FIELD
The present disclosure relates to an air conditioner outdoor unit including a casing and a heat exchanger.
BACKGROUND
A known conventional air conditioner outdoor unit includes a box-shaped casing and a heat exchanger disposed in the casing, the heat exchanger and the casing being formed of dissimilar metals. The types of metals for the heat exchanger and the casing are selected according to their required characteristics. For example, aluminum is commonly used for the heat exchanger that is required of high thermal conductivity, and iron is commonly used for the casing that is required of strength.
If water adheres to a contact portion between the heat exchanger and the casing of dissimilar metals placed in direct contact with each other, dissimilar metal corrosion occurs in the metal with a lower natural potential. Hereinafter, dissimilar metal corrosion is simply referred to as corrosion. As a means to prevent corrosion, there is known a means of indirectly connecting the heat exchanger and the casing with a non-conductive member such as resin interposed therebetween.
However, when such a means is used, the heat exchanger and the casing are electrically insulated by the non-conductive member, so that parasitic capacitances are generated between the heat exchanger and the casing. Electromagnetic noise generated from an electronic board, a compressor, etc. disposed in the casing causes voltage changes in the parasitic capacitances. The voltage changes further cause electromagnetic noise disadvantageously. An air inlet is formed in the rear of the casing to allow the inflow of outside air. The heat exchanger is disposed at a position facing the air inlet to exchange heat with the outside air. The electromagnetic noise is radiated from between the heat exchanger and the casing through the air inlet to the outside of the casing.
To simultaneously solve two problems, which are the prevention of corrosion and the reduction of electromagnetic noise, Patent Literature 1 discloses a technique in which a conductive connecting member is interposed between the heat exchanger and the casing. The connecting member includes a first connection that is formed of the same type of metal as a metal used for the heat exchanger and is in direct contact with the heat exchanger, and a second connection that is formed of the same type of metal as a metal used for the casing and is in direct contact with the casing. An insulating layer that electrically insulates the first connection and the second connection is provided between the first connection and the second connection.
The technique disclosed in Patent Literature 1 removes a portion of the insulating layer to partially bring the first connection and the second connection of the dissimilar metals into direct contact with each other to provide electrical conduction to reduce electromagnetic noise. On the other hand, a contact portion between the first connection and the second connection is covered with a covering member such as a waterproof tape to block the ingress of water into the contact portion to prevent metal corrosion.
PATENT LITERATURE
- Patent Literature 1: Japanese Patent No. 6583489
However, the technique disclosed in Patent Literature 1 leads to complication of the structure due to the use of a plurality of types of metals for the connecting member and the provision of the insulating layer, and thus disadvantageously increases the number of manufacturing steps and increases the number of parts.
SUMMARY
The present disclosure has been made in view of the above. It is an object of the present disclosure to provide an air conditioner outdoor unit that can achieve both the prevention of corrosion and the reduction of electromagnetic noise with a simple structure.
To solve the above problems and achieve an object, an air conditioner outdoor unit according to the present disclosure includes: a box-shaped casing formed of a first metal; a heat exchanger at least partly formed of a second metal different in natural potential from the first metal, the heat exchanger being disposed in the casing and fixed to the casing with a non-conductive member interposed between the heat exchanger and the casing; and capacitance connection sheet metal formed of the first metal or a third metal that does not cause dissimilar metal corrosion with the first metal, the capacitance connection sheet metal being disposed in the casing. The capacitance connection sheet metal is fixed to the casing and electrically connected to the casing, and the capacitance connection sheet metal is disposed with a space between the heat exchanger and the capacitance connection sheet metal and electrically connected to the heat exchanger through capacitance generated between the heat exchanger and the capacitance connection sheet metal.
The air conditioner outdoor unit according to the present disclosure has the effect of being able to achieve both the prevention of corrosion and the reduction of electromagnetic noise with the simple structure.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is an exploded perspective view schematically illustrating an air conditioner outdoor unit according to a first embodiment.
FIG. 2 is a front view illustrating the air conditioner outdoor unit according to the first embodiment, with a casing front panel of a casing removed.
FIG. 3 is a perspective view illustrating capacitance connection sheet metal, a casing floor panel, and a heat exchanger in the air conditioner outdoor unit according to the first embodiment.
FIG. 4 is a plan view illustrating the capacitance connection sheet metal, the casing floor panel, and the heat exchanger in the air conditioner outdoor unit according to the first embodiment.
FIG. 5 is a schematic diagram illustrating, as an electric circuit, transmission paths of electromagnetic noise generated when the capacitance connection sheet metal is not included in the air conditioner outdoor unit according to the first embodiment.
FIG. 6 is a circuit diagram illustrating, in an equivalent circuit, paths through which current causing electromagnetic noise is transmitted when the capacitance connection sheet metal is not included in the air conditioner outdoor unit according to the first embodiment.
FIG. 7 is a rear view of the air conditioner outdoor unit according to the first embodiment, illustrating places where electromagnetic noise occurs.
FIG. 8 is a circuit diagram illustrating, in an equivalent circuit, paths through which current causing electromagnetic noise is transmitted when the heat exchanger and the casing are placed in direct contact with each other without insulating members interposed therebetween in the air conditioner outdoor unit according to the first embodiment.
FIG. 9 is a plan view illustrating the capacitance connection sheet metal, the casing floor panel, and the heat exchanger in the first embodiment, schematically illustrating parasitic capacitances generated between the heat exchanger and the capacitance connection sheet metal.
FIG. 10 is a schematic diagram illustrating, as an electric circuit, transmission paths of electromagnetic noise generated when the capacitance connection sheet metal is included in the air conditioner outdoor unit according to the first embodiment.
FIG. 11 is a circuit diagram illustrating, in an equivalent circuit, paths through which current causing electromagnetic noise is transmitted when the capacitance connection sheet metal is included in the air conditioner outdoor unit according to the first embodiment.
FIG. 12 is a perspective view illustrating the capacitance connection sheet metal with portions cut out, the casing floor panel, the heat exchanger, and an insulating member in the air conditioner outdoor unit according to a first modification of the first embodiment.
FIG. 13 is a perspective view illustrating the capacitance connection sheet metal, contact sheet metal, the casing floor panel, a casing top panel, the heat exchanger, and the insulating members in the air conditioner outdoor unit according to a second modification of the first embodiment.
