JPH09189358A - Piston pin support structure of piston for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make piston pin supporting structure of a piston for an internal combustion engine in a structure capable of corresponding to deformation due to thermal expansion of a piston main body at the time of driving the internal combustion engine. SOLUTION: A piston pin 20 is supported on pin boss parts 5a through spheric bearings 30 by drilling pin through holes 5b to insert both side parts of the piston pin 20 through on the respective pin boss parts 5a of a piston main body 5, installing the spheric bearings 30 outer surfaces of which are spheric and provided with pin holes 30a to insert the piston pin 20 roughly on a central part on bearing installation parts 5c formed in middle parts of pin insertion holes 5b free to slide, forming inside diameters of the pin insertion holes of the pin boss parts 5a larger than inside diameters of the pin holes 30a of the spheric bearings 30 and inserting the piston pin 20 through the pin holes 30a of the spheric bearings 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston pin support structure for a piston body of a piston used in an internal combustion engine.

[0002]

2. Description of the Prior Art In internal combustion engines such as two-stroke and four-stroke gasoline engines and diesel engines,
The movement of the piston body that reciprocates in the cylinder due to the combustion pressure generated in the combustion chamber surrounded by the cylinder head, the cylinder block, and the piston moves from the piston pin supported by the piston body to the small end portion (small The torque is transmitted as a rotational force from the large end portion (big end) of the connecting rod to the crankshaft via a connecting rod (connecting rod) to which the ends are connected.

In such an internal combustion engine, the piston pin for connecting the piston body and the small end portion of the connecting rod is conventionally directly or through a bearing or the like in a pin insertion hole penetrating the pin boss portion of the piston body. By being inserted as a result, it is supported across the pair of pin boss portions of the piston body.

[0004]

In the conventional piston for an internal combustion engine as described above, the shape of the piston main body is previously set in order to cope with the deformation due to the thermal expansion of the piston main body during the operation of the internal combustion engine. The pin boss portion, which has a large volume and a large expansion amount when viewed from above, is formed into an elliptical shape with a short diameter, and as shown in FIG. The piston body (piston top) side having a large amount is formed in a tapered shape (conical trapezoidal shape) having a small diameter, so that the piston body has a cylindrical shape in a thermally deformed state.

However, as the taper-shaped (frustum-conical) piston body is thermally deformed into a cylindrical shape,
As shown in FIG. 9 (B), since the pin insertion hole 5b of the pin boss portion 5a is distorted so as to fall outward, the pin insertion hole 5b that is about to be deformed is corrected by the inserted piston pin. In this state, the pin boss portion is plastically deformed, and at the same time, as shown in FIG. 10, the end portion of the piston pin 20 comes into edge contact with the inner peripheral surface of the pin insertion hole 5b of the pin boss portion 5a, and the portion C is locally localized. This will cause wear, which will damage the piston body itself.

Further, as the pin insertion hole 5b of the pin boss portion 5a is distorted, as shown in FIG.
Since the piston pin 20 is also deformed so that both sides are curved downward from the central portion, the contact state between the piston pin 20 and the bearing portion (needle bearing) 29 provided at the small end portion of the connecting rod is not correct. It becomes uniform, the life of the bearing portion 29 is shortened, and the piston pin 20
The deformation of the skirt portion of the piston main body 5 such that the lower part of the piston body 5 projects like a dashed line F, and the deformation of the piston skirt portion causes a large friction between the piston main body and the inner peripheral surface of the cylinder bore. As a result, sliding loss occurs.

[0007]

In order to solve the above problems, the present invention provides a pair of pin bosses formed on a piston body that reciprocates in a cylinder as described in claim 1 above. In a piston for an internal combustion engine in which the piston pin that connects the small end of the connecting rod for interlocking the piston body and the crankshaft is supported in the section, insert both sides of the piston pin into each pin boss of the piston body. A spherical bearing having a spherical outer surface and a pin hole for inserting a piston pin in a substantially central portion is provided in a bearing mounting portion formed in the middle of the pin inserting hole for sliding. It is movably mounted, and the inner diameter of the pin insertion hole of the pin boss is larger than the inner diameter of the pin hole of the spherical bearing, and the piston pin is inserted into the pin hole of the spherical bearing. By, is characterized in that the piston pin is supported by the pin boss portion through a spherical bearing.

