Angular position adjusting mechanism

In an angular position adjusting apparatus, tooth profiles of an internal gear 31 and an external gear 21 are formed according to loop shapes 74a and 84a of predetermined trochoid curves 74 and 84.

TECHNICAL FIELD

The present invention relates to an angular position adjusting mechanism, which is employed as a mechanism for steplessly adjusting the angular position of a seat back of a vehicular seat or the height position of a seat cushion thereof and which needs strength in an angular position holding state thereof.

BACKGROUND ART

As shown inFIG. 7, such an angular position adjusting mechanism enabled to steplessly adjust the position is configured by forming an internal gear231in one of brackets and also forming an external gear221in the other bracket so that the internal gear231is meshed with the external gear221, and that these gears are mutually rotatably combined with each other, to thereby enable the adjustment of the angular position and also enable the brackets to firmly hold the position.

As shown inFIG. 3, the tooth profiles employed by these gears are formed according to a cycloid curve274, which is the locus of a basic point271on the circumference of the rolling circle80, by setting, for example, a fixed circle71and a rolling circle80, which rotates while internally touching the fixed circle71. That is, the tooth profile of the external gear221is set like a circular-arc centered at the position of the basic point271shown inFIG. 7, while the tooth profile of the internal gear231is formed in such a way as to have tooth flanks275formed at an equidistance A from a predetermined cycloid curve274(see JP-A-55-068328).

Incidentally, as will be described later, in a case where the fixed circle71and the rolling circle80have a relation similar to that in the aforementioned case, and where the basic point is set at a place, which is not on the circumference of the rolling circle, the locus of the basic point is called a trochoid curve that is distinguished from the cycloid curve.

DISCLOSURE OF INVENTION

Similarly to the aforementioned background art, the mesh between the external gear221, which has a circular-arc-like tooth profile, and the internal gear231, which has a tooth profile formed according to the cycloid curve, is such that the internal gear abuts against the external gear at each of many meshing points M. Thus, a large meshing ratio is obtained. However, the inclination D (seeFIG. 7) of the tooth flank F to a surface E (seeFIG. 7), which is perpendicular to the direction of rotation of the external gear, is large, so that a large load is liable to act upon the gear. Therefore, the background art is disadvantageous in ensuring meshing strength.

Accordingly, a technical problem to be solved by the invention is to obtain an angular position adjusting mechanism using an internal gear and an external gear, which have tooth profiles that provides higher meshing strength.

(1) According to one configuration of the invention, there is provided a technical configuration in which the tooth profiles of the internal gear and the external gear are formed according to the loop shapes of a predetermined trochoid curve.

(2) Preferably, the tooth profiles of the internal gear and the external gear are adapted so that tooth flanks, each of which is at a constant distance from an associated one of the loop shapes, are formed.

(3) Preferably, the tooth profiles of the internal gear and the external gear are adapted so that tooth flanks, each of which is away in a direction of rotation of a constant angle from an associated one of the loop shapes, are formed.

(4) Preferably, at least one of the tooth profiles of the internal gear and the external gear has a relief flank portion, which differs from the loop shapes of the predetermined trochoid curves, and a gap is formed between each bottom land of the internal gear and an associated top land of the external gear in a state in which the internal gear meshes with the external gear.

(5) Preferably, the tooth profile of the external gear is adapted so that the tooth flanks are formed according to the loop shapes of the predetermined trochoid curve. The top lands are formed in such a way as to have flat shapes, and a curved surface is applied to a corner portion serving as a boundary between each tooth flank and an associated one of the top lands thereof.

(6) Preferably, each relief flank portion for forming a gap between each bottom land of the internal gear and an associated one of the top lands is formed of an associated one of the top lands and an associated one of the corner portions.

(7) Preferably, the tooth profile of the internal gear is adapted so that each of the bottom lands is formed of a curved surface.

(8) Preferably, the tooth profile of the internal gear is adapted so that the tooth flanks are formed according to the loop shapes of the predetermined trochoid curve. The top lands are formed in such a way as to have flat shapes. A curved surface is applied to a corner portion serving as a boundary between each tooth flank and an associated one of the top lands thereof.

(9) Preferably, each relief flank portion for forming a gap between each bottom land of the internal gear and an associated one of the top lands is formed of an associated one of the top lands and an associated one of the corner portions.

