Title:
Swash plate type Refrigeration Compressor with Cylinder Bores having multiple axial taper Oil Separation Grooves for all Automotive and Non-Automotive air-conditioning and Refrigeration applications
Field of Invention:
This invention relates to the design method and system of a very efficient swash plate type piston Compressor (both single acting and double acting designs) which has the innovative feature Cylinder Bores having multiple axial taper Oil Separation Grooves near the bottom dead center (BDC) of piston operation in the cylinder blocks for the cooling capacity range from 0.5 kW to 50 kW which can be used for all Air Conditioning applications like Car air-conditioning, Bus air-conditioning, Rail coaches Air-Conditioning, truck refrigeration units for transport of refrigerated goods and domestic refrigeration and Air Conditioning products.
Background of the invention:
General Scenario:
Compressors are used for sucking the low pressure super heated (any type of refrigerants, HFCs (Hydrofluoro Carbon, R134a) , HFOs (hydrofluoro-olefin, R1234ze, R1234yf), NH3, . CO2 and etc..) refrigerant gas from Evaporator (through Internal Heat Exchanger (IHX) if it is connected in the circuit), compressing the sucked super heated gas from low pressure to high pressure and discharging the compressed high pressure further super heated refrigerant gas at high temperature to Condenser for de-superheating, Condensing and sub-cooling the refrigerant medium in the vapour compression Refrigeration systems used in the chemical industry, Process industry, Air Conditioning applications, Power generation units and many other applications. Though our disclosed invention put forward by the current patent application may find a number of other embodiments, we are presenting the invention through an embodiment especially applicable to the automotive Air Conditioning systems having swash plate type piston Compressors (both single acting and double acting designs) for the applications like Car air-conditioning,. Bus air
conditioning, Rail coaches Air-Conditioning and truck refrigeration units for transport of refrigerated goods.
Automotive sector has been growing at a fast pace and due to tighter environment norms and steep competition the quest for efficiency increment and compactness and weight reduction is increasing continually.
The prime goal of the designers of automotive air conditioning systems is to design the main components like Compressor, Condenser and Evaporator to achieve highest cooling capacity by lowest power consumption. Whereas the OEM's demands are increasing in terms of compact and light weight parts day by day due to the need of competing with overall efficiency of the vehicle in terms of fuel economy and emission levels as well. The efficiency of the system is directly related with efficiency of the parts in the system.
Problem Statement:
There exists a need of a high efficient compressor which can provide higher COP for the wider operating conditions with their rated cooling capacities at the same time the compressor has to be as compact as possible and as light weight as possible The internal parts of the compressor are lubricated by splash type of lubrication by the rotation of swash plate in the oil sump, due to which suction refrigerant gas is mixed with lubricating oil, get compressed and discharged in to the system. The (OCR) Oil Circulation rate is directly affects the heat transfer phenomenon in the Condenser and Evaporator. The higher the OCR , lower is the cooling capacity of the system and very low OCR level will eventually leads to inadequate lubricating of bearings, Pistons, lip seal and Shoes, hence the compressor will have more frictional power loss and lower operating life. In order to ensure the optimum OCR level, the present invention addresses such a need. More particularly, the invention relates to devices and methods employing swash plate type piston Compressor which has the innovative features of Cylinder Bores having multiple axial taper Oil Separation Grooves near the bottom dead center (BDC) of piston operation in the cylinder blocks for the cooling capacity ranges for all Air Conditioning applications like Car air-conditioning, Bus air-conditioning, Rail coaches Air-Conditioning, truck refrigeration units for transport of refrigerated goods and domestic refrigeration and Air Conditioning products..

Prior Art:
The European Patent Application No. EP1092873 publication titled "Cylinder bore of swash plate compressor with grooves" dated 18th April 2001, by Sugiura, Manabu and Iwama, Kazuaki of TOYODA AUTOMATIC LOOM WORKS (JP) disclosed that compressor for compressing refrigerant gas that contains lubricating oil, the compressor having a housing having a crank chamber, a rotatably axially extending drive shaft, extending through the crank chamber, and a cam plate connected to the drive shaft so as to rotate integrally with the drive shaft, said compressor comprising: a cylinder block having a cylinder bore formed therein; a piston having a hollow main body and a connecting portion, the main body of the piston is disposed in the cylinder bore to define a compression chamber and the connecting portion is operably coupled to the cam plate, wherein the cam plate converts rotation of the drive shaft to reciprocating movement of the piston in the cylinder bore from a bottom dead center position to a top dead center position to compress the refrigerant gas supplied to the compression chamber; and a groove in the inner circumferential surface of the cylinder bore, wherein the groove forms a blow-by gas passage for the refrigerant gas and the lubricating oil therein to flow from the compression chamber to the crank chamber.
