JPH08200497A - Stress reducing structure for piston - Google Patents

Stress reducing structure for piston

Info

Publication number
JPH08200497A
JPH08200497A JP7027364A JP2736495A JPH08200497A JP H08200497 A JPH08200497 A JP H08200497A JP 7027364 A JP7027364 A JP 7027364A JP 2736495 A JP2736495 A JP 2736495A JP H08200497 A JPH08200497 A JP H08200497A
Authority
JP
Japan
Prior art keywords
center
piston
crown
support part
center support
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
JP7027364A
Other languages
Japanese (ja)
Inventor
Yoshihisa Fujiwara
芳久 藤原
Hiroaki Oda
博章 小田
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Heavy Industries Ltd
Original Assignee
Mitsubishi Heavy Industries Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mitsubishi Heavy Industries Ltd filed Critical Mitsubishi Heavy Industries Ltd
Priority to JP7027364A priority Critical patent/JPH08200497A/en
Publication of JPH08200497A publication Critical patent/JPH08200497A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B2275/00—Other engines, components or details, not provided for in other groups of this subclass
    • F02B2275/48—Tumble motion in gas movement in cylinder
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Landscapes

  • Pistons, Piston Rings, And Cylinders (AREA)

Abstract

PURPOSE: To decrease fluctuating stress induced in a crown part and in a tightening bolt by setting a position of a center support part to a position where force considered with the center of the center support part serving as the reference is balanced in the case of applying a gas pressure at engine operating time to act in the crown part. CONSTITUTION: A center position of a center support part 1 is set to a position where the sum total of force acting in a region outside from the center of the center support part and the sum total of force acting in a region to the piston center inside from the center of the center support part are balanced in the case that a gas pressure at engine operating time acts in a crown part 2. In this way, generating deformation such as tumbling the peripheral part of a piston crown toward the outside is prevented. Accordingly, by reducing fluctuating stress of the piston crown and a tightening bolt 4 in the vicinity of a connecting part between the center support part 1 and an insertion metal 3 of the piston crown, generating a fatigue crack in a screw bottom in a crown side of the tightening bolt 4 can be suppressed.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】本発明はディーゼルエンジン用ピ
ストンのクラウン部に発生する変動応力を低減させる構
造に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for reducing fluctuating stress generated in a crown portion of a diesel engine piston.

【０００２】[0002]

【従来の技術】図２は、クロスヘッド形のクランク機構
によってクランク軸を回転させる大形ディーゼルエンジ
ン用ピストンのクラウン部の縦断面図である。ピストン
のクラウン部に作用するガス圧荷重をシリンダ径のおよ
そ７０％相当の円周上で支える中支え形の構造であり、
図において１は中支え部、２はクラウン部、３ｔは勾配
付き内挿金物、４は締め付けボルト、５はピストンロッ
ドで、Ｐはエンジン作動時のガス圧である。2. Description of the Related Art FIG. 2 is a longitudinal sectional view of a crown portion of a piston for a large diesel engine in which a crankshaft is rotated by a crosshead type crank mechanism. It is a center support type structure that supports the gas pressure load acting on the crown part of the piston on the circumference equivalent to about 70% of the cylinder diameter,
In the figure, 1 is a middle support part, 2 is a crown part, 3t is a sloped insert, 4 is a fastening bolt, 5 is a piston rod, and P is a gas pressure during engine operation.

【０００３】図２を参照してピストンのクラウン部２に
発生する変動応力に対応するための構造について説明す
る。ピストンのクラウン部２の内部下面のシリンダ径の
およそ７０％相当の位置に、ピストンロッド５の頂面と
対向するように突出させて中支え部１が形成されてい
る。該中支え部１との間に勾配付きの内挿金物３ｔを介
在させ、複数の締め付けボルト４によりピストンロッド
５が中支え部下面に締結されている。A structure for coping with the fluctuating stress generated in the crown portion 2 of the piston will be described with reference to FIG. An inner support portion 1 is formed at a position corresponding to about 70% of the cylinder diameter on the inner lower surface of the crown portion 2 of the piston so as to project so as to face the top surface of the piston rod 5. An inclined insert 3t is interposed between the inner supporting portion 1 and a piston rod 5 is fastened to the lower surface of the inner supporting portion by a plurality of tightening bolts 4.