Further, in the piston pin support structure for a piston for an internal combustion engine described in claim 1, as described in claim 2, the inner diameter of the pin insertion hole of the pin boss portion is the thermal expansion of the piston body. The feature is that the piston pin is formed larger than the inner diameter of the pin hole of the spherical bearing by the amount that the piston pin is not brought into contact with the pin boss portion at the time of deformation.

Further, in the piston pin support structure for a piston for an internal combustion engine according to claim 1 or 2, as described in claim 3, from the outer peripheral surface of the piston body to the bearing mounting portion of the pin boss portion. A groove hole for inserting a spherical bearing, which is formed so as to penetrate therethrough, is provided so as to be inclined with respect to the axial direction of the piston.

Further, in the piston pin support structure of the internal combustion engine piston according to claim 1 or 2, the spherical bearing has a half-split structure as described in claim 4. It is what

Further, in the piston pin support structure for the internal combustion engine piston according to any one of claims 1 to 4, as described in claim 5, when the piston is cold, the spherical bearing has the bearing mounting portion. Is formed so that the radius of the spherical surface of the spherical bearing in the axial direction is smaller than the radius of the spherical surface of the bearing mounting portion so that the central portion in the axial direction contacts and the gaps are formed on both sides thereof. It is characterized by that.

Further, in the piston pin support structure for a piston for an internal combustion engine according to claim 1 or 2, the spherical bearing is cast in the piston body as described in claim 6. It is a feature.

Further, in the piston pin support structure of the internal combustion engine piston according to any one of claims 1 to 6,
As described in claim 7, chamfering is performed on the corner of the inner opening edge of the pin hole formed in at least one spherical bearing and the corner of the outer peripheral edge of at least one end of the piston pin. It is characterized by being applied.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a piston pin support structure for a piston for an internal combustion engine of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show a two-cycle three-cylinder diesel engine to which the piston pin support structure of the present invention is applied. The engine 1 has a cylinder block 3 above a crankcase 2 and a main body thereof. Cylinder heads 4 are sequentially stacked and integrally connected, and a piston body 5 having piston rings 22 and 23 mounted therein is slidably installed in a cylinder bore 3a of a cylinder block 3. Are connected to a crank shaft 7 in the crank chamber 2 a via a connecting rod 6.

The cylinder head 4 is divided into an upper member 8 and a lower member 9, and a sub combustion chamber 10a is formed at a boundary portion between both members 8 and 9, and the sub combustion chamber 10a is formed.
Is the main combustion chamber 1 of the cylinder bore 3a due to the small diameter passage 8a.
0b, and a glow plug 11 for starting ignition and a fuel injection valve 12 are provided for the auxiliary combustion chamber 10a.

The main body of the engine 1 includes a crankcase 2
And a cylinder block 3 define a crank chamber 2a, and the cylinder block 3 is formed with an intake opening 3b which opens to the crank chamber 2a.
The intake pipe 13 is connected, and a reed valve 14 for preventing backflow of intake air from the crank chamber 2a to the intake pipe 13 is provided.
It has a structure capable of primary compression of fresh air sucked into a.

A plurality of scavenging ports 15a (only one is shown) are opened in the cylinder bore 3a of the cylinder block 3, and each scavenging port 15a communicates with the crank chamber 2a through a scavenging passage (not shown). In addition, the main exhaust port 16a connected to the main exhaust passage 16b is opened, and a pair of auxiliary exhaust ports 17a are opened slightly above the main exhaust port 16a at intervals in the circumferential direction of the cylinder bore 3a. Each sub exhaust passage 17b connected to the exhaust port 17a joins with the main exhaust passage 16b on the downstream side and is connected to the exhaust pipe 18.

In the sub exhaust passage 17b, an exhaust control valve 19 driven by a drive device (not shown) is arranged so as to intersect the sub exhaust passage 17b and penetrate at least a part of the sub exhaust passage 17b. The exhaust control valve 19 allows the sub-exhaust passage 17b to have a variable cross-sectional area and be fully closed.

