JP2010090850A - Variable valve timing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To further reduce the axial dimension of a variable valve timing device previously developed for transmitting rotation of an electric motor to a camshaft only by a reduction mechanism. <P>SOLUTION: An annular retainer section 10b of an intermediate shaft 10 has a comb shape projecting in an axial direction and having openings on a tip side, and spaces formed in the comb shape having the openings on the tip side are used as pockets 10a for holding rollers. With this, the length of the retainer section 10b is shortened, and the axial dimension of the variable valve timing device previously developed for transmitting rotation of the electric motor to the camshaft only by the reduction mechanism can be further reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a variable valve timing device that changes opening and closing timings of an intake valve and an exhaust valve of an engine.

  A variable valve timing device that changes the opening / closing timing of one or both of the intake valve and exhaust valve of an engine according to the driving situation of an automobile uses an oil pressure as a drive source of the rotation of the engine and the camshaft that drives the valve. There are many hydraulic types that change the phase with rotation, but the hydraulic type has variable valve timing control accuracy due to lack of hydraulic pressure at cold or engine start, or reduced responsiveness of hydraulic control Therefore, an electric type using an electric motor as an actuator has been proposed.

  As such an electric variable valve timing device, as shown in FIGS. 6A and 6B, the camshaft 51 that drives the valve of the engine and the rotation transmitted from the engine rotate the camshaft 51. The sprocket 52 to be driven is arranged coaxially so as to be relatively rotatable, and the rotation of the output shaft 54 of the electric motor 53 arranged coaxially with the camshaft 51 is rotated via the speed reduction mechanism 55 and the link mechanism 56. And the camshaft 51 is rotated relative to the sprocket 52 to change the rotational phase difference between the two and change the valve opening and closing timing (see, for example, Patent Document 1).

  The speed reduction mechanism 55 includes an external gear provided in a housing 58 in which a part of teeth of an internal gear 57 rotatably supported by a bearing on an eccentric shaft portion 54 a of an output shaft 54 of an electric motor 53 is integrated with a sprocket 52. 59, when the output shaft 54 is rotated relative to the sprocket 52 so as to mesh with the gear 59, the internal gear 57 is rotated around the eccentric shaft portion 54a. Further, the rotation of the guide plate 60 is transmitted to the cam plate 51a that rotates integrally with the camshaft 51 via the link mechanism 56 constituted by the arms 56a and 56b, and the camshaft 51 is sprocketed. Rotate relative to 52.

JP 2008-57349 A

  The electric variable valve timing apparatus described in Patent Document 1 has a problem that the mechanism for transmitting the rotation of the electric motor to the camshaft has a complicated structure combining a speed reduction mechanism and a link mechanism, and the apparatus cannot be designed compactly. is there.

  In response to this problem, the present inventors have provided a speed reduction mechanism for transmitting the rotation of the output shaft of the electric motor to the camshaft, a housing in which the eccentric shaft portion having a circular cross section is provided on the output shaft of the electric motor and integrated with the sprocket. An inner gear having a plurality of cam ridges formed on the inner diameter surface of the cylindrical portion is provided to face the eccentric shaft portion, and a plurality of rollers that are in rolling contact with the outer diameter surface of the opposed eccentric shaft portion and the inner gear are held. When the output shaft of the electric motor is rotated with the intermediate shaft having an annular cage portion provided with a pocket arranged coaxially with the camshaft, the roller held in the pocket is the outer diameter surface of the eccentric shaft portion. The variable valve timing device for transmitting the revolution of these rollers to the camshaft via the intermediate shaft has been filed earlier (Japanese Patent Application No. 2008-215547).

  The previously developed variable valve timing device can transmit the rotation of the electric motor to the camshaft only by the reduction mechanism, and can be designed in a compact manner, but it is desired to further reduce the axial dimension. Yes.

  Accordingly, an object of the present invention is to further reduce the axial dimension of the previously developed variable valve timing device that transmits the rotation of the electric motor to the camshaft only by the speed reduction mechanism.

