U.S. patent application number 12/730356 was filed with the patent office on 2010-09-30 for seat reclining apparatus.
This patent application is currently assigned to AISIN SEIKI KABUSHIKI KAISHA. Invention is credited to Takashi Kitano, Hiroki Morimoto, Mitsutoshi Watariguchi.
Application Number | 20100244530 12/730356 |
Document ID | / |
Family ID | 42352674 |
Filed Date | 2010-09-30 |
United States Patent
Application |
20100244530 |
Kind Code |
A1 |
Kitano; Takashi ; et
al. |
September 30, 2010 |
SEAT RECLINING APPARATUS
Abstract
A seat reclining apparatus includes a support frame tiltable
about a support axis relative to a first frame, an angle adjustment
unit causing a second frame to tiltably move forward or rearward
relative to the support frame by a driving force of an actuator,
the second frame being displaced in a direction to approach and
separate from the support axis, a lock mechanism selectively
operated to an unlocked state and a locked state, and a front
stopper provided at the first frame to specify a forward tilt limit
of the seat back by making contact with a forward tilt contact
portion provided at the second frame in a state where the lock
mechanism is in the unlocked state, the front stopper including a
linearly-shaped contact surface that makes contact with the forward
tilt contact portion and that matches or approximates a virtual
straight line passing through the support axis.
Inventors: |
Kitano; Takashi; (Anjo-shi,
JP) ; Watariguchi; Mitsutoshi; (Kariya-shi, JP)
; Morimoto; Hiroki; (Okazaki-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, L.L.P.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
AISIN SEIKI KABUSHIKI
KAISHA
Kariya-shi
JP
|
Family ID: |
42352674 |
Appl. No.: |
12/730356 |
Filed: |
March 24, 2010 |
Current U.S.
Class: |
297/362 ;
297/361.1 |
Current CPC
Class: |
B60N 2/2252 20130101;
B60N 2/20 20130101; B60N 2/206 20130101; B60N 2/2352 20130101 |
Class at
Publication: |
297/362 ;
297/361.1 |
International
Class: |
A47C 1/025 20060101
A47C001/025; A47C 1/024 20060101 A47C001/024 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2009 |
JP |
2009-085538 |
Claims
1. A seat reclining apparatus comprising: a support frame tiltable
about a support axis relative to a first frame constituting a seat
cushion; an angle adjustment unit causing a second frame
constituting a seat back to tiltably move forward or rearward
relative to the support frame by a driving force of an actuator,
the second frame being displaced in a direction to approach and
separate from the support axis in a case where the second frame
tiltably moves forward or rearward relative to the support frame; a
lock mechanism selectively operated to an unlocked state where the
support frame is allowed to integrally tiltably move with the angle
adjustment unit about the support axis and a locked state where the
support frame is prohibited to integrally tiltably move with the
angle adjustment unit; and a front stopper provided at the first
frame to specify a forward tilt limit of the seat back by making
contact with a forward tilt contact portion provided at the second
frame in a state where the lock mechanism is in the unlocked state,
the front stopper including a linearly-shaped contact surface that
makes contact with the forward tilt contact portion and that
matches or approximates a virtual straight line passing through the
support axis.
2. The seat reclining apparatus according to claim 1, wherein the
first frame is constituted by a plate member and the front stopper
serves as a reinforcement member connected to the first frame.
3. The seat reclining apparatus according to claim 1, further
comprising a back stopper arranged adjacent to the support frame
and specifying a rearward tilt limit of the seat back by making
contact with a rearward tilt contact portion provided at the
support frame in a state where the lock mechanism is in the
unlocked state, the back stopper serving as a connection member
connecting the front stopper to the first frame.
4. The seat reclining apparatus according to claim 2, further
comprising a back stopper arranged adjacent to the support frame
and specifying a rearward tilt limit of the seat back by making
contact with a rearward tilt contact portion provided at the
support frame in a state where the lock mechanism is in the
unlocked state, the back stopper serving as a connection member
connecting the front stopper to the first frame.
5. The seat reclining apparatus according to claim 1, wherein the
lock mechanism includes a lock arm rotatably supported by the front
stopper and being engageable and disengageable relative to the
support frame by a rotation of the lock arm.
6. The seat reclining apparatus according to claim 2, wherein the
lock mechanism includes a lock arm rotatably supported by the front
stopper and being engageable and disengageable relative to the
support frame by a rotation of the lock arm.
7. The seat reclining apparatus according to claim 3, wherein the
lock mechanism includes a lock arm rotatably supported by the front
stopper and being engageable and disengageable relative to the
support frame by a rotation of the lock arm.
8. The seat reclining apparatus according to claim 4, wherein the
lock mechanism includes a lock arm rotatably supported by the front
stopper and being engageable and disengageable relative to the
support frame by a rotation of the lock arm.
