EP1301692A1 - Selectable 2 stroke / 4 stroke camshaft drive system - Google Patents

Selectable 2 stroke / 4 stroke camshaft drive system

Info

Publication number
EP1301692A1
EP1301692A1 EP01949668A EP01949668A EP1301692A1 EP 1301692 A1 EP1301692 A1 EP 1301692A1 EP 01949668 A EP01949668 A EP 01949668A EP 01949668 A EP01949668 A EP 01949668A EP 1301692 A1 EP1301692 A1 EP 1301692A1
Authority
EP
European Patent Office
Prior art keywords
camshaft
gear set
planetary gear
stroke
engine
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.)
Granted
Application number
EP01949668A
Other languages
German (de)
French (fr)
Other versions
EP1301692B1 (en
Inventor
Jonathan Austin 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.)
MA (Innovation) 2T4 Ltd
Original Assignee
MA (Innovation) 2T4 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
Priority claimed from GB0017206A external-priority patent/GB0017206D0/en
Priority claimed from GB0022373A external-priority patent/GB2364745A/en
Application filed by MA (Innovation) 2T4 Ltd filed Critical MA (Innovation) 2T4 Ltd
Publication of EP1301692A1 publication Critical patent/EP1301692A1/en
Application granted granted Critical
Publication of EP1301692B1 publication Critical patent/EP1301692B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • F02B69/00—Internal-combustion engines convertible into other combustion-engine type, not provided for in F02B11/00; Internal-combustion engines of different types characterised by constructions facilitating use of same main engine-parts in different types
    • F02B69/06—Internal-combustion engines convertible into other combustion-engine type, not provided for in F02B11/00; Internal-combustion engines of different types characterised by constructions facilitating use of same main engine-parts in different types for different cycles, e.g. convertible from two-stroke to four stroke
    • 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
    • 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
    • F01L1/022—Chain drive
    • 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
    • F01L1/024—Belt drive
    • 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
    • F01L1/34—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift
    • F01L1/344—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift changing the angular relationship between crankshaft and camshaft, e.g. using helicoidal gear
    • F01L1/352—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift changing the angular relationship between crankshaft and camshaft, e.g. using helicoidal gear using bevel or epicyclic gear
    • 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
    • F01L2311/00—Differential gears located between crankshafts and camshafts for varying the timing of valves
    • 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
    • F01L2710/00—Control of valve gear, speed or power
    • F01L2710/003—Control of valve gear for two stroke engines
    • 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
    • F01L2800/00—Methods of operation using a variable valve timing mechanism
    • 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
    • F02B2075/025—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle two
    • 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

