JPWO2014054613A1 - Hollow poppet valve - Google Patents

Abstract

Provided is a hollow poppet valve that has an excellent heat-drawing effect and can simplify manufacturing equipment. A hollow portion (S) is formed from the umbrella portion (14) to the shaft portion (12) of the poppet valve integrally formed with the umbrella portion (14) on one end side of the shaft portion (12), and the hollow portion (S) is formed. Instead of the conventional metal Na, a Zn—Al alloy was loaded as a coolant (19). Zn-Al alloy and metal Na have substantially the same thermal conductivity, and the same heat-drawing effect as before can be obtained. Since the coolant (19) is difficult to oxidize, the coolant (19) can be stored and loaded in the atmosphere. Cost can also be reduced.

Description

  The present invention relates to a hollow poppet valve in which a coolant is loaded in a hollow portion formed from an umbrella portion to a shaft portion of the poppet valve.

  In the following Patent Documents 1, 2, etc., a hollow part is formed from the umbrella part of the poppet valve integrally formed on one end side of the shaft part to the shaft part, and has a higher thermal conductivity than the base material of the valve. A hollow poppet valve is described in which a coolant (eg, metallic sodium, melting point about 98 ° C.) is loaded into the hollow portion with an inert gas.

  Since the hollow portion of the valve extends from the inside of the umbrella portion into the shaft portion, and so much coolant can be loaded into the hollow portion, the thermal conductivity of the valve (hereinafter referred to as the heat extraction effect of the valve) can be increased. it can.

  That is, although the combustion chamber becomes hot due to the driving of the engine, if the temperature of the combustion chamber is too high, knocking occurs and a predetermined engine output cannot be obtained, leading to deterioration of fuel consumption (deterioration of engine performance). Therefore, as a method of actively conducting heat generated in the combustion chamber 10A through the valve in order to lower the temperature of the combustion chamber (a method for increasing the heat-sucking effect of the valve), the coolant is hollowed with an inert gas. Various hollow valves loaded in the part have been proposed.

WO2010 / 041337 JP2011-179328

  As a coolant to be loaded in the hollow part of this type of hollow valve, sodium potassium alloy is known in addition to metallic sodium. Sodium potassium alloy is designated as a deleterious substance by the Poisonous and Deleterious Substances Control Law, Due to contact with water leading to flames and explosions, it has not been adopted. Conventionally, metallic sodium has been adopted as a coolant.

  However, metallic sodium is very easy to oxidize, and when oxidized, the thermal conductivity is significantly reduced. For this reason, in order not to touch the air, for example, in order to store it in oil, or to load a valve, it is necessary to manage and load metal sodium, such as loading with an inert gas in an inert gas atmosphere. Very troublesome. Furthermore, metallic sodium is designated as a third class hazardous material and is subject to various restrictions such as the Fire Service Act when handled.

  For these reasons, the automotive engine valve industry has been demanding a new material to replace metallic sodium as a coolant used in hollow valves.

  As a result of investigating whether or not there is a metal having excellent thermal conductivity and easy handling as a coolant to be loaded in this kind of hollow valve, the inventor has developed zinc-aluminum that has been developed as a superplastic metal for damping dampers. We focused on the alloy (Zn-22wt% Al).

  That is, physical properties of Fe as a valve material, metallic sodium as a coolant, and zinc-aluminum alloy (Zn-22 wt% Al) as a superplastic metal are as shown in FIG.

  Zinc-aluminum alloy (Zn-22wt% Al), which is known as a superplastic metal, has almost the same thermal conductivity as that of metallic sodium, is difficult to oxidize, and is easy to handle.

  The melting point of zinc-aluminum alloy (Zn-22wt% Al) is about 500 ° C, much higher than the melting point of metallic sodium. ) Combustion chamber, suction and exhaust passage temperature is 500-800 ° C, far exceeding the melting point (500 ° C), so zinc-aluminum alloy (Zn-22wt% Al) exhibits a sufficient heat-drawing effect It becomes a liquid that can be made.

  Zinc-aluminum alloy (Zn-22wt% Al) is an alloy containing 22wt% of aluminum with respect to 78wt% of zinc. Its specific gravity is smaller than the specific gravity of the valve material, but much larger than the specific gravity of metallic sodium. Therefore, the merit of reducing the weight of the valve is low. However, as can be seen from the equilibrium diagram of the zinc-aluminum alloy shown in FIG. 9, the density (specific gravity) of the zinc-aluminum alloy can be adjusted by adjusting the component ratio (weight ratio) of zinc and aluminum, The melting point and thermal conductivity can be similarly adjusted.

  In particular, since zinc-aluminum alloys are difficult to oxidize, they can be stored in the atmosphere and do not need to be loaded with an inert gas like metallic sodium. Furthermore, since zinc-aluminum alloy is not designated as a hazardous material like metallic sodium, it is easy to handle and there are no restrictions as in the case of handling metallic sodium.

  As described above, as a result of examining the possibility of using “zinc-aluminum alloy” as a coolant to be loaded in the hollow portion of the valve, we are confident that “zinc-aluminum alloy” can be adopted as a coolant in place of metallic sodium. This is the result of this application.

  The present invention has been made on the basis of the above-mentioned knowledge of the inventor with respect to the prior art document. The purpose of the present invention is to replace the conventional metallic sodium as a coolant to be loaded in the hollow part of the valve with “zinc” which is easy to handle. By using “aluminum alloy”, it is to provide a hollow poppet valve that has an excellent heat-drawing effect and can simplify the manufacturing equipment.

  In order to achieve the object, in the hollow poppet valve according to the present invention (Claim 1), a hollow portion is formed from the umbrella portion of the poppet valve integrally formed on one end side of the shaft portion to the shaft portion. The zinc-aluminum alloy, which is a coolant, is loaded into the hollow portion.