【０００４】前記内挿金物３ｔの中支え部１と接合する
側の表面には、半径方向に外側に向って低くなる勾配が
つけられている。この勾配によって形成される接合面の
隙間は、燃焼時のガス圧及び熱によるピストンクラウン
部１の変形量を吸収するためのもので、エンジンの構成
各部が定常運転時の状態になると隙間無しとなるように
隙間寸法が設定されている。The surface of the insert 3t that is to be joined to the center support portion 1 is provided with a gradient that decreases toward the outside in the radial direction. The gap of the joint surface formed by this gradient is for absorbing the deformation amount of the piston crown portion 1 due to the gas pressure and heat at the time of combustion, and there is no gap when each component of the engine is in the state of steady operation. The gap size is set so that

【０００５】[0005]

【発明が解決しようとする課題】前記従来例において
は、エンジン作動時にガス圧Ｐがクラウン部２に作用し
た際、中支え部１の中心より外側のクラウン外周部の領
域に作用する力の総和が、中支え部１の中心より内側の
ピストン中心までの領域に作用する力の総和より大きく
なるので、クラウン部２の外周部が外側に向って倒れる
ような変形を生じることになる。この変形を抑えこむよ
うにしようとすると、締め付けボルト４及びクラウン部
２に過大な応力が発生し、エンジン構成部品として成立
しなくなる。In the above-mentioned conventional example, when the gas pressure P acts on the crown portion 2 when the engine is operating, the total force acting on the outer peripheral portion of the crown outside the center of the center support portion 1. Is larger than the sum of the forces acting on the region from the center of the center support portion 1 to the center of the piston on the inner side, so that the outer peripheral portion of the crown portion 2 is deformed so as to fall outward. If an attempt is made to suppress this deformation, excessive stress will be generated in the tightening bolt 4 and the crown portion 2, and it will not be realized as an engine component.

【０００６】このため、内挿金物３ｔの中支え部１との
接合面に、半径方向に外側に向って低くなる勾配をつ
け、この勾配によって形成される隙間で前記の変形を吸
収させている。しかし、エンジンの作動時にガス圧Ｐが
繰り返し作用することにより、ピストンクラウンの中支
え部１と内挿金物３ｔの接合部の応力が変動すると共
に、締め付けボルト４に軸力の変動が誘起され、ピスト
ンクラウン側のねじ底で疲労き裂を引き起こすことにな
る。For this reason, the joining surface of the insert 3t with the center support portion 1 is provided with a gradient that decreases toward the outside in the radial direction, and the above-mentioned deformation is absorbed by the gap formed by this gradient. . However, as the gas pressure P repeatedly acts when the engine is operated, the stress at the joint between the center support portion 1 of the piston crown and the insert 3t fluctuates, and at the same time the fluctuation of the axial force is induced in the tightening bolt 4, Fatigue cracks will occur at the screw bottom on the piston crown side.

【０００７】本発明の目的はディーゼルエンジン用ピス
トンにおいて、ピストンのクラウン部及びピストンロッ
ドに組み付けるボルトに誘起される変動応力を低減さ
せ、該締め付けボルトのピストンクラウン側のねじ底か
らの疲労き裂を抑止し得る構造を提供するにある。An object of the present invention is to reduce fluctuation stress induced in a bolt assembled to a crown portion of a piston and a piston rod in a piston for a diesel engine, and to prevent fatigue cracks from a screw bottom on the piston crown side of the tightening bolt. To provide a deterrent structure.

