Valve opening / closing time control device

Abstract

Valve opening / closing time control device (1) with: a drive-side rotating component (A) which is rotatably arranged about a rotational axis (X) and rotates synchronously with a crankshaft (2) of an internal combustion engine (E); a driven-side rotary component (B) which is rotatably arranged about the axis of rotation (X) and is integrally connected with a camshaft (3) for opening and closing a valve (3B) of the internal combustion engine (E) in a state in which the driven-side rotary component (B) is rotatable relative to the drive-side rotary component (A); a phase adjustment mechanism (C) that specifies a relative rotational phase between the drive-side rotary component (A) and the driven-side rotary component (B) by means of a drive force of an electric actuator (M), wherein the phase adjustment mechanism (C) comprises a ring gear (21), an inner gear (22) and a drive shaft (24), the ring gear (21) being arranged coaxially with the axis of rotation (X) and having an internal toothed section (21A), the inner gear (22) being arranged coaxially with an eccentric axis (Y) arranged parallel to the axis of rotation (X) and having an external toothed section (22A) which engages with a portion of the internal toothed section (21A) of the ring gear (21), the drive shaft (24) being fitted into the inner gear (22) and being coaxial with the axis of rotation (X), the phase adjustment mechanism (C) being designed as a differential reduction gear mechanism in which the inner gear (22) rotates about the axis of rotation (X) while in a state in which the drive shaft (24) is driven by a driving force of the electric actuator (M) to rotate about the axis of rotation (X) is driven to rotate around the eccentric axis (Y); a preloading component (25) provided on an outer circumference of the drive shaft (24), wherein the preloading component (25) exerts a preload force to engage the external toothed section (22A) of the inner gear (22) with the internal toothed section (21A) of the ring gear (21); and a limiting section (R) which is provided on the drive shaft (24) to limit a displacement of the inner wheel (22) in a direction in which the inner wheel (22) is separated from the ring gear (21) against the preload force of the preloading component (25), in which the drive shaft (24) has an eccentric surface (24BS) defined with respect to the eccentric axis (Y) and in which a recessed section (24D) is provided, wherein a spring (25) serving as the preload element is fitted into the recessed section (24D), the boundary section (R) is formed by at least one of opposite outer edge sections of the recess section (24D) in a circumferential direction of the eccentric surface (24BS), wherein at least one of the opposite outer edge sections projects outwards in a radial direction.

Description

TECHNICAL AREA

[0001] This disclosure relates generally to a valve opening / valve closing time control device. BACKGROUND

[0002] A known valve opening / closing timing control device, which specifies a relative rotational phase between a drive-side rotary component and a driven-side rotary component by a driving force of an electric actuator, is described, for example, in JP 2008-38 886 A, hereinafter referred to as Document 1. More precisely, Document 1 discloses a differential reduction gear mechanism with a ring gear (an inner gear section) arranged coaxially with an axis of rotation, an inner gear (a planet gear or a second gear component) arranged coaxially with an eccentric axis parallel to the axis of rotation, and a drive shaft (a planet carrier) fitted internally to the inner gear such that an external toothed section of the inner gear engages with a portion of an internal toothed section of the ring gear.

[0003] The valve opening / closing timing control device disclosed in Document 1 further comprises a preloading element (a spring element) located in an external area of ​​the drive shaft at a position that does not coincide with or overlap a position where the external toothed section of the inner gear engages with the internal toothed section of the ring gear (i.e., does not coincide with or overlap in an eccentric direction). The preloading element applies a preload force to engage the external toothed section of the inner gear with the internal toothed section of the ring gear.

[0004] Furthermore, in the valve opening / closing time control device disclosed in document 1, a recessed section (a receiving section) is provided on the outer circumference of the drive shaft, so that a leaf spring, which forms the spring component, is fitted into the recessed section to exert the preload force.

[0005] According to the valve opening / closing timing control device disclosed in Document 1, the inner gear (the planet gear or the second gear component) is supported by at least three sections, which include a section where an inner circumferential surface of a central bore of the inner gear and a line of application of the elastic force intersect, a section where the inner circumferential surface of the central bore of the inner gear and an outer circumferential surface of the drive shaft (of the planet carrier) come into contact with each other, and a section where the inner gear and the ring gear (the internal toothing section) are in mesh with each other.

[0006] With the aforementioned design, even when a cam oscillation torque is transmitted to the valve opening / closing timing control device, the clearance of the inner gear is limited, thus preventing the generation of abnormal noise. That is to say, according to the valve opening / closing timing control device disclosed in Document 1, the inner gear is supported at the three sections to stabilize its position, while the gap at a toothed section between the inner gear and the ring gear is also reduced, thus limiting the generation of abnormal noise and phase variation.

