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 that has a shoe surface for slidably guiding a running chain CH. A plate guide groove extending along a chain running direction D and guiding link plates L of the chain CH is provide in the shoe surface. An oil guide part having a pair of guide walls is provided in the bottom surface of the plate guide groove. The pair of guide walls are each formed such as to face a rear side in the chain running direction D and converge to each other toward a front side in the chain running direction D.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a guide shoe that has a shoe surface for slidably guiding a running chain. 
         [0003]    2. Description of the Related Art 
         [0004]    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). 
         [0005]    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 
       [0006]    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. 
         [0007]    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. 
         [0008]    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. 
         [0009]    To solve the problems described above, the present invention provides a guide shoe having a shoe surface for slidably guiding a running chain, including: a plate guide groove provided in the shoe surface, extending along a chain running direction and guiding link plates of the chain; and an oil guide part having a pair of guide walls and formed in a bottom surface of the plate guide groove, the pair of guide walls each being formed such as to face a rear side in the chain running direction and converge to each other toward a front side in the chain running direction. 
         [0010]    According to an aspect of the invention as set forth in claim  1 , a plate guide groove extending along the chain running direction is provided in the shoe surface to restrict the track for the chain to run on, so that the lubricating oil is held in the plate guide groove to prevent a shortage of oil in portions where the chain slides on. Moreover, 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 in the bottom surface of the plate guide groove, 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 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. 
         [0011]    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. 
         [0012]    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. 
         [0013]    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. 
         [0014]    According to an aspect of the invention as set forth in claim  5 , an inclined guide surface inclined toward the plate guide groove is provided on either side of the plate guide groove, so that the link plates of the chain are guided into the plate guide groove by the inclined guide surfaces. This ensures that the link plates runs on portions where the oil film thickness is increased by wall-pair converging portions, and the lubricating oil around the plate guide groove can be guided into the plate guide groove. 
         [0015]    According to an aspect of the invention as set forth in claim  6 , a plurality of oil guide parts are arranged in a zigzag pattern on the bottom surface of the plate guide groove, so that the oil guide parts can be provided in the bottom surface of the plate guide groove 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. 
         [0016]    According to an aspect of the invention as set forth in claim  7 , the plurality of oil guide parts are arranged side by side both in the chain running direction and in the shoe width direction, whereby the burden of production of the guide shoe can be reduced. For example, the production of metal molds for the pattern of the bottom surface of the plate guide groove is made easy. 
         [0017]    According to an aspect of the invention as set forth in claim  8 , 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 
         [0018]      FIG. 1  is a diagram showing a form of use of a guide shoe according to a first embodiment; 
           [0019]      FIG. 2  is an explanatory diagram showing a guide shoe according to the first embodiment; 
           [0020]      FIG. 3  is an explanatory diagram showing a bottom surface of a plate guide groove according to the first embodiment; 
           [0021]      FIG. 4  is a diagram for explaining the distance between wall-pair converging portions of guide walls in the first embodiment; 
           [0022]      FIG. 5  is an explanatory diagram showing a bottom surface of a plate guide groove according to a modification of the first embodiment; 
           [0023]      FIG. 6  is a cross-sectional view showing a guide shoe according to a second modification of the first embodiment; 
           [0024]      FIG. 7  is an explanatory diagram showing a bottom surface of a plate guide groove according to a second embodiment; 
           [0025]      FIG. 8  is an explanatory diagram showing a bottom surface of a plate guide groove according to a modification of the second embodiment; 
           [0026]      FIG. 9  is an explanatory diagram showing a bottom surface of a plate guide groove according to a third embodiment; 
           [0027]      FIG. 10  is an explanatory diagram showing a bottom surface of a plate guide groove according to a fourth embodiment; 
           [0028]      FIG. 11  is an explanatory diagram showing a bottom surface of a plate guide groove according to a modification of the fourth embodiment; 
           [0029]      FIG. 12  is an explanatory diagram showing a bottom surface of a plate guide groove according to a first reference example; 
           [0030]      FIG. 13  is an explanatory diagram showing a bottom surface of a plate guide groove according to a second reference example; 
           [0031]      FIG. 14  is an explanatory diagram showing a bottom surface of a plate guide groove according to a third reference example; and 
           [0032]      FIG. 15  is an explanatory diagram showing a bottom surface of a plate guide groove according to a fourth reference example. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0033]    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 . 
         [0034]    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. 
         [0035]    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. 
