JPH11325248A - Piston for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the scrape-down malfunction of oil during moving down a piston without complicating a piston structure, reduce the consumption amount of oil and improve a fuel cost. SOLUTION: A piston 2 for an internal combustion engine, wherein at least one piston ring 1 is mounted in a ring groove 20, is so constructed that sliding resistance between the upper face 11 of at least one piston ring 1 and the ceiling face 23 of the ring groove 20 is greater than sliding resistance between the lower face 12 of the piston ring 1 and the floor face 22 of the ring groove 20. The greater sliding resistance is achieved by forming the rough surface of the upper face 11 of the piston ring 1 or the ceiling face 23 of the ring groove 20. The sliding resistance can also be increased by forming a plurality of circumferential adjacent grooves 7 extending almost perpendicular to the radial direction of the piston 2 on the upper face 11 of the piston ring 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston of an internal combustion engine, and more particularly to a piston of an internal combustion engine by changing a sliding resistance between a piston ring and a ring groove while the piston is moving up and down.
The present invention relates to a piston of an internal combustion engine that improves fuel efficiency without increasing oil consumption.

[0002]

2. Description of the Related Art A piston of an internal combustion engine performs suction, compression, explosion, and exhaust operations in a cylinder, but gas leakage in the cylinder cannot be prevented by the piston alone. Therefore, three to four piston rings are generally mounted on the piston. The piston ring is fitted into a ring groove provided around the piston top (crown) and mounted on the piston.

[0003] The piston ring has a compression ring for maintaining gas tightness of the cylinder, preventing gas leakage into the crankcase, transmitting heat received by the piston to the cylinder liner, and an oil for lubricating the cylinder liner. (Lubricant)
There are two types of oil rings for scraping off excess oil. The oil consumption of the internal combustion engine depends on the shape and tension of the piston ring, and the force by which the piston ring tends to spread out, that is, when the tension is increased, the oil consumption of the engine is reduced, and the oil consumption of the piston ring is reduced. Reducing the tension tends to increase the oil consumption of the engine.

[0004] In recent years, one of the improvements in fuel economy of internal combustion engines is described.
As one means, there is a demand to lower the tension of the piston ring. However, as described above, when the tension of the piston ring is reduced, the effect of scraping off the oil on the cylinder wall surface is reduced, so that the oil consumption increases and the amount of HC discharged increases, resulting in an increase in emissions. There is a problem of worsening.

[0005] This problem will be described with reference to FIG. FIG.
(a) illustrates the function of the piston ring 1 when the engine is in the low to medium rotation range. As can be seen from this figure, when the piston ring 1 rises in the cylinder bore 5 with the rise of a piston (not shown), the oil 6 is scraped up by the piston ring 1, and when the piston ring 1 descends in the cylinder bore 5, the piston ring The oil is scraped down by 1. As described above, when the engine is in the low to medium rotation range, the oil 6 is sufficiently scraped down by the piston ring 1.

FIG. 1B illustrates the function of the piston ring 1 when the engine is rotating at a high speed or when the cylinder bore 5 is deformed. As can be seen from this figure, when the piston ring 1 rises in the cylinder bore 5 with the rise of a piston (not shown), the oil 6 is scraped up by the piston ring 1, but when the piston ring 1 rapidly descends in the cylinder bore 5. Then, the piston ring 1 is separated from the cylinder bore 5, and the piston ring 1 does not sufficiently scrape the oil 6 down. in this way,
When the engine is in the high rotation region or when the cylinder bore 5 is deformed, the piston ring 1 may cause the oil 6 to be poorly scraped.

In response to such a problem, the present applicant has
A piston with a mechanism that can increase the tension of the piston ring during descent compared to when the piston is ascended has been proposed.

[0008]

However, the piston provided with a mechanism that can increase the tension of the piston ring during descent rather than during ascending proposed by the present applicant,
Since it is necessary to incorporate a mechanism for varying the tension of the piston ring inside the piston, there has been a problem that the cost of the piston increases.