9. The seat reclining apparatus according to claim 1, wherein the
angle adjustment unit includes an internal gear formed at the
support frame, an external gear formed at a tilt frame connected to
the second frame and having fewer teeth compared to the internal
gear, and an eccentric member integrally rotating with a drive
shaft which is driven to rotate by the actuator, a portion of the
internal gear engaging with a portion of the external gear, the
external gear being rotatably mounted at an outer periphery of the
eccentric member, and the seat reclining apparatus further
comprises a power transmission mechanism moving a meshed position
between the external gear and the internal gear along an inner
periphery of the internal gear by a rotational force of the
eccentric member when the actuator is driven, the power
transmission mechanism causing the tilt frame to tilt by an angle
corresponding to a difference of a number of teeth between the
external gear and the internal gear in a case where the external
gear rotates one turn along the inner periphery of the internal
gear, the tilt frame being displaced in the direction to approach
and separate from the support axis when the meshed position between
the external gear and the internal gear moves along the inner
periphery of the internal gear.
10. The seat reclining apparatus according to claim 2, wherein the
angle adjustment unit includes an internal gear formed at the
support frame, an external gear formed at a tilt frame connected to
the second frame and having fewer teeth compared to the internal
gear, and an eccentric member integrally rotating with a drive
shaft which is driven to rotate by the actuator, a portion of the
internal gear engaging with a portion of the external gear, the
external gear being rotatably mounted at an outer periphery of the
eccentric member, and the seat reclining apparatus further
comprises a power transmission mechanism moving a meshed position
between the external gear and the internal gear along an inner
periphery of the internal gear by a rotational force of the
eccentric member when the actuator is driven, the power
transmission mechanism causing the tilt frame to tilt by an angle
corresponding to a difference of a number of teeth between the
external gear and the internal gear in a case where the external
gear rotates one turn along the inner periphery of the internal
gear, the tilt frame being displaced in the direction to approach
and separate from the support axis when the meshed position between
the external gear and the internal gear moves along the inner
periphery of the internal gear.
11. The seat reclining apparatus according to claim 3, wherein the
angle adjustment unit includes an internal gear formed at the
support frame, an external gear formed at a tilt frame connected to
the second frame and having fewer teeth compared to the internal
gear, and an eccentric member integrally rotating with a drive
shaft which is driven to rotate by the actuator, a portion of the
internal gear engaging with a portion of the external gear, the
external gear being rotatably mounted at an outer periphery of the
eccentric member, and the seat reclining apparatus further
comprises a power transmission mechanism moving a meshed position
between the external gear and the internal gear along an inner
periphery of the internal gear by a rotational force of the
eccentric member when the actuator is driven, the power
transmission mechanism causing the tilt frame to tilt by an angle
corresponding to a difference of a number of teeth between the
external gear and the internal gear in a case where the external
gear rotates one turn along the inner periphery of the internal
gear, the tilt frame being displaced in the direction to approach
and separate from the support axis when the meshed position between
the external gear and the internal gear moves along the inner
periphery of the internal gear.
12. The seat reclining apparatus according to claim 4, wherein the
angle adjustment unit includes an internal gear formed at the
support frame, an external gear formed at a tilt frame connected to
the second frame and having fewer teeth compared to the internal
gear, and an eccentric member integrally rotating with a drive
shaft which is driven to rotate by the actuator, a portion of the
internal gear engaging with a portion of the external gear, the
external gear being rotatably mounted at an outer periphery of the
eccentric member, and the seat reclining apparatus further
comprises a power transmission mechanism moving a meshed position
between the external gear and the internal gear along an inner
periphery of the internal gear by a rotational force of the
eccentric member when the actuator is driven, the power
transmission mechanism causing the tilt frame to tilt by an angle
corresponding to a difference of a number of teeth between the
external gear and the internal gear in a case where the external
gear rotates one turn along the inner periphery of the internal
gear, the tilt frame being displaced in the direction to approach
and separate from the support axis when the meshed position between
the external gear and the internal gear moves along the inner
periphery of the internal gear.
13. The seat reclining apparatus according to claim 5, wherein the
angle adjustment unit includes an internal gear formed at the
support frame, an external gear formed at a tilt frame connected to
the second frame and having fewer teeth compared to the internal
gear, and an eccentric member integrally rotating with a drive
shaft which is driven to rotate by the actuator, a portion of the
internal gear engaging with a portion of the external gear, the
external gear being rotatably mounted at an outer periphery of the
eccentric member, and the seat reclining apparatus further
comprises a power transmission mechanism moving a meshed position
between the external gear and the internal gear along an inner
periphery of the internal gear by a rotational force of the
eccentric member when the actuator is driven, the power
transmission mechanism causing the tilt frame to tilt by an angle
corresponding to a difference of a number of teeth between the
external gear and the internal gear in a case where the external
gear rotates one turn along the inner periphery of the internal
gear, the tilt frame being displaced in the direction to approach
and separate from the support axis when the meshed position between
the external gear and the internal gear moves along the inner
periphery of the internal gear.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and claims priority under 35
U.S.C. .sctn.119 to Japanese Patent Application 2009-085538, filed
on Mar. 31, 2009, the entire content of which is incorporated
herein by reference.
