Auto Air Conditioning Compressor Runs Entire System

When considering how air is cooled in your home or in your car, the auto air conditioning compressor works exactly the same as the one in your house or office. Its job is to move hot air and humidity from an evaporator inside your vehicle to a condenser outside the vehicle by compressing gas inside the system. Without a properly functioning auto air conditioning compressor the cooling effects of the system is nullified.
Since the 1940’s people have been able to ride in comfort the same as they have had the comfort of air conditioning in their homes and in extremely hot and humid climates have been able to enjoy the effects of air conditioning seamlessly, except for short walks between their home and car, and from their car to work. However, if something goes wrong with the auto air conditioning compressor the transit will be much warmer.
The auto air conditioning compressor is essentially a pump with an intake side and a discharge side. On the intake side, refrigerant is pulled from the output of the evaporator coils located inside the vehicle. Inside the auto air conditioning compressor the gas is compressed and sent to the condenser on the outside of the vehicle, along with the heat and humidity drawn from the vehicle.
Newer Requirements Help Protect Environment
In the early days of air conditioning, the gases used in the system were considered dangerous and some, like propane had explosive potential. A gas referred to as R-12, known by its trade name of Freon, has been determined to cause damage to the Earth’s ozone atmosphere. As a result, technicians have to be certified to work with it, or even buy it and in all cases when an air conditioning system is opened the gas must be captured through specialized equipment.
Whenever work is done on an auto air conditioning compressor it must be done by a certified technician and in cases where the compressor must be replaced, a newer upgraded model may be required. A newer gas R-134a is being required in all vehicles after 2010, and if the vehicle is going to have its system filled with the new gas it will also have to be retrofitted with a new auto air conditioning compressor that can produce the higher pressure needed for this gas.
Since the technician has to pay more for the expensive equipment and the gas repair costs are going to be higher as well. Car owners will need to make the decision about paying the cost to replace their auto air conditioning compressor, driving in the heat or perhaps replacing the vehicle.
Roland Parris Jefferson III is an online researcher based out of Los Angeles, California. For free tips, tricks and expert advice on air conditioning, please visit our Auto Air Conditioning Compressor Resource.
Article Source: http://EzineArticles.com/?expert=Roland_Jefferson

Assembly of counter-balance weight of hermetic reciprocating compressor for refrigeration

The assembling process can be divided into two main stages: In the first stage, the sub-assembly of the balancing weight. This involves joining the Crank Weight to the Crank Weight Base by resistance welding. The next stage is to assemble the counter-balance weight to the crankshaft eccentric. The details of the two assembly stages are as follows:

Stage One: Sub-Assembly Process
During the sub-assembly process, the required Crank Weight is welded onto the Crank Weight Base using a resistance-welding machine. Basically, it consists of a jig, a clamp, and two electrodes. Some safety features have also been built into the machine to ensure the safety of the operator.

During operation, the operator will place the required Crank Weight Base onto the jig with the dimples facing upward. The Crank Weight Base will be resting on top of the lower electrode. The correct Crank weight is then placed on top of the Crank Weight Base. By pressing the two “Start” buttons with both hands, the clamp will push the Crank Weight and Crank Weight Base against the jig to align the two parts together. This is followed by the upper electrode moving down to press on the two parts. At this point, high current of about 13kA will flow through the two electrodes, causing the contacts between the Crank Weight and the Crank Weight Base to melt and fuse together. The upper electrode will then retract back, followed by the clamp, and the counter-balance weight is then removed from the jig. The part is now ready for assembly onto the crankshaft.

The sub-assembly process is normally carried out in stand-alone stations to provide the parts required for the main assembly line.

Stage Two: Main Assembly Process
In the main assembly process, the counter-balance weight is assembled onto the crankshaft eccentric by shrink fitting. The equipment used for the shrink fitting process consists of a heater coil, a jig and a timer.

During operation, the operator will place the counter-balance weight onto the jig, which is just above the heater coil. By pressing the “Start’ button, the current will flow through the coil, causing the temperature to rise quickly. This will in turn heat up the counter-balance weight, causing it to expand. After about 3 seconds, the siren will be activated, and the current to the heater coil will be cut off. The operator will then transfer the heated counter-balance weight onto the crankshaft in the main assembly line using a plier and to align the notched portion of the counter-balance weight to the marking on the crankshaft. A punch will then be activated to press on the counter-balance weight against the crankshaft. This will provide good sitting of the balancing weight onto the crankshaft and at the same time helps to cool the counter-balance weight faster by heat transfer.

Processing of counter-balance weight of hermetic reciprocating compressor

Stamping Process
The stamping layout of a counter-balance weight base is divided into eight stations and the operations performed in each station are indicated as hatch area. The detail of each operation is discussed as follows:

a) Station 1: Piercing & Notching
In this station, two pilot holes are pierced to provide accurate positioning of the stock for the subsequent operations. Notching is also performed to make marking on the counter-balance weight base, which will be used for positioning during assembly onto the crankshaft.

b) Station 2: Piercing
The hole for assembly onto the crankshaft is pierced in this station. Stringent but achievable roundness specification has been added to this hole to ensure firm grip with the crankshaft after assembly.

c) Station 3: Piercing
The cavities of the counter-balance weight base are pierced in this station. These cavities are required to control the center-of-gravity position of the part thus providing the necessary balancing force required.

d) Station 4: Chamfering
The hole for assembly onto the crankshaft is chamfered on the reverse side of the stock in this station to facilitate easy insertion during assembly.

e) Station 5: Piercing
The cavity for controlling the heat transfer rate during the assembly process of the counter-balance weight base is pierced in this station.

f) Station 6: Piercing
In this station, the front and the back profile of the design are pierced.

g) Station 7: Nipple
The dimples on the counter-balance weight base are made in this operation to facilitate resistance welding to be carried out later.

h) Profiling & Parting-off
This is the last station of the progressive die, which performs both the profiling and parting off operations. During profiling operation, the top and bottom portion of the stock strip is cut off, revealing almost the complete shape of the counter-balance weight base. At this stage, the part remains attached to the scrap skeleton until the parting-off operation where it is cut off to produce the complete work piece.

