JP2004339998A - Piston for internal combustion engine - Google Patents

Abstract

In a piston for an internal combustion engine in which a part of a piston skirt in an axial direction of a piston pin hole is cut to reduce the weight, lubricating oil is supplied to the piston pin hole at a relatively high pressure, and Improve strength.
A piston pin boss (5) is connected to an end surface (2a) of a piston head (2) substantially perpendicular to a reciprocating direction of a piston (1) and an outer radial end of a region where a piston skirt (6) is cut out. An oil introduction pipe in which a lubricating oil passage 10 communicating the oil ring groove 3a provided in the piston head 2 with the piston pin hole 4 and supplying the lubricating oil in the oil ring groove 3a to the piston pin hole 4 is formed. 9 is provided to be inclined with respect to the reciprocating direction of the piston 1.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a piston for an internal combustion engine.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a piston for an internal combustion engine, a piston used in a reciprocating engine has a structure in which a piston is connected to a rotating crankshaft by a connecting rod and reciprocates. Then, after the piston is combined with the connecting rod, the piston pin is connected to the connecting rod by inserting the piston pin into the piston pin hole.It is known that the surrounding area is a place where lubrication with lubricating oil is difficult. I have.
[0003]
On the other hand, in order to reduce the weight, for example, there is known a structure in which the end of the piston pin boss is moved toward the center of the piston body and the axial side surface of the piston pin boss having the piston pin hole of the piston skirt is cut off. Have been.
[0004]
In such a piston, the piston ring groove provided on the outer periphery of the piston head for mounting the piston ring communicates with the piston pin hole, and lubricating oil scraped off by the piston ring is introduced into the piston pin hole. Thus, there is known one that achieves a good lubrication function between the piston pin hole and the piston pin (for example, see Patent Document 1).
[0005]
[Patent Document 1]
Japanese Utility Model Laid-Open No. 4-136356 [Patent Document 2]
Japanese Utility Model Application Laid-Open No. 6-60747 [Patent Document 3]
JP-A-60-190954 [Patent Document 4]
Japanese Utility Model Laid-Open Publication No. 7-8541
[Problems to be solved by the invention]
By the way, in order to supply sufficient lubricating oil around the piston pin where the direction changes due to the reciprocating motion of the piston and the high surface pressure is applied alternately, it is necessary to pump lubricating oil to this portion. That is, it is necessary to supply the lubricating oil at a high pressure in order to introduce the lubricating oil into the narrow clearance in the piston pin hole.
[0007]
Conventionally, since the lubricating oil passage communicating with the piston ring groove is provided in the groove bottom direction of the piston ring groove, that is, in a direction substantially orthogonal to the direction of the reciprocating movement of the piston, the piston reciprocates. However, the lubricating oil only acts to move the lubricating oil in the direction substantially perpendicular to the direction of the passage (width direction of the passage) in the lubricating oil passage, and is suitable for supplying the lubricating oil to the piston pin hole. The desired lubrication may not be achieved due to insufficient hydraulic pressure.
[0008]
On the other hand, when the combustion pressure acts on the piston during the operation of the internal combustion engine, a large load generated by the combustion pressure acts on the piston head, so that the piston head may be deformed to fall down (on the connecting rod side).
[0009]
In such a case, the piston pin hole is also deformed, resulting in one-sided contact, insufficient lubrication, and the occurrence of seizure.
[0010]
The present invention has been made in view of the above-described circumstances, and in a piston for an internal combustion engine in which a part of a piston skirt in an axial direction of a piston pin hole is cut out to reduce weight, a relatively high An object is to supply lubricating oil to a piston pin hole with pressure and to improve the strength of a piston.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention employs the following configurations.
[0012]
That is, a piston pin boss provided inside the outer peripheral edge of the piston head (piston crown) and provided with a piston pin hole through which a piston pin connecting the piston and the connecting rod is inserted,
In an internal combustion engine piston in which a side surface of a piston skirt facing the piston pin hole of the piston pin boss is cut,
The piston pin boss is connected to an end of the piston head that is substantially perpendicular to the reciprocating direction of the piston and that is an end surface on the piston pin boss side in an outer radial direction of a region where the piston skirt is cut out. A tubular portion having a lubricating oil passage formed therein, which communicates a piston ring groove provided in the piston head with the piston pin hole and supplies lubricating oil in the piston ring groove to the piston pin hole. Provided,
The gist is that the tubular portion is provided to be inclined with respect to the reciprocating direction of the piston.
