Patent Publication Number: US-2023160476-A1

Title: Sliding component

Description:
TECHNICAL FIELD 
     The present invention relates to a pair of sliding components that slide relative to each other by sliding surfaces, for example, a mechanical seal, a sliding bearing, and other sliding components suitable for a sliding portion. In particular, the present invention relates to a sliding component including a sealing ring or a bearing that is required to have fluid interposing between sliding surfaces to reduce friction and prevent fluid from leaking from the sliding surfaces. 
     BACKGROUND ART 
     As a sealing device configured to prevent leakage of sealed fluid, there is known a sealing device (for example, a mechanical seal) including a pair of sliding components that relatively slide on sliding surfaces. In such a sealing device, it is necessary to maintain favorable sealing performance while reducing sliding torque by forming a fluid lubrication film by the sealed fluid between the sliding surfaces. As one method for achieving favorable sealing performance and low sliding torque, there is known a technique of arranging a plurality of dimples in a sliding surface. 
     For example, it is known that favorable sealing performance and low sliding torque may be achieved by arranging dimples each including a circular opening portion in a sliding surface on a virtual circumference line having a center coincide with a rotation center of a sliding component. (For example, see Patent Literature 1). 
     In addition, it is also known that dimples each including an elongated rectangular opening portion whose end portion is semicircular are arranged at a predetermined dimple angle θ, and a ratio L1/L2 of a dimple circumferential length L1 on a circle passing through a dimple center to a circumferential length L2 of a land portion between adjacent dimples on the same circle is set to 0.001≤L1/L2≤0.1, thereby optimally adjusting sealing performance and sliding torque of the dimples as a whole (see, for example, Patent Literature 2). 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP-A-2010-133496 
     Patent Literature 2: Japanese Patent No. 5456772 
     SUMMARY OF INVENTION 
     Technical Problem 
     According to the technique of Patent Literature 1, even though favorable sealing performance and low sliding torque may be achieved under specific operating conditions, the favorable sealing performance and low sliding torque cannot be achieved in a wide rotation speed range. 
     In addition, according to the technique of Patent Literature 2, since the dimple angle is fixed, even though leakage of sealed fluid and sliding torque may be reduced under specific operating conditions, favorable sealing performance and low sliding torque cannot be achieved in a wide rotation speed range. In particular, when used in reverse rotation, there is a tendency that the sealing performance is lowered and the sliding torque is increased. 
     An object of the present invention is, in a pair of sliding components that relatively slide on sliding surfaces, to provide the sliding components capable of achieving favorable sealing performance and low sliding torque regardless of a rotation direction and when used in a wide rotation speed range. 
     Solution to Problem 
     In order to solve the above problem, a sliding component of the present invention is: 
     a pair of sliding members slidable relative to each other on sliding surfaces of the sliding members. 
     At least one of the sliding surfaces includes a dimple group in which a plurality of dimples is arranged, each of the dimples having an opening portion whose shape has of a long axis and a short axis orthogonal to the long axis, and 
     the dimple group includes: a clockwise dimple group in which the dimples are arranged in a clockwise direction from an inner diameter side to an outer diameter side of the sliding surface; and a counterclockwise dimple group in which the dimples are arranged in a counterclockwise direction from the inner diameter side to the outer diameter side of the sliding surface. 
     According to this feature, since the clockwise dimple group from the inner diameter side to the outer diameter side of the sliding surface and the counterclockwise dimple group from the inner diameter side to the outer diameter side are included, favorable sealing performance and low sliding torque may be exhibited regardless of rotation directions. 
     The sliding component according to the present invention is characterized in that 
     the clockwise dimple group includes a first dimple group in which the long axes of the dimples are aligned, and the counterclockwise dimple group includes a second dimple group in which the long axes of the dimples are aligned. 
     According to this feature, since the long axes of the dimples are aligned respectively in the first dimple group of the clockwise dimple group and the second dimple group of the counterclockwise dimple group, strength of suction effect and dynamic pressure effect of the dimples may be easily adjusted, and thus the dimple group as a whole may exhibit favorable sealing performance and low sliding torque over a wide rotation speed range. 
