Sprocket structure

Abstract

This provides a sprocket structure that prevents incorrect assembly of the timing chain into the groove. [Solution] The cam sprocket 3 is fixed to the axial end of the camshaft 16 provided in the engine 1 for a vehicle, and the timing chain 5 is attached to it. The cam sprocket 3 includes teeth 31 that mesh with the inner plate portion 51 of the timing chain 5, an annular portion 32 having an outer diameter corresponding to the outer diameter of the teeth 31 and arranged at an axial distance from the teeth 31, and a groove 33 arranged between the teeth 31 and the annular portion 32. The axial width Ws1 of the groove 33 is narrower than the axial width Wc2 of the outer plate portion 52, which consists of a pair of outer plates 52A arranged on both axial sides of the inner plate portion 51 of the timing chain 5.

Description

Technical Field

[0001] The present invention relates to a sprocket structure for a vehicle engine.

Background Art

[0002] An engine used in an automobile, a motorcycle, etc. transmits the rotation of a crankshaft to a camshaft, and the intake valve and the exhaust valve are opened and closed by the camshaft. As a method of transmitting the rotation of the crankshaft to the camshaft, for example, a method of fixing sprockets to the crankshaft and the camshaft respectively and stretching a timing chain between the two sprockets is common. As a conventional structure related to the sprocket of such a vehicle engine, for example, in FIG. 2 of Patent Document 1, etc., a structure in which the sprocket has a tooth portion for hanging a timing chain and a flange portion having a diameter larger than the standard outer diameter of the tooth portion is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, regarding the conventional sprocket structure disclosed in Patent Document 1 above, the axial width of the groove portion formed between the tooth portion and the flange portion (the distance between the tooth portion and the flange portion) can be wider than the width of the timing chain hung on the tooth portion, so there is a possibility that the timing chain may be accidentally assembled in a state where it has fallen off the groove portion of the sprocket.

[0005] If the timing chain falls into the groove and the end of the timing chain's connecting pin engages with the teeth of the sprocket, the crankshaft's rotation can be transmitted to the camshaft, and there is a risk that no discrepancy will occur in the opening and closing timing of the intake and exhaust valves. In such a situation, it becomes difficult to detect the incorrect assembly of the timing chain into the sprocket groove during engine operation testing.

[0006] Furthermore, in an engine where various components such as the timing chain are assembled, the area around the sprocket is covered by a cover, making it impossible to visually confirm if the timing chain has fallen into the groove of the sprocket. For this reason, it is difficult to detect if the timing chain is incorrectly assembled to the sprocket even when the engine is mounted on the vehicle, and there was room for improvement in the conventional sprocket structure described above.

[0007] This invention was made in view of the above-mentioned points, and aims to provide a sprocket structure that can prevent incorrect assembly of the timing chain into the groove. [Means for solving the problem]

[0008] To achieve the above objective, one aspect of the present invention provides a sprocket structure fixed to the axial end of a shaft provided in an engine for a vehicle, on which a timing chain is attached. The sprocket includes teeth that mesh with the inner plate portion of the timing chain, an annular portion having an outer diameter corresponding to the outer diameter of the teeth and arranged at an axial distance from the teeth, and a groove portion arranged between the teeth and the annular portion, wherein the axial width of the groove portion is narrower than the axial width of the outer plate portion, which consists of a pair of outer plates arranged on both axial sides of the inner plate portion of the timing chain. [Effects of the Invention]

[0009] The sprocket structure according to the present invention can prevent incorrect assembly of the timing chain into the groove. [Brief explanation of the drawing]

[0010] [Figure 1] This is a partial cross-sectional perspective view showing a vehicle engine to which a sprocket structure according to one embodiment of the present invention is applied. [Figure 2] This is a magnified perspective view of the area around the camshaft sprocket in Figure 1. [Figure 3] This is a front view showing an enlarged view of the upper part of the cam sprocket and the timing chain in the above embodiment. [Figure 4] This figure illustrates the assembly state of the timing chain to the cam sprocket in the above embodiment. [Figure 5] This is a perspective view showing a conventional structure in which the timing chain is incorrectly assembled into the groove of the cam sprocket. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Figure 1 is a partial cross-sectional perspective view showing an engine 1 for a vehicle to which a sprocket structure according to one embodiment of the present invention is applied. In the drawings described below, the direction of arrow F indicates the front in the vehicle's longitudinal direction, the direction of arrow U indicates the upward direction in the vehicle's vertical direction, and the directions of arrows R and L indicate the right and left sides when viewed from inside the vehicle's interior.

