Vehicle seat and manufacturing method for vehicle seat

Abstract

To widen a space in front of a seat cushion and facilitate assembling work in a vehicle seat.SOLUTION: A vehicle seat includes: a base provided on a floor; a seat back rotatably provided on the base; a seat cushion rotatably provided on the seat back; and a driving device 61 connected to the base and the seat back and rotating the seat back with respect to the base. The driving device 61 is arranged behind the front end of the seat cushion.SELECTED DRAWING: Figure 12

Description

[Technical field]

[0001] The present invention relates to a vehicle seat and a method for manufacturing a vehicle seat. [Background technology]

[0002] Patent Document 1 discloses a dive-down seat in which the seat cushion moves toward the floor when in a storage configuration. The seat cushion and the floor are connected by front and rear legs, and the seat cushion, floor, front and rear legs form a four-joint link. The front legs and the floor are connected by a drive means having a screw rod that reciprocates by the driving force of an electric motor. When the drive means is driven, the angle of the front legs relative to the floor changes, and the seat cushion moves. As a result, the seat changes from a usage configuration to a storage configuration. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-262294 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the seat disclosed in Patent Document 1, the drive means is provided on the floor in front of the front legs. This causes a problem that the space in front of the seat cushion becomes narrow. In addition, the drive means needs to be attached to the floor separately from the seat, which causes a problem that the assembly work of the seat is complicated.

[0005] In view of the above background, an object of the present invention is to provide a vehicle seat that provides a large space in front of a seat cushion and that can be easily assembled. [Means for solving the problem]

[0006] In order to solve the above problems, one aspect of the present invention is a vehicle seat (1, 200) having a base (7) provided on a floor (4), a seat back (3) rotatably provided on the base (7), a seat cushion (2) rotatably provided on the seat back (3), and a drive device (61) connected to the base and the seat back (3) and for rotating the seat back (3) relative to the base (7), and the second drive device (61) is positioned rearward of the front end of the seat cushion (2).

[0007] According to this aspect, since the second drive device is disposed rearward of the front end of the seat cushion, the space in front of the seat cushion can be made larger. Also, since the second drive device is connected to the base and the seat back, it is not necessary to fix the second drive device to the floor, which makes the assembly work easier.

[0008] In the above-mentioned aspect, the base (7) has left and right base side members (11) extending in the front-rear direction, and base cross members (13, 213) extending in the left-right direction and connected to the left and right base side members (11), and the drive device has a case (61A) supported on the base cross member (13, 213), a nut (61B) rotatably supported on the case, an electric motor (61D) connected to the case and generating a driving force to rotate the nut (61B), and a screw shaft (61C) threadedly engaged with the ball screw nut (61B), extending in the front-rear direction, and rotatably connected at its rear end to the seat back (3).

[0009] According to this aspect, since the drive device is disposed on the base cross member provided between the left and right base side members, the seat back can be rotated with good stability by a single drive device.

[0010] In the above aspect, the case may be connected to the base cross member (13, 213) via a hinge.

[0011] According to this embodiment, the ball screw shaft (61C) can be rotated in accordance with the angle of the seat back, so that the seat back can be rotated efficiently.

[0012] In the above aspect, the base cross member (213) may be formed of a pipe material having at least one bent portion.

[0013] According to this aspect, the configuration of the base cross member can be simplified and the rigidity can be improved.

[0014] In the above-described aspect, the seat back (3) has left and right back side members (17) and a lower member (19) extending left and right and connected to the left and right back side members (17), and the rear end of the ball screw shaft (61C) is rotatably connected to the lower member (19).

[0015] According to this aspect, since the threaded shaft is connected to the lower member disposed between the left and right back side members, the load from the threaded shaft can be transmitted to the seat back with good stability.

[0016] In the above aspect, the left and right back side members (17) have a plate-shaped main body portion whose faces face left and right and an edge wall portion protruding inwardly to the left and right from the edge of the main body portion, and the lower member (19) has a first channel material (19A) having a groove-shaped cross section and welded to the edge wall portion at the left and right ends.

[0017] According to this aspect, the rigidity of the lower member can be improved, thereby enabling the driving force from the drive unit to be efficiently transmitted to the seat back.

[0018] In the above aspect, the lower member (19) has a second channel member (19B) having a groove-shaped cross-section that is arranged inside the first channel member (19A) and connected to the first channel member (19A), and a rear end of the ball screw shaft (61C) is connected to the first channel member (19A) at a position corresponding to the second channel member (19B) in the left-right direction.

[0019] According to this aspect, the rigidity of the portion of the lower member to which the ball screw shaft is connected can be improved, thereby enabling the driving force from the driving device to be efficiently transmitted to the seat back.

[0020] In the above-described aspect, the lower member (19) is provided with a bracket (217) that rotatably supports the ball screw shaft (61C), and when the seat back (3) is extended vertically, the bracket (217) extends downward and forward from the lower member (19) and supports at its tip portion the rear end of the ball screw shaft (61C) rotatably about an axis extending left and right.

[0021] According to this aspect, when the seat back is extended horizontally, i.e., when the seat is in a stowed state, the bracket extends downward from the lower member, so that the rear ends of the bracket and the screw shaft are positioned below the rear surface of the seat back.

[0022] In the above embodiment, the electric motor (61D) is disposed rearward of the base cross member (213).

[0023] According to this aspect, the distance between the electric motor and the nut and the seat back can be shortened, and the screw shaft can be shortened, thereby making it possible to reduce the size of the drive device.

[0024] In the above aspect, it is preferable that the rotation shaft of the electric motor (61D) extends in the left-right direction, and the axis of the ball screw shaft (61C) extends in the front-rear direction in a plan view.

[0025] According to this aspect, the distance between the electric motor and the nut and the seat back can be shortened, and the screw shaft can be shortened, thereby making it possible to reduce the size of the drive device.

[0026] Another aspect of the present invention is a manufacturing method for a vehicle seat (1, 200), comprising the steps of: rotatably mounting a seat back (3) on a base (7); rotatably mounting a seat cushion (2) on the seat back (3); and connecting a drive device (61) for rotating the seat back (3) relative to the base (7) to the base (7) and the seat back (3) and positioning the drive device (61) rearward of a front end of the seat cushion (2).

[0027] According to this aspect, the vehicle seat including the second drive device can be unitized, which makes it easier to attach the vehicle seat to the vehicle. Effect of the Invention

[0028] One aspect of the present invention is a vehicle seat (1, 200) having a base (7) provided on a floor (4), a seat back (3) rotatably provided on the base (7), a seat cushion (2) rotatably provided on the seat back (3), and a drive device (61) connected to the base and the seat back (3) and for rotating the seat back (3) relative to the base (7), and the second drive device (61) is positioned rearward of the front end of the seat cushion (2).