  According to a second aspect of the present invention, in the hollow poppet valve according to the first aspect of the present invention, the hollow portion is filled with the coolant (zinc-aluminum alloy) together with the atmosphere (air).

  (Operation) For example, the thermal conductivity of zinc-aluminum alloy (Zn-22 wt% Al) is 135 W / m / K, which is almost the same as the thermal conductivity of metallic sodium 132 W / m / K.

  Since the melting point of zinc-aluminum alloy (Zn-22wt% Al) (approximately 500 ° C) is higher than the melting point of metallic sodium (97.8 ° C), the zinc-aluminum alloy (Zn-22wt% Al) remains solid. Although the heat-absorbing effect cannot be fully exhibited, the temperature of the combustion chamber, intake and exhaust passages during normal driving of the automobile (when the engine is driven) is 500 to 800 ° C, far exceeding the melting point. The zinc-aluminum alloy (Zn-22 wt% Al) thus formed becomes a liquid, and in the present invention, the heat drawing effect comparable to that of a conventional hollow valve loaded with metallic sodium can be sufficiently exhibited.

Zn-22wt% Al has a melting point of 500 ° C, a thermal conductivity of 135 W / m / K, and a density of 5.14 g / cm ^3. The higher the thermal conductivity of the “alloy”, the lower the melting point, and the lower the melting point, and the lower the density (specific gravity), in order to further reduce the weight of the valve.

  FIG. 9 shows an equilibrium diagram of “zinc-aluminum alloy”. The melting point of “zinc-aluminum alloy” varies depending on the component ratio (weight ratio). As shown in the figure, the eutectic point (eutectic temperature) of “zinc-aluminum alloy” is 382 ° C., for example, when the aluminum content is 100-5 wt% (zinc content is 0-95 wt%), The melting point gradually changes from 660 ° C. to 382 ° C. (eutectic temperature), and the lower the aluminum content (the higher the zinc content), the lower the melting point.

  Further, the thermal conductivity of the “zinc-aluminum alloy” is higher as the aluminum content is higher (the zinc content is lower) from the thermal conductivity of aluminum and zinc (see FIG. 8). . On the other hand, the density (specific gravity) of “zinc-aluminum alloy” is higher as the aluminum content is higher (the zinc content is lower) from the density (specific gravity) of aluminum and zinc (see FIG. 8). Lower.

  Therefore, as the coolant to be loaded in the hollow portion, “Zinc-” in which the component ratio (weight ratio) is adjusted so that the melting point, the thermal conductivity, and the density (specific gravity) meet the needs of the heat drawing effect and weight reduction. It is desirable to use “aluminum alloy”.

  In addition, since “zinc-aluminum alloy” is difficult to oxidize, it can be stored in the atmosphere and does not need to be loaded into the hollow portion together with an inert gas like metallic sodium. That is, in the atmosphere, as in claim 2, “zinc-aluminum alloy” can be loaded into the hollow portion of the valve together with the atmosphere (air).

  Furthermore, since “zinc-aluminum alloy” is not designated as a hazardous material like metallic sodium, it is easy to handle and there are no restrictions as in the case of handling metallic sodium.

In Claim 3, in the hollow poppet valve of Claim 1 or 2,
A frustoconical large-diameter hollow portion having a tapered outer peripheral surface that follows the outer shape of the umbrella portion is provided in the umbrella portion, and a ceiling surface of the frustoconical large-diameter hollow portion is provided in the shaft portion. A linear small-diameter hollow portion that communicates perpendicularly to the large-diameter hollow portion is provided, and the opening peripheral edge of the small-diameter hollow portion to the large-diameter hollow portion is formed as a central axis of the valve. Zinc, which is a coolant in the large-diameter hollow portion when the valve reciprocates in the axial direction by forming a bowl-shaped annular stepped portion in the communication portion. A circulating flow (convection) in the longitudinal direction is formed around the central axis of the valve in the aluminum alloy (liquid).

  (Operation) When the valve shifts from the closed state to the open state (when the valve descends), as shown in FIG. 2 (a), the inertial force is upward on the coolant (liquid) in the hollow portion. Act on. And since the inertial force (upward) acting on the coolant in the central part of the large-diameter hollow part is larger than the inertial force acting on the coolant in the peripheral area of the large-diameter hollow part, the coolant in the large-diameter hollow part It tries to move to the small-diameter hollow part via. However, since the communication portion is formed with a bowl-shaped annular step portion, in other words, the ceiling surface of the large-diameter hollow portion (the opening peripheral edge of the small-diameter hollow portion in the large-diameter hollow portion) is in the central axis of the valve. On the other hand, since it is composed of a plane that is substantially orthogonal, the coolant cannot smoothly move to the small-diameter hollow portion like a conventional hollow valve in which the communicating portion is formed in a smooth shape.

  That is, an upward inertial force acts on the coolant in the large-diameter hollow portion, and as shown in FIG. 3 (a), the communicating portion along the annular stepped portion (the ceiling surface of the large-diameter hollow portion). Flows F1 and F2 toward the center (radially inside) are generated. Then, the flows F2 heading toward the center (radially inner side) of the communication portion along the annular stepped portion collide with each other, and in the communication portion, the flow F3 toward the bottom surface side of the large-diameter hollow portion and the small-diameter hollow portion S2 An upward flow F4 is generated. In the communicating portion, the flow F3 toward the bottom surface side of the large-diameter hollow portion wraps around the bottom surface of the large-diameter hollow portion from the outside in the radial direction along the bottom surface of the large-diameter hollow portion, and again along the ceiling surface of the large-diameter hollow portion. Thus, the flows F1 and F2 are directed toward the center (radially inward) of the communication portion. On the other hand, in the communicating portion, the flows F4 and F5 directed upward of the small-diameter hollow portion are turbulent as shown in FIG.