[0013]
When the piston operates, the lubricating oil that is scraped off by the piston ring attached to the piston ring groove and that is not necessary for forming an oil film on the cylinder wall has an inertial force to move it in the reciprocating direction of the piston. Works. In the present invention, since the tubular portion is provided to be inclined with respect to the direction of the reciprocating motion of the piston, lubricating oil can be supplied to the piston pin hole at a relatively high pressure by the action of the inertial force. it can.
[0014]
Further, the tubular portion is provided so as to connect the piston pin boss to the end face of the piston head on the piston pin boss side in the cutout region of the piston skirt and the vicinity of the piston ring groove. Thereby, the strength of the piston can be improved. Therefore, it is possible to prevent a deformation that occurs in the piston head when the combustion pressure acts on the piston during the operation of the internal combustion engine, that is, a deformation in which the piston head falls down to the piston pin boss side. Thereby, it is possible to prevent deformation occurring in the piston pin hole when the combustion pressure acts on the piston, to suppress the one-side contact between the piston pin and the piston pin hole, and to maintain a good lubrication state. It becomes possible.
[0015]
Here, it is preferable that the lubricating oil passage in the piston head is formed so as to communicate the tubular portion and the piston ring groove while maintaining the inclined state of the tubular portion. However, the lubricating oil passage in the piston head is not particularly limited. Since the tubular portion is provided on the end face on the piston pin boss side of the piston head and in the outer radial direction, that is, near the piston ring groove, the lubricating oil is scraped off by the operation of the piston, so that the tubular portion is scraped off. Lubricating oil can be sent from the piston ring groove to the tubular portion. For example, even if a passage is provided in a direction substantially perpendicular to the direction of the reciprocating movement from the piston ring groove, its length is small and does not pose a problem.
[0016]
In the above configuration, it is preferable that the lubricating oil passage communicates with a groove bottom of the piston ring groove.
[0017]
When the lubricating oil passage is provided on the side wall of the piston ring groove, the piston ring mounted on the piston ring groove may block the lubricating oil passage when the piston operates, If the passage is provided at the groove bottom of the piston ring groove, the passage will not be blocked by the piston ring, and the lubricating oil can be more reliably supplied to the piston pin hole. Here, the lubricating oil passage may include at least a part of the groove bottom of the piston ring groove, and may communicate with the region including the groove bottom and the side wall. The lubricating oil can be more reliably supplied to the piston pin hole through the lubricating oil passage.
[0018]
Further, in the above configuration, a lubricating oil reservoir for storing lubricating oil is provided on an inner peripheral surface of the piston pin hole,
Preferably, the lubricating oil passage communicates with the lubricating oil reservoir.
[0019]
As a result, the lubricating oil can always be stored in the lubricating oil reservoir, so that the lubricating state between the piston pin hole and the piston pin can be always improved, and problems such as wear and seizure can be more reliably prevented. It can be prevented.
[0020]
It should be noted that the above configurations can be employed in combination as much as possible.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
(Embodiment 1)
Hereinafter, the piston for an internal combustion engine of the present invention will be described in more detail with reference to the embodiment shown in FIGS. FIG. 1 is a schematic diagram showing a side surface of a piston for an internal combustion engine according to Embodiment 1 of the present invention. FIG. 2 is a schematic diagram showing the bottom surface of the piston for an internal combustion engine according to the present embodiment. FIG. 3 is a schematic view showing a cross section AA shown in FIG. 2, and shows a portion A in FIG.
[0022]
The piston 1 is inserted into a cylinder of an internal combustion engine (not shown), and has a piston head 2 defining a combustion chamber and having a piston ring groove 3 provided on an outer peripheral surface, and a piston pin hole 4 through which a piston pin is inserted. A piston pin boss 5 and a piston outer peripheral portion 7 which covers the piston pin boss 5 and has an outer periphery of the piston head 2 and a lower part of a piston skirt 6 integrated therewith.
[0023]
Normally, a total of three piston ring grooves 3 are formed on the upper side surface of the piston 1, that is, the outer peripheral surface of the piston head 2, and a piston skirt 6 is formed below the piston ring grooves 3. The upper two of the piston ring grooves 3 are for a compression ring, and the lower one is an oil ring groove 3a for an oil ring. In the present embodiment, the piston ring groove particularly represents an oil ring groove 3a for mounting an oil ring.
[0024]
The illustrated piston 1 is not in a so-called columnar shape, but in the piston pin axial direction (opposed to the piston pin hole 4) in the piston skirt 6 so as to reduce the lateral pressure relatively in order to reduce the weight and reduce the friction loss. Side) is partially cut away.
