JP2004278763A - Crank shaft of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crank shaft of an internal combustion engine capable of reducing mechanical noise, setting the outside diameter of a crank web to be large, and reducing split crank web to be small even when a split type crank web is employed. <P>SOLUTION: The crank shaft 1 converts the reciprocation of a piston of an internal combustion engine into the rotational motion. A helical gear 2 is provided on a crank web W4a of the crank shaft 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a crankshaft in an internal combustion engine, and particularly to a crankshaft having a drive gear.
[0002]
[Prior art]
The crankshaft provided with the drive gear for taking out power on the crank web can reduce the width of the internal combustion engine without requiring a special drive gear separately, and is therefore already widely applied to the internal combustion engine of a vehicle.
[0003]
The drive gear used there is a spur gear.
In the case of an integral crankshaft integrally formed by forging or casting, since the spurs of such a spur gear are ground by a gear cutting machine, the outer diameters of the crank webs on both sides of the drive gear are restricted.
[0004]
That is, when grinding the gear teeth of the drive gear, the outer diameter of the crank web cannot be larger than the root diameter of the spur teeth of the drive gear so that the crank webs on both sides do not interfere.
Therefore, it was difficult to obtain a sufficient counterweight by increasing the diameter.
[0005]
Therefore, there has been proposed an example in which the crank web is of a split type and the split crank web is integrally attached to the crank web on the main body side of the crankshaft later (for example, see Patent Document 1).
[0006]
[Patent Document 1]
JP-A-8-93746
In Patent Literature 1, the outer diameter of the main body-side crank web of the crankshaft is smaller than the root diameter of the spur teeth of the drive gear to facilitate tooth grinding, and the outer diameter of the outer diameter larger than the root diameter is later increased. The split crank webs mainly acting as counterweights are united together.
[0008]
[Problems to be solved by the invention]
Conventionally, since a drive gear provided on a crank web of a crankshaft is a flat gear, the load applied to each tooth fluctuates greatly and mechanical noise may occur.
[0009]
In the case of an integral crankshaft, the outer diameter of the crank web cannot be set large because of the restriction on the root diameter of the spur teeth.
Therefore, if a split crank web is used to obtain a sufficient counterweight, the crank web on the main body side of the crankshaft is restricted by the root diameter of the spur teeth, so that the split crank web becomes large.
[0010]
SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and its object is to reduce mechanical noise, set a large outer diameter of a crank web, and reduce a split crank web even in the case of a split crank web. The point is to provide the crankshaft of the internal combustion engine.
[0011]
Means for Solving the Problems and Functions and Effects
In order to achieve the above object, the invention according to claim 1 is directed to a crankshaft for converting reciprocating motion of a piston in an internal combustion engine into rotary motion, wherein the helical gear is provided on a crank web of the crankshaft. It was a crankshaft.
[0012]
The helical gear provided on the crank web of the crankshaft has a large meshing ratio, less variation in the load applied to each tooth, reduces mechanical noise, and can realize quiet and smooth transmission.
[0013]
If the gear provided on the crank web of the crankshaft is a helical gear, the helical gear can be slanted by the helix angle of the tooth trace, so the crank webs on both sides of the helical gear should be smaller than the root diameter of the helical gear. No need.
[0014]
According to a second aspect of the present invention, in the crankshaft for the internal combustion engine according to the first aspect, the helical gear is formed integrally by engraving helical teeth on a peripheral edge of a crank web.
[0015]
Even if a helical gear is integrally formed by engraving a helical gear on the periphery of the crank web, it is easy to obtain a sufficient counterweight by increasing the diameter of the crank web as described above.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment according to the present invention will be described below with reference to FIGS.
The crankshaft 1 according to the present embodiment is applied to, for example, a four-cycle parallel four-cylinder internal combustion engine of a motorcycle, and a side view of the entire crankshaft 1 is shown in FIG.
[0017]
Referring to FIG. 1, a crankshaft 1 has five rotation shaft portions including a rotation center axis L including both ends, namely, crank journals J1, J2, J3, J4, and J5 in order from the left. Crankpins P1, P2, P3, P4 connected to the piston via a connecting rod are displaced from the rotation center axis L.