Definitions

  • the present invention relates to a camshaft drive system for operating an internal combustion engine according to the two-stroke cycle or the four-stroke cycle.
  • a camshaft drive system for a selectable two-stroke/four-stroke internal combustion engine with exhaust and intake poppet valves opened and closed by at least one camshaft, wherein the camshaft is connected permanently to a planetary gear set which is driven continuously by the engine crankshaft, and wherein means are provided for setting the planetary gear set in one of two selectable stable modes to function either as a gear box or as a rigid coupling.
  • the camshaft is driven by the planetary gear set according to the selectable mode at either the same speed as the engine crankshaft or half the speed of the engine crankshaft, and the phasing of the camshaft in relation with the crank angle position of the piston is adjustable using the planetary gear set to position the exhaust and intake gas exchange events appropriately for either the two-stroke or the four-stroke engine cycle respectively.
  • the planetary gear set is mounted concentrically to the camshaft.
  • it may be mounted concentrically to the engine crankshaft or it may be mounted separately next to the camshaft and the crankshaft.
  • the input from the engine may be connected to any one of the three members of the planetary gear set which may be the ring gear, the sun gear or the planetary gear carrier, the output to the camshaft may be connected to any one of the remaining two members, and the mode setting means may be provided in the remaining last member which is the reaction member between the input and output members .
  • the means for setting the planetary gear set to function as a gear box is a device for holding the reaction member of the gear set stationary relative to a fixed datum so that the gears rotate relative to one another within the gear set
  • the means for setting the planetary gear set to function as a rigid coupling is a device for holding the reaction member of the gear set stationary relative to either the rotating input member or the rotating output member so that the gears are locked relative to one another within the gear set and the whole assembly rotate together.
  • the ring gear is the input member driven by the engine at half crankshaft speed
  • the sun gear is the output member connected to the camshaft
  • the planetary gear carrier is the reaction member of the gear set.
  • the speed ratio between the ring gear and the sun gear is 1:2.
  • means are provided for setting the planetary gear carrier in one of two selectable stable modes such that in the two-stroke mode the carrier is held stationary relative to the engine frame so that the gear set acts as a gear box, and in the four-stroke mode the carrier is held stationary relative to the rotating ring gear so that the entire gear set acts as a rigid coupling. Additionally, means are provided for allowing the carrier to slip and rotate relative to the engine frame or relative to the rotating ring gear in order to adjust the phasing and the speed of the camshaft during a mode change.
  • the carrier which has been held stationary relative to the rotating ring gear in the four-stroke mode, is first allowed to slip and rotate relative to the rotating ring gear in order to adjust the phasing and the speed of the camshaft progressively towards the two-stroke mode, at which point the carrier is then held stationary relative to the engine frame thereafter.
  • the planetary gear set acts as a gear box in which the camshaft is driven at twice the speed of the ring gear and each engine valve along the camshaft is opened and closed at a predetermined two-stroke valve timing once during every engine revolution consistent with the two-stroke cycle.
  • the carrier which has been held stationary relative to the engine frame in the two-stroke mode, is first allowed to slip and rotate relative to the engine frame in order to adjust the phasing and the speed of the camshaft progressively towards the four-stroke mode, at which point the carrier is then held stationary relative to the rotating ring gear thereafter.
  • the planetary gear set acts as a rigid coupling in which the camshaft is driven at the same speed as the ring gear and each engine valve along the camshaft is opened and closed at a predetermined four-stroke valve timing once during every two engine revolutions consistent with the four-stroke cycle.
  • the air blower for two-stroke operation may in this case be used to supply boosted air for four-stroke operation.
  • the above example is only one of many possible configurations for the camshaft to be driven by a mode selectable planetary gear set of the present invention.
  • the planetary gear carrier is the input member driven at half crankshaft speed
  • the sun gear is the output member connected to the camshaft
  • the ring gear is the reaction member of the gear set.
  • the speed ratio between the carrier and the sun gear is 1:2.
