JP2004270757A - Crankshaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crankshaft capable of largely reducing cost by enabling common use in a plurality of kinds of engines. <P>SOLUTION: The crankshaft comprises a crankshaft body 33 where a gear 24 for rotation output is formed on one side of a crank pin 17d and a balance weight attaching section 30g is formed on the other side of the crank pin 17d, and a balance weight 31g to be attached to the balance weight attaching section 30g. The crankshaft body 33 is provided with a second balance weight attaching section 30a separated from the balance weight attaching section 30g, and the second balance weight attaching section 30a is provided with a second balance weight 31a. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a crankshaft for an engine.
[0002]
[Prior art]
For example, in an engine used for a motorcycle or the like, a piston is reciprocated by thermal energy obtained by burning an air-fuel mixture, and the reciprocating motion of the piston is converted into a rotational motion of a crankshaft via a connecting rod. I have. As a conventional crankshaft used in such an engine, a rotation output gear is formed on one side of a crankpin supporting a connecting rod connected to a piston, and another is provided on the other side of the crankpin. There is one in which a balance weight attachment portion to which a balance weight of a body is attached is formed (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP-A-8-93746
In the above-described conventional crankshaft, in order to avoid interference with a processing tool forming a gear on one side of the crankpin, a crank web originally provided on the other side of the crankpin is provided with a balance weight mounting portion and a balance weight. Is divided into In other words, the balance weight mounting portion is sized to avoid interference with the processing tool during gear processing. In this way, the gear is formed by performing gear processing while avoiding interference with the processing tool at the balance weight mounting portion. Thereafter, the balance weight is attached to the balance weight attachment portion.
[0005]
[Problems to be solved by the invention]
By the way, in the conventional crankshaft including the above-described structure, it is substantially difficult to share the crankshaft in a plurality of types of engines because it is necessary to match the moments of inertia of the crankshafts in engines having different engine characteristics. However, if the crankshaft can be shared by a plurality of types of engines, the cost can be significantly reduced.
[0006]
Therefore, an object of the present invention is to provide a crankshaft capable of achieving a great cost reduction by enabling sharing of a plurality of types of engines.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 includes a crankpin (for example, a connecting rod 18d in the embodiment) supporting a connecting rod (for example, a connecting rod 18d in the embodiment) connected to a piston (for example, the piston 19d in the embodiment). A gear for rotation output (for example, the primary drive gear 24 in the embodiment) is formed on one side of the crank pin 17d in the embodiment, and a balance weight mounting portion (for example, the balance in the embodiment) is provided on the other side of the crank pin. A crankshaft main body (e.g., the crankshaft main body 33 in the embodiment) formed with the weight attachment portion 30g) and a balance weight (e.g., the balance weight 31g in the embodiment) attached to the balance weight attachment portion. In the crankshaft (for example, the crankshaft 12 in the embodiment), a second balance weight mounting portion (for example, the balance weight mounting portion 30a in the embodiment) is formed on the crankshaft main body separately from the balance weight mounting portion. A second balance weight (for example, the balance weight 31a in the embodiment) is attached to the second balance weight attachment portion.
[0008]
In this way, the crank web is divided into a balance weight mounting portion and a balance weight in order to perform gear processing while avoiding interference with a processing tool. On the other hand, in order to adjust the moment of inertia by changing the balance weight attached to the balance weight attachment portion, and further to provide balance in the axial direction of the crankshaft, another balance weight attachment portion is provided. The second balance weight is also changed. As a result, the engine can be mounted on a plurality of types of engines simply by changing the balance weight and the second balance weight.
[0009]
According to a second aspect of the present invention, in the first aspect, the balance weight attaching portion is provided outside a crankpin at one end of the plurality of crankpins (for example, the crankpin 17d in the embodiment). The second balance weight mounting portion is provided outside a crankpin at the other end (for example, the crankpin 17a in the embodiment).
[0010]
As described above, the balance weight attaching portion is provided outside the crank pin at one end of the plurality of crank pins, and the second balance weight attaching portion is provided outside the crank pin at the other end. Thus, the positional balance between the balance weight mounting portion and the second balance weight mounting portion can be maintained, so that when changing the balance weight and the second balance weight, they can be set relatively easily.