[0025]
FIG. 1 is a view of the piston 1 as viewed from the thrust side. The piston skirt 6 whose width has been reduced due to the provision of the notch as described above has the front side and the opposite side (opposite side) in the drawing. ), That is, provided on the outer peripheral portion of the piston facing in a direction substantially perpendicular to the axis of the piston pin hole 4. Further, a piston pin boss 5 is formed on the back surface of the piston head 2, and the piston pin boss 5 is formed with a piston pin hole 4 for connecting to a connecting rod (not shown).
[0026]
In the piston 1 shown in FIG. 1, a pair of sidewalls 8 are formed so as to connect the opposed piston skirts 6 from inside. The sidewalls 8 are provided in parallel to the direction intersecting the piston skirt 6 so as to cross the piston, and the pistons 8 are respectively formed with the piston pin bosses 5 on each of the sidewalls 8. Is formed with a piston pin hole 4 for connection to the piston pin. A piston pin (not shown) is inserted into the piston pin hole 4, so that the piston 1 and the connecting rod are connected.
[0027]
As a characteristic configuration of the present embodiment, an outer radial end portion of a region where the piston skirt 6 is cut off on the end surface 2a on the back side of the piston head 2 (on the side where the piston pin boss 5 is provided), The piston pin hole 4 is connected to the end face 5a of the piston pin boss 5 which is substantially orthogonal to the axial direction, and the oil ring groove 3a communicates with the piston pin hole 4 to lubricate the oil in the oil ring groove 3a to the piston pin hole 4. An oil introduction pipe 9 as a tubular part in which a lubricating oil passage 10 to be supplied is formed is provided to be inclined with respect to the reciprocating direction of the piston.
[0028]
The lubricating oil passage 10 has an oil hole 11 in the piston head provided in the piston head 2 for communicating the oil introduction pipe 9 with the oil ring groove 3a, and an oil introduction pipe 9 and the piston pin hole 4 provided in the piston pin boss 5. It comprises an oil hole 12 in the pin boss and an oil introduction pipe 9 communicating with each other.
[0029]
The oil hole 11 in the piston head is provided so as to penetrate from the back surface of the piston head 2 to the oil ring groove 3a while maintaining the inclined state of the oil introduction pipe 9, that is, the oil hole 11 in the piston head and the oil introduction pipe. The lubricating oil passage formed by the pipe 9 is provided substantially linearly.
[0030]
The pin boss inner oil hole 12 is provided so as to penetrate from the end face 5 a of the piston pin boss 5 to the piston pin hole 4. Here, the oil hole 12 in the pin boss only needs to supply lubricating oil between the piston pin hole 4 and a piston pin (not shown), and is not limited to the one penetrating through the piston pin boss 5. For example, a passage having an open portion such as a groove may be used.
[0031]
When the piston 1 is operated in such a configuration, lubricating oil unnecessary for forming an oil film on the cylinder wall surface is scraped off by an oil ring (not shown), and is fed from the oil ring groove 3a to the oil hole 11 in the piston head.
[0032]
When the piston 1 operates, an inertial force acting on the lubricating oil in the lubricating oil passage 10 in the direction of the reciprocating motion acts on the lubricating oil along with the reciprocating motion of the piston 1. The lubricating oil passage 10, particularly the oil hole 11 in the piston head and the oil introduction pipe 9, is provided to be inclined with respect to the direction of the reciprocating motion of the piston 1 and has a component in the direction of the reciprocating motion of the piston 1. Therefore, by the action of the inertial force, the lubricating oil in the passage can be sent to the downstream side, that is, can be sent to the piston pin hole 4 by pressure.
[0033]
Here, the direction of the reciprocating motion of the piston 1 depends on the specifications of the engine, and is not particularly limited in the present embodiment. However, the direction of the reciprocating motion of the piston 1 is a component of the direction of gravity. In the case of having the lubricating oil, the function of pumping the lubricating oil to the downstream side by the weight of the lubricating oil is further added, and the lubricating oil can be more effectively pumped to the piston pin hole 4. In this case, when the internal combustion engine is stopped, the lubricating oil remaining in the oil introduction pipe 9 of the lubricating oil passage 10 and the oil hole 11 in the piston head drops to the piston pin hole 4 side (by its own weight). Sufficient lubrication can be provided when starting the internal combustion engine where lubrication is most important.
