JP2018062972A - Piston pin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston pin that facilitates securing an oil film at a slide boundary surface between a piston pin and a slide mating object.SOLUTION: A piston pin 1 connects a piston 91 to a bearing 94 of a small end part 920 of a con rod 92. The piston pin 1 includes a pin body 2 and a weight 3. The pin body 2 is supported to the bearing 94. The pin body 2 has a weight arrangement hole 20 extending in an axial direction. The weight 3 is arranged in the weight arrangement hole 20.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a piston pin that is interposed between a piston and a small end portion of a connecting rod and transmits a force acting on the piston to the connecting rod.

  The piston (see, for example, Patent Document 1) is supported from the lower side (bottom dead center side when viewed from the top dead center in the stroke direction of the piston) to the small end portion of the connecting rod via the bearing and the piston pin. Yes. A combustion chamber is defined on the upper side of the piston (on the top dead center side when viewed from the lower starting point in the piston stroke direction).

Japanese Patent Laid-Open No. 8-200231

  Recent diesel engines tend to set the engine speed low from the viewpoint of improving fuel efficiency. However, if the engine speed is set low, the centrifugal force (inertial force accompanying the rotation of the crankshaft) acting on the piston is reduced accordingly.

  Moreover, if the engine speed is set low, the output of the engine will be reduced accordingly. In some cases, a supercharger is used to compensate for the decrease in output. However, when a supercharger is used, the exhaust pressure (in-cylinder combustion pressure) acting on the piston becomes higher from the combustion chamber (that is, from the upper side).

  Thus, in recent diesel engines, the centrifugal force acting on the piston from the lower side becomes smaller, while the exhaust pressure acting on the piston from the upper side tends to become higher. For this reason, the piston pin is easily pressed against a sliding counterpart (a bearing at the small end of the connecting rod, a boss of the piston, etc.). Therefore, it is difficult to secure an oil film at the sliding interface between the piston pin and the sliding counterpart.

  Then, an object of this invention is to provide the piston pin which is easy to ensure an oil film at the sliding interface between a piston pin and a sliding counterpart.

  In order to solve the above problems, a piston pin of the present invention connects a piston and a bearing at a small end of a connecting rod, is supported by the bearing, and has a pin body having a weight arrangement hole extending in the axial direction, And a weight arranged in the weight arrangement hole.

  In order to reduce the weight of the engine, it is preferable that the piston and the piston pin are inherently light. In this regard, the piston pin of the present invention admits the demerit of being heavy and dares to have a weight. According to the piston pin of the present invention, the weight of the piston pin can be increased by the weight. For this reason, the centrifugal force which acts on a piston can be enlarged. Therefore, it is easy to introduce the lubricating oil into the sliding interface between the piston pin and the sliding counterpart (the bearing at the small end of the connecting rod, the boss of the piston, etc.). That is, it is easy to ensure an oil film at the sliding interface.

It is an axial sectional view of an engine provided with the piston pin of a first embodiment. It is the II-II direction sectional drawing of FIG. It is a disassembled perspective view of the same piston pin. It is an axial direction sectional view near the piston of an engine provided with the piston pin of a second embodiment. (A) is an expanded view of the boss | hub part of a piston and the internal peripheral surface of a bearing. (B) is an expanded view of the outer peripheral surface of a pin main body.

  Hereinafter, embodiments of the piston pin of the present invention will be described.

<First embodiment>
[Piston pin arrangement]
First, the arrangement of the piston pins of this embodiment will be described. In the following figures, the “vertical direction” is the stroke direction of the piston. The “upper side” is the top dead center side when viewed from the bottom dead center in the same stroke direction. The “lower side” is the bottom dead center side when viewed from the top dead center in the same stroke direction. FIG. 1 shows an axial cross-sectional view of an engine provided with the piston pin of the present embodiment. FIG. 2 shows a cross-sectional view in the II-II direction of FIG. As shown in FIGS. 1 and 2, the engine 9 includes a cylinder 90, a piston 91, a connecting rod (connecting rod) 92, a crankshaft 93, a bearing 94, a snap ring 95, a piston ring 96, and a piston. Pin 1 is provided. The engine 9 is a diesel turbo engine.