[0011]
The invention according to claim 3 is the invention according to claim 1 or 2, wherein the gear is a helical gear.
[0012]
As described above, by making the gear a helical gear, the gear meshing noise can be reduced and the quietness can be improved.However, in order to machine the helical gear, it is necessary to incline the machining tool with respect to the gear to perform machining. Since the possibility of interference with the crank web on the opposite side to the gear via the crank pin increases, it is more preferable to divide the crank web into the balance weight mounting portion and the balance weight as described above. Be effective.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
A crankshaft according to an embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 schematically shows the overall configuration of an engine 11 to which the crankshaft of the present embodiment is applied. Specifically, the engine 11 is an in-line four-cylinder engine for a motorcycle.
[0014]
The engine 11 includes a crankshaft 12 and a crank that rotatably supports a plurality of, specifically five, crank journals 13a to 13e of the crankshaft 12 at five crank journal receiving portions 14a to 14e. A plurality of, specifically, four pistons respectively connected to the case 15 and a plurality of, specifically, four, crank pins 17a to 17d of the crankshaft 12 through four, specifically, four connecting rods 18a to 18d. 19a to 19d, a cylinder block 21 mounted on the upper side of the crankcase 15 to guide the sliding of each piston 19 on each of the cylinder inner surfaces 20a to 20d, and a valve mechanism (not shown) mounted on the upper side of the cylinder block 21 And a cylinder head 22 for holding the same.
[0015]
The engine 11 is provided with a transmission 25 whose output is transmitted via a primary drive gear 24 of the crankshaft 12, and a clutch 26 that switches between transmission and cutoff of driving force from the crankshaft 12 to the transmission 25.
[0016]
As shown in FIG. 2, the crankshaft 12 of the present embodiment includes, from one side in the axial direction, a crank journal 13a, a crank web 28a, a crank pin 17a, a crank web 28b, a crank journal 13b, a crank web 28c, a crank pin 17b. , A crank web 28d, a crank journal 13c, a crank web 28e, a crank pin 17c, a crank web 28f, a crank journal 13d, a primary drive gear 24 (gear), a crank pin 17d, a crank web 28g, and a crank journal 13e.
[0017]
The crankshaft 12 is rotatably supported by the crank journal receiving portions 14a to 14e of the crankcase 15 shown in FIG. 1 at the respective crank journals 13a to 13e provided on the same axis. On the other hand, connecting rods 18a to 18d are rotatably supported by respective crank pins 17a to 17d provided offset in the radial direction. Here, both outer crank pins 17a and 17d in the axial direction of the crankshaft 12 are in phase with each other in the rotational direction of the crankshaft 12, and both inner crankpins 17b and 17c in the axial direction of the crankshaft 12 are mutually aligned. The phases in the rotational direction of the crankshaft 12 are matched, and the phases of the crank pins 17b and 17c on the inner side are different from those of the crank pins 17a and 17d on the outer side by 180 degrees.
[0018]
Here, the crank web 28g which is outside the crank pin 17d at one end of the plurality of crank pins 17a to 17d and is opposite to the primary drive gear 24 via the crank pin 17d is shown in FIGS. As shown in the figure, the balance weight attachment portion (balance weight attachment portion) is composed of 30 g and the balance weight (balance weight) 31 g, and the other of the plurality of crank pins 17 a to 17 d is located outside the other crank pin 17 a. As shown in FIGS. 2 and 4, the crank web 28a also includes a balance weight mounting portion (second balance weight mounting portion) 30a and a balance weight (second balance weight) 31a.
[0019]
The crank journals 13a to 13e, the crank webs 28b to 28f, the crank pins 17a to 17d, and the balance weight mounting portions 30a and 30g are formed in an integral crankshaft main body 33.
