JP2005194971A - Piston for gas engine - Google Patents

Piston for gas engine Download PDF

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JP2005194971A
JP2005194971A JP2004003902A JP2004003902A JP2005194971A JP 2005194971 A JP2005194971 A JP 2005194971A JP 2004003902 A JP2004003902 A JP 2004003902A JP 2004003902 A JP2004003902 A JP 2004003902A JP 2005194971 A JP2005194971 A JP 2005194971A
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piston
outer peripheral
ring
combustion chamber
combustion
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JP4256790B2 (en
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Yoshitaka Sumihama
義隆 角濱
Kengo Tanaka
健吾 田中
Nagatomo Tsuji
長知 辻
Yoichi Matsushita
陽一 松下
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Mitsubishi Heavy Industries Ltd
Osaka Gas Co Ltd
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Mitsubishi Heavy Industries Ltd
Osaka Gas Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a piston for a gas engine preventing deterioration of engine performance and drivability and degradation of exhaust emission and reducing fuel consumption rate caused by occurrence of knocking, and reducing thermal stress of an piston outer circumference shoulder part and preventing burning thereof by improving cooling effect of the piston outer circumference shoulder part, lowering height position of a first piston ring to reduce volume in a gap at a upper part of the ring, and reducing unburnt gas quantity staying in the gap at the upper part of the ring. <P>SOLUTION: In the piston of the gas engine, a combustion chamber is constructed to continuously increase depth from outer circumference upper part of a combustion surface to a center part, thickness of a crown plate between a combustion surface and an upper surface of the cooling chamber is made constant thickness, and thickness of am outer circumference annular part formed between an outer circumference surface of the cooling chamber and a ring groove inner circumference is made smaller than thickness of the crown plate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は、ガス燃料をピストン上部に区画形成された燃焼室に供給して燃焼させるガスエンジンに適用され、前記燃焼室の裏側に冷却室を備えたガスエンジンのピストンに関する。   The present invention relates to a piston of a gas engine that is applied to a gas engine that supplies gas fuel to a combustion chamber defined in the upper part of a piston and burns it, and that has a cooling chamber on the back side of the combustion chamber.

直接噴射式ディーゼルエンジンや、ガス燃料をピストン上部に区画形成された燃焼室に供給して燃焼させるガスエンジンにおいては、前記燃焼室の外周部を中央部よりも深く形成し該外周部に向けて燃料を噴射しあるいはガス噴流を噴出させるようにした所謂リエントラント燃焼室を備えたピストンが多く用いられている（これに類似する先行技術文献として特許文献１がある）。   In a direct injection type diesel engine or a gas engine in which gas fuel is supplied to a combustion chamber defined in the upper part of the piston and burned, the outer peripheral portion of the combustion chamber is formed deeper than the central portion and directed toward the outer peripheral portion. Many pistons having a so-called reentrant combustion chamber that injects fuel or jets a gas jet are used (Patent Document 1 is similar to this).

図３はかかるリエントラント燃焼室を備えたガスエンジン用ピストンの１例を示すピストン上部近傍の断面図である。
図において、１００はピストン、２１はシリンダライナ、２０はシリンダヘッド、２２は該シリンダヘッド２０の中心部に形成され副室ガストーチ着火がなされる副室、２３は該トーチ着火ガス噴出用の噴孔を備えた副室口金、２４は前記副室２２へのトーチ着火ガス通路を開閉する副室弁、２５は副室２２内のガスに点火してトーチ着火をなさしめる点火プラグである。 FIG. 3 is a sectional view in the vicinity of the upper part of the piston showing an example of a piston for a gas engine provided with such a reentrant combustion chamber.
In the figure, 100 is a piston, 21 is a cylinder liner, 20 is a cylinder head, 22 is a sub chamber formed in the center of the cylinder head 20 and ignited by a sub chamber gas torch, and 23 is a nozzle hole for ejecting the torch ignition gas. , A sub chamber valve 24 for opening and closing a torch ignition gas passage to the sub chamber 22, and 25 an ignition plug for igniting the gas in the sub chamber 22 to cause torch ignition.

