Patent Publication Number: US-7722334-B2

Title: Compressor and overload protecting apparatus

Description:
TECHNICAL FIELD 
   The present invention relates to a compressor and, more particularly, to an overload protecting therefore of a compressor for preventing an overload to a compressor. 
   BACKGROUND ART 
   A compressor, a device for sucking fluid and increasing pressure, is widely used for an air-conditioner, refrigerator, or the like. There are many kinds of compressors according to a driving method, including a reciprocating compressor, a scroll compressor and a turbo compressor, etc. 
   The compressor consists of a compression mechanism unit for performing compression of the fluid and a driving unit for driving the compression mechanism unit. The driving unit commonly uses a motor converting electric energy to kinetic energy. 
   An overload protecting apparatus for sensing heat generated from a rotor and a stator is installed near the motor. If an overheat is generated, the overload protecting apparatus stops driving of the motor so that the motor may not be damaged from the overload. 
   However, as for the overheating of the compressor, generally, the motor may be overloaded, and in addition, if the temperature of the discharged fluid is too high due to an abnormal operation, carbonization of oil, damage of parts and an unstable operation would cause degradation of a reliability of the compressor. 
   DISCLOSURE OF THE INVENTION 
   Therefore, an object of the present invention is to provide a compressor having an overload protecting apparatus that is capable of stopping operation of a motor not only when the motor is overheated but also when a temperature of a discharge fluid is too high due to an abnormal operation. 
   In order to achieve the above objects, there is provided a compressor including: a suction unit for sucking fluid; a compression unit for compressing the fluid sucked through the suction unit; a discharge unit for discharging the fluid compressed in the compression unit; an electric mechanism unit for driving the compression unit connected to the compression unit; and an overload preventing unit installed at the discharge unit for stopping operation of the electric mechanism unit if a temperature of the fluid discharged through the discharge unit is higher than a pre-set temperature. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a longitudinal sectional view of a compressor in accordance with the present invention; 
       FIG. 2  is a partial detailed view showing a construction of an overload preventing unit of  FIG. 1 ; and 
       FIGS. 3A and 3B  show operation of the compressor in accordance with the present invention. 
   

