Mazda Training manual - part 263

Air Conditioning Fundamentals

TC070-05-01S

5 – AIR CONDITIONING   
COMPONENTS 

 

26

COMPRESSOR 
 
The compressor (Figure 10) is the refrigerant pump for the A/C system. 
A drive belt and pulley connect the compressor to the engine 
crankshaft, which provides the power to operate the compressor. It 
draws in warm, low-pressure vapor from the evaporator, drastically 
raises the pressure (and temperature) of the vapor, and then passes it 
on to the condenser. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
The compressor operates only with refrigerant in its gaseous state. 
Liquid refrigerant in the compressor will lock it up, damaging the 
compressor and other A/C components. 

 

 

There are two types of compressors commonly used today. 

 

1. Axial (Piston-Type) 

 

2. Vane (Non-piston-Type) 

 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
 
 
 
 
 
 
 
 

FIGURE 10. The 
compressor draws in 
warm, low-pressure 
vapor from the 
evaporator and 
compresses it into a 
hot, high- pressure 
vapor, which moves 
on to the condenser. 

 

Air Conditioning Fundamentals

TC070-05-01S

5 – AIR CONDITIONING   
COMPONENTS 

 

27

 
 
 
 
 
FIGURE 11. An axial 
compressor draws in 
low-pressure vapor, 
compresses it in a 
cylinder, and outputs 
high-pressure vapor. 
 

Piston on 
downstroke 

 

Inlet valve   

 

Low-pressure 

vapor (from 
evaporator) 

 

Piston on 

upstroke  

 

High-pressure 
vapor (to 
condensor) 

 

Axial (Piston-Type) Compressors 

 

Axial compressors create suction and pressure as shown in Figure 11. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Piston movement pressurizes the refrigerant vapor as follows: 

 

The piston moves down in the cylinder, creating suction. 

  The discharge valve closes and the inlet valve opens. 

  Low-pressure refrigerant vapor is drawn into the cylinder. 

 

The piston starts to move up again. The inlet valve closes, 
causing the pressure in the cylinder to rise. 

  When the piston nears the top of its stroke, the discharge valve 

opens. The piston forces the high-pressure vapor out of the 
cylinder, into the discharge line to the condenser. 

 

 
 

Discharge valve 

Air Conditioning Fundamentals

TC070-05-01S

5 – AIR CONDITIONING   
COMPONENTS 

 

28

The cylinders on an axial compressor face toward the front and back 
of the compressor, along its axis, as shown in Figure 12. The main 
drive shaft has a round plate, called a swash plate, mounted to the 
shaft on an angle. As the shaft turns, the outer edge of the plate 
moves back and forth. This action moves the pistons back and forth 
in their cylinders. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
There are two different configurations of axial compressors: 

 

1. Double-ended piston axial compressors 

 

2. Single-ended piston axial compressors. 

 

 

 

Double-Ended Piston Axial Compressors 

 

Axial compressors have double-ended pistons that straddle the 
swash plate. Each piston has two opposing cylinders. As one end of 
the piston moves back in one cylinder, the other end of the piston 
moves forward in the opposing cylinder. 
 
 
 
 
 
 

 
 
 
 
 
 
 
 
 
FIGURE 12. 
Double-ended piston 
axial compressors 
have pistons that 
straddle the swash 
plate. 
 

Hemisphere shoe 

Piston 

Thrust bearing 

Shaft seal 
Felt 

Shaft 

Front housing 

Cylinder 

Rear housing 

Discharge valve 

Steel gasket 

Valve plate 
Suction valve 
Swash plate 

 

Air Conditioning Fundamentals

TC070-05-01S

5 – AIR CONDITIONING   
COMPONENTS 

 

29

 

 
 
 
 
 

FIGURE 13. 
Single-ended 
piston axial 
compressors 
have all pistons 
and cylinders 
mounted 
side-by-side in 
the compressor, 
facing the same 
direction.

 

Shaft 

Swash plate

 

Rod

 

Piston

 

Cylinder

 

Drain Plug 

 

 

Single-Ended Piston Axial Compressors 
 
Single-ended piston axial compressors have all their pistons and cylinders 
mounted side-by-side in the compressor, facing the same direction, as 
shown in Figure 13. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 

Just as with the double-ended piston axial compressor, the pistons travel 
along the outer edge of the swash plate, connected to a similar plate by 
connecting rods and ball-sockets. As the swash plate turns, it moves the 
adjoining plate, which moves pistons back and forth in the cylinders. 

 

 

 

Vane (Non-Piston-Type) Compressors 

 

The vane-type compressor (see Figure 14) operates in a similar way to air 
pumps, power steering pumps, and other impeller-style pumps. The vanes 
in some compressors are driven outward by centrifugal force as well as the 
pressure behind the back of the vane. 
 
 
The benefit of the vane-type compressor is that there is no efficiency loss 
from reciprocating pistons. The compressor provides low-friction operation 
by having vanes and a rotor in an elliptical housing. The vanes compress 
the refrigerant vapor into a smaller area and push it through spring-loaded 
discharge reed valves.