Reclining apparatus

A compact and lightweight round reclining apparatus having a neutral position return function of automatically returning and securing the backrest to the preset neutral position when the backrest that has been reclined forward is raised is provided. A memory plate in approximately disc form having a center shaft at its center and a spring member for pressing the memory plate so that the memory plate always rotates in one direction intervene between a base plate and a gear plate. A guide portion, which is a long hole in approximately arc form, for restricting the movement of the lock gear outward in the direction of the radius through contact with the protrusion of the above described lock gear is provided inside the disc of the memory plate, and at least one notch is provided in the outer periphery of the memory plate so that an engaging portion provided on the above described gear plate enters into the notch and the memory plate is rotatable relative to the gear plate within the range of the notch.

BACKGROUND OF THE INVENTION

The present invention relates to a reclining apparatus installed in a seat for a vehicle, and in particular, to a reclining apparatus having a neutral position return function where the backrest which has been reclined forward through the operation by a passenger can be returned and secured to a preset position (within a range of an adjustment of the inclination angle) with a simple operation.

Various types of conventional apparatuses have been proposed as a reclining apparatus installed in a seat for a vehicle. From among these, reclining apparatuses which are mounted in seats in the front row of coupe style vehicles and three door hatchback style vehicles and seats in the second row of minivans and cab wagon style vehicles so that the passengers can get into and leave from the seats in the rear row are put into practice, and many vehicles are equipped with these. Such reclining apparatuses have a neutral position return function which makes it possible for the backrest to recline forward to a great degree and automatically return and be secured to the preset position (neutral position) by simply raising the above described backrest after the completion of getting into and leaving from the seats in the rear row.

Apparatuses such as those described in Japanese Unexamined Patent Publication H2 (1990)-177908, for example, are publicly known as reclining apparatuses having the above described neutral position return function. The apparatus described in this publication adopts a configuration wherein a sector plate 8, in which a sector gear 9 having external cogs is formed, is secured to a rotational bracket 5 on the backrest side, a lock plate 11, in which a lock gear 17 is formed, is secured to a stationary bracket 3 on the seat side with an axis, and a memory plate 20 for preventing the engagement between the sector gear 9 and the lock gear 17 under certain conditions is provided so as to intervene in between. Thus, the above described memory plate 20 works to allow the backrest to return and be secured to the preset neutral position simply by raising the backrest that has been reclined forward.

Meanwhile, as for compact and lightweight reclining apparatuses which can be easily attached to a seat, apparatuses which are referred to as round reclining apparatuses (circular reclining apparatuses) are put into practice. In these round reclining apparatuses, a base plate in approximately disc form and a gear plate in approximately disc form are combined so as to face each other, and a locking mechanism is provided in the internal space across which the two plates face each other so that the two plates rotate relative to each other with a center shaft as a fulcrum, making it possible to be secured at a desired position, or phase.

As a concrete configuration of these round reclining apparatuses, the one described in Japanese Patent No. 3343039, for example, is publicly known. In the apparatus described in this patent, two pegs 12 (corresponding to “protrusions”) are formed so as to protrude from a follower 5 (corresponding to a “lock gear”) in the direction of the axis, in addition to the above described respective components, so that one peg 12 allows the locking mechanism to be held in a released position in a predetermined range while the other peg 12 and a thin plate 14 having a circular orbit P (corresponding to a “guide hole”) with a step, control the release of the lock. That is to say, the seats to which such an apparatus is attached have such a configuration that when the backrest is reclined forward at the time of getting into or leaving from the rear seat of the vehicle, the locking mechanism is maintained in a release position even after the operation of the operation member is released, and the backrest is returned and secured to the front end in the range of the adjustment (the highest raised position where the backrest is raised the most as long as it can be secured) when the backrest that has been reclined forward is raised.

In addition, a reclining apparatus is proposed in Japanese Unexamined Patent Publication H8 (1996)-300990 as a reclining apparatus where a function of returning and being secured to a position within the range of the adjustment is added to the above described round reclining apparatus, and a function (full memory function) of automatically returning to the original position where the angle has been adjusted to the angle before the backrest is reclined forward when the backrest is reclined backward starting from the forward reclined position is provided. The reclining apparatus described in this publication is provided with a ring 11 having a first side plate 8 (a plate in disc form) and a second side plate 9 (a plate in disc form) and a pair of internal cogs 19, with a locking and lock releasing mechanism M between the cogs 12 of the above described ring 11 and the first side plate 8 (a conventional angle adjustment mechanism) and a second mechanism (a full memory mechanism) for locking and lock releasing between the cogs 12 of the above described ring 11 and the second side plate 9, and for storing the adjusted location when working together with a crossing plate. That is to say, the round reclining apparatus according to this publication has a conventional mechanism M for adjusting the reclining angle, and a second mechanism for performing the full memory function, and thus adopts a configuration where the angle adjustment mechanisms in conventional reclining apparatuses are combined so as to be duplicated.

SUMMARY OF THE INVENTION

The technologies described in the above patent documents have disadvantages as follows. First, the reclining apparatus described in Japanese Unexamined Patent Publication H2 (1990)-177908 has a configuration in which a neutral position return function made of a sector plate 8, in which a sector gear 9 having external cogs is formed, a lock plate 11 where a lock gear 17 is formed, and a memory plate 20 for preventing the engagement between the sector gear 9 and the lock gear 17 under certain conditions is adopted. Therefore, when mass produced, it is difficult for such a neutral position return function to be incorporated in the round reclining apparatus where a base plate in approximately disc form and a gear plate in approximately disc form are combined so as to face each other, and a lock mechanism is provided in the internal space across which the two plates face each other.

