GB2214981A - Method of four stroke engine valve operation - Google Patents

Method of four stroke engine valve operation Download PDF

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Publication number
GB2214981A
GB2214981A GB8804215A GB8804215A GB2214981A GB 2214981 A GB2214981 A GB 2214981A GB 8804215 A GB8804215 A GB 8804215A GB 8804215 A GB8804215 A GB 8804215A GB 2214981 A GB2214981 A GB 2214981A
Authority
GB
United Kingdom
Prior art keywords
valve
camshaft
speed
rocker arm
stroke
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Withdrawn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
GB8804215A
Other versions
GB8804215D0 (en
Inventor
Colin Hardie Brown
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.)
Individual
Original Assignee
Individual
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 Individual filed Critical Individual
Priority to GB8804215A priority Critical patent/GB2214981A/en
Publication of GB8804215D0 publication Critical patent/GB8804215D0/en
Publication of GB2214981A publication Critical patent/GB2214981A/en
Withdrawn legal-status Critical Current

Links

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
    • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
    • F01L1/12—Transmitting gear between valve drive and valve
    • F01L1/18—Rocking arms or levers
    • F01L1/181—Centre pivot rocking arms
    • 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
    • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
    • F01L1/02—Valve drive
    • F01L1/04—Valve drive by means of cams, camshafts, cam discs, eccentrics or the like
    • F01L1/06—Valve drive by means of cams, camshafts, cam discs, eccentrics or the like the cams, or the like, rotating at a higher speed than that corresponding to the valve cycle, e.g. operating fourstroke engine valves directly from crankshaft
    • 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
    • F02B75/00—Other engines
    • F02B75/02—Engines characterised by their cycles, e.g. six-stroke
    • F02B2075/022—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle
    • F02B2075/027—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle four

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Valve-Gear Or Valve Arrangements (AREA)
  • Valve Device For Special Equipments (AREA)

Abstract

One camshaft 5 rotates at the same speed of the engine and the other 2 at half the speed of the engine. The position of the half speed camshaft lobe determines whether or not the full speed camshaft lobe opens the valve 10. If the half speed camshaft lobe is not in contact with the rocker arm then the full speed camshaft lobe will not contact the rocker arm 7. On the next revolution of the full speed camshaft however, the half speed camshaft lobe will be in contact with the rocker arm, the full speed camshaft will now contact the rocker arm and cause the valve to open. <IMAGE>

Description

METHOD OF FOUR STROKE ENGINE VALVE OPERATION This invention relates to a method of four stroke engine valve operation.
Cylinder breathing in a four stroke engine is normally controlled by the use of valves in the cylinder head. Normally two valves are used per cylinder, the inlet valve allows air or a fuel air mixture into the cylinder and the exhaust valve allows burnt gasses to escape from the cylinder.
A valve is operated by the use of a camshaft which rotates at half the speed of the engine. A lobe on the camshaft acts or the valve stem, causing the valve to lift off its seat allowing gasses to flow past. There are several ways of transmitting the action of the camshaft lobe to the valve stem. It can either act directly on the valve, or act through a rocker, a pushrod and rocker or a hydraulic circuit.
Engine breathing efficiently is a term used in connection with the speed and volume of gasses passing through an engine. Increasing breathing efficiency invariably increases engine performance.
There are various methods to increase breathing efficiency in high performance engines. Steep ramps on camshaft lobes combined with precise valve timing allow the valves to remain open for as long a period as possible during the four stroke cycle allowing a maxinu: flow of gasses to and from the cylinders, or up to five valves car be used per cylinder in order to allow gasses to flow more freely.
However, there are limits of breathing efficiency, one limiting factor in engines with conventional camshafts is the period a valve can be kept fully open during the four stroke cycle. This is restricted by the period spent opening and closing the valve.
According to the present invention, there is provided a method of four stroke engine valve operation where lobes of two camshafts, driven at different speeds from the crank shaft, operate each valve.
One camshaft rotates at half the speed of the engine (half speed camshaft, HSC) the other at full speed (full speed camshaft, FSC).
As with conventional valve operation, there are several ways of transmitting the action of the camshaft lobe to the cylinder valve, for the purpose of explanation, in this description the two camshafts act on a rocker arm retained in position by the use of a spring and a bracket fixed to the cylinder head.
The bracket hasan slongated hole in which a dowel, fixed to the rocker arm is free to move up and down but not from side to side. A means of valve clearance adjustment is provided on the rocker arm. The rocker arm acts on cylinder head valve which has a conventional return spring. The valve in this description is an inlet valve.
A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows the valve in the open position during the induction stroke Figure 2 shows the valve in the closed position during the compression stroke Figure 3 shows the valve in the closed position during the power stroke Figure 4 shows the valve in the closed position during the exhaust stroke In Figure 1 both camshaft (2 and 5) lobes are active against the rocker arm (7). The rocker arm has forced the cylinder valve (10) into the open position against its spring (9) pressure. This is during the induction stroke.
During the compression stroke, shown in Figure 2, the FSC (5) has come off its lobe allowing the valve (10) to reassert itself under spring (9) pressure.
The HSC (2) is however, still partially on its lobe, but has no effect on the valve.
The itsc (2) lobe is completely off the rocker arm (7) in Figure 3 and the rocker arm is pulled towards the HSC (2) by the rocker return spring (3).
This has the effect of the HSC (5) lobe having an idle revolution, since it does not touch the rocker arm (7) due to the valve clearance, which would be set musing the adjuster (8) with the engine at rest, but in this position. The cylinder is now on the power stroke.
In Figure 4 the ESC (2) is again acting on the rocker arm (7) and the FOC (5) is not, therefore, no valve movement is caused on- this the exhaust stroke.
The cycle would now be repeated.
The exhaust valve is operated in the same manner, but the eSkaus valve is open during the exhaust stroke.
This method of valve operation enables rapid opening and closing of valve, effectively halting the crankshaft angles used in opening and closing cylinder valves in relation to the use of a conventional camshaft, assuring that the same steepness of ramp is used on the fullspeed camshaft as on the conventional one.
When both camshafts are on contact with the rocker arm they should both come on peak and both come off peak at the same time or, the half speed camshaft should come to its peak first and off it last otherwise the rapid operation effect would be decreased.

