A when the indoor unit is in operation.
The air conditioner in this embodiment includes an indoor unit 1 to be installed in a room and an outdoor unit (not shown) to be installed outside the room, both connected to each other via refrigerant piping and electric wires.
A construction of the indoor unit 1 is explained hereinafter with reference to Fig. 1, Figs. 2A and 2B, and Figs. 3A and 3B.
The indoor unit 1 in this embodiment has an upper suction opening 2a defined in an upper wall 1 a thereof, through which indoor air is sucked from above, and a front suction opening 2b defined in a front wall 1 b thereof through which indoor air is sucked from front. The indoor unit 1 includes a front panel 2 for covering the front suction opening 2b in the front wall 1b. When the indoor unit 1 is not in operation, the front suction opening 2b is closed by the front panel 2, but when the indoor unit 1 is brought into operation, the front panel 2 moves forward to open the front suction opening 2b, thereby increasing the amount of air sucked into the indoor unit 1 through the front suction opening 2b.
Also, the indoor unit 1 has a discharge opening 3 defined therein through which air sucked into the indoor unit 1 is blown into a room. The indoor unit 1 also includes a plurality of vertical wind direction changing blades 3a mounted in the discharge opening 3 to vertically change a wind direction and a plurality of horizontal wind direction changing blades 3b mounted in the discharge opening 3 to horizontally change the wind direction. The indoor unit 1 accommodates therein an indoor heat exchanger 5 generally in the form of an inverted V as viewed from the side, as shown in Figs. 3A and 3B, an indoor fan 6 for conveying air heat-exchanged by the indoor heat exchanger 5 toward the room, and an air filter 7 for collecting dust in the air sucked into the indoor unit 1. The air filter 7 is held by a filter frame 7a (see Fig. 6), on which an automatic cleaning device for automatically cleaning the air filter 7 is mounted, but explanation of the automatic cleaning device is omitted.
Operation of the indoor fan 6 causes indoor air to be sucked into the indoor unit 1 through the upper suction opening 2a and the front suction opening 2b. The air sucked into the indoor unit 1 is heat exchanged with a refrigerant by the indoor heat exchanger 5 so that cold or warm air may be introduced into a room during cooling or heating.
In the indoor unit 1 of the above-described construction, an electrical unit 8 is disposed in a space delimited by the upper wall 1a having the upper suction opening 2a, the front wall 1b having the front suction opening 2b, and an inclined front face 5a of the indoor heat exchanger 5. This arrangement of the electrical unit 8 can make effective use of the dead space delimited by the upper wall 1 a and the front wall 1 b of the indoor unit 1 and the indoor heat exchanger 5. Accordingly, it is not necessary to arrange the electrical unit 8 at a right or left side portion of the indoor heat exchanger 5 and, hence, a lateral size of the indoor heat exchanger 5 can be increased, thus making it possible to enhance the heat exchanging performance of the indoor heat exchanger 5.
Also, the electrical unit 8 includes a substrate (described later in detail), on which electrical components are placed, and accordingly generates heat, but the electrical unit 8 of the above-described arrangement is cooled by indoor air sucked through the upper suction opening 2a and front suction opening 2b. Further, because the electrical unit 8 is disposed obliquely above the indoor heat exchanger 5, drainage water generated in the indoor heat exchanger 5 is prevented from dripping on the electrical unit 8, thus making it possible to enhance the reliability of the air conditioner.
A construction of the electrical unit 8 is explained hereinafter. Fig. 4 is a perspective view of the electrical unit 8 and Fig. 5 is an exploded perspective view of the electrical unit 8. Fig. 6 is an exploded perspective view depicting a positional relationship between the electrical unit 8 and the filter frame 7a in a state in which the electrical unit 8 has been separated from the filter frame 7a.
As shown in Figs. 4 to 6, the electrical unit 8 includes a support plate 8a made of a metal plate, a base 8b made of a flame-retardant resin, a substrate 8c on which electrical components are placed, a cover 8d made of a flame-retardant resin, and a metal cover 8e made of a metal plate.
The substrate 8c is placed on the base 8b, covered with the cover 8d, and accommodated within the electrical unit 8. The cover 8d is rotatably mounted on the base 8b, but details are explained later. The support plate 8a is secured to the base 8b on a rear side thereof opposite to a side on which the substrate 8c is mounted. The metal cover 8e is mounted on the cover 8d so as to cover it from above.
In this embodiment, the base 8b and the cover 8d are both made of a flame-retardant resin such as, for example an ABS resin, but the materials of the base 8b and the cover 8d are not limited to the ABS resin. That is, the base 8b and the cover 8d are made of different flame-retardant resins.