FIG. 14 is a side view illustrating the contact sheet metal, the casing top panel, a covering member, and the heat exchanger in the air conditioner outdoor unit according to the second modification of the first embodiment.
DETAILED DESCRIPTION
Hereinafter, an air conditioner outdoor unit according to an embodiment will be described in detail with reference to the drawings.
First Embodiment
FIG. 1 is an exploded perspective view schematically illustrating an air conditioner outdoor unit 1 according to a first embodiment. As illustrated in FIG. 1, the air conditioner outdoor unit 1 includes a casing 2, capacitance connection sheet metal 3, a partition plate 4, a fan 5, a heat exchanger 6, two insulating members 7, a compressor 8, and an electronic board box 9. In the following, the air conditioner outdoor unit 1 is sometimes simply referred to as the outdoor unit 1.
In the following, when directions are described for the components of the outdoor unit 1, the depth direction of the outdoor unit 1 is referred to as the X-axis direction, the height direction of the outdoor unit 1 as the Y-axis direction, and the width direction of the outdoor unit 1 as the Z-axis direction. The positive direction of the X-axis direction is defined as the forward direction, and the negative direction of the X-axis direction as the rearward direction. The positive direction of the X-axis direction is a direction from the negative side to the positive side of the X-axis, and the negative direction of the X-axis direction is a direction from the positive side to the negative side of the X-axis. The positive direction of the Y-axis direction is defined as the upward direction, and the negative direction of the Y-axis direction as the downward direction. The positive direction of the Y-axis direction is a direction from the negative side to the positive side of the Y-axis, and the negative direction of the Y-axis direction is a direction from the positive side to the negative side of the Y-axis. The positive direction of the Z-axis direction is defined as the rightward direction, and the negative direction of the Z-axis direction as the leftward direction. The positive direction of the Z-axis direction is a direction from the negative side to the positive side of the Z-axis, and the negative direction of the Z-axis direction is a direction from the positive side to the negative side of the Z-axis. In the present embodiment, the positive direction of the X-axis direction in which air flow produced by the fan 5 in the outdoor unit 1 is discharged to the outside is the front, and the side opposite to the front is the rear.
FIG. 2 is a front view illustrating the air conditioner outdoor unit 1 according to the first embodiment, with a casing front panel 2e of the casing 2 removed. In FIG. 2, to facilitate understanding, the heat exchanger 6 is dot-hatched. As illustrated in FIGS. 1 and 2, the casing 2 is a box-shaped member serving as an outer shell of the outdoor unit 1. The casing 2 is formed of a first metal. The first metal is preferably a metal having high strength. The first metal is, for example, iron or an iron alloy.
As illustrated in FIG. 1, the casing 2 includes a casing floor panel 2a, a casing top panel 2b, a first connecting panel 2c, and a second connecting panel 2d. The casing floor panel 2a constitutes the bottom of the outer shell of the outdoor unit 1. The plan view shape of the casing floor panel 2a is a rectangle with four rounded corners. The casing top panel 2b is disposed above the casing floor panel 2a and away from the casing floor panel 2a. The casing top panel 2b constitutes the ceiling of the outer shell of the outdoor unit 1. The plan view shape of the casing top panel 2b is the same as the plan view shape of the casing floor panel 2a.
The first connecting panel 2c and the second connecting panel 2d connect the casing floor panel 2a and the casing top panel 2b. The first connecting panel 2c has an L shape in plan view. The first connecting panel 2c includes the casing front panel 2e extending along the Z-axis direction, and a casing side panel 2f extending rearward from the left edge that is one edge of the casing front panel 2e in the Z-axis direction.
The casing front panel 2e connects the front edge of the casing floor panel 2a and the front edge of the casing top panel 2b. The casing front panel 2e constitutes the front of the outer shell of the outdoor unit 1. An air outlet 2j is formed in the casing front panel 2e. The air outlet 2j is an opening for discharging air flow produced by the fan 5 to the outside of a fan chamber 10 to be described later. The casing side panel 2f connects the left edge of the casing floor panel 2a and the left edge of the casing top panel 2b. The casing side panel 2f constitutes the left side of the outer shell of the outdoor unit 1. The casing front panel 2e and the casing side panel 2f are integrally formed in the present embodiment, but may be separately formed.
The second connecting panel 2d has an L shape in plan view. The second connecting panel 2d includes a casing side panel 2g extending along the X-axis direction, and a casing rear panel 2h extending leftward from the rear edge that is one edge of the casing side panel 2g in the X-axis direction.
The casing side panel 2g connects the right edge of the casing floor panel 2a and the right edge of the casing top panel 2b. The casing side panel 2g constitutes the right side of the outer shell of the outdoor unit 1. The casing rear panel 2h connects a portion of the rear edge of the casing floor panel 2a and a portion of the rear edge of the casing top panel 2b. The casing rear panel 2h constitutes a portion of the rear of the outer shell of the outdoor unit 1. The casing side panel 2g and the casing rear panel 2h are integrally formed in the present embodiment, but may be separately formed.
With the panels illustrated in FIG. 1 assembled, the left edge of the casing rear panel 2h and the rear edge of the casing side panel 2f are separated from each other. An air inlet 2i to allow the inflow of outside air is formed between the left edge of the casing rear panel 2h and the rear edge of the casing side panel 2f. The air inlet 2i is an opening to allow air outside the casing 2 to flow into the fan chamber 10, which is described later. The air inlet 2i formed is enclosed by the casing floor panel 2a, the casing top panel 2b, the casing rear panel 2h, and the casing side panel 2f.
The capacitance connection sheet metal 3 is a metal member disposed near the heat exchanger 6 in the casing 2. The capacitance connection sheet metal 3 is in contact with the casing 2, and fixed to the casing 2 to be electrically connected to the casing 2. The capacitance connection sheet metal 3 is not in contact with the heat exchanger 6. The capacitance connection sheet metal 3 is disposed with a space between the heat exchanger 6 and the capacitance connection sheet metal 3, and is electrically connected to the heat exchanger 6 via capacitance generated between the heat exchanger 6 and the capacitance connection sheet metal 3. That is, the capacitance connection sheet metal 3 is electrically connected to the heat exchanger 6 at high frequencies by capacitance generated between the heat exchanger 6 and the capacitance connection sheet metal 3. In the present description, the metal members “being electrically connected at high frequencies” refer to a state in which the metal members are not in contact with each other, but impedance through the space formed between the metal members is small, and conductivity between the metal members is high.