Cleaning Process
After the stamping process, the parts are covered with oil, dirt and other contaminants. To remove all these unwanted substances, they will need to undergo a cleaning process. This section is intended to describe the cleaning process of not only the counter-balance weight, but also for all other compressor parts at the end of the fabrication process.

Equipment Used
(a) Aqueous Ultrasonic machine
(b) Baskets to contain parts to be cleaned

Parameters
Cleaning Agent : Petroleum Solvents [3]
Temperature : Room Temperature
Spraying Pressure : 0.2 ~ 0.25 MPa
Cleaning Time : 1.5 ~ 3 minutes
(Actual cleaning time may be adjusted depending on the parts cleaned.)

Procedures
(a) The parts to be cleaned are placed inside the baskets.
(b) The baskets are then placed on the conveyor system that will travel through the Power Washer machine, which includes soaking, rinsing and drying stations.
(c) After going through the ultrasonic machine, the parts are cleaned and ready for compressor assembly.

Process Control
In order to ensure proper cleaning of the parts, the following process control must be adhered:
(a) The direction of spray nozzle must be adjusted to obtain best cleaning effectiveness.
(b) Parts to be cleaned must be placed such that they can be sprayed directly onto the metal surface.
(c) Set up a magnet near the filter of a cleaning bath and spray clean petroleum solvents to the parts at all times.
(d) Care must be taken to clean parts with “Hard to reach area” such as grooves or holes,
(e) After cleaning, the petroleum solvents must be changed if oil films or dirt are remained on the cleaned parts.

Different types of counter-balance weight for hermetic reciprocating compressor

In order to have a better understanding on the design of counter-balance weight, extensive time has been spent on the study of some existing designs commonly used in the industry.

Caulking-Type Balancing Weight
This design is currently used in a series of compressors, and because of its easy availability, it is used as one of the base designs to compare with the new balancing weight. In this design, Caulking Pins are used to fasten the Crank Weight onto the Crank Weight Base. The required number of Crank Weights can be varied to suit the different inertial loads exerted with different model of compressors. Thus for this design, it has the advantage of using the same Crank Weight Base and Crank Weight for different models of compressors. However, this design requires 2 die sets for the production of the parts; one for the Crank Weight Base and the other for the Crank Weight. The design may also involve many parts, especially in the case of volumetric displacement 9.1cm3 and 10.0cm3, which is undesirable for assembly process.

Folding-Type Balancing Weight
In this design, the part is being pressed out and then bent along the fold line. Caulking is then performed to force material into the small hole to hold the folded portion in place. This design reduces the total number of parts required by eliminating the need for caulking pins as required in the caulking-type counter-balance weight. However, this design is found to be patented [1] in the Europe and North America market, and thus cannot be used for the design in this project. This design is currently used in Japan domestic market only.

Welding-Type Balancing Weight
The last type of counter-balance weight observed is the welding-type balancing weight. This design is used in one of the competitor’s compressors. The design is quite similar to the caulking type balancing weight except that the crank weights are spot-welded to the crank weight base instead of caulking. This can help to reduce the number of parts required by eliminating the need for the caulking pins. However, the application of this design is unknown.

The assembly method of the respective types of Counter-Balance Weight to the crankshaft is to be noted. For the caulking- and folding-type balancing weight, they are attached onto the eccentric portion of the crankshaft by interference force fitting, whereas fasteners, such as screws and dowel pins, are used for the welding-type balancing weight. The former will cause formation of slivers during interference force fitting, which is undesirable for quality issue and it also requires higher machining precision, and thus increases the manufacturing cost. The latter will incur additional cost on the fasteners. These existing methods of coupling counter-balance weight to the crankshaft are not cost effective enough, and the formation of the slivers has to be eliminated. Therefore, an alternative way of coupling the balancing weight to the crankshaft has to be explored.

Introduction to Hermetic Reciprocating compressor

Hermetic-Reciprocating compressors typically consist of a crankshaft having an eccentric portion coupled to a compression mechanism, which is driven when the crankshaft rotates. The compression mechanism comprises a piston sliding in a cylinder; the piston operatively coupled to the eccentric portion of the rotating crankshaft by means of a connecting rod, whereby the orbiting motion of the eccentric about the axis of rotation of the crankshaft imparts reciprocating motion to the piston. Due to the dynamic imbalance of the operating compression mechanism, counter-balance weights are often attached to the crankshaft, in some cases directly attached to the eccentric of the crankshaft, to offset the inertial loads generated by the moving members of the compression mechanism and by the eccentric itself.

As the name implies, the function of a counter-balance weight is to serve as the balancing force to offset the inertial load generated in a system. In the case of hermetic reciprocating compressor, the need for an optimum counter-balance weight is of utmost important as it will affect the vibration and noise performance of the compressor. However, with the increasing stiff competition from other compressors’ manufacturers, cost has also become an essential factor in determining the success of the product. Therefore, a new series of welded counter-balance weights have been designed and developed with the intention to minimize compressors’ noise and vibration level at minimal cost.