JPH04113079A - Piston for internal combustion engine - Google Patents

Abstract

PURPOSE:To effectively prevent an oil rise by providing a pressure introducing passage extending with the radial direction of a piston as the longitudinal direction between the upper side surface of a ring channel and the upper side surface of an oil ring. CONSTITUTION:A right-angled step part 5 is formed in the middle of the upper side surface 3b of the ring channel 3 of a piston 2 with leaving a contact surface on its inside. This is continuously formed in the circumferential direction of the piston, whereby a ring pressure introducing passage 6 continued in the circumferential direction of the piston, having a rectangular section, and extending with the radial direction of the piston as the longitudinal direction is provided. Thus, when an internal combustion engine is operated at high speed, the oil raise of a lubricating oil can be effectively prevented by effectively utilizing the gas pressure, and a reduction in lubricating oil consumption and purification of exhaust gas can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piston for an internal combustion engine that is effective in preventing lubricating oil from rising, particularly when the internal combustion engine is operated at high speed.

[Conventional technology]

Pistons for internal combustion engines are equipped with a compression ring to ensure the airtightness of the combustion chamber, and an oil ring to scrape off lubricating oil supplied to the inner peripheral surface of the cylinder and collect it into the crank chamber. ing.

Conventionally, as shown in FIG. 7, an oil ring 1 has been installed with vertical side pressure in a ring groove 3 formed on the outer circumferential surface of a piston 2 that slides within a cylinder 4. This is to efficiently collect lubricating oil by constantly sealing the lubricating oil on the top and bottom surfaces during the internal combustion engine cycle of intake, compression, combustion, and exhaust. This effectively prevents lubricating oil from entering the chamber (oil leakage), reducing lubricating oil consumption and purifying exhaust gas.

Here, when the internal combustion engine is operated at high speed, the actual behavior of the oil ring 1 is as shown in Fig. 9, a check valve-like movement that is ideal in terms of sealing performance (Fig. 8). ), or during such high-speed operation, the behavior of the upper sight rail 11 from the compression stroke to the combustion stroke is very important for preventing oil leakage.

In other words, it has been confirmed that pushing the a-side rail 11 downward (towards the crank chamber) from the compression stroke to the combustion stroke is effective in preventing oil from rising. - It is effective to push down the sight rail 11 as early as possible before compression top dead center. As shown in FIG. 10, by forming a gap between the oil ring 1 and the upper side surface 3b of the ring groove 3, the lubricating oil can be smoothly drawn into the ring groove 3, and the This is thought to be because the lubricating oil can be blown back into the crank chamber from the oil return passage 2a by the blow-by gas from the combustion chamber side.

[Problem to be solved by the invention]

Considering the mechanism of oil ring behavior described above,
The inertial force applied to the oil ring, the blow pie gas pressure from above, the frictional force between the cylinder inner circumferential surface, etc. are acting on the oil ring, and in order to effectively push down the oil ring, it is necessary to apply the blow pie gas pressure effectively. There is. Here, in order to increase the pressure of the blow gas, it is possible to increase the blow gas itself or reduce the volume between the lands from the top of the piston, but in the former case, the internal combustion engine may be damaged. There is a risk that
In the latter case, there is a limit due to the strength of the piston land, and it has been difficult to increase the force caused by the gas pressure acting on the oil ring.

The present invention has been developed in view of the above-mentioned conventional circumstances, and can effectively prevent oil from rising by increasing the pressure-receiving area of the oil ring during high-speed operation by increasing the pressure-receiving area of the oil ring. The purpose of the present invention is to provide a piston for an internal combustion engine.

[Means to solve the problem]

A piston for an internal combustion engine according to the present invention that achieves the above object is provided with a ring groove formed on the outer peripheral surface of the piston; an oil ring for scraping off lubricating oil is installed in the piston for an internal combustion engine, and the piston is located on the combustion chamber side. A step is formed between the upper side surface of the ring groove and the upper side surface of the piston ring by leaving a contact surface on the inner peripheral side at the mating surface between the upper side surface of the ring groove and the upper side surface of the piston ring. The piston is characterized in that a pressure introduction passage is provided around the entire circumference, extending in the radial direction of the piston.

