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

Definitions

• the present invention is related generally to methods and apparatus for altering the rotational position of internal combustion engine camshafts to alter variable valve timing, and in particular, to a compact, electronically actuated, cam phase position adjustment system.
• Camshaft phase position adjustment systems are used in internal combustion engines to vary the timing of valve opening and closing in order to improve fuel consumption and exhaust gas quality. It is possible, with adequate cam phase adjustment to tune valve timing for maximum comfort and/or maximum torque, or for the highest engine performance.
• cam phasers There are many types of cam phasers, most of which are hydraulic powered.
• a hydraulically powered cam phaser consists of a hydraulic shifter unit, a regulation valve, and a control circuit.
• the shifter unit must have low leakage rate and a sufficiently large piston or vane to ensure adequate stiffness.
• the regulation valve must ensure high flow rate during the adjustment and a precise regulation to maintain the set-point angles.
• Some cam phasers require a separate high-pressure hydraulic fluid supply.
• the present disclosure provides a cam phase position adjustment system, and more specifically, an electric cam phaser (ECP) for a camshaft of an internal combustion engine.
• ECP electric cam phaser
• the ECP includes an axial flux electric machine which is axially integrated with a positive differential gear train, and which is capable of providing frictional locking between rotating components.
• the gear train has three co-axial relatable branches. The first branch is connected to an input shaft, the second branch is connected to the output shaft, and the third branch is integrated with the rotor of the electric machine.
• the third branch is the control branch through which the gear train can be unlocked only during phase adjustment by applying toque though the electric machine to the control branch.
• the electric cam phaser of the present disclosure has three operating modes, each corresponding to a unique electric machine operation.
• the ECP first mode of operation is the neutral mode in which the electric machine is switched off, neither consuming electric power, nor generating any electric power.
• the differential gear train With no actuation torque exerting on the control branch, the differential gear train is partially locked or "internally jammed" and can only be rotated as unit.
• the output shaft rotates with the input shaft in the same direction at the same angular velocity and there is no phase shifting between the input shaft and the output shaft.
• the ECP second mode of operation is the generating mode, in which the electric machine applies a resistant torque to the control branch, rotationally slowing the rotor down. In doing so the electric machine converts mechanical power into electric power, acting as a generator.
• the resistant torque unlocks differential gear train to allow the output shaft to rotate with the input shaft in the same direction but at either a faster or slower angular velocity.
• the generating operational mode there is either a continuous phase advancing or phase retarding of the rotation of the output shaft with respect to the rotation of the input shaft.
• the ECP third mode of operation is the motoring mode, in which the electric machine applies a driving torque to the gear train, speeding the rotor up.
• the electric machine draws electric power for a power supplier and converts it into mechanical power, acting as a motor.
• the driving torque unlocks the differential gear train allowing the output shaft to rotate with the input shaft in the same direction, but either at a slower or faster angular velocity.
• the motoring operational mode there is either a continuous phase retarding or advancing of output shaft with respect to the input shaft.
• Figure 1 is a perspective view of the external features of an electric cam phaser of the present disclosure
• Figure 2 is a perspective sectional view of the electric cam phaser of Fig. 1 ;
• Figure 3 is a perspective sectional view of the planet carrier assembly and the associated rotor of the axial flux motor, viewed axially opposite as shown in Fig. 2;
• Figure 4 is a perspective view of the sun and planet gear assembly
• Figure 5 is an exploded view of the electric cam phaser of Fig. 1 ;
• Figure 6 is an exploded view of the electric cam phaser of Fig 1 , viewed from the opposite direction axial direction as shown in Fig. 5;
• an electric cam phaser is shown generally at A, comprising a sprocket 10, an input shaft 1 1 , a differential gear train 12, an axial-flux electric machine 13 disposed axially adjacent to the differential gear train 12, and an output shaft 14.
• the differential gear train 12 and axial-flux electric machine 13 are contained within a housing 26.
• the differential gear train 12 is further comprised of an input sun gear 15 coupled to the input shaft 1 1 , an output sun gear 16 coupled to the output shaft 14, a first set of planet gears 17, a second set of planet gears 18, and a carrier 19.
• the first and second sets planet gears 17 and 18 may be assembled as separate planet gears co-axially disposed on a common planet carrier 19, or may each be integrally formed as unitary planet gears, such as shown in Figs. 2 and 3 having common gear teeth.
• the input sun gear 15 meshes with the first set of planet gears 17, and the output sun gear 16 meshes with the second set of planet gears 18.
• Each planet gear in the first set of planet gears 17 couples to, and thus rotates as a unit with, a corresponding planet gear in the second set of planet gears 18. Together they form integrated planetary gears.
• the integrated planetary gears are each supported on a carrier 19 by a set of planet shafts 20, through sleeve bearings or needle bearings 29.
