AUTOMATIC FOOD REFUSE DISPOSAL APPARATUS Technical Field [1] The present invention relates to an automatic food refuse disposal apparatus, capable of rapidly and hygienically grinding and collecting food refuse, using an automatic system. Background Art [2] As is generally known, food refuse discharged from house kitchens is filtered using a filtering net and then collected. However, such a disposal method is problematic in that an offensive odor may be given off and flies or the like may be attracted thereto, so that the disposal method is very unhygienic. [3] In the case of large restaurants where a large amount of food refuse is discharged, the food refuse may be ground using a grinder and then collected. However, the grinder uses a rotary blade, so that it is very dangerous and noisy. In order to reduce noise, a compression screw was proposed. However, the compression screw is problematic in that the separation and discharge of water are inefficient while the grinding operation is carried out. [4] Further, various food refuse disposal structures using a high-speed rotary means, a compressor, etc. have been proposed. After food refuse is burned up or ground, the high-speed rotary means dries the powdered food refuse using hot air or dehydrates the powdered food refuse. Meanwhile, the compressor uses a compression plate to compress the food refuse. However, such refuse disposal apparatuses are problematic in that the structures are complex, costly, and excessively large in volume, so that the refuse disposal apparatuses may be used only for industrial applications, but are not suitable for homes, restaurants, or the like. [5] Meanwhile, a conventional food refuse disposal apparatus used in homes or restaurants is problematic in that a user must manually manipulate the apparatus so as to grind food refuse, and manually collect the ground food refuse, so that it is very in¬ convenient. Especially, when food refuse is input into the refuse disposal apparatus, the apparatus is operated immediately, regardless of whether the amount of food refuse is large or small. Thus, due to frequent operation of the refuse disposal apparatus, the life-span of the apparatus is shortened, and energy is wasted. Further, a refuse collecting container must be frequently checked so as to confirm whether the collecting container is full of food refuse, so that it is complicated to use. Furthermore, when the collecting container is checked, the collecting container is frequently emptied, so that garbage bags are wasted. Disclosure of Invention Technical Problem [6] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an automatic food refuse disposal apparatus, which automates the entire food refuse disposal process, including a refuse inputting operation and a refuse collecting operation, thus more efficiently and hygienically executing the food refuse disposal process. Technical Solution [7] In order to accomplish the above object, the present invention provides an automatic food refuse disposal apparatus, including a pair of compression gears; a protective net surrounding the compression gears, and having an inlet so that food refuse is fed into the protective net; a grinding container housing the compression gears and the protective net therein, and having a refuse discharge pipe and a drain pipe; a collecting container to collect the food refuse which is ground by the compression gears, and thereafter discharged through the refuse discharge pipe; a drive motor to drive the pair of compression gears; an outer casing to house the grinding container, the collecting container, and the motor therein; a first sensor to detect an amount of food refuse held in the grinding container; and a circuit board having a mi¬ croprocessor, the microprocessor being operated such that the drive motor is operated for a preset time, when the amount of food refuse detected by the first sensor reaches a predetermined amount. Thus, although a user need not perform a special action, the food refuse is automatically ground and collected when the food refuse reaches a pre¬ determined amount. [8] The disposal apparatus further includes a second sensor to detect an amount of food refuse collected in the collecting container; and an indicator lamp, operated by the circuit board having the microprocessor when the amount of food refuse detected by the second sensor has reached a predetermined amount, thus allowing the user to know the time at which the treated food refuse is collected. [9] According to this invention, the disposal apparatus further includes a blowing fan to dry the food refuse collected in the collecting container; and a blowing motor operated for a preset period by the circuit board having the microprocessor, and rotating the blowing fan, when the drive motor operates, thus drying the ground food refuse, therefore preventing the food refuse from emitting an offensive odor. [10] The disposal apparatus further includes an anion sterilizer provided at a position above the collecting container, and operated for a preset period by the circuit board having the microprocessor, thus eliminating an offensive odor emitted by the ground food refuse. [11] According to this invention, the disposal apparatus further includes a control panel used to input an operation time of the drive motor to the circuit board having the mi¬ croprocessor, thus allowing the apparatus to be operated as desired. Advantageous Effects [12] According to the present invention, an automatic food refuse disposal apparatus causes food refuse to be appropriately input, a motor to be automatically driven for a preset period, and a collecting time to be automatically indicated, thus being convenient to use and saving electricity. The automatic food refuse disposal apparatus completely dries and sterilizes the food refuse, prior to the food refuse being collected, thus keeping an indoor space pleasant. Further, it is unnecessary to use a garbage bag for food refuse, thus being economically efficient. Brief Description of the Drawings [13] FIG. 1 is a perspective view showing a grinding container of an automatic food refuse disposal apparatus, according to an embodiment of the present invention; [14] FIG. 2 is a sectional view of the automatic food refuse disposal apparatus, according to this invention; and [15] FIG. 3 is a plan view of the automatic food refuse disposal apparatus of FIG. 2. Best Mode for Carrying Out the Invention [16] The preferred embodiment of this invention will be described in detail with reference to the accompanying drawings. For brevity of description of this invention, repetitive descriptions will be avoided. [17] FIG. 1 is a perspective view showing a grinding container of an automatic food refuse disposal apparatus, according to an embodiment of the present invention, FIG. 2 is a sectional view of the automatic food refuse disposal apparatus, according to this invention, and FIG. 3 is a plan view of the automatic food refuse disposal apparatus of FIG. 2. [18] Referring to FIGS. 1 to 3, the automatic food refuse disposal apparatus, according to this invention, includes a pair of compression gears 22, a protective net 23, a grinding container 20, a guide net 24, a collecting container 30, a mesh net 31, a drive motor 21, an outer casing 10, a first sensor 25, a second sensor 34, a blowing fan 32, a blowing motor 33, an anion sterilizer 40, a control panel (not shown), a circuit board 50, and other components. [19] The construction of the automatic food refuse disposal apparatus will be described below in detail. [20] The compression gears 22 engage with each other, and are operated to grind food refuse. [21] The protective net 23 prevents the removal of the food refuse which moves while being ground by the pair of compression gears 22. An inlet 23' is provided at a lower position on the protective net 23 such that the food refuse is fed into the protective net 23. [22] The pair of compression gears 22 and the protective net 23 are housed in the grinding container 20. The grinding container 20 is provided with a refuse discharge pipe 26 and a drain pipe 27. The food refuse is ground by the compression gears 22, and subsequently discharged through the refuse discharge pipe 26. Water separated from the food refuse is discharged through the drain pipe 27. [23] The guide net 24 is installed at a position adjacent to the inlet 23' of the protective net 23, and is inclined toward an inner wall of the grinding container 20. [24] The collecting container 30 collects the food refuse which is discharged through the refuse discharge pipe 26. [25] The mesh net 31 is provided at a lower position in the collecting container 30, and prevents the food refuse from interfering with the blowing fan 32 that will be described hereafter. [26] The drive motor 21 drives the pair of compression gears 22. [27] The grinding container 20, the collecting container 30, and the drive motor 21 are installed in the outer casing 10. [28] The first sensor 25 detects the amount of food refuse which has been input into the grinding container 20. Such a first sensor 25 need not detect the amount of input food refuse precisely, but need only detect the approximate amount of input food refuse. That is, the first sensor 25 detects the piled height of the input food refuse, the weight of the input food refuse or the like. [29] The second sensor 34 detects the amount of food refuse which has collected in the collecting container 30. Similarly to the first sensor 25, the second sensor 34 need only detect the approximate amount of collected food refuse. That is, the second sensor 34 detects the piled height of the collected food refuse, the weight of the collected food refuse or the like. [30] The blowing fan 32 is isolated from the food refuse by the mesh net 31. The blowing fan 32 is mounted to the bottom of the collecting container 30. [31] The blowing motor 33 rotates the blowing fan 32. [32] The anion sterilizer 40 is provided at a position above the collecting container 30, and sterilizes the food refuse collected in the collecting container 30. [33] The control panel is manipulated by a user so that a time is set and input. That is, the user inputs operation times of the drive motor 21, the blowing motor 33, and the anion sterilizer 40 using the control panel. Further, an indicator lamp having an alarm bell is mounted on the control panel and indicates various states of operation of the automatic food refuse disposal apparatus, thus indicating the operation and the completion of operation of each component, in addition to giving warnings to a user. [34] The circuit board 50 has a microprocessor to control a series of processes. Thus, while the food refuse disposal process is carried out, the drive motor 21, the blowing motor 33, and the anion sterilizer 40 are operated for preset periods which have been previously input by a user. When