Control device for variable displacement type compressor

A control device for controlling displacement of a variable displacement type compressor for an air conditioning apparatus, the compressor having a suction pressure region, a discharge pressure region and a crank chamber in a housing, the displacement being variable according to the pressure in the crank chamber, the control device comprising:

• a first passage defined in the housing communicating with the discharge pressure region;
• a second passage defined in the housing communicating with the suction pressure region;
• a third passage defined in the housing communicating with the crank chamber;
• a displacement control valve placed in the first passage for adjusting an opening degree of the first passage;
• an auxiliary valve placed between the suction pressure region and the crank chamber in the housing connecting the first passage and the second passage to the third passage, the auxiliary valve comprising;
• a valve chamber defined in the housing, the valve chamber having an inner surface;
• a spool valve accommodated in the valve chamber so as to slide relative to the inner surface, on which the third passage is open, the spool valve dividing the valve chamber into a first pressure chamber and a second pressure chamber, to communicate the first pressure chamber with the first passage and to communicate the second pressure chamber with the second passage;
• and
• an urging means placed in the valve chamber for urging the spool valve toward the first pressure chamber,
• wherein the third passage communicates with the first pressure chamber and/or the second pressure chamber by the movement of the spool valve due to the differential pressure between the first pressure chamber and the second pressure chamber, which varies in accordance with the opening degree of the first passage.