JP2015168368A - seat back - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seat back which hardly causes accidents even when a passenger seating on a back seat leans forward and collides against a seat back frame.SOLUTION: A seat back comprises: a seat back pad formed of a synthetic resin foam whose bending flexible amount measured in accordance with a method described in JIS K7221-2:2006, is 20 mm or more, the synthetic resin foam requiring a load of 2-100 N to be bent by 20 mm, a back rest part of the seat back pad being deformable rearward; a space part for allowing bending deformation of the back rest part toward the rear side of the back rest part of the seat back pad; a seat back frame for supporting a peripheral edge of the seat back pad; and a frame rear side covering part for covering the rear side of the seat back frame and formed of a synthetic resin foam.

Description

  The present invention relates to a seat back that can reduce the weight of the seat back, has excellent recyclability, has a good fit and cushioning, and particularly incorporates safety measures against a collision of a rear seat occupant with a front seat.

  In general, in the case of a vehicle seat back, for example, a seat back includes a metal seat frame and a wire, and generally urethane foam is used as a cushioning material and the whole is covered with a skin material. The occupant's load is supported mainly by bending the urethane foam layer sandwiched between the seat frame or wire and the skin material in the compression direction, and the cushioning and fitting properties are mainly in the compression direction of the urethane foam layer. It was obtained by the reaction force, the restoring force, and the bending when bent.

  Further, as a technique related to weight reduction of a vehicle seat back, Patent Document 1 shows a frame shape of a seat frame, a cross section of the seat frame has a chevron shape, and one side of the chevron on the inner peripheral side of the frame shape of the seat frame. A concave curved surface is formed by covering the seat frame with an elastic net and pulling its peripheral edge from above the chevron of the seat frame and fixing it to the other side of the chevron. A technique is disclosed in which the seating surface is stretched so as to form a seating surface, and an angle is provided between the net and the inclined surface of the seat frame.

  As another technique related to weight reduction, Patent Document 2 discloses a base plate detachably attached to a seat frame, a block disposed on the base plate, a spring plate disposed on the block, and the spring plate. And the block is disposed so as to form a predetermined space between the base plate and the spring plate, and the spring plate is PP (elastic foam). Polypropylene) beads foam, PE (polyethylene) beads foam, PP foam, PE foam, AS resin (acrylonitrile / styrene resin) foam, EVA (ethylene vinyl acetate copolymer resin) and urethane foam material The spring seat is molded from the foam that is formed , Technical relates to a vehicle seat deflected into said space is disclosed when a force to said base plate direction was added.

JP 2002-28044 A Japanese Patent No. 4009490

In conventional general vehicle seat backs, urethane foam is used as a cushioning material, and since the cushioning property is extremely high and the comfort is excellent, it is still frequently used. However, the urethane foam has a problem that it is inferior in recycling performance. Furthermore, the vehicle seat back is required to have a function of supporting the occupant's body at an optimal position against the longitudinal and lateral acceleration applied to the occupant as the automobile moves, in addition to the general cushioning property. It is necessary to support the body in an optimal position to reduce fatigue when riding for a long time. For this reason, the function cannot be satisfied with only a very lightweight and flexible urethane foam, and in order to obtain a certain degree of rigidity, the density of the urethane foam needs to be a certain level or more. There was no problem.

In addition, since the seat back pad made of urethane foam is only folded on the rear side of the seat frame, if the body moves forward from the rear side due to a collision etc., the urethane foam with extremely flexibility is There was a problem that it was difficult to be a safe defense and was likely to cause injury such as bruises, cuts and fractures.

In the technology described in Patent Document 1, the net material that supports the load by the occupant is drawn into the seat frame installed around the seat back and firmly fixed, and the load applied by the occupant's seating is finally transmitted through the net material. It was supported by the rigidity of the seat frame. Therefore, the structure of the seat frame must maintain a certain level of strength. For this reason, although the weight of the net material itself corresponding to the conventional cushion material is light, the weight of the seat frame tends to increase and the overall weight There was a problem that the reduction effect was not sufficient.

