Patent ID: 12246624

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment to which the present invention is applied will be described below with reference to the drawings. A vehicle seat10illustrated inFIG.1is a front seat of a car, and each of a front/rear direction, a left/right direction, and an upper/lower direction in the following description means a direction using as a position reference a vehicle on which the vehicle seat10is mounted. The left/right direction is also referred to as a vehicle width direction, the vehicle width direction includes a center side of the vehicle seat10as a seat inner side, and left and right lateral sides as seat outer sides. For example, a right side and a left side of a left side frame14of a pair of the left and right side frames14described below are the seat inner side and the seat outer side, and a left side and a right side of the right side frame14are the seat inner side and the seat outer side.

The vehicle seat10includes a seat cushion11that is a seat surface part, and a seat back12that is a backrest part. The seat back12is supported near a rear end part of the seat cushion11tiltably in the front/rear direction. A cushion frame13that constitutes a framework of the seat cushion11adopts a frame-shaped structure that includes a pair of left and right side frames (seat frames)14that are disposed apart from each other in the vehicle width direction, and extend in the front/rear direction, and connects the pair of side frames14by a cylindrical front pipe15and rear pipe16extending in the vehicle width direction. Illustration of a seat back frame that constitutes a framework of the seat back12is omitted.

Main parts of the cushion frame13including the side frames14are provided separately to left and right side parts of the vehicle seat10, andFIGS.2to10illustrate the left frame structure. Although basic parts of frame structures are common between the left and right frame structures, a driving unit30(details thereof will be described below) that is a driving source, and parts related to the driving unit30are included only in the left frame structure. A right frame structure operates accompanying the left frame structure via the front pipe15and the rear pipe16.

The seat cushion11and the seat back12are supported movably in the front/rear direction by a pair of left and right seat tracks attached to a vehicle floor surface. Each seat track includes a lower rail17that is fixed to the vehicle floor surface, and an upper rail18that is movably in the front/rear direction with respect to the lower rail17. The lower rails17slide in the front/rear direction with respect to the upper rails18, so that it is possible to adjust a position in the front/rear direction of the vehicle seat10. A slide lock mechanism whose illustration is omitted fixes positions of the upper rails18with respect to the lower rails17.

A pair of front and rear support brackets19are fixed to an upper face side near a front end and a rear end of each upper rail18. Each of the pair of left and right side frames14is supported on the support brackets19with a lifter mechanism20interposed therebetween. The lifter mechanism20adopts a four-link structure that a front link21and a rear link22that are each rotatable with respect to the side frame14and the support brackets19are disposed apart from each other in the front/rear direction, and an operation of the lifter mechanism20can adjust a height position of the vehicle seat10with respect to the vehicle floor surface.

The front link21connects a connection part21anear one end in a longitudinal direction rotatably with respect to the front support bracket19, and connects a connection part21bnear an other end in the longitudinal direction rotatably with respect to the side frame14. The pair of left and right front links21are connected by the front pipe15, and the front pipe15connects to a vicinity of a center (an intermediate position of the connection part21aand the connection part21b) in the longitudinal direction of each front link21.

The rear link22connects a connection part22anear one end in the longitudinal direction rotatably with respect to the rear support bracket19, and is provided with a circular through hole22bformed near an other end in the longitudinal direction. The rear link22includes a linear arm part22cthat extends from the connection part22ato the through hole22b, and a fan-shaped sector gear plate22dthat is located on an upper side of the arm part22cand widens toward a front direction. At a front edge of the sector gear plate22d, an arc-shaped sector gear22ewhose center is the through hole22bis formed. The sector gear22eincludes a plurality of gear teeth that are continuously disposed in a circumferential direction. Note that the drawings omit illustration of the individual gear teeth of the sector gears22e. The rear link22further includes an arc-shaped long hole22fthat is formed between the sector gear22eand the through hole22band whose center is the through hole22b. The sector gear plate22dis a drive input gear that is rotatable about the rear pipe16that is a rotary shaft, and enmeshes with a pinion33of the driving unit30described below, and transmits a driving force from the driving unit30to the lifter mechanisms20.

