JP2002122126A - Crank shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crank shaft capable of preventing a fatigue failure to be generated in a connecting end and seizure of a crank pin and a journal part. SOLUTION: A curvature radius of a fillet part 7 formed in a connecting end of a crank pin 2 and an arm part 3 is formed larger at the axis center side of a journal part 4, and a curvature radius of a fillet part 7 formed in a connecting end of the journal part 4 and the arm part 3 is formed larger at a side close to the crank pin 2. Strong tensile force to be generated at a part B and a part C is relaxed by the fillet part 7 having a relatively large curvature radius, and the generation of fatigue failure is prevented. A part of the crank pin 2 near a surface A is strongly pushed by a connecting rod 5, but a contact area of the crank pin 2 with a bearing 6 is large at this pushed part, the generation of seizure is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a crankshaft in an internal combustion engine.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional crankshaft 50.

As shown in FIG. 5, in a conventional crankshaft 50, an R-shaped recess is formed at a connecting end of a crankpin 51 and an arm 52 and a connecting end of a journal 53 and an arm 52. A certain fillet portion 54 is formed so as to go around the outer periphery of the crank pin 51 or the journal portion 53 along the coupling end.

[0004] The fillet portion 54 is formed to alleviate the concentration of the tensile force applied to the coupling end portion and to prevent the occurrence of fatigue failure.

[0005]

The enlargement of the fillet portion 54 is effective for alleviating the concentration of the tensile force applied to the connecting end. However, recently, along with downsizing of the engine, the total length of the crankshaft 50 has been reduced, and when the fillet portion 54 is to be enlarged, the crankpin 52 and the outer periphery of the crankpin 52 Contact width W1 with a bearing (not shown)
Alternatively, similarly, the contact width W2 between the journal portion 53 and a bearing (not shown) interposed on the outer periphery of the journal portion 53 must be reduced. Then, the surface pressure between the crankpin 52 or the journal portion 53 and the bearing becomes excessive, and there is a problem that both are seized.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a fatigue fracture occurring at a joint end within a limited total length of a crankshaft, and
An object of the present invention is to provide a crankshaft that can prevent seizure in a crankpin and a journal portion.

[0007]

According to a first aspect of the present invention, the power of a piston is transmitted by a transmission member to perform a rotary motion while being supported by a support portion, and a connecting end portion between a crankpin and an arm portion, or In a crankshaft in which a fillet portion is formed at a joint end portion of a journal portion and an arm portion, at least one fillet portion of the fillet portion includes a portion having a strongest tensile force generated by a force transmitted from the transmission member. The main point is that the radius of curvature is large.

According to a second aspect of the present invention, in the crankshaft according to the first aspect, a portion having the strongest tensile force generated by the force transmitted from the transmission member at a connection end of the crank pin and the arm portion. Is intended to be closer to the axis of the crankshaft.

According to a third aspect of the present invention, in the crankshaft according to the first or second aspect, a tensile force generated by a force transmitted from the transmission member at a connecting end of the journal and the arm. The strongest part of
The gist is that it is closer to the crankpin.

(Operation) According to the first aspect of the present invention,
The concentration of the strongest tensile force generated at the connecting end of the crankpin and the arm or the connecting end of the journal and the arm is reduced by the portion of the fillet having a large radius of curvature. Also, at the joint end of the crank pin and the arm, or at the joint end of the journal and the arm, at a portion where the radius of curvature of the fillet is relatively small, the crank pin and the transmission member, or
Since the contact area between the journal portion and the transmission member is large, the surface pressure of both is reduced.

According to the second aspect of the present invention, the strongest tensile force applied to the side closer to the axis of the crankshaft at the connection end portion between the crankpin and the arm portion is concentrated by the fillet portion having a large radius of curvature. Be relaxed. On the side farther from the axis of the crankshaft of the crankpin, which is strongly pressed by the transmission member, the radius of curvature of the fillet portion is relatively small, so that the contact area with the transmission member is large and the surface pressure of both is low. .

According to the third aspect of the present invention, the strongest tensile force applied to the side near the crank pin at the joint end of the journal and the arm is reduced in concentration by the fillet having a large radius of curvature. You. Also, since the radius of curvature of the fillet portion on the side of the journal portion far from the crankpin is relatively small, the contact area with the support portion is large,
Surface pressure decreases.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a crankshaft according to the present invention will be described below with reference to FIGS.

FIG. 1 shows a front view of the crankshaft 1. FIG. 2 shows a cross-sectional view of a main part in FIG.

[0015] As shown in FIG.
Is configured such that a plurality of (four in the figure) crank pins 2, an arm portion 3, and a journal portion 4 are integrally connected to each other.

