JP2575465Y2 - Ring land structure of piston - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston structure of an internal combustion engine, and more particularly, to a reduction in wear of a ring / liner and a reduction in stress of a boss portion in a piston having an FCD (spheroidal graphite cast iron) integrated structure. It is intended.

[0002]

2. Description of the Related Art The prior art is shown in FIGS. As shown in FIGS. 9 to 15, the thickness of the back portion of the first ring is conventionally configured to be constant in the circumferential direction. That is, in a normal engine other than a cogeneration engine, the load fluctuation is relatively large, and the thermal load and thermal deformation of the piston also vary greatly. As a result, the deformation state of the piston changes, so that the wear shape of the ring sliding surface is naturally formed in an arc shape. As a result, the amount of wear on the ring and liner was also small.

FIG. 9 is a side sectional view showing a ring land structure of a conventional piston, and FIG. 10 is a view showing the inclination of a lower surface 4a of a first ring groove in a cross section perpendicular to a pin axis when the conventional piston is thermally deformed during operation. FIG. 11 is a side view showing a state of a load applied to a piston top surface 5 of a conventional piston in a pin axial section and a section perpendicular to a pin, and FIG. 12 is a conventional lower surface of a first ring groove and an inner surface of a liner at a top dead center of explosion. , FIG. 13 is a conventional drawing showing the angle between the sliding surface of the first ring and the inner surface of the liner when gas pressure is not applied, and FIG. 14 is a cross-sectional view of a conventional piston pin shaft. FIG. 15 is a plan view showing that the wall thickness 1 near the pin and the wall thickness 2 near the cross section perpendicular to the pin are the same, and FIG. 15 shows a conventional structure which is used in a cogeneration engine and which is operated at a constant rotational load. Minimum oil film thickness in a state in which the state and the acute angle profile the Le is a diagram showing that very small.

Conventionally, as shown in FIG. 9, the thickness tP of the thick portion 1 near the cross section of the pin axis and the thickness tT of the thick portion 2 near the cross section perpendicular to the pin have the same thickness. is there. Therefore, as shown in FIG. 10, the ring groove lower surface 4a of the first ring groove 4 when the piston is thermally deformed during operation.
Is the same as the angle θP, which is the inclination angle of the angle. Also, as shown in FIG.
Is also mostly applied to the inner boss 8. Further, as shown in FIG. 12, near the top dead center of the explosion, the angle of the ring groove lower surface 4a of the first ring groove 4 in a state where the piston is deformed was "angle θP = angle θP". Therefore, in FIG. 13 in which the gas pressure is not acting, in FIG. 13, the angle θP ′ and the angle θT ′ between the inner surface of the liner and the cross section of the tip of the first ring 7 when the first ring 7 returns to the horizontal state by the elastic force. Was also the same.

As shown in FIG. 14, conventionally, the thickness tT and the thickness tP of the thick portion 1 near the cross section of the pin axis are the same, so that the angle θT ′ which is the wear angle of the tip of the first ring 7 is shown.
And the angle θP ′ becomes substantially the same, and even if the first ring 7 rotates 360 ° with the operation of the engine, the first ring 7 always comes into contact with the inner surface of the liner at the same angle, and the tip shape is not the arc-shaped profile 7b. This is the sharp profile 7a. Due to the acute angle profile, the oil film layer on the inner surface of the liner 9 was severely scraped, the minimum oil film thickness was reduced, and the ring and liner were severely worn. Further, the in-cylinder pressure load on the piston top surface 5 was applied only to the inner boss 8, and the inner boss portion was in an overloaded state.

[0006]

As described above, in the case of an engine such as a cogeneration engine which is operated for a long time at a constant rotation and a constant load, the deformation state of the piston is always constant, so that the ring sliding surface profile is constant. This tends to be tapered, making it difficult to form an oil film and increasing the wear of the ring and the liner 9. The present invention combines the wear mechanism of the ring sliding surface and the characteristics of the ring rotation with the change in the circumferential direction of the piston deformation, so that even in the case of a cogeneration engine under constant rotation and constant load,
The configuration is such that an arc-shaped profile advantageous for oil film formation can be automatically formed. Further, in the conventional piston structure, the transmission of the in-cylinder pressure load at the top of the piston to the pin is concentrated on the inner boss, resulting in excessive stress. The present invention also solves this problem.

[0007]

The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described. FCD integrated structure with cooling cavity
From the first ring 7 of the piston
The thickness of the ring land portion is set to the thick portion 1 near the pin axis section.
Thickness tP, the thickness of the thick portion 2 near the cross section perpendicular to the pin
tT is made thin, and the thickness tT and the thickness t are set along the circumferential direction.
P is gradually changed .