  • the ring gear may be set in one of two selectable modes such that in the two-stroke mode the ring gear is held stationary relative to the engine frame so that the planetary gear set acts as a gear box and the camshaft is driven at crankshaft speed, and in the four-stroke mode the ring gear is held stationary relative to the carrier so that the entire gear set acts as a rigid coupling and the camshaft is driven at half crankshaft speed.
  • the sun gear is the input member driven at crankshaft speed
  • the planetary gear carrier is the output member connected to the camshaft
  • the ring gear is the reaction member of the gear set.
  • the speed ratio between the sun gear and the carrier is 2:1.
  • the ring gear may be set in one of two selectable modes such that in the two-stroke mode the ring gear is held stationary relative to the carrier so that the entire gear set acts as a rigid coupling and the camshaft is driven at crankshaft speed, and in the four-stroke mode the ring gear is held stationary relative to the engine frame so that the epicycle gear set acts as a gear box and the camshaft is driven at half crankshaft speed.
  • the principle of operating a planetary gear set in several selectable modes is well known and is commonly used in automotive automatic transmission systems for driving a vehicle.
  • the present invention proposes to apply the same principle for driving a camshaft in order to enable the engine to be operated in either the two-stroke or the four- stroke mode with smooth and rapid transition and with the minimum risk of misfire during a mode change even at high speed.
  • This provides a camshaft drive which is permanently in mesh and avoids the abruptness and uncertainty caused by temporarily de-coupling and then re-coupling the camshaft and the crankshaft as proposed in the previously known systems such as US Patent 4,907,544 and US Patent 2,178,152 which are unacceptable for automotive application.
  • the technology for controlling the planetary gear set to operate in the selectable modes and to change mode smoothly and imperceptibly using brakes, clutches, and sensors is well advanced in the automatic transmission field and may be transferred readily to the camshaft drive system of the present invention.
  • Figure 1 shows two planetary gear sets each comprising a ring gear 10, a sun gear 12, and three planetary gears 14 with additional idler gears 15 mounted on a carrier 16.
  • the speed ratio between the ring gear 10 and the sun gear 12 is 1:2.
  • the ring gear 10 is the input member driven at half crankshaft speed by a timing belt or chain 22 from the crankshaft 20 of the engine
  • the sun gear 12 is the output member connected directly to one camshaft of the engine
  • the carrier 16 is the reaction member.
  • Respective braking or clutching means are provided for engaging the carrier 16 to either the engine frame or the rotating ring gear 10, enabling the carrier 16 to be held stationary relative to either the engine frame or the rotating ring gear 10, and to slip and rotate when desired relative to either the engine frame or the rotating ring gear 10.
  • the use of such braking and clutching means is common practice in the automatic transmission field for selecting between different speed ratios and direct drive, and would be obvious to a person familiar with the state-of- the-art .
  • Sensors are also provided in a closed-loop control system for sensing the angular positions of the camshaft and the crankshaft, thereby enabling accurate control of the phasing and the speed of the camshaft progressively during a mode change.
  • Electro-magnetic or electro-hydraulic controlled latches may also be provided and energised when the gear set is approaching the desired camshaft position in order to engage the appropriate members of the gear set precisely at the required position relative to one another.
  • each planetary gear set acts as a gear box in which each camshaft is driven at twice the speed of the ring gear 10 and each engine valve along the camshaft is opened and closed according to a predetermined two-stroke valve timing once during every engine revolution.
  • each planetary gear set acts as a rigid coupling in which each camshaft is driven at the same speed as the ring gear 10 and each engine valve along the camshaft is opened and closed according to a predetermined four-stroke valve timing once during every two engine revolutions.
  • the phasing of the camshaft in relation with the crankshaft may at any time be re-positioned using the planetary gear set by briefly allowing the reaction member to slip while operating in either the two-stroke or the four-stroke mode.
  • the invention enables a selectable two-stroke/four stroke internal combustion engine to be used in a road vehicle to suit different operating conditions resulting in a better combination of engine performance, fuel economy, exhaust emissions, noise, vibrations, and drive quality while the mode transitions could be controlled and refined to be imperceptible to the driver.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Valve Device For Special Equipments (AREA)
  • Valve-Gear Or Valve Arrangements (AREA)