necessary, the indicator lamp or the like indicates a certain operation state. [35] The outer casing 10 constructed as described above is installed under a sink, and the drain pipe 27 provided on the bottom of the grinding container 20 is connected to an inlet of a sewer pipe which is provided on the bottom. [36] The operation of the automatic food refuse disposal apparatus according to the embodiment of this invention will be described below. [37] First, a user sets a time using the control panel. In a detailed description, the operation time of the drive motor 21, the operation time of the blowing motor 33, and the operation time of the anion sterilizer 40 are set and input by the user. [38] According to this embodiment, the drive motor 21 which drives the pair of compression gears 22 installed in the grinding container 20 is operated for about 4 minutes. The blowing motor 33, which drives the blowing fan 32 provided on the bottom of the collecting container 30, and the anion sterilizer 40, which is provided above the collecting container 30, are operated for about one hour. Of course, the operation time of each component may be predetermined, rather than be input by a user. [39] Meanwhile, as soon as food refuse is generated, the food refuse is input from the sink to the grinding container 20. [40] The food refuse input into the grinding container 20 is guided by the guide net 24 which is obliquely installed at a position in the grinding container 20. Afterwards, the guided food refuse is fed into the inlet 23' of the protective net 23 surrounding the pair of compression gears 22. [41] Subsequently, the input food refuse gradually accumulates, and thereby reaches a predetermined level in the grinding container 20. The first sensor 25 detects that the input food refuse has reached a predetermined level. In response to the detection, the circuit board having the microprocessor emits an alarm sound for about 5 seconds. Thereafter, the drive motor 21, the blowing motor 33, and the anion sterilizer 40 are operated. At this time, it is preferable that the input of the food refuse temporarily cease. [42] As the drive motor 21 is operated, the compression gears 22 mounted to a shaft of the drive motor 21 are driven, so that the food refuse is compressed and ground. At this time, water is removed from the food refuse by compressing the food refuse. The removed water is discharged through the drain pipe 27 provided on the bottom of the grinding container 20. Simultaneously, the dehydrated and ground food refuse is fed upwards by the operation of the pair of compression gears 22. The fed ground food refuse is discharged through the refuse discharge pipe 26 provided above the compression gears 22, prior to being collected in the collecting container 30. [43] While the drive motor 21 and the pair of compression gears 22 are operated for a previously input time, for example, 4 minutes, all of the input food refuse is ground and is completely fed through the refuse discharge pipe 26 into the collecting container 30. As such, when the grinding and feeding operations are completed, more food refuse is input into the apparatus. The above-mentioned operations are repeated. [44] Meanwhile, when the drive motor 21 is operated, the blowing motor 33 mounted to the bottom of the collecting container 30 is operated. As the blowing motor 33 operates, the blowing fan 32 rotates, thus supplying air to the interior of the collecting container 30. Since the blowing fan 32 is protected by the mesh net 31 provided at a central portion in the collecting container 30, the ground food refuse does not contact the blowing fan 32. Moving air generated by the blowing fan 32 is supplied through the mesh net 31 to the interior of the collecting container 30, thus drying the ground food refuse. Simultaneously, the anion sterilizer 40 is continuously operated, thus eliminating offensive odors and keeping an indoor space pleasant. According to ex¬ perimental result, the blowing fan 32 and the anion sterilizer 40 need be operated only for one hour. [45] One hour is sufficient to grind food refuse filling the grinding container 20, con¬ tinuously feed the ground food refuse into the collecting container 30 using the pair of compression gears 22 that are repeatedly operated by 4 minutes, load the ground food refuse in the collecting container 30, and completely sterilize and dry the food refuse collected in the collecting container 30. [46] Further, when the ground food refuse fed into the collecting container 30 reaches a predetermined amount, the second sensor 34 detects that the ground food refuse has reached the predetermined amount. Thereafter, the detected result is indicated by the indicator lamp of the control panel, thus allowing a user to conveniently and rapidly know the time when the collected food refuse is dumped. [47] Meanwhile, the automatic food refuse disposal apparatus according to this invention emits an alarm sound if the drive motor 21 is overloaded and stops. At this time, the drive motor 21 rotates backwards for about 3 seconds, and thereafter rotates forwards. The automatic food refuse disposal apparatus may be manually operated. [48] Although the preferred embodiment of the present invention has been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Industrial Applicability [49] As described above, the present invention can be adapted to various food refuse disposal applications. [50]