JP2005083235A - Scroll compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scroll compressor securing sufficient reliability and high performance even if carbon dioxide is used as working medium, without largely changing constitution of a compression mechanism part and lubricating structure of the related art. <P>SOLUTION: The scroll compressor has a working medium compression mechanism including: a fixed scroll 5 having a spiral lap; a swirl scroll 6 having a spiral lap meshed with the lap of the fixed scroll 5 to form a plurality of compression chambers 7; and a self-rotation prevention part preventing self-rotation of the swirl scroll 6 to make the swirl scroll 6 perform only swirling. The swirl scroll 6 is made of an aluminum alloy and its lap tip surfaces 6b are approximately the same flat surfaces. The fixed scroll 5 is made of cast iron material and the surface including at least the overall surface in slide-contact with the swirl scroll 6 is coated with metal nitride coating 26. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a scroll compressor that is applied to refrigeration, air conditioning, heating cycles, and the like, and more particularly, to a scroll compressor that provides high reliability and sliding performance even when carbon dioxide is used as a working gas. .

  Also in the conventional scroll compressor, in order to suppress leakage from a plurality of compression chambers formed by the orbiting scroll and the fixed scroll, and to ensure high compression efficiency, there are various devices in the structure of the compression mechanism and the lubrication structure. It is made. For example, orbital scrolls can be used to ensure precise shape accuracy for the spiral wrap geometry, etc. easily by machining, as well as excellent reliability as a combination of sliding materials. And the fixed scroll are made of aluminum alloy and cast iron material, respectively, and the high pressure lubricating oil in the compressor's sealed container is supplied to each sliding surface of the compression mechanism to ensure the compression chamber is sealed and lubricated. Is known (for example, see Patent Document 1).

  The configuration and operation of a conventional scroll compressor will be described with reference to FIGS. A compression mechanism and an electric motor 102 for driving the compression mechanism are accommodated in an airtight container 101 having a discharge pressure atmosphere having an oil reservoir 104 for storing lubricating oil at the bottom. A stator 102a of the electric motor 102 is fixed to the hermetic container 101, and a crankshaft 103 that drives a compression mechanism is coupled to the rotor 102b. The compression mechanism includes a fixed scroll 105, a turning scroll 106 that meshes with the fixed scroll 105 to form a plurality of compression chambers 107, and a rotation prevention component 108 that prevents the turning scroll 106 from rotating and only turns. Yes. An orbiting drive shaft 109 is projected on the opposite side of the orbiting scroll 106, and the orbiting drive shaft 109 is fitted into an eccentric bearing 111 provided on the main shaft 110 of the crankshaft 103. Is driven to turn. Axial movement limiting plane part 114 that limits the axial movement of orbiting scroll 106 with a small gap between main bearing 112 that rotatably supports main axis 110 and end plate back surface 113 on the back of orbiting scroll 106. Are fixed to the fixed scroll 105.

  A sliding partition ring 116 that divides the pressure acting on the end plate back surface 113 into a discharge pressure acting on the central portion and a pressure lower than the discharge pressure acting on the outer peripheral portion is disposed on the axial movement restriction plane portion 114. ing. The back pressure chamber 117 formed in the space radially outward of the sliding partition ring 116 is connected to the center of the back plate 113 through a communication passage 119 having a throttle mechanism 118 provided inside the end plate of the orbiting scroll 106. It communicates with the space 120 where the discharge pressure of the part acts. Further, the space 120 on which the discharge pressure acts is also communicated with a lap seal storage groove 122 formed at the lap tip of the orbiting scroll 106 via a communication passage 121.

  Further, the crankshaft 103 is provided with an oil supply passage 123 penetrating the crankshaft 103, and an end portion of the oil supply passage 123 on the side opposite to the compression mechanism is communicated with the oil reservoir 104 via an oil pump 124, and an end on the compression mechanism side is provided. The portion communicates with a space 120 in which the discharge pressure at the center of the end plate back surface 113 of the orbiting scroll 106 acts.

