JP6374269B2 - Piston pin lubrication structure - Google Patents

Description

  The present invention relates to a piston pin lubrication structure.

  Conventionally, in an internal combustion engine such as a vehicle, a piston pin is slidably inserted into both an insertion hole of a piston and a small end hole of a connecting rod, whereby the piston is swingably connected to a small end portion of the connecting rod. It has been known. In this structure, in order to prevent seizure of the sliding surface between the piston pin and the piston and the sliding surface between the piston pin and the connecting rod, lubricating oil is supplied to these sliding surfaces to form an oil film. It is planned to do. For example, in the lubrication structure described in Patent Document 1, an oil groove extending in the axial direction of the piston pin is formed on the outer peripheral surface of the piston pin, and lubricating oil is supplied from the oil groove, thereby lubricating the sliding surface. I am trying.

Japanese Patent No. 2768978

  In the lubricating structure of Patent Document 1, the lubricating oil supplied to the oil groove is guided to the sliding surface by rotating the piston pin. In recent years, in order to improve fuel efficiency, it has been required to increase the engine to a high Pme (net average effective pressure). When the engine is made to have a high Pme, the cylinder internal pressure increases and the force to push down the piston pin increases, so that the rotation of the piston pin is suppressed. Therefore, in the lubricating structure of Patent Document 1, when used in an engine having a high Pme, the lubricating oil supplied to the oil groove is not guided to the sliding surface because the piston pin is difficult to rotate, and the sliding There was a possibility that the oil film on the surface was cut and seizure occurred.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a piston pin lubricating structure capable of suppressing the occurrence of seizure even when the piston pin is difficult to rotate.

  A piston pin lubrication structure according to the present invention includes a piston, a connecting rod, and a rod-like piston pin that is slidably inserted into both of an insertion hole of the piston and a small end hole of the connecting rod. The piston pin has an oil groove extending from the opening edge on one side of the hole to the opening edge on the other side, and the piston pin intersects the axial direction of the piston pin on the first surface of the outer peripheral surface facing the small end hole. The first groove extends in the first direction and communicates with the oil groove at all rotational positions around the axis of the piston pin.

  In this lubrication structure, the first groove and the oil groove communicate with each other at all rotational positions around the axis of the piston pin, so that the lubricating oil supplied to the oil groove enters the first groove. The lubricating oil that has entered the first groove travels through the first groove and flows out of the first groove, and is supplied to the contact surface between the piston pin and the small end hole. Therefore, according to this lubricating structure, even when the piston pin is difficult to rotate, lubricating oil can be supplied to the contact surface between the piston pin and the small end hole, and the occurrence of seizure can be suppressed. It becomes.

  In the piston pin lubrication structure according to the present invention, the first direction may intersect the circumferential direction of the piston pin. According to this lubricating structure, since the lubricating oil spreads in the axial direction of the piston pin by being transmitted through the first groove, the lubricating oil is effectively supplied to the contact surface between the piston pin and the small end hole. Is possible.

In the piston pin lubricating structure according to the present invention, the first direction may be a direction satisfying the following expression (1).
tan θ1 ≦ n × L1 / πD (1)
However, θ1: angle formed between the first direction and the circumferential direction of the piston pin, n: number of first grooves, L1: length of the first surface in the axial direction of the piston pin, D: diameter of the piston pin . According to this lubricating structure, the first groove and the oil groove can be communicated with each other at all rotational positions around the axial direction of the piston pin. Further, since the first groove makes at least one round around the piston pin in the circumferential direction, a part of the first groove is necessarily arranged in the contact surface between the piston pin and the small end hole. For this reason, it becomes possible to supply lubricating oil reliably to the contact surface of a piston pin and a small end hole.

  In the piston pin lubrication structure according to the present invention, the piston pin extends to the second surface of the outer peripheral surface facing the insertion hole in the second direction intersecting the axial direction of the piston pin, and You may have the 2nd groove | channel which follows one groove | channel. In this lubricating structure, the lubricating oil transmitted through the first groove enters the second groove and is transmitted through the second groove. The lubricating oil flows out of the second groove and is supplied to the contact surface between the piston pin and the insertion hole. Therefore, according to this lubrication structure, even when the piston pin is difficult to rotate, the lubricating oil can be supplied to the contact surface between the piston pin and the insertion hole, and the occurrence of seizure can be suppressed. Become.