In addition, the round reclining apparatus described in Japanese Patent No. 3343039 is provided with a follower 5 and a thin plate 14 in such a manner that two pegs 12 are formed in the follower 5 so that one peg 12 allows the locking mechanism to be maintained in the release position and the other peg 12 and the thin plate 14 control the lock release. Therefore, in this apparatus, though the backrest is kept in a forward reclined position even when the operation of the operation means is released, the backrest is returned and secured to the front end position in the range of the adjustment when the backrest is raised, and thus, a neutral position return function is not provided and the apparatus is insufficient in convenience.

In addition, in the round reclining apparatus described in Japanese Unexamined Patent Publication H8 (1996)-300990, though a more convenient full memory function is provided, the apparatus has a conventional mechanism M for adjusting the angle, and a second mechanism for performing a full memory function, and therefore, angle adjustment mechanisms are combined so as to be duplicated in the configuration, making the apparatus large scale and the structure complicated, and there is a disadvantage that the apparatus becomes expensive.

The present invention is provided in order to solve the above described difficulties and disadvantages, and an object thereof is to provide a compact and lightweight round reclining apparatus having a neutral position return function which allows the backrest to automatically return and be secured to the preset neutral position when the backrest that has been reclined forward is raised.

Embodiments of the invention may include a reclining apparatus provided with a base plate in approximately disc form secured to either a seat cushion or a backrest of a seat, a gear plate in approximately disc form having internal cogs which is combined with the base plate so as to be rotatable and face the base plate1, a number of lock gears having external cogs which can engage with the internal cogs of the above described gear plate, which are placed within a guide portion made of at least a pair of protrusions provided in the above described base plate so as to be moveable in the direction of the radius in the base plate, a cam6for controlling the movement of the above described lock gear in the direction of the radius so that the lock gear engages with the internal cogs of the gear plate, a spring for pressing the above described cam so that the cam rotates in such a direction that the above described lock gear engages with the above described internal cogs, a lever plate which rotates together with the above described cam and engages with a protrusion provided and protruded from in the above described lock gear so as to control the movement of the lock gear inward in the direction of the radius, a center shaft which penetrates through approximately the center of the above described base plate and gear plate so as to be rotatable together with the cam, and an operation member which is connected to the center shaft so as to rotate and drive the center shaft against the force of the above described spring, in which the configuration is characterized in that a memory plate in approximately disc form having the above described center shaft at the center and a spring member for pressing the memory plate in one direction so that the memory plate always rotates to intervene between the above described base plate and gear plate, a guide portion, which is a long hole in approximately arc form for restricting the movement of the lock gear outwards in the direction of the radius through contact with the protrusion of the above described lock gear, is provided and protruded inside the disc of the memory plate, at least one notch is provided in the outer periphery of the memory plate so that an engaging portion provided in and protruding from the above described gear plate enters into the notch and the memory plate is rotatable relative to the gear plate within the range of the notch, when the backrest is in a range from the most forward reclined position to the highest raised position, the protrusion of the above described lock gear makes contact with the above described guide portion so as to form a lock free range where the external cogs of the lock gear are released from the engagement with the internal cogs of the gear plate, when the backrest is in a range from the highest raised position to the most backward reclined position, the protrusion of the above described lock gear is released from making contact with the above described guide portion so as to form a range of the adjustment where the external cogs of the lock gear engage with the internal cogs of the gear plate, the above described spring member presses the memory plate so that the memory plate rotates in such a direction that the protrusion of the lock gear disengages from the guide portion, and when the backrest is reclined backward in a state where the protrusion of the above described lock gear makes contact with the guide portion of the above described memory plate, the memory plate rotates together with the base plate against the force of the above described spring members so that the protrusion of the above described lock gear is released from making contact with the above described guide portion and the external cogs of the lock gear engage with the internal cogs of the gear plate.

The memory plate and the spring member for pressing the memory plate in such a direction that the backrest always reclines backward relative to the gear plate implement the neutral position return function, and thus, the neutral position return function can be easily incorporated inside the compact and lightweight round reclining apparatus. In addition, the backrest that has returned to the neutral position makes it easy to sit down afterwards, and the reclining apparatus can be readjusted to the originally adjusted position or a desired adjusted position with a slight adjustment starting from the neutral position, and therefore, effects can be gained in which the apparatus is easy to use.

In some embodiments, the above described gear plate is formed in approximately bowl form having steps in stair form, in which a first step where the above described internal cogs are formed around the inner periphery of the opening, a second step of which the radius of the circumference is smaller than that of the first step and which slides against the outer periphery of the above described lever plate, and a third step of which the radius of the circumference is smaller than that of the second step and which slides against the outer periphery of the above described memory plate are formed, and the above described spring member is provided between the memory plate and the gear plate.

Where the gear plate is formed in approximately bowl form having steps in stair form in such a manner that the lever plate and the memory plate engage with these steps so as to be slidable, functions separated from each other can be collected in a layer structure, and in addition, the spring member is contained within the round reclining apparatus, and therefore, effects can be gained in which a compact and simple configuration can be implemented.