TECHNICAL FIELD
[0002] This disclosure relates to a seat reclining apparatus.
BACKGROUND DISCUSSION
[0003] A known seat reclining apparatus includes a mechanism for
adjusting a tilt angle of a seat back relative to a seat base by
means of a driving force of an actuator and a stopper structure for
determining a tilt limit of the seat back when a locked state
between the seat back and the seat base is released. Such seat
reclining apparatus is disclosed in JP61-48311A (hereinafter
referred to as Reference 1). A reclining apparatus disclosed in
Reference 1 includes a base provided at a seat cushion, an arm
provided at a seat back so as to be rotatably connected to each
other, and a sub plate arranged at a position where the sub plate
is sandwiched between the base and the arm. The reclining apparatus
further includes a lock mechanism of a planetary gear type between
the sub plate and the arm. A sun gear included in the lock
mechanism is manually operated so as to achieve a stepless
reclining adjustment of the seat back relative to the seat
base.
[0004] According to the reclining apparatus disclosed in Reference
1, a sub plate holding member is provided to obtain a locked state
where the sub plate is connected to the base as a unit and an
unlocked state where the sub plate is disconnected from the base.
When the sub plate holding member is rotated in a predetermined
direction by a manual operation to thereby release an engagement of
an engagement projection of the sub plate holding member with the
sub plate, the sub plate is disconnected from the base. Then, a
locked state of the arm, which is connected to the sub plate by the
lock mechanism, relative to the base is released. As a result, the
seat back is tiltable forward. Afterwards, when the seatback is
pulled back (i.e., returned), the sub plate holding member is
rotated in a direction opposite from the aforementioned
predetermined direction so that the engagement projection of the
sub plate holding member engages with the sub plate. As a result,
the sub plate, in addition to the arm, is locked at an original
tilt position relative to the base.
[0005] In addition, according to a seat reclining apparatus for a
vehicle disclosed in JP2002-65388A (hereinafter referred to as
Reference 2), a driving force of a drive mechanism on which a speed
reduction is conducted is transmitted to a seat back. Specifically,
the seat reclining apparatus disclosed in Reference 2 includes
lower arms attached to respective side portions of a seat cushion
via lower brackets and upper arms attached to respective side
portions of the seat back. Each of the lower arms is formed by an
annular internal gear portion. Each of the upper arms is formed by
an external gear portion that projects from a general flat portion
of the upper arm attached to the seat back. The external gear
portion of the upper arm has one fewer tooth or less compared to
the internal gear portion of the lower arm. The external gear
portion of the upper arm partially engages with the internal gear
portion of the lower arm.
[0006] The seat reclining apparatus disclosed in Reference 2
further includes a pair of wedges and the like by means of which
the driving force of the drive mechanism is transmitted to the
external gear portion of the upper arm. Then, the external gear
portion rotates about an axial center eccentric to a center of a
drive shaft. As a result, a meshed position of the external gear
portion with the internal gear portion moves sequentially along an
inner periphery of the internal gear portion to thereby adjust an
angle of the upper arm relative to the lower bracket.
[0007] According to the seat reclining apparatus disclosed in
Reference 2, the speed reduction of the driving force of the drive
mechanism is achieved by the rotation of the external gear portion
about a position eccentric to the center of the drive shaft,
thereby specifying a position of the seat back. Thus, in a case
where the meshed position between the external gear portion and the
internal gear portion moves in the circumferential direction by the
driving of the drive mechanism (i.e., the actuator), a portion of
the internal gear portion with which the external gear portion is
meshed is displaced away from the center of the drive shaft.
[0008] In addition, according to the seat reclining apparatus
disclosed in Reference 2, in a case where the seat back is tilted
forward so as to achieve a walk-in function in the same way as the
apparatus disclosed in Reference 1, a certain structure is required
for supporting a reclining operation mechanism including the
actuator, the external gear portion, the internal gear portion and
the seat back to be rotatable about an axial center relative to the
seat cushion. Then, the entire reclining operation mechanism is
tilted forward by a release of a locked state between the seat back
and the seat cushion in a case where the seat back is tilted
forward.
[0009] When the entire reclining operation mechanism is tilted
forward, a stopper is required to determine a forward tilt limit.
For example, it is considerable to use a structure where a frame of
the seat back makes contact with the stopper provided at the seat
cushion. However, depending on the tilt angle of the seat back that
is specified by the reclining operation mechanism, a contact
position of the frame of the seat back with the stopper may vary,
which fails to maintain the forward tilt limit at a target forward
tilt angle.