     The sliding component according to the present invention is characterized in that 
     the clockwise dimple group further includes a third dimple group in which the short axes of the dimples constituting the second dimple group are aligned, and the counterclockwise dimple group further includes a fourth dimple group in which the short axes of the dimples constituting the first dimple group are aligned. 
     According to this feature, since the clockwise dimple group further includes the third dimple group in which the short axes are aligned while the counterclockwise dimple group further includes the fourth dimple group in which the short axes are aligned, the strength of the suction effect and the dynamic pressure effect may be easily adjusted by combining the first dimple group to the fourth dimple group having different characteristics, and thus the dimple group as a whole may exhibit favorable sealing performance and low sliding torque over a wide rotation speed range. 
     The sliding component according to the present invention is characterized in that 
     the dimples constituting the first dimple group and the dimples constituting the second dimple group have different depths. 
     According to this feature, since the dimples constituting the first dimple group and the dimples constituting the second dimple group have different depths, the strength of the suction effect and the dynamic pressure effect of the first dimple group to the fourth dimple group may be easily changed, and thus the dimple group as a whole may exhibit favorable sealing performance and low sliding torque in a wide rotation speed range. 
     The sliding component according to the present invention is characterized in that 
     the first dimple group forms a curve that is convex outward in a radial direction of the sliding surface, and the second dimple group forms a curve that is convex outward in the radial direction of the sliding surface. 
     According to this feature, since the dimples are arranged along the curves, angles of the dimples may be gradually changed, and thus the dimple group as a whole may exhibited favorable sealing performance and low sliding torque in a wide rotation speed range. 
     The sliding component according to the present invention is characterized in that 
     the shape of each of the opening portions of the dimple is an ellipse. 
     According to this feature, even though the dimples having the elliptical opening portions are ellipses having the same shape and size, the suction effect and the dynamic pressure effect may be improved by changing inclination of the long axis of each dimple, and thus favorable sealing performance and low sliding torque may be achieved in a wide rotation speed range by arranging the dimple while changing the inclination of the long axis of the dimple. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a vertical cross-sectional view showing an example in which a sliding component according to the present invention is applied to a mechanical seal; 
         FIG.  2    is taken along line W-W of  FIG.  1   , which shows an example of a sliding surface of a sliding component according to Embodiment 1 of the present invention; 
         FIG.  3    is taken along line W-W of  FIG.  1   , which shows an example of a sliding surface of a sliding component according to Embodiment 2 of the present invention; 
         FIG.  4    is taken along line W-W of  FIG.  1   , which shows an example of a sliding surface of a sliding component according to Embodiment 3 of the present invention; 
         FIG.  5    is taken along line W-W of  FIG.  1   , which shows an example of a sliding surface of a sliding component according to Embodiment 4 of the present invention; and 
         FIGS.  6 A to  6 D  show other embodiments of a dimple of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, modes for carrying out the present invention will be exemplified based on embodiments with reference to the drawings. However, unless otherwise specified, dimensions, materials, shapes, relative positions, and the like of components described in the embodiments are not intended to limit the scope of the present invention. 
     Embodiment 1 
     A sliding component according to Embodiment 1 of the present invention will be described with reference to  FIGS.  1  and  2   . In the following embodiment, a mechanical seal, which is an example of a sliding component, will be described as an example. However, the present invention is not limited thereto, and for example, the present invention may be used as a sliding component of a bearing that slides on a rotation shaft while sealing lubricating oil on one side in an axial direction of a cylindrical sliding surface. An outer peripheral side of the sliding component constituting the mechanical seal will be described as a sealed fluid side (a high-pressure fluid side), and an inner peripheral side will be described as a leakage side (a low-pressure fluid side, for example, an atmosphere side). 
       FIG.  1    is a vertical cross-sectional view showing an example of a mechanical seal  1 , which belongs to an inside type in which sealed fluid leaking from an outer periphery of a sliding surface S toward an inner peripheral direction is sealed, and includes a rotation-side cartridge and a fixed-side cartridge. The rotation-side cartridge includes a sleeve  2  fitted to a rotation shaft  10 , an annular rotation-side sealing ring  3  that is one sliding component, and a packing  8  that seals space between the sleeve  2  and the rotation-side sealing ring  3 . The rotation-side cartridge rotates together with the rotation shaft  10 . 
