System for controlling compressor of cooling system and method for controlling the same

Abstract

Disclosed is a system for controlling a compressor of a cooling system. The system includes: the compressor having a driving shaft that is rotatable clockwise and counterclockwise and operated by a power of a motor outputting different torque characteristics depending on the rotational directions of the driving shaft; a selector for selecting an output torque characteristic of the motor; a switching part for turning on or off the motor; and a control unit for controlling the selector to drive the compressor in a torque characteristic suitable for an object to be cooled. In an aspect of the invention, there is provided a method for controlling an operation of a compressor in a cooling system. The method includes the steps of: (a) an initial starting step of starting the compressor equipped with a motor different torque characteristics depending on rotary directions of a driving shaft at a first torque characteristic; (b) determining the operation torque characteristic of the motor; (c) when it is determined that the motor operates at the first torque characteristic in consequence of performing the step (b), if a first condition is met during an operation of the compressor, stopping the compressor, (d) determining whether it is suitable to continuously operate the motor at the first torque characteristic in a state that the compressor is stopped, and if it is determined that it is suitable, maintaining the operation torque characteristic of the motor, while if it is determined that it is not suitable, converting the operation torque characteristic of the motor from the first torque characteristic to a second torque characteristic, and if a second condition is met, operating the compressor.

1 . A system for controlling a compressor of a cooling system, the controlling system comprising: 
 the compressor having a driving shaft that is rotatable clockwise and counterclockwise and operated by a power of a motor outputting different torque characteristics depending on the rotational directions of the driving shaft;    a selector for selecting an output torque characteristic of the motor;    a switching part for turning on or off the motor; and    a control unit for controlling the selector to drive the compressor in a torque characteristic suitable for an object to be cooled.    
   
   
       2 . The system of  claim 1 , further comprising means for sensing information on the object to be cooled, wherein the control unit controls the selector and the switching part on the basis of information transmitted from the sensing means.  
   
   
       3 . The system of  claim 2 , wherein the sensing means comprises a temperature sensor for measuring the temperature of the object to be cooled.  
   
   
       4 . The system of  claim 1 , further comprising an overload protector provided between the motor and the switching part.  
   
   
       5 . The system of  claim 1 , wherein the motor comprises: 
 a first winding connecting a first terminal and a common terminal and rotating the driving shaft in a first torque characteristic; and    a second winding a second terminal and the common terminal and rotating the driving shaft in a second torque characteristic.    
   
   
       6 . The system of  claim 5 , wherein the selector comprises: 
 a first contact point connected with the first terminal;    a second contact point connected with the second terminal; and    a common contact point connected with a power and selected connected to the first contact point or the second contact point.    
   
   
       7 . The system of  claim 1 , wherein the switching part comprises a thermostat of which contact point is turned on or off depending on the temperature of the object to be cooled.  
   
   
       8 . The system of  claim 7 , further comprising means for determining whether the motor is turned on or off.  
   
   
       9 . The system of  claim 8 , wherein the determining means comprises a current sensor for sensing a current through the switching part.  
   
   
       10 . The system of  claim 8 , wherein the control unit controls the selector on the basis of whether the motor is turned on or off and an elapse of time.  
   
   
       11 . The system of  claim 7 , further comprising a second switching part connected in series with the switching part, wherein the control unit controls the selector and the second switching part on the basis of the elapse degree of time.  
   
   
       12 . The system of  claim 1 , wherein the compressor comprises: 
 the driving shaft having a predetermined sized eccentric part and being rotatable clockwise and counterclockwise;    a cylinder forming a predetermined inner volume;    a roller rotating in contact with an inner circumference of the cylinder, installed rotatably on an outer circumference of the eccentric part, performing a rolling motion along the inner circumference and forming a fluid chamber to suck and compress fluid along with the inner circumference;    a vane installed elastically in the cylinder so as to be in contact with the roller continuously, and partitioning the fluid chamber into two independent spaces;    upper and lower bearings installed respective at upper and lower sides of the cylinder, for rotatably supporting the driving shaft and sealing the inner volume;    discharge ports communicating with the fluid chamber;    discharge valves for opening the respective discharge ports at a predetermined pressure or more; and    at least one suction port communicating with the fluid chamber.    
   
   
       13 . The system of  claim 12 , wherein the suction and discharge ports are formed in the cylinder.  
   
   
       14 . The system of  claim 13 , wherein the discharge ports are spaced apart by a predetermined distance to face with each other with respect to the vane.  
   
   
       15 . The system of  claim 14 , wherein the suction port is one that is located to face with the vane on an imaginary line passing on the vane.  
   
   
       16 . The system of  claim 14 , wherein the suction port is located at a side on an imaginary line passing on the vane.  
   
   
       17 . The system of  claim 12 , wherein the suction and discharge ports are formed in the bearing, further comprising a valve assembly for selectively opening one of the suction ports depending on the rotary direction of the driving shaft.  
   
   
       18 . The system of  claim 17 , wherein the discharge ports comprise first and second discharge ports that are located to face with each about the vane.  
   