  In order to solve the above problems, the present invention provides a camshaft that drives at least one of an intake valve and an exhaust valve of an engine, and a sprocket that receives rotation from the engine and drives the camshaft to rotate. A rotation phase difference of the camshaft with respect to the sprocket is transmitted to the camshaft through a speed reduction mechanism by rotating the output shaft of the electric motor arranged coaxially with the camshaft so as to be relatively rotatable. The opening / closing timing of the valve is changed, the deceleration mechanism is provided with an eccentric shaft portion having a circular cross section on the output shaft of the electric motor, and the inner diameter surface of the cylindrical portion of the housing integrated with the sprocket In addition, an internal gear having a plurality of cam ridges formed at equal pitches in the circumferential direction is provided opposite to the eccentric shaft portion, and these are opposed An intermediate shaft having an annular cage portion provided with a pocket for holding a plurality of rollers for rolling contact with the outer diameter surface of the mandrel and the internal gear is arranged coaxially with the camshaft, and the annular cage A pocket for holding the roller at a position where the number of dividing points when the part is divided at equal pitches in the circumferential direction is different from the number of the cam crests by all or part of the dividing points. The locus of one pitch of the cam crest is revolved along the outer diameter surface of the eccentric shaft portion when the output shaft of the electric motor is rotated. In this variable valve timing device, the revolving of these rollers is transmitted to the camshaft through the intermediate shaft so as to coincide with the outer diameter side envelope of the annular retainer. Comb with open end The shape, the distal end side of the space formed between the comb-shaped opening was employed a configuration in which a pocket for holding the roller.

  That is, by making the annular cage portion into a comb shape that projects in the axial direction and opens on the tip side, and the space formed between the comb shapes that opens on the tip side is a pocket that holds the roller, The cage length is shorter than that of the previously developed variable valve timing device, where the pocket was formed in a closed window shape so that the overall axial dimension of the device can be further reduced. did. Moreover, this variable valve timing apparatus can insert the roller hold | maintained at the pocket of a holder | retainer part from an axial direction, and can also make it easy to incorporate in the pocket of a roller.

  By providing chamfers on both sides of the opening on the axial front end side of the pocket formed between the combs, the roller can be easily incorporated into the pocket.

  By providing the fillet at the comb-shaped base corner of the pocket formed between the comb shapes, the strength of the cage-shaped cage portion can be ensured.

  By forming the cage portion of the intermediate shaft from a resin material, it is possible to prevent the roller from being damaged by sliding contact with the pocket surface of the cage portion.

  By forming the intermediate shaft having the cage portion by pressing a metal plate, the intermediate shaft can be manufactured at low cost.

  By providing an inward flange that faces the opening of the pocket in the axial direction on one side of the cylindrical portion of the housing, it is possible to prevent the roller held in the pocket by this flange from coming off in the axial direction. it can.

  In the variable valve timing device of the present invention, the annular cage portion is formed in a comb shape that projects in the axial direction and opens at the tip side, and the space formed between the comb shapes that opens at the tip side is held by the roller. Therefore, the length of the cage portion can be shortened to further reduce the axial dimension of the previously developed variable valve timing device. Moreover, this variable valve timing apparatus can insert the roller hold | maintained at the pocket of a holder | retainer part from an axial direction, and can also make it easy to incorporate in the pocket of a roller.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 3 show a first embodiment. As shown in FIG. 1, the variable valve timing device is configured to relatively connect a camshaft 1 that drives an intake valve (not shown) of an engine and a sprocket 2 that receives rotation from the engine and drives the camshaft 1 to rotate. The rotation of the output shaft 4 of the electric motor 3 arranged coaxially so as to be rotatable and coaxial with the camshaft 1 is transmitted to the camshaft 1 via the speed reduction mechanism 5, and the rotational position of the camshaft 1 relative to the sprocket 2 is transmitted. The opening / closing timing of the intake valve is changed by changing the phase difference.