     The fixed-side cartridge includes a housing  4  attached to a casing  9 , an annular fixed-side sealing ring  5  that is another sliding component, a bellows  7  that seals space between the fixed-side sealing ring  5  and the housing  4 , and a coiled wave spring  6  that urges the fixed-side sealing ring  5  toward the rotation-side sealing ring  3  via the bellows  7 . The housing  4  is fixed to the casing  9  in a rotation direction and an axial direction. 
     In the mechanical seal  1  having the above configuration, the sliding surface S of the rotation-side sealing ring  3  and the sliding surface S of the fixed-side sealing ring  5  slide relative to each other so as to prevent the sealed fluid from flowing out from the outer peripheral side to the inner peripheral side. Although  FIG.  1    shows a case where a width of the sliding surface of the rotation-side sealing ring  3  is wider than a width of the sliding surface of the fixed-side sealing ring  5 , the present invention is not limited thereto, and it is needless to say that the present invention may also be applied in an opposite case. 
     Materials of the rotation-side sealing ring  3  and the fixed-side sealing ring  5  are selected from silicon carbide (SiC) that has good wear resistance, carbon that has good self-lubricating performance, and the like. For example, both of the rotation-side sealing ring  3  and the fixed-side sealing ring  5  may be made of SiC, or the rotation-side sealing ring  3  may be made of SiC while the fixed-side sealing ring  5  is made of carbon. 
     As shown in  FIG.  2   , on the sliding surface S of the fixed-side sealing ring  5 , clockwise dimple groups  51  and  53  and counterclockwise dimple groups  52  and  54  are formed. Dimples  11  and  12  have substantially the same size and depth. The dimple groups  51  and  54  include a plurality of the dimples  11 , and the dimple groups  52  and  53  include a plurality of the dimples  12 . Each of the dimple groups  51 ,  52 ,  53 , and  54  includes the same number of dimples. 
     In the present invention, each of the dimples  11  and  12  is a recess that includes an opening portion surrounded by the flat sliding surface S and a bottom portion that is recessed relative to the sliding surface S. Each of opening portions  11   a  and  12   a  of the dimples has a shape having a long axis L and a short axis K orthogonal to each other. In addition, the dimples  11  and  12  are spaced apart from each other with land portions R interposed therebetween. In the present invention, the long axis is an imaginary straight line that passes through a centroid of the shape of each opening portion and connects maximum width portions of the opening portion. In addition, the short axis is an imaginary straight line that passes through the centroid and is orthogonal to the long axis to connect the opening portion. In the present embodiment, as an example, each of the opening portions of the dimples  11  and  12  is an ellipse having the long axis L and the short axis K orthogonal to each other. However, the shape is not limited to an ellipse, and may also be an oval shape, a rhombus shape, a polygonal shape, or any shape formed by closed curves  91 ,  92 ,  93 , or  94  as shown in  FIGS.  6 A to  6 D , as long as the shape has the long axis L and the short axis K orthogonal to each other. 