Furthermore, the cushioning property of the net material is limited because it is obtained mainly by the elongation of the material, and there is a tendency that sagging occurs due to long-term use and the merchantability is inferior. In addition, since the flat net material is stretched around the seat frame, the basic seat back shape is flat, and the three-dimensional shape necessary to support the occupant's body in an optimal position is obtained. As a result, there is a problem that the passengers feel uncomfortable. This is because an unstable hammock-like net material cannot stably support the occupant's body when a lateral G is applied to the occupant by the movement of the automobile.

FIGS. 2 to 5 of Patent Document 1 depict a configuration in which “the rear end of the seatback frame is close to the exposed state”, so that a seated person in the rear seat is turned forward and the seatback frame is viewed from the rear. There was also a problem that hitting the rear end of the side wall of the car easily caused bruises, cuts and fractures.

Next, as for the technique of Patent Document 2, the spring plate is a plate-like foam having a substantially rectangular outer shape, and a plurality of grooves are formed in the lateral direction on the side of the spring plate on which an occupant sits. However, if the groove is shallow, flexibility cannot be given, and if the groove is deep, when the cushion material bends, excessive tensile force concentrates on the connecting part of the remaining groove bottom, causing large elongation deformation. There was a high risk of permanent deformation that could not be restored or fracture. If even a part of the connecting portion at the groove bottom is broken, the support is lost at once, the apparent hardness of the entire cushioning material is drastically lowered, and the function as the cushioning material is greatly impaired. Therefore, it is practically difficult to design the deflection of the cushion material to a certain level or more in order to avoid breakage, and it is difficult to provide a sufficient fit and comfort when seated.

Moreover, although the technique of patent document 2 has described that it can obtain a favorable seating feeling personally by selecting suitably the block from which height differs according to a passenger | crew's physique, There was a problem that in reality it had to be difficult to implement, because it had to be changed to a block of height suitable for me before sitting down by light weight.

In paragraph [0076] or [0077] of Patent Document 2, it is described that “a vehicle seat has a structure in which a base plate and a spring plate are placed on a metal frame and covered with a skin”, and FIG. The rear seat side is covered only by the skin, and the skin is described as “fabric, genuine leather, synthetic leather, etc.” in paragraph [0042] and is generally thin. If a seat occupant turns forward and hits the rear end of the seat back frame from the rear, there is a problem that bruises, cuts, broken bones, etc. are likely to occur.

Therefore, the object of the present invention is excellent in cushioning and fitting properties when seated by a person, lightweight and excellent in recyclability, and is less likely to be injured even if a seated person in the rear seat falls forward and collides with the seat back frame. It is to provide a seat back.

In the present invention, the synthetic resin foam is flexible and capable of bending deformation and is excellent in resilience. The method described in JIS K7221-2: 2006 (23 ° C. ± 2 ° C., relative humidity 50 ± 350mm long with skin removed in 5% atmosphere
A load is applied to a test piece having a width of 100 mm and a thickness of 25 mm at a distance of 300 mm between the fulcrums 6 at a test speed of 20 ± 1 mm / min until the maximum deflection is 90 mm, and a load deflection curve is recorded. ) Refers to a synthetic resin foam molded article having a bending deflection of 20 mm or more and a load of 2 to 100 N when bent by 20 mm. Specifically, it refers to foamed polypropylene, foamed polyethylene, other polyolefin resin foams, modified polystyrene resin foams, and the like. The synthetic resin foam includes a bead foam molded body, and examples of the bead foam molded body include a polypropylene-based bead foam molded body and a polyethylene-based bead foam.

In the specific selection of the material, both ends of a bar-shaped or flat plate-shaped test piece having a length of about 400 mm are supported, the center is pushed back and forth by 25 mm and held for 30 minutes, and then the load is released to recover from the deformation of the sample. 90% or more is desirable. Alternatively, in accordance with a test performed with a conventional urethane foam cushion, the center portion of the sample supporting both ends is repeatedly pressed down and deformed a predetermined number of times, and the residual strain (also referred to as residual displacement) measured thereafter is determined. It is desirable to be below the fixed amount.

