Abstract:
An air conditioner has an electronic dust collector incorporated in its casing. A mounting plate is grounded which, in turn, grounds the casing of the air conditioner. This reduces adsorption of dust to the casing, thereby preventing soiling of the casing with dust or fine particles.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an air conditioner with electronic dust collector. 
     2. Description of the Prior Art 
     Hitherto, there has been known an air conditioner which incorporates a deodorant device using an adsorptive catalyst or the like, in addition to the original air conditioning function, in the interior unit to enhance the function (ref. Japanese Patent Publication Unexamined HEI 6-180127). Likewise, there have been attempts to incorporate an electronic dust collector in the interior unit. The electronic dust collector generates a corona discharge by applying a high voltage between a discharge electrode and a dust collection electrode. The corona discharge ionizes fine particles and dust in the surrounding air. The dust collection electrode then adsorbs them. Among such electronic dust collectors, there has been developed a maintenance-free type one in which the dust collection electrode is provided with a heater for self-cleaning so that the dust deposited on the dust collection electrode is burned, and thereby is removed. 
     However, when such an electronic dust collector is incorporated in the interior unit of the air conditioner, because of the corona discharge, the body or the casing itself is charged with static electricity. This presents the problem that dust is attracted and held in the vicinity of the inside walls, especially near the air intake and outlet ports, and on outside walls of the casing, rather having it collected by the dust collection electrode. This soils these areas. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an air conditioner with electronic dust collector which solves the problems of the prior art. 
     It is a further object of the invention to provide an air conditioner with electronic dust collector having a constitution of the electronic dust collector incorporated in the casing of the interior unit of the air conditioner in which electrification of the casing is prevented and dust is less apt to be adsorbed to the casing, thereby preventing generation of dust. 
     Briefly stated, the present invention provides an air conditioner which has an electronic dust collector incorporated in its casing. A mounting plate is grounded which, in turn, grounds the casing of the air conditioner. This reduces adsorption of dust to the casing, thereby preventing soiling of the casing with dust or fine particles. 
     According to an embodiment of the invention, there is provided an air conditioner with electronic dust collector for conditioning air in a room and purifying air by collecting dust in air by the use of electric discharge effect, comprising: a casing having an air suction port and an air outlet port, a heat exchanger in said casing facing said air suction port, a fan for circulating air into said suction port, through air passages in said casing and said heat exchanger, and out said air outlet port, an electronic dust collector in said air passages for collecting dust in air which passes through said air passages by using said electric discharge effect; and means for grounding said casing. 
     According to a feature of the invention, there is provided an air conditioner with electronic dust collector for conditioning air in a room and purifying air by collecting dust in air by the use of electric discharge effect, comprising; a casing having an air suction port and an air outlet port, a heat exchanger in said casing facing said suction port, a fan for circulating air into said air suction port ,through air passages in said heat exchanger and said casing and out said air outlet port, an electronic dust collector in said air passages for collecting dust in air which passes through said air passages by using said discharge effect; and means for permitting grounding of said casing. 
     In order to attain the above object, the present invention in an air conditioner with electronic dust collector for conditioning air in a room and purifying air by collecting dust in air by the use of electric discharge effect, comprising: a casing having an air suction port and an air outlet port; a heat exchanger provided in said casing facing the suction port; a fan for circulating air into the suction port through the air passages and out through the outlet port in the heat exchanger and the casing; and an electronic dust collector arrayed in said air passages for collecting dust in air which passes through the air passages by using the discharge effect, so that the casing can be grounded. 
     In the above constitution, the air taken in from the suction port during the air conditioning operation undergoes heat exchange through the heat exchanger to be cooled or heated, and further is discharged through the air outlet port in the casing. Simultaneously, by the operation of the electronic dust collector, dust or fine particles floating in the air passing through the air passage are electrified by adhesion of ions or electrons from by the corona discharge of the dust collector, ion blow is generated, which is attracted to the dust collection electrode side of the dust collector to cause electric dust collection. Further, the casing per se tends to be electrified by the static electricity by the corona discharge of the dust collector, but when the casing is grounded, static electricity of the casing is eliminated, and accordingly, the casing is prevented from soiling with dust or fine particles. Though it is desirable for the ground resistance of the casing to be small, the ground resistance may be approximately 2 Ma or less. 
     The dust collector may be one comprising a discharge electrode and a dust collection electrode spaced apart a predetermined distance and between which a high voltage is applied. The dust collection electrode can include a heater for self cleaning. By this constitution, the dust collection electrode is self-cleaned to become maintenance-free. Alternatively, a catalyst layer may be provided on the surface of the dust collection electrode. With this constitution, when air contains fine particles of odorous component, the odorous component is adsorbed by the catalyst layer and deodorized. 