[0012] In Figure 1, the sprocket structure of this embodiment is applied to a vehicle engine 1, which is an internal combustion engine mounted on a vehicle such as an automobile. The engine 1 comprises a cylinder block 11, a cylinder head 12 provided on the upper part of the cylinder block 11, and an oil pan 13 provided on the lower part of the cylinder block 11.

[0013] The cylinder block 11 houses a plurality (3) of cylinders 14 that house pistons (not shown) that can move up and down, and a crankshaft 15 that converts the up-and-down motion of the pistons into rotational motion. Each cylinder 14 is arranged in the left-right direction (vehicle width direction). The crankshaft 15 is a cylindrical shaft member that extends in the left-right direction. The crankshaft 15 is rotatably supported by bearings (not shown) fixed to the cylinder block 11. The axial end (right end) of the crankshaft 15 penetrates the right wall of the cylinder block 11 and protrudes to the outside of the cylinder block 11. A sealing member (not shown) is provided at the contact point between the crankshaft 15 and the cylinder block 11 to prevent engine oil from leaking out of the cylinder block 11.

[0014] The cylinder head 12 houses two camshafts 16, 16. Each camshaft 16, 16 is a cylindrical shaft member that extends parallel to each other along the direction of arrangement (left-right direction) of each cylinder 14. One of the two camshafts 16, 16 is equipped with an intake cam, and the other is equipped with an exhaust cam. Each camshaft 16, 16 is rotatably supported by bearings (not shown) fixed to the cylinder head 12. The axial end (right end) of each camshaft 16, 16 penetrates the right wall of the cylinder head 12 and protrudes to the outside of the cylinder head 12. A cylinder head cover (not shown) is provided on the top of the cylinder head 12, and the components housed inside the cylinder head 12 are covered by the cylinder head cover.

[0015] A crank sprocket 2 is fitted onto the axial side (right side) of the crankshaft 15. Additionally, cam sprockets 3, 3, each having the same structure, are fixed to the axial end (right end) of each camshaft 16, 16 with bolts or the like. A sprocket cover 4 is attached to the outside of each cam sprocket 3, 3. However, Figure 1 shows the sprocket cover that covers the front cam sprocket 3 removed. In this embodiment, each camshaft 16, 16 corresponds to the "shaft" of the present invention, and each cam sprocket 3, 3 corresponds to the "sprocket" of the present invention.

[0016] A timing chain 5 is stretched across the crank sprocket 2 and each cam sprocket 3,3. The rotation of the crankshaft 15 is transmitted from the crank sprocket 2 to each cam sprocket 3,3 via the timing chain 5, causing each camshaft 16,16 to rotate in sync with the rotation of the crankshaft 15.

[0017] A chain tensioner 6 and a chain guide 7 are provided on the outer right wall of the cylinder block 11 and cylinder head 12. The chain tensioner 6 is positioned between the crank sprocket 2 and the rear cam sprocket 3, and extends upward while curving backward, contacting the timing chain 5 from the rear. The chain tensioner 6 adjusts the tension of the timing chain 5 by pressing it toward its inner circumference and curving it. The chain guide 7 is positioned between the crank sprocket 2 and the front cam sprocket 3, and extends upward while gently curving forward, contacting the timing chain 5 from the front. The chain guide 7 guides the position of the timing chain 5. A chain cover (not shown) is also provided on the outer right wall of the cylinder block 11 and cylinder head 12, covering the area around the timing chain 5 stretched between the crank sprocket 2 and each cam sprocket 3, 3 from the outside.

[0018] Here, the specific structures of the cam sprocket 3 and the timing chain 5 will be described in detail while referring to FIGS. 2 and 3. FIG. 2 is a perspective view of an enlarged periphery of the cam sprocket 3 in FIG. 1 as viewed obliquely forward and from the left. FIG. 3 is a front view of an enlarged upper portion of the cam sprocket 3 and the timing chain 5 in the present embodiment as viewed from the front. The timing chain 5 is shown on the upper side of FIG. 3, and the upper portion of the cam sprocket 3 is shown on the lower side of FIG. 3.

