JP3470379B2 - Mounting structure of oil pump gear for 4-cycle internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-stroke internal combustion engine used for a prime mover such as a motorcycle, and more particularly to a structure for mounting an oil pump gear for an oil pump drive. 2. Description of the Related Art Conventionally, in a four-cycle internal combustion engine mounted on a motorcycle or the like, generally, a camshaft drive sprocket is provided on a side near a crankpin or a crank web, and an oil pump is provided adjacent to the sprocket. Arrange gears. Here, the camshaft drive sprocket is formed integrally with the crankshaft without being subjected to gear cutting.After the camshaft drive sprocket is geared, the oil pump gear is fitted to the crankshaft, and the crankshaft is connected to the oil pump gear. Provide a detent with the shaft. Conventionally, the rotation of the oil pump gear with respect to the crank is generally performed using a key or a pin. That is, as shown in FIG. 5A, a key groove b is formed on one side of an outer periphery of a crankshaft a (a side extending from the crank chamber to the outside), and a key groove is formed on one side of an inner diameter portion of an oil pump gear c. The groove d is formed, the oil pump gear c is fitted to the crankshaft a, and the respective key grooves b and d are aligned, and the key e is fitted into each of the key grooves b and d to prevent rotation. As shown in (b), a pin hole f is formed on the outer periphery of the crankshaft a, a key groove d is formed on one side of the inner diameter portion of the oil pump gear c, a pin h is embedded in the pin hole f, and oil is inserted into the crankshaft a. Generally, a pin h is fitted into the key groove d by fitting the pump gear c, and the pin h is used to stop the rotation. In FIG. 5, i is a camshaft drive sprocket, and j is an oil pump gear c.
And k is a crank web. The crank pin is fitted into the hole k1 of the crank web k. [0004] However, the structure of mounting the oil pump gear of the four-stroke internal combustion engine If the oil pump gear is prevented from rotating with respect to the crankshaft by a key or a pin as in the above-mentioned conventional art, (1) A keyway or a pin hole needs to be formed in the crankshaft. (2) Requires keys or pins. (3) The keyway needs to be machined in the inner diameter portion of the gear. (4) An operation of inserting a key or a pin into a key groove or a pin hole is required. Therefore, conventionally, there is a problem that the structure is complicated from (1) to (3), and there are many processing steps and assembling steps from (1) and (3) to (4). SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and a four-cycle internal combustion engine capable of reducing the number of parts to simplify the structure and reducing the machining and assembling operations to reduce the cost. An object of the present invention is to provide an oil pump gear mounting structure. According to the first aspect of the present invention, a camshaft drive sprocket and a flange are provided integrally with a crankshaft so that the camshaft drive sprocket and the flange are close to each other, and the flange is interposed therebetween. An attachment structure for an oil pump gear of a four-stroke internal combustion engine, in which an oil pump gear is fitted to a crankshaft from the opposite side of a camshaft drive sprocket and is adjacent to a flange, wherein the flange is smaller than the root circle of the camshaft drive sprocket. Formed into a large diameter, and the teeth of the camshaft drive sprocket and the flange are collectively subjected to gear cutting to form a groove on the outer periphery of the flange, and a projection is formed on the side of the oil pump gear facing the flange. When the oil pump gear is fitted to the crankshaft and The projecting portion is fitted into a groove on the outer periphery of the flange, and has a configuration of a mounting structure of an oil pump gear of a four-cycle internal combustion engine. In the mounting structure of the oil pump gear of the four-stroke internal combustion engine, the camshaft drive sprocket and the flange are provided integrally with each other on the crankshaft so as to be close to each other, and the opposite side of the camshaft drive sprocket across the flange. The oil pump gear is fitted to the crankshaft and is adjacent to the flange, and the flange is formed to have a diameter larger than the root circle of the camshaft drive sprocket. For example, a slotter (vertical cutting machine, slotting) When the outer periphery of the camshaft drive sprocket is subjected to gear cutting by a machine, the outer periphery of the flange is also processed at the same time, and a groove is formed on the outer periphery of the flange. Further, a projection is formed on the side of the oil pump gear facing the flange, and