Cooling device and controlling method thereof for reefer container

Abstract

A cooling device and a controlling method thereof for a reefer container are disclosed. The cooling device has a controlling circuit comprising a controller; a compressor relay, a condenser fan relay and an evaporator fan relay connected in parallel; a pressure switch connected to the compressor relay in series; and a pressure sensing and controlling device for controlling the pressure switch to turn on or off. The pressure sensing and controlling device controls the pressure switch to turn off when air pressure inside container drops to a preset pressure, and controls the pressure switch to turn on when air pressure inside container rises higher than the preset pressure. The controlling method comprises steps of detecting and controlling air pressure inside container. The invention can be implemented in a simple structure and at a low cost, as only a few of electric elements are added to conventional controlling circuits.

1 . A cooling device with a controlling circuit for a reefer container, the controlling circuit comprising a compressor relay, a condenser fan relay and an evaporator fan relay which are connected in parallel, as well as a controller for controlling operating states of the compressor relay, the condenser fan relay and the evaporator fan relay, the controlling circuit further comprising: 
 a pressure switch which is connected to the compressor relay in series; and    a pressure sensing and controlling device which can control the pressure switch to turn on or off,    wherein, when the air pressure inside the container drops to a preset pressure, the pressure sensing and controlling device controls the pressure switch to turn off; and when the air pressure inside the container rises higher than the preset pressure, the pressure sensing and controlling device controls the pressure switch to turn on.    
   
   
       2 . The cooling device for a reefer container according to one of claims  1 , the controlling circuit further comprises: 
 a time delay relay which is controlled by the pressure sensing and controlling device and can delay the pressure switch to turn on, the time delay relay being connected in parallel to the pressure switch and the compressor relay connected in series,    wherein, when the air pressure inside the container drops to the preset pressure, the pressure sensing and controlling device controls a contact of the time delay relay to disconnect; and when the air pressure inside the container rises higher than the preset pressure, the pressure sensor controls the contact of the time delay relay to connect, and the time delay relay delays the pressure switch to turn on.    
   
   
       3 . The cooling device for a reefer container according to  claim 2 , wherein the pressure sensing and controlling device is a vacuum pressure switch, and the vacuum pressure switch is disposed inside the container.  
   
   
       4 . The cooling device for a reefer container according to  claim 2 , wherein the pressure sensing and controlling device comprising a controlling device and a pressure sensor which is disposed inside the container, wherein the controlling device can acquire information of the air pressure inside the container from the pressure sensor and transmit control signals.  
   
   
       5 . The cooling device for a reefer container according to  claim 1 , wherein the pressure switch and the compressor relay connected in series are connected to the condenser fan relay and the evaporator fan relay in parallel.  
   
   
       6 . The cooling device for a reefer container according to one of claims  5 , the controlling circuit further comprises: 
 a time delay relay which is controlled by the pressure sensing and controlling device and can delay the pressure switch to turn on, the time delay relay being connected in parallel to the pressure switch and the compressor relay connected in series,    wherein, when the air pressure inside the container drops to the preset pressure, the pressure sensing and controlling device controls a contact of the time delay relay to disconnect; and when the air pressure inside the container rises higher than the preset pressure, the pressure sensor controls the contact of the time delay relay to connect, and the time delay relay delays the pressure switch to turn on.    
   
   
       7 . The cooling device for a reefer container according to  claim 6 , wherein the pressure sensing and controlling device is a vacuum pressure switch, and the vacuum pressure switch is disposed inside the container.  
   
   
       8 . The cooling device for a reefer container according to  claim 6 , wherein the pressure sensing and controlling device comprising a controlling device and a pressure sensor which is disposed inside the container, wherein the controlling device can acquire information of the air pressure inside the container from the pressure sensor and transmit control signals.  
   
   
       9 . The cooling device for a reefer container according to  claim 1 , wherein the pressure switch and the compressor relay connected in series are connected to the evaporator fan relay in parallel, and the condenser fan relay is connected to the compressor relay in parallel.  
   
