EP0167691A2 - Dispositif de décompression pour moteur à combustion interne - Google Patents

Dispositif de décompression pour moteur à combustion interne Download PDF

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Publication number
EP0167691A2
EP0167691A2 EP84307380A EP84307380A EP0167691A2 EP 0167691 A2 EP0167691 A2 EP 0167691A2 EP 84307380 A EP84307380 A EP 84307380A EP 84307380 A EP84307380 A EP 84307380A EP 0167691 A2 EP0167691 A2 EP 0167691A2
Authority
EP
European Patent Office
Prior art keywords
cam
decompression
engine
periphery
valve
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Withdrawn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
EP84307380A
Other languages
German (de)
English (en)
Other versions
EP0167691A3 (fr
Inventor
Hiroshi Yamaguchi
Hiroaki Kaneko
Yasuyo Hisano
Akio Iwashita
Masahiro Terai
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.)
Subaru Corp
Original Assignee
Fuji Jukogyo KK
Fuji 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 Fuji Jukogyo KK, Fuji Heavy Industries Ltd filed Critical Fuji Jukogyo KK
Publication of EP0167691A2 publication Critical patent/EP0167691A2/fr
Publication of EP0167691A3 publication Critical patent/EP0167691A3/fr
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
    • F01L13/08—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for decompression, e.g. during starting; for changing compression ratio
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
    • F01L13/08—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for decompression, e.g. during starting; for changing compression ratio
    • F01L13/085—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for decompression, e.g. during starting; for changing compression ratio the valve-gear having an auxiliary cam protruding from the main cam profile
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L2820/00—Details on specific features characterising valve gear arrangements
    • F01L2820/02—Formulas
    • 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
    • F02B3/00—Engines characterised by air compression and subsequent fuel addition
    • F02B3/06—Engines characterised by air compression and subsequent fuel addition with compression ignition