[0020]
One of the balance weight mounting portions 30g is provided with a fitting circular portion 35g coaxial with the crank journals 13a to 13e, which is provided on the outer side, that is, the side of the adjacent crank journal 13e, in the axial direction of the crankshaft 12, and with the inner, ie, adjacent, crank pin 17d. And a base portion 36g that extends radially outward from the fitting circular portion 35g on the side of the crankshaft 12. The base portion 36g has a width such that one side half in the radial direction of the crankshaft 12 gradually becomes closer to the radial front end side. A narrowing portion is formed as a tapered extension portion 37g whose outer peripheral portion is formed in an arc shape coaxial with the crank journals 13a to 13e. A circle having a wide shape and an outer periphery coaxial with the crank journals 13a to 13e. There is a previously wide extending portion 38g constituting the Jo. Here, the flared extension 38g is formed on the opposite side of the adjacent crank pin 17d via the central axis of the crank journals 13a to 13e.
[0021]
In the balance weight mounting portion 30g, the tip outer diameters of the narrower portion 37g and the wider portion 38g having the largest outer diameter are the same, and these are disposed adjacent to each other via the crank pin 17d. The outer diameter does not interfere with a hob cutter or the like which is a processing tool when processing the primary drive gear 24. Here, the primary drive gear 24 is a helical gear.
[0022]
In the base portion 36g of the balance weight attaching portion 30g, a plurality of, specifically five screw holes (only one is shown in FIG. 2) are arranged in an arc shape at a predetermined pitch on the widening portion 38g. 40 g are drilled along the axial direction of the crankshaft 12.
[0023]
The balance weight 31g held by the balance weight mounting portion 30g is fitted into a fitting circular portion 35g of the balance weight mounting portion 30g after passing through the outer crank journal 13e in the axial direction of the crankshaft 12. 42g is formed in the center portion, and one half in the radial direction of the fitting hole 42g is a semi-annular portion 43g that forms an annular shape, and the opposite half is a radius that is heavier than the semi-annular portion 43g. The weight portion 44g has a shape that spreads outward in the direction and gradually widens toward the distal end in the radial direction, and the distal end side is a weight portion 44g that forms an arc shape coaxial with the crank journals 13a to 13e.
[0024]
The balance weight 31g has an arc-shaped protruding portion 45g that forms an arc along the outer edge of the weight portion 44g and that protrudes to one side in the axial direction along the edge. The base portion 36g is fitted to the arc-shaped protruding portion 45g while the fitting circular portion 35g is fitted to the fitting hole 42g. A plurality of, specifically, five mounting holes 47g are arranged in the weight portion 44g in an arc shape at the same pitch as the above-mentioned screw hole 40g along the axial direction of the crankshaft 12. Here, each of the mounting holes 47g has a conical surface 48g on the side opposite to the protruding side of the arc-shaped protruding portion 45g.
[0025]
The balance weight 31g is fitted into the fitting hole 42g from the outside in the axial direction of the crankshaft 12 with the fitting circular portion 35g of the balance weight attaching portion 30g, while the balance weight attaching portion 30g is fitted to the arc-shaped protruding portion 45g. In a state where the flared extension 38g side of the base portion 36g is fitted and its end surface is brought into contact with the end surface of the base portion 36g, each screw 50g having a conical surface 49g is inserted into each mounting hole 47g and each screw is inserted. By being screwed into the hole 40g, it is fixed to the balance weight attaching portion 30. In this state, the balance weight 31g is disposed on the opposite side of the crank pin 17d adjacent to the weight pin 44g via the central axis of the crank journals 13a to 13e.
[0026]
The other balance weight mounting portion 30a is provided with a fitting circular portion 35a coaxial with the crank journals 13a to 13e provided on the outer side, that is, the side of the adjacent crank journal 13a in the axial direction of the crankshaft 12, and the inner side, that is, the adjacent crank pin. The base portion 36a is located on the 17a side and extends radially outward from the fitting circular portion 35a. The base portion 36a is such that one half in the radial direction of the crankshaft 12 gradually increases in width toward the radial end. Of the crankshaft 12 is narrower and the outer half in the radial direction of the crankshaft 12 is gradually narrowed toward the distal end in the radial direction. And the outer periphery is coaxial with the crank journals 13a to 13e. There is a previously wide extending portion 38a forming a circular arc shape. Here, the flared extension 38a is formed on the opposite side of the adjacent crank pin 17a via the center axis of the crank journals 13a to 13e.
