JP5288312B2 - 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. 9A and 9B, 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 speed reduction mechanism and can be designed compactly. However, the roller that is in rolling contact with the outer diameter surface of the eccentric shaft portion is provided inside. When passing through the top of the cam crest of the gear, it may come into contact with the top of the sharp cam crest with a large contact pressure, and noise may be generated. In addition, cracks may occur in the cam crest due to excessive contact pressure. Furthermore, there is a problem that it is difficult to make a tool shape such as a broach for processing a sharp cam crest on an internal gear, or a die shape such as press punching or die forging. When processing by press punching, the life of the mold is shortened.

  Accordingly, an object of the present invention is a variable valve timing device that has been developed previously that transmits the rotation of an electric motor to a camshaft using only a speed reduction mechanism. When a roller passes the top of a cam crest of an internal gear, an excessive contact pressure is required. Is to prevent this from occurring.

  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 to each other. 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. The variable valve timing device is adapted to transmit the revolutions of these rollers to the camshaft via the intermediate shaft so as to match the outer diameter side envelope of the inner gear, and at the top of the cam crest of the internal gear, the eccentricity Rolling contact with the outer diameter surface of the shaft Employing the configuration as a gap is formed between the La.

  In other words, at the top of the cam crest of the internal gear, a gap is formed between the outer diameter surface of the eccentric shaft portion and the roller that is in rolling contact, so that the rotation of the electric motor is transmitted to the camshaft only by the speed reduction mechanism. In the previously developed variable valve timing system, excessive contact pressure was not generated when the roller passed the top of the cam crest of the internal gear.

  The means for forming a gap with the roller at the top of the cam crest of the internal gear can be easily formed with the roller by notching the top of the cam crest. . In addition, it is possible to easily make a tool shape such as a broach for processing a cam crest in an internal gear, or a die shape such as press punching or die forging. When processing by press punching, the life of the mold can be extended.

  The notch shape at the top of the cam crest can be a flat shape.

  The notch shape at the top of the cam crest may be an R shape that is convex or concave toward the inner diameter side.

  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.

  The cam crest of the separate internal gear can be formed by broach grinding, press punching or die forging.

  The strength and wear resistance of the cam crest can be improved by induction-hardening the cam crest portion of the internal gear.

  In the cage portion of the intermediate shaft, the rollers in the pocket are usually held in a state where a gap is formed between the inner surfaces of the pocket in both circumferential directions so that the rollers can roll. When the intermediate shaft retainer is configured to include an elastic member that supports the roller in the pocket while pressing the roller in the circumferential direction from both sides in the circumferential direction, the roller supported from the circumferential direction by the elastic member is the intermediate shaft retainer. It is reliably supported in the pocket of the part, and the behavior of the roller can be stabilized.

  When adopting a configuration in which the cage portion of the intermediate shaft is provided with the elastic member, a configuration is adopted in which storage recesses for the elastic member are formed on both inner walls facing the circumferential direction of the pocket of the cage portion of the intermediate shaft. can do. If it does in this way, an elastic member can be easily arrange | positioned in the holder | retainer part of an intermediate shaft by accommodating an elastic member in an accommodation recessed part.

  Further, if the elastic member supporting the roller is a coil spring, it is preferable that stress is not concentrated on the end portion in contact with the roller, and even if the elastic member is broken, the function is not immediately lost completely.

  A portion where a gap is formed between the inner gear and the roller at the top of the cam crest can be coated with a buffer material in order to absorb shock and vibration caused by the collision of the roller during operation.

  In the variable valve timing device of the present invention, a gap is formed between the outer diameter surface of the eccentric shaft portion and the roller that is in rolling contact with the top portion of the cam crest of the internal gear. This is a variable valve timing device that was previously developed to transmit to the camshaft only, so that excessive contact pressure does not occur when the roller passes the top of the cam crest of the internal gear, Generation of cracks can be prevented.

1 is a longitudinal sectional view showing a variable valve timing device according to a first embodiment. Sectional view along line XX in FIG. Sectional drawing which expands and shows the principal part of FIG. Sectional drawing which shows the state which coated the buffer material on the top part of the cam mountain of FIG. a and b are sectional views showing modifications of the notch shape of the cam crest in FIG. Cross-sectional view showing a variable valve timing device of Embodiment 2 Sectional drawing which expands and shows the principal part of FIG. Sectional drawing along the YY 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 ZZ of a.

  A variable valve timing device according to a first embodiment of the present invention will be described below with reference to FIGS.

  In the first embodiment, as shown in FIG. 1, 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 are relatively rotated. The rotation of the output shaft 4 of the electric motor 3 arranged coaxially with the camshaft 1 is transmitted to the camshaft 1 via the speed reduction mechanism 5, and the rotational phase difference of the camshaft 1 with respect to the sprocket 2 is transmitted. To change the opening / closing timing of the intake valve.

  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.

  A portion of the cam crest 8a of the internal gear 8 is processed by broach grinding and subjected to induction hardening. The cam peak 8a can be processed by press punching or die forging. 29 cam ridges 8a are formed at equal pitches in the circumferential direction, and pockets 10a holding the rollers 9 are divided with respect to the dividing points when the annular cage portion 10b is divided into 30 at equal pitches in the circumferential direction. It is provided at 15 positions thinned out every other one, 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 an enlarged view in FIG. 3, the top of the cam crest 8a of the internal gear 8 is notched in a flat shape, and the roller 9 held in the pocket 10a and rolling with the outer ring 6a of the ball bearing 6 is cam cam crest. When passing through the top of 8a, a gap δ is formed between them. Therefore, an excessive contact pressure does not occur when the roller 9 passes the top of the cam peak 8a.