A terminal block 8f is disposed separately from the electrical unit 8 and connected to electric wires that connect the electrical components on the substrate 8c with those accommodated in an outdoor unit (not shown). The terminal block 8f is positioned lateral to the electrical unit 8 (in this embodiment, on a right side of the electrical unit 8). A connecting portion of the terminal block 8f to which the electric wires are connected is directed toward the front wall 1 b of the indoor unit 1 to allow a worker to work from the side of the front wall 1 b of the indoor unit 1.
As shown in Fig. 6, the support plate 8a is supported by right and left side frame portions 7b of the filter frame 7a that holds the filter 7. This configuration and the fact that the support plate 8a is formed of a metal plate can restrain the electrical unit 8 from deforming during, for example, transportation. Also, even if a worker applies an external force to the electrical unit 8 during maintenance, the support plate 8a formed of a metal plate acts to avoid a reduction in the distance between the electrical unit 8 and the filter frame 7a, thereby ensuring a predetermined amount of air to be sucked through the filter 7. It is to be noted that the support plate 8a may be screwed to or engaged with the filter frame 7a.
In the case of the electrical unit 8 in this embodiment, the substrate 8c is positioned on the right side of the support plate 8a and an opening 8g is formed in the support plate 8a on the left side thereof. In the absence of the opening 8g, an air current is largely impeded from flowing toward the filter 7 because the support plate 8a is supported by the right and left side frame portions 7b of the filter frame 7a to horizontally cover the filter 7. In this embodiment, however, the substrate 8c is placed on the right side of the support plate 8a and the opening 8g is formed on the left side of the support plate 8a, thereby enabling air to flow toward the filter 7 through the opening 8g. That is, the opening 8g acts to reduce an air resistance. The arrangement of the substrate 8c and the opening 8g may be reversed horizontally. Alternatively, the substrate 8c and the opening 8g may be arranged vertically.
Fig. 7 is a cross-sectional view taken along line B-B in Fig. 4 and Fig. 8 is an enlarged cross-sectional view of a mating portion between the base 8b and the cover 8d shown in Fig. 7. As shown in Figs. 7 and 8, the base 8b has a groove portion 9 defined therein so as to extend along an outer periphery thereof. That is, the base 8b has an inner side wall 9a and an outer side wall 9b along the outer periphery thereof so as to confront each other, and the groove portion 9 is formed between the inner side wall 9a and the outer side wall 9b.
On the other hand, the cover 8d has a protrusion 10 formed therewith at a location confronting the groove portion 9. The cover 8d is mounted to the base 8b by fitting the protrusion 10 into the groove portion 9. The base 8b preferably engages with the cover 8d without any gap therebetween, but a gap 11 is created due to, for example, manufacturing errors.
In view of this, in this embodiment, a flame-retardant member 12 is placed in the gap 11 between the inner side wall 9a of the base 8b and a portion of the cover 8d confronting the inner side wall 9a. In the case of this embodiment, an EPT sealing material is used as the flame-retardant member 12. Because the EPT sealing material is flexible or elastic, it deforms when sandwiched between the base 8b and the cover 8d, thereby filling the gap 11 between the base 8b and the cover 8d.
By doing so, it becomes possible to prevent external foreign substances from entering the electrical unit 8 and also prevent fire, which may occur inside the electrical unit 8 (in a space formed between the base 8b and the cover 8d), from spreading outside.
As described above, the groove portion 9 is formed between the inner side wall 9a and the outer side wall 9b, and it is preferred that a height H1 of the inner side wall 9a be higher than a height H2 of the outer side wall 9b. For example, even if foreign substances enter the groove portion 9 over the outer side wall 9b, they are prevented from penetrating inside of the electrical unit 8 because of the presence of the higher inner side wall 9a.
Further, as shown in Fig. 5, the metal cover 8e made of a metal plate is mounted on the cover 8d so as to cover it to prevent fire, which may occur inside the electrical unit 8, from spreading outside.
Also, it is preferred that an outer surface of the metal cover 8e be coated or painted to thereby restrain a worker from being injured by edges or burrs of the metal cover 8e during maintenance.
Both the cover 8d and the metal cover 8e have respective shapes that allow the electrical unit 8 to be arranged along the upper wall 1a of the indoor unit 1 having the upper suction opening 2a and along the front wall 1 b of the indoor unit 1 having the front suction opening 2b. In this embodiment, both the cover 8d and the metal cover 8e are generally formed into a trapezoidal shape as viewed from the side of the indoor unit 1. This shape allows the electrical unit 8 to be accommodated in a generally triangular dead space that is formed by the upper wall 1 a and the front wall 1 b of the indoor unit 1 and the inclined front face 5a of the indoor heat exchanger 5.