(10) Preferably, the tooth profile of the internal gear is adapted so that each of the bottom lands is formed of a curved surface.

(11) Preferably, the angular position adjusting apparatus further includes a shaft rotatably supported in the fixed bracket. The internal gear is formed around the shaft in the fixed bracket. The external gear is formed around the shaft in the rotating bracket, and the number of teeth of the external gear is smaller than that of teeth of the internal gear by at least one.

(12) Preferably, the internal gear is formed in a bore part of a concave portion formed by pushing the fixed bracket thereinto in a direction of thickness thereof. The external gear is formed in an outside diameter part of a convex portion formed by pushing the rotating bracket thereinto in a direction of thickness thereof.

(13) Preferably, the angular position adjusting apparatus further includes a backlash adjusting mechanism, which is provided around the shaft between the fixed bracket and the rotating bracket, for pushing the internal gear and the external gear in a direction in which the internal gear and the external gear mesh with each other.

(14) Preferably, the angular position adjusting apparatus further includes a collar portion formed around a center axis of the internal gear and around the shaft in the fixed bracket, and a bore surface portion provided around a center axis of the external gear and around the collar portion in the rotating bracket. The backlash mechanism is configured by comprising a wedge member disposed between the collar portion and the bore surface portion, and a spring member for pushing the wedge member so that the wedge member is pushed against the collar portion and the bore surface portion.

(15) Preferably, the angular position adjusting apparatus further includes a first holding bracket, which is mounted on the fixed bracket and adapted to cooperate with the fixed bracket to sandwich the rotating bracket in an axial direction of the shaft, and a second holding bracket, which is mounted on the rotating bracket and adapted to cooperate with the rotating bracket to sandwich the fixed bracket in the axial direction of the shaft. The internal gear and the external gear is mesh-engaged with each other.

(16) Preferably, a fixed member to which the fixed bracket is supported is a seat cushion of a vehicular seat. A movable member to which the rotating bracket is supported is a seat back of the vehicular seat. An angle of inclination of the seat back to the seat cushion is adjusted by adjusting an angular position of the rotating bracket with respect to the fixed bracket.

(17) Preferably, the fixed member is a seat cushion of a vehicular seat. The movable member is a link mechanism connected to a seat slide of the vehicular seat. A height position of the seat cushion with respect to the seat slide is adjusted by adjusting an angular position of the rotating bracket with respect to the fixed bracket.

According to the configuration of (1), the following advantages are obtained. That is, because the tooth profiles are formed according to the trochoid curve, a large contact ratio is obtained in a meshing range in which the internal gear and the external gear mesh with each other. Moreover, the loop shapes are used, so that the inclination of the tooth flat at the meshing point, at which the gears abut against each other, can be set to be smaller than that of a surface perpendicular to the direction of rotation of the external gear. Thus, the strength of teeth can be increased.

According to the configuration of (2), (3), (5), (7), (8), and (10), a press working die for forming the tooth profiles of the internal gear and the external gear, to which the trochoid curves are applied, can be made with high precision by using a numerically controlled machine tool. Consequently, the tooth profiles of the gears can be formed with good accuracy. Also, the strength needed in designing the tooth profiles can easily be ensured.

According to the configuration of (4), (6), and (9), a gap is formed between each top land of the external gear and the associated bottom land of the internal gear and serves as a space, in which lubricating grease is accumulated. Thus, the securement of the durability of the gears is facilitated.

According to the configuration of (12), reduction in the number of components is enabled.

According to the configuration of (13) and (14), in a state in which the angular position is held, backlash is set to be small. Alternatively, when the angular position is adjusted, the adjustment thereof is performed so that backlash is set to be large. Thus, in a state in which the angular position is held, the meshing strength of the gears is set to be high. When the angular position is adjusted, the gears mesh and rotate with a light load to thereby enable an adjusting operation.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an angular position adjusting mechanism5, which is a first embodiment of the invention, is described with reference toFIGS. 1-4, and6.

