Air compressor and expander

The present invention relates to an air compressor and expander including: a first rotor coupled around a driving shaft; a second rotor coupled around a driven shaft so as to operate in cooperation with the first rotor; a casing adapted to form an air compression or expansion space by the rotation of the first rotor and the second rotor; first and second end covers adapted to close the both end portions of the casing in such a manner as to have the driving shaft and the driven shaft passed therethrough in the axial direction, thereby to have the first rotor or the second rotor disposed between them; a gear part disposed on any one side of the first and second end covers in such a manner as to be coupled around the driving shaft and the driven shaft for transmitting power to the driving shaft and the driven shaft; and a clearance-preventing means disposed at the opposite side to the gear part for preventing the clearance between the end covers and the rotors.

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Description
BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an air compressor and expander, and more particularly, to an air compressor and expander that is capable of preventing the generation of clearance between end covers and rotors in an air cycle during which air is compressed and expanded, thereby improving refrigerating effects.

2. Background of the Related Art

As the global warming and environmental problems become severe, recently, so as to replace a refrigerant like R-134a as used up to now with new refrigerant, many endeavors for developing alternative refrigerant systems have been made by all the refrigeration companies over the world, and especially, they have studied on a new system that is environment-friendly and has a high refrigerating efficiency, without any replacement of the refrigerant itself.

An air cycle that is recently considered as a most effective alternative cycle is called a reverse Bryton air cycle, which uses air as refrigerant and reversely activates Bryton air cycle first developed as a gas power cycle, thereby obtaining the refrigerating effects.

FIG. 1 is a schematic view showing the basic principle of a general air cycle, and FIG. 2 is a graph showing the relation of T-s of the general air cycle.

As shown, an air cycle is formed wherein a compressor 1, an expander 2, and first and second heat exchangers 3 and 4 conduct their respective compression process (1→2), temperature-falling process (2→3), expansion process (3→4), and temperature-rising process (4→1).

In the compression process (1→2), air enters the compressor 1, and after compressed therein, it is raised at pressure and temperature.

In the temperature-falling process (2→3), the high pressure and temperature compressed air is transmitted to outside heat source through the first heat exchanger 3, and the temperature of air falls under constant pressure condition (under the condition where pressure is slightly dropped). At this time, the high temperature air transmitted to the outside heat source can be used as a heat source for heating an air conditioning space or for producing heated water.

In the expansion process (3→4), the air that falls at the temperature is decreased at its pressure through the expander 2 (which has a similar structure to the compressor), and the temperature of air falls to below zero. At this time, the heat extracted from the expander 2 is used as power for generating electricity or returns to the compressor 1 for decreasing the consumption power of the compressor 1.

In the temperature-rising process (4→1), the air that falls at the temperature and pressure is passed through the second heat exchanger 4, such that the temperature of air rises, and at this time, since heat is absorbed from the air conditioning space, it is served for refrigeration (or freezing).

The efficiency of the air cycle is greatly dependant upon the efficiencies of the compressor 1 and the expander 2. In the past days, the compressor 1 and the expander 2 have an efficiency of about 80%, so that the whole efficiency of the system is kept low. However, recently, the isentropic efficiency of them is raised, so that the whole efficiency of the system is increased to 80% or more.

In other words, when the efficiency of the compressor 1 is low, power of the compressor 1 is increased and the compressed temperature is raised (see the compression process (1→2) in FIG. 2). When the efficiency of the expander 2 is low, the temperature of air is not sufficiently low, such that the refrigerating performance is decreased (see the expansion process (3→4) in FIG. 2).

FIG. 3 is a sectional view showing a conventional air compressor and expander, and FIG. 4 is a perspective view showing a first rotor in the conventional air compressor and expander.

Hereinafter, since the air compressor and the air expander have the similar parts to each other, they will be referred to as an air compressor and expander, for the brief description of the present invention.

As shown, the air compressor and expander includes: a first rotor 1 coupled around a driving shaft 1a and having a spiral type protrusion 1b formed on the outer periphery thereof; a second rotor 1 coupled around a driven shaft 2a so as to operate in cooperation with the first rotor 1 and having a spiral type groove 1b corresponding to the spiral type protrusion 1b formed on the outer periphery thereof; a casing 3 adapted to form an air compression space by the rotation of the first and second rotors 1 and 2 and having first and second air flow ports 3a and 3b formed on the both surfaces thereof in such a manner as to be disposed perpendicular to the shafts; a closing member 4 and an end cover 5 adapted to close the both end portions of the casing 3; a gear part 6 formed on one side of the closing member 4 in such a manner as to be coupled around the driving shaft 1a and the driven shaft 2a for transmitting power from the driving shaft 1a and the driven shaft 2a; and a gear box 7 adapted to cover the gear part 6.