Such materials satisfying, for example, the density of the foamed polypropylene ^{0.06g / cm 3 ~0.015g / cm 3} , more preferably a density 0.035g ^/ cm ³ ~0.015g ^/ cm 3 or polyethylene foam, such as density 0.08g ^/ cm ³ ~0.03g ^/ cm 3 are preferred. On the other hand, rigid foamed urethane, polystyrene foam and the like which are poor in flexibility and can be easily broken by bending deformation are not preferable.

The inventors have studied materials in order to reduce the weight. As an example of a material that can be changed to urethane foam that has an open cell structure, synthetic resin foam that has a closed cell structure is generally lighter, more rigid, and more recyclable than urethane foam that has been commonly used as a cushioning material. Although it had the advantage of being easy, etc., when using bending and restoring force in the compression direction as a cushion, the reaction force tends to increase rapidly with the deformation of the foam due to the repulsive force of the air included It was inferior in comfort because it felt stiff and lacked cushioning.

In general, when a synthetic resin foam having a closed cell structure is used as a cushioning material by being bent in the compression direction like a urethane foam, it gradually loses its recovery force and generates creep as it is used for a long period of time. This is largely due to fatigue due to repeated deformation of the resin film constituting the bubbles and a drop in the pressure of the air contained therein. Therefore, it was not preferable as a material for a cushion used for a long time.

Therefore, the inventors analyzed the physical properties of the synthetic resin foam from various angles, so that it is not a structure that has been bent in the compression direction that has been used as a conventional general cushioning material, but can be bent and deformed. The present inventors have found that a method of utilizing the bending deformation and recoverability of a support made of a synthetic resin foam excellent in the above as a cushioning material is optimal.

In order to solve the problem described in “Problems to be Solved by the Invention”, the seat back 2 according to claim 1 has a bending deflection amount of 20 mm or more measured according to the method described in JIS K7221-2: 2006. The seat back pad 4 is made of a synthetic resin foam having a load of 2 to 100 N when bent by 20 mm, and the backrest portion 21 is bent and deformed rearward. The backrest portion 21 of the seatback pad 4 is behind the backrest portion 21. A space 10 that allows bending deformation of the bent portion 21, a seat back frame 5 that supports the peripheral portion 30 of the seat back pad 4, and a frame rear covering portion that covers the rear side of the seat back frame 5. 7.

  A seat back 2 according to a second aspect of the present invention is the seat back 2 according to the first aspect, wherein the frame rear covering portion 7 is integrally formed with the seat back pad 4 as a first form from the peripheral edge of the entire circumference of the seat back pad 4. A frame rear bent piece 8 that extends rearward and is bent so as to cover the rear side of the seat back frame 5. As a second form, it is different from the seat back pad 4 and is rearward of the seat back frame 5. It is a plate-like frame rear mounting cover 6 that is mounted on the side from behind and covers the seat back frame 5, or is molded integrally with the seat back pad 4 as a third form at the boundary with the seat back pad 4. It is a plate-like frame rear folding cover 16 that is folded and covers the rear side of the seat back frame 5.

The seat back 2 according to claim 1 can replace the urethane foam generally used in the past with the synthetic resin foam for the seat back pad 4, and therefore, the weight reduction and recyclability can be achieved. Improvement is possible. Despite the use of synthetic resin foam, which is relatively hard and inferior to cushioning, fit, and creep resistance, it is possible to give high cushioning and fit, and freedom of design High degree of comfort that can support the seated person's body properly and high comfort, and even with long-term use, it exhibits good creep resistance equivalent to conventional urethane foam, so it has a high commercial value Play.

Further, since the seat back pad 4 is supported by the leg and forms a space portion 10 that can be bent and deformed, the entire backrest surface of the seat back pad 4 that the seat occupant abuts on due to a load received from the occupant is easily elastic. It can be bent and deformed within the range. Accordingly, the body can be sunk into the backrest surface without feeling a sense of impact when the seated person contacts the backrest portion 21.

