Patent Publication Number: US-2005132703-A1

Title: Rotating fluid machine

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      The present non-provisional application claims priority under 35 USC 119 to Japanese Patent Application No. 2003-401321 filed on Dec. 1, 2003 the entire contents thereof is hereby incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a rotating fluid machine including a casing, a rotor rotatably supported at the casing, a working section provided at the rotor, and a rotary valve which is provided between the casing and the rotor for controlling an expansion or compression stroke and an exhaust or intake stroke of a working medium with respect to the working section.  
      2. Description of the Related Art  
      A rotating fluid machine having a rotary valve including a fixed side valve plate supported at the casing side and a movable side valve plate supported at the rotor side which are in contact with each other on a slide surface is known, for example, as disclosed in Japanese Patent Application Laid Open No. 2002-256805. A circular steam supply passage and an arc-shaped steam discharge passage open to the slide surface of the fixed side valve plate; and seven steam passages, which communicate with seven expansion chambers of the rotor, open to the slide surface of the movable side valve plate equidistantly in the circumferential direction.  
      Accordingly, a high-temperature high-pressure steam, which is supplied from the steam supply passage of the fixed side valve plate to a predetermined steam passage of the movable side valve plate, expands in the expansion chamber to drive the piston. The resultant low-temperature low-pressure steam, which has finished expansion work, is discharged from the predetermined steam passage of the movable side valve plate to the steam supply/discharge passage of the fixed side valve plate. This operation is performed sequentially for the seven expansion chambers, thereby driving the rotor to rotate.  
      Of the circular steam supply passage and the arc-shaped steam discharge passage, which open to the slide surface of the fixed side valve plate, the circular steam supply passage has a small opening area, while the arc-shaped steam discharge passage has a large opening area. Therefore, the expansion region of the slide surface of the fixed side valve plate opposed to the steam passage connecting to the expansion chamber in the expansion stroke has a large sliding area since only the circular steam supply passage opens, while the exhaust region of the slide surface of the fixed side valve plate opposed to the steam passage connecting to the expansion chamber in the exhaust stroke has a small sliding area since the arc-shaped steam discharge passage opens. Thus, in the slide surface of the fixed side valve plate, the area of the expansion region and the area of the exhaust region are imbalanced, so that the abrasion of the exhaust region with the smaller sliding area, of the slide surface of the fixed side valve plate and the slide surface of the movable side valve plate, is promoted to impair the flatness of the sliding surface, leading to a fear of leakage of the working medium from the rotary valve.  
     SUMMARY OF THE INVENTION  
      The present invention has been achieved in view of the above circumstances, wherein one object is to prevent uneven abrasion of a slide surface of a rotary valve of a rotating fluid machine and to inhibit leakage of a working medium.  
      In order to attain the above-described object, according to a first feature of the present invention, there is provided a rotating fluid machine comprising: a casing; a rotor rotatably supported by the casing; a working section provided in the rotor; and a rotary valve provided between the casing and the rotor for controlling an expansion or compression stroke and an exhaust or intake stroke of a working medium with respect to the working section, the rotary valve having a fixed side valve plate supported at the casing side and a movable side valve plate supported at the rotor side which are in contact with each other on a slide surface, supply and discharge passages for the working medium formed in the fixed side valve plate being open to the slide surface, wherein the slide surface of the fixed side valve plate has an expansion or compression region with a small opening area of the supply and discharge passages and an exhaust or intake region with a large opening area of the supply and discharge passages, and wherein a sliding area of the expansion or compression region and a sliding area of the exhaust or intake region are set to be substantially equal.  
      According to a second feature of the present invention, in addition to the first feature, the rotating fluid machine is an expander having the expansion stroke and the exhaust stroke, and has the intake stroke at an early stage of the expansion stroke.  
      An axial piston cylinder group A of the embodiment corresponds to the working section of the present invention, an expander E of the embodiment corresponds to the rotating fluid machine of the present invention, and a second steam passage P 2  and a fifth steam passage P 5  of the embodiment correspond to the supply and discharge passages of the present invention.  
