JP5139209B2 - Variable valve timing device - Google Patents

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 applied variable valve timing device can transmit the rotation of the electric motor to the camshaft only by the speed reduction mechanism, and a compact design is possible, but since the output shaft of the electric motor has an eccentric shaft portion, Unevenness of rotation occurs due to the imbalance of the weight around the axis, and there is a risk that vibrations occur in the speed reduction mechanism.

  Therefore, an object of the present invention is to provide a variable valve timing device that can transmit the rotation of an electric motor to a camshaft only by a speed reduction mechanism and that does not cause vibration in 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. In the variable valve timing apparatus that changes the opening / closing timing of the valve by changing the valve, the speed reduction mechanism is provided with an eccentric shaft portion having a circular cross section on the output shaft of the electric motor, and a housing integrated with the sprocket An internal gear having a plurality of cam ridges formed at equal pitches in the circumferential direction on the inner diameter surface of the cylindrical portion of the cylindrical portion An intermediate shaft having an annular retainer portion provided with a pocket for holding a plurality of rollers that are in rolling contact with the outer diameter surfaces of the opposed eccentric shaft portions and the internal gear is coaxial with the camshaft. The number of dividing points when the annular retainer portion is divided at equal pitches in the circumferential direction is thinned out at all positions or a part of the dividing points that differ from the number of the cam crests by one. A pocket for holding the roller is provided at a position, and when the output shaft of the electric motor is rotated with the shape corresponding to one pitch of the cam crest, the roller held in the pocket is The revolving of these rollers is transmitted to the camshaft through the intermediate shaft in accordance with the outer envelope of the trajectory revolving along the outer diameter surface, and the eccentric shaft of the output shaft of the electric motor The weight bar around its output shaft Adopting a structure in which a balance adjusting unit that adjusts the Nsu.

  That is, a speed reduction mechanism for transmitting the rotation of the output shaft of the electric motor to the camshaft is provided with an eccentric shaft portion having a circular cross section on the output shaft of the electric motor, and a plurality of inner diameter surfaces of the cylindrical portion of the housing integrated with the sprocket An internal gear having cam ridges formed at equal pitches in the circumferential direction is provided to face the eccentric shaft portion, and a pocket for holding a plurality of rollers that are in rolling contact with the outer diameter surface of the opposed eccentric shaft portion and the internal gear. The number of dividing points when the intermediate shaft having the annular retainer portion provided is coaxially arranged with the cam shaft and the annular retainer portion is divided at an equal pitch in the circumferential direction is the number of cam peaks. When a pocket for holding a roller is provided at all or a part of a part where only one different dividing point is thinned out, and the shape of one pitch of the cam crest is rotated when the output shaft of the electric motor is rotated, Roller held in pocket is eccentric The revolving of these rollers is transmitted to the camshaft via the intermediate shaft in accordance with the outer envelope of the trajectory revolving along the outer diameter surface of the section, and the eccentric shaft portion of the output shaft of the electric motor In addition, by providing a balance adjusting unit that adjusts the weight balance around the output shaft, the rotation of the electric motor can be transmitted to the camshaft only by the speed reduction mechanism, so that there is no possibility of vibration in the speed reduction mechanism.

  The balance adjusting portion may be an axial through hole provided on the eccentric side of the eccentric shaft portion.

  When a roller bearing is externally fitted to the eccentric shaft portion and the roller is brought into rolling contact with the outer diameter surface of the outer ring, the balance adjusting portion is notched in the outer diameter portion provided on the eccentric side of the eccentric shaft portion. It can be.

  The notch in the outer diameter portion of the eccentric shaft portion may be a portion in which the outer diameter portion is notched flat with a string.

  The cutout of the outer diameter part of the eccentric shaft part may be a part of the outer diameter part notched in a concave shape.

  By setting the balance adjusting portion to have the same cross-sectional dimension in the axial direction of the eccentric shaft portion, the balance adjusting portion can be easily formed by pressing or forging.