[0029] According to this aspect, since the second drive device is disposed rearward of the front end of the seat cushion, the space in front of the seat cushion can be made larger. Also, since the second drive device is connected to the base and the seat back, it is not necessary to fix the second drive device to the floor, which makes the assembly work easier.

[0030] In the above-mentioned aspect, the base (7) has left and right base side members (11) extending in the front-rear direction, and base cross members (13, 213) extending in the left-right direction and connected to the left and right base side members (11), and the drive device has a case (61A) supported on the base cross member (13, 213), a nut (61B) rotatably supported on the case, an electric motor (61D) connected to the case and generating a driving force to rotate the nut (61B), and a screw shaft (61C) threadedly engaged with the ball screw nut (61B), extending in the front-rear direction, and rotatably connected at its rear end to the seat back (3).

[0031] According to this aspect, since the drive device is disposed on the base cross member provided between the left and right base side members, the seat back can be rotated with good stability by a single drive device.

[0032] In the above aspect, the case may be connected to the base cross member (13, 213) via a hinge.

[0033] According to this embodiment, the ball screw shaft (61C) can be rotated in accordance with the angle of the seat back, so that the seat back can be rotated efficiently.

[0034] In the above aspect, the base cross member (213) may be formed of a pipe material having at least one bent portion.

[0035] According to this aspect, the configuration of the base cross member can be simplified and the rigidity can be improved.

[0036] In the above-described aspect, the seat back (3) has left and right back side members (17) and a lower member (19) extending left and right and connected to the left and right back side members (17), and the rear end of the ball screw shaft (61C) is rotatably connected to the lower member (19).

[0037] According to this aspect, since the threaded shaft is connected to the lower member disposed between the left and right back side members, the load from the threaded shaft can be transmitted to the seat back with good stability.

[0038] In the above aspect, the left and right back side members (17) have a plate-shaped main body portion whose faces face left and right and an edge wall portion protruding inwardly to the left and right from the edge of the main body portion, and the lower member (19) has a first channel material (19A) having a groove-shaped cross section and welded to the edge wall portion at the left and right ends.

[0039] According to this aspect, the rigidity of the lower member can be improved, thereby enabling the driving force from the drive unit to be efficiently transmitted to the seat back.

[0040] In the above aspect, the lower member (19) has a second channel member (19B) having a groove-shaped cross-section that is arranged inside the first channel member (19A) and connected to the first channel member (19A), and a rear end of the ball screw shaft (61C) is connected to the first channel member (19A) at a position corresponding to the second channel member (19B) in the left-right direction.

[0041] According to this aspect, the rigidity of the portion of the lower member to which the ball screw shaft is connected can be improved, thereby enabling the driving force from the driving device to be efficiently transmitted to the seat back.

[0042] In the above-described aspect, the lower member (19) is provided with a bracket (217) that rotatably supports the ball screw shaft (61C), and when the seat back (3) is extended vertically, the bracket (217) extends downward and forward from the lower member (19) and supports at its tip portion the rear end of the ball screw shaft (61C) rotatably about an axis extending left and right.

[0043] According to this aspect, when the seat back is extended horizontally, i.e., when the seat is in a stowed state, the bracket extends downward from the lower member, so that the rear ends of the bracket and the screw shaft are positioned below the rear surface of the seat back.

[0044] In the above embodiment, the electric motor (61D) is disposed rearward of the base cross member (213).

[0045] According to this aspect, the distance between the electric motor and the nut and the seat back can be shortened, and the screw shaft can be shortened, thereby making it possible to reduce the size of the drive device.

[0046] In the above aspect, it is preferable that the rotation shaft of the electric motor (61D) extends in the left-right direction, and the axis of the ball screw shaft (61C) extends in the front-rear direction in a plan view.

[0047] According to this aspect, the distance between the electric motor and the nut and the seat back can be shortened, and the screw shaft can be shortened, thereby making it possible to reduce the size of the drive device.

[0048] Another aspect of the present invention is a manufacturing method for a vehicle seat (1, 200), comprising the steps of: rotatably mounting a seat back (3) on a base (7); rotatably mounting a seat cushion (2) on the seat back (3); and connecting a drive device (61) for rotating the seat back (3) relative to the base (7) to the base (7) and the seat back (3) and positioning the drive device (61) rearward of a front end of the seat cushion (2).

[0049] According to this aspect, the vehicle seat including the second drive device can be unitized, which makes it easier to attach the vehicle seat to the vehicle. [Brief description of the drawings]

[0050] [Figure 1] FIG. 1 is a perspective view of a frame of a seat according to an embodiment; [Diagram 2] Side view of the seat frame [Diagram 3] FIG. 2 is a perspective view of the seat frame from below and rear, showing a state in which a plate member is removed; [Figure 4] FIG. 1 is a perspective view showing a lower portion of a seat back frame. [Diagram 5] FIG. 3 is a perspective view of a second drive device [Figure 6] Front view showing the lower part of the seat back frame [Figure 7] FIG. 3 is a cross-sectional view showing a connection portion between the lower member and the second drive device. [Figure 8] A side view showing the lower end of the lower part of the side member [Figure 9] FIG. 1 is an explanatory diagram showing a connection structure of a control cable and a harness. [Figure 10] Side views showing the seat in (A) the use position, (B) the transition from the use position to the storage position, and (C) the storage position. [Figure 11] FIG. 11 is a cross-sectional view showing a connection portion between a lower member and a second driving device according to a modified embodiment. [Figure 12] Front view of the bottom of the seat [Figure 13] Perspective view of the seat [Figure 14] FIG. 11 is a perspective view showing a base cross member and its surrounding structure according to a second embodiment; [Figure 15] (A) Rear view and (B) side view of the bracket [Figure 16] FIG. 3 is a cross-sectional view showing a main portion of the seat in a stored state. [Figure 17] FIG. 1 is a perspective view of a second drive unit equipped with a strain sensor; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] Hereinafter, with reference to the drawings, an embodiment in which a vehicle seat according to the present invention is applied to a rear seat (including the second and third rows) of an automobile will be described. As will be described later, the vehicle seat changes its form between a usage form (seating form) and a storage form. Unless otherwise specified, the shape and orientation of each component of the vehicle seat will be described based on the usage form. Furthermore, when it is described that each member is connected, the connection form includes welding and fastening, unless otherwise specified.

[0052] As shown in FIG. 1 and FIG. 10, the seat 1 has a seat cushion 2 and a seat back 3. The seat back 3 is rotatably supported on a floor 4, and the seat cushion 2 is rotatably supported on the seat back 3. A lock device 5 that selectively restricts the rotation of the seat back 3 relative to the floor 4 is provided between the seat back 3 and the floor 4. In the usage mode of the seat 1, the seat back 3 stands up relative to the floor 4, and the seat cushion 2 is spaced upward from the floor 4. From the usage mode of the seat 1, the seat back 3 rotates forward to change the seat 1 into the storage mode. As the seat 1 changes from the usage mode to the storage mode, the seat cushion 2 moves downward and approaches the floor 4. In the storage mode of the seat 1, the seat back 3 extends substantially horizontally and overlaps above the seat cushion 2.