  The piston 91 is accommodated in the cylinder 90. A combustion chamber C is defined in the cylinder 90 by the piston 91. The piston 91 includes a boss portion 910, an outer peripheral ring groove 911, and an inner peripheral ring groove 912. A pair of outer peripheral ring grooves 911 are arranged on the outer peripheral surface of the piston 91 side by side in the vertical direction. The boss portion 910 protrudes radially inward from the outer peripheral surface of the piston 91. A pair of boss portions 910 are arranged side by side in the diameter direction (front-rear direction) of the piston 91. The pair of front and rear boss portions 910 are disposed at the center of the piston 91 in the left-right direction. The inner peripheral ring groove 912 is disposed on the inner peripheral surface of the boss portion 910. The pair of piston rings 96 are mounted in the pair of outer peripheral ring grooves 911. The pair of piston rings 96 are in sliding contact with the inner peripheral surface of the cylinder 90.

  The crankshaft 93 is disposed on the lower side of the cylinder 90. The crankshaft 93 includes a main journal 930, a crankpin 931, and a crank arm 932. The crank pin 931 is eccentrically connected to the main journal 930 via a crank arm 932. That is, the center a2 of the crank pin 931 is eccentric with respect to the center a1 of the main journal 930.

  As shown in FIGS. 1 and 2, the connecting rod 92 includes a small end portion 920, a large end portion 921, and a rod portion 922. The large end portion 921 has an annular shape. A crank pin 931 is connected to the large end portion 921 through a connecting rod bearing 921a. The small end portion 920 has an annular shape with a smaller diameter than the large end portion 921. The small end portion 920 includes an oil hole 920a. The oil hole 920a penetrates the small end 920 in the radial direction. The rod portion 922 connects the large end portion 921 and the small end portion 920.

  As shown in FIGS. 1 and 2, the bearing 94 is a sliding bearing. The bearing 94 has a cylindrical shape. The bearing 94 is disposed on the radially inner side of the small end portion 920. The bearing 94 includes an oil hole 940. The oil hole 940 penetrates the bearing 94 in the radial direction. The oil hole 940 is continuous with the oil hole 920a of the small end 920 in the radial direction.

  Of the pair of snap rings 95, the front snap ring 95 is mounted in the inner ring groove 912 of the front boss 910. The rear snap ring 95 is provided in the inner ring groove 912 of the rear boss 910. The piston pin 1 is disposed between a pair of front and rear snap rings 95. The piston pin 1 is inserted through the pair of front and rear boss portions 910 and the bearing 94 in the radial direction.

[Configuration of piston pin]
Next, the structure of the piston pin of this embodiment is demonstrated. FIG. 3 shows an exploded perspective view of the piston pin of the present embodiment. As shown in FIG. 3, the piston pin 1 includes a pin body 2 and a weight 3. The pin body 2 has a cylindrical shape extending in the front-rear direction. That is, the pin body 2 includes a weight arrangement hole 20. The weight arrangement hole 20 penetrates the pin body 2 in the front-rear direction (axial direction). When the pin body 2 is viewed from the front side or the rear side, the center A1 of the perfect circular outer peripheral surface and the center B1 of the perfect circular inner peripheral surface coincide with each other. The weight 3 has a cylindrical shape. The weight 3 is press-fitted and fixed at the center in the front-rear direction of the weight arrangement hole 20. When the weight 3 is viewed from the front side or the rear side, the center A2 of the perfect circular outer peripheral surface is different from the center B2 of the perfect circular inner peripheral surface. That is, the center A2 of the outer peripheral surface of the weight 3 is coincident with the center A1 of the outer peripheral surface of the pin body 2 and the center B1 of the inner peripheral surface. However, the center B2 of the inner peripheral surface of the weight 3 is arranged above the center A2 of the outer peripheral surface of the weight 3. Thus, the inner peripheral surface of the weight 3 is eccentric to the upper side (radial direction) with respect to the outer peripheral surface. Therefore, the center of gravity G of the piston pin 1 is biased downward (in the radial direction) with respect to the axis of the pin body 2 (the center of the outer peripheral surface of the pin body 2 = the center of the inner peripheral surface of the boss portion 910) A1. I have a heart.