Also, the closing member 4 and the end cover 5 are shaft-coupled to bearings 8, for supporting the rotation of the driving shaft 1a and the driven shaft 2a.

Further, oil seals 9 are coupled around the first rotor 1 and the second rotor 2 sides on the closing member 4, for preventing lubricating oil used for lubricating the gear part 6 inside the gear box 7 and the bearings 8 on the closing member 4 from flowing to the inside of the casing 3.

Further, fixing nuts 10 are coupled to the other side of the gear part 6 coupled to the first rotor 1 and the second rotor 2, for fixing the first rotor 1 and the second rotor 2 to the driving shaft 1a and the driven shaft 2a.

The conventional air compressor and expander under the above configuration is disposed and driven in the air cycle.

According to the air compressor and expander, if the driving shaft 1a is rotated, the first rotor 1 coupled around the driving shaft 1a is rotated. When the first rotor 1 is rotated, the second rotor 2 coupled around the driven shaft 2a is rotated. At this time, since the driving shaft 1a and the first rotor 1, are coupled on end portions thereof by means of the fixing nut 10 and the driven shaft 2a and the second rotor 2 are coupled on one end portions thereof by means of the fixing nut 10, they are rotated together while the shafts are driven.

Moreover, the air flowing in through the first air flow port 3a is compressed or expanded, while being passed through the spiral type protrusion 1b of the first rotor 1 and the spiral type groove 2b of the second rotor 2, and is then discharged through the second air flow port 3b, thereby forming the air cycle.

At this time, in case of an open-air cycle where cool air is supplied directly to an air conditioning space, refrigerant is respired as air itself by human beings, such that the air contaminated through mixing oil with pure air cannot be used. Thus, the air compressor and expander should be designed to make a clearance between the first rotor and the second rotor set to a minimum size, such that the spiral type protrusion 1b of the first rotor 1 and the spiral type groove 2b of the second rotor 2 do not abut with each other. If the minimal clearance is not maintained well, the efficiencies of the compressor and the expander are decreased, thereby making the system performance and efficiency undesirably deteriorated.

By the way, most of oil injection type screw compressors are configured wherein the rotors are rotated in the engagement with each other and oil is supplied for sealing and cooling the screw threads on the rotors. However, the oil injection type screw compressors can not be applied to the open-air cycle where refrigerant is respired as air itself by human beings.

According to the above-mentioned air compressor and expander, the first rotor 1 and the second rotor 2 are moved up and down by the pressure variations inside the casing 3 during the rotation of the first rotor 1 and the second rotor 2, and the gear part 6 rotating the driving shaft 1a and the driven shaft 2a is formed of a helical gear that is capable of reducing backlash. However, a force is generated to have the first rotor 1 and the second rotor 2 form clearances.

That is to say, the spiral type protrusion 1b of the first rotor 1 and the spiral type groove 2b of the second rotor 2 interfere with each other by the large clearance of the first rotor 1 and the second rotor 2 from the gear part 6, and thus, they are abraded, such that the temperature of air is raised to decrease refrigerating efficiencies and the chips coming off from the rotors are collected and attached in a low pressure space (see FIG. 4).

In more detail, in a case where the rotors are rotated to the upper side of the drawing, the gear part 6 coupled to the shafts has a protrusion 6a adapted to abut with the inner wheels of the bearings 8, thereby preventing the first rotor 1 and the second rotor 2 from forming a clearance from the upper side of the gear part 6, but in a case where the rotors are rotated to the lower side of the drawing, they do not have any structure capable of preventing forming the clearance, such that the protrusion 1b of the first rotor 1 and the groove 2b of the second rotor 2 abut with each other. Especially, while the first and second rotors 1 and 2 are rotated at a high speed, the upper and lower bearings 8 do not serve to sufficiently support the rotation, such that the interference between the protrusion 1b and the groove 2b is much generated.

Also, according to the conventional air compressor and expander, the upper bearings are formed not abutting with oil, and during the rotation of the rotors at a high speed, the heat generated from the bearings 8 is directly transmitted to the air inside the casing 3, thereby decreasing the refrigerating performance.