[0010] In addition, the aforementioned reclining operation
mechanism may often include a spring for biasing the seat back in
the forward tilt direction. In a case where it is impossible to
restrict the forward tilt of the seat back at the target forward
tilt angle, an upper surface of the seat cushion strongly makes
contact with a front surface of the seat back by the biasing force
of the spring before the forward tilt of the seat back is
restricted or the forward tilt angle of the seat back is
insufficient at a time when the locked state between the seat back
and the seat cushion is released.
[0011] A need thus exists for a seat reclining apparatus which is
not susceptible to the drawback mentioned above.
SUMMARY
[0012] According to an aspect of this disclosure, a seat reclining
apparatus includes a support frame tiltable about a support axis
relative to a first frame constituting a seat cushion, an angle
adjustment unit causing a second frame constituting a seat back to
tiltably move forward or rearward relative to the support frame by
a driving force of an actuator, the second frame being displaced in
a direction to approach and separate from the support axis in a
case where the second frame tiltably moves forward or rearward
relative to the support frame, a lock mechanism selectively
operated to an unlocked state where the support frame is allowed to
integrally tiltably move with the angle adjustment unit about the
support axis and a locked state where the support frame is
prohibited to integrally tiltably move with the angle adjustment
unit, and a front stopper provided at the first frame to specify a
forward tilt limit of the seat back by making contact with a
forward tilt contact portion provided at the second frame in a
state where the lock mechanism is in the unlocked state, the front
stopper including a linearly-shaped contact surface that makes
contact with the forward tilt contact portion and that matches or
approximates a virtual straight line passing through the support
axis.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The foregoing and additional features and characteristics of
this disclosure will become more apparent from the following
detailed description considered with the reference to the
accompanying drawings, wherein:
[0014] FIG. 1 is a side view illustrating a first frame and a
second frame of a seat according to an embodiment disclosed
here;
[0015] FIG. 2 is a plan view illustrating a structure of the first
frame;
[0016] FIG. 3 is a cross-sectional view taken along line III-III in
FIG. 2;
[0017] FIG. 4 is a cross-sectional view taken along the line IV-IV
in FIG. 2;
[0018] FIG. 5 is a cross-sectional view illustrating an angle
adjustment unit according to the embodiment disclosed here;
[0019] FIGS. 6A and 6B are cross-sectional views each illustrating
a meshed state between an internal gear and an external gear
according to the embodiment disclosed here;
[0020] FIG. 7 is a side view illustrating a lock mechanism in a
locked state according to the embodiment disclosed here;
[0021] FIG. 8A is a side view illustrating a state where a front
stopper and a forward tilt contact portion make contact with each
other and FIG. 8B is a side view illustrating a state where a back
stopper and a rearward tilt contact portion make contact with each
other according to the embodiment disclosed here;
[0022] FIG. 9 is an exploded perspective view illustrating a
structure of the right angle adjustment unit; and
[0023] FIG. 10 is an exploded perspective view illustrating a
structure of the left angle adjustment unit.
DETAILED DESCRIPTION
[0024] An embodiment disclosed here will be explained with
reference to the attached drawings.
[0025] [Overall Structure]
As illustrated in FIGS. 1 and 2, a reclining-type seat for a
vehicle such as a passenger car includes a seat cushion A of which
a center portion in a width direction of the vehicle is formed by a
seated surface and a seat back B attached at a rear edge of the
seat cushion A so as to be tiltable in a longitudinal direction of
the vehicle. In the embodiment, directions and orientations such as
left, right, front, rear, top, and bottom correspond to those when
viewed from a passenger seated on the seat for a vehicle.
[0026] The seat cushion A includes two first frames (i.e., left and
right first frames) 1 constituting left and right side portions of
the seat cushion A. The seat back B includes two second frames
(i.e., left and right second frames) 2 constituting left and right
side portions of the seat back B. The first frames 1 and the second
frames 2 are tiltably connected to each other at left and right
sides of the seat, respectively, about a support axis X. The seat
also includes two angle adjustment units (i.e., left and right
angle adjustment units) C at connecting portions between the first
frames 1 and the second frames 2 respectively so as to arbitrarily
specify a tilt amount (i.e., a tilt angle) of the second frames 2
relative to the first frames 1 by means of a driving force of a
single actuator. Further, the seat includes two lock mechanisms
(i.e., left and right lock mechanisms) L that achieve a locked
state where each of the second frames 2 is maintained at a fixed
tilt angle relative to each of the first frames 1 and an unlocked
state where each of the second frames 2 is tiltable relative to
each of the first frames 1. A seat reclining apparatus according to
the present embodiment is constituted by a structure where the seat
is tiltable by the first frames 1 and the second frames 2, the
angle adjustment units C, and the lock mechanisms L.