[0018]
The crank webs W1a and W1b on both sides of the crankpin P1 connect the crankpin P1 and the crank journals J1 and J2, and the crank webs W2a and W2b on both sides of the crankpin P2 connect the crankpin P2 and the crank journals J2 and J3, The crank webs W3a and W3b on both sides of the crankpin P3 connect the crankpin P3 and the crank journals J3 and J2, and the crank webs W4a and W4b on both sides of the crankpin P4 connect the crankpin P4 and the crank journals J4 and J5. I have.
[0019]
The entire crankshaft 1 having the above-described configuration is integrally formed by forging or casting.
The outer peripheral surface of the crank web W4a connecting the crank pin P4 and the crank journal J4 is ground with a helical tooth h having a torsion angle of about 30 degrees to constitute the primary drive gear 2 in which the crank web W4a itself is a helical gear. I have.
[0020]
When the crankshaft 1 is incorporated in the internal combustion engine, the primary drive gear 2 meshes with a primary driven gear fixed to an outer part of a clutch provided at an end of a main shaft in the transmission, and rotates the crankshaft 1 toward the transmission. Transmit via clutch.
[0021]
The tip diameter (maximum diameter) of the helical teeth h of the primary drive gear 2 is D1, and the root diameter is D2.
The crank webs W1a, W2b, W3a, W4b have counterweights C1, C2, C3, C4 on the opposite side of the rotation center axis L with respect to the holding side of the crankpins P1, P2, P3, P4.
[0022]
In particular, the crank webs W1a and W4b at both ends are formed by combining a separate crank web with a main body side crank web integrally formed with a crankshaft.
Both of the crank webs W1a and W4b are of the split type having the same structure, and the crank web W4b adjacent to the primary drive gear 2 will be described with reference to FIGS.
[0023]
The main body-side crank web 3 of the crank web W4b has a circular shape with a diameter d1 cut out at two locations, and has a contour-like contour shape (see FIG. 2). 3a and the large deployed portion 3b are deployed, and the crank pin P4 is formed to project from the small deployed portion 3a, and the large deployed portion 3b is a part of the counterweight C4.
[0024]
As shown in FIG. 5, the outer diameter d1 of the main body side crank web 3 is larger than the root diameter D2 of the adjacent primary drive gear 2 and smaller than the tooth tip diameter D1, that is, the outer diameter d1 of the main body side crank web 3 is D2. <D1 <D1.
[0025]
Five screw holes 3d having the same diameter are formed at equal intervals along the outer peripheral edge of the large deployment portion 3b.
At the center of the main body side crank web 3, a middle diameter cylindrical portion 3c bulges somewhat, and a small diameter crank journal J5 is formed through the middle diameter cylindrical portion 3c.
[0026]
On the other hand, the divided crank web 4 has an outer diameter smaller than the outer diameter d1 of the main body side crank web 3 and an annular portion 4a having the same inner diameter as the medium-diameter cylindrical portion 3c, and a half of the annular portion 4a has a radial direction. The developing portion 4b includes a developing portion 4b that extends in a fan shape, and an arc portion 4c whose outer peripheral edge extends in the axial direction.
[0027]
The unfolded portion 4b of the split crank web 4 has the same shape as the large unfolded portion 3b of the main body-side crank web 3, and has an outer diameter somewhat larger than the large unfolded portion 3b.
The developing portion 4b has five insertion holes 4d formed in a conical shape corresponding to the five screw holes 3d of the large developing portion 3b.
[0028]
The extended axial width of the arc portion 4c is substantially equal to the width of the large deployed portion 3b of the main body side crank web 3, the inner diameter of the arc portion 4c is equal to the outer diameter d1 of the main body side crank web 3, and 4c is larger than the maximum diameter D1 of the primary drive gear 2.
[0029]
Therefore, when the divided crank web 4 is combined with the main body side crank web 3, when the annular portion 4a of the divided crank web 4 is fitted to the medium diameter cylindrical portion 3c of the main body side crank web 3, the arc portion 4c of the divided crank web 4 is formed. Are fitted so as to cover the outer periphery of the large deployed portion 3b of the main body side crank web 3.
[0030]
The bolts 5 with hexagonal holes are respectively inserted into the screw holes 3d of the five matching crank webs 3 and the insertion holes 4d of the split crank webs 4 and screwed into the screw holes 3d, and the split crank webs 4 are split into the main body crank webs 3. Tighten together.