前記ピストン１００において、３１は燃焼室、０１は該燃焼室を区画形成する燃焼面である。該燃焼室３１は外周部０１ｂを中央部０１ａよりも深く形成して前記副室２２からのトーチ着火ガスを外周部０１ｂに向けて噴出するようにしたリエントラント形式に構成されている。０２はピストンの上面、０１４は外周肩部、１０１はピストン中心、３２はピストンピン穴である。
０４はピストン内部の前記燃焼室３１の裏側に環状に形成された冷却室で、潤滑油通路（図示省略）から供給された冷却液としての潤滑油が該冷却室０４内を流動してピストンを冷却するようになっている。１０ｂ、１０ｃはリング溝１０ａに夫々嵌合された第１、第２ピストンリング、１１はオイルリングである。
特開２００１−３３６４２２号公報 In the piston 100, 31 is a combustion chamber, and 01 is a combustion surface that defines the combustion chamber. The combustion chamber 31 has a reentrant type in which the outer peripheral portion 01b is formed deeper than the central portion 01a and the torch ignition gas from the sub chamber 22 is ejected toward the outer peripheral portion 01b. 02 is the upper surface of the piston, 014 is the outer shoulder, 101 is the center of the piston, and 32 is the piston pin hole.
04 is a cooling chamber formed in an annular shape on the back side of the combustion chamber 31 inside the piston. Lubricating oil as a coolant supplied from a lubricating oil passage (not shown) flows in the cooling chamber 04 to cause the piston to move. It is designed to cool. Reference numerals 10b and 10c denote first and second piston rings fitted in the ring groove 10a, respectively, and 11 denotes an oil ring.
JP 2001-336422 A

図３に示されるリエントラント形式の燃焼室３１を備えたピストンにあっては、燃焼室３１の外周部０１ｂを中央部０１ａよりも深く形成しているため、環状の前記冷却室０４は深さの深い外周部０１ｂの裏側つまり下方に位置することとなり、これにより最高温度発生部である外周肩部０１４と前記冷却室０４との距離が大きくなり、該外周肩部０１４の温度が上昇する。
このため、前記第１ピストンリング１０ｂの温度が上昇して該第１ピストンリング１０ｂの焼き付きが発生し易くなる。 In the piston having the reentrant type combustion chamber 31 shown in FIG. 3, the outer peripheral portion 01b of the combustion chamber 31 is formed deeper than the central portion 01a. It is located behind the deep outer peripheral portion 01b, that is, below the deep outer peripheral portion 01b. As a result, the distance between the outer peripheral shoulder portion 014 that is the highest temperature generating portion and the cooling chamber 04 is increased, and the temperature of the outer peripheral shoulder portion 014 is increased.
For this reason, the temperature of the first piston ring 10b rises and seizure of the first piston ring 10b is likely to occur.

かかる焼き付きの発生を防止するため、図３に示される従来技術にあっては、該第１ピストンリング１０ｂの高さ位置つまり図３においてピストン上面０２からの距離Ｈ０を大きくして該第１ピストンリング１０ｂを下方に位置せしめ、高温の外周肩部０１４から遠ざけるとともに前記冷却室０４に近づけることにより該第１ピストンリング１０ｂの温度を下げている。 In order to prevent the occurrence of such seizure, in the prior art shown in FIG. 3, the height position of the first piston ring 10b, that is, the distance H 0 from the piston upper surface 02 in FIG. The temperature of the first piston ring 10b is lowered by positioning the piston ring 10b below, away from the high-temperature outer peripheral shoulder 014, and close to the cooling chamber 04.

しかしながら、前記のように第１ピストンリング１０ｂを下方に位置せしめて該第１ピストンリング１０ｂの高さ位置（距離Ｈ０）を増大すると、ピストン１００の上部外周面即ちピストン上面０２と該第１ピストンリング１０ｂとの間の距離Ｈ０部分の外周面と前記シリンダライナ２１内面との間に形成されるリング上部隙間３０の容積が増大する。 However, if the first piston ring 10b is positioned downward and the height position (distance H 0 ) of the first piston ring 10b is increased as described above, the upper outer peripheral surface of the piston 100, that is, the piston upper surface 02 and the first piston ring 10b are increased. The volume of the ring upper gap 30 formed between the outer peripheral surface of the distance H 0 portion between the piston ring 10b and the inner surface of the cylinder liner 21 increases.

このため前記従来のピストン１００を備えたガスエンジンにあっては、前記のようなリング上部隙間３０の容積増大によって、該リング上部隙間３０内に滞留する未燃ガスの量が増大しノッキングが発生し易くなってエンジンの性能及び運転性の低下を引き起こすとともに、前記未燃ガス量の増大によりエンジンの燃料消費率が増大し、さらには未燃ガス排出量の増大に伴う排気ガス状態の悪化を引き起こす。   For this reason, in the gas engine provided with the conventional piston 100, the volume of the ring upper gap 30 as described above increases the amount of unburned gas remaining in the ring upper gap 30 and causes knocking. The engine performance and operability are reduced, the fuel consumption rate of the engine increases due to the increase in the amount of unburned gas, and the exhaust gas state deteriorates due to the increase in the amount of unburned gas. cause.

