Abstract:
In the vane pump comprising the housing, the vane, and the cap, the sliding surface of the cap is configured as arc shape in the view from the rotational axis direction and the width toward the sliding direction of the cap is configured to be smaller than the width at the sliding angle field which is virtual area for contacting the inner surface of the pump room among the circumference including the arc shape of the sliding surface of the cap and to be bigger than the width at the high loading area where the load added to the sliding surface which is bigger than the predetermined value among the sliding angle field.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a vacuum pump attached to an engine body. 
       BACKGROUND ART 
       [0002]    Conventionally, a vane type vacuum pump which is used as a vacuum pump for a car is known (Patent Literature 1). The conventional vacuum pump is configured to provide lubrication oil to a sliding part of a rotor which rotates in pump room of the housing and the lubrication oil after lubrication at the sliding member is discharged with gas through discharge passage to outer part of the pump room with rotation of the rotor. 
         [0003]    In this vane of the vacuum pump, a cap sliding on the inner surface at the rotation is attached. The cap is pressed to the housing at the rotation of the vane and constructed to seal between the surface of the housing and the vane (for example, it is described in the Patent Literature 1 and in the Patent Literature 2.). 
       PRIOR ART REFERENCE 
     Patent Literature 
       [0004]    Patent Literature 1: the Japanese Granted Patent Publication No. 4165608 
         [0005]    Patent Literature 2: the Japanese Unexamined Patent Publication No. 2004-263690 
       DISCLOSURE OF INVENTION 
     Problems to Be Solved by the Invention 
       [0006]    In the vane and the cap of the vacuum pump described in the above prior art, it is necessary that the weight saving of the vacuum pump is attained and the product cost is restrained by keeping the strength of the vane and the cap and attaining the weight saving. 
         [0007]    In consideration of the above problems, the present invention provides the vacuum pump which attains the weight saving and the restraint of the product cost by the weight saving of the vane and the cap with keeping the strength of the vane and the cap. 
       Means for Solving the Problems 
       [0008]    Problems to be solved by the invention are described as above and the means for solving the problems is explained. 
         [0009]    According to the invention of claim  1 , in a vacuum pump comprising, a housing which has a pump room inward, a vane which is disposed in the pump room and rotated by a rotor and divides the pump room to workspaces, and a cap in which a sliding surface slid on inner surface of the pump room is configured and which is attached at the tip of the vane, the sliding surface of the cap is configured as arc shape in the view from the rotational axis direction, and the width toward the sliding direction of the cap is configured to be smaller than the width at the sliding angle field which is virtual area for contacting the inner surface of the pump room among the circumference including the arc shape of the sliding surface of the cap and to be bigger than the width at the high loading area where the load added to the sliding surface which is bigger than the static value among the sliding angle field. 
         [0010]    According to the invention of claim  2 , the width of the vane is configured to be equal to the width toward the sliding direction of the cap. 
       Effect of the Invention 
       [0011]    As effects of the invention, the effects shown as below are caused. 
         [0012]    Namely, by the vacuum pump according to this invention, the weight saving and the restraint of the product cost are attained by the weight saving of the vane and the cap with keeping the strength of the vane and the cap. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]      FIG. 1  is a sectional view of a vacuum pump according to this embodiment. 
           [0014]      FIG. 2  is a sectional view at A-A line in the  FIG. 1 . 
           [0015]      FIG. 3  is a view in which the rotation angle of the vane is shown. 
           [0016]      FIG. 4  is an enlarged view in which the relation between the vane and the cap. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    A vane pump  1  according to an embodiment of the vacuum pump of this invention is explained with  FIG. 1  to  FIG. 4 . 
         [0018]    The vane pump  1  is fixed at the side of the engine room which is not shown and for example the vane pump  1  is acted as a negative pressure source of a power brake which is not shown. 
         [0019]    The vane pump  1  provides a housing  2  shaped as stepped cylinder which has a pump room  2 A shaped as substantially circle, a rotor  3  which is disposed in the pump room  2 A and disposed as the center of axis is eccentric from the center of the pump room  2 A, vane  4  which is disposed in the pump room  2 A and rotated with the rotor  3  to the direction of the arrow and always divides the pump room  2 A to workspaces, and the cover  5  which shut an opening of a large-diameter portion  2 B of the housing  2 , namely an opening of one edge of the pump room  2 A. 
         [0020]    The housing  2  provides the large-diameter portion  2 B in which the pump room  2 A is configured, a small-diameter portion  2 C which is configured adjacent to the edge surface of the large-diameter portion  2 B, and a cap portion  2 D which shut an opening part of the small-diameter portion  2 C and holds the rotor  3  rotatably by the inner surface of the small-diameter portion  2 C. In the large-diameter portion  2 B of the housing  2 , a suction passage  6  to suck gas (air) from the power brakes to the pump room  2 A is provided and in the suction passage  6  a clack valve which is not shown is provided to keep the negative pressure of the power brake. 