Abstract

A camshaft drive system is described for a selectable two-stroke/four-stroke internal combustion engine with exhaust and intake poppet valves opened and closed by at least one camshaft. In the system, the camshaft is connected permanently to a planetary gear set (10, 12, 14, 15, 16) which is driven continuously by the engine crankshaft (20), and means are provided for setting the planetary gear set in one of two selectable stable modes to function either as a gearbox or as a rigid coupling.

Description

SELECTABLE 2 STROKE / 4 STROKE CAMSHAFT DRIVE SYSTEM
Field of the invention
The present invention relates to a camshaft drive system for operating an internal combustion engine according to the two-stroke cycle or the four-stroke cycle.
Background of the invention
Conventional internal combustion engines operate according to thermodynamic principles following either the two-stroke cycle or the four-stroke cycle and are commonly classified as two-stroke engines or four-stroke engines respectively. Both type of engines can operate using a range of fuels including gasoline, diesel, alcohol and gaseous fuels; the fuel can be introduced into the engine by a range of devices including carburettors and fuel injectors into the air intake system and fuel injectors aimed directly into the engine cylinder; and the fuel-air mixture can be ignited by a range of methods including spark ignition and compression ignition. Each engine cycle type has different merits and shortcomings making it a subject of continuous debate as to which is more suitable for automotive application taking into account various parameters such as power density, fuel consumption, exhaust emissions, noise, vibration, engine size, weight and cost etc. Currently, the automotive manufacturer must first decide on the engine cycle type, then design the engine accordingly.
Summary of the invention
With a view of combining the merits of both engine cycle types, there is provided a camshaft drive system for a selectable two-stroke/four-stroke internal combustion engine with exhaust and intake poppet valves opened and closed by at least one camshaft, wherein the camshaft is connected permanently to a planetary gear set which is driven continuously by the engine crankshaft, and wherein means are provided for setting the planetary gear set in one of two selectable stable modes to function either as a gear box or as a rigid coupling.
In the invention, the camshaft is driven by the planetary gear set according to the selectable mode at either the same speed as the engine crankshaft or half the speed of the engine crankshaft, and the phasing of the camshaft in relation with the crank angle position of the piston is adjustable using the planetary gear set to position the exhaust and intake gas exchange events appropriately for either the two-stroke or the four-stroke engine cycle respectively.
Preferably, the planetary gear set is mounted concentrically to the camshaft. Alternatively, it may be mounted concentrically to the engine crankshaft or it may be mounted separately next to the camshaft and the crankshaft.
Various configuration are possible in using the planetary gear set to drive the camshaft according to the present invention. The input from the engine may be connected to any one of the three members of the planetary gear set which may be the ring gear, the sun gear or the planetary gear carrier, the output to the camshaft may be connected to any one of the remaining two members, and the mode setting means may be provided in the remaining last member which is the reaction member between the input and output members .
In the case where the planetary gear carrier is the reaction member, idler gears coupled with the planetary gears may be additionally provided on the planetary gear carrier such that the ring gear and the sun gear rotate in the same direction. In the invention, the means for setting the planetary gear set to function as a gear box is a device for holding the reaction member of the gear set stationary relative to a fixed datum so that the gears rotate relative to one another within the gear set, whereas the means for setting the planetary gear set to function as a rigid coupling is a device for holding the reaction member of the gear set stationary relative to either the rotating input member or the rotating output member so that the gears are locked relative to one another within the gear set and the whole assembly rotate together.
In a preferred example, the ring gear is the input member driven by the engine at half crankshaft speed, the sun gear is the output member connected to the camshaft, and the planetary gear carrier is the reaction member of the gear set. The speed ratio between the ring gear and the sun gear is 1:2.
In this example, means are provided for setting the planetary gear carrier in one of two selectable stable modes such that in the two-stroke mode the carrier is held stationary relative to the engine frame so that the gear set acts as a gear box, and in the four-stroke mode the carrier is held stationary relative to the rotating ring gear so that the entire gear set acts as a rigid coupling. Additionally, means are provided for allowing the carrier to slip and rotate relative to the engine frame or relative to the rotating ring gear in order to adjust the phasing and the speed of the camshaft during a mode change.
In operation, when the two-stroke mode is selected, the carrier, which has been held stationary relative to the rotating ring gear in the four-stroke mode, is first allowed to slip and rotate relative to the rotating ring gear in order to adjust the phasing and the speed of the camshaft progressively towards the two-stroke mode, at which point the carrier is then held stationary relative to the engine frame thereafter. In this case, the planetary gear set acts as a gear box in which the camshaft is driven at twice the speed of the ring gear and each engine valve along the camshaft is opened and closed at a predetermined two-stroke valve timing once during every engine revolution consistent with the two-stroke cycle.
In addition to the above, a combination of various operating parameters in the engine necessary for executing the two-stroke cycle is implemented, and this would be obvious to a person familiar with the state-of-the-art. For example, an air blower would be necessary to supply pressurised air for the two-stroke scavenging process and the frequency and timing of the fuel injection and/or spark ignition would be scheduled appropriately.
When the four-stroke mode is selected, the carrier, which has been held stationary relative to the engine frame in the two-stroke mode, is first allowed to slip and rotate relative to the engine frame in order to adjust the phasing and the speed of the camshaft progressively towards the four-stroke mode, at which point the carrier is then held stationary relative to the rotating ring gear thereafter. In this case, the planetary gear set acts as a rigid coupling in which the camshaft is driven at the same speed as the ring gear and each engine valve along the camshaft is opened and closed at a predetermined four-stroke valve timing once during every two engine revolutions consistent with the four-stroke cycle.