the projection fits into the groove on the outer periphery of the flange when the oil pump gear is fitted on the crankshaft and brought into contact with the flange. With this configuration, since the flange is integrally rotatable with the crankshaft, the oil pump gear is prevented from rotating with respect to the crankshaft. [0008] Therefore, a key or a pin for preventing rotation required in the conventional oil pump gear is not required, so that the number of parts can be reduced and the structure can be simplified. In addition, a key groove or a pin hole is not required, so that a machining operation can be reduced. (On the other hand, a groove formed on an outer periphery of a flange can be formed at the time of gear cutting of a camshaft drive sprocket. Yes,
Therefore, the present invention does not increase the number of machining operations for forming a groove in the flange). Further, since the assembling of the key or the pin becomes unnecessary, the assembling work can be reduced. As described above, the cost can be reduced in order to reduce the number of parts, simplify the structure, and reduce machining and assembling operations. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. . FIG. 1 is an explanatory view of a configuration of a four-cycle internal combustion engine mounted on a motorcycle according to an embodiment of the present invention, and FIG. 2 is an explanatory view of a mounting state of a camshaft drive sprocket, a flange, and an oil pump gear with respect to a crankshaft of the internal combustion engine. FIGS. 3A and 3B are explanatory diagrams of a configuration of an oil pump gear, and FIGS. 4A and 4B are explanatory diagrams of a configuration of a modified example of the oil pump gear. As shown in FIG. 1, an internal combustion engine 10 according to the embodiment is a single cylinder having an upper portion of a cylinder 12 inclined in a vehicle traveling direction and having a cylinder head 12a.
(Overhead camshaft) type in which a camshaft 14 is disposed. Further, the internal combustion engine 10 has a crank chamber 18 behind the cylinder 12,
A crankshaft 16 extends left and right from the crank chamber 18, and a camshaft drive sprocket 22 and an oil pump gear 24 are disposed on the right side as opposed to FIG.
On the left side, a primary pulley 25a of an automatic transmission (a V-belt type that changes the driving force of the internal combustion engine and transmits the driving force to the rear wheels) 25 is shafted. In the automatic transmission 25, a centrifugal clutch 25b and a reduction gear 25c are provided on the secondary side of the V-belt, and a rear wheel is supported on an output shaft 25d of the reduction gear 25c. Although not shown in FIG. 1, a drive gear of the oil pump meshes with the oil pump gear 24. The crankshaft 16 of the internal combustion engine is located on the right outside of the crankcase 18 opposite to FIG.
A camshaft drive sprocket 22 is formed integrally with the crankshaft 16 in the vicinity of 0, and the camshaft drive sprocket 22 and an oil pump gear 24 are arranged on the crankshaft 16 in close proximity to each other. The oil pump gear 24 is fitted on the crankshaft 16. Also, the crankshaft 16 has a camshaft drive sprocket 22 side 2
A flange 26 for mounting an oil pump gear is provided adjacent to 4a. The flange 26 is formed integrally with the crankshaft 16 for rotation. As shown in FIG. 2B, before the gear cutting of the camshaft drive sprocket 22, the outer diameter L1 of the flange 26 is larger than the diameter L2 of the root circle 22a of the camshaft drive sprocket 22. Large diameter (L1> L
2) and formed into a disk shape. Further, the camshaft drive sprocket 22 has a disk shape before the gear cutting, and is fitted to the crankshaft 16 together with the flange 26 or is integrally formed. Further, the outer periphery of the camshaft drive sprocket 22 and the outer periphery of the flange 26 are collectively subjected to a gear cutting process so that a groove 2 is formed on the outer periphery of the flange.
6a is formed. Forming protrusions 2 4 b on the side 24a facing the flange 26 of the oil pump gear 24. In this case, the protrusions 2 4 b is so fitted into the grooves 26a of the flange circumference when fitted to the oil pump gear 24 on the crankshaft 16 is in contact with the flange 26. The camshaft drive sprocket 2
The gear cutting process 2 is performed with a slotter (vertical cutting machine). The slotter cutting tool performs forward and backward movements (forward and backward steps) in parallel with the crankshaft 16 to perform gear cutting. The flange 26 is formed such that its outer diameter L ₁ is larger than the diameter L ₂ of the root circle 22 a of the camshaft drive sprocket 22 (L ₁ > L ₂ ). When the cutting tool is cutting, the outer periphery of the flange 26 is cut before the cutting tool finishes cutting to the root circle 22a.
