JPWO2015121920A1 - Poppet valve - Google Patents

Abstract

Providing a poppet valve that can block all three forms of heat transfer and achieve maximum combustion efficiency. In the poppet valve integrally formed with the umbrella portion (14) on one end side of the shaft portion (12), the umbrella portion (14) has a hollow portion (19) extending along the umbrella surface (24). A metal layer (17) that blocks radiant heat is formed on the ceiling surface (25) of the hollow portion (19), and a heat insulating portion is provided between the metal layer (17) and the bottom surface of the hollow portion (19). Is formed. The heat insulation portion blocks conduction and convection in the heat transfer form by the metal layer (17).

Description

  The present invention relates to a poppet valve that suppresses heat transfer from a combustion chamber, particularly heat dissipation due to radiation.

  Patent Document 1 describes a poppet valve in which an umbrella portion is integrally formed at a shaft end portion. A poppet valve used in an internal combustion engine is seated on a valve seat of a cylinder head to which an intake passage or an exhaust passage is connected, and drives the engine by opening and closing the intake passage or the exhaust passage.

  Normally, the combustion efficiency of an internal combustion engine improves as the loss of energy generated in the combustion chamber decreases. The energy loss includes a cooling loss due to heat scattered outside. The heat in the combustion chamber is often dissipated to the outside through the poppet valve and the combustion chamber wall. Therefore, a space is formed on or near the umbrella surface of the poppet valve that contacts the combustion chamber, and the space is evacuated, filled with an inert gas, or heated by the material constituting the poppet valve. A material with low conductivity is filled to form an adiabatic space to suppress heat dissipation in the combustion chamber (see Patent Document 1).

  There are three types of heat transfer (heat transfer) modes: heat conduction, convection, and radiation (heat radiation). In heat conduction, when an object does not move but directly touches, convection transfers heat indirectly by mediating the flow of fluid, and in both cases, heat is transferred as thermal vibration. On the other hand, in the radiation, heat is carried by the object at the transportation source emitting electromagnetic waves and the object at the transportation destination absorbing it. In the case of radiation, there is no intermediary between the two objects, and heat is transferred even in a vacuum.

  Heat transfer from the engine combustion chamber to the poppet valve also occurs in three ways: heat conduction, convection and radiation. In Patent Document 1 described above, a concave portion is formed on the valve head surface, and the concave portion is filled with a heat insulating porous material to suppress heat dissipation from the combustion chamber. Examples of the material of the porous material include a nonwoven fabric (paragraph 0036) made of a heat-resistant metal such as stainless steel. However, in a normal heat insulating material, even though heat transfer by heat conduction and convection can be interrupted among the heat transfer of the above three modes, the radiant heat is transmitted and the temperature drop in the combustion chamber cannot be avoided. Patent Document 1 has no description about radiation and does not conceive of blocking radiant heat.

  In Patent Document 2, the inner wall of the combustion chamber of the engine is covered with a heat insulating porous layer made of ceramics and a surface dense layer made of ceramics (paragraph 0023). It is disclosed that radiant heat is reflected by the surface dense layer during fuel combustion (paragraph 0024).

JP2012-72748 WO 2013 / 080389A1

http://www.landinst.jp/info/faq/faq3.html http://www.fintech.co.jp/etc-data/housharitsu.htm

  According to the inventors' investigation, the rough nonwoven fabric described in Patent Document 1 hardly reflects heat including radiation, and the ceramic described in Patent Document 2 is radiant heat contrary to the description in Patent Document 2. It has become clear that there is no sufficient reflection. For example, Non-Patent Document 1 and Patent Document 2 describe the emissivity of electromagnetic waves from metals, ceramics, etc., and the emissivity is defined by (emissivity = 1-reflectance-transmittance). Therefore, the reflectance is high when the emissivity is low, but the emissivity of ceramics is considerably high from 0.4 to 0.95. Therefore, it can be seen that the reflectance is quite low and the reflection efficiency of electromagnetic waves is not sufficient. The emissivity of aluminum and copper is 0.05 to 0.09, and the reflectivity is considerably high. The reflection by metal is largely due to free electrons, and since the electromagnetic waves are reflected by collective vibration of free electrons, the reflection effect is high, and the above-mentioned reflection has directivity. However, it is clear that aluminum and copper metals lack high temperature resistance and cannot be used in engines where the combustion gas temperature reaches 2000 ° C to 2500 ° C.