Claims (2)

1. A method of four stroke engine valve operation, where valves are operated by cam lobes on two separate camshafts, driven at different speed by tLe crankshaft. One camshaft is driven at full engine speed, the other camshaft is driven at half engine speed.
2. A method of four stroke engine valve operation substantially as described herein with reference to Figures 1 - 4 of the accompanying drawings.
GB8804215A 1988-02-23 1988-02-23 Method of four stroke engine valve operation Withdrawn GB2214981A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8804215A GB2214981A (en) 1988-02-23 1988-02-23 Method of four stroke engine valve operation

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8804215A GB2214981A (en) 1988-02-23 1988-02-23 Method of four stroke engine valve operation

Publications (2)

Publication Number Publication Date
GB8804215D0 GB8804215D0 (en) 1988-03-23
GB2214981A true GB2214981A (en) 1989-09-13

Family

ID=10632232

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8804215A Withdrawn GB2214981A (en) 1988-02-23 1988-02-23 Method of four stroke engine valve operation

Country Status (1)

Country Link
GB (1) GB2214981A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10357083A1 (en) * 2003-12-06 2005-06-30 Ina-Schaeffler Kg Variable valve drive for external ignition combustion engine has lift function adjustment auxiliary cam on secondary camshaft rotating at primary camshaft revolution rate, actuating element pivot point guided on auxiliary cam
WO2017213566A1 (en) * 2016-06-07 2017-12-14 Scania Cv Ab Four stroke internal combustion engine and thereto-related method

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB467242A (en) * 1935-12-16 1937-06-14 Geoffrey Arthur Plunket Sander Improvements in or relating to cam operated rocker mechanism

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB467242A (en) * 1935-12-16 1937-06-14 Geoffrey Arthur Plunket Sander Improvements in or relating to cam operated rocker mechanism

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10357083A1 (en) * 2003-12-06 2005-06-30 Ina-Schaeffler Kg Variable valve drive for external ignition combustion engine has lift function adjustment auxiliary cam on secondary camshaft rotating at primary camshaft revolution rate, actuating element pivot point guided on auxiliary cam
WO2017213566A1 (en) * 2016-06-07 2017-12-14 Scania Cv Ab Four stroke internal combustion engine and thereto-related method
US20190153906A1 (en) * 2016-06-07 2019-05-23 Scania Cv Ab Four stroke internal combustion engine and thereto-related method

Also Published As

Publication number Publication date
GB8804215D0 (en) 1988-03-23

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Legal Events

Date Code Title Description
WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)