JP7790964B2 - Reclining device - Google Patents

Description

The present invention relates to a reclining device.

In contrast to conventional seat cushions, the seat reclining device 300, which holds the seat back tiltably, has an external gear 310 connected to the seat back or the frame of the seat cushion, with external teeth formed on its outer circumferential surface, and with a through hole coaxial with the axial direction formed in its inner circumferential surface and a through hole boss 310a formed in this through hole; an internal gear 320 connected to the seat cushion or the seat back, with internal teeth formed on its outer circumferential surface that can mesh with the external teeth, and with a cylindrical boss 320a coaxial with the axial direction formed in its inner circumferential surface, a cam 350, a bushing 330, and an elastic body 370, as shown in FIG. 8.

The bushing 330 presses against the through-hole boss portion 310a of the external gear 10, but this through-hole boss portion 310a of the external gear 10 is a protruding part like a burring part, and has low rigidity, making it prone to breakage.

The present invention was developed in consideration of these issues, and aims to provide a reclining device that eliminates the through-hole boss portion of the external gear and prevents damage to the through-hole boss portion by pressing the highly rigid bottom surface of the external gear.

To achieve the above-mentioned objectives, the present invention employs the following measures.

The reclining device of the present invention comprises:
A seat reclining device that tiltably holds a seat back frame that constitutes a seat back relative to a seat cushion frame that constitutes a seat cushion,
an externally toothed gear attached directly or indirectly to one of the seat cushion frame and the seat back frame, the externally toothed gear having external teeth formed on an outer peripheral surface and a through hole formed coaxially with the axial direction on an inner peripheral surface;
an internal gear attached directly or indirectly to the other of the seat cushion frame and the seat back frame, the internal gear having internal teeth that are provided on an inner peripheral surface of the seat cushion frame and that are at least one more than the external teeth and that can mesh with the external teeth, a cylindrical boss that is coaxial with the axial direction, and a bottom-up bottom surface portion that is raised above a bottom surface portion formed around the cylindrical boss;
a bushing arranged between the inner periphery of the through hole of the external gear and the outer periphery of the cylindrical boss of the internal gear, the bushing being formed in an annular shape by two arch-shaped members, a first bushing and a second bushing, the bushing being formed so that the center of the outer periphery and the center of the cylindrical boss are eccentric, the bushing having a wedge-shaped cam accommodating portion on the inner periphery side and a protrusion on the front side;
a pair of wedge-shaped cams that are disposed in the wedge-shaped cam accommodating portion of the bush, and restrict relative rotation between the external gear and the internal gear by contacting an outer peripheral surface of the cylindrical boss of the internal gear and an inner peripheral surface of the wedge-shaped cam accommodating portion, and allow relative rotation between the external gear and the internal gear by sliding the outer peripheral surface of the cylindrical boss of the internal gear and the inner peripheral surface of the through hole of the external gear;
a biasing member that biases the wedge-shaped cams in a direction separating the wedge-shaped cams;
a drive member that is coaxially and rotatably fitted into the cylindrical boss of the internal gear, the drive member having an engagement hole on the inside and a protrusion on the outer periphery that engages with the protrusion of the bush;
a rotating shaft that is fitted to the driving member and rotates the bushing via the driving member;
Equipped with
The bushing is characterized in that it contacts the side surface of the bottom surface portion of the external gear.

In the reclining device of the present invention, the bushing is positioned higher than the bottom surface of the internal gear, so that the point where the bushing comes into contact with the external gear comes into contact with the side of the bottom surface of the external gear. By adopting this configuration, pressure is applied to the side of the bottom surface, which has high rigidity, rather than to the through-hole boss portion, which is vulnerable to stress in the direction of tilt, as in conventional devices, preventing damage to the external gear.

Furthermore, in the reclining device according to the present invention, the upper bottom surface portion may be raised to at least a position corresponding to the bottom surface portion of the external gear.

By adopting this configuration, the entire bushing presses against the side of the bottom surface of the external gear, further preventing damage to the external gear.