[0019] As shown in FIGS. 1 to 3, the cam sprocket 3 has a generally cylindrical shape extending in the axial direction (left - right direction) of the camshaft 16. Inside the cylinder of the cam sprocket 3, a shaft hole 3A into which the tip (right end portion) of the camshaft 16 is inserted and a through - hole 3B through which bolts or the like are inserted are formed (FIGS. 1 and 2). Inside the right end portion of the camshaft 16, a screw groove (not shown) is formed, and by tightening bolts or the like inserted through the through - hole of the cam sprocket 3 into the screw groove, the cam sprocket 3 is fixed to the right end portion of the camshaft 16. A tooth portion 31 is formed on the left side portion of the cam sprocket 3, and an annular portion 32 is formed on the right side portion of the cam sprocket 3.

[0020] The tooth portion 31 is configured to mesh with an inner plate portion 51 of the timing chain 5 described later. Specifically, the tooth portion 31 has a plurality of teeth 31A protruding radially outward (FIGS. 2 and 3). The plurality of teeth 31A are arranged at a predetermined interval in the circumferential direction of the tooth portion 31. The diameter of the circle connecting the tips of each tooth 31A represents the outer diameter of the tooth portion 31.

[0021] The annular portion 32 has an outer diameter corresponding to the outer diameter of the tooth portion 31 and is arranged at an axial interval with respect to the tooth portion 31. In the present embodiment, the outer diameter of the annular portion 32 is designed to be equal to the outer diameter of the tooth portion 31. The annular portion 32 is formed in an annular shape extending from the right end of the cam sprocket 3 beyond the axial center portion. A plurality of recessed portions 32A recessed radially inward are formed at a plurality of locations on the radially outer surface of the annular portion 32 (FIGS. 1 to 3). Further, at a predetermined location on the peripheral portion located on the side of the tooth portion 31 on the radially outer surface of the annular portion 32, a timing mark 32B for confirming the assembly position is formed (FIG. 2). Furthermore, the above-described shaft hole 3A and through hole 3B are formed on the radially inner surface of the annular portion 32 (FIGS. 1 and 2).

[0022] A groove portion 33 is formed between the tooth portion 31 and the annular portion 32 in the cam sprocket 3 (FIGS. 1 to 3). The axial width Ws1 of the groove portion 33 corresponds to the distance from the right end of the tooth portion 31 to the left end of the annular portion 32 (FIG. 3). The surface (radially outer surface) of the groove portion 33 has a bottom surface 33A, a vertical surface 33B, and an inclined surface 33C.

[0023] The bottom surface 33A has an axial width Ws2 narrower than the axial width Ws1 of the groove portion 33 and extends in the circumferential direction of the cam sprocket 3. The diameter of the cylindrical outer peripheral surface formed by the bottom surface 33A (corresponding to the outer diameter of the groove portion 33) is smaller than the outer diameters of the tooth portion 31 and the annular portion 32.

[0024] The vertical surface 33B extends radially outward from one axial end of the bottom surface 33A, here the left end located on the side of the tooth portion 31, and is connected to the tooth portion 31. That is, the vertical surface 33B of the groove portion 33 forms a boundary surface with the tooth portion 31.

[0025] The inclined surface 33C extends from the other axial end of the bottom surface 33A, in this case the right end located on the side of the annular portion 32, to the right as it extends radially outward (away from the teeth portion 31), and connects to the annular portion 32. In other words, the inclined surface 33C of the groove portion 33 forms an interface with the annular portion 32. The axial width Ws1 of the groove portion 33, as described above, corresponds to the distance between the upright surface 33B and the radially outer end of the inclined surface 33C.

[0026] The timing chain 5 is an endless transmission member that spans the crank sprocket 2 and each cam sprocket 3,3 (Figure 1). The timing chain 5 includes an inner plate portion 51, an outer plate portion 52, and a connecting pin 53 (Figures 2 and 3).

[0027] The inner plate section 51 has multiple inner plates 51A that mesh with the teeth 31 of the cam sprocket 3, and each inner plate 51A is alternately connected in the longitudinal direction of the timing chain 5 by connecting pins 53. Each inner plate 51A has basically the same shape, and although not shown in the illustration, a valley is formed between a pair of peaks. Through holes are provided at the position of each peak through which the connecting pins 53 are inserted. The tips of the teeth 31A of the teeth 31 of the cam sprocket 3 abut against the valleys. In this embodiment, the inner plate section 51 has three inner plates 51A stacked in the axial direction (left-right direction), and the central inner plate 51A is connected to the left and right inner plates 51A by connecting pins 53 with the central inner plate 51A offset in the front-rear direction.