   
       19 . The system of  claim 17 , wherein the suction port comprises: 
 a first suction port located adjacent to the vane; and    a second suction port spaced apart by a predetermined angle from the first suction port with respect to a center of the cylinder.    
   
   
       20 . The system of  claim 17 , wherein the roller compresses the fluid by using the overall fluid chamber when the driving shaft rotates only in either the clockwise direction or counterclockwise direction.  
   
   
       21 . The system of  claim 17 , wherein the roller compresses the fluid by using a part of the fluid chamber when the driving shaft rotates only in either the clockwise direction or counterclockwise direction.  
   
   
       22 . The system of  claim 19 , wherein the valve assembly comprises: 
 a first valve installed rotatably between the cylinder and the bearing and having a penetration hole through which the driving shaft is inserted; and    a second valve fixed between the cylinder and the bearing, having a site portion accommodating the first valve, and for guiding a rotary motion of the first valve.    
   
   
       23 . The system of  claim 22 , wherein the first valve is comprised of a circular plate member that is in contact with the eccentric part of the driving shaft to rotate in the rotary direction of the driving shaft.  
   
   
       24 . The system of  claim 22 , wherein the first valve comprises: 
 a first opening communicating with the first suction port when the driving shaft rotates in one of the clockwise direction or the counterclockwise direction; and    a second opening communicating with the second suction port when the driving shaft rotates in the other the clockwise direction or the counterclockwise direction.    
   
   
       25 . The system of  claim 24 , wherein the suction port further comprises a third suction port located on the second suction port and the vane, and the first opening no sooner opens the third suction port than the second suction port is opened.  
   
   
       26 . The system of  claim 22 , wherein the valve assembly further comprises means for controlling a rotary angle of the first valve so as to precisely open the corresponding suction port with respect to each rotary direction.  
   
   
       27 . The system of  claim 26 , wherein the control means comprises: 
 a protruded portion protruded in a radius direction of the first valve; and    a groove formed in the second valve and accommodating the protruded portion movably.    
   
   
       28 . A cooling system comprising: 
 a compressor having a driving shaft that can be rotatable clockwise and counterclockwise and operated by a power of a motor outputting different torque characteristics depending on the rotational directions of the driving shaft;    a compressor control part including a selector for selecting an output torque characteristic of the motor; a switching part for turning on or off the motor; and a micom for controlling the selector to operate the compressor at a torque characteristic suitable for an object to be cooled;    first and second heat exchangers which heat-exchange coolant forcibly delivered from the compressor with an indoor or an outdoor respectively; and    an expansion unit provided in a coolant tube connecting the first and second heat exchangers.    
   
   
       29 . A method for controlling an operation of a compressor in a cooling system, the method comprising the steps of: 
 (a) an initial starting step of starting the compressor equipped with a motor different torque characteristics depending on rotary directions of a driving shaft at a first torque characteristic;    (b) determining the operation torque characteristic of the motor,    (c) when it is determined that the motor operates at the first torque characteristic in consequence of performing the step (b), if a first condition is met during an operation of the compressor, stopping the compressor;    (d) determining whether it is suitable to continuously operate the motor at the first torque characteristic in a state that the compressor is stopped, and if it is determined that it is suitable, maintaining the operation torque characteristic of the motor, while if it is determined that it is not suitable, converting the operation torque characteristic of the motor from the first torque characteristic to a second torque characteristic, and if a second condition is met, operating the compressor.    
   
   
       30 . The method of  claim 29 , wherein the first torque characteristic has a torque greater than the second torque characteristic.  
   
   
       31 . The method of  claim 30 , wherein the first condition is a question ‘Is the temperature of an object to be cooled below a lower limit of a set temperature?’.  
   
   
       32 . The method of  claim 31 , wherein the step (c) comprises the step of (c0) computing an absolute value (P) of an average temperature variation rate of the object to be cooled during a predetermined time period while the compressor operates.  
   
   
       33 . The method of  claim 32 , wherein the step (d) comprises the steps of: 
 (d1) determining a conversion condition of the torque characteristic in the state that the compressor is stopped, and if the conversion condition is met, converting the torque characteristic of the motor to the second torque characteristic;    (d2) determining the conversion condition of the torque characteristic in the state that the compressor is stopped, and if the conversion condition is not met, maintaining the torque characteristic of the motor at the first torque characteristic; and    (d3) after the step (d1) or (d2), if the second condition is met, operating the compressor while if the second condition is not met, continuing to determining whether the second condition is met or not.    
   
   
       34 . The method of  claim 33 , wherein the conversion condition of the torque characteristic is a question “Does an absolute value (P) of average temperature variation rate of the object to be cooled exceed a critical value (P+) of an absolute value of temperature variation rate for torque characteristic conversion of the motor?”.  
   
   
       35 . The method of  claim 33 , wherein the second condition is a question “Does the temperature of the object to be cooled exceed an upper limit of a set temperature?.  
   
   
       36 . The method of  claim 29 , wherein the step (b) is performed after the step (d).  
   