     As shown in  FIG.  2   , the dimple group  51  is formed by arranging the long axis L of each dimple  11  in contact with an imaginary spiral SP 1 , and a predetermined number (7 in the example of  FIG.  2   ) of the dimples  11  are arranged at equal intervals along the spiral SP 1  in a clockwise direction from an inner diameter side to an outer diameter side of the sliding surface S. The dimple group  53  is arranged such that the short axis K of each dimple  12  is in contact with an imaginary spiral SP 3 , and the same number of dimples  12  as the number of the dimples  11  are arranged at equal intervals along the spiral SP 3  in the clockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. The dimple group  51  and the dimple group  53  are alternately arranged on the sliding surface S at equal intervals in a circumferential direction in a staggered arrangement. Here, the staggered arrangement refers to an arrangement in which the long axes L of the dimples  12  whose short axes K are aligned is located between one dimple  11  and another dimple  11  whose long axes L are aligned when the dimple group  51  and the dimple group  53  are arranged adjacent to each other in the circumferential direction. In addition, the dimple group  52  is formed by arranging the long axis L of each dimple  12  in contact with an imaginary spiral SP 2  extending in a counterclockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. The dimple group  54  is formed by arranging the short axis K of each dimple  11  in contact with an imaginary spiral SP 4  extending in the counterclockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. The long axis L of each dimple  11  is formed to be in contact with the imaginary spiral SP 1 , the short axis K of each dimple  11  is formed to be in contact with the imaginary spiral SP 4 , the long axis L of each dimple  12  is formed to be in contact with the imaginary spiral SP 2 , and the short axis K of each dimple  12  is formed to be in contact with the imaginary spiral SP 3 . On the sliding surface S, the clockwise dimple group  51  and the clockwise dimple group  53  are alternately arranged in the circumferential direction. The counterclockwise dimple group  52  and the counterclockwise dimple group  54  are alternately arranged in the circumferential direction. 
     The number of the dimples  11  constituting the clockwise dimple group  51  are the same as the number of the dimples  11  constituting the counterclockwise dimple group  54 , and such dimples are symmetrical relative to a radial axis passing through the middle between the dimple group  51  and the dimple group  54 . In addition, the number of the dimples  12  constituting the counterclockwise dimple group  52  and the number of the dimples  12  constituting the clockwise dimple group  53  are the same, and such dimples are symmetrical to a radial axis passing through the middle between the dimple group  52  and the dimple group  53 . 
     Functions of the dimples  11  and  12  will be described. When the rotation-side sealing ring  3  rotates in the clockwise direction, fluid between the sliding surfaces S and fluid in the dimples  11  and  12  are moved following a moving direction of the rotation-side sealing ring  3  due to viscosity of the fluid. Since a flow path of the fluid flowing into the dimples  11  and  12  rapidly expands, negative pressure is generated on an upstream side of the dimples  11  and  12 , and thus cavitation occurs. However, since a magnitude of the negative pressure in the cavitation is limited by a value of fluid vapor pressure, the negative pressure does not become large. In addition, on a downstream side of the dimples  11  and  12 , positive pressure (dynamic pressure effect) is generated by a wedge effect due to rapid contraction of a flow path. Due to the negative pressure generated on the upstream side of the dimples  11  and  12 , the dimples  11  and  12  exhibit a suction effect of suctioning surrounding fluid. On the other hand, since the positive pressure generated on the downstream side of the dimples  11  and  12  is larger than the negative pressure in the cavitation, the dimples  11  and  12  as a whole has positive pressure. Due to the positive pressure generated by the plurality of dimples  11  and  12  arranged on the sliding surface S, space between the sliding surfaces S is expanded, and thus the fluid flows onto the sliding surface S to exert a lubricating function. 
     Next, functions of the dimple groups  51 ,  52 ,  53 , and  54  will be described. When the rotation-side sealing ring  3  rotates in the clockwise direction, the dimples  11  and  12 , which are located in the vicinity of a leakage-side peripheral edge  5   a,  of the clockwise dimple groups  51  and  53  exhibit a pumping function of suctioning fluid from the leakage side. In addition, since suction and discharge are continuously repeated between the adjacent dimples  11  and  12  while the fluid gradually moves from the leakage side to the sealed fluid side, leakage may be extremely reduced. Further, since high-pressure fluid is supplied to the sliding surface S by the dynamic pressure effect of the dimples  11  and  12 , the sliding surface S is maintained in a fluid lubricating state, and thus sliding torque may be reduced. 
