Valves and internal combustion engines

Abstract

To provide a valve that can be readily identified, and to provide an internal combustion engine.SOLUTION: A valve provided in a combustion chamber of an internal combustion engine has: a stem part which extends in one direction; and an umbrella part which is provided in a tip of the stem part and in which a concave part is formed on a surface on an opposite side to the stem part, wherein the concave part includes a nitride layer exposed to the surface.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a valve and an internal combustion engine. [Background technology]

[0002] Patent Document 1 describes that a recess is formed on the surface of an intake valve and a flat surface is formed on the surface of an exhaust valve so that a fast tumble flow is generated in the combustion chamber of an internal combustion engine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-241531 Summary of the Invention [Problem to be solved by the invention]

[0004] When an internal combustion engine contains a mixture of intake valves with recesses on their surfaces and exhaust valves without recesses on their surfaces, it is possible to detect incorrect assembly positions of intake valves and exhaust valves, for example, on an internal combustion engine production line, by processing surface images of each valve.

[0005] However, due to limitations on the thickness of the intake valve head, for example, it is difficult to form a recess deep enough to be clearly distinguishable on an image. This makes it difficult to distinguish between the intake valve and the exhaust valve and detect an incorrect assembly position. This problem is not limited to cases where recesses are provided only on the intake valve; it can also occur when recesses are provided on the exhaust valve as well, if some valves have recesses and some do not.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to provide a valve and an internal combustion engine that can be easily identified. [Means for solving the problem]

[0007] The valve of the present invention is a valve to be installed in a 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. The surface roughness of the surface other than the recessed portion is smaller than the surface roughness of the recessed portion. .

[0009] 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 to the stem portion, and the recess has a nitride layer exposed on the surface. The surface roughness of the surface other than the recessed portion is smaller than the surface roughness of the recessed portion. . [Effects of the Invention]

[0011] According to the present invention, the valves of an internal combustion engine can be easily identified. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic cross-sectional view showing an example of an engine. [Figure 2] 1A and 1B show underside and cross-sectional views of an example valve. [Figure 3] 1 is a flowchart illustrating an example of a manufacturing process for a valve. DETAILED DESCRIPTION OF THE INVENTION

[0013] (Engine configuration) Fig. 1 is a schematic cross-sectional view showing an example of an engine 2. The engine 2 is a gasoline engine and is an example of an internal combustion engine. Only one of the multiple cylinders of the engine 2 is depicted in Fig. 1.

[0014] The engine 2 has, for each cylinder, 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. The combustion chamber 20 is a space surrounded by a cylinder head and a cylinder block (not shown) and the top surface of the piston 26.

[0015] An ignition 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 timing of the addition of fuel to the spark plug 25 are controlled by control means (not shown).

[0016] When the intake valve 24 opens, a mixture of fuel and air flows into the combustion chamber 20 through the intake port 22. The spark plug 25 ignites the mixture. This burns the mixture, causing the piston 26 to move vertically on the page of 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 opens, exhaust gas in the combustion chamber 20 is discharged into the exhaust system through the exhaust port 21.

[0017] (Valve configuration) The valves used as the exhaust valve 23 and the intake valve 24 will be described below.

[0018] 2 is a diagram showing a lower surface 110 and a cross section of an example of the valve 1. The lower surface 110 is substantially circular and is the surface of the valve 1 that faces the combustion chamber 20. The cross section is taken along line AA that passes through the center of the lower surface 110.

[0019] The valve 1 has a stem portion 10 and an umbrella portion 11 integrally formed from steel. The stem portion 10 is a rod-like 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 of the stem portion 10. A recess 110a having a generally circular outer periphery is provided in the center of the underside 110. Furthermore, 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.

[0020] When the valve 1 is used as an exhaust valve 23 and an intake valve 24, the recess 110a faces the combustion chamber 20, and therefore the speed of the tumble flow in the combustion chamber 20 increases more than when the recess 110a is not present. This improves the combustion efficiency of the engine 2.

