JP2013199938A - Speed reduction mechanism with electric motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of an edge load of a roller, and seizing and abrasion in a rolling face of the roller, in a variable valve timing device transmitting rotation of an electric motor, with only a speed reduction mechanism making the roller roll on an outer diameter face of an eccentric shaft part and an internal gear.SOLUTION: In a speed reduction mechanism 5 transmitting rotation of an output shaft 4 of an electric motor 3 to a camshaft 1, a plurality of rollers 9 which are retained in pockets 10a disposed to a retainer part 10b of an intermediate shaft 10 are rolled on an eccentric shaft part 4a disposed to an output shaft 4 and an internal gear 8 disposed to a cylinder part of a housing 7 to transmit revolution of the rollers 9 to the camshaft 1 through the intermediate shaft 10, and crownings preventing an edge load are disposed on both end parts of a body part of the roller 9.

Description

  The present invention relates to a reduction mechanism with an electric motor that is mainly used in 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. 16A and 16B, 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 can be designed in a compact manner. However, the roller held in the cage section has a high surface pressure reduction. As a result of slipping, the roller contacts the outer diameter surface and the internal gear of the eccentric shaft, which may cause edge load on the roller and seizure and wear on the roller's rolling contact surface. There is a problem that the durability life is shortened.

  Accordingly, an object of the present invention is a variable valve timing device that transmits the rotation of an electric motor to a camshaft only by a reduction mechanism that rolls the roller in contact with an outer diameter surface of an eccentric shaft portion and an internal gear. Generation, and seizure and wear on the rolling contact surface of the roller.

  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 with the outer diameter side envelope of the trajectory revolving along the outer diameter surface, the revolutions of these rollers are transmitted to the camshaft through the intermediate shaft, and at least both ends of the body of the roller With crowning It was adopted.

  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 at least at both ends of the body of the roller By providing the crowning, the rotation of the electric motor can be transmitted to the camshaft only by the speed reduction mechanism, and the edge load is prevented from occurring on the roller that is in rolling contact with the outer diameter surface of the eccentric shaft portion of the speed reduction mechanism and the internal gear.

  Further, 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 relative to each other on a coaxial basis. And the rotation of the output shaft of the electric motor arranged coaxially with the camshaft is transmitted to the camshaft through a speed reduction mechanism, and the rotational phase difference of the camshaft with respect to the sprocket is changed, and the valve In the variable valve timing apparatus configured to change the opening / closing timing of the motor, 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 on the inner diameter surface of the cylindrical portion of the housing integrated with the sprocket. An internal gear having a plurality of cam ridges formed at equal pitches in the circumferential direction is provided to face the eccentric shaft portion. An intermediate shaft having an annular cage portion provided with a pocket for holding a plurality of rollers that are in rolling contact with the outer diameter surface of the eccentric shaft portion and the internal gear is arranged coaxially with the camshaft, and the annular The number of division points when the cage portion of the cage is divided at equal pitches in the circumferential direction is set at a position where all or some of the division points differ from the number of the cam crests by thinning out the rollers. A pocket to be held is provided, and when the output shaft of the electric motor is rotated so that the shape of one pitch of the cam crest is rotated, the roller held in the pocket extends along the outer diameter surface of the eccentric shaft portion. Matching the outer diameter side envelope of the trajectory of revolution, the revolution of these rollers is transmitted to the camshaft via the intermediate shaft, and an infinite number of minute recesses are formed on the surface of at least the body of the roller. Randomly formed on the surface roughness Configuration in which the parameter SK value -1.6 or less were also adopted.

  That is, similar to the variable valve timing device, the rotation of the electric motor is transmitted to the camshaft only by a speed reduction mechanism for rolling the roller to the outer diameter surface of the eccentric shaft portion and the internal gear. By forming innumerable minute recesses at least on the surface of the body portion and setting the parameter SK value of the surface roughness to −1.6 or less, the outer diameter surface of the eccentric shaft portion and the internal gear A sufficient oil film was formed on the rolling contact surface of the roller to prevent seizure and wear on the rolling contact surface of the roller.

