Seat back frame for vehicle seat

A seat back frame for a vehicle seat includes first and second side members spaced apart from each other, each of the first and second side members being made of ultra-high tensile strength steel, the first side member having a first longitudinal body of a substantially U-shape in cross-section, the first longitudinal body comprising a pair of first spaced apart flange sections and a first main plate section interconnecting the first spaced apart flange sections, the first side member having a first upper region and a first lower region, the second side member having a second longitudinal body of a substantially U-shape in cross-section, the second longitudinal body comprising a pair of second spaced apart flange sections and a second main plate section interconnecting the second spaced apart flange sections, the second side member having a second upper region and a second lower region, an upper member arranged between the first and second upper regions of the first and second side members, the upper member being made of ultra-high tensile strength steel, the upper member having first and second end portions, the upper member being mounted, by spot-welding, to the first and second upper regions of the first and second side members with the first and second end portions thereof being fitted in the first and second side members, and a lower member arranged between the first and second lower regions of the first and second side members, the lower member being made of ultra-high tensile strength steel, the lower member having third and fourth end portions, and the lower member being mounted, by spot-welding, to the first and second lower regions of the first and second side members with the third and fourth end portions thereof being fitted in the first and second side members.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a substantially quadrilateral-shaped seat back frame for a vehicle seat, which is assembled from components which are each made of a thin plate of ultra-high tensile strength steel and formed into a predetermined shape by press-machining the thin plate.

2. Description of the Prior Art

Generally, a seat back frame for a vehicle seat comprises a main pipe of a substantially inverted U-shape in outline, an upper plate member bridged between upper regions of both side portions of the inverted U-shaped pipe and mounted to the upper regions of the both side portions of the inverted U-shaped pipe by arc welding, side plate members mounted to the both side portions of the inverted U-shaped pipe by arc welding, and a lower pipe bridged between lower regions of the both side portions of the inverted U-shaped pipe and mounted to the lower regions of the both side portions of the inverted U-shaped pipe by arc welding. Each of the upper plate member and side plate members is formed into a predetermined shape by cutting a steel plate. The seat back frame is assembled from the components into a substantially quadrilateral-shape.

The conventional seat back frame is heavy in weight and weak in mechanical strength. As discussed above, the upper plate member, the side plate members, and the lower pipe member are mounted to the inverted U-shaped main pipe by arc welding. To carry out the welding while assuring a dimensional precision is troublesome.

SUMMARY OF THE INVENTION

The present invention has been made with a view to overcoming the foregoing problems of the prior art seat back frame.

It is therefore an object of the present invention to provide a seat back frame for a vehicle seat, which is light in weight and improved in mechanical strength and dimensional precision.

It is another object of the invention to provide a seat back frame for a vehicle seat, which can be easily assembled.

In accordance with the present invention, there is provided a seat back frame for a vehicle seat. The seat back frame comprises first and second side members spaced apart from each other, each of the first and second side members being made of ultra-high tensile strength steel, the first side member having a first longitudinal body of a substantially U-shape in cross-section, the first longitudinal body comprising a pair of first spaced apart flange sections and a first main plate section interconnecting the first spaced apart flange sections, the first side member having a first upper region and a first lower region, the second side member having a second longitudinal body of a substantially U-shape in cross-section, the second longitudinal body comprising a pair of second spaced apart flange sections and a second main plate section interconnecting the second spaced apart flange sections, the second side member having a second upper region and a second lower region, an upper member arranged between the first and second upper regions of the first and second side members, the upper member being made of ultra-high tensile strength steel, the upper member having first and second end portions, the upper member being mounted, by spot-welding, to the first and second upper regions of the first and second side members with the first and second end portions thereof being fitted in the first and second side members, and a lower member arranged between the first and second lower regions of the first and second side members, the lower member being made of ultra-high tensile strength steel, the lower member having third and fourth end portions, and the lower member being mounted, by spot-welding, to the first and second lower regions of the first and second side members with the third and fourth end portions thereof being fitted in the first and second side members.

The first side member may be provided at an upper area of the first main plate section thereof with a first reinforcing rib portion. The first reinforcing rib portion may be formed by embossing a region of the upper area of the first main plate section and making the region of the upper area of the first main plate section concave in such a manner that the region of the upper area of the first main plate section protrudes inward. The second side member may be provided at an upper area of the second main plate section thereof with a second reinforcing rib portion. The second reinforcing rib portion may be formed by embossing a region of the upper area of the second main plate section and making the region of the upper area of the second main plate section concave in such a manner that the region of the upper area of the second main plate section protrudes inward. The upper member may be provided at the first and second end portions thereof with first and second tongue-shaped pieces. The first and second tongue-shaped pieces are spot-welded to inward protruding surfaces of the first and second reinforcing rib portions. The inward protruding surfaces of the first and second reinforcing rib portions are made flat.

