JP2005177171A - Seat pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a seat pad absorbing or reducing predetermined vibrations giving discomfort to an occupant, providing the occupant with a superior riding comfort and facilitating a trial production and mass production. <P>SOLUTION: This seat pad comprises a cushion body 12 composed of polyurethane foam and constituting a seat part, and a sheet-type low permeability foam 14 integrally provided with the bottom face of the cushion body 12, so that a resonance magnification calculated from a frequency characteristic of the seat pad 10, which is measured in conformity with JASO B 408 (performance test methods for pad materials for automobile seats), is at least 4.0 or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a seat pad, and more particularly, to a seat pad that absorbs and reduces predetermined vibrations that cause discomfort to the occupant, provides a good ride comfort to the occupant, and is easy to prototype and mass-produce. Is.

  In the development of seats for vehicles such as automobiles, the improvement of the ride comfort is one of the major improvements from the past. In the past, this improvement in ride comfort has been achieved by increasing the cushioning property of the seat, that is, the impact resilience. For example, as shown in FIG. 4A, in the case of a so-called full-foam seat pad whose main structure is made of only polyurethane foam, the rebound resilience is around 70% and a good cushioning property is secured. However, when the rebound resilience exceeds 70%, for example, a problem that the occupant's stability when riding on a rough road (hereinafter simply referred to as stability) deteriorates is pointed out. For this reason, in recent seats, a seat pad with a low rebound resilience so as to exhibit adequate cushioning properties while at the same time exhibiting sufficient stability can be used. There is a search for ways to improve this.

  On the other hand, a so-called spring combined type seat pad, the main structure of which is a polyurethane foam and a metal spring provided at the bottom of the foam (see FIG. 4B). Has been used in some areas. In the case of this spring combined seat pad, a part of the polyurethane foam that increases the resilience elastic modulus is a spring, and the rebound resilience is a suppressed value of about 62 to 68%, resulting in stability. And a cushioning property are combined, and a seat that expresses a more comfortable ride than a full foam seat pad can be manufactured. Note that the full-form seat pad or the spring combined seat pad is merely selectively used because it has a different vehicle body structure and seat structure for each vehicle type.

  As one of the evaluation methods of ride comfort, it is evaluated by the “vibration exposure evaluation curve in the vertical direction of the human body” in the acceleration / frequency relationship in accordance with JASO B 408 (performance test method for pad material of automobile seats). A vibration characteristic is mentioned. This evaluation is carried out by a measuring device 50 as shown in FIG. 5 (a), in which a disk pad to be measured is placed on a vibration table 52 as a test piece and a load of 300 N is applied thereon. The pressure plate 54 is placed, the required vibration is applied to the vibration table 52, and the absolute displacement amount of the load center point 54a on the pressure plate 54 is measured. Here, the load applied to the seat pad 10 is achieved by setting the weight of the pressure plate 54 to 50 kg, and the vibration applied by the vibration table 52 is set from 1 Hz to at least a resonance frequency (described later) +2 Hz (the present invention). Is set every 0.1 Hz in the range of 1 to 10 Hz (described later ([0024])), and at each frequency (frequency), an input amplitude of 5 mm (total amplitude of 10 mm in JASO B 408). Measured how much amplitude is transmitted (output) to the resonance frequency, and the output / input value at this time is the highest output / input frequency in this measurement. The result of (transmissibility) is calculated as the resonance magnification, and Fig. 5 (b) is a graph showing an example of the measurement result obtained in this measurement.

  The ride comfort of the seat pad is generally achieved by lowering the magnitude of vibration in the above-described frequency range, that is, the resonance magnification. It is known that the frequency that passengers feel most uncomfortable is around 4 to 8 Hz, especially around 6 Hz (generally referred to as the built-in resonance point). Riding comfort can be improved by moving the resonance frequency away from this range. Can be expected. In the case of the above-mentioned full-form seat pad and the spring combined seat pad, the spring combined seat pad has a lower resonance magnification at 3.5 to 4.0 Hz, and the ride characteristics are improved from its vibration characteristics. It can be said. Such a seat pad is generally called a vibration absorbing seat pad. However, it has been difficult to say that sufficient riding comfort, that is, adequate cushioning and sufficient stability are achieved.

