US20180195503A1

US20180195503A1 - Fluid compressor

Info

Publication number: US20180195503A1
Application number: US15/868,355
Authority: US
Inventors: Terry Lyons; Joseph Hill; Tri Minh Huynh; John Williams; Michael Young
Original assignee: Bristol Compressors International LLC
Current assignee: Kulthorn Kirby Public Co Ltd
Priority date: 2017-01-11
Filing date: 2018-01-11
Publication date: 2018-07-12
Also published as: WO2018132591A1

Abstract

A fluid compressor includes a housing; a compression chamber within the housing; a motor; a shaft that is rotated by the motor; and a piston assembly including at least two pistons directly connected to each other without any connecting rods. The piston assembly performs a reciprocating motion when acted on by the shaft such that the at least two pistons move within the compression chamber to compress a fluid.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) to U.S. Application No. 62/445,218, filed Jan. 11, 2017. This application is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

This application relates to various improvements in structures for fluid compressors.
Refrigerant compressors are utilized to compress a refrigerant for use in a refrigerant cycle.
In two known types of refrigerant compressors, significant drawbacks exist that reduce performance and increase cost. First, in conventional reciprocating compressors, a pair of pistons are driven to reciprocate within compression chambers by a motor. Fluid enters through an entry passage in each compression chamber and exits through a discharge passage. These passages are generally in a same surface of the compression chamber, in a surface opposite the face of the piston. This close proximity between the entry and discharge passages allows heat from the discharge passage to travel to the suction entry passage, heating up the fluid entering the chamber. This causes the fluid to expand, which reduces the amount of fluid entering the chamber for each stroke of the piston. Thus, the capacity of the compressor is reduced, and performance is reduced.
Second, in conventional scroll compressors, there are many places throughout the travel path of the fluid that can leak, especially at higher pressures. Accordingly, scroll compressors cannot provide high pressure operation or compression ratios. For example, compression ratios of over 7:1 are very problematic for scroll compressors, likely leading to leaks as well as higher friction levels within the compression passages and reduced performance.
The present invention seeks to address these deficiencies.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, a fluid compressor includes a housing; a compression chamber within the housing; a motor; a shaft that is rotated by the motor; and a piston assembly including at least two pistons directly connected to each other without any piston rods. The piston assembly performs a reciprocating motion when acted on by the shaft such that the at least two pistons move within the compression chamber to compress a fluid.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a compressor in accordance with one embodiment of the present invention;

FIG. 2 is a side and cross-sectional view of the shaft and piston assembly shown in FIG. 1;

FIG. 3 is a top view of an embodiment with 4 pistons that simultaneously proceed through their compression cycles;

FIG. 4 is an embodiment of a piston assembly for a 4 piston fluid compressor that does not simultaneously compress;

FIG. 5 is a cross-section through an assembly of a horizontal embodiment of the present invention;

FIG. 6 is a cross-section through a compression chamber of an alternative embodiment of the present invention; and

