Seat

Abstract

To disclose an example of a seat in which the mass of seat, an increase in the manufacturing cost of the seat, etc. are taken into consideration.SOLUTION: A seat includes: first front-side links 71A, 71B that rotate integrally with a first connecting pipe 13; second front-side links 72A, 72B whose one-end sides are rotatably connected to the other-end sides of the first front-side links 71A, 71B and whose other-end sides are rotatably connected to a movable rail 9A, the second front links 72A, 72B being such that a rotation center axis of a connecting portion thereof is parallel to a seat width direction; and an actuator 74 that generates a force for changing angles formed by the first front-side links 71A, 71B and the second front-side links 72A, 72B. Thus, the seat does not require two connecting pipes on the front-end side of the seat cushion. Therefore, an increase in the mass and manufacturing cost of the seat can be restricted.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a seat in which the position of the seat cushion can be changed. [Background technology]

[0002] Patent document 1 describes a vehicle seat that allows the position of the seat cushion to be changed, and is configured with two links provided on the left and right sides of the front end of the seat cushion, and two connecting pipes that extend in the left-right direction and connect the links. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Chinese Patent No. 113968176A Summary of the Invention [Problem to be solved by the invention]

[0004] The seat described in Patent Document 1 requires two connecting pipes on the front end side of the seat cushion, which causes problems such as an increase in the weight of the seat and manufacturing costs. The present disclosure discloses an example of a seat that takes these points into consideration. [Means for solving the problem]

[0005] A seat that can displace the seat cushion (3) between a comfortable position in which the front end side of the seat cushion (3) is higher than the rear end side of the seat cushion (3) and a normal position in which the front end side is lower than the comfortable position, desirably has at least one of the following constituent features:

[0006] That is, the constituent features are a first side frame (11) constituting a part of the cushion frame (10), the first side frame (11) being arranged at one end in the seat width direction and extending in the seat front-rear direction; a second side frame (12) constituting a part of the cushion frame (10), the second side frame (12) being arranged at the other end in the seat width direction and extending in the seat front-rear direction; a connecting body (13) extending in the seat width direction and rotatably connected to the front end side of the first side frame (11) and the front end side of the second side frame (12), the connecting body (13) constituting a part of the cushion frame (10) and having a rotation center axis parallel to the seat width direction; and a base member (9A) having a rear end connecting portion (9C) rotatably connected directly or indirectly to the rear end side of the cushion frame (10). a base member (9A) having a rotation center axis of the rear end connecting portion (9C) parallel to the seat width direction; first front links (71A, 71B) having one end fixed to a connecting body (13) and rotating integrally with the connecting body (13); and a second front link (71A, 71B) having one end rotatably connected to the other end of the first front link (71A, 71B) and having the other end rotatably connected to the base member (9A). The actuator (74) is a front link (72A, 72B) having a rotation center axis of the connection point thereof parallel to the seat width direction, and the actuator (74) generates a force to change the angle between the first front link (71A, 71B) and the second front link (72A, 72B), and changes the posture of the seat cushion (3) between a comfortable posture and a normal posture.

[0007] This eliminates the need for two connecting pipes on the front end side of the seat cushion, thereby preventing increases in the seat weight and manufacturing costs. In addition, in the seat, the cushion frame (10), the first front links (71A, 71B), and the second front links (72A, 72B) are configured to displace within a range that satisfies the requirement that the second distance (L2) is equal to or less than the front-to-rear fastening distance (L3) and equal to or greater than the first distance (L1).