As illustrated in FIG. 2, the capacitance connection sheet metal 3 is in contact with and fixed to only the casing floor panel 2a in the present embodiment. However, the capacitance connection sheet metal 3 may be in contact with and fixed to at least one of the casing floor panel 2a, the casing top panel 2b, the casing front panel 2e, the casing rear panel 2h, and the casing side panels 2f and 2g. The capacitance connection sheet metal 3 is formed of the first metal like the casing 2 or a third metal that does not cause dissimilar metal corrosion with the casing 2. For example, when the first metal is one of iron or an iron alloy, the third metal is the other of iron and an iron alloy. The first metal and the third metal only need to be metals having equal natural potential, or metals whose difference in natural potential is small enough not to cause dissimilar metal corrosion.
Portions where the casing 2 and the capacitance connection sheet metal 3 are in contact with each other are joined by welding, screws, or the like. If the panel surfaces of the casing 2 are coated, for example, and have high electrical resistance, the joints may be partly or entirely masked in advance, or serration screws may be used to peel off the coating at the time of screwing, for example, to lower the electrical resistance of each panel surface.
As illustrated in FIG. 2, the partition plate 4 is a metal member that partitions the inside of the casing 2 into the fan chamber 10 and an electric chamber 11. The fan chamber 10 and the electric chamber 11 are formed side by side in the Z-axis direction. The partition plate 4 extends in the Y-axis direction from the casing floor panel 2a to the electronic board box 9. The partition plate 4 extends in the X-axis direction from the casing front panel 2e to the casing rear panel 2h illustrated in FIG. 1.
As illustrated in FIG. 2, the fan 5 is a device disposed in the fan chamber 10 to produce air flow. The fan 5 includes a support column 5a erected from the casing floor panel 2a, a fan motor 5b attached to the support column 5a, and a propeller fan 5c attached to a rotating shaft of the fan motor 5b to rotate with the rotation of the fan motor 5b. The top end of the support column 5a is fixed to the casing top panel 2b. The bottom end of the support column 5a is fixed to the casing floor panel 2a. The fan motor 5b is electrically connected to an electronic board 9a to be described later through a fan drive wire 12. The fan motor 5b rotates when receiving a drive signal output from the electronic board 9a through the fan drive wire 12. When the fan motor 5b rotates, driving the propeller fan 5c, the fan chamber 10 becomes under negative pressure, so that air outside the outdoor unit 1 flows into the fan chamber 10 through the air inlet 2i. The air flowing into the fan chamber 10 passes through the heat exchanger 6, and becomes air flow by the fan 5 and is discharged to the outside of the fan chamber 10 through the air outlet 2j illustrated in FIG. 1.
The heat exchanger 6 is a member disposed in the fan chamber 10 to exchange heat between a refrigerant and outside air. Outside air to be taken into the fan 5 passes through the heat exchanger 6. The heat exchanger 6 is, for example, a parallel-flow heat exchanger. The heat exchanger 6 is disposed in the casing 2 and is fixed to the casing 2 with the insulating members 7 that are non-conductive members interposed therebetween. At least part of the heat exchanger 6 is formed of a second metal different in natural potential from the first metal. The second metal is preferably a metal having high thermal conductivity. The second metal is, for example, aluminum or an aluminum alloy. Although not illustrated, the heat exchanger 6 includes a plurality of fins and refrigerant tubing. The refrigerant flows through the refrigerant tubing.
As illustrated in FIG. 1, the heat exchanger 6 has an L shape in plan view. The heat exchanger 6 extends along the Z-axis direction and then extends forward along the X-axis direction. A portion of the heat exchanger 6 along the Z-axis direction is disposed behind the fan 5. A portion of the heat exchanger 6 along the X-axis direction is disposed to the left of the fan 5 when viewed from the front. The heat exchanger 6 and the fan 5 are disposed at a distance from each other and electrically insulated, or are disposed with an insulating member (not illustrated) interposed therebetween and electrically insulated.
The heat exchanger 6 includes a planar heat exchanger side end 6a extending in the Y-axis direction. The heat exchanger side end 6a constitutes the front end of the portion of the heat exchanger 6 along the X-axis direction. The heat exchanger side end 6a has a quadrangular shape. The heat exchanger side end 6a is a plane perpendicular to the X-axis direction. The heat exchanger 6 includes a pair of heat exchanger side surfaces 6b and 6c. The heat exchanger side surfaces 6b and 6c extend from both edges of the heat exchanger side end 6a in the Z-axis direction in a direction away from a sheet metal facing wall 3a to be described later. The heat exchanger side surfaces 6b and 6c have a quadrangular shape. In the present embodiment, the Z-axis direction is a direction perpendicular to the vertical direction.
The heat exchanger 6 and the first connecting panel 2c and the second connecting panel 2d are disposed at a distance from each other and electrically insulated, or are disposed with an insulating member (not illustrated) interposed therebetween and electrically insulated. As illustrated in FIG. 2, the top of the heat exchanger 6 is fixed to the casing top panel 2b with the insulating member 7 interposed therebetween. The bottom of the heat exchanger 6 is fixed to the casing floor panel 2a with the insulating member 7 interposed therebetween. The heat exchanger 6 is electrically insulated from the casing top panel 2b and the casing floor panel 2a. The heat exchanger 6 is disposed without being electrically connected to metal members including the casing 2 and the fan 5 disposed around the heat exchanger 6. However, as described above, the heat exchanger 6 is electrically connected to the capacitance connection sheet metal 3 at high frequencies by capacitance generated between the heat exchanger 6 and the capacitance connection sheet metal 3.
As the material of the two insulating members 7 illustrated in FIG. 1, a material having electrical insulation properties such as resin is used. Hereinafter, when the two insulating members 7 are distinguished from each other, the insulating member 7 provided at the bottom of the heat exchanger 6 is referred to as a first insulating member 7a, and the insulating member 7 provided at the top of the heat exchanger 6 is referred to as a second insulating member 7b. The present embodiment uses the first insulating member 7a and the second insulating member 7b having the same plan view shape and the same size as the heat exchanger 6, to entirely cover the bottom surface and the top surface of the heat exchanger 6 to electrically insulate the heat exchanger 6 from the casing 2, but is not intended to limit means for electrically insulating both members. For example, bases formed of a material having electrical insulation properties may be provided at the bottom of the heat exchanger 6 in several places to interpose the bases between the heat exchanger 6 and the casing floor panel 2a. With this configuration, the heat exchanger 6 and the casing floor panel 2a are separated from each other in the Y-axis direction, so that the heat exchanger 6 can be electrically insulated from the casing floor panel 2a.