With such a configuration, the lubricating oil guided from the oil reservoir 104 to the space 120 where the discharge pressure at the center of the end plate back surface 113 of the orbiting scroll 106 acts by the oil pump 124 passes through the communication passage 119 and the throttle mechanism 118. The chip seal storage groove is supplied to the outermost compression chamber 107 through the communication passage 121 and sufficiently supplied to the space formed between the chip seal storage groove 122 and the back surface of the chip seal 125 from the communication passage 121. The leakage passage to the low pressure side formed in the longitudinal direction of 122 is blocked, and the lubricant leaking from the chip seal storage groove 122 crosses the chip seal 125 in the perpendicular direction to the outer lower pressure compression chamber 107. In addition, the lubricating oil is supplied to the wall surface of the wrap forming the compression chamber 107 so that the compression passage 107 is closed. It is to ensure the lubrication of the sliding portions with.
JP 2000-213477 A

  By the way, in recent years, carbon dioxide, which is a natural refrigerant, has been used in place of HCFC-based and HFC-based so-called chlorofluorocarbon refrigerants in the fields of refrigeration, air conditioning, heating, etc., from the viewpoint of protecting the ozone layer and preventing environmental warming. Attention has been paid. When carbon dioxide is used as a working gas (refrigerant), for example, in air conditioning applications, the operating pressure is about 12 MPa, the high pressure is about 4 MPa, and the pressure is about 4 MPa. The pressure difference between the operating pressure itself and the high and low pressures becomes very large. For this reason, there is a strong demand for a highly reliable structure and lubricating structure of a compression mechanism that can be sufficiently put into practical use even at high operating pressures, and a scroll compressor having a structure with high compressor efficiency even at high differential pressure operation.

  However, the conventional scroll compressor has a structure corresponding to a CFC-based refrigerant having a low operating pressure of about several MPa at a high pressure and a relatively small pressure difference between a high pressure and a low pressure. With this structure, carbon dioxide is used as a refrigerant. When used, closed containers can be overcome by using high-strength materials and increasing the thickness of parts. As a result of high differential pressure operation, high pressure gas and lubricating oil leak to the compression chamber due to the tip seal housing groove on the wrap tip of the orbiting scroll, and the compressor performance deteriorates due to increased compression loss. Therefore, there is a problem that it is difficult to ensure sufficient reliability and performance.

  In view of the above-described conventional problems, the present invention provides a scroll compressor that can ensure sufficient reliability and high performance even when working gas having a large operating pressure and high / low pressure difference such as carbon dioxide is used. And

  The scroll compressor according to the present invention prevents the rotation of the orbiting scroll, the fixed scroll having the spiral wrap, the orbiting scroll having the spiral wrap that meshes with the wrap of the fixed scroll and forms a plurality of compression chambers. In the scroll compressor having a working gas compression mechanism having a rotation preventing part that only turns, the orbiting scroll is made of an aluminum alloy material, and its wrap tip surface is substantially the same flat surface. Is made of cast iron material and coated with a metal nitride coating on at least the entire surface in sliding contact with the orbiting scroll.

  According to this configuration, even in an operating state where the operating pressure is very high and the pressure difference between the high pressure and the low pressure is large, the wear resistance of the sliding portion between the orbiting scroll and the fixed scroll is ensured, and the sealing surface that defines the compression chamber There is no high-pressure compressed gas and lubricating oil leakage due to the tip seal at the wrap front end surface of the orbiting scroll, and sufficient reliability and high performance can be ensured without deterioration in compression performance.

  In addition, the structure and the lubrication structure of the compression mechanism portion are provided with an electric motor, a compression mechanism, and a turning drive means for transmitting the power of the electric motor to the orbiting scroll in a closed container having an oil reservoir for storing lubricating oil at the bottom. The orbiting drive means is constituted by an orbiting drive engaging portion provided on the back of the end plate on the side opposite to the orbiting of the orbiting scroll so as to engage with the crankshaft driven by the electric motor and its eccentric engaging portion. A sliding partition ring that divides the pressure acting on the back surface of the end plate at a radially outward position of the engaging portion into a discharge pressure acting on the center portion of the back surface of the end plate and a pressure lower than the discharge pressure acting on the outer peripheral portion of the back surface of the end plate A throttling mechanism is provided on the back, supplying high-pressure lubricating oil from the oil reservoir to the center of the back of the mirror plate, and communicating the back pressure chamber formed in the outer space of the center of the back of the mirror and the sliding partition ring. A structure in which the passage is formed inside the end plate is preferable.

  Further, when the metal nitride film is formed by a low temperature salt bath nitriding method at a processing temperature of 430 to 490 ° C., deformation of the lap shape and dimensional change due to nitriding treatment can be prevented, and deterioration of surface roughness can be suppressed. This is preferable.

  Further, when carbon dioxide is used as the working gas, it is preferable from the viewpoint of environmental protection and can be suitably used in the scroll compressor of the present invention.