In the case of a seat back pad made of a conventional urethane foam, since the urethane foam is extremely flexible and has no rigidity, the groove portion into which the seat back frame is fitted in advance is molded as an undercut shape when molding the urethane foam, A seatback frame was fitted in the groove. Thereby, the back of the seat back frame could be covered with urethane foam. However, since urethane foam has a continuous foam structure, it easily bottoms out when subjected to a strong impact such as a collision accident, and the rear seat occupies a disaster such as a cut or fracture when it collides with the seat back frame. There was a problem that it was easy to encounter.

In contrast, the seat back 2 of the present invention has a closed cell structure, unlike urethane foam (soft foam polyurethane), and is harder and more rigid than soft foam polyurethane. When subjected to a large load or impact, the air contained in the closed cells does not easily leak and a reaction force is generated against the applied load or impact. For this reason, it does not easily bottom out, and effectively exhibits energy absorption in a range of 50% to 80% in the thickness direction. For this reason, the impact applied to the occupant is buffered compared to the soft foam polyurethane that does not generate almost any reaction force and easily bottoms out, and the seat back frame mainly made of metal is not exposed, making the occupant in the rear seat effective. Can be protected.

The seat back 2 according to the second aspect has the same effect as the first aspect. Further, when the synthetic resin foam in the present invention is used as a material, it is difficult to previously form a groove into which the seatback frame 5 is fitted, as in the case where urethane foam is used. Since the synthetic resin foam in the present invention has rigidity, it is difficult to release with a normal mold structure and lacks moldability. If it is intentionally molded, a special mold structure having a movable core is required, and there is a problem that it becomes a very expensive mold or an economical problem that a molding tact becomes long.

Therefore, the rear seat side of the seat back frame 5 is covered even by a material having rigidity by the method of any one of the first form, the second form and the third form according to claim 2. There is an effect that can be.

It is an isometric view schematic diagram of a vehicle seat. 1 is a schematic perspective view of a vehicle seat back. It is explanatory drawing of a frame back bending piece, Comprising: It is sectional drawing of an AA cross section, (a) shows the state before bending, (b) is the figure which showed the state after bending. It is explanatory drawing of a flame | frame back bending piece, Comprising: It is sectional drawing of a BB cross section, (a) shows the state before bending, (b) is the figure which showed the state after bending. It is explanatory drawing which shows the form of a seat back pad and a frame back mounting cover. It is AA sectional drawing of a seat back (except skin) at the time of frame back mounting cover use. It is explanatory drawing of the form of frame back folding cover use, (a) shows the form at the time of shaping | molding, (b) shows the form in the middle of frame back folding cover folding, (c) is after frame back folding cover folding It is the figure which showed the form. It is a perspective schematic diagram of a seat back frame. In the form seen from the front view of the seat back pad, (a) is a conceptual diagram of a form in which the bending deformation part is a rod-like body, and (b) is a form in which the bending deformation part is a combination of a flat plate and a rod-like body. It is a schematic diagram of a load durability test. It is a schematic diagram of a back pressure jig, (a) is a top view, (b) is a front view, and (c) is a side view. It is a residual displacement amount diagram by repeated load. It is a comparison figure of the bending test by JISK7221-2 with a foam and a non-foam.

Hereinafter, embodiments of the seat back 2 according to the present invention will be described. As shown in FIG. 1, a vehicle seat 1 according to the present invention includes a seat back 2 and a seat cushion 3. The seat back 2 includes a seat back pad 4 as shown in FIG. 3 and a seat back frame 5 as shown in FIG.

The seat back 2 is made of a synthetic resin foam having a bending deflection amount of 20 mm or more measured according to the method described in JIS K7221-2: 2006, and a load when the deflection is 20 mm is 2 to 100 N, and the backrest portion 21 is rearward. A seat back pad 4 that is bent and deformed, a space 10 that allows the back rest 21 to be bent and deformed behind the back rest 21 of the seat back pad 4, and a peripheral portion 30 of the seat back pad 4. A seat back frame 5 to be supported, and a frame rear covering portion 7 that covers the rear side of the seat back frame 5 are provided.

