Valve timing control apparatus for internal combustion engine

Abstract

A valve timing control apparatus for an internal combustion engine, including a drive rotation member, a follower rotation member, an electric motor, and a speed reducer including an internal gear portion, an eccentric cam on an inner peripheral side of the internal gear portion, rollers disposed between the internal gear portion and the eccentric cam, and a cage rotatable relative to the internal gear portion by rotation of the eccentric cam. A motor output shaft is arranged in series relative to the eccentric cam in an axial direction thereof. A needle bearing is rollably disposed on a part of an outer peripheral surface of the follower rotation member. The eccentric cam and the motor output shaft are press-fitted onto an outer peripheral portion of the needle bearing. The needle bearing extends over both the eccentric cam and the motor output shaft.

1 . A valve timing control apparatus for an internal combustion engine, the internal combustion engine including a crankshaft and a camshaft, the valve timing control apparatus comprising:
 a drive rotation member to which a rotational force is transmitted from the crankshaft;   a follower rotation member fixed to the camshaft;   an electric motor comprising a rotor that is rotatable relative to the drive rotation member;   a speed reducer comprising a trochoid curve-shaped internal gear portion that is rotatable with the drive rotation member, a sleeve-shaped eccentric cam disposed on an inner peripheral side of the internal gear portion, the eccentric cam having an outer peripheral portion eccentric relative to a central axis thereof, a plurality of rollers disposed between the internal gear portion and the eccentric cam, and a comb shaped cage that is rotatable with the follower rotation member, the cage supporting the plurality of rollers, the cage being rotated relative to the internal gear portion by rotation of the eccentric cam,   a tubular motor output shaft fixed to an inner periphery of the rotor, the motor output shaft being arranged in series relative to the eccentric cam in an axial direction thereof, and   a needle bearing that is rollable on a part of an outer peripheral surface of the follower rotation member,   wherein the eccentric cam and the motor output shaft are press-fitted onto an outer peripheral portion of the needle bearing, the needle bearing extending over both the eccentric cam and the motor output shaft in an axial direction thereof.   
     
     
         2 . The valve timing control apparatus as claimed in  claim 1 , wherein the eccentric cam supports a rolling bearing having an outer peripheral portion that is rotatable relative to an inner peripheral portion of the rolling bearing. 
     
     
         3 . The valve timing control apparatus as claimed in  claim 2 , wherein the rolling bearing is a ball bearing. 
     
     
         4 . The valve timing control apparatus as claimed in  claim 3 , wherein the needle bearing comprises needle rollers, a center of a ball of the ball bearing is placed within a region of an axial length of the respective needle rollers. 
     
     
         5 . The valve timing control apparatus as claimed in  claim 3 , wherein the eccentric cam has an eccentric cylindrical sleeve shape having an eccentric outer peripheral surface with respect to an inner peripheral surface thereof into which the needle bearing is press-fitted. 
     
     
         6 . The valve timing control apparatus as claimed in  claim 5 , wherein the eccentric cam is arranged in an inner race of the ball bearing with a slight press-fit. 
     
     
         7 . The valve timing control apparatus as claimed in  claim 5 , wherein the motor output shaft has one axial end portion that abuts against both the eccentric cam and an inner race of the ball bearing in an axial direction of the motor output shaft. 
     
     
         8 . The valve timing control apparatus as claimed in  claim 5 , further comprising a restraining plate disposed between one axial end portion of the motor output shaft and an inner race of the ball bearing, the restraining plate cooperating with the one axial end portion of the motor output shaft to restrain an axial movement of the inner race of the ball bearing. 
     
     
         9 . The valve timing control apparatus as claimed in  claim 1 , wherein the motor output shaft and the eccentric cam each have press-fit portions press-fitted onto the outer peripheral portion of the needle bearing in the axial direction, the press-fit portion of the motor output shaft having a length shorter than that of the press-fit portion of the eccentric cam. 
     
     
         10 . The valve timing control apparatus as claimed in  claim 3 , further comprising a second ball bearing, the second ball bearing comprising an outer race that abuts on an axial end of the needle bearing, and an inner race fixed to the follower rotation member. 
     
     
         11 . The valve timing control apparatus as claimed in  claim 10 , wherein the inner race of the second ball bearing is fixed in an axial direction of the second ball bearing in such a state that the inner race is disposed between the follower rotation member and a cam bolt serving to fix the camshaft to the follower rotation member. 
     