  Note that the dynamic repulsion rate (hereinafter referred to as the dynamic repulsion rate) measured according to JASO B 408 and employed in the present invention is also shown in FIG. ) Is measured using the measuring device 50 shown in FIG. The dynamic repulsion rate is measured by placing a disk-shaped pressure plate 54 that applies a load of 300 N on the vibration table 52 with the seat pad 10 to be measured as a test piece, and then pressing the pressure plate. 54 is lifted to an arbitrary height of 20 mm when measured just below the load center point 54a, and the relationship between the displacement amount of the load center point 54a and the elapsed time when it is freely dropped, that is, the attenuation waveform is measured. Then, using the first amplitude A and the second amplitude B in the attenuation waveform, the calculation is performed by the equation (B / A) * 100. FIG. 6B is a graph showing an example of the measurement result obtained in the main measurement.

By the way, recent vehicle seats can express the characteristics of the vehicle more clearly and suitably depending on the use application of the adopted automobile, for example, the difference in models such as family use model, sporty model or SUV and vehicle size. It is desired to be developed as follows. This means that a design of a seat pad having suitable physical properties, that is, suitable riding comfort is desired for each individual vehicle type. And in order to manufacture the seat pad which expresses suitable riding comfort, in order to control a resilience elastic modulus, the following method can be considered. That is,
(1) By designing the polyurethane foam that achieves the riding comfort required for each vehicle model by changing the material of the polyurethane foam that constitutes the seat pad, that is, the composition of each raw material, it is used as a seat pad. .
(2) A highly elastic material is used as the foam material to ensure cushioning, and air permeability is controlled by crushing only some cells in the polyurethane foam by crushing. A polyurethane foam that achieves comfort is obtained and used as a seat pad.
(3) As described above ([0003]), the spring constant is changed in a so-called spring combined type seat pad whose main structure is a polyurethane foam and a metal spring provided on the lower side of the foam. A seat pad that achieves the desired ride comfort is obtained by using a spring that has been removed.

However, the following problems are pointed out in the methods (1) to (3) described above.
(1) Manufacture of a seat pad that expresses the ride comfort is designed, for example, by designing a polyurethane foam composition that constitutes the seat pad by controlling the glass transition point so as to substantially match the operating temperature range. In such a case, examination by a very time-consuming method such as so-called trial and error is required. In addition, various physical properties relating to ride comfort are prototyped and evaluated based on the shape of the seat pad actually used, so that much labor is required. Furthermore, in mass production, it is necessary to change the polyurethane foam composition every time the production vehicle type is changed, and mass production efficiency is greatly reduced, and the cost is greatly deteriorated.

  (2) In the same manner as (1) described above, it takes time to determine the composition of the polyurethane foam that can be suitably used for the seat pad, and time for trial production. Further, the crushing for foaming the cells of the polyurethane foam is basically a conventionally known method in which the polyurethane foam is passed and compressed between the rollers, or the cells are expanded by lowering the pressure by setting the polyurethane foam to a required reduced pressure state. However, since the repetition accuracy is not high, even when foams having the same composition are used, the expressed riding comfort varies and the yield deteriorates.

  (3) Since the cushion body on which the occupant sits basically does not change in the seat pad, it is only necessary to change the spring disposed at the bottom, the composition design according to the above (1) and (2) The labor of trial manufacture can be avoided. However, since the expensive solid spring is generally used, the manufacturing cost increases. Further, the spring having durability is made of steel as a material, and the number of components increases, so that the total weight of the vehicle increases.

In order to overcome the above-mentioned problems and achieve the intended purpose, a seat pad according to the present invention is made of polyurethane foam, and a cushion body constituting a seating portion;
A seat pad comprising a sheet-like low breathable foam integrally provided on the bottom surface of the cushion body,
The resonance magnification calculated from the vibration characteristics of the seat pad measured according to JASO B 408 is at least 4.0 or less.

In order to overcome the above-mentioned problems and achieve the intended purpose, a seat pad according to another invention of the present application is made of polyurethane foam, constitutes a seating portion, and has a hardness measured in accordance with JASO B 408. A cushion body set to at least 0.01 MPa or less;
A seat pad comprising a sheet-like low breathable foam integrally provided on the bottom surface of the cushion body,
The dynamic repulsion rate of the seat pad calculated from a method based on JASO B 408 is at least 45% or less.

  As described above, according to the seat pad according to the present invention, the low breathability foam is integrally provided at the bottom of the cushion body constituting the seat pad to absorb the vibration that deteriorates the riding comfort, and the resilience elastic modulus. In other words, the dynamic rebound rate can be kept low under control, and a good riding comfort having both passenger stability and cushioning properties can be achieved. In addition, it is possible to manufacture a seat pad that expresses various physical properties by selecting only the low-breathing foam set to a predetermined breathability. In this case, since it is not necessary to replace the material of the seat pad for each production vehicle type, mass production of the seat pad that expresses a suitable riding comfort for each of many vehicle types becomes easy.

