JP2024058289A - Valves and internal combustion engines - Google Patents

Abstract

[Problem] To provide an easily identifiable valve and internal combustion engine. [Solution] The valve is installed in the combustion chamber of an internal combustion engine, and has a stem portion extending in one direction, and a head portion provided at the tip of the stem portion and having a recess formed on the surface opposite to the stem portion, and the recess has a nitride layer exposed on the surface. [Selected Figure] Figure 2

Description

The present invention relates to a valve and an internal combustion engine.

Patent document 1 describes how a recess is formed on the surface of the intake valve and a flat surface is formed on the surface of the exhaust valve so that a fast tumble flow is generated in the combustion chamber of the internal combustion engine.

JP 2012-241531 A

When an internal combustion engine contains a mixture of intake valves with recesses on their surfaces and exhaust valves without recesses on their surfaces, for example on an internal combustion engine production line, it is possible to detect incorrect assembly positions of intake valves and exhaust valves by processing surface images of each valve.

However, due to restrictions on the thickness of the intake valve's umbrella, for example, it is difficult to form a recess deep enough to be clearly distinguished on an image. This makes it difficult to distinguish between the intake valve and the exhaust valve and detect an error in the assembly position. This problem is not limited to cases where recesses are provided only on the intake valve, but can also occur when recesses are provided on the exhaust valve as well, if valves with and without recesses are mixed.

Therefore, the present invention was made in consideration of the above problems, and aims to provide a valve and an internal combustion engine that can be easily identified.

The valve of the present invention is a valve installed in the combustion chamber of an internal combustion engine, and has a stem portion extending in one direction and a head portion provided at the tip of the stem portion and having a recess formed on the surface opposite the stem portion, and the recess has a nitride layer exposed on the surface.

In the above valve, the surface roughness of the surface other than the recess may be less than the surface roughness of the recess.

The internal combustion engine of the present invention has a combustion chamber for burning fuel, an intake port and an exhaust port connected to the combustion chamber, an intake valve for opening and closing the intake port, and an exhaust valve for opening and closing the exhaust port, and at least one of the intake valve and the exhaust valve has a stem portion extending in one direction and a head portion provided at the tip of the stem portion and having a recess formed on the surface opposite the stem portion, and the recess has a nitride layer exposed on the surface.

In the above internal combustion engine, the surface roughness of the surface in the area other than the recess may be smaller than the surface roughness of the recess.

The present invention makes it easy to identify valves in an internal combustion engine.

1 is a schematic cross-sectional view showing an example of an engine. 1A and 1B show underside and cross-sectional views of an example valve. 4 is a flowchart illustrating an example of a manufacturing process for a valve.

(Engine configuration)
Fig. 1 is a schematic cross-sectional view showing an example of an engine 2. The engine 2 is a gasoline engine, which is an example of an internal combustion engine. Only one of a plurality of cylinders of the engine 2 is illustrated in Fig. 1.

The engine 2 has a combustion chamber 20, an exhaust port 21, an intake port 22, an exhaust valve 23, an intake valve 24, an ignition plug 25, and a piston 26 for each cylinder. The combustion chamber 20 is a space surrounded by the cylinder head and cylinder block (not shown) and the top surface of the piston 26.

A spark plug 25 is attached approximately in the center of the top of the combustion chamber 20. An intake port 22 and an exhaust port 21 are provided on either side of the spark plug 25. The intake port 22 is opened and closed relative to the combustion chamber 20 by an intake valve 24, and the exhaust port 21 is opened and closed relative to the combustion chamber 20 by an exhaust valve 23. The opening and closing of the exhaust valve 23, the opening and closing of the intake valve 24, and the addition timing of the spark plug 25 are controlled by a control means (not shown).