Each side frame14is formed by performing press working or the like on a metal plate material. The left side frame14includes a base part14awhose plate thickness direction is the vehicle width direction, and a flange part14bthat protrudes from a peripheral edge of the base part14ato the seat inner side. At a part close to a front end of the side frame14, a front step part14cthat protrudes toward the seat inner side from the base part14ais formed. In a rear direction of the front step part14c, a rear step part14dthat protrudes toward the seat inner side from the base part14ais formed. Shapes that protrude in the vehicle width direction from the base part14aare formed like the flange part14b, the front step part14c, and the rear step part14dto enhance cross-sectional strength of the side frame14. Faces of the front step part14cand the rear step part14dthat face the seat inner side and the seat outer side have flat shapes, and serve as a position reference of each member to be assembled to the side frame14.

As illustrated inFIG.4, a support hole14ethat penetrates in the vehicle width direction is formed in the front step part14c. A connection part21aof the front link21is supported rotatably in the support hole14e.

As illustrated inFIG.4, a circular through hole14fand through hole14gthat respectively penetrate in the vehicle width direction are formed in the rear step part14d. The through hole14fis located near a rear end of the rear step part14d, and the through hole14gis disposed in the front direction with a predetermined interval spaced apart from the through hole14f. In the rear step part14d, a fastening hole14h(seeFIG.10) located between the through hole14fand the through hole14gin the front/rear direction, and a pair of fastening holes14ilocated in the front direction of the through hole14gare further formed.

The rear link22is disposed on the seat inner side of the side frame14, and the rear pipe16is inserted in the through hole22band the through hole14f. The rear pipe16is fixed to the through hole22b, and is supported rotatably in the through hole14f.

Consequently, the rear link22is connected to the side frame14rotatably about the rear pipe16. In other words, the sector gear plate22dis rotatably supported with the rear pipe16serving as the rotary shaft.

Front parts of the pair of left and right side frames14interlock via the front pipe15connected to the pair of left and right front links21. Furthermore, rear parts of the pair of left and right side frames14are connected and interlock via the rear pipe16. Thus, the pair of left and right side frames14integrally move in the front/rear direction or the upper/lower direction.

On a face on the seat inner side of the rear step part14dof the side frame14, a reinforcement plate25that is a reinforcement member is attached. As illustrated inFIGS.9and10, the reinforcement plate25is formed by a metal plate material having a larger thickness in the vehicle width direction than that of the side frame14, is formed separately from the side frame14, and then is fixed to the side frame14. In the present embodiment, the reinforcement plate25is welded and fixed to the side frame14. Welding positions W (three portions) of the reinforcement plate25are illustrated inFIG.8. Note that different positions from the welding positions W can be also welded, and a fixing method other than welding can be also selected. Note that the reinforcement plate25may have the same thickness in the vehicle width direction as that of the side frame14, or may have a thinner thickness than that of the side frame14. Furthermore, although the reinforcement plate25is fixed to the side frame14by welding using a metal in the present embodiment, the reinforcement plate25may be made of a resin and fixed to the side frame14by means such as adhesion other than welding.

As illustrated inFIGS.7and8, the reinforcement plate25has a shape that is elongated in the front/rear direction. A front end of the reinforcement plate25is located in the front direction of the through hole14gand in the rear direction of the fastening holes14i. A rear end of the reinforcement plate25is located in the rear direction of the fastening hole14h, and in the front direction of the through hole14f. That is, the reinforcement plate25exists within a range that overlaps the through hole14gand the fastening hole14hof the side frame14. Furthermore, in the reinforcement plate25, a through hole25athat continues to the through hole14gand a receiving hole (insertion part)25bthat continues to the fastening hole14hare formed to penetrate in the vehicle width direction (seeFIGS.4and10). As illustrated inFIG.10, the through hole25ais a circular hole having substantially the same diameter as that of the through hole14g, and respective center positions of the through hole25aand the through hole14gmatch. The receiving hole25bis a circular hole having a larger diameter than that of the fastening hole14h, and respective center positions of the receiving hole25band the fastening hole14hmatch.