[0053] 1 and 2, a base 7 is provided on the floor 4. The base 7 includes left and right base side members 11 that extend in the front-rear direction on the upper surface of the floor 4 and are joined to the floor 4, left and right base pillars 12 that extend upward from rear ends of the left and right base side members 11, and a base cross member 13 that extends in the left and right direction and is joined to the left and right base side members 11. Each of the base side members 11, the base pillars 12, and the base cross member 13 is formed from sheet metal.

[0054] As shown in Figs. 1 to 3, the left and right base side members 11 have bottom wall portions 11A whose faces face up and down and are joined to the floor 4, and vertical wall portions 11B that extend upward from the side edges of the bottom wall portions 11A. The base pillars 12 and the base side members 11 may be formed from a common sheet metal, or may be formed from sheet metal independent of each other. In this embodiment, the right base pillar 12 is formed integrally with the base side member 11. The left base pillar 12 is formed from sheet metal independent of the base side member 11, and is joined to the base side member 11. The base pillar 12 has a plate-shaped pillar main body portion 12A whose faces face up and down, and pillar edge wall portions 12B that extend outward to the left and right from the front and rear edges of the pillar main body portion 12A.

[0055] The base cross member 13 has a lower channel member 13A having a groove-shaped cross section that opens upward, and an upper channel member 13B having a groove-shaped cross section that opens downward. The length of the upper channel member 13B in the left-right direction is shorter than the length of the lower channel member 13A in the left-right direction. The upper channel member 13B and the lower channel member 13A cooperate to form a closed cross-sectional structure. The upper channel member 13B may be fitted inside the lower channel member 13A. The left and right ends of the lower channel member 13A are joined to the corresponding vertical wall portion 11B of the base side member 11. The left end of the upper channel member 13B is joined to the left vertical wall portion 11B. The right end of the upper channel member 13B is disposed to the left of the center in the left-right direction of the lower channel member 13A. The bottoms of the lower channel member 13A and the upper channel member 13B may be provided with an uneven structure such as a bead to increase rigidity.

[0056] As shown in FIG. 1 and FIG. 4, the seat back 3 has a seat back frame 16. A pad (not shown) is supported on the seat back frame 16, and the pad and the seat back frame 16 are covered with a skin material (not shown). The seat back frame 16 has left and right back side members 17, an upper member 18, a lower member 19, a first cross member 21, a second cross member 22, a third cross member 23, and a plate member 24. The left and right back side members 17 extend vertically at a distance from each other on the left and right. The upper member 18 extends horizontally and is connected to the upper ends of the left and right back side members 17. The lower member 19 extends horizontally below the upper member 18 and is connected to the lower parts of the left and right back side members 17. The first to third cross members 21 to 23 extend horizontally between the upper member 18 and the lower member 19 and are connected to intermediate parts of the left and right back side members 17.

[0057] The left and right back side members 17 have a side member upper portion 17A and a side member lower portion 17B joined to the side member upper portion 17A. The left and right side member upper portions 17A and the upper member 18 are formed by bending a continuous pipe material. The left and right side member lower portions 17B are formed from sheet metal and have a main body portion 17C whose faces face left and right, and edge wall portions 17D bent inwardly left and right from the edges of the main body portion 17C.

[0058] The upper member 18 is provided with left and right headrest support portions 26. The left and right headrest support portions 26 are spaced apart from each other and joined to the front surface of a central portion in the left-right direction of the upper member 18. The left and right headrest support portions 26 are formed in a cylindrical shape and extend downward from the upper member 18.

[0059] As shown in Figs. 4 to 7, the lower member 19 has a rear channel 19A having a groove-shaped cross section that opens forward, and a front channel 19B having a groove-shaped cross section that opens forward. The length of the front channel 19B in the left-right direction is shorter than the length of the rear channel 19A in the left-right direction. The rear channel 19A and the front channel 19B cooperate to form a closed cross-sectional structure. The front channel 19B may be fitted inside the rear channel 19A. The left and right ends of the rear channel 19A are disposed inside the edge wall portions 17D of the corresponding side-member lower parts 17B on the left and right, and are welded to the edge wall portions 17D. The ends of the edge wall portions 17D of the side-member lower parts 17B may be welded to the rear surface of the rear channel 19A. The ends of the rear channel 19A have extension portions 19C to enlarge the contact area with the edge wall portions 17D of the side-member lower parts 17B. The extension 19C may be provided at the tip of the side wall portion that forms the groove shape of the rear channel member 19A.

[0060] The left end of the front channel member 19B is joined to the main body portion 17C of the left side-member lower portion 17B. The right end of the front channel member 19B is disposed to the left of the center in the left-right direction of the rear channel member 19A. A protrusion 19D such as a bead may be provided at the bottom of the rear channel member 19A and the front channel member 19B to increase rigidity. The protrusion 19D may bulge toward the front channel member 19B and abut against the front channel member 19B. The protrusion 19D may extend left and right along the rear channel member 19A.

[0061] As shown in Fig. 1 and Fig. 4, the first cross member 21 and the second cross member 22 are formed of rod-shaped members having a circular cross section. The first cross member 21 extends laterally below the upper member 18 and above the lower member 19. The left and right ends 21A of the first cross member 21 are bent upward with respect to the center and welded to the corresponding side member upper portion 17A. The second cross member 22 extends laterally below the first cross member 21 and above the lower member 19. The left and right ends of the second cross member 22 are bent upward with respect to the center and welded to the corresponding side member upper portion 17A.

[0062] The third cross member 23 extends laterally below the second cross member 22 and above the lower member 19, and is welded to the left and right side member lower parts 17B. The third cross member 23 may be formed from a plurality of sheet metal members. The third cross member 23 has a main body portion 23A whose faces face forward and backward, and a bent portion 23B that extends forward and upward from the lower edge of the main body portion 23A and then bends further to extend downward. An anchor 23C that protrudes forward is provided on the lower edge of the third cross member 23. The anchor 23C is used to engage a hook of a child seat.