【０００８】[0008]

【課題を解決するための手段】本発明のピストンの応力
低減構造は、ピストンロッドと連接されるディーゼルエ
ンジンのピストンにおいて、エンジン作動時のガス圧が
クラウン部２に作用した際に、中支え部１の中心より外
側の領域に作用する力と、中支え部１の中心より内側の
ピストン中心までの領域に作用する力とがつり合う位置
に中支え部１の中心位置を設定し、且つ中支え部１と内
挿金物３は全面での平行面接合として締め付けボルト４
によってピストンロッド５に組み付け、エンジン作動時
のガス圧及び熱応力が作用した場合に、前記中支え部と
前記内挿金物との接合部近傍における前記クラウン部の
変動応力及び前記締め付けボルトの変動応力を低減させ
る構造としたことを特徴とする。DISCLOSURE OF THE INVENTION A piston stress reducing structure of the present invention is a piston for a diesel engine which is connected to a piston rod, and when a gas pressure during engine operation acts on the crown portion 2, a middle supporting portion. The center position of the middle support part 1 is set at a position where the force acting on the region outside the center of 1 and the force acting on the region from the center of the middle support part 1 to the center of the piston are balanced. Part 1 and insert 3 are tightened bolts 4 as parallel surface joints on the entire surface.
When the piston rod 5 is assembled with the piston rod 5 and the gas pressure and the thermal stress at the time of operating the engine act, the fluctuation stress of the crown portion and the fluctuation stress of the tightening bolt in the vicinity of the joint portion between the middle support portion and the inserted metal object. It is characterized by having a structure for reducing

【０００９】[0009]

【作用】エンジン作動時のガス圧がクラウン部２に作用
した際に、中支え部１の中心より外側の領域に作用する
力の総和と、中支え部１の中心より内側のピストン中心
までの領域に作用する力の総和とがつり合う位置に中支
え部１の中心位置を設定することにより、ピストンクラ
ウンの外周部が外側に向って倒れるような変形を生じる
ことがなくなる。When the gas pressure at the time of engine operation acts on the crown portion 2, the sum of the forces acting on the area outside the center of the middle supporting portion 1 and the center of the piston inside the center of the middle supporting portion 1 By setting the center position of the center support portion 1 at a position where the total force acting on the region is balanced, the outer peripheral portion of the piston crown is prevented from being deformed such that it falls toward the outside.

【００１０】従って、ピストンクラウンの中支え部１と
内挿金物３のピストンロッド５への取り付けが強固にで
き、ピストンクラウンの中支え部１と内挿金物３との接
合部近傍におけるピストンクラウンの変動応力及び締め
付けボルトの変動応力が低減され、該締め付けボルトの
クラウン側のねじ底での疲労き裂の発生を抑えることが
できる。Therefore, the central support part 1 of the piston crown and the insert 3 can be firmly attached to the piston rod 5, and the piston crown in the vicinity of the joint between the central support 1 of the piston crown and the insert 3 can be fixed. The fluctuating stress and the fluctuating stress of the tightening bolt are reduced, and the occurrence of fatigue cracks at the screw bottom on the crown side of the tightening bolt can be suppressed.

【００１１】[0011]

【実施例】図１に本発明の実施例に係るクロスヘッド形
のクランク機構によってクランク軸を回転させる大形デ
ィーゼルエンジン用ピストンのクラウン部の縦断面図を
示した。図において１は中支え部、２はクラウン部、３
は内挿金物、４は締め付けボルト、５はピストンロッド
である。なお、Ｐはエンジン作動時のガス圧、Ａはピス
トンの半径、Ｂはピストンの中心から中支え部１の中心
までの距離、Ｃ−Ｃはピストンの中心線である。図２で
示した従来例の構成に類似しているが、内挿金物３の中
支え部１側の接合面には勾配が設けられていない。1 is a vertical sectional view of a crown portion of a piston for a large diesel engine in which a crankshaft is rotated by a crosshead type crank mechanism according to an embodiment of the present invention. In the figure, 1 is a middle support portion, 2 is a crown portion, 3
Is an insert, 4 is a tightening bolt, and 5 is a piston rod. Note that P is the gas pressure during engine operation, A is the radius of the piston, B is the distance from the center of the piston to the center of the center support portion 1, and C-C is the center line of the piston. Although it is similar to the configuration of the conventional example shown in FIG. 2, no slope is provided on the joint surface on the side of the center support portion 1 of the insert 3.