Further, according to the air compressor and expander having the first rotor 1 with the spiral type protrusion 1b formed thereon and the second rotor 2 with the spiral type groove 2b formed thereon, undesirably, the space occupied by the air that flows to the rotors and is compressed therein is relatively smaller than a projection space of the whole rotors.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made in view of the above-mentioned problems occurring in the prior art, and it is an object of the present invention to provide an air compressor and expander that is capable of having a sufficient air flow quantity to flow therein by improving the shapes of a first rotor and a second rotor and is capable of minimizing the clearance between the first and second rotors, the clearance between the rotors and a casing, and the clearance between the rotors and end covers by improving the tooth shapes of the first and second rotors, by disposing a closing cover at both end portions of a casing for housing the first rotor and the second rotors, and by disposing a clearance-preventing means at one side of the closing cover.

To accomplish the above object, according to the present invention, there is provided an air compressor and expander including: a first rotor coupled around a driving shaft; a second rotor coupled around a driven shaft so as to operate in cooperation with the first rotor; a casing adapted to form an air compression or expansion space by the rotation of the first rotor and the second rotor; first and second end covers adapted to close the both end portions of the casing in such a manner as to have the driving shaft and the driven shaft passed therethrough in the axial direction, thereby to have the first rotor or the second rotor disposed between them; a gear part disposed on any one side of the first and second end covers in such a manner as to be coupled around the driving shaft and the driven shaft for transmitting power to the driving shaft and the driven shaft; and a clearance-preventing means disposed at the opposite side to the gear part for preventing the clearance between the end covers and the rotors.

The clearance-preventing means is adapted to make the ends of the rotors or come into close contact with the end covers, such that the first rotor or the second rotor does not have clearance from the end covers.

The clearance-preventing means comprises T-shaped bushings, one side of which is coupled to central portion of the rotors and the other side of which contacts with bearings supporting the rotors, and fastening members adapted to the end portions of the driving shaft and the driven shaft thereto to support the other side of the bearings for maintaining a predetermined distance between the gear part and the end cover.

The first end cover has a rear cover formed at the outside thereof, and the second end cover has a front cover formed at the outside thereof.

The first rotor and the second rotor are formed twisted at a predetermined twisting angle along the axial direction, and the predetermined twisting angle of the first rotor and the second rotor is within a range between 90° and 270°.

The first rotor and the second rotor are coated with Teflon on the surfaces thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic view showing the basic principle of a general air cycle;

FIG. 2 is a graph showing the relation of T-s of the general air cycle;

FIG. 3 is a sectional view showing a conventional air compressor and expander;

FIG. 4 is a perspective view showing a first rotor in the conventional air compressor and expander;

FIG. 5 is a perspective view showing an air compressor and expander according to a first embodiment of the present invention;

FIG. 6 is a side view showing first and second rotors of the air compressor and expander according to the first embodiment of the present invention;

FIG. 7 is a sectional view showing the air compressor and expander according to the first embodiment of the present invention;

FIG. 8 is a sectional view taken along the line A-A of FIG. 7;

FIG. 9 is a perspective view showing an air compressor and expander according to a second embodiment of the present invention; and

FIG. 10 is a side view showing first and second rotors of the air compressor and expander according to the second embodiment of the present invention.

 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, an explanation of an air compressor and expander according to the preferred embodiments of the present invention will be given with reference to the attached drawings.

FIGS. 5 to 8 show an air compressor and expander according to a first embodiment of the present invention;

As shown, the air compressor and expander according to the first embodiment of the present invention includes a first rotor 10, a second rotor 20, a casing 30, first and second end covers 40 and 50, a gear part 60, and a clearance-preventing means 70.

The first rotor 10 is coupled around a driving shaft 11, and the second rotor 20 is coupled around a driven shaft 21 so as to operate in cooperation with the first rotor 10. In this case, the first rotor 10 and the second rotor 20 have a cycloid toothed shape.

Moreover, the first rotor 10 and the second rotor 20 are formed twisted at a predetermined twisting angle along the axial direction, and the predetermined twisting angle of the first rotor 10 and the second rotor 20 is within a range between 90° and 270°. Desirably, the first rotor 10 and the second rotor 20 are coated with Teflon on the surfaces thereof.

The casing 30 is adapted to form an air compression or expansion space by the rotation of the first rotor 10 and the second rotor 20.

The first and second end covers 40 and 50 are adapted to close the both end portions of the casing 30 in such a manner as to have the driving shaft 11 and the driven shaft 21 passed therethrough in the axial direction, thereby to have the first rotor 10 or the second rotor 20 disposed between them.

An oil seal O is coupled around the driving shaft 11 and the driven shaft 21 between the first end cover 40 and the casing 30 and between the second end cover 50 and the casing 30, for preventing oil from entering the inside of the casing 30.