In addition to the above, a combination of various operating parameters in the engine necessary for executing the four-stroke cycle is implemented, and this would be obvious to a person familiar with the state-of-the-art. The air blower for two-stroke operation may in this case be used to supply boosted air for four-stroke operation. The above example is only one of many possible configurations for the camshaft to be driven by a mode selectable planetary gear set of the present invention. In another example, the planetary gear carrier is the input member driven at half crankshaft speed, the sun gear is the output member connected to the camshaft, and the ring gear is the reaction member of the gear set. The speed ratio between the carrier and the sun gear is 1:2.
In this case, the ring gear may be set in one of two selectable modes such that in the two-stroke mode the ring gear is held stationary relative to the engine frame so that the planetary gear set acts as a gear box and the camshaft is driven at crankshaft speed, and in the four-stroke mode the ring gear is held stationary relative to the carrier so that the entire gear set acts as a rigid coupling and the camshaft is driven at half crankshaft speed.
In a further example, the sun gear is the input member driven at crankshaft speed, the planetary gear carrier is the output member connected to the camshaft, and the ring gear is the reaction member of the gear set. The speed ratio between the sun gear and the carrier is 2:1.
In this case, the ring gear may be set in one of two selectable modes such that in the two-stroke mode the ring gear is held stationary relative to the carrier so that the entire gear set acts as a rigid coupling and the camshaft is driven at crankshaft speed, and in the four-stroke mode the ring gear is held stationary relative to the engine frame so that the epicycle gear set acts as a gear box and the camshaft is driven at half crankshaft speed.
The principle of operating a planetary gear set in several selectable modes is well known and is commonly used in automotive automatic transmission systems for driving a vehicle. The present invention proposes to apply the same principle for driving a camshaft in order to enable the engine to be operated in either the two-stroke or the four- stroke mode with smooth and rapid transition and with the minimum risk of misfire during a mode change even at high speed. This provides a camshaft drive which is permanently in mesh and avoids the abruptness and uncertainty caused by temporarily de-coupling and then re-coupling the camshaft and the crankshaft as proposed in the previously known systems such as US Patent 4,907,544 and US Patent 2,178,152 which are unacceptable for automotive application.
The technology for controlling the planetary gear set to operate in the selectable modes and to change mode smoothly and imperceptibly using brakes, clutches, and sensors is well advanced in the automatic transmission field and may be transferred readily to the camshaft drive system of the present invention.
Brief description of the drawing
The invention will now be described further, by way of example, with reference to a single drawing of a schematic view of a preferred embodiment of the invention in which two planetary gear sets are used to drive separately the intake and exhaust camshafts of an internal combustion engine.
Detailed description of the preferred embodiment
Figure 1 shows two planetary gear sets each comprising a ring gear 10, a sun gear 12, and three planetary gears 14 with additional idler gears 15 mounted on a carrier 16. The speed ratio between the ring gear 10 and the sun gear 12 is 1:2. The ring gear 10 is the input member driven at half crankshaft speed by a timing belt or chain 22 from the crankshaft 20 of the engine, the sun gear 12 is the output member connected directly to one camshaft of the engine, and the carrier 16 is the reaction member. Respective braking or clutching means (not shown) are provided for engaging the carrier 16 to either the engine frame or the rotating ring gear 10, enabling the carrier 16 to be held stationary relative to either the engine frame or the rotating ring gear 10, and to slip and rotate when desired relative to either the engine frame or the rotating ring gear 10. The use of such braking and clutching means is common practice in the automatic transmission field for selecting between different speed ratios and direct drive, and would be obvious to a person familiar with the state-of- the-art .
Sensors (not shown) are also provided in a closed-loop control system for sensing the angular positions of the camshaft and the crankshaft, thereby enabling accurate control of the phasing and the speed of the camshaft progressively during a mode change. Electro-magnetic or electro-hydraulic controlled latches (not shown) may also be provided and energised when the gear set is approaching the desired camshaft position in order to engage the appropriate members of the gear set precisely at the required position relative to one another. Once again the use of such control system in operating the braking, clutching and latching means would be obvious to a person familiar with the state- of-the-art.
In operation, when the two-stroke mode is selected, the carrier 16 in each planetary gear set, which has been held stationary relative to the rotating ring gear 10 in the four-stroke mode, is first allowed to slip and rotate relative to the rotating ring gear 10 in order to adjust the phasing and the speed of each camshaft progressively towards the two-stroke mode, at which point the carrier 16 is then held stationary relative to the engine frame thereafter. In this case each planetary gear set acts as a gear box in which each camshaft is driven at twice the speed of the ring gear 10 and each engine valve along the camshaft is opened and closed according to a predetermined two-stroke valve timing once during every engine revolution.
When the four-stroke mode is selected, the carrier 16 in each planetary gear set, which has been held stationary relative to the engine frame in the two-stroke mode, is first allowed to slip and rotate relative to the engine frame in order to adjust the phasing and the speed of each camshaft progressively towards the four-stroke mode, at which point the carrier 16 is then held stationary relative to the rotating ring gear 10 thereafter. In this case, each planetary gear set acts as a rigid coupling in which each camshaft is driven at the same speed as the ring gear 10 and each engine valve along the camshaft is opened and closed according to a predetermined four-stroke valve timing once during every two engine revolutions.
It would be clear in the invention that the same cam profile carried on the camshaft driven at one or the other selectable mode would automatically give the appropriate duration of valve opening to suit each engine cycle mode respectively, namely, the two-stroke valve opening duration would be half the four-stroke valve opening duration.
It would also be clear in the invention that the phasing of the camshaft in relation with the crankshaft may at any time be re-positioned using the planetary gear set by briefly allowing the reaction member to slip while operating in either the two-stroke or the four-stroke mode.
The invention enables a selectable two-stroke/four stroke internal combustion engine to be used in a road vehicle to suit different operating conditions resulting in a better combination of engine performance, fuel economy, exhaust emissions, noise, vibrations, and drive quality while the mode transitions could be controlled and refined to be imperceptible to the driver.

