JPH09177603A - Piston structure of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the consumption of the lubricating oil and the amount of the blow-by gas by arranging two horizontal bosses to connect an outer edge part of a piston pin boss to a piston skirt from a center of a pin boss to its upper part, and to connect the lower part of the pin boss and the lower part of the skirt in a piston. SOLUTION: In a piston 1 to be cast of ductile cast iron, two horizontal bosses (a) to connect an outer edge part of a pin boss (p) to a piston skirt 1s are arranged from the center of the pin boss (p) toward upper and lower parts. One horizontal boss (a) is provided between the center and the upper part of the pin boss (p) in a similar manner to the conventional design, and another horizontal boss (b) is provided so as to connect the lower part of the pin boss (p) to the lower part of the skirt 1s. The rigidity is improved by providing the horizontal bosses a, b so as to be connected to circumferential ribs of the skirt 1s. Deformation of the piston 1 is suppressed, and the consumption of the lubricating oil and the amount of the blow-by gas is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for casting a piston of an internal combustion engine with ductile cast iron.

[0002]

2. Description of the Related Art Conventionally, a technique relating to a piston structure of an internal combustion engine made of cast metal has been known. For example, it is like the technique described in Japanese Utility Model Laid-Open No. 63-74560.

[0003]

In the prior art, the lateral boss of ductile cast iron is provided at one place from the center of the pin boss p to the upper part. However, in this configuration, the rigidity of the lower portion of the piston skirt 1s is small,
When the slap force is applied, the deformation becomes excessive, the swinging becomes large, and the generation rate of lubricating oil consumption in which the lubricating oil is supplied to the combustion chamber and burned increases, and this also increases the generation of blow-by gas. It was. Also, since the piston skirt 1s is supported only from the center to the upper side against the thrust force, there is a problem that the surface pressure becomes excessive and seizure easily occurs. Claim 1 of the present invention
Reduces lubricating oil consumption and blow-by gas, and prevents piston seizure.

Further, in the prior art, the lateral boss f is provided in the range from the upper part to the center of the piston skirt 1s. Therefore, the rigidity of the lower part of the piston skirt 1s is small, and when the slap force is applied, the deformation becomes excessive, the swinging becomes large, and the consumption of lubricating oil and the generation of blow-by gas increase. Further, since the thrust force is supported only from the center to the upper part of the skirt, there is a problem that the surface pressure becomes excessive and seizure easily occurs.
Claim 2 of the present invention improves these.

Further, in the prior art, the thickness of the piston skirt portion of the ductile cast iron piston was uniform in the circumferential direction. However, in this case, the thrust section, which is highly effective in supporting the piston when the slap force is applied, and the pin section, which is not so effective, have the same thickness, and the structure does not have proper rigidity. For this reason, if the skirt wall pressure is thin, the rigidity near the thrust cross section is insufficient, and if it is thick, the weight becomes excessive. According to the third aspect of the present invention, the weight of the ductile cast iron piston 1 is reduced, the consumption of lubricating oil is reduced, and seizure is prevented.

Further, in the conventional piston made of ductile cast iron, the circumferential rib of the skirt portion has a constant height in all circumferential directions. However, in such a conventional configuration, the circumferential rib stress when the slap force is applied becomes excessive in the thrust cross section, and there is a risk of cracking in terms of strength. In addition, there is a problem that the skirt is greatly deformed in the thrust cross section when subjected to the slap force. Claim 4 of the present invention improves on this point.

Further, in the prior art, the skirt of the ductile cast iron piston is joined only at the upper and lower parts of the pin boss, and not near the center of the pin boss. However, in such a configuration, the skirt of the thrust cross section is excessively deformed when it receives a slap force, and the large deformation causes a large swing of the piston, resulting in a large amount of lubricating oil consumption and blow-by gas. There was. Claim 5 of the present invention improves this point.

[0008]

The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described. According to a first aspect of the present invention, in a configuration in which a piston of an internal combustion engine is cast by ductile cast iron, a lateral boss that connects an outer edge portion of a piston pin boss and a piston skirt is arranged from a center of the pin boss to an upper portion, and a lower portion of the piston pin boss and a lower portion of the skirt are arranged. It is provided in two places to connect.