   
       10 . The cooling device for a reefer container according to one of claims  9 , the controlling circuit further comprises: 
 a time delay relay which is controlled by the pressure sensing and controlling device and can delay the pressure switch to turn on, the time delay relay being connected in parallel to the pressure switch and the compressor relay connected in series,    wherein, when the air pressure inside the container drops to the preset pressure, the pressure sensing and controlling device controls a contact of the time delay relay to disconnect; and when the air pressure inside the container rises higher than the preset pressure, the pressure sensor controls the contact of the time delay relay to connect, and the time delay relay delays the pressure switch to turn on.    
   
   
       11 . The cooling device for a reefer container according to  claim 10 , wherein the pressure sensing and controlling device is a vacuum pressure switch, and the vacuum pressure switch is disposed inside the container.  
   
   
       12 . The cooling device for a reefer container according to  claim 10 , wherein the pressure sensing and controlling device comprising a controlling device and a pressure sensor which is disposed inside the container, wherein the controlling device can acquire information of the air pressure inside the container from the pressure sensor and transmit control signals.  
   
   
       13 . The cooling device for a reefer container according to  claim 1 , wherein the compressor relay, the condenser fan relay and the evaporator fan relay connected in parallel are connected to the pressure switch in series.  
   
   
       14 . The cooling device for a reefer container according to one of claims  13 , the controlling circuit further comprises: 
 a time delay relay which is controlled by the pressure sensing and controlling device and can delay the pressure switch to turn on, the time delay relay being connected in parallel to the pressure switch and the compressor relay connected in series,    wherein, when the air pressure inside the container drops to the preset pressure, the pressure sensing and controlling device controls a contact of the time delay relay to disconnect; and when the air pressure inside the container rises higher than the preset pressure, the pressure sensor controls the contact of the time delay relay to connect, and the time delay relay delays the pressure switch to turn on.    
   
   
       15 . The cooling device for a reefer container according to  claim 14 , wherein the pressure sensing and controlling device is a vacuum pressure switch, and the vacuum pressure switch is disposed inside the container.  
   
   
       16 . The cooling device for a reefer container according to  claim 14 , wherein the pressure sensing and controlling device comprising a controlling device and a pressure sensor which is disposed inside the container, wherein the controlling device can acquire information of the air pressure inside the container from the pressure sensor and transmit control signals.  
   
   
       17 . A method of controlling a cooling device with a controlling device for a reefer container, the controlling circuit comprising a compressor relay, a condenser fan relay and an evaporator fan relay which are connected in parallel, as well as a controller for controlling operating states of the compressor relay, the condenser fan relay and the evaporator fan relay, the controlling circuit further comprising a pressure switch which is connected to the compressor relay in series and a pressure sensing and controlling device which can control the pressure switch to turn on or off, the method comprising the following steps: 
 a). detecting the air pressure inside the container by the pressure sensing and controlling device;    b). when the air pressure inside the container drops to a preset pressure, controlling the pressure switch to turn off by the pressure sensing and controlling device, and when the air pressure inside the container rises higher than the preset pressure, controlling the pressure switch to turn on by the pressure sensing and controlling device.    
   
   
       18 . The method of controlling a cooling device for a reefer container according to  claim 17 , wherein the controlling circuit further comprises a time delay relay which is controlled by the pressure sensing and controlling device and can delay the pressure switch to turn on, and which is connected in parallel to the pressure switch and the compressor relay connected in series, 
 wherein, at the step b), when the air pressure inside the container drops to the preset pressure, controlling a contact of the time delay relay to disconnect by the pressure sensing and controlling device, and when the air pressure inside the container rises higher than the preset pressure, controlling the contact of the time delay relay to connect by the pressure sensing and controlling device so that the time delay relay  6  is energized, and delaying the pressure switch to turn on by the time delay relay.    
   
   
       19 . The method of controlling a cooling device for a reefer container according to  claim 17 , wherein the pressure sensing and controlling device comprises a controlling device and a pressure sensor which is disposed inside the container, 
 wherein, at the step a), the air pressure inside the container is detected by the pressure sensor, and the controlling device acquires information of the air pressure inside the container from the pressure sensor and transmits control signals.