GB2274878A - I.c.engine valve timing. - Google Patents

I.c.engine valve timing. Download PDF

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Publication number
GB2274878A
GB2274878A GB9302077A GB9302077A GB2274878A GB 2274878 A GB2274878 A GB 2274878A GB 9302077 A GB9302077 A GB 9302077A GB 9302077 A GB9302077 A GB 9302077A GB 2274878 A GB2274878 A GB 2274878A
Authority
GB
United Kingdom
Prior art keywords
engine
exhaust
intake
valves
valve timing
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Withdrawn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
GB9302077A
Other versions
GB9302077D0 (en
Inventor
Thomas Tsoi-Hei Ma
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.)
Ford Motor Co
Original Assignee
Ford Motor Co
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 Ford Motor Co filed Critical Ford Motor Co
Priority to GB9302077A priority Critical patent/GB2274878A/en
Publication of GB9302077D0 publication Critical patent/GB9302077D0/en
Publication of GB2274878A publication Critical patent/GB2274878A/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Withdrawn legal-status Critical Current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
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
    • F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
    • F02D13/0203—Variable control of intake and exhaust valves
    • F02D13/0215—Variable control of intake and exhaust valves changing the valve timing only
    • F02D13/0219—Variable control of intake and exhaust valves changing the valve timing only by shifting the phase, i.e. the opening periods of the valves are constant
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
    • F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
    • F02D13/0223—Variable control of the intake valves only
    • F02D13/0234—Variable control of the intake valves only changing the valve timing only
    • F02D13/0238—Variable control of the intake valves only changing the valve timing only by shifting the phase, i.e. the opening periods of the valves are constant
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
    • F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
    • F02D13/0261—Controlling the valve overlap
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/01—Internal exhaust gas recirculation, i.e. wherein the residual exhaust gases are trapped in the cylinder or pushed back from the intake or the exhaust manifold into the combustion chamber without the use of additional passages
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
    • F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
    • F02D2013/0292—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation in the start-up phase, e.g. for warming-up cold engine or catalyst
    • 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

Abstract

The opening times of the intake valves are advanced when the engine is operating below a predetermined temperature so as to prolong the period during which the intake valves are open at the end of the engine exhaust strokes. This causes exhaust gases to be forced into the intake ports for the purpose of improving charge preparation during cold starts and cold running. The closing times of the exhaust valves may also be advanced. <IMAGE>