Claims

1. A camshaft drive system for a selectable two- stroke/four-stroke internal combustion engine with exhaust and intake poppet valves opened and closed by at least one camshaft, wherein the camshaft is connected permanently to a planetary gear set (10, 12, 14, 15, 16) which is driven continuously by the engine crankshaft (20) , and wherein means are provided for setting the planetary gear set in one of two selectable stable modes to function either as a gear box or as a rigid coupling.
2. A camshaft drive system as claimed in claim 1, wherein the camshaft is driven by the planetary gear set according to the selectable mode at either the same speed as the engine crankshaft or half the speed of the engine crankshaft, and wherein the phasing of the camshaft in relation with the crank angle position of the piston is adjustable using the planetary gear set to position the exhaust and intake gas exchange events appropriately for either the two-stroke or the four-stroke engine cycle respectively.
3. A camshaft drive system as claimed in claim 1 or 2, wherein the input from the engine is connected to any one of the three members of the planetary gear set which may be the ring gear (10), the sun gear (12) or the planetary gear carrier (16), the output to the camshaft is connected to any one of the remaining two members, and the mode setting means is provided in the remaining last member which is the reaction member between the input and output members.
4. A camshaft drive system as claimed in claim 3, wherein idler gears (15) coupled with the planetary gears (14) are additionally provided on the planetary gear carrier (16) such that the ring gear (10) and the sun gear (12) rotate in the same direction.
5. A camshaft drive system as claimed in claim 3 or 4, wherein means are provided for setting the reaction member of the planetary gear set in one of two selectable stable modes such that in one mode the reaction member is held stationary relative to the engine frame so that the gear set acts as a gear box, and in the other mode the reaction member is held stationary relative to the rotating input or output members so that the entire gear set acts as a rigid coupling.
6. A camshaft drive system as claimed in claim 3 or 4, wherein additional means are provided for allowing the reaction member of the planetary gear set to slip and rotate relative to the engine frame or relative to the rotating input and output members in order to adjust the phasing and the speed of the camshaft during a mode change.
7. A camshaft drive system as claimed in claim 5 or
6, wherein respective braking and clutching means are provided for holding the reaction member of the planetary gear set in the respective selectable modes, and for allowing the reaction member to slip and rotate relative to the engine frame or relative to the rotating input and output members .
8. A camshaft drive system as claimed in claim 6 or
7, wherein sensors are provided in a closed-loop control system for sensing the angular positions of the camshaft and the crankshaft, thereby enabling accurate control of the phasing and the speed of the camshaft progressively during a mode change .
EP01949668A 2000-07-14 2001-07-12 Selectable 2 stroke / 4 stroke camshaft drive system Expired - Lifetime EP1301692B1 (en)