Referring toFIG. 6, the angular position adjusting mechanism5is applicable to, for example, a reclining apparatus50for adjusting a reclining angle of a seat back11of a vehicular seat10, or to a vertical apparatus60for adjusting a height of a seat cushion12thereof. That is, the reclining apparatus50is configured so that the angular position adjusting mechanism5is mounted between a frame11aof the seat back11and a frame12aof the seat cushion12, and that an angle of inclination of the seat back11can arbitrarily be adjusted by rotating an operating handle47. When the operating handle47is not operated, predetermined strength is ensured so as to hold the position of the seat back11. Thus, an occupant can be supported. Similarly, the vertical apparatus60is configured so that the angular position adjusting mechanism5is mounted in a front end portion of the frame12aof the seat cushion12and connected to a seat slide14through a link mechanism9, that further, the seat cushion12is rotated around a pivot shaft15, which connects a rear end portion of the frame12ato the seat slide14, by turning the operating handle47, and that thus, the height of the seat cushion12can arbitrarily be adjusted. Similarly, in this case, when the operating handle47is not operated, the weight of the occupant is supported and the height thereof is held. Thus, the angular position adjusting mechanism5has a function of firmly holding the position in addition to a position adjusting function.

Next, the configuration of the angular position adjusting mechanism5is described with reference toFIGS. 1 and 2.

The basic configuration of the angular position adjusting mechanism5according to the embodiment is similar to a known adjusting mechanism configured by combining an internal gear and an external gear, which are eccentric from each other. That is, the angular position adjusting mechanism5has a fixed plug3, which is fixedly mounted on the frame12a(fixed member) of the seat cushion12, and a rotating bracket2, which is rotatably supported by this fixed bracket3and fixedly mounted on the frame11a(movable member) of the seat back11, in the example of application thereof to the seat reclining apparatus50. An internal gear31is formed in the fixed bracket3, while an external gear21is formed in the rotating bracket2. The number of teeth of the external gear21is set to be smaller than that of teeth of the internal gear31by at least one. Incidentally, in the embodiment shown inFIG. 1, that of teeth of the internal gear31is set at34, while that of teeth of the external gear21is set at33. The external gear21is formed by using what is called a half-die-cutting method of pressing the rotating bracket2thereinto in the direction of thickness thereof by about half or about one-third the thickness thereof by press-working. The external gear21is thus formed in an outside diameter part of a convex portion formed on the rotating bracket2, which is formed by this half-die-cutting method. The internal gear31is formed by using what is called a half-die-cutting method of pressing the fixed bracket3thereinto in the direction of thickness thereof by about half to about two-thirds the thickness thereof by press-working. The internal gear31is thus formed in an inside-diameter part of a concave portion formed on the fixed bracket3, which is formed by this half-die-cutting method. Incidentally, the mechanism may be formed so that the external gear21is formed in the fixed bracket3, and that the internal gear31is formed in the rotating bracket2.

A cylindrical collar part3ais formed in a central portion of the internal gear31along the central axis31athereof in such a way as to protrude therefrom. A shaft43is disposed in the bore of the collar portion3ain such a manner as to penetrate therethrough. An interlocking member46for interlocking the shaft46with an angular position adjusting mechanism (not shown) mounted on an opposite side surface of the vehicular seat10is connected to the shaft43.

A first holding bracket35is mounted on the bottom part (shown in a lower part ofFIG. 2) of the fixed bracket3. A second holding bracket25is mounted on the top part (shown in an upper part ofFIG. 2) of the rotating bracket2. The top part (shown in the upper part ofFIG. 2) of the fixed bracket3is sandwiched by the rotating bracket2and the second holding bracket in an axial direction of the shaft43. The bottom part (shown in the lower part ofFIG. 2) of the rotating bracket2is sandwiched by the fixed bracket3and the first holding bracket35in the axial direction of the shaft43. Consequently, the rotating bracket2and the fixed bracket3are combined with each other so that the external gear21is mesh-engaged with the internal gear31while the angular position of the rotating bracket2with respect to the fixed bracket3can be adjusted.

The collar portion3aof the fixed bracket3and a hole2a, through which the shaft43penetrates, are formed in the central portion of the external gear21formed in the rotating bracket2. A bearing member2chaving a bore surface portion2bis mounted by being press-fitted into the bore of the hole2a. The bore surface portion2bis concentric with the center of21aof the external gear21. The diameter of the bore surface portion2bis set to be larger than the outside diameter of the collar portion3a.

Next, a backlash adjusting mechanism4to be disposed between the internal gear31and the external gear21is described.

