EP2373875A1 - Compact electric cam phaser - Google Patents

Compact electric cam phaser

Info

Publication number
EP2373875A1
EP2373875A1 EP09799789A EP09799789A EP2373875A1 EP 2373875 A1 EP2373875 A1 EP 2373875A1 EP 09799789 A EP09799789 A EP 09799789A EP 09799789 A EP09799789 A EP 09799789A EP 2373875 A1 EP2373875 A1 EP 2373875A1
Authority
EP
European Patent Office
Prior art keywords
planet
phase shift
gear
mechanism according
sun gear
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Withdrawn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
EP09799789A
Other languages
German (de)
French (fr)
Inventor
Xiaolan Ai
Carl Davenport
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.)
JTEKT Bearings North America LLC
Original Assignee
Koyo Bearings North America LLC
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 Koyo Bearings North America LLC filed Critical Koyo Bearings North America LLC
Publication of EP2373875A1 publication Critical patent/EP2373875A1/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Withdrawn legal-status Critical Current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
    • F01L1/34—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)

Abstract

An electric cam phaser (ECP) for a camshaft of an internal combustion engine includes an axial flux electric machine (13) which is axially integrated with a positive differential gear train (12), and which is capable of providing frictional locking. The differential gear train (12) has three co-axial relatable branches. The first branch is connected to an input shaft (11), the second to the output shaft (14), and the third is integrated with a rotor (24) of the electric machine (13). The third branch is the control branch through which the differential gear train (12) can be unlocked from a neutral or "locked" mode of operation during phase adjustment by applying either a resistive torque in a second mode of operation, or a driving torque in a third mode of operation, though the electric machine (13) to the control branch.

Description

COMPACT ELECTRIC CAM PHASER CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is related to, and claims priority from, U.S. Provisional Patent Application Serial No. 61/121 ,694 filed on December 1 1 , 2008, and which is herein incorporated by reference. BACKGROUND OF THE INVENTION
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, also know as cam phasers, 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. There are many types of cam phasers, most of which are hydraulic powered. In general, 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. Such systems are somewhat complex, expensive, and require regular maintenance. The major shortcoming of hydraulic cam phasers is the dependency on engine oil pressure to supply the required hydraulic fluid pressure. Engine oil pressure varies with engine speed and temperature. During cracking, or at cold start, engine oil pressure is often inadequate to properly power a hydraulically driven cam phaser.
It is thus desirable to develop a compact, highly responsive and yet low manufacturing cost camshaft shifter that is free from complex hydraulic systems and electronically controlled for simplicity and high precision. BRIEF SUMMARY OF THE INVENTION Briefly stated, 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. 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. 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. Thus, 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. In 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. In the motoring operational mode, there is either a continuous phase retarding or advancing of output shaft with respect to the input shaft. -A-
The foregoing features, and advantages set forth in the present disclosure as well as presently preferred embodiments will become more apparent from the reading of the following description in connection with the accompanying drawings. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
In the accompanying drawings which form part of the specification:
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;
Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. It is to be understood that the drawings are for illustrating the concepts set forth in the present disclosure and are not to scale.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. DETAILED DESCRIPTION
The following detailed description illustrates the invention by way of example and not by way of limitation. The description enables one skilled in the art to make and use the present disclosure, and describes several embodiments, adaptations, variations, alternatives, and uses of the present disclosure, including what is presently believed to be the best mode of carrying out the present disclosure. Turning to the figures, and in particular to Figure 1 and Figure 2, 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 rotor 24, having a set of alternatively arranged magnets 24a mounted to its annular face, is integrated into one axial end of the planet carrier 19, forming an integrated rotor and carrier as best seen in Figure 3. As the rotor 24 rotates, 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. To prevent excessive angular displacement between the two shafts, an angular position limiting device (not shown) may be employed to provide mechanical stops in both rotational directions.
The differential gear train has a basic gear ratio defined as:
SR0 = _ ^Sl yc ωsι -ωc
(1 ) where ωSi = angular velocity of the input sun gear 15; a>s2 = angular velocity of the output sun gear 16; and coc = angular velocity of the carrier 19.
The basic gear ratio can be determined by tooth numbers of the gears in the differential gear train, as below:
SR0 = Nsi ' Np2
^S2 ' ^P\ /2\
where
Nsi = the number of teeth for the input sun gear 15;
Ns2 = the number of teeth for the output sun gear 16; Np1 = the number of teeth on each planet gear in the first set 17; and
Np2 = the number of teeth on each planet gear in the second set 18.
The phase shifting angle for the output shaft 14 with respect to the input shaft 1 1 is determined as: Aθ = (l- SR0) j(ωsl -ωc)dτ
(3)
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. To illustrate this feature, reference is made to Figures 2 and 4 where 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. For involute gears, and many other types of gears with conjugant teeth profiles, 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. Thus the frictional resistant torque is also in proportion to the transmitted torque. On the other hand, 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:
μ • ( \ • tan 6Ir1 + A2 • t an a2 ) > Z1 • 1 - SR0
(4) where i, =^ A =- 4 = —
NSl RS1 RS2
Np1 = the number of teeth for each planet gear in the first set 17;
Nsi = the number of teeth for the input sun gear 15; r= the effective bore radius for planet support bearing 29; Rs 1= pitch circle radius for the input sun gear 15;
Rs 2= pitch circle radius for the output sun gear 16; ai = pressure angle for the input sun gear 15 and each planet gear in the first set 17;
Ct2= pressure angle for the output sun gear 16 and each planet gear in the second set 18; and μ = maximum available friction coefficient for planet support bearings 29.
The electric cam phaser A has three operational modes. The first is called the neutral mode in which the electric machine 13 is switched off, exerting no torque on the planet carrier 19, and the differential gear train 12 is thus frictionally locked or "internally jammed". Under these conditions, the differential gear train 12 can only be rotated as unit. Hence the output shaft 14 rotates with the input shaft 1 1 in the same direction and at the same angular velocity. Therefore, coc = COs1. From equation (3), one can see Δθ = 0, there will be no phase change between the input shaft 1 1 and the output shaft 14. 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 SR0 > 1 , or retarding if SR0 < 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, ωc > CDs1. 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. As a result, 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 SR0 > 1 , or advancing if SR0 < 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.
Thus, low cost gears and bearings can be employed. For the same reason, the cost of electric machines, such as switched reluctance motor, can be used to reduce the overall cost. It may be apparent to those skilled in the art that the axial flux electric motor 13 can be replaced with a radial flux electric motor without deviating from the sprit of current invention. Similarly, the motor can be a pneumatic, or hydraulically operated type.
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.

