Patent Publication Number: US-6663369-B2

Title: Fluid compressor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a Continuation Application of PCT Application No. PCT/JP01/06338, filed Jul. 23, 2001, which was not published under PCT Article 21 (2) in English. 
    
    
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-241523, filed Aug. 9, 2000, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fluid compressor of helical-blade type that constitutes, for example, the refrigeration cycle of an air conditioner. 
     2. Description of the Related Art 
     Reciprocating compressors and rotary compressors are known as compressors for use in, for example, refrigeration cycles of air conditioners. These compressors may become debased in sealing property or may be complicated in structure. 
     Recently, it is proposed that helical-blade type compressors be used in place of reciprocating compressors or rotary compressors. This is because helical-blade type compressors are relatively simple in structure, has improved sealing property and can compress fluid with high efficiency. In addition, the components of a helical-blade type compressor are easy to manufacture and assemble. 
     FIG. 11 shows a part of a helical type compressor. In this helical-blade type compressor, the roller  102  is eccentrically arranged in the fixed cylinder  101  and has a helical groove  103  in its outer circumferential surface. A blade  104  is fitted in the groove  103  such that it can move in the depth direction of the groove  104 . 
     As the roller  102  revolves, the blade  104  divides the space between the cylinder  101  and the roller  102  into a plurality of compression chambers  105 . Each compression chamber has a smaller volume than the immediately adjacent chamber that is more close to one end of the roller  102 . The coolant gas introduced into the compression chamber  105  at that end of the roller  102  is gradually compressed to a high pressure until it is forced out of the compression chamber  105  provided at the other end of the roller  102 . 
     As FIG. 12 shows, the helical groove  103  and the blade  104  have a rectangular cross section, taken along a line extending at right angles to their axes. Having a rectangular cross section, the helical groove  103  is easy to cut in the outer circumferential surface of the roller  102 . 
     The blade  104  has a width a little smaller than the width of the helical groove  103 . In other words, the widths of the groove  103  and blade  104  are predetermined so that the blade  104  can move in the depth direction of the helical groove  103 . 
     Since the helical groove  103  and the blade  104  have a rectangular cross section, the blade  103  remains in contact with both sides of the helical groove  103  even when it completely lies within the helical groove  103 . 
     Hence, the bottom space  106  defined between the lower surface of the blade  104  and the bottom of the helical groove  103  cannot sufficiently communicate with the high-pressure compression chamber  105 A. 
     Consequently, the pressure of the coolant gas in the bottom space  106 , which lies at the bottom of the helical groove  103 , is lower than the pressure in the high-pressure compression chamber  105 A. The coolant gas is inevitably forced out at a low pressure. Thus, the coolant gas cannot gain an optimal pressure rise. This may result in a decrease of compression efficiency. 
     When the blade  104  protrudes from the helical groove  103  to a maximum degree, it receives the highest possible pressure. At this time, the blade  104  is most deformed and cannot smoothly move with respect to the helical groove  103 . This may degrade the sealing property of the compressor. 
     In the process of assembling the compression mechanism unit, the blade  104  having a rectangular cross section must be fitted into the helical groove  103  having a rectangular cross section. This work is extremely cumbersome, lowering the efficiency of assembling the compression mechanism unit. 
     An object of the present invention is to provide a fluid compressor in which the bottom space lying at the bottom of the helical groove can easily communicate with the high-pressure compression chamber to enhance the compression efficiency, and the blade can smoothly move with respect to the helical groove to improve the sealing property. 
     BRIEF SUMMARY OF THE INVENTION 
     A fluid compressor according to the present invention comprises: 
     a hollow cylinder; 
     a roller provided in the cylinder, with an axis deviated from the axis of the cylinder, and having a helical groove made in an outer circumferential surface and having turns arranged at a pitch that gradually increases from one end to the other end; 
     a blade fitted in the helical groove of the roller and being movable with respect to the helical groove; and 
     a plurality of compression chambers provided between the cylinder and the roller, defined by the blade and designed to compress the fluid to a high pressure gradually as the fluid flows in an axial direction of the roller, from one end to the other end of the roller, 
     wherein the helical groove has one side positioned at a high-pressure compression chamber and another side positioned at a low-pressure compression chamber, and the one side and the another side are inclined at the same angle such that the groove gradually opens toward the outer circumferential surface of the roller, an opening angle θ defined by the one side and another side is: 
     