In addition, in the reclining device according to the present invention,
A seat reclining device that tiltably holds a seat back frame that constitutes a seat back relative to a seat cushion frame that constitutes a seat cushion,
an externally toothed gear attached directly or indirectly to one of the seat cushion frame and the seat back frame, with external teeth formed on its outer peripheral surface and a cylindrical boss formed on its inner peripheral surface coaxial with the axial direction, and with an upper bottom surface portion raised higher than a bottom surface portion formed around the cylindrical boss;
an internal gear attached directly or indirectly to the other of the seat cushion frame and the seat back frame, the internal gear having internal teeth on an inner circumferential surface that are capable of meshing with the external teeth, the internal teeth being at least one more than the external teeth, and having a through hole formed therein that is coaxial with the axial direction;
a first bushing and a second bushing, the first bushing being disposed between the inner periphery of the through hole of the internal gear and the outer periphery of the cylindrical boss of the external gear, the first bushing being formed in an annular shape by two arch-shaped members, the second bushing being formed so that the center of the outer periphery and the center of the cylindrical boss are eccentric, the first bushing having a wedge-shaped cam accommodating portion on the inner periphery side and a protrusion on the front side;
a pair of wedge-shaped cams that are arranged in the wedge-shaped cam accommodating portion of the bushing, and that restrict relative rotation between the external gear and the internal gear by contacting the outer circumferential surface of the cylindrical boss of the external gear and the inner circumferential surface of the wedge-shaped cam accommodating portion, and allow relative rotation between the external gear and the internal gear by sliding the outer circumferential surface of the cylindrical boss of the external gear and the inner circumferential surface of the through hole of the internal gear;
a biasing member that biases the wedge-shaped cams in a direction separating the wedge-shaped cams;
a drive member that is coaxially and rotatably fitted into the cylindrical boss of the external gear, and has an engagement hole on the inside and a protrusion on the outer circumferential side that engages with the protrusion of the bush;
a rotating shaft that is fitted to the driving member and rotates the bushing via the driving member;
Equipped with
The bushing is characterized in that it contacts the side surface of the bottom surface of the internal gear.

This invention differs from the above-mentioned inventions in that a cylindrical boss is provided on the external gear and a through hole is formed in the internal gear. However, similarly, by positioning the bushing higher than the bottom surface of the external gear, the position where the bushing comes into contact with the internal gear comes into contact with the side of the bottom surface of the internal gear. By adopting this configuration, pressure is applied to the side of the bottom surface, which has greater rigidity, preventing damage to the external gear.

Furthermore, in the reclining device according to the present invention, the upper bottom surface portion may be raised to at least a position corresponding to the bottom surface portion of the internal gear.

By adopting this configuration, the entire bushing presses against the side of the bottom surface of the internal gear, further preventing damage to the internal gear.

FIG. 1 is a schematic diagram of a vehicle seat 200 to which a reclining device 100 according to the first embodiment is attached. FIG. 2 is a front view showing the internal structure of the reclining device 100 according to the first embodiment. FIG. 3 is an exploded perspective view of the reclining device 100 according to the first embodiment. FIG. 4 is a cross-sectional view of the reclining device 100 taken along the line AA according to the first embodiment. FIG. 5 is a perspective view of the external gear 10 of the reclining device 100 according to the first embodiment. FIG. 6 is a front view showing the relationship between the bushing 30 and the wedge-shaped cam 50 of the reclining device 100 according to the first embodiment. FIG. 7 is an exploded perspective view of the reclining device 100 according to the second embodiment. FIG. 8 is a cross-sectional view of a conventional reclining device 300.

The reclining device 100 according to an embodiment of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic diagram of a vehicle seat 200, FIG. 2 is a front view showing the internal structure of the reclining device 100, and FIG. 3 is an exploded perspective view of the reclining device 100. FIG. 4 is a cross-sectional view taken along the line A-A in FIG. 2. Note that the embodiments and drawings described below exemplify some of the embodiments of the present invention and are not intended to limit the present invention to these configurations. Note that corresponding components in each drawing are designated by the same or similar reference numerals. In addition, the directions indicated by the arrows in FIG. 3 are referred to as the "front" and "rear," respectively.

