JPS63243570A - Piston pin for internal combustion engine - Google Patents

Abstract

PURPOSE:To make it possible to hold a piston pin stably by reducing the area of the crossing section of both ends of the piston gradually toward the outer side of the axial direction, so as to make the piston pin bent along the inner surface of a holding hole in the operational condition. CONSTITUTION:At the boss 15 of a piston 12, a holding hole 16 is formed, in which both ends of the hollow piston pin 17 are held, and at the center of the piston pin 17, the smaller end 18 of a connecting rod 13 is connected. Furthermore, the inside diameter in the scope of a specific length L1 at the both ends of the piston pin 17 is expanded gradually toward the outer side of the axial direction, so that the both ends can be bent along the inside of the holding hole 16 in the operational condition of the internal combustion engine. In other words, the area of the crossing section of the both ends of the piston pin 17 is reduced gradually toward the outer side of the axial direction, and the rigidity of the both sides is reduced toward the outer axial side. The axial length L1 to the length (a) of the holding portion of the holding hole 16 is set within the formula: (2/3)a<=L1<=a.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a piston pin for an internal combustion engine.

[Prior Art] In an internal combustion engine, both ends of a piston pin are supported in support holes provided in the piston, a small end of a connecting rod is connected to the piston pin, and a large end of the connecting rod is connected to a crank pin of a crankshaft. is connected to. This makes it possible to transmit the explosive force acting on the top surface of the piston to the crankshaft via the piston pin and connecting rod.

At this time, the small end of the connecting rod swings around the axis of the piston pin, and the piston pin rotates around its own axis within the support hole as the connecting rod swings. Each circumferential part of the bearing provided at the end (for example, each needle of a needle bearing) is made to contact the entire circumference of the piston pin evenly to prevent local wear of the small end bearing and ensure smooth operation of the connecting rod. We are sure that it will be possible to secure the following.

[Problems to be Solved by the Invention] However, when the internal combustion engine is operated, the explosive force on the piston side and the reaction force on the connecting rod side exert a bending moment on the piston pin, and this bending moment bends and deforms the piston pin. let Corresponding to the bending deformation of the piston pin, deformation also occurs around the support hole of the piston.
The bending deformation of the piston pin and the deformation of the inner surface of the support hole do not match.

In particular, since the portion of the piston at the outer end of the support hole has high rigidity, both ends of the piston pin make extremely strong contact with the inner surface of the outer end of the support hole.

As a result, the piston pin becomes difficult to rotate around its own axis within the support hole due to thermal discoloration at both ends, or both ends becoming stuck to the inner surface of the support hole. This results in localized wear on the small end bearing of the connecting rod, which may lead to malfunction and seizure of the connecting rod.

In addition, if the piston pin that has been bent and deformed as described above comes into contact with the piston support hole with a strong force,
There is also a risk that large permanent deformation will occur in the piston and seizure will occur on the outer surface of the piston that slides into contact with the cylinder sleeve.

An object of the present invention is to enable a piston pin to be stably supported within a piston-side support hole without strong contact during operation of an internal combustion engine.

[Means for Solving the Problems] The present invention provides a piston pin for an internal combustion engine that is used with both ends supported by support holes provided in the piston and the small end of a connecting rod connected to the central part. ”-The cross-sectional area of each of the two end portions is gradually reduced in the axial direction outward so that the end portions are bent along the inner surface of the support hole in the above-mentioned state of use. .

[Function] During operation of an internal combustion engine, the piston pin is bent and deformed within the piston support hole due to the action of the bending moment based on the explosive force on the piston side and the reaction force on the connecting rod side, and the area around the piston support hole is bent. It also causes deformation. At this time, according to the present invention, the end of the piston pin bends in accordance with the deformed state of the inner surface of the support hole. Therefore, the piston pin can be stably supported within the support hole by equalizing the contact surface pressure with the inner surface of the support hole without causing strong local contact.

[Embodiment] Fig. 1 is a sectional view showing the main parts of an engine to which the first embodiment of the present invention is applied, and Fig. 2 is a schematic diagram schematically showing the deformed state of the engine shown in Fig. 1 during operation. 3 is a schematic diagram showing the piston pin shown in FIG. 1 taken out, and FIG. 6 is a sectional view showing an example of an engine to which the present invention is applied.