  As shown in FIGS. 1 and 2, the speed reduction mechanism 5 is provided with an eccentric shaft portion 4a having a circular cross section on the output shaft 4 of the electric motor 3, and a ball bearing 6 is fitted and fixed to the eccentric shaft portion 4a. A separate internal gear 8 formed with a plurality of cam ridges 8 a is fitted on the inner diameter surface of the cylindrical portion 7 a of the housing 7 integrated with the sprocket 2 so as to face the outer diameter surface of the outer ring 6 a of the ball bearing 6. An intermediate shaft 10 having an annular retainer portion 10b provided with a pocket 10a that is fixed and holds a plurality of rollers 9 that are in rolling contact with the outer diameter surfaces of the opposed outer rings 6a and the internal gear 8 is connected to the camshaft 1. It is arranged on the same axis, and its intermediate shaft 10 is connected to the camshaft 1 by a spline 11, and the rotation of the output shaft 4 of the electric motor 3 is transmitted to the camshaft 1 via the intermediate shaft 10 by a mechanism described later. To do.

  The output shaft 4 of the electric motor 3 is supported by an inward flange portion 7b provided on one side of the cylindrical portion 7a of the housing 7 by a ball bearing 12 having a negative gap, and the intermediate shaft 10 is a four-point contact type. The ball bearing 13 is supported by the housing 7 through the extended cylindrical portion of the internal gear 8, and the reverse resistance from the camshaft 1 to the output shaft 4 is suppressed by the rotational resistance of the ball bearing 12 having a negative clearance. In addition, the swing of the intermediate shaft 10 is suppressed by the four-point contact type ball bearing 13. Further, on the eccentric side of the eccentric shaft portion 4a, a through hole 4b is provided as a balance adjusting portion that adjusts the weight balance around the shaft center of the output shaft 4.

  As shown in FIG. 2, 29 cam ridges 8a of the internal gear 8 are formed at equal pitches in the circumferential direction, and the pockets 10a for holding the rollers 9 are arranged at equal pitches in the circumferential direction of the annular cage portion 10b. Are provided at 15 positions which are thinned out every other division point when divided into 30, and the number of division points is one more than the cam crest 8a. Further, the shape of one pitch of the cam crest 8a is such that when the output shaft 4 is rotated, the outer diameter of the outer ring 6a of the ball bearing 6 in which the roller 9 held in the pocket 10a is externally fitted to the eccentric shaft portion 4a. It coincides with the outer envelope of the trajectory revolving along the surface.

  As shown in FIG. 3, the cage portion 10b of the intermediate shaft 10 has a comb shape that projects in the axial direction and opens at the tip side, and a space formed between the comb shapes that opens at the tip side is a roller. 9 is a pocket 10 a for holding 9. A chamfer 14 is provided on both sides of the opening at the tip end in the axial direction of the pocket 10a formed between the combs, and an R-shaped fillet 15 is provided at the comb-shaped base corner of the pocket 10a. Moreover, as shown in FIG. 1, the opening part of the pocket 10a has opposed the inner surface of the collar part 7b of the housing 7, and the roller 9 hold | maintained at the pocket 10a is prevented from coming off in the axial direction.

  Below, the deceleration mechanism of the said deceleration mechanism 5 is demonstrated. As indicated by the arrows in FIG. 2, the output shaft 4 rotates clockwise, and the minimum portion A of the annular space between the outer diameter surface of the eccentric outer ring 6a and the internal gear 8 on which the cam ridge 8a is formed is clockwise. If the output angle is 0 ° and the maximum portion B is 180 °, the minimum portion A and the maximum portion B move clockwise as the output shaft 4 rotates, and the right half of the annular space becomes narrower. Tendency, the left half of the annular space tends to widen. For this reason, the roller 9 present in the right half of the annular space moves in the outer diameter direction down the cam peak 8a of the internal gear 8, and the roller 9 present in the left half of the annular space moves in the inner diameter direction above the cam peak 8a. As indicated by the arrows in the figure, the cage portion 10 b of the intermediate shaft 10 that holds the roller 9 rotates in the same clockwise direction as the output shaft 4.

  In this embodiment, since the number N of the dividing points of the cage portion 10b is one more than the number of the cam peaks 8a, each roller 9 rotates clockwise by one pitch of the cam peaks 8a when the output shaft 4 rotates once. And the reduction ratio between the output shaft 4 and the intermediate shaft 10 is equal to the number N of division points. When the number N of division points is one less than the number of cam peaks 8a, each roller 9 revolves counterclockwise, and the intermediate shaft 10 rotates in the direction opposite to the output shaft 4.