[0063] The plate member 24 has a surface facing forward and backward, and is welded to the left and right back side members 17, the upper member 18, the lower member 19, and the third cross member 23. The upper edge of the plate member 24 is located above the upper member 18 and extends left and right. The lower edge of the plate member 24 is located below the lower member 19 and extends left and right. The left and right side edges of the plate member 24 are located outwardly to the left and right of the left and right back side members 17 and extend up and down. Each edge of the plate member 24 is provided with a curved portion 24A curved in an arc shape. The curved portion 24A has a semicircular cross section that is convex toward the front, and extends along each edge. Each curved portion 24A may be provided with a concave-convex structure such as a plurality of beads. Each concave-convex structure may extend in a direction perpendicular to the extension direction of the curved portion 24A. Each curved portion 24A and each concave-convex structure improve the rigidity of the plate-shaped portion.

[0064] The plate member 24 has a flat portion 24B whose surface faces forward and backward, and a plurality of raised portions 24C raised from the flat portion 24B. The raised portions 24C may be raised forward or backward from the flat portion 24B. Each raised portion 24C is formed by pushing the plate-shaped portion forward or backward. The raised portions 24C improve the rigidity of the plate member 24.

[0065] As shown in Fig. 4 and Fig. 6, at least one through hole 19E penetrating from the front to the rear is formed in the rear channel material 19A and the front channel material 19B of the lower member 19. The through hole 19E of the front channel material 19B is arranged at a position overlapping with the through hole 19E of the rear channel material 19A in the front to rear direction. The plate member 24 is provided with a mark for aligning with the lower member 19. The mark may be a hole, a protrusion, a recess, a pattern, or the like. When the plate member 24 is arranged at an appropriate position with respect to the lower member 19, the mark is exposed forward through the through hole 19E.

[0066] In other embodiments, the left and right back side members 17, the upper member 18, and the lower member 19 may be formed integrally with the plate member 24. For example, the plate member 24 may be press-molded to form a three-dimensional shape, and this three-dimensional shape may constitute the back side members 17, the upper member 18, and the lower member 19.

[0067] 1 and 4, the left and right side-member lower parts 17B are rotatably supported on the corresponding left and right base pillars 12 via locking devices 5. The rotation axes of the left and right side-member lower parts 17B extend laterally and are arranged coaxially with each other. The locking devices 5 are arranged coaxially with the rotation axes of the side-member lower parts 17B.

[0068] As shown in FIG. 8, the locking device 5 has an operating shaft 5A that extends along the rotation axis of the back side member 17, penetrates the back side member 17, and protrudes inwardly to the left and right of the back side member 17, and the rotation of the operating shaft 5A allows or restricts the rotation of the side member relative to the floor 4. A known reclining mechanism can be applied to the locking device 5. The locking device 5 may have, for example, a first portion connected to the base pillar 12, a second portion connected to the side member lower portion 17B and rotatably supported on the first portion, a locking claw provided on the second portion and movable between a connected position connected to the first portion and a released position separated from the first portion, a spring 5D that biases the locking claw to the connected position, the operating shaft 5A that is arranged coaxially with the rotation axis of the second member relative to the first member and rotatable relative to the second member, and a cam that is connected to the operating shaft 5A and rotates to move the locking claw to the released position against the biasing force of the spring 5D. When no external operating force is applied to the operating shaft 5A, the operating shaft 5A returns to its initial position by the biasing force of the spring 5D. When the operating shaft 5A rotates relative to the back side member 17, the seat back 3 becomes rotatable relative to the floor 4. An operating lever 5B extending radially is provided at the end of each operating shaft 5A.

[0069] As shown in FIG. 1, the seat cushion 2 has a seat cushion frame 31. A pad is supported on the seat cushion frame 31, and the pad and the seat cushion frame 31 are covered with a skin material. The seat cushion frame 31 has left and right cushion side members 32, a front member 33, a rear member 34, and a center plate 35. The left and right cushion side members 32 extend in the front-rear direction at a distance from each other on the left and right. The front member 33 extends in the left and right direction and is connected to front ends of the left and right cushion side members 32. The rear member 34 extends in the left and right direction and is connected to rear ends of the left and right back side members 17. The center plate 35 extends in the front-rear direction and is connected to the front member 33 and the rear member 34.

[0070] Left and right rear links 37 extending rearward and upward are connected to the rear ends of the left and right cushion side members 32. The left and right rear links 37 move integrally with the left and right cushion side members 32. The rear ends of the left and right rear links 37 are supported by the left and right side member lower parts 17B so as to be rotatable about axes extending laterally. In this way, the seat cushion 2 is rotatably connected to the seat back 3.

[0071] The front ends of the left and right cushion side members 32 are connected to the front end of the base side member 11 via left and right front links 38. One end of the front link 38 is connected to the front end of the cushion side member 32 so as to be rotatable about an axis extending left and right. The other end of the front link 38 is connected to the front end of the base side member 11 so as to be rotatable about an axis extending left and right.

[0072] As shown in Fig. 1, the seatback frame 16 is provided with a first drive device 41 that drives the lock device 5 and an electronic control device 42 that controls the first drive device 41. The electronic control device 42 is composed of a CPU, a non-volatile memory (ROM), a volatile memory (RAM), etc. The first drive device 41 and the electronic control device 42 are arranged vertically side by side on one side of the seatback frame 16 in the left-right direction. In this embodiment, the first drive device 41 and the electronic control device 42 are arranged vertically side by side on the right side of the seatback frame 16.

[0073] As shown in FIG. 4, the electronic control device 42 is coupled to the plate member 24 via a first bracket 44. The first bracket 44 may be welded to the plate member 24 or may be fastened to the plate member 24 by fastening members such as bolts and nuts. The first bracket 44 is coupled to at least one of the flat portion 24B and the raised portion 24C so as to overlap the flat portion 24B and the raised portion 24C when viewed from a direction perpendicular to the plate member 24. The first bracket 44 has a first portion 44A coupled to the flat portion 24B and a second portion 44B disposed offset forward from the first portion 44A and abutting against the raised portion 24C. The second portion 44B may be coupled to the raised portion 24C. The electronic control device 42 is fastened to the second portion 44B by fastening members such as bolts and nuts. The first portion 44A may be coupled to the back side member 17 in addition to the flat portion 24B.

[0074] The electronic control device 42 and the first bracket 44 are disposed in a corner portion defined by one of the left and right back side members 17 and the upper member 18. In this embodiment, the electronic control device 42 and the first bracket 44 are disposed in a corner portion defined by the right side member and the upper member 18. In addition, at least a part of the electronic control device 42 is disposed between the corresponding back side member 17 on the left and right and the headrest support portion 26. In this embodiment, an upper portion of the electronic control device 42 is disposed between an upper portion of the right back side member 17 and the right headrest support portion 26. In addition, the electronic control device 42 and the first bracket 44 are disposed above the first cross member 21. The electronic control device 42 is disposed in a space defined by the corresponding back side member 17 and the headrest support portion 26 on the left and right, the upper member 18, and the first cross member 21.

