JPH0542661U - Piston for internal combustion engine - Google Patents

Abstract

(57) [Summary] [Purpose] The function of sealing the compression piston ring and the inner wall of the cylinder is improved, and the infiltration of combustion gas into the back clearance is minimized to prevent the unburned air-fuel mixture discharged outside the combustion chamber. To provide a piston for an internal combustion engine capable of reliably reducing the amount. A compression ring groove 23 is formed on the outer peripheral portion of the piston body 21 while leaving the top land portion 22, and the outer periphery of the top land portion 22 and the inner wall 25a of the cylinder 25 are formed.
A gap 28 having a predetermined width is formed between the compression piston ring 26 and the top land portion 22 so as to straddle the gap 28.
The upper and lower leg portions 26b and 26c of the cylinder 25 are located inside the combustion chamber 25b of the cylinder 25 and inside the compression ring groove 23, respectively.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 This invention relates to a piston for an internal combustion engine.

[0002]

[Prior Art]

 As a conventional piston for an internal combustion engine, for example, the one disclosed in Japanese Patent Publication No. 60-32359 is known. According to this piston for an internal combustion engine, as shown in FIGS. 5 and 6, the crown surface 2 of the piston body 1 is smoothly lowered from the center thereof toward the top land 3 side, and is lowered from the piston crown surface 2. When viewed from a vertical cross section including the piston center line below the top land in the vertical position, the vertical portion 4 is formed, and the lower surface is lowered inward in the lateral direction from the lower end, and the lower surface 6 is a horizontal wedge portion 7. A keystone ring groove 8 is provided in which a vertical portion is formed, and as it goes inward from its lower end, the upper surface is lowered substantially parallel to the upper surface 5 of the L-shaped keystone ring groove 8 and the lower surface is a horizontal wedge portion 18. A keystone ring 12 consisting of the above is fitted with a gap for introducing combustion pressure to cover the uppermost surface of the keystone ring 12 with the top land 3, and the outer diameter of the top land 3 is made smaller than the outer diameter of the second land. It is constructed by forming a gap for the combustion pressure introduced between it faces the cylinder plane.

During operation of the internal combustion engine, the combustion gas pressure in the combustion chamber 17 reaches the portion of the gap 13 through the gap 16, and when the combustion gas pressure in the combustion chamber 17 is high, the keystone ring 12 is formed. A large tension is applied, and the tension applied to the keystone ring 12 is reduced as the combustion gas pressure in the combustion chamber 5 becomes lower. Therefore, the tension control by the gas pressure is enabled.

[0004]

[Problems to be solved by the device]

 However, in the conventional piston for an internal combustion engine, the reciprocating movement of the piston body 1 causes the keystone ring 12 to reciprocate between the upper surface 5 and the lower surface 6 of the L-shaped keystone ring groove 8 as well. A gap (a so-called back clearance) is created between the keystone ring 12 and the keystone ring 12, so that the so-called Clenbis volume is increased, and the sealing function between the keystone ring 12 and the cylinder inner surface 15 is reduced, and the amount of unburned gas blow-by is increased. It is also conceivable that the combustion gas will be retained in the back clearance and that the unburned air-fuel mixture amount of the exhaust gas will be increased as a result.

The present invention has been made to solve the above-mentioned conventional problems, and improves the sealing function between the compression piston ring and the inner wall of the cylinder, and minimizes the intrusion of combustion gas into the back clearance portion. An object of the present invention is to provide a piston for an internal combustion engine that can reliably reduce the amount of unburned air-fuel mixture discharged to the outside of the combustion chamber.

[0006]

[Means for Solving the Problems]

 In order to achieve the above object, the internal combustion engine piston according to the present invention forms a compression ring groove in the outer periphery of the piston body while leaving a top land portion, and also, between the outer periphery of the top land portion and the inner wall of the cylinder. A clearance having a predetermined width is formed in the top land portion, and a compression piston ring having a U-shaped cross section is fitted into the top land portion so as to straddle the gap, and upper and lower legs of the compression piston ring are respectively attached to the cylinder. It was constructed by being positioned on the combustion chamber side and in the compression ring groove.