   MODE FOR CARRYING OUT THE PREFERRED EMBODIMENTS 
   The present invention will now be described with reference to accompanying drawings. 
   A compressor of the present invention includes: a suction unit for sucking fluid; a compression unit for compressing the fluid sucked through the suction unit; a discharge unit for discharging the fluid compressed in the compression unit; an electric mechanism unit for driving the compression unit connected to the compression unit; and an overload preventing unit installed at the discharge unit for stopping operation of the electric mechanism unit if a temperature of the fluid discharged through the discharge unit is higher than a pre-set temperature. 
   The compressor in accordance with the present invention can be any compressor regardless of kinds of compressors such as a piston type compressor, a scroll compressor, a turbo compressor, a so-called Z-type compressor and a reciprocating (linear) compressor. 
   As shown in  FIG. 1 , the scroll compressor includes: a casing  10  having a sealed space therein; a compression unit  20  installed inside the casing for compressing fluid; an electric mechanism unit  50  for providing driving force to the compression unit  20 ; and a lubrication unit  60  for allowing the electric mechanism unit  50  and the compression unit  20  to smoothly operate. 
   At one side of the casing  10 , a suction pipe  11  for sucking fluid from outside and a discharge pipe  12  for discharging the compressed fluid are installed. 
   The compression unit  20  includes a fixed scroll  21  having a discharge passage  23  for discharging compressed fluid at the central portion with a fixed scroll wrap  22  in an involute shape and being fixedly mounted inside the casing  10 ; and an orbiting scroll  25  having an orbiting scroll wrap  26  in a involute shape corresponding to the fixed scroll wrap  22  and being mounted to form four compression spaces P 2  in a crescent space as the fixed scroll wrap  22  and the orbiting scroll wrap  26  are engaged with an angular difference of 180°. 
   A high/low pressure separating plate  24  is installed at an upper side of the fixed scroll  21  to section the inner space of the casing  10  into a high pressure side P 3  and a low pressure side P 1  and form a discharge side muffler at an upper side of the discharge passage  23 . 
   A check valve  40  is mounted at an upper side of the discharge passage  23  to prevent the fluid from flowing backward and introduction of the compressed fluid at the high pressure side P 3  into the compression space P 2 . 
   The electric mechanism unit  50  includes: a stator  51  fixed inside the casing  10 , a rotor  52  for converting electric force to a rotating force in the stator  51 , a rotational shaft  53  for transmitting the rotating force of the rotor  52  to the orbiting scroll  25 , an Oldham ring  56  mounted between the rotational shaft  53  and the orbiting scroll  25  in order to change the rotational motion of the rotational shaft  53  to an orbiting motion; and a main frame  54  and a lower frame  55  fixedly installed inside the casing  10  in which the rotational shaft  53  is fixed. 
   The lubrication unit  60  is formed in the rotational shaft  53  and supplies oil  61  filled at the lower portion of the casing  10  to a frictional part inside the casing  10 . 
   The overload protecting device  72  is fixedly installed at the side of the discharge passage  23 . As shown in  FIG. 1 , to facilitate installation of the overload protecting device, a fixing recess  71  is formed at the high/low pressure separating plate  24  and the overload protecting device  72  is installed in the fixing recess  71 . 
   With reference to  FIGS. 1 and 2 , the overload protecting device  72  is connected to a winding coil  51   a  of the electric mechanism unit  50  and senses a temperature of a compressed fluid being discharged to the discharge passage  23 . If the sensed temperature is higher than a pre-set value, the connection of the winding coil is cut off to stop operation of the electric mechanism unit  50 . Then, the operation of the compressor is stopped, and accordingly, the electric mechanism unit  50  and the compressor are protected. In order to prevent flowing electricity to other members, an insulation member  73  is preferably installed inside the fixing recess  71 . 
   In particular, as shown in  FIG. 2 , the overload protecting device  72  includes a bimetal switching element  72   a  installed at the muffler and a terminal element  72   b  for connecting between the motor and the bimetal switching element  72   a . The bimetal switching element  72   a  may be connected to the winding coil  51   a  and the connection may be cut off at a pre-set temperature. At this time, by using the effect that temperature goes up according to a value of a flowing current, if the flowing current is above a pre-set value, the bimetal switching element  72   a  stops operation of the electric mechanism unit  50  to protect the electric mechanism unit  50 . 
   In addition to the overload protecting apparatus  72 , in order to prevent a damage of the electric mechanism unit  50  due to a high heat near the electric mechanism unit  50 , a second overload protecting apparatus  57  may be installed at an upper side of the stator  51  in order to measure a heat generated by the stator  51  and the rotor  52  and stop operation of the electric mechanism unit  50  in occurrence of overheat. 
   In the scroll compressor constructed as described above, the compression space (P 2 ) is formed by the fixed scroll  21  and the orbiting scroll  25  respectively having the involute shaped fixed scroll wrap  22  and orbiting scroll wrap  26 . The fixed scroll  21  is fixed and the orbiting scroll  25  makes an orbiting motion along a circle with a certain radius in a state that it is fixed not to be rotated, in order to continuously compress the fluid. 
   As compression proceeds, the check valve  40  opens the discharge passage  23  due to a pressure difference, the compressed fluid flows to the high pressure side P 3  through the discharge passage  23 , the compressed fluid of the high pressure side P 3  is discharged to outside the casing  10  through the discharge pipe  12 . 
   At this time, the overload protecting device  72  is connected to the winding coil  51   a  wound at the stator  51 , and if a temperature of the compressed fluid at the high pressure side P 3  is below a pre-set temperature, the overload protecting device  72  mounted at the fixing recess  71  of the high/low pressure separating plate  24  is maintained at the connection state as shown in  FIG. 3A . Meanwhile, if the compressed fluid has a temperature higher than the pre-set temperature, the winding coil  51   a  is disconnected to prevent an overload of the electric mechanism unit  50 , as shown in  FIG. 3B . 
   Besides, if the current flow along the winding coil  51   a  of the electric mechanism unit  50  is above the pre-set value, the winding coil  51   a  is disconnected owing to the heat generated according to the current flow, thereby preventing an overload. 
   In this manner, the overload protecting apparatus for a compressor has such a structure that the temperature of the fluid discharged to the high pressure side P 3  after being compressed in the compression unit is detected for preventing an overload, so that it can cope with an overheat of the compressor due to an abnormal operation. 
   Especially, in the scroll compressor having the high/low pressure separating plate separating into the high pressure side P 3  and the low pressure side P 1 , if the overload protecting apparatus is installed in the vicinity of the electric mechanism unit as in the conventional art, it is not possible to detect an excessive increase in the temperature of a discharged fluid due to an abnormal operation, failing to quickly cope with the overheat of the compressor. But in the case of the scroll compressor having the high/low pressure separating plate separating into the high pressure side P 3  and the low pressure side P 1  in accordance with the present invention, an excessive increase in the temperature of the discharged fluid due to an abnormal operation can be detected, so that it can quickly cope with the overheat of the compressor. 
   INDUSTRIAL APPLICABILITY 
   As so far described, the compressor of the present invention has many advantages. 
   That is, for example, first, if fluid is compressed in an overheated state due to an overheat of a motor, etc., the discharged fluid has an excessively high temperature. Then, by stopping the operation of the compressor, the compressor can be prevented from breaking down. 
   In addition, if the temperature of the discharged fluid after being compressed increases due to an abnormal operation, the compressor is stopped from operating, so that oil carbonization of oil or damage to parts according to melting can be prevented. 
   Moreover, temperature increase of the fluid discharged after being compressed due to an over-compression in or leakage from the compression unit can be prevented. 
   Furthermore, the compressor can quickly cope with an overheat or an over-compression inside the casing, so that leakage of the fluid is prevented and thus a reliability can be improved.