Internal combustion engine engineer 0 is a two-stroke internal combustion engine for outboard motors,
As shown in FIG. 6, a piston 1 is provided in the engine body 11.
2 is housed therein, and the piston 12 is connected to a crankshaft 14 via a connecting rod 13.

As shown in FIG. 1, a support hole 16 is formed in the boss portion 15 of the piston 12, both ends of a hollow piston pin 17 are supported in the support hole 16, and a connecting rod is provided in the center of the piston pin 17. 13 small ends 18 are joined. 19 is a needle bearing of the small end portion 18, and 20 is a C-shaped clip. Note that the large end 21 of the connecting rod 13 is coupled to a crank pin 22 of the crankshaft 14.

This allows the internal combustion engine 10 to transmit the explosive force acting on the top surface of the piston 12 to the crankshaft 14 via the piston pin 17 and the connecting rod 13. At this time, the small end 18 of the connecting rod 13 swings around the axis of the piston pin 17, and the piston pin 17 rotates around its own axis inside the support hole 16 as the connecting rod 13 swings.
As a result, each needle of the needle bearing 19 provided at the small end 18 is brought into even contact with the entire circumference of the piston pin 17, and local wear of the needle bearing 19 is prevented.
This makes it possible to ensure smooth operation of the connecting rod 13.

Furthermore, in this first embodiment, the piston pin 17 has a predetermined position at each of its both ends so that the both ends are bent along the inside of the support hole 16 in the operating state of the internal combustion engine 10, as shown in FIG. The inner diameter within the range of length Ll is gradually expanded axially outward. That is, the piston pin 17 gradually reduces the cross-sectional area of both ends toward the outside in the axial direction, thereby gradually decreasing the rigidity of each of the ends in the axial direction. There is.

In this first embodiment, the central portion of the piston pin 17 excluding the length Ll of both ends may be solid instead of hollow.

Next, the operation of the first embodiment will be explained.

During operation of the internal combustion engine 10, as shown in FIG.
The piston pin 17 is bent and deformed inside the support hole 16 of the piston 12 under the action of the bending moment based on the explosive force on the piston 12 side and the reaction force on the connecting rod 13 side, and the piston pin 17 is bent and deformed inside the support hole 16 of the piston 12, and the periphery of the support hole 16 is bent. Also causes deformation. At this time, according to the first embodiment, the stiffness of the end of the piston pin 17 is gradually reduced toward the outside in the axial direction. No matter how the support hole 16 is deformed, it will bend along with the deformation state of the inner surface of the support hole 16. Therefore, the piston pin 17 can be stably supported without causing strong local contact inside the support hole 16, with uniform contact surface pressure with the inside of the support hole 16. As a result, piston pin 1
7 can freely rotate around its own axis while being supported in the support hole 16, thereby ensuring smooth operation of the connecting rod 13.

FIG. 7 shows that in the first embodiment, the axial length Ll of the portion where the cross-sectional area of the piston pin 17 is gradually reduced is
FIG. 4 is a diagram showing the influence on the amount of deformation F of the cross section of the piston 12 (the difference between the long sleeve diameter and the short axis diameter after the cross section of the piston 12 is deformed). Note that Ll is expressed based on the length a of the portion where the support hole 16 supports the piston pin 17. According to this Figure 7, Ll is (2/3)
It is recognized that if it is less than a, excessive deformation will occur in the piston 12. Furthermore, if Ll exceeds a, the rigidity of the piston pin 17 itself will decrease.

Not valid, i.e. Ll is (2/3)a≦Ll≦a It is preferable to set it to .

FIG. 4 is a partially cutaway schematic diagram showing a piston pin 30 according to a second embodiment of the present invention. This piston pin 30
, both ends of which are connected to the support hole 16 when the internal combustion engine 10 is in normal rotation.
The outer diameter within a predetermined length Ll at each of both ends is gradually reduced in a curved state outward in the axial direction by crowning so that the outer diameter is bent along the inner surface of the outer diameter. That is, the piston pin 30 has its respective cross-sectional areas gradually reduced in the axially outward direction, and the contour shape of the both ends is adjusted in advance to the shape of the support hole 16 that will occur when the internal combustion engine 10 is operated. This corresponds to the deformed state of the inner surface. Note that this contour shape includes points formed in an arc shape and Ll
It differs from chamfering in that it is relatively long.