  Next, a preferred embodiment of the seat pad according to the present invention will be described below with reference to the accompanying drawings. The inventor of the present application constitutes a cushion body that becomes a seating portion with a polyurethane foam that is used for general purposes, and integrally provides a sheet-like low-breathing foam with controlled breathability at the bottom of the cushion body, By setting the resonance magnification calculated from the vibration characteristics of the seat pad measured by a method based on JASO B 408 (a performance test method for the pad material of an automobile seat) to at least 4.0 or less, the stability of the passenger and It has been found that it has a ride comfort that optimizes both cushioning properties, and can reduce various labors required for trial production and mass production.

Further, as is clear from FIG. 5B, the measurement of the vibration characteristics requires man-hours, that is, the measurement needs to be repeated according to the vibration frequency. For this reason, the ride comfort can be evaluated by both the dynamic repulsion rate (previously described [0006]) having a great correlation with the vibration characteristics and empirically positive correlation and hardness. Specifically, the hardness measured according to JASO B 408 in the cushion body is set to at least 0.01 MPa (30 kgf / 314 cm ² ) or less, and the air permeability of the sheet-like low-breathing foam is controlled. It has also been found that by setting the dynamic repulsion rate of the seat pad calculated from the method in conformity with JASO B 408 to 45% or less, the same effect as when the resonance magnification is set to at least 4.0 or less is exhibited. . This dynamic rebound rate is a dynamic evaluation of the rebound resilience, which is a static, in other words, material property, when the seat pad is placed, and has a high affinity for the evaluation of the ride comfort of the seat pad. It is a physical property value that has a positive correlation with the rebound resilience, and decreases in proportion to the rebound resilience. This dynamic repulsion rate has a great relationship with the ride comfort of the seat pad and can be easily measured, but it is difficult to make a quantitative evaluation thereof, that is, what value is suitable. In the above, the above-described vibration characteristics that can be numerically determined are mainly defined.

  As shown in FIG. 1, a seat pad 10 according to a preferred embodiment of the present invention is basically a cushion body 12 and a sheet-like low air permeability provided integrally at a required position at the bottom of the cushion body 12. Form 14 is formed. Further, in the embodiment, the low air-permeable foam 14 is disposed on the bottom surface of the cushion body 12 corresponding to the seating area of the occupant, in particular, where the intended ride comfort is indispensable, that is, the hip part of the occupant (FIG. 1). (See (b)). In this embodiment, the low air permeability foam 14 is provided only in the seating area of the occupant. However, the low air permeability foam 14 may be provided over the entire seat pad 10 as shown in FIG. . In this case, a suitable riding comfort in which the stability and cushioning properties are harmonized can be achieved over the entire area of the seat pad 10. In the present embodiment, the seat pad 10 is described as forming the seat portion 42 of the vehicle seat 40 as shown in FIG. 3, but the present invention is not limited to this, and the vehicle seat is also the same. 40 can also be used as a backrest portion 44 constituting 40. In the case of a normal seat pad 10, a surface made of fabric, synthetic leather or leather is affixed to the surface of the cushion body 12, but this is not necessary in the description of the present invention, so the description thereof is omitted. This is omitted in all the drawings.

  The cushion main body 12 is made of polyurethane foam, and constitutes a main part of the seat pad 10 and a part where an occupant is seated. In order to avoid troublesome labor during trial production and mass production, a polyurethane foam that is generally used for an ordinary seat pad and has a clear physical property and has established a mass production process by molding is suitably employed. The cushion body 12 is manufactured by a general molding method.

  As described above ([0008]), changing the resilience elastic modulus while maintaining various physical properties as the seat pad 10 in the polyurethane foam must consider the selection of the main raw material and the composition of each raw material. This is a time-consuming work. However, in the seat pad 10 according to the present invention, by changing the air permeability of the low air permeability foam 14 provided at the bottom of the cushion body 12, the resilience elastic modulus expressed in the entirety of the seat pad 10, in other words, the dynamic resilience rate. In order to control (ie, vibration characteristics), it is not necessary to change the raw material composition of the cushion body 12 which is the main part. In particular, in the molding of the seat pad 10, changing the composition may cause various manufacturing conditions such as injection temperature, pressure, and rise time at the time of molding to fluctuate. The effect that does not change is significant in achieving stable mass production.

  The low air-permeable foam 14 is a sheet-like polyurethane foam provided at the bottom of the cushion body 12, and by setting the air flow rate low, it absorbs the energy applied as if it were a steel spring. This is a member that improves the vibration characteristics under control. The vibration characteristic thus manifested is defined by the resonance magnification calculated in accordance with JASO B 408 described above ([0004]) in the present invention, and this resonance magnification is at least 4.0 or less. . The resonance characteristic of 4.0 or less is specifically determined by the air permeability and thickness of the low air permeability foam 14.