       
         0°&lt;θ≦20°,  
       
     
     the blade has one side positioned at a high-pressure compression chamber and another side positioned at a low-pressure compression chamber, and both sides of the blade are inclined at substantially the same angle as both sides of the helical groove.” 
     The helical groove has one side positioned at a high-pressure compression chamber and another side positioned at a low-pressure compression chamber, and the one side is inclined to the another side such that the groove gradually opens toward the outer circumferential surface of the roller. 
     Thus, a gap develops between one side of the helical groove and one side of the blade, which opposes the side of the groove, when the blade moves, protruding from the helical groove. The space lying at the bottom of the helical groove therefore reliably communicates with the high-pressure compression chamber. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     FIG. 1 is a cross-sectional view of a helical-blade type compressor according to an embodiment of the invention, which is a fluid compressor; 
     FIG. 2 is a cross-sectional view, showing the helical groove and the blade; 
     FIG. 3 is a characteristic diagram representing the relation between the opening angle of the groove and the compression efficiency (COP); 
     FIG. 4 is a cross-sectional view depicting a helical groove and a blade, the groove having sides that define an angle greater than 20°; 
     FIG. 5 is a cross-sectional view, showing the helical groove and blade of a second embodiment of this invention; 
     FIG. 6 is a cross-sectional view, illustrating the helical groove and blade of a third embodiment of the invention; 
     FIG. 7 is a cross-sectional view, displaying the helical groove and blade of a fourth embodiment of the present invention; 
     FIG. 8 is a cross-sectional view, showing the helical groove and blade of a fifth embodiment of this invention; 
     FIG. 9 is a cross-sectional view, illustrating the helical groove and blade of a sixth embodiment of the invention; 
     FIG. 10 is a cross-sectional view, depicting the helical groove and blade of a seventh embodiment of this invention; 
     FIG. 11 is a cross-sectional view of a conventional helical-blade type compressor, which is a fluid compressor; and 
     FIG. 12 is a cross-sectional view showing the helical groove and blade of the conventional compressor. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of this invention will be described, with reference to the accompanying drawings. 
     FIGS. 1 to  3  show the first embodiment of the present invention. FIG. 1 depicts a so-called “horizontal helical-blade type compressor,” which is a fluid compressor. This helical-blade type compressor comprises a closed case  1  extending horizontally, a shaft  2  held in the closed case  1  and having a horizontal axis, a compression mechanism unit  3 , and an electric motor unit  4 . The shaft  2  connects the compression mechanism unit  3 , or the right-side unit, to the electric motor unit  4 , or the left-side unit. 
     A coolant inlet pipe Pa is coupled to one end of the closed case  1 , or to a lower part of the end. A coolant outlet pipe Pb is coupled to this end of the closed case  1 , or to an upper part of the end. Outside the case  1 , the inlet pipe Pa and the outlet pipe Pb are connected by a condenser, an expansion valve and an evaporator (not shown). The pipes Pa and Pb, condenser, expansion valve and evaporator constitute the refrigeration cycle of, for example, an air conditioner. 
     The compression mechanism unit  3  will be described in detail. As FIGS. 1 and 2 show, a cylinder  5  is provided. The cylinder  5  has a flange  5   a  formed integral with and protruding from one end. The flange  5   a  is fitted, contacting the inner circumferential surface of the closed case  1 , and is secured to the case  1  by, for example, welding performed on the outer circumferential surface of the case  1 . 