【００１２】次に、図１を参照してピストンクラウンに
エンジン作動時のガス圧Ｐが作用した場合の力のつり合
いを考察する。 Ａ ； ピストンの半径 Ｂ ； ピストンの中心から中支え部の中心までの距離 故に、中支え部の中心より外側のクラウン外周部の領域
の面積をＳａとすると Ｓａ＝π（Ａ2 −Ｂ2 ） また、中支え部の中心より内側のピストン中心までの領
域の面積をＳｂとすると Ｓｂ＝πＢ2 Next, the balance of forces when the gas pressure P acts on the piston crown during engine operation will be considered with reference to FIG. A: Radius of piston B: Distance from center of piston to center of center support part. Therefore, let Sa be the area of the crown outer area outside the center of the center support part. Sa = π (A 2 -B 2 ). If the area of the region from the center of the center support portion to the center of the piston is Sb, then Sb = πB 2

【００１３】従って、ガス圧Ｐによる面積Ｓａの領域に
作用する力と、ガス圧Ｐによる面積Ｓｂの領域に作用す
る力がつり合うための条件は、ＰＳａ＝ＰＳｂより π（Ａ2 −Ｂ2 ）＝πＢ2 ， 故に、Ｂ＝（Ａ／２
1/2 ） 即ち中支え部１の中心位置を、半径をＢとしたとき、Ｂ
＝（Ａ／２1/2 ）なる円周上に配すれば前記の力のつり
合いが成立する。Therefore, the condition for balancing the force acting on the area Sa of the gas pressure P and the force acting on the area Sb of the gas pressure P is π (A 2 -B 2 ) from PSa = PSb = ΠB 2 , therefore B = (A / 2
1/2 ) That is, when the radius of the center position of the center support part 1 is B, B
If they are arranged on the circumference of = (A / 2 1/2 ), the above balance of forces will be established.

【００１４】前記条件に合致する位置に中支え部１の位
置を設定することによって、エンジン作動時にガス圧Ｐ
が作用した場合に、ピストンクラウンを下死点側に押し
下げる軸力のみが作用することとなる。このため、従来
例での内挿金物３ｔで設けていた半径方向に外側に向っ
て低くなる勾配は不要となり、ピストンクラウンの中支
え部１と内挿金物３は組立て初期から全面での平面接合
で締め付けボルト４により確実に組み付けられる。By setting the position of the center support portion 1 to a position that meets the above conditions, the gas pressure P when the engine is operating.
When is applied, only the axial force that pushes the piston crown toward the bottom dead center is applied. For this reason, the gradient of the inner insert 3t in the conventional example, which becomes lower in the radial direction toward the outside, is not necessary, and the middle support portion 1 of the piston crown and the inner insert 3 are planar bonded over the entire surface from the initial stage of assembly. It is securely assembled with the tightening bolt 4.

【００１５】従って、ピストンクラウンの中支え部１と
内挿金物３のピストンロッド５への取り付けが強固にで
き、ピストンクラウンの中支え部１と内挿金物３との接
合部近傍におけるピストンクラウンの変動応力及び締め
付けボルトの変動応力が低減され、該締め付けボルトの
クラウン側のねじ底での疲労き裂の発生を抑えることが
できる。Accordingly, the center support portion 1 of the piston crown and the insert 3 can be firmly attached to the piston rod 5, and the piston crown in the vicinity of the joint between the center support portion 1 of the piston crown and the insert 3 can be fixed. The fluctuating stress and the fluctuating stress of the tightening bolt are reduced, and the occurrence of fatigue cracks at the screw bottom on the crown side of the tightening bolt can be suppressed.

【００１６】[0016]

【発明の効果】クロスヘッド形のクランク機構によって
クランク軸を回転させる大形ディーゼルエンジン用の中
支え形構造のピストンにおいて、ピストンクラウンの中
支え部の位置を、エンジン作動時のガス圧がピストンク
ラウンに作用した際、中支え部の中心を基準として考察
した力のつり合いが成立する位置に設定し、且つ中支え
部と内挿金物は全面での平面接合として組み付けること
とした。In a piston having a middle-supporting structure for a large diesel engine in which the crankshaft is rotated by a crosshead-type crank mechanism, the position of the center-supporting portion of the piston crown is determined by the gas pressure during engine operation. It was decided to set the position where the balance of the forces considered with reference to the center of the middle support portion is established when acting on, and the middle support portion and the insert are assembled as a plane joint on the entire surface.