The seat back pad 4 made of a synthetic resin foam is lighter and more rigid than urethane foam, so it is bent and deformed instead of compressive deformation like urethane foam to ensure cushioning properties. It has a structure.

Therefore, to facilitate bending deformation, a gap 22 is provided in the seat back pad 4 as shown in FIG. 3, FIG. 9 (a) or (b), or as shown in FIG. 3, FIG. 4, FIG. The space portion 10 is provided behind the bending deformation portion 20. Thereby, cushioning properties can be secured by the seat back pads 4 and 14 made of a synthetic resin foam that is lighter and more rigid than urethane foam. Here, the gap 22 may not be provided by reducing the thickness of the bending deformation portion 20 that is the backrest portion 21 of the seat back pad 4.

Generally, urethane foam is used as the material for the seat back pad, and the back of the seat back frame 5 is covered with the urethane foam. However, since the urethane foam is a continuous foam structure, it easily bottoms out due to impact. There is a problem that when a seated person in the rear seat turns forward and collides with the seat back frame 5 of the front seat, it is likely to be injured such as bruise, cut and fracture.

The present invention is a synthetic resin foam such as expanded polypropylene, expanded polyethylene, other polyolefin resin foam, modified polystyrene resin foam, polypropylene bead foam molded product or polyethylene bead foam. Cover the back. Since the synthetic resin foam has high energy absorption efficiency, it can be safely protected even when a seated person in the rear seat collides with the seat back frame 5 of the front seat.

In general, in the case of a seat back pad made of urethane foam, since the urethane foam has extremely flexibility, the seat back frame 5 can be fitted by pushing the groove wall open during manufacture. A groove for fitting is formed.

On the other hand, the synthetic resin foam, which is the material of the seat back pad 4 of the present invention, is generally filled with granular raw material beads in a mold, vented with high temperature steam into the mold, and heated to melt the bead surface. As a result, the beads are fused to form a single piece.

However, the synthetic resin foam is harder and more rigid than urethane foam (soft foam polyurethane), so if it is overhanging more than a certain amount in the mold, it cannot be released, so it is a single part. Thus, it was not possible to obtain a structure in which the rear portion of the seat frame behind the seat was covered with the synthetic resin foam part disposed on the front surface of the seat. In order to achieve a shape that would have greatly overhanged conventional soft foam polyurethane and covered the back of the seat frame, a complicated and expensive mold structure such as a movable core was required in the mold. did.

Therefore, the present invention contemplates the frame rear covering portion 7 as a structure capable of covering the rear of the seat back frame 5 while suppressing the cost increase of the mold.

As shown in FIG. 3 or FIG. 4, the frame rear covering portion 7 is formed integrally with the seat back pad 4 and extends rearward from the peripheral edge of the entire circumference of the seat back pad 4. A frame rear bent piece 8 bent so as to cover the rear side of the back frame 5, and as a second form, as shown in FIG. 5 or FIG. It is a plate-like frame rear mounting cover 6 that is mounted on the rear side of the frame 5 from behind and covers the seat back frame 5, or as a third embodiment, as shown in FIG. 7, integrated with the seat back pad 4 A plate-like frame rear folding cover 16 which is molded and folded at the boundary so as to operate like a hinge at the boundary with the seat back pad 4 and covers the rear side of the seat back frame 5. There is a certain form.

The material of the frame rear covering portion 7 made of the synthetic resin foam to be bent and deformed as in the first embodiment or the third embodiment has viscoelasticity or flexibility in the synthetic resin foam. For example, there are foamed polypropylene and foamed polyethylene.