  The front / rear direction (axial direction) position of the piston pin 1 is regulated by a pair of front and rear snap rings 95. That is, the snap ring 95 prevents the piston pin 1 from dropping off from the boss portion 910. An oil clearance O is defined between the outer peripheral surface of the pin body 2 and the pair of boss portions 910 and the inner peripheral surface of the bearing 94. Lubricating oil is supplied to the oil clearance O via oil holes 920a and 940. An oil film is formed on the oil clearance O by the lubricating oil. As described above, the piston pin 1 connects the piston 91 and the bearing 94 of the small end portion 920 of the connecting rod 92 in a full floating manner.

[Piston pin movement]
Next, the movement of the piston pin of this embodiment will be described. As shown in FIG. 1, when the engine 9 is driven, the piston 91 repeatedly executes a cycle including a compression stroke, an expansion stroke, an exhaust stroke, and an intake stroke as the crankshaft 93 rotates.

  When the crank rotation angle (angle of the center a2 with respect to the center a1) region is in the range of -90 ° to 0 ° (top dead center) (the second half of the compression stroke), as shown in FIG. The centrifugal force F1 acts upward. Further, a weight F2 (the own weight of the piston 91 and the piston pin 1) F2 acts on the piston 91 and the piston pin 1 downward. Here, a weight 3 is arranged on the piston pin 1. For this reason, the centrifugal force F <b> 1 increases by the amount of the weight 3. The piston pin 1 and the piston 91 move upward with respect to the bearing 94 by the centrifugal force F1. Therefore, the lower portion (specifically, the lower portion of the sliding interface between the piston pin 1 and the bearing 94) O1 becomes wider. Therefore, an oil film can be sufficiently formed in the portion.

  Further, when the piston pin 1 contacts the upper portion of the inner peripheral surface of the bearing 94 due to the centrifugal force F <b> 1, the piston 91 moves upward with respect to the piston pin 1. For this reason, the upper portion (specifically, the upper portion of the sliding interface between the piston pin 1 and the boss portion 910) O2 of the oil clearance O becomes wider. Therefore, an oil film can be sufficiently formed in the portion.

  As shown in FIG. 1, when the crank rotation angle region is a section of 0 ° to 90 ° (first half of the expansion stroke), the centrifugal force F1 is applied upward to the piston 91 and the piston pin 1 as in the second half of the compression stroke. The weight F2 acts downward. In addition, the exhaust pressure (combustion pressure of the air-fuel mixture in the combustion chamber C) F3 acts on the piston 91 and the piston pin 1 downward. Here, a weight 3 is arranged on the piston pin 1. For this reason, the centrifugal force F <b> 1 increases by the amount of the weight 3. Therefore, the press contact from the upper side of the piston pin 1 to the bearing 94 can be suppressed. Moreover, the pressure contact from the upper side of the piston 91 with respect to the piston pin 1 can be suppressed.

  Thus, when the crank rotation angle region is within 0 ° ± 90 ° (the second half of the compression stroke, the first half of the expansion stroke, the second half of the exhaust stroke, the first half of the suction stroke), the piston 91 and the piston pin 1 have a centrifugal force F1 upward. Works. Further, the centrifugal force F1 is increased by the amount of the weight 3. For this reason, the lower part O1 of the oil clearance O can be widened except for the first half of the expansion stroke in which the exhaust pressure F3 acts on the piston 91 and the piston pin 1. In addition, the upper portion O2 of the oil clearance O can be widened.