The first side member may be provided at a middle area of the first main plate section thereof with a third reinforcing rib portion and provided at a lower area of the first main plate section thereof with a fourth reinforcing rib portion. The second side member may be provided at a middle area of the second main plate section thereof with a fifth reinforcing rib portion and provided at a lower area of the second main plate section thereof with a sixth reinforcing rib portion.

The upper member may comprise an upper section and a base section. The upper section and the base section are combined with each other.

The lower member may comprise a longitudinal body, and bracket portions provided at both end portions of the longitudinal body of the lower member. The bracket portions are spot-welded to the lower regions of the first and second side members.

The seat back frame may further include a supplementary member for reinforcing the lower member. The supplementary member is spot-welded to the lower member. The supplementary member may comprise a longitudinal body and bracket portions provided at both end portions of the longitudinal body of the supplementary member. The bracket portions of the supplementary member are spot-welded to the bracket portions of the lower member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A seat back frame for a vehicle seat according to the present invention will be discussed hereinafter with reference to the accompanying drawings.

In an illustrated embodiment, the present invention is applied to a seat back frame for a vehicle seat including a height adjustable head rest, recliner devices for allowing a seat back of the vehicle seat to be pivotally moved relative to a seat cushion of the vehicle seat, and a slide rail mechanism for allowing the vehicle seat to be moved forward and rearward in a vehicle.

Referring toFIGS. 1 and 2, there is illustrated the seat back frame according to the embodiment of the present invention. The seat back frame comprises a pair of spaced apart side members1,2, an upper member3interconnecting upper portions of the side members1,2, a lower member4interconnecting lower portions of the side members1,2, and a supplementary member5for reinforcing the lower member4. Each of the components of the seat back frame is made of ultra-high tensile strength steel, and is formed into a predetermined shape by press-machining a thin plate of ultra-high tensile strength steel. The upper member3and the lower member4are mounted to the spaced apart side members1,2by spot-welding. Though tension springs are not shown inFIG. 1, the tension springs are to be stretched between the spaced apart side members1,2.

Each of the side members1,2has a longitudinal body of a substantially U-shape in cross-section. The longitudinal body of the first side member1comprises a pair of first and second flange sections11,12which are spaced apart from each other in a direction perpendicular to a sheet ofFIG. 1, and a main plate section10interconnecting the spaced apart flange sections11,12. The main plate section10has an outer surface which forms a portion corresponding to an area of a seat back which extends from one shoulder portion of the seat back to one side portion of the seat back. Similarly, the longitudinal body of the second side member2comprises a pair of third and fourth flange sections21,22which are spaced apart from each other in the direction perpendicular to the sheet ofFIG. 1, and a main plate section20interconnecting the spaced apart flange sections21,22. The main plate section20has an outer surface that forms a portion corresponding to an area of the seat back which extends from the other shoulder portion of the seat back to the other side portion of the seat back. An upper region of each of the side members1,2is curved inward to form a portion corresponding to a corresponding shoulder portion of the seat back.

Each of the flange sections11,12,2122has an upper region, a middle region, and a lower region. Upper regions11a,12aof the first and second flange sections11,12lengthily extend inwardly as compared to middle regions11b,12bof the first and second flange portions11,12. Similarly, upper regions21a,22aof the third and fourth flange sections21,22extend inwardly as compared to middle regions21b,22bof the third and fourth flange sections21,22. Further, the upper region12aof the second flange section12lengthily extends inwardly as compared to the upper region11aof the first flange section11. A lower region12cof the second flange section12lengthily extends inwardly as compared to a lower region11cof the first flange section11. Similarly, the upper region22aof the fourth flange section22lengthily extends inwardly as compared to the upper region21aof the third flange section21. A lower region22cof the fourth flange section22lengthily extends inwardly as compared to a lower region21cof the third flange section21.

