Patent Publication Number: US-9835157-B2

Title: Rotor with a resin layer that has circular or spiral grooves

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Phase Application under 35 U.S.C. 371 of International Application No. PCT/JP2015/054668, filed Feb. 19, 2015 and published in Japanese as WO2015/125888 A1 on Aug. 27, 2015. This application claims priority to Japanese Patent Application 2014-032141, filed on Feb. 21, 2014. The entire disclosures of the above applications are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to rotors and rotary fluid machines. 
     RELATED ART 
     Rotary fluid machines are known that suction and discharge fluid by moving a rotor and a vane within a space formed by closing both ends of a cylinder. Regarding these rotary fluid machines, there has been a demand for preventing seizure and abrasion of the rotor. As a technique for solving this problem, for example, Patent Document 1 describes a rotary compression machine having a modified surface layer, which is formed by modifying both or one of the inner circumference of the cylinder and the outer circumference of the rotor using sulphonitriding treatment or sulfurizing treatment. 
     SUMMARY 
     Technical Problem 
     With the technique described in JP 2004-278309A, an oil film cannot be easily formed on a thrust surface of the rotor, and therefore, there has been a problem in that a leakage loss and consumption of motive power at the time of compression increase. 
     The present invention provides a technique that facilitates formation of an oil film on a thrust surface of a rotor so that a leakage loss and consumption of motive power at the time of compression can be reduced. 
     Solution to Problem 
     The present invention provides a rotor including: a base housed in a space formed by a cylindrical member and a closing plate that closes an opening portion at each of both ends of the cylindrical member in an axial direction, the base rotating around an axis in the same direction as the axial direction; a resin layer formed on a thrust surface of the base; and a plurality of concentric circular grooves or a spiral groove formed on the resin layer, the center of circles of the circular grooves or the center of a spiral of the spiral groove being different from a rotation center of the base. 
     An amount of eccentricity of the center of the circles of the circular grooves or an amount of eccentricity of the center of the spiral of the spiral groove relative to the rotation center of the base may be greater than or equal to a groove pitch. 
     The present invention also provides a rotary fluid machine including: a cylindrical member; a closing plate that closes opening portions at both ends of the cylindrical member in an axial direction; and the above-described rotor. 
     Effects of the Invention 
     According to the present invention, formation of an oil film on a thrust surface of a rotor is facilitated, and thus, a leakage loss and consumption of motive power at the time of compression can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a partial cross-sectional view showing a rotary compression machine according to an embodiment. 
         FIG. 2  is a cross-sectional view of compression mechanism  6  as viewed along arrows II-II shown in  FIG. 1 . 
         FIG. 3  is a side view of rotor  41 . 
         FIG. 4  is a plan view of rotor  41 . 
         FIG. 5  is a cross-sectional view of grooves C as viewed along arrows III-III shown in  FIG. 4 . 
         FIG. 6  is a diagram showing a modification of a rotary fluid machine. 
         FIG. 7  is a diagram showing a modification of a rotary fluid machine. 
         FIG. 8  is a diagram showing a modification of grooves C. 
         FIG. 9  is a plan view showing a modification of rotor  41 . 
     
    
    
     DESCRIPTION 
     1. Embodiment (Structure of Rotary Compression Machine) 
     Hereinafter, in the drawings, the space in which each configuration of rotary compression machine  9  is arranged will be shown as an xyz right-handed coordinate system in order to describe the arrangement of the configuration. Among coordinate signs shown in the drawings, a circle sign that is white on the inside with a black circle therein indicates an arrow extending from the distal side toward the proximal side of paper. A circle sign that is white on the inside and in which two intersecting lines are drawn indicates an arrow extending from the proximal side toward the distal side of paper. In the space, a direction parallel with an x-axis will be referred to as an x-axis direction. Of the x-axis direction, a direction in which the x component increases will be referred to as a +x direction, and a direction in which the x component decreases will be referred to as a −x direction. Regarding y and z components as well, a y-axis direction, a +y direction, a −y direction, a z-axis direction, a +z direction, and a −z direction are defined in conformity to the above definition. 
       FIG. 1  is a partial cross-sectional view showing rotary compression machine  9  according to an embodiment of the present invention. Rotary compression machine  9  is an example of a rotary fluid machine according to the present invention, and is used to compress gas such as coolant gas in air conditioning machines for, for example, automobiles, household, railways, or business use. Rotary compression machine  9  is provided with motor  7  that is housed in an upper part within closed casing  8  and serves as a driving source, and compression mechanism  6  that is arranged in a lower part within closed casing  8  and driven by motor  7  mentioned above to suction and discharge coolant gas. 
