Patent Application
20070246975
The present invention relates to a vehicle seat for use in vehicles of any kind.
Sitting on normal vehicle seats, for example in mass-produced automobiles, can become unpleasant particularly on long drives and following physical exertions before the drive, at high temperatures and/or high relative humidity. Since air is unable to circulate between the body and the vehicle seat, the body starts to perspire there in particular. As a result, moisture collects in the body contact region, and the temperature also rises in this region. This effect is not just unpleasant, but can also contribute to driver fatigue.
A vehicle seat has therefore been proposed, for example in the U.S. patent application No. US 2002/0003362 A1, which provides for ventilation of the body contact areas by means of openings in the sitting area and the backrest through which air is routed onto the body. However, the perspiration is only partially dried in the process, since most of the openings are occluded by the seated body, making it impossible for air to escape from them. The greater the number of openings which are occluded, the greater the air flow through the remaining openings. The air flowing from the remaining openings, for example between the legs, is perceived as unpleasant by some people. It does little to avoid the accumulation of moisture in the body contact region, and poor circulation of air between the body and the vehicle seat continues. Consequently, the temperature in the body contact regions continues to rise over time.
The present invention therefore has for its object to provide a vehicle seat having improved demoistening and simultaneous cooling for a person sitting on the vehicle seat.
This object is achieved by a vehicle seat having the features of the independent claim. Its appendant claims indicate advantageous refinements and elaborations of the invention.
A vehicle seat according to the present invention comprises a seat element where a cushion element is disposed underneath an outer air-vapor-permeable seat cover layer and an air-permeable spacer is disposed between the seat cover and the cushion element. In this connection, the seat element described hereinbelow concerns not just the sitting region of a seat but also the backrest or other elements of a multipart seat structure. The term “central regions” refers to regions in which the body of a human being of average build is in contact with the vehicle seat (“body contact regions”). These central regions are air-impermeable and water-vapor-permeable, since, for example, either the seat cover itself comprises an extremely closely woven fabric or, preferably, an air-impermeable water-vapor-permeable layer is disposed under the seat cover. The seat element, as well as the central region, possesses at least one edge region. If, for example, the sitting region of a vehicle seat is considered, the side cheeks or the front corner region of the seat are referred to as edge regions. The edge regions are usually not in contact with the person sitting on the seat, and advantageously possess an air-permeable seat cover layer.
The air permeability of sheetlike structures is determined according to the European standard EN ISO 9237 (1955) and is reported in I/m2/s. For the purposes of the present invention, air impermeability is defined by a value <0.1 I/m2s Pa. This makes it possible, in the body contact regions, to guide a first air stream underneath the seat cover in a direction parallel to the seat cover without the person sitting on the seat being aware of it. In the edge regions of the vehicle seat, by contrast, air can be passed outwardly through the seat cover.
However, the most important prerequisite is that moisture, for example perspiration, is able to pass through the seat cover. This is readily ensured in the case of textile covers, since textile covers act with regard to moisture like a wick. Standard leather automotive seat covers are barely breathable if at all; that is, they can at best only remove minimal amounts of water vapor. But there are also breathable leathers which, without aperturing, are sufficiently moisture-permeable and therefore useful for seat covers. Instead of vapor-permeable leather covers it is also possible of course to use apertured leather or Alcantara for the seat cover.
A leather cover will typically have its outer surface substantially sealed with a protective layer. The moisture permeability of a leathery seat cover is therefore substantially dependent on the water vapor transport properties of the protective layer. For the purposes of the present invention, the leather cover should preferably have a DIN 53 333 moisture vapor transmission rate (MVTR) of greater than 10 mg/cm2h. Particular preference is given to breathable leathers having an MVTR value of more than 12 mg/cm2h. Such leathers are available for example from leathermakers Lederfabrik Vogl of Mattighofen in Austria. In the case of a nonbreathable, especially fully sealed leather cover, macro- or microaperturing of the cover is also an option. The microapertured leather is a leather having pores, typically produced in a needling operation, ranging in pore diameter from 80 μm to 100 μm. Customary microapertured leathers between 1.9 mm and 2.5 mm thick achieve an MVTR value between 2 and 6 mg/cm2h, which is not satisfactory for the purposes of the present invention, however. Macroapertured leathers, where the holes are visible, achieve MVTR values of >10 mg/cm2h, depending on hole density and hole size, and therefore are more suitable for the purposes of the present invention.