[0027]
The tip outer diameters of the tapered extension 37a and the widened extension 38a having the largest outer diameter in the balance weight mounting portion 30a have the same diameter, and these are the tapered extensions of the balance weight mounting portion 30g described above. The diameter is the same as the outer diameter of the distal end of the protruding portion 37g and the divergent extension portion 38g.
[0028]
The base portion 36a of the balance weight attachment portion 30a has a plurality of screw holes 40a arranged in an arc shape at a predetermined pitch in a widening portion 38a thereof along the axial direction of the crankshaft 12 as described above. It is drilled similarly to the screw hole 40g of the part 30g.
[0029]
In the balance weight 31a held by the balance weight attachment portion 30a, a fitting hole 42a is formed in the center of the balance weight attachment portion 30a to be fitted into the fitting circular portion 35a after passing through the outer crank journal 13a. One half of the fitting hole 42a in the radial direction is a semi-annular portion 43a having an annular shape, and the opposite half is spread outward in the radial direction so as to be heavier than the semi-annular portion 43a. The weight portion 44a has a shape gradually increasing in width toward the distal end and has a circular arc shape coaxial with the crank journals 13a to 13e on the distal end.
[0030]
In addition, the balance weight 31a has an arc-shaped protruding portion 45a that forms an arc along the outer edge of the weight portion 44a and that protrudes toward one side in the axial direction. The base portion 36a is fitted to the arc-shaped protrusion 45a while the fitting circular portion 35a is fitted to the fitting hole 42a. A plurality of, specifically, five mounting holes 47a are arranged in the weight portion 44a in an arc shape at the same pitch as the above-described screw holes 40a, and are specifically formed at five locations along the axial direction of the crankshaft 12. Here, each mounting hole 47a has a conical surface 48a on the opposite side to the protruding side of the arc-shaped protruding portion 45a.
[0031]
The balance weight 31a is fitted into the arc-shaped projection 45a of the balance weight mounting portion 30a while the fitting circular portion 35a of the balance weight mounting portion 30a is fitted into the fitting hole 42a from the outside in the axial direction of the crankshaft 12. Each screw 50a having a conical surface 49a is inserted into each mounting hole 47a in a state where the flared extension portion 38a side of the base portion 36a is fitted and its end surface is in contact with the end surface of the base portion 36a. By being screwed into the hole 40a, it is fixed to the balance weight attaching portion 30a. In this state, the balance weight 31a is disposed on the opposite side of the crank pin 17a adjacent to the weight portion 44a via the central axis of the crank journals 13a to 13e.
[0032]
As described above, in the crankshaft 12 of the present embodiment, the primary drive gear 24 for rotational output is formed on one side of the crankpin 17d of which the crankshaft main body 33 supports the connecting rod 18d connected to the piston 19d. At the same time, a balance weight attachment portion 30g to which a separate balance weight 31g is attached is formed on the other side of the crank pin 17d, and a balance weight attachment portion to which a separate balance weight 31a is attached separately from the balance weight attachment portion 30g. 30a is provided. In addition, one balance weight mounting portion 30g is provided outside the crank pin 17d at one end of the plurality of crank pins 17a to 17d, and the other balance weight mounting portion 30a is provided outside the crank pin 17d at the other end. It is provided in.
[0033]
According to the above-described crankshaft 12 of the present embodiment, since the gear machining of the primary drive gear 24 is performed while avoiding interference with a gear machining tool such as a hob cutter, a crank provided near the primary drive gear 24 is provided. Utilizing a structure in which the web 28g is divided into a balance weight attachment portion 30g and a balance weight 31g, for example, for a plurality of models having different engine characteristics and the like, the balance weight 31g attached to the balance weight attachment portion 30g. Is changed to adjust the moment of inertia. Further, in order to balance in the axial direction of the crankshaft 12, the balance weight 31a provided on another balance weight mounting portion 30a is also changed. Thus, the moment of inertia can be changed only by changing the balance weights 31a and 31g, and can be mounted on a plurality of types of engines. Therefore, the crankshaft main body 33 except for the balance weights 31a and 31g can be shared by a plurality of types of engines, and the cost can be significantly reduced.