As shown in FIG. 2, the connecting rod 6 connecting the piston body 5 and the crankshaft 7 has a small end 6a connected to the piston pin 20 via a bearing 29, and a large end 6b connected to the bearing. It is connected to the crank pin 21 via the portion 28.

Although the lubricating structure for the bearings 28, 29 of the small end 6a and the large end 6b of the connecting rod 6 is not shown, engine speed and load information are input to the diesel engine 1. An oil pump that is driven and controlled by the output signal from the ECU is installed.
The oil guided from the oil tank to the oil pump through the oil filter by driving the oil pump is
The oil is distributed and supplied to the oil discharge port portion opened to each cylinder bore 3a of each cylinder and the crank journal portion 25 of each cylinder via the oil distribution pipe.

The oil discharge port of each cylinder is shown in FIG.
When the piston as shown in FIG. 6 is at the bottom dead center position, it is located near the second piston ring 23 provided below the first piston ring 22 and is opened to the inner peripheral surface of the cylinder bore 3a. .

The crank journal portion 25 of each cylinder
The oil supplied to the oil passage 2 is formed on the crank journal 25 side as shown in FIG.
The oil supplied from 5a to the journal bearing portion 27 sealed by the seal member 26 and accumulated in the oil collecting space of the journal bearing portion 27 is formed on the crankshaft side from the oil groove 7a formed on the end face of the crank web. Through the oil passages 7b and 7c which are opened, the crank pin 21
And is introduced into the bearing portion 28 between the outer peripheral surface of the crank pin 21 and the inner peripheral surface of the connecting rod large end portion 6b.

In addition, the large end portion 6b of the connecting rod 6 is provided with an oil pool groove on the small end portion side of the inner peripheral surface thereof.
An oil hole 6c opened on the surface of the large end portion 6b is penetrated from this oil collecting groove, and the oil collected in the oil collecting groove is centrifugally generated by the rotation of the crankshaft 7 and the oil hole 6c.
Through c, it is scattered from the surface of the large end 6b toward the small end 6a of the connecting rod 6 and the back side of the top of the piston body 5.

By the way, in the engine body 1 as described above, the piston pin 20 for connecting the piston body 5 slidably inserted in the cylinder bore 3a and the small end portion 6a of the connecting rod 6 has the following components. As shown in the embodiment, it is supported by the pin boss portion of the piston body 5 via a spherical bearing.

FIGS. 4 to 7 show a first embodiment of the structure for supporting the piston pin 20 by means of the spherical bearing 30. As shown in FIG. 4, a pair of pin bosses formed integrally with the piston body 5 are provided. The portion 5a is provided with a pin insertion hole 5b for inserting each side of the piston pin 20, and a bearing mounting portion 5c is formed in the middle of each pin insertion hole 5b. A spherical bearing 30 having a spherical outer surface and a pin hole 30a into which the piston pin 20 is inserted is provided at a substantially central portion 5c so as to be slidable.

As shown in FIG. 2, the piston pin 20 in which the small end portion 6a of the connecting rod is fitted into the center portion of the piston rod 20 through the bearing 29 has spherical surfaces on both sides thereof as shown in FIG. It is inserted into the pin hole 30a of the bearing 30 and is supported by the piston body 5 by the pin boss portion 5a in a state in which it is prevented from coming off from the pin insertion hole 5b by the circlip 31.

The inner diameter of the pin insertion hole 5b formed in the pin boss portion 5a of the piston body 5 is larger than the inner diameter of the pin hole 30a of the spherical bearing 30, and as shown in FIG. Hole 5b and piston pin 20
A gap D is formed between the pin insertion hole 5 and the pin insertion hole 5 when the piston body 5 is thermally deformed in this embodiment.
It has the minimum necessary size so that the inner peripheral surface of b and the end of the piston pin 20 do not come into contact with each other.

In this embodiment, in order to insert the spherical bearing 30 into the bearing mounting portion 5c provided in the pin insertion hole 5b of the pin boss portion 5a, the bearing mounting portion 5c is inserted from the outer peripheral surface of the piston body 5. Up to 5 d groove hole for spherical bearing insertion
As shown in FIG. 7, the groove hole 5d is formed so that the groove hole 5d for inserting the spherical bearing is inclined with respect to the piston axial direction.

