US3540424A - Decompression device for valve-controlled combustion engine - Google Patents

Decompression device for valve-controlled combustion engine Download PDF

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Publication number
US3540424A
US3540424A US720870A US3540424DA US3540424A US 3540424 A US3540424 A US 3540424A US 720870 A US720870 A US 720870A US 3540424D A US3540424D A US 3540424DA US 3540424 A US3540424 A US 3540424A
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United States
Prior art keywords
decompression
valve
rocker
spindle
cam
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Expired - Lifetime
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US720870A
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English (en)
Inventor
Manfred Dietel
Karlheinz Spiess
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Motorenfabrik Hatz GmbH and Co KG
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Motorenfabrik Hatz GmbH and Co KG
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    • 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

Definitions

  • ABSTRACT A decompression device for valve-controlled internal combustion engines.
  • a decompression control cam is nonrotatably mounted on a spindle coaxial with the valve rocker arm spindle and is operatively connected to the rocker [54] arm so that rotation of the cam from a reference position 6
  • the cam may be operated to g maintain decompression indefinitely, or it may be set to act, US.
  • This invention 'relates to internal combustion'engines; and in particular it relates to a decompressiondevice for valvecontrolled internal combustion engines;
  • Decompression devices for valve-controlled combustion engines are known. They are used to assist the starting of small engines, particularly diesel combustion engines, which often are started manually by means of a handcrank. To this end a valve is held open during the starting operation with the help of the aforesaid decompression device, whereby that part of the resistance to the turning of the handcrank attributable to the compression in the engine is greatly reduced. A further easing of the starting procedure is afforded. by automatically eliminating the decompression after a preselected number of rotations of the crankshaft.
  • Known decompression devices additionally provide both (a) prolonged lifting of thevalve until the decompression means is manually removed and (b) means for automatically eliminating the valve decompression means. The prolonged valve lift is of importance at extremelylow temperatures. It enables the film of lubricant on the cylinder walls to be warmed before the actual starting procedure is commenced, and this in turn facilitates starting.
  • a purpose of the present invention therefore is to provide an improved decompression device which is distinguished from the known constructions by a simple structure and a notably greater-functional reliability.
  • the decompression cam and the driving element referred to hereafter as a driving disc
  • a decompression spindle which is disposed coaxially with the axis of the valve rocker, and which preferably has one end projectingout of the housing of the valve gear and coupled to a hand adjusting lever.
  • the decompression cam preferably comprises a disc provided with two lateral flanges, these flanges providing a very simplemethod of coaxially guiding anabutment piece which bears'against the surface of the cam and is coupled to the rocker.
  • the driving disc which is spacially' separated from the decompression cam, is arranged on the same spindle as the latter, is axially displaceable and nonrotatably arranged on this spindle, and is in the form of a bush which is provided over a part of its periphery, at the face thereof confronting an actuating member, with'a-saw tooth profile.
  • This arrangement has the attributes of accurate guidance of the driving bush on the spindle, and of small frictional effects on the driving bush. Because of the physical separation of the decompression cam and the driving disc or bush, .a correct disengagement of these elements if ensured when this becomes necessary.
  • An advantage of the present invention is its simplicity. This simplification of the structure is achieved in that the actuating member is preferably formed as a disc which is mounted on the rocker spindle and is nonpositively coupled to the rocker.
  • the disc used as the actuating element has two lugs which are bent over in the axial direction, one of these lugs being in operative engagement with the saw tooth profile of the driving disc, and the other lug engaging nonpositively in a recess in the rocker.
  • a helical compression spring may be placed between the decompression cam and the driving disc, which preferably is in the form of a bush.
  • the resilient element which is required for the indexing movement thereby consists of a compression spring and offers the advantage that the pressure between the driving disc'and the actuating member can be accurately controlled.
  • FIG. 1 is a section through the decompression device taken through the axis of the valve
  • FIG. 2 is a sectional view taken on line II-II of FIG. 1;
  • FIG. 3 is a plan view of the device illustrated in FIG. 1;
  • FIG. 4 is a view inthe direction of arrow A of FIG. 3;
  • FIG. 5 illustrates the end face of the driving disc viewed from the right as shown in FIG. 2 and showing the partially saw-toothed profile of the disc
  • FIG. 6 is a partial elevational view taken in the direction of the arrow A in FIG. 3.
  • an exhaust valve member 2 in the valve housing 1 of an injection type internal combustion engine of known construction is pressed upwards against a valve seat 4 by a closure-spring 3.
  • the rocker 6 is mounted in the valvehousing 1 on a rocker spindle 7.
  • the decompression cam is constituted by a plate having two radial side flanges 16 and is nonrotatably connected to a decompression spindle 9 extending coaxially with the rocker spindle 7.
  • a decompression spindle 9 extending coaxially with the rocker spindle 7.
  • the driving disc 10 mounted on the decompression spindle 9, adjacent the decompression cam 8, and held on this spindle. so as also to be nonrotatable but axially displaceable on the same, is the driving disc 10 which is in the form ofa bush.
  • the driving disc 10 has at the end face thereof directed towards an actuating member 13, an area 18 with a sawtooth profile, and a further area 19 which is nontoothed, [.e. is flat.
  • the actuating member 13 is in the form of a plate provided on the axis of spindle 7 and nonpositively connected on the rocker 6.
  • the member 13 has two lugs 14 and 15 which are bent over so as to extend in the axial direction, one such lug 14 being in operative engagement with end face of driving disc 10 having the sawtooth profile 18 of the driving disc 10 as best shown in FIG. 6, and the other lug 15 engaging nonpositively in a corresponding recess in the rocker 6. Referring to FIG. 5, wherein the'rest position of lug 14 is superimposed in dotted lines, the lug 14 rides through the range Y over that portion of the end face on the right and just below the horizontal plane through the axis of the end face.