The main plate section10of the first side member1has first reinforcing means for reinforcing the main plate section10. The first reinforcing means includes a first vertically extending rib portion13of a substantially rectangular shape (seeFIG. 2) provided at an upper region of the main plate section10and a second vertically extending rib portion14of a substantially rectangular shape (seeFIG. 2) provided at a middle region of the main plate section10. Similarly, the main plate section20of the second side member2has second reinforcing means for reinforcing the main plate section20. The second reinforcing means includes a third vertically extending rib portion23of a substantially rectangular shape provided at an upper region of the main plate section20and a fourth vertically extending rib portion24of a substantially rectangular shape provided at a middle region of the main plate section20. The first and second reinforcing means are formed by embossing portions of the main plate sections10,20and making the portions of the main plate sections10,20concave in such a manner that the portions of the main plate sections10,20protrude inwardly. As will be discussed in greater detail hereinafter, both ends of the upper member3are to be welded to inwardly protruding surfaces of the first and third rib portions13,23of the first and second side members1,2by spot-welding. For this purpose, an inwardly protruding surface of each of the first and third rib portions13,23is formed flat. In a case where a first arm rest is provided at the middle region of the main plate section10at which the second rib portion14is provided, and a second arm rest is provided at the middle region of the main plate section20at which the fourth rib portion24is provided, the second and fourth rib portions14,24also serve as means to reinforce surfaces of the middle regions of the main plate sections10,20on which the first and second arm rests are provided.

As shown inFIG. 2, a bead-like projection15for reinforcing a lower region of the main plate section10is provided on the lower region of the main plate section10. Similarly, though not shown inFIG. 1, a bead-like projection for reinforcing a lower region of the main plate section20is provided on the lower region of the main plate section20. Further, as shown inFIG. 1, bead-like projections16a,16bfor reinforcing the lengthily extending upper region12aof the flange section12are provided on the lengthily extending upper region12aof the flange section12, and bead-like projections26a,26bfor reinforcing the lengthily extending upper region22aof the flange section22are provided on the lengthily extending upper region22aof the flange section22a. In addition to serving as the reinforcing means, each of the bead-like projections15,16a,16b,26a,26band unshown bead-like projection of the lower region of the main plate section20serves as means to prevent a plate of ultra-high tensile strength steel from warping when the plate is press-machined in order to make each of the first and second side members1,2.

Referring toFIGS. 3 to 5, the upper member3comprises an upper section3athat forms a portion corresponding to an upper portion of the seat back, and a base section3bfor receiving and supporting the upper section3a.

As shown inFIGS. 3 and 5, the upper section3aof the upper member3comprises a top horizontal surface portion30a, a front side surface portion30bcontinuously extending downward from the top surface portion30a, a bottom surface portion30ccontinuously extending from the front side surface portion30bin substantially parallel with the top horizontal surface portion30a, a downward extending surface portion30dcontinuously extending and hanging from the bottom surface portion30c, and a lower flange portion30eextending along a lower edge of the downward extending surface portion30d. In addition, a rear side surface portion30fcontinuously extends downward from the top surface portion30a. The top surface portion30ais provided at both sides thereof with downward bent tongue-shaped pieces31a,31bwhich are to be welded to the side members1,2by spot-welding. The tongue-shaped pieces31a,31bare formed by bending both end portions of the top surface portion30adownward, and continuously extend from the top surface portion30aand the rear side surface portion30fat upper regions thereof.

The downward extending surface portion30dof the upper section3ahas a first end region30d-1, a second end region30d-2, and a middle region30d-3between the first end region30d-1and the second end region30d-2. The first and second end regions30d-1,30d-2are projected forward from the middle region30d-3. The flange portion30eis protruded forward from the downward extending surface portion30d. The top surface portion30ais formed with a pair of spaced apart through-holes32a,32b. Similarly, a pair of spaced apart through-holes (not shown) are formed in the bottom surface portion30cand aligned with the pair of the spaced apart through-holes32a,32bof the top surface portion30a. Holders for head rest stays (not shown) are to be inserted in the through-holes32a,32bof the top surface portion30aand the unshown through-holes of the bottom surface portion30c. Further, in order to make the upper section3alighter in weight, an opening33is formed in the front surface portion30bby punchin g a central portion of the front surface portion30b.

As shown inFIGS. 4 and 5, the base section3bof the upper member3comprises a base body34aand a rising portion34brising upwardly from the base body34a. A front side edge of the base body34ais formed into a substantially bow-shape so as to protrude forward at both end portions of the base body34a. A downward protruding flange34cis provided along the bow-shaped edge of the base body34a. The base body34ais provided at both side regions thereof with downward bent tongue-shaped pieces35a,35bwhich are to be welded to the side members1,2by spot-welding. The rising portion34bof the base section3bcomprises a first end region34b-1, a second end region34b-2, and a middle region34b-3between the first end region34b-1and the second end region34b-2. The first and second end regions34b-1,34b-2are protruded forward from the middle region34b-3. An upper flange34dis provided along an upper edge of the rising portion34band protruded forward from the rising portion34b.

