Compressor HVAC
Compressor
1. GENERAL
The vane rotor type compressor turns around the center axis of the elliptical cylinder, and the vanes, with their ends in contact with the inside wall of the cylinder, move up and down the rotor grooves. The vanes are positioned around the rotor, each equally spaced apart from another. Both sides of the cylinder are sealed by side blocks. The space, enclosed by the neighboring vanes, two side blocks, outer circumference of the rotor and inside wall of the cylinder, becomes smaller as the rotor turns, thereby compressing the internal gas. When the end of a vane sliding on the inside wall of the cylinder goes past the suction port, the vane closes the suction port. The compression stroke at the position. When the gas ahead of the vane is compressed and discharged through the discharge valve, the next vane is already on the suction stroke. Since suction and compression of the gas are separately performed in this manner, the compressed gas left behind in the discharge port never returns to the suction port. Since no suction valve is required, there is no loss caused by a suction valve. (A low pressure check valve is provided on the front head and a high pressure trigger valve provided on the rear head to apply a pressure to the back plane of vane.)
2. FUNCTION
During the period the truly round rotor turns through halt a rotation (180 degrees), a cycle of the suction, compression and discharge strokes is completed. Each time the rotor turns through a rotation (360 degrees), the vanes complete two cycles each, or 10 cycles in total.
1. Suction
The refrigerant gas, that leaves the evaporator as the compressor turns, enters the low pressure chamber of the compressor, and is drawn in from the suction port as the vanes turn.
2. Compression
When suction is completed, the refrigerant gas in the cylinder chamber enclosed by the vanes is compressed as the vanes rotate. In this case, air tightness between the vane ends and cylinder inside surface is maintained by a lubricant.
3. Discharge
When continuous compression causes the pressure in the cylinder chamber to rise to the extent that the pressure exceeds the pressure in the high pressure chamber, the refrigerant gas is discharged. Even when the pressure in the cylinder chamber is lower than that in the high pressure chamber, the cylinder gas never flows back to the cylinder chamber, as the discharge valve is pressed into the closed position by the pressure in the high pressure chamber.
The compressor repeated the above-mentioned cycle. Each time the rotor turns through a rotation, the five chambers partitioned by the vanes in the cylinder go through the suction, compression and discharge strokes twice each.
3. TRIGGER VALVE
To ensure that when the compressor is started, the vanes move out smoothly under all conditions, and minimize the noise that will be produced when the vanes strike the cylinder at the time, a mechanism combining the low pressure side check valve and high pressure side trigger valve has been adopted. When the vehicle is parked for a long period in the middle of summer for example, the suction side pressure may be slightly higher than the discharge side pressure. When the compressor is started under such a condition, the low pressure side check valve introduces the low pressure side gas to the back plane of vane, thereby causing the vane to move out.
When the compressor starts compression, the check valve is closed by the vane back pressure. When the balance pressure or discharge side pressure is slightly higher, the high pressure side trigger valve, immediately after the compressor has been started, introduces the high pressure side pressure to the back plane of vane, thereby causing the vane to move out.
When the compressor normally starts compression and causes the discharge pressure to rise, the trigger valve closes.
1. When compressor is stopped
The pressure in the compressor is maintained constant, as the valves are kept in the opened state by springs.
2. When compressor is restarted
When the compressor resumes rotation, the high pressure side trigger valve is placed in the opened state, thereby applying the high pressure side pressure directly to the back plane of vane to cause the vane to move out.
3. When compressor is in regular operation
When the high pressure side pressure rises to the extent that it overcomes spring action, the valve closes, and the centrifugal force causes the vane to move out.
4. COMPRESSOR SAVING SENSOR
The compressor saving sensor, mounted on the surface of the compressor case, forces the compressor to the OFF state when the gas temperature rises or the case surface temperature becomes abnormally high due to poor lubrication.
When the compressor case surface temperature falls, the compressor restarts.
5. MAGNET CLUTCH
The magnet clutch serve to transmit engine power to the compressor unit. It is built into the compressor shaft. When current flow through the magnet clutch coil, the drive plate is attracted so that the pulley and compressor shaft rotate as a unit. When the compressor is not in use, the pulley alone rotates freely.