According to a second aspect of the present invention, in the structure in which the piston of the internal combustion engine is cast and formed from ductile cast iron, the range in the height direction of the lateral boss that connects the outer edge of the piston pin boss and the piston skirt is from the upper part of the skirt to the lower part of the skirt. It has a wide area and is connected to the lateral boss at the bottom of the skirt and the circumferential ribs at the bottom of the skirt.

According to a third aspect of the present invention, in the structure in which the piston of the internal combustion engine is cast by ductile cast iron, the thickness of the piston skirt is thick between the thrust section and the lateral boss, and between the lateral boss and the pin axis section. It is configured to have an uneven thickness in the circumferential direction so as to be thin.

According to a fourth aspect of the present invention, in the structure in which the piston of the internal combustion engine is cast by ductile cast iron, the cross-sectional shape of the circumferential rib of the piston skirt changes in the circumferential direction such that it is low in the thrust cross section and high in the lateral boss position. It was made.

According to a fifth aspect of the present invention, in a structure in which the piston of the internal combustion engine is cast and formed by ductile cast iron, the piston skirt can be joined almost all around the pin boss, and the circumferential rib of the piston skirt can be joined to the pin boss. In addition, a plurality of piston skirts are arranged from the top to the bottom.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described. FIG. 1 is a cross-sectional plan view showing a configuration in which horizontal bosses are vertically arranged at two positions a and b, and FIG.
FIG. 3 is a vertical cross-sectional view showing the structure arranged at two positions of b. In FIG. 3, the range of the horizontal boss connecting the outer edge of the piston boss and the piston skirt in the height direction is wide from the upper part of the skirt to the lower part of the skirt. FIG. 4 is a vertical cross-sectional view of an embodiment in which the lateral boss is connected to the lower circumferential rib of the skirt. FIG. 4 shows that the thickness of the piston skirt is thick between the thrust cross section and the lateral boss, and thin between the lateral boss and the pin shaft cross section. So that
FIG. 5 is a vertical cross-sectional view of an embodiment in which the thickness is uneven in the circumferential direction, and FIG. 5 is a plan cross-sectional view of FIG.

FIG. 6 is a longitudinal sectional view of an embodiment in which the sectional shape of the circumferential rib of the piston skirt is changed in the circumferential direction so that it is low at the thrust cross section and high at the lateral boss position, and FIG. 7 is a plan cross section of FIG. FIG. 8 is a longitudinal sectional view showing the prior art in the technologies of FIGS. 1 to 7, FIG. 9 is a plan sectional view of the prior art of FIG. 8, and FIG. 10 is a piston skirt joined around almost the entire circumference of a pin boss. In addition, a plurality of circumferential ribs of the piston skirt are arranged from the upper part to the lower part of the piston skirt height so that they can be joined to the pin boss. 12 is a drawing showing a conventional technique with respect to the technique of FIGS. 10 and 11, and FIG. 13 is a plan sectional view of FIG.

FIG. 14 is a plan view showing the inner cut ring in the piston ring, in which the cut amount of the cut portion 2a is large on the mating side A and small on the opposite mating side B,
15 is a side sectional view of the same, FIG. 16 is a front sectional view showing a state in which the inner cut ring is deformed, and FIG. 17 is another example in which the cut amount is large on the mating side A and small on the mating side B. 18 is a front sectional view showing the change in the twist amount in the circumferential direction, FIG. 19 is a plan view showing a conventional structure of the inner cut ring, FIG. 20 is a front sectional view of the conventional inner cut ring, and FIG. It is a front sectional view showing a deformed state of a conventional inner cut ring.

The invention of claim 1 will be described with reference to FIGS. 1 and 2. A surface forming a combustion chamber with the cylinder is arranged on the upper surface of the piston 1, and a piston ring groove w into which a piston ring is fitted and an oil ring groove x into which an oil ring is fitted are formed on the entire circumference of the side surface. Has been done. The piston 1 below the pin boss p is called a piston skirt 1s. The portion of the pin boss p is a portion into which the piston pin is fitted. A connecting rod is pivotally connected to the piston pin.

