Patent Publication Number: US-7588433-B2

Title: Vane pump

Description:
FIELD OF THE INVENTION 
   The present invention relates to a vane pump, and in particular to a vane pump adapted to intermittently feed a lubricating oil to a pump room owing to rotation of a rotor. 
   BACKGROUND ART 
   A conventional vane pump includes a housing having a pump room in which an approximately circular, inner wall is formed; a rotor rotating at an eccentric position relative to the center of the pump room and sliding in contact with a part of the inner wall of the pump room; and a vane rotated by the rotor, for dividing the pump room into a plurality of spaces full-time. 
   In the rotor and the housing, an oil supply passage intermittently communicating with a pump room owing to rotation of the rotor is formed. A lubricating oil is intermittently fed through a communicating hole of the oil supply passage formed in the pump room. The communicating hole is formed at a position on the side of an intake passage from a center line drawn between the center of the pump room and the center of rotation of the rotor in the housing. 
   SUMMARY OF THE INVENTION 
   The lubricating oil has, in addition to an effect of lubricating the vane and the pump room, an effect of sealing a gap between the vane and the pump room to maintain airtight of a space divided by the vane. When the lubricating oil is not sufficiently fed into the pump room, such as at the time of engine start, the sealing is not fully effected. 
   In the case of the conventional vane pump, the communicating hole is formed at a position on the side of the intake passage from the center line. Thus, even if the vane passes the communicating hole, a pressure in the space divided by the vane becomes negative, and so the lubricating oil is made to flow into the pump room only in a manner that the lubricating oil is dragged to the rotational direction of the vane. 
   Therefore, it takes a considerable time until the lubricating oil is fed between the vane and the pump room, and sealing the gap between the vane and the pump room is fully effected. There also arose a problem that, during this time period, the vane pump cannot fulfill its original performance. 
   In view of such problems, an object of the present invention is to provide a vane pump which can rapidly exert its original performance, even when the amount of the lubricating oil fed to a pump room is small, such as at the time of engine start. 
   The vane pump according to the present invention comprises: a housing having a pump room, the pump room having an approximately circular inner wall; a rotor rotating at an eccentric position relative to a center of the pump room and sliding in contact with a part of the inner wall of the pump room; and a vane rotated by the rotor, for dividing the pump room into a plurality of spaces full-time. In the housing, among spaces divided by a center line drawn between the center of the pump room and a center of rotation of the rotor, an intake passage in one space and an exhaust passage in the other space are formed, respectively. In the rotor and the housing, an oil supply passage intermittently communicating with the pump room owing to the rotation of the rotor is formed. A lubricating oil is intermittently fed through a communicating hole of the oil supply passage formed in the pump room, and the communicating hole is formed in a space on a side of the exhaust passage from a center line in the pump room. The vane passes the communicating hole at the same time when the oil supply passage and the pump room are adapted to communicate with each other. 
   According to the present invention, when the vane passes the exhaust passage, the pump room is divided into three spaces by the vane. Among them, the space on the side where the rotor contacts with the pump room is divided into a space on the side of the intake passage and a space on the side of the exhaust passage relative to the center line by the rotor. 
   At this time, the pressure in the space on the side of the intake passage from the center line, the side where the rotor contacts with the pump room, is made negative due to suction of a gas through the intake passage. The pressure in the space on the side where the rotor does not contact with the pump room is made negative, because its volume is increased by the rotation of the vane. 
   Further, the space on the side of the exhaust passage from the center line, the side where the rotor contacts with the pump room, has higher pressure than the space in which the pressure is negative due to increase of the volume as described above. While its volume is decreased, the lubricating oil and the gas are discharged from the exhaust passage. 
   In such a manner, even when the vane passes the communicating hole after it passes the exhaust passage, the differential pressure between the space having the negative pressure due to increase of the volume and the space having the higher pressure than the relevant space is also generated, and thus the lubricating oil in the space having the higher pressure is spouted into the space having the negative pressure through a gap between the vane and the pump room. 