         [0021]    In the small-diameter portion  2 C and the lower part of the cap portion  2 D according to the  FIG. 1  and the  FIG. 2 , the through hole is provided in the axial direction to pierce from the pump room  2 A to the small-diameter portion  2 C and the outside of the cap portion  2 D. This through hole is configured as a discharge passage  7  to discharge the gas from the pump room  2 A to the outside of the housing  2 . Thus, the edge of the through hole at the cap portion  2 D is configured as the discharge-side outlet of the discharge passage  7 . 
         [0022]    As shown in the  FIG. 2 , the discharge-side outlet of the discharge passage  7  is openably covered by a thin platy reed valve  22  which has elasticity. In detail, a platy stopper  21  which has high hardness is disposed to overlap the reed valve  22  and the reed valve  22  and stopper  21  is fixed on the cap portion  2 D and the small-diameter portion  2 C (described as the small-diameter portion  2 C in the following) by the bolt which is fastener and so on. The reed valve  22  and stopper  21  is configured as arc shaped along the outer surface of the small-diameter portion  2 C. 
         [0023]    At the edge in the axial direction of the rotor  3  in the pump room  2 A, a guide groove  3 A in the diameter direction is configured and a platy vane  4  is attached with the guide groove  3 A slidably in the diameter direction. Each cap  4 A,  4 A which is slid on the inner surface  23  of the pump room  2 A is attached with the one of both edges of the vane  4 . As shown in the  FIG. 1  and the  FIG. 3 , when the rotor  3  and the vane  4  are rotated toward arrow direction, both caps  4 A,  4 A are slid on the inner surface  23  of the pump room  2 A to keep the airtight and both end faces  4 B,  4 B in the axial direction of the vane  4  are slid on the inner wall of a cover  5  and inner wall of the pump room  2 A and the part of the outer surface of the rotor  3  is kept to contact the inner surface  23  of the pump room  2 A. Therefore, the inner space of the pump room  2 A is divided as the expandable workspace. As shown in the  FIG. 3 , the position in which the cap  4 A is closest to the inner surface  23  of the pump room  2 A is defined as the rotation angle α=0 degree and the rotation angle α is increased as the counter clockwise direction in the view from the rotation axle direction of the rotor (the orthogonally cross direction to the paper in the  FIG. 1 ,  FIG. 3 , and  FIG. 4 ). According to this embodiment, the sliding direction of the cap  4 A is defined as the orthogonally cross direction to the diameter direction of the rotor  3 (As shown in the  FIG. 4 ). 
         [0024]    From the axis part at other edge side of the rotor  3  to the inner surface of the housing  2 , the oil supplying passage  11  to supply the lubrication oil to the inner part of the pump room  2 A is configured. The oil supplying passage  11  is consisted of a hole in the axis direction  3 B which is provided at the axis part of the rotor  3  and connected to the oil supplying pipe  12 , a hole in the diameter direction  3 C which is continued from the other edge of the hole in the axis direction  3 B, and further the groove in the axial direction  2 F of the housing  2  which is connected to the hole in the diameter direction  3 C intermittently when the rotor  3  is rotated to the arrow direction. 
         [0025]    When the engine is driven, the rotor  3  and the vane  4  are rotated to the arrow direction in  FIG. 1  with the drive of the engine and the volume of each workspace is extended or reduced. Following this, the gas (air) in the power brake is sucked through a suction passage  6  into each workspace and the gas in each workspace is discharged into the engine room which is the outside of the pump room  2 A through the discharge passage  7 . When the rotor  3  and the vane  4  are rotated, the lubrication oil is supplied into the pump room  2 A and to the sliding part of the vane  4  through the oil supplying passage  11 . After the lubrication oil which flowed into the pump room  2 A is primary-stored in the lower part of the pump room  2 A, the lubrication oil is moved by the vane  4  and the cap  4 A which are rotated and flowed through the discharge passage  7 . The lubrication oil is discharged from the discharge-side outlet into the engine room which is the outside of the housing  2  at the time of opening the reed valve. 
         [0026]    As described above, because the vane is attached slidably with the guide groove  3 A of the rotor  3 , when the rotor  3  and the vane  4  are rotated, the load of the vane  4  is greatly added to the cap  4 A which is disposed at the side of the center of gravity (the center part in the longitudinal direction) to the center of the rotor  3 . Thus, the rotation angle α becomes more than 90 degrees and less than 270 degrees in the  FIG. 3 , the greater load than the predetermined value is added as the load added to the sliding surface  41   f,  the cap  4 A which is disposed at the side in which the most part of the vane  4  is extended from the rotor  3 . 
         [0027]    Next, the relation between the vane  4  and cap  4 A is described with the  FIG. 4 . As shown in the  FIG. 4 , the hollow  4 H and the bearing surface  4 S are configured at both edges in the longitudinal direction. The hollow  4 H is the schematic square shaped hollow which is extended along the longitudinal direction of the vane  4 . The bearing surface  4 S is configured at both side surfaces in the longitudinal direction of the vane  4 . 