     In addition, the clockwise dimple group  51  is arranged along the spiral SP 1  by aligning the long axes  1 , of the dimples  11 , whereas the clockwise dimple group  53  is arranged along the spiral SP 3  by aligning the short axes K of the dimples  12 . As a result, even though both of the dimple groups  51  and  53  are clockwise dimple groups, pumping effects and fluid lubricating effects thereof are different to each other. Specifically, since a dynamic pressure generating effect is improved in the clockwise dimple group  51  that is disposed along the spiral SP 1  by aligning the long axes L of the dimples  11 , the fluid lubricating function is exhibited even at low rotation speed. On the other hand, since the clockwise dimple group  53  that is disposed along the spiral SP 3  by aligning the short axes K of the dimples  12  has a favorable suction effect, the pumping function may be exhibited even at low rotation speed. As a result, even when operating in a wide rotation speed range, functions of the clockwise dimple groups  51  and  53  complement each other, and thus favorable fluid lubricating function and sealing function may be exhibited. 
     On the other hand, when the rotation-side sealing ring  3  rotates in the counterclockwise direction, the dimples  11  and  12 , which are located in the vicinity of the leakage-side peripheral edge  5   a,  of the counterclockwise dimple groups  52  and  54  exhibit the pumping function of suctioning fluid from the leakage side. In addition, since suction and discharge are continuously repeated between the adjacent dimples  11  and  12  while the fluid gradually moves from the leakage side to the sealed fluid side, leakage may be extremely reduced. Further, since high-pressure fluid is supplied to the sliding surface S by the dynamic pressure effect of the dimples  11  and  12 , the sliding surface S is maintained in a fluid lubricating state, and thus sliding torque may be reduced. 
     In addition, the counterclockwise dimple group  52  is arranged along the spiral SP 2  by aligning the long axes L of the dimples  12  to each other, whereas the counterclockwise dimple group  54  is arranged along the spiral SP 4  by aligning the short axes K of the dimples  11  to each other. As a result, even though the dimple groups  52  and  54  are all counterclockwise dimple groups, pumping effects and fluid lubricating effects thereof are different. Specifically, since a dynamic pressure generating effect is improved in the counterclockwise dimple group  52  that is disposed along the spiral SP 2  by aligning the long axes L of the dimples  12 , the fluid lubricating function is exhibited even at low rotation speed. On the other hand, since the counterclockwise dimple group  54  that is disposed along the spiral SP 4  by aligning the short axes K of the dimples  11  has a favorable suction effect, the pumping function may be exhibited even at low rotation speed. As a result, even when operating in a wide rotation speed range, functions of the counterclockwise dimple groups  52  and  54  complement each other, and thus favorable fluid lubricating function and sealing function may be exhibited. 
     In this way, the clockwise dimple group  51  and the counterclockwise dimple group  54 , and the counterclockwise dimple group  52  and the clockwise dimple group  53  are provided symmetrically relative to the radial direction, and thus high sealing performance and low sliding torque may be exhibited regardless of rotation directions since the clockwise dimple groups and the counterclockwise dimple groups are included. 
     Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and changes and additions without departing from the spirit of the present invention are also included in the present invention. 
     Although the shapes and the sizes of the dimples  11  and  12  are substantially the same in the above embodiment, the present invention is not limited thereto. For example, the clockwise dimple groups  51  and  52  and the counterclockwise dimple groups  53  and  54  may be constituted by the dimples  11  and the dimples  12  having different depths. Since the fluid holding effect of holding the fluid in the dimples, the suction effect, and the dynamic pressure effect may be changed by changing the depths of the dimples, favorable sealing performance and low sliding torque may be exhibited even at a wider rotation speed range by arranging the dimples having the different depths. 
     In addition, although the dimple groups  51 ,  52 ,  53 , and  54  are provided with the dimples  11  and  12  along the spirals, curves that extend clockwise or counterclockwise from the inner diameter side toward the outer diameter side of the sliding surface S and are convex outward in the radial direction such as circular arcs, parabolas, sine waves, or trochoid curves, or straight lines may be formed instead of the spirals. In addition, a combination of curves and straight lines may also be formed. 
     Embodiment 2 
     A sliding component according to Embodiment 2 of the present invention will be described.  FIG.  3    shows the sliding surface S of the sliding component according to Embodiment 2 in which the number of dimples  15  and  16  constituting clockwise dimple groups  55  and  56  and the number of the dimples  15  and  16  constituting counterclockwise dimple groups  57  and  58  are different, which is different from Embodiment 1. Other configurations are the same as those of Embodiment 1. Hereinafter, the same members and configurations as those of Embodiment 1 will be denoted by the same reference numerals, and redundant description thereof will be omitted. 