  Further, a portion where a gap δ is formed between the top of the cam crest 8a of the internal gear 8 and the roller 9 absorbs shock and vibration caused by the collision of the roller 9 when the roller 9 passes. Material 14 can be coated (see FIG. 4).

  Since the wear of the top of the cam crest 8a of the internal gear 8 due to the impact and vibration of the roller 9 can be reduced by the coating of the buffer material 14, the life of the internal gear 8 can be extended. Examples of the buffer material 14 include urethane resin and synthetic rubber.

  5A and 5B show a modification of the notch shape at the top of the cam crest 8a. FIG. 5A shows a notch shape having a concave R shape toward the inner diameter side, and FIG. 5B shows a R shape convex toward the inner diameter side.

  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 the first embodiment, the number N of the dividing points of the cage portion 10b is one more than the number of the cam peaks 8a. Therefore, when the output shaft 4 makes one rotation, each roller 9 is rotated by one pitch of the cam peaks 8a. Revolving around, the reduction ratio of the output shaft 4 and the intermediate shaft 10 becomes 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.

A variable valve timing device according to a second embodiment of the present invention will be described with reference to FIGS.
The second embodiment is different from the first embodiment in that the cage portion 10b of the intermediate shaft 10 includes an elastic member that supports the roller 9 in the pocket 10a while pressing the roller 9 from both sides in the circumferential direction. The other configuration is the same as that of the first embodiment, and the same reference numerals are used for the same configuration, and the description of the configuration and the operation effect is omitted.

  In the second embodiment, the retainer portion 10b of the intermediate shaft 10 is formed with a housing recess 16 of a coil spring 15 that is an elastic member on both inner walls facing the pocket 10a in the circumferential direction. The coil spring 15 is put in the storage recess 16 in a compressed state, and the roller 9 in the pocket 10a is pressed from both sides in the circumferential direction by its restoring force.

  As the elastic member, the coil spring 15 is not necessarily required, and a member capable of pressing the roller 9 from both sides in the circumferential direction is applicable. The coil spring 15 is preferable because stress hardly concentrates on the end in contact with the roller, and even if it is broken, the function is not lost completely immediately.

  As shown in FIG. 7, the storage recess 16 is open to the outside in the radial direction of the circumferential cage portion 10b of the cage portion 10b. For this reason, the coil spring 15 can be easily put into the housing recess 16 from the outside in the radial direction while the roller 9 is held in the pocket 10a.

  In addition, two corners 17 (see FIG. 8) formed by the inner surface facing the circumferential direction and the inner side surface facing the axial direction of the storage recess 16 are rounded, and the cage portion 10b is cracked due to stress concentration. Is preventing.

  Furthermore, the two corners 18 formed by the inner side surface of the storage recess 16 facing the axial direction and the inner surface of the pocket 10a in the circumferential direction are also rounded. This prevents the roller 9 from touching the corner 18 during operation and being damaged.

  In the second embodiment, the coil spring 15 in the housing recess 16 reliably supports the roller 9 in the pocket 10a while pressing the roller 9 from both sides in the circumferential direction, so that the behavior of the roller in the pocket 10a is stabilized. As a result, it is possible to suppress the occurrence of vibration during operation.

  The speed reduction mechanism of the speed reduction mechanism 5 of the second embodiment is the same as that of the first embodiment. As indicated by the arrows in FIG. 6, the output shaft 4 rotates clockwise and the outer diameter of the eccentric outer ring 6a is increased. Assuming that the minimum portion C of the annular space between the surface and the internal gear 8 on which the cam crest 8a is formed is at a position of 0 ° clockwise and the maximum portion B is at a position of 180 °, the output shaft 4 is rotated. The minimum portion C and the maximum portion B move clockwise, and the right half of the annular space tends to be narrow and the left half of the annular space tends to be wide. 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 an arrow 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.

  Also in the second embodiment, the number N of the dividing points of the cage portion 10b is one more than the number of the cam peaks 8a. Therefore, when the output shaft 4 makes one rotation, each roller 9 is equivalent to one pitch of the cam peaks 8a. Revolving clockwise, 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.

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 Portion 11 Spline 12, 13 Ball bearing 14 Buffer material 15 Coil spring 16 Recessed recess 17, 18 Corner

Claims (11)

  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, a gap is formed between the outer diameter surface of the eccentric shaft portion and the roller that is in rolling contact at the top of the cam crest of the internal gear. To be formed Variable valve timing apparatus according to claim and.   2. The variable valve timing device according to claim 1, wherein the means for forming a gap between the top of the cam crest of the internal gear and the roller cuts out the top of the cam crest.   The variable valve timing device according to claim 2, wherein a notch shape at the top of the cam crest is a flat shape.   The variable valve timing device according to claim 2, wherein a notch shape at the top of the cam crest is an R shape that is convex or concave toward the inner diameter side.   5. 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 of 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 claim 5, wherein the cam crest of the separate internal gear is formed by broach grinding, press punching, or die forging.   The variable valve timing device according to claim 1, wherein a cam crest portion of the internal gear is induction-hardened.   8. The variable valve timing device according to claim 1, wherein the retainer portion of the intermediate shaft includes an elastic member that supports the roller in the pocket while pressing the roller in the circumferential direction from both sides in the circumferential direction.   9. The variable valve timing device according to claim 8, wherein a housing concave portion of the elastic member is formed on both inner walls facing the circumferential direction of the pocket of the cage portion of the intermediate shaft.   The variable valve timing device according to claim 8, wherein the elastic member is a coil spring.   11. The variable valve timing device according to claim 1, wherein a buffer material is coated on a portion that forms a gap with the roller at the top of the cam crest of the internal gear.

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