JP2017096177A - Piston structure of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston structure of an internal combustion engine which can reduce a variation of a temperature distribution in a combustion chamber by a simple configuration.SOLUTION: In a piston structure 100 of an internal combustion engine having a piston 2 which reciprocates in a cylinder 1, and whose upper face 2u constitutes a part of a combustion chamber 5, and a plurality of piston rings 3 which are fitted to an outer peripheral face of the piston 2, and come into close contact with an inner peripheral face of the cylinder 1, at least piston rings 31, 32 out of the plurality of the piston rings 3, which are arranged at the combustion chamber 5 side are inclined so as to approach the combustion chamber 5 side as progressing toward an exhaust side from an intake side of the combustion chamber 5.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a piston structure of an internal combustion engine that can reduce variations in temperature distribution in a combustion chamber.

  The piston of the internal combustion engine has an upper surface that constitutes a part of the combustion chamber, and reciprocates in the cylinder by the combustion of a mixture of fuel and air in the combustion chamber. Since heat generated by combustion of the air-fuel mixture in the combustion chamber is directly transmitted to the piston, a large heat load is applied to the piston. In order to reduce the thermal load applied to the piston, a piston having a cooling cavity is known (Patent Document 1). The piston described in Patent Document 1 includes a cavity serving as a combustion chamber at the center of the top surface, and includes a cooling cavity between the cavity and the piston ring groove.

  It is desirable that the piston be uniformly cooled in the circumferential direction. This is because the cooling degree of the piston affects the temperature distribution in the combustion chamber. In Patent Document 1, the cooling effect due to the collision of the fuel is taken into consideration, and the cooling effect by the cooling cavity is reduced in the portion of the combustion chamber wall where the fuel collides, and the portion of the combustion chamber wall where the fuel does not collide Then, the variation in temperature distribution in the circumferential direction of the piston is reduced by increasing the cooling effect by the cooling cavity. Specifically, the difference between the wall of the combustion chamber and the wall of the cooling cavity at the location where the fuel collides is larger than the interval between the wall of the combustion chamber and the cooling cavity at the location where the fuel does not collide. The piston is provided with a cooling cavity having a shape.

JP-A-10-141135

  The piston of Patent Document 1 needs to use a complicated core in the manufacturing process in order to provide a cooling cavity having an irregular shape in the piston, resulting in poor productivity and high cost.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide a piston structure for an internal combustion engine that can reduce variations in temperature distribution in the combustion chamber with a simple configuration.

  A piston structure of an internal combustion engine according to an aspect of the present invention includes a piston that reciprocates in a cylinder, an upper surface constituting a part of a combustion chamber, and an outer periphery of the piston that is in close contact with the inner peripheral surface of the cylinder. And a plurality of piston rings. Of the plurality of piston rings, at least a piston ring arranged on the combustion chamber side is inclined so as to approach the combustion chamber side as it goes from the intake side to the exhaust side of the combustion chamber.

  The piston structure of the internal combustion engine can efficiently transfer the heat of the piston to the cylinder via the piston ring, and can reduce variations in temperature distribution in the combustion chamber with a simple configuration. When the internal combustion engine is driven, the temperature in the combustion chamber tends to be higher on the exhaust side than on the intake side. The piston ring is inclined so as to approach the combustion chamber side as it goes from the intake side to the exhaust side of the combustion chamber, so that the distance between the upper surface of the piston constituting a part of the combustion chamber and the piston ring is As the temperature increases from the intake side to the exhaust side, the heat becomes shorter and heat can be transferred to the cylinder more quickly on the higher temperature side of the combustion chamber. On the other hand, since the distance increases as it goes from the exhaust side to the intake side of the combustion chamber, the transfer of heat to the cylinder is delayed on the side where the temperature in the combustion chamber is low. Therefore, by increasing the heat dissipation on the exhaust side where the temperature is higher than the heat dissipation on the intake side where the temperature is low in the combustion chamber, it is possible to suppress the occurrence of bias in the heat dissipation effect on the intake side and on the exhaust side, Variations in temperature distribution in the combustion chamber can be reduced. By reducing the variation in temperature distribution in the combustion chamber, it is possible to suppress a part of the fuel from being abnormally heated to a high temperature in the combustion chamber and to suppress knocking due to early ignition.

1 is a cross-sectional view of an internal combustion engine including a piston structure for an internal combustion engine according to Embodiment 1.

  An embodiment of a piston structure of an internal combustion engine of the present invention will be described below with reference to the drawings. In the figure, the same reference numerals indicate the same names.

