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
  • F01L1/34—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
  • 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
• • 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

Definitions

• Camshaft phase shifting mechanisms are used in internal combustion engines to vary valve timing to achieve benefits of improving fuel consumption and improve exhaust gas quality. It is possible, with an adequate camshaft shifter, to vary valve timing for maximum comfort and/or maximum torque and for the highest performance.
• camshaft phase shifting mechanisms are hydraulic powered. These camshaft phase shifting mechanisms generally consist of a hydraulic shifter unit, a regulation valve and a control circuit.
• the shifter unit has to have a low leakage rate and a sufficiently large chamber/piston to ensure adequate stiffness.
• the regulation valve has to ensure high flow rate during adjustment cycles while providing a precise regulation to fix the set-point angles.
• Some camshaft phase shifting mechanisms require a separate high-pressure supply. These current mechanisms are complex, expensive and need regular maintenance. Additionally, the performance of these current mechanisms depends mainly on temperature parameters.
• This invention relates to a phase shifting mechanism, and more specifically to an electro-mechanical phase shifting mechanism for a camshaft of an internal combustion engine.
• Th ⁇ phase shifting mechanism of the present disclosure comprises a positive epicyclic gear train with frictional locking capability.
• the gear train has three co-axial rotatable branches. The first branch operatively couples to an input shaft (i.e., the crankshaft), the second branch operatively couples to an output shaft and the third branch, a lockable branch, operatively couples to a rotor of an electric machine.
• the gear train can only be unlocked during phase adjustment by the electric machine that is connected to the third branch, the lockable branch.
• the input shaft couples to the crankshaft
• the output shaft couples to the camshaft
• the planetary gear train co-axially aligns around the input shaft and the output shaft.
• An input sun gear of the planetary gear train couples to the input shaft and an output sun gear of the planetary gear train couples to the output shaft.
• the planetary gear train has first and second planet gears that engage the input and output sun gears, respectively, and are united to rotate about a common axis at the same angular velocity.
• the carrier includes a planet shaft and a first planet bearing and a second planet bearing on which the united first and second planet gears respectively rotate.
• a locking mechanism of the phase shifting mechanism locks the planetary gear train in a locked condition by preventing the planet gears from rotating relative to the carrier to rotate the input sun gear, the output sun gear and the carrier as a unit such that the phase shift angle for the output shaft with respect to the input shaft remains the same and the output shaft rotates with the input shaft at the same angular velocity.
• the electric machine applies torque to the locking mechanism in order to unlock the locking mechanism such that the output shaft rotates at a different angular velocity with respect to the input shaft.
• Fig. 1 illustrates a schematic view of components of an internal combustion engine illustrating a drive, a camshaft and a phase shifting mechanism constructed in accordance with and embodying the present disclosure
• Fig. 2 illustrates a cross sectional view of an input shaft, an output shaft and the phase shifting mechanism
• Fig. 3 illustrates an exploded view of a phase shifting mechanism constructed in accordance with and embodying the present disclosure illustrating a planetary gear train and locking mechanism of the phase shifting mechanism wherein first and second planet gears of the planetary gear train are identical and integrated with one another
• Fig. 4 illustrates another exploded view of components of the phase shifting mechanism of Fig. 3;
• Fig. 5 illustrates a cross sectional view of the gear train and locking mechanism constructed in accordance with and embodying the present disclosure
• Fig. 6 illustrates a perspective view of an input sun gear and an extension of a limiting device of the phase shifting mechanism
• Fig. 7 illustrates a perspective view of an output sun gear and another embodiment of an extension of a limiting device of the phase shift mechanism. DESCRIPTION OF THE PREFERRED EMBODIMENT
• an electro-mechanic phase shifting mechanism generally shown as A is shown (Figs. 1 and 2).
• the phase shifting mechanism A is located between a drive 10 and a camshaft 12 of an internal combustion engine 14.
• the phase shifting mechanism A comprises a sprocket 16, an input shaft 18 -A-
• the epicyclic gear train 20 co-axially aligns around the input shaft 18 and the output shaft 26.