[Function and effect]
Next, the effect of the piston pin of this embodiment is demonstrated. As shown in FIG. 2, the piston pin 1 of this embodiment includes a weight 3. For this reason, compared with the conventional piston pin (equivalent to the pin main body 2 single body shown in FIG. 3), the weight of the piston pin 1 can be increased by the weight 3. Therefore, the centrifugal force F1 can be increased. Therefore, it is easy to introduce lubricating oil into the oil clearance O (the sliding interface between the piston pin 1 and the sliding counterpart (bearing 94 and boss 910)). That is, it is easy to secure an oil film in the oil clearance O. Further, even when the exhaust pressure F3 acts on the piston 91 and the piston pin 1, the pressure contact between the piston pin 1 and the sliding counterpart (the bearing 94 and the boss portion 910) can be suppressed.

  Here, in order to increase the centrifugal force F <b> 1 acting on the piston 91 and the piston pin 1, in addition to the form in which the weight 3 is arranged on the piston pin 1, a form in which the piston 91 itself is made heavy can be considered. This form is not excluded from the scope of rights of the present application. In order to make the piston 91 heavier, the material of the piston 91 may be changed. However, materials that can be used for the piston 91 are limited from the viewpoints of strength, wear resistance, heat resistance, heat transfer, workability, and the like. For this reason, the freedom degree of material selection, ie, the freedom degree of the adjustable weight, will become low. The same applies to the configuration in which the pin body 2 itself is heavy.

  Moreover, in order to enlarge centrifugal force F1, the form which changes the shape (for example, thickness etc.) of piston 91 is also considered. This form is not excluded from the scope of rights of the present application. However, in this case, the weight balance of the piston 91 may be lost. For this reason, it becomes easy for the piston 91 to “one-contact” with the inner peripheral surface of the cylinder 90. Further, in the combustion chamber C, there is a possibility that a desired combustion state (combustion time, combustion speed, etc.) cannot be secured. For this reason, it is difficult to change the shape of the piston 91. The same applies to the form of changing the shape of the pin body 2. Thus, due to various restrictions, it is difficult to change the material and shape of the piston 91 and the pin body 2.

  On the other hand, the piston pin 1 of this embodiment includes a weight 3 that is separate from the pin body 2. For this reason, the centrifugal force F1 acting on the piston 91 and the piston pin 1 can be easily increased without changing the material and shape of the piston 91 and the pin body 2. Further, the weight of the piston pin 1 and the weight balance of the piston 91 can be adjusted by changing the shape, material, number of arrangements, etc. of the weight 3.

  Further, according to the piston pin 1 of the present embodiment, the centrifugal force F1 acting on the piston 91 and the piston pin 1 can be obtained only by adding the weight 3 to the conventional piston pin (corresponding to the single pin body 2 shown in FIG. 3). Can be easily enlarged. For this reason, versatility is high.

  Moreover, according to the piston pin 1 of this embodiment, the weight 3 is arrange | positioned in the center of the front-back direction of the pin main body 2, as shown in FIG. For this reason, the weight balance of the front-back direction of the piston 91 and the piston pin 1 is favorable. Therefore, it is difficult for the piston ring 96 and the piston 91 to “contact each other” on the inner peripheral surface of the cylinder 90. Therefore, uneven wear of the piston ring 96, the piston 91, and the cylinder 90 can be suppressed.

  Moreover, according to the piston pin 1 of this embodiment, the weight 3 is arrange | positioned in the center of the left-right direction of the pin main body 2 as shown in FIG. For this reason, the weight balance of the left-right direction of the piston 91 and the piston pin 1 is favorable. Therefore, it is difficult for the piston ring 96 and the piston 91 to “contact each other” on the inner peripheral surface of the cylinder 90. Therefore, uneven wear of the piston ring 96, the piston 91, and the cylinder 90 can be suppressed.

  Further, according to the piston pin 1 of the present embodiment, as shown in FIG. 2, the weight 3 is disposed not on the outer peripheral surface of the pin body 2, that is, on the inner peripheral surface, not on the sliding surface. For this reason, the weight of the piston pin 1 can be increased without inhibiting the sliding characteristics of the pin body 2.

  In addition, the outer diameter of the weight 3 is equal to or larger than the inner diameter of the weight arrangement hole 20 before being arranged on the pin body 2. For this reason, the weight 3 can be easily fixed to the pin body 2 simply by press-fitting the weight 3 into the weight arrangement hole 20.