[0008] The rotational center axis of the rear end connecting portion (9C) is the first axis (Ls1), the rotational center axis of the connecting portion between the base member (9A) and the second front link (72A, 72B) is the second axis (Ls2), the rotational center axis of the connecting portion between the first front link (71A, 71B) and the second front link (72A, 72B) is the third axis (Ls3), the rotational center axis of the connecting body (13) is the fourth axis (Ls4), the first axis (Ls1) projected onto an imaginary plane perpendicular to the seat width direction is the first center point (O1), the second axis (Ls2) projected onto the imaginary plane is the second center point (O2), The third axis (Ls3) projected onto the imaginary plane is the third center point (O3), the fourth axis (Ls4) projected onto the imaginary plane is the fourth center point (O4), the distance between the first center point (O1) and the second center point (O2) is the front-rear fastening distance (L3), the distance from the first center point (O1) to the imaginary line passing through the second center point (O2) and the fourth center point (O4) that is the shortest due to a change in the posture of the seat cushion (3) is the first distance (L1), and the distance from the first center point (O1) to the imaginary line passing through the second center point (O2) and the third center point (O3) is the second distance (L2).

[0009] The sheet may have the following configuration, for example. That is, it is desirable to provide a stopper (76) that is arranged on the second axis (Ls2) and contacts the first front link (71A) to prevent the front end of the seat cushion (3) from being displaced downward from a predetermined position.

[0010] This can prevent a bending moment from being generated in the second front link (72A) when a large downward load acts on the front end side of the seat cushion (3). The actuator (74) is preferably configured to include a sector gear (74A) that rotates together with the connecting body (13) around the fourth axis (Ls4) as its central axis, the sector gear (74A) having an internal tooth portion (74B) with multiple teeth protruding upward, a pinion (74D) that meshes with the sector gear (74A), and an electric motor (74E) that rotates the pinion (74D).

[0011] This prevents the ends of the carpet from getting caught in the internal teeth portion (74B) and the pinion (74D) even when the carpet is laid on the seat. Furthermore, the carpet is prevented from getting soiled with grease applied to the internal teeth portion (74B).

[0012] It is desirable to provide a second internal tooth portion (74C) that meshes with the pinion (74D) and has a tooth thickness greater than that of the internal tooth portion (74B) of the sector gear (74A), thereby making it possible to suppress rattle caused by backlash.

[0013] Incidentally, the symbols in each of the parentheses above are examples showing the correspondence with the specific configurations, etc. described in the embodiments described below, and the present disclosure is not limited to the specific configurations, etc. shown by the symbols in the parentheses above. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram showing a vehicle seat according to a first embodiment. [Figure 2] 1 is a diagram showing a vehicle seat according to a first embodiment. [Figure 3] 1 is a diagram showing a vehicle seat according to a first embodiment. [Figure 4] FIG. 2 is an exploded view of the cushion frame and the like according to the first embodiment. [Figure 5] FIG. 2 is an exploded view of the actuator and other components according to the first embodiment. [Figure 6] FIG. 2 is an enlarged view of a tooth portion of a sector gear according to the first embodiment. [Figure 7] 1A to 1C are diagrams illustrating features of a vehicle seat according to a first embodiment. [Figure 8] FIG. 10 is a diagram showing an actuator according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following "embodiments of the invention" are examples of embodiments that fall within the technical scope of the present disclosure. In other words, the invention-specific matters described in the claims are not limited to the specific configurations and structures shown in the following embodiments.

[0016] This embodiment is an example in which a seat according to the present disclosure is applied to a seat (hereinafter referred to as a vehicle seat) mounted on a vehicle such as a car. Arrows and diagonal lines indicating directions are added to each figure to make it easier to understand the relationship between the figures and the shapes of components or parts.

[0017] Therefore, the vehicle seat is not limited to the orientation shown in each drawing. The orientation shown in each drawing is the orientation when the vehicle seat according to this embodiment is assembled to a vehicle. Diagonally shaded drawings do not always represent cross-sectional views.

[0018] At least one of a component or part that is described with a reference numeral is provided unless otherwise specified, such as "one." The seat shown in the present disclosure includes at least one of the components such as the component or part that is described with a reference numeral and the structural parts shown in the drawings.

[0019] (First embodiment) <1. Overview of vehicle seats> As shown in Fig. 1, the vehicle seat 1 includes at least a seat cushion 3, a seat back 5, and a position change mechanism 7. The seat cushion 3 is a part for supporting the buttocks of the seated occupant. The seat back 5 is a part for supporting the back of the seated occupant.