The grooves defined in the application are having uniform (Constant) groove depth, which leads to higher blow-by gas leakage, complex manufacturing process and higher wear & tear, whereas the design disclosed by us is of the multiple axial taper grooves having highest groove depth at the swash chamber side and gradually decreasing to zero towards the working chamber side as illustrated in the figure 4 of 8 and figure 5 of 8.
The European Patent Application No. EP1092871 publication titled "Hollow swash plate compressor piston with bores" dated 18th April 2001, by Sugiura, Manabu and Iwama, Kazuaki of TOYODA AUTOMATIC LOOM WORKS (JP) disclosed that A unilateral-headed swash plate type compressor comprising: a housing for defining cylinder bores, a crank chamber, a suction chamber and a discharge chamber; pistons adapted to reciprocate in the cylinder bores, respectively; a drive shaft driven by an external drive source and supported rotatably by the housing; and a swash plate supported on the drive shaft in a
manner capable of synchronous rotation and causing the piston to be driven; wherein the portion of said piston body in sliding contact with the inner peripheral surface of the cylinder bore is formed with a cavity for realizing a reduced weight and with an annular groove, fitted with a piston ring in sliding contact with the inner peripheral surface of the cylinder bore, said piston body having at least a through hole open to the inner peripheral side of said cylinder bore and communicating with said crank chamber through said cavity.
The United States Patent No. 6523455 dated 25th Feb 2003, titled "Compressor having an oil collection groove" issued to Callahan, Rodney James and Mangiapane, Ronald James of Visteon Global Technologies, Inc. (Dearborn, Ml) disclosed that A swash plate-type compressor is provided. The compressor has a housing member that defines a plurality of grooves having features that allow the grooves to direct lubricating oil splashed against the housing member toward a central opening that houses a bearing and shaft. Preferably, the grooves comprise an annular groove and a series of oil collection grooves emanating outward from the annular groove. Each oil collection groove has a first wall that is substantially perpendicular to the plane of the housing member and a second wall that is angled with respect to both the first wall and the plane of the housing member. Also, each oil collection groove is in fluid communication with the annular groove. The housing member may further define one or more axial holes disposed within the annular groove.
Disadvantages of prior art:-
1. Compressors having very high OCR by which the cooling capacity is reduced or having very low OCR, causes the higher frictional power loss and lower operating life of compressors.
2. Separate Oil Separator makes the compressor expensive and complex in design.
3. Oil groove designs proposed have high manufacturing complexity and wear & tear due to multiple edges engaged in the stroke of Piston.
4. Capacity loss from oil groove.
SUMMARY OF THE INVENTION:
In summary,
This invention relates to the design method and system of a very efficient swash plate type piston Compressor which has the innovative features of (both single acting and double acting designs) which has the innovative feature Cylinder Bores having multiple axial taper Oil Separation Grooves near the bottom dead center (BDC) of piston operation in the cylinder blocks. The oil is get collected due to Surface tension, Viscous Force & Capillary action into the grooves and groove parameters are optimized (Groove depth, Groove taper angle and groove length) with Optimum Differential pressure to push the collected oil in the grooves to swash chamber with minimum most refrigerant gas blow-by.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 of 8 - Schematic cross-section view of Swash plate type compressor
Figure 2 of 8 - Isometric view of Cylinder Block showing the Cylinder Bores having
multiple axial Annular equi-spaced Oil Separation Grooves
Figure 3 of 8 - Sketch of Cylinder bore showing the uniform depth Oil Separation Groove
Figure 4 of 8 - Isometric view of Cylinder Block showing the Cylinder Bores having multiple axial taper Oil Separation Grooves, placed annularly equi-spaced.
Figure 5 of 8 - Sketch of Cylinder bore showing the gradually varying depth Oil Separation Groove
Figure 6 of 8 - Graph showing the Oil drain and Refrigerant gas leakage by blow-by to optimize the groove parameters (Groove depth, Groove taper angle and groove length) Figure 7 of 8 - Graph showing the Optimum Differential pressure to push the collected oil in the grooves due to Surface tension, Viscous Force & Capillary action (Groove depth, Groove taper angle and groove length) Figure 8 of 8 - Prior art
DETAILED DESCRIPTION
1. A fixed displacement Swash plate type compressor includes Front Head Cylinder, Rear Head Cylinder, Front Side Cover, Rear Side Cover, Shaft with Swash plate and multiple double headed pistons having the mating cylindrical bore in the housing at equal-angular distance between the pistons.