[0034]
Further, one balance weight mounting portion 30g is provided outside the crank pin 17d at one end of the plurality of crank pins 17a to 17d, and the other balance weight mounting portion 30a is provided outside the crank pin 17a at the other end. , The balance weight mounting portion 30a and the balance weight mounting portion 30g can be balanced in position, and therefore, when changing the balance weights 31a and 31g, the balance weights 31a and 31g can be set relatively easily. can do.
[0035]
Further, by making the primary drive gear 24 a helical gear, the meshing noise of the primary drive gear 24 can be reduced and quietness can be improved. However, a gear machining tool such as a hob cutter is inclined with respect to the primary drive gear 24 for machining the helical gear. Therefore, the possibility of interference with the crank web 28g located on the opposite side to the primary drive gear 24 via the crank pin 17d increases, so that the crank web 28g is removed as described above. It is more effective to divide the balance weight attachment portion 30g and the balance weight 31g.
[0036]
The balance weight 31a and the balance weight 31g can be formed in the same shape or in different shapes due to the adjustment of the moment of inertia.
[0037]
【The invention's effect】
As described in detail above, according to the first aspect of the invention, the crank web is divided into a balance weight mounting portion and a balance weight in order to perform gear processing while avoiding interference with a processing tool. By using, for example, for a plurality of models with different engine characteristics, etc., in order to adjust the moment of inertia by changing the balance weight attached to this balance weight mounting part, and to balance in the axial direction of the crankshaft The second balance weight provided on another second balance weight mounting portion is also changed. As a result, the moment of inertia can be changed only by changing the balance weight and the second balance weight, and can be mounted on a plurality of types of engines. Therefore, the crankshaft main body excluding the balance weight and the second balance weight can be shared by a plurality of types of engines, and the cost can be significantly reduced.
[0038]
According to the invention according to claim 2, the balance weight attaching portion is provided outside the crank pin at one end of the plurality of crank pins, and the second balance weight attaching portion is located outside the crank pin at the other end. , The balance weight mounting portion and the second balance weight mounting portion can be balanced in position, so that when the balance weight and the second balance weight are changed, they can be set relatively easily. can do.
[0039]
According to the third aspect of the present invention, when the gears are helical gears, the meshing noise of the gears can be reduced and the quietness can be improved. Therefore, since the possibility of interference with the crank web on the opposite side to the gear via the crank pin is increased, the crank web is divided into the balance weight mounting portion and the balance weight as described above. The configuration is more effective.
[Brief description of the drawings]
FIG. 1 is a view schematically showing an engine to which a crankshaft according to an embodiment of the present invention is applied.
FIG. 2 is a front view showing a part of a crankshaft according to an embodiment of the present invention in cross section.
FIG. 3 is a side view of the crankshaft according to the embodiment of the present invention as viewed from the right side in FIG. 2;
FIG. 4 is a side view of the crankshaft according to the embodiment of the present invention as viewed from the left in FIG.
[Explanation of symbols]
12 Crank shafts 17a to 17d Crank pins 18a to 18d Connecting rods 19a to 19d Piston 24 Primary drive gear (gear)
30a Balance weight attachment part (second balance weight attachment part)
30g Balance weight attachment part 31a Balance weight (second balance weight)
31g Balance weight 33 Crankshaft body

Claims (3)

A crankshaft main body having a rotation output gear formed on one side of a crankpin supporting a connecting rod connected to a piston and a balance weight mounting portion formed on the other side of the crankpin; A crankshaft having a balance weight attached to the attachment portion,
A second balance weight mounting portion is formed on the crankshaft main body separately from the balance weight mounting portion, and a second balance weight is mounted on the second balance weight mounting portion. And the crankshaft. The balance weight mounting portion is provided outside a crank pin at one end of the plurality of crank pins, and the second balance weight mounting portion is provided outside a crank pin at the other end. The crankshaft according to claim 1, wherein The crankshaft according to claim 1, wherein the gear is a helical gear.

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