In the piston pin lubricating structure according to the present invention, the second direction may be a direction satisfying the following expression (2).
tan θ2 ≦ n × L2 / πD (2)
However, (theta) 2: The angle which a 2nd direction and the circumferential direction of a piston pin make, L2: The length in the axial direction of the piston pin of a 2nd surface. According to this lubrication structure, since the second groove makes at least one round around the piston pin in the circumferential direction, a part of the second groove is always arranged in the contact surface between the piston pin and the insertion hole. Is done. For this reason, it becomes possible to supply lubricating oil reliably to the contact surface of a piston pin and an insertion hole.

  According to the present invention, it is possible to provide a piston pin lubricating structure capable of suppressing the occurrence of seizure even when the piston pin is difficult to rotate.

It is sectional drawing which shows the lubricating structure of the piston pin which concerns on one Embodiment of this invention. It is a figure which shows a connecting rod, (a) is a side view, (b) is the BB sectional drawing of (a). It is a figure which shows a piston pin, (a) is a side view, (b) is a front view. It is an expanded view of the outer peripheral surface of a piston pin. It is an expanded view of the outer peripheral surface of the piston pin which concerns on a modification. It is an expanded view of the outer peripheral surface of the piston pin which concerns on another modification. It is an expanded view of the outer peripheral surface of the piston pin which concerns on another modification.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted. In the present specification, directions such as “up” and “down” are for convenience based on the state shown in the drawings.

  FIG. 1 is a cross-sectional view illustrating a piston pin lubricating structure according to an embodiment. 2A and 2B are diagrams showing a connecting rod, in which FIG. 2A is a side view and FIG. 2B is a cross-sectional view taken along line BB in FIG. FIG. 3 is a view showing a piston pin, in which (a) is a side view and (b) is a front view. FIG. 4 is a development view of the outer peripheral surface of the piston pin. The piston pin lubrication structure 1 of this embodiment is provided in an internal combustion engine such as a gasoline engine or a diesel engine. The piston pin lubrication structure 1 includes a piston 10, a connecting rod 20, and a piston pin 30.

  The piston 10 is a member that reciprocates in a cylinder of the internal combustion engine. The piston 10 is made of metal and is made of, for example, an aluminum alloy. The piston 10 has a substantially cylindrical outer shape, for example. The piston 10 has at least a head part 12 positioned on the top side and a pin boss part 14 projecting downward from the head part 12.

  A cavity 16 constituting the bottom surface of the combustion chamber is formed on the top surface of the head portion 12. A pair of pin bosses 14 are provided so as to face each other. Each of the pin boss portions 14 is formed with an insertion hole 18 having a circular cross section. A piston pin 30 is slidably inserted into the insertion hole 18. A connecting rod housing recess 19 that is recessed upward is formed between the pair of pin boss portions 14 on the lower side of the head portion 12. The connecting rod housing recess 19 houses the small end 22 of the connecting rod 20.

  The connecting rod 20 is a member that connects the piston 10 and a crankshaft (not shown) and converts the reciprocating motion of the piston 10 into the rotational motion of the crankshaft. The connecting rod 20 is made of metal, and is formed of, for example, steel. The connecting rod 20 has, for example, a rod shape. The connecting rod 20 has a small end portion 22 formed on one end side and a large end portion (not shown) formed on the other end side. The small end portion 22 has a tapered shape. The small end portion 22 is formed with a small end hole 24 having a circular cross section extending in the extending direction of the insertion hole 18 (the axial direction D1 of the piston pin 30). A piston pin 30 is slidably inserted into the small end hole 24. A large end hole is formed in the large end portion, and the crankshaft is connected to the large end hole.