[0008]

Next, the operation will be described. The angle of the ring groove lower surface 4a of the first ring groove 4 is deformed at the time of load operation, and the angle θP of the pin shaft cross-section side at the time of this deformation is an angle of the pin right-angle cross section side because of the thick rigidity and large rigidity. It is smaller than θT. Thus, the angle θP on the pin shaft cross-section side,
When the first ring 7 rotates on the circumference of the piston along with the operation of the engine due to the difference in the angle θT on the cross section side perpendicular to the pin, the wear shape of the ring sliding surface 7a naturally becomes circular as shown in FIG. It is formed in an arc shape.

[0009]

Next, an embodiment will be described. FIG. 1 is a side cross-sectional view showing the ring land structure of the piston of the present invention, and FIG. 2 is a cross-sectional view of the piston of the present invention showing the inclination of the first ring sliding surface 4a when thermally deformed during operation. FIG. 3 is a side view showing the state of the load on the piston top surface 5 of the piston according to the present invention in the pin axis section and the section perpendicular to the pin, and FIG. FIG. 5 is a view showing the angle of inclination between the right-angled surface, FIG. 5 is a view showing the angle between the first ring sliding surface and the inner surface of the liner when gas pressure is not acting, and FIG. FIG. 7 is a plan view showing a state in which a wall thickness 1 and a wall thickness 2 near a pin perpendicular section are different, and FIG. 7 is a drawing showing a state in which the ring tip gradually becomes an arc-shaped profile as the ring rotates around the piston. 8 is the arc-shaped professional It illustrates a variation of the oil film thickness in a state in which it became the Iru.

Referring to FIG. That is, in a piston of an engine used for a cogeneration engine or the like, the thickness of the thick portion 1 on the back side of the first ring groove 4 near the pin shaft cross section, which is a cross section in the direction along the piston pin insertion hole 3 in the present invention. The thickness tP is set to be larger than the thickness tT of the thick portion 2 in the section perpendicular to the pin. Actually, as shown in FIG. 6, the thickness tT and the thickness tP gradually change along the circumferential direction.

With this configuration, the angle of the ring groove lower surface 4a of the first ring groove 4 is deformed by the amount of thermal deformation at the time of load operation. , Is smaller than the angle θT on the section perpendicular to the pin. Thus, the angle θP on the pin shaft cross-section side
And the angle θT on the section perpendicular to the pin is different,
When the first ring 7 rotates on the circumference of the piston along with the operation of the engine, the wear shape of the ring sliding surface 7a naturally forms an arc shape as shown in FIG.

3 and 6, the piston top 5
Will be described. According to the conventional piston structure, the transmission of the in-cylinder pressure load of the piston top surface 5 to the pin is concentrated on the inner boss 8, and the inner boss 8 has excessive stress. The present invention can solve this problem. That is, conventionally, the thickness tP and the thickness tT of the thick portion 1 near the pin shaft cross section and the thick portion 2 near the pin perpendicular cross section were the same, and the thickness was thin. They received less. In the present invention, the thick portion 1 near the pin axis cross section is replaced with the thick portion 2 near the pin perpendicular cross section.
By making the part thicker than the part, the excessive stress state on the inner boss 8 part can be eliminated.

FIG. 4 shows the state of the first ring 7 near the top dead center of the explosion. The thick portion 1 near the pin axis cross section has a large thickness tP, so that the deformation amount is small, and the thick portion 2 near the pin perpendicular cross section has a thickness tT.
Is thin, the amount of deformation is large, and the angle θP <the angle θT, which is the inclination angle of the lower surface 4a of the first ring groove, is satisfied. FIG. 5 shows a case where the gas pressure is not acting. In this case, the first ring 7 returns to the horizontal state by the elastic force, and the inner wall of the liner 9 and the first ring 7
Are the angles θP ′ and θT ′. Also in this case, the state of “angle θP ′ <angle θT ′” is maintained.

Next, FIG. 7 will be described. As shown in FIG. 6, in the circumference of the piston, the thickness tP is greater than the thickness tT in the portion of the thick portion 2 near the section perpendicular to the pin, so that the angle θP <the angle θT is satisfied. Angle θ
As the first ring 7 rotates in accordance with the operation of the engine on the circumference where the angle T and the angle θP are different, as shown in FIG. 7, the leading end surface of the first ring 7 has two stages of the angle θP ′ and the angle θT ′. Are repeated to form an arc-shaped profile.