[0021] The recess 110a also has a nitride layer 121 exposed on its surface. The nitride layer 121 is formed by subjecting the forged valve 1 to a soft nitriding treatment. The nitride layer 121 has a configuration 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 that has not been soft nitriding treated, and has high fatigue strength, wear resistance, and corrosion resistance. The nitride layer 121 is also resistant to high-temperature environments such as those in the combustion chamber 20, and is not easily peeled off.

[0022] Furthermore, the nitride layer 121 has a different color from the portion of the steel material exposed in the flat portion 110b. For example, the steel material in the flat portion 110b is silver-white, while the nitride layer 121 is blackish-brown. Therefore, for example, in the manufacturing process of the engine 2, if valves 1 having recesses 110a and other types of valves without recesses 110a are assembled together as exhaust valves 23 and intake valves 24, the color patterns of the recesses 110a and flat portion can be detected by image processing of the underside 110 of the valve 1.

[0023] 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.

[0024] Furthermore, 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 distinguished from one another 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.

[0025] In addition, a nitride layer 120 is also formed on the surface of the stem portion 10 and the surface of 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 resistant to damage.

[0026] The surface area of the underside 110 of the umbrella portion 11 is larger than when the recessed portion 110a is not present. In other words, the recessed portion 110a includes a sloped portion adjacent to the flat portion 110b, so the surface area is larger than when the recessed portion 110a is not present. This increases the S / V ratio (Surface Volume Ratio), which increases cooling loss and may worsen the fuel efficiency of a vehicle equipped with the engine 2.

[0027] In contrast, the surface area can be reduced by reducing the surface roughness of the recess 110a through surface processing such as grinding, polishing, or cutting, but when the lower surface 110 is viewed from the front, the recess 110a is located further back than the flat portion 110b, making processing difficult.

[0028] 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 therefore can be easily formed to a predetermined surface roughness. The lower the surface roughness of the flat portion 110b, the smaller its surface area. This reduces the S / V ratio, suppresses an increase in cooling loss, and improves the fuel efficiency of a vehicle equipped with the engine 2.

[0029] Examples of the surface roughness include, but are not limited to, the arithmetic mean roughness (Ra), maximum height (Ry), ten-point mean roughness (Rz), etc., as defined in the Japanese Industrial Standard (JIS). As an example, when the arithmetic mean roughness (Ra) is used, the Ra of the recessed portion 110a is 20 μm or less, while the Ra of the flat portion 110b is preferably 5 μm or less, and more preferably 1 μm or less, from the viewpoint of reducing the S / V ratio.

[0030] (Valve manufacturing method) 3 is a flowchart showing an example of a manufacturing process for the valve 1. First, a forging step St1 is performed, whereby the stem portion 10 and the head portion 11 are formed from a steel material having a predetermined shape.

[0031] Next, the soft-nitriding step St2 is performed. In this step, the surfaces of the stem portion 10 and the umbrella portion 11 are soft-nitrided. The soft-nitriding method is not limited, but examples include plasma nitriding, gas nitriding, and salt bath nitriding. As a result, the entire stem portion 10 and the 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.

[0032] Next, a polishing step St3 is performed. In this step, the flat portion 110b of the underside 110 of the head 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 for 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 a diesel engine.

[0033] The above-described embodiment is a preferred example of the present invention, but the present invention is not limited to this and can be modified in various ways without departing from the spirit of the present invention. [Explanation of symbols]

[0034] 1 valve 2. Engine (internal combustion engine) 10 Stem 11 Umbrella section 20 Combustion chamber 21 Exhaust port 22 Intake port 23 Exhaust valve 24 intake valve 110a recess 110b Flat area 120,121 Nitrided layer

Claims

1. A valve provided in a combustion chamber of an internal combustion engine, a stem portion extending in one direction; a cap portion provided at the tip of the stem portion, the cap portion having a recess formed on a surface opposite to the stem portion, the recessed portion has a nitride layer exposed on the surface; the surface roughness of the region other than the recessed portion of the surface is smaller than the surface roughness of the recessed portion; valve.

2. 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 the tip of the stem portion, the cap portion having a recess formed on a surface opposite to the stem portion, the recessed portion has a nitride layer exposed on the surface; the surface roughness of the region other than the recessed portion of the surface is smaller than the surface roughness of the recessed portion; Internal combustion engine.

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