In a state where the upper section3aand the base section3bare combined with each other as shown inFIG. 5, the lower flange30eof the downward extending portion30dand the upper flange34dof the rising portion34bare abutted against each other at the end portions30d-1,30d-2,34b-1,34b-2.

Referring toFIG. 6, the lower member4comprises a longitudinal body40, a pair of bracket portions41a,41bprovided at both ends of the longitudinal body40, and upwardly extending pieces42a,42bcontinuously extending from the longitudinal body40and the bracket portions41a,41b. The bracket portions41a,41band the upwardly extending pieces42a,42bare to be attached to the side members1,2by spot-welding. The lower member is provided at the longitudinal body40thereof with a bead-like embossed portion43, whereby the longitudinal body40is reinforced. The bead-like embossed portion43extends along the longitudinal body40and is protruded forward. Further, forward bent flange portions44a,44bextend along upper and lower edges of the longitudinal body40.

Substantially disc-like recliner devices (not shown) are to be mounted on outer surfaces of the bracket portions41a,41b. The bracket portions41a,41bare formed with a plurality of fastening holes45a,45bfor allowing the recliner devices to be mounted on the bracket portions41a,41bby bolts, and through-holes46a,46bthrough which a connecting shaft (not shown) for interconnecting the recliner devices is to be inserted. A lower region of each of the bracket portions41a,41bis formed into a circular arc-shape which matches with a shape of a corresponding disc-like recliner device. Each of the bracket portions41a,41bis provided along its peripheral edge with a flange47a(or47b).

The supplementary member5comprises a longitudinal body5ahaving the shape of a substantially Ohm-symbol in cross-section. The longitudinal body5aof the supplementary member5comprises a pair of spaced apart longitudinal portions, a connecting longitudinal portion interconnecting the spaced apart longitudinal portions, and protruding fin portions extending along edges of the spaced apart longitudinal portions and protruding from the spaced apart longitudinal portions. The supplementary member5is to be attached to the lower member4by spot-welding so as to cover the embossed portion43of the lower member4. The supplementary member5has a width enough to cover the embossed portion43of the lower member4. Spaced apart rising tongue-shaped pieces50aand spaced apart rising tongue-shaped pieces50bare provided at upper and lower edges of the fin portion of the spaced apart longitudinal portions of the supplementary member5. The tongue-shaped pieces50a,50bare to be welded to the longitudinal body40of the lower member4by spot-welding. Further, the connecting longitudinal portion of the supplementary member5is provided at both ends thereof with forward bent tongue-shaped pieces51a,51bwhich are to be welded to the flange portions41a,41bof the lower member4.

Referring toFIGS. 7 to 10, assembling of the seat back frame will be discussed hereinafter.

As shown inFIG. 7, the upper member3is combined with the side members1,2with the both sides thereof being fitted in the U-shaped side members1,2and with the tongue-shaped pieces31a,31bthereof being contacted with upper regions of the inward protruding surfaces of the rib portions13,23of the side members1,2.

The upper section3aof the upper member3is mounted to the side members1,2by spot-welding the front side surface portion30bof the upper section3ato the first and third flange portions11,21of the side members1,2, spot-welding the downward extending surface portion30dand rear side surface portion30fof the upper section3ato the second and fourth flange portions12,22of the side members1,2, and spot-welding the tongue-shaped pieces31a,31bof the upper section3ato the upper regions of the inward protruding surfaces of the rib portions13,23. Incidentally, the welding points are denoted by a reference designator X inFIGS. 7 to 10.

The base section3bof the upper member3is mounted to the side members1,2by spot-welding both side regions of the rising portion34bof the base section3bto the second and fourth flange portions12,22of the side members1,2, and spot-welding the tongue-shaped pieces35a,35bof the base section3bto lower regions of the inward protruding surfaces of the rib portions13,23of the side members1,2, whereby the upper section3ais received and supported by the base section3b. Incidentally, the mounting of the upper section3ato the side members1,2is preferably carried out after the base section3bis mounted to the side members1,2.

As shown inFIG. 8, the supplementary member5is applied onto an inner surface of the longitudinal body40of the lower member4and is mounted to the lower member4by spot-welding the tongue-shaped pieces50a,50bof the supplementary member5to the longitudinal body40of the lower member4, and spot-welding the tongue-shaped pieces51a,51bof the supplementary member5to the bracket portions41a,41bof the lower member4.