(First embodiment)
1, the reclining device 100 according to the first embodiment is a device attached to a seat cushion 210 of a vehicle seat 200 at a central position of the tilt of a seat back 220 that is tiltably attached to the seat cushion 210, and that provides a tilting function to the seat back 220. Specifically, the reclining device 100 is attached between a seat cushion frame disposed inside the seat cushion 210 and a seat back frame disposed inside the seat back 220, either directly or indirectly via another mounting plate 230 (hereinafter referred to as a "mounting plate or the like").

As shown in Figures 2 to 4, the reclining device 100 according to the present invention mainly comprises an external gear 10, an internal gear 20, a bushing 30 consisting of a first bushing 31 and a second bushing 32, a rotating shaft 40, a wedge-shaped cam 50, a driving member 60, a spring 70 as a biasing member, a plate cover 80, and a shaft locking member 90. Note that the rotating shaft 40 and driving member 60 have been omitted from Figure 2 to make the internal structure easier to see.

As shown in Figure 3, the external gear 10 is formed in a disk shape, with external teeth 11 formed on its outer periphery and a through hole 12 in its center. The external gear 10 is provided with a protrusion 13 that fits into a fitting hole formed in a mounting plate or the like 230 and is attached to the vehicle seat by welding or the like. As shown in Figure 5, the external gear 10 has a standing portion 16 formed on its outer periphery, but does not have a cylindrical boss (the so-called burring portion of conventional examples) formed on its inside.

The internal gear 20 is formed in a disk shape with a larger diameter than the external gear 10, and has a recess 10a formed therein so that the external gear 10 can be fitted thereto. Internal teeth 21 are formed on the inner circumferential surface of this recess 10a. The number of internal teeth 21 is at least one more than the number of teeth of the external teeth 11 of the external gear 10. As shown in FIG. 2 , the external gear 10 and the internal gear 20 are eccentrically arranged such that the center _C1 of the external gear 10 and the center _C2 of the internal gear 20 are eccentric as indicated by arrow d, and they mesh with the internal teeth 21 and the external teeth 11. Therefore, the external gear 10 and the internal gear 20 form a differential gear, and when the internal gear 20 makes one revolution around the external teeth 11, it rotates by the difference in teeth between the internal teeth 21 and the external teeth 11. In other words, for example, if there is a difference of only one tooth, when the external gear 10 makes one revolution around the internal gear 20, it rotates by one tooth. As shown in FIG. 3 , a cylindrical boss 22 is provided at the center of the internal gear 20, and the periphery of this cylindrical boss 22 has a raised bottom surface portion 23. This raised bottom surface portion 23 forms the contact surface with the bushing 30, which will be described later. The raised bottom surface portion 23 is formed so that its outer periphery is circular, and is preferably raised above a position corresponding to the bottom surface 18 (see FIG. 5 ) of the external gear 10 when assembled. In other words, as shown in FIG. 4 , the raised amount of the raised bottom surface portion 23 is preferably raised above the position f of the bottom surface 18 of the external gear 10. This construction allows the entire thickness of the bushing 30 to come into contact with the side surface of the external gear. The internal gear 20 is provided with a protrusion 26, which is fitted into a fitting hole provided in a mounting plate or the like 230 and attached to the vehicle seat by welding or the like.