      With arrangement of the first feature, the slide surface of the fixed side valve plate including the expansion or compression region with the small opening area of the supply and discharge passages as well as the exhaust or intake region with the large opening area of the supply and discharge passage is set so that the sliding area of the expansion or compression region and the sliding area of the exhaust or intake region are substantially equal. Therefore, the uneven abrasion of the slide surface due to the slide area difference between the expansion or compression region and the exhaust or intake region is prevented to suppress leakage of the working medium, thus enhancing the efficiency of the rotating fluid machine.  
      With arrangement of the second feature, the rotating fluid machine is the expander having the expansion stroke and the exhaust stroke, and has the intake stroke at the early stage of the expansion stroke. Therefore, the sliding area of the expansion region corresponding to the expansion stroke following the intake stroke is decreased to suppress the uneven abrasion of the slide surface effectively. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:  
       FIG. 1  is a longitudinal sectional view of an expander;  
       FIG. 2  is an enlarged view of the section  2  in  FIG. 1 ;  
       FIG. 3  is an exploded perspective view of a rotor;  
       FIG. 4  is an enlarged view of the section  4  in  FIG. 1 ;  
       FIG. 5  is a view taken along the line  5 - 5  in  FIG. 4 ;  
       FIG. 6  is a view taken along the line  6 - 6  in  FIG. 4 ;  
       FIG. 7  is a view taken along the line  7 - 7  in  FIG. 4 ;  
       FIG. 8  is a view taken along the line  8 - 8  in  FIG. 4 ; and  
       FIG. 9  is a perspective view of a coil spring, a packing retainer and a V packing. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      As shown in  FIG. 1  to  FIG. 3 , an expander E of this embodiment is used in, for example, a Rankine cycle system. The expander E converts the thermal energy and the pressure energy of high-temperature high-pressure steam as a working medium into mechanical energy that is outputted. A casing  11  of the expander E is formed from a casing body  12 , a front cover  15  joined via a seal  13  to a front opening of the casing body  12  by a plurality of bolts  14 , a rear cover  18  joined via a seal  16  to a rear opening of the casing body  12  by a plurality of bolts  17 , and an oil pan  21  joined via a seal  19  to a lower opening of the casing body  12  by a plurality of bolts  20 .  
      A rotor  22  is arranged rotatably around an axis L and extends in the fore-and-aft direction through the center of the casing  11  with a front part supported by combined angular bearings  23  provided in the front cover  15 , and a rear part thereof supported by a radial bearing  24  provided in the casing body  12 . A swash plate holder  28  is formed integrally with a rear face of the front cover  15 . A swash plate  31  is rotatably supported by the swash plate holder  28  via an angular bearing  30 . The axis of the swash plate  31  is inclined relative to the axis L of the rotor  22 , and the angle of inclination is fixed.  
      The rotor  22  includes an output shaft  32  supported in the front cover  15  by the combined angular bearings  23 , three sleeve support flanges  33 ,  34 , and  35  formed integrally with a rear part of the output shaft  32 , a rotor head  38  that is joined by a plurality of bolts  37  to the rear sleeve support flange  35  via a metal gasket  36  and is supported in the casing body  12  by the radial bearing  24 , and a heat-insulating cover  40  that is fitted over the three sleeve support flanges  33 ,  34 , and  35  from the front and joined to the front sleeve support flange  33  by a plurality of bolts  39 .  
      Sets of five sleeve support holes  33   a,    34   a,  and  35   a  are formed in the three sleeve support flanges  33 ,  34 , and  35  respectively at intervals of 72° around the axis L. Five cylinder sleeves  41  are fitted into the sleeve support holes  33   a,    34   a,  and  35   a  from the rear. A flange  41   a  is formed on the rear end of each of the cylinder sleeves  41 , and axial positioning is carried out by abutting this flange  41   a  against the metal gasket  36  while fitting the flange  41   a  into a step  35   b  formed in the sleeve support holes  35   a  of the rear sleeve support flange  35  (see  FIG. 8 ). A piston  42  is slidably fitted within each of the cylinder sleeves  41 , the front end of the piston  42  abutting against a dimple  31 a formed on the swash plate  31 , and a steam expansion chamber  43  is defined between the rear end of the piston  42  and the rotor head  38 .  
      Next, the structure of a rotary valve  71  which supplies and discharges steam to and from five expansion chambers  43  of the rotor  22  will be described with reference to  FIG. 4  to  FIG. 9 .  