Definitions

  • the present invention relates to decompression apparatus for an internal combustion engine, designed to make starting easier and to avoid the risk caused by reversal of rotation, or "kick-back".
  • a decompression device which is either automatically or manually operated to open either an inlet valve or an exhaust valve a small extent to reduce the compression pressure in the combustion chambers during starting and thereby to reduce the starting load of the engine.
  • a decompression shaft which is provided on the cylinder head or a rocker shaft, is manually operated to hold a rocker arm in a decompression position; the engine is then started using a starting handle or a recoil starter.
  • Japanese Patent publication No. 50-95630 discloses an automatic decompression device which is operated by centrifugal force and which automatically reduces the compression pressure in the combustion chambers during starting of engine.
  • a cam lobe for decompression is provided on an inlet valve cam.
  • the decompression cam lobe of an ordinary gasoline engine is provided at a position adjacent bottom dead centre at the beginning of compression stroke as shown in Figure 8 of the accompanying drawings, which figure shows the relationship between crank angle and cam-lift. Accordingly, the compression period is increased and the operational load becomes heavy during starting of the engine, especially in the case of a diesel engine.
  • various auxiliary means other than the automatic decompression device such as auxiliary fuel injection nozzles, means for retarding the ejecting timing and means for increasing the flywheel-mass, have been employed.
  • line E represents a relationship between time and cranking speed which is too low to cause starting ignition of the engine; line F shows that the -ranking speed is in the zone in which the reverse revolution occurs at a point X on the line F; line G shows a sufficient cranking speed for the engine to start; line H shows the limit of the decompression condition; line I shows the limit of decompression release; and line J shows the limit of starting of engine.
  • the reverse revolution phenomenon occurs, so that an operator attempting to start the engine with a starting handle may be subject to shock; if rope-starting is used, kick-back will cause the rope to be wound up and stress to be given to the operator's arm.
  • An object of the present invention is to provide a centrifugal decompression apparatus which enables an engine to be started under light load and without the danger of reverse revolution of the engine.
  • the present invention relates to apparatus for reducing the compression of an internal combustion engine which has a camshaft carrying an inlet valve cam and an exhaust valve cam and tappets engaged with those valves, and is characterised in that the apparatus comprises a supporting member secured to, and rotating with, the camshaft; a decompression device having a shaft which is rotatably supported in the supporting member and which has a decompression cam formed thereon, the decompression cam being engageable with the tappet of either the inlet valve cam or the exhaust valve cam to cause lifting of the tappet; and a weight which is rotatably mounted on the supporting member so as to be subject to centrifugal force on rotation of the carshaft and which is operatively engaged with the decompression device so that rotation of the weight is accompanied by rotati on of the decompression device; the weight and the decompression device being so arranged that, when the rotational speed of the camshaft is below the speed which causes reverse engine movement, the periphery of the decompression cam projects beyond the peripher
  • a camshaft 1 carries an inlet valve cam 4 and an exhaust valve cam 5 and has on its end a cam gear 6.
  • Cams 4 and 5 cooperate with tappets 2 and 3, which in turn engage with push rods 18 and 19, respectively.
  • Camshaft 1 is rotated by the engine crankshaft (not shown) through cam gear 6.
  • a groove 7 is formed in one side of the cam gear 6 and communicates with the other side by a bore 8 which is parallel to camshaft 1.
  • the position of the bore 8 is, as shown in Figure 2, in advance of the compression top dead centre position K of the camshaft by an angle ⁇ , i.e. it is displaced by 8 from top dead centre in the rotational direction of the cam gear.
  • Figure 3 shows a decompression device 9 which consists of a pin or a shaft 10, a U-shaped engagement member 11 which is formed on an end of the shaft 10 and is at right angles thereto, and a decompression cam 12 formed on the other end of shaft 10, the cam 12 having a semicircular cross section with a diametrical flat 12a.
  • the shaft 10 is rotatably located in the bore 8, as shown in Figure 1, with the engagement member 11 within the groove 7 and the cam 12 protruding from the cam gear 6 into a recess 4a formed in part of the periphery of inlet valve cam 4.
  • the normal operative contour of cam 4 is unaffected, being defined by the unrecessed part of its periphery.
  • the engagement member can turn within groove 7, the central portion of the gear 6 being cut away at 17 for that purpose.
  • Groove 7 also accommodates a weight 13, one end of which is pivotably mounted on a pin 14 secured to cam gear 6, and the other end of which carries a pin 15 which is received between the arms of the U-shaped part 11 of the decompression device 9; the device 9 is thus interconnected with the weight 13 and turns in the bore 8 as weight 13 turns on pin 14.
  • Pin 14 is located on a radius of the cam gear 6 which is approximately perpendicular to a line connecting the centre of shaft 10 with the centre of cam shaft l.
  • a coil spring 16 is provided around the pin 14, one end of the spring being anchored to cam gear 6 and the other end attached to weight 13 so as to urge the weight towards the centre of cam shaft 1.
  • crank speed range which is higher than the range which may cause the reverse engine movement.
  • This crank speed range varies according to the characteristics of the engine with which the decompression device is employed and is selected by experience or experiment on the engine.
  • Vnl represents, as shown in Figure 5, the volume of a combustion chamber 20 in the period from the valve closing position to decompression starting position;
  • Vcl is the volume of the combustion chamber during the period from the decompression starting position to the compression top dead centre position of a piston 21;
  • Vn2 is the volume in the period from decompression ending position to compression top dead centre position;
  • Vn2 is the volume at the compression top dead centre position.
  • the force of the return coil spring 16 is initially greater than the centrifugal force, so that the weight 13 and the decompression device 9 are held at the solid line positions in Figure 2 and as shown in Figure 6.
  • the semicircular periphery of the cam 12 of the decompression pin 10 projects from the periphery of the cam 4, so that the semicircular part pushes up the tappet 2 and slightly opens the inlet valve to cause the half-compression condition in the combustion chamber.
  • the compression ratio can be made smaller by dividing the compression into the first and second compression ranges Land M, which are made equal to each other in order to make the work loads equal, so that the operation requires less power.
  • the load during starting of the engine can be lightened.
  • the half-compression condition can be released at an early stage of the starting operation and at a low rotational speed.
  • the operational period of the decompression device 9 is made to overlap part of the corpression stroke and the values of compression ratic E 1 and E 2 are equalized, the device 9 can be made to provide the decompression condition throughout the period of the compression strode.
  • the angle e can be chosen so that the work in the first compression range becomes equal to the total work of the second compression range and of the inlet stroke. By that, the driver can easily start the engine.
  • the decompression device is not limited to the shape in the embodiment but can be changed so as to ensure a large displacement of the pin 15 on movement of the weight 13.
  • the exhaust cam may be used in place of the inlet cam to cause decompression with the decompression device.
  • the coil spring 16 can be omitted.
  • the rotational crank speed range in which decompression is released is chosen to be higher than the range in which reverse engine movement occurs, and decompression is made throughout the period or in a part of the period of the compression stroke, so that the driver is able to start the engine easily and lightly without complicated handling before starting. Also the risk of the engine reversal can be avoided.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Valve Device For Special Equipments (AREA)
  • Valve-Gear Or Valve Arrangements (AREA)
  • Output Control And Ontrol Of Special Type Engine (AREA)
EP84307380A 1984-07-10 1984-10-26 Dispositif de décompression pour moteur à combustion interne Withdrawn EP0167691A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP143786/84 1984-07-10
JP14378684A JPH066888B2 (ja) 1984-07-10 1984-07-10 エンジンのデコンプ装置

Publications (2)

Publication Number Publication Date
EP0167691A2 true EP0167691A2 (fr) 1986-01-15
EP0167691A3 EP0167691A3 (fr) 1986-07-30

Family

ID=15346962

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84307380A Withdrawn EP0167691A3 (fr) 1984-07-10 1984-10-26 Dispositif de décompression pour moteur à combustion interne