[0027] As illustrated in FIGS. 1 to 5, 9, and 10, each of the angle
adjustment units C includes an upper gear plate 12 serving as a
tilt frame, a lower gear plate 13 serving as a support frame, a
fixed plate 14 and a lock release arm 15 that are arranged in this
order along an axial center X (which is equal to the support axis
X) of each drive shaft 11 (i.e., each of left and right drive
shafts) rotatably supported by the first frame 1. According to the
present embodiment, the lock release arm 15 is provided at only one
of the angle adjustment units C (for example, at the right angle
adjustment unit C).
[0028] Inner ends of the left and right drive shafts 11 are
connected to an intermediate shaft 16. An outer end of one of the
drive shafts 11 is provided with a first power transmission
mechanism where a gear reduction mechanism 17 performs a speed
reduction on a driving force of an electric motor M serving as the
actuator and performs a power transmission of the resulting driving
force.
[0029] Left and right torsion springs 18, each having a coil shape,
are provided at facing portions of the left and right first frames
1. One end of each of the torsion springs 18 engages with a support
block 1A of the first frame 1 while the other end of each of the
torsion springs 18 engages with the upper gear plate 12. As a
result, the second frames 2 are biased forward.
[0030] As illustrated in FIGS. 7, 8A and 8B, each of the lower gear
plates 13 includes multiple lock recess portions 13A at a lower
side. Each lock arm (i.e., each of left and right lock arms) 19
including multiple protruding portions 19A engageable and
disengageable relative to the multiple lock recess portions 13A is
supported at a side surface of each of the left and right first
frames 1 so as to be rotatable about a lock support shaft 20. The
lock arm 19 includes a guide portion 19B having a cutout shape
along which a control roller 22 is movable. Each of the
aforementioned lock mechanisms L is obtained by engagement and
disengagement between the lock arm 19 and the lower gear plate
13.
[0031] The lock release arm 15 is movably supported about the
support axis X at an outer wall portion of one of the fixed plates
14, specifically, the right fixed plate 14. Then, a linking arm 35
is provided at a position facing the lock release arm 15 across the
right first frame 1. The linking arm 35 is movable about the
support axis X. The right control roller 22 is supported at both
ends by the lock release arm 15 and the right linking arm 35. An
arm portion 15A of the lock release arm 15 is provided with a grip
of which a user takes hold.
[0032] An operation arm 36 is movably supported about the support
axis X at an outer wall portion of the other of the fixed plates
14, specifically, the left fixed plate 14. The operation arm 36 is
provided at a position symmetrical to a position where the lock
release arm 15 is provided. The left control roller 22 is supported
at both ends by the operation arm 36 and the left linking arm
35.
[0033] The left and right linking arms 35 are connected to a
linking shaft 23 within which the intermediate shaft 16 is
coaxially fitted. The left linking arm 35 and the operation arm 36
receive a biasing force from a lock spring 21 (see FIG. 7) to
thereby maintain the control roller 22 at a locked position.
[0034] The guide portion 19B of each of the lock arms 19 includes a
lock area and an unlock area continuously formed as illustrated in
FIGS. 7, 8A and 8B. Specifically, in a case where the control
roller 22 is positioned at the lock area as illustrated in FIG. 7,
the protruding portions 19A engage with the respective lock recess
portions 13A. In a case where the control roller 22 is positioned
at the unlock area as illustrated in FIGS. 8A and 8B, the
protruding portions 19A of the lock arm 19 disengage from the
respective lock recess portions 13A.
[0035] When the arm portion 15A of the lock release arm 15 is
manually operated upward in a state where each of the lock
mechanisms L is in the locked state, i.e., the protruding portions
19A engage with the respective lock recess portions 13A, the
control roller 22 moves along the guide portion 19B from the lock
area to the unlock area. Because the left and right linking arms 35
are connected to each other by means of the linking shaft 23, the
left and right control rollers 22 both move to the respective
unlock areas from the respective lock areas at the same time. As a
result, the left and right lock arms 19 are allowed to move in a
direction where the locked states of both of the lock mechanisms L
are released. Then, as illustrated in FIGS. 8A and 8B, the
protruding portions 19A of each of the lock arms 19 disengage from
the respective lock recess portions 13A of each of the lower gear
plates 13, thereby bringing each of the lock mechanisms L to the
unlocked state.
[0036] Each of the lock mechanisms L is brought to the unlocked
state so that the seat back B is tilted forward by the biasing
force of the left and right torsion springs 18. In addition, in a
case where a force to tilt the seat back B rearward is applied
thereto when each of the lock mechanisms L is brought to the
unlocked state, the seat back B is tilted rearward against the
biasing force of the left and right torsion springs 18.
[0037] [Angle adjustment unit]
The angle adjustment unit C transmits the driving force of the
electric motor M from the gear reduction mechanism 17 to a second
power transmission mechanism serving as a power transmission
mechanism provided between the upper gear plate 12 and the lower
gear plate 13. Then, the speed reduction is conducted on the
driving force by the second power transmission mechanism to thereby
tilt the upper gear plate 12 relative to the lower gear plate
13.
