In a case where the interior-side heat exchange unit is of the wall-mounted type, there is mostly provided an air suction port on the front side of the housing, below which there is provided an air blow-off port for blowing off air heat exchanged. 
The air blow-off port is provided with a wind direction plate for changing the direction of a wind of air blown off and the air blow-off port is closed by the window direction plate when the operation is stopped.  This is partly because dust or the like is prevented from entering the air blow-off port while the operation is stopped, and partly because the design quality is enhanced by hiding the interior of the air blow-off port. 
For the same purpose, the air suction port is also provided with a louver in such a manner that the louver is opened during operation and that the louver is closed while the operation is stopped.  An example of the prior art will be described with reference to FIGS.  6 and 7.  This prior art has been disclosed in Japanese Patent Laid-Open No.  9-210401, and FIG.  6 is a cross-sectional view showing an interiorside heat exchange unit, and FIG.  7 is its partial transverse sectional view. 
First, the entire housing is composed of three members: a back cabinet 30 mounted onto an indoor wall with predetermined engaging means; a cover case 40 to be mounted on its front surface as a vanity cover; and a front panel 50 to be mounted on the front surface of this cover case 40. 
The back cabinet 30 is provided with a heat exchanger 31 and a blower fan 32 as the main component elements.  The cover case 40 is used to cover these component elements, air suction ports are provided on the top surface and the front surface, and an air blow-off port 41 having two wind direction plates 41a and 41b is provided below. 
The front panel 50 is detachably mounted to the air suction port located on the front side of the cover case 40.  A plurality of louvers 51 (three louvers in this example) is provided on this front panel 50 to enable them to be opened and closed. 
Each louver 51 is coupled to an interlocking plate 52 so as to be simultaneously opened and closed.  More specifically, the interlocking plate 52 is capable of vertically moving in FIG.  6 in such a manner that each louver 51 is opened when the interlocking plate 52 moves upward, and that each lower 51 is closed when the interlocking plate 52 moves downward. 
in order to vertically move the interlocking plate 52, there is provided, on the side of the cover case 40, driving means composed of a motor 42, a pinion 43 and a rack 44 and the like as shown in FIG.  7, and the interlocking plate 52 is coupled to the rack 44. 
In other words, the rotary motion obtained by the motor 42 is transformed into rectilinear motion by a motion transformation mechanism consisting of the pinion 43 and the rack 44, and this rectilinear motion is transmitted to the interlocking plate 52 to thereby move the interlocking plate 52 up and down.  This prior art has, however, the following problem. 
First, since the gear mechanism consisting of the pinion 43 and the rack 44 is used, accurate alignment is required not to cause any displacement in the meshed portion.  Even if accurate alignment is performed, any influence of backlash in the meshed portion cannot be avoided, but variations are prone to occur in the opening angle of each louver 51 and the like.  Not only the variations,but also foreign matters enter the meshed portion to possibly cause an obstruction to smooth meshing. 
Also, the louver 51 is flexible because it consists of a band plate made of synthetic resin.  Therefore, it is necessary to mount the interlocking plates 52 to both sides of each louver 51 for simultaneously driving each of them by the pinion 43 and the rack 44.  For this reason, it is undeniable that the number of parts increases, resulting in complicated structure and an increase in cost. 
Further, in the case of the above-described gear mechanism, large feed by the gear is required to open and close the louver 51 Therefore, the amount of rotation of the motor 42 increases by that much, and a high degree of accuracy is also required for controlling the amount of rotation.  This becomes an extra burden for the designer.