As shown in FIG. 5, the surface roughness parameter SK value is a value representing the relativity of the amplitude distribution curve with respect to the average line of the surface roughness, and is defined by the following equation (1). .
SK = ∫ (x−x ₀ ) ³ · P (x) dx / σ ³ (1)
Here, x: height of roughness, x ₀ : average height of roughness, P (x): probability density function of amplitude of roughness, and σ: mean square roughness.

  The parameter SK value is positive when there are many peaks in the amplitude distribution curve with respect to the average surface roughness line as shown in FIG. 5A, and the peaks and valleys are equal as shown in FIG. 5B. When the number of valleys is large as shown in FIG. Therefore, by setting the parameter SK value to negative −1.6 or less, a sufficient oil film can be formed on the rolling contact surface of the roller.

  The roller is first quenched after carbonitriding and cooled to a temperature below the A1 transformation point, and then subjected to a heat treatment that is second-quenched at a lower temperature than the first quenching to refine the austenite crystal grains of the roller. Thus, the rolling fatigue strength of the roller can be increased. Therefore, the roller can be shortened to be more compact, and the friction torque can be reduced to improve the transmission efficiency.

  By using grease or oil having extreme pressure properties for lubricating the roller, seizure and wear on the rolling contact surface of the roller can be more reliably prevented.

  By providing a coating with a low coefficient of friction on at least the inner surface of the pocket of the cage portion, it is possible to reduce torcross due to sliding contact with the inner surface of the pocket of the roller. As the film having a low coefficient of friction, a phosphate film, a resin film, or the like can be employed.

  The output shaft of the electric motor includes an output shaft support bearing that coaxially supports the cam shaft, and a rolling bearing in which an axial center of the output shaft support bearing is externally fitted to the eccentric shaft portion. It is possible to adopt a configuration that is positioned within the range of the bearing width or within the range of the bearing width of the intermediate shaft support bearing provided on the outer peripheral portion of the intermediate shaft.

  According to this configuration, the output shaft of the electric motor is supported by the output shaft support bearing within the range of the bearing width of the rolling bearing or within the range of the bearing width of the intermediate shaft support bearing. For this reason, the shaft width dimension of the output shaft and the intermediate shaft of the electric motor in the housing can be shortened, and the variable valve timing device can be thinned.

  The output shaft of the electric motor includes an output shaft cylindrical portion in order to position the axial center of the output shaft support bearing within a bearing width range of a rolling bearing that is externally fitted to an eccentric shaft portion, and the output shaft cylindrical portion It is possible to adopt a configuration in which the eccentric shaft portion is formed on the outer periphery of the output shaft and the output shaft support bearing is fitted between the output shaft cylindrical portion and the cam shaft.

  With this configuration, the output shaft support bearing is positioned within the range of the shaft width dimension of the eccentric shaft portion of the output shaft. For this reason, the shaft width dimension of the output shaft of the electric motor in the housing is shortened, and the variable valve timing device can be thinned.

  On the other hand, in order to position the center in the axial direction of the output shaft support bearing within the range of the bearing width of the intermediate shaft support bearing, the output shaft of the electric motor includes an output shaft cylindrical portion, and the output shaft cylindrical portion and the intermediate shaft A configuration in which the output shaft support bearing is fitted between the intermediate shaft cylindrical portion of the shaft can be employed.

  If it does in this way, an output-shaft support bearing will be located in the range of the width dimension of the intermediate shaft cylindrical part of an intermediate shaft. For this reason, the shaft dimension including the output shaft and the intermediate shaft of the electric motor in the housing is shortened, and the variable valve timing device can be thinned.

  Further, 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, the slip between the roller and the outer diameter surface of the eccentric shaft portion is prevented. Can be suppressed.

  In addition, if the rolling bearing externally fitted to the eccentric shaft portion is a roller bearing without a cage, and the inner ring of the roller bearing is formed by the outer peripheral portion of the eccentric shaft portion, the number of rollers is increased. Thus, the load capacity in the radial direction can be increased. Further, as the number of rollers increases, the contact surface pressure between the roller end surface and the collar can be lowered, so that the load capacity in the axial direction can be improved and the wear between them can be reduced.