As illustrated inFIGS.9and10, the reinforcement plate25is located between the side frame14and the rear link22in the vehicle width direction. In other words, the reinforcement plate25is disposed to fill the gap between the side frame14and the rear link22in the vehicle width direction. The reinforcement plate25and the rear link22are not in contact in the vehicle width direction, and there is a gap therebetween. The long hole22fof the rear link22is located with a predetermined interval spaced apart from the receiving hole25bof the reinforcement plate25to the seat inner side. As illustrated inFIG.10, a width of the long hole22fin a radial direction of the sector gear plate22dis larger than a diameter (inner diameter) of the receiving hole25b.

On the seat outer side of the side frame14, the driving unit30that is the driving source of the lifter mechanisms20is attached. The driving unit30includes a motor31, a gear housing32, and the pinion33. The pinion33is rotatable about a pinion shaft33athat extends in the vehicle width direction. Rotation of an output shaft of the motor31decelerates via a gear train (not illustrated) disposed in the gear housing32, and is transmitted to the pinion shaft33a, and the pinion33rotates about the pinion shaft33a. The pinion33protrudes from the gear housing32toward the seat inner side. A proximal end part of the pinion33is provided with a cylindrical pinion base part34that has a larger diameter than that of a tooth part of the pinion33. The pinion base part34is integrally formed as part of the pinion33.

A face on the seat inner side of the gear housing32is provided with a seat surface plate35, and, when the driving unit30is attached to the side frame14, the seat surface plate35is placed in contact with a face on the seat outer side of the rear step part14d(seeFIGS.9and10). In this case, the pinion33is inserted in the through hole14gand the through hole25afrom the seat outer side to the seat inner side. When the driving unit30is moved until the seat surface plate35comes into contact with the rear step part14d, the pinion base part34is located on inner sides of the through hole14gand the through hole25a, and the pinion33protrudes toward the seat inner side compared to the side frame14and the reinforcement plate25. Furthermore, the pinion33reaches the same position as that of the sector gear plate22din the vehicle width direction, and the sector gear22eand the pinion33enmesh with each other.

The driving unit30is fixed to the side frame14by using a support plate40. As illustrated inFIGS.4and5, the support plate40includes a base plate part41, a pinion cover part42, and a rear extension part43.

The base plate part41overlaps a face on the seat inner side of the rear step part14d. The base plate part41has a shape that is elongated in the front/rear direction, and a vicinity of a front end of the rear step part14dto a vicinity of the pair of fastening holes14iis a range where the base plate part41overlaps the side frame14.

The pinion cover part42is located in the rear direction of the base plate part41, and has a shape that covers the pinion33protruding toward the seat inner side compared to the base plate part41.

The rear extension part43is located closer to the seat inner side than the base plate part41in the vehicle width direction, is located in the rear direction of the pinion cover part42in the front/rear direction, and covers part of the rear link22(mainly the sector gear plate22d) from the seat inner side. The rear extension part43and the rear link22are not in contact in the vehicle width direction, and there is a gap therebetween.

As illustrated inFIG.4, a pair of fastening holes41athat penetrate in the vehicle width direction are formed at positions of the base plate part41near the pinion cover part42. The pair of fastening holes41aare provided at positions meeting (aligned in the vehicle width direction with) the pair of fastening holes14iof the side frame14. In the pinion cover part42, a pinion support hole42athat penetrates in the vehicle width direction is formed. The pinion support hole42ais provided at a position meeting (aligned in the vehicle width direction with) the through hole14gof the side frame14and the through hole25aof the reinforcement plate25, and a center position of the pinion support hole42aand the center positions of the through hole14gand the through hole25amatch. In the rear extension part43, a fitting hole43athat penetrates in the vehicle width direction is formed. The fitting hole43ais provided at a position meeting (aligned in the vehicle width direction with) the fastening hole14hof the side frame14and the receiving hole25bof the reinforcement plate25, and a center position of the fitting hole43amatches with the center positions of the fastening hole14hand the receiving hole25b.