Some embodiments will include a base plate in approximately disc form secured to either a seat cushion or a backrest of a seat, a gear plate in approximately disc form having internal cogs, which is combined with the base plate so as to be rotatable and face the base plate, a number of lock gears having external cogs that can engage with the internal cogs of the above described gear plate, which are placed within a guide portion made of at least a pair of protrusions provided in the above described base plate so as to be moveable in the direction of the radius in the base plate, a cam for controlling the movement of the above described lock gear in the direction of the radius so that the lock gear engages with the internal cogs of the gear plate, a spring for pressing the above described cam so that the cam rotates in such a direction that the above described lock gear engages with the above described internal cogs, a lever plate that rotates together with the above described cam and engages with a protrusion provided in the above described lock gear so as to control the movement of the lock gear inward in the direction of the radius, a center shaft which penetrates through approximately the center of the above described base plate and gear plate so as to be rotatable together with the cam, and an operation member connected to the center shaft so as to rotate and drive the center shaft against the force of the above described spring, of which the configuration is characterized in that a memory plate in approximately ring form having the above described center shaft at the center and a spring member for pressing the memory plate in one direction so that the memory plate always rotates intervene between the above described base plate and gear plate, a guide portion in approximately arc form for restricting the movement of the lock gear outwards in the direction of the radius through contact with the protrusion of the above described lock gear is formed in the inner peripheral portion of the ring of the memory plate, at least one notch is provided in the outer periphery of the memory plate so that an engaging portion provided in and protruding from the above described gear plate enters into the notch and the memory plate is rotatable relative to the gear plate within the range of the notch when the backrest is in a range from the most forward reclined position to the highest raised position, the protrusion of the above described lock gear makes contact with the above described guide portion so as to form a lock free range where the external cogs of the lock gear are released from the engagement with the internal cogs of the gear plate, when the backrest is in a range from the highest raised position to the most backward reclined position, the protrusion of the above described lock gear is released from making contact with the above described guide portion so as to form a range of the adjustment where the external cogs of the lock gear engage with the internal cogs of the gear plate, the above described spring member presses the memory plate so that the memory plate rotates in such a direction that the protrusion of the lock gear disengages from the guide portion, and when the backrest is reclined backward in a state where the protrusion of the above described lock gear makes contact with the guide portion of the above described memory plate, the memory plate rotates together with the base plate against the force of the above described spring members so that the protrusion of the above described lock gear is released from making contact with the above described guide portion and the external cogs of the lock gear engage with the internal cogs of the gear plate.

The spring member for pressing the memory plate in such a direction that the backrest always reclines backward relative to the gear plate implements the neutral position return function, and thus, the neutral position return function can be easily incorporated inside the compact and lightweight round reclining apparatus. In addition, the backrest that has returned to the neutral position makes it easy to sit down afterwards, and the reclining apparatus can be readjusted to the originally adjusted position or a desired adjusted position with a slight adjustment starting from the neutral position, and therefore, effects can be gained in which the apparatus is easy to use.

In some embodiments, the above described gear plate is formed in approximately bowl form having steps in stair form, in which a first step where the above described internal cogs are formed around the inner periphery of the opening, a second step of which the radius of the circumference is smaller than that of the first step and which slides against the outer periphery of the above described lever plate, and a third step of which the radius of the circumference is smaller than that of the second step and which slides against the outer periphery of the above described memory plate are formed, the above described spring member is a spiral spring in such a form that the end on the outer side of the spiral is bent backward in the direction opposite to the direction in which the spiral winds and the end on the center side is bent in the same direction as the direction in which the spiral winds, where the end on the outer side engages with a hook portion in hook form provided on the inner periphery of the above described memory plate and the end on the center side engages with a protrusion in approximately columnar form provided and protruded from in the bottom portion of the gear plate, and the above described spiral spring is placed in the above described third step.

Where the gear plate is formed in approximately bowl form having steps in stair form in such a manner that the lever plate and the memory plate engage with these steps so as to be slidable, functions separated from each other can be collected in a layer structure, and in addition, the spring member is contained within the round reclining apparatus, and therefore, a compact and simple configuration can be implemented. In addition, the spring member is provided as a spiral spring in such a form that the end on the outer side of the spiral is bent backward in the direction opposite to the direction in which the spiral winds and the end on the center side is bent in the same direction as the direction in which the spiral winds, and the configuration allows the spring member to be placed inside the hallow memory plate, and therefore, effects can be gained in which the space for providing a spring member in the direction of the axis of the center shaft can be eliminated so as to make the configuration compact.

In some embodiments an arc portion where no internal cogs are formed is provided in the above described gear plate, and this arc portion is thicker in the direction of the radius than the internal cogs portions, an inclined portion, which inclines outward in the direction of the radius, is provided in an end portion of the guide portion provided in the above described memory plate, and when the backrest is reclined forward within the above described lock free range, the external cogs of the lock gear ride on the above described arc portion, and after that, the protrusion of the lock gear is moved towards the center along the radius by the above described inclined portion so as to be guided to and make contact with the guide portion.

Where the inner periphery of the gear plate is provided with an arc portion where no internal cogs are formed and which is thicker in the direction of the radius than the internal cogs, and an inclined portion which inclines outwards in the direction of the radius is provided in an end portion of the guide portion provided in the memory plate, and thus, when the backrest is reclined forward within the lock free range, the external cogs of the lock gear ride on the above described arc portion, and after that, the protrusion of the lock gear is moved toward the center along the radius by the above described inclined portion and guided to the guide portion. By providing such a configuration, effects can be gained in which the engagement between the lock gear and the gear plate in the vicinity of the highest raised position can be achieved without fail.