The bushing 30 is an annular member formed by combining a first bushing 31 and a second bushing 32 and is disposed between the inner peripheral surface 12a of the through hole 12 of the external gear 10 and the outer peripheral surface 22a of the cylindrical boss 22 of the internal gear 20, and as shown in Fig. 6, the first bushing 31 is formed eccentrically so that the center _C3 of the circularly formed outer peripheral surface 33 and the center _C4 of the outer peripheral surface 22a of the cylindrical boss 22 are approximately equal to the amount of eccentricity between the centers of the external gear 10 and the internal gear 20. The first bushing 31 of the bushing 30 is a bow- or crescent-shaped member disposed in the direction in which the through hole 12 of the external gear 10 is eccentric (the direction of the arrow in Fig. 6), and a wedge-shaped cam accommodating portion 35 is formed on its inner peripheral side and is disposed so as to have a gap between each of a pair of wedge-shaped cams 50 described below, as shown in Fig. 6. The wedge angle of the wedge-shaped cam housing 35 is set so that the gap between the bushing 30 and the cylindrical boss 22 narrows as the distance from the opposing side increases. The bushing 30 can press and move the external gear 10 and the internal gear 20 in the eccentric direction by a wedge-shaped cam 50 (described later), preventing rattling in the locked state. The second bushing 32 is a bow-shaped or crescent-shaped member located on the opposite side from the direction in which the through hole 12 of the external gear 10 is eccentric (the direction of the arrow), and is located close enough to both side ends of the first bushing 31 to create a small gap. A protrusion 36 is provided at or near the end of the first bushing 31, and is the part to which rotation of a rotating shaft 40 (described later) is transmitted.

As shown in Figures 3 and 6, the wedge-shaped cams 50a and 50b are formed symmetrically with respect to their planes. The concave surface 51 (inner surface) of the wedge-shaped cam 50 has the same curve as the curved surface of the outer peripheral surface 22a of the cylindrical boss 22, while the convex surface 52 (outer surface) is formed so that its thickness gradually decreases from the opposing side. The wedge-shaped cams 50a and 50b are arranged so that their thicker proximal ends 53 face each other and, as described above, are disposed within the wedge-shaped cam accommodating portion 35 of the bushing 30 so as to contact the inner peripheral surface 12a of the through hole 12 of the external gear 10.

The spring 70 serving as a biasing member is made of an elastic material and, as shown in Figure 3, has an annular portion 71 and two ends 72a and 72b that rise from the annular portion 71 and bend at a 90° angle. The ends 72a and 72b each contact the proximal end 53 of the wedge-shaped cam 50, biasing the pair of wedge-shaped cams 50a and 50b in the direction of moving apart.

The rotating shaft 40 is arranged coaxially and rotatably relative to the cylindrical boss 22 of the internal gear 20. The rotating shaft 40 is rotated when adjusting the tilt of the seat back 220, and has serrations 41 on its inner cylindrical surface to receive the rotational force of the tilt motor. The rotating shaft 40 has a cylindrical shaft portion 42 that is inserted into the drive member 60 (described below), and is provided with multiple locking portions 43 so that it rotates synchronously with the drive member 60.

The drive member 60 has a mating hole 61 on its inner periphery that fits into the locking portion 43 of the rotating shaft 40, and is rotated as the rotating shaft 40 rotates. It also has two engagement portions 63 that are formed to sandwich the protrusions 36 on the bushing 30 from both sides. The drive member 60, which is rotated by the rotation of the rotating shaft 40, can rotate by pressing the protrusions 36 of the bushing 30 with the engagement portions 63.

The plate cover 80 is a component that secures the external gear 10, internal gear 20, bushing 30, rotating shaft 40, bushing 30, wedge cam 50, drive member 60, and spring 70 so that they do not come off, and its shape is not particularly limited.

The shaft locking member 90 is a member that secures the rotating shaft 40.

The reclining device 100 thus constructed operates as follows. When no force is applied to the rotating shaft 40 and it is not rotating, the spring 70 urges the pair of wedge-shaped cams 50a and 50b in directions separating them, pressing the outer peripheral surface 22a of the cylindrical boss 22 of the internal gear 20 against the wedge-shaped cam housing portion 35 of the bushing 30, causing the bushing 30 to be in pressing contact with the inner peripheral surface 12a of the through-hole 12 of the external gear 10. As a result, the relative movement of the internal gear 20 and the external gear 10 is locked, and the seat back 220 is in a locked state.