またかかる従来技術にあっては、前記のように冷却室０４が深さの深い前記外周部０１ｂの下方に位置して前記外周肩部０１４と冷却室０４との距離が大きくなることにより、外周肩部０１４の冷却が十分になされず該外周肩部０１４の温度が上昇して、熱応力の増大や該外周肩部０１４の過熱による焼損が発生し易い、
等の問題点を有している。 Further, in this conventional technique, the cooling chamber 04 is positioned below the deep outer peripheral portion 01b as described above, and the distance between the outer peripheral shoulder portion 014 and the cooling chamber 04 is increased. The cooling of the shoulder 014 is not sufficiently performed, the temperature of the outer peripheral shoulder 014 is increased, and the thermal stress is increased or the outer peripheral shoulder 014 is easily burned out due to overheating.
And so on.

本発明はかかる従来技術の課題に鑑み、ピストン外周肩部の冷却効果を向上せしめ、第１ピストンリングの高さ位置を小さくしてリング上部隙間の容積を減少せしめ、該リング上部隙間内に滞留する未燃ガス量を低減することにより、ノッキングの発生に伴うエンジン性能及び運転性の低下並びに排気ガス状態の悪化を防止するとともに燃料消費率を低減し、さらには外周肩部の高温化による熱応力の増大や外周肩部の焼損の発生を防止し得るガスエンジンのピストンを提供することを目的とする。   In view of the problems of the prior art, the present invention improves the cooling effect of the outer peripheral shoulder of the piston, reduces the height position of the first piston ring, reduces the volume of the ring upper gap, and stays in the ring upper gap. By reducing the amount of unburned gas to be generated, the engine performance and operability associated with knocking are prevented from being deteriorated and the exhaust gas state is prevented from being deteriorated. An object of the present invention is to provide a gas engine piston capable of preventing an increase in stress and the occurrence of burnout of the outer peripheral shoulder.

本発明はかかる課題を解決するため、請求項１の発明として、ガス燃料をピストンの燃焼面に区画形成された燃焼室に供給して燃焼させるガスエンジン用のピストンであって、前記燃焼室の裏側に冷却液が供給される冷却室を備えたガスエンジンのピストンにおいて、前記燃焼室を前記燃焼面の外周上部から中心部に亘り深さが連続的に増大するように構成するとともに、前記燃焼面の曲率半径ＲをＲ／Ｄ≧０．２（Ｄはシリンダ内径）とした燃焼室形状を有し、前記冷却室と燃焼室面との距離ｔをｔ／Ｄ≦０．０８とし、さらに、第一圧縮ピストンリングの頂面からの高さＨをＨ／Ｄ≦０．１に構成したことを特徴とするガスエンジンのピストンを提案する。   In order to solve such a problem, the present invention provides a piston for a gas engine in which gas fuel is supplied to a combustion chamber defined on the combustion surface of the piston and burned. In a piston of a gas engine having a cooling chamber to which a coolant is supplied on the back side, the combustion chamber is configured so that the depth continuously increases from the outer peripheral upper portion to the center of the combustion surface, and the combustion A combustion chamber shape having a curvature radius R of the surface of R / D ≧ 0.2 (D is a cylinder inner diameter), a distance t between the cooling chamber and the combustion chamber surface being t / D ≦ 0.08, Then, a gas engine piston is proposed in which the height H from the top surface of the first compression piston ring is configured to satisfy H / D ≦ 0.1.

請求項１において、好ましくは請求項２あるいは３のように構成する。
即ち、請求項２においては、前記燃焼室を、前記ピストン上面の外周部を底面半径としピストン中心部を頂部とする逆円錐体状に形成しその逆円錐面を燃焼室中央部において滑らかな球殻面で接続する。
また請求項３においては、前記燃焼室を、前記ピストン上面の外周部から燃焼室中央部にかけて一定の曲率半径で接続した球殻状に形成する。 In Claim 1, it is preferably configured as in Claim 2 or 3.
That is, according to the second aspect of the present invention, the combustion chamber is formed in an inverted cone shape with the outer peripheral portion of the upper surface of the piston as the bottom radius and the central portion of the piston as the top portion, and the reverse conical surface is a smooth sphere at the central portion of the combustion chamber. Connect with shell surface.
According to a third aspect of the present invention, the combustion chamber is formed in a spherical shell shape connected at a constant radius of curvature from the outer peripheral portion of the upper surface of the piston to the central portion of the combustion chamber.

かかる発明によれば、燃焼室を、請求項２の逆円錐体と球殻との組み合わせあるいは請求項３の球殻状のような、燃焼面の外周上部から中心部に亘り深さが連続的に増大するように形成するとともに燃焼面と冷却室の上面との間の天板の厚さを一定の厚さに形成することにより、冷却室をピストン外周寄りのピストン上面に近い位置に形成して、該冷却室を最高温度発生部である外周肩部に近づけて形成することが可能となる。これによりピストン外周肩部の冷却効果が向上する。   According to this invention, the depth of the combustion chamber is continuous from the outer peripheral upper part to the center of the combustion surface as in the combination of the inverted cone of claim 2 and the spherical shell, or the spherical shell shape of claim 3. The cooling chamber is formed at a position close to the piston upper surface near the outer periphery of the piston by forming the top plate between the combustion surface and the upper surface of the cooling chamber to a constant thickness. Thus, the cooling chamber can be formed close to the outer peripheral shoulder which is the maximum temperature generating portion. Thereby, the cooling effect of the outer peripheral shoulder of the piston is improved.