[0028] The outer plate portion 52 consists of a pair of outer plates 52A arranged on both axial sides of the inner plate portion 51. The pair of outer plates 52A are formed in a shape that omits the valleys of the inner plate 51A and are connected together with adjacent inner plates 51A by connecting pins 53. The inner spacing between the pair of outer plates 52A is set to be slightly wider than the tooth width of the teeth 31 of the cam sprocket 3. When the inner plate portion 51 is engaged with the teeth 31 of the cam sprocket 3, the inner surface of each outer plate 52A faces the side surface of each tooth 31A in the tooth width direction.

[0029] Each connecting pin 53 has a substantially cylindrical shape extending in the axial direction. Both axial ends of each connecting pin 53 protrude outside a pair of outer plates 52A in a state where the inner plate portion 51 and the outer plate portion 52 are connected.

[0030] In the timing chain 5 having the above-described structure, the axial width Wc1 of the inner plate portion 51 corresponds to the distance between the right side surface of the inner plate 51A located on the right side of and sandwiching the central inner plate 51A and the left side surface of the inner plate 51A located on the left side (FIG. 3). Further, the axial width Wc2 of the outer plate portion 52 corresponds to the distance between the right side surface of the outer plate 52A located on the right side of and sandwiching the inner plate portion 51 and the left side surface of the outer plate 52A located on the left side.

[0031] With respect to the axial width Wc1 of the inner plate portion 51 and the axial width Wc2 of the outer plate portion 52 in the timing chain 5 having the above-described structure, the groove portion 33 of the cam sprocket 3 has a magnitude relationship as shown in FIG. 3.

[0032] That is, the axial width Ws1 of the groove portion 33 in the cam sprocket 3 is designed to be narrower than the axial width Wc2 of the outer plate portion 52 in the timing chain 5 (Ws1 < Wc2). In other words, the distance from the right end of the tooth portion 31 to the left end of the annular portion 32 in the cam sprocket 3 (or the distance between the upright surface 33B of the groove portion 33 and the radially outer end of the inclined surface 33C) is designed to be narrower than the distance between the right side surface of the outer plate 52A located on the right side of and sandwiching the inner plate portion 51 and the left side surface of the outer plate 52A located on the left side in the timing chain 5.

[0033] In addition, the axial width Ws1 of the groove portion 33 in the cam sprocket 3 of the present embodiment is designed to be wider than the axial width Wc1 of the inner plate portion 51 in the timing chain 5 (Wc1 < Ws1 < Wc2). In other words, the distance from the right end of the tooth portion 31 to the left end of the annular portion 32 in the cam sprocket 3 (or the distance between the radially outer ends of the vertical surface 33B and the inclined surface 33C of the groove portion 33) is designed to be wider than the distance between the right side surface of the inner plate 51A located on the right side and the left side surface of the inner plate 51A located on the left side with the central inner plate 51A in the timing chain 5 interposed therebetween.

[0034] Furthermore, in the present embodiment, the axial width Ws2 of the bottom surface 33A in the groove portion 33 of the cam sprocket 3 is designed to be narrower than the axial width Wc1 of the inner plate portion 51 in the timing chain 5 (Ws2 < Wc1 < Ws1 < Wc2). In other words, the distance between the radially inner ends of the vertical surface 33B and the inclined surface 33C of the groove portion 33 in the cam sprocket 3 is designed to be narrower than the distance between the right side surface of the inner plate 51A located on the right side and the left side surface of the inner plate 51A located on the left side with the central inner plate 51A in the timing chain 5 interposed therebetween.

[0035] Next, the assembly state of the timing chain 5 to the cam sprocket 3 in the present embodiment will be described in detail with reference to FIG. 4. For the cam sprocket 3 having the above-described structure, as shown by the solid line in FIG. 4, when the timing chain 5 is correctly assembled to the tooth portion 31 of the cam sprocket 3, each tooth 31A of the tooth portion 31 meshes with the valley portion of each inner plate 51A in the inner plate portion 51 of the timing chain 5. At this time, the inner side surfaces of the pair of outer plates 52A in the outer plate portion 52 of the timing chain 5 face the side surfaces in the tooth width direction of each tooth 31A. By such a pair of outer plates 52A, the timing chain 5 hung on the tooth portion 31 of the cam sprocket 3 is correctly guided with respect to each tooth 31A, and displacement in the tooth width direction of the timing chain 5 is prevented.