   
       37 . The method of  claim 36 , further comprising, when it is determined that the motor operates at the second torque characteristic as a result of performing the step (b), the step (e) determining whether or not it is proper to operate the motor at the second torque characteristic based on the state of the object to be cooled and stopping the compressor.  
   
   
       38 . The method of  claim 37 , wherein the step (e) comprises the steps of: 
 (e1) measuring an absolute value (P) of an average temperature variation rate of the object to be cooled for a selected time interval while the compressor operates;    (e2) determining whether the absolute value (P) of the average temperature variation rate of the object to be cooled is less than an absolute value (P−) of a preset minimum temperature variation rate for a selected time interval; and    (e3) if the step (e2) is met, determining that it is not proper to operate the motor at the second torque characteristic and stopping the compressor.    
   
   
       39 . The method of  claim 38 , further comprising the step (e4) of, determining whether the temperature of the object to be cooled is less than the lower limit of the set temperature, if so, determining that it is proper to operate the motor at the second torque characteristic and stopping the compressor.  
   
   
       40 . The method of  claim 39 , when in the step (e4), it is determined that the temperature of the object to be cooled is equal to or greater than the lower limit of the set temperature, further comprising the step of returning to the step (e1).  
   
   
       41 . The method of  claim 38 , further comprising the steps of: 
 (f) if a compression key is stopped by the step (e3), after a time delay, converting the torque characteristic of the motor to the first torque characteristic; and    (g) after the step (f), driving the motor to operate the compressor, and going to the step (b).    
   
   
       42 . The method of  claim 39 , further comprising the step of, if the compressor is stopped by the step (e4), driving the motor and operating the compressor when the temperature of the object to be cooled meets an upper limit of the set temperature, and going to the step (b).  
   
   
       43 . The method of  claim 30 , wherein the first condition is a question “Is the compressor turned off?”.  
   
   
       44 . The method of  claim 43 , wherein whether or not the compressor is stopped is determined by On or Off of a motor switching part which is automatically turned on or off by a condition of the object to be cooled.  
   
   
       45 . The method of  claim 44 , wherein whether or not the compressor is stopped is determined by whether or not current is sensed by a current sensor connected in series to the motor switching part.  
   
   
       46 . The method of  claim 43 , wherein the step (c) comprises the step (c5) of counting an elapse time.  
   
   
       47 . The method of  claim 46 , wherein the step (d) comprises the steps of: 
 (d5) determining the conversion condition of the torque characteristic in a stop state of the compressor, and if the conversion condition is met, converting the torque characteristic to the second torque characteristic;    (d6) determining the conversion condition of the torque characteristic in the stop state of the compressor, and if the conversion condition is not met, maintaining the first torque characteristic;    (d7) resetting the elapse time after the step (d5) or (d6); and    (d8) after the step (d7), if the second condition is met, operating the compressor, and if the second condition is not met, continuing to determining whether or not the second condition is met.    
   
   
       48 . The method of  claim 47 , wherein the conversion condition of the torque characteristic is a question “doesn't the elapse time reach a minimum limit time? 
   
   
       49 . The method of  claim 47 , wherein the second condition is a question “Is the compressor turned on?”.  
   
   
       50 . The method of  claim 47 , wherein the step (b) is performed after the step (c).  
   
   
       51 . The method of  claim 50 , after the step (b), when it is determined that the motor operates at the second torque characteristic, determining whether or not it is proper to operate the motor at the second torque characteristic based on whether or not a predetermined time elapses, and stopping the compressor the compressor.  
   
   
       52 . The method of  claim 51 , wherein the step (k) comprises the steps of: 
 (k1) counting an elapse time (T) while the compressor operates;    (k2) determining whether the elapse time (T) exceeds a preset maximum limit time (T+) or the elapse time (T) is under a preset start success determining time (Tt) of the compressor; and    (k3) if the step (k2) is met, determining that it is not proper to operate the motor at the second torque characteristic and stopping the compressor.    
   
   
       53 . The method of  claim 52 , further comprising the step of (k4), if the step (k2) is not met, determining whether or not the compressor is in Off-state, and if the compressor is in Off-state, determining that it is proper to operate the motor at the second torque characteristic.  
   
   
       54 . The method of  claim 53 , further comprising the step of ( 1 ) after the step (k4), resetting the elapse time (T).  
   
   
       55 . The method of  claim 53 , further comprising the step of, in the step (k4), if it is determined that the compressor is not in Off-state, returning to the step (k1).  
   
   
       56 . The method of  claim 54 , after the step ( 1 ), determining whether the compressor is turned on, if it is determined that the compressor is turned on, returning to the step (b), and if it is determined that the compressor is not turned on, returning to the step ( 1 ).  
   
   
       57 . The method of  claim 52 , further comprising the steps of: 
 (n) if the compressor is stopped by the step (k3), after a predetermined time delay, converting the torque characteristic of the motor to the first torque characteristic; and    (o) after the step (n), resetting the elapse time (T), operating the compressor and then returning to the step (b).