[0020] The position change mechanism 7 is a mechanism that changes the position of the seat cushion 3 between a comfortable position and a normal position. The comfortable position is a position in which the front end side of the seat cushion 3 is higher than the rear end side of the seat cushion 3, as shown in Figure 3.

[0021] 1 and 2, the normal posture is a posture in which, compared to the comfortable posture, the difference in height between the front end of the seat cushion 3 and the rear end of the seat cushion 3 is smaller. In other words, the normal posture is a posture suitable for a driver of a vehicle when driving the vehicle.

[0022] 1 shows the state in which the seat cushion 3 is at its lowest position in the vertical direction, while Fig. 2 shows the state in which the seat cushion 3 is at its highest position in the vertical direction. In other words, the seat cushion 3 can be displaced up and down while maintaining its normal posture.

[0023] As shown in Fig. 2, the seat back 5 is connected to the rear end of the seat cushion 3. The seat cushion 3 is connected to a slide device 9 via a position change mechanism 7. The slide device 9 is a mechanism that enables the seat cushion 3 to be displaced in the front-rear direction.

[0024] The slide device 9 is configured to include at least a movable rail 9A, which is an example of a base member, and a fixed rail 9B. The fixed rail 9B is a rail member fixed to the vehicle. The movable rail 9A is a member slidably connected to the fixed rail 9B.

[0025] <2. Configuration of cushion frame and posture change mechanism> <2.1 Cushion frame configuration> The cushion frame 10 is a strength member that forms the framework of the seat cushion 3. As shown in Fig. 4, the cushion frame 10 is configured to include at least a first side frame 11, a second side frame 12, a first connecting pipe 13, a second connecting pipe 14, a front panel 15, and the like.

[0026] The first side frame 11 is a lower arm disposed at one end of the seat width direction and extending in the front-rear direction of the seat, and the second side frame 12 is a lower arm disposed at the other end of the seat width direction and extending in the front-rear direction of the seat.

[0027] The first connecting pipe 13 is an example of a connecting body that extends in the seat width direction and is rotatably connected to the front end side of the first side frame 11 and the front end side of the second side frame 12. Therefore, the rotation center axis Ls4 of the first connecting pipe 13 is parallel to the seat width direction.

[0028] The second connecting pipe 14 extends in the seat width direction and is rotatably connected to the rear end sides of the first side frame 11 and the second side frame 12. Therefore, the rotation center axis Ls5 of the second connecting pipe 14 is parallel to the seat width direction.

[0029] The front panel 15 constitutes the front end side of the cushion frame 10. Specifically, the front panel 15 is a panel-shaped member that extends so as to widen in the seat width direction and connects the front end side of the first side frame 11 and the front end side of the second side frame 12.

[0030] 2.2 Configuration of attitude change mechanism As shown in FIG. 4, the posture change mechanism 7 is configured to include at least first front links 71A, 71B, second front links 72A, 72B, rear links 73A, 73B (see FIG. 2), actuators 74, 75, and a stopper 76.

[0031] <First front link and second front link> The first front links 71A and 71B are members whose one ends are fixed to the first connecting pipe 13 by welding or the like and which rotate integrally with the first connecting pipe 13. The first front link 71A is provided in a position close to the first side frame 11. The first front link 71B is provided in a position close to the second side frame 12.

[0032] As shown in FIG. 3, one end of the second front links 72A, 72B is rotatably connected to the other end of the first front links 71A, 71B, and the other end is rotatably connected to the movable rail 9A.

[0033] Specifically, the upper end of the second front link 72A is rotatably connected to the lower end of the first front link 71A. The lower end of the second front link 72A is rotatably connected to the movable rail 9A on the first side frame 11 side.

[0034] The upper end of the second front link 72B is rotatably connected to the lower end of the first front link 71B. The lower end of the second front link 72B is rotatably connected to the movable rail 9A on the second side frame 12 side.