     The air conditioner body containing the above casing may be designed to permit to be fixed to a wall through a fixing plate, with the fixing plate grounded. By this constitution, just by fixing the air conditioner body to the fixing plate the grounding of the casing is easily realized, and the wall to which the air conditioner is fixed and the surroundings are made less apt to collect dust. 
     The above dust collector may be to be fixed to a casing through a dust collector fixing plate, so that the dust collector fixing plate can be grounded. By this constitution, static electricity on the dust collector fixing plate can be eliminated, and deposition of dust on the dust collector fixing plate per se is suppressed. At the same time, the dust collector fixing plate has a function of the shield plate for heat for the heater for self-cleaning. 
     The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partially broken perspective view of an air conditioner with electronic dust collector according to an embodiment of the present invention. 
     FIG. 2 is a side view of an air conditioner with electronic dust collector showing the flow of air during air conditioning. 
     FIG. 3 is a partial perspective view of an electronic dust collector. 
     FIG. 4 is a partial side view of an electronic dust collector. 
     FIG. 5 is a partial bottom view of an electronic dust collector. 
     FIG. 6 is a sectional view of a part of the dust collector. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG.  1  through FIG. 5, an air conditioner with dust collector  1  has both an air conditioning function for cooling or heating air in room and a dust collection function for removing dust contained in interior air to clean the air passing therethrough. The device is to be fixed to wall or the like through a fixing plate  2 . The air conditioner  1  has a casing  10  having an air inlet  11  on its front face. Casing  10  also includes an air outlet port  12  at the bottom of casing  10 . A front panel  20  having a front grill  21  is fitted over the air inlet  1   1  of the casing  10 . A heat exchanger  30  in the casing  10  faces the inlet  11  of the casing  10 . A cross-flow type fan  40  behind the air outlet port  12  circulates air from the air inlet  11  to the air outlet port  12 . The air passes through the heat exchanger  30 , and an electronic dust collector  50  disposed in the air passage  31  behind the heat exchanger  30 . A filter  32  is disposed between the front panel  20  and the heat exchanger  30 . An angle adjusting type looper  13  at the air outlet port  12  of the casing  10  directs the outgoing air at a selectable angle. A control circuit  15  (control means) in the casing  10  controls the operation of the air conditioner  1 . The heat exchanger  30  is connected to a heat exchanger of an external unit (not illustrated) and a coolant pipe. 
     The electronic dust collector  50  includes a horizontally stretched linear discharge electrode  60  and a bar-like dust collection electrode  70  spaced a predetermined distance from the discharge electrode  60 . The dust collection electrode  70  contains a sheathed heater  71  for self-cleaning. A heat shielding plate  80  serves as a dust collector plate for shielding heat of the sheathed heater  71  of the dust collection electrode  70 . The discharge electrode  60  and the dust collection electrode  70  are mounted to the heat shielding plate  80 . The discharge electrode  60  and the dust collection electrode  70 , with the heat shielding plate  80 , are fixed to the surface of a vertical back plate  18 . 
     A discharge line  61  which constitutes a discharge electrode  60  is tensioned in place by a tensile spring  64  connected, at its outer end to an electrode  63 . Electrode  63  is fixed to a holding member  62 . A similar holding member  63  (not shown) fixes the other end of the discharge line  61 . A voltage is applied from the electrode  63  through the tensile spring  64  to the discharge line  61 . 
     The dust collection electrode  70  is disposed on the downstream side of the air passage  31  spaced a predetermined distance from the discharge electrode  60 . Lengthwise end parts  72  of dust collection electrode  70  are fixed to holding members  74  by stopper members  73 . Positive DC voltage and the negative DC voltage are applied to the discharge electrode  60  and the dust collection electrode  70 , respectively, during air purification. The holding member  62  and the holding member  74  are fixed to the heat shielding plate  80 . 
     The casing  10 , which is the body of the air conditioner  1 , can be grounded. Without grounding the casing  10  would be electrified by the electric line force produced by the corona discharge of the dust collector  50  disposed inside. This would cause soiling by adhesion of dust. To prevent this, the static electricity on the casing  10  is eliminated by grounding. 
     Although the casing  10  per se may be grounded, it is preferable that, as shown in FIG. 2, the fixing plate  2  and/or the heat shielding plate  80  are grounded by an earth line E. The grounding resistances are desirably small. It is believed that a grounding resistance of less than about  2  Ma may be acceptable. 