Therefore, the present invention is to reduce the amount of protrusion of the piston ring from the piston during the lowering of the piston without incorporating a variable piston ring tension mechanism, which causes an increase in the cost of the piston, inside the piston. It is an object of the present invention to provide a piston of an internal combustion engine that can prevent oil consumption and reduce oil consumption and improve fuel efficiency.

[0010]

The features of the present invention to achieve the above object are shown below as first to fifth inventions. A structural feature of the first invention is a piston of an internal combustion engine in which at least one piston ring is mounted around a piston in a ring groove provided in the piston.
Of the piston rings, the sliding resistance between the upper surface of at least one piston ring and the ceiling surface of the ring groove,
That is, the sliding resistance is larger than the sliding resistance between the lower surface of the piston ring and the floor surface of the ring groove.

According to a second aspect of the present invention, in the first aspect, the surface roughness of the upper surface of the piston ring or the ceiling surface of the ring groove is made larger than the surface roughness of the lower surface of the piston ring or the floor surface of the ring groove. By doing so, the sliding resistance is increased. A structural feature of the third invention is that, in the second invention, a portion for increasing the surface roughness is implemented only in a portion that prevents the piston ring from immersing in the ring groove.

A fourth aspect of the invention is characterized in that, in any one of the first to third aspects, a plurality of grooves extending in a direction substantially perpendicular to a radial direction of the piston are formed on an upper surface of the piston ring in a circumferential direction. Is formed adjacent to. A structural feature of the fifth invention is that, in the fourth invention, the grooves are formed so that the ends of the plurality of grooves do not overlap with each other.

In the first aspect of the present invention, the back pressure applied to the piston ring during the downward movement of the piston is reduced, so that the piston ring is easily separated from the cylinder bore. However, the sliding resistance between the piston ring and the piston is reduced during the downward movement of the piston. Since the piston ring is large, it is difficult for the piston ring to sink into the ring groove, and it is difficult to separate from the cylinder bore, which is equivalent to a state in which the tension of the piston ring is increased. In addition, since the sliding resistance between the piston and the piston ring during the upward movement of the piston is smaller than that at the time of the downward movement of the piston, deterioration of fuel efficiency is prevented.

In the second aspect, the effect of the first aspect can be realized only by changing the surface roughness of the piston ring or the ring groove. According to the third aspect, a region where the surface roughness of the piston ring or the ring groove is increased can be minimized. According to the fourth aspect, it is possible to easily increase or decrease the sliding resistance.

According to the fifth aspect of the present invention, it is possible to prevent gas leakage from the abutment of the piston ring.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 2A is an assembled perspective view showing an example of the configuration of the piston 2 of the internal combustion engine of the present invention. A plurality of ring grooves 20 are provided around the head of the piston 2, and the piston ring 1 is mounted in each of the ring grooves 20. Also,
The connecting rod 4 is attached to the skirt 21 of the piston 2 from below.
Is inserted and connected to the piston 2 by the piston pin 3 so as to be swingable.

The piston ring 1 includes a compression ring that maintains airtightness and prevents compression leakage and combustion gas leakage, and an oil ring that acts as an oil scraper.
Generally, the number of compression rings is two from the top (top ring and second ring), and an oil ring is attached below it. The piston ring 1 is the piston 2
In order to fit into the ring groove 20, the abutment 10 is provided in the middle instead of a ring continuous all around.

In the piston 2 constructed as described above, in the embodiment of the present invention, at least one of the piston rings 1, for example, the upper surface of the oil ring and the ceiling surface of the ring groove 20 are formed. Is greater than the sliding resistance between the lower surface of the piston ring 1 and the floor of the ring groove 20. As a method for increasing the sliding resistance, the surface roughness of the upper surface of the piston ring 1 or the ceiling surface of the ring groove 20 is determined by reducing the surface roughness of the piston ring 1.
May be made larger than the surface roughness of the lower surface of the base or the floor surface of the ring groove 20.