  The variable valve timing device of the present invention is a cylindrical portion of a housing in which a speed reduction mechanism for transmitting rotation of an output shaft of an electric motor to a camshaft is provided, an eccentric shaft portion having a circular cross section is provided on the output shaft of the electric motor, and integrated with a sprocket. An inner gear having a plurality of cam ridges formed at equal pitches in the circumferential direction is provided opposite to the eccentric shaft portion on the inner diameter surface of the inner surface, 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. The number of dividing points when an intermediate shaft having an annular cage portion provided with a pocket for holding the roller is coaxially arranged with the camshaft and the annular cage portion is divided at equal pitches in the circumferential direction. However, a pocket for holding the roller is provided at all or a part of the dividing points that differ by one from the number of cam peaks, and the shape of one pitch of the cam peaks is set to the output shaft of the electric motor. When you rotate the The rollers held in the shaft are matched with the outer envelope of the trajectory of revolving along the outer diameter surface of the eccentric shaft portion, and the revolution of these rollers is transmitted to the camshaft via the intermediate shaft. Since the balance adjustment part that adjusts the weight balance around the output shaft is provided in the eccentric shaft part of the motor output shaft, the rotation of the electric motor can be transmitted to the camshaft only by the speed reduction mechanism and can be designed compactly. In addition, vibration can be prevented from occurring in the speed reduction mechanism.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 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 having a plurality of cam ridges 8 a formed on the inner diameter surface of the cylindrical portion of the housing 7 integrated with the sprocket 2 is fitted and fixed so as to face the outer diameter surface of the outer ring 6 a of the ball bearing 6. The intermediate shaft 10 having an annular retainer portion 10b provided with pockets 10a for holding 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 coaxial with the camshaft 1. The 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 through the intermediate shaft 10 by a mechanism described later. .

  On the eccentric side of the eccentric shaft portion 4a, a through hole 4b is provided as a balance adjusting portion for adjusting the weight balance around the shaft center of the output shaft 4. The through hole 4b has the same cross-sectional dimension in the axial direction of the output shaft 4 including the eccentric shaft portion 4a. The output shaft 4 of the electric motor 3 is supported on the housing 7 by a ball bearing 12, and the intermediate shaft 10 is supported on the housing 7 by a ball bearing 13 via an extended cylindrical portion of the internal gear 8.

  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.

  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.

  3 and 4 show a second embodiment. This variable valve timing device has the same basic configuration as that of the first embodiment, and the balance adjusting unit that adjusts the weight balance around the axis of the output shaft 4 is the eccentric of the eccentric shaft 4a. The difference is that a part of the outer diameter portion is formed into a notch 4c that is cut into a flat shape with a string on the side. The notch 4c has the same cross-sectional dimension in the axial direction of the eccentric shaft portion 4a. Other parts are the same as those of the first embodiment.

  FIG. 5 shows a modified example of the notch 4c as the balance adjusting portion. The notch 4c is formed by notching the outer diameter portion on the eccentric side of the eccentric shaft portion 4a in a concave shape, and has the same cross-sectional dimension in the axial direction of the eccentric shaft portion 4a.

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 longitudinal cross-sectional view which shows the variable valve timing apparatus of 2nd Embodiment Sectional view along line IV-IV in FIG. Sectional drawing which shows the modification of the notch of FIG. 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 Camshaft 2 Sprocket 3 Electric motor 4 Output shaft 4a Eccentric shaft part 4b Through-hole 4c Notch 5 Reduction mechanism 6 Ball bearing 6a Outer ring 7 Housing 8 Internal gear 8a Cam crest 9 Roller 10 Intermediate shaft 10a Pocket 10b Cage part 11 Spline 12, 13 Ball bearing

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. In the variable valve timing device thus configured, the speed reduction 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 peaks are formed on the inner diameter surface of the cylindrical portion of the housing integrated with the sprocket. An internal gear formed at an equal pitch in the circumferential direction is provided to face the eccentric shaft portion, and these opposed eccentricity An intermediate shaft having an annular retainer portion provided with a pocket for retaining a plurality of rollers that are in rolling contact with the outer diameter surface of the portion and the internal gear is disposed coaxially with the camshaft, and the annular retainer portion is A pocket for holding the roller is provided at a position where the number of division points when divided at equal pitches in the circumferential direction is different from the number of the cam crests by all or a part of the division points. When the output shaft of the electric motor is rotated, the roller held by the pocket revolves along the outer diameter surface of the eccentric shaft portion. The revolutions of these rollers are transmitted to the camshaft via the intermediate shaft in conformity with the radial envelope, and the weight balance around the output shaft is provided on the eccentric shaft portion of the output shaft of the electric motor. A balance adjustment unit is provided to adjust the Variable valve timing apparatus according to claim and.   The variable valve timing device according to claim 1, wherein the balance adjusting portion is an axial through hole provided on an eccentric side of the eccentric shaft portion.   A rolling bearing is externally fitted to the eccentric shaft portion, the roller is brought into rolling contact with the outer diameter surface of the outer ring, and the balance adjusting portion is provided with a notch in the outer diameter portion provided on the eccentric side of the eccentric shaft portion. The variable valve timing device according to claim 1.   4. The variable valve timing device according to claim 3, wherein a notch in the outer diameter portion of the eccentric shaft portion is formed by cutting a part of the outer diameter portion flat with a string.   The variable valve timing device according to claim 3, wherein a notch in the outer diameter portion of the eccentric shaft portion is formed by notching a part of the outer diameter portion in a concave shape.   The variable valve timing device according to claim 2, wherein the balance adjusting portion has the same cross-sectional dimension in the axial direction of the eccentric shaft portion.

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