As illustrated in FIG. 2, the compressor 8 is a device disposed in the electric chamber 11 to compress the refrigerant flowing through the heat exchanger 6. The compressor 8 is disposed on the casing floor panel 2a in a lower space of the electric chamber 11. The compressor 8 is fixed to the casing floor panel 2a with screws or the like.
The electronic board box 9 is a member that houses the electronic board 9a such as a control board required to operate the outdoor unit 1. The electronic board box 9 is formed in a hollow rectangular parallelepiped shape. The electronic board box 9 is fixed to the top of the partition plate 4, and is disposed across the fan chamber 10 and the electric chamber 11. A heat sink 9b extending downward is attached to a portion of the electronic board box 9 disposed in the fan chamber 10. The heat sink 9b is exposed to the fan chamber 10. The heat sink 9b is cooled by air flow produced by the fan 5.
A portion of the electronic board box 9 disposed in the electric chamber 11 is disposed above the compressor 8. A compressor drive wire 13 is connected to a portion of the electronic board 9a disposed in the electric chamber 11. The compressor 8 is electrically connected to the electronic board 9a through the compressor drive wire 13. The compressor 8 works when receiving a drive signal output from the electronic board 9a through the compressor drive wire 13.
The electric chamber 11 formed is enclosed by the casing floor panel 2a, the partition plate 4, the casing side panel 2g, the electronic board box 9, the casing front panel 2e and the casing rear panel 2h that are illustrated in FIG. 1, and has a waterproof structure that can prevent ingress of water such as rainwater from outside the casing 2. A stop valve 17 is provided at a lower portion of the outer surface of the casing side panel 2g. The stop valve 17 serves as a terminal for connecting refrigerant pipes connected to an indoor unit (not illustrated).
The compressor 8 and the stop valve 17 are connected to each other via a plurality of refrigerant pipes 18. The compressor 8 and the heat exchanger 6 are connected to each other via a plurality of refrigerant pipes 18. Connections 19 between the heat exchanger 6 and the refrigerant pipes 18 are disposed in the electric chamber 11 having the waterproof structure. By thus disposing the connections 19 in the electric chamber 11, contact between the connections 19 and water can be prevented, so that the corrosion of the connections 19 can be prevented. To further enhance the waterproofing effect on the connections 19, the connections 19 may be waterproofed by winding a waterproof tape or the like around the connections 19. Although not specifically illustrated, valve devices such as a four-way valve that switches the refrigerant's flow direction and an expansion valve that expands the refrigerant to a predetermined pressure are connected to the refrigerant pipes 18. The connection form of the refrigerant pipes 18 is not limited to the illustrated example.
An interface panel 20 is installed in an upper space of the electric chamber 11. The interface panel 20 is fixed to the inner surface of the casing side panel 2g and the lower surface of the electronic board box 9. A terminal block 21 is installed on the interface panel 20. An external AC power line 14 and an internal power line 15 are connected to the terminal block 21. The external AC power line 14 is electrically connected to the internal power line 15 via the terminal block 21. The internal power line 15 is electrically connected to the electronic board 9a. Power to the electronic board 9a is supplied through the external AC power line 14, the terminal block 21, and the internal power line 15. The voltage of the power supplied to the electronic board 9a is, for example, single-phase 200 V, but is not limited to this voltage.
The interface panel 20 is formed of the first metal like the casing side panel 2g. Therefore, the interface panel 20 is joined to the casing side panel 2g with low electrical resistance. The interface panel 20 is connected to a signal ground of the electronic board 9a. The interface panel 20 includes a ground connection point 20a to which a ground wire 16 is connected. The interface panel 20 is grounded through the ground connection point 20a and the ground wire 16. The casing 2 joined to the interface panel 20 and the partition plate 4 joined to the casing 2 are grounded through the ground connection point 20a and the ground wire 16. The heat exchanger 6 is electrically connected to the ground connection point 20a through the connections 19 between the heat exchanger 6 and the refrigerant pipes 18, the compressor 8, etc., but is not directly short-circuited to the casing 2 and the partition plate 4.
In the casing side panel 2g, an opening 2k is formed to allow communication between the inside and the outside of the casing 2. The interface panel 20 and the terminal block 21 installed in the electric chamber 11 can be visually seen and handled through the opening 2k. Work to connect various power lines can be performed through the opening 2k. An interface cover (not illustrated) is detachably attached to the casing side panel 2g, and the opening 2k is covered with the interface cover.
Next, with reference to FIGS. 3 and 4, the configuration of the capacitance connection sheet metal 3 will be further described. FIG. 3 is a perspective view illustrating the capacitance connection sheet metal 3, the casing floor panel 2a, and the heat exchanger 6 in the air conditioner outdoor unit 1 according to the first embodiment. FIG. 4 is a plan view illustrating the capacitance connection sheet metal 3, the casing floor panel 2a, and the heat exchanger 6 in the air conditioner outdoor unit 1 according to the first embodiment.
The location of the capacitance connection sheet metal 3 is not particularly limited as long as the location is near the heat exchanger 6. In the present embodiment, the location is near the heat exchanger side end 6a of the heat exchanger 6. The capacitance connection sheet metal 3 includes the sheet metal facing wall 3a, a pair of sheet metal side walls 3b and 3c, and a plurality of sheet metal fixed portions 3d. The sheet metal facing wall 3a, the sheet metal side walls 3b and 3c, and the sheet metal fixed portion 3d are all flat portions. The sheet metal facing wall 3a has a quadrangular shape. The sheet metal facing wall 3a is disposed in front of the heat exchanger side end 6a with a space between the heat exchanger side end 6a and the sheet metal facing wall 3a. The sheet metal facing wall 3a faces the heat exchanger side end 6a.