Conventionally, as in the prior art shown in FIGS. 8 and 9, the lateral boss f of ductile cast iron is provided at one place from the center of the pin boss p to the upper part. However, in this structure, the rigidity of the lower portion of the piston skirt 1s is small, the deformation becomes excessive when the slap force is applied, the swinging becomes large, and the lubricating oil is supplied to the combustion chamber and the amount of lubricating oil consumed is increased. The generation rate was high, and as a result, the generation of blow-by gas was large. Also, since the piston skirt 1s is supported only from the center to the upper side against the thrust force, there is a problem that the surface pressure becomes excessive and seizure easily occurs.

According to the present invention, the lateral boss that connects the outer edge portion of the piston pin boss and the piston skirt is arranged from the center of the pin to the upper part, and is provided at two locations to connect the lower part of the piston boss and the lower part of the skirt. That is, in the structure of the piston made of ductile cast iron, the lateral boss that connects the pin boss p and the skirt 1s is hung on the upper center of the pin boss p, and one lateral boss a is provided as in the conventional case. In addition to this, one lateral boss b is provided so as to connect the lower part of the pin boss p and the lower part of the skirt 1s, and the lateral bosses a and b are provided at a total of two positions. Each horizontal boss a
・ B is connected to the circumferential rib of the skirt 1s to increase the rigidity.

Next, referring to FIG. 3, the invention of claim 2 will be described. In the conventional technique shown in FIGS. 8 and 9, the lateral boss f is provided in the range from the upper part to the center of the piston skirt 1s. Therefore, the rigidity of the lower part of the piston skirt 1s is small, and when the slap force is applied, the deformation becomes excessive, the swinging becomes large, and the consumption of lubricating oil and the generation of blow-by gas increase. Further, since the thrust force is supported only from the center to the upper part of the skirt, there is a problem that the surface pressure becomes excessive and seizure easily occurs. Claim 2 of the present invention improves these.

That is, the range in the height direction of the lateral boss c that connects the outer edge portion of the pin boss p and the piston skirt 1s is made wide from the upper portion of the skirt 1s to the lower portion of the skirt 1s,
At the lower part of the skirt 1s, the lateral boss c is connected to the circumferential skirt lower rib s.

Next, referring to FIGS. 4 and 5, the invention of claim 3 will be described. In the prior art shown in FIGS. 8 and 9, the thickness of the piston skirt portion of the ductile cast iron piston was uniform in the circumferential direction. However, in this case, the thrust section, which is highly effective in supporting the piston when the slap force is applied, and the pin section, which is not so effective, have the same thickness, and the structure does not have proper rigidity. For this reason, if the skirt wall pressure is thin, the rigidity near the thrust cross section is insufficient, and if it is thick, the weight becomes excessive.

According to the third aspect of the present invention, the weight of the ductile cast iron piston 1 is reduced, the consumption of lubricating oil is reduced, and seizure is prevented. That is, piston skirt 1
In the cross-sectional view in the thrust direction shown in FIG. 5, the wall thickness of s is a thick skirt d between the normal lateral bosses f and the angle β between f, and the lateral boss f and the pin boss p-axis cross section are formed. The space is formed to have a thin walled skirt e with uneven thickness in the circumferential direction.

Next, the fourth aspect of the present invention will be described with reference to FIGS. 6 and 7. In the prior art shown in FIGS. 8 and 9, the circumferential rib of the skirt portion has a constant height in all circumferential directions. However, in such a conventional configuration, the circumferential rib stress when the slap force is applied becomes excessive in the thrust cross section, and there is a risk of cracking in terms of strength. In addition, there is a problem that the skirt is greatly deformed in the thrust cross section when subjected to the slap force. Claim 4 of the present invention improves on this point.

In the fourth aspect, the sectional shape of the skirt circumferential rib 1f of the piston skirt is a sectional view in the direction in which the thrust force is applied as shown in FIG. 7, in which the lateral boss f is connected to the skirt lower circumferential rib s. It is configured such that the cross section of the portion g is high and the height is low at a position between the horizontal bosses f.

Next, the invention of claim 5 will be described with reference to FIGS. 10 and 11. In FIG. 12 and FIG. 13 which are conventional techniques, the piston skirt 1s is joined only at the upper and lower portions of the pin boss, and the vicinity of the center of the pin boss is not joined. However, in such a configuration, the skirt of the thrust cross section is excessively deformed when it receives a slap force, and the large deformation causes a large swing of the piston, resulting in a large amount of lubricating oil consumption and blow-by gas. There was. Claim 5 of the present invention improves this point.