The spherical bearing 30 is inserted into the groove 5d for inserting the spherical bearing in a laterally laid state in which the axial direction of the pin insertion hole 5b and the axial direction of the spherical bearing 30 are orthogonal to each other. In order to prevent the slot 5d from becoming too large in terms of the strength of the main body 5, the axial size of the spherical bearing 30 is set as follows.
It is desirable that the angle E connecting the spherical center of the spherical bearing 30 and both end edges in the axial direction be within 90 °.

Further, in this embodiment, as shown in FIG. 6, the corner portion 3 of the inner opening edge of the pin hole 30a of the spherical bearing 30.
0b is chamfered, and the piston pin 20
A chamfering process is also applied to the corner portion 20b at the outer peripheral edge of the end portion of the.

According to the piston pin support structure of the first embodiment as described above, as shown in FIG. 8 (A), the piston body 5 formed in a taper shape (frustroconical shape) is formed as shown in FIG.
As shown in (B), when it is thermally deformed into a cylindrical shape, the pin boss portion 5a is distorted so that the pin insertion hole 5b is inclined outward downward, but between the pin boss portion 5a and the piston pin 20. The sliding of the spherical bearing 30 interposed between the piston pin 20 and the pin boss 5a maintains the piston pin 20 in its original state.

Therefore, as shown in FIG. 8B, even if the pin boss portion 5a is thermally deformed, the end portion of the piston pin 20 comes into edge contact with the inner peripheral surface of the pin insertion hole 5b of the pin boss portion 5a. Partial wear does not occur in the portion, and the effect of strain due to thermal deformation of the pin boss portion 5a is not transmitted to the piston pin 20.
The pin boss 5a will not be plastically deformed in the state of being corrected by 0, and the piston pin 20 will not be deformed by the thermal deformation of the pin boss 5a.

The pin insertion hole 5b and the piston pin 20
The gap D between the pin insertion hole 5b and the piston is set to be the minimum necessary size so that the inner peripheral surface of the pin insertion hole 5b and the end of the piston pin 20 do not come into contact with each other when the piston body 5 is thermally deformed. Even if the circlip 31 of the conventional size is used, the clearance D of the pin 20 does not become so large,
Since the engagement state of the circlip 31 with the circlip engagement groove of the pin insertion hole 5b does not become so shallow, the piston pin 20 can be reliably held in the pin insertion hole 5b by the circlip 31.

Further, the groove 5d for inserting the spherical bearing serves also as the groove for engaging and disengaging the circlip in the conventional piston, and the groove 5d is provided in a state of being inclined with respect to the piston axial direction. Therefore, the risk of piston damage due to the provision of such a slot in the direction orthogonal to the piston axial direction can be avoided, and the crankshaft 7
When the piston pin 20 receives the maximum load due to the rotation of, the force can be received at the portion apart from the groove hole 5d of the piston body 5, and the damage from the groove hole 5d of the piston body 5 can be prevented. You can

Further, since the corner portion 30b of the inner opening edge of the pin hole 30a of the spherical bearing 30 and the corner portion 20b of the outer peripheral edge of the end portion of the piston pin 20 are chamfered respectively, as shown in FIG. As shown in the drawings, when the piston pin 20 is inserted into one of the pin insertion holes 5b of the pin boss 5a and assembled with the piston body 5 with the spherical bearing 30 mounted, the piston pin 20 is mounted on the spherical bearing. Thirty
The work can be done smoothly without getting caught in.

12 to 14 show a second embodiment of the structure for supporting the piston pin 20 by means of the spherical bearing 30. In this embodiment, the spherical bearing 30 has a half-split structure, and the piston main body 5 is shown. From the outer peripheral surface of the pin boss 5
A groove hole like the groove hole 5d for spherical bearing insertion in the first embodiment described above is not formed up to the bearing mounting portion 5c of a.