  According to the scroll compressor of the present invention, the orbiting scroll is formed of an aluminum alloy system, and the wrap tip surface is formed to be substantially the same flat surface, the fixed scroll is formed of a cast iron material, and the surface of the main part is coated with a metal nitride film. With this coating, the wear resistance of the sliding part can be secured even when working gas with high operating pressure and high differential pressure operation is used, and high-pressure compressed gas and lubrication on the wrap end surface of the orbiting scroll Oil leakage can be prevented and compression performance is not lowered, and sufficient reliability and high performance can be ensured.

  Hereinafter, an embodiment of a scroll compressor of the present invention will be described with reference to FIGS.

  1 to 3, a compression mechanism and an electric motor 2 for driving the compression mechanism are accommodated and disposed in a sealed container 1 having a discharge pressure atmosphere having an oil reservoir 4 for storing lubricating oil at the bottom. The hermetic container 1 is made of a high-strength material that guarantees a design pressure and a design temperature suitable for using carbon dioxide as a refrigerant. The electric motor 2 also employs chemically and thermally stable resins and insulating materials in the presence of carbon dioxide and lubricating oil. A stator 2a of the electric motor 2 is fixed to the hermetic container 1, and a crankshaft 3 that drives a compression mechanism is coupled to the rotor 2b.

  The compression mechanism includes a fixed scroll 5, a turning scroll 6 that meshes with the fixed scroll 5 to form a plurality of compression chambers 7, and a rotation prevention component 8 that prevents the turning of the turning scroll 6 and only turns. Yes. The orbiting scroll 6 is a high silicon-based aluminum alloy material that has good machinability that can be easily obtained by machining, has a low thermal expansion coefficient, and has excellent sliding characteristics with cast iron materials. The entire front end surface 6b of the spiral wrap is formed with substantially the same flat surface. The fixed scroll 5 is made of a cast iron material that has a good machinability that can be easily obtained by machining and has excellent sliding characteristics with a high silicon-based aluminum alloy. The metal nitride film 26 is formed by nitriding the surface portion including at least the entire surface that is in sliding contact with the orbiting scroll 6 after finishing.

  An orbiting drive shaft 9 is provided on the opposite side of the orbiting scroll 6 so that the orbiting drive shaft 9 is fitted into an eccentric bearing 11 provided on the main shaft 10 of the crankshaft 3. Is driven to turn. Axial movement limiting plane portion 14 that limits the axial movement of orbiting scroll 6 by providing a minute gap between main bearing 12 that rotatably supports main shaft 10 and end plate rear surface 13 on the back of orbiting scroll 6. Are fixed to the fixed scroll 5.

  A sliding partition ring 16 that divides the pressure acting on the back plate 13 into a discharge pressure acting on the central portion and a pressure lower than the discharge pressure acting on the outer peripheral portion is disposed on the axial movement restriction plane portion 14. ing. A back pressure chamber 17 formed in a space radially outward of the sliding partition ring 16 is connected to the center of the back plate 13 through a communication passage 19 having a throttle mechanism 18 provided inside the end plate of the orbiting scroll 6. It communicates with the space 20 where the discharge pressure of the part acts.

  Further, the crankshaft 3 is provided with an oil supply passage 23 penetrating through the crankshaft 3, and an end portion of the oil supply passage 23 on the side opposite to the compression mechanism is communicated with the oil reservoir 4 via an oil pump 24. The portion communicates with a space 20 in which the discharge pressure at the center portion of the end plate back surface 13 of the orbiting scroll 6 acts.

  With such a configuration, the lubricating oil is guided from the oil reservoir 4 to the space 20 where the discharge pressure at the center of the rear surface 13 of the orbiting scroll 6 acts by the oil pump 24, and the lubricating oil in this space 20 communicates. An appropriate amount is supplied to the compression chamber 7 on the outermost periphery through the passage 19 through the throttle mechanism 18, and lubricating oil is supplied to the wrap wall surface forming the compression chamber 7 to ensure the sealing of the compression chamber 7 and lubrication of the sliding portion. doing.

  Next, the metal nitride film 26 formed on the surface of the fixed scroll 5 made of cast iron material will be described in detail. In general, nitriding treatment such as salt bath soft nitriding, gas nitriding, gas soft nitriding or the like is known as one method for forming a hard and wear-resistant coating on the surface of an iron-based material. By this nitriding treatment, a hard coating having a hardness of about HV (Vickers hardness) of about 1000 and having excellent wear resistance can be obtained thickly (about 1 mm), so it is widely used for improving the wear resistance of sliding parts. . However, on the other hand, it has been pointed out that the processing temperature is as high as 500 to 600 ° C., the processing time is as long as several tens of hours, the deformation, distortion and dimensional change of parts are large, and the surface roughness deteriorates.