First, the frame rear covering piece 8 which is a 1st form is demonstrated. The frame rear covering piece 8 is a piece extended rearward from the peripheral edge portion 30 of the seat back pad 4 as shown in FIG. 3 (a) or FIG. 4 (a). After the seat back frame 5 is fitted to the seat back pad 4, the frame rear covering piece 8 is formed so as to cover the rear of the seat back frame 5 as shown in FIG. 3B or FIG. b) or bent in the direction of the arrow in FIG. Thereby, the back of the seat back frame 5 is covered with the frame rear covering piece 8.

Next, the frame rear mounting cover 6 according to the second embodiment will be described. As shown in FIG. 5 or 6, the frame rear mounting cover 6 is separate from the seat back pad 4, and the front side of the seat back frame 5 is the seat back pad 4 and the rear side is the frame rear mounting cover 6. The seatback frame 5 is sandwiched between the seatback pad 4 in the direction of the arrow shown in FIG.

The shape of the frame rear mounting cover 6 may be a frame shape that matches the shape of the seat back frame 5 as shown in FIG. 5, or may be a substantially square shape (not shown) that covers the back of the seat back pad 4. . In any case, the shape of the frame rear mounting cover 6 only needs to cover the rear portion of the seat back frame 5. The frame rear mounting cover 6 is separate from the seat back pad 4 and need not be made of the same material as the seat back pad 4.

Next, the frame back bending cover 16 which is a 3rd form is demonstrated. The frame rear folding cover 16 is integrally formed with the seat back pad 4 and has a substantially rectangular shape that can cover the back of the seat back pad 4 including the seat back frame 5 as shown in FIG. There is a substantially square frame shape that can cover the back of 5.

The rear side of the seat back frame 5 is covered by folding the boundary with the seat back pad 4 at the boundary so as to bend like a hinge. FIG. 7A shows a state in which the frame rear folding cover 16 and the seat back pad 4 are integrally formed, FIG. 7B shows the middle of folding the frame rear folding cover 16, and FIG. 7C shows the frame rear folding. The cover 16 is bent and the rear side of the seat back frame 5 is covered.

Next, the synthetic resin foam will be described. The synthetic resin foam is flexible, can be flexibly deformed, and has excellent resilience. The method described in JIS K7221-2: 2006 (in an atmosphere of 23 ° C. ± 2 ° C. and relative humidity of 50 ± 5%) The test piece having a length of 350 mm, width of 100 mm, and thickness of 25 mm with the skin removed in step 3 is loaded up to a maximum of 90 mm at a distance of 300 mm between the fulcrums 6 and a test speed of 20 ± 1 mm / min, and a load deflection curve is recorded. It refers to a synthetic resin foam molded article having a bending deflection of 20 mm or more and a load at the time of 20 mm deflection of 2 to 100 N. A synthetic resin foam molded article that causes fracture when the bending deflection is less than 20 mm is not suitable from the viewpoint of durability. When the cross section of the support body 2a required for supporting the load by the body becomes very large and the load at the time of 20 mm bending is more than 100N, it is difficult to generate a preferable bending amount, and it is difficult to design a preferable one. Specifically, it refers to foamed polypropylene, foamed polyethylene, other polyolefin resin foams, modified polystyrene resin foams, and the like. Among the foams, an in-mold molded body of resin foam particles is preferable from the viewpoint of shape flexibility (designability) considering a fit.

The polyolefin resin constituting the expanded particles used in the present invention is a polyolefin resin having an olefin component unit as a main component, specifically, a polypropylene resin, a polyethylene resin, and a mixture of two or more thereof. Is mentioned. The above-mentioned “main component” means that the olefin component unit is contained in the polyolefin resin in an amount of 50% by weight or more, and the content thereof is preferably 75% by weight or more, more preferably 85% by weight. % Or more, more preferably 90% by weight or more.

