JP2016148257A - Engine valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine valve capable of suppressing heat loss during a low load, and of suppressing knocking during a high load by performing heat dissipation.SOLUTION: An engine valve 1 uses an aluminum alloy containing 50 to 86 mass% aluminum and magnesium as an alloy element, as a cooling medium 10 to be filled in a hollow part 13 formed from a shaft part 11 to an umbrella part 12. The engine valve 1 uses a magnesium alloy containing 50 to 85 mass% magnesium and aluminum as an alloy element, as the cooling medium 10. Besides, the engine valve 1 uses a sodium alloy containing barium and 50 to 72 mol% sodium, a sodium alloy containing bismuth and 50 to 75 mol% sodium, or a sodium alloy containing tin and 50 to 79 mol% sodium, as the cooling medium 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an engine valve. More specifically, the present invention relates to an engine valve in which a refrigerant is sealed in a hollow portion formed from a shaft portion to an umbrella portion.

  2. Description of the Related Art Conventionally, a sodium sealed valve in which a refrigerant made of metallic sodium is sealed in a hollow portion formed from a shaft portion of an engine valve (poppet valve) to an umbrella portion is known (see, for example, Patent Documents 1 and 2). The enclosed metallic sodium liquefies during operation of the engine and moves in the hollow portion as the engine valve opens and closes. Thereby, the combustion chamber is cooled by releasing the heat received from the exhaust gas in the combustion chamber to the valve guide. Therefore, this sodium-enclosed valve can suppress knocking that is likely to occur when the ignition timing is advanced for the purpose of improving fuel efficiency at high loads, as compared with a solid valve.

  However, this sodium sealed valve takes heat away from the combustion chamber not only in the knock region where knocking occurs but also in the MBT region where knocking does not occur at low load. As a result, heat loss increases, and fuel consumption deteriorates.

  Sodium is solid at room temperature, but since it has a melting point of 98 ° C. and low temperature, it liquefies immediately after the engine is started. At the time of cold start, the combustion chamber is required to be warmed up early from the viewpoint of stabilization of combustion, but the sodium-filled valve takes heat of combustion through liquefied metallic sodium, so it is long to stabilize the combustion. It takes time.

  Furthermore, metallic sodium is very easy to oxidize, and when it becomes an oxide, the thermal conductivity is remarkably lowered. For this reason, metallic sodium is not easy to handle and contributes to a rise in the price of sodium-filled valves. Based on the above, various studies have been made on refrigerants other than metallic sodium (see, for example, Patent Documents 3 to 7).

JP-A-60-145410 JP 2012-87620 A Japanese Patent Laid-Open No. 11-117718 JP 09-184404 A International Publication No. 2014/054613 Japanese Utility Model Publication No. 56-142204 Japanese Utility Model Publication No. 58-151306

  However, in the engine valve of Patent Document 3, although the refrigerant is powder, the heat conduction due to the convection of the refrigerant is not as high as that of the liquid, but the powder is agitated in the hollow portion by the opening and closing operation of the engine valve. However, heat is drawn and heat loss occurs. In addition, since the powder is not liquefied even in the knock region, the heat-drawing effect due to the convection of the refrigerant cannot be obtained, and the knocking suppression effect cannot be obtained.

  Further, in the engine valve of Patent Document 4, since the refrigerant is a low melting point alloy, the exhaust temperature of the gasoline engine is 150 ° C. to 190 ° C. even during the lowest idling, so it is always liquid during engine operation after the completion of warm-up. Therefore, heat is drawn also in the MBT region, and heat loss occurs.

  Moreover, in the engine valve of patent documents 5-7, although a refrigerant | coolant is an aluminum alloy or a magnesium alloy, no examination is made | formed about the composition of these alloys. Furthermore, there is no mention of heat loss due to heat pulling at a low engine temperature range such as that described above at low loads or knocking suppression due to heat pulling at a high engine temperature range such as during medium to high loads.

  The present invention has been made in view of the above, and an object of the present invention is to provide an engine valve that can suppress heat loss when the engine is under a low load and can suppress knocking by performing heat drawing when the engine is under a high load. is there.

  (1) The present invention includes a shaft portion (for example, a shaft portion 11 to be described later) and an umbrella portion (for example, an umbrella portion 12 to be described later) provided integrally on one end side in the axial direction of the shaft portion. An engine valve (for example, an engine valve 1 described later) in which a hollow portion (for example, a later-described hollow section 13) is formed from the shaft portion to the umbrella portion, and aluminum enclosed in the hollow portion A refrigerant composed of an alloy (for example, refrigerant 10 described later) is provided, and the aluminum alloy contains aluminum in an amount of 50 mass% to 86 mass% and magnesium in an amount of 14 mass% to 50 mass%, or magnesium and And at least one selected from the group consisting of lithium, beryllium, calcium, zinc, strontium, indium, tin, barium and bismuth, To provide an engine valve containing 50 mass%.