また、前記冷却室の外周面とピストンリングのリング溝内周との間の外周環状部の厚さを、表面（燃焼面）にガス圧が作用する天板の厚さよりも小さい最小限の厚さに形成したので、ピストンリングの冷却室内の冷却液からの冷却作用が促進される。
従って、前記冷却室によるピストン外周肩部の冷却効果及びピストンリングの冷却効果の向上により、第１ピストンリングの温度上昇を招くことなく該第１ピストンリングを外周肩部に近づけることが可能となり、該第１ピストンリングの高さ位置を小さくすることができてリング上部隙間の容積を減少することができる。 The thickness of the outer peripheral annular portion between the outer peripheral surface of the cooling chamber and the inner periphery of the ring groove of the piston ring is set to a minimum thickness smaller than the thickness of the top plate on which the gas pressure acts on the surface (combustion surface). Therefore, the cooling action from the coolant in the cooling chamber of the piston ring is promoted.
Therefore, by improving the cooling effect of the piston outer shoulder by the cooling chamber and the cooling effect of the piston ring, it becomes possible to bring the first piston ring closer to the outer shoulder without causing an increase in the temperature of the first piston ring, The height position of the first piston ring can be reduced, and the volume of the ring upper gap can be reduced.

かかるリング上部隙間の容積減少によって、該リング上部隙間内に滞留する未燃ガス量を低減することが可能となって、該未燃ガスの量の増大によるノッキングの発生及びこれに伴うエンジン性能及び運転性の低下を防止することができる。
また、前記未燃ガス量の増大によるエンジンの燃料消費率の増大を回避することができるとともに、未燃ガス排出量の増大に伴う排気ガス状態の悪化を防止することができる。 By reducing the volume of the ring upper gap, it is possible to reduce the amount of unburned gas remaining in the ring upper gap, causing the occurrence of knocking due to the increase in the amount of unburned gas, and the accompanying engine performance, A decrease in drivability can be prevented.
Further, it is possible to avoid an increase in the fuel consumption rate of the engine due to the increase in the amount of unburned gas, and it is possible to prevent the exhaust gas state from deteriorating due to an increase in the amount of unburned gas discharged.

さらには、前記のように冷却室を最高温度発生部である外周肩部に近づけて形成することが可能となるので、該外周肩部の冷却効果が向上する。これにより該外周肩部の高温化を回避できて、該外周肩部の高温化による外周肩部近傍における熱応力の増大や外周肩部の焼損の発生を防止することができる。   Furthermore, as described above, the cooling chamber can be formed close to the outer peripheral shoulder which is the maximum temperature generating portion, so that the cooling effect of the outer peripheral shoulder is improved. As a result, it is possible to avoid the high temperature of the outer peripheral shoulder, and to prevent an increase in thermal stress in the vicinity of the outer peripheral shoulder due to the high temperature of the outer peripheral shoulder and the occurrence of burnout of the outer peripheral shoulder.

以上記載の如く本発明によれば、ピストンの燃焼室を、請求項２の逆円錐体と球殻との組み合わせあるいは請求項３の球殻状のような、燃焼面の外周上部から中心部に亘り深さが連続的に増大するように形成するとともにピストンの天板厚さを一定厚さに形成することにより、冷却室を最高温度発生部である外周肩部に近づけて形成することが可能となり、これによりピストン外周肩部の冷却効果が向上する。
また、冷却室とリング溝内周との間に形成される外周環状部の厚さを、表面にガス圧が作用する天板の厚さよりも小さい最小限の厚さに形成したことにより、ピストンリングの冷却作用が促進される。 As described above, according to the present invention, the combustion chamber of the piston is arranged from the upper part of the outer periphery of the combustion surface to the central part, such as the combination of the inverted cone of claim 2 and the spherical shell. It is possible to form the cooling chamber close to the outer peripheral shoulder, which is the maximum temperature generation part, by forming the span continuously increasing and forming the piston top plate thickness to a constant thickness. As a result, the cooling effect on the outer peripheral shoulder of the piston is improved.
In addition, since the thickness of the outer peripheral annular portion formed between the cooling chamber and the inner periphery of the ring groove is set to a minimum thickness smaller than the thickness of the top plate on which the gas pressure acts on the surface, the piston The cooling action of the ring is promoted.

