GF83.55-P-2100-02R Refrigerant Compressor, Function
GF83.55-P-2100-02R Refrigerant Compressor, Function
Component Identification:
Function
Operating mechanism
The rotary motion of the belt pulley (1) is transmitted via the refrigerant compressor shaft (13) to the stop plate (12). The rotation of the stop plate (12) is then transmitted to the pivoting swash plate (4) by means of a hinged mechanism.
The conversion of the swash plate rotary motion into the oscillating piston movement takes place via two sliding shoes (11) between the piston (6) and swash plate (4). Seven pistons (6) are connected to the swash plate (4) at equal spacings around its circumference. The damping reservoir on the pressure (5) and suction sides (7) reduces gas pulsation in the refrigerant compressor, by ensuring that the refrigerant flow remains constant. This helps to prevent noises in the compression process.
Volume regulation mechanism
The refrigerant compressor volume of between 2 % (min. swept volume) and 100 % (max. swept volume) is regulated by the externally-controllable refrigerant compressor regulating valve (8) by means of the control current.
Depending on the refrigeration capacity requested, the corresponding control current is transmitted to the refrigerant compressor control valve (8) via the AAC control and operating unit (N22).
The refrigerating capacity requirement is determined essentially by the specified values of the passenger compartment temperature, the value of the in-car temperature sensor and the air humidity. Basically, the swash plate position and thus the variable swept volume (displacement) is determined by the crankcase pressure, diaphragm pressure in the refrigerant compressor control valve (8) (approx. 2 bar) and the suction pressure as a function of the thermal load in the air conditioning system by recording, processing and evaluating the controlled variables in the air conditioning system. The change in the suction pressure as a function of the regulating current at the refrigerant compressor control valve (8) causes a change in the crankcase pressure and thus a change in the swash plate position either in the direction of max. swept volume/displacement (suction pressure = crankcase pressure; regulating current = max.) or variable swept volume (crankcase pressure > suction pressure; regulating current between min. switch-on current and max. control current; that is, min. switch-on current < regulating current < max. control current).
A/C OFF
If the air conditioning is controlled or switched off by the AC OFF button (control current at control valve = 0), the refrigerant compressor control valve (8) is fully opened.
Thus refrigerant flows freely over the high-pressure side into the crankcase (2), which, in turn, leads to a rapid increase in crankcase pressure.
The coil body (10) for closing off the refrigerant compressor displaces itself to the right up against the valve plate (9) until the refrigerant flow is fully sealed off from the suction side. The coil body (10) is designed such that at a delivery rate of 3 < 5 cm the refrigerant flow is interrupted by closing off the intake passage, even when the refrigerant compressor is active.
Internal refrigerant compressor lubrication when air conditioning switched off
The refrigerant compressor is equipped with an internal lubrication circuit to ensure that all mechanically moving parts such as sliding shoe (11), swash plate (4), front and rear radial shaft bearings and pistons (6) are supplied with lubricant. Lubrication is ensured by way of a minimum refrigerant compressor delivery rate. The delivery rate is controlled by two valves.
The minimum refrigerant compressor delivery volume of 2 % when the refrigerant compressor is switched OFF causes the refrigerant, along with the compressor oil in the crankcase, to be transported via the drilled refrigerant compressor shaft (13). The refrigerant/refrigeration oil mixture enters the cylinder housing on the suction side, is compressed and finally pumped into the air conditioning circuit on the pressure side. Refrigerant and compressor oil mixture returns through a valve from the pressure side to the crankcase (2).
Component Identification:
Control valve, function
Variable volume control in partial load range
(e.g. at lower ambient temperature or lower cooling capacity requirement).
The cooling capacity output is always dependent on the intake pressure, which means the following:
If the suction pressure (Ps) drops below the diaphragm pressure (Ps1) in the refrigerant compressor control valve and the control current is reduced at the same time, the passage from high pressure (Pd) to crankcase pressure (Pc) is released by the control plunger (2) in the refrigerant compressor control valve. As a result, refrigerant flows from the high pressure side into the crankcase, which results in an increase in crankcase pressure (Pc)
The sum of the forces on the left-hand side, resulting from the crankcase pressure (Pc), the return force of the swash plate (centrifugal force) and the spring return force is thus greater than total piston force. The swash plate is then positioned in the vertical, which leads to a reduction in the piston lift or displacement volume.
Additionally, the refrigerant output is regulated depending on the air humidity, i.e.:
at high air humidity the control valve is regulated externally (PWM signal), whereby an adjustment of the refrigerant output is achieved (prevents windows from fogging up).
The refrigerant compressor is automatically switched off at a volumetric flow of less than 5 cm(3).
Component Identification:
Control valve, function
Control at max. swept volume
(e.g. at higher ambient temperature or higher cooling capacity requirement).
If the suction pressure (Ps) rises above the diaphragm pressure (Ps1) in the refrigerant compressor control valve and the control current is increased at the same time, in the refrigerant compressor control valve the passage - high pressure (Pd) to crankcase pressure (Pc) - is closed by the control plunger (2). The crankcase pressure (Pc) drops, as no refrigerant flows from the high pressure side into the crankcase via the refrigerant compressor control valve.
In the long-term the bypass (1) sets up a pressure compensation between the suction pressure (Ps) and crankcase pressure (Pc), i.e. the reaction force on the left side from the crankcase pressure (Pc), return force of the swash plate (centrifugal force) and the spring return force is therefore smaller than the sum of the piston forces. The swash plate angle extends to beyond the "0-position ", i.e. the inclined position increases continuously to the swash plate's mechanical limit stop at the stop plate. The piston stroke increases linear to the swash plate's inclination till it reaches max. volumetric flow.
Belt pulley, function in normal operation
Under normal operating conditions the rubber (2) is deformation resistant. Thus the rubber (2) transmits the belt pulley's (3) torque to the hub (1) and at the same time to the refrigerant compressor shaft, whereby the hub (1) and belt pulley (3) turn in the direction of the arrow. This operating condition is governed by the following torque ratios:
Refrigerant compressor torque < rubber torque limit .
In this operating condition the rubber (2) acts as a shock absorber by inhibiting resonance via the belt with other engine components.
Function of belt pulley when refrigerant compressor locks up
When the refrigerant compressor locks up, the torque required for driving the refrigerant compressor is greater than the torque at the belt pulley (3). This causes slip to occur between the belt pulley (3) and hub (1) because of the deformation and wear of the rubber (2). Thus the belt pulley (3) continues to rotate even with a locked up refrigerant compressor. In this operating condition the following torque ratios occur:
Refrigerant compressor torque > rubber torque limit.
In this operating condition the rubber (2) acts as a belt pulley protector.
Pressure relief valve, function
The pressure relief valve is a pressure sensitive wax valve. It is used when all other pressure-dependent safety devices could not prevent a pressure rise in the refrigerant compressor (A9).
The wax can withstand a pressure of < 35 bar. If the pressure value increases to greater than 35 bar, the wax fuse is destroyed and a loss of pressure follows through the created opening.