Each of the plurality of crank pins 2 is provided with a connecting rod 5 as a transmission member indicated by a two-dot chain line. More specifically, as shown in FIG. 2, the crankpin 2 is rotatably supported in a circular hole 5 a formed in the connecting rod 5. As shown in FIG. 2, a metal plate-shaped bearing 6 is interposed on the outer periphery of the crank pin 2 on the connecting rod 5 side as a transmission member to reduce frictional force.

Further, the other end of the connecting rod 5 is shown in FIG.
Above, is connected to a piston (not shown).

The journal portion 4 is provided in a journal receiving portion as a support portion for a cylinder block (not shown).
Like the crank pin 2, the journal portion 4 is rotatably supported with a bearing (not shown) interposed therebetween.

A fillet portion 7 is formed at each of the connecting ends of the crankpin 2 and the arm portion 3. The fillet portion 7 has an R-shaped recess formed by cutting, and is formed so as to make a round around the outer periphery of the crankpin 2 along a joint end portion between the crankpin 2 and the arm portion 3. I have.

The radius of curvature of the fillet portion 7 varies in size during one round of the outer circumference of the crank pin 2, and the center of the journal portion 4 (= the center of the crank shaft 1). ) Side (the lower side in FIG. 2) is formed with a large radius of curvature.

Similarly, an R-shaped recessed fillet portion 7 is formed at the joint end between the journal portion 4 and the arm portion 3 by cutting, and along the circumference of the journal portion 3. The size thereof is variable, and the radius of curvature near the crankpin 2 connected to the arm 3 on the coupling end side where the fillet portion 7 is formed is formed large.

The operation of the crankshaft 1 constructed as described above will now be described.

When the piston slides up and down, the connecting rod 5 connected to the piston also moves up and down, and the crankshaft 1 rotates around the journal 4 as a rotation axis.

In this case, in FIG. 1, the power of the piston is transmitted to the connecting rod 5 and is applied to the crankpin 2 in the direction indicated by the arrow F, so that the crankpin 2 on the side farther from the axis of the journal portion 4 is moved. The surface A is strongly pressed by the connecting rod 5. Then, near the point A, a strong frictional force is generated between the bearing 6 and the crankpin 2.

When the portion indicated by the point A of the crank pin 2 is strongly pressed, the journal portion 4 is pressed against the journal receiving portion, so that the connecting rod 5 is pressed.
On the surface D farther from the crankpin 2 pressed by the
And a strong frictional force is generated.

However, in the vicinity of the surface A of the crankpin 2, the radius of curvature of the fillet portion 7 formed at the joint end between the crankpin 2 and the arm portion 3 is relatively small. The contact width W1 between the bearing and the bearing 6 is wide. Then, since the contact area between the crank pin 2 and the bearing 6 is large, the surface pressure acting between the two is relatively low, and the frictional force is reduced.

Similarly, in the vicinity of the surface D of the journal portion 4, the radius of curvature of the fillet portion 7 formed at the connecting end of the journal portion 4 and the arm portion 3 is relatively small. The contact width W2 between the minute journal portion 4 and the bearing is wide. Then, since the contact area between the journal portion 4 and the bearing is large, the surface pressure acting between the two is relatively low, and the frictional force is reduced.

Further, when the vicinity of the surface A of the crankpin 2 is strongly pressed by the connecting rod 5, the arm 3 is connected to the crankpin 2 as shown by a two-dot chain line in FIG. Is trying to spread the opposite end in a C-shape. Then, a fillet portion 7 is formed at a portion B on the side near the axis of the journal portion 4 at the connection end portion between the crankpin 2 and the arm portion 3 and at the connection end portion between the journal portion 4 and the arm portion 3. Part C on the side close to the crank pin 2 connected to the arm part 3 on the connected end side
, The strongest tensile force is generated.

However, since the fillet portion 7 has a large radius of curvature in the vicinity of the portions B and C, the strongest tensile force generated in the portions B and C is reduced by the fillet portion 7. .

Next, the features of the crankshaft 1 configured as described above will be described below.

(1) The radius of curvature of the fillet portion 7 formed at the connection end portion between the crankpin 2 and the arm portion 3 is increased on the side where the tensile force is large, that is, on the side close to the axis of the journal portion 4. Since the concentration of the pulling force is reduced, the fillet portion 7 is reduced on the opposite side, the contact width W1 with the bearing 6 is increased, and the surface pressure between the crankpin 2 and the bearing 6 is reduced. In one limited overall length, it is possible to prevent fatigue destruction at the connection end portion between the crank pin 2 and the arm portion 3 and to prevent the crank pin 2 and the bearing 6 from burning.

(2) The radius of curvature of the fillet portion 7 formed at the joint end portion between the journal portion 4 and the arm portion 3 is increased on the side where the tensile force is large, that is, on the side close to the crankpin 2, and Concentration is alleviated, and the opposite side is reduced in the size of the fillet portion 7 so that the contact width W2 with the bearing is reduced.
And the surface pressure between the journal portion 4 and the bearing is reduced, so that the fatigue end of the joint end portion between the journal portion 4 and the arm portion 3 can be prevented over a limited total length of the crankshaft 1, and the journal can be prevented. Seizure of the part 4 and the bearing can be prevented.