   The lubricating oil spouted into the space having the negative pressure is spouted in the direction opposite to the rotational direction of the vane, so that the lubricating oil positively impact on the vane which subsequently passes the communicating hole. 
   As a result, the spouted lubricating oil seals the gap between the vane and the pump room, and accordingly the vane pump can rapidly exert its original performance, even if the lubricating oil is not sufficiently fed into the pump room. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an elevational view of a vane pump; 
       FIG. 2  is a cross-sectional view taken along the line II-II in  FIG. 1 ; 
       FIG. 3  is an elevational view of the vane pump showing a situation that a vane moves from  FIG. 1 ; and 
       FIG. 4  is a view showing the experiment result. 
   

   DETAILED DESCRIPTION 
   An embodiment of the present invention will be described hereinafter.  FIGS. 1 to 3  show a vane pump  1  of this embodiment. The vane pump  1  is fixed on the side surface of an engine of an automobile, and adapted to generate the negative pressure in a booster of a brake control system. 
   The vane pump  1  includes: a housing  2  having an approximately circular pump room  2 A formed therein; a rotor  3  rotated at an eccentric position relative to the center of the pump room  2 A by a driving force of the engine; a hollow vane  4  rotated by the rotor  3 , for dividing the pump room  2 A into a plurality of spaces full-time; and a cover  5  for covering the pump room  2 A. 
   In the housing  2 , an intake passage  6  located above the pump room  2 A, in communication with the booster of the brake control system, for sucking in a gas from the booster, and an exhaust passage  7  located below the pump room  2 A, for discharging the gas sucked in from the booster and a lubricating oil fed from an oil supply groove  13  are provided, respectively. In the intake passage  6 , a check valve  8  is provided to hold the negative pressure in the booster, especially at stop of the engine. 
   The rotor  3  includes a cylindrical rotor portion  3 A rotating in the pump room  2 A, and an outer surface of the rotor portion  3 A contacts with an inner wall surface of the pump room  2 A. The intake passage  6  and the exhaust passage  7  are disposed oppositely across a center line L drawn between the center of the rotor portion  3 A and the center of the pump room  2 A. 
   The rotor  3  is arranged to rotate counterclockwise. In the following description, an upstream side in the rotational direction means a space adjacent to a clockwise side from a line drawn between the center of rotation of the rotor  3  and an arbitrary point of the pump room  2 A, and a downstream side in the rotational direction means a space adjacent to a counterclockwise side from the line. 
   Further, in a central portion of the rotor portion  3 A, a hollow portion  3   a  and a groove  9  in the diametrical direction are provided, and the vane  4  is adapted to move slidably along in the groove  9  in the direction perpendicular to the axial direction of the rotor  3 . 
   Moreover, on both ends of the vane  4 , caps  10  of which fore ends are formed to be semicircular are provided. The fore ends of the caps  10  slides in contact with the inner wall surface of the pump room  2 A, and a slight gap is present between the vane  4  and the caps  10 . 
   To the pump room  2 A, the lubricating oil is arranged to be fed through an oil supply groove  13 , and a communicating hole of the oil supply groove  13  is formed on the downstream side in the rotational direction of the vane  4  from a position at which the exhaust passage  7  is formed. 
   Therefore, the vane  4  is arranged to pass the oil supply groove  13  after passing the exhaust passage  7 , so that the lubricating oil fed from the oil supply groove  13  is not discharged, just as it is, from the exhaust passage  7 . 
   In addition, as shown in  FIG. 1 , the vane  4  is shown as oriented in the vertical direction. Hereinafter for illustrative purposes, a space situated on the right side shown of the vane  4  and above the rotor portion  3 A in the pump room  2 A is called the “first space A”, a space situated on the left side of the vane  4  is called the “second space B” and a space situated on the right side of the vane  4  and below the rotor portion  3 A is called the “third space C”. 
     FIG. 2  shows a cross-sectional view taken along the line II-II in situations shown in  FIG. 1 . In the housing  2 , a bearing  2 B adjacent to the pump room  2 A for supporting the rotor  3  is formed, and the cover  5  is provided on the opposite side to the bearing  2 B. 
