Patent Application
20230167755
The present invention relates to an engine valve and a manufacturing method therefor.
Conventionally, in an engine valve that constitutes a part of a combustion chamber wall surface of an engine, there is one in which a head front surface of an engine valve has been mirror-finished (Patent Literature 1). As a result, the engine valve can suppress a temperature rise of an intake air and improve a knocking resistance.
Patent Literature 1: JP2018-087562A
Since the temperature rise of the intake air usually depends on the temperature of the engine valve, it is necessary to suppress the temperature of the engine valve as much as possible. However, the temperature of the engine valve is raised by roughening an outer peripheral surface of a head portion of the engine valve in order to suppress the temperature rise of the intake air during a compression stroke. This is because the heat input from the combustion gas to the engine valve has a great effect, and the temperature rise of the engine valve causes the temperature rise of the intake air. In addition, in an intake stroke, the intake air enters a combustion chamber after coming into contact with a head rear surface of an intake valve, resulting in the temperature rise of the intake air. Furthermore, in an exhaust stroke, since a heat of an exhaust gas also is input to the head rear surface of the exhaust valve, which has a wider surface area than the head front surface of an exhaust valve, it was not sufficient to suppress the temperature rise of the intake air and to suppress the temperature rise of the engine valve only by mirror-finishing to the head front surface.
The present invention has been made in view of the above problems. An object of the present invention is to provide an engine valve and a manufacturing method therefor that can suppress the temperature rise of the intake air and the temperature rise of the engine valve.
(1) According to the first aspect of the present invention, an engine valve having a shaft portion and a head portion expanding in diameter like a head at an edge of the shaft portion, and being to open and close a port provided in a cylinder head, wherein the head portion has a head front surface on a bottom side facing a combustion chamber side, a head rear surface on a top side facing the port side, and an outer peripheral surface of the head portion formed between the head front surface and the head rear surface, and the head portion is provided a mirror-finished mirror portion on the entire area of the head front surface exposed to the combustion chamber and the entire area of the outer peripheral surface.
According to the first aspect of the present invention, in the engine valve, it is possible to suppress the heat input from the head front surface and the outer peripheral surface due to the combustion gas in the engine.
(2) According to the second aspect of the present invention, in the first aspect described above, the mirror-finished mirror portion is provided on a part or the entire area of the head rear surface.
According to the second aspect of the present invention, in the engine valve, the intake valve can suppress the heating of the intake air from the head rear surface in the engine, and the exhaust valve can suppress the heat input from the head rear surface due to the exhaust gas in the engine.
(3) According to the third aspect of the present invention, in the first aspect or the second aspect described above, the engine valve is to open and close the port by axially slidably supporting the shaft portion in a valve guide, and the shaft portion has a mirror-finished mirror portion at a portion exposed from the valve guide when the engine valve is closed.
According to the third aspect of the present invention, in the engine valve, the intake valve can suppress the heating of the intake air in the engine from the shaft portion, and the exhaust valve can suppress the heat input from the shaft portion due to the exhaust gas in the engine.
(4) According to the fourth aspect of the present invention, in any one of the first to third aspects described above, the mirror portion is a coated mirror portion coated with a metal having high temperature resistance and corrosion resistance.
According to the fourth aspect of the present invention, in the engine valve, it is possible to prevent the growth of releasable oxide film, intergranular corrosion, etc., and improve the durability of the engine valve.
(5) According to a fifth aspect of the present invention, a manufacturing method of an engine valve according to any one of the first to third aspects described above, comprising: a step of forming a rod-shaped material into a semi-finished product having the same shape as a finished product by processing including at least forging; and a final step of mirror-finishing at least a portion of a surface of a semi-finished product head portion corresponding to the head portion in the semi-finished product; wherein the final step is either a brushing processing or a plastic working.
(6) According to the sixth aspect of the present invention, in the above fifth aspect described above, the final step is the brushing processing, and a part of the engine valve is mirror-finished by any one of a cutting, a polishing, the brushing processing, or the plastic working in a pre-step of the final step.
