hereinafter , a chain guide 100 according to the first embodiment of the present invention will be described with reference to fig1 to fig4 . 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 fig1 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 fig1 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 fig1 and pressed against the chain ch by a tensioner t . the chain guide 100 includes , as shown in fig1 and fig2 , 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 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 fig2 . 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 . 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 fig2 and fig3 , 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 . 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 fig3 . 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 fig3 . 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 . 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 fig3 . 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 . 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 fig4 . next , a modification of the first embodiment will be described with reference to fig5 . the difference between the first embodiment shown in fig3 and the modification shown in fig5 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 . in the modification shown in fig5 , 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 fig5 are the same as those of the first embodiment . next , a second modification of the first embodiment will be described with reference to fig6 . 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 fig6 , they may be formed as flat surfaces . next , a chain guide 200 according to the second embodiment will be described with reference to fig7 . 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 fig7 , 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 . 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 fig7 . the configurations of various parts of these oil guide parts 225 are the same as those of the first embodiment . next , a modification of the second embodiment will be described with reference to fig8 . the difference between the second embodiment shown in fig7 and the modification shown in fig8 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 . in the modification shown in fig8 , 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 . next , a chain guide 300 according to the third embodiment will be described with reference to fig9 . 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 fig9 , 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 . 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 fig9 . the configurations of various parts of these oil guide parts 325 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 fig1 . 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 fig1 , 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 . 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 fig1 . the configurations of various parts of these oil guide parts 425 are the same as those of the first embodiment . next , a modification of the fourth embodiment will be described with reference to fig1 . the difference between the fourth embodiment shown in fig1 and the modification shown in fig1 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 . in the modification shown in fig1 , 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 . next , a chain guide 500 according to a first reference example will be described with reference to fig1 . 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 ). next , a chain guide 600 according to a second reference example will be described with reference to fig1 . 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 . next , a chain guide 700 according to a third reference example will be described with reference to fig1 . 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 . next , a chain guide 800 according to a fourth reference example will be described with reference to fig1 . 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 . 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 . 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 .