When the rotating shaft 40 is rotated counterclockwise from this locked state, as shown in Figure 2, the drive member 60 fitted to the rotating shaft 40 rotates first. The rotational force of the drive member 60 is transmitted from the engagement portion 63 to the protrusion 36, causing the bushing 30 to rotate. A wedge angle is set between the wedge-shaped cam 50b and the inner wall of the wedge-shaped cam accommodating portion 35 of the bushing 30, and the inner wall of the wedge angle is in contact with the wedge-shaped cam 50. As the bushing 30 rotates, a gap is created between the inner wall of the wedge angle and the wedge-shaped cam 50, causing the wedge to disengage. As a result, gaps are created between the bushing 30 and the cylindrical boss 22, and between the bushing 30 and the through-hole 12 of the internal gear 20, allowing the external gear 10 to rotate relative to the internal gear 20. Accordingly, the wedge-shaped cam 50a rotates counterclockwise due to the biasing force of 70, filling this gap. The wedge-shaped cam 50 rotates counterclockwise, sliding along with the rotating shaft 40 and bushing 30. In this way, the external gear 10, internal gear 20, and rotating shaft 40 form a differential gear mechanism. Clockwise rotation can also be achieved in the same way.

In the reclining device 100 manufactured in this manner, the bushing 30 is formed in a ring shape. When an external force is applied to the internal gear 20 or external gear 10, the internal gear 20 or external gear 10 attempts to move in the direction of the external force or the reaction force. However, the bushing 30 is sandwiched perpendicular to the direction of the attempted movement between the outer surface 22a of the cylindrical boss 22 of the internal gear 20 and the through hole 12 of the external gear 10, minimizing the component force components and acting as a bearing. This stabilizes sliding and ensures smooth rotation.

In addition, when the rotating shaft 40 is rotated, the bushing 30's protrusion 36 engages with the engagement portion 63, which has no gap in the direction of rotation, allowing the gear mechanism to operate immediately without any time lag. During this process, the bushing 30 rotates via the engagement portion 63 to the protrusion 36, rotating to follow the eccentric direction of the internal gear 20 and external gear 10. During rotation, the bushing 30 contacts most of the outer surface 22a of the cylindrical boss 22, stabilizing sliding and ensuring smooth rotation. Meanwhile, the wedge-shaped cam 50 biases the external gear 10 to move in the eccentric direction relative to the internal gear 20, preventing rattling when locked.

In addition, the reclining device 100 according to the first embodiment does not have a boss portion around the through hole 12 of the external gear 10. The bushing 30 is positioned in a raised position by the raised bottom surface portion 23 of the internal gear 20 and directly presses against the side of the bottom surface of the external gear 10, eliminating the possibility of pressing against and damaging the boss portion as in the past. Furthermore, because the raised bottom surface portion 23 of the internal gear 20 raises the bottom surface, the height of the cylindrical boss 22 of the internal gear 20 can be made lower than in the past, thereby increasing the rigidity of the cylindrical boss portion.

Second Embodiment
An exploded perspective view of the reclining device 100 according to the second embodiment is shown in Figure 7. The reclining device 100 according to the second embodiment is the same as the first embodiment except that a through hole 25 is formed in the internal gear 20 and a cylindrical boss 15 is provided on the external gear 10, and therefore a description thereof will be omitted.

As shown in Figure 7, the external gear 10 is formed in a disk shape, with external teeth 11 formed on its outer periphery and a cylindrical boss 15 provided in the center. The periphery of the cylindrical boss 15 has a raised bottom surface portion 17. This raised bottom surface portion 17 is the part that makes contact with the bushing 30. The raised bottom surface portion 17 is formed so that its outer periphery is circular, and preferably is raised above a position corresponding to the bottom surface of the internal gear 20 (see Figure 4) when assembled.