      As shown in  FIG. 4 , the rotary valve  71  disposed along the axis L of the rotor  22  includes a valve body portion  72 , a fixed side valve plate  73  made of carbon, and a movable side valve plate  74  made of carbon, TEFLON®, metal or the like. In a state in which the movable side valve plate  74  is positioned by a knock pin  75  in the rotating direction on a rear surface of the rotor  22 , the movable side valve plate  74  is fixed by a bolt  76  which is screwed into an oil passage closing member  45  (see  FIG. 2 ). The bolt  76  also has a function of fixing the rotor head  38  to the output shaft  32 .  
      In the valve body part  72 , a circular flange  72   a,  which is integrally formed at a rear portion of the valve body part  72 , abuts to a rear surface of the rear cover  18  via a seal member  91 , and is fixed by a plurality of bolts  92 . In this case, a support portion  72   b  with a circular section, which is integrally formed at a front portion of the valve body part  72 , is fitted in a support hole  18   a  of the rear cover  18 . An annular holder  79  is fixed by a plurality of bolts  80  to a support surface  18   b  leading to the support hole  18   a  of the rear cover  18 . The fixed side valve plate  73 , which is held within the holder  79  via a seal member  82 , is prevented from rotating by knock pins  81  and  81  coated with TEFLON®. The fixed side valve plate  73  is positioned in the rotating direction by the knock pins  81  and  81 , but is floatingly supported to be slightly movable in the radial direction and the direction of the axis L.  
      A pressure chamber  84  with a circular section is opened to a mating surface  83  where the valve body part  72  abuts to the fixed side valve plate  73 . A steam supply pipe  85 , which penetrates through the valve body part  72  via a seal member  93 , extends through a center of the pressure chamber  84  to reach the mating surface  83 . Inside the pressure chamber  84 , a coil spring  86 , a packing retainer  87  and a V packing  88  are sequentially disposed on an outer periphery of the steam supply pipe  85 .  
      A small gap is provided between a tip end of the steam supply pipe  85  and the mating surface  83  of the fixed side valve plate  73 , so that even if the steam supply pipe  85  thermally expands in the direction of the axis L, the tip end does not interfere with the mating surface  83 . One through-hole  85   a  which is formed in the steam supply pipe  85  communicates with a rear part of the pressure chamber  84 . The high-temperature high-pressure steam supplied to the pressure chamber  84  urges the fixed side valve plate  73  toward the movable side valve plate  74  to bring slide surfaces  77  of the valve plates  73  and  74  into close contact with each other, thereby exhibiting a function of improving the sealing performance. A plurality of through-hole  85   a  may be provided in correspondence to the strength of the steam supply pipe  85  and the required steam supply amount to the pressure chamber  84 .  
      As is obvious from  FIG. 4  and  FIG. 9 , the packing retainer  87 , which is urged by the coil spring  86  which are formed of a uniform diameter without tapering, includes a flat surface  87   a  to which the coil spring  86  abuts, a conical surface  87   b  which is formed on an opposite side from the flat surface  87   a,  and a through-hole  87   c  which is loosely fitted on an outer periphery of the steam supply pipe  85 . Formed on the V packing  88  held by the packing retainer  87  are a conical surface  88 a which is supported on the conical surface  87   b  of the packing retainer  87 , a first seal lip S 1  which seals a gap to the mating surface  83  of the fixed side valve plate  73 , and a second seal lip S 2  which seals a gap to an inner peripheral surface  84 a of the pressure chamber  84 .  
      The V packing  88  has a main object of sealing the gap to the inner peripheral surface  84   a  of the pressure chamber  84  so that the second seal lip S 2  is deformed outwardly in a radial direction by the steam pressure of the pressure chamber  84  to be in close contact with the inner peripheral surface  84   a.  Accordingly, the second seal lip S 2  excellently follows the extension of the inner diameter of the inner peripheral surface  84   a  of the pressure chamber  84  due to thermal expansion of the valve body section  72 , to thereby ensure the sealing performance.  
      The coil spring  86  functions to provide a preliminary load to press the V packing  88  against the mating surface  83  via the fixed side valve plate  73  before the development of the pressure of the high-temperature high-pressure steam, and to dampen the vibration of the fixed side valve plate  73  in cooperation with the seal member  82  and the pressure of the high-temperature high-pressure steam in the pressure chamber  84 . The packing retainer  87  functions to hold the V packing  88  in an appropriate posture inside the pressure chamber  84 , and to enhance the durability of the V packing  88  by blocking the heat of the high-temperature high-pressure steam.  