A groove 26a is formed as shown in FIG. Further, the oil pump gear 24, as shown in FIG. 3, butt raised portion 24b which projects to the side facing the flange
To form The collision caused section 2 4 b, the crankshaft 16
The position perpendicular to the center C is a position that is larger than the radius (L2 / 2) of the root circle 22a and the flange 2
6 is formed in a smaller position than the radius to the outer circumference (L1 / 2) of, collision raised portion 24b when brought into a position coaxially with the oil pump gear 24 on the flange is a flange 26
Is located in the groove 26a. The collision caused <br/> unit 24b, be formed by embossing, as shown in FIG. 3, also, the oil pump gear 24 as shown in FIG. 4
It may be formed by cutting and raising (by bending a plate) from the inner periphery of the sheet. The oil pump gear 24 shown in FIGS.
May be formed by pressing a metal plate material together with the outer peripheral teeth. The camshaft drive sprocket 2
After machining of the outer circumferential groove 26a of the second cut teeth machining and the flange 26 is completed, and the-fitted the oil pump gear 24 on the crankshaft 16, If we push axially, impact force of the oil pump gear 24 24b fits into the groove on the outer periphery of the flange 26. Therefore, the flange 26 is connected to the crankshaft 1
6, the oil pump gear 2
Reference numeral 4 denotes a rotation stop for the crankshaft 16. This eliminates the need for a key or pin for preventing rotation required in the conventional oil pump gear, thereby reducing the number of parts and simplifying the structure. Further, since a keyway or a pinhole is not required, the number of processing operations can be reduced. Further, since the assembling of the key or the pin becomes unnecessary, the assembling work can be reduced. As described above, according to the present invention, the flange is rotatable with respect to the crankshaft, and the projection is fitted into the groove on the outer periphery of the flange. Is stopped. Therefore, a key or a pin required for the conventional oil pump gear for preventing rotation is not required, so that the number of parts can be reduced and the structure can be simplified. Further, since a keyway or a pinhole is not required, the number of processing operations can be reduced. On the other hand, the groove formed on the outer periphery of the flange can be formed at the time of gear cutting of the camshaft drive sprocket, and therefore, the present invention increases the processing work for forming the groove in the flange. is not.
Further, since the assembling of the key or the pin becomes unnecessary, the assembling work can be reduced. As described above, the cost can be reduced because the number of parts is reduced, the structure is simplified, and machining and assembling operations are reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration explanatory diagram of a four-cycle internal combustion engine mounted on a motorcycle according to an embodiment of the present invention. FIGS. 2 (a) and 2 (b) are explanatory views illustrating how a camshaft drive sprocket, a flange, and an oil pump gear are attached to a crankshaft of the internal combustion engine of FIG. 1; FIGS. 3 (a) and 3 (b) are a perspective view and a longitudinal sectional view illustrating the configuration of an oil pump gear. [4] (a), (b) is a perspective view illustrating the configuration of another embodiment of the oil pump gears, a longitudinal sectional view. FIGS. 5A and 5B are explanatory views of a conventional structure for preventing a rotation of an oil pump gear with respect to a crankshaft. [Description of reference numerals] 10 side 2 facing the internal combustion engine 12 cylinder head 14 the camshaft 16 crankshaft 18 crank chamber 20 the crank chamber wall 22 the camshaft drive sprocket 22a root circle 24 oil pump gear 24a flanges 4 b protruding portion 26 the flange 26a groove

Claims (1)

(57) [Claims 1] A camshaft drive sprocket and a flange are provided so as to rotate integrally with a crankshaft so as to be close to each other, and oil is applied to the crankshaft from the opposite side of the camshaft drive sprocket across the flange. An attachment structure for an oil pump gear of a four-stroke internal combustion engine in which a pump gear is fitted and is adjacent to a flange, wherein the flange is formed to have a diameter larger than a root circle of a camshaft drive sprocket, and the outer periphery of the camshaft drive sprocket The outer periphery of the flange is collectively subjected to gear cutting to form a groove on the outer periphery of the flange, a projection is formed on the side of the oil pump gear facing the flange, and the oil pump gear is fitted to the crankshaft. That the protruding portion fits into a groove on the outer periphery of the flange when contacting the flange. Mounting structure of the oil pump gears of a four-cycle internal combustion engine according to symptoms.