Title:
Swash plate type Refrigeration Compressors with Convergent conical shape Pistons and matching Cylinder bores 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 and Compressors which have the innovative features of special convergent Conical shape (variable cross-section at the ends) of Pistons for the cooling capacity range from 1 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 to high pressure and discharging the compressed refrigerant gas at high temperature to Condenser for de-superheating, Condensing and sub-cooling the refrigerant medium in the vapour compression Refrigeration systems (shown in figure 1 of 6 ) 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.
Refrigerant Vapor Compression Refrigeration circuit:
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 and hence the COP is raised.
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 (shown in figure 2 of 6).
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.
Problem Statement:
There exists a need of a high efficient compressor which can provide higher COP for the rated cooling capacity, which is only possible by reducing the power consumption of the compressor.. The present invention addresses such a need. More particularly, the invention relates to devices and methods employing swash plate type piston Compressors which have the innovative features of special convergent Conical shape (variable cross-section ends) of Pistons which have less clearance volume to enhance COP of Overall system for rated cooling capacity without compromising the overall dimension of the compressor boundary in comparison with the Conventional Swash plate having the Cylindrical Pistons and Cylindrical Bores.
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.
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.
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.
(Table Removed)
Disadvantages of prior art:-
1. Higher clearance volume
2. Lower volumetric efficiency.
3. low COP
4. for the rated power consumption, lower cooling capacity
5. contributing to more global warming
SUMMARY OF THE INVENTION:
The swash plate type compressor with multiple double ended pistons having the convergent conical shape at the ends of the piston and mating bore is made as integral part of the housing as shown in Figure-4 of 6.
The swash plate type compressor with multiple double ended pistons having the convergent conical shape at the ends of the piston and mating bore for this conical shape is made by additional part interference fitted in the housing as shown in Figure-5 of6.
In summary,
The theoretical volumetric efficiency of compressor having this disclosed concept with the conventional compressor is shown as below.
(Formula Removed)
D ranges from 20 mm to 50mm d/D - ranges from 1 to 0.5
The Convergent Conical shape piston converges to conventional cylindrical piston with the diameter ratio d/D being 1.0 as shown in the figure 6 of 6.
Lowest the diameter ratio, the reduction in dead end volume is highest, whereas the optimum value is depends on the suction and discharge valve sizes and mounting locations.
BRIEF DESCRIPTION OF THE DRAWINGS
For a detailed description of the preferred embodiments of the invention, reference will
now be made to the accompanying drawings in which:
Figure: 1 of 6 -Refrigerant Vapor Compression Refrigeration circuit
Figure 2 of 6 - PV Diagram of Reciprocating type compressor with clearance volume
Figure 3 of 6 - Patent References (3a, 3b, 3c)
Figure 4 of 6 - Convergent Conical double ended Pistons and integral mating portion
of Cylinder for Swash Plate type Compressor as disclosed in this invention
Figure 5 of 6 - Convergent Conical double ended Pistons and additional mating portion
of Cylinder for Swash Plate type Compressor as disclosed in this invention
Figure 6 of 6 - Convergent Conical double ended Pistons for Swash Plate type
Compressor as disclosed in this invention
DETAILED DESCRIPTION
1. According to one aspect of the invention, swash plate compressor with multiple double ended pistons having convergent conical shape. The proposed swash plate compressor has the mating conical bore with clearance to avoid piston locking due to thermal expansion.
2. Each Piston having a part of cylindrical portion and the end of both the sides having Convergent Conical shape as shown in the figure -6 of 6.
3. Each cylinder is having mating part of cylindrical portion and the end of both the side having Convergent Conical shape as shown in the figure-4 of 6 and figure-5 of 6.
4. The compression load of Piston is transmitted to swash plate through shoes on either side of the swash plate.
5. 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.
6. 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 Convergent
Conical shape double ended Pistons, mating convergent Conical, shape
cylinders, 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 and radial bearings for taking the axial and radial loads in
addition to provide the axial and radial constraints to the input shaft with
negligible friction.
πd2/4
2. The convergent conical end of the piston has the top surface area —
πD2/4 which is lower than the conventional cylindrical Piston surface area πD2/4 by
the factor of [d/D]2.
3. The clearance volume is reduced with the reduction of piston top surface area and hence the volumetric efficiency is increased compared to the conventional swash plate type compressors under the rated cooling capacities.
4. As per this invention, the piston weight is reduced by
(Formula Removed) in the case of single ended single acting
design and by (Formula Removed) in the case of double
ended double acting design. Where as p is density of the piston material
5. The weight reduction stated in the point no. 5 (as above) would result to reduce the inertia force required for the movement of pistons by the same factor, which in turn increases the overall mechanical efficiency.
6. The Convergent conical Shape of piston is assisting the piston to get self-centered with respect to the cylinder bore, hence the smoothness of operation has improved and higher service life.
7. Double ended conical piston is made up of entirely using either of Aluminium alloy or Non-metallic materials like PTFE, PEEK , PPS but not limited to only these materials.
PTFE PolyTetraFluoroEthylene
PEEK PolyEtherEtherKetone
PPS PolyPhenylene Sulfide