That is, the spherical bearing 3 according to the present embodiment.
As shown in FIGS. 13A and 13B, 0 indicates that the spherical bearing 30 having a ring shape when viewed from the axial direction is divided into two parts 301 and 302,
It is formed in a so-called half-divided state, and the size of each of the portions 301 and 302 in the axial direction is as shown in FIG.
As shown in, when one of the portions is laid down, the outer shape thereof is set to fit within the inner diameter of the spherical bearing 30.

Therefore, as shown in FIG. 14, a groove for inserting a spherical bearing is formed in the pin insertion hole 5b of the pin boss portion 5a of the piston body 5 from the outer peripheral surface of the piston body 5 to the bearing mounting portion 5c. Even if it is not necessary, each of the halved portions 301 and 302 of the spherical bearing 30 can be mounted on the bearing mounting portion 5c through the pin insertion holes 5b one by one.

The spherical bearing 30 halved as described above
According to the piston pin support structure of the second embodiment according to
The spherical bearing 30 is not particularly provided with a slot for inserting the bearing.
Since it can be mounted on the piston main body 5, it is not necessary to form a groove for inserting the bearing by merely providing a groove for engaging and disengaging the circlip as in the conventional piston.

Therefore, compared with the case where the slot is provided,
The contact area between the spherical surface of the spherical bearing 30 and the bearing mounting portion 5c can be increased (by the amount of the groove hole that enters into the bearing mounting portion 5c), and the surface pressure applied to the spherical bearing 30 can be reduced, Since there is only a small slot for engaging and disengaging the circlip, and no large slot for mounting the spherical bearing 30, the strength around the pin boss portion 5a of the piston body 5 can be increased.

In each of the above embodiments, as shown in FIG. 15A, the spherical surface of the spherical bearing 30 is substantially the same as the spherical surface of the bearing mounting portion 5c when the piston body 5 is cold. The spherical bearing 30 and the bearing mounting portion 5 are formed to have a rounded spherical surface, and due to a difference in thermal expansion coefficient between the spherical bearing 30 and the piston body 5 during operation of the engine.
An appropriate clearance is generated between c.

However, regarding the spherical shape of the spherical bearing 30, as shown in FIG. 15B, when the piston is cold, the spherical bearing 30 and the bearing mounting portion 5c are in contact with each other in the central portion in the axial direction, and both sides thereof are in contact with each other. The radius R1 of the spherical surface in the axial direction of the spherical bearing 30 may be formed to be smaller than the radius R2 of the spherical surface of the bearing mounting portion 5c so that a clearance is generated at the portion.

That is, on the spherical surface of the spherical bearing 30,
The radius of the circular arc of the bearing in the axial direction is made smaller than the radius of the circular arc of the bearing in the circumferential direction, so that the spherical surface of the spherical bearing 30 is not a perfect spherical surface but a circle of the outer peripheral surface of the bearing. The spherical bearing 30 is formed into a curved surface such that the central portion in the circumferential direction projects further outward, and the spherical bearing 30 is partially brought into contact with the bearing mounting portion 5c at the central portion in the circumferential direction of the outer peripheral surface thereof, so that the piston It is possible to effectively suppress the movement of the spherical bearing 30 rotating in the axial direction with respect to the piston body 5 when cold.

Even if the spherical surface of the spherical bearing 30 has such a shape, the entire surface between the spherical bearing 30 and the bearing mounting portion 5c is generated due to the difference in thermal expansion coefficient between the spherical bearing 30 and the piston body 5 during engine operation. Since a clearance is generated, the spherical bearing 30 can slide sufficiently with respect to the bearing mounting portion 5c.

16 to 18 show a third embodiment of the structure for supporting the piston pin 20 by the spherical bearing 30. In this embodiment, the spherical bearing 30 is cast integrally with the piston body 5. As shown in FIG. 16, from the outer peripheral surface of the piston body 5 to the bearing mounting portion 5c of the pin boss portion 5a, as in the second embodiment, the spherical bearing insertion portion is formed. The slot 5d is not formed.