Description

ENGINE VALVE TIMING Field of the Invention The present invention relates to the control of engine valve timing and is particularly concerned with the control of valve timing during cold starting and cold running of an internal combustion engine.
Background of the Invention In any engine which has fixed crank angles at which the intake and exhaust valves open and close, the values of the crank angles are set at a comprise to provide acceptable performance over a range of operating conditions. For this reason, engines with variable valve and/or event timing have been proposed to enable the engine characteristics to be better optimised in dependence upon the operating conditions.
It is known for example that under high load and high speed operation, an increased degree of valve overlap is advantageous and systems have been proposed in the past to delay or retard the times at which the exhaust valve closes as engine speed increases. Systems have also been proposed to vary the times of opening and closing the intake valves for a variety of reasons, for example to improve volumetric efficiency in dependence upon engine speed.
Hitherto, the effects of varying the valve timing on engine operation during cold starts and during warm-up have not been considered.
The present invention therefore seeks to provide an internal combustion engine in which engine valve timing is modified as a function of temperature in order to assist engine operation during cold start and warm-up.
Summary of the invention According to the present invention there is provided an internal combustion engine having means for advancing the opening times of the intake valves when the engine is operating below a predetermined temperature so as to prolong the period during which the intake valves are open near the end of the engine exhaust strokes.
The early opening of the intake valves as the piston is moving up the exhaust stroke forces exhaust gases into the intake ports. The hot exhaust gases, entering the intake ports with high velocity, improve charge preparation within the intake port.
Advantageously means should also be provided to advance the instant of closing of the exhaust valve when the engine is operating below a predetermined temperature so that near the end of the exhaust stroke of each piston, the exhaust gases are diverted from the exhaust port to the intake port.
The important times for the purpose of the present invention, which is concerned with improving charge preparation in the intake port, are the instants at which the intake valves open and the exhaust valves close. In an engine having variable event timing, these instants can be controlled without reference to the instants at which the intake valve closes and the exhaust valve opens, but when the intake and exhaust valves are controlled by fixed cams (so that the valve event durations cannot change) then the instants at which the intake valves close and the exhaust valves open would also be corresponding advanced within the engine cycle.
During cold start and cold running, substantial amounts of excess fuel are injected into the intake port but most of the fuel ends up merely wetting the walls of the intake manifold or the intake port and does not reach the combustion chambers as part of the combustion charge. As a result it is necessary to inject more fuel than is required for combustion and this results in considerable hydrocarbon emissions during cold start. By enhancing charge preparation during cold starting and the warm-up phase of the engine, the invention permits lower levels of enrichment to be used thereby reducing the unburnt hydrocarbon content in the exhaust gases of the engine over the measured statutory drive cycle.
The effect of wall-wetting is to cause an excess of fuel to reach the combustion chambers during deceleration modes.
When the engine is operated with the throttle closed the manifold vacuum results in evaporation of the fuel wetting the intake ports, the fuel reaching the combustion chambers at times when there is insufficient oxygen to burn it and it is this that causes high hydrocarbon emissions during deceleration modes. By reducing the wall-wetting effect and enhancing fuel preparation in the intake port, the present invention assists in alleviating this problem. Furthermore, by ensuring that more of the fuel injected into the intake ports finds its way into the combustible charge, the engine fires and starts more easily.
Various systems have been proposed for phase-shifting cams having a fixed profile. For example, some systems have incorporated a helix on the cam which resulted in the camshaft being changed in phase when axially advanced with reference to a drive cog. The present invention may be used with any system capable of advancing the intake valve opening and inasmuch as the exhaust valve can be advanced by the same phase and at the same time, the invention may even be applied to an engine with a single camshaft. The phase advancement may either be continuous or in discrete steps, depending on the type of phase change mechanism employed in implementing the invention.In the former case, the extent of advancement of the valve timing may be gradually reduced as the engine warms up and in the latter case, a fixed degree of advancement may be employed until the engine coolant reaches a predetermined temperature.
Brief description of the drawings The invention will now be described further, by way of example, with reference to the accompanying drawings, in which the single figure shows graphs of valve opening and closing times during different phases of operation of an engine.
Description of the preferred embodiment Several systems have been proposed to control valve timing.
Systems are known for phase shifting cams operating the intake and exhaust valves relative to one another as well as relative to the phase of the engine crankshaft. Such systems can operate on engines with single or dual overhead camshafts. Systems have also been proposed and implemented for enabling event duration to be modified. Because any such system may be used in implementing the invention, it is felt that a detailed description of the valve train mechanism required to vary the valve timing is not required within the present context and the description will instead be confined to the valve timing strategy.
Under normal operating conditions, the lifting of the valves is as shown at A in the drawing in which the curve 10a represents the exhaust valve lift and the curve 12a the intake valve lift.
At B in the drawing, there is represented the valve timing during cold starts. The inlet valve timing has been advanced as compared with the values shown at A for normal engine running and as a consequence the inlet valve opens at an earlier instant while the engine piston is approaching TDC at the end of its exhaust stroke. The effect of such advancing of the intake valve timing is to cause hot exhaust gases to be forced into the intake port at the end of the exhaust stroke in order to assist in charge preparation by evaporating any fuel on the walls of the intake port and improving the mixing of the fuel with the intake air.
To further assist in directing the exhaust gases into the intake port, it is useful also to advance the time at which the exhaust valve closes. By closing the exhaust valve earlier, more exhaust gases are diverted towards the intake port to assist in charge preparation. This valve timing strategy is represented at C in the drawing. As well as improving charge preparation, the strategy of advancing both the intake and the exhaust valve timing, as shown at C, is preferred as it can be implemented even in engines having a single camshaft driving both the intake and the exhaust valves.
The advancement of the phase of the intake valves may be performed as a continuous function of temperature, in other words the extent of the advancement may be gradually decreased with increasing engine coolant temperature.
Alternatively, if a phase change mechanism is used that can only alter the timing in discrete increments, then the valve timing may be returned to its normal setting, as represented at A in the drawing, in a single step when the engine temperature exceeds a preset threshold value.
It will be appreciated that the above description is given by way of example only and that various modifications may be made within the scope of the invention as set out in the appended claims. For example, it is not essential that the valve event should remain of constant duration and in any engine capable of variable event timing, the opening times of the intake valves may be advanced without correspondingly advancing the closing times. Similarly, the exhaust valve closing times may be advanced without advancing the opening times.