     The cylinder  5  opens at the left and right ends. A main bearing  6  is fitted in the left end of the cylinder  5 . A sub-bearing  7  is fitted in the right end of the cylinder  5 . 
     The main bearing  6  comprises a boss part  6   a  and a flange part  6   b . The boss part  6   a  supports the middle part of the shaft  2 , allowing the shaft  2  to rotate freely. The flange part  6   b  is formed integral with one end of the boss part  6   a . It protrudes from the boss part  6   a  and closes the open end of the cylinder  5 . 
     The sub-bearing  7  comprises a boss part  7   a  and a flange part  7   b . The boss part  7   a  supports one end portion of the shaft  2 , allowing the shaft  2  to rotate freely. The flange part  7   b  is formed integral with the boss part  7   a  and closes the open end of the cylinder  5 . 
     The coolant inlet pipe Pa extends into the closed case  1 , passing through the end of the closed case  1 . Its distal end is connected to a connection hole  22  that is made in the flange part  7   b  of the sub-bearing  7 . The cylinder  5  has an inlet-pipe guiding recess  5   b  made in one end. The recess  5   b  opposes the connection hole  22 . 
     A lubricant-guiding plate  9  and a closing plate  10  are secured to the outer surface of the sub-bearing  7  with fixture members. An oil-pumping pipe  11  is connected to the lubricant-guiding plate  9 . Lubricant oil is pumped up from the bottom of the closed case  1  and applied into the oil-guiding groove  11   a  cut in the outer circumferential surface of the shaft  2 . The closing plate  10  abuts on the end of the shaft  2 , closing the open part of the guiding plate  9 . 
     An eccentric crank  12  is formed integral with the shaft  2  and positioned between the boss part  6   a  of the main bearing  6  and the boss part  7   a  of the sub-bearing  7 . The eccentric crank  12  has its axis deviated by a prescribed distance from the axis of the shaft  2 . 
     A roller  14  is eccentrically arranged in the cylinder  5 . Its axis is deviated from the axis of the shaft  2  by the same distance as the axis of the roller  14  is deviated. The roller  14  has an axial length a little smaller than that of the cylinder  5 . A part of the outer circumferential surface of the roller is set in rolling contact, along an axial direction, with the inner circumferential surface of the cylinder  5 . 
     The roller  14  has a support hole  15 . The eccentric crank  12  of the shaft  2  is inserted in the support hole  15  and can rotate. The eccentric crank  12  rotates as the shaft  2  rotates. As a result, the roller  14  performs an eccentric rotation. 
     An Oldham mechanism  16  lies between the flange part  7   b  of the sub-bearing  7  and the lower part of the roller  14 . The Oldham mechanism  16  makes the roller  14  to revolve, preventing it from undergoing rotation. 
     A helical groove  17  is made in the outer circumferential surface of the roller  14 . The turns of the groove  17  are arranged at a pitch that gradually decreases from the right end of the roller  14  toward the left end thereof. A helical blade  18  is fitted in the helical groove  17  and can move in the depth direction of the helical groove  17 . 
     The outer peripheral surface of the blade  18  lies in close contact with the inner circumferential surface of the cylinder  5 . The helical groove  17  and the blade  18  have specific cross sections, which will be described later in detail. 
     The blade  18  is made of synthetic resin, such as fluororesin, which provides smooth surfaces. Its inside diameter is larger than the diameter of the roller  14 . The blade  18  has been fitted into the helical groove  17  by forcedly reducing the diameter of the blade  18 . 
     Thus, the blade  18  is incorporated, together with the roller  14 , in the cylinder  5 , with its outer peripheral surface kept in resilient contact with the inner circumferential surface of the cylinder  5 . 