  When the rolling bearing adopts a configuration in which it is a roller bearing without a cage, the eccentric shaft portion is an eccentric ring externally fitted to the output shaft of the electric motor, and the inner ring of the roller bearing is the eccentric ring. It can be set as the structure formed by. If the eccentric ring is externally fitted to the output shaft of the electric motor, the output shaft does not need to be eccentric in the outer peripheral portion, and the eccentric shaft portion can be easily provided.

  In addition, the outer diameter end of the cylindrical roller can be crowned to prevent edge load. Furthermore, for the purpose of improving strength and wear resistance, it is possible to subject the raceway surface of the roller bearing to induction hardening.

  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 locus 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 crowning is provided on at least both ends of the body of the motor, the rotation of the electric motor can be transmitted to the camshaft only with the speed reduction mechanism, and the edge load is applied to the roller that is in rolling contact with the outer diameter surface of the eccentric shaft portion of the speed reduction mechanism Can be prevented from occurring.

  Also, the variable valve timing device of the present invention, similar to the variable valve timing device, can rotate the electric motor to the camshaft only by a speed reduction mechanism that rolls the roller on the outer diameter surface of the eccentric shaft portion and the internal gear. With the variable valve timing device that transmits, since the surface ruggedness of the surface roughness parameter SK value is set to -1.6 or less, innumerable minute recesses are randomly formed on the surface of at least the body of the roller. Surface seizure and wear can be prevented.

A longitudinal sectional view showing the first embodiment of the variable valve timing device Sectional view along the II-II line of FIG. a is a front view showing the roller of FIG. 1, b is an expanded plan view showing an enlarged surface of the body of a Schematic diagram showing the heat treatment pattern of the roller of FIG. Conceptual diagram illustrating definition of parameter SK value of surface roughness Longitudinal sectional view showing Modification 1 of the first embodiment Sectional drawing along the VII-VII line of FIG. Longitudinal sectional view showing Modification 2 of the first embodiment Sectional drawing along the IX-IX line of FIG. Longitudinal sectional view showing the second embodiment Longitudinal sectional view showing Modification 1 of the second embodiment Longitudinal sectional view showing Modification 2 of the second embodiment Longitudinal sectional view showing the third embodiment Longitudinal sectional view showing Modification 1 of the third embodiment Longitudinal sectional view showing Modification 2 of the third embodiment a is a longitudinal sectional view showing a conventional variable valve timing device, and b is a sectional view taken along line XVI-XVI of a.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. 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 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.

  As shown in FIG. 3A, the roller 9 is provided with crowning 9a at both ends of the body. Therefore, it is possible to prevent the edge load of the roller 9 that is in rolling contact with the outer diameter surface of the outer ring 6 a and the inner gear 8. The crowning 9a may be provided over the entire length of the trunk.

  As shown in an enlarged view in FIG. 3B, the surface of the body of the roller 9 is randomly formed with innumerable minute recesses 9b, and the parameter SK value of the surface roughness is −1.6 or less. It is said that. In addition, an oil having extreme pressure is used for lubricating the roller 9. Accordingly, a sufficient oil film is formed on the rolling contact surface of the roller 9 between the outer diameter surface of the outer ring 6a and the internal gear 8, and seizure and wear on the rolling contact surface of the roller 9 are prevented.

  The roller 9 is made of high carbon chromium bearing steel SUJ2 as a raw material, as shown in FIG. 4, after first quenching at a temperature T1 after carbonitriding and cooling to a temperature below the A1 transformation point, rather than the primary quenching. The austenite crystal grain of the microstructure is refined | miniaturized by the heat processing which secondary quenches in oil at low temperature T2, and is tempered.

  Although not shown, the cage portion 10b is subjected to a phosphate coating treatment as a low friction coefficient coating including the inner surface of the pocket 10a that holds the roller 9.

  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.

  In the first embodiment, a ball bearing is applied to the rolling bearing 6 fitted on the eccentric shaft portion 4 a of the output shaft 4 of the electric motor 3. For example, as a first modification of the rolling bearing 6, FIG. As shown in 6 and 7, needle roller bearings without a cage can be applied.