The rear extension part43is located closer to the seat inner side than the rear link22, and the support plate40is attached to the seat inner side of the side frame14so as to cover the rear link22and the reinforcement plate25. A distal end of the pinion shaft33athat is part of the pinion33is inserted in the pinion support hole42a. The distal end of the pinion shaft33aand the pinion support hole42aare respectively circular, and the pinion shaft33ais rotatably supported in the pinion support hole42a.

In this state, the driving unit30and the support plate40are fastened and fixed to the side frame14using a pair of fixing screws44and one fixing screw45. The fixing screws44and the fixing screw45include shaft parts that protrude from head parts of large diameters, and male screws are formed on outer circumferential surfaces of the shaft parts. The shaft part of the fixing screw45is longer than the shaft parts of the fixing screws44.

The shaft part of each fixing screw44protrudes toward the seat inner side through a through hole35a(FIG.4) formed in the seat surface plate35. Furthermore, the shaft part of each fixing screw44is inserted in the fastening hole14iand the fastening hole41afrom the seat outer side to the seat inner side, and protrudes from the support plate40to the seat inner side. This protrusion part of the fixing screw44is screwed with a nut46(seeFIGS.2and5).

As illustrated inFIGS.9and10, the reinforcement plate25and the rear link22(sector gear plate22d) are disposed between the rear step part14dof the side frame14and the rear extension part43of the support plate40in the vehicle width direction. The rear step part14dand the rear extension part43face each other with an interval equal to or more than a sum of the thicknesses of the reinforcement plate25and the rear link22spaced apart from each other. To fill this interval in the vehicle width direction and fasten the rear step part14dand the rear extension part43, a collar47is attached to the support plate40(seeFIGS.9and10).

As illustrated inFIG.10, the collar47has a cylindrical shape that extends in the vehicle width direction, and an internal through hole47athat penetrates in the vehicle width direction is formed therein. At an end part on the seat inner side of the collar47, a fitting step part47bthat has a smaller diameter than that of a main body part of the collar47is formed. The fitting step part47bis inserted and fitted in the fitting hole43aof the rear extension part43to fix the collar47to the rear extension part43. The support plate40and the collar47are coupled in advance prior to assembly of the cushion frame13, and prepared as a support member (support plate assembly) formed by combining the support plate40and the collar47. The collar47constitutes a vehicle width direction extended part that is part of this support member.

The shaft part of the fixing screw45protrudes toward the seat inner side through a through hole35b(seeFIGS.4and10) that is formed in the seat surface plate35. Furthermore, the shaft part of the fixing screw45is inserted in the fastening hole14hand the inner through hole47a(that includes an insertion area of the collar47with respect to the fitting hole43a) from the seat outer side to the seat inner side, and protrudes from the support plate40to the seat inner side. This protrusion part of the fixing screw45is screwed with a nut48. A thickness of the rear extension part43is set slightly larger than a protrusion amount of the fitting step part47bin the width direction, and, when the fixing screw45and the nut48are screwed, the nut48is mainly in contact with a face on the seat inner side of the rear extension part43. A face on the seat outer side of the rear extension part43is in contact with one end (surroundings of a proximal end part of the fitting step part47b) of the collar47, an other end of the collar47is in contact with the rear step part14d, and thereby the rear extension part43and the collar47are sandwiched between the nut48and the side frame14.