  As shown in FIG. 2, the small end portion 22 has an oil groove 26 formed on the inner peripheral surface of the small end hole 24, and a communication hole 28 opened to the oil groove 26. The oil groove 26 is, for example, a groove having a rectangular cross section and a constant width and depth. From the opening edge 24A on one side of the small end hole 24 to the opening edge 24B on the other side, it extends in a direction parallel to the extending direction of the small end hole 24 (the axial direction D1 of the piston pin 30). The communication hole 28 is a hole that communicates the oil groove 26 with the large end hole. Lubricating oil is supplied to the oil groove 26 from the large end side through the communication hole 28.

  The piston pin 30 is a member that pivotably connects the piston 10 and the small end portion 22 of the connecting rod 20. The piston pin 30 is made of metal and is formed of, for example, chrome molybdenum steel. The piston pin 30 has a rod shape having a circular outer peripheral surface, and is formed in a hollow cylindrical shape here. The piston pin 30 may be formed in a solid cylindrical shape. Both end portions of the piston pin 30 are slidably inserted into the insertion holes 18 of the piston 10. The central portion of the piston pin 30 is slidably inserted into the small end hole 24 of the connecting rod 20. That is, the piston pin 30 is rotatable around the axis in the insertion hole 18 and the small end hole 24. The axial direction D1 of the piston pin 30 coincides with both the extending direction of the insertion hole 18 and the extending direction of the small end hole 24. As shown in FIG. 1, the outer diameter of the piston pin 30 is set slightly smaller than the inner diameters of the insertion hole 18 and the small end hole 24. For this reason, a slight gap (clearance) exists between the piston pin 30 and the insertion hole 18 and between the piston pin 30 and the small end hole 24.

  As shown in FIGS. 1 and 3, in the piston pin 30, the first surface S <b> 1 facing the small end hole 24 in the outer peripheral surface 30 </ b> A is a sliding surface with respect to the small end hole 24. Further, the second surface S <b> 2 facing the insertion hole 18 in the outer peripheral surface 30 </ b> A serves as a sliding surface with respect to the insertion hole 18. When the piston 10 reciprocates in the cylinder, for example, when the internal pressure of the cylinder increases with the combustion of fuel in the combustion chamber, the piston pin 30 is located at the lower side of the center portion as shown in FIG. Thus, the small end hole 24 is brought into contact with the insertion hole 18 at the upper side of both end portions.

  The piston pin 30 is essentially in a state in which the piston pin 30 does not contact the insertion hole 18 and the small end hole 24 due to inertial force while the piston 10 is positioned on the top dead center side of the exhaust stroke in the engine cycle. It is assumed that the motor rotates about the axis. When the piston pin 30 rotates about the axis, the lubricating oil supplied to the oil groove 26 is caught in the piston pin 30, and the lubricating oil is supplied to the sliding surface.

  However, as described above, in the case of an engine having a high Pme, the force that pushes down the piston 10 when the cylinder internal pressure is increased with the combustion of fuel in the combustion chamber increases, Hard to rotate. In particular, when the engine is at a part of the operating point, the piston pin 30 is difficult to rotate. For example, when the engine speed is low, the inertial force that the piston 10 tries to move upward is smaller than when the engine speed is high. For this reason, since the force which pushes down the piston 10 becomes relatively large, the piston pin 30 is unlikely to be in contact with the insertion hole 18 and the small end hole 24, and the piston pin 30 is difficult to rotate.

  When the piston pin 30 is difficult to rotate in this way, the piston pin 30 may always contact the small end hole 24 and the insertion hole 18 on the same surface. As a result, since a large load continues to act on the contact surface, the oil film on the contact surface may break and seizure may occur. In order to prevent the occurrence of seizure, conventionally, in order to reduce the cylinder internal pressure, the maximum pressure is suppressed by timing retard and the compression pressure is suppressed by restricting the intake amount. These measures are accompanied by performance deterioration such as fuel consumption deterioration and smoke increase. Therefore, in the piston pin lubrication structure 1 of this embodiment, even if the piston pin 30 is difficult to rotate, it is configured to be able to supply lubricating oil to the contact surface, thereby suppressing the occurrence of seizure. .