In some embodiments the periphery which reaches the end portion of the above described guide portion protrudes towards the center from the arc of the guide portion having the center shaft at the center.

Where the periphery which reaches the end portion of the guide portion protrudes toward the center from the arc of the guide portion having the center shaft at the center, effects can be gained in which the memory plate can be prevented from rotating by following the gear plate within a certain range where the above described memory plate is rotatable relative to the gear plate. In the case where the memory plate rotates without the notch of the memory plate making contact with the engaging portion of the gear plate through the friction between the periphery of the memory plate and the gear plate, the position where the external cogs of the lock engage with the internal cogs of the gear plate shifts from the center position by this amount. Therefore, the protrusion of the above described guide portion provides resistance against the rotation of the memory plate, and thus, it becomes possible for the notch of the memory plate to make contact with the engaging portion of the gear plate before the protrusion of the lock disengages from the guide portion.

DETAILED DESCRIPTION OF EMBODIMENTS AS EXAMPLES

FIGS. 1 to 9show a reclining apparatus105according to the first embodiment. First, the outline of the present embodiment is described below.

FIG. 1is a diagram showing the state of a seat100having a seat cushion101and a backrest102, to which a reclining apparatus105according to the present invention is attached, as viewed from the side of the seat100. As shown in the cross sectional diagram ofFIG. 2, in the reclining apparatus105according to the present embodiment, a base plate1in approximately disc form and a gear plate2in approximately disc form are combined so as to face each other. In the present invention, “in approximately disc form” means that the outer shape is round (circular form). One of these plates1or2is secured to a lower bracket103, and the other plate is secured to upper bracket104. As shown inFIG. 1, in the present embodiment, the lower end portion of the above-described lower bracket103is attached to the rear end portion of the seat cushion101. Meanwhile, the upper end portion of the above-described upper bracket104is attached to the lower end portion of the backrest102.

InFIGS. 1 and 2, symbol106indicates the center shaft provided at the center of the reclining apparatus105, and symbol107indicates an operation lever of which one end is attached to the above described center shaft106. When the locked state of the reclining apparatus105is released through the operation of this operation lever107by a passenger, the backrest102shown inFIG. 1can be adjusted and secured at an arbitrary inclination angle within the range of adjustment a from the highest raised position A to the most reclined position D. In addition, the backrest102is not locked within the lock free range b from the highest raised position A to the most forward reclined position B even in a state where the operation lever107is released by the passenger.

Here, the position “C” inFIG. 1is a neutral position where the backrest102automatically returns and is secured when the backrest102is raised from the most forward reclined position toward the backward reclined position, and the position having the highest possibility of being used when the passenger sits down is preset as the position C in the range of adjustment a. Therefore, it is easy to sit down when the backrest is in the neutral position C in comparison with when the backrest is at the highest raised position A, and in addition, with a slight adjustment, the backrest can be readjusted to the originally adjusted position or a desired adjusted position at which the backrest was locked before being reclined forward.

Next, a concrete configuration of the reclining apparatus105is described in detail in reference toFIGS. 2 to 8. In the reclining apparatus105according to the present embodiment, a base plate1in approximately disc form and a gear plate2in approximately disc form face each other, and a center shaft106penetrates through the center portion of these so that the base plate1and the gear plate2are rotatable around the center shaft106relative to each other. In addition, a ring member3is provided around the outer periphery of the circle of the reclining apparatus105, and this ring member3is caulked, and thus, the outer peripheral portions of the above described base plate1and gear plate2are held so as not to separate from each other and to be slidable against each other.

In addition, a cavity (space)4is provided between the above described base plate1and gear plate2, which face each other. A publicly known lock mechanism made of two lock gears5and5, a center cam6and two spiral springs7and7and a lever plate8is contained within this cavity4. In the same manner, a member which forms a neutral position return mechanism of a memory plate9and a coil spring10is also contained within the cavity4.

A number of circular protrusions17and27are formed on the outer surfaces of the above described base plate1and gear plate2(surfaces opposite to the above described surfaces which face each other), respectively. The base plate1is attached to the lower bracket103with circular protrusions17while the gear plate2is attached to the upper bracket104with circular protrusions27. Therefore, the base plate1and the gear plate2rotate around the center shaft106in the reclining apparatus105relative to each other, and the relative angle is fixed so that the relative rotation position of the lower bracket103and the upper bracket104is adjusted and secured, and the inclination angle of the backrest102relative to the seat cushion101is adjusted and fixed.

The inner surface of the base plate1(the surface which faces the above described gear plate2) is in approximately bowl form having steps in concentric circular form. A hole1athrough which the above described center shaft106penetrates is provided at the center. In addition, as shown inFIG. 3, a pair of guide portions50amade of protrusions11and12are integrally formed on the inner surface of the base plate1through press processing. The two guide portions50aare provided at symmetric positions relative to the above described hole1a, and the surfaces11aand12aof the respective protrusions11and12which face each other are set so as to be parallel to each other. In addition, the lock gears5contained inside the two guide portions50aare slidable in the direction of the radius of the base plate1in a state where they slide against the surfaces11aand12a.