       FIG. 2  is a cross-sectional view of compression mechanism  6  as viewed along arrows II-II shown in  FIG. 1 . Compression mechanism  6  is a compression mechanism using a so-called rotary vane system (sliding vane system). Compression mechanism  6  has a cylindrical member (hereinafter referred to as cylindrical member  1 ) having an axis in the up-down direction (z-axis direction) in  FIG. 1 , first closing plate  2  that closes an end face and an opening portion (hereinafter referred to as first opening portion K 1 ) on the lower side of cylindrical member  1 , second closing plate  3  that closes an end face and an opening portion (hereinafter referred to as second opening portion K 2 ) on the upper side of cylindrical member  1 , and operation portion  4 . Cylindrical member  1  is a so-called cylinder. Operation chamber  5  is formed within cylindrical member  1  by sandwiching cylindrical member  1  from both sides in the axial direction thereof (i.e., from above and below in  FIG. 1 ) using first closing plate  2  and second closing plate  3  and fastening a plurality of portions of cylindrical member  1  in the circumferential direction with a plurality of bolts  81 . 
     Operation portion  4  has driving shaft  40 , rotor  41 , vanes  42 , and vane grooves  44 . Although vanes  42  are provided at two portions in the example shown in  FIG. 2 , vane  42  may be provided at a single portion, or vanes  42  may be provided at three or more portions. Driving shaft  40 , which passes through holes provided in first closing plate  2  and second closing plate  3  and leads to the outside of operation chamber  5 , penetrates the inner circumferential side of rotor  41 . Driving shaft  40  is connected to motor  7 , and driving shaft  40  and rotor  41  rotate in the D 1  direction by the driving force of motor  7 . Lubricating oil  80  is stored in a lower part within closed casing  8 , and when rotor  41  is rotated, lubricating oil  80  is supplied to an inner circumferential face and an outer circumferential face of rotor  41  via an oil passage (not shown) formed within a lower end portion of driving shaft  40 . 
     Driving shaft  40  and rotor  41  rotate around the same axis, whereas the center of driving shaft  40  and the center of the inner circumference of cylindrical member  1  are different. Therefore, a hoof-shaped space (operation chamber  5 ) shown in  FIG. 2  is formed between rotor  41  and an inner circumferential face of cylindrical member  1 . Rotor  41  is provided with vane grooves  44  that house vanes  42 , and vanes  42  project from vane grooves  44  due to backing pressure and receive force in a direction toward the inner circumferential face of cylindrical member  1 . With the rotation of rotor  41 , tips of vanes  42  move along vane grooves  44  while coming into contact with the inner circumferential face of cylindrical member  1 . For this reason, operation chamber  5  is partitioned into a plurality of cells by vanes  42 , and fluid that fills each cell moves from suction port  13  to discharge port  14 . As each vane  42  approaches discharge port  14 , the internal pressure of operation chamber  5  partitioned by vane  42  increases. When the internal pressure exceeds discharge pressure, the fluid that fills the inside of operation chamber  5  is discharged from discharge port  14  against discharge valve  15 . 
       FIG. 3  is a side view of rotor  41 . Rotor  41  has a cylindrical base  411 , and resin layers  410  formed on surfaces (hereinafter referred to as thrust surfaces) of base  411  each opposed to first closing plate  2  or second closing plate  3 . Resin layers  410  contain, as binder resin, at least one of, for example, polyamide-imide resin, polyimide resin, diisocyanate modification and BPDA modification of these resins, sulfone-modified resin, epoxy resin, polyetheretherketone resin, phenolic resin, polyamide, and elastomer. Resin layers  410  also contain, as a solid lubricant, at least one of, for example, graphite, carbon, molybdenum disulfide, polytetrafluoro-ethylene, boron nitride, tungsten disulfide, fluororesin, and soft metal (e.g., Sn or Bi). Base  411  may be made of cast iron, or may be formed by performing various kinds of treatment, such as sintering, forging, cutting, pressing, and welding, on any kind of material such as aluminum or stainless steel. Base  411  may be made of ceramic, or may be made of resin. 
       FIG. 4  is a plan view of rotor  41 . A plurality of concentric circular grooves C are formed on each resin layer  410 . Center O 2  of the circles of grooves C is located at a position different form rotation center O 1  of rotor  41  (shaft center of driving shaft  40 ). It is desirable that the amount of eccentricity of center O 2  of grooves C relative to rotation center O 1  of rotor  41  is greater than or equal to a single pitch of grooves C (in the case where grooves C are arranged at equal intervals). 
       FIG. 5  is a cross-sectional view of grooves C as viewed along arrows III-III shown in  FIG. 4 . The cross-section of each groove C has a shape resembling a U-shape or a semi-circle with a width that is narrower at a deeper position and changes more sharply on the side closer to the bottom. Grooves C are formed by moving an edge of a cutting tool along the surface of each resin layer  410 . Width w of each groove C is the width of groove C in a cross-section orthogonal to the extending direction of groove C, and is the length of a line connecting both end portions of groove C in this cross-section. Interval P of the grooves, i.e., the pitch of the grooves, is the interval between two adjoining grooves C, and is the length of a line connecting the centers of these grooves C in a cross-section orthogonal to the extending direction of grooves C. Interval p is, for example, 0.1 to 0.15 mm. In this example, width w of each groove C is the same as interval p of grooves C. 