  In this needle roller bearing, the inner ring is formed by the outer peripheral portion of the eccentric shaft portion 4a, and the raceway surface 4d is formed on the outer peripheral portion of the eccentric shaft portion 4a. The outer diameter end of the cylindrical roller 6c is crowned to prevent the occurrence of edge loading.

  Moreover, in order to improve the lubricity at the time of rolling, the cylindrical roller 6c is subjected to processing (HL processing) for providing innumerable minute concave recesses on the surface (particularly the rolling surface). As a processing method, a finished surface having a desired surface roughness can be obtained by special barrel polishing, but shot peening, shot blasting, or the like may be used. Further, the cylindrical roller 6c may be subjected to a carbonitriding process (AS process) to increase the hardness and improve the wear resistance.

  On both axial sides of the raceway surface 4d on the outer peripheral portion of the eccentric shaft portion 4a, a pair of flange portions for restricting the movement of the cylindrical roller 6c in the axial direction is formed. Of the pair of collar portions, the collar portion opposite to the intermediate shaft 10 with respect to the raceway surface 4d is formed by an annular collar ring 14 along the eccentric shaft portion 4a.

  Moreover, induction hardening can be performed on the raceway surface of the outer ring 6a and the raceway surface 4d of the eccentric shaft portion 4a. In this case, the quenched portion is cured, and the strength and wear resistance are improved.

  In the first modification, by using the roller bearing 6 as a needle roller bearing without a cage, it is possible to increase the number of cylindrical rollers 6c and increase the load capacity in the radial direction. Further, as the number of cylindrical rollers 6c increases, the contact surface pressure between the roller end face and the collar can be lowered, so that the load capacity in the axial direction can be improved and the wear between them can be reduced.

  As a variation 2 of the rolling bearing 6, instead of applying a needle roller bearing to the rolling bearing 6 and forming the inner ring of the needle roller bearing at the outer peripheral portion of the eccentric shaft portion 4a, the output of the electric motor 3 is used. It can be formed by an eccentric ring 6b fitted on the shaft 4 (see FIGS. 8 and 9).

  The eccentric ring 6b is made of metal, and a raceway surface 4d is formed on the outer periphery of the eccentric ring 6b. A pair of collar portions for restricting movement of the cylindrical roller 6c in the axial direction are formed on both sides in the axial direction of the raceway surface 4d. Is formed. Of the pair of collar portions, the collar portion opposite to the intermediate shaft 10 with respect to the raceway surface 4d is formed by an annular collar ring 14 along the eccentric ring 6b. The eccentric ring 6b is heat-treated only on this. For this reason, it is not necessary to heat-process the output shaft 4 of the electric motor 3, and the influence of the dimensional accuracy by the heat processing of the output shaft 4 can be suppressed.

  In addition, the outer diameter end portion of each cylindrical roller 6c is crowned in order to prevent the occurrence of edge load, and high frequency is applied to the raceway surface of the outer ring 6a of the rolling bearing 6 and the raceway surface 4d of the eccentric ring 6b. Quenched. In this case, the quenched portion is cured, and the strength and wear resistance are improved.

  In the second modification, if the eccentric ring 6b is externally fitted to the output shaft 4 of the electric motor 3, the output shaft 4 does not need to be eccentric in the outer peripheral portion, and the eccentric shaft portion 4a can be easily provided. Further, a needle roller bearing having the eccentric ring 6 b as an inner ring can be assembled in advance, and the needle roller bearing can be fitted and fixed to the outside of the output shaft 4 of the electric motor 3. For this reason, it becomes possible to improve assemblability.

  The support structure of the output shaft 4 of the electric motor 3 is supported by the ball bearing 12 on the housing 7, and the rotation of the output shaft 4 of the electric motor 3 is transmitted to the camshaft 1 via the speed reduction mechanism 5. As long as the rotational phase difference of the camshaft 1 with respect to the sprocket 2 can be changed, it can be changed as appropriate. As an example, FIG. 10 shows a second embodiment of the present invention. In the following description, differences from the first embodiment will be mainly described, and the same reference numerals are used for the same conceivable configurations, and description thereof will be omitted.