[0007] At this point, in an assumed design where the inner gear is arranged to rotate about the eccentric axis, and the toothed section of the inner gear and the toothed section of the ring gear are engaged in a state where a preload force is applied in the direction in which the toothed sections of the inner and outer gears engage with each other, the aforementioned engagement state is maintained by the large preload force. Consequently, the generation of abnormal noise is limited, and phase variation is also limited.

[0008] Nevertheless, the high preload force causes the tooth surfaces of the inner gear and the tooth surfaces of the ring gear to come into strong contact with each other, generating frictional resistance that can increase the rotational load. Consequently, the response speed of the valve opening / closing timing control device can be reduced.

[0009] Therefore, there is a need for a valve opening / closing time control device that limits the generation of abnormal noise at a gear section without increasing the preload force of a preload component and that limits phase variation.

[0010] JP 2009- 215 954 A discloses a valve timing control device in which a contour of an eccentric outer circumferential surface part is elliptically formed, with a secondary axis direction in a base diameter direction. SUMMARY

[0011] A valve opening / closing time control device according to the invention has the features of claim 1. Further developments of the invention are specified in the dependent claims.

[0012] Accordingly, in a design where the preloading component is used with a low preload force (small spring constant), the displacement of the outer tooth section of the inner gear relative to the inner tooth section of the ring gear is limited by the limiting section when the outer tooth section is displaced away from the inner tooth section due to the application of a cam oscillation torque. This prevents the inner gear from moving beyond the limiting section's setpoint. Abnormal noise at the tooth sections is suppressed, as is phase variation. Additionally, as the cam oscillation torque decreases, the preload force of the preloading component engages the outer tooth section of the inner gear appropriately with the inner tooth section of the ring gear.

[0013] Additionally, without using a preload component with a large preload force (large spring constant), the external and internal gear sections are prevented from drifting significantly apart. An increase in torsional load due to frictional resistance between a tooth face of the inner gear and a tooth face of the ring gear is limited, and a deterioration in the response speed of the valve opening / closing timing control device is inhibited. Accordingly, without increasing the preload force of the preload component, the generation of abnormal noise at the gear teeth is limited, and phase variation is restricted. The torsional load is reduced, and the response speed is ensured. Due to a reduction in the elasticity of the preload component, its service life may be increased.

[0014] The drive shaft has an eccentric surface defined with respect to the eccentric axis, in which a recessed section is provided into which a spring, serving as the preload element, is fitted. The boundary section is formed by at least one of opposing outer edge sections of the recessed section in a circumferential direction of the eccentric surface, wherein at least one of opposing outer edge sections projects radially outwards.

[0015] Due to the limiting section obtained by the outer edge section of the recess section on the drive shaft, which projects in the radial direction and into which the spring (the preload component) is fitted, the displacement of the inner wheel can be accommodated at a suitable position.

[0016] The inner wheel is supported on the eccentric surface by a bearing which has an inner circumferential surface onto which the preload force is applied by the preloading component, wherein the limiting section is designed to contact the inner circumferential surface of the bearing in order to limit a displacement of the inner wheel.

[0017] Accordingly, even when a design is used in which the inner wheel is rotatably mounted on the eccentric surface via the bearing, for example a ball bearing, the preload force of the preloading component is applied to the inner wheel, the displacement of which, in a case where the inner wheel is displaced in the direction away from the ring gear, is limited by the limiting section.

[0018] The limiting section is formed by a limiting component that is carried on the outer circumference of the drive shaft.

[0019] The limiting section is formed by the limiting component, which is mounted on the outer circumference of the drive shaft. Thus, for example, several limiting components with different projection lengths are provided, so that the appropriate projection length is used depending on the positional accuracy of the drive shaft. Consequently, the distance between a projection surface of the limiting component and an inner circumference of the ring gear can be specified appropriately. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The preceding and additional features and characteristics of this disclosure will become clearer with reference to the following detailed description and the accompanying drawings. These show: Fig. 1 a cross-sectional view of a valve opening / closing time control device according to a first embodiment disclosed herein; Fig. 2 a cross-sectional view along a line II-II in Fig. 1; Fig. 3 a cross-sectional view along a line III-III in Fig. 1; Fig. 4 a perspective exploded view of the valve opening / closing time control device according to the first embodiment; Fig. 5 an enlarged cross-sectional view showing a relationship between a boundary section and a spring; Fig. 6 an enlarged cross-sectional view showing a boundary state obtained by the boundary section; Fig. 7 an enlarged cross-sectional view showing a relationship between the limiting section and the spring according to a second embodiment disclosed herein; and Fig. 8 a perspective view showing a boundary piece according to the second embodiment. DETAILED DESCRIPTION