  Therefore, the nitriding treatment method for forming the metal nitride film 26 of the fixed scroll 5 according to the present embodiment can prevent the complicated spiral wrap shape deformation and dimensional change due to the nitriding treatment after the machining finish, and the surface roughness. The main objective is to suppress the deterioration of That is, by adopting a low-temperature salt bath nitriding method (treatment temperature 430 to 490 ° C., treatment time 240 minutes) with little deformation after treatment, small dimensional change, and little deterioration in surface roughness, the compression chamber 7 is good. Secures hermeticity. The compression chamber 7 is defined by a wrap wall surface including the wrap tip surfaces 5 a and 6 b of the fixed scroll 5 and the orbiting scroll 6, a wrap root surface 6 a of the orbiting scroll 6, and a wrap root surface 5 b of the fixed scroll 5. And by ensuring the sealing performance of those sliding contact surfaces, the favorable sealing performance of the compression chamber 7 is ensured, and the performance of the scroll compressor can be secured. Furthermore, the metal nitride film 26 obtained by the low-temperature salt bath nitriding treatment is a film having a surface hardness of about 650 HV (Vickers hardness) and a thickness of about 6 to 8 μm and excellent wear resistance with a high silicon-based aluminum alloy. .

  The orbiting scroll 6 and the fixed scroll 5 are arranged in such a manner that the respective spiral wraps are meshed with each other in the same manner as in the compression mechanism portion of the conventional configuration, and act on the back plate 13 during operation. The fixed scroll 5 has a back pressure application structure similar to that of the conventional configuration such as a sliding partition ring 16 that divides the pressure into a discharge pressure acting on the central portion and a pressure lower than the discharge pressure acting on the outer peripheral portion. The wrap tip surface 5a and the wrap root surface 6a of the orbiting scroll 6 are swung in a sealed state. On the other hand, the wrap tip surface 6b of the orbiting scroll 6 and the wrap root surface 5b of the fixed scroll 5 are set so that a minute gap is generated during operation. This small gap is caused by the difference in thermal expansion between the wrap portion of the high silicon-based aluminum alloy orbiting scroll 6 and the cast iron fixed scroll 5 when the temperature rises during operation, and the wrap root surface of the orbiting scroll 6 and the fixed scroll 5. It is set in order to avoid the problem of wear due to contact with the surface 5b.

  By the way, the capacity per unit mass of carbon dioxide is much larger than that of chlorofluorocarbon refrigerants. For example, under the air conditioning conditions, the refrigeration effect per unit mass is about 8 times the theoretical value, and the same capability is achieved. The same capacity can be obtained with a capacity of about 1/8 compared to the conventional compressor capacity. In a scroll compressor, as a means of securing the strength of the lap section under high operating pressure and reducing the compressor capacity, the lap height is significantly lower than the lap height dimensions of conventional chlorofluorocarbon working gas compressors. Dimensions are possible. As the wrap height decreases, the minute gap can be set smaller.

  According to such a configuration, the conventional refrigerant scroll compressor has a lower operating pressure than the case where carbon dioxide is used as the refrigerant, and the differential pressure between the high pressure and the low pressure is small. The method using the tip seal 125 as a means for preventing the working gas leakage in the chamber was effective. However, when the working gas is carbon dioxide, the pressure difference between the high pressure and the low pressure becomes very large at a significantly high operating pressure, and the tip seal 125 has a low pressure. Acts as a leakage passage for the working gas across all the compression chambers 107 from the high pressure to the high pressure, and the amount of leakage increases dramatically in accordance with the increase in the differential pressure between the high pressure and the low pressure, and the tip seal 125 and the tip seal storage groove 122 The high-pressure lubricating oil contained in the working gas that leaks into the compression chambers 107 from the gaps also significantly increases, thereby reducing the compression efficiency. In this way, when the working gas is carbon dioxide, the entire surface of the wrap front end surface 6b of the orbiting scroll 6 is formed with substantially the same flat surface without using the tip seal 125 and the tip seal storage groove 122 that cause performance degradation. The wrap root surface 5b of the fixed scroll 5 and the wrap front end surface 6b of the orbiting scroll 6 are provided with a finer gap as described above, so that the entire width of the wrap thickness is a leakage gas in each compression chamber 7. Therefore, the amount of compressed gas leaking across the wrap tip surface 6b can be reduced, and high compression efficiency can be achieved.