  As described above, the coolant in the large-diameter hollow portion is formed with a circulation flow (convection) in the longitudinal direction around the central axis of the valve, as indicated by arrows F1 → F2 → F3 → F1, and the small-diameter hollow portion In this coolant, a turbulent flow as indicated by F4 and F5 occurs.

  On the other hand, when the valve transitions from the open state to the closed state (when the valve rises), the inertial force acts downward on the coolant in the hollow portion, as shown in FIG. Since the inertial force (downward) acting on the coolant in the central portion of the large-diameter hollow portion is larger than the inertial force acting on the coolant in the peripheral region of the large-diameter hollow portion, as shown in FIG. In the coolant in the diameter hollow portion, a flow F6 directed radially outward from the center portion of the large diameter hollow portion along the bottom surface is generated, and at the same time, the flow toward the lower side through the communicating portion also in the small diameter hollow portion ( Turbulence) F7 occurs. The flow F6 along the bottom surface of the large-diameter hollow portion flows from the outside of the large-diameter hollow portion to the ceiling surface side to become a flow F8 along the ceiling surface of the large-diameter hollow portion S1, and the central portion of the large-diameter hollow portion , Merges with downward flows F6 and F7.

  That is, as indicated by arrows F6 → F8 → F6, the large-diameter hollow portion is formed with a circulating flow (convection) in the longitudinal direction around the central axis of the valve. A turbulent flow as shown by an arrow F7 is formed.

  As described above, when the valve is opened and closed, the circulating material F1 → F2 → F3; F6 → F8 or turbulent flow F4 as shown in FIGS. , F5, F7, F9, and F10 are formed, and the upper layer portion, middle layer portion, and lower layer portion of the coolant are positively stirred, so that the heat drawing effect (thermal conductivity) of the valve is remarkably improved.

In Claim 4, in the hollow poppet valve in any one of Claims 1-3,
The inner diameter of the small-diameter hollow portion near the valve shaft end is formed larger than the inner diameter of the small-diameter hollow portion near the valve umbrella, and an annular step portion is provided at a predetermined position in the axial direction in the small-diameter hollow portion. The zinc-aluminum alloy (liquid), which is the coolant, is loaded up to a position beyond the stepped portion.

  (Operation) When the valve shifts from the closed state to the open state (when the valve descends), the coolant (liquid) in the small-diameter hollow part is changed from the small-diameter hollow part near the valve umbrella part having a small inner diameter to the inner diameter. When moving to the small-diameter hollow portion near the large valve shaft end, as shown in FIG. 3A, a turbulent flow F9 is formed on the downstream side of the step portion, and the coolant (liquid) in the small-diameter hollow portion is Stir.

  On the other hand, when the valve transitions from the open state to the closed state (when the valve rises), the coolant (liquid) once moved upward in the small-diameter hollow portion by the valve-opening operation is When moving from the small-diameter hollow portion near the portion to the small-diameter hollow portion near the valve umbrella portion having a small inner diameter, a turbulent flow F10 is formed on the downstream side of the annular stepped portion as shown in FIG. The coolant (liquid) in the small-diameter hollow portion is agitated.

  Thus, when the coolant (liquid) moves in the axial direction in the small-diameter hollow portion along with the opening / closing operation (vertical reciprocating operation) of the valve, turbulent flow is generated in the vicinity of the step portion, thereby reducing the small diameter. Since the coolant (liquid) in the hollow portion is agitated, the heat drawing effect (thermal conductivity) in the valve shaft portion is further enhanced.

  According to the hollow poppet valve according to the present invention, the heat conductivity of the zinc-aluminum alloy, which is the coolant loaded in the hollow portion, is approximately the same as the heat conductivity of metal sodium conventionally employed as the coolant. Therefore, the heat drawing effect comparable to that of the conventional hollow valve is exhibited.

  On the other hand, the specific gravity of zinc-aluminum alloy is larger than that of metallic sodium, so it is inferior to conventional hollow valves in terms of weight reduction. However, zinc-aluminum alloy is designated as a third class hazardous material like metallic sodium. Since it is easy to handle, such as not subject to various restrictions such as the Fire Service Act, it has the following specific effects.

  First, since the zinc-aluminum alloy, which is the coolant loaded in the hollow portion, is difficult to oxidize, store the coolant (zinc-aluminum alloy) in a state of being cut off from the atmosphere, such as when storing metallic sodium. Therefore, the facility for storing the coolant (zinc-aluminum alloy) is simplified.

  Second, since the coolant (zinc-aluminum alloy) can be loaded into the hollow portion of the valve in the air instead of the inert gas atmosphere, the equipment and environment for loading the coolant in the process of manufacturing the valve are also included. Be concise.

  As a result, the manufacturing cost of the hollow poppet valve can be greatly reduced.

  According to the second aspect, since the coolant (zinc-aluminum alloy) can be loaded into the hollow portion of the valve together with the atmosphere (air), facilities and work for loading the coolant into the hollow portion of the valve are simplified. The manufacturing cost of the hollow valve can be further reduced.

  According to the third aspect of the present invention, when the valve is opened and closed, the zinc-aluminum alloy (liquid) as the coolant circulates in a wide area from the large-diameter hollow portion to the small-diameter hollow portion. The effect (thermal conductivity) is significantly improved and the performance of the engine is improved accordingly.

  In particular, a large amount of “zinc-aluminum alloy”, which is a coolant, can be loaded into the large-diameter hollow portion, and formed into a zinc-aluminum alloy (liquid) that is the coolant in the large-diameter hollow portion when the valve opens and closes. Since the circulating flow (convection) in the longitudinal inner direction becomes active, the heat drawing effect (thermal conductivity) of the valve is further improved, and the engine performance is further improved.