[0075] The external shape of the electronic control device 42 may be formed in a shape that does not cause discomfort to the back of the seated occupant. For example, the external shape of the left part of the electronic control device 42 provided on the right side of the seat back 3 may be formed by a surface that is inclined backward toward the left. In addition, the external shape of the left part of the electronic control device 42 may be formed by a smoothly curved surface. With this configuration, it is possible to reduce the discomfort that the electronic control device 42 provided on the seat back 3 causes to the back of the seated occupant.

[0076] As shown in FIG. 1 and FIG. 4, the first driving device 41 has a first electric motor 41A and an output portion 41B that is displaced in response to the driving of the first electric motor 41A. The first driving device 41 is coupled to the back side member 17 via a second bracket 46. In this embodiment, the second bracket 46 has a main body portion 46A to which the first driving device 41 is fastened, at least one first protruding piece portion 46B that protrudes rightward from the main body portion 46A and is coupled to the side member upper portion 17A, and at least one second protruding piece portion 46C that protrudes leftward from the main body portion 46A and is coupled to the flat portion 24B or the raised portion 24C of the plate member 24. The main body portion 46A, the first protruding piece portion 46B, and the second protruding piece portion 46C may be formed from different members and coupled to each other. Also, the main body portion 46A, the first protruding piece portion 46B, and the second protruding piece portion 46C may be formed from one plate member 24.

[0077] The first protrusions 46B are curved in a semicircular shape and extend along the outer periphery of the side-member upper portion 17A. In this embodiment, two first protrusions 46B are arranged vertically with a gap between them. The upper first protrusion 46B is arranged below the end 21A of the first cross member 21. The end 21A of the first cross member 21 is bent to the side opposite the second bracket 46. The two first protrusions 46B may be welded to or fastened to the side-member upper portion 17A. The second protrusion 46C may be welded to or fastened to the plate member 24.

[0078] The second protrusion 46C and the first driving device 41 are disposed below the electronic control device 42. In addition, the second protrusion 46C and the first driving device 41 are disposed below the first cross member 21. In other words, the first cross member 21 passes between the first driving device 41 and the electronic control device 42 and extends to the left and right.

[0079] As shown in Fig. 4, a relay lever 51 is rotatably provided on the left side of the plate member 24 and on the right side of the left back side member 17. The relay lever 51 is biased to an initial position by a spring (not shown). The first drive device 41 is connected to the relay lever 51 via a first control cable 52 (transmission member). The relay lever 51 is connected to the operation lever 5B of the left locking device 5 via a second control cable 53 (transmission member), and is connected to the operation lever 5B of the right locking device 5 via a third control cable 54 (transmission member).

[0080] A protruding portion 5C protruding in the radial direction of the rotation shaft of the right operation lever 5B is provided at the base end of the right side operation lever 5B. A sensor 57 for detecting the position of the operation lever 5B is provided at the lower end of the back side member 17. The sensor 57 is disposed on the right side surface of the right side member lower portion 17B around the operation lever 5B. The sensor 57 may be a limit switch that is pushed and rotated by the protruding portion 5C of the operation lever 5B. When the seat back 3 is in the seating position, the sensor 57 is disposed between the corresponding back side member 17 and the rear link 37. That is, the sensor 57 is disposed between the right back side member 17 and the right rear link 37. The operation lever 5B is connected to the side member lower portion 17B via a spring 5D and is biased toward the initial position.

[0081] As shown in Figs. 4 and 5, the base 7 is provided with a second drive device 61 for rotating the seat back frame 16 relative to the base 7. The second drive device 61 connects the base 7 and the seat back 3, and rotates the seat back 3 relative to the base 7 by expanding and contracting. The second drive device 61 has a case 61A, a ball screw nut 61B rotatably supported by the case 61A, a ball screw shaft 61C screwed into the ball screw nut 61B, and an electric motor 61D coupled to the case 61A and rotating the ball screw nut 61B. The case 61A is connected to the base cross member 13 via a hinge 63 so as to be rotatable about an axis extending in the left-right direction. The hinge 63 has a lower hinge bracket 63A fastened to the upper channel member 13B of the base cross member 13, and an upper hinge bracket 63B rotatably connected to the lower hinge bracket 63A about an axis extending in the left-right direction and fastened to the case 61A. A work hole 13C, which is a through hole, is formed in the bottom of the lower channel member 13A of the base cross member 13. A bolt 13D fastening the upper channel member 13B and the lower hinge bracket 63A is exposed downward through the work hole 13C. This allows a worker to perform the fastening work of the upper channel member 13B and the lower hinge bracket 63A through the work hole 13C.

[0082] A bracket 64 extending downward is welded to the lower member 19 of the seat back frame 16. The bracket 64 may be welded to the outer surface of the lower side wall of the rear channel member 19A of the lower member 19. The tip of the ball screw shaft 61C is coupled to the bracket 64 so as to be rotatable about an axis extending in the left-right direction. In another embodiment, as shown in FIG. 11, a bent portion 61E bent upward may be provided at the tip of the ball screw shaft 61C. The bent portion 61E may be coupled to a coupling portion 19F formed integrally with the rear channel member 19A so as to be rotatable about an axis extending in the left-right direction. The coupling portion 19F may be formed, for example, by cutting and raising the rear channel member 19A.

[0083] As shown in FIG. 5 and FIG. 12, the second driving device 61 is disposed rearward of the front end of the seat cushion 2. Specifically, the second driving device 61 is provided on the base cross member 13, which is rearward of the front member 33 of the seat cushion frame 31. The second driving device 61 is disposed on the left part of the base cross member 13. The axis of the ball screw shaft 61C extends in the front-rear direction. The axis of the ball screw shaft 61C is perpendicular to the rotation axis of the electric motor 61D in a plan view. With this configuration, the front end of the second driving device 61 is disposed rearward of the front member 33 of the seat cushion 2, thereby preventing the legs of a seated occupant from contacting the electric motor 61D.

[0084] The electric motor 61D is disposed rearward of the base cross member 13. The rotation shaft of the electric motor 61D extends in the left-right direction and generally parallel to the base cross member 13. The front end of the electric motor 61D is disposed at a distance from the base cross member 13. This configuration allows the distance between the electric motor 61D and the seat back 3 to be shortened, and the ball screw shaft 61C to be shortened. This allows the drive device to be made more compact.

[0085] The upper wall portion of the electric motor 61D may be located higher than the upper part of the right part of the base cross member 13. The upper wall portion of the electric motor 61D may be on the same horizontal plane as the upper part of the right part of the base cross member 13. The upper wall portion of the electric motor 61D may be located lower than the upper part of the right part of the base cross member 13. This configuration allows the electric motor 61D and the base cross member 13 to be arranged compactly.