The lock gears5contained in the above described guide portions50ahave a pair of parallel side walls which face the surfaces11aand12aof the above described protrusions11and12, which face each other. External cogs51are formed in an end portion of a side which connects the pair of side walls (one end portion in the direction of the radius which slides within the above described guide portions50a) and can engage with the internal cogs of the above described gear plate2. A pressing portion5ain curve form is formed on the other end portion in this lock gear5(end portion toward the center of the base plate1), and it is possible for the pressing portion to make contact with the curved surface (cam surface) of the above described cam6. In addition, protrusions52for guiding are integrally provided to the surface of this lock gear5, which faces the gear plate2.

A cam6is provided approximately at the center of the above described base plate1so as to intervene between the lock gears5and5. This cam6is approximately in plate form and has a square hole61at the center through which the center shaft106penetrates and rotates together with the center shaft106when a passenger operates the above described operation lever107. In addition, a pair of cam surfaces6ais formed at locations which are rotationally symmetric with the square hole61of the above described cam6at the center. The cam surfaces6apress the pressing portions5aof the above described lock gears5when the cam6rotates. The lock gears5move to the outside in the direction of the radius of the base plate1when pressed by these cam surfaces6a.

In addition, a pair of hook engaging portions6bis integrally formed in this cam6so as to be adjacent to the above described cam surfaces6aso that one end of each of the spiral springs7engages with its corresponding hook engaging portion. The center of each of the spiral springs7, which is the other end with which the spiral spring7; engages with the above described hook engaging portion6b, engages with a half moon protrusion13, which is integrally formed on the base plate1. Here, these spiral springs7press the above described cams6so that the cams6rotate in such a direction that the lock gears5press the cams6outward in the direction of the radius (the clockwise direction inFIG. 3). In addition, a pair of protrusions62in columnar form are provided at locations which are rotationally symmetrical with the above described square hole61at the center in the direction towards the gear plate2, and the cam is attached to the below described lever plate8so that they rotate together.

As shown inFIG. 3, a circular lever plate8(illustrated with a double dot chain line) is mounted on the lock gears5, the cam6and the spiral springs7, which are mounted on the above described base plate1, and furthermore, is sandwiched between the base plate1and a base plate2. This lever plate8has a circular hole in the center portion through which the center shaft106penetrates. The protrusions62in columnar form on the above described cam6engage with engaging holes8aof the lever plate8. Through this engagement, the cam6and the lever plate8move together.

A pair of cam holes81is provided in the above described lever plate8at locations that are rotationally symmetric with the center shaft106at the center. The protrusions52for guiding, which are provided in the above described lock gears5, loosely engage with the above described cam holes81. In addition, when the lever plate8rotates, the peripheries of the above described cam holes81make contact with the protrusions52so as to pull the protrusions toward the center in the direction of the radius, and thus, the lock gears5can be moved toward the center in the direction of the radius. Accordingly, the cam6rotates together with the center shaft106. When the cam6rotates, the lock gears5move in the direction of the radius of the base plate1.

The above described components are placed within the cavity4so as to be layered in the direction of the axis. The outer shape of the above described gear plate2is approximately disc form, with a hole2athrough which the center shaft106penetrates provided in the center portion. In addition, the inner surface facing the base plate1is in approximately bowl form where a first step23provided with internal cogs21and arc portions22on the inner periphery, a second step24placed inside thereof and a third step25are sequentially formed in stair form in the direction of the axis. In addition, the first step23of the gear plate2engages with the outer form portion (inside the outer periphery) of the base plate1so that the external cogs51are set to disengage from the internal cogs21of the gear plate2as the above described lock gears5slide in the direction of the radius.

In addition, in the case where the operation lever107is not operated by a passenger, the spiral springs7press the cam6and the lever plate8so that they rotate together, and the external cogs51of the lock gear5engage with the internal cogs21of the gear plate2so that the reclining apparatus105is in a locked state. In this state, when the passenger operates the operation lever107against the force of the spiral springs7, the cam6and the lever plate8rotate together (rotate in the counterclockwise direction inFIG. 3), and the pressure applied to the lock gear5by the cam6is released. At the same time, the protrusions52of the lock gears5are guided by guide holes81of the lever plate8so that the lock gears5move toward the center shaft106. Then, the engagement between the external cogs51of the lock gears5and the internal cogs21of the gear plate2is released so that the reclining apparatus105becomes of a state where the adjustment is possible from the locked state.

Here, the lock mechanism formed of the above described lock gears5, the cam6, the lever plate8and the like has a configuration of publicly known lock mechanisms, and the operations of locking and releasing the locking are also publicly known. In addition, when the external cogs51of the lock gears5are at such locations as to make contact with the arc portions22of the gear plate2, the reclining apparatus105is not locked, and this implements a state where the backrest102is in a state corresponding to the lock free range b ofFIG. 1.

Next, the memory plate9and the coil spring10, which are main components of the neutral position return mechanism, are described. The memory plate9is made of a plate material in approximately disc form as described above. The memory plate9according to the present embodiment is pressed by the coil spring10in such a direction that the memory plate rotates (seeFIG. 2). As shown inFIG. 4, the memory plate9is provided with a circular hole91at the center through which the center shaft106penetrates so as to be rotatable and a pair of long holes92in approximately arc form, which are located rotationally symmetric with the circular hole91at the center. In addition, two notches93are provided at an appropriate interval in the outer periphery of this memory plate9, and a hole94is provided between the circular hole91and one long hole92. As described below, one end of the coil spring10engages with this hole94.