  Moreover, in patent document 2, since it has a radiant heat reflection mechanism in the outermost layer part by the side of a combustion chamber, the heat-resistant temperature requested | required of material is high, applicable material is restricted, and adhesion of combustion residue As a result of the generation of the oxide layer, the reflection function deteriorates. Therefore, even if ceramic is applied to the valve head surface of the poppet valve of Patent Document 1, it does not lead to suppression of heat dissipation due to reflection of radiant heat.

  The present invention has been made on the basis of the above-mentioned knowledge of the inventor with respect to the prior art, and its purpose is to reflect the radiant heat from the combustion chamber of the poppet valve toward the combustion chamber, thereby suppressing heat dissipation due to radiation. Therefore, an object of the present invention is to provide a poppet valve that can stably maintain a high combustion efficiency for a long period of time.

  In order to achieve the above object, in the poppet valve according to the present invention (Claim 1), in the poppet valve in which the umbrella portion is integrally formed on one end side of the shaft portion, the umbrella portion is positioned on the combustion chamber side. The heat insulation part to perform and the metal layer which interrupts | blocks the radiant heat located in the axial part side were comprised.

  (Operation) When the poppet valve having such a configuration is used as an engine valve, the combustion flame generated by the fuel combustion in the combustion chamber and the heat of the combustion gas by the combustion are combusted in the form of heat conduction, convection and radiation. It is transmitted from the chamber toward the poppet valve. The heat of the combustion gas is cut off from heat conduction and convection heat in a heat insulating space (heat insulating portion) filled with a heat insulating material in the heat insulating space on the combustion chamber side of the valve head of the valve head umbrella portion. The Radiant heat, in which heat is carried as electromagnetic waves, passes through the heat insulating region and comes into contact with a glossy metal.

  Since heat due to heat conduction and convection is blocked by the heat insulating part and does not reach the metal, the temperature of the combustion gas in contact with the metal is greatly reduced, and even if the metal lacks high temperature resistance, radiation heat does not deteriorate. It is possible to improve the combustion efficiency by preventing the cooling of the heat of the combustion gas by the valve by keeping the radiant heat in the combustion chamber without passing through the valve body and diffusing it. . In particular, the metal receives heat mainly from the combustion gas through the heat insulating part, in other words, radiation that cannot be blocked by the heat insulating part, and does not directly transfer the heat of the combustion gas to the metal. Selectable. In addition, by having a radiant heat reflection mechanism inside the bulb, it is possible to prevent a reduction in reflection ability due to contamination such as adhesion of combustion residues and generation of an oxide layer. The metal of the present invention includes a metal alloy.

  The metal layer of the present invention needs to have a radiation heat shielding property. A metal having a radiant heat blocking property usually has a glossy surface or a mirror surface, but even if it does not have the glossy surface or mirror surface, it can be used as the metal of the present invention as long as it has a radiant heat blocking property. In the case of a metal that does not have radiant heat shielding properties, the surface can be polished or mirror-finished to impart radiant heat shielding properties and used as the metal of the present invention. In particular, if the temperature of the combustion gas generated in the combustion chamber is 2500 ° C, the wavelength of radiation due to the heat of the combustion gas is 1.0 μm (the wavelength at 1500 ° C is 1.6 μm) from the Viennese displacement law. Since the reflectance in the wavelength region is high, the radiant heat blocking characteristic is enhanced. Therefore, the metal that can be used in the present invention has a radiation heat shielding property that is considerably larger than that of ceramics or the like.

  In the poppet valve according to claim 1, in the poppet valve according to claim 1, a hollow portion extending along the surface of the umbrella is formed in the umbrella portion, and a metal layer that blocks radiant heat is formed on a ceiling surface of the hollow portion. The heat insulating part is formed between the metal layer and the bottom surface of the hollow part.

  (Operation) In the poppet valve having such a configuration, the hollow portion is filled with a heat insulating material such as gas or a low heat conductive material, or the hollow portion is maintained in a vacuum. The optimum heat shielding effect can be obtained by appropriately selecting the conditions of the hollow portion.