• the epicyclic gear train 20 comprises a first branch in the form of an input sun gear 28, a second branch in the form of an output sun gear 30, a lockable third branch in the form a carrier 32, a first set of planet gears 34 and a second set of planet gears 36.
• the input sun gear 28 meshes with the first set of planet gears 34
• the output sun gear 30 meshes with the second set of planet gears 36.
• Each planet gear 34 in the first planet gear set couples to, and thus rotates as a unit with, a corresponding planet gear 36 in the second planet gear set.
• the planet gears 34, 36 are substantially identically formed and are integrated as a single gear. Planet gears 34, 36 together form a planetary gear pair to rotate about a common axis at the same angular velocity.
• the planetary gear pairs are supported by a set of planet shafts 38 (Fig. 1 ), through bearings.
• the carrier 32 is supported in a housing 40 though bearings 42. As shown in Fig.
• the input shaft 18 connects to sprocket 16 at one end and to the input sun gear 28 at the other end.
• the input shaft 18 is supported in the housing 40 though bearing 44.
• the output shaft 26 connects to the output sun gear 30 at one end and couples to camshaft 12 (Fig. 1 ) at the other end.
• the electric machine 24 includes a rotor 46 and a stator 48. The rotor
• stator 48 mounts to the housing 40.
• the input shaft 18 and output shaft 26 may extend beyond the input sun gear 28 and the output sun gear 30 with one piloted on the other through bearing 49 (Fig. 1 ).
• Input shaft 18 is allowed to rotate with respect to the output shaft 26 when phase shift between the two shafts 18, 26 is desirable.
• an angular position limiting device generally shown as 50 (Figs. 1 , 3-5) may be employed to provide mechanical stops in both rotating directions.
• the limiting device 50 rotatably couples the input sun gear 28 with the output sun gear 30.
• the limiting device 50 in an embodiment, comprises a slot 52 positioned on a face 54 of the input sun gear 28 and comprises an extension 56 protruding from another face 58 of the output sun gear 30 such that the extension 56 slidably engages with the slot 52.
• the extension 56 comprises pins protruding from the output sun gear 30.
• an extension 60 comprise key members protruding from the face 54 of the input sun gear 28 (Fig. 6) and/or protruding from the face 58 of the output sun gear 30 (Fig. 7).
• the epicyclic gear train 20 has a basic gear ratio
• ⁇ S j angular velocity of the input sun gear 28
• ⁇ S2 angular velocity of the output sun gear 30
• we angular velocity of the carrier 32.
• the basic gear ratio can be determined by tooth numbers of the gears in the epicyclic gear train 20, as below where
• Nsi the number of teeth for the input sun gear 28
• Ns 2 the number of teeth for the output sun gear 30
• Np 1 the number of teeth for the first planet gear 34
• Np 2 the number of teeth for the second planet gear 36.
• phase shifting angle for the output shaft 26 with respect to the input shaft 18 is determined as
• the locking mechanism 22 of the epicyclic gear train 20 is designed to have a configuration and internal geometry that ensure an internal jam or lock when no external torque is applied to the carrier 32.
• the locking mechanism 22 comprises conical bearings 62, 64, that, under radial load, impose frictional resistant torque on the planetary gear pairs 34, 36 that tend to prevent them from rotating about their support shafts 38.
• the radial load is in direct proportion to the amount of torque being transmitted.
• the frictional resistant torque is also in proportion to the input and output torque.
• the input torque from the input sun gear 28 and the output torque from the output sun gear 30 result in a differential torque that tries to rotate the planetary gears 34, 36.
• the epicyclic gear train 20 is frictionally locked.
• the following internal geometry relationship between the planetary gear train 20 and the coefficients of friction between the first planet gear 34 and the first planet bearing 42 and between the second planet gear 36 and the second planet bearing 44 is characterized as
• O 1 pressure angle for the input sun gear 28 and the first planet gear
• the locking mechanism 22 prevents the planet gears 34, 36 from rotating relative to the carrier 32 to rotate the input sun gear 28, the output sun gear 30 and the carrier 32 as a unit such that the phase shift angle for the output shaft 26 with respect to the input shaft 18 remains the same and the output shaft 26 rotates with the input shaft 18 at the same angular velocity.
• the locking mechanism 22 comprises friction torques caused by coefficients of friction between the first planet gear 34 and the first planet bearing 62 and between the second planet gear 36 and the second planet bearing 64.
• the electric machine 24 couples to the carrier 32.