     
         12 . The valve timing control apparatus as claimed in  claim 11 , wherein the outer race of the second ball bearing is press-fitted into an inner peripheral surface of the motor output shaft, the outer race having an outer diameter smaller than an outer diameter of the needle bearing. 
     
     
         13 . The valve timing control apparatus as claimed in  claim 1 , wherein the follower rotation member has a plurality of through-holes in a portion thereof to which one axial end portion of the eccentric cam is opposed, the through-holes being arranged in a circumferential direction of the follower rotation member. 
     
     
         14 . The valve timing control apparatus as claimed in  claim 1 , wherein the needle bearing is immersed in lubricating oil that is supplied from a side of the camshaft at least after the internal combustion engine is started. 
     
     
         15 . The valve timing control apparatus as claimed in  claim 1 , wherein the electric motor comprises a stator fixed to the drive rotation member, and a rotor rotatably disposed relative to the stator, and the electric motor is supplied with electric current from a non-rotation portion through brushes and slip rings. 
     
     
         16 . The valve timing control apparatus as claimed in  claim 15 , wherein the rotor of the electric motor has a coil winding, the stator has permanent magnet pieces, and the motor output shaft has a commutator that serves to carry out changeover of energization of the coil winding to form a magnetic flux. 
     
     
         17 . A valve timing control apparatus for an internal combustion engine, the internal combustion engine including a crankshaft and a camshaft, the valve timing control apparatus comprising:
 a drive rotation member to which a rotational force is transmitted from the crankshaft;   a follower rotation member fixed to the camshaft;   an electric motor comprising a rotor that is rotatable relative to the drive rotation member;   a speed reducer comprising a trochoid curve-shaped internal gear portion that is rotatable with the drive rotation member, a ball bearing disposed on an inner peripheral side of the internal gear portion, the ball bearing comprising an outer race, an inner race having an outer peripheral surface eccentric relative to an inner peripheral surface thereof, a plurality of rollers disposed between the internal gear portion and the outer race of the ball bearing, and a comb-shaped cage that is rotatable with the follower rotation member, the cage supporting the plurality of rollers, the cage being rotated relative to the internal gear portion by rotation of the inner race of the ball bearing,   a tubular motor output shaft fixed to an inner periphery of the rotor, the motor output shaft having an axial end that serves to restrain an axial movement of the inner race of the ball bearing, and   a needle bearing that is rollable on a part of an outer peripheral surface of the follower rotation member,   wherein the inner race of the ball bearing and the motor output shaft are press-fitted onto an outer peripheral portion of the needle bearing, the needle bearing extending over both the inner race of the ball bearing and the motor output shaft in an axial direction thereof.   
     
     
         18 . The valve timing control apparatus as claimed in  claim 17 , further comprising a washer disposed between one axial end portion of the motor output shaft and one axial end portion of an inner race of the ball bearing, the washer having an outer diameter larger than an inner diameter of the inner race of the ball bearing, the washer serving to restrain an axial movement of the inner race of the ball bearing. 
     
     
         19 . A valve timing control apparatus for an internal combustion engine, the internal combustion engine including a crankshaft and a camshaft, the valve timing control apparatus comprising:
 a drive rotation member to which a rotational force is transmitted from the crankshaft;   a follower rotation member fixed to the camshaft;   an electric motor comprising a rotor that is rotatable relative to the drive rotation member;   a speed reducer comprising at least one engagement portion, the one engagement portion being disposed in a transmission path through which a rotational force is transmitted from the electric motor, the speed reducer serving to reduce a rotational force transmitted from the rotor to an input portion and transmit the rotational force reduced to the follower rotation member,   a tubular motor output shaft fixed to the rotor;   a sleeve disposed such that an axial end portion thereof is opposed to an axial end portion of the motor output shaft, the sleeve being fixed to the input portion of the speed reducer, and   a bearing that is rollable on a part of an outer peripheral surface of the follower rotation member,   wherein the sleeve and the motor output shaft are press-fitted onto an outer peripheral portion of the bearing, the bearing extending over both the sleeve and the motor output shaft in an axial direction thereof.   
     
     
         20 . The valve timing control apparatus as claimed in  claim 19 , wherein at least one of the one engagement portion of the speed reducer and the follower rotation member is changed in size so as to adjust a clearance between the one engagement portion of the speed reducer and the follower rotation member.