  In the second embodiment, a ball bearing 6 (externally fitted to the eccentric shaft portion 4a at the center in the axial direction of a ball bearing 12 (output shaft support bearing) that supports the output shaft 4 of the electric motor 3 coaxially with the camshaft. It is located within the range of the bearing width of the rolling bearing.

  More specifically, the output shaft 4 of the electric motor 3 includes an output shaft cylindrical portion 4c, and an eccentric shaft portion 4a is formed on the outer periphery of the output shaft cylindrical portion 4c. The output shaft cylindrical portion 4c and the camshaft 1 The ball bearing 12 is fitted between the two. By fitting the ball bearing 12, the center of the ball bearing 12 in the axial direction can be positioned within the range of the bearing width of the ball bearing 6 that is externally fitted to the eccentric shaft portion 4a.

  As a result, the ball bearing 12 is positioned in the axial width center of the eccentric shaft portion 4 a of the output shaft 4 of the electric motor 3. For this reason, the axial length of the output shaft 4 of the electric motor 3 in the housing 7 can be made shorter than in the case of the first embodiment, and the variable valve timing device can be made thinner. it can.

  Further, the intermediate shaft 10 is supported by the housing 7 by ball bearings 13, and the sprocket 2 is formed so that its axial width is smaller than that of the first embodiment. The variable valve timing device is also made thinner by the shape of the sprocket 2.

  In the second embodiment, a ball bearing is applied to the rolling bearing 6 fitted to the eccentric shaft portion 4a of the output shaft cylindrical portion 4c provided in the output shaft 4 of the electric motor 3, but the first described above. Similar to the rolling bearing 6 of the embodiment, it can be appropriately modified.

  As Modification 1 of the rolling bearing 6, for example, as shown in FIG. 11, a needle roller bearing without a cage is applicable.

  In the first modification, the same configuration as that of the rolling bearing 6 in the first modification in the first embodiment is applied. That is, in the needle roller bearing, the inner ring is formed by the outer peripheral portion of the eccentric shaft portion 4a, and the raceway surface 4d is formed on the outer peripheral portion of the eccentric shaft portion 4a. On both sides in the axial direction of the raceway surface 4d, a pair of flange portions for restricting the movement of the cylindrical roller 6c in the axial direction are formed. Of the pair of collar portions, the collar portion opposite to the intermediate shaft 10 with respect to the raceway surface 4d is formed by an annular collar ring 14 along the eccentric shaft portion 4a.

  In addition, the outer diameter end portion of the cylindrical roller 6c is crowned to prevent the occurrence of edge load, and induction hardening is applied to the raceway surface of the outer ring 6a and the raceway surface 4d of the eccentric shaft portion 4a. Has been.

  As the second modification of the rolling bearing 6, a needle roller bearing without a cage is applied, and the same configuration as that of the rolling bearing 6 of the second modification in the first embodiment can be applied. That is, as shown in FIG. 12, the inner ring of the needle roller bearing is formed by an eccentric ring 6 b that is externally fitted to the output shaft 4 of the electric motor 3.

  A raceway surface 4d is formed on the outer peripheral portion of the eccentric ring 6b, and a pair of collar portions for restricting movement of the cylindrical roller 6c in the axial direction are formed on both axial sides of the raceway surface 4d. Of the pair of collar portions, the collar portion opposite to the intermediate shaft 10 with respect to the raceway surface 4d is formed by an annular collar ring 14 along the eccentric ring 6b.

  In addition, the outer diameter end portion of each cylindrical roller 6c is crowned in order to prevent the occurrence of edge load, and high frequency is applied to the raceway surface of the outer ring 6a of the rolling bearing 6 and the raceway surface 4d of the eccentric ring 6b. Quenched.

A third embodiment of the present invention will be described with reference to FIG.
In this embodiment, the ball bearing 13 (output shaft support bearing) that supports the output shaft 4 of the electric motor 3 coaxially with the camshaft is provided on the outer periphery of the intermediate shaft 10 at the center in the axial direction. The intermediate shaft support bearing) is positioned within the range of the bearing width.