(Second Embodiment) Next, a second embodiment of the crankshaft according to the present invention will be described with reference to FIGS.

In the first embodiment, the fillet portion 7 shown in FIGS. 1 and 2 is formed only by cutting, but in the present embodiment, a rolling process is performed after the cutting process. It is what went.

As shown in FIG. 3, the rolling process is a rolling process in which a disk-shaped rotating body 9 is rotatably supported by a device body 8 about a central axis indicated by a dashed line. This is a processing method using the device 10. Then, in a state where the rotating body 9 is rotated, the rotating body 9 is connected to the fillet portion 7 formed at the connection end of the crank pin 2 and the arm portion 3, and the journal portion 4 and the arm The fillet portion 7 formed at the connection end of the portion 3
, A compressive residual stress is generated.

As described above, the fillet portion 7 in which the compressive residual stress has been generated has an increased proof stress against tensile force.

The shape of the fillet 7 in this embodiment is the same as that of the fillet 7 in the first embodiment.

Further, the crank pin 2 or
In order to roll the fillet portions 7 having different curvature radii while making a round around the outer periphery of the journal portion 4, the following processing method can be considered.

As shown in FIG. 3, the first method is a method of processing by moving the apparatus main body 8 right and left as indicated by an arrow A in synchronization with the rotation of the work. For example,
When the roll processing is performed on a portion having a relatively large radius of curvature in the fillet portion 7, the roll processing can be performed by moving the apparatus main body 8 to the right side in FIG.

In the second method, as shown in FIG. 4, the rotating body 11 provided in the rolling device 10 is constituted by a continuous body having a large and small R, and the rotating body 11 is synchronized with the rotation of the work.
This is a method of processing by attaching a mechanism that changes the angle of one rotation axis. For example, the fillet portion 7
When the roll processing is performed on a portion having a relatively small radius of curvature, the angle of the rotation axis of the rotating body 11 is set as shown in FIG.
By performing the adjustment as shown in FIG. 2 and setting the rotating body 11 in a relatively upright state, the roll processing is performed by the small R portion of the rotating body 11. In addition, when rolling is performed on a relatively large radius of curvature of the fillet portion 7, the rotation angle of the rotating body 11 is adjusted as shown in FIG. When the rotating body 11 is in a state where the rotating body 11 is placed in a target lying state, the rolling process is performed by the large R portion of the rotating body 11.

Next, the features of the crankshaft 1 configured as described above will be described below.

Since the fillet portion 7 is rolled, a compressive residual stress is generated in the fillet portion 7 and the proof stress against the tensile force can be increased. In addition to the effects described in the first embodiment, Further, it is possible to prevent fatigue fracture occurring at the joint end.

In the first and second embodiments, the fillet portion 7 has an R shape. However, if the fillet portion 7 has a smooth curved surface and a shape that can reduce the concentration of tensile force, It is not particularly limited to the R shape.

[0044]

According to the first and second aspects of the present invention, it is possible to prevent the occurrence of fatigue failure at the joint end between the crankpin and the arm, and to seize the crankpin and the transmission member. Can be prevented from occurring.

According to the first and third aspects of the present invention, it is possible to prevent the occurrence of fatigue failure at the joint end portion between the journal portion and the arm portion and to cause seizure on the journal portion and the support portion. Can be prevented from occurring.

[Brief description of the drawings]

FIG. 1 is a front view of a crankshaft 1 according to a first embodiment.

FIG. 2 is a sectional view of an essential part of the same.

FIG. 3 is a front view of the roll processing apparatus 10.

FIG. 4 is an explanatory view of the operation of the rolling process.

FIG. 5 is a front view of a conventional crankshaft 50.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Crankshaft, 2 ... Crank pin, 3 ... Arm part, 4 ... Journal part, 5 ... Connecting rod as transmission member, 6 ... Bearing as transmission member, 7 ... Fillet part

Claims (3)

[Claims] The power of a piston is transmitted by a transmission member and is rotated by a transmission member, and a fillet portion is provided at a coupling end of a crankpin and an arm or a coupling end of a journal and an arm. The crankshaft characterized in that, in at least one of the fillet portions, a radius of curvature of a portion where a tensile force generated by a force transmitted from the transmission member is strongest is large. 2. The crankshaft according to claim 1, wherein a portion of the joint end between the crankpin and the arm portion where a tensile force generated by a force transmitted from the transmission member is strongest is an axis of the crankshaft. A crankshaft characterized by being close to the heart. 3. The crankshaft according to claim 1 or 2, wherein, at a joint end portion between the journal portion and the arm portion, a portion having the highest tensile force generated by a force transmitted from the transmission member, A crankshaft, which is closer to the crankpin.