Variable Displacement Compressor
V-6 Variable Displacement CompressorGENERAL INFORMATION
1. The V-6 variable compressor differs from previous units. The vent temperatures of the V-6 variable compressor do not drop too far below 5 °C (41 °F) when:
Evaporator intake air temperature is less than 20 °C (68 °F). Engine is running at speeds less than 1500 rpm.
This is because the V-6 compressor provides a means of "capacity control".
2. The V-6 variable compressor provides refrigerant control under varying conditions. During cold winters it may not produce high refrigerant pressure discharge (compared to previous units) when used with air conditioning systems.
3. A "clanking" sound may occasionally be heard during refrigerant charge. The sound indicates that the tilt angle of the swash plate has changed and is not a problem.
4. For air conditioning systems with the V-6 compressor the clutch remains engaged unless: the system main switch fan switch or ignition switch is turned OFF. When ambient (outside) temperatures are low or when the amount of refrigerant is insufficient the clutch is disengaged to protect the compressor.
DESCRIPTION
General
The variable compressor is basically a swash plate type that changes piston stroke in response to the required cooling capacity.
The tilt of the swash plate allows the piston's stroke to change so that refrigerant discharge can be continuously changed from 14.5 to 184 cu.cm (0.885 to 11.228 cu in).
Operation
1. Control Valve
- By changing high-pressure valve lift amount built-in compressor control valve executes the following:
- Controls high-pressure valve discharge amount.
- Changes crankcase pressure in compressor. Changes angle of swash plate.
- Amount of high-pressure valve lift is determined by factors.
- Low pressure applied to diaphragm
- Spring load of set spring
- Balance of magnetic force generated in magnet coil
- Electronic control valve (ECV) magnet coil receives electric signal from auto amplifier (display and NC auto amp.). Then magnetic force generated by electric current is changed to control high-pressure valve lift amount.
2. Maximum Cooling
High pressure valve is closed by magnetic force generated by electric signal sent from automatic amplifier. At this time cylinder moves full stroke due to pressure balance between inside crankcase (Pc) and suction line (Ps).
Under this condition the swash plate is set to the maximum stroke position.
3. Capacity Control
When no electric signal is sent from automatic amplifier (current: OFF) high pressure valve is opened by spring force.
Since suction pressure is low it makes the suction port close and the discharge port open. Thus crankcase pressure becomes high as high pressure enters the crankcase.
- The force acts around the journal pin near the swash plate and is generated by the pressure difference before and behind the piston.
The drive lug and journal pin are located where the piston generates the highest pressure. Piston pressure is between suction pressure Ps and discharge pressure Pd which is near suction pressure Ps. If crankcase pressure Pc rises due to capacity control the force around the journal pin makes the swash plate angle decrease and also the piston stroke decrease. In other words crankcase pressure increase triggers pressure difference between the piston and the crankcase. The pressure difference changes the angle of the swash plate.