According to the invention of (1), the melting point is lowered to about 450 ° C. by using, as a refrigerant, an aluminum alloy alloyed with magnesium or an aluminum alloy alloyed with a predetermined amount of an alloy element containing magnesium. Can be made. As a result, during idling operation, the refrigerant can maintain a solid state in an engine low temperature region such as an operation in which the net fuel consumption rate (BSFC) is the least in the MBT region or a low load operation. Can be suppressed. Therefore, since heat loss from the engine valve can be suppressed, fuel efficiency can be improved.
In addition, because the refrigerant can maintain a liquid state in the engine high temperature range such as during knock range operation such as rated point operation, torque point operation, and medium and high load operation, the combustion chamber can be operated by drawing heat from the engine valve. Cooling can suppress knocking. As a result, knocking can be suppressed, the ignition timing can be advanced, and the output and fuel consumption can be improved.

  (2) The present invention includes a shaft portion (for example, a shaft portion 11 to be described later) and an umbrella portion (for example, an umbrella portion 12 to be described later) provided integrally on one end side in the axial direction of the shaft portion. An engine valve (for example, an engine valve 1 described later) in which a hollow portion (for example, a later-described hollow section 13) is formed from the shaft portion to the umbrella portion, and magnesium enclosed in the hollow portion It is provided with a refrigerant made of an alloy (for example, refrigerant 10 described later), and the magnesium alloy contains 50 mass% to 85 mass% of magnesium and 15 mass% to 50 mass% of aluminum, or aluminum and And at least one selected from the group consisting of lithium, beryllium, calcium, zinc, strontium, indium, tin, barium and bismuth, To provide an engine valve containing 50 mass%.

  According to the invention of (2), a magnesium alloy alloyed with aluminum or a magnesium alloy alloyed with a predetermined amount of alloy element containing aluminum is used as a refrigerant, so that its melting point is lowered to about 437 ° C. Can be made. Thereby, the same effect as the invention of (1) is produced.

  (3) The present invention includes a shaft portion (for example, a shaft portion 11 to be described later) and an umbrella portion (for example, an umbrella portion 12 to be described later) provided integrally on one end side in the axial direction of the shaft portion. An engine valve (for example, an engine valve 1 described later) in which a hollow portion (for example, a later-described hollow section 13) is formed from the shaft portion to the umbrella portion, and sodium sealed in the hollow portion A refrigerant comprising an alloy (for example, refrigerant 10 described later), the sodium alloy containing barium and containing 50 mol% to 72 mol% of sodium, containing bismuth and 50 mol% of sodium; An engine valve is provided which is a sodium alloy containing 75 mol% or a sodium alloy containing tin and 50 mol% to 79 mol% sodium.

  According to the invention of (3), by using a sodium alloy alloyed with a predetermined amount of barium, bismuth or tin as a refrigerant, the melting point thereof is about 197 ° C., 444 ° C. or 357 ° C. to 441 ° C., respectively. Can be increased. Thereby, the same effect as the invention of (1) is produced.

  (4) In the invention of (1), the shaft portion and the umbrella portion are made of heat-resistant steel, and the alloy element of the aluminum alloy is made of magnesium, beryllium, calcium, strontium, indium, tin, barium and bismuth. It is preferable to consist of at least one selected from the group.

  Lithium and zinc have liquid metal embrittlement characteristics for engine valves composed of shafts and umbrellas made of heat-resistant steel such as austenitic stainless steel. On the other hand, according to the invention of (4), since an aluminum alloy that does not contain lithium and zinc as an alloy element is used as a refrigerant, weakening of the engine valve can be suppressed.

  (5) In the invention of (2), the shaft part and the umbrella part are made of heat-resistant steel, and the alloy element of the magnesium alloy is made of aluminum, beryllium, calcium, strontium, indium, tin, barium and bismuth. It is preferable to consist of at least one selected from the group.

  According to the invention of (5), since a magnesium alloy not containing lithium and zinc is used as an alloy element as a refrigerant, the same effect as that of the invention of (4) is exerted.

  ADVANTAGE OF THE INVENTION According to this invention, the engine valve which can suppress a heat loss at the time of an engine low load, and can suppress knocking by performing heat drawing at the time of an engine high load can be provided.