  • a helical compression spring 11 is arranged between the decompression cam 8, which is nonrotatably fastened to the decompression spindle 9 by a clamping pin 25, and the driving disc 10 which is axially displaceable on the same spindle 9.
  • the driving element 10 is provided with a longitudinal slot 24 into which passes a cylindrical pin 23 secured to the decompression spindle 9.
  • the decompression cam 8 is formed by a plate ofcylindrical contour which is flattened over a part of its periphery by a milled portion 31.
  • An abutment member 17 is axially guided on the surface of the decompression cam 8 between the radial side flanges 16.
  • This member 17 is pivotally secured in the valve housing 1 by means of a split pin 21 and with an interposed compression spring 22.
  • the spring 22 serves to provide a nonpositive coupling between member 17 and the decompression cam 8.
  • This abutment member 17 is a main link between cam 8 and rocker 6. Unhampered movement of the rocker 6, and thus closing of the valve 2, is possible only when the abutment member 17 bears against the flat 31 of the decompression cam.
  • the member 17, together with the setscrew on one end of the rocker 6, provides an adjustable abutment.
  • the decompression device When the internal combustion engine is running the decompression device is out of action because the abutment member 17 bears on the milled out or flat part 31 ofthe decompression cam 8. With the decompression cam set in this way, the setscrew 20 of the rocker 6 does not strike the abutment piece 17 and this means that the exhaust valve 2 can be closed. Moreover the automatic decompression terminating means is inoperative because the lug 14 of the actuating member 13 moves over the flat, nontoothed area 19 of the driving disc 10. The hand adjusting lever 12 occupies the position B illustrated in solid lines in FIG. 4 and is held in this position by the ball catch 29.
  • the hand adjusting lever 12 When protracted lifting of the exhaust valve 2 is required, the hand adjusting lever 12 is moved into the position C illustrated in dotted lines in FIG. 4, and when automatic decompression termination is required, the lever 12 is turned to position D as also shown in dotted lines in FIG. 4.v In both instances the abutment member 17 is moved away from the flat 31 of the decompression cam to the raised cylindrical part of the surface of the latter, as a result of which the exhaust valve 2 is opened a predetermined amount through the agency of the setscrew 20 and the rocker 6. The hand adjusting lever is held in positions C or D by ball catch 29 as it was when in position B.
  • the number of turns of the starting crank before the decompression is automatically terminated can be selected by means of the hand adjusting lever 12.
  • lever 12 In position D lever 12 is set for the maximum number of turns since tooth 18a is now located adjacent lug l4 and the disc 10 will now turn clockwise (FIG. 5) until the last tooth 18b is turned by lug 14, at which time the rest position B (as shown in FIGS. 5 and 6) will be reached. If the hand setting lever 12 is turned in the counterclockwise direction (FIG. 4) from position D, this means a correspondingly smaller number of turns of the starting crank before the decompression terminates. The user thus has a choice of the period for which decompression is to be applied.
  • This angular magnitude Y corresponds to the angular distance between two teeth 18. Since in this position the point of projection 14 would be behind the axis-parallel plane of a tooth 18, part 10 is carried along with projection 14, in the case of this revolution of parts 6 and 14, through the range Y from the solid line position oflug 14 in FIG. 6, to the dotted line position of lug 14 in FIG. 6. The friction in the notch 29, 30 will be overcome through the positive engagement of parts 14 and 18, so that part 10 and shaft 9 (via 23) together with the decompression cam 8 (via 25) are turned by an angular value corresponding to the distance Y between the teeth. If subsequently the rocker arm 6 is then moved clockwise (FIG.
  • a decompression device for a valve-controlled combustion engine including a valve, a rocker mounted for rotating movement to open the valve and to permit closing of the valve, a decompression cam nonrotatably mounted on a spindie, said spindle mounted for rotation about an axis coaxial with the axis of rotation of the rocker, mechanical means acting in response to the position of the decompression cam for either permitting or preventing the necessary movement of the rocker arm to permit the valve to close, and a decompression termination means including a driving disc nonrotatably mounted on the spindle, including an actuating means comprising a actuating member for operatively engaging the rocker and said driving disc to control rotation of the disc in response to movement of the rocker and thereby control rotation of the spindle and decompression cam, said driving disc being mounted on the spindle for axial displacement along said spindle and being provided at one end with a sawtooth profile extending over a part of its circumference, said actuating member comprising at least one lug bent over
  • a decompression device according to claim 1 wherein said spring is formed as a helical compression spring encircling said spindle between the decompression cam and the driving disc.
  • the decompression device of claim 1 including a handle attached to the spindle for manually adjusting the position of the spindle.
  • a decompression device according to claim 1 wherein the decompression cam is constituted by a disc which is provided with two lateral flanges, and said mechanical means is an abutment piece connected to the rocker and applied against the peripheral surface of the cam between these flanges.
  • a decompression device according to claim 1 wherein the said actuating member is constituted by a plate which is mounted on the axis of the rocker and is positively coupled to this rocker.
  • a decompression device according to claim 5 wherein the plate has two lugs bent over in the axial direction, one of these lugs being the said lug operatively engaged with the said tooth profile of the driving disc, and the other lug operatively engaging in a recess in the rocker.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Valve Device For Special Equipments (AREA)
  • Output Control And Ontrol Of Special Type Engine (AREA)
US720870A 1967-04-15 1968-04-12 Decompression device for valve-controlled combustion engine Expired - Lifetime US3540424A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DEF31998U DE1964020U (de) 1967-04-15 1967-04-15 Dekompressionsvorrichtung fuer ventilgesteuerte brennkraftmaschinen, insbesondere einspritz-brennkraftmaschinen.