The sheet metal side walls 3b and 3c have a quadrangular shape. The sheet metal side wall 3b extends from one edge of the sheet metal facing wall 3a in the Z-axis direction toward the heat exchanger side surface 6b, and is disposed with a space between the heat exchanger side surface 6b and the sheet metal side wall 3b. The sheet metal side wall 3c extends from the other edge of the sheet metal facing wall 3a in the Z-axis direction toward the heat exchanger side surface 6c, and is disposed with a space between the heat exchanger side surface 6c and the sheet metal side wall 3c. The sheet metal side wall 3b faces the heat exchanger side surface 6b. The sheet metal side wall 3c faces the heat exchanger side surface 6c. The sheet metal side walls 3b and 3c are bent at right angles toward the rear from the edges of the sheet metal facing wall 3a in the Z-axis direction.
The sheet metal fixed portions 3d are portions fixed to the casing 2. The sheet metal fixed portions 3d have a quadrangular shape. The sheet metal fixed portions 3d are provided at the lower end of the sheet metal facing wall 3a and the lower ends of the pair of sheet metal side walls 3b and 3c, one for each. The sheet metal fixed portion 3d provided at the lower end of the sheet metal facing wall 3a extends in a direction away from the heat exchanger side end 6a. The sheet metal fixed portion 3d provided at the lower end of the sheet metal side wall 3b extends in a direction away from the heat exchanger side surface 6b. The sheet metal fixed portion 3d provided at the lower end of the sheet metal side wall 3c extends in a direction away from the heat exchanger side surface 6c.
The sheet metal fixed portions 3d are in contact with and fixed to only the casing floor panel 2a in the present embodiment, but may be in contact with and fixed to at least one of the casing floor panel 2a, the casing top panel 2b, the casing front panel 2e, the casing rear panel 2h, and the casing side panels 2f and 2g illustrated in FIG. 1. The sheet metal fixed portions 3d are electrically connected to the casing floor panel 2a. Portions where the sheet metal fixed portions 3d and the casing 2 are in contact with each other are joined by welding, screws, or the like. If the panel surfaces of the casing 2 are coated, for example, and have high electrical resistance, the joints may be partly or entirely masked in advance, or serration screws may be used to peel off the coating at the time of screwing, for example, to lower the electrical resistance of each panel surface.
The space formed between the heat exchanger side end 6a and the sheet metal facing wall 3a and the spaces formed between the heat exchanger side surfaces 6b and 6c and the sheet metal side walls 3b and 3c communicate with each other. As illustrated in FIG. 4, a dielectric 3e is inserted into the space formed between the heat exchanger 6 and the capacitance connection sheet metal 3 in the present embodiment, but the dielectric 3e may not be inserted. In FIG. 4, to clarify the position of the dielectric 3e, the dielectric 3e is hatched. The dielectric 3e plays a role in adjusting the magnitude of capacitance generated between the heat exchanger 6 and the capacitance connection sheet metal 3.
Note that the pair of sheet metal side walls 3b and 3c may not be provided, or one of the pair of sheet metal side walls 3b and 3c may be omitted. Furthermore, the capacitance connection sheet metal 3 is disposed with a space between the capacitance connection sheet metal 3 and the heat exchanger side end 6a and a space between the capacitance connection sheet metal 3 and each of the heat exchanger side surfaces 6b and 6c, but may be disposed with a space between any surface of the heat exchanger 6 and the capacitance connection sheet metal 3.
Next, the operation and effects of the outdoor unit 1 according to the first embodiment will be described.
As illustrated in FIG. 2, when power is supplied from the external AC power line 14 through the internal power line 15 to the electronic board 9a, the electronic board 9a enters a standby state. When receiving an operation start command signal from the indoor unit (not illustrated) through a communication signal line between the indoor unit and the outdoor unit 1, the electronic board 9a starts the operation of the outdoor unit 1. Specifically, the electronic board 9a outputs a drive signal to the fan motor 5b through the fan drive wire 12 to drive the fan motor 5b. The electronic board 9a outputs another drive signal to the compressor 8 through the compressor drive wire 13 to drive the compressor 8. At this time, as the drive signals output from the electronic board 9a, rectangular wave pulses generated by the switching of power semiconductors are commonly used. Consequently, the drive signals contain high-frequency components that are not essentially necessary to drive AC motors of the compressor 8 and the fan motor 5b, such as switching noise of the power semiconductors and harmonic components of the rectangular wave pulses. These high-frequency components become electromagnetic noise sources, which causes electromagnetic noise to radiate to the outside of the casing 2 through transmission paths to be described later.
FIG. 5 is a schematic diagram illustrating, as an electric circuit, transmission paths of electromagnetic noise generated when the capacitance connection sheet metal 3 is not included in the air conditioner outdoor unit 1 according to the first embodiment. In FIG. 5, to facilitate understanding, the heat exchanger 6 is dot-hatched. For example, when a three-phase motor is used as the AC motor of the compressor 8, electromagnetic noise generated in the electronic board 9a is transmitted via a three-phase motor winding neutral point 8d through parasitic capacitance 8b existing between motor windings 8a and a casing of the compressor 8, to the casing of the compressor 8. Part of the electromagnetic noise transmitted to the casing of the compressor 8 is transmitted to the casing floor panel 2a and then returned to the electronic board 9a. However, due to impedance components such as contact resistance 8c between the casing of the compressor 8 and the casing floor panel 2a, part of the electromagnetic noise transmitted to the casing of the compressor 8 is transmitted to the heat exchanger 6 through the refrigerant pipes 18.
The characteristics of parasitic impedance components of the heat exchanger 6 vary depending on the structure of the heat exchanger 6. Here, as an example, it is assumed that the heat exchanger 6 is a parallel-flow heat exchanger including corrugated fins and flat refrigerant tubing. An equivalent circuit in which parasitic inductances 23 of the heat exchanger 6 are combined as illustrated in FIG. 5 is illustrated as an example. The parasitic impedance components including the parasitic inductances 23 of the heat exchanger 6 complicatedly exist as a distributed constant circuit as illustrated in FIG. 5. Since the heat exchanger 6 and the casing 2 are electrically insulated by the first insulating member 7a and the second insulating member 7b, parasitic capacitances 22a and 22b are generated between the heat exchanger 6 and the casing 2. That is, the parasitic capacitances 22a are generated between the heat exchanger 6 and the casing floor panel 2a, and the parasitic capacitances 22b are generated between the heat exchanger 6 and the casing top panel 2b. The parasitic capacitances 22a and 22b are generated on the transmission paths of the electromagnetic noise.
