A/C Compressor
Design:
- A total of seven pistons (6) with the same pitch are connected around the circumference of the swash plate (4) by means of sliders (10).
- The swash plate (4) is connected to the stop plate (12) in the crankcase (2) by two guide pins (3) and mounted flexibly on the A/C compressor shaft (13).
- The stop plate (12) and pulley (1) are permanently mounted on the A/C compressor shaft (13).
- The externally actuated A/C compressor control valve (8) for adjustment of the swash plate (4) is located in the rear section of the housing.
A/C compressor, purpose
The A/C compressor is responsible for sucking in and compressing the refrigerant.
- A total of seven pistons (6) with the same pitch are connected around the circumference of the swash plate (4) by means of sliders (10).
- The swash plate (4) is connected to the stop plate (12) in the crankcase (2) by two guide pins (3) and mounted flexibly on the A/C compressor shaft (13).
- The stop plate (12) and pulley (1) are permanently mounted on the A/C compressor shaft (13).
- The externally actuated A/C compressor control valve (8) for adjustment of the swash plate (4) is located in the rear section of the housing.
A/C compressor, purpose
The A/C compressor is responsible for sucking in and compressing the refrigerant.
Component Identification:
Function
Operation
The rotary motion of the pulley (1) is transferred by the A/C, compressor shaft (13) to the stop plate, (12) which is permanently connected, to the A/C compressor shaft (13) with a pressed fit. The rotation of the stop plate (12) is transferred to the pivoting swash plate (4) by an articulated mechanism. The conversion of the swash plate rotation to an oscillating motion is accomplished by two sliders (10) between the piston (6) and swash plate (4). Six pistons (6) with the same pitch are connected at the circumference of the swash plate (4). Damping reservoirs on the pressure side (5) and intake side (7) reduce the gas pulsation in the A/C compressor by providing for a uniform refrigerant flow. This helps avoid noises in the compression process.
Volume control mechanism
The A/C compressor volume is changed between 2 % (minimum stroke volume) and 100% (max. stroke volume) by the control flow via the externally controlled A/C compressor control valve (8). The appropriate control flow is given to the A/C compressor control valve (8) via the automatic A/C pushbutton control module depending on the refrigeration requirement.
The refrigeration requirement is determined primarily by the temperature setting for the vehicle passenger compartment and the value measured by the in-car temperature sensor. The swash plate position and therefore the variable stroke volume is determined by the crankcase pressure, the diaphragm pressure in the A/C compressor control valve (approx. 2 bar) and the intake pressure as a function of the thermal load in the air conditioning system by measuring, processing and evaluating the control variables/parameters in the air conditioning system. A change in the intake pressure depending on the control flow at the A/C compressor control valve (8) causes a change in the crankcase pressure and therefore the, swash plate position either in the direction of max. stroke volume (intake pressure = crankcase pressure; control flow = max.) or variable stroke volume (crankcase pressure > intake pressure; control flow between min. switch-on flow rate and max. control flow, i.e. min. switch-on flow < control flow < max. control flow).
Regulation of A/C compressor output depending on humidity
The A/C compressor output is regulated in relation to humidity measured by the multifunction sensor as follows:
Humid outdoor air
If the outdoor air is humid the A/C compressor operates at max. output, i.e. the evaporator temperature is cold (approx. 2 °C), so that the air is dried to a high degree.
In the heater mode the air is reheated as required in the heater core.
Dry outdoor air
If the outdoor air is dry the A/C compressor operates at lower output, i.e. the evaporator temperature can then be up to approx. 14 °C when the required air exit temperature is not lower.
Air conditioning OFF
If the air conditioning is switched off with the automatic A/C pushbutton control module or the EC button (control current on control valve = 0), the A/C compressor control valve (8) is opened completely. This allows refrigerant to flow unimpeded into the crankcase (2) to the high pressure side leading to an extremely rapid increase in the crankcase pressure. The coil element (10) for closing the A/C compressor moves to the right against the valve plate (9) until the refrigerant flow is shut off completely on the intake side. The coil element (10) is designed so that the refrigerant flow is interrupted by closing the intake passage at a flow rate of < 5 cubic cm even when the A/C compressor is switched on.
Internal A/C compressor lubrication with air conditioning switched off
The A/C compressor (7SE16C) has an internal lubrication circuit to ensure, supply of lubrication oil to the parts moving mechanically in relation to one another such as the slider/swash plate, front and rear radial shaft bearing and piston/cylinder sleeve. The lubrication is ensured by minimum A/C compressor output volume. This output volume is regulated by the A/C compressor control valve (1) and the valve (2) controlled by spring force. The minimum A/C compressor output volume of 2 % with the A/C compressor OFF ensues that refrigerant with the compressor oil located in the crankcase is transported through the hollow A/C compressor shaft (Pc => Ps).
The refrigerant/refrigeration oil mixture enters into the crankcase on the intake side is compressed and then pumped into the air conditioning circuit on the output side (Ps => Pd). From the output side the refrigerant/compressor oil mixture flows back through the open passage in the control valve (Pd => Pc open) into the crankcase.