  According to a third aspect of the present invention, in the poppet valve according to the first aspect, a metal layer that blocks radiant heat is formed on the bottom surface of the umbrella portion, and a heat-insulating surface treatment is performed on the combustion chamber side of the metal layer that blocks the radiant heat. A layer was formed to form.

  (Operation) Since the poppet valve having such a configuration does not form a hollow portion, the manufacturability of the valve can be improved.

  According to a fourth aspect of the present invention, in the poppet valve according to the first aspect, the metal is selected from aluminum, copper and an aluminum alloy. Examples of the metal other than aluminum constituting the aluminum alloy include copper, manganese, silicon, magnesium, zinc, and nickel.

  (Operation) Aluminum and copper are suitable materials because they are relatively light and have high radiant heat reflection efficiency. Aluminum alloy also has radiant heat reflectivity and can achieve improved fuel efficiency.

  According to a fifth aspect, in the poppet valve according to the first or second aspect, the metal is configured in a foil shape or a sheet shape. Aluminum foil and copper foil are usually glossy themselves, and sticking to the combustion chamber side of the valve head directly through a heat insulating region can prevent the heat from scattering to the outside due to radiant heat reflection. And can contribute to the improvement of fuel efficiency accompanying the improvement of combustion efficiency. Similarly, when the metal is formed into a sheet shape, the radiant heat can be reflected by using it in a predetermined position.

  According to a sixth aspect of the present invention, in the poppet valve according to the first aspect, the metal layer is a film formed by a surface treatment selected from physical vapor deposition (PVD), thermal spraying and plating. The metal layer of the present invention may be an existing foil or sheet, but the metal layer may be formed by the surface treatment. According to such a surface treatment, a metal layer having a high radiant heat blocking property can be formed.

  According to the poppet valve according to the present invention, heat generated in the combustion chamber is effectively blocked by effectively interrupting all forms of heat conduction, convection and radiation of the heat of the combustion flame and combustion gas in the combustion chamber. By preventing scattering, the loss of combustion efficiency due to cooling can be reduced. Even if the metal that forms the metal layer with high radiant heat blocking properties is not sufficiently resistant to high temperatures, only the heat caused by radiation is removed from the heat of the combustion gas due to heat conduction and convection at the heat insulating part. Reaches the metal layer, so that metal degradation hardly occurs.

It is a longitudinal cross-sectional view of the poppet valve which is the 1st Example of this invention. It is an AA line expanded sectional view of FIG. It is a longitudinal cross-sectional view of the poppet valve which is the 2nd Example of this invention. It is a longitudinal cross-sectional view of the poppet valve which is the 3rd Example of this invention.

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

  1 and 2 show a hollow poppet valve for an internal combustion engine according to a first embodiment of the present invention.

  In FIG. 1, reference numeral 10 denotes a heat-resistant alloy in which a valve umbrella portion 14 is integrally formed on one end side of a valve shaft portion 12 that extends straight through an R-shaped fillet portion 13 that gradually increases in outer diameter. A tapered face portion 16 is provided on the outer periphery of the valve umbrella portion 14 in the made poppet valve. An umbrella outer shell 14 a is integrally formed on one end side of the shaft portion 12 to constitute the shell 11.

  On the ceiling surface 14b of the valve umbrella portion 14 on the umbrella surface 24 side, a radiant heat reflecting surface (a metal layer that blocks radiant heat) 17 made of foil-like or sheet-like metal, preferably having a mirror surface, is formed by thermal spraying or the like. And it joins by the method of welding etc., or the metal shape | molded by the sheet form is joined. Usable metals include aluminum and copper, and further include alloys of these metals, particularly aluminum.

  Usually, a foil-like metal has a mirror surface and has a radiant heat blocking property, and thus may be used as it is. However, a metal formed by sheet or surface treatment may not have a sufficient radiant heat blocking property. In that case, it is necessary to improve the radiation heat blocking property by performing a treatment so that the surface is glossy. An example of metal gloss treatment is polishing of the metal surface.