FIG. 6 is a circuit diagram illustrating, in an equivalent circuit, paths through which current causing electromagnetic noise is transmitted when the capacitance connection sheet metal 3 is not included in the air conditioner outdoor unit 1 according to the first embodiment. The electromagnetic noise transmitted from the electronic board 9a through the compressor 8 to the heat exchanger 6 and the casing 2 illustrated in FIG. 5 produces resonance with the parasitic inductances 23 of the heat exchanger 6, and produces resonance with the parasitic capacitances 22a and 22b, and further produces resonance with parasitic impedance components such as parasitic inductances 24 of the panels of the casing 2. At this time, changes in voltage due to the resonance occur in the parasitic capacitances 22a and 22b.
FIG. 7 is a rear view of the air conditioner outdoor unit 1 according to the first embodiment, illustrating places where electromagnetic noise occurs. In FIG. 7, to facilitate understanding, the heat exchanger 6 is dot-hatched. Spaces G1, G2, G3, and G4 are formed between the heat exchanger 6 and the panels of the casing 2 to provide electrical insulation. In FIG. 7, the positions of the spaces G1, G2, G3, and G4 are enclosed by broken lines. In FIG. 7, part of the space between the heat exchanger 6 and the casing 2 is illustrated without the spaces G1, G2, G3, and G4, but in actuality, the spaces G1, G2, G3, and G4 in an elongated shape are present, extending around the four sides of the heat exchanger 6. The spaces G1, G2, G3, and G4 are places where electromagnetic noise occurs. Voltage changes occur between the heat exchanger 6 and the casing floor panel 2a and between the heat exchanger 6 and the casing top panel 2b through the parasitic capacitances 22a and 22b illustrated in FIG. 5. As a result, the spaces G1, G2, G3, and G4 function as slot antennas, and further generate electromagnetic noise according to changes in voltage applied across the spaces G1, G2, G3, and G4. The electromagnetic noise generated in the spaces G1, G2, G3, and G4 is radiated to the outside of the casing 2 through the air inlet 2i.
FIG. 8 is a circuit diagram illustrating, in an equivalent circuit, paths through which current causing electromagnetic noise is transmitted when the heat exchanger 6 and the casing 2 are placed in direct contact with each other without the insulating members 7 interposed therebetween in the air conditioner outdoor unit 1 according to the first embodiment. By removing the first insulating member 7a and the second insulating member 7b illustrated in FIG. 7, the heat exchanger 6 and the panels of the casing 2 are electrically connected. That is, the heat exchanger 6 and the panels of the casing 2 are electrically short-circuited. Thus, as illustrated in FIG. 8, the parasitic capacitances 22a and 22b generated between the heat exchanger 6 and the panels of the casing 2 are short-circuited. Consequently, no voltage changes occur between the heat exchanger 6 and the casing floor panel 2a and between the heat exchanger 6 and the casing top panel 2b illustrated in FIG. 7 through the parasitic capacitances 22a and 22b illustrated in FIG. 8, and no electromagnetic noise occurs in the spaces G1, G2, G3, and G4.
In a case where the heat exchanger 6 and the casing 2 illustrated in FIG. 7 are formed of dissimilar metals, if the insulating members 7 are not provided between the heat exchanger 6 and the casing 2, the generation of electromagnetic noise in the spaces G1, G2, G3, and G4 can be prevented to reduce radiation of electromagnetic noise to the outside of the casing 2, but corrosion occurs in the heat exchanger 6 having lower natural potential at contact portions between the heat exchanger 6 and the casing 2. On the other hand, when the insulating members 7 are provided between the heat exchanger 6 and the casing 2, corrosion of the heat exchanger 6 having lower natural potential at contact portions between the heat exchanger 6 and the casing 2 can be prevented, but electromagnetic noise is generated in the spaces G1, G2, G3, and G4, increasing the amount of radiation of electromagnetic noise to the outside of the casing 2.
FIG. 9 is a plan view illustrating the capacitance connection sheet metal 3, the casing floor panel 2a, and the heat exchanger 6 in the first embodiment, schematically illustrating parasitic capacitances 22c generated between the heat exchanger 6 and the capacitance connection sheet metal 3. FIG. 10 is a schematic diagram illustrating, as an electric circuit, transmission paths of electromagnetic noise generated when the capacitance connection sheet metal 3 is included in the air conditioner outdoor unit 1 according to the first embodiment. FIG. 11 is a circuit diagram illustrating, in an equivalent circuit, paths through which current causing electromagnetic noise is transmitted when the capacitance connection sheet metal 3 is included in the air conditioner outdoor unit 1 according to the first embodiment. As illustrated in FIGS. 9 and 10, the outdoor unit 1 includes the box-shaped casing 2 formed of the first metal, the heat exchanger 6 that is formed of the second metal different in natural potential from the first metal and is disposed in the casing 2 and fixed to the casing 2 with the insulating members 7 interposed therebetween, and the capacitance connection sheet metal 3 that is formed of the first metal or the third metal that does not cause corrosion with the first metal and is disposed in the casing 2. The capacitance connection sheet metal 3 illustrated in FIG. 9 is fixed to the casing 2 and electrically connected to the casing 2, and is disposed with a space between the heat exchanger 6 and the capacitance connection sheet metal 3. Consequently, the parasitic capacitances 22c are generated between the heat exchanger 6 and the capacitance connection sheet metal 3. The separation distance between the heat exchanger 6 and the capacitance connection sheet metal 3 is smaller than the separation distance between the heat exchanger 6 and each panel of the casing 2, and the area where the heat exchanger 6 and the capacitance connection sheet metal 3 face each other is relatively large, so that the parasitic capacitances 22c have a larger capacitance than the parasitic capacitances 22a and 22b. The parasitic capacitances 22c have, for example, a capacitance of some thousands of pF to some tens of thousands of pF. The magnitude of capacitance generated between the capacitance connection sheet metal 3 and the heat exchanger 6, is determined by the separation distance between the capacitance connection sheet metal 3 and the heat exchanger 6, the area where the capacitance connection sheet metal 3 and the heat exchanger 6 face each other, and the magnetic permeability of the dielectric 3e when the dielectric 3e is inserted into the space between the capacitance connection sheet metal 3 and the heat exchanger 6.