As shown inFIG. 4, the long holes92of the above described memory plate are made to have a wide portion92aand a narrow portion92bsuch that a portion of the periphery in approximately arc form on the outside of the wide portion92ain the direction of the radius in the direction in which the backrest reclines backward (counterclockwise direction in the figure) protrudes in the direction toward the center so as to be a guide portion92d, and thus, the above described narrow portion92bis provided. In addition, the protrusions52of the lock gears5loosely engage with these long holes92so that the movement of the lock gears5in the direction of the radius can be guided. In addition, stoppers25a, which are formed in the second step25of the gear plate2so as to protrude in the direction toward the center, loosely engage with the above described notches93and93, and thus, the range of the rotation of the memory plate9relative to the gear plate2is restricted. In the present embodiment, the gear plate2is secured to the backrest, and thus, the gear plate2rotates as this backrest reclines. Therefore, the wide portions92ain the above described guide portions92dare located in the direction in which the backrest reclines backward. Here, the present invention is not limited to this, and the base plate1may be secured to the backrest. In this case, the wide portions92ain the above described guide portions92dare located in the direction in which the backrest reclines forward.

The above described wide portions92ahave approximately the same angular width (length) so as to correspond to the range of adjustment a shown inFIG. 1, and the narrow portions92balso have approximately the same angular width (length) so as to correspond to the free width b. In addition, when the protrusions52of the lock gears5are located in the above described wide portions92a, the protrusions do not make contact with the periphery in approximately arc form in the wide portions92a, and thus the cam holes81of the lever plate8allow the lock gear5to move in the direction of the radius of the gear plate2without hindrance. In addition, when the protrusions52of the lock gears5are located within the narrow portions92b, the above described guide portions92dprevent the lock gears5from moving in the direction of the radius of the gear plate2irrelevant of the locations of the cam holes81of the lever plate8, and thus the external cogs52of the lock gears5do not engage with the internal cogs21of the gear plate2.

The above described coil spring10is a twisted coil spring which presses the memory plate9so that the memory plate rotates in such a direction that the protrusions52of the lock gears5disengage from the guide portions92d, and as shown inFIG. 2, has a center diameter through which the center shaft106can penetrate and is contained in a recess26created at approximately the center of the third step25of the gear plate2. In addition, one end of the coil spring10engages with the hole94provided in the above described memory plate9, and the other end engages in a hole26aprovided in the bottom portion of the recess26so that the memory plate9is set to be always pressed by the coil spring10in the counterclockwise direction in the state shown inFIG. 4.

Subsequently, the operation of the reclining apparatus105, which is formed as described above, is described in reference toFIG. 3. When the operation lever107is not operated by a passenger, the spiral springs7press the cam6and the lever plate, which is integrated with the cam, so that they rotate in the clockwise direction. Therefore, the pressing portions5aof the two lock gears5are pressed against the cam surfaces6aof the cam6, and the external cogs51of the lock gears5engage with the internal cogs21of the gear plate2. Accordingly, the base plate1and the gear plate2are prevented from rotating relative to each other by means of the lock gears5, which engage with the guide portions50aof the base plate1so as to be slidable in the direction of the radius.

That is to say, in this state, the reclining apparatus105is locked by a publicly known lock mechanism made of the lock gears5, the cam6, the spiral springs7, the lever plate8and the like, and the inclination angle of the backrest102is fixed. In addition, in the state shown inFIG. 3, the external cogs51of the lock gears5are located so as to make contact with the arc portions22at the end portions of the gear plate2in the counterclockwise direction, and the backrest102corresponds to the highest raised position A shown inFIG. 1. Here, in this state, the protrusions52of the lock gears5loosely engage with the cam holes81of the lever plate8, and at the same time, as shown inFIG. 4, are set to be located within the wide portions92aof the long holes92created in the memory plate9, and thus, neither the cam holes81nor the long holes92prevent the lock gears5from sliding in the direction of the radius.

Next, when the operation lever107is rotated (lifted up in the clockwise direction inFIG. 1) through the operation by a passenger in the state where the above described reclining apparatus105is locked, the cam6and the lever plate8, which is integrated with the cam, are rotated in the counterclockwise direction against the force of the spiral springs7from the state ofFIG. 3. Then, the pressure applied to the pressing portions5aof the two lock gears5by the cam surfaces6aof the cam6is released, and at the same time, the protrusions52of the lock gears5are guided by the cam holes81of the lever plate8so that the lock gears5slide in the direction toward the center shaft106, and the engagement between the external cogs51of these lock gears5and the internal cogs21of the gear plate2is released. As a result, the locking of the reclining apparatus105is released, and it becomes possible to adjust the angle of inclination of the backrest102. In this state, when the backrest102is adjusted within the range of adjustment of reclining a ofFIG. 1and the operation of the operation lever107is discontinued, the angle of inclination of the backrest102is fixed at a readjusted position.

The above described operations relate to the locking and adjusting functions of publicly known lock mechanisms, and in this state, the protrusions52of the lock gears5which loosely engage with the long holes92created in the memory plate9through the cam holes81of the lever plate8are set to always be located within the wide portions92a. Therefore, the operation of the two lock gears is not limited by the long holes92created in the memory plate9, and the memory mechanism made of the memory plate9and the coil spring10does not relate to the above described operations.