[0038] Specifically, as illustrated in FIGS. 3 to 6, 9 and 10, each
of the lower gear plates 13 is formed by a circular-shaped gear
accommodating portion at a center. The gear accommodating portion
is formed by press working, or the like, and is dent in a thickness
direction of the lower gear plate 13. A support boss portion 13B is
formed at a center of the gear accommodating portion by burring, or
the like so as to protrude along the support axis X. A bore 13H is
formed at an inner periphery of the support boss portion 13B. In
addition, an internally toothed gear (internal gear) 13G is
integrally formed at an inner periphery of the gear accommodating
portion of the lower gear plate 13 so as to be coaxial with the
support boss portion 13B.
[0039] Each of the upper gear plates 12 is formed by a
circular-shaped bulged portion at a center. The bulged portion is
formed by a press working, or the like, and is dent in a thickness
direction of the upper gear plate 12. A circular-shaped bore 12H
penetrates through a center of the bulged portion. In addition, an
externally toothed gear (external gear) 12G is integrally formed at
an outer periphery of the bulged portion of the upper gear plate 12
so as to be coaxial with the bore 12H. The external gear 12G has
one fewer tooth or less compared to the internal gear 13G.
[0040] A pair of wedge pieces 25 is arranged at an outer periphery
of the support boss portion 13B so as to be slidable on the outer
periphery thereof in a circumferential direction. The wedge pieces
25 are examples of eccentric members. Each of the wedge pieces 25
is integrally formed by a projecting portion 25A along the support
axis X. A loop-shaped spring 26 is disposed to bias the pair of
wedge pieces 25 to separate them each other in the circumferential
direction of the support boss portion 13B. A cam plate 27 including
an engagement recess portion 27A that makes contact with the
projecting portions 25A of the pair of wedge pieces 25 so as to
apply a rotational force thereto is provided at each of the drive
shafts 11. The pair of wedge pieces 25 collectively forms an outer
peripheral shape that partially constitutes a periphery eccentric
to the axial center X of each of the drive shafts 11 when viewed in
a direction along the axial center X. The pair of wedge pieces 25
is arranged to make contact with an inner periphery of the bore 12H
of each of the upper gear plates 12.
[0041] Accordingly, a center of the external gear 12G formed at
each of the upper gear plates 12 is positioned eccentric to the
axial center X of the drive shaft 11. Consequently, a portion of
the internal gear 13G of each of the lower gear plates 13 is meshed
with a portion of the external gear 12G of each of the upper gear
plates 12.
[0042] In the aforementioned arrangement between the internal gear
13G and the external gear 12G, in a case where each of the drive
shafts 11 is driven to rotate, end faces of the engagement recess
portion 27A of the cam plate 27 make contact with the respective
projecting portions 25A of the pair of wedge pieces 25. The
rotational force of the drive shaft 11 is transmitted to the pair
of wedge pieces 25 via the contacting portion between the cam plate
27 (i.e., the engagement recess portion 27A) and the pair of wedge
pieces 25, thereby slidably rotating the pair of wedge pieces 25 on
the outer periphery of the support boss portion 13B in the
circumferential direction. According to such rotation of the pair
of wedge pieces 25, the center of the external gear 12G of the
upper gear plate 12 moves along a circumferential locus so as to be
away from the axial center X of the drive shaft 11. While the
center of the external gear 12G is moving, the meshed position
between the external gear 12G and the internal gear 13G is moving
along the inner periphery of the internal gear 13G. As a result,
the external gear 12G tiltably moves relative to the internal gear
13G.
[0043] According to a principle of the speed reduction of the
second power transmission mechanism, because the external gear 12G
has one fewer tooth or less compared to the internal gear 13G, the
external gear 12G rotates one turn on the inner periphery of the
internal gear 13G and the internal gear 13G rotates by an angle
(i.e., an angle shown by an arrow in FIG. 6B) corresponding to a
difference of the number of teeth between the internal gear 13G and
the external gear 12G when the drive shaft 11 rotates one turn, for
example. As a result, a large speed reduction by a large reduction
gear ratio is achieved. As a result, according to the second power
transmission mechanism of the present embodiment, the second frames
2 move tiltably along with rotations of the drive shafts 11,
thereby arbitrarily specifying the angle of the seat back B
relative to the seat cushion A.
[0044] Specifically, according to each of the angle adjustment
units C of the present embodiment, the meshed position between the
external gear 12G and the internal gear 13G moves along the inner
periphery of the internal gear 13G. Thus, each of the second frames
2 in addition to each of the upper gear plates 12 including the
external gear 12G is displaced in a direction to approach and
separate from the support axis X.
[0045] [Tilt limiting mechanism]
In a case where the left and right lock arms 19 are operated in a
direction where the locked state of each of the lock mechanisms L
is released by an operation of the lock release arm 15 so that the
lock mechanism L is brought to the unlocked state, each of the
upper gear plates 12 and each of the lower gear plates 13 are
connected to each other via the second power transmission mechanism
so as to be integrally tiltable about the support axis X.
