Title:
Double ended Labyrinth Pistons for Swash plate type Refrigeration Compressors 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 Labyrinth 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 or entirely made up 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 double ended Labyrinth 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.
The conventional compressor having plain cylindrical piston and mating plain cylindrical bore is having the leakage of compressed refrigerant to the extent of 10% ~ 25% which is as per the bush sealing prediction. Whereas the labyrinth Pistons able to reduce the leakage rate by about 7% ~12 % from the existing conventional designs. Also, based on the no. of labyrinth profiles on both the sides of double ended pistons, the weight reduction is the additional benefit over the leakage reduction.
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 with the disclosed labyrinth profiles.
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 fnotional 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 labyrinth 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 or entirely made up 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.
PTFE PolyTetraFluoroEthylene PEEK PolyEtherEtherKetone PPS PolyPhenylene Sulfide
Prior Art:
The U.S. Patent no. 5492459 dated 20 Feb' 1996 by Burkett et al. disclosed the invention related to air conditioning compressors in general, and specifically to a one sided piston for a swash plate compressor, having concave (divergent) section to increase the stability, but without any features for reduction of leakages.
The U.S. Patent no. 5921756 dated 13 Jul'1999 by Matsuda et al. disclosed the invention related swash plate type compressor with double ended pistons of unequal diameters to substantially reduce the axial load acting on the thrust bearings, but the piston surface is plain cylindrical and hence will contribute to more leakages.
The U.S. patent no. 6623258 dated 23 Sep'2003 by Iversen et al. disclosed the invention of axial piston refrigeration compressor having piston of variable cross-section towards the working end of the piston, but without any features for reduction of leakages.
The U.S. Patent application No. 20090193966 dated 6 August 20Q9, issued to Phlegm et al. disclosed that double ended plain cylindrical 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 plain cylindrical pistons are contributing for higher leakage of compressed refrigerants from the compression chamber to swash plate chamber, but without any features for reduction of leakages.
The Indian Patent application No. 1475/DEL/2012 dated 15 May 2012, by Selvaraji Muthu et al. disclosed that Swash plate type Refrigeration Compressors with Convergent conical shape Pistons and matching Cylinder bores.
The Indian Patent application No. 1476/DEL/2012 dated 15 May 2012, by Selvaraji Muthu et al. disclosed that Swash plate type Refrigeration Compressors with Composite 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.
(Table Removed)
Disadvantages of prior arfc-
1. Double Ended plain cylindrical Pistons entirely made of Aluminium Alloy, which is higher in weight.
2. Double Ended plain cylindrical Pistons, which is contributing for higher leakage of compressed refrigerants.
3. Higher surface area in contact, higher is the frictional power loss.
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 have the innovative features of double ended labyrinth 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 or entirely made up of Non-metallic materials like PTFE, PEEK, PPS through injection molding process.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 of 5 - Double ended labyrinth Pistons of for Swash Plate type Compressor
Figure 2 of 5 -Section view A-A of Double ended labyrinth Pistons of for Swash Plate type Compressor
Figure 3 of 5 - Detail B of Double ended labyrinth Pistons of for Swash Plate type Compressor
Figure 4 of 5 - Detail C of Double ended labyrinth Pistons of for Swash Plate type Compressor
Figure 5 of 5 - Detail D of Double ended labyrinth Pistons of for Swash Plate type Compressor
DETAILED DESCRIPTION
1. A Swash plate type compressor includes multiple double ended labyrinth pistons having the mating cylindrical bore in the housing at equal-angular distance between the pistons.
2. Double ended Labyrinth 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 labyrinth 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.

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
Labyrinth 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 labyrinth 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 or entirely made up of
Non-metallic materials like PTFE, PEEK, PPS through injection molding
process.
3. The labyrinth profile fin thickness ranges from 0.1 to 0.5 mm and the
spacing between fins ranges from 0.5 to 2.0 mm and the depth of the profile
ranges from 0.5 to 2 mm, with the applicable taper angle of the profile from
5 to 60 degrees are covered.
4. The Composite Construction of Double ended Piston is disclosed in our
Patent Application no. 1476/DEL/2012 dated 14Th May 2012.
5. The Non-metallic Material grades are disclosed in our Patent Application no.
1476/DEL/2012 dated 14Th May 2012.
6. Composite Double ended labyrinth 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.
7. The range of labyrinth piston nominal diameters covered in the point no.8 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.
8. Apart from the labyrinth profiles shown from the Figure 3 of 5 to 5 of 5, having possibilities of complex shaped pistons with honeycomb, spiral & helical toothed profiles for reduction of leakages.