     Referring now to FIG. 6, the dust collection electrode  70  self-contains the sheathed heater  71 . The sheathed heater  71  includes an aluminum metal tube  75  containing an electric resistance line  76  therein. The surface of the metal tube  75  is coated with one or more catalyst layers  77 . The catalyst layers  77  are preferably catalytic substances such as, for example, represented by zeolite, active alumina, manganese dioxide, etc. The catalyst layers  77  may be formed by any convenient means such as, for example, plating or welding. Zeolite (generally called zeolite) has a three-dimensional net structure having hollow parts, which accelerate the reaction of the molecules adsorbed to the inside of the hollow part. Active alumina (Al2O3) is alumina powder having high adsorption capacity, with small crystal particle size and large surface area. Active alumina is suitable as a catalyst, catalyst carrier, and adsorbing agent. Manganese dioxide (MnO2) can function as a catalyst in the same manner as in zeolite and active alumina as stated above. Further, in order to prevent mutual contact between the metal tube  75  and the electric resistance line  76 , an insulator such as magnesium oxide  78  fills the metal tube  75  and supports the electric resistance line  76  generally centered therein. End parts  75   a  of the metal tube  75  are sealed by glass sealing member  79  (only one of which is shown). This sheathed heater  71  may be of small energy per unit area, e.g., approximately 180 W (Watt). 
     Next, the operation of the air conditioner  1  with dust collector constituted as above is described. During air conditioning, operation of the heat exchanger  30  and the fan  40  passes room air inward through the front grill  21  of the front panel  20  and the filter  32 , and into the casing  10 . After being cooled or heated in the course of the passage through the heat exchanger  30 , the air flows vertically downward through the air passage  31 . The air which passes through the air passage  31  passes the periphery of the dust collector  50 . Here, a high voltage is applied between the discharge electrode  60  and the dust collection electrode  70  of the dust collector  50  to generate a corona discharge between the two electrodes  60  and  70 . As a result, dust such as fine particles of tar (oil smoke) of tobacco or cotton dust present in the air passing by the discharge electrode  60  has deposited thereon positive ions formed by the corona discharge. The fine particles and dust become positively charged. As a result, the fine particles and dust are attracted by Coulomb force between the two electrodes toward the negatively-charged dust collection electrode  70  where they are caught and removed from the air stream to effect electric dust collection. If the fine particles in the air include odorous components, the odorous components are adsorbed by the catalyst layer  77  of the dust collection electrode  70  and deodorized. Thus, the air which passed through the heat exchanger  30  is purified in the course of passing through the air passage  31  on the back side thereof and discharged into the room through the air outlet port  12 . 
     Because the dust collection electrode  70  is disposed to the lee side of the discharge electrode  60 , the wind force of air flowing through the air passage  31  and the Coulomb force sustained by dust from the dust collection electrode  70 , the dust is directed toward the dust collection electrode  70 . This collecting a larger amount of dust on the dust collection electrode  70  to improve the dust collection effect by the dust collector  50 . 
     Electricity is slowly increased to the heater  71  of the dust collection electrode  70  so as to increase its temperature slowly. As a result, dust of soot or cotton dust which adhered to the surface of the dust collection electrode  70  is gradually decomposed by oxidation under the catalytic action of the catalyst and finally converted to colorless, odorless carbon dioxide and vapor at about the temperature exceeding 300° C. and removed from the dust collection electrode  70 . By oxidizing the dust slowly, the dust collection electrode  70  can be cleaned while suppressing generation of smoke and odor resulting from the firing of dust. The ultimate temperature is desirably controlled to a level lower than about 400° C. which is the lower limit of the firing temperature of the substances contained in the dust. 
     By grounding the fixing plate  2  of the casing  10  and/or the heat shielding plate  80  through the earth line E, static electricity charged thereon is eliminated. As a result, adhesion of dust and fine particles to these elements is suppressed to prevent their soiling. Further, by grounding the fixing plate  2 , the casing  10  and the peripheral parts thereof are easily grounded by simply fixing the body of the air conditioner  1  to the fixing plate  2 . 
     As used herein, the term air conditioner is taken to mean a device which performs any one of the functions of heating, cooling and cleaning air. 
     Without being limited to the foregoing embodiment, various modifications are feasible in the present invention. For example, in the above embodiment, there is shown about the self-cleaning of the electronic dust collection electrode provided on the air conditioner, but the invention may be applied to the reproduction method for the catalyst of the deodorizing apparatus of adsorptive type thermal decomposition system.