It is a longitudinal cross-sectional view of the engine valve which concerns on one Embodiment of this invention, and is a figure which shows the state which the engine valve closed when a refrigerant | coolant is solid. It is a longitudinal cross-sectional view of the engine valve which concerns on the said embodiment, and is a figure which shows the state which the engine valve opened when the refrigerant | coolant is solid. It is a longitudinal cross-sectional view of the engine valve which concerns on the said embodiment, and is a figure which shows the state which the engine valve closed when a refrigerant | coolant is a liquid. It is a longitudinal cross-sectional view of the engine valve which concerns on the said embodiment, and is a figure which shows the state which the engine valve opened when a refrigerant | coolant is a liquid. It is a figure which shows the BSFC map of an engine. It is a figure which shows an engine torque curve and an engine output curve. It is a figure which shows the MBT area | region and knock area | region of an engine. It is a figure which shows the driving | operation area of a normal gasoline engine. It is a figure which shows the operation area of a hybrid engine. It is a phase diagram of a binary aluminum-magnesium alloy. It is a phase diagram of a binary sodium-barium alloy. It is a phase diagram of a binary sodium-bismuth alloy. It is a phase diagram of a binary sodium-tin alloy.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a longitudinal sectional view of an engine valve 1 according to an embodiment of the present invention, and shows a state in which the engine valve 1 is closed when a refrigerant 10 described later is solid. In FIG. 1, the example which applied the engine valve 1 which concerns on this embodiment as an exhaust valve of a gasoline engine is shown (FIGS. 2-4 is also the same).

  The engine valve 1 according to the present embodiment is provided on the cylinder head 2 of the engine and is disposed on the combustion chamber 4 side of the exhaust passage 3 formed in the cylinder head 2. The engine valve 1 opens and closes an exhaust port 5 that connects the exhaust passage 3 and the combustion chamber 4 by reciprocating movement by a valve lifter interlocked with a cam that rotates according to the rotation of the engine (not shown).

  As shown in FIG. 1, the engine valve 1 according to the present embodiment includes a shaft portion 11 and an umbrella portion 12. The engine valve 1 is made of heat-resistant steel made of an alloy having an iron content of 50% by mass or more.

  The shaft portion 11 has a substantially cylindrical shape extending in a rod shape. The shaft portion 11 is inserted into a valve insertion hole 21 formed in the cylinder head 2. More specifically, the valve insertion hole 21 is inserted so as to be in sliding contact with a cylindrical valve guide 22 provided on the inner peripheral surface of the valve insertion hole 21. That is, the shaft portion 11 slides in the valve guide 22 by the reciprocating motion of the engine valve 1.

  The umbrella portion 12 is provided integrally with the shaft portion 11 on one end side in the axial direction of the shaft portion 11 (lower end side on the combustion chamber 4 side). The umbrella section 12 has a substantially circular cross-sectional shape (cross-sectional shape in a direction orthogonal to the central axis of the engine valve 1), and the diameter of the umbrella portion 12 increases toward the tip (the lower end on the combustion chamber 4 side, the same applies hereinafter). Has a shape. That is, the outer wall 121 of the umbrella part 12 is inclined with respect to the central axis of the engine valve 1.

  On the distal end side of the outer wall 121 of the umbrella portion 12, a valve face 122 formed in a tapered shape is provided over the entire circumferential direction. The valve face 122 is enlarged in diameter toward the tip side. When the engine valve 1 moves to the upper exhaust passage 3 side, the valve face 122 is brought into pressure contact with a substantially annular valve seat 23 provided on the inner peripheral surface of the exhaust port 5 of the cylinder head 2. 5 is closed. On the other hand, when the engine valve 1 moves to the lower combustion chamber 4 side, the valve face 122 is separated from the valve seat 23, so that the exhaust port 5 is opened. In this manner, the exhaust port 5 is opened and closed by the valve face 122 coming into contact with the valve seat 23.

  Further, as shown in FIG. 1, a hollow portion 13 is formed in the inside from the shaft portion 11 to the umbrella portion 12. The hollow portion 13 has a substantially cylindrical shape and is formed on the central axis of the engine valve 1. The upper end of the hollow portion 13 is located at a position where the hollow portion 13 wraps with a range of approximately 70% of the total length of the valve guide 22. The lower end of the hollow portion 13 is located in the vicinity of the lower end 12 a of the umbrella portion 12.