Claims

CLAIMS:
1. In an internal combustion engine including a camshaft and a drive for the camshaft, a cam phase shift mechanism (A) located between the drive and the camshaft for controlling a phase shift angle between the camshaft and the drive, the cam phase shift mechanism (A) comprising: an input shaft (1 1 ) coupled to the drive; an output shaft (14) coupled to the camshaft; a differential gear train (12) co-axially aligned around the input shaft (1 1 ) and the output shaft (14), the differential gear train (12) having an input sun gear (15) coupled to the input shaft (1 1 ), an output sun gear (16) coupled to the output shaft (14), and first and second planet gear sets (17, 18) that engage the input sun gear (15) and output sun gear (16), respectively, said planet gear sets (17,
18) united to rotate about a common axis at the same angular velocity, and having a planet carrier (19) with planet bearing (29) on which the united first and second planet gear sets (17, 18) respectively rotate; a locking means for locking the differential gear train (12) in a locked condition by preventing the planet gear sets (17, 18) from rotating relative to the planet carrier (19), such that the sun gears (15, 16) and planet carrier (19) rotate as a unit and the phase shift angle between the input shaft (1 1 ) and output shaft (14) remains unchanged to enable the output shaft (14) to rotate at the same angular velocity as the input shaft (1 1 ), said locking means consisting of frictional torque resulting from friction between the first planet gear set (17) and the planet bearing (29) and between the second planet gear set (18) and the planet bearing (29); and an axial flux electric machine (13) axially adjacent to and coupled to, the planet carrier (19), the axial flux electric machine (13) configured to apply a torque to the differential gear train (12) for overcoming the frictional torques of the locking means, enabling the planet carrier (19) to rotate relative to at least one of the input sun gear (15) and the output sun gear (16) to alter the phase shift angle between the input shaft (1 1 ) and the output shaft (14) so that the output shaft (14) assumes a different angular velocity with respect to the input shaft (1 1 ).
2. The cam phase shift mechanism according to Claim 1 wherein the phase shift angle is a function of a gear ratio SR0 of the differential gear train (12).
3. The cam phase shift mechanism according to Claim 2 wherein the gear ratio SR0 of the differential gear train is characterized by the equation:
where ωS1 = angular velocity of the input sun gear (15); ωS2 = angular velocity of the output sun gear (16); and coC = angular velocity of the planet carrier (19).
4. The cam phase shift mechanism according to Claim 3 wherein the change in the phase shift angle is characterized by the equation:
5. The cam phase shift mechanism according to Claim 2 wherein the gear ratio SR0 is characterized by the equation:
SR0 = Nsi ' Np2
^ S2 ' ™ Pl where
Nsi = the number of teeth for the input sun gear (15); Ns2 = the number of teeth for the output sun gear (16); NPI = the number of teeth for each gear of the first planet gear set (17); and Np2 = the number of teeth for each gear of the second planet gear set (18).
6. The cam phase shift mechanism according to Claim 1 wherein a relationship between geometric parameters of the differential gear train (12) and the coefficients of friction between the first planet gear set (17) and the planet bearing (29), and between the second planet gear set (18) and the planet bearing (29) is characterized by the equation:
μ'(Λ1't3Ra[+λλ'tana2)≥i['l-SR v io where
. Nn h = 2 =
N A = X