  That is, the output shaft 4 of the electric motor 3 includes the output shaft cylindrical portion 4c, and the intermediate shaft 10 is formed integrally with the intermediate shaft cylindrical portion 10c having the cage portion 10b and the end of the intermediate shaft cylindrical portion 10c on the sprocket 2 side. The intermediate shaft ring portion 10d.

  A ball bearing 13 is provided on the outer peripheral portion of the intermediate shaft cylindrical portion 10c, and the ball bearing 12 is fitted between the outer peripheral portion of the output shaft cylindrical portion 4c of the output shaft 4 on the inner peripheral portion of the intermediate shaft cylindrical portion 10c. Is done. Further, the inner peripheral portion of the intermediate shaft annular portion 10d is provided so as to be integrally rotatable with respect to the cam shaft 1. By fitting the ball bearing 12, the center of the ball bearing 12 in the axial direction is positioned within the range of the bearing width of the ball bearing 13 that is externally fitted to the intermediate shaft 10.

  Thereby, the ball bearing 12 is positioned in the axial width range of the intermediate shaft 10 (the intermediate shaft cylindrical portion 10c and the intermediate shaft annular portion 10d) at the center in the axial direction, and the output shaft 4 of the electric motor 3 and The shaft width dimension of the intermediate shaft 10 is smaller than that of the first embodiment, and the variable valve timing device can be made thinner.

  In this embodiment, the axial width of the sprocket 2 is smaller than that of the first embodiment, as in the case of the second embodiment. For this reason, the variable valve timing device is also made thinner by the shape of the sprocket 2.

  In the third embodiment, a ball bearing is applied to the rolling bearing 6 that is externally fitted to the eccentric shaft portion 4a provided on the output shaft 4 of the electric motor 3, but the rolling bearing 6 of the first embodiment described above. Similarly to the above, it can be appropriately modified. As a first modification of the rolling bearing 6, for example, as shown in FIG. 14, a needle roller bearing without a cage is applicable.

  In the first modification, the same configuration as that of the rolling bearing 6 in the first modification in the first embodiment is applied. That is, in the needle roller bearing, the inner ring is formed by the outer peripheral portion of the eccentric shaft portion 4a, and the raceway surface 4d is formed on the outer peripheral portion of the eccentric shaft portion 4a. On both sides in the axial direction of the raceway surface 4d, a pair of flange portions for restricting the movement of the cylindrical roller 6c in the axial direction are formed. Of the pair of collar portions, the collar portion opposite to the intermediate shaft 10 with respect to the raceway surface 4d is formed by an annular collar ring 14 along the eccentric shaft portion 4a.

  In addition, the outer diameter end portion of the cylindrical roller 6c is crowned to prevent the occurrence of edge load, and induction hardening is applied to the raceway surface of the outer ring 6a and the raceway surface 4d of the eccentric shaft portion 4a. Has been.

  As the second modification of the rolling bearing 6, a needle roller bearing without a cage is applied, and the same configuration as that of the rolling bearing 6 of the second modification in the first embodiment can be applied. That is, as shown in FIG. 15, the inner ring of the needle roller bearing is formed by an eccentric ring 6 b that is externally fitted to the output shaft 4 of the electric motor 3.

  A raceway surface 4d is formed on the outer peripheral portion of the eccentric ring 6b, and a pair of flange portions for restricting the axial movement of the cylindrical roller 6c is formed on both axial sides of the raceway surface 4d. Of the pair of collar portions, the collar portion opposite to the intermediate shaft 10 with respect to the raceway surface 4d is formed by an annular collar ring 14 along the eccentric ring 6b.

  In addition, the outer diameter end portion of each cylindrical roller 6c is crowned in order to prevent the occurrence of an edge load. Quenched.