The backlash adjusting mechanism4has paired wedge members41and a spring member42, which are disposed in the gap between the bore surface portion2band the collar portion3b. The wedge41is shaped so that the thickness of an upper part thereof is larger than the thickness of a lower part thereof, and the thickness thereof decreases towards the bottom thereof from the top thereof in a state, as viewed inFIG. 1. The paired wedge members41are disposed on the outside diameter of the collar portion3ain such a way as to be spaced apart from each other at the top and the bottom thereof, as shown inFIG. 1. The spring member42is mounted in such a manner as to apply an action force in a direction, in which the distance between the tops of the paired wedge members41, so as to push the wedge members41so that each of the wedge members41is pressed against the collar portion3aand the bore surface portion2b. This mechanism is configured so that the action force of the spring member42acts, as shown inFIG. 1, that the wedge members41are thus pushed against the collar portion3aand the bore surface portion2b, and that consequently, the wedge members41orbit around the collar portion3ato the downward side thereof to thereby raise the bore surface portion2bupwardly, as viewed inFIG. 1, with respect to the collar portion3a. Thus, the bore surface portion2bis upwardly raised, so that an amount of eccentricity of the center21aof the external gear21with respect to the center31aof the internal gear31increases. This mechanism is configured so that the external gear21and the internal gear31are pushed against each other in such a way as to eliminate the gap between the teeth of the external gear21and those of the internal gear31, that is, eliminate backlash.

The backlash mechanism4has a pawl portion44, which is spaced apart from the center of rotation of the shaft43and integrally formed therewith. An end part of the pawl portion44extends in parallel with a center axis of rotation of the shaft43and is inserted between the bottoms of the paired wedge members41. The shaft43extends so that an end portion thereof projects toward a lateral side of the angular position adjusting mechanism5, and that the operating handle47is fixedly attached to an end thereof.

The operating handle47is operated in such a way as to rotate, so that the pawl portion44abuts against the bottom portion of one of the wedge members41. When the wedge members41are raised against the action force of the spring member42, the distance between the center21aof the external gear21and the center31aof the internal gear31decreases. Consequently, the mesh between both the gears is loosened, so that the backlash increases. The increase of the backlash enables the rotation of both the gears with small meshing resistance thereof.

When an operation of turning the operating handle47is continued, the center21aof the external gear21moves around the center31aof the internal gear31. The positions of the paired wedge members41are turned from those shown inFIG. 1. Thus, the meshing positions, at which the teeth of the external gear21and the internal gear31mesh with each other, are turned in sequence. One revolution of the operating handle47causes the position of the rotating bracket2to turn with respect to the fixed bracket3by an angle corresponding to an angular pitch of teeth of the gear. Consequently, the mechanism is enabled to adjust the angular position between the fixed bracket3and the rotating bracket2.

Next, the tooth profiles of the internal gear31and the external gear21provided in the angular position adjusting mechanism5, which are formed by employing the trochoid curve, are described with reference toFIGS. 3 and 4.

As shown inFIG. 3, a rolling circle80, which internally touches a first fixed circle71in such a way as to roll therealong, is set. When a basic point70is set in the rolling circle80, the locus of the basic point70is a first trochoid curve74. The first trochoid74has a loop shape74a. When the rolling circle80internally touches and rolls along a second fixed circle81set in such a manner as to internally touch the first fixed circle71, the locus of the basic point70is a trochoid curve84, which similarly has a loop shape84a.

As shown inFIG. 4, the tooth profiles of the internal gear31and the external gear21are formed according to the loop shapes74aand84a, respectively. That is, the tooth flank of the internal gear31is set at a constant distance A from the loop shape74a, and that of the internal gear21is set at a constant distance A from the loop shape84a. The internal gear31and the external gear21mesh with each other so that the tooth flanks thereof formed in this manner abut against each other at plural meshing points M. A meshing line connecting the meshing points M extends by bending almost along the direction of an inner circumference of the internal gear31and along the direction of an outer circumference of the external gear21. Consequently, a larger number of meshing points M can be obtained, as compared with the case of ordinary internal and external gears having tooth profiles constituted by, for instance, involute curves, in which the meshing line is a straight line. Thus, a contact ratio obtained by averaging the number of the meshing points occurring at each revolution increases. Consequently, higher strength mesh between the gears can be realized.