FIG. 2B shows a first example of the piston ring 1 shown in FIG.
FIG. 4 is a partially enlarged cross-sectional view of the piston ring 1 when the piston 2 equipped with the embodiment rises inside the cylinder bore 5. In the first embodiment, the surface roughness of the upper surface 11 of the piston ring 1 is roughened, and the surface roughness of the ceiling surface 23 of the ring groove 20 is also roughened. As a method of roughening this surface roughness, increasing the feed speed of the cutting tool,
There are methods such as corrosion of the surface and surface treatment (alumite treatment or the like).

In this manner, as shown in FIG. 2 (b), when the piston 2 is raised, the piston ring 1 is pressed against the floor surface 22 of the ring groove 20, and the piston ring 1
Of the cylinder (back pressure) P
Is added. Since the surface roughness of the lower surface 12 of the piston ring 1 and the surface roughness of the floor surface 22 of the ring groove 20 are normal, the piston ring 1 comes into close contact with the cylinder bore 5 due to the tension and the back pressure P when the piston 2 rises.

On the other hand, as shown in FIG.
Is lowered, the piston ring 1 is pressed against the ceiling surface 23 of the ring groove 20 when the pressure in the cylinder decreases. In this state, no back pressure P is applied to the back of the piston ring 1. At this time, when the descending speed of the piston 2 is high, an external force E such as flutter or resonance is applied to the piston ring 1 to draw the piston ring 1 into the ring groove 20. Due to this external force E, the piston ring 1 tries to enter the ring groove 20.

However, in the first embodiment, the surface roughness of the upper surface 11 of the piston ring 1 and the ceiling surface 23 of the ring groove 20 are different.
Are rough, the sliding resistance between the upper surface 11 of the piston ring 1 and the ceiling surface 23 of the ring groove 20 is large.
Immersion into 0 is prevented. As a result, in the piston 2 of the first embodiment, since the piston 2 descends with the piston ring 1 sufficiently protruding, the oil scraping effect of the piston ring 1 does not deteriorate.

FIGS. 3A and 3B show the second embodiment of the piston 2 of the present invention.
FIG. 3 (a) corresponds to the state of FIG. 2 (b), and FIG. 3 (b) corresponds to the state of FIG. 2 (c). Therefore, the same components are denoted by the same reference numerals, and description thereof will be omitted. The difference between the piston 2 of the second embodiment and the piston 2 of the first embodiment is that the piston 2
The surface roughness of the surface of the piston ring 1 and the surface roughness of the ceiling surface 23 of the ring groove 20 correspond to the piston ring 1 during operation of the piston 2.
Is limited only to the movement range of. That is, even if the piston ring 1 is fully immersed in the ring groove 20, FIG.
(a) and (b) move only to the position indicated by the two-dot chain line. Therefore, in the second embodiment, the surface roughness of the ceiling surface 23 at the depth of the ring groove 20 is substantially the same as that of the floor surface 22.

As a result, in the piston 2 of the second embodiment,
Since the piston 2 descends in a state where the piston ring 1 is sufficiently protruded, the effect of scraping oil by the piston ring 1 does not deteriorate. FIGS. 4 (a) and 4 (b) show a third embodiment of the piston 2 of the present invention, and FIG.
4 (b) corresponds to the state of FIG. 2 (c). Therefore, the same components are denoted by the same reference numerals, and description thereof will be omitted.

The difference between the piston 2 of the third embodiment and the piston 2 of the first embodiment is that the sliding resistance of the upper surface 11 of the piston ring 1 increases in the direction in which the piston ring 1 enters the ring groove 20. And the sliding resistance of the ceiling surface 23 of the ring groove 20 increases in the direction from the entrance side to the depth side of the ring groove 20.

With this configuration, the sliding resistance between the upper surface 11 of the piston ring 1 and the ceiling surface 23 of the ring groove 20 is:
It is small in the direction in which the piston ring 1 protrudes from the ring groove 20, and large in the direction of immersion in the ring groove 20. Therefore, in a state where the upper surface 11 of the piston ring 1 and the ceiling surface 23 of the ring groove 20 are in contact with each other, the piston ring 1 can easily protrude from the ring groove 20, but is hardly immersed in the ring groove 20. ing.