Claims (4)

1. An internal combustion engine having means for advancing the opening times of the intake valves when the engine is operating below a predetermined temperature so as to prolong the period during which the intake valves are open near the end of the engine exhaust strokes.
2. An internal combustion engine as claimed in claim 1, wherein means are provided for advancing the closing times of the exhaust valves when the engine is operating below a predetermined temperature so that near the end of the exhaust stroke of each piston, the exhaust gases are diverted from the exhaust port to the intake port.
3. An internal combustion engine as claimed in claim 1 or claim 2, wherein the advancement of the valve timing is gradually reduced as the engine warms up.
4. An internal combustion engine as claimed in claim 1 or claim 2, wherein a fixed degree of advancement is employed until the engine coolant reaches a predetermined temperature.
GB9302077A 1993-02-03 1993-02-03 I.c.engine valve timing. Withdrawn GB2274878A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9302077A GB2274878A (en) 1993-02-03 1993-02-03 I.c.engine valve timing.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9302077A GB2274878A (en) 1993-02-03 1993-02-03 I.c.engine valve timing.

Publications (2)

Publication Number Publication Date
GB9302077D0 GB9302077D0 (en) 1993-03-24
GB2274878A true GB2274878A (en) 1994-08-10

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB9302077A Withdrawn GB2274878A (en) 1993-02-03 1993-02-03 I.c.engine valve timing.

Country Status (1)

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GB (1) GB2274878A (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0761950A1 (en) * 1995-09-12 1997-03-12 Toyota Jidosha Kabushiki Kaisha A valve timing control device for an internal combustion engine
EP0814237A1 (en) * 1996-06-18 1997-12-29 Dr.Ing.h.c. F. Porsche Aktiengesellschaft Valve drive in an internal combustion engine
GB2341204A (en) * 1998-09-04 2000-03-08 Caterpillar Inc Cold starting method for diesel engine with variable valve timing
GB2350400A (en) * 1999-05-22 2000-11-29 Ford Global Tech Inc I.C. engine with internal exhaust gas recirculation generated by variable valve timing
GB2367859A (en) * 2000-10-12 2002-04-17 Lotus Car Methods of operating i.c. engines having electrically controlled actuators for the inlet and/or exhaust valves

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB969207A (en) * 1959-10-17 1964-09-09 Maschf Augsburg Nuernberg Ag Re-use of waste gases in the working process of piston internal combustion engines
GB2134596A (en) * 1983-02-04 1984-08-15 Fev Forsch Energietech Verbr Fresh charge intake quantity control in an internal combustion engine

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB969207A (en) * 1959-10-17 1964-09-09 Maschf Augsburg Nuernberg Ag Re-use of waste gases in the working process of piston internal combustion engines
GB2134596A (en) * 1983-02-04 1984-08-15 Fev Forsch Energietech Verbr Fresh charge intake quantity control in an internal combustion engine

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0761950A1 (en) * 1995-09-12 1997-03-12 Toyota Jidosha Kabushiki Kaisha A valve timing control device for an internal combustion engine
EP0814237A1 (en) * 1996-06-18 1997-12-29 Dr.Ing.h.c. F. Porsche Aktiengesellschaft Valve drive in an internal combustion engine
US5931124A (en) * 1996-06-18 1999-08-03 Dr. Ing. H.C.F. Porsche Ag Valve timing for internal-combustion engines
GB2341204A (en) * 1998-09-04 2000-03-08 Caterpillar Inc Cold starting method for diesel engine with variable valve timing
US6092496A (en) * 1998-09-04 2000-07-25 Caterpillar Inc. Cold starting method for diesel engine with variable valve timing
GB2350400A (en) * 1999-05-22 2000-11-29 Ford Global Tech Inc I.C. engine with internal exhaust gas recirculation generated by variable valve timing
GB2367859A (en) * 2000-10-12 2002-04-17 Lotus Car Methods of operating i.c. engines having electrically controlled actuators for the inlet and/or exhaust valves

Also Published As

Publication number Publication date
GB9302077D0 (en) 1993-03-24

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