  The refrigerant 10 is sealed in the hollow portion 13 described above. The refrigerant 10 is sealed in the hollow portion 13 together with air so as to satisfy at least 50 to 60% by volume in the hollow portion 13. The refrigerant 10 conducts heat by letting the heat received from the exhaust in the combustion chamber 4 escape to a valve guide 22 that is cooled by oil (not shown) provided in the cylinder head 2 or cooling water in a water jacket. That is, heat removal by the refrigerant 10 is performed by transferring heat to the valve guide 22 through the shaft portion 11 of the engine valve 1. Here, the valve guide 22 is made of a material such as brass having a higher thermal conductivity than the engine valve 1 made of austenitic stainless steel or the like as will be described later. Therefore, the closer the distance between the refrigerant 10 and the valve guide 22, the higher the heat extraction efficiency.

  As the refrigerant 10, which will be described in detail later, a refrigerant having a higher melting point than that of conventional metal sodium or the like is used. Therefore, the refrigerant 10 can take a solid state and a liquid state during engine operation. Hereinafter, the behavior when the refrigerant 10 is solid and liquid will be described with reference to FIGS.

FIG. 2 is a vertical cross-sectional view of the engine valve 1 and shows a state where the engine valve 1 is opened when the refrigerant 10 is solid.
As shown in FIGS. 1 and 2, when the refrigerant 10 is solid, the refrigerant 10 itself does not move in the hollow portion 13, and convection does not occur in the refrigerant 10. Therefore, the movement of the heat received by the refrigerant 10 from the exhaust gas in the combustion chamber 4 with the engine valve 1 opened is less than when the refrigerant 10 described later is liquid. Therefore, for example, when the engine 10 is under a low load such as idling operation, the temperature of the exhaust gas in the combustion chamber 4 is low, so that the refrigerant 10 is solid, and the engine valve 1 is used as compared with the case where the refrigerant 10 is liquid. The heat pull is small. That is, heat loss from the engine valve 1 is small, and fuel efficiency is improved.

On the other hand, FIG. 3 is a longitudinal sectional view of the engine valve 1 and shows a state in which the engine valve 1 is closed when the refrigerant 10 is liquid. FIG. 4 is a vertical cross-sectional view of the engine valve 1 and shows a state where the engine valve 1 is opened when the refrigerant 10 is liquid.
As shown in FIGS. 3 and 4, when the refrigerant 10 is a liquid, when the engine valve 1 moves downward and opens, convection occurs in the refrigerant 10 and the refrigerant 10 is forcibly agitated and hollow. It moves to the upper part in the part 13, and the upper part in the hollow part 13 is satisfy | filled with the refrigerant | coolant 10 (refer FIG. 4). Therefore, the movement of the heat received by the refrigerant 10 from the exhaust in the combustion chamber 4 with the engine valve 1 opened is greater than when the refrigerant 10 is solid. In addition, since the distance between the refrigerant 10 and the valve guide 22 is reduced, heat is efficiently transferred from the engine valve 1 to the valve guide 22. Therefore, for example, when the refrigerant 10 is liquid because the exhaust temperature in the combustion chamber 4 is high in a high engine temperature range such as during knock operation or during mid-high load operation, compared to when the refrigerant 10 is solid. Therefore, the heat drawn by the engine valve 1 is large. That is, the heat loss from the engine valve 1 is large, and knocking that tends to occur in the high temperature range of the engine is suppressed. Furthermore, since knocking is suppressed, the ignition timing can be advanced, and the output and fuel consumption are improved.

  Therefore, in the present embodiment, a refrigerant that is solid at the time of idling operation with the lowest engine load is used as the refrigerant 10. Therefore, at the time of idling operation in which knocking does not occur, the refrigerant 10 becomes solid, so that the heat absorption due to the movement of the refrigerant 10 in the hollow portion 13 is suppressed. Thereby, the heat loss from the engine valve 1 is reduced and the fuel consumption is improved.

Moreover, in this embodiment, the refrigerant | coolant which is a solid in the operation area | region where the net fuel consumption rate (BSFC) is the smallest among MBT area | regions as the refrigerant | coolant 10 is used preferably.
Here, FIG. 5 is a diagram showing a BSFC map of the engine. In FIG. 5, the horizontal axis represents the engine speed, and the vertical axis represents the engine torque. The BSFC map in FIG. 5 represents the engine speed that is most efficient with respect to the requested engine torque, and in the order of the operation region a <operation region b <operation region c <operation region d in FIG. The consumption rate (g / kWh) is large. For this reason, the gear ratio is controlled so that the engine is operated in the driving region a having the best fuel consumption, that is, the least BSFC, by the multistage transmission having the stepped gear and the application of the continuously variable transmission. Is done. As shown in FIG. 5, the operation region a is usually in the MBT region, and in the operation region a having the smallest BSFC in the MBT region, the exhaust temperature is relatively low, so that the refrigerant 10 becomes solid at this time. As a result, heat loss from the engine valve 1 is reduced, and fuel consumption is further improved.