[0021] A first embodiment disclosed herein is described with reference to the accompanying drawings. As in Fig. Figures 1 to 4 show a valve opening / closing timing control device 1 configured to include an input rotary component A rotating synchronously with a crankshaft 2 of an internal combustion engine E, an output rotary component B rotating integrally with an intake crankshaft 3, and a phase adjustment mechanism C specifying a relative rotational phase between the input rotary component A and the output rotary component B by means of a driving force of a phase control motor M, which serves as an example of an electric actuator.

[0022] The internal combustion engine E is designed as a four-stroke engine, with pistons 4 being housed in respective cylinder bores in a cylinder block and the pistons 4 being connected to the crankshaft 2 by respective connecting rods 5. A timing belt 6, which can alternatively be a timing chain, is wound, for example, around an output pulley 2S of the crankshaft 2 of the internal combustion engine E and a drive pulley 11S of the drive-side rotating component A.

[0023] With the aforementioned design, the valve opening / closing timing control device 1 rotates as a whole about a rotational axis (center of rotation) X when the internal combustion engine E is operated. The output-side rotating component B can be displaced or moved relative to the input-side rotating component A by actuating the phase adjustment mechanism C in the same direction as the rotation of the valve opening / closing timing control device 1 or in an opposite direction.

[0024] In the valve opening / closing timing control device 1, a drive of the phase control motor M is controlled by a control unit such as an ECU. Due to the aforementioned control, the phase adjustment mechanism C specifies the relative rotational phase between the drive-side rotating component A and the output-side rotating component B, which enables the opening and closing timing of each intake valve 3B to be controlled by a cam section 3A of the intake camshaft 3.

[0025] The drive-side rotary component A has a structure in which an outer housing 11, on which the drive disk 11S is provided, and a front plate 12 are fastened to one another by several fastening bolts 13. The output-side rotary component B and the phase adjustment mechanism C, which is designed as a hypotrochoid reduction gear serving as an example of a differential reduction gear mechanism, are accommodated in an interior space defined by the outer housing 11.

[0026] The output-side rotary component B is formed by a ring gear 21, which has an internal toothed section 21A with a number of internal teeth. The phase adjustment mechanism C comprises the ring gear 21, an inner gear 22, which has an external toothed section 22A with a number of external teeth, wherein the external toothed section 22A engages with the internal toothed section 21A of the ring gear 21, a drive shaft 24 fitted to the inner gear 22, and a connecting component 30, which serves as a connecting mechanism that connects the inner gear 22 to the input-side rotary component A.

[0027] As in Fig. As shown in Figure 2, the ring gear 21 is arranged coaxially with the axis of rotation X, while the inner gear 22 is arranged coaxially with an eccentric axis (an eccentric axis center) Y, which is arranged parallel to the axis of rotation X. A portion of the external tooth section 22A of the inner gear 22 engages with a portion of the internal tooth section 21A of the ring gear 21. The number of teeth of the external tooth section 22A of the inner gear 22 is one less (one tooth less) than the number of teeth of the internal tooth section 21A of the ring gear 21.

[0028] As in Fig. As shown in Figures 1 to 4, the phase control motor M (electric motor) is supported on the internal combustion engine E by a support frame 7 such that an output shaft Ma of the motor M is arranged coaxially with the axis of rotation X.

[0029] The ring gear 21 has a structure in which an output plate 21P, arranged orthogonally to the axis of rotation X, is integrally provided with an annular section on which the internal toothed section 21A is provided. The ring gear 21 is connected to the intake camshaft 3 such that, in a state in which a connecting bolt 35 is inserted, positioned in a central bore section of the output plate 21P and screwed to the intake camshaft 3, it is coaxial with the axis of rotation X.

[0030] The drive shaft 24 has a first support section 24A at a first end (an outer end) along the axis of rotation X and a second support section 24B at a second end (an inner end) along the axis of rotation X. The first support section 24A forms an outer circumferential surface with respect to the axis of rotation X. The second support section 24B forms an outer circumferential surface with respect to the eccentric axis Y. A single recess section 24D is formed on an outer circumference of the second support section 24B such that a spring 25, which serves as a preload element, fits into the recess section 24D. An imaginary straight line connecting the axis of rotation X and the eccentric axis Y is, as shown in Fig. Figure 5 is shown as a deviation direction line L. A preload direction F, in which the preload force is applied by the spring 25 to the inner wheel 22 (more precisely, to an inner ring of a second bearing 27, which is positioned on a radially inner side), is aligned with the deviation direction line L.