As a result, in the piston 2 of the third embodiment,
Since the piston 2 descends in a state where the piston ring 1 is sufficiently protruded, the effect of scraping oil by the piston ring 1 does not deteriorate. FIGS. 5 (a) and 5 (b) show a fourth embodiment of the piston 2 of the present invention, and FIG.
5 (b) corresponds to the state of FIG. 2 (c). Therefore, the same components are denoted by the same reference numerals, and description thereof will be omitted.

The difference between the piston 2 of the fourth embodiment and the piston 2 of the first embodiment is that the portion that increases the sliding resistance between the upper surface 11 of the piston ring 1 and the ceiling surface 23 of the ring groove 20 is as follows. The only difference is that the portion between the back surface of the piston ring 1 and the inner peripheral surface of the ring groove 20 is limited to the ceiling surface 23 of the ring groove 20. That is, the surface roughness of the ceiling surface 23 of the ring groove 20 at a portion between the back surface of the piston ring 1 and the inner peripheral surface of the ring groove 20 is rougher than other portions. Therefore, the sliding resistance when the piston ring 1 is immersed in the ring groove 20 from the state in which the piston ring 1 protrudes to the maximum from the ring groove 20 increases.

As a result, even in the piston 2 of the fourth embodiment,
Since the piston 2 descends in a state where the piston ring 1 is sufficiently protruded, the effect of scraping oil by the piston ring 1 does not deteriorate. FIG. 6 (a) shows a fifth embodiment of the piston ring 1 used for the piston 2 of the present invention. In the fifth embodiment, on the upper surface 11 of the piston ring 1,
A plurality of grooves 7 are provided side by side in the circumferential direction of the piston ring 1. Upper surface 11 of piston ring 1 at this time
FIG. 6 shows a local cross section taken along line XX of FIG.
As shown in FIG. 6 (b), it is not necessary to increase the surface roughness.
As shown in (c), the surface roughness may be higher than other parts.

As shown in FIG. 7 (a), the formation position of the groove 7 on the upper surface 11 of the piston ring 1 is substantially perpendicular to the radial direction of the piston indicated by a dashed line, and
The middle point is a portion located at substantially the center of the width of the piston ring 1. That is, the upper surface 11 of the piston ring 1 in the groove 7
May be formed along the sides of a regular polygon drawn on the piston ring 1 (a regular octagon is indicated by a two-dot chain line in FIG. 7A). The reason for this is that if the groove 7 is provided near the outer periphery or the inner periphery of the piston ring 1, the posture and the rigidity of the piston ring 1 may change.

The upper surface 11 of the piston ring 1 in the groove 7
As shown in FIG. 7 (b), the formation position in may be a circumferential groove divided into several parts. Such a groove 7
Is about 0.1 to 0.5 mm, and the depth of the groove 7 is 0.1 to 0.5 mm.
It can be about 0.2 mm. The ends of the adjacent grooves 7 do not overlap, and are not connected to the inner peripheral portion or the outer peripheral portion of the piston ring 1. Each groove 7 is an independent groove. ing.
The reason why each groove 7 has an independent structure is that the sealing property is taken into consideration. And the number of grooves 7, the depth,
The width may be changed depending on the degree of close contact between the piston ring 1 and the cylinder bore.

FIG. 8A shows a portion of the ring groove 20 of the piston 2 in which the piston ring 1 having the shape shown in FIG. 6B is incorporated, and corresponds to the state shown in FIG. I have.
Therefore, the same components are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, a plurality of grooves 8 are also provided on the ceiling surface 23 of the ring groove 20. Thus, the upper surface of the piston ring 1 and the ceiling surface 2 of the ring groove 20
3 are provided with grooves 7 and 8, respectively.
During operation, oil enters the grooves 7, 8 and the viscosity of the oil makes the piston ring 1 difficult to move. For this reason,
The sliding resistance when the piston ring 1 is immersed in the ring groove 20 increases.