When the intake valve 24 is open, a mixture of fuel and air flows into the combustion chamber 20 from the intake port 22. The spark plug 25 ignites the mixture. This burns the mixture, causing the piston 26 to move vertically on the paper in FIG. 1. The piston 26 is connected to a crankshaft (not shown), which is the output shaft of the engine 2, via a connecting rod (not shown). When the exhaust valve 23 is open, the exhaust gas in the combustion chamber 20 is discharged into the exhaust system via the exhaust port 21.

(Valve configuration)
The valves used as the exhaust valve 23 and the intake valve 24 will be described below.

Figure 2 shows the underside 110 and cross section of an example of the valve 1. The underside 110 is approximately circular and is the surface of the valve 1 that faces the combustion chamber 20. The cross section is taken along line A-A, which passes through the center of the underside 110.

The valve 1 has a stem portion 10 and an umbrella portion 11 integrally formed from steel material. The stem portion 10 is a rod-shaped member extending in one direction, and the umbrella portion 11 is a generally umbrella-shaped member provided at the tip of the stem portion 10. The underside 110 of the umbrella portion 11 corresponds to the surface on the opposite side to the stem portion 10. A recess 110a having a generally circular outer periphery is provided in the center of the underside 110. In addition, a flat portion 110b that is flatter than the recess 110a is provided around the recess 110a on the underside 110. The flat portion 110b is the area of the underside 110 other than the recess 110a.

When the valve 1 is used as an exhaust valve 23 and an intake valve 24, the recess 110a faces the combustion chamber 20, so the speed of the tumble flow in the combustion chamber 20 is increased compared to when the recess 110a is not present. This improves the combustion efficiency of the engine 2.

The recess 110a also has a nitride layer 121 exposed on the surface. The nitride layer 121 is formed by subjecting the forged valve 1 to a nitrocarburizing treatment. The nitride layer 121 has a structure in which nitrogen atoms are chemically bonded to metal elements of the steel material forming the valve 1. The nitride layer 121 is harder than an area not subjected to the nitrocarburizing treatment, and has high fatigue strength, wear resistance, and corrosion resistance. The nitride layer 121 is also resistant to high-temperature environments such as the combustion chamber 20, and is not easily peeled off.

Furthermore, the nitride layer 121 has a different color from the part of the steel material exposed in the flat portion 110b. For example, the steel material in the flat portion 110b is silver-white, whereas the nitride layer 121 is blackish brown. For this reason, for example, in the manufacturing process of the engine 2, if a valve 1 having a recess 110a and another type of valve without a recess 110a are mixed and assembled as the exhaust valve 23 and the intake valve 24, the color pattern of the recess 110a and the flat portion can be detected by image processing of the underside 110 of the valve 1.

This makes the outer periphery of the recess 110a clear in the image of the underside 110, making it possible to easily distinguish and identify the valve 1 from other types of valves, and therefore making it easy to detect errors in the assembly position of the valve 1 and other types of valves.

In addition, for example, if two types of valves 1 with different diameters of the recesses 110a are mixed in the engine 2, the two types of valves 1 can be identified by detecting the diameter of the recesses 110a through image processing of the underside 110 of each valve 1. This makes it easy to detect errors in the assembly positions of the two types of valves 1.

A nitride layer 120 is also formed on the surface of the stem portion 10 and the umbrella portion 11 on the stem portion 10 side (hereinafter referred to as the upper surface). When the valve 1 closes the intake port 22 or the exhaust port 21, the upper surface of the umbrella portion 11 comes into contact with the inner wall of the combustion chamber 20, but because it is coated with the nitride layer 120, it is hard and not easily damaged.

The surface area of the underside 110 of the umbrella portion 11 is larger than when the recess 110a is not present. In other words, the recess 110a includes a sloped portion adjacent to the flat portion 110b, so the surface area is larger than when the recess 110a is not present. This increases the S/V ratio (surface volume ratio), which increases the cooling loss and may worsen the fuel efficiency of the vehicle equipped with the engine 2.