従って、冷却室によるピストン外周肩部及びピストンリングの冷却効果の向上により、第１ピストンリングの温度上昇を招くことなく第１ピストンリングの高さ位置を小さくすることができて、リング上部隙間の容積を減少することができる。
そして、かかるリング上部隙間の容積減少によって、該リング上部隙間内に滞留する未燃ガス量を低減することが可能となって、該未燃ガスの量の増大によるノッキングの発生及びこれに伴うエンジン性能及び運転性の低下を防止することができ、また前記未燃ガス量の増大によるエンジンの燃料消費率の増大を回避することができ、さらに未燃ガス排出量の増大に伴う排気ガス状態の悪化を防止することができる。 Therefore, by improving the cooling effect of the piston outer periphery shoulder and the piston ring by the cooling chamber, the height position of the first piston ring can be reduced without incurring a temperature rise of the first piston ring, and the ring upper gap The volume can be reduced.
And, by reducing the volume of the ring upper gap, it becomes possible to reduce the amount of unburned gas that stays in the ring upper gap, and the occurrence of knocking due to the increase in the amount of unburned gas and the accompanying engine It is possible to prevent a decrease in performance and operability, to avoid an increase in the fuel consumption rate of the engine due to the increase in the amount of unburned gas, and to reduce the exhaust gas state accompanying an increase in the amount of unburned gas discharged. Deterioration can be prevented.

また、前記のように冷却室を最高温度発生部である外周肩部に近づけて形成することが可能となるので、該外周肩部の冷却効果が向上されて該外周肩部の高温化を回避でき、該高温化による外周肩部近傍における熱応力の増大や外周肩部の焼損の発生を防止することができ、ピストンの耐久性が向上する。   Further, as described above, the cooling chamber can be formed close to the outer peripheral shoulder which is the maximum temperature generating portion, so that the cooling effect of the outer peripheral shoulder is improved and the high temperature of the outer peripheral shoulder is avoided. It is possible to prevent an increase in thermal stress in the vicinity of the outer peripheral shoulder due to the increase in temperature and the occurrence of burnout of the outer peripheral shoulder, thereby improving the durability of the piston.

以下、図面を参照して本発明の好適な実施例を例示的に詳しく説明する。但しこの実施例に記載されている構成部品の寸法、材質、形状、その相対的配置等は特に特定的な記載がない限りは、この発明の範囲をそれに限定する趣旨ではなく、単なる説明例に過ぎない。   Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

図１は本発明の第１実施例に係るガスエンジン用ピストンのピストン上部近傍の断面図、図２は第２実施例を示す図１対応図である。   FIG. 1 is a cross-sectional view of the vicinity of an upper portion of a piston for a gas engine according to a first embodiment of the present invention, and FIG. 2 is a view corresponding to FIG.

第１実施例を示す図１において、１００はピストンで、シリンダライナ２１の内面に沿って往復摺動する。２０はシリンダヘッド、２２は該シリンダヘッド２０の中心部に形成され副室ガストーチ着火がなされる副室、２３は該トーチ着火ガス噴出用の噴孔を備えた副室口金、２４は前記副室２２へのトーチ着火ガス通路を開閉する副室弁、２５は副室２２内のガスに点火してトーチ着火をなさしめる点火プラグである。   In FIG. 1 showing the first embodiment, reference numeral 100 denotes a piston, which reciprocates along the inner surface of the cylinder liner 21. 20 is a cylinder head, 22 is a sub chamber formed in the center of the cylinder head 20 and is ignited by a sub chamber gas torch, 23 is a sub chamber base having a nozzle hole for ejecting the torch ignition gas, and 24 is the sub chamber. A sub-chamber valve 25 for opening and closing the torch ignition gas passage to 22 is an ignition plug for igniting the gas in the sub-chamber 22 to cause torch ignition.

３１は前記ピストン１００の上部に形成された燃焼室、１は該燃焼室３１を区画形成する燃焼面（触火面）、２はピストンの上面、１４は外周肩部、１０１はピストン中心、３２はピストンピン穴である。
１０ｂ、１０ｃは前記ピストン１００のリング溝１０ａに夫々嵌合された第１、第２ピストンリング、１１はオイルリングである。
該燃焼室３１は、Ｒ／Ｄ≧０．２（Ｄはシリンダ内径）なる燃焼室形状を有し、ピストン１００の上面２の外周部を底面半径としピストン中心１０１を頂部とする大きな曲率半径Ｒの逆円錐体状に形成され、逆円錐状の円錐状面１ａの曲率半径を燃焼室３１中央部において曲率半径Ｒ０の球殻面１ｂで滑らかに接続して形成され、前記燃焼面１の上面２外周部からピストン中心１０１に亘り深さが連続的に増大するようになっている。 31 is a combustion chamber formed in the upper part of the piston 100, 1 is a combustion surface (catalyst surface) that defines the combustion chamber 31, 2 is an upper surface of the piston, 14 is an outer shoulder, 101 is the center of the piston, 32 Is a piston pin hole.
Reference numerals 10b and 10c denote first and second piston rings respectively fitted in the ring groove 10a of the piston 100, and 11 denotes an oil ring.
The combustion chamber 31 has a combustion chamber shape of R / D ≧ 0.2 (D is a cylinder inner diameter), and has a large curvature radius R with the outer peripheral portion of the upper surface 2 of the piston 100 as the bottom surface radius and the piston center 101 as the top portion. Are formed by smoothly connecting the radius of curvature of the conical surface 1a of the inverse conical shape with the spherical shell surface 1b of the radius of curvature R0 at the center of the combustion chamber 31. The depth continuously increases from the outer peripheral portion of the upper surface 2 to the piston center 101.