Further, bearings B are mounted on each of the first and second end covers 40 and 50 in such a manner as to be coupled around the driving shaft 11 and the driven shaft 21, for supporting the rotation of the driving shaft 11 and the driven shaft 21, and especially, at least two or more bearings B are mounted on the second end cover 50 side, for minimizing the vibration upon the high speed rotation of the driving shaft 11 and the driven shaft 21.

The gear part 60 is disposed on any one side of the first and second end covers 40 and 50 in such a manner as to be coupled around the driving shaft 11 and the driven shaft 21 for transmitting power to the driving shaft 11 and the driven shaft 21, and the gear part 60 is formed of a helical gear for preventing backlash or may be formed of a high precision spur gear.

The clearance-preventing means 70 is disposed at the opposite side to the gear part 60 for preventing clearance between the end covers 50 and the rotors 10 or 20. The clearance-preventing means 70 comprises T-shaped bushings 71, one side of which is coupled to central portion of the rotors and the other side of which contacts with bearings supporting the rotors, and fastening members 72 adapted to the end portions of the driving shaft 11 and the driven shaft 21 thereto to support the other side of the bearings for maintaining a predetermined distance between the gear part 60 and the end cover 40.

The gear part 60 has a protrusion 61 formed on one side thereof, for providing a predetermined distance from the bearings B coupled to the first end cover 40.

That is to say, at the state where the protrusion 61 of the gear part 60 is spaced apart from the bearings B of the first end cover 40 by a predetermined distance, the gear part 60 is coupled around the driving shaft 11 and the driven shaft 21, and at the opposite side to the gear part 60, the first rotor 10 and the second rotor 20 are coupled inside the casing 30 by means of the clearance-preventing means 70 having the T-shaped bushings 71, the bearings B, and the fastening members 72, such that even though a force is generated, the first rotor 10 and the second rotor 20 do not have clearance.

On the other hand, the first rotor 10 and the second rotor 20 have a ring-shaped bushing 73 coupled around the driving shaft 11 and the driven shaft 21 at the sides abutting with the first end cover 40, for completely preventing the first rotor 10 and the second rotor 20 from having the clearances from the driving shaft 11 and the driven shaft 21.

The gear part 60 has a rear cover 80 formed around the outside thereof, for closing the gear part 60, and bearings B are fixed on the rear cover 80, for supporting the driving shaft 11 and the driven shaft 21. Moreover, an oil seal O is mounted around the driving shaft 11 passed through the rear cover 80.

The respective bearings B that support the gear part 60, the driving shaft 11 and the driven shaft 21 by means of the rear cover 80 are lubricated by oil, and the oil does not enter the casing 30 by means of the oil seals O, such that only air is compressed or expanded inside the casing 30.

Further, the second end cover 50 has a front cover 90 formed at the outside thereof and has a through hole 51 formed for discharging or absorbing the compressed or expanded air within the casing 30 to and from a second air flow hole 91 formed at the outside of the front cover 90.

In other words, the second air flow hole 91 corresponding to a first air flow hole 31 formed on one surface of the casing 30 is formed in the axial direction on the front cover 90.

In this case, if the air compressor and expander of the present invention is used as an air compressor, the first air flow hole 31 is an air absorption hole, and the second air flow hole 91 is an air discharge hole. To the contrary, if used as an air expander, the second air flow hole 91 is an air absorption hole, and the first air flow hole 31 is an air discharge hole.

FIGS. 9 and 10 show an air compressor and expander according to a second embodiment of the present invention.

As shown, the air compressor and expander according to the second embodiment of the present invention has the same parts as in the first embodiment of the present invention, except that the first rotor 10 and the second rotor 20 are an involute toothed shape, and therefore, a detailed explanation on them is avoided.

Now, an explanation of the operation of the air compressor and expander according to the preferred embodiment of the present invention will be in detail given.

The first rotor 10 is coupled around the driving shaft 11, and the second rotor 20 is coupled around the driven shaft 21. After that, the first rotor 10 and the second rotor 20 are disposed in the casing 30.

Also, the first and second end covers 40 and 50 are disposed at the both end portions of the casing 30. In this case, the bearings B, the oil seals O, and the ring-shaped bushings 73 are shaft-coupled at the first end cover 40 side, and the T-shaped bushings 71, the oil seals O, and the bearings B are shaft-coupled at the second end cover 50 side, while being fixed by means of the fastening members 72 at the end portions of the driving shaft 11 and the driven shaft 21.