The heat exchanger 6 and the panels of the casing 2 illustrated in FIG. 10 are electrically connected through the parasitic capacitances 22a and 22b and, in addition, the parasitic capacitances 22c having a larger capacitance than the parasitic capacitances 22a and 22b. That is, for a high-frequency signal such as electromagnetic noise, conductivity between the heat exchanger 6 and each panel of the casing 2 is enhanced. Consequently, changes in voltage generated through the parasitic capacitances 22a and 22b between the heat exchanger 6 and the casing 2 are reduced, and electromagnetic noise emitted from the spaces G1, G2, G3, and G4 illustrated in FIG. 7 is reduced. Furthermore, the amount of radiation of electromagnetic noise of about 30 MHz to 300 MHz generated from the casing 2 can be reduced by the parasitic capacitances 22c. On the other hand, as illustrated in FIGS. 9 and 10, since the heat exchanger 6 is not in contact with the casing 2 and the capacitance connection sheet metal 3, corrosion due to contact between the heat exchanger 6 and the casing 2 and the capacitance connection sheet metal 3 can be prevented. In addition, in the present embodiment, since the capacitance connection sheet metal 3 is formed of the first metal like the casing 2 or the third metal that does not cause corrosion with the first metal, corrosion due to contact between the casing 2 and the capacitance connection sheet metal 3 can be prevented. That is, by the structure simply including the capacitance connection sheet metal 3, both the prevention of corrosion and the reduction of electromagnetic noise can be achieved.
In the present embodiment, as illustrated in FIG. 2, the capacitance connection sheet metal 3 is fixed and electrically connected only to the casing floor panel 2a, but may be fixed to all of the casing floor panel 2a, the casing top panel 2b, the casing front panel 2e, the casing rear panel 2h, and the casing side panels 2f and 2g illustrated in FIG. 1. This can strengthen electrical connections between the panels and reduce the contact resistance of the casing 2 and the parasitic inductances 23 illustrated in FIG. 10. Consequently, electromagnetic noise transmitted to the electronic board 9a, the compressor 8, and the panels of the casing 2, that is, conducted emissions, disturbance power intensity, and the like can be reduced.
In the present embodiment, as illustrated in FIG. 9, since the dielectric 3e is inserted into the space formed between the heat exchanger 6 and the capacitance connection sheet metal 3, the magnitude of capacitance generated between the heat exchanger 6 and the capacitance connection sheet metal 3 can be easily adjusted by changing the magnetic permeability of the dielectric 3e.
In the present embodiment, since the first metal is one of iron and an iron alloy, and the third metal is the other of iron and an iron alloy, even when the capacitance connection sheet metal 3 illustrated in FIG. 9 is formed of the third metal, corrosion due to contact between the casing 2 formed of the first metal and the capacitance connection sheet metal 3 can be prevented. Further, in the present embodiment, since the second metal is aluminum or an aluminum alloy, the thermal conductivity of the heat exchanger 6 formed of the second metal can be enhanced.
In the present embodiment, as illustrated in FIG. 9, the heat exchanger 6 includes the planar heat exchanger side end 6a extending in the vertical direction, and the capacitance connection sheet metal 3 includes the sheet metal facing wall 3a disposed with a space between the heat exchanger side end 6a and the sheet metal facing wall 3a. Consequently, the parasitic capacitance 22c can be generated between the heat exchanger 6 and the capacitance connection sheet metal 3 with a simple structure.
In the present embodiment, as illustrated in FIG. 9, the heat exchanger 6 includes the pair of heat exchanger side surfaces 6b and 6c extending in a direction away from the sheet metal facing wall 3a from both edges of the heat exchanger side end 6a in the Z-axis direction. On the other hand, the capacitance connection sheet metal 3 includes the sheet metal side wall 3b, which extends toward the heat exchanger side surface 6b from one edge of the sheet metal facing wall 3a in the Z-axis direction and is disposed with a space between the heat exchanger side surface 6b and the sheet metal side wall 3b. The capacitance connection sheet metal 3 includes the sheet metal side wall 3c, which extends toward the heat exchanger side surface 6c from the other edge of the sheet metal facing wall 3a in the Z-axis direction and is disposed with a space between the heat exchanger side surface 6c and the sheet metal side wall 3c. These configurations can increase the area where the heat exchanger 6 and the capacitance connection sheet metal 3 face each other, to increase the parasitic capacitances 22c generated between the heat exchanger 6 and the capacitance connection sheet metal 3.
In the present embodiment, as illustrated in FIG. 9, the space formed between the heat exchanger side end 6a and the sheet metal facing wall 3a and the space formed between the heat exchanger side surface 6b and the sheet metal side wall 3b communicate with each other. The space formed between the heat exchanger side end 6a and the sheet metal facing wall 3a and the space formed between the heat exchanger side surface 6c and the sheet metal side wall 3c communicate with each other. This can create a space into which the single dielectric 3e is inserted.
An aluminum parallel-flow heat exchanger uses aluminum as the material of fins and refrigerant tubing. Thus, when iron is used as the material of the casing 2, corrosion can occur in both the fins and the refrigerant tubing. If corrosion occurs in the refrigerant tubing, making a hole, the refrigerant in the refrigerant tubing leaks into the atmosphere. The leakage of the refrigerant into the atmosphere impairs heating and cooling functions as the air conditioner. Thus, corrosion has a substantial harmful effect on an aluminum parallel-flow heat exchanger, and therefore it is highly important to take measures to prevent corrosion. It is also necessary to take measures to reduce electromagnetic noise caused by taking measures to prevent corrosion. Therefore, it is particularly useful to achieve both the prevention of corrosion and the reduction of electromagnetic noise using the capacitance connection sheet metal 3 and the insulating members 7 illustrated in FIG. 2 as in the present embodiment when a heat exchanger on which corrosion has a substantial harmful effect such as an aluminum parallel-flow heat exchanger is used. In other words, achieving both the prevention of corrosion and the reduction of electromagnetic noise using the capacitance connection sheet metal 3 and the insulating members 7 as in the present embodiment is particularly useful when using a heat exchanger in which the natural potential of refrigerant tubing is lower than the natural potential of peripheral members including the casing 2.