  In the present embodiment, as the refrigerant 10, a refrigerant that is liquid at the rated point operation with the highest engine load is used. Furthermore, as the refrigerant 10, a refrigerant that is liquid during torque point operation is preferably used, and a refrigerant that is liquid throughout the knock region where knocking occurs is more preferably used.

  Here, FIG. 6 is a diagram showing an engine torque curve and an engine output curve. In FIG. 6, the horizontal axis represents the engine speed, and the vertical axis represents the engine torque or the engine output. As shown in FIG. 6, the engine load is highest at the rated point at which the engine output is highest. During the rated point operation with the highest engine load, knocking is likely to occur, and the exhaust temperature becomes the highest. Therefore, when the refrigerant 10 becomes liquid during the rated point operation, the inside of the combustion chamber 4 is cooled by the heat drawn to the valve guide 22 by the convection and movement of the refrigerant 10, and knocking is suppressed. Furthermore, since knocking is suppressed, the ignition timing can be advanced, and the output and fuel consumption are improved.

  Further, since the rotational speed is too fast at the rated point in the high rotation region and combustion cannot sufficiently catch up, the torque point in the lower rotation region is more likely to knock. Therefore, knocking is further suppressed and the output and fuel consumption can be further improved by the refrigerant 10 becoming liquid during this torque point operation.

  FIG. 7 is a diagram showing an MBT region and a knock region of the engine. In FIG. 7, the horizontal axis represents the engine speed, and the vertical axis represents the engine torque. As shown in FIG. 7, the knock region is an operation region that is located outside the MBT region and deviates from the MBT region by increasing the engine speed and torque and knocking occurs. Since the refrigerant 10 becomes liquid in the entire knock region including the above-described rated point and torque point, knocking is further suppressed, and output and fuel consumption can be further improved.

  Here, in this specification, during idling operation, rated point operation, torque point operation, and knock range operation, the engine is stably operated in idling, rated point, torque point, and knock range. Represents a state. That is, they do not include the cold start.

The engine valve 1 according to the present embodiment is preferably applied to a hybrid engine. Here, FIG. 8A is a diagram showing an operation area of a normal gasoline engine, and FIG. 8B is a diagram showing an operation area of a hybrid engine.
In general, both a normal gasoline engine and a hybrid engine travel in an area with the best fuel efficiency. In the case of a normal gasoline engine, it is necessary to output directly in response to the driver's request, so it may be forced to operate in an area with poor fuel consumption at low load or high load. NA is as shown by a broken line in FIG. 8A.

  On the other hand, in the case of a hybrid engine, the engine is operated in the fuel efficiency optimum region when the load is low, and surplus torque is collected in the battery. In addition, when the load is high, the vehicle operates in the optimum fuel efficiency range, and the insufficient torque is compensated by the battery. Therefore, in the hybrid engine, the driving ratio in the optimum fuel efficiency region is higher than that of a normal gasoline engine, and the driving area HA is as shown by a broken line in FIG. 8B. Therefore, in this operation area HA, it is preferable that the refrigerant 10 is solid, thereby avoiding fuel consumption loss due to heat loss from the engine valve 1.

Based on the above, in the engine valve 1 according to the present embodiment, a specific aluminum alloy, a specific magnesium alloy, or a specific sodium alloy is used as a specific material that can realize the refrigerant including the above-described preferred mode as the refrigerant 10. Used.
Hereinafter, each of these alloys will be described in detail.

[Aluminum alloy]
The aluminum alloy used as the refrigerant 10 of the present embodiment is an aluminum alloy containing two or more elements. Specifically, it contains 50% to 86% by weight of aluminum and 14% to 50% by weight of magnesium, or magnesium and lithium, beryllium, calcium, zinc, strontium, indium, tin, An alloying element consisting of at least one selected from the group consisting of barium and bismuth and 14 to 50% by mass in total is contained. That is, the aluminum alloy of the present embodiment contains at least magnesium as an alloy element, and may further contain one or more of the alloy elements listed above.

Here, FIG. 9 is a phase diagram of a binary aluminum-magnesium alloy. In FIG. 9, the horizontal axis represents mass% of magnesium, and the vertical axis represents temperature (° C.).
As shown in FIG. 9, the aluminum-magnesium alloy has a melting point of about 437 ° C. if the magnesium content is 14 mass% to 85 mass%, that is, the aluminum content is in the range of 15 mass% to 86 mass%. It turns out that it is -450 degreeC.

