Title:
Swash plate type Refrigeration Compressor with Composite Pistons for all automotive air-conditioning applications
Field of Invention:
This invention relates to the design method and system of a very efficient swash plate type piston Compressor which has the innovative features of double ended pistons made up of composite materials partially using metallic materials (Aluminium, Cast-iron, Steel) etc...(by forging, machining, casting, molding)) and the rest with either of Non-metallic materials like PTFE, PEEK , PPS through injection molding process 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 and truck refrigeration units for transport of refrigerated goods.
Background of the invention:
General Scenario:
Compressors are used for sucking the low pressure super heated (any type of refrigerants, HFC (Hydrofluoro Carbon), HFO (hydrofluoro-olefin), NH3, C02 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 or delivering 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 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 is increasing day by day.
The prime goal of the designers of automotive air conditioning systems is to minimize the power consumption of compressor by increasing the volumetric efficiency and also increasing the mechanical efficiency, which together are responsible for the higher COP to provide the rated cooling capacity of the system. While comparing the power consumed by other auxiliary equipments like condenser fan motor and evaporator blower fan motor, the power consumed by the compressor is about 90-97% of the total power consumption in the system, which clearly indicates the direction of invention to reduce the compressor . power consumption for the rated cooling capacity to raise the COP. However, as per the fundamental derivation of volumetric efficiency of Piston type reciprocating compressors, the volumetric efficiency is disproportional to clearance volume, pressure ratio and gas index), for the defined application of compressor, the pressure ratio and gas index are fixed, hence to increase the volumetric efficiency, only the reduction of clearance volume is left for innovation.
The clearance volume is the retained volume having the compressed refrigerant under discharge pressure, sum of axial dead volume on the top of piston head, discharge port in the valve plate, suction cavity in the suction valves and the cavity of suction valve stopper. The dead volume on the top of piston is account about 50-70% of the total clearance volume. Also the suction and discharge port clearance volumes are constrained with the limitation of lower velocity of refrigerant during suction and discharge with acceptable pressure drop. Hence the innovation to reduce the dead volume on the top of piston is focused here.
The operating volumetric efficiency is the function of theoretical volumetric efficiency and the leakage rate during the compression and discharge phases from the compression chamber side of the piston to the opposite side of piston , which is usually connected to suction manifold. The leakage rate is the function of pressure difference across the piston and the radial clearance between the cylinder and piston under operating conditions.
The cylinder and piston made up of common material (like usjng Aluminium Alloy) performs at its optimum performance only at the design optimized rated loading conditions. The off-design operating conditions make either larger operating clearance than the optimum, which causes lower performance, or in-adequate operating clearance which causes the piston rubbing and seizure.
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, which is possible by reducing the power consumption of the compressor in terms of reducing the frictional and interia losses and improving the volumetric efficiency. 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 double ended pistons made up of composite materials partially using metallic materials (Aluminium, Cast-iron, Steel) etc..) by casting, forging, machining and the rest with either of Non-metallic materials like PTFE, PEEK , PPS through injection molding process for the cooling capacity ranges for all Air Conditioning applications like Car air-conditioning, Bus air-conditioning, Rail coaches Air-Conditioning and truck refrigeration units for transport of refrigerated goods.
PAI PolyAmide Imide
PI Poly Imide
PF Phenol Resin
EP Epoxy Resin
PTFE PolyTetraFluoroEthylene
PEEK PolyEtherEtherKetone
PPS PolyPhenylene Sulfide
Prior Art:
The U.S. Patent No. 6364646 dated 2 April 2002, issued to Kirtley et al. disclosed that the vane of rotary vane compressor is made up of entirely using PEEK material, where as the structural strength is limited.
The U.S. Patent No. 6589021 dated 8 July 2003, issued to Kato et al. disclosed that the Shoe of the Swash plate type compressor is mainly comprised of a resin, namely PAI, PI, PEEK, PF, EP, PPS.
The U.S. Patent application No. 20090193966 dated 6 August 2009, issued to Phlegm et al. disclosed that double ended piston is entirely made of engineered polymer, such as PEEK with 30% carbon filled and synthetic composite of PEEK with 15% of PTFE (15% carbon filled) by weight, whereas pistons made of entirely using engineered polymers are having limited structural strength, which inherently has very high stress concentration at the contact surface with shoe, by which the resultant force is transmitted to swash plate.