  Further, as shown in FIG. 2, the piston pin 1 floats with respect to the bearing 94 and the boss portion 910 via an oil film. That is, the piston pin 1 connects the piston 91 and the bearing 94 of the small end 920 of the connecting rod 92 in a full floating manner. Here, as shown in FIG. 1, the small end portion 920 of the connecting rod 92, that is, the bearing 94 moves around the axis of the piston pin 1 as the crankshaft 93 rotates (the outer periphery of the pin body 2 shown in FIGS. 2 and 3). It reciprocates in the vertical direction while swinging around the center A1 of the surface. For this reason, a circumferential oscillating force acts on the piston pin 1 from the bearing 94. Therefore, the piston pin 1 rotates due to the swinging force. In this regard, according to the piston pin 1 of the present embodiment, as shown in FIGS. 2 and 3, the inner peripheral surface of the weight 3 is eccentric to the upper side (radial direction) with respect to the outer peripheral surface. For this reason, the center of gravity G of the piston pin 1 is eccentric to the lower side (radial direction) with respect to the axial center (center of the outer peripheral surface of the pin body 2) A1. Therefore, the rotational direction position of the piston pin 1 is stabilized so that the center of gravity G comes below (directly below) the axis A1. Therefore, the rotation of the piston pin 1 can be suppressed.

  Further, according to the piston pin 1 of the present embodiment, since the rotation of the piston pin 1 can be suppressed, the inner peripheral surface of the sliding counterpart (bearing 94 and boss portion 910) among the outer peripheral surfaces of the pin body 2. The surface treatment can be applied to only the portion that is easily pressed against the surface, in a focused or local manner. Similarly, the surface treatment can be performed on the inner peripheral surface of the sliding counterpart only or only on the portion that is easily pressed against the outer peripheral surface of the pin body 2. Therefore, compared with the case where surface treatment is performed uniformly over the entire outer peripheral surface of the pin body 2, man-hours and costs required for the surface treatment can be reduced. Similarly, the man-hour and cost required for the surface treatment can be reduced as compared with the case where the surface treatment is uniformly performed over the entire inner peripheral surface of the sliding counterpart.

  In addition, according to the piston pin 1 of the present embodiment, the center of gravity of the piston pin 1 can be easily adjusted with respect to the axis A1 of the pin body 2 by adjusting the position and shape of the weight arrangement hole 20 with respect to the pin body 2. G can be decentered. Further, by adjusting the position and shape of the weight 3 with respect to the weight arrangement hole 20, the center of gravity G of the piston pin 1 can be easily decentered with respect to the axis A1 of the pin body 2.

<Second embodiment>
The difference between the piston pin of the present embodiment and the piston pin of the first embodiment is that the weight is not hollow but solid. Here, only differences will be described. FIG. 4 shows an axial sectional view of the vicinity of a piston of an engine provided with the piston pin of the present embodiment. In addition, about the site | part corresponding to FIG. 2, it shows with the same code | symbol.

  As shown in FIG. 4, the weight 3 has a cylindrical shape. When viewed from the front side or the rear side, the center A1 of the circular outer peripheral surface of the pin body 2, the center B1 of the circular inner peripheral surface of the pin main body 2, and the center of the circular outer peripheral surface of the weight 3 (The center of gravity of the weight 3) A2 matches. For this reason, the axial center (center of the outer peripheral surface of the pin main body 2) A1 of the pin main body 2 and the gravity center G of the piston pin 1 coincide.

  The piston pin of the present embodiment and the piston pin of the first embodiment have the same operational effects with respect to the parts having the same configuration. Like the piston pin 1 of the present embodiment, the axis A1 of the pin body 2 and the center of gravity G of the piston pin 1 may be matched. Further, the weight 3 may be solid.

<Others>
The embodiment of the piston pin of the present invention has been described above. However, the embodiment is not particularly limited to the above embodiment. Various modifications and improvements that can be made by those skilled in the art are also possible.

