Seat cushion for vehicle seat and vehicle seat

1. A seat cushion for a vehicle seat, the seat cushion comprising:

a seat cushion base layer supported by a cushion frame; and

a seat cushion cushioning layer disposed on the seat cushion base layer,

wherein the seat cushion base layer comprises

left-right base support parts provided in a range including positions corresponding to seated person's left-right ischial tuberosities, apart from each other in a width direction of the cushion frame,

wherein the left-right base support parts are coupled with each other through base support part elastic members, and supported to be movable by the cushion frame, and

wherein the respective left-right base support parts are movable with 6 degrees of freedom with the positions corresponding to ischial tuberosities centered.

2. A seat cushion for a vehicle seat, the seat cushion comprising:

a seat cushion base layer supported by a cushion frame; and

a seat cushion cushioning layer disposed on the seat cushion base layer,

wherein the seat cushion base layer comprises:

left-right base support parts provided in a range including positions corresponding to seated person's left-right ischial tuberosities, apart from each other in a width direction of the cushion frame; and

base support part elastic members bridged between the left-right base support parts, in which restoring force acts in directions bringing the left-right base support parts close to each other, near a middle in a width direction of the cushion frame.

3. The seat cushion according to claim 2 , wherein the base support part elastic members are composed of coil springs, and disposed in plurality along a front-rear direction of the cushion frame between the left-right base support parts.

4. The seat cushion according to claim 2 ,

wherein the left-right base support parts each comprise:

a support fabric whose front portion, rear portion, and outer portion are supported by the cushion frame; and

a buffer member stacked on the support fabric.

5. The seat cushion according to claim 4 , wherein the buffer member is configured to have a three-dimensional knitted fabric.

6. The seat cushion according to claim 5 , wherein the buffer member is configured to have an outer pad member in a substantially rectangular frame shape, an inner pad member disposed in an inner space of the outer pad member, and cover members covering a front surface and a back surface of the inner pad member and made to adhere to a front surface and a back surface of the outer pad member.

7. The seat cushion according to claim 6 , wherein the outer pad member is a bead foam, and the inner pad member is a three-dimensional knitted fabric.

8. A vehicle seat including a seat cushion and a seat back,

wherein, as the seat cushion, the seat cushion according to claim 2 is used.

9. The vehicle seat according to claim 8 ,

wherein the seat back comprises:

a seat back base layer supported by a back frame; and

a seat back cushioning layer disposed by covering the seat back base layer, and

wherein the seat back base layer comprises:

a seat back base fabric bridged between left-right side frames of the back frame; and

a lumbar support elastically supported through spring members in a range close to a portion more downward than a substantially middle portion in an up-down direction of the back frame.

10. The vehicle seat according to claim 9 , wherein the seat back base fabric has a size which is longer than an up-down-direction length of the lumbar support and covers a portion between a frame disposed close to an upper portion of the back frame and a frame disposed close to a lower portion thereof.

11. The vehicle seat according to claim 9 ,

wherein the lumbar support comprises

a lumbar flat support member having a plate-shaped lumbar bead foam, three-dimensional knitted fabrics disposed in hole portions formed in the lumbar bead foam, and cover members covering a front surface and a back surface of each of the three-dimensional knitted fabrics and made to adhere to a front surface and a back surface of the lumbar bead foam.

12. The vehicle seat according to claim 9 ,

wherein when, in a load-deflection characteristic of the seat cushion in pressurizing the seat cushion with a pressure board having a diameter of 200 mm, at a speed of 50 mm/min, and up to a load of 1000 N, in a range of connecting an origin, a maximum displacement point, and a maximum load point, in the range, a ratio between an outward area (a 1 ) of a range including an outward curve and an inward area (b 1 ) of a range including an inward curve is set as a load characteristic area ratio of the seat cushion (b 1 /a 1 ), and

in a load-deflection characteristic of the seat back in pressurizing the seat back with a pressure board having a diameter of 200 mm, at a speed of 50 mm/min, and up to a load of 500 N, in a range of connecting an origin, a maximum displacement point, and a maximum load point, in the range, a ratio between an outward area (a 2 ) of a range including an outward curve and an inward area (b 2 ) of a range including an inward curve is set as a load characteristic area ratio of the seat back (b 2 /a 2 ),

there is a relationship of

(b 1 /a 1 )>(b 2 /a 2 ).

13. The vehicle seat according to claim 12 , wherein a difference between the load characteristic area ratio of the seat cushion (b 1 /a 1 ) and the load characteristic area ratio of the seat back (b 2 /a 2 ) is in a range of 3 to 15%.

14. The vehicle seat according to claim 12 ,

wherein spring constants at a balanced point on outward curves of a load-deflection characteristic of the seat back are each 15000 N/m or more.

15. The vehicle seat according to claim 9 , wherein a damping ratio of the seat back is larger than a damping ratio of the seat cushion, in which the respective damping ratios are found from free damped waveforms when a weight of 6.7 kg is made to fall from a height of 20 mm onto the seat cushion and the seat back.

16. The vehicle seat according to claim 15 ,

wherein in a load-deflection characteristic of the seat back in pressurizing the seat back with a pressure board having a diameter of 200 mm, at a speed of 50 mm/min, and up to a load of 500 N,

from an intersection of the seat cushion and the seat back, a deflection difference at each of 100 mm and 300 mm upward measuring points in the seat back is 4 mm or more and less than 10 mm.

17. A vehicle seat including a seat cushion and a seat back,

wherein, as the seat cushion, the seat cushion according to claim 1 is used.