     As the shaft  2  rotates, the position at which the roller  14  assumes rolling contact with the inner circumferential surface of the cylinder  5  gradually moves in the circumferential direction of the cylinder  5 . At the rolling-contact position, the blade  18  moves toward the bottom of the helical groove  17  until its outer peripheral surface becomes flush with the inner circumferential surface of the roller  14 . 
     At any other position than the rolling-contact position, the blade  18  moves protrudes from the helical groove  17 , more or less in accordance with the distance from the rolling-contact position. At the position away from the rolling-contact position by 180° in the circumferential direction, the blade  18  projects by a maximum distance (or a maximum height). Thereafter, the blade  18  approaches the rolling-contact position. Hence, the blade  18  repeats the motion described above. 
     In a plane extending along the diameters of the cylinder  5  and roller  14 , the roller  14  is eccentric with respect to the cylinder  5 . The roller  14  therefore has a part of its outer circumferential surface set in rolling contact with the inner circumferential surface of the cylinder  5 . Hence, a space having a crescent cross section is provided between the cylinder  5  and the roller  14 . 
     The blade  18  partitions the space between the outer circumferential surface of the roller  14  and the inner circumferential surface of the cylinder  5 , into a plurality of spaces that are arranged in the axial direction of the roller  14 . These spaces are continuous to one another, defining a helical space extending around and along the outer circumferential surface of the roller  14 . 
     These spaces are called “compression chambers 20.”Because of the varying pitch of the turns of the helical groove  17 , each compression chamber  20  has a smaller volume than the immediately adjacent chamber  20  that is more close to the left end of the roller  14 . 
     The rightmost compression chamber  20  faces an inlet section  20 S that communicates with the inlet-pipe guiding recess  5   b  made in the cylinder  5  and the connection hole  22  of the coolant inlet pipe Pa. The leftmost compression chamber  20  faces an outlet section  20 D that communicates with a coolant outlet hole  21  made in the flange part  6   b  of the main bearing  6 . 
     The cylinder  5  has a blade stopper  23  that opposes the blade  18 . The blade  18  moves, projecting from and sinking into the helical groove  17  as the roller  14  revolves. At the same time, a force acts on the blade  18  to pull the blade  18  from the end of the helical groove  17 . The blade  18  abuts, at its end, on the blade stopper  23 . The end portion of the blade  18  is therefore prevented from projecting from the helical groove  17 . 
     The electric motor unit  4  comprises a rotor  31  and a stator  32 . The rotor  31  is mounted on the shaft  2 . The stator  32  is secured to the inner circumferential surface of the rotor  31 . It faces the circumferential surface of the rotor  31 , with a narrow gap provided between it and the rotor  31 . 
     The helical groove  17  and the blade  18  have specific cross-sections, as will be described below. 
     As FIG. 2 shows, the cross section that the helical groove  17  has in a plane extending at right angles to its axis has two sides  17   a  and  17   b.    
     The sides  17   a  and  17   b  lie adjacent to a low-pressure compression chamber  20 B and a high-pressure compression chamber  20 A, respectively. The sides  17   a  and  17   b  are inclined such that the groove  17  gradually opens toward its top. Hence, the cross section is shaped like an inverted trapezoid, having a base shorter than the top. 
     The sides  17   a  and  17   b  of the helical groove  17  define an opening angle θ, which satisfies the following formula (1): 
     