FIG. 8 (b) shows a portion of the ring groove 20 of the piston 2 in which the piston ring 1 having the shape shown in FIG. 6 (c) is incorporated, and corresponds to the state of FIG. 2 (b). I have.
Therefore, the same components are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, a groove 7 is further provided on the upper surface 11 of the piston ring 1 of the first embodiment described with reference to FIGS. 2 (b) and 2 (c). Therefore, oil enters the groove 7 when the piston 2 operates, and the viscosity of the oil makes it difficult for the piston ring 1 to move. For this reason, the sliding resistance when the piston ring 1 enters the ring groove 20 becomes larger than that of the first embodiment.

As described above, also in the piston 2 of the fifth embodiment, since the piston 2 descends with the piston ring 1 sufficiently protruding, the oil scraping effect of the piston ring 1 does not deteriorate. FIG. 9 is an explanatory view for explaining the operation of the piston ring 1 in the piston 2 of the present invention when the cylinder bore 5 is not deformed, and the left half is at each part of the cylinder bore 5 of the piston ring 1 when the piston 2 rises. The right half shows the operation of each part of the cylinder bore 5 of the piston ring 1 when the piston 2 descends.

When the piston 2 rises, the piston ring 1
The piston ring 1 is in contact with the floor surface 22 of the ring groove 20 at any part of the cylinder bore 5. In this state, in addition to the tension W, the piston ring 1
The pressure (back pressure) P in the cylinder acting on the back side of the piston ring 1 is acting. Therefore, the operation of the piston ring 1 when the piston 2 is raised according to the present invention is not different from the conventional one.

On the other hand, when the piston 2 descends, the piston ring 1 is pressed against the floor surface 22 of the ring groove 20 by the pressure of the combustion gas in the cylinder in the initial stage of descending. Therefore, in this state, the back pressure P * due to the pressure of the combustion gas in the cylinder acts on the back of the piston ring 1. Therefore, piston ring 1
Is in close contact with the cylinder bore 5. Since the pressure due to the combustion gas in the cylinder decreases as the piston 2 descends, the piston ring 1 is moved from a certain position to the ring groove 20.
Is pressed against the ceiling surface 23. In this state, the back pressure P * due to the pressure of the combustion gas in the cylinder does not act on the back of the piston ring 1.

On the other hand, when the piston 2 descends, the piston ring 1 indicated by the symbol R in the right-hand view of FIG.
The force to draw in may be added. This retraction force R is
The inclination of the connecting rod, the inclination caused by the clearance between the piston pin hole and the piston pin, the inclination caused by the piston offset, the inclination caused by the center of gravity of the piston, the abnormal motion due to the inertial force or the gas pressure, the ring flutter generated when the descending speed of the piston 2 is large, , The force generated by resonance due to the swinging of the connecting rod, etc. acts as the force for moving the piston,
This occurs because it affects the piston ring 1.

In this case, in the conventional piston 2, FIG.
As described in (b), the piston ring 1 is separated from the cylinder bore 5 and poor oil scraping occurs. However, in the piston 2 of the present invention, even if the retraction force R is applied to the piston ring 1, The sliding resistance ff acting between the upper surface 11 of the ring 1 and the ceiling surface 23 of the ring groove 20 prevents the piston ring 1 from entering the ring groove 20. As a result, in the piston 2 of the present invention, poor scraping of oil when the piston 2 descends does not occur, an increase in oil consumption is suppressed, deterioration of emission is prevented, and fuel efficiency is improved.

FIG. 10 is an explanatory view for explaining the operation of the piston ring 1 in the piston 2 of the present invention when the cylinder bore 5 is deformed. The left half of the cylinder ring 5 of the piston ring 1 when the piston 2 rises. The right half shows the operation in each part of the cylinder bore 5 of the piston ring 1 when the piston 2 descends. The deformation of the cylinder bore 5 is caused by the pulling force of the head bolt when assembling the cylinder head, the thin part of the cylinder block being deformed, the cylinder block being thermally deformed, or the cylinder block being exploded in the cylinder. Of the cylinder bore, so that the central portion of the cylinder bore generally swells outward.