４はピストン内部の前記燃焼室３１の裏側に環状に形成された冷却室である。該冷却室４の冷却室上面５と前記燃焼面１との間の壁部つまり天板部３の厚さは冷却室と燃焼室面との距離ｔをｔ／Ｄ≦０．０８とする最小厚さに形成されている。
また、前記冷却室４の円筒表面に形成された冷却室外周面６を前記第１ピストンリング１０ｂが嵌挿されるリング溝１０ａに近接せしめ、該冷却室外周面６と前記第１ピストンリング１０ｂ及び第２ピストンリング１０ｃのリング溝１０ａ内周との間に形成される外周環状部１２の厚さＳを前記天板部３厚さｔよりも小さく形成する。
さらに前記冷却室４の前記外周肩部１４側内面には丸み７を形成し、内周側内面には丸み８を形成して、応力集中の少ない滑らかな内面形状としている。 Reference numeral 4 denotes a cooling chamber formed in an annular shape on the back side of the combustion chamber 31 inside the piston. The thickness of the wall portion between the cooling chamber upper surface 5 of the cooling chamber 4 and the combustion surface 1, that is, the thickness of the top plate portion 3, is the minimum in which the distance t between the cooling chamber and the combustion chamber surface is t / D ≦ 0.08. It is formed to a thickness.
Further, the cooling chamber outer peripheral surface 6 formed on the cylindrical surface of the cooling chamber 4 is brought close to the ring groove 10a into which the first piston ring 10b is inserted, and the cooling chamber outer peripheral surface 6 and the first piston ring 10b, A thickness S of the outer peripheral annular portion 12 formed between the inner periphery of the ring groove 10a of the second piston ring 10c is formed smaller than the thickness 3 of the top plate portion 3.
Further, a roundness 7 is formed on the inner surface of the cooling chamber 4 on the outer peripheral shoulder 14 side, and a roundness 8 is formed on the inner peripheral side inner surface to form a smooth inner shape with less stress concentration.

図２に示される第２実施例においては、前記燃焼室３１を、ピストン１００の上面２外周部から該燃焼室３１中央部にかけて一定の曲率半径Ｒ０で接続した球面を燃焼面１とした球殻状に形成している。そして該燃焼面１と前記冷却室４の冷却室上面５との間の壁部つまり天板部３の厚さは最小厚さｔに形成される。
その他の構成は図１に示される第１実施例と同様であり、これと同一の部材は同一の符号で示す。 In the second embodiment shown in FIG. 2, a spherical surface in which the combustion chamber 31 is connected with a constant curvature radius R 0 from the outer peripheral portion of the upper surface 2 of the piston 100 to the central portion of the combustion chamber 31 is used as the combustion surface 1. It is formed in a shell shape. The wall portion between the combustion surface 1 and the cooling chamber upper surface 5 of the cooling chamber 4, that is, the thickness of the top plate portion 3 is formed to a minimum thickness t.
Other configurations are the same as those of the first embodiment shown in FIG. 1, and the same members are denoted by the same reference numerals.