  According to the fourth aspect, the entire zinc-aluminum alloy (liquid), which is the coolant in the small-diameter hollow portion, is also actively agitated along with the opening / closing operation (vertical operation) of the valve. It is possible to provide a hollow poppet valve that is further superior in thermal conductivity.

It is a longitudinal cross-sectional view of the hollow poppet valve which is the 1st Example of this invention. It is a figure which shows the inertial force which acts on the coolant in the hollow part at the time of the same hollow poppet valve reciprocatingly, (a) shows the inertial force which acts on the coolant at the time of valve opening operation | movement (lowering operation | movement). Sectional drawing and (b) are sectional drawings which show the inertial force which acts on the coolant at the time of valve closing operation | movement (rise operation | movement). It is a figure which expands and shows the motion of the coolant in a hollow part when the hollow poppet valve opens and closes (reciprocates in an axial direction), and (a) is the coolant at the time of shifting from a valve closing state to a valve opening state (B) is a figure which shows a motion of the coolant at the time of transfering from a valve opening state to a valve closing state. FIGS. 4A and 4B are diagrams showing a manufacturing process of the hollow poppet valve, wherein FIG. 4A shows a hot forging process for forging a shell which is an intermediate product of the valve, and FIG. 4B shows a hole corresponding to a small-diameter hollow portion formed in a shaft portion. Shows a hole drilling step, (c) shows a hole drilling step for drilling a hole corresponding to a small-diameter hollow portion near the shaft end, (d) shows a shaft contact step for axially contacting the shaft end member, (E) shows a step of filling the small-diameter hollow portion with a coolant, and (f) shows a step of welding a cap to the opening of the concave portion (large-diameter hollow portion) of the umbrella outer shell in an inert gas atmosphere (large The diameter hollow part sealing process) is shown. It is a longitudinal cross-sectional view of the hollow poppet valve which is the 2nd Example of this invention. It is a longitudinal cross-sectional view of the hollow poppet valve which is the 3rd Example of this invention. It is a longitudinal cross-sectional view of the hollow poppet valve which is the 4th Example of this invention. It is a graph which shows the physical property of metals, such as Fe, Na, and zinc-aluminum alloy (Zn-22wt% Al). It is an equilibrium diagram of a zinc-aluminum alloy.

  Next, embodiments of the present invention will be described based on examples.

  1 to 4 show a hollow poppet valve for an internal combustion engine according to a first embodiment of the present invention.

  In these drawings, reference numeral 10 denotes a heat-resistant alloy in which an umbrella portion 14 is integrally formed on one end side of a shaft portion 12 that extends straight through an R-shaped fillet portion 13 that gradually increases in outer diameter. In the hollow poppet valve, a tapered face portion 16 is provided on the outer periphery of the umbrella portion 14.

  Specifically, a shaft-integrated shell (hereinafter simply referred to as a shell) 11 (see FIGS. 1 and 4), which is a valve intermediate product in which an umbrella outer shell 14a is integrally formed on one end of a cylindrical shaft portion 12a; The shaft end member 12b axially contacted with the shaft portion 12a of the shell 11 and the disc-shaped cap 18 welded to the opening portion 14c in the frustoconical recess 14b of the umbrella outer shell 14a of the shell 11 A hollow poppet valve 10 having a hollow portion S provided from the portion 14 to the shaft portion 12 is configured. In the hollow portion S, a zinc-aluminum alloy (Zn-22 wt% Al) that is a coolant 19 is combined with air (air). It is loaded.

As shown in FIGS. 8 and 9, the characteristics of the zinc-aluminum alloy (Zn-22wt% Al) as the coolant 19 are as follows: melting point: about 500 ° C., thermal conductivity: 135 W / m / K, density (specific gravity): 5.14 g / At cm ³ , the thermal conductivity (135 W / m / K) is approximately equal to that of metallic sodium (132 W / m / K).

  The melting point of zinc-aluminum alloy (Zn-22wt% Al) (about 500 ° C) is higher than the melting point of metallic sodium (97.8 ° C). Since the temperature of the combustion chamber and the intake and exhaust passages during normal driving (when the engine is driven) is 500 to 800 ° C., which exceeds the melting point, the zinc-aluminum alloy (Zn-22wt) that is the coolant 19 in the hollow portion S % Al) becomes a liquid and exhibits the same heat-drawing effect as a conventional hollow valve filled with metallic sodium.

  In addition, although the larger the amount of the coolant 19 is, the better the heat-drawing effect is. However, if the amount is larger than the predetermined amount, the difference as the heat-drawing effect is small, so the cost-effectiveness (the more the coolant 19 is, the higher the cost). For example, an amount of about 1/2 to about 4/5 of the volume of the hollow portion S may be loaded.

  In FIG. 1, reference numeral 2 denotes a cylinder head, and reference numeral 6 denotes an exhaust passage extending from the combustion chamber 4, and a tapered surface with which the face portion 16 of the valve 10 abuts the opening peripheral edge of the exhaust passage 6 to the combustion chamber 4. An annular valve seat 8 provided with 8a is provided. Reference numeral 3 denotes a valve insertion hole provided in the cylinder head 2, and an inner peripheral surface of the valve insertion hole 3 is constituted by a valve guide 3 a with which the shaft portion 12 of the valve 10 is slidably contacted. Reference numeral 9 is a valve spring for urging the valve 10 in the valve closing direction (upward in FIG. 1), and reference numeral 12c is a cotter groove provided at the end of the valve shaft.

  The shell 11 and the cap 18 that are exposed to the high-temperature gas in the combustion chamber 4 and the exhaust passage 6 are made of heat-resistant steel. The shaft end member 12b that does not require as much heat resistance as 18 is made of a general steel material.