Examples of the polypropylene-based resin include resins having a propylene component unit of 50% by weight or more, and examples thereof include a propylene homopolymer or a copolymer with another olefin copolymerizable with propylene. Examples of other olefins copolymerizable with propylene include ethylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1 Examples thereof include α-olefins having 4 to 10 carbon atoms such as heptene and 3-methyl-1-hexene. The copolymer may be a random copolymer or a block copolymer, and may be not only a binary copolymer but also a ternary copolymer. The other olefin copolymerizable with propylene in the copolymer is preferably contained in a proportion of 25% by weight or less, particularly 15% by weight or less, and the lower limit is 0.3% by weight. Preferably there is. These polypropylene resins can be used alone or in combination of two or more. Polypropylene resin has a tensile elastic modulus (E) specified in JIS K7161: 1994 (test piece: JIS K 7162 (1994), test piece 1A type (direct molding by injection molding), test speed: 1 mm / min)). A resin foam obtained by foaming a base resin having a value of 600 MPa or more is preferable.

Examples of the polyethylene resin include resins having an ethylene component unit of 50% by weight or more, such as high density polyethylene, low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer. A copolymer, an ethylene-propylene-butene 1 copolymer, an ethylene-butene 1 copolymer, an ethylene-hexene 1 copolymer, an ethylene-4 methylpentene 1 copolymer, an ethylene-octene 1 copolymer, and the like. The mixture of 2 or more types is mentioned.

Then, in the specific selection of the synthetic resin foam, both ends of a rod-shaped test piece having a length of about 400 mm are supported, the center is pushed back and forth by 25 mm and held for 30 minutes, and then the load is released, and then the deformation from the sample is changed. Residual strain measured after the center portion of the sample that supported both ends was repeatedly pressed down and deformed in accordance with tests performed on materials with 90% or more recovery or conventional urethane foam seat cushions. A material in which is less than a predetermined amount is desirable. The predetermined number or the predetermined amount conforms to a specification arbitrarily determined by each manufacturer when selecting a conventional material.

Such materials satisfying, for example, the density of the foamed polypropylene ^{0.06g / cm 3 ~0.015g / cm 3} , more preferably a density ^{0.035g / cm 3 ~0.015g / cm 3} , or of foamed polyethylene such as density 0.08g ^/ cm ³ ~0.03g ^/ cm 3 are preferred. Such a material is obtained by the method described in JIS K7221-2: 2006 (a test piece having a length of 350 mm, a width of 100 mm, and a thickness of 25 mm with the skin removed in an atmosphere of 23 ° C. ± 2 ° C. and a relative humidity of 50 ± 5%. In a test conducted in accordance with a distance of 300 mm at the fulcrum 6 and a load of up to 90 mm at a test speed of 20 ± 1 mm / min and recording a load deflection curve), the load when the bending deflection is 20 mm is 2 to 100 N and Flexural rigidity is excellent as well as flexibility, but on the other hand, a flexible urethane foam that has been generally used is not suitable as a material constituting the cushion body 1 of the present invention because the bending rigidity is greatly inferior at 0.46 N.

  Below, the creep property and bending rigidity at the time of using a synthetic resin foam are demonstrated. First, in order to evaluate the creep property, compression set according to JIS K 6767: 1999 was measured. A test piece having a length of 50 mm, a width of 50 mm, and a thickness of 25 mm is compressed into a 25% distorted state and left at a temperature of 23 ° C. ± 2 ° C. for 22 hours. The thickness is measured 24 hours after the end of compression. The compression set was determined by compression set (%) = (test piece original thickness (mm) −thickness 24 mm after completion of compression (mm)) ÷ test piece original thickness (mm) × 100.

As a result of the test, the compression set of the 45-fold polypropylene foam particle molded body was 11%. On the other hand, the compression set of the polyurethane foam by the same measuring method is 2% or less. This is because conventional urethane foam, which is generally used as a cushioning material for seat cushions, exhibits cushioning properties by compression deformation. If it is simply replaced with a synthetic resin foam, compression set is generated, and the original cushion It is shown that it is difficult to maintain the product and the commercial value is lowered.