[0031] The spring 25 is designed as a U-shaped spring plate having a pair of plate-shaped sections positioned essentially parallel to each other. One of the plate-shaped sections is in contact with a bottom surface of the recessed section 24D, while the other of the plate-shaped sections is in contact with an inner circumferential surface S of the second bearing 27, which serves as a bearing.

[0032] The drive shaft 24 has a bore section 24C defined with respect to the axis of rotation X. A pair of engagement grooves 24T is provided on one circumference of the bore section 24C, extending parallel to the axis of rotation X, such that an engagement component 28 of the output shaft Ma of the phase control motor M engages with the pair of engagement grooves 24T.

[0033] In addition, a single lubrication groove 24G, extending parallel to the axis of rotation X, is provided on the circumference of the bore section 24C. A single lubrication flow channel 24R, extending from the lubrication groove 24G to an outer surface of the drive shaft 24, and a pair of lubrication flow channels 24R, extending from the pair of engagement grooves 24T to the outer surface of the drive shaft 24, are also provided on the circumference of the bore section 24C.

[0034] As in Fig. As shown in Figure 1, a first bearing 26 is arranged between an opening at a center of the front plate 12 and the first support section 24A of the drive shaft 24, so that the drive shaft 24 is supported in such a way that it is rotatable about the axis of rotation X with respect to the drive-side rotating component A.

[0035] As in Fig. As shown in Figure 2, the second bearing 27 is formed by a ball bearing and is arranged between an inner circumference of the inner wheel 22 and the second support section 24B of the drive shaft 24, so that the inner wheel 22 is supported in such a way that it is rotatable about the eccentric axis Y. The preload force of the spring 25 is applied to the inner circumferential surface S of the second bearing 27. In addition, a C-ring 29 (see Figure 2) is also present. Fig. 1 and Fig. 4), which serves as a retaining ring to prevent the spring 25 from being removed from the second support section 24B of the drive shaft 24 or from being disengaged from it.

[0036] Accordingly, the inner gear 22 is mounted so that it can rotate about the eccentric axis Y, while part of the outer toothed section 22A is engaged with part of the inner toothed section 21A of the ring gear 21, as shown in Fig. 2 is shown, and the engagement is maintained by the preload force of the spring 25. An operation for specifying the relative rotational phase between the drive-side rotary component A and the output-side rotary component B of the valve opening / closing time control device 1 is described below.

[0037] The connecting component 30, which forms the connection mechanism, is formed by pressing a plate component, such as in Fig. 3 and Fig. The connecting element 30 is shown in Figure 4. It integrally comprises a pair of first engagement arms 31 projecting outwards with respect to the axis of rotation X, a pair of second engagement arms 32 projecting in a direction orthogonal to the axis of rotation X in the direction in which the first engagement arms 31 project, and an annular section 33 connecting the pair of first engagement arms 31 and the pair of second engagement arms 32. Recessed sections 32A are formed on the respective second engagement arms 32 such that they open towards a center of the connecting element 30 (i.e., in the direction of the axis of rotation X).

[0038] The outer housing 11, which forms the drive-side rotating component A, has a pair of through slots AT extending radially from the inner chamber of the housing 11 to an outer chamber of the same with respect to the axis of rotation X. A pair of first guide surfaces G1 is provided at each of the through slots AT and extends in the same direction as the through slots AT, with the two first guide surfaces G1 extending parallel to each other. A pair of connecting sections 22T is formed projecting from an end face of the inner gear 22 such that they are opposite each other with respect to the eccentric axis Y. A pair of second guide surfaces G2 is provided at each of the connecting sections 22T and extends radially with respect to the axis of rotation X.

[0039] With the aforementioned configuration, the first engagement arms 31 of the connecting component 30 engage with the respective through-grooves AT, and the engagement recess sections 32A of the second engagement arms 32 of the connecting component 30 engage with the respective connecting sections 22T, so that the connecting component 30 can operate as an Oldham coupling.

[0040] In addition, a pair of linear sections of each of the first engagement arms 31 comes into contact with the pair of first guide surfaces G1 of each of the through grooves AT, and a pair of linear sections of each of the engagement recess sections 32A of the second engagement section 32 comes into contact with the pair of second guide surfaces G2 of each of the connecting sections 22T.