     As shown in  FIG.  3   , the sliding surface S of the fixed-side sealing ring  5  is provided with a plurality of the clockwise dimple groups  55  and  56  in which the dimples  15  and  16  are arranged in the clockwise direction from the inner diameter side to the outer diameter side of the sliding surface  5 , and a plurality of the counterclockwise dimple groups  57  and  58  in which the dimples  15  and  16  are arranged in the counterclockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. 
     As shown in  FIG.  3   , the clockwise dimple group  55  is arranged such that the long axis L of each dimple  15  is arranged at a predetermined angle along an imaginary spiral SP 5 , and a predetermined number ( 13  in the example of  FIG.  3   ) of the dimples  15  are arranged at equal intervals along the spiral SP 5  in the clockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. The clockwise dimple group  56  is arranged such that the short axis K of each dimple  16  is arranged at a predetermined angle along the imaginary spiral SP 5  extending in the clockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. The counterclockwise dimple group  57  is arranged such that the short axis K of each dimple  17  is arranged at a predetermined angle along an imaginary spiral SP 7 , and a predetermined number (4 in the example of  FIG.  3   ) of the dimples  17  are arranged along the spiral SP 7  in the counterclockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. The counterclockwise dimple group  58  is arranged such that the long axis L of each dimple  16  is arranged at a predetermined angle along an imaginary spiral SP 8  extending in the counterclockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. On the sliding surface S, the clockwise dimple group  55  and the clockwise dimple group  56  are alternately arranged in the circumferential direction. The counterclockwise dimple group  57  and the counterclockwise dimple group  58  are alternately arranged in the circumferential direction. 
     When the rotation-side sealing ring  3  rotates in the clockwise direction, the clockwise dimple groups  55  and  56  exhibit a sealing function and a fluid lubricating function, and thus leakage and sliding torque may be reduced. On the other hand, when the rotation-side sealing ring  3  rotates in the counterclockwise direction, the counterclockwise dimple groups  57  and  58  exhibit the sealing function and the fluid lubricating function, and thus leakage and sliding torque may be reduced. 
     Since the number of the dimples  15  and  16  constituting the clockwise dimple groups  55  and  56  is larger than the number of the dimples  15  and  16  constituting the counterclockwise dimple groups  57  and  58 , the sealing function and the fluid lubricating function during clockwise rotation may be improved. In addition, since an angle θ 1  formed by the spiral SP 5 , the spiral SP 6 , and the leakage-side peripheral edge  5   a  is smaller than an angle θ 2  formed by the spiral SP 7 , the spiral SP 8 , and the leakage-side peripheral edge  5   a,  the clockwise dimple groups  55  and  56  may exhibit a pumping effect from low rotation speed during clockwise rotation, which is particularly effective in a case where an operating rotation speed range during clockwise rotation reaches low-speed rotation. 
     According to the sliding component of Embodiment 1, the number of the dimples  11  and  12  constituting the clockwise dimple groups  51  and  53  are the same as the number of the dimples  11  and  12  constituting the counterclockwise dimple groups  52  and  54 , and therefore, the same sealing function and fluid lubricating function are exhibited during clockwise rotation and counterclockwise rotation. On the other hand, according to the sliding component according to Embodiment 2, the number of the dimples  15  and  16  constituting the clockwise dimple groups  55  and  56  is larger than the number of the dimples  15  and  16  constituting the counterclockwise dimple groups  57  and  58 , and therefore, the sealing function and the fluid lubricating function may be improved during clockwise rotation as compared with counterclockwise rotation. In addition, since the angle θ 1  of the spiral SP 5 , the spiral SP 6 , and the leakage-side peripheral edge  5   a  is smaller than the angle θ 2  of the spiral SP 7 , the spiral SP 8 , and the leakage-side peripheral edge  5   a,  the clockwise dimple groups  55  and  56  may exhibit the pumping effect from lower rotation speed as compared with the counterclockwise dimple groups  57  and  58 . 