The external gear21is provided with top lands22each obtained by eliminating a part of an associated end portion of a shape, which is formed of points positioned at a constant distance A from the loop shape84a, so that the distance from the top of the associated end portion to the base of the eliminated part is B and that the top of the rest of the associated end portion is flat. By employing this profile, even at a top dead center position (the position shown in a right-hand side part ofFIG. 4) C, at which the external gear21most deeply meshes with the internal gear31, the gap is maintained between the internal gear31and each of the top lands22of the external gear21. Grease serving as a lubricant is accumulated in the gap. Thus, the mechanism is configured so that a smooth operation and durability are ensured. Incidentally, the mechanism may be configured so that the gap between the external gear21and each of top lands of the internal gear31is maintained by setting the shape of each of the top lands of the internal gear31to be flat.

As shown inFIG. 4, the teeth of the external gear21is set in such a way as to have a predetermined tooth height. A curved surface R1is applied to a corner portion serving as a boundary between the top land22and a side surface23of each of the teeth. Another curved surface R3is applied to a bottom land thereof. On the other hand, another curved surface R3is provided as a corner portion of a top land32of the internal gear31. Thus, the internal gear31is shaped so that the teeth of the internal gear31and the external gear21do not cause interference when the internal gear31and the external gear21mesh with each other and rotate. The shape of each of the curved surfaces R1, R2, and R3are needed for a press die used in the half-die-cutting method employing press-working. The durability of the press die is ensured by setting these curved surfaces R1, R2, and R3. The external gear21is provided with a tooth flank portion (a relief flank portion)24, which differs from a trochoid curve similarly to the curved surfaces R1and R2of the tooth profile and the top land22but formed in such a way as to relieve a load from the side surfaces23and33, which relate to the abutment of the teeth, to a side, on which the teeth do not abut against each other. Thus, the external gear21is set so that at the position C (FIG. 4) of the upper dead center of the meshing gears, no abutment of the gears against each other occurs. Thus, the meshing points M are disposed by being dispersed on both lateral sides of the position of the upper dead center C. In the case of employing the gears formed in such a way as to have such configurations, the load is dispersed to many gears at the plural meshing points M without being concentrated onto the teeth at the position of the upper dead center C, even when shape errors occur in the tooth profile. Incidentally, the mechanism may be configured so that the curved surface R3is applied to the bottom land of each of the teeth of the external gear21, and that the internal gear31has the tooth surface portions24.

The gears, whose tooth profiles are formed according to the loop shapes74aand84a, are adapted so that the closer to the bottom land of each of the teeth of the external gear21and the closer to the top land of each of the teeth of the internal gear31, the closer toward the radial direction the side surface23of the external gear and the side surface33of the internal gear are bent. Thus, as shown in a left-side part ofFIG. 4, at a position distant from the position of the upper dead center C, the inclination D of the tooth flank F of each of the external gear21and the internal gear31to a surface E perpendicular to the direction of rotation of the external gear is small at the meshing point M. Thus, the mechanism is configured so that the securement of the strength against the load applied in the direction of rotation thereof is more facilitated.

Although the tooth flanks are set on the tooth profiles of the internal gear31and the external gear21, which are formed of points positioned at the constant distance A from the loop shapes74aand84ain the aforementioned embodiment, the tooth flanks may be set at positions laterally turned from the direction of rotation of each of the internal gear31and the external gear21by a predetermined angle with respect to the loop shapes74aand84a, respectively.

As described above, the internal gear31and the external gear21are formed in the rotating bracket2and the fixed bracket3by the half-die-cutting method using press-forming or the like. However, a forming die can be made with good precision by applying a trochoid curve, which is strictly defined by a theoretical expression, and by using a numerically controlled machine tool. The strength of teeth of the gears can accurately and easily be set according to an intended use by such a theoretical expression.

Referring toFIG. 5, there is shown a tooth profile according to a second embodiment, which is employable in the angular position adjusting mechanism5according to the invention. In the embodiment shown inFIG. 5, a circle having a smallest diameter is set to be a fixed circle180. This embodiment is adapted so that the inner circumferences of rolling circles171and181internally touch the outer circumference of the fixed circle180. Trochoid curves174and184, which are drawn by moving the basic point170when the rolling circles171and181are rolled, are obtained. In this case, loops are formed in an orientation opposite to the orientation, in which the loop shapes74aand84aof the first embodiment are looped, in the direction of a diameter of each of the fixed circle and the rolling circle. An external gear121and an internal gear131, which respectively have tooth profiles obtained according to the trochoid curves174and184, can operate similarly to the external gear and the internal gear of the first embodiment by being applied to the angular position adjusting mechanism5.