かかる構成からなるピストンにおいて、前記冷却室４内には冷却液としての潤滑油が流動し、該ピストン１００の天板部３、外周肩部１４、外周環状部１２を介して第１ピストンリング１０ｂ及び第２ピストンリング１０ｃ等の高温部を冷却する。
しかして、かかる実施例においては、ピストン１００上部の燃焼室３１を、第１実施例のように円錐状面１ａ及び球殻面１ｂからなる逆円錐体と球殻との組み合わせ、あるいは第２実施例のように一定の曲率半径Ｒ０からなる球殻状体のような、燃焼面１の外周上部から中心部に亘り深さが連続的に増大するように形成するとともに前記天板部の厚さを最小厚さｔに形成したので、冷却室４をピストン１００外周寄りのピストン上面２に近い位置に設置するのが可能となる。 In the piston having such a configuration, lubricating oil as a coolant flows in the cooling chamber 4 and the first piston ring 10b is passed through the top plate portion 3, the outer peripheral shoulder portion 14, and the outer peripheral annular portion 12 of the piston 100. And high temperature parts, such as the 2nd piston ring 10c, are cooled.
Therefore, in this embodiment, the combustion chamber 31 on the upper side of the piston 100 is formed by combining the inverted cone having the conical surface 1a and the spherical shell surface 1b and the spherical shell as in the first embodiment, or the second embodiment. Like the example, a spherical shell having a constant radius of curvature R 0 is formed so that the depth continuously increases from the outer peripheral upper part of the combustion surface 1 to the central part, and the thickness of the top plate part. Since the thickness is formed to the minimum thickness t, the cooling chamber 4 can be installed at a position close to the piston upper surface 2 near the outer periphery of the piston 100.

これにより、該冷却室４を最高温度発生部である外周肩部１４に近づけて形成することが可能となり、該ピストン外周肩部１４の冷却効果が向上し、該外周肩部１４近傍の温度が低下する。
また、前記冷却室４の冷却室外周面６と第１、第２ピストンリング１０ｂ、１０ｃのリング溝１０ａ内周との間の外周環状部１２の厚さを、表面（燃焼面１）にガス圧が作用する天板部３の厚さｔよりも小さい最小限の厚さＳに形成したので、ピストンリング１０ｂ、１０ｃの冷却室４内の冷却液からの冷却作用が促進される。 As a result, the cooling chamber 4 can be formed close to the outer peripheral shoulder 14 which is the maximum temperature generating portion, the cooling effect of the piston outer peripheral shoulder 14 is improved, and the temperature in the vicinity of the outer peripheral shoulder 14 is increased. descend.
Further, the thickness of the outer peripheral annular portion 12 between the cooling chamber outer peripheral surface 6 of the cooling chamber 4 and the inner periphery of the ring groove 10a of the first and second piston rings 10b, 10c is set on the surface (combustion surface 1). Since the minimum thickness S is smaller than the thickness t of the top plate portion 3 on which the pressure acts, the cooling action from the coolant in the cooling chamber 4 of the piston rings 10b, 10c is promoted.

従って、前記冷却室４によるピストン外周肩部１４の冷却効果及び外周環状部１２を介しての第１ピストンリング１０ｂ及び第２ピストンリング１０ｃの冷却効果の向上により、第１ピストンリング１０ｂの温度上昇を招くことなく該第１ピストンリング１０ｂをピストン１００の外周肩部１４に近づけることが可能となる。
これにより、該第１ピストンリング１０ｂの高さ位置ＨをＨ／Ｄ≦０．１に小さくすることができ、リング上部隙間３０の容積を減少することができる。 Therefore, the temperature of the first piston ring 10b increases due to the cooling effect of the piston outer shoulder 14 by the cooling chamber 4 and the cooling effect of the first piston ring 10b and the second piston ring 10c via the outer ring portion 12. It is possible to bring the first piston ring 10b closer to the outer peripheral shoulder 14 of the piston 100 without incurring the above.
Thereby, the height position H of the first piston ring 10b can be reduced to H / D ≦ 0.1, and the volume of the ring upper gap 30 can be reduced.

そして、かかるリング上部隙間３０の容積減少によって、該リング上部隙間３０内に滞留する未燃ガス量を低減することが可能となって、該未燃ガスの量の増大によるノッキングの発生を防止することができる。
また、前記未燃ガス量の増大によるエンジンの燃料消費率の増大を回避することができ、さらに該未燃ガス排出量の増大に伴う排気ガス状態の悪化を防止することができる。 The volume reduction of the ring upper gap 30 makes it possible to reduce the amount of unburned gas remaining in the ring upper gap 30 and prevent knocking due to an increase in the amount of unburned gas. be able to.
Further, it is possible to avoid an increase in the fuel consumption rate of the engine due to the increase in the amount of unburned gas, and it is possible to prevent the deterioration of the exhaust gas state due to the increase in the amount of unburned gas discharged.

また、前記のように冷却室４を最高温度発生部である外周肩部１４に近づけて形成することが可能となるので、該外周肩部１４の冷却効果が向上し該外周肩部１４の高温化が回避される。
これにより、該外周肩部１４の高温化による該外周肩部１４近傍における熱応力の増大や該外周肩部１４の焼損の発生を防止することができる。 Further, as described above, the cooling chamber 4 can be formed close to the outer peripheral shoulder 14 which is the maximum temperature generating portion, so that the cooling effect of the outer peripheral shoulder 14 is improved, and the high temperature of the outer peripheral shoulder 14 is increased. Is avoided.
As a result, it is possible to prevent an increase in thermal stress in the vicinity of the outer peripheral shoulder portion 14 due to the high temperature of the outer peripheral shoulder portion 14 and the occurrence of burnout of the outer peripheral shoulder portion 14.