[0036] On the other hand, when the timing chain 5' is incorrectly assembled to the side of the groove portion 33 beyond the tooth portion 31 of the cam sprocket 3, like the timing chain 5' shown by the two-dot chain line in FIG. 4, the axial width Ws1 of the groove portion 33 in the cam sprocket 3 is narrower than the axial width Wc2 of the outer plate portion 52 in the timing chain 5' (Ws1 < Wc2), so the timing chain 5' will not fall off the groove portion 33. When the outer plate portion 52 of the timing chain 5' straddles the tooth tip portion of the tooth portion 31 and the left end portion of the annular portion 32 in the cam sprocket 3, the end portion (left end portion) protruding toward the tooth portion 31 in the connecting pin 53 of the timing chain 5' is located above the tooth tip of the tooth portion 31, so the end portion of the connecting pin 53 will not mesh with the tooth portion 31 of the cam sprocket 3.

[0037] Also, since the axial width Ws1 of the groove portion 33 in the cam sprocket 3 is wider than the axial width Wc1 of the inner plate portion 51 in the timing chain 5' (Wc1 < Ws1), even when the timing chain 5' tries to move beyond the groove portion 33 to the side of the annular portion 32, the end portion (right end portion) located on the side of the annular portion 32 in the inner plate portion 51 abuts against the radially outer end portion of the inclined surface 33C of the groove portion 33, restricting the movement of the timing chain 5' to the side of the annular portion 32. Thereby, even when the engine 1 is started with the timing chain 5' incorrectly assembled, it is prevented that the timing chain 5' runs wild and damages various components (chain tensioner 6, chain guide 7, oil pump (not shown), etc.) in the chain cover.

[0038] Furthermore, even when the timing chain 5” is disposed above the groove portion 33 in a state inclined with respect to the axial direction, like the timing chain 5” shown by the two-dot chain line in FIG. 4, the surface connecting the bottom surface 33A of the groove portion 33 and the annular portion 32 in the cam sprocket 3 is an inclined surface 33C, and the axial width Ws2 of the bottom surface 33A is narrower than the axial width Wc1 of the inner plate portion 51 in the timing chain 5” (Ws2 < Wc1). Thus, the inclination of the timing chain 5” is likely to be restricted along the inclined surface 33C of the groove portion 33. As a result, the end portion (left end portion) protruding toward the tooth portion 31 in the connecting pin 53 of the timing chain 5” is arranged at a position separated from each tooth 31A, so that the end portion of the connecting pin 53 is less likely to mesh with the tooth portion 31 of the cam sprocket 3.

[0039] FIG. 5 shows a state where the timing chain 200 is erroneously assembled to the groove portion 103 of the cam sprocket 100 when assuming a cam sprocket 100 in which a groove portion 103 wider than the width of the timing chain 200 is formed between the tooth portion 101 and the annular portion 102, similar to the conventional sprocket structure described above. When the timing chain 200 thus drops off into the groove portion 103 of the cam sprocket 100, when the end portion protruding toward the tooth portion 101 in the connecting pin 203 of the timing chain 200 meshes with the tooth portion 101, the rotation of the crankshaft can be transmitted to the camshaft, and no deviation occurs in the opening and closing timing of the intake valve and the exhaust valve. In such a situation, it becomes difficult to detect a state where the timing chain 200 is erroneously assembled to the groove portion 103 of the cam sprocket 100 during the operation test of the engine. The problems in the conventional structure as described above are avoided by applying the structure of the cam sprocket 3 according to the present embodiment shown in FIGS. 1 to 4.

[0040] As described above, in the structure of the cam sprocket 3 according to the present embodiment, the axial width Ws1 of the groove portion 33 disposed between the tooth portion 31 and the annular portion 32 is narrower than the axial width Wc2 of the outer plate portion 52 of the timing chain 5 (Ws1 < Wc2). According to such a structure, it is possible to prevent the timing chain 5 from falling off into the groove portion 33 of the cam sprocket 3. When the timing chain 5 is assembled across the tooth portion 31 and the annular portion 32 of the cam sprocket 3, the timing chain 5 spanned between the crank sprocket 2 and the like is in an over-tensioned state, making it difficult to correctly assemble separate components such as the chain tensioner 6 and / or the chain guide 7. Therefore, it is possible to easily detect a state where the timing chain 5 is erroneously assembled above the groove portion 33 of the cam sprocket 3. Further, compared with the conventional structure, since the axial width Ws1 of the groove portion 33 in the cam sprocket 3 becomes narrower, the distance between the timing mark 32B formed on the annular portion 32 and the timing chain 5 becomes closer, so that it is possible to easily perform timing adjustment during the assembly of the timing chain 5 and the workability is improved. In addition, since the width Ws1 of the groove portion 33 becomes narrower, the overall axial length of the cam sprocket 3 also becomes shorter, so that the cam sprocket 3 can be miniaturized and lightened.