   The rotor  3  includes a shank  3 B supported by the bearing  2 B, for driving rotationally the rotor portion  3 A. The shank  3 B projects from the bearing  2 B to the right side and is linked to a coupling  11  driven rotationally by a camshaft of the engine. 
   End surfaces of the rotor portion  3 A and the vane  4  on the left side slide in contact with the cover  5 , and an end surface of the vane  4  on the right side rotates slidably in contact with an inner surface of the pump room  2 A on the side of the bearing  2 B. 
   Moreover, a bottom surface  9   a  of the groove  9  formed in the rotor  3  is formed on the side of the shank  3 B slightly from a surface on which the vane  4  and the pump room  2 A slide, and a gap between the vane  4  and the bottom surface  9   a  is present. 
   In the shank  3 B, specifically in its central portion, an oil passage  12  for circulating the lubricating oil from the engine and constituting an oil supply passage is formed, and this oil passage  12  branches at a predetermined position in the same direction as the groove  9  and includes a branch passage  12   a  open into an outer surface of the shank  3 B. 
   Further, in the bearing  2 B, an oil supply groove  13  formed in the axial direction of the bearing  2 B, for constituting the oil supply passage forming the communicating hole into the pump room  2 A, is formed. As shown in  FIG. 1 , a width of the oil supply groove  13  along the rotational direction of the vane  4  is not smaller than that of the vane  4 . 
   Owing to such a configuration, when the branch passage  12   a  coincides with the oil supply groove  13  due to rotation of the rotor  3 , the lubricating oil from the oil passage  12  flows into the pump room  2 A through the oil supply groove  13 , and approximately half of the lubricating oil is arranged to flow into the hollow portion  3   a  of the rotor  3  from the gap between the vane  4  and the bottom surface  9   a  of the groove  9 . 
   Further, the rest of the lubricating oil is arranged to be sucked down into the pump room  2 A of which pressure becomes negative due to rotation of the vane  4 , being sprayed into the pump room  2 A through the gap between the vane  4  and the bottom surface  9   a  of the groove  9  or the gap between the vane  4  and the cap  10 . 
   With the configuration described above, the operation of the vane pump  1  according to this embodiment will be described. The rotor  3  is rotated counterclockwise as shown in  FIG. 1  by the operation of the engine through the coupling  11 , and then the vane  4  rotates while reciprocating in the groove  9  of the rotor  3 . The space divided by the vane  4  in the pump room  2 A changes in volume depending on rotation of the rotor  3 . 
     FIG. 3  shows a situation when the vane  4  is passing the oil supply groove  13  due to the rotation of the rotor  3 . 
   The first space A in  FIG. 1  is located on the left side of the vane  4  in  FIG. 3  due to the rotation of the rotor  3 , and the second space B in  FIG. 1  is located on the right lower side of the vane  4  and the rotor  3  in  FIG. 3 . 
   The first space A has an increased volume compared to that in  FIG. 1 , and further sucked the gas from the booster through the intake passage  6 . Accordingly, the pressure in the first space A becomes negative. 
   On the one hand, the volume of the second space B is decreased compared to that in  FIG. 1 . The lubricating oil along with the gas in the second space B is also discharged from the exhaust passage  7 , at this time, in order to force the lubricating oil in the exhaust passage  7  to be removed. The gas in the second space B is compressed to have the higher pressure than the gas in the first space A. 
   During the change from  FIG. 1  to  FIG. 3 , the differential pressure between the first space A and the second space B is generated. As a result, the lubricating oil which could not be removed through the exhaust passage  7  by the vane  4  is sprayed into the first space A through the gap between the pump room  2 A and the vane  4 , and through the gap between the vane  4  and the cap  10 , respectively, due to the differential pressure. 
   Further, in  FIG. 3 , the branch passage  12   a  in the oil supply passage and the groove  9  of the rotor  3  are placed in the same direction, if the vane  4  and the oil supply groove  13  coincide with each other in position as shown, at the same time, the branch passage  12   a  and the oil supply groove  13  also coincide with each other. 
