Abstract:
An object of the present invention is to provide a guide shoe that can prevent a shortage of lubricating oil and supply the lubricating oil onto a sliding surface of the shoe in a favorable manner. To achieve the above object, the present invention provides a guide shoe  120  that has a shoe surface  121  for slidably guiding a running chain CH. An oil guide part  124  with a pair of guide walls  124   a  is provided in the shoe surface  121 . The pair of guide walls  124   a  are each formed such as to face a rear side in a chain running direction D and converge to each other toward a front side in the chain running direction D.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a guide shoe that has a shoe surface for slidably guiding a running chain. 
     2. Description of the Related Art 
     A chain guide has hitherto been known, which is incorporated in a timing system in the engine room of a car to slidably guide the chain running between sprockets and keep an appropriate chain tension (see, for example, Japanese Patent Application Laid-open No. 2006-242357). 
     This conventional chain guide includes a guide shoe that has a shoe surface for slidably guiding the running chain, and a base member that supports this guide shoe along the longitudinal direction of the guide. 
     SUMMARY OF THE INVENTION 
     Lubricating oil is supplied on the shoe surface during use of the conventional chain guide for the purpose of reducing friction between the surface of the guide shoe and the chain, and wear of the shoe surface. However, sometimes there is a shortage of oil or variation in the oil film thickness on the shoe surface, leading to the problem of accelerated wear of the guide shoe due to increased friction between the shoe surface and the chain. 
     It is also known to provide dimples, grooves, or the like in the shoe surface for the purpose of forming oil pockets in the surface of the guide shoe. While these dimples and the like can function as oil pockets, the lubricating oil held in the dimples or the like could hardly be pulled out onto the sliding shoe surface depending on the viscosity of the lubricating oil and the running speed of the chain, and could not be supplied to the sliding surface of the shoe in a favorable manner. 
     The present invention is directed at solving these problems and it is an object of the invention to provide a simple-structured guide shoe that can prevent a shortage of lubricating oil and supply the lubricating oil onto the sliding surface of the shoe in a favorable manner. 
     To solve the problems described above, the present invention provides a guide shoe that has a shoe surface for slidably guiding a running chain, including an oil guide part with a pair of guide walls on the shoe surface. The pair of guide walls each face a rear side in a chain running direction and converge to each other toward a front side in the chain running direction. 
     According to an aspect of the invention as set forth in claim  1 , an oil guide part having a pair of guide walls that converge to each other toward the front side in the chain running direction is formed on the shoe surface, so that the lubricating oil held in oil pockets is guided by the pair of guide walls to approach each other as the chain runs, and the oil film thickness increases due to an oil pressure buildup at the wall-pair converging portion of the pair of guide walls. Friction between the shoe surface and the chain is thereby reduced, and thus the guide shoe can smoothly guide the chain and exhibit excellent wear resistance. 
     According to an aspect of the invention as set forth in claim  2 , the distance between a plurality of wall-pair converging portions in a shoe width direction as viewed in a chain running direction is set to or smaller than the plate thickness of link plates of the chain. This ensures that each of the plurality of link plates that form the chain runs on the wall-pair converging portions of the walls where the oil film thickness is increased, so that the friction reducing effect can be successfully exploited. 
     According to an aspect of the invention as set forth in claim  3 , each guide wall is formed as a flat surface, so that the pair of guide walls converge to each other linearly. As the lubricating oil is guided linearly toward the wall-pair converging portion of the walls, the pressure of the lubricating oil can be increased even more at the wall-pair converging portion. 
     According to an aspect of the invention as set forth in claim  4 , the pair of guide walls are connected to each other at the wall-pair converging portion, so that the lubricating oil cannot flow anywhere out of the wall-pair converging portion, which improves the oil film forming effect at the wall-pair converging portion. 
     According to an aspect of the invention as set forth in claim  5 , a plurality of oil guide parts are arranged in a zigzag pattern on the shoe surface, so that the oil guide parts can be provided in the shoe surface in a high density, and in particular, the distance between the plurality of wall-pair converging portions in the shoe width direction as viewed in the chain running direction can be reduced. This ensures that each of the plurality of link plates that form the chain runs on the parts where the oil film thickness is increased. 
     According to an aspect of the invention as set forth in claim  6 , the plurality of oil guide parts are arranged side by side both in the chain running direction and in the shoe width direction, which makes the production of metal molds for the shoe surface pattern easy, i.e., reduces the burden of production of the guide shoe. 