(7) According to the seventh aspect of the present invention, in the above fifth aspect described above, the final step is the plastic working, and a part of the engine valve is mirror-finished by any one of a cutting, a polishing, the brushing processing, or the plastic working in a pre-step of the final step.
According to the present invention, the temperature rise of the intake air in the engine can be suppressed, and the temperature rise of the engine valve can be suppressed.
Hereinafter, the present invention will be described in detail through one embodiment of the present invention with reference to
An engine 1 shown in
The cylinder block 11 has a cylindrical cylinder 11a that forms a combustion chamber 10. The piston 13 is a substantially columnar shape and is connected to a crankshaft (not shown) via a rod-shaped connecting rod 13a and can reciprocate by sliding up and down inside the cylinder 11a
The cylinder head 12 is arranged above the cylinder block 11 and has a combustion chamber ceiling portion 12a covering an upper surface of the cylinder 11a. The cylinder head 12 also has an intake port 12b and an exhaust port 12c.
Engine valves 20, 20 are provided inside the intake port 12b and the exhaust port 12c, respectively. Annular valve seats 121, 121 are provided at the boundary between the intake port 12b and the combustion chamber 10 and at the boundary between the exhaust port 12c and the combustion chamber 10 respectively.
In the engine valve 20, a shaft portion 21, which will be described later, is axially slidably supported by a cylindrical valve guide 20A provided in the cylinder head 12. The engine valve 20 on a side of the intake port 12b can open and close the intake port 12b by being seated on or off the valve seat 121 (valve closing or valve opening). The engine valve 20 on a side of the exhaust port 12c can open and close the exhaust port 12c by being seated on or off the valve seat 121 (valve closing or valve opening).
The ignition plug 14 is attached between the intake port 12b and the exhaust port 12c so that an ignition portion at an edge of the ignition plug 14 protrudes into the combustion chamber 10 from the combustion chamber ceiling portion 12a.
As shown in
As shown in
As shown in
A head rear surface 25 on an upper surface of the head portion 23 has a face surface 25a on the side of the head front surface 24 and a neck portion 25b on the side of the shaft portion 21. The face surface 25a extends straight in an upward direction and in a centripetal direction from an upper portion of an outer peripheral surface 26. The neck portion 25b is provided continuously from an upper edge of the face surface 25a and extends toward the shaft portion 21 while curving in an upward direction and in a centripetal direction. The face surface 25a can come into contact with a lower edge of the valve seat 121 (refer to
As shown in
In the engine valve 20 of the present embodiment, a portion that is likely to be exposed to high temperatures is mirror-finished. Specifically, as shown in
In addition, along with the head front surface 24, the mirror-finished mirror portion M is provided over the entire outer peripheral surface 26. As a result, the engine valve 20 can suppress heat input from the head front surface 24 and the outer peripheral surface 26 exposed in the combustion chamber 10. By suppressing the heat input from the portion that is likely to be exposed to high temperatures in this way, an actual temperature rise (high temperature) of the engine valve 20 is suppressed. This allows the engine valve 20 to withstand use in high temperature environments. In addition, a non-mirror-finished area excluding the head front surface 24 and the outer peripheral surface 26 is referred to as a non-mirror portion N.
In addition to the mirror-finishing each component of the engine valve 20 described above, some surface or whole surface within the combustion chamber 10 may be mirror-finished.
The mirror portion M of the present embodiment has a constant surface roughness (for example, Ra (arithmetic mean roughness) is 0.3). In addition, the mirror-finishing of the mirror portion M may be performed by removal processing such as cutting or polishing and may be performed by surface treatment by plating process (hot dip plating, vacuum plating, etc.) using a metal having high temperature resistance and corrosion resistance (a portion mirror-finished by the plating process is referred to as a coated mirror portion). For example, Cr plating, Ni-Cr plating, or the like is adopted as the plating process. When the plating process is performed, the engine valve 20 may be subjected to base preparation by polishing or the like or may be performed without base preparation. By mirror-finishing the engine valve 20 by plating process in this way, it is possible to prevent the growth of releasable oxide film, intergranular corrosion, etc., and improve the durability of the engine valve 20.