Embodiment 1
-Whole structure The piston structure 100 of the internal combustion engine of Embodiment 1 is utilized for the component of the internal combustion engine mounted in a motor vehicle. An internal combustion engine typically includes a laminated structure in which an oil pan, a cylinder block, a cylinder head, and a cylinder head cover are assembled in this order from the bottom (all not shown). As shown in FIG. 1, the cylinder block has a cylinder 1 and houses a main motion system such as a piston 2 that reciprocates within the cylinder 1. The cylinder head includes an intake port 6 for introducing air, a combustion chamber 5 for burning an air-fuel mixture including air and fuel introduced from the intake port 6, and an exhaust port 7 for exhausting exhaust gas generated in the combustion chamber 5. It is arranged at the boundary between each port 6, 7 and the combustion chamber 5, and houses a valve operating system such as an intake valve 60 and an exhaust valve 70 that opens and closes the combustion chamber 5. The internal combustion engine performs four-cycle operation such as intake, compression, combustion, and exhaust using air introduced from the intake port 6 and fuel injected from an injector (not shown). The fuel is directly injected from the injector into the combustion chamber 5 or injected into the intake port 6. When the fuel is gasoline, the internal combustion engine includes a spark plug 9 in the combustion chamber 5.

  As shown in FIG. 1, the piston structure 100 of the internal combustion engine according to the first embodiment includes a piston 2 and a plurality of piston rings 3 attached to the outer periphery of the piston 2. The piston 2 is connected to the connecting rod via a piston pin, and reciprocates in the cylinder 1 by combustion of the air-fuel mixture in the combustion chamber 5. An upper surface 2 u of the piston 2 constitutes a part of the combustion chamber 5. The piston ring 3 is disposed in close contact with the inner peripheral surface of the cylinder 1 so as to fill a gap (piston clearance) between the cylinder 1 and the piston 2. In this example, three piston rings 31, 32, and 33 are arranged. The main feature of the piston structure 100 of the internal combustion engine according to the first embodiment is that the piston ring arranged at least on the combustion chamber 5 side among the plurality of piston rings 3 is directed from the intake side to the exhaust side of the combustion chamber 5. Therefore, it is inclined so as to approach the combustion chamber 5 side. Details will be described below. In the following description, it is assumed that the intake port 6 and the exhaust port 7 are viewed from the left and right in the direction orthogonal to the axial direction of the piston 2, and the intake port 6 in the combustion chamber 5 is disposed. The side on which the exhaust port 7 is disposed (the left side in FIG. 1) and the side on which the exhaust port 7 is disposed (the right side in FIG. 1) are referred to as the exhaust side.

Piston In the piston 2, the piston head on the upper surface 2 u constitutes the bottom of the combustion chamber 5. In this example, the piston head (upper surface 2 u) is a flat surface. However, in order to avoid contact with the intake valve 60 and the exhaust valve 70, a piston head provided with a recess (valve recess) may be used. The outer diameter of the piston 2 is slightly smaller than the inner diameter of the cylinder 1 so that the piston 2 can reciprocate in the cylinder 1, and a gap (piston clearance) is provided between the piston 2 and the cylinder 1. Therefore, a piston ring 3 described later is mounted on the outer periphery of the piston 2.

  On the outer peripheral surface of the piston 2, a ring groove 20 in which the piston ring 3 is mounted is formed in the vicinity of the upper surface 2u. In this example, since three piston rings 3 are mounted, a first ring groove 21, a second ring groove 22, and a third ring groove 23 are provided in order from the upper surface 2u side. Each ring groove 21, 22, 23 may be provided corresponding to the arrangement form of the piston ring 3 described later. Therefore, the ring grooves 21, 22, and 23 will be described in detail in the description of the piston ring 3 described later.

  The piston 2 is generally made of an aluminum alloy that is lightweight and has high thermal conductivity.

Piston ring The piston ring 3 generally includes a compression ring that mainly maintains the airtightness of the combustion chamber 5 and an oil ring that mainly scrapes off the lubricating oil on the inner wall of the cylinder 1. In this example, two compression rings 31 and 32 and one oil ring 33 are provided. In each of the three piston rings 3, the first compression ring 31 is mounted in the first ring groove 21, the second compression ring 32 is mounted in the second ring groove 22, and the oil ring 33 is mounted in the third ring groove 23. Each ring 31, 32, 33 is in close contact with the inner peripheral surface of the cylinder 1 with the respective tension.

  Of the plurality of piston rings 3, at least the piston ring disposed on the combustion chamber 5 side is inclined so as to approach the combustion chamber 5 side from the intake side toward the exhaust side. In this example, among the three piston rings 3, the first compression ring 31 and the second compression ring 32 on the combustion chamber 5 side are inclined. When the first compression ring 31 (second compression ring 32) is inclined, the distance between the upper surface 2u of the piston 2 constituting a part of the combustion chamber 5 and the first compression ring 31 (second compression ring 32) is It becomes shorter as it goes from the intake side to the exhaust side.

  The piston ring which does not incline among the plurality of piston rings 3 is arranged in parallel with an orthogonal plane orthogonal to the axial direction of the piston 2 as in the conventional case. In this example, the oil ring 33 is not inclined.

  The piston rings 31 and 32 that are inclined among the plurality of piston rings 3 may be inclined with respect to the orthogonal plane orthogonal to the axial direction of the piston 2 and the degree of inclination can be selected as appropriate. Further, it is sufficient that at least the piston ring disposed on the combustion chamber 5 side is inclined, and the number of the inclined piston rings 3 can be appropriately selected. For example, when three piston rings 3 are provided as in this example, only the first compression ring 31 on the combustion chamber 5 side is inclined, or the second compression ring 32 is inclined in addition to the first compression ring 31. (See FIG. 1), all the piston rings 31, 32, 33 may be inclined. In this example, two compression rings are provided, but one compression ring may be provided.