The first rotor 10 and the second rotor 20, which are coupled around the driving shaft 11 and the driven shaft 21 and are disposed inside the casing 30, are supported at one sides thereof by means of the bearings B of the gear part 60 and are fixed at the other sides thereof by means of the clearance-preventing means 70, i.e. the T-shaped bushings 71, the bearings B and the fastening members 72, such that as the first rotor 10 and the second rotor 20 do not interfere with each other, they are not abraded, thereby improving the refrigeration capability.

Also, the rear cover 80 is fixed at the first end cover 40 side, and the front cover 90 is disposed at the second end cover 50, such that air is absorbed and discharged through the second air flow port 91 formed on the front cover 90 and through the first air flow port 31 formed on the casing 30.

Referring to the air flow when the air compressor and expander of the present invention is used as the air compressor, air is absorbed through the first air flow port 31, i.e. an air absorption port, and the absorbed air is compressed, while being passed through the absorption space generated between the first rotor 10 and the second rotor 20 in the casing 30 during their rotation. Next, the compressed air is discharged to the second air flow port 91 of the front cover 90. i.e. the discharge port, through the through hole 51 of the second end cover 50.

In this process, the first rotor 10 and the second rotor 20 are fixed around the driving shaft 11 and the driven shaft 21, so as not to generate a clearance from the driving shaft 11 and the driven shaft 21, thereby generating no force.

Referring to the air flow when the air compressor and expander of the present invention is used as the air expander, air is absorbed through the second air flow port 91 of the front cover 90 of the second end cover 50, i.e. an air absorption port, and the absorbed air is expanded, while being passed through the absorption space generated between the first rotor 10 and the second rotor 20 in the casing 30 during their rotation. Next, the expanded air is discharged to the first air flow port 31 of the casing 30, i.e. the discharge port.

As described above, there is provided an air compressor and expander according to the present invention that is provided with the first and second end covers disposed at the both end portions of the casing housing the first rotor and the second rotor therein and with the clearance-preventing means disposed at any one side of the first and second end covers, thereby preventing the clearance between the end covers and the rotors.

Additionally, the air compressor and expander of the present invention has a pair of air flow ports disposed in a perpendicular relation to each other, thereby minimizing the pressure drop of air.

While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.

Claims

1-7. (canceled)

8. An air compressor and expander comprising:

a first rotor coupled around a driving shaft;
a second rotor coupled around a driven shaft so as to operate in cooperation with the first rotor;
a casing adapted to form an air compression or expansion space by the rotation of the first rotor and the second rotor;
first and second end covers adapted to close the both end portions of the casing in such a manner as to have the driving shaft and the driven shaft passed therethrough in the axial direction, thereby to have the first rotor or the second rotor disposed between them;
a gear part disposed on any one side of the first and second end covers in such a manner as to be coupled around the driving shaft and the driven shaft for transmitting power to the driving shaft and the driven shaft; and
a clearance-preventing means disposed at the opposite side to the gear part for preventing clearance between the end covers and the rotors.

9. The air compressor and expander according to claim 8, wherein the clearance-preventing means is adapted to make the ends of the rotors come into close contact with the end covers, such that the first rotor or the second rotor does not have clearance from the end covers.

10. The air compressor and expander according to claim 8, wherein the clearance-preventing means comprises T-shaped bushings, one side of which is coupled to central portion of the rotors and the other side of which contacts with bearings supporting the rotors, and fastening members adapted to the end portions of the driving shaft and the driven shaft thereto to support the other side of the bearings for maintaining a predetermined distance between the gear part and the end cover.

11. The air compressor and expander according to claim 8, wherein the first end cover has a rear cover formed at the outside thereof, and the second end cover has a front cover formed at the outside thereof.

12. The air compressor and expander according to claim 8, wherein the first rotor and the second rotor are formed twisted at a predetermined twisting angle along the axial direction, and the predetermined twisting angle of the first rotor and the second rotor is within a range between 90° and 270°.

13. The air compressor and expander according to claim 9, wherein the first rotor and the second rotor are formed twisted at a predetermined twisting angle along the axial direction, and the predetermined twisting angle of the first rotor and the second rotor is within a range between 90° and 270°.

14. The air compressor and expander according to claim 8, wherein the first rotor and the second rotor are coated with Teflon on the surfaces thereof.

Patent History
Publication number: 20070186578
Type: Application
Filed: Feb 9, 2007
Publication Date: Aug 16, 2007
Inventor: Junkang Lee (Daejeon-si)
Application Number: 11/704,518
Classifications
Current U.S. Class: Motor-type Expander (62/402); Rotary Internal Reacting Member (418/164)
International Classification: F01C 1/00 (20060101); F25D 9/00 (20060101);