If, then, moisture in the form of perspiration collects between the body of the person sitting on the seat and the vehicle seat (“body contact areas”), it will be conducted away from the body, through the water-vapor-permeable seat cover, owing to a partial pressure difference, and arrives at the spacer. There, the moisture is captured by the first air stream extending parallel to the seat cover and transported away by said first air stream, whereby demoistening and cooling take place in the body contact regions. The seat cover on one side of the spacer and the air-impermeable cushion on the other side define an air-routing passageway for the air guided through the spacer. The spacer is constructed such that the first air stream has a velocity between 10 and 100 cm/s, preferably between 20 and 70 cm/s in the spacer in a direction parallel to the seat cover given a pressure drop between 10 and 50 Pa over 40 cm. In the overwhelming majority of driving situations, however, only much smaller amounts of moisture have to be transported away, so that air velocities are actually significantly lower most of the time. To time-limit the noise development of the fans which is associated with air stream generation, it is advisable to provide a seat temperature closed loop control system similarly to the internal temperature closed loop control system of state of the art vehicle air conditioners. In such a case, for example, the user preselects a desired seat temperature which is then achieved after a short time through automatic continuous closed loop control of the fans. The demoistening and heat conduction lower the temperature at the body contact areas, which the person sitting in the seat directly perceives as a pleasant effect. The arrangement of the spacer directly underneath the seat cover creates short diffusion paths for moisture and good heat conduction.
The seat of the present invention combines this first air stream with a second air stream which emerges from the edge regions of the seat. The fact that the second air stream emerges from the seat cover in edge regions of the seat creates an additional cooling effect which the person sitting in the seat perceives at once. In order that this second air stream does not lead to unpleasant draft phenomena, which each person will perceive differently, the second air stream can preferably be individually reduced, or completely shut off, via a suitable open loop control system. It has been determined that, surprisingly, it is only the combination of the two above-described functionalities which provides a distinctly improved seat comfort which is immediately noticeable. Furthermore, such a vehicle seat possesses a simple construction and is simple to integrate into a sitting and backrest element.
In a particularly preferred elaboration of the present invention, the central region of the vehicle seat comprises a separate water-vapor-permeable air-impermeable layer disposed between the spacer and the seat cover. Suitable materials for the air-impermeable water-vapor-permeable layer are in particular polyurethane (PU), polypropylene and polyesters, including polyether esters and their laminates, as described in US-A-4,725,418 and US-A-4,493,870. Particular preference, however, is given to expanded microporous polytetrafluoroethylene (ePTFE) as described for example in US-A-3,953,566 and US-A-4,187,390. This layer can be a textile or a membrane or a membrane laminate, in which case the membrane is advantageously for example microporous (e.g., ePTFE) or monolithic (e.g., PU). When the membrane used is a microporous membrane of expanded polytetrafluoroethylene (ePTFE), it preferably has a thickness between 10 and 150 μm and a porosity between 70 and 85%. Microporous refers to a layer whose average pore size is between about 0.1 μm and about 2.0 μm. The pore size can be measured using a Coulter Porometer (trade name), which is manufactured by Coulter Electronics, Inc., Hialeath, Fla., USA.
The microporous membrane further has an RET value between 4.0 and 6.0 m2Pa/W. The RET value defines a water vapor transmission resistance as a specific material property of textile fabrics and other textile material constructions. The latent heat flow of evaporation through a given area as a consequence of an existing stationary partial pressure is determined. The RET value is determined by means of the Hohenstein skin model experiment described in the September 1987 standard test method Ne. BPI 1.4 of Hohenstein Institute for Clothing Physiology.
The first air stream in the spacer is preferably generated using at least one blowing means. For example, axial and radial fans developed by Papst specifically for the vehicle sector can be used as blowing means. A blowing means of low power, for example 0.5 to 2 W, is sufficient for this air stream in the spacer. The blowing means can be operated via the vehicle's battery, even when the engine is switched off. The blowing means can for example turn on automatically when the vehicle is unlocked. Activation through remote control or time switching is likewise possible. Similarly, cycling of the blowing means can be sensible, in which case the cycling frequency and the cooling time per cycle can be adjusted automatically as a function of the seat temperature.
The edge regions of the vehicle seat, normally without body contact, advantageously utilize somewhat stronger blowing means, for example at 2 to 5 W, to generate a sufficient second air stream which is blown outwardly through the seat cover layer. This air stream in the edge region has a velocity between 5 cm/s and 1 m/s at a pressure drop between 30 and 100 Pa. The seat cover layer in the edge regions is air-permeable, by which is meant for the purposes of the present invention that the air permeability value is greater than 0.1 I/m2s Pa and preferably >0.5 I/m2s Pa. This blowing means is preferably adjustable individually in order that the air stream may be adapted to circumstances and preferences. This includes the option that the blowing means for this region can also be switched off completely if desired, whereby the person sitting on the seat can choose between “no air draft” and “direct air flow”.