[0034]
Further, in order to reduce the weight and reduce the friction loss, the piston skirt 6 has a shape in which a part of a side surface of the piston skirt 6 facing the axial direction of the piston pin hole 4 is cut away so that the lateral pressure is relatively reduced. In the configuration described above, the deformation of the piston head 2 falling down (toward the piston pin boss 5) when the combustion pressure acts on the piston 1 during operation of the internal combustion engine can be prevented. Thereby, when the combustion pressure acts on the piston 1, it is possible to prevent deformation of the piston pin hole 4, and to suppress the one-sided contact between the piston pin and the piston pin hole 4, and to reduce the lubrication state. It is possible to keep good. For example, when the piston pin boss 5 is provided at the center side of the piston 1 for weight reduction and the radial length is small, the oil introduction pipe 9 is provided so that when the combustion pressure acts on the piston 1, Deformation occurring in the pin hole 4 can be more effectively prevented.
[0035]
In the figure, two oil introduction pipes 9 are provided on the outer peripheral side of the piston so as to sandwich the piston pin hole 4, but the invention is not limited to this. Depending on the lubrication state and the intensity distribution of the combustion pressure acting on the piston head, the size of the cross section of the lubricating oil passage in the oil introducing pipe 9 (in the direction perpendicular to the passage), the number and thickness of the oil introducing pipe 9 May be determined as appropriate. The oil introduction pipe 9 may be provided independently of the piston main body and attached to the piston main body, or may be provided integrally with the piston main body. In this case, for example, a lubricating oil passage may be formed by forming a cavity with a salt core. Further, in the case where the lubricating oil passage is provided in the groove bottom direction of the oil ring groove (direction substantially orthogonal to the direction of reciprocation of the piston) as in the related art, Although it cannot be set larger than the groove width of the ring groove, as in the present embodiment, by providing the oil hole 11 in the piston head inclined with respect to the direction of reciprocation of the piston, the size of the passage is reduced. The lubricating oil can be easily sent into the piston pin hole 4.
[0036]
In the piston pin boss 5, the position where the oil introduction pipe 9 is connected is not particularly limited as long as lubricating oil is supplied to the piston pin hole 4, but the lower side of the piston pin boss (opposite to the piston head 2). Side), the length of the oil introduction pipe 9 can be increased. Thus, the action of the inertial force during the operation of the piston can be further increased, and the lubricating oil can be more effectively pumped to the piston pin hole 4. In addition, when the combustion pressure acts on the piston 1, deformation occurring in the piston pin hole 4 can be more effectively prevented.
[0037]
As described above, since the lubrication of the piston pin hole 4 can be performed more reliably, the wear of the piston pin hole 4 and the piston pin in contact therewith can be prevented, the friction is reduced, the scuff is prevented, and the temperature is suppressed from rising. Can be achieved. Further, since the swinging motion of the piston 1 is also smooth, uneven wear and seizure of the cylinder can be prevented. As a result, fuel consumption is reduced and engine life is extended.
[0038]
(Embodiment 2)
FIG. 4 is a schematic view showing a main part of an internal combustion engine piston according to Embodiment 2 of the present invention, and corresponds to a cross section AA (A in FIG. 1) of FIG. 2 shown in Embodiment 1. FIG. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
[0039]
In FIG. 1 shown in the first embodiment, the oil hole 11 in the piston head is provided to penetrate the side wall 3b of the oil ring groove 3a (the lower side in the figure, the piston pin boss 5 in the direction of the reciprocating motion of the piston). However, in the present embodiment, as shown in FIG. 4, the oil hole 11 in the piston head penetrates the groove bottom 3c of the oil ring groove 3a.
[0040]
Thus, when the piston 1 is operated, the oil ring in the oil ring groove 3a does not block the oil hole 11 in the piston head, and the lubricating oil is more reliably supplied to the oil hole in the piston head. 11 will be sent. Therefore, in addition to the effects described in the first embodiment, lubricating oil can be more reliably supplied to the piston pin holes.
[0041]
In the drawing, the oil hole 11 in the piston head is provided only from the groove bottom 3c. However, the oil hole 11 in the piston head may be provided in both the groove bottom 3c and the side wall 3b.
[0042]
Here, in the oil ring mounted on the oil ring groove 3a, a communication portion for feeding the scraped lubricating oil into the oil hole 11 in the piston head is provided. FIG. 5 is a schematic diagram for explaining a state in which oil ring 20 is mounted in oil ring groove 3a.