         [0028]    As shown in the  FIG. 1  and the  FIG. 4 , the cap  4 A is attached with the both edges in the longitudinal direction of the vane  4 . The body part  41  and the leg part  42  are configured at the cap  4 A. The sliding surface  41   f  which is configured as arc-shaped in the rotation axis direction of the rotor  3  is configured at the side of the housing  2  of the body part  41 . As shown in the  FIG. 4 , the distance between the center  0  of the circumference R which includes the sliding surface  41   f  of the cap  4 A and the sliding surface  41   f  is the radius of the cap r. 
         [0029]    The leg part  42  is the part which is extended to the side of the vane  4  from the center of the right and left direction at the side of the vane  4  of the body part  41 . The leg part  42  is configured to be smaller than hollow  4 H of the vane  4 . In the leg part  42 , the length of the vane along the longitudinal direction is configured to be shorter than the depth of the hollow  4 H. The cap  4 A is attached with the both edges in the longitudinal direction of the vane  4  by fitting the leg part  42  to the hollow  4 H of the vane  4 . Thus, the body part  41  of the cap  4 A is disposed at the outside in the longitudinal direction of the vane  4 . 
         [0030]    As shown in the  FIG. 4 , there is the sliding angle field AF which is virtual field contacted with the inner surface  23  of the pump room  2 A on the circumference R which includes the sliding surface  41   f  of the cap  4 A. The sliding angle field AF is defined as the field contacted with the inner surface  23  of the pump room  2 A in case that it is presumed that the circumference surface with the circumference R exists while the rotation angle α of the cap  4 A increases from 0 degree to 360 degrees (until the vane  4  is rotated once). Thus, the sliding angle field AF is the field in which the circumference surface with the circumference R is contacted with the inner surface  23  while the cap  4  is rotated once along the inner surface  23  of the pump room  2 A. In other words, while the cap  4  is rotated once along the inner surface  23  of the pump room  2 A, the part except for the sliding angle field AF in the circumference surface with the circumference R is not contacted to the inner surface  23 . As shown in the  FIG. 4 , the half of the angle which is configured between the two lines from the both edges of the sliding angle field AF to the center O of the circumference R is defined as the sliding angle θ. Thus, the width D 1  of the sliding angle field AF is 2r·sin θ. The point in which the outermost part of the sliding angle field AF is contacted with the inner surface  23  is an adjacent the point in which the rotation angle α of the vane is 60 degrees (300 degrees). 
         [0031]    As shown in the  FIG. 4 , there is the high load field AH in which the load added to the sliding surface  41   f  is bigger than the predetermined value in the sliding angle field AF. The high load field AH is the field of the sliding angle field AF in which the circumference surface with the circumference R is contacted with the inner surface  23  while the load of the vane  4  is greatly added to the cap  4 A at the side of the center of gravity vane  4  against the center of the rotor  3 , and thus the vane  4  is disposed as the rotation angle α is the range of 90 degrees to 270 degrees. Thus the width of the high load field AH is width D 2 . The field except for the high load field AH in the sliding angle field AF is defined as the low load field AL. Thus, the circumference surface with the circumference R is contacted with the inner surface  23  of the pump room  2 A at the low load field AL of the sliding surface  41   f  while the rotation angle α of the vane  4  is less than 90 degrees and more than 270 degrees. 
         [0032]    As shown in the  FIG. 4  according to this embodiment, the width of cap Lc which is the width in the sliding direction of the cap is configured as to be shorter than the width D 1  of the sliding angle field AF and to be longer than the width D 2  of the high load field AH. Thus, the sliding surface  41   f  is contacted with the inner surface  23  at the high load field AH and the strength of the cap  4 A is able to be kept. As the sliding surface  41   f  is smaller than the sliding angle field AF, the cap  4 A is able to be downsized. In the low load field AL the sliding surface is not existed and the corner of the cap  4 A (the both edges of the sliding surface  41   f ) is contacted with the inner surface  23 . The load added to the cap  4 A in the low load field AL is small and the problem to concentrate the stress at the inside the cap  4 A for the overload and so on is not occurred. 
         [0033]    According to this embodiment, width of vane Lv which is the width in the sliding direction of the vane is configured to be equal to the width of cap Lc. Therefore, the force added to the cap  4 A from the vane  4  is transmitted by the whole bearing surface  4 S and the strength of the vane  4  is able to be kept. The width of vane Lv is smaller than the width D 1  of the sliding angle field AF and the cap  4 A is able to be downsized. Therefore, the downsizing of the vane pump  1  is attained and the product cost is restrained. 
       INDUSTRIAL APPLICABILITY 
       [0034]    The present invention is acceptable to the skill of the vacuum pump and acceptable to the vacuum pump attached to the engine body. 
       DESCRIPTION OF NOTATIONS 
       [0035]      1  vane pump (vacuum pump) 
         [0036]      2  housing 
         [0037]      2 A pump room 
         [0038]      4  vane 
         [0039]      4 A cap 
         [0040]      23  inner surface 
         [0041]      41   f  sliding surface 
         [0042]    AF sliding angle field 
         [0043]    AH high load field