The mirror portion M can be modified and changed as follows. Further, it is possible to appropriately combine the respective configuration (portion), treatment, condition, etc. in the embodiment of the present invention described above and the modified examples described below.
Along with the head front surface 24 and the outer peripheral surface 26 which are mirror-finished in the above embodiment, the head rear surface 25 may be mirror-finished. Specifically, a mirror-finished mirror portion M may be provided on a part or the entire area of either or both the face surface 25a and the neck portion 25b on the head rear surface 25. As a result, the engine valve 20 suppresses the temperature rise of the intake gas and suppresses the heat input from the head rear surface 25 by the exhaust gas, thereby the engine valve 20 can suppress an actual temperature rise (high temperature).
On the shaft portion 21 of the engine valve 20, a mirror-finished mirror portion M may be provided in a part or the entire area exposed from the valve guide 20A of the engine valve 20 (
As described above, in the engine valve 20, the effect of suppressing the high temperature of the engine valve 20 can be enhanced as the area of the mirror portion M is increased.
As shown in
As shown in
The surface roughness (degree of mirror finish) may be appropriately changed for each part of the engine valve 20. For example, so that the head front surface 24 has an Ra of 0.3, the outer peripheral surface 26 and the head rear surface 25 have an Ra of 0.4, and the shaft portion 21 has an Ra of 0.5, the roughness of the surface may be smoothed step by step from the shaft portion 21 toward the head front surface 24, the head front surface 24 (which may include the outer peripheral surface 26) may be the smoothest, and the other portions may be rougher than the head front surface 24.
A mirror portion M formed on a part or the entire area of the shaft portion 21, the head rear surface 25, or the outer peripheral surface 26 of the engine valve 20 has an annular shape.
Next, a manufacturing process of the engine valve 20 will be described. The manufacturing process consists of a molding step and a mirror step.
As shown in
The second semi-finished product 40 has the same shape (structure) as the engine valve 20, which is a finished product, and the only difference is whether the head portion 23 is mirror-finished. That is, the second semi-finished product 40 is the non-mirror portion N over the entire area, and the engine valve 20 is provided the mirror portion M on a portion of the head portion. For convenience of explanation, each structure corresponding to each structure of the engine valve 20 in the second semi-finished product 40 will be described as a shaft portion 41, a head portion 43, a head front surface 44, a recessed portion 44a, an annular portion 44b, a head rear surface 45, a face surface 45a, a neck portion 45b, and an outer peripheral surface 46.
As shown in
Here, in the conventional mirror processing of engine valves, it is necessary to gradually reduce the roughness of the surface to smooth it out. Therefore, for example, as shown in
Specifically, in the cutting, for example, the surface is smoothed by cutting a machining allowance (for example, about 0.1 mm) of the engine valve using an NC lathe. In addition, in the polishing, an abrasive cloth and paper and a special abrasive film are used, and a grain size becomes finer as the step proceeds. Specifically, the grain size can be used, for example, 60 (#60) in the rough processing, 400 (#400) in the medium processing, 1000 (#1000) in the finish processing, and 1500 (#1500) in the super-finish processing.
In this way, in conventional mirror processing, the engine valves must be polished step by step in four steps. In addition, it was necessary to change a polishing method (for example, change from the mechanical polishing to the manual polishing) depending on a portion to be processed. As a result, the number of work steps increases, resulting in increasing of cost and time.
As shown in
In the case of the mirror processing of the present embodiment, the grain size of the abrasive cloth and paper or the like employed in the first step is, for example, 200 (#200). This is a finer grain size than the rough processing in conventional processing methods. Thereby, the polishing load in the finish processing can be reduced.