1 Camshaft 2 Sprocket 3 Electric Motor 4 Output Shaft 4a Eccentric Shaft (Inner Ring)
4b Through-hole 4c Output shaft cylindrical portion 4d Raceway surface 5 Reduction mechanism 6 Ball bearing (rolling bearing)
6a Outer ring 6b Eccentric ring (inner ring)
6c cylindrical roller 7 housing 8 internal gear 8a cam crest 9 roller 9a crowning 9b recess 10 intermediate shaft 10a pocket 10b cage portion 10c intermediate shaft cylindrical portion 10d intermediate shaft ring portion 11 spline 12 ball bearing (output shaft support bearing)
13 Ball bearing (intermediate shaft support bearing)
14 collar

Claims (13)

An electric motor;
An eccentric shaft portion having a circular cross section provided on the output shaft of the electric motor;
A rolling bearing externally fitted to the eccentric shaft portion;
An internal gear provided facing the outer diameter surface of the outer ring of the rolling bearing and having a plurality of cam ridges formed at equal pitches in the circumferential direction;
A plurality of rollers in rolling contact with the outer diameter surface of the outer ring of the rolling bearing and the internal gear;
It consists of an intermediate shaft having an annular cage part provided with a pocket for holding these rollers,
In the pocket, the number of dividing points when the annular cage part is divided at a constant pitch in the circumferential direction is thinned out at all positions or a part of the dividing points which differ from the number of the cam crests by one. In place,
The outer diameter of the locus in which the roller held in the pocket revolves along the outer diameter surface of the outer ring of the rolling bearing when the output shaft of the electric motor is rotated in the shape of one pitch of the cam crest. In accordance with the side envelope, the revolution of these rollers shall be transmitted to the intermediate shaft,
Only one eccentric shaft portion is provided on the output shaft of the electric motor,
Reduction mechanism with electric motor.   The reduction mechanism with an electric motor according to claim 1, wherein crowning is provided on at least both ends of the body of the roller.   An infinitesimal number of minute recesses are randomly formed on the surface of at least the body of the roller, and an SK value, which is a value representing the relativity of the amplitude distribution curve with respect to the average line of the surface roughness, is −1.6. The reduction mechanism with an electric motor according to claim 1, wherein:   4. The roller according to claim 1, wherein after the carbonitriding treatment, the roller is first quenched and cooled to a temperature lower than the A1 transformation point, and then subjected to a second quench at a lower temperature than the first quench. Reduction mechanism with electric motor.   The speed reduction mechanism with an electric motor according to any one of claims 1 to 4, wherein grease or oil having extreme pressure is used for lubricating the roller.   The reduction mechanism with an electric motor according to any one of claims 1 to 5, wherein a film having a low coefficient of friction is provided on at least an inner surface of the pocket of the cage portion.   The output shaft of the electric motor includes an output shaft support bearing that supports the output shaft coaxially with the intermediate shaft, and a bearing width of a rolling bearing in which an axial center of the output shaft support bearing is externally fitted to the eccentric shaft portion. The reduction with an electric motor according to any one of claims 1 to 6, characterized in that it is positioned within a range of a bearing width of an intermediate shaft support bearing provided on an outer peripheral portion of the intermediate shaft. mechanism.   The output shaft of the electric motor includes an output shaft cylindrical portion, the eccentric shaft portion is formed on the outer peripheral portion of the output shaft cylindrical portion, and the output shaft support bearing is fitted between the output shaft cylindrical portion and the camshaft. The speed reduction mechanism with an electric motor according to claim 7, wherein the speed reduction mechanism is combined.   The output shaft of the electric motor includes an output shaft cylindrical portion, and the output shaft support bearing is fitted between the output shaft cylindrical portion and the intermediate shaft cylindrical portion of the intermediate shaft. A reduction mechanism with an electric motor according to 1.   The rolling bearing externally fitted to the eccentric shaft portion is a roller bearing without a cage, and an inner ring of the roller bearing is formed at an outer peripheral portion of the eccentric shaft portion. A reduction mechanism with an electric motor according to claim 1.   The rolling bearing externally fitted to the eccentric shaft portion is a roller bearing without a cage, the eccentric shaft portion is an eccentric ring externally fitted to the output shaft of the electric motor, and the inner ring of the roller bearing is the eccentric The speed reduction mechanism with an electric motor according to claim 1, wherein the speed reduction mechanism is formed by a ring.   The speed reduction mechanism with an electric motor according to claim 10 or 11, wherein the outer diameter end of the roller bearing is crowned.   The speed reduction mechanism with an electric motor according to any one of claims 10 to 12, wherein the raceway surface of the roller bearing is subjected to induction hardening.

Images