Publications (1)

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US3540424A true US3540424A (en) 1970-11-17

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ID=33335165

Family Applications (1)

Application Number Title Priority Date Filing Date
US720870A Expired - Lifetime US3540424A (en) 1967-04-15 1968-04-12 Decompression device for valve-controlled combustion engine

Country Status (5)

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US (1) US3540424A (enExample)
JP (1) JPS4838648B1 (enExample)
DE (1) DE1964020U (enExample)
FR (1) FR1563334A (enExample)
GB (1) GB1177033A (enExample)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4862841A (en) * 1988-08-24 1989-09-05 Stevenson John C Internal combustion engine
US20080121477A1 (en) * 2006-11-28 2008-05-29 Pietro Bianchi Decompression braking device in endothermic engines

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS51139952U (enExample) * 1975-05-02 1976-11-11
AT383398B (de) * 1980-04-15 1987-06-25 List Hans Dekompressionseinrichtung an brennkraftmaschinen
RU2136903C1 (ru) * 1998-03-25 1999-09-10 Дронов Евгений Анатольевич Одноцилиндровый четырехтактный двигатель внутреннего сгорания

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4862841A (en) * 1988-08-24 1989-09-05 Stevenson John C Internal combustion engine
US20080121477A1 (en) * 2006-11-28 2008-05-29 Pietro Bianchi Decompression braking device in endothermic engines
US7992540B2 (en) * 2006-11-28 2011-08-09 Iveco S.P.A. Decompression braking device in endothermic engines

Also Published As

Publication number Publication date
FR1563334A (enExample) 1969-04-11
GB1177033A (en) 1970-01-07
JPS4838648B1 (enExample) 1973-11-19
DE1964020U (de) 1967-07-13

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