      The coil spring  86  has a structure in which a spring seat is eliminated in order to secure a large number of winding of the spring in the small space inside the pressure chamber  84 . The packing retainer  87  interposed between the coil spring  86  and the V packing  88  is used as a spring seat without causing the coil spring  86  to directly abut to the V packing  88 . Therefore, a special spring seat is not needed to be provided in the V packing  88 , and the size of the pressure chamber  84  is reduced in the direction of the axis L while securing the maximum length of the coil spring  86 .  
      As is clear from  FIG. 4  to  FIG. 8 , the steam supply pipe  85  is disposed on the axis L of the rotor  22 . A steam discharge pipe  89  is disposed to be eccentrically positioned outwardly in the radial direction of the steam supply pipe  85 . A first steam passage P 1  formed inside the steam supply pipe  85  communicates with the slide surface  77  via a second steam passage P 2  formed in the fixed side valve plate  73 . Five third-steam-passages P 3 , which are equidistantly disposed to surround the axis L, penetrate through the movable side valve plate  74 . Opposite ends of five fourth-steam-passages P 4 , which are formed in the rotor  22  to surround the axis L, communicate respectively with the third steam passages P 3  and the expansion chamber  43 . While a portion at which the second steam passage P 2  opens to the slide surface  77  is circular, a portion at which a fifth steam passage PS opens to the slide surface  77  is formed into an arc shape with the axis L as the center.  
      On the slide surface  77  of the fixed side valve plate  73 , the arc-shaped fifth steam passage P 5  and two arc-shaped sixth steam passages P 6  and P 6 , which communicate with one another, are each provided in a concave form. The sixth steam passage P 6  and P 6  communicate with seventh steam passages P 7  and P 7 , which are formed in the valve body section  72 , at the mating surface  83 . A steam discharge chamber  94  is formed between the casing body  12  and the rear cover  18 . The steam discharge chamber  94  communicates with the steam discharge pipe  89 , and communicates with the seventh steam passages P 7  and P 7  which are formed in the valve body  72 .  
      As is obvious from  FIG. 6 , the circular second steam passage P 2  for supplying the high-temperature high-pressure steam, and the arc-shaped fifth steam passage P 5  for discharging low-temperature low-pressure steam are opened to the slide surface  77  of the fixed side valve plate  73  of the rotary valve  71 . An intake stroke starts at the moment when one of the five third-steam-passages P 3  of the movable side valve plate  74  communicates with the circular second steam passage P 2 . An expansion stroke is performed from the time when the third steam passage P 3  is shut off from the communication with the second steam passage P 2  until the third steam passage P 3  communicates with the arc-shaped fifth steam passage P 5 . An exhaust stroke is performed while the third steam passage P 3  is communicating with the arc-shaped fifth steam passage P 5 .  
      The slide surface  77  of the fixed side valve plate  73  is divided into two on the left and the right by the line a-a connecting the starting points of the second steam passage P 2  and the fifth steam passage P 5 . When the right side is defined as an expansion region and the left side as an exhaust region, only a part of the circular second steam passage P 2  and a part of the arc-shaped fifth steam passage P 5  open in the expansion region on the right side, while most part of the arc-shaped fifth steam passage P 5  opens in the exhaust region on the left side. Therefore, the sliding area of the expansion region is larger than the sliding area of the exhaust region in this situation.  
      Thus, in this embodiment, the radius of a recessed portion  73   a  formed at the central part of the fixed side valve plate  73  is made large in the expansion region on the right side, and is made small in the exhaust region on the left side; and an arc-shaped notch  73   b  is formed to extend over 180° along the outer peripheral portion of the expansion region on the right side, whereby the sliding area in the expansion region on the right side and the sliding area in the exhaust region on the left side are set to be substantially equal.  
      Next, the operation of the expander E of the present embodiment with the above-described construction will be described.  