     Embodiment 3 
     A sliding product according to Embodiment 3 of the present invention will be described.  FIG.  4    shows the sliding surface S of a sliding component according to Embodiment 3. In Embodiment 1, the same number of the clockwise dimple groups  51  and the clockwise dimple groups  53  are alternately arranged in the circumferential direction. However, the number of clockwise dimple groups  61  and the number of clockwise dimple groups  62  are arranged to be different from each other in Embodiment 3, which is different from Embodiment 1. Other configurations are the same as those of Embodiment 1. Hereinafter, the same members and configurations as those of Embodiment 1 will be denoted by the same reference numerals, and redundant description thereof will be omitted. 
     As shown in  FIG.  4   , the sliding surface S of the fixed-side sealing ring  5  is provided with a plurality of the clockwise dimple groups  61  and  62  in which dimples  19  and  20  are arranged in the clockwise direction from the inner diameter side to the outer diameter side of the sliding surface S, and a plurality of counterclockwise dimple groups  59  and  60  in which the dimples  19  and  20  are arranged in the counterclockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. 
     As shown in  FIG.  4   , the clockwise dimple group  61  is arranged such that the long axis L of each dimple  19  is in contact with an imaginary spiral SP 9 , and a predetermined number (6 in the example of  FIG.  4   ) of the dimples  19  are arranged at equal intervals along the spiral SP 9  in the clockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. The clockwise dimple group  62  is arranged such that the short axis K of each dimple  20  is in contact with an imaginary spiral SP 10  extending in the clockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. The counterclockwise dimple group  59  is arranged such that the long axis L of each dimple  20  is in contact with an imaginary spiral SP 12 , and a predetermined number (4 in the example of  FIG.  3   ) of the dimples  20  are arranged along the spiral SP 12  in the counterclockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. The counterclockwise dimple group  60  is arranged such that the short axis K of each dimple  19  is in contact with an imaginary spiral SP 11  extending in the clockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. On the sliding surface S, three consecutive dimple groups  61 , one dimple group  62 , one dimple group  61 , and one dimple group  62  are arranged in this order in the circumferential direction. 
     When the rotation-side sealing ring  3  rotates in the clockwise direction, the clockwise dimple groups  61  and  62  exhibit a sealing function and a fluid lubricating function, and thus leakage and sliding torque may be reduced. On the other hand, when the rotation-side sealing ring  3  rotates in the counterclockwise direction, the dimple groups  59  and  60  extending in the counterclockwise direction exhibit the sealing function and the fluid lubricating function, and thus leakage and sliding torque may be reduced. However, since the number of the clockwise dimple groups  61  is larger, the sealing function and the fluid lubricating function may be improved during clockwise rotation as compared with counterclockwise rotation. 
     According to the sliding component of Embodiment 1, the same number of the clockwise dimple groups  51  and the clockwise dimple groups  53  are alternately arranged in the circumferential direction. In contrast, the sliding component of Embodiment 3 is arranged with a larger number of the clockwise dimple groups  61 , which is effective in a case where clockwise rotation is frequent. 
     Embodiment 4 
     A sliding product according to Embodiment 4 of the present invention will be described.  FIG.  5    shows the sliding surface S of a sliding component according to Embodiment 4 which is different in that clockwise dimple groups  63 ,  64 , and  65  arranged adjacent to each other are constituted by different dimples  24 ,  25 , and  26 . Hereinafter, the same members and configurations as those of Embodiment 1 will be denoted by the same reference numerals, and redundant description thereof will be omitted. 
     As shown in  FIG.  5   , the sliding surface S of the fixed-side sealing ring  5  is provided with a plurality of the clockwise dimple groups  63 ,  64  and  65  in which the dimples  24 ,  25  and  26  are arranged in the clockwise direction from the inner diameter side to the outer diameter side of the sliding surface S, and a plurality of counterclockwise dimple groups  66  in which the dimples  24  are arranged in the counterclockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. The dimples  24 ,  25 , and  26  are different from each other in at least one of size, depth, and dimple angle, and characteristics of the respective dimples are different from each other. The dimple angle refers to an angle formed by a radial axis, which passes through an intersection of the long axis L and the short axis K, and the long axis L. 