Applications Claiming Priority (7)

Application Number Priority Date Filing Date Title
GB0017206A GB0017206D0 (en) 2000-07-14 2000-07-14 Dual cycle internal combustion engine
GB0017206 2000-07-14
GB0017354A GB0017354D0 (en) 2000-07-14 2000-07-17 Dual cycle internal combustion engine
GB0017354 2000-07-17
GB0022373A GB2364745A (en) 2000-07-14 2000-09-12 Camshaft drive system for selectable two-stroke/ four-stroke i.c. engine
GB0022373 2000-09-12
PCT/GB2001/003116 WO2002006639A1 (en) 2000-07-14 2001-07-12 Selectable 2 stroke / 4 stoke camshaft drive system

Publications (2)

Publication Number Publication Date
EP1301692A1 true EP1301692A1 (en) 2003-04-16
EP1301692B1 EP1301692B1 (en) 2006-03-01

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP01949668A Expired - Lifetime EP1301692B1 (en) 2000-07-14 2001-07-12 Selectable 2 stroke / 4 stroke camshaft drive system

Country Status (5)

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EP (1) EP1301692B1 (en)
CN (1) CN1291137C (en)
AU (1) AU2001270788A1 (en)
DE (1) DE60117553T2 (en)
WO (1) WO2002006639A1 (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9732682B2 (en) 2012-09-07 2017-08-15 Ford Global Technologies, Llc Internal combustion engine which may be selectively operated by the two-stroke method or the four-stroke method and method for operating such an internal combustion engine
FR3009337B1 (en) * 2013-08-01 2015-08-21 Peugeot Citroen Automobiles Sa MECHANICAL TRANSMISSION DEVICE WITH SWITCHABLE EPICYCLOIDAL TRAIN
DE102014112464A1 (en) * 2014-08-29 2016-03-03 Thyssenkrupp Presta Teccenter Ag Adjustment unit for a camshaft of an internal combustion engine
US10683782B2 (en) 2014-09-29 2020-06-16 Volvo Truck Corporation Two stroke, opposed piston engine with compression release brake arrangement and method
CN104863724A (en) * 2015-05-25 2015-08-26 曲严忠 Extra-high compression ratio supercharging direct-injection gasoline engine and running state switching method thereof
US10716447B2 (en) 2018-08-27 2020-07-21 Tti (Macao Commercial Offshore) Limited Floor cleaner

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Publication number Priority date Publication date Assignee Title
DE3842267A1 (en) * 1988-12-15 1990-06-21 Gerd Mager Variable valve overlap for four-stroke engines by means of planetary gearing with adjustment
JPH04234508A (en) * 1990-12-29 1992-08-24 Isuzu Ceramics Kenkyusho:Kk 2-4 cycle switching clutch
DE69818946T2 (en) * 1997-11-21 2004-05-13 Mazda Motor Corp. Device for controlling the rotation phase

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Title
See references of WO0206639A1 *

Also Published As

Publication number Publication date
CN1291137C (en) 2006-12-20
WO2002006639A1 (en) 2002-01-24
DE60117553D1 (en) 2006-04-27
AU2001270788A1 (en) 2002-01-30
EP1301692B1 (en) 2006-03-01
CN1388852A (en) 2003-01-01
DE60117553T2 (en) 2006-08-10

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