  The hollow portion S in the valve 10 includes a truncated cone-shaped large-diameter hollow portion S1 provided in the valve umbrella portion 14 and a linear (rod-shaped) small-diameter hollow portion S2 provided in the valve shaft portion 12. The circular ceiling surface of the large-diameter hollow portion S1 (the bottom surface of the truncated cone-shaped concave portion 14b of the umbrella outer shell 14a that is the opening peripheral portion of the small-diameter hollow portion S1) 14b1 10 planes orthogonal to the central axis L.

  That is, the communicating portion P with the small-diameter hollow portion S2 in the large-diameter hollow portion S1 has a bowl-shaped annular step portion as viewed from the large-diameter hollow portion S1 instead of the smooth shape as in the prior art documents 1 and 2. 15 is formed, and the side (surface) 14b1 facing the large-diameter hollow portion S1 of the annular step portion 15 is configured by a plane orthogonal to the central axis L of the bulb 10. In other words, the bowl-shaped annular step portion 15 is defined by the opening peripheral edge portion (bottom surface of the truncated cone-shaped concave portion 14b of the umbrella outer shell 14a) 14b1 and the inner peripheral surface of the small-diameter hollow portion S2. It is made.

  The small-diameter hollow portion S2 is composed of a small-diameter hollow portion S21 having a relatively large inner diameter near the valve shaft end portion and a small-diameter hollow portion S22 having a relatively small inner diameter near the valve umbrella portion 14, and the small-diameter hollow portion. An annular step portion 17 is formed between S21 and the small-diameter hollow portion S22, and a zinc-aluminum alloy (Zn-22wt% Al) that is a coolant 19 is loaded up to a position beyond the step portion 17. Yes.

  For this reason, when the valve 10 opens and closes, the coolant 19 in the large-diameter hollow portion S1 has an arrow F1 → F2 → F3; F6 → F8 in FIGS. A circulation flow (convection) inward in the vertical direction is formed, and at the same time, turbulence is formed in the coolant 19 near the large-diameter hollow portion S1 in the small-diameter hollow portion S2, as indicated by arrows F4, F5, and F7. Furthermore, a turbulent flow is formed in the coolant 19 in the vicinity of the annular stepped portion 17 as indicated by arrows F9 and F10 in FIGS.

  That is, when the valve 10 is opened and closed, the lower layer, middle layer, and upper layer of the coolant 19 in the hollow portion S are circulated by the circulating flow (convection) or turbulent flow formed in the coolant 19 in the hollow portion S. The part is actively stirred, so that the heat drawing effect (thermal conductivity) in the valve 10 is greatly improved.

  In particular, in this embodiment, the circular ceiling surface (the upper surface of the truncated cone) 14b1 and the outer peripheral surface (the outer circumferential surface of the truncated cone) 14b2 of the large-diameter hollow portion S1 form an obtuse angle. The flow of the coolant 19 from the radially outer side of the large-diameter hollow portion S1 toward the communicating portion P along the ceiling surface of the large-diameter hollow portion S1 (F1, F2 in FIG. 3 (a) and in FIG. 3 (b) Since the generation of F8) becomes smoother, the circulating flow (convection) in the longitudinal direction formed in the coolant 19 in the large-diameter hollow portion S2 becomes active, so that the coolant 19 in the hollow portion S is agitated. As a result, the heat sink effect (thermal conductivity) in the valve 10 is remarkably improved.

  Next, the movement of the coolant when the valve 10 is opened and closed will be described in detail with reference to FIGS.

  When the valve 10 shifts from the closed state to the open state (when the valve 10 is lowered), the inertial force is upwardly applied to the coolant (liquid) 19 in the hollow portion S as shown in FIG. Act on. Since the inertial force (upward) acting on the coolant 19 in the central portion of the large-diameter hollow portion S1 is larger than the inertial force acting on the coolant 19 in the peripheral region of the large-diameter hollow portion S1, the inside of the large-diameter hollow portion S1 The coolant 19 tries to move to the small-diameter hollow portion S2 via the communication portion P. However, since the communication portion P is formed with the bowl-shaped annular step portion 15, the communication portion is formed in a smooth shape, and the small-diameter hollow portion S <b> 2 can be smoothly smooth like the conventional hollow valve shown in the prior art. Cannot move to the side.

  In other words, an upward inertia force acts on the coolant 19 in the large-diameter hollow portion S1, and as shown in FIG. 3A, the annular step portion 15 (the ceiling surface of the large-diameter hollow portion S1). Flows F1 and F2 are formed along the line 14b1) toward the center (radially inner side) of the communication portion P. Then, the flows F2 toward the center (radially inner side) of the communication portion P along the annular stepped portion 15 collide with each other, and in the communication portion P, the flow F3 toward the bottom surface side of the large-diameter hollow portion S1 and the small diameter A flow F4 directed upward of the hollow portion S2 is generated.

  In the communication portion P, the flow F3 toward the bottom surface side of the large-diameter hollow portion S1 wraps around the large-diameter hollow portion S1 from the outside in the radial direction along the bottom surface of the large-diameter hollow portion S1, and The flows F1 and F2 are directed toward the center (radially inward) of the communication portion P along the ceiling surface. On the other hand, in the communication part P, the flows F4 and F5 directed upward of the small-diameter hollow part S2 are turbulent flows as shown in FIG.

  Thus, when the valve 10 shifts from the closed state to the open state (when the valve 10 is lowered), the coolant 19 in the large-diameter hollow portion S1 has an arrow F1-> F2-> F3-> F1. As shown in the figure, a circulating flow (convection) inward in the vertical direction is formed around the central axis L of the valve 10, and turbulent flows as shown in F4 and F5 are formed in the coolant 19 in the small diameter hollow portion S2. The

  Furthermore, when the valve shifts from the closed state to the open state (when the valve 10 is lowered), the coolant 19 in the small-diameter hollow portion S2 is moved into the small-diameter hollow portion S2 by the inertial force acting upward. As shown in FIG. 3A, when moving from a small-diameter hollow portion S22 near the valve umbrella portion 14 having a small inner diameter to a small-diameter hollow portion S21 near the valve shaft end portion having a large inner diameter, A turbulent flow F9 is formed on the downstream side of the stepped portion 17.