Therefore, it can be seen that the refrigerant 10 of the present embodiment, which is an aluminum alloy containing magnesium as an alloy element and has an aluminum content of 50 mass% to 86 mass%, is solid up to approximately 450 ° C. Thereby, the refrigerant | coolant 10 of this embodiment can maintain a solid state at the time of idling operation whose exhaust gas temperature is 150 to 190 degreeC.
On the other hand, since the exhaust temperature normally exceeds 700 ° C. at the time of high load, the refrigerant 10 can maintain a liquid state. Further, since the exhaust temperature normally exceeds 450 ° C. during medium load, the refrigerant 10 can maintain a liquid state.

  Here, as can be seen from FIG. 9, when the aluminum content in the aluminum alloy exceeds 86 mass%, the melting point rapidly rises from 450 ° C., and when it reaches pure aluminum, the melting point is very high at 660 ° C. It becomes. Therefore, when an aluminum alloy having an aluminum content exceeding 86% by mass is used as the refrigerant, knocking cannot be improved without melting even in the knock range at medium and high loads. Therefore, in the present embodiment, aluminum is alloyed so that the aluminum content is in the range of 50% by mass to 86% by mass, so that the melting point is lowered and used as a refrigerant. Thereby, it melt | dissolves reliably in a knock area | region and can knock now.

  Moreover, the thermal conductivity of pure aluminum is about 230 (W / (m · K)), which is higher than the thermal conductivity of the heat-resistant steel constituting the engine valve 1. On the other hand, in the present embodiment, aluminum is alloyed to reduce the thermal conductivity when solid, and is used as a refrigerant. As a result, heat dissipation can be suppressed in the MBT region, and heat loss can be further reduced.

  Moreover, melting | fusing point can be lowered | hung by making a 2 component type aluminum-magnesium alloy contain specific alloy elements other than aluminum and magnesium. Examples of the specific alloy element include typical elements having a low melting point. Among them, as listed above, at least one selected from the group consisting of lithium, beryllium, calcium, zinc, strontium, indium, tin, barium and bismuth. A seed is used. Thereby, melting | fusing point of the refrigerant | coolant 10 can be lowered | hung, and it is solid in the operation area | region with few BSFC among MBT areas by making content of the said alloy element into the range of 14 mass%-50 mass% in total. It can be set as the refrigerant | coolant which can maintain a state.

By the way, the alloy element is preferably an element that does not cause liquid metal embrittlement with respect to the heat-resistant steel constituting the engine valve 1. When an element that causes liquid embrittlement is used, the heat resistant steel becomes brittle when the alloy is liquefied, and in the worst case, the engine valve may be damaged. For example, when SUH35, which is austenitic stainless steel containing nickel, is used, if lithium or zinc is used as the alloy element, SUH35 may cause liquid metal embrittlement when the refrigerant 10 is in a liquid state.
Therefore, in this embodiment, it is preferable to use at least one selected from the group consisting of beryllium, calcium, strontium, indium, tin, barium and bismuth among the alloy elements listed above except for magnesium.

[Magnesium alloy]
The magnesium alloy used as the refrigerant 10 of the present embodiment is a magnesium alloy containing two or more elements. Specifically, magnesium is contained in an amount of 50% by mass to 85% by mass and aluminum is contained in an amount of 15% by mass to 50% by mass, or aluminum and lithium, beryllium, calcium, zinc, strontium, indium, tin, An alloying element consisting of at least one selected from the group consisting of barium and bismuth and 15% by mass to 50% by mass is contained. That is, the magnesium alloy of this embodiment includes at least aluminum as an alloy element, and may further include one or more of the alloy elements listed above.

As shown in FIG. 9 described above, the refrigerant 10 of the present embodiment, which is a magnesium alloy containing aluminum as an alloy element and has a magnesium content of 50% by mass to 85% by mass, is solid up to about 437 ° C. I understand. Thereby, the refrigerant | coolant 10 of this embodiment can maintain a solid state at the time of idling operation whose exhaust gas temperature is 150 to 190 degreeC.
On the other hand, since the exhaust temperature normally exceeds 700 ° C. at the time of high load, the refrigerant 10 can maintain a liquid state. Further, since the exhaust temperature normally exceeds 450 ° C. during medium load, the refrigerant 10 can maintain a liquid state.