  As shown in FIGS. 3 and 4, the piston pin 30 has a first groove G1 on the first surface S1 and a second groove G2 on the second surface S2. The first groove G1 extends in the first direction on the first surface S1, and extends from one side boundary to the other side boundary in the axial direction D1 of the first surface S1. The second groove G2 extends in the second direction on the second surface S2, and extends from one side boundary to the other side boundary in the axial direction D1 of the second surface S2. The first groove G1 and the second groove G2 are continuous at each other end. The first groove G1 and the second groove G2, for example, have a rectangular cross section and have a constant width and depth. In the present embodiment, both the first groove G1 and the second groove G2 extend clockwise.

The first direction that is the extending direction of the first groove G1 is a direction that intersects the axial direction D1 of the piston pin 30, and in this embodiment, also intersects the circumferential direction D2. In the present embodiment, the first direction is a direction that satisfies the following expression (3).
tan θ1 = L1 / πD (3)
However, θ1: angle formed by the first direction and the circumferential direction D2 of the piston pin 30; L1: maximum length of the first surface S1 in the axial direction D1 of the piston pin 30 (the piston pin 30 and the small end hole 24) D: the diameter of the piston pin 30. The first groove G1 makes one turn around the piston pin 30 around the circumferential direction D2 on the first surface S1.

The second direction, which is the extending direction of the second groove G2, is a direction that intersects the axial direction D1 of the piston pin 30, and in this embodiment, also intersects the circumferential direction D2. In the present embodiment, the second direction is a direction that satisfies the following expression (4).
tan θ2 = L2 / πD (4)
However, θ2: angle formed between the second direction and the circumferential direction D2 of the piston pin 30; L2: maximum length in the axial direction D1 of the piston pin 30 on the second surface S2 (the piston pin 30 and the insertion hole 18 Length of contact surface). The second groove G2 makes one round around the piston pin 30 around the circumferential direction D2 on the second surface S2.

  The first groove G1 communicates with the oil groove 26 at all rotational positions around the axis of the piston pin 30 because the circumference of the piston pin 30 is made around the circumferential direction D2 on the first surface S1. Is done. That is, the first groove G1 and the oil groove 26 communicate with each other regardless of the rotation posture of the piston pin 30. For this reason, the lubricating oil supplied to the oil groove 26 enters the first groove G1. The lubricating oil that has entered the first groove G1 travels through the first groove G1 and flows out from the first groove G1, and is supplied to the contact surface between the piston pin 30 and the small end hole 24. The Here, since the first groove G1 goes around the circumference of the piston pin 30 around the circumferential direction D2, a part of the first groove G1 is a contact surface between the piston pin 30 and the small end hole 24. Always be placed in. For this reason, the lubricating oil flows out from the part, so that the lubricating oil is reliably supplied to the contact surface between the piston pin 30 and the small end hole 24. Further, since the first groove G1 intersects the circumferential direction D2 of the piston pin 30, the lubricating oil transmitted through the first groove G1 spreads in the axial direction D1 of the piston pin 30. Thereby, the lubricating oil is effectively supplied to the contact surface between the piston pin 30 and the small end hole 24.

  The second groove G2 is continuous with the first groove G1. For this reason, the lubricating oil transmitted through the first groove G1 enters the second groove G2 and is transmitted through the second groove G2. The lubricating oil flows out from the second groove G2 and is supplied to the contact surface between the piston pin 30 and the insertion hole 18. Here, since the second groove G2 goes around the circumference of the piston pin 30 around the circumferential direction D2, a part of the second groove G2 is in the contact surface between the piston pin 30 and the insertion hole 18. Always be placed in. For this reason, the lubricating oil flows out from the part, so that the lubricating oil is reliably supplied to the contact surface between the piston pin 30 and the insertion hole 18. Further, since the second groove G2 intersects the circumferential direction D2 of the piston pin 30, the lubricating oil transmitted through the second groove G2 spreads in the axial direction D1 of the piston pin 30. Thereby, the lubricating oil is effectively supplied to the contact surface between the piston pin 30 and the insertion hole 18.