[0041] Also, in the structure of the cam sprocket 3 according to the present embodiment, the axial width Ws1 of the groove portion 33 is wider than the axial width Wc1 of the inner plate portion 51 of the timing chain 5 (Wc1 < Ws1). According to such a structure, since the movement of the timing chain 5 from above the groove portion 33 toward the annular portion 32 is restricted, even when the engine 1 is started in a state where the timing chain 5 is erroneously assembled, it is possible to prevent components such as the chain tensioner 6, the chain guide 7, and the oil pump provided in the chain cover from being damaged by the timing chain 5.

[0042] Furthermore, in the structure of the cam sprocket 3 according to the present embodiment, the groove portion 33 has a bottom surface 33A, a vertical surface 33B, and an inclined surface 33C, and the axial width Ws2 of the bottom surface 33A is narrower than the axial width Wc1 of the inner plate portion 51 of the timing chain 5 (Ws2 < Wc1). According to such a structure, even when the timing chain 5 is disposed above the groove portion 33 in a state inclined with respect to the axial direction, the inclination of the timing chain 5 is likely to be restricted along the inclined surface 33C of the groove portion 33, and the end portion (left end portion) of the connecting pin 53 of the timing chain 5 is difficult to mesh with the tooth portion 31 of the cam sprocket 3. Therefore, it is possible to effectively prevent the timing chain from being erroneously assembled into the groove portion.

[0043] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above-described embodiments, and various modifications and changes are possible based on the technical idea of the present invention. For example, in the above-described embodiment, an example in which the sprocket structure according to the present invention is applied to each of the cam sprockets 3, 3 among the crank sprocket 2 and the front and rear cam sprockets 3, 3 over which the timing chain 5 is stretched has been described. However, it is possible to apply the same structure as that of each of the cam sprockets 3, 3 to the crank sprocket 2.

[0044] Also, in the above-described embodiment, an example in which the outer diameter of the annular portion 32 in the cam sprocket 3 is designed to be equal to the outer diameter of the tooth portion 31 has been described. However, if the outer diameter of the annular portion 32 corresponds to the outer diameter of the tooth portion 31, a significant difference may occur between the respective outer diameters.

[0045] Furthermore, in the above-described embodiment, an example in which the groove portion 33 of the cam sprocket 3 has an inclined surface 33C has been shown. However, the surface located on the side of the annular portion 32 in the groove portion 33 may be a vertical surface similar to the surface located on the side of the tooth portion 31.

Explanation of Reference Numerals

[0046] 1... Engine 11... Cylinder Block 12…Cylinder head 13… Oil pan 14 cylinders 15…Crankshaft 16…Camshaft (shaft) 2... Crank sprocket 3... Cam sprocket (sprocket) 3A... Shaft hole 3B…Through hole 31… Teeth 31A… Teeth 32... Ring section 32A…recess 32B... Timing Mark 33… Groove 33A…Bottom surface 33B…Upright surface 33C…Slanted surface 4…Sprocket cover 5…Timing chain 51...Inner plate section 51A...Inner plate 52...Outer plate section 52A...Outer plate 53…Connecting pin 6... Chain tensioner 7... Chain guide Wc1...Axial width of the inner plate portion Wc2...Axial width of the outer plate portion Ws1...Axial width of the groove Ws2…Axial width of the base

Claims

1. A sprocket structure that is fixed to the axial end of a shaft provided in a vehicle engine and on which a timing chain is attached, The aforementioned sprocket is The timing chain has teeth that mesh with the inner plate portion, An annular portion having an outer diameter corresponding to the outer diameter of the tooth portion and arranged at an axial distance from the tooth portion, It includes a groove portion disposed between the tooth portion and the annular portion, The sprocket structure is characterized in that the axial width of the groove is narrower than the axial width of the outer plate portion, which consists of a pair of outer plates arranged on both sides of the axial direction of the inner plate portion in the timing chain.

2. The sprocket structure according to claim 1, characterized in that the axial width of the groove is wider than the axial width of the inner plate.

3. The groove portion has a bottom surface, an upright surface extending radially outward from one axial end of the bottom surface and connecting to the teeth, and an inclined surface extending radially outward from the other axial end of the bottom surface and connecting to the annular portion, The sprocket structure according to claim 2, characterized in that the axial width of the bottom surface is narrower than the axial width of the inner plate portion.

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