Although this piston pin 30 is shown in a hollow state, it may be in a solid state. Further, the radius 4ph of the diameter reduction grinder applied to both ends of the piston pin 30 is preferably set to about 1/1000 or more of the total length LO of the piston pin 30. Moreover, the above-mentioned crowning process is applied to both ends of the piston pin 30.

This is done by copying by turning, barrel machining, grinding, etc.

Even in the case of the L piston pin 30, when the internal combustion engine 10 is operating, the end of the piston pin 30 is shaped so that its contour shape matches the deformed state of the inner surface of the support hole 16 that occurs during the operation of the internal combustion engine 10. Since the support hole 16 is processed in such a manner that it bends in accordance with the deformed state of the inner surface of the support hole 16.

Therefore, the piston pin 30 can be stably supported within the support hole 16 by equalizing the contact surface pressure with the inner surface of the support hole 16 without causing strong local contact.

FIG. 5 is a partially cutaway schematic diagram showing a piston pin 40 according to a third embodiment of the present invention. This piston pin 40
This piston pin is different from the piston pin 30 of the second embodiment in that the outer diameter of the entire length LO is gradually reduced in a curved manner from the center toward both ends by crowning. As a result, the piston pin 40, like the piston pin 30, gradually reduces the cross-sectional area of each end in the axial direction outward, and the contour shape of the both ends is adjusted in advance to allow operation of the internal combustion engine 10. This is to match the deformed state of the inner surface of the support hole 16 that sometimes occurs.

Note that the above 11i! is added to both ends of the piston pin 40!
The radius value is 1/ of the total length LO of the piston pin 40.
It is best to set it to about 1000 or less.

Even in the piston pin 40, the piston pin 3
It has the same effect as 0.

[Effects of the Invention] As described above, the present invention provides a piston pin for an internal combustion engine that is used with both ends supported by support holes provided in the piston and the small end of a connecting rod connected to the center part. The cross-sectional area of each of the two end portions is gradually reduced in the axially outward direction so that the end portions are bent along the inner surface of the support hole in the use state.

During operation of an internal combustion engine, the piston pin is bent and deformed within the support hole of the piston under the action of a bending moment based on the explosive force on the piston side and the reaction force on the connecting rod side.
Deformation also occurs around the support hole of the piston. At this time, according to the present invention, the end of the piston pin bends in accordance with the deformed state of the inner surface of the support hole. Therefore, the piston pin can be stably supported within the support hole by equalizing the contact surface pressure with the inner surface of the support hole without causing strong local contact.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the main parts of an engine to which the first embodiment of the present invention is applied, FIG. 2 is a schematic view schematically showing the deformed state of the engine in FIG. 1 during operation, and FIG. The figure is a schematic diagram showing the piston pin shown in FIG. 1 taken out, FIG. 4 is a schematic diagram showing a partially broken piston pin according to the second embodiment of the present invention, and FIG. 5 is a schematic diagram showing the piston pin according to the second embodiment of the present invention. FIG. 6 is a cross-sectional view showing an example of an engine to which the present invention is applied, and FIG. 7 is a schematic diagram showing a partially broken piston pin according to an example, and FIG. FIG. 3 is a diagram showing the relationship with deformation of a piston. 10... Internal combustion engine, 12... Piston, 13...
・Connecting rod, 16... Support hole, 17... Piston pin, 18... Small end, 30... Piston pin, 40...
...Piston pin. Agent Patent Attorney Osamu Shiokawa* 1 Figure 20 Figure 6 Figure 7

Claims (2)

[Claims] (1) For a piston pin for an internal combustion engine that is used with both ends supported by support holes provided in the piston and the small end of a connecting rod connected to the center, the cross-sectional area of each of the above-mentioned ends is calculated as follows: A piston pin for an internal combustion engine, characterized in that the end portion is gradually contracted axially outward so as to bend along the inner surface of the support hole in the above-mentioned state of use. (2) In claim 1, an axial length L1 of a portion of the piston pin whose cross-sectional area is gradually reduced.
is a piston pin for an internal combustion engine that is set within the range of (2/3)a≦L1≦a with respect to the length a of a portion of a support hole provided in the piston that supports the piston pin.