[Effect]

In the internal combustion engine piston of the present invention, by providing a pressure introduction passage that extends in the radial direction of the piston between the upper side surface of the ring groove and the upper side surface of the oil ring,
During high-speed operation, blow-by gas is introduced from this pressure introduction passage to the upper side surface of the oil ring, and the pressure is applied to separate the upper side surface of the ring groove and the upper side surface of the oil ring. A gas flow path is formed to effectively blow back lubricating oil into the crank chamber using blow-by gas.

Since the pressure introduction passage is formed from the step formed on the mating surface of the upper side surface of the ring groove and the upper side surface of the oil ring, this is different from when the oil ring is in the lowered position as described above. When the oil ring is in the raised position, the upper side surface of the ring groove on the inner side of the piston from the stepped portion and the upper side surface of the oil ring are in contact with each other as in the conventional oil ring. Therefore, a situation in which lubricating oil is sucked up from within the ring groove to the combustion chamber side due to negative pressure on the combustion chamber side during engine braking or the like does not occur.

〔Example〕

The piston for an internal combustion engine of the present invention will be specifically described based on examples. Incidentally, the oil ring 1 shown in the following embodiment is a combination ring, and as shown in FIG. The spacer expander 13 is biased by the spring force of the spacer expander 13 to expand both site rails 11°1.
The tip of the piston 2 is brought into pressure contact with the inner circumferential surface of the cylinder. ◇ Fig. 1 is a sectional view schematically showing the main parts of a piston according to a first embodiment of the present invention.

In the piston 2 of this embodiment, the upper side surface 3b of the ring groove 3
A right-angled stepped portion 5 is formed in the middle of the groove, leaving a contact surface on the inside thereof. This stepped portion 5 is formed continuously in the circumferential direction of the piston, and is formed between the upper side surface 3b of the ring groove and the upper side surface of the upper sight rail 11 (the upper side surface of the oil ring). An annular pressure introduction passage 6 is provided which extends in the radial direction of the piston and has a rectangular cross-sectional shape and is continuous in the circumferential direction of the piston.

FIGS. 2 and 3 are cross-sectional views schematically showing essential parts of pistons according to second and third embodiments of the present invention.

In the embodiment shown in FIG. 3, an inclined step portion 5 is formed in the middle of the upper side surface 3b of the ring groove 3, and the piston is positioned between the upper side surface 3b of the circumferential groove and the upper side surface of the upper sight rail 11. An annular pressure introducing passage 6 is provided which extends in the radial direction and has a wedge-shaped cross section and is continuous in the circumferential direction of the piston.

In the embodiment shown in FIG. 3, a stepped portion 5 having a curved surface is formed in the middle of the upper side surface 3b of the ring groove 3, and between the upper side surface 3b of the ring groove and the upper side surface of the upper sight rail 11. An annular pressure introduction passage 6 is provided which is continuous in the circumferential direction of the piston and has a cross-sectional shape with a curved surface extending longitudinally in the radial direction of the piston.

In the above embodiment, if the depth of the ring groove 3 is 1, then the length from the outer peripheral surface of the piston to the stepped portion 5 (the cut length of the pressure introduction passage 6) and the step of the stepped portion 5 ( It is preferable that the width of each pressure introduction passage 6 is set to 0°5 or less, and the width of the pressure introduction passage 6 should be very small (several tens of microns) as it is sufficient to introduce pressure as described later. good.

The operation of the first embodiment will be explained with reference to FIGS. 4 and 5. In FIG. 4, the structure of the oil ring 1 is simplified and only the upper sight rail 11 is shown.

First, as shown in FIG. 4(a), during the compression/combustion stroke, pressure P caused by blow-by gas or the like acts on the upper site rail 11 from the gap between the piston 2 and the cylinder 4. This pressure P acts not only on the tip of the upper sight rail 11 but also on a wide range of the upper side surface of the upper sight rail through the pressure introduction passage 6. As a result, as shown in FIG.
is pushed down by the force of the pressure P and separated from the upper side surface 3b of the ring groove, forming a passage leading to the bottom of the ring groove 3. As a result, the lubricating oil accumulated in the ring groove 3 and the lubricating oil scraped up by the upper site rail 11 during the upward stroke of the piston 2 is blown from the oil return passage 2a into the crank chamber by the blow-by gas flowing through the passage. be returned.

