JP2010048233A - Variable valve timing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable an electrically operated variable valve timing device having resistance to a reverse input, to be designed in a compact size. <P>SOLUTION: The variable valve timing device is provided with a reverse output control unit that controls a reverse output from a camshaft 1 to an output shaft 4. In the reverse output control unit, a reduction gear 5 for transmitting rotation of the output shaft 4 of an electric motor 3 to the camshaft 1 is configured such that a plurality of rollers 9 held in pockets 10a are made to be in rolling contact with an eccentric shaft section 4a provided to the output shaft 4 and with an inner gear 8 provided to a circular tube section of a housing 7 integrated with a sprocket 2, wherein the above pockets 10a are formed in a retainer section 10b of an intermediate shaft 10 by dividing the retainer section 10b at equal intervals at split points the number of which is different by one than the number of cam crests 8a of the inner gear 8. The construction above allows, when the output shaft 4 is rotated by one rotation, the rollers 9 to revolve by one pitch of the cam crests 8a along the outer diameter surface of the eccentric shaft section 4a, and the revolution of the rollers 9 is transmitted to the camshaft 1 through the intermediate shaft 10. <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 addition, the electric motor has a problem that it has no resistance against reverse input compared to a hydraulically driven actuator.

  Accordingly, an object of the present invention is to enable a compact design of an electric variable valve timing device having resistance against reverse input.

  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 Matching the outer diameter side envelope of the trajectory revolving along the outer diameter surface, the revolution of these rollers is transmitted to the camshaft via the intermediate shaft, and the reverse to the output shaft of the electric motor Provide reverse input suppression means to suppress input It has adopted the configuration.

  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 diameter side envelope of the trajectory revolving along the outer diameter surface of the part, and the reverse input to the output shaft of the electric motor By providing a reverse input suppression means that suppresses the rotation, the rotation of the electric motor can be transmitted to the camshaft only by the speed reduction mechanism, and an electric variable valve timing device having resistance against reverse input can be designed in a compact manner. did.

  The said reverse input suppression means shall set a negative clearance to the rolling bearing which supports the output shaft of the said electric motor, and shall give rotational resistance to this rolling bearing.

  The reverse input suppression means is provided with a contact seal on a rolling bearing that supports the output shaft of the electric motor, and imparts rotational resistance to the rolling bearing to suppress reverse input to the output shaft. You can also.

  The reverse input suppression means indirectly suppresses reverse input to the output shaft by setting a rotational width to the roller so that the width of the pocket of the cage portion of the intermediate shaft is equal to or less than the diameter of the roller. It can also be.

  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.

  A pocket for holding the roller of the cage part is provided at a position where a part of the dividing point is thinned out, and by making this thinning interval uniform in the circumferential direction, the rotation balance of the intermediate shaft is kept well, The number of pockets and the number of rollers can be reduced.

  By forming the outer diameter surface of the eccentric shaft portion with which the roller is in rolling contact with the outer diameter surface of the outer ring of the rolling bearing fitted on the eccentric shaft portion, slip between the roller and the outer diameter surface of the eccentric shaft portion is reduced. The intermediate shaft can be smoothly rotated.

  The inner ring of the rolling bearing externally fitted to the eccentric shaft portion is formed integrally with the eccentric shaft portion, thereby making it easy to assemble the rolling bearing without the need for press-fitting into the eccentric shaft portion of the inner ring and reducing the number of parts. Can be reduced.

  By forming the internal gear on the inner diameter surface of the cylindrical portion of the housing with a separate internal gear that is fitted and fixed to the inner diameter surface of the cylindrical portion, the processing of the internal gear can be facilitated.

  By using a four-point contact type ball bearing as the rolling bearing that supports the intermediate shaft, it is possible to suppress the whirling of the intermediate shaft.

  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 reverse input suppression means for suppressing the reverse input to the output shaft of the motor is provided, the electric variable valve timing device that can transmit the rotation of the electric motor to the camshaft only by the speed reduction mechanism and has resistance to the reverse input. It can be designed compactly.

  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. .