When a predetermined tightening torque is applied to the fixing screws44and the nuts46, the seat surface plate35, the side frame14(rear step part14d), and the base plate part41of the support plate40are sandwiched between the head parts of the fixing screws44and the nuts46, and are stacked and fixed in the vehicle width direction. Furthermore, when a predetermined tightening torque is applied to the fixing screw45and the nut48, the seat surface plate35, the side frame14(rear step part14d), the collar47, and the rear extension part43of the support plate40are sandwiched between the head part of the fixing screw45and the nut48, and are stacked and fixed in the vehicle width direction. Note that the collar47functions as a spacer in the vehicle width direction, and therefore a fastening force of the fixing screw45and the nut48does not act on the sector gear plate22dand the reinforcement plate25. Thus, the driving unit30is fastened and fixed to the side frame14.

As illustrated inFIGS.9and10, the collar47is inserted in the long hole22fof the rear link22. A width of the long hole22fin the radial direction of the sector gear plate22dis set a predetermined size or more larger than a diameter of the collar47such that there is a sufficient gap between the long hole22fand the collar47. The long hole22fis an arc-shaped groove whose center is the through hole22b(rear pipe16), and enables rotation (swing) of the rear link22about the rear pipe16at a time of an operation of the lifter mechanisms20without being interfered by the collar47.

As illustrated inFIG.10, the collar47is further inserted in the receiving hole25bof the reinforcement plate25. The diameter (inner diameter) of the receiving hole25bis smaller than the width of the long hole22f, yet is set to have a predetermined gap or more with respect to the collar47. That is, an outer circumferential surface of the collar47is designed to not contact an inner circumferential surface of the receiving hole25bwhen the support plate40(rear extension part43) and the driving unit30(seat surface plate35) are fixed to the side frame14by the fixing screw45and the nut48, so that it is possible to absorb a precision error (assembly error) between the reinforcement plate25and the support plate40more or less.

To sum up the main pats of the left frame structure with reference toFIGS.9and10, the reinforcement plate25, the rear link22(the sector gear plate22din particular) that constitutes the lifter mechanism20, and the support plate40are disposed in order from the side close to the side frame14on the seat inner side that is one side in the vehicle width direction with respect to the side frame14. The reinforcement plate25is fixed to the face on the seat inner side of the side frame14. The rear extension part43of the support plate40is located apart from the side frame14to the seat inner side with the sector gear plate22dand the reinforcement plate25interposed therebetween, and the collar47extended from the rear extension part43to the vehicle width direction (seat outer side) is placed in contact with the side frame14, and is fastened and fixed to the side frame14using the fixing screw45and the nut48. The sector gear plate22dis supported rotatably about the rear pipe16with respect to the side frame14without contacting the support plate40and the reinforcement plate25.

The driving unit30is disposed on the seat outer side that is the other side in the vehicle width direction with respect to the side frame14. The driving unit30is fastened and fixed to the side frame14in such a manner that the driving unit30is tightened together with the support plate40(rear extension part43) on the seat inner side using the fixing screw45and the nut48. Consequently, it is possible to reduce the number of the fixing screws45that are fixing members. Furthermore, it is possible to reduce the number of holes to be formed in the side frame14to insert the fixing screws45therein, so that it is possible to suppress a decrease in strength of the side frame14.

The lifter function-equipped cushion frame13is formed by assembling the lifter mechanisms20and the driving unit30to the side frame14as described above. When the motor31is driven to rotate the pinion33, the rear link22operates while changing an enmeshing position of the sector gear22ewith respect to the pinion33to change a position of the rear pipe16with respect to the connection part22aon the upper rail18(support bracket19) side. The front link21also operates accompanying this change to change a position of the connection part21bon the side frame14side with respect to the connection part21aon the upper rail18(support bracket19) side. As a result, a height position of the side frame14changes.

Unlike the above-described left frame structure, the right frame structure does not include the driving unit30(seeFIG.1). Accordingly, it is possible to use a type that does not include a sector gear for the rear link (illustration thereof is omitted) that constitutes the lifter mechanism20in the right frame structure.