     In this embodiment, each crest portion B formed on resin layers  410  comes into line contact with first closing plate  2  or second closing plate  3 . Here, since center O 2  of grooves C is located at a position different from rotation center O 1  of rotor  41 , the direction of a tangent line at each point of grooves C is different from the rotation direction of rotor  41  (except a point on a line passing through center O 2  and rotation center O 1 ). For this reason, lubricating oil  80  is drawn into spaces between crest portions B and first and second closing plates  2  and  3  due to a wedge effect (also called a wedge-film effect), facilitating formation of oil films. Accordingly, according to this embodiment, air tightness and lubricity at contact portions between resin layers  410  and first and second closing plates  2  and  3  increase as compared with a case where center O 2  of grooves C is located at the same position as rotation center O 1  of rotor  41 . 
     2. Modifications 
     The embodiment is as described above, whereas the content of this embodiment may be modified as follows. The following modifications may also be combined. 
     2-1. Application Example 
     The above-described embodiment mentions air conditioning machines for automobiles, household, railways, or business use as apparatuses to which rotary compression machine  9  is to be applied. However, rotary compression machine  9  may also be applied to freezing chambers, refrigerating apparatuses, and the like, and may also be used in various kinds of apparatuses such as water temperature adjustment, thermostat bathes, humidistat bathes, painting equipment, powder conveying apparatuses, food processing apparatuses, and air separators. Although the above-described embodiment takes rotary compression machine  9  as an example of the rotary fluid machine according to the present invention, in addition, a rotary air blower that deals with gas, a rotary pump that deals with liquid, and the like can also be considered to be the rotary fluid machine according to the present invention. 
     2-2. Modification 1 
       FIG. 6  is a diagram showing a modification of a rotary fluid machine. Operation portion  4   a  has driving shaft  40   a , rotor  41 , and vane  42   a . Driving shaft  40   a  is provided with an eccentric portion (not shown) having a circular column shape whose center is an axis different from the axis of driving shaft  40   a  itself, and this eccentric portion is fitted into the inner circumferential side of rotor  41   a  (so-called rolling piston). For this reason, upon driving shaft  40   a  rotating, rotor  41   a  accordingly rotates eccentrically along an inner circumferential face of cylindrical member  1   a.    
     Vane  42   a  is a member having a plate shape (plate-shaped member) that extends from the inner circumferential face of cylindrical member  1   a  and is in contact with an outer circumferential face of rotor  41   a . Vane  42   a  projects from the inner circumferential face of cylindrical member  1   a  due to spring  43   a  and receives force in a direction toward driving shaft  40   a , and a tip of vane  42   a  presses the outer circumferential face of rotor  41   a  due to this force. Operation chamber  5   a , which is a space formed between rotor  41   a  and cylindrical member  1   a , is partitioned by vane  42   a  that presses the outer circumferential face of rotor  41   a.    
     Suction port  13   a  is an opening portion provided in the inner circumferential face of cylindrical member  1   a , and causes coolant gas to be suctioned from the outside into operation chamber  5   a . Upon operation portion  4   a  rotating clockwise along arrow D 2 , the space in operation chamber  5   a  partitioned by the outer circumferential face of rotor  41   a  moves clockwise along the inner circumferential face of cylindrical member  1   a . Discharge port  14   a  is closed by discharge valve  15   a  when the internal pressure of operation chamber  5   a  is smaller than predetermined discharge pressure. When the internal pressure of operation chamber  5   a  becomes greater than or equal to the discharge pressure, the coolant gas is discharged from discharge port  14   a.    
     In this modification as well, as in the above-described embodiment, a plurality of concentric circular grooves are formed on the resin layers provided on the thrust surfaces of rotor  41   a , thereby facilitating formation of oil films between the resin layers and the first and second closing plates. However, in this modification, rotor  41   a  eccentrically rotates, and therefore the wedge effect is generated regardless of the position of the center of the groove circles. Accordingly in this modification, the position of the center of the groove circles is not limited. 