Fig. 9A is an enlarged perspective view of a portion C of the electrical unit 8 encircled by a dotted line in Fig. 4 (that is, right end portions of the cover 8d and the metal cover 8e) and Fig. 9B is a front view of the portion C as viewed from a direction of D in Fig. 9A.
As shown in Figs. 9A and 9B, the cover 8d has a groove portion 13 defined therein, in which an end portion of the metal cover 8e is inserted. When the metal cover 8e is stacked on the cover 8d, the end portion of the metal cover 8e is inserted into the groove portion 13.
Insertion of the end portion of the metal cover 8e into the groove portion 13 in the cover 8d covers the former with the latter, thus enhancing safety during maintenance.
How to rotatably mount the cover 8d to the base 8b is explained hereinafter. The cover 8d can rotate with respect to the base 8b about a centerline extending laterally of the indoor unit 1. Fig. 10 depicts a connecting portion for rotatably connecting the cover 8d to the base 8b.
As shown in Fig. 10, the cover 8d is connected to the base 8b so as to be rotatable about a plurality of connections 14. When the electrical unit 8 is installed in the indoor unit 1, the cover 8d can be opened upward via the plurality of connections 14. That is, the connections 14 are provided on an upper portion of the electrical unit 8.
The base 8b and the cover 8d have respective mating portions formed at lower portions thereof (lower portions in a state in which the electrical unit 8 has been installed in the indoor unit 1) that can engage with each other to restrain free rotation of the cover 8d with respect to the base 8b. In this embodiment, the base 8b has a protrusion 16 formed therewith or otherwise rigidly secured thereto so as to protrude forward of the indoor unit 1, while the cover 8d has an engagement hole 15 defined therein in which the protrusion 16 is engaged.
By this construction, engagement of the protrusion 16 of the base 8b in the engagement hole 15 in the cover 8d is released by holding a portion of the resinous cover 8d in proximity to the engagement hole 15 and merely applying a force to that portion in a direction forward of the indoor unit 1, thus making it possible to rotate the cover 8d. Because the protrusion 16 and the engagement hole 15 are respectively provided at the lower portions of the base 8b and the cover 8d and the connections (center of rotation) 14 are provided at the upper portion of the electrical unit 8, a worker can rotate the cover 8d upward by first holding the cover 8d and then releasing engagement of the protrusion 16 of the base 8b in the engagement hole 15.
A configuration of the connections 14 is explained hereinafter. Fig. 11A is an exploded perspective view of one of the plurality of connections 14 between the base 8b and the cover 8d, and Fig. 11B is a perspective view of the connection of Fig. 11A after assemblage. Maintenance work for the electrical unit 8 includes replacement of the substrate 8c and, hence, the connections 14 are provided in consideration of the working efficiency for the replacement of the substrate 8c.
In this embodiment, as shown in Figs. 11A and 11B, each connection 14 includes a shaft hole 17 formed in the base 8b and a rotary shaft 18 mounted to the cover 8d and rotatably inserted into the shaft hole 17 to allow rotation of the cover 8d with respect to the base 8b.
The rotary shaft 18 is provided with a stopper (retaining ring) 19 to avoid removal of the rotary shaft 18 from the shaft hole 17. The rotary shaft 18 has a circumferentially-extending groove defined therein, in which the stopper 19 is received. The stopper 19 is generally formed into a C and accordingly has an opening for insertion of the rotary shaft 18 and subsequent insertion of the stopper 19 into the circumferentially-extending groove in the rotary shaft 18.
Fig. 12A depicts an example of the stopper 19 and Fig. 12B depicts another example of the stopper 19.
As shown in Fig. 12A, the stopper 19 employed in this embodiment is a so-called E-ring (E-type retaining ring) having two recesses defined therein at an inner periphery thereof. That is, the stopper 19 has two narrowed portions 20 each having a width L (distance between an inner peripheral edge and an outer peripheral edge) shorter than that of other portions.
The narrowed portions 20 allow the stopper 19 to elastically deform outward when the stopper 19 is received in the groove in the rotary shaft 18, thus resulting in easy insertion of the stopper 19 into the groove. Although in this embodiment the stopper 19 has been described as having the two narrowed portions 20, but the present invention is not limited thereto. By way of example, as shown in Fig. 12B, the stopper 19 may be a so-called C-ring (C-type retaining ring) having only one narrowed portion 20.