By the way, when another vehicle or the like causes rear end collision (so-called rear collision) for a vehicle on which the vehicle seat10is mounted, a passenger sitting on the vehicle seat10is strongly pressed against the seat cushion11and the seat back12due to an inertia, and a load is applied in a lower rear direction to the frame structure of the vehicle seat10. The enmeshing part of the pinion33and the sector gear22ereceives a load of a force that lowers the vehicle seat10downward. In this regard, in a case where a countermeasure according to present embodiment described below is not taken, when a strong load to move the vehicle seat10in the lower rear direction is applied, the pinion33and the sector gear22ecause an enmeshing failure, and the teeth of the sector gear22eand the pinion33cannot withstand the load and break.

As a result of study and experiments conducted by the applicants, it has been found that, when the countermeasure according to the present embodiment is not taken, and a very strong rear collision load acts, deformation that extends the rear part of the side frame14in the rear direction occurs, an inter-axial distance between the pinion33and the sector gear plate22dbecomes longer, and an enmeshing amount of the pinion33and the sector gear22ein the front/rear direction becomes small. Furthermore, the very strong rear collision load causes a tilt of one or both of the pinion33and the sector gear plate22din the vehicle width direction, respective tooth surfaces of the pinion33and the sector gear22edo not appropriately meet each other face to face, and a load of an irregular direction that crosses the upper/lower direction is input to an enmeshing portion. These phenomena are assumed as causes of the above-described enmeshing failure.

To prevent such a failure, the frame structure according to the present embodiment has the improved strength around the gear mechanisms as described below. First, the reinforcement plate25that is the reinforcement member is attached to a rear part area of the side frame14in which the pinion33and the sector gear plate22dare disposed. Cross-sectional strength is improved by adding a thickness of the reinforcement plate25to the original thickness of the side frame14, and the side frame14hardly deforms.

The reinforcement plate25has a shape that overlaps the rear step part14din an area between the rear pipe16(the through hole14fand the through hole22b) that is a rotary shaft of the sector gear plate22d, and the through hole14gthat is a position reference of the pinion33. Furthermore, the thickness of the reinforcement plate25is larger than the thickness of the side frame14. Consequently, the reinforcement plate25can effectively suppress deformation of the side frame14that changes the interval between the through hole14fand the through hole14g.

As a more detailed configuration, as illustrated inFIGS.7to10, the reinforcement plate25includes a first area25c(first extension part) that extends toward the rear pipe16side, and a second area25d(second extension part) that extends toward a side (front) opposite to the rear pipe16using as a position reference the through hole25ato be penetrated by the pinion base part34that is part of the pinion33. The first area25chas a longer length from the through hole25a(longer in the front/rear direction) than the second area25d, and the first area25coverlaps the rear step part14din an almost entire range between the pinion33and the rear pipe16in the front/rear direction. That is, the reinforcement plate25reinforces large part of the range from the pinion33to the rear pipe16by the first area25c. Furthermore, the reinforcement plate25includes the second area25dthat protrudes in the front direction compared to the pinion33, so that improvement of strength around the pinion33is realized.

The receiving hole25bof the reinforcement plate25is formed in the first area25c. As described above, the diameter (inner diameter) of the receiving hole25bis set to have a predetermined gap or more with respect to the collar47. When a strong rear collision load is applied to the vehicle seat10, and the side frame14slightly deforms, the gap between the collar47and the receiving hole25bnarrows, and the outer circumferential face of the collar47and the inner circumferential face of the receiving hole25bcontact. This contact provides a reinforcement effect of preventing the side frame14from deforming more between the reinforcement plate25and the support plate40.

When, for example, a load is applied in a direction to increase the inter-axial distance between the pinion33and the sector gear22e, the outer circumferential surface of the collar47contacts a part on a side in the front direction of the inner circumferential surface of the receiving hole25b, and a portion that withstands the load is formed. Consequently, the reinforcement plate25plays both of a role of reinforcing the side frame14itself, and a role of receiving the load to be applied to the support plate40and reducing the load on the side frame14, so that it is possible to effectively suppress an increase in an inter-axial distance (a decrease in an enmeshing amount) between the pinion33and the sector gear22e.