Next, the operation of the neutral position return mechanism which characterizes the present invention is described. The range of the angle b shown inFIG. 1is a lock free range in which the backrest102is not locked and an unlocked state is maintained even when the fingers are released from the operation lever107, and the backrest102is first locked in the neutral position C (position which is reclined backward by a predetermined angle from the initial locked position) in the figure when the backrest102is reclined backward from the lock free range b in the figure in the state where the fingers are released.

FIGS. 5 to 8are diagrams showing the operations of the gear plate2, the lock gears5, the cam6, and the memory plate9during the period where the above described backrest102rotates from the lock free range b to the neutral position C so that the reclining apparatus is locked. Here, for the purpose of convenience for the description, the parts other than the above are omitted. In addition, the left side and right side ofFIGS. 5 to 8are shown opposite to those ofFIGS. 1 to 4so that the direction of rotation corresponds to that of the backrest102inFIG. 1, andFIGS. 5 to 8show the parts in such a manner that the parts inFIG. 3are seen from the rear side of the figure.

FIG. 5shows the backrest102shown inFIG. 1in a state of being at the most forward position, which is the front end of the lock free range b. This is the state where the operation lever107is pulled up in the same manner as in the operation of conventional adjustments of inclination so that the lock gears5and5retreat in the direction toward the center along the radius and the backrest102is reclined forward. When the backrest102is reclined forward in a state where the lock gears5and5do not engage with the internal cogs21, the gear plate2attached to the backrest102rotates together, and the memory plate9also rotates together with the gear plate2in a state where one side25aaof one of the engaging portions25ain the third step25makes contact with an engaging end93aof the notch93of the memory plate9.

In addition, when the memory plate9rotates in the direction of being reclined forward (counterclockwise direction in the figure), the protrusions52of the lock gears5are pressed toward the center in the direction of the radius by inclining portions92cof the long holes92so as to be located in the narrow portions92b. When the protrusions52of the lock gears5are located in the above described narrow portions92b, the movement of the protrusions52is restricted by the guide portions92dof the above described narrow portions92b, and the backrest102is then not locked even when the fingers are released from the operation lever so that the force of the spiral springs7rotates the cam6and pushes the lock gears5outward in the direction of the radius. Passengers usually get in and leave from the rear seat in this state.

Next, in order for passengers to sit in these seats in the state ofFIG. 5, it is necessary for the backrest102of this seat to be reclined backward.FIG. 6shows the backrest102in a state where the backrest rotates so as to be reclined backward by the difference in the angle α-β between a predetermined angle range α of the above described notch93and a predetermined angle range β of the above described engaging portion25aafter starting to return from the state ofFIG. 5. During this period, only the backrest102and the gear plate2rotate. This is because in this stage the spiral springs7rotate the cam6and press the lock gears5outward in the direction of the radius in such a manner that the frictional force, which is created when the respective protrusions52press the above described narrow portions92b, is greater than the force of the coil spring10, which presses the memory plate9so that the memory plate rotates in such a direction as to be reclined backward, and thus, the memory plate9is maintained at the location ofFIG. 5. Here, when the gear plate2rotates by the difference in the angle α-β between a predetermined angle range α of the notch93and a predetermined angle range β of the above described engaging portion25a, the other side25abof the engaging portion25aof the second step25in the gear plate2makes contact with the engaging end93bof the notch93in the memory plate9.

In addition, when the backrest102is further reclined backward from the state where the other side25abof the engaging portion25ain the third step25of the gear plate2makes contact with the engaging end93bof the notch93in the memory plate9(FIG. 6), the memory plate9rotates together with the backrest102and the gear plate2, and the protrusions52and52of the lock gears5and5slide over the guide portions92dof the long holes92. When the backrest102rotates (is reclined backward) from the state where the protrusion52of the lock gear5shown inFIG. 7is in the inclining portion92cprovided at the end of the guide portion92dwhere the narrow portion92band the wide portion92ameet in the long hole92of the memory plate9, contact between the long hole92and the protrusion52is disengaged, the lock gear5is pressed outward in the direction of the radius when the cam6rotates by means of the spiral springs7, and the internal cogs21of the gear plate2and the external cogs51of the lock gear5engage so that the backrest102is locked.

In addition, as shown inFIG. 8, contact between the long hole92and the protrusion52is disengaged, and thus, the frictional force caused by the above described protrusions52when pressing the guide portion92dis eliminated, and therefore, the force of the coil spring10rotates the memory plate9in the direction in which the backrest is reclined backward (counterclockwise direction in the figure) until a side25aaof one of the engaging portions25ain the third step25makes contact with the engaging end93aof the notch93in the memory plate9. As a result, there is a difference in the angle of rotation between the memory plate9and the gear plate2, which is the difference in the angle α-β between a predetermined angle range α of the above described notch93and a predetermined angle range β of the above described engaging portion25a, when the backrest102becomes of the state shown inFIG. 6from the most forward reclined position B (state shown inFIG. 5), and thus, the angle of inclination of the backrest102shown inFIG. 8becomes the angle by which the reclining apparatus reclines backward by the angle of α-β from the initial position which can be locked when the protrusion52of the lock gear5is in the wide portion92aof the long hole92.