     As shown in  FIG.  5   , the clockwise dimple group  63  is arranged such that the long axis L of each dimple  24  is arranged at a predetermined angle along an imaginary spiral SP 13 , and a predetermined number (6 in the example of  FIG.  5   ) of the dimples  24  are arranged at equal intervals along the spiral SP 13  in the clockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. The clockwise dimple group  64  is arranged such that the short axis K of each dimple  25  is arranged at a predetermined angle along a spiral SP 14  extending in the clockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. The clockwise dimple group  65  is arranged such that the short axis K of each dimple  26  is arranged at a predetermined angle along an imaginary spiral SP 15  extending in the clockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. The counterclockwise dimple group  66  is arranged such that the short axes of dimples  27  are arranged each at a predetermined angle along an imaginary spiral SP 16  extending in the counterclockwise direction from the inner diameter side to the outer diameter side of the sliding surface S. The clockwise dimple groups  65 ,  63 , and  64  are arranged in this order in the circumferential direction. Here, although the dimples  24  constituting the clockwise dimple group  63 , the dimples  25  constituting the clockwise dimple group  64 , and the dimples  26  constituting the clockwise dimple group  65  have the same shape, arrangement angles of the dimples relative to the long axes L or the short axes L are different. As a result, sealing performance efficiency and lubricating performance efficiency of the clockwise dimple groups  63 ,  64  and  65  may be arranged to be highest each at different rotation speed. That is, since the clockwise dimple groups  63 ,  64 , and  65  exhibit a favorable sealing function and a fluid lubricating function each at different rotation speed, the mechanical seal  1  may exhibit favorable sealing function and fluid lubricating function even when used in a wide rotation speed range. 
     Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and changes and additions without departing from the spirit of the present invention are also included in the present invention. 
     Although the outer peripheral side is the sealed fluid side while the inner peripheral side is the leakage side in the above embodiment, the present invention is not limited thereto, and the present invention is also applicable to a case where the inner peripheral side is the sealed fluid side while the outer peripheral side is the leakage side. In addition, although each dimple group is formed by arranging the long axis or the short axis of each dimple along the spirals, the present invention is not limited thereto. For example, each dimple may be arranged along a curve such as a parabola, a trochoid curve, or a sine curve so as to form the dimple group. 
     REFERENCE SIGNS LIST 
       1 : mechanical seal 
       2 : sleeve 
       3 : rotation-side sealing ring 
       4 : housing 
       5 : fixed-side sealing ring 
       5   a : side peripheral edge 
       6 : coiled wave spring 
       7 : bellows 
       8 : packing 
       9 : casing 
       10 : rotation shaft 
       11 : dimple 
       11   a : opening portion 
       12 : dimple 
       12   a : opening portion 
       15 : dimple 
       16 : dimple 
       21 : dimple 
       22 : dimple 
       24 : dimple 
       25 : dimple 
       26 : dimple 
       51 : clockwise dimple group (first dimple group) 
       52 : counterclockwise dimple group (second dimple group) 
       53 : clockwise dimple group (third dimple group) 
       54 : counterclockwise dimple group (fourth dimple group) 
       55 : clockwise dimple group 
       56 : clockwise dimple group 
       57 : counterclockwise dimple group 
       58 : counterclockwise dimple group 
       59 : counterclockwise dimple group 
       60 : counterclockwise dimple group 
       61 : clockwise dimple group 
       62 : clockwise dimple group 
       63 : clockwise dimple group 
       64 : clockwise dimple group 
       65 : clockwise dimple group 
       66 : counterclockwise dimple group 
       91 : closed curve 
       92 : closed curve 
       93 : closed curve 
       94 : closed curve 
     K: short axis 
     L: long axis 
     R: land portion 
     S: sliding surface 
     S: dimple sliding surface 
     θ: dimple angle 
     θ 1 : angle 
     θ 2 : angle