That is, the spherical bearing 3 according to the present embodiment.
0 is obtained by casting the piston body 5 in a state where the spherical bearing 30 is set in the mold, and as shown in FIG. 17, the pin boss portion 5a of the intermediate product 5A of the piston body 5 molded by the mold The spherical bearing 30 is integrally cast, and as shown in FIG. 18, when the intermediate product 5A is processed into the piston body 5, the spherical bearing 30 is also cut at the same time, and as shown in FIG. Is processed into an inner diameter suitable for inserting.

Spherical bearing 30 cast into piston body 5
Is made of cast iron, iron-based sintered material, etc., which has excellent wear resistance and seizure resistance, and has a smaller coefficient of thermal expansion than the material of the piston body 5 (aluminum alloy). Is subjected to a nitriding treatment.

When the spherical bearing 30 is set in the mold and the piston body 5 is cast, the set spherical bearing 30 is in a state of being cooled or not heated, and the set spherical bearing 30. A release agent such as oil is applied to the outer peripheral surface of 30.

When the intermediate product 5A of the piston body 5 is machined and the spherical bearing 30 is machined, the pin boss portion 5a of the piston body 5 and the spherical bearing 30 are processed as shown in FIG.
By inserting the pin 33 over and, the rotation of the spherical bearing 30 in the circumferential direction is prevented when the inner diameter is machined.
In the cutting process, both end portions of the spherical bearing 30 are dropped so that the spherical bearing 30 can slide easily.

In the spherical bearing 30 integrated with the piston body 5 by casting as in this embodiment, a clearance is generated between the spherical bearing 30 and the piston body 5 due to the difference in coefficient of thermal expansion during engine operation. The spherical bearing 30 can be slid.

The third type in which the spherical bearing 30 is cast as described above.
According to the piston pin support structure of the embodiment, it is possible to eliminate the need for spherical processing of the bearing mounting portion 5c with respect to the piston body 5, and the piston pin 5 with the piston body 5 and the spherical bearing 30 being prevented from rotating by the pin 33. By assembling 20, the assembling work can be facilitated, and the clearance between the spherical bearing 30 and the bearing mounting portion 5c can be made minimum and appropriate by thermal expansion during engine operation.

The piston pin support structure of the piston for an internal combustion engine according to the present invention has been described above with reference to the respective embodiments of the two-cycle three-cylinder diesel engine. However, the present invention is not limited to such a diesel engine, but is forced lubrication. Any type of cylinder injection type engine can be effectively applied to a gasoline engine instead of a diesel engine and a four-cycle engine instead of a two-cycle engine.

[0054]

According to the piston pin support structure of the piston for an internal combustion engine of the present invention as described above, when the piston body is deformed by thermal expansion during operation of the internal combustion engine, the pin boss portion of the piston body is plastic. This prevents damage to the piston body without causing deformation or local wear, and also prevents deformation of the piston pin, improving the service life of the bearing provided between the piston pin and the small end of the connecting rod. It is possible to reduce the sliding loss of the piston in the cylinder.

[Brief description of the drawings]

FIG. 1 is a diagram to which the piston pin support structure of the present invention is applied 3
AA of FIG. 2 showing a cylinder two-cycle diesel engine
A vertical cross-sectional view taken along a line.

FIG. 2 is a partial vertical cross-sectional view taken along the cylinder arrangement direction of the 3-cylinder 2-cycle diesel engine shown in FIG.

FIG. 3 is a partially enlarged vertical sectional view showing the vicinity of a connecting rod large end portion of the diesel engine shown in FIG.

FIG. 4 is a longitudinal sectional view of a piston showing a first embodiment of a piston pin support structure of the present invention.

5 is an enlarged vertical sectional view of a part of the embodiment shown in FIG.

FIG. 6 is an assembly explanatory sectional view of a portion shown in FIG.

7 is a side view of the piston shown in FIG.

FIG. 8 is an explanatory view showing a state of (A) before thermal deformation of a piston to which the piston pin support structure of the present invention is applied and a state of (B) thermally deformed in comparison.

FIG. 9 is an explanatory view showing a state of the conventional piston body before (A) heat deformation and (B) heat deformation state in comparison.

FIG. 10 is a partially enlarged explanatory view showing a state of a pin boss portion of a piston body and a piston pin when a conventional piston is thermally deformed.