[0007]

[Action]

 According to this structure, at the end of the compression stroke of the internal combustion engine, the compression piston ring is located on the combustion chamber side due to inertial force and has a clearance between itself and the crown surface of the piston body. The combustion pressure increases as it approaches the top dead center, and the compression piston ring is positioned on the crank chamber side, eliminating the clearance from the crown surface of the piston body and the crown of the upper leg and the piston body. The surface is in close contact with the surface of the cylinder and the compression piston ring itself is in close contact with the inner wall of the cylinder by the tension and combustion pressure of the compression piston ring to seal the inflow of combustion gas into the crank chamber.

[0008]

【Example】

 An embodiment of this invention will be described below with reference to FIGS.

FIG. 1 is a vertical partial sectional view showing a piston for an internal combustion engine, and FIG. 2 is a plan view of a compression piston ring used for the piston of the internal combustion engine shown in FIG.

Reference numeral 21 in the drawing denotes a piston main body, and an annular bottomed annular compression ring groove 23 and oil ring groove 24 are formed side by side on the outer peripheral portion of the piston main body 21, leaving a top land portion 22. ing. The diameter of the top land portion 22 is smaller than the general outer diameter of the piston body 21 so as to form a gap 28 having a predetermined width between the top land portion 22 and the inner wall 25a of the cylinder 25.

Reference numeral 26 is a compression piston ring, and the compression piston ring 26 has a U-shaped cross section, and has one mating port 27 if necessary. In the compression piston ring 26 thus configured, the base portion 26a is located in the gap 28 formed between the top land portion 22 and the cylinder inner wall 25a, and the upper and lower side leg portions 26b, 26b, 26c is fitted in the top land portion 22, so that the upper and lower both side leg portions 26b, 26c are located in the combustion chamber 25b side of the cylinder 25 and in the compression ring groove 23, respectively. The distance between the crown surface 21 a of the piston body 21 and the lower surface of the compression ring groove 23 is set to be larger than the distance between the lower surface of the upper leg portion 26 b and the lower surface of the lower leg portion 26 c of the compression piston ring 26. Set and form back clearance.

An oil ring 29 is inserted in an oil ring groove 24 formed on the outer circumference of the piston body 21.

In the above embodiment, the case where only 26 is used as the compression piston ring has been described, but the present invention is not limited to this, and a plurality of compression piston rings may be used as necessary.

In the structure as described above, the compression piston ring 26 is positioned on the combustion chamber 25b side due to its own inertial force at the end of the compression stroke of the internal combustion engine, and is connected to the crown surface 21a of the piston body 21. Will have a certain clearance between them. The combustion pressure increases as the piston body 21 approaches the top dead center. As the combustion pressure rises, the compression piston ring 26 comes to be positioned on the crank chamber 25c side of the cylinder 25. Therefore, the clearance with the crown surface 21a of the piston body 21 is eliminated. As a result, the upper leg portion 26b of the compression piston ring 26 and the crown surface 21a of the piston body 21 come into close contact with each other. Therefore, the back clearance formed between the compression piston ring 26 and the bottom surface of the compression ring groove 23 is sealed from the combustion chamber 25b to prevent the combustion gas from staying at this portion. Further, since the compression piston ring 23 has tension in itself and receives the combustion pressure from the combustion chamber 25b side, the base of the compression piston ring 23 is the inner wall of the cylinder 25 due to these tension and combustion pressure. The seal function is improved by closely adhering to 25a and preventing combustion gas from entering the crank chamber 25c from the combustion chamber 25b.

3 and 4 show an internal combustion engine in which the bore ratio (compression height / bore ratio), which is the diameter of the piston body 21 with respect to the compression height formed by the skirt portion 31 of the piston body 21, is 0.4 or less. 2 shows an embodiment according to the present invention when applied to a piston for a vehicle, both of which are intended to reduce the weight of the piston. Both of them are similar to the embodiment shown in FIG. 1 and FIG. A compression ring groove 23 is formed in the outer peripheral portion of the main body 21 leaving the top land portion 22 and a gap 28 having a predetermined width is formed between the outer periphery of the top land portion 22 and the inner wall 25a of the cylinder 25. A compression piston ring 26 having a U-shaped cross section is fitted into the topland portion 22 so as to straddle the upper and lower leg portions 26b and 26c of the compression piston ring 26. The cylinders 25 are located on the combustion chamber 25b side and the compression ring groove 23, respectively.