     According to an aspect of the invention as set forth in claim  7 , the oil guide part includes a pair of second guide walls arranged to oppose the pair of guide walls on the rear side in the chain running direction of the pair of guide walls. The pair of second guide walls each face the front side in the chain running direction and converge to each other toward the front side in the chain running direction. The pair of second guide walls formed on the rear side of the pair of guide walls can also guide the lubricating oil toward the wall-pair converging portion, so that the oil film forming effect at the wall-pair converging portion of the walls can be improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing a form of use of a chain guide according to a first embodiment; 
         FIG. 2  is an explanatory diagram showing a guide shoe according to the first embodiment; 
         FIG. 3  is an explanatory diagram showing a shoe surface according to the first embodiment; 
         FIG. 4  is a diagram for explaining the distance between wall-pair converging portions of guide walls in the first embodiment; 
         FIG. 5  is an explanatory diagram showing a shoe surface according to a modification of the first embodiment; 
         FIG. 6  is an explanatory diagram showing a shoe surface according to a second embodiment; 
         FIG. 7  is an explanatory diagram showing a shoe surface according to a modification of the second embodiment; 
         FIG. 8  is an explanatory diagram showing a shoe surface according to a third embodiment; 
         FIG. 9  is an explanatory diagram showing a shoe surface according to a fourth embodiment; 
         FIG. 10  is an explanatory diagram showing a shoe surface according to a modification of the fourth embodiment; 
         FIG. 11  is an explanatory diagram showing a shoe surface according to a first reference example; 
         FIG. 12  is an explanatory diagram showing a shoe surface according to a second reference example; 
         FIG. 13  is an explanatory diagram showing a shoe surface according to a third reference example; and 
         FIG. 14  is an explanatory diagram showing a shoe surface according to a fourth reference example. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, a chain guide  100  according to the first embodiment of the present invention will be described with reference to  FIG. 1  to  FIG. 4 . 
     The chain guide  100  of the first embodiment is incorporated in a timing system in an engine room, and slidably guides a chain CH running between sprockets S 1  to S 3  as shown in  FIG. 1  to keep an appropriate chain tension. More specifically, the chain guide  100  guides the chain CH passing over the sprockets S 1 , and S 2  and S 3  respectively provided to a crankshaft and cam shafts as shown in  FIG. 1  to stabilize the running chain CH and keep the tension of the chain CH appropriately. While the chain guide  100  is configured as a fixed guide fixedly installed in the engine room in this embodiment, the chain guide  100  may be configured as a pivot guide G pivotally supported inside the engine room such as the one shown in  FIG. 1  and pressed against the chain CH by a tensioner T. 
     The chain guide  100  includes, as shown in  FIG. 1  and  FIG. 2 , a guide shoe  120  for slidably guiding the running chain CH, and a metal base member  110  that supports the guide shoe  120  along a chain running direction (longitudinal direction of the guide) D. The base member  110  is fixed to an engine block (not shown) to which the base member is to be mounted. 
     The guide shoe  120  is made of a synthetic resin material and has a shoe surface  121  extending along the chain running direction D on the side that faces the engine room, and guide sections  125  on both sides in a width direction of the guide shoe  120 . A plurality of diagonal L-shaped indentations  122  are formed in a zigzag pattern in the shoe surface  121  as shown in  FIG. 2  and  FIG. 3 , i.e., a plurality of oil guide parts  124  are formed in a zigzag pattern on the shoe surface  121 . In this embodiment, protruded parts on the shoe surface  121  (where no indentations  122  are formed) function as the sliding surface with the chain CH, while the recessed parts in the shoe surface  121  (indentations  122 ) function as oil pockets. 
     Each oil guide part  124  has a pair of guide walls  124   a  that are inner wall faces on the front side of the indentation  122 , a wall-pair converging portion  124   b  where the pair of guide walls  124   a  converge to each other, and a pair of second guide walls  124   c  that are inner wall faces on the rear side of the indentation  122 , as shown in  FIG. 3 . 
     Each guide wall  124   a  is formed as a flat surface and faces the rear side in the chain running direction D as shown in  FIG. 3 . The pair of guide walls  124   a  extend diagonally to the chain running direction D toward the front side of the chain running direction D such as to converge and connect to each other at the wall-pair converging portion  124   b.    