The blowing means should be disposed such that they aspirate air from floor vicinity, since the air is cooler there. Preferably, the blowing means are provided in the vicinity of the ventilation outlets of the vehicle which are situated for example underneath the seat, so that air exiting from these outlets, which is cooled and dry in the event of an air conditioner being used, is aspirated. Alternatively, the vehicle seat of the present invention can be connected directly to the air conditioner. In this case, there is no need for separate blowing means for the vehicle seat and a person sitting on the seat can arrange for cold air from the vehicle's air conditioner to flow around him- or herself in the regions without body contact. The air aspirated by the blowing means can also be precooled via separate cooling means, for example a Peltier element.
In every one of the cases described, the air flowing along underneath the body contact regions will be guided away in one or more regions which are sufficiently remote from the aspirating region of the blowing means in order thereby to avoid aspirating the guided-away air, which is in a warmed-up state and contains the moisture removed from the body contact areas.
A particular elaboration provides a conjoint blowing means for generating both the air streams. In this case, the air stream flowing through the seat cover in the regions without body contact can advantageously be individually adjusted via a valve.
Furthermore, the first and second air streams can be generated by a conjoint blowing means. That is, the air flows for example from the middle of the central seating region parallel along the seat cover into the edge regions and from there outwardly through the air-permeable seat cover layer of the edge regions. The air stream in the spacer which is generated by this blowing means can have a very high velocity, since the person sitting on the seat is unable to sense the air stream underneath the seat cover if, as preferred, an air-impermeable layer (a membrane, for example) is disposed between the outer seat cover layer and the spacer.
The spacer between the seat cover and the cushion can be any sheetlike open structure which, on the one hand, permits flow therethrough to remove water vapor passing through the seat cover and which, on the other, is sufficiently flexible and yet pressure stable, so that it does not collapse under the weight of a person sitting on it. Especially three-dimensional textiles are suitable, examples being wovens, drawn-loop knits or formed-loop knits composed of polymeric fibers. But it is also possible to use wovens, drawn-loop knits or formed-loop knits composed of metal fibers. If, for example, a membrane is disposed between the spacer and the seat cover, it can be firmly bonded to the surface of the spacer, for example by stitching or adhering.
In a preferred embodiment of the present invention, the spacer is a three-dimensional formed-loop spacer knit having two outer air-permeable layers. Elements are disposed in between which vertically connect and space the two outer layers. At least the outer layer facing the seat cover consists of mutually adjacent yarns, directly adjacent yarns being in each case locally connected to each other in the horizontal direction. The elements between the outer layers meander between the two layers and are alternately connected to the one outer layer and to the other outer layer.
The formed-loop spacer knit is preferably flexible and consists of polyester, polyamide, polypropylene and/or polyethylene. It is a shape-stable three-dimensional formed-loop fiber knit which is also known as “3D mesh”. For example, Article No. 5911 or 5556 from Müiller Textil of 51674 Wiehl-Drabenderhöhe in Germany can be used. The construction of the formed-loop spacer knit is designed to be very simple. Furthermore, such a formed-loop spacer knit offers sufficient by way of flexibility for a comfortable sitting experience and of pressure stability for a long service life. The simple construction makes it very highly compatible with most seat covers.
The membrane and the formed-loop spacer knit are preferably laminated. To prevent the spacer structure pressing through to the seat cover, a further, finer spacer fabric, for example a nonwoven, can be provided between the formed-loop spacer knit and the seat cover. The nonwoven preferably consists of wool or manufactured fibers or a blend thereof. To continue to ensure reliable removal of moisture, the nonwoven is made as thin as possible and as thick as necessary. Since this nonwoven can be very thin, moisture transport in the formed-loop spacer knit is not significantly impaired. As a result, moisture can continue to advance into the formed-loop spacer knit and be transported away from there. A further advantage of the additional nonwoven is that the sitting comfort provided by the vehicle seat of the present invention is further enhanced.
Seat heating can additionally be integrated in the nonwoven. For example, a network of conductive material, for example carbon, metal or polymeric fibers, can be provided in the nonwoven which are preferably flat and for example 3 mm wide. In regions between the heating wires, the nonwoven can possess gaps in order that water vapor transport may be impaired as little as possible.