  As described above, in the piston pin lubrication structure 1, the first groove G <b> 1 and the oil groove 26 are communicated with each other at all rotational positions around the axis of the piston pin 30, so that the lubrication supplied to the oil groove 26 is performed. Oil enters the first groove G1. The lubricating oil that has entered the first groove G1 travels through the first groove G1 and flows out of the first groove G1, and is supplied to the contact surface between the piston pin 30 and the small end hole 24. Therefore, according to this lubricating structure, even when the piston pin 30 is difficult to rotate, the lubricating oil can be supplied to the contact surface between the piston pin 30 and the small end hole 24, and the occurrence of seizure is suppressed. It becomes possible to do.

  Further, according to the piston pin lubrication structure 1, since the lubricating oil spreads in the axial direction D <b> 1 of the piston pin 30 by being transmitted through the first groove G <b> 1, the contact between the piston pin 30 and the small end hole 24. Lubricating oil can be effectively supplied to the surface.

  Further, in the piston pin lubricating structure 1, the first groove G <b> 1 makes at least one round around the piston pin 30 around the circumferential direction D <b> 2, and therefore, in the contact surface between the piston pin 30 and the small end hole 24. The first groove G1 is necessarily arranged. For this reason, it becomes possible to reliably supply the lubricating oil to the contact surface between the piston pin 30 and the small end hole 24.

  Further, in the piston pin lubricating structure 1, the lubricating oil transmitted through the first groove G1 enters the second groove G2 and is transmitted through the second groove G2. The lubricating oil flows out from the second groove G2 and is supplied to the contact surface between the piston pin 30 and the insertion hole 18. Therefore, according to this lubrication structure, even when the piston pin 30 is difficult to rotate, the lubricating oil can be supplied to the contact surface between the piston pin 30 and the insertion hole 18 to suppress the occurrence of seizure. It becomes possible.

  Further, in the piston pin lubrication structure 1, the second groove G <b> 2 makes at least one turn around the circumferential direction D <b> 2 around the piston pin 30, so that the second groove G <b> 2 is within the contact surface between the piston pin 30 and the insertion hole 18. Two grooves G2 are necessarily arranged. For this reason, it becomes possible to reliably supply the lubricating oil to the contact surface between the piston pin 30 and the insertion hole 18.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. The present invention is not limited to the scope described in the claims and can be modified or applied to other embodiments. May be.

In the above-described embodiment, the first groove G1 and the second groove G2 make one round around the piston pin 30 around the circumferential direction D2 in the first surface S1 and the second surface S2. Although demonstrated, it is good also as a structure which makes the circumference | surroundings of the piston pin 30 at least 1 circumference | surroundings around the circumferential direction D2, and a 1st direction and a 2nd direction are not restricted to the example of the said embodiment. That is, the first direction of the first groove G1 may be a direction that satisfies the following expression (5).
tan θ1 ≦ L1 / πD (5)
The second direction of the second groove G2 may be a direction that satisfies the following expression (6).
tan θ2 ≦ L2 / πD (6)
For example, as shown in FIG. 5, both the first groove G1 and the second groove G2 may make one or more rounds around the piston pin 30 around the circumferential direction D2. Alternatively, either one of the first groove G1 and the second groove G2 may make one or more rounds around the piston pin 30 around the circumferential direction D2.

  Further, one of the first groove G1 and the second groove G2 may extend clockwise and the other may extend counterclockwise. For example, as shown in FIG. 6, the first groove G1 may extend clockwise and the second groove G2 may extend counterclockwise.

In the embodiment, the example in which the first groove G1 and the second groove G2 are one has been described. However, the number of the first grooves G1 and the second grooves G2 is not limited to this, and the number is n. (N = 1, 2,...) In this case, for example, in order to allow the first groove G1 to communicate with the oil groove 26 at all the rotational positions around the axis of the piston pin 30, the first surface S1 has at least once during the development length πD. What is necessary is just to form so that one groove | channel G1 may appear. For example, when the extending direction of the n first grooves G1 is the same direction, the first direction of the first grooves G1 may be a direction that satisfies the following expression (7).
tan θ1 ≦ n × L1 / πD (7)
Similarly, the second direction of the second groove G2 may be a direction that satisfies the following expression (8).
tan θ2 ≦ n × L2 / πD (8)
As an example, as shown in FIG. 7, the number of first grooves G1 and second grooves G2 may be two.