     Each second guide wall  124   c  is formed as a flat surface, faces the front side in the chain running direction D, and opposes each guide wall  124   a , as shown in  FIG. 3 . The pair of second guide walls  124   c  extend diagonally to the chain running direction D toward the front side of the chain running direction D such as to converge and connect to each other. 
     As viewed in the chain running direction D, the distance W 1  in the width direction of the shoe between the plurality of wall-pair converging portions  124   b  is set to or smaller than the plate thickness W 2  of link plates L of the chain CH, as shown in  FIG. 4 . 
     Next, a modification of the first embodiment will be described with reference to  FIG. 5 . 
     The difference between the first embodiment shown in  FIG. 3  and the modification shown in  FIG. 5  is that the concavity and convexity on the shoe surface  121  are inverted. More specifically, the indentations  122  in the first embodiment are replaced with protrusions  123 . In this modification, protruded parts on the shoe surface  121  (protrusions  123 ) function as the sliding surface with the chain CH, while the recessed parts in the shoe surface  121  (where no protrusions  123  are formed) function as oil pockets. 
     In the modification shown in  FIG. 5 , each oil guide part  124 ′ has a pair of guide walls  124   a  that are outer wall faces on the rear side of the protrusion  123 , and a wall-pair converging portion  124   b  where the pair of guide walls  124   a  converge to each other. Other configurations of the guide walls  124   a  and wall-pair converging portions  124   b  in the modification shown in  FIG. 5  are the same as those of the first embodiment. 
     Next, a chain guide  200  according to the second embodiment will be described with reference to  FIG. 6 . The second embodiment is basically the same as the previously described first embodiment except for some parts. Therefore, elements of the second embodiment that are identical to those of the first embodiment denoted by numerals beginning with “1” herein and in the drawings will be numbered the same but beginning with “2” instead of “1”, and will not be described again. 
     In the chain guide  200  of the second embodiment, as shown in  FIG. 6 , a plurality of diagonal L-shaped indentations  222  are arranged side by side in the chain running direction D and in the shoe width direction in the shoe surface  221 , i.e., a plurality of oil guide parts  224  are formed side by side both in the chain running direction D and in the shoe width direction in the shoe surface  221 . 
     The oil guide part  224  includes a pair of guide walls  224   a , a wall-pair converging portion  224   b , and a pair of second guide walls  224   c , as shown in  FIG. 6 . The configurations of various parts of these oil guide parts  224  are the same as those of the first embodiment. 
     Next, a modification of the second embodiment will be described with reference to  FIG. 7 . 
     The difference between the second embodiment shown in  FIG. 6  and the modification shown in  FIG. 7  is that the concavity and convexity on the shoe surface  221  are inverted. More specifically, the indentations  222  in the second embodiment are replaced with protrusions  223 . 
     In the modification shown in  FIG. 7 , each oil guide part  224 ′ has a pair of guide walls  224   a  that are outer wall faces on the rear side of the protrusion  223 , a wall-pair converging portion  224   b  where the pair of guide walls  224   a  converge to each other, and a pair of second guide walls  224   c  that are outer wall faces on the front side of the protrusion  223  that follows after the protrusion  223  formed with the guide walls  224   a . The configurations of various parts of these oil guide parts  224  are the same as those of the first embodiment. 
     Next, a chain guide  300  according to the third embodiment will be described with reference to  FIG. 8 . The third embodiment is basically the same as the previously described first embodiment except for some parts. Therefore, elements of the third embodiment that are identical to those of the first embodiment denoted by numerals beginning with “1” herein and in the drawings will be numbered the same but beginning with “3” instead of “1”, and will not be described again. 
     In the chain guide  300  of the third embodiment, as shown in  FIG. 8 , a plurality of zigzag indentations  322  extending along the width direction of the shoe are arranged side by side in the chain running direction D in the shoe surface  321 , i.e., a plurality of oil guide parts  324  are formed side by side both in the chain running direction D and in the shoe width direction on the shoe surface  321 . 
     Each oil guide part  324  in the chain guide  300  has a pair of guide walls  324   a  that are inner wall faces on the front side of the indentation  322 , a wall-pair converging portion  324   b  where the pair of guide walls  324   a  converge to each other, and a pair of second guide walls  324   c  that are inner wall faces on the rear side of the indentation  322 , as shown in  FIG. 8 . The configurations of various parts of these oil guide parts  324  are the same as those of the first embodiment. 