  Further, according to this configuration, the wrap root surface 6 a of the orbiting scroll is placed on the wrap tip surface 5 a of the fixed scroll 5 against the gas compression force that tries to separate the orbiting scroll 6 from the fixed scroll 5 in the direction of the main shaft 10. The back pressure mechanism that abuts and seals is the same as in the case of using a conventional chlorofluorocarbon refrigerant as the working gas, but in this embodiment, the surface includes at least the entire surface that is in sliding contact with the orbiting scroll 6 of the fixed scroll 5. The parts are covered with a metal nitride coating 26 formed by a low temperature salt bath nitriding method after machining finish, thereby sufficiently ensuring sufficient wear resistance of the sliding sealing surface. As a result, when carbon dioxide is used as the working gas, the high sliding surface pressure during normal operation due to high operating pressure, and the very high sliding due to compression in the liquid or wet gas state at the start of the compressor Lubrication feedback delay from refrigeration, air conditioning, and heating cycle due to poor lubrication due to surface pressure, low lubricity of the refrigerant itself, and the above-mentioned reduction in compressor capacity when using carbon dioxide as the working gas It is possible to secure the wear resistance of the sliding sealing surface against obstacles such as poor lubrication due to the above.

  Note that the effect of improving the wear resistance of the sliding sealing surface can be obtained by using a salt bath soft nitriding method, a gas nitriding method or a gas soft nitriding method instead of the low temperature salt bath nitriding method.

  The scroll compressor of the present invention can ensure the wear resistance of the sliding portion even when the operating pressure is high and the high differential pressure operation, and can prevent high-pressure compressed gas and lubricating oil leakage from the compression chamber. Therefore, sufficient reliability and high performance can be ensured without degrading the compression performance, so that refrigeration, air conditioning and heating using working gas with high operating pressure and high differential pressure such as carbon dioxide can be ensured. Useful for scroll compressors in cycles.

It is a longitudinal cross-sectional view of the scroll compressor of one Embodiment of this invention. It is an expanded sectional view of the compression mechanism part of the embodiment. It is an expanded sectional view which shows the meshing state of the scroll wrap of the embodiment. It is a longitudinal cross-sectional view of the scroll compressor of a prior art example. It is an expanded sectional view of the compression mechanism part of the conventional example. It is an expanded sectional view which shows the meshing state of the scroll wrap of the prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Airtight container 2 Electric motor 3 Crankshaft 4 Oil sump 5 Fixed scroll 6 Orbiting scroll 7 Compression chamber 8 Anti-rotation component 9 Orbit drive shaft (eccentric drive engagement part)
11 Eccentric bearing (Eccentric engaging part)
13 Back of end plate 16 Sliding partition ring 17 Back pressure chamber 18 Throttle mechanism 19 Communication passage

Claims (4)

  A fixed scroll having a spiral wrap; a orbiting scroll having a spiral wrap that meshes with the fixed scroll wrap to form a plurality of compression chambers; and an anti-spinning component that prevents the orbiting scroll from rotating and only rotates. In the scroll compressor provided with a working gas compression mechanism, the orbiting scroll is formed of an aluminum alloy material, the wrap tip surface is substantially the same flat surface, and the fixed scroll is formed of a cast iron material. A scroll compressor characterized in that a surface including at least the entire surface in sliding contact with the orbiting scroll is coated with a metal nitride film.   An electric motor, a compression mechanism, and orbiting drive means for transmitting the power of the electric motor to the orbiting scroll are arranged in a closed container having an oil reservoir for accumulating lubricating oil at the bottom, and the orbiting drive means is a crank driven by the electric motor. Consists of a revolving drive engagement portion provided on the back surface of the orbiting scroll on the side opposite to the end of the orbiting scroll so as to engage with the shaft and its eccentric engagement portion, and at the radially outward position of the orbiting drive engagement portion A sliding partition ring that divides the pressure acting on the center of the back of the end plate and the pressure lower than the discharge pressure acting on the outer periphery of the back of the end plate is disposed on the back of the end plate, A high pressure lubricating oil is supplied from an oil reservoir, and a passage having a throttle mechanism that connects a back pressure chamber formed in a space outside the back of the end plate and the sliding partition ring is formed inside the end plate. The scroll compressor according to claim 1.   The scroll compressor according to claim 1, wherein the metal nitride film is formed by a low temperature salt bath nitriding method at a processing temperature of 430 to 490 ° C. The scroll compressor according to claim 1, wherein the working gas is carbon dioxide.

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