  Next, the cap 18 is attached to the ceiling surface 14b of the valve umbrella portion 14 on which the radiant heat reflecting surface 17 is formed. The cap 18 has a disk shape having an upward bent portion 18a formed by bending the peripheral edge upward, and a circular donut-shaped ring equally divided into four on the inner upper surface. The arc-shaped rib 18b is formed by integral molding or welding. When the upward bent portion 18 a of the cap 18 is fixed to the ceiling surface 14 b of the valve umbrella portion 14 by welding or the like, the ribs 18 b are connected to the ceiling of the valve umbrella portion 14 via the radiant heat reflecting surface 17. The surface 14b is supported. A hollow portion 19 is formed between the upper surface of the cap 18 and the ceiling surface 14 b of the valve umbrella portion 14. By forming a vacuum in the formed space, heat conduction from the combustion chamber side is insulated and functions as a heat insulation space. Moreover, it fills in this space with gas, such as air or argon, and functions as a heat insulation space. In the case of FIG. 1, the upper surface of the cap 18 becomes the bottom surface 25 of the hollow portion.

  In FIG. 1, reference numeral 2 denotes a cylinder head, and reference numeral 6 denotes an exhaust passage extending from the combustion chamber 4. The opening peripheral edge of the exhaust passage 6 to the combustion chamber 4 has a taper with which the face portion 16 of the valve 10 can abut. An annular valve seat 8 provided is provided. Reference numeral 3 denotes a valve insertion hole provided in the cylinder head 2, and the valve insertion hole 3 includes a cylindrical valve guide 3 a with which the shaft portion 12 of the valve 10 is slidably contacted. Reference numeral 9 is a valve spring that urges the valve 10 in the valve closing direction (upward in FIG. 1), and reference numeral 12 c is a cotter groove provided at the end of the valve shaft 12. A vertical hollow portion 21 is formed in the shaft portion 12, and the hollow portion 21 communicates the hollow portion (heat insulating portion) 19 with the lower surface of the shaft end member 12b.

  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.

  When fuel burns in the combustion chamber 4 of the hollow poppet valve 10 configured in this way, heat of high-temperature combustion gas is generated, and the heat of this combustion gas passes through the cap 18 of the poppet valve 10 and the hollow portion. (Insulation part) 19 is reached. Of the heat conduction, convection and radiation, which is the heat transfer mode of the combustion gas heat, the heat conduction and convection are blocked by the heat insulating portion 19, and the heat of the combustion gas is directed from the radiant heat reflecting surface 17 toward the valve umbrella portion 14. Not transmitted. Radiant heat in the heat of the combustion gas is reflected by the radiant heat reflecting surface 17 made of aluminum or the like, passes through the cap 18, and returns to the combustion chamber 4. Therefore, in the poppet valve 10 of the present embodiment, heat conduction, convection, and radiation, which are heat transfer modes of the combustion gas heat, are suppressed, and energy generated by the combustion of the fuel is taken outside through the valve body as heat. The amount is reduced (cooling loss is reduced).

  In the present embodiment, aluminum, copper, or an aluminum alloy can be used as the material for the radiant heat reflecting surface. Unlike ceramics described in Patent Document 2, it is clear that most of the radiant heat can be reflected and returned to the combustion chamber. It was.

  FIG. 3 shows a poppet valve for an internal combustion engine according to a second embodiment of the present invention. The hollow poppet valve 10A of the second embodiment is a modification of the first embodiment, and the same members as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted. In the second embodiment, a hollow portion 19 ′, which is a spherical (dome-shaped) space, is formed between the ceiling surface 14b ′ and the bottom surface 25 ′ of the disc-shaped cap 18 ′. A radiant heat reflecting surface 17 'is formed on the inner peripheral surface except the outer peripheral surface, and the disc-shaped cap 18' is fitted to the lower end of the hollow portion 19 '. A small-diameter hollow portion S is formed from slightly above the radiant heat reflecting surface 17 ′ in the shaft portion 12, and in the small-diameter hollow portion S, a coolant having a higher thermal conductivity than the base material of the engine valve. 23 (for example, metallic sodium, melting point about 98 ° C.) is loaded with an inert gas. A stepped portion 22 is formed in the small-diameter hollow portion S. For this reason, when the coolant 23 in the small-diameter hollow portion S moves in the vertical direction by the inertial force that acts when the valve 10A is opened and closed. Furthermore, a turbulent flow is generated in the vicinity of the stepped portion 22 and the coolant 23 is agitated, so that the heat drawing effect (thermal conductivity) in the valve shaft portion 12 is improved. By shutting off the heat of the combustion gas on the combustion chamber side, heat is not dissipated through the valve, and the heat-resistant temperature required for the material can be lowered by the effect of heat drawing of the valve shaft.