[0041] As in Fig. As shown in Figure 4, the groove depth L1 of the through-groove AT is specified such that it is sufficiently greater than the thickness L2 of the first engagement arm 31. Thus, while a front surface of the first engagement arm 31 and the front plate 12 are in contact with each other, a distance is defined between a rear surface of the first engagement arm 31 and a bottom section of the through-groove AT.

[0042] Furthermore, several projecting sections 12A are formed on an inner surface of the front plate 12. The several projecting sections 12A come into contact with an end face of the ring gear 21, so that the ring gear 21 is positioned in the direction along the axis of rotation X.

[0043] The valve opening / closing timing control device 1 includes the control unit for controlling the phase control motor M. To maintain the relative rotational phase between the drive-side rotating component A and the output-side rotating component B, the drive shaft 24 is driven to rotate at a speed that is essentially equal to the rotational speed of the intake camshaft 3.

[0044] On the other hand, to specify the relative rotational phase between the drive-side rotating component A and the output-side rotating component B to a target phase, the output shaft Ma of the phase control motor M is driven to rotate at a faster speed or a lower speed than the rotational speed of the inlet camshaft 3.

[0045] When the drive shaft 24 rotates with the driving force of the phase control motor M in a state where the internal combustion engine E is stopped, the second support section 24B rotates about the axis of rotation X, causing the inner gear 22 to begin rotating about the axis of rotation X. As the inner gear 22 rotates about the axis of rotation X, a position where the external toothed section 22A of the inner gear 22 and the internal toothed section 21A of the ring gear 21 are engaged shifts along an inner circumference of the ring gear 21. Consequently, the inner gear 22 receives a force to set the inner gear 22 into rotation about the eccentric axis Y.

[0046] That is, in a case where the inner wheel 22 rotates once around the axis of rotation X, a rotational force is generated and exerted which causes the inner wheel 22 to rotate by an angle which corresponds to a difference between the number of teeth of the internal toothed section 21A of the ring gear 21 and the number of teeth of the external toothed section 22A of the inner wheel 22 (in the embodiment, an angle which corresponds to one tooth).

[0047] As mentioned previously, the connecting element 30 is designed to limit the rotation of the inner gear 22 relative to the outer housing 11, thus preventing rotation of the inner gear 22 relative to the outer housing 11. Consequently, due to the torque applied to the inner gear 22, the ring gear 21 rotates relative to the outer housing 11. Since the ring gear 21 is connected to the intake camshaft 3, its rotation relative to the outer housing 11 adjusts the rotational phase of the intake camshaft 3.

[0048] More precisely, when the inner gear 22 completes one revolution around the axis of rotation X, the intake camshaft 3 rotates relative to the outer housing 11 by the angle corresponding to the difference in the number of teeth of the internal toothed section 21A of the ring gear 21 and the external toothed section 22A of the inner gear 22. Therefore, the rotational phase of the intake camshaft 3 is adjustable with a high reduction ratio.

[0049] The internal combustion engine E has a belt housing that accommodates the toothed belt 6 for driving the intake camshaft 3 and an exhaust camshaft. The valve opening / closing timing control device 1 is located in the belt housing. Due to the aforementioned design and positional relationship, a portion of the lubricant supplied to the camshaft flows from the opening in the center of the front plate 12 to the bore section 24C of the drive shaft 24 and is supplied, for example, via the lubrication channels 24R to each section of the inner space of the outer housing 11, thus ensuring the smooth operation of the phase adjustment mechanism C. The lubricant, which provides lubrication in the manner described above, is discharged to the outside from the through-grooves AT provided in the drive-side rotating component A.

[0050] As in Fig. Figure 5 shows that limiting sections R are provided to limit movement of the inner wheel 22 in a direction away from the ring wheel 21 against the preload force of the spring 25 (of the preload component) on the outer circumference of the drive shaft 24.

[0051] The boundary sections R are formed by a pair of boundary projections 41 which are integrally provided on the second support section 24B, wherein the boundary projections 41 are formed by circumferentially opposing outer edge sections of the recess section 24D which project outwards (i.e. radially outwards).

[0052] As in Fig. As shown in Figure 5, in a state where the external tooth section 22A of the inner gear 22 is engaged with the internal tooth section 21A of the ring gear 21, a projecting end of each of the limiting projections 41 of the limiting section R is located away from the inner circumferential surface S of the second bearing 27 (more precisely, from the inner circumferential surface of the inner section of the second bearing 27). With the aforementioned design, a distance (gap) is defined between the projecting end of the limiting section 41 and the inner circumferential surface S of the second bearing 27. When the inner gear 22 is displaced away from the ring gear 21, the projecting end of each of the limiting sections 41 comes into contact with the inner circumferential surface S of the second bearing 27 (i.e., in contact with the inner circumferential surface of the inner section of the second bearing 27), thus limiting the displacement of the inner gear 22.