Next, the sample plate 21 is placed at room temperature using a back-shaped pressurizing jig 40 as shown in FIG. 11 (elliptical horizontal length 440 mm, depth (width) 290 mm, height 60 mm in front view) in plan view. A load durability test was performed by measuring the residual displacement after applying a load of 490 N repeatedly 5,000 times, 10,000 times, and 15,000 times. In order to investigate the amount of residual displacement when the synthetic resin foam is bent and deformed, as shown in FIG. 10, it is a flat polypropylene foam 45 times expanded product having a thickness of 20 mm and a width (depth) of 600 mm. The sample plate 41 was used as both-end support at an interval of 340 mm. The results of the load durability test are shown in FIG.

From FIG. 12, the specification required for the conventional urethane foam is a residual displacement of 5 mm or less (line C in FIG. 12), whereas in the case of the synthetic resin foam of the present invention (line D in FIG. 12). Indicates that the residual displacement is 2.5 mm, which is within the range of the specification.

Therefore, from FIG. 12, when the bending and deformation of a synthetic resin foam capable of bending deformation and excellent in resilience is used as a cushioning material, it is comparable to a conventionally used urethane foam, or It has been shown to have greater creep resistance.

When the synthetic resin foam is used as the support 2a, the creep resistance is higher than that of the urethane foam. When the center part is pushed down and bending deformation occurs, each part of the member is pulled, compressed, sheared, etc. The member deforms, but the degree of each deformation is less than the amount of direct deformation in the case of using a cushion material by simply compressing the member as in the past, and the recovery range is not impaired. Because it stops at.

Next, FIG. 13 selects foamed polypropylene as an example of a synthetic resin foam, a sample made of a non-foamed resin plate (thickness 1 mm) made of an equivalent resin, and a sample made of a foamed polypropylene 45 times foamed product (thickness 45 mm). ) JIS K7221-2: 2006 (length of 350 mm, width 25 mm, sample weight equivalent, thickness of the specimen with any thickness removed between the fulcrum 6 under the atmosphere of 23 ° C. ± 2 ° C. and relative humidity 50 ± 5%. A load is applied up to 90 mm at a distance of 300 mm and a test speed of 20 ± 1 mm / min, and a load deflection curve is recorded. The width was kept constant at 25 mm, and the thickness was adjusted so that the sample weight was equal. The case of a non-foamed resin plate is represented by a load-displacement amount diagram M, and the case of a sample made of a foamed polypropylene 45-fold product is represented by a load-displacement diagram H.

FIG. 13 shows that although the weights of the samples are the same, bending rigidity is greatly increased by using a foam. Conventionally, it was not common to bend a foam and use it as a cushioning material. However, by using a foam, the weight of components required to obtain the same bending rigidity can be reduced. It is shown that the weight can be reduced.

DESCRIPTION OF SYMBOLS 1 Seat 2 Seat back 3 Seat cushion 4 Seat back pad 5 Seat back frame 6 Frame rear mounting cover 7 Frame rear covering part 8 Frame rear bending piece 9 Skin 10 Space part 16 Frame rear bending cover 20 Bending deformation part 21 Backrest part 22 Gap 30 Edge

Claims (2)

  A seat back made of a synthetic resin foam having a bending deflection measured according to the method of JIS K7221-2: 2006 of 20 mm or more and a load of 2 to 100 N when the deflection is 20 mm, and the backrest portion is bent and deformed backward. A pad, a space that allows bending deformation of the backrest behind the backrest of the seatback pad, a seatback frame that supports a peripheral portion of the seatback pad, and a rear of the seatback frame A frame back comprising: a frame rear covering portion that covers the side.   The frame rear covering portion is molded integrally with a seat back pad as a first form, and is extended rearward from the peripheral edge of the entire periphery of the seat back pad so as to cover the rear side of the seat back frame. The frame is a folded back piece of the frame, and as a second form, is a plate-like frame rear mounting cover that is separate from the seat back pad and is mounted on the rear side of the seat back frame from behind to cover the seat back frame. Alternatively, as a third embodiment, the present invention is a plate-like frame rear folding cover that is integrally formed with the seat back pad and is folded at the boundary with the seat back pad to cover the rear side of the seat back frame. Item 1. The seat back according to Item 1.

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