Gas Compressor

Abstract

In order to reduce operation in a rotation-prohibited frequency range and to prevent resonance in a gas compressor wherein inverter control is performed, this gas compressor has: a compressor main body that compresses a gas; a motor that rotationally drives the compressor main body; an inverter that changes the rotational speed of the motor; a check valve arranged downstream from the compressor main body; a pressure detection means that detects load-side pressure downstream from the check valve; and a control device that, in accordance with the pressure detected by the pressure detection means, controls the frequency output by the inverter. The control device performs a control whereby compressed gas having a prescribed pressure is generated/maintained by increasing/decreasing the frequency, and when the frequency that generates the compressed gas having the prescribed pressure includes a specific frequency, the inverter's output frequency is increased or decreased when the pressure detected by the pressure detection means reaches a pressure corresponding to a frequency that has a more constant pressure width than the prescribed pressure and does not include the specific frequency.

1 . A gas compressor comprising:
 a compressor main body that compresses gas;   a motor that drives and rotates the compressor main body;   an inverter that changes a rotational speed of the motor;   a check valve that is arranged downstream of the compressor main body;   pressure detection means that detects a load-side pressure downstream of the check valve; and   a controller that controls an output frequency from the inverter according to the pressure detected by the pressure detection means, wherein   the controller performs control to generate and keep compressed gas with a predetermined pressure by control of increasing and decreasing the frequency, and   in a case where a specific frequency is included in a frequency at which to generate the compressed gas with the predetermined pressure, the controller increases or decreases the output frequency from the inverter when the pressure detected by the pressure detection means reaches a pressure which is higher or lower than the predetermined pressure by a certain pressure margin and which corresponds to a frequency not including the specific frequency.   
     
     
         2 . The gas compressor according to  claim 1 , wherein
 the controller decreases the output frequency to a frequency not including the specific frequency when the detected pressure is higher than the predetermined pressure, and increases the output frequency to a frequency not including the specific frequency when the detected pressure is lower than the predetermined pressure.   
     
     
         3 . The gas compressor according to  claim 1 , wherein
 the frequency not including the specific frequency has a predetermined range to the frequency the frequency at which to generate the compressed gas with the predetermined pressure.   
     
     
         4 . The gas compressor according to  claim 1 , comprising input means that inputs, to the controller, the predetermined pressure, the specific frequency, the frequency not including the specific frequency, and a pressure not including the specific frequency. 
     
     
         5 . The gas compressor according to  claim 1 , comprising display means that displays the predetermined pressure, the specific frequency, the frequency not including the specific frequency, and a pressure not including the specific frequency. 
     
     
         6 . The gas compressor according to  claim 1 , wherein the specific frequency is a resonant frequency. 
     
     
         7 . A gas compressor, comprising:
 a compressor main body that compresses gas;   a motor that drives and rotates the compressor main body;   an inverter that changes a rotational speed of the motor;   a check valve that is arranged downstream of the compressor main body;   air release means that releases the compressed gas upstream of the check valve;   pressure detection means that detects a load-side pressure downstream of the check valve; and   a controller that controls an output frequency from the inverter according to the pressure detected by the pressure detection means, wherein   the controller controls a no-load operation to generate and keep compressed gas with a predetermined pressure by releasing the compressed gas from the air release means and decreasing the frequency, and   in a case where a specific frequency is included in a frequency at which to generate the compressed gas with the predetermined pressure, the controller increases the output frequency to a frequency where the detected pressure has a pressure width than a certain pressure margin and which does not include the specific frequency when the pressure detected by the pressure detection means is lower than the predetermined pressure, and thereafter keeps the frequency until a pressure higher than the predetermined pressure is detected.   
     
     
         8 . The gas compressor according to  claim 7 , wherein the pressure higher than the predetermined pressure is a lower limit pressure at which to switch the no-load operation to a load operation. 
     
     
         9 . The gas compressor according to  claim 8 , wherein the load operation is an operation with the air release means closed. 
     
     
         10 . The gas compressor according to  claim 7 , comprising input means that inputs, to the controller, the predetermined pressure, the specific frequency, the frequency not including the specific frequency, and a pressure not including the specific frequency. 
     
     
         11 . The gas compressor according to  claim 7 , comprising display means that displays the predetermined pressure, the specific frequency, the frequency not including the specific frequency, and a pressure not including the specific frequency. 
     
     
         12 . The gas compressor according to  claim 7 , wherein the specific frequency is a resonant frequency.