  The material of the pin body 2 and the weight 3 is not particularly limited. It may be a metal, resin, ceramic or the like. The shapes of the pin body 2 and the weight 3 are not particularly limited. A cylindrical shape (cylindrical shape, polygonal cylindrical shape), a columnar shape (columnar shape, polygonal columnar shape), a block shape, or the like may be used.

  A plurality of weights 3 each having a different weight may be arranged to be interchangeable with respect to a single pin body 2. In this way, the magnitude of the centrifugal force (inertial force) F1 can be adjusted. In addition, the position of the center of gravity G can be adjusted. For this reason, the centrifugal force F1 and the center of gravity G can be adjusted according to the type of the engine 9.

  The position and shape of the weight arrangement hole 20 with respect to the pin body 2 are not particularly limited. Further, the position and shape of the weight 3 with respect to the weight arrangement hole 20 are not particularly limited. For example, a weight arrangement hole 20 having a perfectly circular cross section is arranged at the axis A1 of the pin body 2 (center of the outer peripheral surface of the pin body 2), and the weight 3 having a perfectly circular cross section is shifted with respect to the axis A1. May be arranged. In this way, the center of gravity G of the piston pin 1 can be eccentric in the radial direction with respect to the axis A1 of the pin body 2.

  Further, the weight arrangement hole 20 having a perfectly circular cross section may be arranged in the axis A <b> 1 of the pin body 2, and the weight 3 having an elliptical section or a cam shape may be arranged in the weight arrangement hole 20. In this way, the center of gravity G of the piston pin 1 can be eccentric in the radial direction with respect to the axis A1 of the pin body 2.

  The arrangement method of the weight 3 with respect to the weight arrangement hole 20 is not particularly limited. For example, the weight 3 may be arranged in the weight arrangement hole 20 by adhesion, welding, or the like. Further, the weight 3 may be arranged in the weight arrangement hole 20 by forming screw parts on the inner peripheral surface of the weight arrangement hole 20 and the outer circumference surface of the weight 3 and screwing both screw parts together. In this way, attachment / detachment of the weight 3, adjustment of the position in the front-rear direction, increase / decrease of the number of weights 3 can be easily performed. That is, the weight and weight balance of the piston pin 1 can be easily adjusted. The weight arrangement hole 20 may not penetrate the pin body 2 in the front-rear direction. That is, one end (front end or rear end) of the weight arrangement hole 20 in the axial direction may be closed.

  The piston pin 1 may be fixed to the boss portion 910. That is, the piston pin 1 is a fixed type, and may connect the piston 91 and the bearing 94 of the small end portion 920 of the connecting rod 92. Even in this case, a sufficient oil film can be formed on the lower portion (specifically, the lower portion of the sliding interface between the piston pin 1 and the bearing 94) O1 of the oil clearance O shown in FIG. .

  In the above embodiment, as shown in FIG. 1, an upward centrifugal force F1 is applied to the piston 91 and the piston pin 1 in a crank rotation angle region within 0 ° ± 90 °. However, the crank rotation angle region where the centrifugal force F1 acts is not particularly limited. The crank rotation angle region may be less than 0 ° ± 90 °, for example, within 0 ° ± 80 °.

  The type of surface treatment applied to the outer peripheral surface of the pin body 2 and the inner peripheral surface of the sliding counterpart (bearing 94 and boss portion 910) is not particularly limited. Examples of the surface treatment include shot peening, coating (DLC (Diamond Like Carbon) coating, ceramic coating, resin coating, etc.), plating, polishing, lining, painting, thermal spraying, and the like.

  FIG. 5A shows a development view of the boss portion of the piston and the inner peripheral surface of the bearing. FIG. 5B is a development view of the outer peripheral surface of the pin body. In addition, about the site | part corresponding to FIG. 2, it shows with the same code | symbol. When the exhaust pressure F3 shown in FIG. 2 acts on the piston 91 and the piston pin 1, the lower portion O1 of the oil clearance O becomes narrow. For this reason, pressure contact and wear tend to occur. Therefore, as shown by the solid line hatching, the ± 90 ° region (lower surface treatment region R1 in the lower half) centered on the lower portion O1 of the outer peripheral surface of the pin body 2 and the inner peripheral surface of the bearing 94 is the surface. Surface layer L1 is laminated by processing. For this reason, the strength and wear resistance of the surface treatment region R1 can be improved.