      The high-temperature high-pressure steam generated by heating water by a vaporizer passes through the first steam passage P in the steam supply pipe  85 , the mating surface  83  and the second steam passage P 2  of the fixed side valve plate  73 , to reach the slide surface  77  of the movable side valve plate  74 . The second steam passage P 2  which opens to the slide surface  77  instantly communicates, at a predetermined timing, with the five third-steam-passages P 3  formed in the movable side valve plate  74  which rotates integrally with the rotor  22 , so that the high-temperature high-pressure steam passes from the third steam passage P 3  through the fourth steam passage P 4  formed in the rotor  22 , to be supplied to the expansion chamber  43  in the cylinder sleeve  41 .  
      Even after the communication between the second steam passage P 2  and the third steam passage P 3  is shut off with the rotation of the rotor  22 , the high-temperature high-pressure steam expands in the expansion chamber  43 , whereby the piston  42  fitted in the cylinder sleeve  41  is pushed forward from the top dead center to the bottom dead center, and the front end of the piston  42  presses the dimple  31   a  of the swash plate  31 . As a result, a rotation torque is given to the rotor  22  due to the reaction force which the piston  42  receives from the swash plate  31 . Thus, every time the rotor  22  makes one-fifth of a turn, the high-temperature high-pressure steam is supplied into a new adjacent expansion chamber  43 , thereby continuously driving the rotor  22  to rotate.  
      While the piston  42  having reached the bottom dead center with the rotation of the rotor  22  retreating to the top dead center by being pressed by the swash plate  31 , the low-temperature low-pressure steam pushed out of the expansion chamber  43  is supplied to a condenser via the fourth steam passage P 4  of the rotor  22 , the third steam passage P 3  of the movable side valve plate  74 , the slide surface  77 , the fifth steam passage P 5  and the sixth steam passages P 6  and P 6  of the fixed side valve plate  73 , the mating surface  83 , the seventh steam passages P 7  and P 7  of the valve body section  72 , the steam discharge chamber  94  and the steam discharge pipe  89 .  
      The rotary valve  71  supplies and discharges steam to and from an axial piston cylinder group A via the flat slide surface  77  between the fixed side valve plate  73  and the movable side valve plate  74 , thereby effectively preventing the leakage of the steam. This is because the flat slide surface  77  is easily machined with high precision and the control of the clearance is easier as compared with a cylindrical slide surface. In addition, when the pressure of the high-temperature high-pressure steam supplied to the expander E becomes high, the high-temperature high-pressure steam becomes likely to leak from the slide surface  77  of the fixed side valve plate  73  and the movable side valve plate  74 , but the pressing load, which the pressure chamber  84  generates in accordance with the increase in the pressure, increases to enhance the surface pressure of the slide surface  77 , thus exhibiting a sealing performance corresponding to the pressure of the high-temperature high-pressure steam.  
      Uniform surface pressure acts on the slide surface  77  of the fixed side valve plate  73  and the movable side valve plate  74 , but when the sliding area of the expansion region and the sliding area of the exhaust region in  FIG. 6  are imbalanced, the region with the smaller sliding area is abraded earlier by the increase in the surface pressure to impair the flatness of the slide surface  77 , leading to a fear that the steam leaks from the slide surface  77  to reduce the efficiency of the expander E. However, as described above, the unsymmetrical recessed portion  73   a  formed in the central portion of the slide surface  77  and the arc-shaped notch  73   b  formed along the outer peripheral portion of the expansion region, make the sliding area in the expansion region and the sliding area in the exhaust region substantially correspond to each other to make the surface pressure uniform, thereby preventing the uneven abrasion of the slide surface  77  to suppress the leakage of the steam.  
      Especially in the expander E, the second steam passage P 2  opens to the starting points of the expansion region, from which no opening exists substantially over 180° in the slide surface  77 . Therefore, the imbalance in the sliding area between the expansion region and the exhaust region where the fifth steam passage P 5  opens to the most part of the exhaust region is significant. However, according to this embodiment, the imbalance is compensated to effectively prevent the uneven abrasion of the slide surface  77 .  
      The embodiment of the present invention has been described, but various changes in design can be made without departing from the subject matter of the invention.  
      For example, the expander E of the embodiment includes the axial piston cylinder group A as the working section, but the structure of the working section is not limited thereto.  
      The rotating fluid machine of the present invention is not limited to the expander E, and can be applied to a compressor. When the present invention is applied to a compressor, the expansion stroke and the expansion region of the expander E become the compression stroke and the compression region, respectively, and the exhaust stroke and the exhaust region become the intake stroke and the intake region, respectively.