And air permeability is set to 20 ml / cm < ² > / sec or less by the measuring method based on JISL1096. This value generally defines a low air permeability foam, and the energy absorption behavior does not change significantly in this range. It has been empirically known that favorable results can be obtained especially when the air permeability is ² ml / cm ² / sec or less. If the air permeability exceeds the above-mentioned value, when the occupant sits on the seat pad 10, the air inside the low air-permeable foam 14 easily escapes, and as a result, the required damping characteristics can be exhibited. It will disappear. Moreover, the thickness of the low air permeability foam 14 is set to a range of 5.0 to 40%, preferably 20 to 35% of at least the thickness of the entire seat pad 10. If this thickness is less than 5.0%, even if the low air-permeable foam 14 achieves air permeability of 20 ml / cm ² / sec or less, it cannot achieve suitable vibration absorption like a spring. . On the other hand, when it exceeds 40%, it shifts to the high frequency side of the resonance frequency and approaches the built-in resonance point of 6 Hz, and the improvement in stability due to the reduction of the resonance magnification is offset and the ride comfort deteriorates. End up. Note that the upper limit of the resonance frequency here is the resonance frequency of the human body, and is set to 4.0 Hz, which is empirically known that the ride comfort deteriorates sensuously. In the present invention, the upper limit is 4.0 Hz or less. It defines that ride comfort does not deteriorate. Particularly when the thickness of the low air-permeable foam 14 is set in the range of 20 to 35% of the total thickness of the seat pad 10, the resonance magnification is 3.5 or less, the resonance frequency is 3.8 or less, The seat pad 10 having a dynamic repulsion rate of 40% or less and further suitable riding comfort and vibration absorption can be obtained.

  Since the shape of the low air-permeable foam 14 is a general sheet shape, it can be easily and stably manufactured and mass-produced by any manufacturing method such as slab foaming. Therefore, the low-breathing foam 14 having a wide variety of breathability and thickness can be made on a trial basis without using a required mold as in the seat pad 10 and without requiring troublesome work. For this reason, when evaluating the seat pad 10 having a shape actually used as described above ([0006]), a cushion body 12 having a general and mass-productive composition can be obtained by a conventionally known method which is easy to manufacture. It is possible to easily manufacture the seat pad 10 that achieves a suitable riding comfort for a wide variety of vehicle models by simply manufacturing and integrating the low breathability foam 14 having a wide variety of breathability and thickness. .

  Further, as described above ([0013]), the ride comfort of the seat pad 10 can be expressed by both the hardness of the cushion body 12 and the rebound resilience of the seat pad 10 as a whole. In this case, the cushion body 12 is required to have a hardness according to JASO B 408 of at least 0.01 MPa. If this hardness exceeds 0.01 MPa, the resonance magnification does not become 4.0 or less even if the dynamic repulsion rate described later reaches 45% or less. In addition, the dynamic repulsion rate calculated by a method based on JASO B 408 in the seat pad 10 integrally provided with the low breathability foam 14 that plays a role of keeping the dynamic repulsion rate low under control is at least 45% or less. It is said. It is empirically known that this dynamic repulsion rate basically shows a positive correlation with the resonance magnification in the vibration characteristics. Therefore, when the dynamic repulsion rate exceeds 45%, the resonance magnification also exceeds 4.0 times, and a suitable riding comfort cannot be obtained.

(Example of manufacturing method)
Next, an example of a manufacturing method for suitably manufacturing the seat pad 10 according to the embodiment will be described below. The seat pad 10 according to the embodiment is implemented by a conventionally known manufacturing method, for example, a general method using a mold having an inner contour shape that matches the outer contour shape of the seat pad 10. Prior to injecting the raw material of the cushion body 12, the low-breathing foam 14 is set in a required portion of the mold and the raw material is foamed, so that the volume expansion accompanying the foaming of the raw material and the adhesive action of the raw material Thus, the low air permeability foam 14 is provided integrally with the cushion main body 12. In addition to this, the cushion body 12 is manufactured by a mold having an inner contour shape that matches the outer contour shape of the cushion body 12, and a low-breathing foam is produced by using an adhesive means such as urethane adhesive. 14 may be provided integrally with the cushion body 12.