FIG. 7 is a close up cross-sectional view of the connection between the stator laminates and the housing of one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A fluid compressor 20 is illustrated in FIG. 1 having a suction tube 22 providing a suction refrigerant into a suction chamber 24. A motor 26 is mounted within a housing, and drives a rotary shaft 28. Rotary shaft 28 causes a piston assembly 30 to reciprocate a pair of attached pistons 35 through the connection of yoke 29 and an eccentric pin 31. Thus, the pistons 35 are directly connected to piston assembly 30. Conventional compressors may attach the pistons to connecting rods which requires more labor and maintenance. The present invention eliminates these problems.
Suction plenums 32 lead the refrigerant from suction chamber 24 through inlet valves 33 and into compression chambers 36, defined by a crankcase or housing 34. Discharge valve assemblies 38 are placed at an opposite end of each compression chamber 36 from the inlet valves 33. The refrigerant passes outwardly through the discharge valves 38 into a discharge chamber 40, and then through a discharge tube 42. This dramatic separation of the suction discharge gas flow from the intake gas flow results in less heat pickup in the intake suction stream. This results in more dense gas into compression chamber, which allows compressor 20 to provide more capacity out of a smaller mechanism.
Further, the separation of the discharge valve 38 from the inlet valve 33 maximizes the discharge volumetric geometry, allowing reduced pressure drops and improved fluid flow. This can be accomplished whether the gas is brought in through a valve on a face of the piston or through a valve in the bore (a side of the compression chamber) that is exposed when the piston retreats during the suction stroke. For example, FIG. 6 shows a compression chamber with an inlet valve 33 on a lower side surface of the compression chamber. When the piston 35 retreats for a suction stroke, the valve 33 is exposed to the compression chamber. This again allows a maximizing of the distance between the intake and discharge valves, maximizing the discharge volumetric geometry.
By maximizing the discharge volumetric geometry, the size of the discharge valve can be made significantly larger. A larger discharge valve doesn't need to open as much to allow the compressed fluid out of the compression chamber. This improves valve timing and reduces backflow into compression chamber, further improving performance.
The disclosed configuration also eliminates the need for any discharge mufflers, internal high pressure exhaust tubes, mechanical mounting springs or mounts, cylinder heads, and valve plates. The elimination of all of these parts also reduces manufacturing costs and maintenance. In particular, the volume in housing 34 of the discharge chamber of compressor 20 becomes a discharge muffler chamber. This eliminates the need for a separate part for a discharge muffler.
FIG. 2 also shows high pressure relief valve 85. This valve is designed to vent the high pressure from the discharge side if that pressure exceeds a critical value. This prevents catastrophic failure of the compressor housing. FIG. 2 also shows seal point 90, onto which an o-ring (not shown) is mounted. This seal prevents high pressure compressed fluid from leaking back into the intake side.
In comparison to a scroll compressor, the present invention includes far fewer possible leakage paths. Thus, the present invention can perform at much higher compression ratios than a scroll compressor, such as greater than a 10:1 compression ratio. Thus allows for usage in such applications as medium and low temperature refrigeration, high ambient temperature air conditioning, and more severe heat pump conditions.
Compressor 20 also includes lower bearing 70 and upper bearing 80. These bearings allow for a smaller sized motor, which results in greater efficiently and lower cost.
As shown in FIG. 1, motor 26 is in direct contact with the inner surface of housing 21. This allows heat generated by motor 26 to more efficiently escape the compressor 20. For example, FIG. 7 shows a close up of the contact between the motor laminate layers 52 and the housing 21. (Although the housing has a circular cross-section, the housing is shown in this view as having straight sides due to the small scale.) Each stator laminate layer 52 has a thickness of approximately 0.020 in. Each stator laminate layer 52 may then line up with a corresponding heat dissipation fin 23 on an outer surface of housing 21 to promote heat transfer from the laminate layer 52, through housing 21, and out corresponding fin 23. Fin 23 is shown with a triangular cross-section, but any shape or configuration suitable for heat dissipation is possible. These modifications are within the scope of the invention as claimed.
Moreover, this direct connection to the outer housing means that the compressor can be deployed in varying configurations, such as standing up or on its side. FIG. 5 shows a horizontal configuration of the present invention. The only changes needed to place the compressor horizontally is the feet need to be moved to support the compressor. Also, the compressor 20 is not completely horizontal, but at approximately 5-10 degrees from horizontal to ensure oil 60 can continue to be drawn into the bottom of lower bearing 70.
Further, as shown in FIG. 1, the outer housing is cylindrical. In contrast, conventional compressor housings have an oval horizontal cross-section. The cylindrical outer housing of the present invention has several advantages. First, the circular cross-section is stronger, and thus higher pressure operation is possible, allowing higher compression ratios and higher performance. Further, the cylindrical shape creates a smaller oil sump volume 60 that must be filled with oil. Reducing the amount of oil needed saves costs throughout the lifetime of the compressor. Additionally, oval cross-sections may vibrate during operation of the compressor. This creates added noise that is not generated by the circular cross-section.
FIG. 3 shows an alternative embodiment which include 4 pistons 135, each of which proceed through the compression cycle simultaneously. Springs 137 are located in the compression chambers at an outer end to push the pistons 135 back when cam 139 moves to remove the force on piston 135. Cam 139 rotates on shaft 128, which is turned by a motor as in the first embodiment. Thus, the forces on the pistons that could cause vibrations in fact cancel out to eliminate bearing load and perfectly balance the mechanism. This reduces noise, vibration, and power usage. Further, either or both of the modifications may be used within the scope of the invention as claimed. That is, 2 piston unsynchronized, 4 piston unsynchronized, 2 piston synchronized, and 4 piston synchronized are all within the scope of the invention as claimed.
In this regard, FIG. 5 shows a piston assembly for a 4 piston unsynchronized configuration. This piston assembly includes a connection portion 30A that extends above the piston surfaces to allow for a perpendicular piston assembly to reciprocate below the portion 30A as the shaft rotates. Thus, 4 pistons can run in an unsynchronized manner to compress fluid.
A worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.

Claims

What is claimed is:

1. A fluid compressor comprising:

a housing;

a compression chamber within the housing;

a motor;

a shaft that is rotated by the motor; and

a piston assembly including at least two pistons directly connected to each other without any connecting rods, the piston assembly performing a reciprocating motion when acted on by the shaft such that the at least two pistons move within the compression chamber to compress a fluid.

2. The fluid compressor as set forth in claim 1, wherein the piston assembly includes 2 pistons.

3. The fluid compressor as set forth in claim 1, wherein the piston assembly includes 4 pistons.

4. The fluid compressor as set forth in claim 3, wherein each of the 4 pistons moves through a compression cycle simultaneously.

5. The fluid compressor as set forth in claim 1, wherein the motor is fixed directly to an inner surface of the outer housing.

6. The fluid compressor as set forth in claim 1, wherein fluid enters the compression chamber through a first surface of the compression chamber and exits the compression chamber through a second surface of the compression chamber that is an opposite surface from the first surface.

7. The fluid compressor as set forth in claim 6, wherein the first surface is a surface of the at least one piston.

8. The fluid compressor as set forth in claim 1, wherein fluid enters the compression chamber through a first surface of the compression chamber and exits the compression chamber through a second surface of the compression chamber that different from the first surface.

9. The fluid compressor as set forth in claim 8, wherein the first surface is a bottom surface of the compression chamber.

10. The fluid compressor as set forth in claim 1, further comprising:

a plurality of heat dissipation fins on an outer surface of the housing.

11. The fluid compressor as set forth in claim 10, wherein each of the plurality of heat dissipation fins corresponds to a layer of stator laminate of the motor within the housing.

12. The fluid compressor as set forth in claim 1, wherein a discharge volume muffles noise created within the compressor.

13. The fluid compressor as set forth in claim 1, further comprising:

an oil sump within a lower bearing that supports the shaft.

14. The fluid compressor as set forth in claim 13, wherein the oil sump has a slanted surface having an angle of approximately 25-35 degrees with a horizontal.