When the piston 2 rises when the cylinder bore 5 is deformed, the piston ring 1 is in contact with the floor surface 22 of the ring groove 20. In this state, a back pressure P acting on the back surface of the piston ring 1 is applied to the piston ring 1 in addition to the tension W. Therefore, when the piston ring 1 moves from the round portion of the cylinder bore 5 to the deformed portion, the piston ring 1 projects from the ring groove 20 by the tension W and the back pressure P, and follows the shape of the cylinder bore 5. When the piston ring 1 shifts from the deformed portion of the cylinder bore 5 to a true circular portion, the piston ring 1
, A pressing force F received from the cylinder bore 5 is applied in addition to the tension W and the back pressure P, so that the piston ring 1 sinks into the ring groove 20 and follows the shape of the cylinder bore 5.
This operation is not different from the operation of the conventional piston ring 1.

On the other hand, when the piston 2 descends, the piston ring 1 is pressed against the floor surface 21 of the ring groove 20 by the pressure of the combustion gas in the cylinder in the initial stage of descending. Therefore, in this state, the back pressure P * due to the pressure of the combustion gas in the cylinder acts on the back of the piston ring 1. Therefore, the piston ring 1 of the present invention is in close contact with the cylinder bore 5.

The state in which the back pressure P * acts on the back surface of the piston ring 1 continues for a while even when the piston ring 1 moves from the round portion of the cylinder bore 5 to the deformed portion. Therefore, the piston ring 1 projects from the ring groove 20 by the tension W and the back pressure P, and follows the shape of the cylinder bore 5. Since the pressure due to the combustion gas in the cylinder decreases as the piston 2 descends, the piston ring 1 is pressed against the ceiling surface 23 of the ring groove 20 from a certain position. In this state, the back pressure P * due to the pressure of the combustion gas in the cylinder does not act on the back of the piston ring 1. When the piston ring 1 shifts from the deformed portion of the cylinder bore 5 to a perfect circle, the piston ring 1 has a pressing force F received from the cylinder bore 5 in addition to the tension W.
Is added, the piston ring 1 sinks into the ring groove 20 against the sliding resistance ff acting between the upper surface 11 of the piston ring 1 and the ceiling surface 23 of the ring groove 20, and follows the shape of the cylinder bore 5. .

Although not shown, a retraction force R for pulling the piston ring 1 into the ring groove 20 described with reference to FIG. In this case, when the descending speed of the piston 2 is high, the inertial force generated in the piston ring 1 by the pressing force F received from the cylinder bore 5 and the retraction force R may be applied. As described in FIG. 1 (b), the piston ring 1 is separated from the cylinder bore 5 and poor oil scraping has occurred. However, in the piston 2 of the present invention, the inertia force and the retraction force R
Is applied, the sliding resistance ff acting between the upper surface 11 of the piston ring 1 and the ceiling surface 23 of the ring groove 20 prevents the piston ring 1 from entering the ring groove 20. As a result, in the piston 2 of the present invention, poor scraping of oil when the piston 2 descends does not occur, an increase in oil consumption is suppressed, deterioration of emission is prevented, and fuel efficiency is improved.

Although the behavior of one piston ring 1 has been described in the above embodiment, the number of piston rings 1 for implementing the present invention is not particularly limited.

[0045]

As described above, the catalytic converter for purifying exhaust gas of an internal combustion engine according to the present invention has the following effects. In the first aspect of the present invention, the sliding resistance between the piston ring and the piston is large during the downward movement of the piston, so that the piston ring is difficult to separate from the piston, which is equivalent to an increase in the tension of the piston ring. Since the sliding resistance between the rising piston and the piston ring is smaller than that at the time of lowering the piston, lowering the setting of the tension of the piston ring prevents deterioration of fuel efficiency.

In the second aspect, the effect of the first aspect can be realized only by changing the surface roughness of the piston ring or the ring groove. In the third aspect, the region where the surface roughness of the piston ring or the ring groove is increased can be minimized, and the cost can be prevented from increasing. According to the fourth aspect, it is possible to easily increase or decrease the sliding resistance.

According to the fifth aspect of the present invention, it is possible to prevent gas leakage from the abutment of the piston ring.