Material (Table Removed)
Disadvantages of prior art:-
1. Double Ended Pistons entirely made of Aluminium Alloy, which is higher in weight
2. Double Ended Pistons entirely made of Aluminium Alloy, which has higher thermal expansion under various operating conditions than the cylinder in the housings.
3. Double Ended Pistons entirely made of Non-Metallic Materials like PTFE, PEEK, PPS, which is inadequate for the required Factor of Safety through out the loading surfaces.
4. The above features either able to provide lower COP or causes piston rubbing and seizure at off-design operating conditions
5. for the rated power consumption, lower cooling capacity
6. contributing to more global warming
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 double ended pistons made up of composite materials partially using metallic materials (Aluminium, Cast-iron, Steel) etc..) by casting, forging, machining and the rest with either of Non-metallic materials like PTFE, PEEK , PPS through injection molding process.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 of 2 - Double ended Pistons made up on Composite materials for Swash Plate
type Compressor
Figure 2 of 2 - Double ended Pistons made up on Composite materials with additional
supports for Swash Plate type Compressor
The portion | 1 | shown in Figure 1 of 2 & Figure 2 of 2 is made up of metallic materials
(Aluminium, Cast-Iron, Steel etc..) by forging, machining, casting, molding.
The portion | 2 | shown in Figure 1 of 2 & Figure 2 of is made up of Non-metallic materials like PTFE, PEEK, PPS through injection molding process.
The portion | 3 | shown in Figure 1 of 2 & Figure 2 of is made up of Non-metallic materials like PTFE, PEEK, PPS through injection molding process.
DETAILED DESCRIPTION
1. A Swash plate type compressor includes multiple double ended pistons having the mating cylindrical bore in the housing at equal-angular distance between the pistons.
2. Double ended pistons made up of composite materials partially using metallic materials (Aluminium, Cast-iron, Steel) etc..) by casting, forging, machining and the rest with either of Non-metallic materials like PTFE, PEEK , PPS through injection molding process.
3. The double ended pistons are connected to Swash plate through Semi-Spherical Shoes on either side of the swash for transferring the compression load and providing the motion to the pistons.
4. The compression load acts to Piston as axial compression force through the non-metallic material portion and transfers to the shoe through the metallic material portion of the piston, by which the stress levels of Piston at the contact surface of Shoe is un-altered, as same as the design with piston entirely made up of Aluminium Alloy.
5. Whereas the stress levels are significantly lower compared to the design of piston entirely made up of Non-metallic materials like PTFE, PEEK, PPS.
6. 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.
7. The drive shaft is guided by either anti-friction type ball or roller bearings or bush bearings on both the sides of swash plate.

Claims:
What is claimed is:
1. A swash plate type Compressor for air conditioning applications in general and automotive application in particular comprising of multiple double ended Pistons, mating cylinders in the form of housings, set of suction and discharge valves, valve plate, drive end and non-drive end covers, the
Swash plate integral 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.
2. Double ended pistons made up of composite materials partially using metallic materials (Aluminium, Cast-iron, Steel) etc..) by casting, forging, machining and the rest with either of Non-metallic materials like PTFE, PEEK, PPS through injection molding process.
3. The non-metallic materials referred in the point no.2 includes the variants of PTFE, PEEK and PPS with 10%, 20%, 30% of Glass Filled and 10%, 20%, 30% of carbon Filled grades.
4. As per the material grades listed in point no.3 , there is about 40% to 50% weight reduction compared to the pistons entirely made up ofr Aluminium Alloy.
5. The weight reduction explained in the point no.4 increases the mechanical efficiency of the compressor by having significantly lower inertia forces due to reduced weight of the pistons.
6. By the use of non-metallic material grades listed in point no.3, the operating axial and radial clearances of double ended pistons are lower, hence the volumetric efficiency is higher than the conventional pistons entirely made up on Aluminium Alloy.
7. Composite Double ended pistons are covered of the sizes ranges from 10 mm to 50mm in nominal Diameter with Length up on nominal Diameter ratio ranges from 1.5 to 4.
8. The range of piston nominal diameters covered in the point no.7 as above,
includes the specific Diameters namely 25, 28.5,29.5, 30.5, 32, 34, 36, 38,
40 ,42,46, 50mm to name a few.