[0035] The rotation center axis Ls3 of the connection between the first front links 71A, 71B and the second front links 72A, 72B is parallel to the seat width direction. In this embodiment, an actuator 74 is provided on the first front link 71B on the second side frame 12 side.

[0036] Therefore, the first front link 71A and the first front link 71B do not have the same shape. However, the first front links 71A and 71B have the same function as links. Similarly, the second front link 72A and the second front link 72B do not have the same shape. However, the second front links 72A and 72B have the same function as links.

[0037] <Stopper> The stopper 76 is a member that prevents the front end of the seat cushion 3 from being displaced downward from a predetermined position. Specifically, as shown in Fig. 4, the stopper 76 is disposed on the rotation center axis Ls2, and contacts the first front link 71A to prevent the seat cushion 3 from being displaced downward.

[0038] The rotation center axis Ls2 is the rotation center axis of the connection portion between the movable rail 9A and the second front link 72A. In this embodiment, the stopper 76 is provided only on the first side frame 11 side, and not on the second side frame 12 side.

[0039] <Back link> As shown in Figure 4, one end of the rear links 73A, 73B is fixed to the second connecting pipe 14 by welding or the like, and rotates integrally with the second connecting pipe 14, and the other end is rotatably connected to the rear end connecting portion 9C of the movable rail 9A.

[0040] That is, the rear end of the cushion frame 10 is indirectly rotatably connected to the rear end connecting portion 9C via the rear links 73A and 73B. The rotation center axis Ls1 of the rear end connecting portion 9C is parallel to the seat width direction.

[0041] <Actuator> The actuator 74 generates a force that changes the angle θ1 (see FIGS. 2 and 3) formed between the first front links 71A, 71B and the second front links 72A, 72B. In other words, the actuator 74 changes the posture of the seat cushion 3 between the comfortable posture and the normal posture.

[0042] Specifically, when the angle θ1 becomes smaller (see FIG. 2), the posture of the seat cushion 3 approaches the normal posture, and when the angle θ1 becomes larger (see FIG. 3), the posture of the seat cushion 3 approaches the comfortable posture.

[0043] 5, the actuator 74 is configured to include at least a sector gear 74A, a pinion 74D, an electric motor 74E, etc. The sector gear 74A is a sector gear that rotates together with the first connecting pipe 13. Therefore, the central axis of rotation of the sector gear 74A coincides with the central axis of rotation Ls4 of the first connecting pipe 13.

[0044] The sector gear 74A is provided with a first internal toothed portion 74B and a second internal toothed portion 74C. The first internal toothed portion 74B and the second internal toothed portion 74C are toothed portions that mesh with the pinion 74D, and have multiple protruding teeth that protrude upward, that is, toward the first connecting pipe 13. The pinion 74D is made of metal, and is rotationally driven by an electric motor 74E.

[0045] 5, the tooth thickness T2 of the second internal tooth portion 74C is greater than the tooth thickness T1 of the first internal tooth portion 74B. Furthermore, the surface hardness of the second internal tooth portion 74C is less than the surface hardness of the first internal tooth portion 74B, and the first internal tooth portion 74B and the second internal tooth portion 74C are in phase with each other.

[0046] The first internal teeth portion 74B is made of metal and is integrally formed with the sector gear 74A. The second internal teeth portion 74C is made of resin. Therefore, the second internal teeth portion 74C is fixed to the sector gear 74A with a fastener such as a screw.

[0047] When the pinion 74D is in mesh with the first internal toothed portion 74B and the second internal toothed portion 74C, the second internal toothed portion 74C is in contact with the teeth of the pinion 74D in a state of slight elastic deformation. In other words, when the tooth pressure generated on the pinion 74D is small, the second internal toothed portion 74C is in contact with the teeth of the pinion 74D in a state of slight elastic deformation.

[0048] When the tooth pressure generated on the pinion 74D increases, the second internal tooth portion 74C undergoes large elastic deformation, causing the pinion 74D to come into contact with the metal first internal tooth portion 74B, and in this state, the first internal tooth portion 74B essentially bears the large load acting on the pinion 74D.