[0086] 4 and 9, the electronic control device 42 is connected to the first driving device 41 by a first harness 66, to the second driving device 61 by a second harness 67, and to the sensor 57 by a third harness 68. The first to third harnesses 66 to 68 are partially bound to each other. A portion of the second harness 67 is fastened to the lower member 19 by a plurality of resin fasteners 69 and is disposed along the lower member 19. In another embodiment, a portion of the second harness 67 may be fastened to the third cross member 23 by a plurality of resin fasteners 69 and is disposed along the third cross member 23.

[0087] Furthermore, the electronic control device 42 is connected to an operation switch 72 by a fourth harness 71, and is connected to a power source 75 by a fifth harness 74. The operation switch 72 outputs a first signal in response to a first operation by the occupant, and outputs a second signal in response to a second operation. The first signal is a signal corresponding to an operation of changing the seat 1 from the usage configuration to the storage configuration, and the second signal is a signal corresponding to an operation of changing the seat 1 from the storage configuration to the usage configuration.

[0088] Next, the operation of the seat 1 will be described. As shown in FIG. 10(A), when the seat 1 is in the use mode, the seat back 3 stands up against the floor 4, and the locking device 5 restricts the rotation of the seat back 3. The seat cushion 2 extends substantially horizontally and is disposed at a distance from the floor 4. When the seat 1 is in the use mode, if an occupant performs a first operation on the operation switch 72, a first signal is output to the electronic control device 42. The electronic control device 42 drives and controls the first drive device 41 based on the first signal. As a result, the first drive device 41 moves the relay lever 51 from the initial position to the drive position by the first control cable 52. When the relay lever 51 moves from the initial position to the drive position, the second control cable 53 and the third control cable 54 pull the left and right operation levers 5B, and the left and right operation levers 5B move from the lock position to the release position. As a result, the left and right locking devices 5 are released, and the seat back 3 becomes rotatable relative to the base 7.

[0089] When the right operating lever 5B reaches the release position, the sensor 57 is pushed by the convex portion 5C of the operating lever 5B and outputs a detection signal to the electronic control device 42. The electronic control device 42 determines that the operating lever 5B reaches the release position, i.e., the locking device 5 is released, based on the signal from the sensor 57. When the electronic control device 42 determines that the locking device 5 is released, it drives and controls the electric motor 61D of the second driving device 61 to extend the second driving device 61. When the electric motor 61D rotates, the ball screw nut 61B rotates relative to the case 61A, and the ball screw shaft 61C protrudes rearward relative to the case 61A. As a result, as shown in FIG. 10(B), the lower end of the seat back 3 is pushed rearward by the second driving device 61, and the upper part of the seat back 3 rotates forward. At the same time, the seat cushion 2 is pushed by the seat back 3 and moves forward and downward. As a result, the seat 1 is in the stored form. The electronic control device 42 detects that the ball screw shaft 61C has reached the longest position based on the drive current of the electric motor 61D of the second drive device 61, and stops the drive of the second drive device 61. The electronic control device 42 also measures the elapsed time from when it was determined that the lock device 5 was released, and stops the drive of the first drive device 41 when the elapsed time reaches a predetermined time. As a result, the lock device 5 changes from the released state to the locked state by the biasing force of the spring 5D of the left and right lock devices 5. As a result, the seat 1 is maintained in the stored form, as shown in FIG. 10(C).

[0090] When the seat 1 is in the stowed form, if the occupant performs a second operation on the operation switch 72, a second signal is output to the electronic control device 42. The electronic control device 42 drives and controls the first drive device 41 based on the second signal. As a result, the first drive device 41 moves the left and right operation levers 5B from the locked position to the unlocked position via the first control cable 52, the relay lever 51, the second control cable 53, and the third control cable 54. As a result, the left and right lock devices 5 are released, and the seat back 3 becomes rotatable relative to the base 7.

[0091] The electronic control device 42 determines that the operating lever 5B has reached the release position, i.e., the lock device 5 has been released, based on the signal from the sensor 57. When the electronic control device 42 determines that the lock device 5 has been released, it controls the driving of the electric motor 61D of the second drive device 61 to contract the second drive device 61. When the electric motor 61D rotates, the ball screw nut 61B rotates relative to the case 61A, and the ball screw shaft 61C moves forward relative to the case 61A. As a result, as shown in FIG. 10(B), the lower end of the seat back 3 is pulled forward by the second drive device 61, and the upper part of the seat back 3 rotates backward. At the same time, the seat cushion 2 is pulled by the seat back 3 and moves backward and upward. As a result, the seat 1 is in the usage mode. The electronic control device 42 detects that the ball screw shaft 61C has reached the shortest position based on the driving current of the electric motor 61D of the second drive device 61, and stops driving the second drive device 61. The electronic control device 42 also measures the elapsed time from when it is determined that the locking device 5 is released, and stops driving the first driving device 41 when the elapsed time reaches a predetermined time. As a result, the locking device 5 changes from the released state to the locked state by the biasing force of the springs 5D of the left and right locking devices 5. As a result, the seat 1 is maintained in the usage configuration as shown in FIG. 10(A).

[0092] According to the seat 1 according to this embodiment, the electronic control device 42 can be disposed in a position that does not interfere with the movement of the seat 1. By disposing the electronic control device 42 in the seat back 3, the thickness of the seat cushion 2 can be reduced. Also, a space can be secured below the seat cushion 2 for the seat cushion 2 to move. Also, the impact that the electronic control device 42 and the first drive device 41 have on the back of the occupant can be suppressed.

[0093] The first bracket 44 supporting the electronic control device 42 is disposed so as to overlap the flat portion 24B and the raised portion 24C of the plate member 24. As a result, the first bracket 44 is disposed in a portion of the plate member 24 that has high rigidity, and the first bracket 44 and the electronic control device 42 are supported by the seat back frame 16 with good stability.

[0094] The electronic control device 42 is disposed in a corner portion defined by the upper member 18 and the back side member 17. Moreover, the electronic control device 42 is disposed in a space defined by the upper member 18, the side member, the first cross member 21, and the headrest pillar. Therefore, the electronic control device 42 can be disposed by effectively utilizing the space formed by the upper member 18, the side member, and the plate member 24. Also, the effect that the electronic control device 42 has on the back of the occupant can be suppressed.

[0095] Since the first drive device 41 is disposed below the electronic control device 42, the electronic control device 42 and the first drive device 41 can be disposed in the seat back 3 with good space efficiency. Furthermore, since the first cross member 21 is disposed between the electronic control device 42 and the first drive device 41, the rigidity of the seat back frame 16 at the portion where the electronic control device 42 and the first drive device 41 are attached can be improved. Since the end portion 21A of the first cross member 21 connected to the back side member 17 is bent upward, interference with the second bracket 46 connected to the back side member 17 can be avoided.