     Next, a chain guide  400  according to the fourth embodiment will be described with reference to  FIG. 9 . The fourth embodiment is basically the same as the previously described first embodiment except for some parts. Therefore, elements of the fourth embodiment that are identical to those of the first embodiment denoted by numerals beginning with “1” herein and in the drawings will be numbered the same but beginning with “4” instead of “1”, and will not be described again. 
     In the chain guide  400  of the fourth embodiment, as shown in  FIG. 9 , a plurality of diamond shaped indentations  422  are formed in a zigzag pattern in the shoe surface  421  with their diagonal lines oriented along the chain running direction D (and the width direction of the shoe), i.e., a plurality of oil guide parts  424  are formed in a zigzag pattern on the shoe surface  421 . 
     Each oil guide part  424  has a pair of guide walls  424   a  that are inner wall faces on the front side of the indentation  422 , and a wall-pair converging portion  424   b  where the pair of guide walls  424   a  converge to each other, as shown in  FIG. 9 . The configurations of various parts of these oil guide parts  424  are the same as those of the first embodiment. 
     Next, a modification of the fourth embodiment will be described with reference to  FIG. 10 . 
     The difference between the fourth embodiment shown in  FIG. 9  and the modification shown in  FIG. 10  is that the concavity and convexity on the shoe surface  421  are inverted. More specifically, the indentations  422  in the fourth embodiment are replaced with protrusions  423 . 
     In the modification shown in  FIG. 10 , each oil guide part  424 ′ has a pair of guide walls  424   a , a wall-pair converging portion  424   b  where the pair of guide walls  424   a  converge to each other, and a pair of second guide walls  424   c . The pair of guide walls  424   a  are the outer wall faces on the rear side of the two protrusions  423  adjacent each other in the shoe width direction, while the second guide walls  424   c  are the outer wall faces on the front side of the protrusion  423  that follows after the aforementioned two protrusions  423 . In this modification, the pair of guide walls  424   a  do not connect to each other at the wall-pair converging portion  424   b . The configurations of other parts of these oil guide parts  424  are the same as those of the first embodiment. 
     Next, a chain guide  500  according to a first reference example will be described with reference to  FIG. 11 . 
     The chain guide  500  of the first reference example has a plurality of stripe indentations  522  extending side by side diagonally both to the chain running direction D and shoe width direction in the shoe surface  521 . 
     Next, a chain guide  600  according to a second reference example will be described with reference to  FIG. 12 . 
     In the chain guide  600  of the second reference example, a plurality of square indentations  622  are arranged side by side in the chain running direction D and shoe width direction in the shoe surface  621 , with their sides oriented along the chain running direction D (and the shoe width direction). 
     Next, a chain guide  700  according to a third reference example will be described with reference to  FIG. 13 . 
     In the chain guide  700  of the third reference example, a plurality of square protrusions  723  are arranged side by side in the chain running direction D and shoe width direction on the shoe surface  721 , with their sides oriented along the chain running direction D (and the shoe width direction). 
     Next, a chain guide  800  according to a fourth reference example will be described with reference to  FIG. 14 . 
     The chain guide  800  of the fourth reference example has a plurality of stripe indentations  822  extending along the chain running direction D and arranged side by side in the shoe width direction in the shoe surface  821 . 
     While the guide wall (and second guide wall) in the embodiments and modifications described above are formed as flat surfaces, specific forms of the guide wall (and second guide wall) are not limited to this. For example, the guide wall (and second guide wall) may be formed as a convex or concave curved surface. 
     The indentations or protrusions in the shoe may have any shapes and arrangements as long as pairs of guide walls are formed such as to converge to each other toward the front side of the chain running direction. 
     While the oil guide parts are formed over the entire area of the shoe surface in the width direction in the embodiments described above, the oil guide parts may be formed only in limited areas in the width direction of the shoe, e.g., areas that make sliding contact with link plates of the chain. 
     The material of the guide shoe may be selected from known suitable materials in accordance with various conditions such as friction resistance, rigidity, durability, formability, cost, and so on. Synthetic resin materials are particularly suitable. 
     The material of the base member may be selected from known suitable metal materials in accordance with various conditions such as rigidity, durability, formability, cost, and so on. 
     The guide shoe and the base member may be formed integral with each other. 
     Various configurations of the embodiments and modifications shown above may be freely combined to form other chain guides.