[0046] Thus, in a case where the lock mechanisms L are each brought
to the unlocked state while a user is not seated on the seat, the
upper gear plates 12 and the lower gear plates 13 are integrally
tilted forward to the utmost limit about the support axis X by the
biasing force of the torsion springs 18. Then, front stoppers 31
that determine a forward tilt limit of the upper gear plates 12 and
the lower gear plates 13 are provided at the respective first
frames 1. In addition, forward tilt contact portions 2S that make
contact with the front stoppers 31 are formed at the respective
second frames 2.
[0047] As illustrated in FIG. 7, each of the front stoppers 31 is
made of a plate member fixed to the first frame 1 by spot welding,
or the like. The front stoppers 31 having the plate shape also
serve as reinforcements of the first frame 1. The front stopper 31
includes a contact surface 31S at an upper end linearly and
horizontally extending. A virtual straight line V obtained by an
extension of the contact surface 31S is configured to pass through
a vicinity of the support axis X. It is desirable that the virtual
straight line V passes through the support axis X, however, the
virtual straight line V is still effective even when passing
through the vicinity of the support axis X.
[0048] The forward tilt contact portions 2S constitute portions of
the second frames 2. Each of the forward tilt contact portions 2S
does not include a specific structure for a contact according to
the present embodiment. However, for example, a projection, a
contact member, or the like may be formed at the forward tilt
contact portion 2S for the contact with the front stopper 31.
[0049] According to the seat reclining apparatus of the present
embodiment, the seat back B is also tiltable forward by the driving
force of the electric motor M of the angle adjustment unit C. In
this case, an angle achieved immediately before each of the forward
tilt contact portions 2S makes contact with each of the front
stoppers 31 is specified to be a forward operation limit of the
seat back B. When the seat back B reaches the forward operation
limit, the electric motor M is automatically stopped by an electric
control. In addition, the seat back B may be configured to be
tilted rearward so as to be positioned substantially horizontally
by the use of the driving force of the electric motor M. Such
configuration is realized by an operation of a switch, for example.
When the seat back B reaches a rearward operation limit, the
electric motor M is automatically stopped by the electric
control.
[0050] When the seat back B is tilted to the forward operation
limit, a space in the rear of the seat back B is open. Therefore,
for example, a wide space is ensured for a user to get in or out of
a seat arranged behind the present seat to thereby ease a walk-in
operation, and the like.
[0051] In a case where the angle adjustment units C are each
brought in the unlocked state when the user, seated on the seat,
leans against the seat back B, the upper gear plates 12 and the
lower gear plates 13 are integrally tilted rearward to the utmost
limit about the support axis X. In order to determine a rearward
tilt limit as illustrated in FIGS. 8A and 8B, back stoppers 32 are
provided at the first frames 1 respectively at positions adjoined
to the lower gear plates 13. Rearward tilt contact portions 13S
making contact with the back stoppers 32 are formed at the
respective lower gear plates 13.
[0052] Each of the back stoppers 32 having a column shape is
provide at the first frame 1 in a projecting manner. The back
stopper 32 also serves as a member supporting the fixed plate 14 to
the first frame 1 and further serves as a connection member
connecting the front stopper 31 to the first frame 1 (see FIG. 1).
The rearward tilt contact portion 13S is a portion of the end
surface of the lower gear plate 13. The rearward tilt contact
portion 13S does not include a specific structure for a contact
according to the present embodiment. Alternatively, a member for
the contact may be separately provided from the lower gear plate
13.
[0053] As illustrated in FIGS. 8A and 8B, when assuming that a
distance between the contact position between the front stopper 31
and the forward tilt contact portion 2S and the support axis X is a
first distance D1 and a distance between the contact position
between the back stopper 32 and the rearward tilt contact portion
13S and the support shaft X is a second distance D2, the first
distance D1 is greater than the second distance D2 (i.e.,
D1>D2). A value of the first distance D1 varies depending on the
tilt angle of the seat back B relative to the seat cushion A by the
angle adjustment units C as mentioned above. However, the
relationship between the first distance D1 and the second distance
D2, i.e., D1>D2, is maintained. At this time, the relationship
of D1>D2 is an example of the present embodiment and may not be
necessarily achieved.
[0054] According to the aforementioned structure, the position of
the forward tilt contact portion 2S formed at each of the second
frames 2 is displaced relative to the support axis X in the
direction to approach and separate therefrom by the operation of
the angle adjustment units C and therefore the contact position of
the forward tilt contact portion 2S relative to the front stopper
31 varies upon the forward tilt of the seat back B with the lock
mechanism L in the unlocked state. However, the variation of the
contact position of the forward tilt contact portion 2S relative to
the front stopper 31 corresponds to the direction to approach and
separate from the support axis X. Thus, the tilt angle of the seat
back B is prevented from varying to thereby retain the seat back B
at a desirable angle.