         [0036]    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  126  on both sides in a width direction of the guide shoe  120 . Two plate guide grooves  122  extending along the chain running direction D are provided in the shoe surface  121 , as shown in  FIG. 2 . While plate guide grooves  122  in this embodiment are each configured to guide two adjacent link plates L, the plate guide groove  122  is not limited to this specific form. For example, the plate guide groove  122  may be formed to have a width with which it can guide one link plate L. 
         [0037]    A plurality of diagonal L-shaped indentations  123  are formed in a zigzag pattern in the bottom surface of each plate guide groove  122  as shown in  FIG. 2  and  FIG. 3 , i.e., a plurality of oil guide parts  125  are formed in a zigzag pattern on the bottom surface of the plate guide groove  122 . In this embodiment, protruded parts on the bottom surface of the plate guide groove  122  (where no indentations  123  are formed) function as the sliding surface with the chain CH, while the recessed parts in the bottom surface of the plate guide groove  122  (indentations  123 ) function as oil pockets. 
         [0038]    Each oil guide part  125  has a pair of guide walls  125   a  that are inner wall faces on the front side of the indentation  123 , a wall-pair converging portion  125   b  where the pair of guide walls  125   a  converge to each other, and a pair of second guide walls  125   c  that are inner wall faces on the rear side of the indentation  123 , as shown in  FIG. 3 . 
         [0039]    Each guide wall  125   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  125   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  125   b.    
         [0040]    Each second guide wall  125   c  is formed as a flat surface, faces the front side in the chain running direction D, and opposes each guide wall  125   a,  as shown in  FIG. 3 . The pair of second guide walls  125   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. 
         [0041]    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  125   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 . 
         [0042]    Next, a modification of the first embodiment will be described with reference to  FIG. 5 . 
         [0043]    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 bottom surface of the plate guide groove  122  are inverted. More specifically, the indentations  123  in the first embodiment are replaced with protrusions  124 . In this modification, protruded parts on the bottom surface of the plate guide groove  122  (protrusions  124 ) function as the sliding surface with the chain CH, while the recessed parts in the bottom surface of the plate guide groove  122  (where no protrusions  124  are formed) function as oil pockets. 
         [0044]    In the modification shown in  FIG. 5 , each oil guide part  125 ′ has a pair of guide walls  125   a  that are outer wall faces on the rear side of the protrusion  124 , and a wall-pair converging portion  125   b  where the pair of guide walls  125   a  converge to each other. Other configurations of the guide walls  125   a  and wall-pair converging portions  125   b  in the modification shown in  FIG. 5  are the same as those of the first embodiment. 
         [0045]    Next, a second modification of the first embodiment will be described with reference to  FIG. 6 . 
         [0046]    In the second modification of the first embodiment, inclined guide surfaces  127  inclined toward the plate guide grooves  122  are provided on both sides in the shoe width direction of the plate guide grooves  122 . While the inclined guide surfaces  127  are formed as curved surfaces in the example shown in  FIG. 6 , they may be formed as flat surfaces. 
         [0047]    Next, a chain guide  200  according to the second embodiment will be described with reference to  FIG. 7 . 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. 
         [0048]    In the chain guide  200  of the second embodiment, as shown in  FIG. 7 , a plurality of diagonal L-shaped indentations  223  are arranged side by side in the chain running direction D and in the shoe width direction in the bottom surface of the plate guide groove  222 , i.e., a plurality of oil guide parts  225  are formed side by side both in the chain running direction D and in the shoe width direction on the bottom surface of the plate guide groove  222 . 
         [0049]    The oil guide part  225  includes a pair of guide walls  225   a,  a wall-pair converging portion  225   b,  and a pair of second guide walls  225   c,  as shown in  FIG. 7 . The configurations of various parts of these oil guide parts  225  are the same as those of the first embodiment. 
         [0050]    Next, a modification of the second embodiment will be described with reference to  FIG. 8 . 
         [0051]    The difference between the second embodiment shown in  FIG. 7  and the modification shown in  FIG. 8  is that the concavity and convexity on the bottom surface of the plate guide groove  222  are inverted. More specifically, the indentations  223  in the second embodiment are replaced with protrusions  224 . 
         [0052]    In the modification shown in  FIG. 8 , each oil guide part  225 ′ has a pair of guide walls  225   a  that are outer wall faces on the rear side of the protrusion  224 , a wall-pair converging portion  225   b  where the pair of guide walls  225   a  converge to each other, and a pair of second guide walls  225   c  that are outer wall faces on the front side of the protrusion  224  that follows after the protrusion  224  formed with the guide walls  225   a.  The configurations of various parts of these oil guide parts  225  are the same as those of the first embodiment. 