[0096] The seat 200 according to the second embodiment is different from the seat 1 according to the first embodiment in the structure around the second drive device 61. In the following explanation, only the different configuration will be explained, and the explanation of the same configuration as the seat 1 according to the first embodiment will be omitted by citing the above description.

[0097] As shown in FIG. 13 and FIG. 14, in the seat 200 according to this embodiment, the base cross member 213 is formed of a pipe material having at least one bent portion 214. The left and right ends of the base cross member 213 are joined to the vertical wall portions 11B of the corresponding base side members 11. The base cross member 213 is partitioned by a plurality of bent portions 214 and has a right portion 213A, a central portion 213B, and a left portion 213C. The right portion 213A, the central portion 213B, and the left portion 213C each extend linearly. The right portion 213A is disposed above the left portion 213C. The central portion 213B is inclined upward toward the right. The left portion 213C is formed longer in the left-right direction than the right portion 213A.

[0098] A bracket 206 is joined to the left part 213C of the base cross member 213. The bracket 206 has a main body 206A whose faces face up and down, and left and right side wall parts 206B that extend downward from the left and right side edges of the main body 206A. A semicircular recess 206C is formed at the lower end of the side wall part 206B. The upper part of the base cross member 213 is received in the recess 206C and welded thereto. A lower hinge bracket 63A is fastened to the main body 206A of the bracket 206. This configuration can simplify the configuration of the base cross member 213 and improve the rigidity. In addition, it is possible to fix the second driving device 61 to the curved base cross member 213 via the bracket 206.

[0099] The lower member 219 of the seat back frame 16 is formed of a channel material with a groove-shaped cross section that opens forward. The lower member 219 has a side wall portion 219A whose surface faces the front and rear, an upper wall portion 219B that extends forward from the upper edge of the side wall portion 219A, and a lower wall portion 219C that extends forward from the lower edge of the side wall portion 219A. The vertical width of the side wall portion 219A is wider than the vertical width of the upper wall portion 219B, and the vertical width of the side wall portion 219A is wider than the vertical width of the lower wall portion 219C. The left and right ends of the side wall portion 219A of the lower member 219 are welded to the inside of the edge wall portion 17D of the corresponding side member lower portion 17B on the left and right. With this configuration, the lower member 219 is joined to the back side member 17 at the side wall portion 219A, which is wider than the upper wall portion 219B and the lower wall portion 219C, so that the rigidity of the joint can be improved.

[0100] As shown in Figs. 14 and 15, a bracket 207 is joined to the lower member 219. The bracket 207 has a rear wall portion 207A whose surface faces the front and rear directions, and left and right edge wall portions 207B extending forward from left and right side edges of the rear wall portion 207A. The rear wall portion 207A and the left and right edge wall portions 207B are formed by bending a metal plate. An upper end portion 207C of the rear wall portion 207A extends upward beyond the upper ends 207C of the left and right edge wall portions 207B, and is in surface contact with the rear surface of the side wall portion 219A of the lower member 219. The upper end portion 207C of the rear wall portion 207A is welded to the rear surface of the side wall portion 219A of the lower member 219. The upper ends of the left and right edge wall portions 207B abut against and are welded to the lower surface of the lower wall portion 219C of the lower member 219. The edge wall portion 207B of the bracket 207 extends downward and forward. The left and right edge wall portions 207B face left and right and correspond to each other with a gap in the left and right direction. The left and right edge wall portions 207B are bent at their middle portions in the up and down direction so that the distance between the lower ends 207D of the left and right edge wall portions 207B is smaller than the distance between the upper ends 207C of the left and right edge wall portions 207B. The lower ends 207D of the left and right edge wall portions 207B are formed with support holes 207E penetrating left and right. The shaft 208 is inserted into the support hole 207E. The rear end of the ball screw shaft 61C is disposed between the left and right edge wall portions 207B and is rotatably supported by the shaft 208. Since the bracket 207 extends downward and forward, when the seat 200 is in the storage form, the bracket 207 can compactly accommodate the ball screw shaft 61C below the seat back 3.

[0101] As shown in FIG. 16, a luggage compartment 201 is provided behind a seat 200 in an automobile. A floor 4 defining the lower part of the luggage compartment 201 is provided with a recess 220 that is recessed downward. The recess 220 can store items 221 such as tires. A luggage compartment board 202 is provided on the upper surface of the floor 4 so as to cover the recess 220. The luggage compartment board 202 is provided detachably to the floor 4 and extends horizontally. The luggage compartment board 202 is made of, for example, resin.

[0102] A cover 203 is provided on the front edge of the luggage compartment board 202. The cover 203 extends in the left-right direction of the seat 200. When the seat 200 is in the stored form, the front end of the cover 203 is disposed on the back surface of the seat back 3. That is, the cover 203 is provided so as to cover the gap between the luggage compartment board 202 and the seat back 3. The cover 203 may be integrally formed with the luggage compartment board 202. When the seat 200 is in the stored form, the cover 203 is disposed above the rear end of the ball screw shaft 61C. When the seat 200 is in the usage form, the bracket 207 extends forward and downward. Therefore, when the seat 200 is in the stored form, it is possible to prevent the bracket 207 and the rear end of the ball screw shaft 61C from contacting the cover 203. With this configuration, when the seat 200 is in the stored form, the cover 203 can hide the gap between the seat 200 and the luggage compartment board 202 and the rear end of the ball screw shaft 61C.

[0103] As shown in FIG. 13, a sensor 204 is provided on the upper part of the seat cushion 2. In detail, the sensor 204 is disposed between the upper surface of the pad constituting the seat cushion 2 and the covering material. The sensor 204 is a load sensor that detects a load. The sensor 204 may be, for example, a piezoelectric element or a membrane switch that deforms in response to the load and connects contacts. The sensor 204 is provided to detect whether or not an object is present on the seat cushion 2. In this embodiment, the sensor 204 is a membrane switch that outputs an ON signal when a load equal to or greater than a predetermined value is applied.

[0104] When viewed from the front-rear direction, at least a portion of the sensor 204 is disposed at a position that vertically overlaps with the second driving device 61. With this configuration, the sensor 204 and the second driving device 61 can be disposed without increasing the left-right width of the seat cushion 2.

[0105] The sensor 204 is connected to the electronic control device 42. The sensor 204 outputs a signal to the electronic control device 42 in response to the detected pressure. When the electronic control device 42 determines that an object is present on the seat cushion 2 based on the signal from the sensor 204, the electronic control device 42 restricts the transformation from the usage form to the storage form. In detail, when the electronic control device 42 receives an ON signal from the sensor 204, it prohibits the driving of the first drive device 41. With this configuration, it is possible to prevent the seat 200 from changing to the storage form when an object is placed on the seat cushion 2 or when a seated person is present.