(Experimental example)
Although the experimental example of the seat pad according to the present invention will be described below, the seat pad according to the present invention is not limited to this. In this experimental example, the polyurethane foam generally used for the seat pad so far is used as the cushion body, and the thickness (mm) shown in Table 1 below and the ratio of the thickness to the total thickness are shown below. Example 1-5 and Comparative Examples 1 to 5 were used by using a low air permeability foam (permeability set to ² ml / cm ² / sec) with a low air permeability foam on the bottom of this polyurethane foam. 3 is manufactured, and the resonance frequency (Hz) and the resonance magnification are calculated from vibration characteristics (1 to 10 Hz, every 0.1 Hz) measured according to JASO B 408 of the seat pad. Calculate the dynamic repulsion rate (%) from the damping characteristics measured according to JASO B 408, and measure the hardness (MPa) of the cushion body measured according to JASO B 408. . The thickness of the seat pad, that is, the total thickness is 115 mm, or a seat pad made of only polyurethane foam made of the same material as that of the cushion body is manufactured as a comparative example, and the same measurement is performed.

(result)
The results of the experiment are also shown in Table 1 above. From the results shown in Table 1, it is easy to provide a low-breathing foam having a ratio (%) of the thickness to the total thickness of 5 to 40% on the bottom surface of a cushion body made of a commonly used polyurethane foam. The resonance magnification calculated from the vibration characteristics of the seat pad is at least 4.0, the resonance frequency is at least 4.0 Hz, and the dynamic repulsion rate is at least 45%. Thus, it was confirmed that a seat pad capable of suitable riding comfort and vibration absorption was obtained. When the thickness ratio is in the range of 20 to 35%, the resonance magnification calculated from the vibration characteristics of the seat pad is at least 3.5 or less, and the resonance frequency is at least 3.8 Hz, It was also confirmed that a more suitable seat pad having a dynamic repulsion rate of at least 40% or less was obtained. Furthermore, since the low-breathable foam is simply provided on the bottom surface of the cushion body provided for normal use, the manufacture of the seat pads according to Examples 1 to 5 and Comparative Examples 1 to 3 was very simple. .

  In view of the above-mentioned problems inherent in the conventional seat pad, the present invention has been proposed to suitably solve this problem. The present invention makes use of various physical characteristics of the seat pad, particularly at the initial pressing stage. By eliminating the strong push-back, a seat pad having a good use feeling and a method for producing the foam can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the seat pad which concerns on the preferred Example of this invention, Comprising: (a) is a perspective view which is notched partially and shows schematically, (b) is bb sectional view taken on the line of (a). It is. It is a longitudinal cross-sectional view which shows the seat pad in which the low air permeability foam is provided over the bottom face whole area of a cushion main body. It is a schematic perspective view of a general vehicle seat. FIGS. 4A and 4B are cross-sectional views schematically showing a configuration of a seat pad according to the prior art. FIG. 4A shows a full-form seat pad, and FIG. 4B shows a spring combined seat pad. It is the schematic which shows the measuring apparatus which measures a vibration characteristic based on JASO B408. It is the schematic which shows the measuring apparatus which measures an attenuation | damping characteristic based on JASO B408.

Explanation of symbols

10 Seat pad 12 Cushion body 14 Low air permeability foam

Claims (6)

Cushion body (12) made of polyurethane foam and constituting the seating part,
A seat pad comprising a sheet-like low air-permeable foam (14) provided integrally on the bottom surface of the cushion body (12),
The resonance magnification calculated from the vibration characteristic of the seat pad (10) measured in accordance with JASO B 408 (performance test method for the pad material of an automobile seat) is at least 4.0 or less. Seat pad to do. A cushion body (12) made of polyurethane foam, constituting a seating portion, and having a hardness measured according to JASO B 408 of at least 0.01 MPa,
A seat pad comprising a sheet-like low air-permeable foam (14) provided integrally on the bottom surface of the cushion body (12),
A seat pad, wherein a dynamic repulsion rate of the seat pad (10) calculated from a method based on JASO B 408 (a performance test method for a pad material of an automobile seat) is at least 45% or less. The seat pad according to claim 1 or 2, wherein the air permeability of the low air permeability foam (14) is set to 20 ml / cm ² / sec or less.   The seat pad according to any one of claims 1 to 3, wherein the thickness of the low air-permeable foam (14) is set in a range of at least 5.0 to 40% of the seat pad (10).   The seat pad according to any one of claims 1 to 4, wherein a resonance frequency calculated from a vibration characteristic of the seat pad (10) is set to at least 4.0 Hz or less. The seat pad according to any one of claims 1 to 5, wherein the low air-permeable foam (14) is disposed only at a buttock portion of an occupant seated on a bottom surface of the cushion body (12).

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