[0049] In addition, the phases of the first internal tooth portion 74B and the second internal tooth portion 74C being consistent means that when a diametrical imaginary line passing through the midpoint of the tooth thickness direction of the first internal tooth portion 74B and a diametrical imaginary line passing through the midpoint of the tooth thickness direction of the second internal tooth portion 74C are projected onto a virtual plane perpendicular to the rotation center axis Ls3, the two imaginary lines are consistent.

[0050] The actuator 75 rotates the rear links 73A, 73B about the rear end connecting portion 9C, thereby generating a force that changes the angle θ2 (see FIG. 2) formed between the rear links 73A, 73B and the movable rail 9A, thereby displacing the seat cushion 3 in the up and down direction while maintaining the normal posture.

[0051] 2.3 Operation of the attitude change mechanism <Changing from normal posture to comfortable posture> When the user operates the comfortable position selection button (not shown), the control unit (not shown) that controls the actuators 74 and 75 first activates the actuator 75 to set the position of the seat cushion 3 to the lowest position (see FIG. 1).

[0052] Next, the control unit operates the actuator 74 to increase the angle θ1 formed between the first front links 71A, 71B and the second front links 72A, 72B, thereby causing the seat cushion 3 to assume a comfortable position as shown in FIG.

[0053] <Changing from a comfortable position to a normal position> When the user operates the normal position selection button (not shown), the control unit operates the actuator 74 to reduce the angle θ1 between the first front links 71A, 71B and the second front links 72A, 72B, thereby placing the seat cushion 3 in the normal comfortable position.

[0054] <When the seat cushion position is changed vertically while in the normal position> When the user operates a switch (not shown) for displacing the position of the seat cushion in the vertical direction, the control unit operates the actuator 75. As a result, the rear links 73A and 73B swing while maintaining the angle θ1 formed between the first front links 71A and 71B and the second front links 72A and 72B.

[0055] That is, the second front links 72A, 72B swing about the rotation axis Ls2 while maintaining the distance between the rotation axis Ls4 of the first connecting pipe 13 and the rotation axis Ls2 of the connection portion between the movable rail 9A and the second front link 72A. Therefore, the seat cushion 3 is displaced up and down according to the swing angle of the rear links 73A, 73B while maintaining the normal posture.

[0056] 3. Features of the vehicle seat according to this embodiment As described above, the vehicle seat 1 according to this embodiment does not require two connecting pipes on the front end side of the seat cushion 3. This prevents increases in the mass and manufacturing costs of the vehicle seat 1, and may also make it possible to arrange other components below the seat cushion 3.

[0057] Furthermore, in the vehicle seat 1, as shown in FIG. 7, the cushion frame 10, the first front links 71A, 71B, and the second front links 72A, 72B are configured to be displaced within a range that satisfies the requirement that the second distance L2 is equal to or less than the front-to-rear fastening distance L3 and equal to or greater than the first distance L1.

[0058] That is, the cushion frame 10, the first front links 71A, 71B, and the second front links 72A, 72B are configured to satisfy L3 ≥ L2 ≥ L1, which may ensure the strength of the first front links 71A, 71B (especially the first front link 71A, which has a small section modulus).

[0059] The front-rear fastening distance L3 is the distance between the first center point O1 and the second center point O2. The second distance L2 is the distance from the first center point O1 to a virtual line that passes through the second center point O2 and the third center point O3.

[0060] The first distance L1 is the distance from the first center point O1 to an imaginary line passing through the second center point O2 and the fourth center point O4, and is the distance that becomes the smallest when the posture of the seat cushion 3 changes.

[0061] The first center point O1 refers to the first axis Ls1 projected onto an imaginary plane perpendicular to the sheet width direction. The second center point O2 refers to the second axis Ls2 projected onto the imaginary plane. The third center point O3 refers to the third axis Ls3 projected onto the imaginary plane. The fourth center point O4 refers to the fourth axis Ls4 projected onto the imaginary plane.