  Here, as can be seen from FIG. 9, when the magnesium content in the magnesium alloy exceeds 85% by mass, its melting point rapidly increases from 437 ° C., and when it reaches pure magnesium, its melting point is 650 ° C., which is very high. It becomes. Therefore, when an aluminum alloy having a magnesium content exceeding 85% by mass is used as the refrigerant, knocking cannot be improved without melting even in the knock range at medium and high loads. Therefore, in the present embodiment, magnesium is alloyed so that the magnesium content is in the range of 50% by mass to 85% by mass, so that the melting point is lowered and used as a refrigerant. Thereby, it melt | dissolves reliably in a knock area | region and can knock now.

  Moreover, the thermal conductivity of pure magnesium is about 160 (W / (m · K)), which is higher than the thermal conductivity of the heat-resistant steel constituting the engine valve 1. On the other hand, in this embodiment, magnesium is alloyed to reduce the thermal conductivity when it is solid, and is used as a refrigerant. As a result, heat dissipation can be suppressed in the MBT region, and heat loss can be further reduced.

  Moreover, similarly to the aluminum alloy mentioned above, the magnesium alloy of this embodiment can also reduce melting | fusing point by containing specific alloy elements other than aluminum. The specific alloy elements are as described above, and it is also the same that elements that do not cause liquid metal embrittlement with respect to the heat-resistant steel constituting the engine valve 1 are preferable.

[Sodium alloy]
The sodium alloy used as the refrigerant 10 of the present embodiment is a sodium alloy containing two or more elements. Specifically, the sodium alloy contains barium and contains 50 mol% to 72 mol% of sodium, a sodium alloy containing bismuth and 50 mol% to 75 mol% of sodium, or tin And a sodium alloy containing 50 mol% to 79 mol% of sodium.

Here, FIG. 10 is a phase diagram of a binary sodium-barium alloy. In FIG. 10, the upper horizontal axis represents barium mass%, the lower horizontal axis represents barium mol%, and the vertical axis represents temperature (° C.).
As shown in FIG. 10, the sodium-barium alloy having a sodium content of 50 mol% or more has a barium content in the range of 28 mol% to 50 mol%, that is, the sodium content is 50 mol% to 72 mol%. If present, the melting point is found to be approximately 197 ° C. As described above, when a normal metal is alloyed, the melting point is lower than that of a single metal. However, a sodium alloy has a characteristic that the melting point is higher than that of pure sodium (melting point: 98 ° C.).

Therefore, it can be seen that the refrigerant 10 of the present embodiment, which is a sodium alloy containing barium as an alloy element and has a sodium content of 50 mol% to 72 mol%, is solid up to about 197 ° C. Thereby, the refrigerant | coolant 10 of this embodiment can maintain a solid state at the time of idling operation whose exhaust gas temperature is 150 to 190 degreeC.
On the other hand, since the exhaust temperature normally exceeds 700 ° C. at the time of high load, the refrigerant 10 can maintain a liquid state. Further, since the exhaust temperature normally exceeds 450 ° C. during medium load, the refrigerant 10 can maintain a liquid state.

  As can be seen from FIG. 10, when the sodium content in the sodium-barium alloy exceeds 72 mol%, the melting point rapidly decreases from 197 ° C. Therefore, when a sodium-barium alloy having a sodium content exceeding 72 mol% is used as the refrigerant, the solid state cannot be maintained during the idling operation. Therefore, in the present embodiment, the above effect is obtained by alloying sodium with barium so that the sodium content is in the range of 50 mol% to 72 mol%.

FIG. 11 is a phase diagram of a binary sodium-bismuth alloy. In FIG. 11, the upper horizontal axis represents mass% of sodium, the lower horizontal axis represents mol% of sodium, and the vertical axis represents temperature (° C.).
As shown in FIG. 11, a sodium-bismuth alloy having a sodium content of 50 mol% or more has a melting point of about 444 ° C. if the sodium content is in the range of 50 mol% to 75 mol%. I understand.

Therefore, it can be seen that the refrigerant 10 of this embodiment, which is a sodium alloy containing bismuth as an alloy element and has a sodium content of 50 mol% to 75 mol%, is solid up to about 444 ° C. Thereby, the refrigerant | coolant 10 of this embodiment can maintain a solid state at the time of idling operation whose exhaust gas temperature is 150 to 190 degreeC.
On the other hand, since the exhaust temperature normally exceeds 700 ° C. at the time of high load, the refrigerant 10 can maintain a liquid state. Further, since the exhaust temperature normally exceeds 450 ° C. during medium load, the refrigerant 10 can maintain a liquid state.

  As can be seen from FIG. 11, when the sodium content in the sodium-bismuth alloy exceeds 75 mol%, the melting point rapidly decreases to approximately 97.8 ° C. Therefore, when a sodium-bismuth alloy having a sodium content exceeding 75 mol% is used as a refrigerant, a solid state cannot be maintained during idling operation. Therefore, in the present embodiment, the above-described effects can be obtained by alloying sodium with bismuth so that the sodium content is in the range of 50 mol% to 72 mol%.