     2-3. Modification 2 
       FIG. 7  is a diagram showing a modification of a rotary fluid machine. In this case, swing bushes  45   b  are provided on an inner circumferential face of cylindrical member  1   b . Operation portion  4   b  has driving shaft  40   b  and rotor  41   b . Rotor  41   b  is a so-called swing piston and has a plate-shaped member (hereinafter referred to as “plate-shaped member  412   b ”) and a cylindrical base (hereinafter referred to as “cylindrical base  411   b ”). Plate-shaped member  412   b  is sandwiched by swing bushes  45   b , thereby maintaining air tightness. That is to say, plate-shaped member  412   b  is integrally provided with cylindrical base  411   b , extends from an outer circumferential face of cylindrical base  411   b  toward the inner circumferential face of the cylindrical member, and is sandwiched by swing bushes  45   b  provided in this inner circumferential face. Operation chamber  5   b  shown in  FIG. 7  is provided between rotor  41   b  and the inner circumferential face of cylindrical member  1   b , and this operation chamber  5   b  is partitioned by plate-shaped member  412   b.    
     Driving shaft  40   b  has an eccentric portion, and this eccentric portion is fitted into an inner circumferential face of cylindrical base  411   b  of rotor  41   b . For this reason, upon driving shaft  40   b  rotating, rotor  41   b  swings. Thereby, the position at which operation chamber  5   b  is partitioned by plate-shaped member  412   b  and cylindrical base  411   b  is moved, fluid that fills each partitioned chamber moves from suction port  13   b  to discharge port  14   b , and the internal pressure of operation chamber  5   b  increase. When the internal pressure exceeds discharge pressure, the fluid is discharged from discharge port  14   b  against discharge valve  15   b.    
     Note that  FIG. 7  does not show the entire body of cylindrical member  1   b , but shows parts (inner circumferential face, suction port  13   b , discharge port  14   b , and discharge valve  15   b ) thereof. In order to also maintain air tightness at plate-shaped member  412   b  held by swing bushes  45   b , it is more favorable to provide a recess portion in an area where swing bushes  45   b  and plate-shaped member  412   b  are present and form a resin layer. Although the shape of cylindrical member  1   b  is a cylindrical shape, it is not limited to a cylindrical shape, but may be any kind of tubular shape. For example, the cross-section thereof may be an ellipse. 
     In this modification as well, as in the above-described embodiment, a plurality of concentric circular grooves are formed on the resin layers provided on the thrust surfaces of cylindrical base  411   b , thereby facilitating formation of oil films between the resin layers and the first and second closing plates. However, in this modification, cylindrical base  411   b  swings, and accordingly the wedge effect is generated regardless of the position of the center of the groove circles. Accordingly in this modification, the position of the center of the groove circles is not limited. 
     2-4. Modification 3 
       FIG. 8  is a diagram showing a modification of grooves C. In this example, width w of each groove C is smaller than interval p between grooves C (w&lt;p). Each crest portion B is provided with a flat surface having width a between grooves C. In this case, it is desirable that width a is smaller than width w (a&lt;w). By setting width a smaller than width w, grooves C will not be completely filled by crest portions B that come into contact with operation portion  4  and undergo elastic deformation. That is to say, even if crest portions B undergo elastic deformation toward grooves C, grooves C retain lubricating oil  80 , and accordingly the air tightness of the rotary fluid machine increases. 
     It is also desirable that depth h of each groove C is smaller than interval p between adjoining grooves C (h&lt;p). In this case, of crest portions B formed between adjoining grooves C, the width of a skirt portion corresponding to interval p is longer than the height corresponding to depth h of each groove C. Accordingly, crest portions B have a relatively strong shape with respect to lateral force in  FIG. 8 . Depth h is 1 to 20 μm, for example. 
     2-5. Modification 4 
     In the above-described embodiment, the cross-sectional shape of base  411  in a plane vertical to driving shaft  40  is a circle. However, the cross-sectional shape of base  411  is not limited to a circle. The cross-sectional shape of base  411  may be, for example, an ellipse, a shape of constant-width such as a Reuleaux polygon, or a shape combining a semi-circle and an ellipse. 
     2-6. Modification 5 
     In the above-described embodiment, grooves C are concentric circular grooves. However, as shown in  FIG. 9 , groove C may have a spiral shape. In this case, since the wedge effect is generated even if the center of the spiral of groove C coincides with the rotation center of rotor  41 , the center of the spiral of groove C may coincide with the rotation center of rotor  41 . However, a greater wedge effect is obtained as a whole when the center of the spiral of groove C is different from the rotation center of rotor  41 . Accordingly, it is desirable that the center of the spiral of groove C is different from the rotation center of rotor  41 . It is also desirable that the amount of eccentricity of the center of the spiral of groove C relative to the rotation center of rotor  41  is greater than or equal to a single pitch of the spiral of groove C (in the case where the pitch of the spiral of groove C is constant). 
     2-7. Modification 6 
     Although the above-described embodiment does not mention the area in which the plurality of grooves C are formed in the resin layers  410 , grooves C do not have to be formed over the entire resin layers  410 , and grooves C may be formed in a part of resin layers  410 . Grooves C may be formed on one of resin layers  410  provided on the two thrust surfaces.