The reinforcement plate25plays a role of preventing an increase in the inter-axial distance between the pinion33and the sector gear22e, and, in addition, suppressing a tilt (a fall in the vehicle width direction direction) of both of the sector gear plate22dand the pinion33.

First, the reinforcement plate25is disposed between the side frame14and the sector gear plate22din the vehicle width direction to fill a space between the side frame14and the sector gear plate22d. Consequently, when the sector gear plate22dsignificantly tends to tilt toward the seat outer side, the sector gear plate22dcontacts a side surface of the reinforcement plate25, and the reinforcement plate25can prevent the sector gear plate22dfrom tilting more.

Furthermore, contact of the collar47, and the receiving hole25band the side frame14suppresses movement and a tilt in the front/rear direction of the support plate40with respect to the side frame14and the reinforcement plate25. The support plate40supports the pinion shaft33aby the pinion support hole42a, so that suppression of the movement and suppression of the tilt in the front/rear direction of the support plate40contributes to suppression of the movement and suppression of the tilt in the front/rear direction of the pinion33. Furthermore, contact of the inner circumferential surface of the through hole25aand the outer circumferential surface of the pinion base part34provides an effect of suppression of the movement and suppression of the tilt in the front/rear direction of the pinion33.

The gap between the collar47and the receiving hole25bis set smaller than the gap between the collar47and the long hole22f, so that the collar47and the receiving hole25bpreferentially contact, and the collar47and the long hole22fkeep a separated state. That is, it is possible to reliably pass the load between the collar47and the reinforcement plate25without influencing position accuracy of the sector gear plate22dand the operation of the rear link22.

According to the above configuration and function, the frame structure according to the present embodiment can suppress a change in relative positions of the pinion33and the sector gear plate22dat a time of input of a rear collision load, and remarkably improve load withstanding performance around the gear mechanisms compared to existing frame structures.

The reinforcement plate25is attached only to a portion of the side frame14for which a high strength request for a rear collision load is demanded, and therefore the plate thickness of the entire side frame14does not need to be increased. Consequently, even a small and light structure that is not accompanied by an increase in a weight of the side frames14can realize improvement of strength of the frame structure. Furthermore, the side frames14of the large plate thicknesses are not used, so that workability of the side frames14is good, material fees are also low, and manufacturing cost can be suppressed. The reinforcement plate25adopts a simple structure that the through hole25aand the receiving hole25bthat penetrate in a plate thickness direction are formed using as a base a flat plate shape along the rear step part14dof the side frame14, and can be obtained at low cost.

The collar47plays a role as a spacer for filling a gap between the rear extension part43of the support plate40and the rear step part14dof the side frame14to fasten, and a role of passing a load between the support plate40and the reinforcement plate25. Consequently, it is possible to contribute to improvement of strength of the frame structure with a simple configuration without making the structure of the support plate40complicated.

Although the above description has focused upon a load that increases the inter-axial distance between the pinion33and the sector gear plate22d, the frame structure according to the present embodiment is effective likewise for a load that decreases an inter-axial distance between the pinion33and the sector gear plate22d. The reinforcement plate25including the first area25clocated between the through hole14gand the through hole14fprovides an effect of suppressing deformation of the side frame14in a direction in which the interval between the through hole14gand the through hole14gis decreased (i.e., the inter-axial distance between the pinion33and the sector gear plate22dis decreased). Furthermore, the outer circumferential surface of the collar47contacts a part on a side in the rear direction of the inner circumferential surface of the receiving hole25b, so that it is possible to withstand a load in a direction in which the inter-axial distance between the pinion33and the sector gear22eis decreased.

A position of the receiving hole25bthat is the insertion part of the reinforcement plate25is set under a condition that the receiving hole25bcan exhibit an effect of suppressing a change in the inter-axial distance between the pinion33and the sector gear plate22d, and adopts a structure (an area and the thickness) that surroundings of the receiving hole25bcan sufficiently withstand a load from the collar47. The first area25cthat is located between the pinion33and the rear pipe16and is longer (i.e., has a larger area) than the second area25dsatisfies the condition, and therefore the receiving hole25bis formed in the first area25c.