Country Status (4)

Country Link
EP (1) EP0167691A3 (fr)
JP (1) JPH066888B2 (fr)
KR (1) KR860001276A (fr)
DE (1) DE167691T1 (fr)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4696266A (en) * 1985-05-14 1987-09-29 Fuji Jukogyo Kabushiki Kaisha Decompression apparatus for engines
EP0362775A1 (fr) * 1988-10-03 1990-04-11 Fuji Jukogyo Kabushiki Kaisha Dispositif de décompression pour moteur à combustion interne
EP0411238A1 (fr) * 1989-06-09 1991-02-06 Kohler Co. Dispositif automatique de décompression pour un moteur à combustion interne
EP0425899A1 (fr) * 1989-11-02 1991-05-08 Kubota Corporation Moteur avec régulation mécanique et dispositif de décompression
US6055952A (en) * 1998-06-08 2000-05-02 Industrial Technology Research Institute Automatic decompression device
US6223708B1 (en) * 1996-09-11 2001-05-01 Motorenfabrik Hatz Gmbh & Co. Kg Automatic decompression system
EP1520963A2 (fr) * 2003-09-30 2005-04-06 Fuji Jukogyo Kabushiki Kaisha Dispositif de décompression pour un moteur
CN101403327B (zh) * 2007-10-03 2011-03-23 本田技研工业株式会社 发动机的减压装置
EP2949891A1 (fr) * 2014-05-27 2015-12-02 Yamaha Hatsudoki Kabushiki Kaisha Moteur et véhicule
CN112384683A (zh) * 2018-07-05 2021-02-19 本田技研工业株式会社 发动机的减压装置及发动机

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3362390A (en) * 1966-02-09 1968-01-09 Wisconsin Motor Corp Automatic compression release
US3901199A (en) * 1974-06-10 1975-08-26 Briggs & Stratton Corp Automatic compression relief mechanism

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3362390A (en) * 1966-02-09 1968-01-09 Wisconsin Motor Corp Automatic compression release
US3901199A (en) * 1974-06-10 1975-08-26 Briggs & Stratton Corp Automatic compression relief mechanism

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4696266A (en) * 1985-05-14 1987-09-29 Fuji Jukogyo Kabushiki Kaisha Decompression apparatus for engines
EP0362775A1 (fr) * 1988-10-03 1990-04-11 Fuji Jukogyo Kabushiki Kaisha Dispositif de décompression pour moteur à combustion interne
EP0411238A1 (fr) * 1989-06-09 1991-02-06 Kohler Co. Dispositif automatique de décompression pour un moteur à combustion interne
AU629906B2 (en) * 1989-06-09 1992-10-15 Kohler Co. Geared automatic compression release for an internal combustion engine
EP0425899A1 (fr) * 1989-11-02 1991-05-08 Kubota Corporation Moteur avec régulation mécanique et dispositif de décompression
US6223708B1 (en) * 1996-09-11 2001-05-01 Motorenfabrik Hatz Gmbh & Co. Kg Automatic decompression system
US6055952A (en) * 1998-06-08 2000-05-02 Industrial Technology Research Institute Automatic decompression device
EP1520963A3 (fr) * 2003-09-30 2009-12-16 Fuji Jukogyo Kabushiki Kaisha Dispositif de décompression pour un moteur
EP1520963A2 (fr) * 2003-09-30 2005-04-06 Fuji Jukogyo Kabushiki Kaisha Dispositif de décompression pour un moteur
CN101403327B (zh) * 2007-10-03 2011-03-23 本田技研工业株式会社 发动机的减压装置
EP2949891A1 (fr) * 2014-05-27 2015-12-02 Yamaha Hatsudoki Kabushiki Kaisha Moteur et véhicule
CN105275529A (zh) * 2014-05-27 2016-01-27 雅马哈发动机株式会社 发动机以及车辆
TWI608161B (zh) * 2014-05-27 2017-12-11 山葉發動機股份有限公司 引擎及車輛
CN105275529B (zh) * 2014-05-27 2018-02-09 雅马哈发动机株式会社 发动机以及车辆
CN112384683A (zh) * 2018-07-05 2021-02-19 本田技研工业株式会社 发动机的减压装置及发动机
US11384725B2 (en) 2018-07-05 2022-07-12 Honda Motor Co., Ltd. Engine decompression device and engine

Also Published As

Publication number Publication date
DE167691T1 (de) 1986-04-10
JPS6123816A (ja) 1986-02-01
EP0167691A3 (fr) 1986-07-30
JPH066888B2 (ja) 1994-01-26
KR860001276A (ko) 1986-02-24

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Inventor name: TERAI, MASAHIRO

Inventor name: KANEKO, HIROAKI

Inventor name: IWASHITA, AKIO

Inventor name: HISANO, YASUYO

Inventor name: YAMAGUCHI, HIROSHI