[0053] This means that if a cam oscillation torque greater than a set value acts on the valve opening / closing timing control device 1, the inner gear 22 is displaced against the preload force of the spring 25 in the direction in which the external toothed section 22A moves away from the internal toothed section 21A of the ring gear 21. In addition, as shown in Fig. Figure 6 shows the two limiting projections 41 of the limiting sections R in contact with the inner circumferential surface S of the second bearing 27, so that the displacement of the inner wheel 22 is limited (i.e., a limited state is obtained by the limiting sections R).

[0054] As previously mentioned, since the preload direction F of the spring 25 coincides with the deviation direction L, the limiting projections 41 of the limiting sections R limit the displacement of the inner gear 22 in a direction opposite to the preload direction F. In addition, the distance between the projecting end of each of the limiting sections 41 and the inner circumferential surface S of the second bearing 27 is specified such that it is less than or equal to a distance between the drive shaft 24 and the inner surface S of the second bearing 27, when an overall tolerance obtained by summing dimensional tolerances of the ring gear 21, the inner gear 22, and the second bearing 27 in the radial direction is an upper limit.This means that as long as the valve opening / closing timing control device 1 is designed such that it has the ring gear 21, the inner gear 22, the second bearing 27 and the drive shaft 24 with dimensions within the respective tolerance ranges, the distance between the projecting end of each of the limiting projections 41 and the inner circumferential surface S of the second bearing 27 is reliably defined and formed.

[0055] The second bearing section 24B of the drive shaft 24 has an outer circumferential surface 24BS (an example of an eccentric surface) with a circular shape about the eccentric axis X. The outer diameter of the outer circumferential surface 24BS is specified to be slightly smaller than the inner diameter of the second bearing 27. A pair of guide projections 42 is provided on a section of the outer circumferential surface 42BS, with the section having a largest diameter in a direction perpendicular to the deviation direction line L. The guide projections 42 extend outwards such that they are in slight contact with the inner circumferential surface S of the second bearing 27. The distance between the outer circumferential surface 24BS and the inner circumferential surface S is actually small, but is exaggerated in the drawings.

[0056] With the aforementioned design, even when the external toothed section 22A of the inner gear 22 is engaged with the internal toothed section 21A of the ring gear 21, a gap is formed between a section (a surface) of the outer circumferential surface 24BS, which is positioned radially opposite the recessed section 24D, and the inner circumferential surface S of the second bearing 27. Accordingly, the external toothed section 22A is engaged with the internal toothed section 21A in a state where the inner circumferential surface S of the second bearing 27 is not in contact with the outer circumferential surface 24BS of the second bearing section 24B.

[0057] In addition, since the pair of guide projections 42 is slightly in contact with the inner circumferential surface S of the second bearing 27, the second bearing 27 is held in a suitable position based on the drive shaft 24.

[0058] In the valve opening / closing timing control device 1, a bushing, serving as a sliding bearing, can be used for each of the first bearing 26 and the second bearing 27. Additionally, without the second bearing 27, a configuration can be used in which the ring gear 21 is directly supported on the second bearing section 24B of the drive shaft 24.

[0059] In a case where the cam oscillation torque is applied to the valve opening / closing timing control device 1 during the operation of the internal combustion engine E, a force is generated and exerted to move or displace the external tooth section 22A of the inner gear 22 in a direction that moves the external tooth section 22A away from the internal tooth section 21A. To limit the aforementioned displacement (separation), the preload force of the spring 25 can be increased. However, with the increased preload force, a tooth surface of each tooth of the internal tooth section 21A and a tooth surface of each tooth of the external tooth section 22A come into strong contact (pressure contact), thus increasing the frictional resistance between the tooth surfaces. Therefore, not only does the rotational load on the valve opening / closing timing control device 1 increase, but its response speed may also deteriorate (i.e.,, response speed may decrease).

[0060] To solve the aforementioned problems, the preload force of spring 25 can be reduced. However, reducing the preload force can cause significant separation between the internal toothed section 21A of the ring gear 21 and the external toothed section 22A of the inner gear 22 when camshaft torque is applied. Repeated contact between the tooth surfaces of the external toothed section 22A and the internal toothed section 21A in the separated state can generate abnormal noise, which can lead to phase variations in the valve opening / closing timing control device 1.