  FIG. 4 shows a second embodiment. This variable valve timing device has the same basic configuration as that of the first embodiment, except that the cage portion 10b of the intermediate shaft 10 is insert-molded with a resin material. The other portions are the same as those of the first embodiment, and the opening of the pocket 10a of the cage portion 10b having a comb shape is opposed to the inner side surface of the flange portion 7b of the housing 7.

  FIG. 5 shows a third embodiment. This variable valve timing device also has the same basic configuration as that of the first embodiment, except that the intermediate shaft 10 having the cage portion 10b is formed by pressing a steel plate. The other portions are the same as those of the first embodiment, and the opening of the pocket 10a of the cage portion 10b having a comb shape is opposed to the inner side surface of the flange portion 7b of the housing 7.

1 is a longitudinal sectional view showing a variable valve timing device according to a first embodiment. Sectional view along the line II-II in FIG. The perspective view which shows the intermediate shaft which has a holder | retainer part of FIG. The longitudinal cross-sectional view which shows the variable valve timing apparatus of 2nd Embodiment The longitudinal cross-sectional view which shows the variable valve timing apparatus of 3rd Embodiment a is a longitudinal sectional view showing a conventional variable valve timing device, and b is a sectional view taken along line VI-VI of a.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cam shaft 2 Sprocket 3 Electric motor 4 Output shaft 4a Eccentric shaft part 4b Through-hole 5 Deceleration mechanism 6 Ball bearing 6a Outer ring 7 Housing 7a Cylindrical part 7b Eave part 8 Internal gear 8a Cam crest 9 Roller 10 Intermediate shaft 10a Pocket 10b Cage Part 11 Spline 12, 13 Ball bearing 14 Chamfer 15 Fillet

Claims (6)

  A camshaft that drives at least one of an intake valve and an exhaust valve of an engine, and a sprocket that receives rotation from the engine and drives the camshaft to rotate are arranged coaxially so as to be relatively rotatable, and the cam The rotation of the output shaft of the electric motor arranged coaxially with the shaft is transmitted to the camshaft through a reduction mechanism, and the opening / closing timing of the valve is changed by changing the rotational phase difference of the camshaft with respect to the sprocket. The decelerating mechanism is provided with an eccentric shaft portion having a circular cross section on the output shaft of the electric motor, and a plurality of cam ridges are equidistant in the circumferential direction on the inner diameter surface of the cylindrical portion of the housing integrated with the sprocket. The internal gear formed in the above is provided so as to face the eccentric shaft portion, and the outer gear surface of the opposed eccentric shaft portion and the internal gear are in rolling contact with each other. A dividing point when an intermediate shaft having an annular cage portion provided with a pocket for holding a roller is arranged coaxially with the camshaft, and the annular cage portion is divided at an equal pitch in the circumferential direction. Is provided with pockets for holding the rollers at the positions where all or some of the dividing points differ from the number of the cam peaks by one, and the shape of one pitch of the cam peaks is formed. When the output shaft of the electric motor is rotated, the rollers held in the pockets match the outer diameter side envelope of the trajectory along which the rollers revolve along the outer diameter surface of the eccentric shaft portion. In the variable valve timing device that transmits the revolution to the camshaft through the intermediate shaft, the annular retainer portion has a comb shape that projects in the axial direction and opens at the tip side, and the tip side opens. Comb Variable valve timing system, wherein a space formed, and a pocket for holding the roller during.   The variable valve timing device according to claim 1, wherein chamfers are provided on both sides of an opening portion on an axial front end side of a pocket formed between the comb shapes.   The variable valve timing device according to claim 1 or 2, wherein a fillet is provided in a comb-shaped base corner of a pocket formed between the combs.   The variable valve timing device according to claim 1, wherein the cage portion of the intermediate shaft is made of a resin material.   4. The variable valve timing device according to claim 1, wherein the intermediate shaft having the cage portion is formed by pressing a metal plate.   An inward flange that is axially opposed to the opening of the pocket is provided on one side of the cylindrical portion of the housing, and a roller held in the pocket is axially retained by the flange. 6. The variable valve timing device according to any one of 5 above.

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