  Each ring groove 21, 22, 23 formed in the piston 2 is formed corresponding to the arrangement form of the piston ring 3. In this example, the first ring groove 21 in which the first compression ring 31 is attached and the second ring groove 22 in which the second compression ring 32 is attached are directed to the combustion chamber 5 side from the intake side toward the exhaust side. Inclined to approach. That is, the distance between the upper surface 2u of the piston 2 and the first ring groove 21 (second ring groove 22) becomes shorter from the intake side toward the exhaust side.

  FIG. 1 shows a partially enlarged cross-sectional view of a close contact portion (portion surrounded by a dotted line) of the piston ring 3 with the cylinder 1. As shown in the partially enlarged cross-sectional view of FIG. 1, the oil ring 33 arranged without being inclined has a substantially rectangular cross-sectional shape, but the first compression ring 31 and the second compression ring arranged with inclination. 32 has a substantially parallelogram-shaped cross-sectional shape. This is because each ring 31, 32, 33 needs to be in close contact with the cylinder 1. By making the cross-sectional shapes of the first compression ring 31 and the second compression ring 32 arranged in an inclined manner into parallelograms, the respective contact areas between the rings 31 and 32 and the cylinder 1 are not inclined. The contact area between the cylinders 31 and 32 and the cylinder 1 can be made equal, and the airtightness of the combustion chamber 5 can be maintained.

  Since the piston ring 3 moves at high speed under high temperature and high pressure conditions, the piston ring 3 is made of a material that is excellent in wear resistance, has little decrease in tension, and is hard to be worn out. The piston ring 3 is generally made of special cast iron or carbon steel.

Effect The piston structure 100 of the internal combustion engine of the first embodiment can efficiently transfer the heat of the piston 2 to the cylinder 1 through the piston ring 3. Generally, the piston ring 3 has a role of transferring heat of the piston 2 to the cylinder 1. The piston structure 100 of the internal combustion engine according to the first embodiment applies the heat transfer function of the piston ring 3 and appropriately selects the arrangement form of the piston ring 3, so that the temperature distribution in the combustion chamber 5 can be achieved with a simple configuration. The variation of can be reduced. When the internal combustion engine is driven, the temperature in the combustion chamber 5 tends to be higher on the exhaust side than on the intake side. Therefore, the piston ring 3 is inclined so as to approach the combustion chamber 5 side as it goes from the intake side to the exhaust side of the combustion chamber 5, thereby making it possible to remove the piston ring 3 from the upper surface 2 u of the piston 2 constituting a part of the combustion chamber 5 on the exhaust side. The distance to the piston ring 3 can be shortened. Therefore, since the heat radiation path from the combustion chamber 5 to the cylinder 1 via the piston ring 3 can be shortened on the exhaust side, heat can be transferred to the cylinder 1 earlier on the higher temperature side in the combustion chamber 5. While the distance from the upper surface 2u of the piston 2 to the piston ring 3 can be shortened on the exhaust side, the distance from the upper surface 2u of the piston 2 to the piston ring 3 is increased on the intake side. That is, on the intake side, the heat radiation path from the combustion chamber 5 to the cylinder 1 via the piston ring 3 becomes longer. Therefore, on the side where the temperature in the combustion chamber 5 is low, the heat transfer to the cylinder 1 is compared to the exhaust side. Will be late. In addition to speeding up the heat transfer on the high temperature side (exhaust side) and slowing down the heat transfer on the low temperature side (intake side), the heat dissipation effect on the exhaust side and the heat dissipation effect on the intake side , And the variation in temperature distribution in the combustion chamber 5 can be reduced.

  Since the piston structure 100 of the internal combustion engine of the first embodiment applies the heat transfer function of the piston ring 3, it is not necessary to provide a cooling cavity with a complicated shape as in the prior art, and is excellent in productivity.

  The piston structure of the internal combustion engine of the present invention can be suitably used to reduce variation in temperature distribution in the combustion chamber in a piston whose upper surface constitutes a part of the combustion chamber.

DESCRIPTION OF SYMBOLS 100 Piston structure of an internal combustion engine 1 Cylinder 2 Piston 2u Upper surface 20 Ring groove 21 First ring groove 22 Second ring groove 23 Third ring groove 3 Piston ring 31 First compression ring 32 Second compression ring 33 Oil ring 5 Combustion chamber 6 Intake port 60 Intake valve 7 Exhaust port 70 Exhaust valve 9 Spark plug

Claims (1)

A piston that reciprocates in the cylinder and whose upper surface forms part of the combustion chamber;
A piston structure of an internal combustion engine comprising a plurality of piston rings attached to an outer periphery of the piston and in close contact with an inner peripheral surface of the cylinder;
A piston structure of an internal combustion engine, wherein a piston ring arranged at least on the combustion chamber side among the plurality of piston rings is inclined so as to approach the combustion chamber side from the intake side to the exhaust side of the combustion chamber.

Images