[0062] The first axis Ls1 refers to the rotational center axis of the rear end connecting portion 9C. The second axis Ls2 refers to the rotational center axis of the connecting portion between the movable rail 9A and the second front links 72A, 72B. The third axis Ls3 refers to the rotational center axis of the connecting portion between the first front links 71A, 71B and the second front links 72A, 72B. The fourth axis Ls4 refers to the rotational center axis of the first connecting pipe 13.

[0063] The stopper 76 is disposed on the second axis Ls2, and when it comes into contact with the first front link 71A, the front end of the seat cushion 3 is displaced downward from a predetermined position, thereby preventing a bending moment from being generated in the second front link 72A when a large downward load acts on the front end of the seat cushion 3.

[0064] The sector gear 74A is configured to have a first internal tooth portion 74B and a second internal tooth portion 74C, each having a plurality of teeth protruding upward. This can provide the following effects, for example, when a carpet or the like is laid on the area where the vehicle seat 1 is installed.

[0065] That is, it is possible to prevent the ends of the fibers of the carpet from becoming entangled between the first internal tooth portion 74B and the second internal tooth portion 74C and the pinion 74D. It is also possible to prevent the carpet from becoming soiled with grease applied to the first internal tooth portion 74B and the second internal tooth portion 74C.

[0066] Furthermore, the sector gear 74A has a second internal tooth portion 74C that has a larger tooth thickness than the first internal tooth portion 74B, which can suppress the occurrence of rattles caused by backlash.

[0067] (Second embodiment) The actuator 74 according to the above-described embodiment is configured to include a sector gear 74A and a pinion 74D. In contrast, the actuator 74 according to the present embodiment is configured to include a nut 74F that is rotationally driven by an electric motor 74E, a male threaded rod 74G that meshes with the nut 74F, and the like, as shown in FIG.

[0068] The nut 74F rotates and the male threaded rod 74G moves relative to the nut 74F, thereby changing the angle θ1 formed between the first front links 71A, 71B and the second front links 72A, 72B. Components that are the same as those in the above-described embodiment are denoted by the same reference numerals. Therefore, redundant explanations will be omitted in this embodiment.

[0069] (Other embodiments) In the above-described embodiment, the stopper 76 is provided only on the first side frame 11 side, and not on the second side frame 12 side. However, the present disclosure is not limited to this. That is, in the present disclosure, it is sufficient that the stopper 76 is provided on at least one of the first side frame 11 side and the second side frame 12 side, for example.

[0070] In the above-described embodiment, the cushion frame 10, the first front links 71A, 71B, and the second front links 72A, 72B are configured to satisfy L3≧L2≧L1. However, the present disclosure is not limited to this.

[0071] In the above-described embodiment, the stopper 76 is disposed on the second axis Ls2. However, the present disclosure is not limited to this. That is, the present disclosure may be, for example, configured such that the stopper 76 is disposed on the first front links 71A, 71B, or may be configured such that the stopper 76 is not disposed.

[0072] The first internal toothed portion 74B and the second internal toothed portion 74C according to the above-described embodiment have a configuration in which multiple teeth protrude upward. However, the present disclosure is not limited to this. That is, the present disclosure may also have, for example, the first internal toothed portion 74B and the second internal toothed portion 74C having multiple teeth protruding downward.

[0073] In the above-described embodiment, the tooth thickness T2 of the second internal teeth portion 74C is larger than the tooth thickness T1 of the first internal teeth portion 74B, and the first internal teeth portion 74B and the second internal teeth portion 74C are in phase with each other. However, the present disclosure is not limited to this. That is, the present disclosure may be configured such that, for example, the tooth thickness T1 and the tooth thickness T2 are equal, and the phase of the first internal teeth portion 74B and the phase of the second internal teeth portion 74C are shifted.

[0074] In the above-described embodiment, the vehicle seat according to the present disclosure is applied to a vehicle. However, the application of the invention disclosed in this specification is not limited thereto. That is, the present disclosure can also be applied to seats used in vehicles such as railway cars, ships, and aircraft, as well as stationary seats used in theaters, homes, etc.