FIG. 12 is a perspective view illustrating the capacitance connection sheet metal 3 with portions cut out, the casing floor panel 2a, the heat exchanger 6, and the insulating member 7 in the air conditioner outdoor unit 1 according to a first modification of the first embodiment. As illustrated in FIG. 12, in the capacitance connection sheet metal 3, cutout portions 3f may be formed by cutting out portions of the capacitance connection sheet metal 3. The cutout portions 3f are formed so as to penetrate through portions of the capacitance connection sheet metal 3 in the thickness direction of the capacitance connection sheet metal 3. The formation of the cutout portions 3f like these in the capacitance connection sheet metal 3 can prevent a decrease in air permeability due to the provision of the capacitance connection sheet metal 3, and adjust the magnitude of capacitance generated between the heat exchanger 6 and the capacitance connection sheet metal 3. The cutout portions 3f are formed in at least one of the sheet metal facing wall 3a, the sheet metal side wall 3b, and the sheet metal side wall 3c of the capacitance connection sheet metal 3. For example, the cutout portions 3f may be formed in either the sheet metal facing wall 3a or the sheet metal side walls 3b and 3c, or may be formed in both the sheet metal facing wall 3a and the sheet metal side walls 3b and 3c. In the present embodiment, the cutout portions 3f are formed only in the sheet metal facing wall 3a. The shape of the cutout portions 3f is an elongated rectangle in the present embodiment, but is not particularly limited. The number of the cutout portions 3f is four in the present embodiment, but is not particularly limited. The four cutout portions 3f are disposed in parallel to the outer shape of the sheet metal facing wall 3a side by side.
FIG. 13 is a perspective view illustrating the capacitance connection sheet metal 3, contact sheet metal 25, the casing floor panel 2a, the casing top panel 2b, the heat exchanger 6, and the insulating members 7 in the air conditioner outdoor unit 1 according to a second modification of the first embodiment. FIG. 14 is a side view illustrating the contact sheet metal 25, the casing top panel 2b, a covering member 26, and the heat exchanger 6 in the air conditioner outdoor unit 1 according to the second modification of the first embodiment. In FIG. 13, to clarify the extent of the insulating member 7, the insulating member 7 is hatched. In FIG. 14, to clarify the extent of the covering member 26, the covering member 26 is hatched. In the above-described embodiment, the casing 2 and the heat exchanger 6 are in contact with each other with the insulating members 7 that are non-conductive members interposed therebetween. Alternatively, as illustrated in FIGS. 13 and 14, a portion of the casing 2 and a portion of the heat exchanger 6 may be in contact with each other with the contact sheet metal 25 that is a conductive member interposed therebetween, and a contact portion between the casing 2 and the heat exchanger 6 may be covered with the covering member 26 such as a waterproof tape. This can enhance the electromagnetic noise reduction effect produced by the capacitance connection sheet metal 3. Furthermore, the portion covered with a waterproof tape or the like is limited, which can prevent problems such as structural complication, an increase in the number of manufacturing steps, and an increase in the number of parts due to the use of the covering member 26 for waterproofing.
The second insulating member 7b illustrated in FIG. 13 covers part of the top of the heat exchanger 6 and does not entirely cover the top of the heat exchanger 6. The rest of the top of the heat exchanger 6 is covered with the contact sheet metal 25. The contact sheet metal 25 is disposed on a top end portion of the portion of the heat exchanger 6 along the Z-axis direction. As illustrated in FIG. 14, the contact sheet metal 25 includes a contact sheet metal horizontal wall 25a, a pair of contact sheet metal vertical walls 25b and 25c, and a pair of contact sheet metal fixed portions 25d and 25e. The contact sheet metal horizontal wall 25a, the contact sheet metal vertical walls 25b and 25c, and the contact sheet metal fixed portions 25d and 25e are all flat portions. The contact sheet metal horizontal wall 25a has a quadrangular shape. The contact sheet metal horizontal wall 25a is disposed on the top end portion of the portion of the heat exchanger 6 along the Z-axis direction. The contact sheet metal vertical walls 25b and 25c have a quadrangular shape. The contact sheet metal vertical wall 25b extends downward from one edge of the contact sheet metal horizontal wall 25a in the X-axis direction, and is disposed on a front end portion of the portion of the heat exchanger 6 along the Z-axis direction. The side surface of the contact sheet metal vertical wall 25b facing the heat exchanger 6 is in direct contact with the heat exchanger 6. The contact sheet metal vertical wall 25c extends downward from the other edge of the contact sheet metal horizontal wall 25a in the X-axis direction, and is disposed on a rear end portion of the portion of the heat exchanger 6 along the Z-axis direction. The side surface of the contact sheet metal vertical wall 25c facing the heat exchanger 6 is in direct contact with the heat exchanger 6. The contact sheet metal vertical walls 25b and 25c are bent downward at right angles from the edges of the contact sheet metal horizontal wall 25a in the X-axis direction.
The contact sheet metal fixed portions 25d and 25e are portions fixed to the casing 2. The contact sheet metal fixed portions 25d and 25e have a quadrangular shape. The contact sheet metal fixed portion 25d protrudes forward of the contact sheet metal vertical wall 25b from one edge of the contact sheet metal horizontal wall 25a in the X-axis direction. The contact sheet metal fixed portion 25e protrudes rearward of the contact sheet metal vertical wall 25c from the other edge of the contact sheet metal horizontal wall 25a in the X-axis direction. The contact sheet metal fixed portions 25d and 25e are in contact with and fixed to the casing top panel 2b. The contact sheet metal fixed portions 25d and 25e are joined to the casing top panel 2b with screws or the like. The contact sheet metal 25 is formed of the first metal like the casing 2 or the third metal that does not cause dissimilar metal corrosion with the casing 2. If water adheres to a contact portion between the contact sheet metal 25 formed of the first metal or the third metal and the heat exchanger 6 formed of the second metal, corrosion occurs in the heat exchanger 6 with lower natural potential. In the present modification, the side surface opposite to the heat exchanger 6 and the lower surface of the contact sheet metal vertical wall 25b are covered with the covering member 26. The side surface opposite to the heat exchanger 6 and the lower surface of the contact sheet metal vertical wall 25c are covered with the covering member 26. That is, the periphery of the contact portion between the contact sheet metal 25 and the heat exchanger 6 is covered with the covering member 26 such as a waterproof tape. This can block the ingress of water into the contact portion between the contact sheet metal 25 and the heat exchanger 6 to prevent the corrosion of the heat exchanger 6.
The heat exchanger 6 does not need to be entirely formed of the second metal. The heat exchanger 6 is only required to be at least partly formed of the second metal. For example, it is only required that at least either the fins or the refrigerant tubing of the heat exchanger 6 be formed of the second metal.
The configurations described in the above embodiment illustrate an example, and can be combined with another known art, and can be partly omitted or changed without departing from the gist.
Patent Application
20250123009