The invention will now be more particularly described by way of example with reference to the accompanying drawings, in which
The seat element 2 in the illustrative embodiment depicted further comprises three edge regions 2b, 2c which are typically not body contact regions (side cheeks 2b) or at least regions of low body contact (front thigh support 2c). The body contact regions 2a of the seat element 2 are constructed such that a first air stream 50 can be guided through underneath in a direction parallel to the outer seat cover, although the first air stream 50 cannot escape outwardly in the body contact regions in order that it may not be perceived by a person sitting on the seat. The first air stream 50 can be routed for example though an opening 19 into the central region and be routed out of that region through an opening 20. The arrangement of the air inlets and outlets can also be chosen differently. It is only in the edge regions where a second air stream 60 can be generated to pass outwardly through the seat cover.
Air is actively flowed through the formed-loop spacer knit 6 in order that the removal of water vapor passing through the seat cover 30 may be made possible.
This keeps the partial pressure difference, acting as driving force for water vapor transport between seat surface and air passageway, at a maximum. The reverse side of the formed-loop spacer knit 6 bears against the cushion 7, which is a closed-cell pad of foam for example. The first air stream 50, which is routed through the formed-loop spacer knit 6 and which is depicted by the thinner arrows in
The material used for the water-vapor-permeable seat cover layer 4 can be breathable leather, apertured leather, micrbfibers such as Alcantara or a woven textile cover. The seat cover layer 4 should preferably have an RET value in the range from 5 to 20 m2Pa/W.
The water-vapor-permeable air-impermeable layer 5 can be for example a microporous or monolithic membrane or a laminate of for example polyurethane, polypropylene and polyester, including polyether ester. Such a membrane 5 is relatively thin compared with the seat cover layer 4 and, in the case of a microporous membrane composed of expanded polytetrafluoroethylene (ePTFE), can possess a thickness between 10 and 150 μm and a porosity between 70 and 85%.
The formed-loop spacer knit 6 can be any open structure which, on the one hand, is flexible (in order that the seat 1 may be endowed with a pleasant seat comfort), but which, on the other, is not completely compressible, so that through-ventilation of the formed-loop spacer knit 6 is ensured under all circumstances. The formed-loop spacer knit possesses a thickness between 2 and 20 mm, preferably between 5 and 12 mm and more preferably of about 10 mm. A particularly preferred formed-loop spacer knit will be described hereinbelow with reference to
Preferably, in the cheek regions 2b, a nonwoven layer (not depicted) is provided between the seat cover 40 of the edge region and the formed-loop spacer knit 6, only in the regions of the blower. This additional nonwoven layer serves as a rebound layer for the second air stream 60 generated by the ventilators and supports a uniform distribution of air in order that air is flowed through the seat cover 40 not just in the regions of the blowing means. The cheek regions 2b of the vehicle seat 1, which for the purposes of the present invention are not body contact regions, therefore make it possible for a second air stream 60 to be blown outwardly through the seat cover 40 over the entire area. It is preferable to use more powerful blowing means 9 for this, for example ventilators rated between 2 and 5 W, which, as is evident from a combined showing of
The vehicle floor 21 is indicated underneath the seat element shown in
The passageway formed between the two outer layers 12 of the formed-loop spacer knit 6 has a cross-sectional area of 30 cm2 for example. To compute the requisite velocity for the first air stream 50 underneath the central region having body contact, the body contact area is assumed to be 0.28 m2 on average and the maximum rate of perspiration is set at 100 g/m2h. Multiplying these two values gives an in-seat perspiration rate of 28 g/h. The relative humidity is for example 35% at the passageway inlet and for example 50% at the passageway outlet, the temperature being assumed to be constant. Under these conditions there is a difference of about 3.0 g/m3 in the moisture content of the air between entry into and exit from the passageway. From the perspiration rate and the humidity difference it is possible to compute that an air stream of 9.3 m3/h, i.e., 2.6 I/s, is required in the passageway. Hence the air stream velocity required in the passageway is 0.86 m/s. The illustratively calculated air stream velocity is deliberately high by virtue of the conservative assumptions. In practice, lower velocities will also be found to be sufficient most of the time, since such high perspiration rates are reached only for a limited period. Furthermore, the seat cover buffers the moisture for a certain period, spreading the moisture removal over a longer period.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/EP05/11400 | Oct 2005 | EP | regional |
| 10/2004 052 076.3 | Oct 2004 | DE | national |