[0031]
The large unfolded portion 3b of the main body side crank web 3 and the unfolded portion 4b of the divided crank web 4 constitute a counterweight C4 of the crank web W4b together with the five hexagon socket head bolts 5.
[0032]
The outer diameter d2 of the crank web W3b on the other side of the primary drive gear 2 is also larger than the root diameter D2 of the primary drive gear 2 and smaller than the tip diameter D1, similarly to the outer diameter d1 of the main body crank web 3. That is, D2 <d2 <D1.
[0033]
As described above, the crank web W4b is divided into the main body side crank web 3 and the split crank web 4, and the outer peripheral surface of the integrally formed crank web W4a of the crankshaft 1 has a helical tooth h having a torsion angle of about 30 degrees. After grinding with a gear cutting machine, the divided crank web 4 can be mounted.
[0034]
When the gear teeth of the primary drive gear 2 are ground, the outer diameters d1 and d2 of the main body side crank web 3 and the crank web W3b on both sides of the primary drive gear 2 are larger than the root diameter D2 of the grinding teeth, but the torsion angle is increased. Since the helical tooth h of about 30 degrees is ground, it is possible to prevent the tangent in the tooth ridge direction of the tooth root at an angle of the helix angle from interfering with the main body side crank web 3 and the crank web W3b. It is possible to grind the teeth h.
[0035]
After the helical gear is formed by grinding the helical teeth h, the split crank web 4 is combined with the main body side crank web 3 as described above to form the crank web W4b, whereby the developed portion 4b of the split crank web 4 is formed. Thus, a counterweight C4 having a sufficient weight can be obtained.
[0036]
By using the helical gear as the primary drive gear 2 as described above, it is not necessary to make the outer diameters d1 and d2 of the adjacent body-side crank web 3 and the crank web W3b smaller than the root diameter of the helical gear.
[0037]
Since the diameter of the main body side crank web 3 can be increased in the split type crank web W4b, a sufficient counter weight can be obtained even if the split crank web 4 is made smaller.
Further, by reducing the size of the divided crank web 4, the size of the hexagon socket head cap screw 5 for attachment to the main body side crank web 3 can be reduced.
[0038]
As described above, in the split type crank web W4b, the outer diameter d1 of the main body side crank web 3 can be made larger than the root diameter D2 of the primary drive gear 2, so that the adjustment by the split crank web 4 is easy and the degree of freedom is large.
[0039]
By using the helical gear for the primary drive gear 2, the meshing ratio with the primary driven gear on the transmission side is increased, the fluctuation of the load applied to each tooth is reduced, mechanical noise is reduced, and quiet and smooth transmission is achieved. Can be realized.
[0040]
Although the above-described embodiment is an integral crankshaft, in the case of an assembled crankshaft in which parts are assembled together by press-fitting or the like, it is easy to form a drive gear on the crank web, and the drive gear By using a helical gear, mechanical noise can be reduced and quiet and smooth transmission can be realized.
[Brief description of the drawings]
FIG. 1 is an overall side view of a crankshaft according to an embodiment of the present invention.
FIG. 2 is a view taken in the direction of the arrow II in FIG.
FIG. 3 is a sectional view taken along line III-III in FIG.
FIG. 4 is a sectional view of a main part.
FIG. 5 is an exploded sectional view of the same.
[Explanation of symbols]
J1, J2, J3, J4, J5: Crank journal, P1, P2, P3, P4: Crank pin, W1a, W1b, W2a, W2b, W3a, W3b, W4a, W4b: Crank web, C1, C2, C3, C4 … Counter weight,
DESCRIPTION OF SYMBOLS 1 ... Crank shaft, 2 ... Primary drive gear, 3 ... Main body side crank web, 4 ... Split crank web, 5 ... Hexagon socket head bolt.

Claims (2)

In a crankshaft that converts a reciprocating motion of a piston in an internal combustion engine into a rotary motion,
A crankshaft for an internal combustion engine, wherein a helical gear is provided on a crank web of the crankshaft. 2. A crankshaft according to claim 1, wherein the helical gear is formed integrally with a helical gear by engraving helical teeth on a peripheral edge of the crank web.

Images