       
         0°&lt;θ≦20°  (1)  
       
     
     The formula (1) derives from the relation between the opening angle and the compression efficiency (COP: coefficient of performance), which is illustrated in FIG.  3 . 
     In the helical-blade type compressor of the structure described above, the rotor  31  is rotated, rotating the shaft  2 , by supplying electric power is supplied to the electric motor unit  4 . The shaft  2  rotates the eccentric crank  12 , which drives the roller  14 . 
     The Oldham mechanism  16  makes the roller  14  to revolve, preventing it from undergoing rotation. As the roller  14  revolves, the rolling-contact position, at which the roller  14  contacts has its outer circumferential surface contacting the cylinder  5  gradually moves in the circumferential direction. The blade  18  moves along the diameter of the roller  14 , protruding from and sinking into the helical groove  17 . 
     As this sequence of operation proceeds, the coolant gas at a low pressure is drawn from the evaporator through the coolant inlet pipe Pa, into the compression chamber  20  that faces the inlet section  20 S. As the roller  14  rotates, the coolant gas is supplied into the compression chamber  20  that faces the outlet section  20 D. 
     Any compression chamber  20  that faces outlet section  20 D has a smaller volume than the adjacent chamber  20  that faces the inlet section  20 S. Therefore, the coolant gas is compressed as it is supplied from one compression chamber to the next one. It gains the prescribed high pressure in the compression chamber  20  that faces the leftmost outlet section  20 D. The high-pressure gas is applied from this compression chamber  20  into the condenser through the coolant outlet hole  21  and the outlet pipe Pb. Thus, a refrigeration-cycle operation of the known type is accomplished. 
     The blade  18  has a cross section that is shaped like an inverted trapezoid, similar to the cross section of the helical groove  17 . As FIG. 2 shows, the sides  18   a  and  18   b  of the blade  18 , which lie adjacent to a low-pressure compression chamber  20 B and a high-pressure compression chamber  20 A, respectively, are inclined at the same angle as the sides  17   a  and  17   b  of the helical groove  17 . 
     As indicated above, the helical groove  17  has a cross section shaped like an inverted trapezoid, in a plane that extends at right angles to its axis. The sides  17   a  and  17   b , which lie on a low-pressure side and a high-pressure side, respectively, are inclined such that the groove  17  gradually opens toward its top. The opening angle θ is 0°&lt;θ≦20° as defined in the formula (1). 
     Therefore, a gap is provided between the side  18   b  of the blade  18 , which lies adjacent to the high-pressure compression chamber  20   a , and the side  17   b  of the helical groove  17 , which opposes the side  18   b , while the blade  18  remains projecting from the helical groove  17  as is illustrated in FIG.  2 . 
     In this case, a space  19  at the bottom of the helical groove  17  reliably communicates with the high-pressure compression chamber  20 A. The coolant gas in the space  19  therefore acquires the same pressure as the coolant gas in the high-pressure compression chamber  20 A. This increases the compression efficiency. Further, the blade  18  would not be prevented from smoothly moving, because no excessive pressure acts on the blade  18 . 
     FIG. 3 shows the relation between the opening angle θ and the compression efficiency (COP: coefficient of performance). The greater the opening angle θ, the larger the space  19  at the bottom of the helical groove  17  becomes and the more reliably it communicates with the high-pressure compression chamber  20 A. It was confirmed that COP remarkably increased when the opening angle θ of the helical groove  17  was: 0°&lt;θ≦20°. It is preferred that the opening angle θ be 0.5° or more. 
     FIG. 4 depicts a helical groove  17 A that has an opening angle θ 1  that is much larger than the upper limit of the range defined by the formula (1). In this case, the angle defined by the sides of the blade  18 A is set at the same value as the opening angle of the helical groove  17 A. 
     Since the opening angle θ 1  of the helical groove  17 A is much greater than 20°, the gap between the side  17   a  of the groove  17 A and the side  18   a  of the blade  18 A and the gap between the side  17   b  of the groove  17 A and the side  18   b  of the blade  18 A are inevitably large when the blade  18 A protrudes most from the helical groove  17 A. 
     In this condition, the blade  18 A can hardly be deformed. The side  18   a  of the blade  18 A cannot closely contact the side  17   a  of the helical groove  17 A. There remains a gap between the side  18   a  and the side  17   a . This degrades the sealing property. 
     FIG. 5 shows the second embodiment of the invention. In this embodiment, the helical groove  17 B has an opening angle θ that falls within the range defined by the formula (1) and the side  17   a  of the groove  17 B and side  18   a  of the blade  18 B are inclined at an angle φ that is defined by the following formula (2): 
     
       
         0°&lt;φ≦θ/2  (2)  
       