Also, the plurality of connections 14 are designed such that all the rotary shafts 18 of the cover 8d are inserted into respective shaft holes 17 in the base 8b from the same direction. In this configuration, the cover 8d can be easily removed from the base 8b by sliding the cover 8d in one direction, thereby enhancing the workability during maintenance.
In working on the substrate 8c disposed inside the electrical unit 8 in the indoor unit 1, which is normally installed high in a room, the substrate 8c can be confirmed even from below the indoor unit 1 by merely rotating the cover 8d of the electrical unit 8 upward, thus facilitating, for example, replacement of the substrate 8c.
A construction of the substrate 8c accommodated within the electrical unit 8 is explained hereinafter. Fig. 13 is a block diagram of the substrate 8c in this embodiment.
In the case of the indoor unit 1 according to this embodiment, an alternating-current power cord (not shown) for connection to an external alternating-current power source 131 extends from a left side portion of the indoor unit 1. In the indoor unit 1, the alternating-current power cord is connected to a left side portion of the electrical unit 8. The substrate 8c includes an alternating-current circuit block 132, a high-voltage direct-current circuit block 133 and a low-voltage direct-current circuit block 134, all arrayed thereon in order from the side of the alternating-current power cord in a longitudinal direction 136 of the substrate 8c (that is, lateral direction of the indoor unit 1). In applications where the substrate 8c is made up of only one printed substrate as in this embodiment, the plurality of circuit blocks 132, 133, 134 are generally arrayed in the longitudinal direction 136 of the substrate 8c to reduce a length of a short side 135 of the substrate 8c, thereby making it possible to reduce a vertical size of the electrical unit 8 (that is, size in a vertical direction of the indoor unit 1). A reduction in vertical size of the electrical unit 8 results in a reduction in resistance of air flowing toward the indoor heat exchanger 5.
The alternating-current circuit block 132 includes an alternating-current circuit, which is electrically connected to the alternating-current power source 131 via the alternating-current power cord and through which an alternating-current flows. The high-voltage direct-current circuit block 133 includes a direct-current circuit, which is electrically connected to the alternating-current circuit block 132 and through which a high-voltage direct-current flows. The low-voltage direct-current circuit block 134 includes a direct-current circuit, which is electrically connected to the high-voltage direct-current circuit block 133 and through which a low-voltage direct-current (low voltage compared with the voltage of the high-voltage direct-current circuit) flows.
The substrate 8c includes, for example, a number of electrical components such as circuits placed thereon that may generate noise. Sources of noise generation are a switching power source 137 placed on the high-voltage direct-current circuit block 133 to function as a control power source, a high-voltage power source 138 placed on the low-voltage direct-current circuit block 134 to generate a high-voltage for air cleaning, and the like.
The electrical components such as circuits that may generate noise accomplish respective objectives by performing a high-speed switching operation using a switching element such as, for example, an FET. However, the high-speed switching operation generates unnecessary radiation noise.
In order not to leak unnecessary radiation noise to a primary side, the alternating-current circuit block 132 connected to the alternating-current power source 131 includes a noise filter 139. However, the noise filter 139 attenuates the unnecessary radiation noise by virtue of an noise attenuation performance that is determined by frequency characteristics of its impedance and, hence, the noise filter 139 cannot completely block all the unnecessary radiation noise.
In view of this, in this embodiment, a GND pattern (ground pattern) 140 that is a stable potential of the low-voltage direct-current circuit block 134 is formed on the substrate 8c so as to extend close to a pattern 141 of the alternating-current circuit block 132 positioned on the primary side of the noise filter 139. Specifically, the GND pattern 140 of the low-voltage direct-current circuit block 134 and the pattern 141 of the alternating-current circuit block 132 positioned on the primary side of the noise filter 139 are placed adjacent to each other so as to form a stray capacitance 143 between an extended portion of the former and the latter. By way of example, the extended portion of the GND pattern 140 of the low-voltage direct-current circuit block 134 and the pattern 141 of the alternating-current circuit block 132 are formed on the substrate 8c so as to extend parallel to each other over a predetermined length with a predetermined space therebetween.
Further, the extended portion of the GND pattern 140 of the low-voltage direct-current circuit block 134 is connected at an end portion thereof to the earth via an insulating impedance 142. By way of example, the extended portion of the GND pattern 140 of the low-voltage direct-current circuit block 134 is connected at an end portion thereof to the indoor heat exchanger 5 that is connected to the earth and accordingly has a stable potential.