Sl R Sl RS2 Npi = the number of teeth for each gear of the first planet gear set (17); Nsi = the number of teeth for the input sun gear (15); r= the effective bore radius for planet support bearing (29); Rsi = pitch circle radius for the input sun gear (15); Rs2 = pitch circle radius for the output sun gear (16); a-i = pressure angle for the input sun gear (15) and the gears of the first planet gear set (17);
(X2 = pressure angle for the output sun gear (16) and the gears of the second planet gear set (18); and μ = maximum available friction coefficient for planet support bearing (29).
7. The cam phase shift mechanism according to Claim 6 wherein the torque applied by the axial flux electric machine (13) to the differential gear train (12) comprises a resistant torque which unlocks the planet carrier (19) by overcoming the torque caused by friction between the gears of the first planet gear set (17) and the planet bearing (29), and between the gears of the second planet gear set (18) and the planet bearing (29) to change the phase shift angle that the output shaft (14) rotates with respect to the input shaft (1 1 ).
8. The cam phase shift mechanism according to Claim 7 wherein continuous phase advancing occurs for the phase shift angle if SR0 > 1.
9. The cam phase shift mechanism according to Claim 7 wherein continuous phase retarding occurs for the phase shift angle if SR0 < 1.
10. The cam phase shift mechanism according to Claim 6 wherein the torque applied by the electric machine (13) to the differential gear train (12) comprises a driving torque which unlocks the planet carrier (19) by overcoming the torques applied by the coefficients of friction between the gears of the first planet gear set (17) and the planet bearing (29), and between the gears of the second planet gear set (18) and the planet bearing (29) to change the phase shift angle that the output shaft (14) rotates with respect to the input shaft (1 1 ).
11. The cam phase shift mechanism according to Claim 10 wherein continuous phase retarding occurs for the phase shift angle if SR0 > 1.
12. The cam phase shift mechanism according to Claim 10 wherein continuous phase advancing occurs for the phase shift angle if SR0 < 1 .
13. The cam phase shift mechanism according to Claim 1 further comprising a limiting device configured to prevent excessive angular displacement between the input shaft (1 1 ) and the output shaft (14).
14. The cam phase shift mechanism according to Claim 1 wherein the gears of the first and second planet gear sets (17, 18) are identically formed and are each integrated as unitary gears.
EP09799789A 2008-12-11 2009-12-08 Compact electric cam phaser Withdrawn EP2373875A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US12169408P 2008-12-11 2008-12-11
PCT/US2009/067070 WO2010068613A1 (en) 2008-12-11 2009-12-08 Compact electric cam phaser

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EP2373875A1 true EP2373875A1 (en) 2011-10-12

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EP09799789A Withdrawn EP2373875A1 (en) 2008-12-11 2009-12-08 Compact electric cam phaser

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KR (1) KR20110104009A (en)
CN (1) CN102317584A (en)
WO (1) WO2010068613A1 (en)

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KR101664534B1 (en) * 2013-12-03 2016-10-10 현대자동차주식회사 Harmonic drive
JP5987868B2 (en) * 2014-07-22 2016-09-07 株式会社デンソー Valve timing adjustment device
KR101689544B1 (en) * 2015-11-18 2016-12-27 계양전기 주식회사 Integral Type CVVT Apparatus
US11821342B2 (en) * 2019-05-03 2023-11-21 Husco Automotive Holdings Llc Systems and methods for controlled relative rotational motion

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KR20110104009A (en) 2011-09-21
CN102317584A (en) 2012-01-11

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