On the other hand, in a conventional piston that does not have a pressure introduction passage as shown in FIG.
If it is not high, the upper sight rail 11 cannot be pushed down.

As shown in Fig. 5, the pressure P increases in accordance with the combustion chamber pressure and the pressure ring passage area, but compared to the conventional example, in this example, the combustion chamber pressure is not so high at an early stage A (compression top dead center). The upper sight rail 11 can be pushed down during the previous period), and the lubricating oil can be blown back into the crank chamber by blow-by gas.

The above-mentioned effect occurs conspicuously when the internal combustion engine is operated under high load and at high speed, and in other conditions, the step portion 5
The upper side surface 3b of the ring groove on the inner side of the piston and the upper side surface of the upper sight rail 11 are in contact with each other like a conventional oil ring, and furthermore, the step 5 is set small (several tens of microns). As a result, the tip of the upper sight rail 11 also comes into contact with the upper sight rail 11, which prevents lubricating oil from being sucked up from inside the ring groove 3 into the combustion chamber due to negative pressure on the combustion chamber side during engine braking. Does not occur.

Note that the embodiment shown in FIG. 2 or FIG. Because of this shape, the blow-by gas flow can be guided and applied directly to the upper site rail 11, thereby making it possible to push down the upper site rail 11 more effectively.

〔Effect of the invention〕

In the internal combustion engine piston of the present invention, a stepped portion is formed on the mating surface between the upper side surface of the ring groove on which the oil ring is attached and the upper side surface of the oil ring, so that the upper side surface of the circumferential groove and the upper side surface of the oil ring Since a pressure introduction passage extending in the radial direction of the piston is provided between the cylinder and the piston, gas pressure can be effectively used to effectively prevent lubricating oil from rising when the internal combustion engine is operating at high speed. This makes it possible to reduce lubricating oil consumption and purify exhaust gas.

[Brief explanation of the drawing]

FIG. 1 is a sectional view schematically showing a main part of a piston for an internal combustion engine according to a first embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view showing a main part of a piston for an internal combustion engine according to a second embodiment of the invention. FIG. 3 is a cross-sectional view schematically showing essential parts of a piston for an internal combustion engine according to a third embodiment of the present invention, and FIG.
b) and (c) are conceptual diagrams comparing and explaining the first embodiment of the present invention and the conventional example, FIG. 5 is a graph showing the relationship between the pressure applied to the oil ring and the combustion chamber pressure, and FIG. 6 is a perspective view showing the configuration of a combination oil ring, FIG. 7 is a conceptual diagram explaining the behavior of a conventional oil ring, FIG. 8 is a time chart explaining the position of the oil ring, and FIG. 9 is a diagram showing the behavior of the oil ring. The time chart to be described, FIG. 10, is a conceptual diagram illustrating the blow-back of lubricating oil by blow-by gas. DESCRIPTION OF SYMBOLS 1... Oil ring, 2... Piston, 3... Ring groove, 3b... Upper side surface of ring groove, 4... Cylinder, 5... Step part, 6... For pressure introduction aisle. (a) (C) Figure 3 Figure 5 Figure 1 Trap fil Se is full 21Pg! L Diagram V and pressure and light decay diagram! O diagram

Claims (1)

[Claims] In a piston for an internal combustion engine equipped with an oil ring for scraping off lubricating oil in a ring groove formed on the outer peripheral surface of the piston, the upper side surface of the ring groove located on the combustion chamber side and the upper side surface of the piston ring are A contact surface is left on the inner circumferential side of the mating surface, and a stepped portion is formed to form a pressure introduction passage extending along the entire circumference between the upper side surface of the ring groove and the upper side surface of the piston ring, extending longitudinally in the radial direction of the piston. A piston for an internal combustion engine characterized by being provided with.