  On the other hand, when the valve 10 shifts from the valve-opened state to the valve-closed state (when the valve 10 is raised), as shown in FIG. 2B, the inertial force is applied downward to the coolant 19 in the hollow portion S. Act on. And since the inertia force (downward) which acts on the coolant 19 of large diameter hollow part S1 center part is larger than the inertial force which acts on the coolant 19 of large diameter hollow part S1 peripheral region, it shows in FIG.3 (b). As described above, the coolant 19 in the large-diameter hollow portion S1 generates a flow F6 directed radially outward from the central portion of the large-diameter hollow portion S1 along the bottom surface, and at the same time, communicates also in the small-diameter hollow portion S2. A downward flow (turbulent flow) F7 is generated through the portion P. The flow F6 along the bottom surface of the large-diameter hollow portion S1 circulates from the outside of the large-diameter hollow portion S1 to the ceiling surface side to become a flow F8 along the ceiling surface of the large-diameter hollow portion S1, and the large-diameter hollow portion S1 In the central portion (communication portion P) of the gas flow merges with the downward flows F6 and F7.

  That is, in the coolant 19 in the large-diameter hollow portion S1, as shown by arrows F6 → F8 → F6, a circulation flow (convection) inward in the vertical direction is formed around the central axis L of the valve 10, and the small-diameter hollow A turbulent flow as shown by an arrow F7 is formed in the coolant 19 in the part S2.

  Furthermore, when the valve 10 shifts from the open state to the closed state (when the valve 10 is raised), the inertial force is applied to the coolant (liquid) 19 once moved upward in the small-diameter hollow portion S2 by the valve opening operation. Acts downward, the coolant 19 moves downward in the small-diameter hollow portion S2, but from the small-diameter hollow portion S21 near the end of the valve shaft having a large inner diameter to the small-diameter hollow portion S22 near the valve umbrella portion having a small inner diameter. When moving, a turbulent flow F10 is formed on the downstream side of the stepped portion 17, as shown in FIG.

  In this way, during the opening / closing operation of the valve 10, the entire coolant 19 in the hollow portion S is positively caused by convection (circulation flow) or turbulent flow formed in the coolant 19 in the entire hollow portion S. As a result of stirring, the heat drawing effect (thermal conductivity) in the valve 10 is greatly improved.

  Further, as shown in FIG. 1, the stepped portion 17 in the small-diameter hollow portion S is provided at a position substantially corresponding to the end portion 3b facing the exhaust passage 6 of the valve guide 3a, and has a shaft end portion having a large inner diameter. By forming the small-diameter hollow portion S21 in the axial direction to be long in the axial direction, the contact area between the valve shaft portion 12 and the coolant 19 is increased without reducing the durability of the valve 10, and the heat transfer efficiency of the valve shaft portion 12 is increased. As a result, the small-diameter hollow portion S21 forming wall becomes thin, and the bulb 10 is also light. That is, the stepped portion 17 in the small-diameter hollow portion S has a predetermined position (in the valve shaft portion 12) that does not enter the exhaust passage 6 when the valve 10 is fully opened (lowered) as shown by the phantom line in FIG. A thin-walled small-diameter hollow portion S21 forming wall is provided at a predetermined position that is not easily affected by heat in the exhaust passage 6. Reference numeral 17X in FIG. 1 indicates the position of the stepped portion 17 in a state where the valve 10 is fully opened (lowered).

  Specifically, since the fatigue strength of the metal decreases as the temperature increases, the region near the valve umbrella portion 14 in the valve shaft portion 12 that is always in the exhaust passage 6 and exposed to high heat reduces the fatigue strength. It must be formed to a thickness that can withstand. On the other hand, in the region near the shaft end portion of the valve shaft portion 12 that is away from the heat source and is always in sliding contact with the valve guide 3 a, heat from the combustion chamber 4 and the exhaust passage 6 is transmitted via the coolant 19. However, since the transmitted heat is immediately radiated to the cylinder head 2 through the valve guide 3a, the temperature does not become as high as that near the valve umbrella portion 14.

  That is, since the fatigue strength does not decrease in the region near the shaft end portion in the valve shaft portion 12 than in the region near the valve umbrella portion 14, even if it is formed thin (the inner diameter of the small-diameter hollow portion S21 is increased), it is strong. There is no problem in (durability such as breakage due to fatigue).

  Therefore, in the present embodiment, the position of the stepped portion 17 is a position substantially corresponding to the lower end portion 3b of the valve guide 3 that is as low as possible and does not enter the exhaust passage 6 when the valve 10 is fully opened (lowered). In addition, the inner diameter of the small-diameter hollow portion S21 is increased, and first, the surface area (contact area with the coolant 19) of the entire small-diameter hollow portion S2 is increased, so that the heat transfer efficiency in the valve shaft portion 12 is increased. Has been enhanced. Secondly, the total weight of the valve 10 is reduced by increasing the volume of the entire small-diameter hollow portion S21.

  Next, the manufacturing process of the hollow poppet valve 10 will be described with reference to FIG.

  First, as shown in FIG. 4A, a shell 11 in which an umbrella outer shell 14a provided with a truncated cone-shaped recess 14b and a shaft 12a are integrally formed is formed by a hot forging process. A bottom surface 14b1 of the truncated conical recess 14b in the umbrella outer shell 14a is formed by a plane orthogonal to the shaft portion 12 (the central axis L of the shell 11).