[0055] That is, the tilt amount, i.e., the tilt angle of the second
frames 2 relative to the first frames 1 is selectable by the
driving force of the electric motor M of the angle adjustment unit
C. In addition, in a case where the seat back B is tilted forward
while the lock mechanisms L are each in the unlocked state, the
forward tilt contact portions 2S of the second frames 2 make
contact with the respective front stoppers 31, thereby determining
the limit of the tilt operation. Further, even when the distance
between each of the second frames 2 and the support axis X varies
depending on the tilt angle specified by the angle adjustment units
C, the forward tilt contact portions 2S make contact with the
respective front stoppers 31 on the respective virtual lines V,
thereby restraining the tilt angle of the seat back B from varying.
The seat back B is maintained at a position of the forward tilt
limit. Accordingly, in a case where the position of the seat back B
varies relative to the support axis X serving as the axial center
of the tilt operation of the seat back B when the reclining
operation of the seat is adjusted by the electric motor M, the
forward operation of the seat back B is restricted at an
appropriate position in a state where the seat back B is tilted
forward with the lock mechanisms L each in the unlocked state.
[0056] According to the aforementioned embodiment, the first frame
1 is constituted by a plate member and the front stopper 31 serves
as a reinforcement member connected to the first frame 1.
[0057] Because the front stopper 31 is formed by the reinforcement
member, the contact surface 31S of the front stopper 31 is easily
linearly formed while the reinforcement of the first frame 1 is
conducted.
[0058] In addition, according to the aforementioned embodiment, the
seat reclining apparatus further includes the back stopper 32
arranged adjacent to the lower gear plate 13 and specifying the
rearward tilt limit of the seat back B by making contact with the
rearward tilt contact portion 13S provided at the lower gear plate
13 in a state where the lock mechanism L is in the unlocked state,
the back stopper 32 serving as a connection member connecting the
front stopper 31 to the first frame 1.
[0059] Accordingly, in a case where the seat back B is tilted
rearward with the lock mechanism L in the unlocked state, the
rearward tilt contact portion formed at the lower gear plate 13
makes contact with the back stopper 32 to thereby determine the
rearward operation limit. The back stopper 32 is provided adjacent
to the rearward tilt contact portion 13S to thereby restrain an
enlargement of the rearward tilt contact portion 13S, i.e., an
enlargement of the lower gear plate 13. In addition, because the
back stopper 32 also serves as a member to connect the front
stopper 31 to the first frame 1, an increase of the number of
components may be restrained.
[0060] Further, according to the aforementioned embodiment, the
lock mechanism L includes the lock arm 19 rotatably supported by
the front stopper 31 and being engageable and disengageable
relative to the lower gear plate 13 by a rotation of the lock arm
9.
[0061] Furthermore, according to the aforementioned embodiment, the
angle adjustment unit C includes the internal gear 13G formed at
the lower gear plate 13, the external gear 12G formed at the upper
gear plate 12 connected to the second frame 2 and having fewer
teeth compared to the internal gear 13G, and the pair of wedge
pieces 25 integrally rotating with the drive shaft 11 which is
driven to rotate by the electric motor M, a portion of the internal
gear 13G engaging with a portion of the external gear 12G, the
external gear 12G being rotatably mounted at an outer periphery of
the pair of wedge pieces 25. The seat reclining apparatus further
includes the second power transmission mechanism moving the meshed
position between the external gear 12G and the internal gear 13G
along an inner periphery of the internal gear 13G by a rotational
force of the pair of wedge pieces 25 when the electric motor M is
driven, the second power transmission mechanism causing the upper
gear frame 12 to tilt by an angle corresponding to a difference of
the number of teeth between the external gear 12G and the internal
gear 13G in a case where the external gear 12G rotates one turn
along the inner periphery of the internal gear 13G, the upper gear
frame 12 being displaced in the direction to approach and separate
from the support axis X when the meshed position between the
external gear 12G and the internal gear 13G moves along the inner
periphery of the internal gear 13G.
[0062] Accordingly, the upper gear plate 12 is displaced in the
direction to approach and separate from the support axis X, which
results in a relatively simple structure with two gears for
obtaining a large speed reduction. Specifically, according to the
seat reclining apparatus of the embodiment, while the
aforementioned second power transmission mechanism is used, the
variation of the forward operation limit when the seat back B is
tilted forward may be restrained.
[0063] The principles, preferred embodiment and mode of operation
of the present invention have been described in the foregoing
specification. However, the invention which is intended to be
protected is not to be construed as limited to the particular
embodiments disclosed. Further, the embodiments described herein
are to be regarded as illustrative rather than restrictive.
Variations and changes may be made by others, and equivalents
employed, without departing from the spirit of the present
invention. Accordingly, it is expressly intended that all such
variations, changes and equivalents which fall within the spirit
and scope of the present invention as defined in the claims, be
embraced thereby.
* * * * *