[Brief description of the drawings]

FIG. 1 (a) is a diagram illustrating a function of scraping and scraping oil of a piston ring when an engine is in a low-speed to medium-speed range, and FIG. FIG. 7 is a diagram illustrating a state in which a failure in scraping oil by a piston ring occurs during the operation.

2 (a) is an assembled perspective view showing the structure of a piston of the internal combustion engine of the present invention, and FIG. 2 (b) is a partially enlarged sectional view of the piston mounted with the piston ring of the first embodiment of FIG. , (C)
FIG. 3A is a partially enlarged cross-sectional view of the piston ring mounted with the first embodiment of the piston ring shown in FIG.

3 (a) is a partially enlarged cross-sectional view of a piston mounted with the piston ring of the second embodiment of FIG. 2 (a) when ascending, and FIG. 3 (b) is a second embodiment of the piston ring of FIG. 2 (a). It is a partial expanded sectional view at the time of descent of the piston to which the example was mounted.

4 (a) is a partially enlarged cross-sectional view of a piston mounted with the piston ring of the third embodiment of FIG. 2 (a) when ascending, and FIG. 4 (b) is a third embodiment of the piston ring of FIG. 2 (a). It is a partial expanded sectional view at the time of descent of the piston to which the example was mounted.

5 (a) is a partially enlarged sectional view of a piston mounted with the piston ring of the fourth embodiment of FIG. 2 (a) when the piston is lifted, and FIG. 5 (b) is a third embodiment of the piston ring of FIG. 2 (a). It is a partial expanded sectional view at the time of descent of the piston to which the example was mounted.

6 (a) is an enlarged perspective view showing a fifth embodiment of the piston ring of FIG. 2 (a), FIG. 6 (b) is a view showing an example of a local cross section taken along line XX of FIG. () Is a diagram showing another example of a local cross section taken along line XX of (a).

7 (a) is a plan view showing a sixth embodiment of the piston ring of FIG. 2 (a), and FIG. 7 (b) is a partial plan view of a modified embodiment of FIG. 2 (a).

FIG. 8 (a) is a partially enlarged sectional view showing a shape of a ring groove combined with a piston ring having a shape shown in FIG. 6 (b),
FIG. 7B is a partially enlarged sectional view showing the shape of a ring groove combined with the piston ring having the shape shown in FIG.

FIG. 9 is an explanatory view illustrating the operation of the piston ring in the piston of the present invention when the cylinder bore is not deformed.

FIG. 10 is an explanatory diagram illustrating the operation of the piston ring in the piston of the present invention when the cylinder bore is deformed.

[Description of Signs] 1 ... Piston ring 2 ... Piston 5 ... Cylinder bore 6 ... Oil 7,8 ... Groove 10 ... Abutment 11 ... Top surface of piston ring 20 ... Ring groove 22 ... Ring groove floor surface 23 ... Ring groove ceiling surface

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tokio Obama 14 Iwatani, Shimowasumi-cho, Nishio-shi, Aichi Japan Auto Parts Research Institute, Inc.

Claims (5)

[Claims] 1. A piston of an internal combustion engine in which at least one piston ring is mounted around a piston in a ring groove provided in the piston, wherein an upper surface of at least one of the piston rings and a top surface of the piston ring are provided. A piston for an internal combustion engine, wherein a sliding resistance between a ring groove and a ceiling surface is larger than a sliding resistance between a lower surface of the piston ring and a floor surface of the ring groove. 2. The piston according to claim 1, wherein a surface roughness of an upper surface of the piston ring or a ceiling surface of the ring groove is larger than a surface roughness of a lower surface of the piston ring or a floor surface of the ring groove. A piston for an internal combustion engine, wherein the sliding resistance is increased. 3. The internal combustion engine according to claim 2, wherein the portion that increases the surface roughness is implemented only in a portion that prevents the piston ring from immersing in the ring groove. piston. 4. The piston according to claim 1, wherein a plurality of grooves extending in a direction substantially perpendicular to a radial direction of the piston are circumferentially adjacent to an upper surface of the piston ring. A piston for an internal combustion engine characterized by being formed by: 5. The piston according to claim 4, wherein the grooves are formed such that ends of the plurality of grooves do not overlap with each other.