FIG. 11 is an explanatory view showing a state of a conventional piston pin of a piston body and a bearing of a connecting rod small end portion when a conventional piston is thermally deformed.

FIG. 12 is a partial cross-sectional side view showing only the piston main body of the piston showing the second embodiment of the piston pin support structure of the present invention.

13 (A) is a front view of the spherical bearing according to the embodiment shown in FIG. 12 as seen from the axial direction of the piston pin, FIG. 13 (B) is a cross-sectional view taken along the line BB in FIG. Explanatory drawing which shows the size of one piece of the spherical bearing split.

FIG. 14 is an explanatory view showing an assembling order of the spherical bearing in the embodiment shown in FIG. 12 to the piston body.

FIG. 15 is an explanatory view showing an example (A) and another example (B) of the spherical shape of the spherical bearing with respect to the bearing mounting portion in the cold state in the piston pin support structure of the present invention.

FIG. 16 is a vertical cross-sectional view of a piston showing a third embodiment of the piston pin support structure of the present invention.

FIG. 17 is a vertical cross-sectional view showing a state of an intermediate product in the embodiment shown in FIG.

18 is a vertical cross-sectional view showing a processed state of the intermediate product according to the embodiment shown in FIG.

[Explanation of Codes] 1 Diesel engine (internal combustion engine) 3a Cylinder bore (cylinder) 5 Piston body 5a Pin boss (on piston body) 5b Pin insertion hole (on piston body) 5c Bearing mounting portion (on piston body) 5d Spherical bearing insertion Slot (for piston body) 6 connecting rod 6a small end (for connecting rod) 7 crankshaft 20 piston pin 30 spherical bearing 30a pin hole (for spherical bearing)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F16C 23/08 F16C 23/08

Claims (7)

[Claims] 1. An internal combustion engine in which a pair of pin boss portions formed on a piston body reciprocating in a cylinder support a piston pin connecting a small end portion of a connecting rod for interlocking the piston body and a crankshaft. In the piston for use, each pin boss portion of the piston body is penetrated with a pin insertion hole for inserting both sides of the piston pin, and the bearing mounting portion formed in the middle of the pin insertion hole has a spherical outer surface. A spherical bearing with a pin hole for inserting the piston pin in the approximate center is slidably mounted,
The inner diameter of the pin insertion hole of the pin boss portion is formed larger than the inner diameter of the pin hole of the spherical bearing, and the piston pin is inserted into the pin hole of the spherical bearing, so that the piston pin is inserted through the spherical bearing. A piston pin support structure for a piston for an internal combustion engine, characterized in that it is supported by a portion. 2. The inner diameter of the pin insertion hole of the pin boss is formed larger than the inner diameter of the pin hole of the spherical bearing by the amount that the piston pin does not come into contact with the pin boss when the piston body is deformed by thermal expansion. The piston pin support structure for the internal combustion engine piston according to claim 1. 3. A groove for inserting a spherical bearing, which is formed so as to penetrate from the outer peripheral surface of the piston body to the bearing mounting portion of the pin boss portion, is provided in a state of being inclined with respect to the axial direction of the piston. A piston pin support structure for a piston for an internal combustion engine according to claim 1 or 2. 4. The piston pin support structure for an internal combustion engine piston according to claim 1, wherein the spherical bearing has a half-split structure. 5. The radius of the spherical surface of the spherical bearing in the axial direction is such that the spherical bearing comes into contact with the bearing mounting portion at its axial center portion and a gap is formed at both sides thereof when the piston is cold. 5. The bearing mounting portion is formed so as to be smaller than the radius of the spherical surface of the bearing mounting portion.
2. A piston pin support structure for a piston for an internal combustion engine as set forth in. 6. The piston pin support structure for an internal combustion engine piston according to claim 1, wherein the spherical bearing is cast in the piston body. 7. A chamfering process is applied to a corner portion of an inner opening edge of a pin hole formed in at least one spherical bearing and a corner portion of an outer peripheral edge of at least one end portion of a piston pin. 7. A piston pin support structure for a piston for an internal combustion engine according to any one of claims 1 to 6.