2. The double headed pistons are connected to Swash plate through Semi-Spherical Shoes on either side of the swash for transferring the gas load and providing the reciprocating motion to the pistons in the axial direction.
3. The compression load acts on Piston is transferred to Swash plate through the pair of shoes.
4. Swash plate with 2 identical thrust bearing of kind anti-friction roller or ball bearings on opposite sides of Swash for transferring the bi-directional thrust loads to the housings.
5. The drive shaft is guided by either anti-friction type ball or roller bearings or bush bearings on both the sides of swash plate.
6. The bearings and shoes are lubricated either by splashing by swash plate or using oil pump (Gear pump or Gerotor pump).
7. The above features of compressor are shown in Figure 1 of 8.
8. The Cylinder Bores are having n number of multiple grooves near the bottom dead center (BDC) of piston operation in the cylinder blocks, which are placed at equi-distance annularly as shown in Figure 2 of 8 to Figure 5 of 8.
9. The groove length is designed in such a way that the swash chamber is connected to working chamber for draining the oil with very minimum most blow-by of refrigerant gas with optimum pressure difference as shown in Figure 6 of 8
10. The groove depth is optimized to drain maximum amount of oil with optimum pressure difference, which in turn related to the average velocity of the Piston during the groove opening as shown in Figure 7 of 8. .

Claims:
What is claimed is:
1. A fixed displacement swash plate type Compressor for air conditioning
applications in general and automotive application in particular comprising of
housings with multiple Cylinder Bores having multiple axial taper Oil
Separation Grooves near the bottom dead center (BDC) of piston operation
in the cylinder blocks, Both front and rear Cylinder blocks are made up of
metallic materials (Aluminium, Cast-Iron, Steel) etc...(by forging, machining,
casting, molding) or Non-metallic materials like PTFE, PEEK , PPS through
injection molding process, the Swash plate press-fitted with the input drive
shaft, set of thrust bearings either of anti-friction roller or ball bearing type
and radial bearings either of anti-friction roller or ball bearing or bush
bearing type for taking the axial and radial loads in addition to provide the
axial and radial constraints to the input shaft with negligible friction, as
shown in Figures 1 of 8.
2. The Compressor according to the claim 1, wherein said the multiple axial
grooves are equi-spaced annularly in the cylinder bores to drain the
maximum amount of lubricating oil with the optimized groove depth δ,
accordingly to the size of the cylinder bores , depth ranges 0.05 mm to 1
mm, number grooves n ranges from 4 to 20, as shown in Figure 2 of 8 and
Figure 3 of 8.
3. The Compressor according to the claim 1, wherein said the axial taper
grooves are equi-spaced annularly in the cylinder bores to drain the
maximum amount of lubricating oil with the optimized groove parameters
(maximum depth δmax and taper angle α, accordingly to the size of the
cylinder bores , maximum depth ranges 1 mm to 3 mm and taper angle ranges from 1° to 5 °, number grooves n ranges from 4 to 20, as shown in Figure 4 of 8 and Figure 5 of 8.
4. The Compressor according to the claim 1, wherein said the multiple spiral
or helical grooves are provided with varying groove depth from maximum
depth at swash chamber side to zero or minimum depth in the compressor

chamber with optimized groove parameters (maximum depth δmax and taper
angle α, accordingly to the size of the cylinder bores , maximum depth ranges 1 mm to 3 mm and taper angle ranges from 1 ° to 5 °, number grooves n ranges from 4 to 20.
5. The Compressor according to the claim 1, wherein said the cylinder bores are covered of the sizes ranges from 10 mm to 50mm in nominal Diameter, which includes the specific Diameters namely 25, 28.5,29.5, 30.5, 32, 34, 36, 38, 40 , 42, 46, 50 mm to name a few.
6. The Compressor according to the claim 1, wherein said the number of Cylinder bores are of the range of 5 to 14 in general and specifically 6, 10 and 14.
7. The invention is also applicable to single acting or single headed pistons of fixed displacement and variable displacement wobble plate and swash plate type of compressors with internal controlled and external controlled solenoid valves having the number of cylinders of 5, 6, 7 and 10.