The base section3bof the upper member3is mounted to the side members1,2by spot-welding both side regions of the rising portion34bof the base section3bto the second and fourth flange portions12,22of the side members1,2, and spot-welding the tongue-like pieces35a,35bof the base section3bto lower regions of the inward protruding surfaces of the rib portions13,23of the side members1,2, whereby the upper section3ais received and supported by the base section3b. Incidentally, the mounting of the upper section3ato the side members1,2is preferably carried out after the base section3bis mounted to the side members1,2.

As shown inFIG. 8, the supplementary member5is applied onto an inner surface of the longitudinal body40of the lower member4and is mounted to the lower member4by spot-welding the tongue-like pieces50a,50bof the supplementary member5to the longitudinal body40of the lower member4, and spot-welding the tongue-like pieces51a,51bof the supplementary member5to the bracket portions41a,41bof the lower member4.

As shown inFIG. 9, the lower member4to which the supplementary member5is mounted is combined with the side members1,2with the bracket portions41a,41b(only one bracket portion41bis shown inFIG. 9) and upward extending pieces42a,42b(only one upward extending pieces42bis shown inFIG. 9) of the lower member4being engaged with the side members1,2(only one side member1is shown inFIG. 9), and is mounted to the side members1,2by spot-welding the upward extending pieces42a,42bof the lower member4to the lower regions12c,22cof the second and fourth flange sections12,22of the side members1,2(only one lower region22cis shown inFIG. 9) and spot-welding the bracket portions41a,41bof the lower member4to lower regions of the main plate sections10,20of the side members1,2(only one main plate section20is shown inFIG. 9).

Referring toFIGS. 10 and 11, there is illustrated the seat back frame which is assembled as discussed above. The seat back frame is formed into a substantially quadrilateral-shape by spot-welding the upper member3including the upper section3aand the base section3b, and the lower member4including the supplementary member5, to the side members1,2at the several points.

The seat back frame is assembled from only the side members1,2, the upper member3, and the lower member4, so that the seat back frame can be made with a few parts. Each of the components of the seat back frame is made of a thin plate of ultra-high tensile strength steel as discussed above, so that the seat back frame is made lighter in weight. Further, each of the components of the seat back frame is formed into a predetermined shape by press-machining the thin plate of ultra-high tensile strength, whereby the components can be precisely shaped and sized. In addition, the both sides of the upper member3and the both sides of the lower member4are engaged with the substantially U-shaped side members1,2and welded to the side members1,2, whereby the mechanical strength of the seat back frame is improved. Also, the connecting of the components is performed by spot-welding, so that it is possible to easily assemble the seat back frame while assuring a dimensional precision.

Referring toFIG. 12, there is illustrated a modification of the supplementary member5. The supplementary member5′ ofFIG. 12is substantially similar to the supplementary member5ofFIGS. 1,2,6,8,9,10and11except that bracket portions5b(only one bracket portion5bis shown inFIG. 12) are provided at both end portions of the longitudinal body5aof the supplementary member5′ in lieu of the tongue-shaped pieces51a,51b. Each of the bracket sections5bis formed into a substantially L-shape as viewed from the front side, and has the shape of Ohm symbol in cross-section. The bracket portions5bare attached to the side members1,2(only one side member2is shown inFIG. 12) by spot-welding fin portions5b′ of the bracket portions5bto the main plate sections10,20of the side members1,2(only one main plate section20is shown inFIG. 12). The bracket portions5bextend between the longitudinal body5aof the supplementary member5′ on the lower member4and the side members1,2, so that the side members1,2and the lower member4are reinforced by the bracket portions5b. Incidentally, the supplementary member5′ may be made as a one-piece member comprising the longitudinal body5aand the bracket portions5b, or may comprise the longitudinal body5aand bracket portions5bwhich are made separately from one another.

Referring toFIG. 13, the vehicle seat in which the seat back frame B constructed as discussed above is employed will be discussed hereinafter. A seat cushion frame S of the vehicle seat comprises a pair of spaced apart base sections7,8and a pan frame section6welded to forward end portions of the base sections7,8. Each of the base sections7,8and pan frame section6is made of a thin plate of ultra-high tensile strength steel. Recliner devices (not shown) are provided between lower regions of side portions of the seat back frame B and rearward regions of the base sections7,8of the seat cushion frame S. The unshown recliner devices are connected to each other through a connecting shaft9.