[0106] Also, instead of the sensor 204, another sensor may be used to detect the pinching of an object between the seat cushion 2 and the seat back 3. The sensor may be, for example, a strain sensor 222 provided between the bracket 63B and the case 61A as shown in FIG. 17. The strain sensor 222 is a known strain sensor and outputs a signal according to the strain to the electronic control device 42. When an object is pinched between the seat cushion 2 and the seat back 3, the seat back 3 is restricted relative to the seat cushion 2. At this time, the ball screw shaft 61C tries to move backward relative to the case 61A, so that the strain sensor 222 is compressed between the bracket 63B and the case 61A. This allows the electronic control device 42 to detect the pinching of an object between the seat cushion 2 and the seat back 3 based on the signal from the strain sensor 222. By using the strain sensor 222, the sensor 204 can be omitted, and the structure of the seat cushion 2 can be simplified. In another embodiment, the electronic control device 42 may detect the pinching of an object between the seat cushion 2 and the seat back 3 based on the current flowing through the electric motor 61D.

[0107] The seat 200 is provided with an indicator 205. The indicator 205 is a display device including, for example, an LED or the like. The indicator 205 may be disposed at the upper end of the left side of the seat back 3. The indicator 205 is connected to the electronic control device 42. The electronic control device 42 turns on the indicator 205 when the ball screw shaft 61C is at the maximum position and the operation lever 5B is at the initial position. With this configuration, the user can visually confirm that the seat 200 has completely changed to the stored form. In another embodiment, the electronic control device 42 may turn on the indicator 205 when the operation lever 5B is not at the initial position. In this case, the user can visually confirm that the lock device 5 is in the released state.

[0108] The manufacturing method of the vehicle seat may include a step of rotatably mounting the seat back 3 on the base 7, a step of rotatably mounting the seat cushion 2 on the seat back 3, and a step of connecting a drive device 61 for rotating the seat back 3 relative to the base 7 to the base 7 and the seat back 3 and mounting the drive device 61 rearward of the front end of the seat cushion 2. According to this embodiment, the vehicle seat 1, 200 including the second drive device 61 can be unitized. This makes it easy to attach the vehicle seat 1, 200 to the vehicle.

[0109] Although the specific embodiment has been described above, the present invention is not limited to the above embodiment and can be modified in a wide range of ways. [Explanation of symbols]

[0110] 1,200:sheets 2: Seat cushion 3: Seat back 4: Floor 5: Locking device 5A: Operation axis 5B: Operating lever 5C: Convex 7: Bass 13, 213: Base cross member 16: Seat back frame 17: Backside member 18: Upper member 19:Lore Member 21: First cross member 21A: End 24: Plate member 24B: Flat part 24C: Ridge 26: Headrest support part 37: Next link 41: First drive unit 41A: First electric motor 42: Electronic control device 44: First bracket 46: Second bracket 57: Sensor 61: Second drive unit 67: 2nd harness 201: Cargo compartment 202: Cargo board 203: Cover 204: Sensor 205 :Indicator 206: Bracket 207: Bracket

Claims

1. A vehicle seat, comprising: A base installed on the floor, A seat back rotatably provided on the base; A seat cushion rotatably provided on the seat back; a drive device connected to the base and the seat back and configured to rotate the seat back relative to the base; The base includes left and right base side members extending in the front-rear direction, and a base cross member extending in the left-right direction and connected to the left and right base side members, The seat cushion has left and right cushion side members extending in the front-rear direction, front ends of the left and right cushion side members are connected to front ends of the left and right base side members via left and right front links so as to be rotatable about an axis extending in the left and right direction, and rear ends of the left and right cushion side members are supported on the seat back via left and right rear links extending rearward and upward and downward so as to be rotatable about an axis extending in the left and right direction, The drive device includes a case supported by the base cross member, a nut rotatably supported by the case, an electric motor coupled to the case and generating a driving force for rotating the nut, and a screw shaft threadedly engaged with the nut, extending in the front-rear direction, and rotatably connected at its rear end to the seat back; the drive device is disposed rearward of a front end of the seat cushion, When the vehicle seat is in a usage configuration, the seat back is rotated forward by being driven by the drive device, and the seat cushion is pushed by the seat back to move downward, thereby placing the vehicle seat in a stored configuration.

2. 2. The vehicle seat according to claim 1, wherein the case is connected to the base cross member via a hinge.

3. 3. The vehicle seat according to claim 1, wherein the base cross member is formed of a pipe material having at least one bent portion.

4. The seat back includes left and right back side members and a lower member extending in the left and right directions and connected to the left and right back side members, 4. The vehicle seat according to claim 1, wherein the rear end of the screw shaft is rotatably connected to the lower member.

5. The left and right back side members each have a plate-shaped main body portion whose surface faces left and right and an edge wall portion protruding left and right inward from an edge of the main body portion, 5. The vehicle seat of claim 4, wherein said lower member includes a first channel having a channel-shaped cross section and welded to said edge wall portions at left and right ends.

6. the lower member includes a second channel having a channel-shaped cross section disposed inside the first channel and connected to the first channel; The vehicle seat according to claim 5 , wherein the rear end of the screw shaft is connected to the first channel member at a position corresponding to the second channel member in the left-right direction.

7. The lower member is provided with a bracket that rotatably supports the screw shaft, 7. The vehicle seat according to claim 6, wherein when the seat back is extended vertically, the bracket extends downward and forward from the lower member and supports at its tip the rear end of the screw shaft so as to be rotatable about an axis extending laterally.

8. The vehicle seat according to any one of claims 1 to 7, wherein the electric motor is disposed rearward of the base cross member.

9. 9. The vehicle seat according to claim 1, wherein a rotating shaft of the electric motor extends in a left-right direction, and an axis of the screw shaft extends in a front-rear direction in a plan view.

10. A method for manufacturing a vehicle seat, comprising the steps of: a step of rotatably mounting a seat back on a base having left and right base side members extending in the front-rear direction and base cross members extending in the left-right direction and connected to the left and right base side members; a step of rotatably mounting a seat cushion on the seat back, the seat cushion having left and right cushion side members extending in the front-rear direction; a step of connecting a drive device having a case supported by the base cross member, a nut rotatably supported by the case, an electric motor coupled to the case and generating a driving force for rotating the nut, and a screw shaft threadedly engaged with the nut, extending forward and backward, and rotatably connected at its rear end to the seat back, to the base and the seat back, and providing the drive device behind the front end of the seat cushion, in order to rotate the seat back relative to the base; a step of providing front ends of the left and right cushion side members via left and right front links to be rotatable about an axis extending in the left and right direction at front ends of the left and right base side members so that the seat cushion is pushed by the seat back and moves downward when the seat back is rotated forward; and mounting the rear ends of the left and right cushion side members to the seat back via left and right rear links extending rearward and upward so as to be rotatable about an axis extending left and right.

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