   In this manner, when the branch passage  12   a  and the oil supply groove  13  coincide with each other, approximately half of the lubricating oil from the oil supply groove  13  flows into the hollow portion  3   a  of the rotor  3  through the gap between the vane  4  and the bottom surface  9   a  of the groove  9 . Subsequently, this lubricating oil goes up in the manner of flowing along an inner surface of the rotor due to a centrifugal force by the rotor  3 , and seals the gap between the cover  5 , the rotor  3  and the vane  4 . 
   On the other hand, as for the rest of the lubricating oil, because the oil supply groove  13  is formed on the downstream side, the lubricating oil from the oil supply groove  13  is made misty to be spouted into the first space A through a bottom portion of the rotor portion  3 A downstream, due to the negative pressure in the first space A. 
   That is, in this embodiment, to the first space A, the lubricating oil is adapted to be fed at two steps, first being sprayed from the second space B as described above, and then being sprayed from the bottom portion of the rotor portion  3 A downstream. 
   Further, each of the lubricating oil spouted into the first space A through the gap between the bottom surface of the rotor portion  3 A and the bottom surface of the pump room  2 A, the lubricating oil through the gap between the vane  4 , the groove  9  and the bottom surface  9   a , and the lubricating oil through the gap between the vane  4  and the cap  10 , is spouted in the direction opposite to the rotational direction of the vane  4 . 
   Therefore, against the vane  4  which, subsequently, reaches the exhaust passage  7  due to the rotation of the rotor  3 , the lubricating oil is blown, and the lubricating oil gets into the gap between the vane  4  and the pump room  2 A, and the gap between the cap  10  and the pump room  2 A. 
   By spouting the lubricating oil positively in the direction opposite to the rotational direction of the vane  4 , the lubricating oil can rapidly circulate around in the gap between the vane  4  and the pump room  2 A or the gap between the cap  10  and the pump room  2 A, when the lubricating oil is not sufficiently distributed in the vane pump  1 , especially such as at start of the engine. 
   Then, the lubricating oil not only lubricates the inside of the vane pump  1 , but plays a role of sealing. By sealing the gap between the vane  4  and the pump room  2 A etc. with the lubricating oil, the gap between the second space B and the first space A can be held airtight. 
   Therefore, even immediately after the start of an engine, the vane pump  1  can rapidly exert its original performance. 
   On the contrary, in the conventional vane pump, because the direction in which the lubricating oil flows is a direction following the rotation of a vane, the gap between the cap and the pump room is not rapidly sealed. Thus, immediately after the engine gets started, the vane pump cannot rapidly exert its original performance. 
     FIG. 4  shows this with the experimental result. In  FIG. 4 , an elapsed time from the engine start is shown in the horizontal axis, and an ability to generate the negative pressure in the booster is shown in the longitudinal axis. It may be seen that the vane pump  1  having the configuration of this embodiment denoted by the solid line brings out a predetermined ability to generate the negative pressure more rapidly compared to the vane pump having the conventional configuration denoted by the broken line. 
   In addition, the oil supply groove  13  may be formed at a position on the side of the exhaust passage  7  relative to the center line L. It is noted that, if the oil supply groove  13  is positioned on the side too much upstream in the rotational direction of the vane  4 , the negative pressure to be generated by increasing the volume of the pump room  2 A is reduced due to inflow of the lubricating oil. Accordingly, the suction becomes insufficient, and thereby the performance of the vane pump cannot be fully provided. 
   Further, in this embodiment, the width of the oil supply groove  13  in the rotational direction has been set slightly larger than that of the vane  4 . It is noted that, here, if the width of the oil supply groove  13  in the rotational direction is set to be narrower than that of the vane  4 , the time for feeding oil is shortened and lubrication cannot be sufficiently performed. On the contrary, if the width of the oil supply groove  13  in the rotational direction is set to be too wide, the amount of the lubricating oil becomes too large and the vane  4  bears a load, when the lubricating oil is removed.