  2 acts on the piston 91 and the piston pin 1, the upper portion O2 of the oil clearance O becomes narrow. For this reason, pressure contact and wear tend to occur. Therefore, as shown by dotted hatching, the surface of the outer peripheral surface of the pin body 2 and the inner peripheral surface of the boss portion 910 is within the ± 90 ° region (upper half surface treatment region R2) centering on the upper portion O2. Surface layer L2 is laminated by processing. For this reason, the strength and wear resistance of the surface treatment region R2 can be improved.

  In addition, the presence or absence of the surface treatment for the region other than the surface treatment regions R1 and R2 (hereinafter referred to as “arbitrary region”) is not particularly limited. Compared to the surface treatment regions R1 and R2, the oil clearance O is less likely to be narrow in any region. For this reason, pressure contact and wear are unlikely to occur. Therefore, it is not necessary to perform surface treatment on an arbitrary region. Further, a surface treatment different from the surface treatment regions R1 and R2 may be applied to an arbitrary region. The position, range, and number of arrangement of the surface treatment regions R1 and R2 are not particularly limited. Only one of the surface treatment region R1 and the surface treatment region R2 may be disposed. In addition, the presence or absence of surface treatment can be confirmed based on the presence or absence of the surface layers L1 and L2 in the outer peripheral surface of the pin main body 2, and the inner peripheral surface of a sliding counterpart as an example.

  The use of the engine 9 is not particularly limited. In addition to vehicles, engines for ships and aircraft may be used. The type of engine 9 is not particularly limited. A four-cycle engine, a mirror cycle engine, a two-cycle engine, or the like may be used. Further, the stroke direction of the piston 91 is not particularly limited. The direction may be ± 30 °, ± 45 °, ± 60 °, ± 90 ° inclined with respect to the vertical direction. That is, the type of the engine 9 may be a series type, a V type, a horizontally opposed type, or the like. Regardless of the stroke direction of the piston 91, if it is of a full floating type and the center of gravity G of the piston pin 1 is eccentric with respect to the axis A1 of the pin body 2, the center of gravity G comes below the axis A1. . Further, the number of cylinders 90 of the engine 9 is not particularly limited.

  Preferably, the engine 9 is a diesel turbo engine. In the case of a diesel turbo engine, since the engine speed is often set low, the centrifugal force F1 shown in FIG. 2 tends to be small. On the other hand, since the turbo is adopted, the exhaust pressure F3 tends to increase. For this reason, an oil film is hardly formed on the oil clearance O. Therefore, when the piston pin of the present invention is employed, an oil film is likely to be formed in the oil clearance O regardless of the diesel turbo engine.

  1: piston pin, 2: pin body, 3: weight, 9: engine, 20: weight arrangement hole, 90: cylinder, 91: piston, 92: connecting rod, 93: crankshaft, 94: bearing, 95: snap ring, 96: Piston ring, 910: Boss part, 911: Outer ring groove, 912: Inner ring ring groove, 920: Small end part, 920a: Oil hole, 921: Large end part, 921a: Connecting rod bearing, 922: Rod part, 930: main journal, 931: crank pin, 932: crank arm, 940: oil hole, A1: center (axial center), A2: center, B1: center, B2: center, C: combustion chamber, F1: centrifugal force, F2: Weight, F3: Exhaust pressure, G: Center of gravity, L1: Surface layer, L2: Surface layer, O: Oil clearance, O1: Lower portion, O2: Upper portion, R1: Surface treatment region, R2: Surface Management area, a1: center, a2: center

Claims (2)

Connect the piston and the bearing at the small end of the connecting rod,
A pin body supported by the bearing and having a weight arrangement hole extending in the axial direction;
A weight placed in the weight placement hole;
Piston pin with   The piston pin according to claim 1, wherein the weight is disposed at an axial center of the weight arrangement hole.

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