Though in conventional reclining apparatuses a lock free range is created when a lock gear5rides on an arc portion22where no internal cogs21are formed on the inner periphery of the gear plate2, a lock free range can be created when the protrusion52of the lock gear5is pulled toward the center in the direction of the radius by the long hole92in the memory plate9, and therefore, the above described arc portion22is not necessary in the reclining apparatus according to the present invention, but it is preferable to provide such an arc portion22in order to ensure the engagement between the lock gear5and the gear plate2in the vicinity of the highest raised position A.

This is because the lock free range b, in the case where no arc portion22is provided as described above, is created by the long hole9, and therefore, the inclining portion92cof the long hole92is located nearby the side of the protrusion52in the highest raised position A. This inclining portion92ccreates an error in the position in the direction of rotation resulting from the accumulated errors in the process precision of the memory plate9and the process precision in the engaging portion25aof the gear plate2and the notch93of the memory plate9, and therefore, as shown inFIG. 9, the protrusion52rides on the above described inclining portion92cin the vicinity of the highest raised position A, so there is a risk that the lock may become incomplete.

Therefore, an arc portion22is provided in the gear plate2in the same manner as in the prior art, and the guide portion92dis provided so as to shift in such a direction that the riding of the protrusion52over the inclining portion92c(clockwise direction inFIG. 9) so that the protrusion52makes contact with the inclining portion92cafter the lock gear5rides on the above described arc portion22when the backrest102reclines forward, and thus, the engagement between the lock gear5in the vicinity of the highest raised position A and the gear plate2can be ensured. Here, the amount by which the inclining portion92cis shifted in the direction of rotation can be adjusted by adjusting the neutral position to which the system returns with the difference in the angle between the engaging portion25aof the gear plate2and the notch93of the memory plate9.

Subsequently, the reclining apparatus according to the second embodiment is described in reference toFIGS. 10 to 12. TheseFIGS. 10 to 12correspond toFIGS. 2 and 4to9relating to the first embodiment. In this embodiment, the forms of the memory plate9and the coil spring10are different from those in the first embodiment. In the following, these differences are described specifically.

First, as shown inFIGS. 10 and 11, the memory plate201in the present embodiment is in approximately ring form (spiral form) with the center shaft106at the center. Two notches201aat an appropriate interval are provided in the outer periphery in the same manner as in the memory plate9. In addition, guide portions201bin approximately arc form for restricting the lock gear5from moving outward in the direction of the radius when the protrusions52of the above described lock gear5make contact and a hook piece201dfor engaging the spiral spring202are formed on the inner periphery in approximately ring form.

In addition, when the protrusions52of the lock gear5are in a range where the guide portions201bare formed, the lock gear5is restricted from moving in the direction of the radius of the gear plate2irrelevant of the positions of the cam holes81in the lever plate8, and the external cogs52of the lock gear5do not engage with the internal cogs21of the gear plate2. In addition, when the protrusions52of the lock gear5are not located in the inner peripheral portions201c, which are not the guide portions201b, the protrusions do not make contact with the periphery in approximately arc form and the lock gear5is moved in the direction of the radius of the gear plate2without hindrance by the cam holes81in the lever plate8.

Next, the end on the outside of the spiral form of the spiral spring202is bent backward in the direction opposite to the direction in which the spiral winds while the end on the center side is bent in the same direction as the direction in which the spiral winds so that the end on the outside engages with the hook piece201dof the above described memory plate201while the end on the center side engages with a protrusion28in approximately columnar form provided in the bottom portion of the gear plate2. A number of protrusions28other than the above described protrusion28with which the spiral spring202engages are provided so as to prevent the position of the spiral spring202from shifting and can elastically change in form efficiently.

The operations of the above describe memory plate201and the spiral spring202are the same as of the memory plate9and the coil spring10, and therefore, the descriptions thereof are omitted, but a spring member for pressing the memory plate can be installed in a space having the same plate thickness as the memory plate201, which cannot be provided in the combination of the memory plate9and the coil spring10, and therefore, the thickness of the reclining apparatus in the direction of the axis can be reduced.

FIG. 12is a plan diagram illustrating an embodiment of the invention in whichFIG. 12is a plan diagram corresponding toFIG. 9. The periphery reaching the end portion of the guide portion201bshown inFIG. 12protrudes toward the center from the arc of the guide portion with the center shaft at the center. By having this configuration, the memory plate201prevents the memory plate201from rotating together with the gear plate2within a certain range where the memory plate201is rotatable relative to the gear plate2.

This is a configuration in which the location where the external cogs51of the lock gear5engage with the internal cogs21of the gear plate2shifts from the neutral position by the amount of which the memory plate rotates through the friction between the periphery of the memory plate201and the gear plate2while the notch201aof the memory plate201does not make contact with the engaging portion25aof the gear plate2, and therefore, the notch201aof the memory plate makes contact with the engaging portion25aof the gear plate before the protrusions52of the lock gear5disengage from the guide portions201bdue to the guide portion which protrudes in order to provide resistance against the rotation of the memory plate201.

In addition, the periphery52athrough which a protrusion52of the lock gear5makes contact with the above described guide portion201bis inclined along the form in which the above described guide portion201bprotrudes as shown by two dot chain lines inFIG. 12, and therefore, the guide portion201bmakes contact with the periphery52aof the protrusion52through a surface until the moment when the protrusion52is removed from the guide portion201b, and thus, the memory plate201can be prevented from rotating together with the gear plate2without fail within a certain range where the above described memory plate201is rotatable relative to the gear plate2.