【００１７】この構造にすることにより、ピストンクラ
ウンの中支え部と内挿金物の接合部近傍におけるピスト
ンクラウンの変動応力及び締め付けボルトの変動応力が
低減し、該締め付けボルトのピストンクラウン側のねじ
底からの疲労き裂の発生を抑えることができる。With this structure, the fluctuation stress of the piston crown and the fluctuation stress of the tightening bolt in the vicinity of the joint between the center support portion of the piston crown and the insert are reduced, and the screw bottom of the tightening bolt on the piston crown side is reduced. It is possible to suppress the occurrence of fatigue cracks.

【図面の簡単な説明】[Brief description of drawings]

【図１】本発明の実施例に係るディーゼルエンジン用ピ
ストンのクラウン部の縦断面図。FIG. 1 is a vertical cross-sectional view of a crown portion of a diesel engine piston according to an embodiment of the present invention.

【図２】従来のディーゼルエンジン用ピストンのクラウ
ン部の縦断面図。FIG. 2 is a vertical sectional view of a crown portion of a conventional diesel engine piston.

【符号の説明】[Explanation of symbols]

１…中支え部、２…クラウン部、３…内挿金物、４…締
め付けボルト、５…ピストンロッド、Ｐ…ガス圧。1 ... Medium support part, 2 ... Crown part, 3 ... Inner insert, 4 ... Tightening bolt, 5 ... Piston rod, P ... Gas pressure.

Claims (1)

【特許請求の範囲】[Claims] 【請求項１】 ピストンロッドと連接されるディーゼル
エンジンのピストンにおいて、エンジン作動時のガス圧
がクラウン部（２）に作用した際に、中支え部（１）の
中心より外側の領域に作用する力と、中支え部（１）の
中心より内側のピストン中心までの領域に作用する力と
がつり合う位置に中支え部（１）の中心位置を設定し、
且つ中支え部（１）と内挿金物（３）は全面での平行面
接合として締め付けボルト（４）によってピストンロッ
ド（５）に組み付け、エンジン作動時のガス圧及び熱応
力が作用した場合に、前記中支え部と前記内挿金物との
接合部近傍における前記クラウン部の変動応力及び前記
締め付けボルトの変動応力を低減させる構造としたこと
を特徴とするピストンの応力低減構造。1. In a piston of a diesel engine connected to a piston rod, when a gas pressure during engine operation acts on a crown portion (2), it acts on a region outside a center of a middle support portion (1). The center position of the middle support part (1) is set at a position where the force and the force acting on the region from the center of the middle support part (1) to the center of the piston are balanced.
In addition, the inner support part (1) and the insert (3) are assembled on the piston rod (5) by tightening bolts (4) as parallel plane joints on the entire surface, and when gas pressure and thermal stress at the time of engine operation act. A structure for reducing a stress of a piston, which is configured to reduce a fluctuating stress of the crown portion and a fluctuating stress of the tightening bolt in the vicinity of a joint portion between the middle support portion and the insert.
JP7027364A 1995-01-23 1995-01-23 Stress reducing structure for piston Withdrawn JPH08200497A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP7027364A JPH08200497A (en) 1995-01-23 1995-01-23 Stress reducing structure for piston

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP7027364A JPH08200497A (en) 1995-01-23 1995-01-23 Stress reducing structure for piston

Publications (1)

Publication Number Publication Date
JPH08200497A true JPH08200497A (en) 1996-08-06

Family

ID=12219004

Family Applications (1)

Application Number Title Priority Date Filing Date
JP7027364A Withdrawn JPH08200497A (en) 1995-01-23 1995-01-23 Stress reducing structure for piston

Country Status (1)

Country Link
JP (1) JPH08200497A (en)

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