The piston body 21 of the embodiment shown in FIG. 3 has a skirt portion 31 that slides on the cylinder 25, and an apron portion 32 that connects the skirt portion 31 and a piston pin boss portion (not shown). The thickness of the portion 32 on the crown surface 21a side is increased, and the thickness of the apron on the lower side of the skirt portion 31 is reduced to further reduce the weight. The inner wall side of the apron portion 32 goes to the lower end. The thin portion 31a is thinned accordingly.

Further, in the piston body 21 of the embodiment shown in FIG. 4, the thickness of the apron portion 32 on the side of the crown surface 21a is thicker and the thickness of the apron portion on the lower side of the skirt portion 31 is thinner. Similar to the above case, the weight is further reduced. In this case, both the inner and outer walls of the lower end of the skirt portion 31 are cut to form a thin portion 32b having substantially the same width. As a modification of FIG. 4, it is conceivable that the thin portion 32b has a shape in which both inner and outer walls which are thinned along the lower end of the apron portion 32 are tapered.

[0018]

[Effect of the device]

 As described above, according to the present invention, the compression ring groove is formed on the outer peripheral portion of the piston main body while leaving the top land portion, and a gap of a predetermined width is formed between the outer periphery of the top land portion and the inner wall of the cylinder. A compression piston ring having a U-shaped cross section is fitted into the top land so as to straddle the gap, and the upper and lower legs of the compression piston ring are respectively positioned in the combustion chamber side of the cylinder and in the compression ring groove. With this configuration, when the piston body approaches top dead center and the combustion pressure increases, the compression piston ring comes to be located on the crank chamber side, eliminating the clearance from the crown surface of the piston body and The back clearance formed between the compression piston ring and the bottom surface of the compression ring groove due to the leg portion closely contacting the crown surface of the piston body is Sealed to, the combustion gas is prevented from you remaining in the back clearance site, reducing the unburned mixture gas of the exhaust gas, and can provide an internal combustion engine to output discharge clean exhaust gases.

Further, due to the tension and combustion pressure of the compression piston ring itself, the base of the compression piston ring is in close contact with the inner wall of the cylinder to improve the sealing function of preventing the entry of combustion gas from the combustion chamber into the crank chamber. As a result, in combination with the above, an internal combustion engine that emits clean exhaust gas will be provided.

[Brief description of drawings]

FIG. 1 is a vertical partial sectional view showing a piston for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a plan view of a compression piston ring used in the internal combustion engine piston shown in FIG.

FIG. 3 is a vertical partial sectional view showing a piston for an internal combustion engine according to another embodiment of the present invention.

FIG. 4 is a vertical partial sectional view showing a skirt portion of a piston for an internal combustion engine showing still another embodiment of the present invention.

FIG. 5 is a vertical partial sectional view showing an L-shaped keystone ring groove which is a seal groove mechanism in a conventional piston for an internal combustion engine.

FIG. 6 is a vertical partial sectional view showing a state where an L-shaped keystone ring is mounted in the ring groove of FIG.

[Explanation of symbols]

 21 Piston main body 22 Top land part 23 Compression ring groove 25 Cylinder 25a Inner wall 25b Combustion chamber 26 Compression piston ring 26a Base part 26b Upper leg part 26c Lower leg part 28 Gap

Claims (1)

[Scope of utility model registration request] 1. A compression ring groove is formed on an outer peripheral portion of a piston body while leaving a top land portion, and a gap of a predetermined width is formed between the outer periphery of the top land portion and an inner wall of a cylinder so as to straddle the gap. A compression piston ring having a U-shaped cross section is fitted to the top land portion, and upper and lower leg portions of the compression piston ring are respectively positioned in the combustion chamber side of the cylinder and in the compression ring groove. Characteristic piston for internal combustion engine.