The internal gear 20 is formed in the shape of a disk with a larger diameter than the external gear 10. A cylindrical recess is formed so that the external gear 10 can be fitted inside, and internal teeth 21 are formed on the inner circumferential surface of this recess. The number of internal teeth is at least one more than the number of external teeth 11 of the external gear 10, and the external gear 10 and internal gear 20 are engaged with the internal teeth 21 and external teeth 11 so that the centers of the external gear 10 and internal gear 20 are eccentric, respectively, as in the first embodiment. A through hole 25 is formed in the center of the internal gear 20, as shown in Figure 7. No boss portion is provided in this through hole 25.

The method of movement of the reclining device 100 in the second embodiment is similar to that of the first embodiment. When no force is applied to the rotating shaft 40 and the rotating shaft 40 is not rotating, the pair of wedge-shaped cams 50a and 50b are biased by the spring 70 in directions separating them, and they are in contact with the inner circumferential surface of the bushing 30 and the outer circumferential surface 15a of the cylindrical boss 15 of the external gear 10. Therefore, the relative motion of the internal gear 20 and the external gear 10 is locked, and the seat back 220 is in a locked state. When the rotating shaft 40 is rotated counterclockwise from this locked state, the drive member 60 fitted to the rotating shaft 40 first rotates, and the rotational force of the drive member 60 is transmitted from the engagement portion 63 to the protrusion 36, causing the bushing 30 to rotate. A wedge angle is set between the wedge-shaped cam 50b and the inner wall of the wedge-shaped cam housing portion 35 of the bushing 30, and the inner wall of the wedge angle contacts the wedge-angled wedge-angled cam 50. As the bushing 30 rotates, a gap is created between the inner wall of the wedge angle and the wedge-shaped cam 50, causing the wedge to disengage. As a result, gaps are created between the bushing 30 and the cylindrical boss 15 of the external gear 10, and between the bushing 30 and the through-hole 25 of the internal gear 20, allowing the external gear 10 to rotate relative to the internal gear 20. Accordingly, the biasing force of the spring 70 causes the wedge-shaped cam 50a to rotate counterclockwise, filling the gap. The wedge-shaped cam 50 rotates counterclockwise, sliding along with the rotating shaft 40 and bushing 30. In this way, the external gear 10, internal gear 20, and rotating shaft 40 form a differential gear mechanism. Clockwise rotation is also possible in the same way. Clockwise rotation is also possible in the same way.

The present invention is not limited to the above-described embodiments, and can be implemented in various forms as long as they fall within the technical scope of the present invention.

As shown in the above-described embodiment, it can be used industrially primarily as a reclining device for vehicle seats.

10...externally toothed gear, 10a...recess, 11...external teeth, 12...through hole, 12a...inner peripheral surface, 13...protrusion, 15...cylindrical boss, 15a...outer peripheral surface, 16...standing portion, 17...raised bottom surface portion, 18...bottom, 20...internal gear, 21...internal teeth, 22...cylindrical boss, 22a...outer peripheral surface, 23...raised bottom surface portion, 25...through hole, 26...protrusion, 30...bush, 31...first bush, 32...second bush, 33...outer peripheral surface, 35...wedge-shaped cam accommodating portion, 36...protrusion, 40...rotating shaft, 41...cell ion, 42...shaft portion, 43...engagement portion, 50...wedge-shaped cam, 50a...wedge-shaped cam, 50b...wedge-shaped cam, 51...concave surface, 52...convex surface, 53...proximal end portion, 60...driving member, 61...fitting hole, 63...engagement portion, 70...spring, 71...annular portion, 72a, 72b...end portions, 80...plate cover, 90...shaft engagement member, 100...recliner device, 200...vehicle seat, 210...seat cushion, 220...seat back, 230...mounting plate,

Claims (4)