[0043]
In the oil ring 20 shown in FIG. 5, a pair of side rails 21 are provided so as to face the side walls of the oil ring groove 3a, respectively, and provided between the pair of side rails 21 to support these side rails 21. 2 shows an oil ring constituted by the expander 22 and the expander 22 which urges the outer diameter direction (cylinder side). The expander 22 has a lubricating oil return passage 23, and has a structure through which the lubricating oil can pass through. The lubricating oil on the cylinder wall surface 24 scraped off by the side rails 21 flows as shown by the arrow in the figure. It will be.
[0044]
(Embodiment 3)
FIG. 6 is a schematic diagram showing a main part of an internal combustion engine piston according to Embodiment 3 of the present invention, and corresponds to a cross section AA (A in FIG. 1) of FIG. 2 shown in Embodiment 1. FIG. The same components as those in the first and second embodiments are denoted by the same reference numerals, and description thereof will be omitted.
[0045]
In the present embodiment, in addition to the configuration described in the first or second embodiment, a lubricating oil reservoir 31 for accumulating lubricating oil is provided on the inner peripheral surface 4a of the piston pin hole 4, and the lubricating oil passage 10 Are communicated with the lubricating oil reservoir 31.
[0046]
As a result, the lubricating oil can always be stored in the lubricating oil reservoir 31, so that the lubrication state between the piston pin hole 4 and the piston pin can always be improved. Further, by providing the lubricating oil reservoir 31 that opens on the inner peripheral surface 4a of the piston pin hole 4, the stress can be dispersed in the piston pin hole 4 having extremely high stress, and the lubricating oil can be dispersed without being hindered by strong stress. Can be supplied. Therefore, in addition to the effects described in the first embodiment or the second embodiment, it is possible to more reliably prevent a problem such as abrasion or burn-in.
[0047]
The lubricating oil reservoir 31 preferably has a receiving portion that intersects the vertical direction and is provided so as to receive (retain) lubricating oil according to gravity. However, the present invention is not limited to this. Since the gap between the piston pin hole 4 and the piston pin is very small, the lubricating oil reservoir 31 can always store lubricating oil if it is open in the piston pin hole 4.
[0048]
【The invention's effect】
As described above, according to the present invention, lubricating oil can be supplied to the piston pin hole at a relatively high pressure, and the strength of the piston can be improved. For this reason, it is possible to reduce wear and friction loss of parts around the pin hole, and to improve fuel efficiency and performance.
[Brief description of the drawings]
FIG. 1 is a side view of a piston for an internal combustion engine according to a first embodiment of the present invention.
FIG. 2 is a bottom view of the internal combustion engine piston according to Embodiment 1 of the present invention.
FIG. 3 is a schematic diagram showing a cross section AA shown in FIG. 2 and showing a portion A in FIG. 1;
FIG. 4 is a schematic diagram showing a main part of a piston for an internal combustion engine according to a second embodiment of the present invention.
FIG. 5 is a schematic diagram showing a main part of a piston for an internal combustion engine according to a second embodiment of the present invention.
FIG. 6 is a schematic diagram showing a main part of a piston for an internal combustion engine according to a third embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 1 piston 2 piston head 2a end surface 3 piston ring groove 3a oil ring groove 3b side wall 3c groove bottom 4 piston pin hole 4a inner peripheral surface 5 piston pin boss 5a end surface 6 piston skirt 7 piston outer peripheral portion 8 sidewall 9 oil introduction pipe 10 lubricating oil Passage 11 oil hole in piston head 12 oil hole in pin boss 20 oil ring 21 side rail 22 expander 23 lubricating oil return passage 24 cylinder wall 31 lubricating oil reservoir

Claims (3)

A piston pin boss provided inside the outer peripheral edge of the piston head and having a piston pin hole through which a piston pin connecting the piston and the connecting rod is inserted,
In an internal combustion engine piston in which a side surface of a piston skirt facing the piston pin hole of the piston pin boss is cut,
The piston pin boss is connected to an end of the piston head that is substantially perpendicular to the reciprocating direction of the piston and that is an end surface on the piston pin boss side in an outer radial direction of a region where the piston skirt is cut out. A tubular portion having a lubricating oil passage formed therein, which communicates a piston ring groove provided in the piston head with the piston pin hole and supplies lubricating oil in the piston ring groove to the piston pin hole. Provided,
The piston for an internal combustion engine, wherein the tubular portion is provided to be inclined with respect to a reciprocating direction of the piston. The piston according to claim 1, wherein the lubricating oil passage communicates with a bottom of the piston ring groove. Providing a lubricating oil reservoir for storing lubricating oil on the inner peripheral surface of the piston pin hole,
The piston for an internal combustion engine according to claim 1 or 2, wherein the lubricating oil passage communicates with the lubricating oil reservoir.

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