On the other hand, if the surface roughness of the recess 110a is reduced by surface processing such as grinding, polishing, or cutting, the surface area can be reduced; however, when the lower surface 110 is viewed from the front, the recess 110a is located further back than the flat portion 110b, making this processing difficult.

Therefore, the surface roughness of the flat portion 110b around the recess 110a is formed to be smaller than the surface roughness of the recess 110a. The flat portion 110b can be easily surface-processed by grinding, polishing, cutting, or the like, and can therefore be easily formed to a predetermined surface roughness. The lower the surface roughness of the flat portion 110b, the smaller its surface area becomes. This reduces the S/V ratio, suppresses an increase in cooling loss, and improves the fuel efficiency of the vehicle equipped with the engine 2.

The surface roughness may be, but is not limited to, the arithmetic mean roughness (Ra), maximum height (Ry), and ten-point mean roughness (Rz) as defined by the Japanese Industrial Standard (JIS). When the arithmetic mean roughness (Ra) is used as an example, the Ra of the recess 110a is 20 (μm) or less, whereas from the viewpoint of reducing the S/V ratio, the Ra of the flat portion 110b is preferably 5 (μm) or less, and more preferably 1 (μm) or less.

(Valve manufacturing method)
3 is a flow chart showing an example of a manufacturing process for the valve 1. First, a forging process St1 is performed, whereby the stem portion 10 and the head portion 11 are formed from a steel material having a predetermined shape.

Next, the soft nitriding process St2 is performed. In this process, the surface of the stem portion 10 and the surface of the umbrella portion 11 are subjected to soft nitriding. The method of soft nitriding is not limited, but examples include plasma nitriding, gas nitriding, and salt bath nitriding. As a result, the entire stem portion 10 and umbrella portion 11 are nitrided, and nitride layers 121, 120 are formed on the lower surface 110 of the umbrella portion 11 including the flat portion 110b, the upper surface of the umbrella portion 11, and the surface of the stem portion 10.

Next, the polishing process St3 is performed. In this process, the flat portion 110b of the underside 110 of the umbrella portion 11 is polished. As a result, the nitride layer formed on the surface of the flat portion 110b is removed, and the surface roughness of the flat portion 110b becomes smaller than the surface roughness of the recessed portion 110a. In this manner, the manufacturing process of the valve 1 is performed. Note that, although the present embodiment has been described as an example in which the valve 1 is applied to a gasoline engine, it can also be used in other internal combustion engines, such as diesel engines.

The above-described embodiment is a preferred example of the present invention. However, the present invention is not limited to this embodiment, and various modifications are possible without departing from the spirit of the present invention.

1 Valve 2 Engine (internal combustion engine)
REFERENCE SIGNS LIST 10 stem portion 11 head portion 20 combustion chamber 21 exhaust port 22 intake port 23 exhaust valve 24 intake valve 110a recess 110b flat portion 120, 121 nitride layer

Claims (4)

A valve provided in a combustion chamber of an internal combustion engine,
A stem portion extending in one direction;
a cap portion provided at a tip of the stem portion and having a recess formed on a surface opposite to the stem portion,
the recessed portion includes a nitride layer exposed on the surface;
valve. The surface roughness of the region other than the recessed portion of the surface is smaller than the surface roughness of the recessed portion.
2. The valve of claim 1. A combustion chamber for burning fuel;
an intake port and an exhaust port connected to the combustion chamber;
an intake valve that opens and closes the intake port;
an exhaust valve that opens and closes the exhaust port,
At least one of the intake valve and the exhaust valve is
A stem portion extending in one direction;
a cap portion provided at a tip of the stem portion and having a recess formed on a surface opposite to the stem portion,
the recessed portion includes a nitride layer exposed on the surface;
Internal combustion engine. The surface roughness of the region other than the recessed portion of the surface is smaller than the surface roughness of the recessed portion.
4. An internal combustion engine according to claim 3.

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