     
     Hence, the helical groove  17 B has a specific opening angle θ and defines a small gap between its low-pressure side  17   a  and the low-pressure side  18   a  of the blade  18  when the blade  18 B most protrudes from the helical groove  17 B. 
     The low-pressure side  18   a  of the blade  18 B is therefore pressed onto the low-pressure side  17   a  of the helical groove  17 B. This can enhance the sealing property. Thus, the sealing property would not decrease as has been explained with reference to FIG.  4 . 
     If φ=θ/2 in the formula (2), that is, the low-pressure side  17   a  and high-pressure side  17   b  of the helical groove  17 B are inclined at the same angle, the helical groove  18 B can be easily cut with a tool (e.g., end mill or the like) which has an inclined edge. 
     FIG. 6 shows the third embodiment of this invention. The opening angle θ of the helical groove  17  falls within the range specified by the formula (1) and explained with reference to FIG.  2 . However, the angle θ b  defined by the sides  18   a  and  18   b  of the blade  18 C is different from the opening angle θ of the helical groove  17 . 
     As seen from the cross section of the blade  18 C, taken along line extending at right angles to the axis of the blade, the opening angle θ b  defined by the low- and high-pressure sides  18   a  and  18   b  of the blade  18 C has the following relation with the opening angle θ of the helical groove  17 : 
     
       
         θ b ≦θ  (3)  
       
     
     Thus, the upper edge of the side  17   a  of the helical groove  17  does not contact the side  18   a  of the blade  18 C even if the blade  18 C most protruding from the helical groove  17  is pressed onto the low-pressure side  17   a  of the helical groove  17 . This mitigates the concentration of stress at the upper edge  17   e  of the side  17   a . Fast wear of the blade  18 C can therefore be prevented, which improve the reliability of the compressor. 
     FIG. 7 displays the fourth embodiment of the present invention. The helical groove  17 B has its low-pressure side  17   a  inclined at an angle φ that satisfies the formula (2), as in the second embodiment described with reference to FIG.  5 . 
     The low-pressure side  18   a  of the blade  18 D is inclined at an angle φ b  that has the following relation with the inclination angle φ of the low-pressure side  17   b  of the helical groove  17 B: 
     
       
         φ b ≦φ  (4)  
       
     
     Hence, the upper edge  17   e  of the side  17   a  does not contact the low-pressure side  18   a  of the blade  18 D even if the blade  18 D most protruding from the helical groove  17 B is pressed onto the low-pressure side  17   a  of the helical groove  17 B. This mitigates the concentration of stress at the upper edge  17   e  of the side  17   a . Fast wear of the blade  18 C can therefore be prevented, which improve the reliability of the compressor. 
     FIGS. 8 to  10  show the fifth, sixth and seventh embodiments of the invention, respectively. 
     In the fifth embodiment shown in FIG. 8, the low-pressure side  17   a  of the helical groove  17 C and the low-pressure side  18   a  of the blade  18 E are inclined at 0°. Namely, they stand almost vertically. 
     The sixth embodiment shown in FIG. 9 is similar in shape to the first embodiment illustrated in FIG.  2 . Nonetheless, the sides  18   a  and  18   b  of the blade  18 F are inclined at 0°, extending parallel to each other. 
     The seventh embodiment shown in FIG. 10 is similar in shape to the first embodiment illustrated in FIG.  2 . Nonetheless, of the two opposing sides  18   a  and  18   b  of the blade  18 G, only the low-pressure side  18   a  is inclined at a prescribed angle. The high-pressure side  18   b  is inclined at 0°, extending almost vertically. 
     Like the first to fourth embodiments, the fifth to seventh embodiments can have its compression efficiency improved, because the high-pressure compression chamber  20 A reliably communicates with the space  19  at the bottom of the helical groove  17 C ( 17 ). In addition, the blades  18 E to  18 G can provide sufficient sealing property. 
     Needless to say, the angle θ defined by the sides  17   a  and  17   b  of the helical groove  17 C or  17  satisfies the formula (1) in the embodiments of FIGS. 8 to  10 . 
     The helical-blade compressors described above are of the type in which the roller revolves. This invention is not limited to this type, nevertheless. The invention can be applied to helical-blade type compressors in which the roller rotates together with the cylinder. 
     As has been described, the space at the bottom of the helical groove reliably communicates with the high-pressure compression chamber in the present invention. This can not only enhance the compression efficiency, but also enable the blade to move smoothly into and from the helical groove, helping to increase the sealing property. Moreover, the blade can be easily fitted into the helical groove, which increases the assembling efficiency.