ノッキングの発生に伴うエンジン性能及び運転性の低下並びに排気ガス状態の悪化を防止するとともに燃料消費率を低減するガスエンジンを提供できる。   It is possible to provide a gas engine that can prevent deterioration in engine performance and operability due to occurrence of knocking and deterioration in exhaust gas state and reduce the fuel consumption rate.

本発明の第１実施例に係るガスエンジン用ピストンのピストン上部近傍の断面図である。It is sectional drawing of the piston upper part vicinity of the piston for gas engines which concerns on 1st Example of this invention. 第２実施例を示す図１対応図である。It is a figure corresponding to FIG. 1 which shows 2nd Example. 従来技術を示す図１対応図である。It is a figure corresponding to FIG. 1 which shows a prior art.

符号の説明Explanation of symbols

１ 燃焼面
１ａ 円錐状面
１ｂ 球殻面
２ 上面
３ 天板部
４ 冷却室
５ 冷却室上面
６ 冷却室外周面
１０ａ リング溝
１０ｂ 第１ピストンリング
１０ｃ 第２ピストンリング
１４ 外周肩部
２０ シリンダヘッド
２１ シリンダライナ
３０ リング上部隙間
３１ 燃焼室
１００ ピストン
１０１ ピストン中心 DESCRIPTION OF SYMBOLS 1 Combustion surface 1a Conical surface 1b Spherical shell surface 2 Upper surface 3 Top plate part 4 Cooling chamber 5 Cooling chamber upper surface 6 Cooling chamber outer peripheral surface 10a Ring groove 10b First piston ring 10c Second piston ring 14 Outer peripheral shoulder 20 Cylinder head 21 Cylinder liner 30 Ring upper gap 31 Combustion chamber 100 Piston 101 Piston center

Claims (3)

ガス燃料をピストンの燃焼面に区画形成された燃焼室に供給して燃焼させるガスエンジン用のピストンであって、前記燃焼室の裏側に冷却液が供給される冷却室を備えたガスエンジンのピストンにおいて、前記燃焼室を前記燃焼面の外周上部から中心部に亘り深さが連続的に増大するように構成するとともに、前記燃焼面の曲率半径ＲをＲ／Ｄ≧０．２（Ｄはシリンダ内径）とした燃焼室形状を有し、前記冷却室と燃焼室面との距離ｔをｔ／Ｄ≦０．０８とし、さらに、第一圧縮ピストンリングの頂面からの高さＨをＨ／Ｄ≦０．１に構成したことを特徴とするガスエンジンのピストン。   A piston for a gas engine for supplying gas fuel to a combustion chamber defined on a combustion surface of the piston and burning the gas fuel, wherein the piston is provided with a cooling chamber to which a coolant is supplied on the back side of the combustion chamber. The combustion chamber is configured such that the depth continuously increases from the outer peripheral upper part to the center of the combustion surface, and the curvature radius R of the combustion surface is set to R / D ≧ 0.2 (D is a cylinder) The inner diameter of the combustion chamber, the distance t between the cooling chamber and the combustion chamber surface is t / D ≦ 0.08, and the height H from the top surface of the first compression piston ring is H / A piston for a gas engine, characterized in that D ≦ 0.1. 前記燃焼室を、前記ピストン上面の外周部を底面半径としピストン中心部を頂部とする逆円錐体状に形成しその逆円錐面を燃焼室中央部において滑らかな球殻面で接続したことを特徴とする請求項１記載のガスエンジンのピストン。   The combustion chamber is formed in an inverted cone shape having an outer peripheral portion of the upper surface of the piston as a bottom radius and a central portion of the piston as a top portion, and the inverted conical surface is connected by a smooth spherical shell surface in the central portion of the combustion chamber. The piston of the gas engine according to claim 1. 前記燃焼室を、前記ピストン上面の外周部から燃焼室中央部にかけて一定の曲率半径で接続した球殻状に形成したことを特徴とする請求項１記載のガスエンジンのピストン。   2. The piston of a gas engine according to claim 1, wherein the combustion chamber is formed in a spherical shell shape connected with a constant radius of curvature from the outer peripheral portion of the upper surface of the piston to the central portion of the combustion chamber.
JP2004003902A 2004-01-09 2004-01-09 Gas engine piston Expired - Lifetime JP4256790B2 (en)

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US10174712B2 (en) 2013-05-31 2019-01-08 Mahle International Gmbh Piston for an internal combustion engine
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JPWO2014203382A1 (en) * 2013-06-20 2017-02-23 トヨタ自動車株式会社 Compression ignition internal combustion engine
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