[0061] Accordingly, the preload force of the spring 25 is set to a value that allows the displacement of the external toothed section 22A from the internal toothed section 21A in the direction in which the external toothed section 22A moves away from the internal toothed section 21A only when the cam oscillation torque, which exceeds the set value, is applied to the valve opening / closing timing control device 1. Accordingly, the displacement of the inner gear 22 is limited by the pair of limiting projections 41.

[0062] With the aforementioned design, at a time when the cam fluctuation torque is not applied, the external gear section 22A is as described in Fig. Figure 5 shows that the preload force of the spring 25 engages with the internal gear section 21A. Therefore, no abnormal noise or phase fluctuation occurs. More precisely, because the tooth surface of each tooth of the internal gear section 21A and the tooth surface of each tooth of the external gear section 22A are in slight contact with each other, the rotational load on the ring gear 21 and the inner gear 22 is reduced, which allows for a high response speed of the valve opening / closing timing control device 1 and enables rapid adjustment of its relative rotational phase.

[0063] In addition, since elastic deformation of the spring 25 is limited, fatigue of the spring 25 is limited, thus increasing its service life.

[0064] Furthermore, in a case where the cam oscillation torque exceeding the set value is applied, the inner gear 22 is rotated in the direction in which the external tooth section 22A moves away from the internal tooth section 21A, as shown in Fig. As shown in Figure 6, the inner gear 22 is displaced. Nevertheless, at the time of displacement, the pair of limiting projections 41 of the limiting sections R come into contact with the inner circumferential surface S of the second bearing 27, thus limiting the displacement of the inner gear 22. Consequently, the outer gear section 22A is prevented from moving far away from the inner gear section 21A, and the generation of the abnormal noise is prevented.

[0065] As mentioned previously, the outer diameter of the outer circumferential surface 24BS of the second bearing section 24B of the drive shaft 24 is specified to be slightly smaller than the inner diameter of the second bearing 27. Thus, compared to a case where the outer circumferential surface 24BS of the second bearing section 24B is a close fit to the inner circumferential surface S of the second bearing 27, for example, strict control of the accuracy of the drive shaft 24 is not necessary, which can simplify the manufacturing of the drive shaft 24. Additionally, the distance between the section (the surface) of the outer circumferential surface 24BS that is positioned radially opposite the recessed section 24D and the inner circumferential surface S of the second bearing 27 is defined.Thus, in a state where the external toothing section 22A is engaged with the internal toothing section 21A, such an engagement state is safely maintained without the inner circumferential surface S of the second bearing 27 contacting the outer circumferential surface 24BS of the second support section 24B.

[0066] A second embodiment with a structure different from that of the aforementioned first embodiment is explained below. Components of the second embodiment with essentially the same functions as in the first embodiment are provided with the same reference numerals as in the first embodiment.

[0067] As in Fig. 7 and Fig. As shown in Figure 8, two recessed sections 24D are provided on the outer circumference of the second support section 24B of the drive shaft 24 such that they are opposite each other with respect to the direction of deviation L. The limiting section R is provided at an intermediate position between the two recessed sections 24D. The two springs 25, each serving as the preload element, are fitted into the respective recessed sections 24D. The limiting section R is formed by a limiting piece 45, which serves as a limiting element that is located in a Fig. 7 is positioned in the direction shown so that it overlaps with the deviation direction line L.

[0068] In addition, the limiting piece 45 has a fitting section 45a on the limiting section R, while the drive shaft 24 has a fitting groove section 24f into which the fitting section 45a fits. The limiting piece 45 is designed for the drive shaft 24 such that the fitting section 45a fits into the fitting groove section 24f. In a design where the limiting section R is integrally formed on the drive shaft 24, the distance between the protruding surface of the limiting section R and the inner circumferential surface S of the second bearing 27 can vary, depending on the manufacturing accuracy and the positional accuracy of the drive shaft 24.

[0069] Therefore, several limit pieces have different projection lengths, so that, for example, one of the several limit pieces 45 with which a suitable distance can be obtained can be used. Consequently, even if the position of the second support section 24B of the drive shaft 24 varies or differs to some extent, the distance between the projecting surface of the limit section R and the inner circumferential surface S of the second bearing 21 can be suitably specified.

[0070] In the second embodiment, a pair of springs 25 is provided. Alternatively, as in the first embodiment, a single spring 25 can be provided in a state in which the limiting section R is maintained by the limiting piece 45, which is provided at least in one of the recessed sections 24D.