         [0053]    Next, a chain guide  300  according to the third embodiment will be described with reference to  FIG. 9 . 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. 
         [0054]    In the chain guide  300  of the third embodiment, as shown in  FIG. 9 , a plurality of zigzag indentations  323  extending along the shoe width direction are arranged side by side in the chain running direction D in the bottom surface of the plate guide groove  322 , i.e., a plurality of oil guide parts  325  are formed side by side both in the chain running direction D and in the shoe width direction on the bottom surface of the plate guide groove  322 . 
         [0055]    Each oil guide part  325  in the chain guide  300  has a pair of guide walls  325   a  that are inner wall faces on the front side of the indentation  323 , a wall-pair converging portion  325   b  where the pair of guide walls  325   a  converge to each other, and a pair of second guide walls  325   c  that are inner wall faces on the rear side of the indentation  323 , as shown in  FIG. 9 . The configurations of various parts of these oil guide parts  325  are the same as those of the first embodiment. 
         [0056]    Next, a chain guide  400  according to the fourth embodiment will be described with reference to  FIG. 10 . 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. 
         [0057]    In the chain guide  400  of the fourth embodiment, as shown in  FIG. 10 , a plurality of diamond shaped indentations  423  are formed in a zigzag pattern in the bottom surface of the plate guide groove  422  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  425  are formed in a zigzag pattern on the bottom surface of the plate guide groove  422 . 
         [0058]    Each oil guide part  425  has a pair of guide walls  425   a  that are inner wall faces on the front side of the indentation  423 , and a wall-pair converging portion  425   b  where the pair of guide walls  425   a  converge to each other, as shown in  FIG. 10 . The configurations of various parts of these oil guide parts  425  are the same as those of the first embodiment. 
         [0059]    Next, a modification of the fourth embodiment will be described with reference to  FIG. 11 . 
         [0060]    The difference between the fourth embodiment shown in  FIG. 10  and the modification shown in  FIG. 11  is that the concavity and convexity on the bottom surface of the plate guide groove  422  are inverted. More specifically, the indentations  423  in the fourth embodiment are replaced with protrusions  424 . 
         [0061]    In the modification shown in  FIG. 11 , each oil guide part  425 ′ has a pair of guide walls  425   a,  a wall-pair converging portion  425   b  where the pair of guide walls  425   a  converge to each other, and a pair of second guide walls  425   c.  The pair of guide walls  425   a  are the outer wall faces on the rear side of the two protrusions  424  adjacent each other in the shoe width direction, while the second guide walls  425   c  are the outer wall faces on the front side of the protrusion  424  that follows after the aforementioned two protrusions  424 . In this modification, the pair of guide walls  425   a  do not connect to each other at the wall-pair converging portion  425   b.  The configurations of other parts of these oil guide parts  425  are the same as those of the first embodiment. 
         [0062]    Next, a chain guide  500  according to a first reference example will be described with reference to  FIG. 12 . 
         [0063]    In the chain guide  500  of the first reference example, a plurality of rectangular indentations  523  are arranged side by side both in the chain running direction D and in the shoe width direction in the bottom surface of the plate guide groove  522 , with their sides oriented along the chain running direction D (and the shoe width direction). 
         [0064]    Next, a chain guide  600  according to a second reference example will be described with reference to  FIG. 13 . 
         [0065]    The chain guide  600  of the second reference example has a plurality of stripe indentations  623  extending along the chain running direction D and arranged side by side in the shoe width direction in the bottom surface of the plate guide groove  622 . 
         [0066]    Next, a chain guide  700  according to a third reference example will be described with reference to  FIG. 14 . 
         [0067]    The chain guide  700  of the third reference example has a plurality of stripe indentations  723  extending side by side diagonally both to the chain running direction D and the shoe width direction in the bottom surface of the plate guide groove  722 . 
         [0068]    Next, a chain guide  800  according to a fourth reference example will be described with reference to  FIG. 15 . 
         [0069]    The chain guide  800  of the fourth reference example has a plurality of stripe indentations  823  extending along the shoe width direction and arranged side by side in the chain running direction D in the bottom surface of the plate guide groove  822 . 
         [0070]    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. 
         [0071]    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. 
         [0072]    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. 
         [0073]    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. 
         [0074]    The guide shoe and the base member may be formed integral with each other. 
         [0075]    Various configurations of the embodiments and modifications shown above may be freely combined to form other chain guides.