The above condition is satisfied, and, moreover, the receiving hole25bhas a degree of freedom to set a formation position thereof. According to, for example, the present embodiment, there are the welding positions W near the rear end of the reinforcement plate25, and the receiving hole25bis disposed at a position (a vicinity of a center in the front/rear direction in the first area25c) that is ahead of and apart to some degree from the welding positions W. However, in a case where there is no restriction on the welding positions W or the like, the receiving hole25bmay be disposed more in the rear direction (near the through hole14f). By setting a load reception portion of the receiving hole25band the collar47close to the rear direction near the through hole14f, it is easy to suppress deformation (stretch) of the side frame14in a direction in which the inter-axial distance between the pinion33and the sector gear plate22dis increased.

FIG.8illustrates a virtual line P1that connects a center of the pinion shaft33aof the pinion33and a center of the rear pipe16seen from the lateral side. An enmeshing position of the sector gear22ewith respect to the pinion33is located substantially on the virtual line P1. Furthermore, by setting the load reception portion of the receiving hole25band the collar47on the virtual line P1or at a position close to the virtual line P1seen from the lateral side, it is possible to enhance an effect of preventing a change in the interval between the pinion33and the rear pipe16(i.e., a change in the inter-axial distance between the pinion33and the sector gear plate22d). In the present embodiment, the receiving hole25bis located in a close range of the virtual line P1, and satisfies the condition. According to a modified example, it is also possible to place the receiving hole25bclose to the virtual line P1compared to the present embodiment, and set an arrangement where the receiving hole25boverlaps the virtual line P1.

In the present embodiment, the collar47in which the fixing screw45is inserted is used as a part on the support plate40side that is inserted in the receiving hole25bof the reinforcement plate25. As described above, the collar47plays a plurality of roles, so that it is possible to realize improvement of the strength of the frame structure while simplifying the configuration of the support plate40side. However, in the modified example different from the present embodiment, it is also possible to apply a part other than a collar for fixing screw insertion as a part on a support member (support plate40) side in which an insertion part (receiving hole25b) of a reinforcement member (reinforcement plate25) is inserted.

Although the above embodiment has exemplified the frame structure that includes the lifter mechanisms20for seat lifting and the driving unit30, the present invention is applicable to a structure that includes a gear mechanism for use other than seat lifting. Consequently, the drive input gear according to the present invention may be a gear other than a sector gear for seat lifting.

Furthermore, the embodiment of the present invention is not limited to the above embodiment and the modified example thereof, and can be variously changed, replaced and modified without departing from the spirit of the technical idea of the present invention. Furthermore, if technical development and other techniques deriving therefrom can realize the technical idea of the present invention by another method, the technical idea of the present invention can be carried out using the another method. Accordingly, the claims cover all embodiments that can be included within the range of the technical idea of the present invention.

REFERENCE SIGNS LIST

10vehicle seat11seat cushion (seat surface part)12seat back13cushion frame14side frame (seat frame)14cfront step part14drear step part14fthrough hole14gthrough hole14hfastening hole14ifastening hole15front pipe16rear pipe (rotary shaft of drive input gear)20lifter mechanism21front link22rear link22bthrough hole22carm part22dsector gear plate (drive input gear)22esector gear (drive input gear)22flong hole25reinforcement plate (reinforcement member)25athrough hole25breceiving hole (insertion part)25cfirst area (first extension part)25dsecond area (second extension part)30driving unit31motor32gear housing33pinion33apinion shaft (part of pinion)34pinion base part (part of pinion)35seat surface plate40support plate (support member)42pinion cover part42apinion support hole43rear extension part43afitting hole44fixing screw45fixing screw (fixing member)46nut47collar (part of support member, vehicle width direction extended part)47ainternal through hole47bfitting step part48nut