• the electric machine 24 applies a torque to the planetary gear train 20 for unlocking the friction torques enabling the carrier 32 to rotate relative to at least one of the input sun gear 28 and the output sun gear 30 wherein the phase shift angle for the output shaft 26 with respect to the input shaft 18 changes so that the output shaft 26 assumes a different angular velocity with respect to the input shaft 18.
• the electro-mechanic camshaft phase shifting mechanism A has three operation modes.
• the first operating mode relates to a neutral mode in which the electric machine 24 is switched off (i.e., consuming no electric power or generating any electric power); and thus, exerting no torque on the carrier 32.
• the epicyclic gear train 20 With no actuation torque exerting on the carrier 32, the epicyclic gear train 20 is frictionally locked or "internally jammed" by the locking mechanism 22. In this locked state, the epicyclic gear train 20 can only be rotated as unit.
• the second operating mode relates to a generating mode, in which the electric machine 24 applies a resistant torque to the gear train 20, slowing the rotor 46 down such that ⁇ c ⁇ S i.
• the epicyclic gear train 20 converts mechanical power into electric power, acting as a generator.
• the resistant torque unlocks the epicyclic gear train 20. Consequently, the output shaft 26 rotates with the input shaft 18 in the same direction but at a faster or slower angular velocity. From equation (3), there will be a continuous phase advancing, if Sf? 0 >1 , or retarding, if Sf?o ⁇ 1 , of the output shaft with respect to the input shaft 18.
• the torque applied by the electric machine 24 to the planetary gear train 20 comprises a resistant torque which unlocks the carrier 32 by overcoming the torque caused by friction between the first planet gear 34 and the first planet bearing 62 and between the second planet gear 36 and the second planet bearing 64.
• the resistant torque unlocks the carrier 32 to change the phase shift angle such that the output shaft 26 rotates with respect to the input shaft 18 at a different angular velocity.
• the output shaft 26 rotates with respect to the input shaft 18 in the same angular direction.
• the third operating mode relates to a motoring mode, in which the electric machine 24 applies a driving torque to the gear train 20, speeding the rotor 46 and carrier 32 up such that ⁇ c > ⁇ s? .
• the electric machine 24 draws electric power from a supplier (not shown) and converts it into mechanical power. In doing so, the electric machine 24 acts as a motor.
• the driving torque unlocks the epicyclic gear train 20.
• the output shaft 26 rotates with the input shaft 18 in the same direction but at a slower or faster angular velocity. From equation (3), there will be a continuous phase retarding, if Sf? 0 >1 or advancing, if Sf? 0 ⁇ 1 of the output shaft 26 with respect to the input shaft 18. Accordingly, in this operating mode, there is a continuous phase retarding or advancing of output shaft 26 with respect to the input shaft 18.
• the torque applied by the electric machine 24 to the planetary gear train 20 comprises a driving torque which unlocks the carrier 32 by overcoming the torques caused by friction between the first planet gear 34 and the first planet bearing 62 and between the second planet gear 36 and the second planet bearing 64.
• the driving torque unlocks the carrier 32 to change the phase shift angle such that the output shaft 26 rotates with respect to the input shaft 18 in the same angular direction and at a different angular velocity.
• the output shaft 26 rotates with respect to the input shaft 18 in the same angular direction.
• phase shifting mechanism A is low manufacturing cost due to the elimination of hydraulic systems. Additionally, since operation occurs under the neutral mode where the epicyclic gear train 20 is internally locked and rotates as a unit, the gears 28, 34, 36 and 30, planet support bearings 62, 64 and pilot bearing 49 experience intermittent usage. Thus, the phase shifting mechanism A uses low cost bearings. For the same reason, the phase shifting mechanism A uses low cost electric machines, such as a switched reluctance motor, to reduce the overall cost. In view of the above, it will be seen that the several objects of the disclosure are achieved and other advantageous results are obtained. As various changes could be made in the above constructions without departing from the scope of the disclosure, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

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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)

Applications Claiming Priority (2)

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• 2007
  • 2007-09-18 EP EP07842677A patent/EP2064417A1/de not_active Withdrawn
  • 2007-09-18 WO PCT/US2007/078755 patent/WO2008036650A1/en active Application Filing
  • 2007-09-18 US US12/441,841 patent/US20100064997A1/en not_active Abandoned
  • 2007-09-18 KR KR1020097005499A patent/KR20090074161A/ko not_active Application Discontinuation
  • 2007-09-18 JP JP2009529342A patent/JP2010504470A/ja not_active Withdrawn

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