FIG. 12 is a phase diagram of a binary sodium-tin alloy. In FIG. 12, the upper horizontal axis represents mol% of tin, the lower horizontal axis represents mass% of tin, and the vertical axis represents temperature (° C.).
As shown in FIG. 12, a sodium-tin alloy having a sodium content of 50 mol% or more has a tin content of 21 mol% to 50 mol%, that is, a sodium content of 50 mol% to 79 mol%. If it exists, it turns out that the melting | fusing point is about 357 degreeC-441 degreeC.

Therefore, it can be seen that the refrigerant 10 of this embodiment, which is a sodium alloy containing tin as an alloy element and has a sodium content of 50 mol% to 79 mol%, is solid up to approximately 357 ° C. to 441 ° C. Thereby, the refrigerant | coolant 10 of this embodiment can maintain a solid state at the time of idling operation whose exhaust gas temperature is 150 to 190 degreeC.
On the other hand, since the exhaust temperature normally exceeds 700 ° C. at the time of high load, the refrigerant 10 can maintain a liquid state. Further, since the exhaust temperature normally exceeds 450 ° C. during medium load, the refrigerant 10 can maintain a liquid state.

  As can be seen from FIG. 12, when the sodium content in the sodium-tin alloy exceeds 79 mol%, the melting point rapidly decreases to approximately 97.8 ° C. For this reason, when a sodium-tin alloy having a sodium content exceeding 79 mol% is used as the refrigerant, the solid state cannot be maintained during idling operation. Therefore, in the present embodiment, the above-described effects can be obtained by alloying sodium with tin so that the sodium content is in the range of 50 mol% to 79 mol%.

  It should be noted that the present invention is not limited to the above-described embodiment, and modifications and improvements within the scope that can achieve the object of the present invention are included in the present invention.

DESCRIPTION OF SYMBOLS 1 ... Engine valve 2 ... Cylinder head 3 ... Exhaust passage 4 ... Combustion chamber 5 ... Exhaust port 10 ... Refrigerant 11 ... Shaft part 12 ... Umbrella part 13 ... Hollow part 21 ... Valve insertion hole 22 ... Valve guide 23 ... Valve seat 121 ... Outer wall 122 ... Valve face

Claims (5)

An engine valve comprising a shaft portion and an umbrella portion integrally provided on one axial end side of the shaft portion, wherein a hollow portion is formed from the shaft portion to the umbrella portion,
Comprising a refrigerant made of an aluminum alloy sealed in the hollow portion;
The aluminum alloy is
While containing 50 mass%-86 mass% of aluminum,
Containing 14% to 50% by weight of magnesium, or
An engine valve containing a total of 14 mass% to 50 mass% of an alloy element composed of magnesium and at least one selected from the group consisting of lithium, beryllium, calcium, zinc, strontium, indium, tin, barium and bismuth. An engine valve comprising a shaft portion and an umbrella portion integrally provided on one axial end side of the shaft portion, wherein a hollow portion is formed from the shaft portion to the umbrella portion,
Comprising a refrigerant made of a magnesium alloy enclosed in the hollow portion;
The magnesium alloy is
While containing 50% to 85% by weight of magnesium,
Contains 15% to 50% by weight of aluminum, or
An engine valve containing a total of 15% to 50% by mass of an alloy element composed of aluminum and at least one selected from the group consisting of lithium, beryllium, calcium, zinc, strontium, indium, tin, barium and bismuth. An engine valve comprising a shaft portion and an umbrella portion integrally provided on one axial end side of the shaft portion, wherein a hollow portion is formed from the shaft portion to the umbrella portion,
Comprising a refrigerant made of a sodium alloy sealed in the hollow part,
The sodium alloy contains barium and contains 50 mol% to 72 mol% of sodium, a sodium alloy containing bismuth and 50 mol% to 75 mol% of sodium, or tin and An engine valve which is a sodium alloy containing 50 mol% to 79 mol% of sodium. The shaft part and the umbrella part are made of heat-resistant steel,
2. The engine valve according to claim 1, wherein the alloy element of the aluminum alloy includes magnesium and at least one selected from the group consisting of beryllium, calcium, strontium, indium, tin, barium, and bismuth. The shaft part and the umbrella part are made of heat-resistant steel,
The engine valve according to claim 2, wherein the alloy element of the magnesium alloy includes aluminum and at least one selected from the group consisting of beryllium, calcium, strontium, indium, tin, barium, and bismuth.

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