The burnishing processing uses a burnishing device BN. The burnishing device BN has a high-strength burnishing edge BN1 such as a small (for example, about 1 mm to 2 mm) roller-shaped diamond chip. A burnishing device BN is used to plastically deform the head front surface 44 and the like of the second semi-finished product 40 to achieve the mirror-finishing.
Specifically, the burnishing device BN is movable to vertical direction and horizontal direction by a driving device (not shown). As shown in
In addition, regarding mirror-finishing of the outer peripheral surface 46 of the second semi-finished product 40, the burnishing edge BN1 is pressed against the outer peripheral surface 46 with a predetermined force in the condition that the second semi-finished product 40 is rotated around the axis L1 at high speed. As a result, the outer peripheral surface 26 can be uniformly performed the rolling compaction and can be mirror-finished. At this time, the entire area of the outer peripheral surface 46 can be mirror-finished. However, by performing the rolling compaction only the upper outer peripheral surface 26a or the lower outer peripheral surface 26b as the above modified example 1-3, a portion of the outer peripheral surface 46 may be mirror-finished.
The burnishing device BN can adjust the position of the burnishing edge BN1 in the pressing direction based on the pressing force of the burnishing edge BN1 against a workpiece detected by a pressure sensor (not shown) provided near the burnishing edge BN1. As a result, the workpiece can be performed the rolling compaction with a constant force (pressing force), so that the recessed portion 44a of the curved head front surface 44 and the head rear surface 45 can also be performed the burnishing processing.
For example, when the head rear surface 45 is performed the burnishing processing, in the condition that the second semi-finished product 40 is rotated around the axis L1 at high speed, the burnishing device BN presses the burnishing edge BN1 against an edge on the side of the outer peripheral surface 46 of the face surface 45a of the second semi-finished product 40 with a predetermined force. Then, while adjusting a position of a pressing direction, the burnishing edge BN1 is moved toward the neck portion 45b while performing the rolling compaction at a predetermined speed. As a result, the head rear surface 45 can be uniformly performed the rolling compaction. In addition, when the shaft portion 41 is also desired to be performed the burnishing processing, the burnishing edge BN1 is continuously moved toward an upper edge of the shaft portion 41 while performing the rolling compaction at a predetermined speed.
As a result of the burnishing processing, the roughness of the mirror portion M can be set to, for example, an average Ra of around 0.1.
In the brushing processing, the head front surface 44 and the like of the second semi-finished product 40 are mirror-finished by brushing with a brush device BR having a brush body BR1.
As shown in
As shown in
As described above, in the brushing processing, the pilus material BR3 can flexibly come into contact with the shape of the workpiece. Therefore, it is possible to polish not only a flat portion (for example, the annular portion 44b of the head front surface 44) of the second semi-finished product 40 but also a curved surface portion and the recessed portion (for example, the shaft portion 41, the recessed portion 44a, the head rear surface 45, the face surface 45a, the neck portion 45b, the outer peripheral surface 46).
As a result of the brushing processing, the roughness of the mirror portion M can be set to, for example, an average Ra of around 0.05.
The brushing processing may be performed while continuously supplying the second semi-finished product 40 with a working liquid in which abrasive grains are mixed with water. In this case, the particle size is gradually reduced (#1000 to #10000).
As for the mirror processing, it is possible to apply the following modifications and changes. In addition, it is possible to appropriately combine the respective structure (portion), treatment, condition, etc. in the embodiment of the present invention described above and modified examples described below.
When the surface of the second semi-finished product 40 is subjected to nitriding treatment, the nitriding treatment may be performed first, and the mirror finishing may be performed after the first step and the second step of the above embodiment. In addition, the nitriding treatment may be performed after the first step, and then the second step may be performed.
In the present embodiment, although the cutting or the polishing is performed in the first step, the brushing processing or the burnishing processing may be performed.
In the present embodiment, although the brushing processing or the burnishing processing is performed in the second step, the brushing processing may be performed after the burnishing processing, or the burnishing processing may be performed after the brushing processing.
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| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/029158 | 7/29/2020 | WO |