In claim 5, the piston skirt 1
s is joined almost all around the pin boss, and the circumferential rib k of the piston skirt is hung from the upper part to the lower part of the piston skirt height so that it can be joined to the pin boss p.
A plurality of circumferential ribs k of the piston skirt portion and lower circumferential ribs s of the skirt are arranged.

Next, referring to FIG. 19, FIG. 20, and FIG. 21, description will be given of the problems of the conventional art of the inner cut ring 2. Conventionally, the cut amount of the cut portion 2a has been configured to be uniform over the entire circumference. That is, the cut width Ta on the abutment side A and the cut width Tb on the opposite abutment side B are the same, the cut height Ha on the abutment side A and the cut height on the opposite side B. Hb is also the same. Therefore, the twist angle Ga on the mating side A of the inner cut ring is small, and the twist angle Ga is small on the mating side B.
Since the inner cutting ring has a large twist angle Gb, the inner cut ring is wavy, so that in an engine with a low cylinder pressure, the ring cannot be restrained on the lower surface, resulting in deterioration of gas sealing property and oil scratching property, and consumption of lubricating oil. The problem was that the amount and blow-by gas increased.

In the present invention, the cut amount of the cut portion 2a is increased on the mating side A where the twist amount is small so that the twist amount is increased and the twist amount is uniform in the circumferential direction. Is. As a result, the undulation of the lower surface of the ring is eliminated, the inner surface of the lower surface uniformly contacts the ring groove, the gas sealability and the oil scraping performance are improved, and the consumption of blow-by gas and lubricating oil can be reduced.

In the configuration shown in FIGS. 14, 15 and 16,
The cut width Ta on the mating side A side is configured to be larger than the cut width Tb on the opposite mating side B side. The cut height Ha on the side of the facing side A and the cut height Hb on the side of the opposite side B are the same. By configuring in this way, the abutment side A
The twist angle Ga on the side and the twist angle Gb on the opposite side B are substantially the same.

In the configurations shown in FIGS. 17 and 18, the cut height Ha on the side of the mating side A is larger than the cut height Hb on the side of the opposite mating side B. In this case, the cut width Ta on the facing side A and the cut width Tb on the opposite side B are the same. As a result, the twist angle Ga on the side of the mating side A and the twist angle Gb on the side of the opposite mating side B become substantially the same. FIG. 18 shows a comparison between the conventional technique and this configuration. The line showing the amount of twist of the prior art is M, and the line showing the amount of twist of the present invention is N.

[0031]

As described above, the present invention has the following advantages. According to the first and second aspects, the rigidity of the lower portion of the piston skirt 1s is improved, so that swinging at the time of slap can be reduced, so that the ring sealing performance is improved, the blow-by gas is reduced, and the lubrication by preventing the liner polish is performed. Oil consumption can be reduced. Also, since the thrust force is supported on the entire skirt,
It is possible to prevent seizure of the piston skirt 1s due to excessive surface pressure.

According to the third aspect of the present invention, since the lateral boss only has a large rigidity due to the thrust cross section that greatly affects the piston support when a slap force is applied, an effective wall thickness arrangement and a large rigidity are achieved. However, the weight increase can be suppressed to the minimum. In addition, the skirt deformation when slap force acts is small, so the swing of the piston is reduced,
The skirt surface pressure can be made uniform to reduce the consumption of lubricating oil and prevent seizure.

According to the fourth aspect of the invention, the stress of the skirt lower circumferential rib s, which greatly affects the increase of the piston rigidity when receiving the slap force, can be made uniform to avoid excessive stress. . Further, the deformation of the thrust cross section of the skirt when subjected to the slap can be reduced without increasing the weight.

According to the fifth aspect of the present invention, the swing of the piston 1 at the time of slap is reduced by increasing the rigidity of the skirt. Also, by reducing the swinging, the gas sealing performance of the top link is improved and the ring behavior becomes stable. Also, if the top link behavior is stable, the consumption of lubricating oil and blow-by gas can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan cross-sectional view showing a configuration in which horizontal bosses are vertically arranged at two positions a and b.