Next, FIG. 8 will be described. In this way, by forming the cross-sectional shape of the outer peripheral surface at the distal end of the first ring 7 into the arc-shaped profile 7b instead of the acute-angled profile 7a, the inner surface of the liner 9 and the arc-shaped profile as shown in FIG. Even if it makes contact, the action of scraping off the oil film surface becomes moderate, the minimum oil film thickness can be left large, and the wear of the ring and the liner 9 can be reduced.

[0016]

[Effects of the Invention] The present invention is constructed as described above, and has the following effects. First, the first ring sliding surface is pressed against the lower surface of the groove by the gas pressure near the top dead center of the explosion, and is worn by the inner surface of the liner 9. For this reason, if the thickness of the first ring groove 4 is changed as in the present invention, the lower surface angle of the first ring groove changes in the circumferential direction due to thermal deformation or in-cylinder pressure deformation during operation, and the ring slides. The taper angle, which is the wear shape of the moving surface, also changes in the circumferential direction. Since the ring rotates around the piston during operation, the ring sliding surface is formed in an arc shape, an oil film is easily formed, and the wear of the ring and the liner is reduced.

Second, by increasing the wall thickness in the vicinity of the cross section of the pin shaft, the internal pressure load on the top surface is dispersed to the inner boss and the back of the ring and transmitted to the pin, so that the boss stress is also reduced. Because

Third, in the case of a cogeneration engine, if a piston having a conventional structure is used, the LOC and blow-by performance tends to deteriorate in a short time due to rapid wear of the ring and the liner. Frequently or the life of the engine is shortened, and the durability required for the cogeneration engine is not satisfied. This problem can be solved by the piston of the present invention.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a ring land structure of a piston according to the present invention.

FIG. 2 is a drawing showing the inclination of the lower surface 4a of the first ring groove in the cross section perpendicular to the pin axis and the pin axis of the piston of the present invention.

FIG. 3 is a side view showing a state of the load on the piston top surface 5 of the piston according to the present invention in a cross section perpendicular to a pin axis and a cross section perpendicular to the pin;

FIG. 4 is a drawing showing an inclination angle between a lower surface of a first ring groove and a surface perpendicular to an inner surface of a liner at a top dead center of an explosion.

FIG. 5 is a view showing an angle between a first ring sliding surface and an inner surface of a liner in a state where gas pressure is not acting.

FIG. 6 is a plan view showing a state in which a thickness 1 near a pin axis cross section and a thickness 2 near a pin perpendicular cross section of the piston of the present invention are different.

FIG. 7 is a drawing showing a state in which the tip of the ring gradually becomes an arc-shaped profile as the ring rotates around the piston.

FIG. 8 is a drawing showing a change in oil film thickness in the state of the arc-shaped profile.

FIG. 9 is a side sectional view showing a ring land structure of a conventional piston.

FIG. 10 is a view showing a tilt due to thermal deformation during operation of a first ring groove lower surface 4a in a cross section perpendicular to a pin axis and a cross section of a conventional piston.

FIG. 11 is a side view showing a state of a load applied to a piston top surface 5 of a conventional piston in a pin axial section and a section perpendicular to the pin.

FIG. 12 is a drawing showing a tilt angle between a lower surface of a first ring groove and a surface perpendicular to an inner surface of a liner at a conventional top dead center of explosion.

FIG. 13 is a drawing showing the angle between the sliding surface of the first ring and the inner surface of the liner in the state where the conventional gas pressure is not acting.

FIG. 14 is a plan view showing that the thickness 1 near the pin axis cross section and the thickness 2 near the pin perpendicular cross section of the conventional piston are the same.

FIG. 15 shows a conventional structure in which a minimum oil film thickness is extremely small when the ring end has an acute profile and an acute profile when used in a cogeneration engine and operated at a constant rotational load. FIG.

[Explanation of symbols]

 1 Thick portion near pin shaft cross section 2 Thick portion near pin perpendicular cross section 3 Piston pin insertion hole 4 First ring groove 4a First ring groove lower surface 5 Piston top surface 7 First ring 7a Sharp profile 7b Arc profile 8 Inside Boss of 9 Liner

Claims (1)

(57) [Scope of request for utility model registration] 1. An FCD-integrated structure having cooling cavities.
At the piston, below the first ring 7 of the piston.
Adjust the thickness of the ring land part to the thickness of the thick part 1 near the pin axis cross section.
Thickness tP, the thickness tT of the thick portion 2 near the cross section perpendicular to the pin.
Are thinned, and the thickness tT and the thickness tP are set along the circumferential direction.
Ring land structure of piston characterized by gradually changing .