  In the embodiment, the example in which the first surface S1 and the second surface S2 are continuous has been described. However, the insertion hole 18 and the small end between the first surface S1 and the second surface S2 are described. There may be a surface that does not face the hole 24. In this case, a groove that is continuous with both the first groove G1 and the second groove G2 may be formed on the surface, and the first groove G1 and the second groove G2 may be continued through the groove. .

  Moreover, although the said embodiment demonstrated the example where the 1st groove | channel G1 extended from the boundary of the one side in the axial direction D1 of the 1st surface S1 to the boundary of the other side, the 1st groove | channel G1 is a piston pin. The first groove G1 may extend only to a part in the axial direction D1 of the first surface S1 as long as it is communicated with the oil groove 26 at all rotational positions around the 30 axis.

  Moreover, although the oil groove 26 extended in the said embodiment in the direction parallel to the extension direction (axial direction D1 of the piston pin 30) of the small end hole 24, for example, the extension direction of the small end hole 24 is described. You may extend in the direction which crosses. In this case, the first groove G1 may be formed so as to communicate with the oil groove 26 at all rotational positions around the axis of the piston pin 30. For example, in the embodiment, the example in which the first groove G1 makes at least one round around the piston pin 30 in the first surface S1 around the circumferential direction D2 has been described. However, the oil groove 26 has the small end hole 24. The first groove G1 does not necessarily have to make one round around the piston pin 30 around the circumferential direction D2.

  Moreover, although the said embodiment demonstrated the example which formed the 2nd groove | channel G2 of the same shape in each of the 2nd 2nd surface S2, even if it formed a groove | channel of a different shape for every 2nd surface S2. Good. Moreover, it is good also as a structure which does not have the 2nd groove | channel G2. In this case, the first groove G1 may be a direction that coincides with the circumferential direction D2 of the piston pin 30.

DESCRIPTION OF SYMBOLS 1 ... Piston pin lubricating structure, 10 ... Piston, 12 ... Head part, 14 ... Pin boss part, 18 ... Insertion hole, 20 ... Connecting rod, 22 ... Small end part, 24 ... Small end hole, 24A ... Opening edge, 24B ... Opening edge, 26 ... oil groove, 28 ... communication hole, 30 ... piston pin, 30A ... outer peripheral surface, D1 ... axial direction, D2 ... circumferential direction, G1 ... first groove, G2 ... second groove, S1 ... first 1 surface, S2 ... 2nd surface.

Claims (6)

A piston, a connecting rod, and a rod-shaped piston pin that is slidably inserted into both the insertion hole of the piston and the small end hole of the connecting rod,
The connecting rod has an oil groove extending from an opening edge on one side of the small end hole to an opening edge on the other side,
The piston pin extends to a first surface of the outer peripheral surface facing the small end hole in a first direction that intersects the axial direction of the piston pin, and rotates around the axis of the piston pin. A piston pin lubrication structure comprising a first groove communicated with the oil groove at a position.   2. The piston pin lubricating structure according to claim 1, wherein the first direction intersects a circumferential direction of the piston pin. 3. 3. The piston pin lubricating structure according to claim 1, wherein the first direction is a direction satisfying the following expression (1). 4.
tan θ1 ≦ n × L1 / πD (1)
However,
θ1: an angle formed by the first direction and the circumferential direction of the piston pin,
n: the number of the first grooves,
L1: Length of the first surface in the axial direction of the piston pin;
D: Diameter of the piston pin.   The piston pin extends to a second surface of the outer peripheral surface facing the insertion hole in a second direction intersecting the axial direction of the piston pin and is continuous with the first groove. The piston pin lubrication structure according to claim 2, further comprising a groove. The said 2nd direction is a direction which satisfy | fills the following Formula (2), The lubricating structure of the piston pin of Claim 4 characterized by the above-mentioned.
tan θ2 ≦ n × L2 / πD (2)
However,
θ2: an angle formed by the second direction and the circumferential direction of the piston pin,
L2: Length of the second surface in the axial direction of the piston pin. The piston rod lubrication structure according to any one of claims 1 to 5, wherein the connecting rod further includes a hole that allows the oil groove and the large end hole to communicate with each other.

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