FIG. 2 is a vertical cross-sectional view showing a configuration in which horizontal bosses are similarly arranged at two locations, a and b, vertically.

FIG. 3 is an embodiment in which the horizontal boss connecting the outer edge of the piston boss and the piston skirt has a wide range in the height direction from the upper part of the skirt to the lower part of the skirt, and at the lower part of the skirt, the lateral boss and the circumferential rib of the lower part of the skirt are connected. FIG.

FIG. 4 is a longitudinal section of an embodiment in which the thickness of the piston skirt is thick between the thrust cross section and the lateral boss, and thin between the lateral boss and the pin shaft cross section in the circumferential direction. Face view.

FIG. 5 is a plan sectional view of FIG.

FIG. 6 is a vertical cross-sectional view of an embodiment in which the cross-sectional shape of the circumferential rib of the piston skirt is changed in the circumferential direction so that the thrust rib has a low cross section and the lateral boss position has a high cross section.

FIG. 7 is a plan sectional view of FIG.

FIG. 8 is a vertical sectional view showing a conventional technique in the technique of FIGS. 1 to 7;

FIG. 9 is a plan sectional view of the related art shown in FIG.

FIG. 10 is an embodiment in which a plurality of piston skirts are arranged from the upper part to the lower part of the piston skirt height so that the piston skirt can be bonded almost all around the pin boss and the circumferential ribs of the piston skirt can be bonded to the pin boss. FIG.

11 is a plan sectional view of FIG.

FIG. 12 is a view showing a conventional technique with respect to the technique of FIGS. 10 and 11;

13 is a plan sectional view of FIG.

FIG. 14 is a plan view showing a structure in which an inner cut ring in a piston ring has a large amount of cut at a cut portion 2a on a mating side A and a small amount on an opposite mating side B;

FIG. 15 is a side sectional view of the same.

FIG. 16 is a front sectional view showing a state where the inner cut ring is deformed.

FIG. 17 is a front sectional view showing another example in which the cut amount is large on the mating side A and small on the opposite mating side B.

FIG. 18 is a drawing showing changes in the twist amount in the circumferential direction.

FIG. 19 is a plan view showing a conventional structure of an inner cut ring.

FIG. 20 is a front sectional view of a conventional inner cut ring.

FIG. 21 is a front sectional view showing a deformed state of a conventional inner cut ring.

[Explanation of symbols]

 1 piston 1s piston skirt a, b, c, f lateral boss d thick skirt e thin skirt p pin boss skirt lower circumferential rib 1f circumferential rib

Claims (5)

[Claims] 1. In a structure in which a piston of an internal combustion engine is cast and formed from ductile cast iron, a lateral boss that connects an outer edge portion of a piston pin boss and a piston skirt is arranged from a center of the pin boss to an upper portion, and a lower portion of the piston pin boss and a lower portion of the skirt are arranged. A piston structure for an internal combustion engine, which is provided in two places for connection. 2. In a structure in which a piston of an internal combustion engine is cast-molded by ductile cast iron, a lateral boss connecting an outer edge portion of a piston pin boss and a piston skirt has a wide range in a height direction from an upper part of the skirt to a lower part of the skirt. The piston structure of the internal combustion engine is characterized in that the lower part is connected to the lateral boss and the circumferential rib of the lower part of the skirt. 3. A piston of an internal combustion engine is cast-molded from ductile cast iron, wherein the thickness of the piston skirt is thick between the thrust section and the lateral boss and thin between the lateral boss and the pin shaft section. In addition, a piston structure of an internal combustion engine, characterized in that it has a wall thickness unevenness in the circumferential direction. 4. In a structure in which a piston of an internal combustion engine is cast-molded from ductile cast iron, the cross-sectional shape of the circumferential rib of the piston skirt is changed in the circumferential direction so that it is low in the thrust cross section and high in the lateral boss position. Characteristic internal combustion engine piston structure. 5. A piston for an internal combustion engine, wherein the piston is cast and formed from ductile cast iron, the piston skirt is joined almost all around the piston pin boss, and the circumferential rib of the piston skirt portion is joined to the pin boss. A piston structure for an internal combustion engine, wherein a plurality of skirts are arranged from the top to the bottom of the skirt height.