  The hot forging process is extrusion forging in which the dies are sequentially replaced, extrusion forging for manufacturing the shell 11 from a heat-resistant steel metal block, or after installing a spherical portion at the end of the heat-resistant steel bar with an upsetter. Any of upsetting forging that forges the shell 11 (the umbrella outer shell 14a) using a mold may be used. In the hot forging process, an R-shaped fillet portion 13 is formed between the umbrella outer shell 14a and the shaft portion 12a of the shell 11, and a tapered face portion is formed on the outer peripheral surface of the umbrella outer shell 14a. 16 is formed.

  Next, as shown in FIG. 4 (b), the shell 11 is arranged so that the concave portion 14b of the umbrella outer shell 14a faces upward, and the diameter decreases from the bottom surface 14b1 of the concave portion 14b of the umbrella outer shell 14a to the shaft portion 12a. The hole 14e corresponding to the hollow part S22 is drilled by drilling (hole drilling step).

  By the hole drilling step, the concave portion 14b of the umbrella outer shell 14a constituting the large-diameter hollow portion S1 and the hole 14e on the shaft portion 12a side constituting the small-diameter hollow portion S22 communicate with each other, so that the concave portion 14b and the hole 14e In the communication portion, a bowl-shaped annular step portion 15 is formed as viewed from the concave portion 14b side.

  Next, as shown in FIG. 4 (c), a hole 14f corresponding to the small-diameter hollow portion S21 is drilled from the shaft end side of the shell 11 (hole drilling step).

  Next, as shown in FIG. 4D, the shaft end member 12b is axially contacted with the shaft end portion of the shell 11 (shaft end member axial contact step).

  Next, as shown in FIG. 4 (e), a predetermined amount of coolant (solid) 19 is inserted into the hole 14e of the recess 14b of the umbrella outer shell 14a of the shell 11 (coolant loading step).

  Since the zinc-aluminum alloy (Zn-22 wt% Al) that is the coolant 19 is solid at room temperature, the coolant (solid) 19 can be inserted into the hole 14e of the shell 11 with a predetermined thickness and By processing in advance into a round bar having a length, the coolant (solid) 19 can be smoothly inserted into the hole 14e of the shell 11 in the coolant loading step shown in FIG.

  Finally, as shown in FIG. 4 (f), a cap 18 is welded (for example, resistance welding) to the opening 14c of the concave portion 14b of the umbrella outer shell 14a of the shell 11 in an air atmosphere, so that the valve 10 The hollow part S is sealed (hollow part sealing step). The welding of the cap 18 may employ electron beam welding or laser welding instead of resistance welding.

  Note that the coolant loading step shown in FIG. 4 (e) and the hollow portion sealing step shown in FIG. 4 (f) are steps of loading the coolant (solid) 19 together with the atmosphere (air) into the hollow portion S of the valve 10. However, in the conventional hollow poppet valve manufacturing process using metallic sodium as the coolant, the environment in which the coolant loading process and the hollow portion sealing process are performed is controlled by argon gas or the like to prevent oxidation of the coolant (metal sodium). In the present embodiment, the zinc-aluminum alloy (Zn-22wt% Al), which is the coolant 19, is used. Since it is difficult to oxidize, the coolant loading step shown in FIG. 4 (e) and the hollow portion sealing step shown in FIG. 4 (f) need only be performed in an air atmosphere, and the facilities and equipment are simplified and the cost does not increase.

  FIG. 5 shows a hollow poppet valve according to a second embodiment of the present invention.

  In the hollow poppet valve 10 of the first embodiment described above, the large-diameter hollow portion S1 in the valve umbrella portion 14 is configured in a truncated cone shape, and the small-diameter hollow portion S2 in the valve shaft portion 12 is a large-diameter hollow portion. In the hollow poppet valve 10A of the second embodiment, the small-diameter hollow portion S2 in the valve shaft portion 12 has a smooth curved region (the inner diameter gradually increases). The change transition region) X communicates with the substantially conical large-diameter hollow portion S1 ′ in the valve umbrella portion 14 via X.

  That is, reference numeral 11A denotes a shell that is a valve intermediate product in which an umbrella outer shell 14a ′ is integrally formed on one end side of a cylindrical shaft portion 12a, and the umbrella outer shell 14a ′ of the shell 11A has a shaft A substantially conical recess 14b ′ is provided that defines a large-diameter hollow portion S1 ′ that smoothly communicates with the small-diameter hollow portion S2 in the portion 12a.

  Others are the same as those of the hollow poppet valve 10 of the first embodiment described above, and the same reference numerals are given to omit redundant description.

  Also in this hollow poppet valve 10A, as with the hollow poppet valve 10 of the first embodiment described above, a zinc-aluminum alloy which is a coolant (liquid) 19 in accordance with the opening / closing operation (vertical operation) of the valve 10A. When (Zn-22wt% Al) moves in the small diameter hollow portion S2 in the axial direction, a turbulent flow (not shown) is generated in the vicinity of the stepped portion 17, and this turbulent flow is a coolant in the small diameter hollow portion S2. (Liquid) 19 is stirred, whereby the middle layer portion is stirred from at least the upper layer portion of the coolant 19 in the entire hollow portion S ′, and heat transfer by the coolant 19 in the hollow portion S is activated, The heat drawing effect of the valve 10A is improved.

  In the first and second embodiments described above, the inner diameter of the small-diameter hollow portion S21 near the valve shaft end portion is formed larger than the inner diameter of the small-diameter hollow portion S22 near the valve umbrella portion 14, and the small-diameter hollow portion S2 is formed. An annular stepped portion 17 is provided at a predetermined position in the axial direction, but the small-diameter hollow portion S2 in the valve shaft portion 12 has a constant inner diameter in the axial direction as in the third embodiment shown in FIG. And a zinc-aluminum alloy (Zn-22 wt% Al) as the coolant 19 is loaded up to a predetermined position of the small-diameter hollow portion S2.