The above-described arrangement forms the stray capacitance 143 between the extended portion of the GND pattern 140 of the low-voltage direct-current circuit block 134 and the pattern 141 of the alternating-current circuit block 132 positioned on the primary side of the noise filter 139 and, hence, these patterns 140, 141 are high-frequency-coupled to each other, thereby allowing unnecessary radiation noise, which cannot be attenuated by the noise filter 139, to escape to the stable potential. As a result, leakage of the unnecessary radiation noise to the primary side can be restrained with a simple construction and without using any special circuit or component.
The stable potential to which the end portion of the extended portion of the GND pattern 140 of the low-voltage direct-current circuit block 134 is connected is not limited to the earth. By way of example, the extended portion of the GND pattern 140 of the low-voltage direct-current circuit block 134 may be connected to a metallic member such as a metal plate that is provided, for example, not to burn the electrical components and separated from the earth. In this case, the insulating impedance can be dispensed with.
According to the air conditioner of the above-described construction, the electrical unit 8 is placed on a front side of the indoor unit 1 (that is, in front of the indoor heat exchanger 5) to increase the lateral size of the indoor heat exchanger 5, thereby enhancing the heat exchanging performance. Also, because the electrical unit 8 is located on an airflow path, not only can the electrical unit 8 be cooled by air, but foreign substances such as dust or dirt contained in air sucked into the indoor unit 1 can be also restrained from entering the electrical unit 8. In addition, leakage of unnecessary radiation noise to the primary side can be restrained. As a result, a highly reliable air conditioner can be provided.
Although the present invention has been fully described by way of a preferred embodiment with reference to the accompanying drawings, it is to be noted here that various changes and modifications will be apparent to those skilled in the art. Therefore, unless such changes and modifications otherwise depart from the scope of the appended claims, they should be construed as being included therein.
The present invention is applicable not only to an air conditioner in which an indoor unit is connected to an outdoor unit, but also to a multi-air conditioner in which a plurality of indoor units are connected to an outdoor unit.

EXPLANATION OF REFERENCE NUMERALS

1: indoor unit
2: front panel
8: electrical unit
8a: support plate
8b: base
8c: substrate
8d: cover
8e: metal cover
8f: terminal block
9: groove portion
10: protrusion
131: alternating-current power source
132: alternating-current circuit block
133: high-voltage direct-current circuit block
134: low-voltage direct-current circuit block
139: noise filter
140: GND pattern

Claims

An air conditioner comprising an indoor unit (1), an electrical unit (8) placed on a front side of the indoor unit (1), an alternating-current power cord connected to the electrical unit (8) and to an external alternating-current power source (131), and a substrate (8c) accommodated within the electrical unit (8), the substrate (8c) comprising an alternating-current circuit block (132), a high-voltage direct-current circuit block (133) and a low-voltage direct-current circuit block (134), all arrayed thereon in order from a side of the alternating-current power cord, characterized in that
the alternating-current circuit block (132) comprises a noise filter (139) to restrain unnecessary radiation noise from leaking to a primary side,
a ground pattern (140) of the low-voltage direct-current circuit block (134) and a pattern (141) of the alternating-current circuit block (132) positioned on the primary side of the noise filter (139) are placed adjacent to each other to form a stray capacitance (143) between the ground pattern (140) of the low-voltage direct-current circuit block (134) and the pattern (141) of the alternating-current circuit block (132), and
the ground pattern (140) of the low-voltage direct-current circuit block (134) is connected at an end portion thereof to the earth.
The air conditioner according to claim 1, wherein the electrical unit (8) comprises a base (8b) for placing the substrate (8c) thereon and a cover (8d) mounted on the base (8b) to cover the substrate (8c), the base (8b) having a groove portion (9) defined therein so as to extend along an outer periphery thereof, the cover (8d) having a protrusion (10) formed therewith so as to be fitted into the groove portion (9) in the base (8b).
The air conditioner according to claim 2, further comprising a flame-retardant member (12) interposed between the base (8b) and the cover (8d).
The air conditioner according to claim 3, wherein the flame-retardant member (12) is flexible.
The air conditioner according to any one of claims 2 to 4, wherein the base (8b) comprises an inner side wall (9a) and an outer side wall (9b) confronting each other, between which the groove portion (9) is formed, the inner side wall (9a) being higher than the outer side wall (9b).
The air conditioner according to any one of claims 2 to 5, further comprising a metal cover (8e) for covering the cover (8d).
The air conditioner according to claim 6, wherein an outer surface of the metal cover (8e) is coated or painted.
The air conditioner according to claim 6 or 7, wherein the cover (8d) has a groove portion defined therein, in which an end portion of the metal cover (8e) is inserted.