A seat reclining device that tiltably holds a seat back frame that constitutes a seat back relative to a seat cushion frame that constitutes a seat cushion,
an externally toothed gear attached directly or indirectly to one of the seat cushion frame and the seat back frame, the externally toothed gear having external teeth formed on an outer peripheral surface and a through hole formed coaxially with the axial direction on an inner peripheral surface;
an internal gear attached directly or indirectly to the other of the seat cushion frame and the seat back frame, the internal gear having internal teeth that are provided on an inner peripheral surface of the seat cushion frame and that are at least one more than the external teeth and that can mesh with the external teeth, a cylindrical boss that is coaxial with the axial direction, and a bottom-up bottom surface portion that is raised above a bottom surface portion formed around the cylindrical boss;
a bushing arranged between the inner periphery of the through hole of the external gear and the outer periphery of the cylindrical boss of the internal gear, the bushing being formed in an annular shape by two arch-shaped members, a first bushing and a second bushing, the bushing being formed so that the center of the outer periphery and the center of the cylindrical boss are eccentric, the bushing having a wedge-shaped cam accommodating portion on the inner periphery side and a protrusion on the front side;
a pair of wedge-shaped cams that are disposed in the wedge-shaped cam accommodating portion of the bush, and restrict relative rotation between the external gear and the internal gear by contacting an outer peripheral surface of the cylindrical boss of the internal gear and an inner peripheral surface of the wedge-shaped cam accommodating portion, and allow relative rotation between the external gear and the internal gear by sliding the outer peripheral surface of the cylindrical boss of the internal gear and the inner peripheral surface of the through hole of the external gear;
a biasing member that biases the wedge-shaped cams in a direction separating the wedge-shaped cams;
a drive member that is coaxially and rotatably fitted into the cylindrical boss of the internal gear, the drive member having an engagement hole on the inside and a protrusion on the outer periphery that engages with the protrusion of the bush;
a rotating shaft that is fitted to the driving member and rotates the bushing via the driving member;
Equipped with
The reclining device is characterized in that the bushing is in contact with a side surface of a bottom portion of the external gear. The reclining device described in claim 1, characterized in that the upper bottom surface portion is raised at least above a position corresponding to the bottom surface portion of the external gear. A seat reclining device that tiltably holds a seat back frame that constitutes a seat back relative to a seat cushion frame that constitutes a seat cushion,
an externally toothed gear attached directly or indirectly to one of the seat cushion frame and the seat back frame, with external teeth formed on its outer peripheral surface and a cylindrical boss formed on its inner peripheral surface coaxial with the axial direction, and with an upper bottom surface portion raised higher than a bottom surface portion formed around the cylindrical boss;
an internal gear attached directly or indirectly to the other of the seat cushion frame and the seat back frame, the internal gear having internal teeth on an inner circumferential surface that are capable of meshing with the external teeth, the internal teeth being at least one more than the external teeth, and having a through hole formed therein that is coaxial with the axial direction;
a first bushing and a second bushing, the first bushing being disposed between the inner periphery of the through hole of the internal gear and the outer periphery of the cylindrical boss of the external gear, the first bushing being formed in an annular shape by two arch-shaped members, the second bushing being formed so that the center of the outer periphery and the center of the cylindrical boss are eccentric, the first bushing having a wedge-shaped cam accommodating portion on the inner periphery side and a protrusion on the front side;
a pair of wedge-shaped cams that are arranged in the wedge-shaped cam accommodating portion of the bushing, and that restrict relative rotation between the external gear and the internal gear by contacting the outer circumferential surface of the cylindrical boss of the external gear and the inner circumferential surface of the wedge-shaped cam accommodating portion, and allow relative rotation between the external gear and the internal gear by sliding the outer circumferential surface of the cylindrical boss of the external gear and the inner circumferential surface of the through hole of the internal gear;
a biasing member that biases the wedge-shaped cams in a direction separating the wedge-shaped cams;
a drive member that is coaxially and rotatably fitted into the cylindrical boss of the external gear, and has an engagement hole on the inside and a protrusion on the outer circumferential side that engages with the protrusion of the bush;
a rotating shaft that is fitted to the driving member and rotates the bushing via the driving member;
Equipped with
A reclining device, wherein the bushing is in contact with a side surface of a bottom surface of the internal gear. 4. The reclining device according to claim 3, wherein the upper bottom surface portion is raised at least to a position corresponding to the bottom surface portion of the internal gear.