  Others are the same as those in the first embodiment, and a duplicate description thereof is omitted.

  FIG. 7 shows a fourth embodiment of the present invention.

  In the first to third embodiments described above, the structure in which the small-diameter hollow portion S2 on the shaft portion 12 side communicates with the large-diameter hollow portions S1 and S′1 on the umbrella portion 14 side, that is, the hollow portion on the shaft portion 12 side. The hollow portions S1 and S′1 on the umbrella portion 14 side have different inner diameters, but in the hollow valve 10C of the fourth embodiment, the hollow portion S ″ provided from the shaft portion 12 to the umbrella portion 14 is used. Is formed to have a constant inner diameter.

  Others are the same as those of the hollow valve 10 of the first embodiment described above, and the same reference numerals are given to omit redundant description.

  In the first to fourth embodiments, the coolant 19 loaded in the hollow portions S, S ′, S ″ of the valves 10, 10A, 10B, 10C is made of zinc-aluminum alloy (Zn-22wt% Al However, the coolant 19 is not limited to Zn-22 wt% Al, and may be one in which the component ratio (weight ratio) of zinc and aluminum is changed.

That is, Zn-22wt% Al loaded in the hollow portions S, S ', S "has a melting point of 500 ° C, a thermal conductivity of 135 W / m / K, and a density of 5.14 g / cm ³ , In order to further improve the effect, the thermal conductivity of the “zinc-aluminum alloy” to be loaded is preferably higher, the melting point is preferably lower, and in order to further reduce the weight of the valve, the density (specific gravity) Is smaller but desirable.

  FIG. 9 shows an equilibrium diagram of “zinc-aluminum alloy”. In the figure, the aluminum content decreases toward the right (the zinc content increases), and the aluminum content increases toward the left ( Low zinc content). As shown in this figure, the melting point of “zinc-aluminum alloy” varies depending on the component ratio (weight ratio).

  Specifically, the eutectic point (eutectic temperature) of “zinc-aluminum alloy” is 382 ° C., and the blending ratio (weight ratio) of “zinc-aluminum alloy” corresponding to this eutectic point is about 5 wt% of aluminum ( About 95 wt% zinc). When the aluminum content is 100 to 5 wt% (zinc content is 0 to 95 wt%), the melting point gradually increases from 660 ° C to 382 ° C as the aluminum content decreases (the zinc content increases). Lower. On the other hand, when the aluminum content is 5 to 0 wt% (zinc content is 95 to 100 wt%), the melting point gradually increases from 382 ° C to 419 ° C as the aluminum content decreases (the zinc content increases). Get higher.

  Further, the thermal conductivity of the “zinc-aluminum alloy” is higher as the aluminum content is higher (the zinc content is lower) from the thermal conductivity of aluminum and zinc (see FIG. 8). . On the other hand, the density (specific gravity) of “zinc-aluminum alloy” is higher as the aluminum content is higher (the zinc content is lower) from the density (specific gravity) of aluminum and zinc (see FIG. 8). Lower.

  Therefore, "Zinc-aluminum alloy" with the component ratio (weight ratio) adjusted so that the melting point, thermal conductivity, and density (specific gravity) meet the needs of the heat-drawing effect and weight reduction is loaded into the hollow part of the valve. You may make it do.

10, 10A, 10B, 10C Hollow poppet valve 11, 11A Shell 12 in which the outer shell and the shaft portion are integrally formed 12 Valve shaft portion 12a Shaft portion 12b Shaft end member 14 Valve umbrella portion 14a, 14a 'Umbrella portion outer shell 14b, 14b 'Umbrella outer shell concave part 14b1 Large-diameter hollow circular ceiling surface 14b2 Umbrella outer shell frustoconical concave inner peripheral surface 15 Small-diameter hollow opening peripheral edge of large-diameter hollow part An annular stepped portion 17 that is an annular stepped portion 18 Cap 19 Coolant L Central axis S, S ', S "of the valve Hollow portion S1, S1' Large-diameter hollow portion S2 Linear small-diameter hollow portion S21 Axis Small-diameter hollow portion S22 near the end Small-diameter hollow portion P near the umbrella portion Communication portion F1->F2->F3;F6-> F8 Circulating flow in the longitudinal direction

Claims (4)

  A hollow portion is formed from the umbrella portion of the poppet valve integrally formed with the umbrella portion on one end side of the shaft portion to the shaft portion, and a zinc-aluminum alloy as a coolant is loaded in the hollow portion. Hollow poppet valve.   The hollow poppet valve according to claim 1, wherein the hollow portion is filled with a zinc-aluminum alloy together with air (air).   A frustoconical large-diameter hollow part having a tapered outer peripheral surface following the outer shape of the umbrella part is provided in the umbrella part, and the ceiling of the frustoconical large-diameter hollow part is provided in the shaft part. A linear small-diameter hollow portion that communicates perpendicularly to the surface is provided, and an opening peripheral portion of the small-diameter hollow portion to the large-diameter hollow portion that forms a ceiling surface of the large-diameter hollow portion is provided on the valve. Consists of a plane perpendicular to the central axis, and when the valve reciprocates in the axial direction, the zinc-aluminum alloy (liquid) in the large-diameter hollow portion circulates in the longitudinal direction around the central axis of the valve. The hollow poppet valve according to claim 1, wherein a flow (convection) is formed.   The inner diameter of the small-diameter hollow portion near the valve shaft end is formed larger than the inner diameter of the small-diameter hollow portion near the valve umbrella, and an annular step portion is provided at a predetermined axial position in the small-diameter hollow portion. The hollow poppet valve according to any one of claims 1 to 3, wherein the zinc-aluminum alloy is loaded up to a position beyond the stepped portion.

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