[0075] Furthermore, the present disclosure is not limited to the above-described embodiments as long as it conforms to the spirit of the disclosure described in the above-described embodiments. Therefore, the present disclosure may be a configuration in which at least two of the above-described embodiments are combined, or a configuration in which any of the components illustrated or described with reference numerals in the above-described embodiments is eliminated. [Explanation of symbols]

[0076] 1... Vehicle seat 3... Seat cushion 5... Seat back 7... Posture change mechanism 9... Slide device 9A... Movable rail 9B... Fixed rail 9C... Rear end connection part 10... Cushion frame 11... First side frame 12... Second side frame 13... First connecting pipe 14... Second connecting pipe 15... Front panel 71A, 71B... First front link 72A, 72B... Second front link 74... Actuator 74A... Sector gear 74D... Pinion 74B... First internal tooth portion 74C... Second internal tooth portion 74E... Electric motor

Claims

1. In a seat in which the seat cushion can be displaced between a comfortable position in which the front end side of the seat cushion is positioned higher than the rear end side of the seat cushion and a normal position in which the height difference between the front end side and the rear end side is smaller than that in the comfortable position, a first side frame constituting a part of the cushion frame, the first side frame being disposed on one end side in the seat width direction and extending in the seat front-rear direction; a second side frame constituting a part of the cushion frame, the second side frame being disposed on the other end side in the seat width direction and extending in the seat front-rear direction; a connecting body extending in the seat width direction and rotatably connected to a front end side of the first side frame and a front end side of the second side frame, the connecting body constituting a part of the cushion frame and having a rotation center axis parallel to the seat width direction; a base member having a rear end side connecting portion rotatably connected directly or indirectly to a rear end side of the cushion frame, the base member having a rotation center axis of the rear end side connecting portion parallel to the seat width direction; a first front link having one end fixed to the connecting body and rotating integrally with the connecting body; a second front link having one end rotatably connected to the other end of the first front link and the other end rotatably connected to the base member, the second front link having a rotation center axis of the connection point parallel to the seat width direction; an actuator that generates a force that changes the angle between the first front link and the second front link, and that changes the posture of the seat cushion between the comfortable posture and the normal posture, a rotational center axis of the rear end connecting portion is defined as a first axis, a rotational center axis of the connecting portion between the base member and the second front link is defined as a second axis, a rotational center axis of the connecting portion between the first front link and the second front link is defined as a third axis, and a rotational center axis of the connecting body is defined as a fourth axis, the first axis projected onto a virtual plane perpendicular to the sheet width direction is defined as a first center point, the second axis projected onto the virtual plane is defined as a second center point, the third axis projected onto the virtual plane is defined as a third center point, and the fourth axis projected onto the virtual plane is defined as a fourth center point, The distance between the first center point and the second center point is defined as a front-rear fastening distance, a first distance is a distance from the first center point to a virtual line passing through the second center point and the fourth center point, the distance being minimized by a change in the posture of the seat cushion; When a distance from the first center point to a virtual line passing through the second center point and the third center point is defined as a second distance, The cushion frame, the first front link, and the second front link are displaced within a range that satisfies the requirement that the second distance is equal to or greater than the first distance and equal to or less than the front-to-rear fastening distance.

2. 2. The seat according to claim 1, further comprising a stopper disposed on the second axis and contacting the first front link to restrict the front end of the seat cushion from being displaced downward beyond a predetermined position.

3. The actuator is a sector gear that rotates together with the connecting body about the fourth axis as a central axis, the sector gear having an internal tooth portion with a plurality of teeth protruding upward; a pinion meshing with the sector gear; and an electric motor that rotates and drives the pinion; 3. The sheet according to claim 1 or 2, comprising:

4. 4. The seat according to claim 3, further comprising a second internal toothing portion that meshes with the pinion and has a tooth thickness greater than that of the internal toothing portion of the sector gear.

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