• the carrier 19, in turn, is supported on the input shaft 1 1 and the output shaft 14 though a sleeve bearing 21 and rolling element bearing 22.
• the axial flux electric machine 13 consists of a rotor 24 and a stator 25.
• the planet carrier 19 rotates with the rotor 24 as a unit.
• the stator 25 is mounted to the housing 26, axially adjacent to the rotor 24.
• the input shaft 1 1 is connected to the sprocket 10 at one axial end, and to the input sun gear 15 at the other axial end.
• the input shaft 1 1 is supported in the housing 26 though a rolling element bearing 27.
• the output shaft 14 is connected to the output sun gear 16 at middle portion and coupled to a camshaft (not shown) at one of its axial ends.
• the output shaft 14 is supported within the housing 26 though rolling element bearing 28 at one end, and in the bore of the input shaft 1 1 though sleeve bearings at the other end.
• Input shaft 1 1 is allowed to rotate with respect to the output shaft 14 when phase shifting between the two shafts is desirable.
• an angular position limiting device may be employed to provide mechanical stops in both rotational directions.
• the differential gear train has a basic gear ratio defined as:
• SR 0 _ ⁇ Sl y c ⁇ s ⁇ - ⁇ c
• the basic gear ratio can be determined by tooth numbers of the gears in the differential gear train, as below:
• Nsi the number of teeth for the input sun gear 15
• Ns 2 the number of teeth for the output sun gear 16
• Np 1 the number of teeth on each planet gear in the first set 17
• Np 2 the number of teeth on each planet gear in the second set 18.
• the differential gear train shown in Figure 2 and Figure 4 is designed with a configuration and an internal geometry that ensures a complete internal locking when no external torque is applied to the plane carrier 19.
• sleeve bearings 29 are used between the planet shafts 20 and the planet gears in each set 17, 18.
• the sleeve bearings 29, under radial load impose frictional resistant torque on the integrated planet gears in the sets 17 and 18, preventing them from rotating about their axis of rotation.
• the radial load pushing the planet gears of the sets 17 and 18 outward, is in direct proportion to the amount of torque being transmitted.
• the frictional resistant torque is also in proportion to the transmitted torque.
• the input torque from the input sun gear 15 and the output torque from the output sun gear 16 result in a differential torque that tends to drive and rotate the integrated planetary gear sets 17 and 18. If the maximum available frictional resistant torque is greater than the differential driving torque, the differential gear train 12 is frictionally locked. To ensure this condition, the following internal geometry relationship is recommended:
• Np 1 the number of teeth for each planet gear in the first set 17;
• the second mode of operation is the generating mode, in which the electric machine 13 applies a resistant torque to the differential gear train 12, slowing the rotation of the rotor 24 and carrier 19 down, coc ⁇ cosi- In doing so, the electric machine 13 converts mechanical power into electric power, acting as a generator.
• the resistant torque unlocks differential gear train 12. Consequently, the output shaft 14 rotates with the input shaft 1 1 in the same direction but at a faster or slower angular velocity. From equation (3) one can see, there will be a continuous phase advancing if SR 0 > 1 , or retarding if SR 0 ⁇ 1 , of the output shaft 14 with respect to the input shaft 1 1 .
• the third mode is the motoring mode, in which the electric machine 13 applies a driving torque to the differential gear train 12, speeding the rotation of the rotor 24 and the carrier 19 up, ⁇ c > CDs 1 .
• the electric machine 13 draws electric power from an external source (not shown) and converts it into mechanical power. In doing so, it acts as a motor.
• the driving torque unlocks the differential gear train 12.
• the output shaft 14 rotates with the input shaft 1 1 in the same direction but at a slower or faster angular velocity. From equation (3), one can see there will be a continuous phase retarding if SR 0 > 1 , or advancing if SR 0 ⁇ 1 , of the output shaft 14 with respect to the input shaft 1 1 .
• One of the advantages for the current invention is radial compactness due to the axial integration of the differential gear train with the axial flux electric motor 13. Radial compactness can be attractive in engine applications where the center distance between the intake and exhaust camshafts (not shown) is small. Another advantage of current invention is low manufacturing cost. Since a good portion operation is under neutral mode where the differential gear train 12 is internally jammed and rotates as a unit, the planet gear sets 17 and 18, the planet support bearings 29, and rotor supporting bearings 22, 23 are under intermittent usage.
• the cost of electric machines such as switched reluctance motor, can be used to reduce the overall cost.
• the axial flux electric motor 13 can be replaced with a radial flux electric motor without deviating from the sprit of current invention.
• the motor can be a pneumatic, or hydraulically operated type.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Valve Device For Special Equipments (AREA)
• Retarders (AREA)

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• 2009
  • 2009-12-08 EP EP09799789A patent/EP2373875A1/de not_active Withdrawn
  • 2009-12-08 CN CN2009801565586A patent/CN102317584A/zh active Pending
  • 2009-12-08 KR KR1020117015839A patent/KR20110104009A/ko not_active Application Discontinuation
  • 2009-12-08 WO PCT/US2009/067070 patent/WO2010068613A1/en active Application Filing

Non-Patent Citations (1)

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