[0071] In the first embodiment, the pair of guide projections 42 extends outwards from the outer circumferential surface 24BS of the second support section 24B of the drive shaft 24. Alternatively, a portion of the cross-section of the second support section 24B can be oval or elliptical, such that one of its longitudinal axes corresponds to a direction in which the largest diameter of the outer circumferential surface 24BS is obtained perpendicular to the deviation direction line L.

[0072] Since the portion of the second bearing section 24B is oval or elliptical in shape, the outer surface of the oval or ellipse is in slight contact with the inner circumferential surface S of the second bearing 27 along its longitudinal axis, and a gap is formed between a section (a surface) of the outer circumferential surface 24BS, which is positioned radially opposite the recessed section 24D, and the inner circumferential surface S of the second bearing 27. Consequently, the external toothed section 22A of the inner gear 22 can be stably engaged with the internal toothed section 21A of the ring gear 21.

[0073] More precisely, in a case where the outer circumferential surface 24BS of the second support section 24B is formed with a non-circular shape and a distance is formed between the outer circumferential surface 24BS and the inner circumferential surface S of the second bearing 27, a high accuracy of the second support section 24B is not necessary, which can lead to a problem-free manufacture of the valve opening / valve closing time control device 1.

[0074] It is explicitly emphasized that all features disclosed in the description and / or the claims are to be considered separate and independent of one another for the purpose of the original disclosure as well as for the purpose of limiting the claimed invention, irrespective of the combinations of features in the embodiments and / or the claims. It is explicitly stated that all range specifications or specifications of groups of units disclose every possible intermediate value or subgroup of units for the purpose of the original disclosure as well as for the purpose of limiting the claimed invention, in particular also as a boundary of a range specification.

Claims

[1] Valve opening / closing time control device (1) comprising: a drive-side rotating component (A) which is rotatably arranged about a rotational axis (X) and rotates synchronously with a crankshaft (2) of an internal combustion engine (E); a driven-side rotary component (B) which is rotatably arranged about the axis of rotation (X) and is integrally connected with a camshaft (3) for opening and closing a valve (3B) of the internal combustion engine (E) in a state in which the driven-side rotary component (B) is rotatable relative to the drive-side rotary component (A); a phase adjustment mechanism (C) that specifies a relative rotational phase between the drive-side rotary component (A) and the driven-side rotary component (B) by means of a drive force of an electric actuator (M), wherein the phase adjustment mechanism (C) comprises a ring gear (21), an inner gear (22) and a drive shaft (24), the ring gear (21) being arranged coaxially with the axis of rotation (X) and having an internal toothed section (21A), the inner gear (22) being arranged coaxially with an eccentric axis (Y) arranged parallel to the axis of rotation (X) and having an external toothed section (22A) which engages with a portion of the internal toothed section (21A) of the ring gear (21), the drive shaft (24) being fitted into the inner gear (22) and being coaxial with the axis of rotation (X), the phase adjustment mechanism (C) being designed as a differential reduction gear mechanism in which the inner gear (22) rotates about the axis of rotation (X) while in a state in which the drive shaft (24) is driven by a driving force of the electric actuator (M) to rotate about the axis of rotation (X) is driven to rotate around the eccentric axis (Y); a preloading component (25) provided on an outer circumference of the drive shaft (24), wherein the preloading component (25) exerts a preload force to engage the external toothed section (22A) of the inner gear (22) with the internal toothed section (21A) of the ring gear (21); and a limiting section (R) which is provided on the drive shaft (24) to limit a displacement of the inner wheel (22) in a direction in which the inner wheel (22) is separated from the ring gear (21) against the preload force of the preloading component (25), in which the drive shaft (24) has an eccentric surface (24BS) defined with respect to the eccentric axis (Y) and in which a recessed section (24D) is provided, wherein a spring (25) serving as the preload element is fitted into the recessed section (24D), the boundary section (R) is formed by at least one of opposite outer edge sections of the recess section (24D) in a circumferential direction of the eccentric surface (24BS), wherein at least one of the opposite outer edge sections projects outwards in a radial direction. [2] Valve opening / valve closing timing control device (1) according to claim 1, in which the inner wheel (22) is mounted on the eccentric surface (24BS) via a bearing (27) having an inner circumferential surface (S) on which the preload force is applied by the preloading component (25), wherein the limiting section (R) is designed such that it comes into contact with the inner circumferential surface (S) of the bearing (27) to limit a displacement of the inner wheel (22). [3] Valve opening / valve closing time control device (1) according to one of claims 1 to 2, wherein the limiting section (R) is formed by a limiting component (45) which is mounted on the outer circumference of the drive shaft (24).

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