  FIG. 4 shows a poppet valve for an internal combustion engine according to a third embodiment of the present invention. The poppet valve 10B of the third embodiment is a modification of the first embodiment, and the same members as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. In the third embodiment, the umbrella portion 14B is integrally formed on the combustion chamber 4 side of the solid shaft portion 12B, and in this embodiment, no hollow portion is formed. A radiant heat reflecting surface 17 ″ is formed on the bottom surface 15 of the umbrella portion 14B of the bulb 10B so that both ends are not exposed, and the surface of the radiant heat reflecting surface 17 ″ has a heat treatment of 3 W / mK or less. A coating of the heat insulating layer 18c or a coating of a plate-like low thermal conductivity material having a thermal conductivity of 3 W / mK or less is formed. The formed surface treatment heat insulation layer 18c has the same effect as the heat insulation space of the hollow portion 19 of the first embodiment, and the heat of the high-temperature combustion gas generated in the combustion chamber is the surface treatment layer of the poppet valve 10B. Through the heat insulation 18c, it reaches the radiant heat reflecting surface 17 ". Of the heat conduction, convection and radiation, which are heat transfer modes of the combustion gas, the heat conduction and convection are caused by the surface treatment heat insulation layer 18c having the low thermal conductivity. The radiation is blocked, and the radiation is reflected into the combustion chamber 4 by the radiant heat reflecting surface 17 ″. At this time, the radiant heat reflecting surface 17 ″ is surrounded by the bottom surface 15 of the umbrella portion 14B and the surface treatment heat insulating layer 18c and is not exposed to the atmosphere. Therefore, a metal having no heat resistance such as aluminum is also included in the radiant heat reflecting surface 17 ″. Can be used as material. Therefore, in the poppet valve 10B of the present embodiment, heat conduction, convection and radiation, which are heat transfer modes of the combustion gas heat, are suppressed, and energy generated by the combustion of the fuel is taken to the outside through the valve body as heat. The amount is reduced (cooling loss is reduced). The formation of the surface-treated heat insulating layer 18c having a low thermal conductivity is covered by atmospheric plasma spraying or the like.

2 Cylinder head 3 Valve insertion hole 3a Valve guide 4 Combustion chamber 6 Exhaust passage 8 Valve seat 9 Valve spring 10, 10A, 10B Poppet valve 11, 11A Shell 12 Shaft portion 12b Shaft end member 12c Cutter groove 13 Fillet portion 14, 14B Umbrella Portion 14a Umbrella outer shell 14b Ceiling surface 15 Bottom surface 16 Face portion 17, 17 ', 17 "Radiant heat reflecting surface (metal layer blocking radiant heat)
18, 18 'Cap 18a Bent part 18b Arc-shaped rib 18c Surface treatment heat insulation layer 19, 19' Hollow part (heat insulation part, heat insulation space)
21 Hollow part 22 Step part 23 Coolant 24, 24 'Umbrella table 25, 25' Bottom

Claims (6)

  In the poppet valve in which an umbrella part is integrally formed on one end side of the shaft part, a heat insulating part located on the combustion chamber side and a metal layer blocking the radiant heat located on the shaft part side are formed on the umbrella part. A poppet valve characterized by that.   A hollow portion extending along the surface of the umbrella is formed in the umbrella portion, a metal layer that blocks radiant heat is formed on a ceiling surface of the hollow portion, and a heat insulating portion is formed between the metal layer and the bottom surface of the hollow portion. The poppet valve according to claim 1, wherein the poppet valve is formed.   The metal layer for blocking radiant heat is formed on the bottom surface of the umbrella portion, and a heat-insulating surface treatment layer is formed on the combustion chamber side of the metal layer for blocking radiant heat. Poppet valve.   The poppet valve according to any one of claims 1 to 3, wherein the metal is selected from aluminum, copper, and an aluminum alloy.   The poppet valve according to any one of claims 1 to 4, wherein the metal is in a foil shape or a sheet shape.   The poppet valve according to claim 1 or 2, wherein the metal layer is a film formed by a surface treatment selected from physical vapor deposition (PVD), thermal spraying, and plating.

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