  The output shaft 4 of the electric motor 3 is supported on the housing 7 by a ball bearing 12 having a negative gap, and the intermediate shaft 10 is supported by a four-point contact type ball bearing 13 through an extended cylindrical portion of the internal gear 8. It is supported by the housing 7. Therefore, the reverse input from the camshaft 1 to the output shaft 4 is suppressed by the rotational resistance of the ball bearing 12 having a negative clearance, and the swinging of the intermediate shaft 10 is suppressed by the four-point contact type ball bearing 13. Is done.

  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.

  FIG. 3 shows a modification of the ball bearing 12 that supports the output shaft 4 of the electric motor 3. The ball bearing 12 is provided with contact seals 12c at both ends of the outer ring 12a. By bringing these contact seals 12c into contact with the inner ring 12b, rotational resistance is imparted to the ball bearing 12 and output from the camshaft 1. The reverse input to the shaft 4 is suppressed. Depending on the magnitude of the reverse input, the contact-type seal 12c can be mounted only on one side.

  4 and 5 show a second embodiment. The basic configuration of the variable valve timing device is the same as that of the first embodiment, and the inner ring of the ball bearing 6 that is externally fitted and fixed to the eccentric shaft portion 4a is formed integrally with the eccentric shaft portion 4a. The cage portion 10b of the intermediate shaft 10 is insert-molded with a resin material, the width of the pocket 10a is set to be equal to or less than the diameter of the roller 9, and rotational resistance is applied to the roller 9 to output from the camshaft 1. The difference is that the reverse input to the shaft 4 is indirectly suppressed. Other parts are the same as those of the first embodiment.

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. FIG. 1 is a partially omitted longitudinal sectional view showing a modification of the ball bearing that supports the output shaft of the electric motor of FIG. The longitudinal cross-sectional view which shows the variable valve timing apparatus of 2nd Embodiment Sectional drawing along the VV line 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 5 Reduction mechanism 6 Ball bearing 6a Outer ring 7 Housing 8 Internal gear 8a Cam mountain 9 Roller 10 Intermediate shaft 10a Pocket 10b Cage part 11 Spline 12 Ball bearing 12a Outer ring 12b Inner ring 12c Contact seal 13 Ball bearing

Claims (10)

  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. In accordance with the radial envelope, the revolution of these rollers is transmitted to the camshaft via the intermediate shaft, and reverse input suppression means for suppressing reverse input to the output shaft of the electric motor is provided. Variable valve timing Apparatus.   2. The variable valve timing device according to claim 1, wherein the reverse input suppression means sets a negative clearance in a rolling bearing that supports the output shaft of the electric motor and gives rotational resistance to the rolling bearing. 3.   2. The variable valve timing device according to claim 1, wherein the reverse input suppression means provides a contact-type seal on a rolling bearing that supports the output shaft of the electric motor, and provides rotational resistance to the rolling bearing.   2. The variable valve timing device according to claim 1, wherein the reverse input suppression unit applies a rotational resistance to the roller by setting a width of a pocket of the cage portion of the intermediate shaft to be equal to or less than a diameter of the roller.   The variable valve timing apparatus according to claim 4, wherein the cage portion of the intermediate shaft is made of a resin material.   The variable valve timing according to any one of claims 1 to 5, wherein a pocket for holding the roller of the cage portion is provided at a position where a part of the dividing point is thinned out, and the thinning interval is made uniform in the circumferential direction. apparatus.   The variable valve timing device according to any one of claims 1 to 6, wherein an outer diameter surface of an eccentric shaft portion to which the roller is in rolling contact is formed by an outer diameter surface of an outer ring of a rolling bearing that is externally fitted to the eccentric shaft portion.   The variable valve timing device according to claim 7, wherein an inner ring of a rolling bearing externally fitted to the eccentric shaft portion is formed integrally with the eccentric shaft portion.   9. The variable valve timing device according to claim 1, wherein the internal gear on the inner diameter surface of the cylindrical portion of the housing is formed by a separate internal gear that is fitted and fixed to the inner diameter surface of the cylindrical portion.   The variable valve timing device according to any one of claims 1 to 9, wherein the rolling bearing that supports the intermediate shaft is a four-point contact type ball bearing.

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