DE102008010740B3 - Airbag module for protecting passenger of motor vehicle during accident situation, has cooling device with openable reservoir for storing cooling agent, where cooling agent arrives in contact with gas for cooling gas - Google Patents

Abstract

The module (1) has an inflatable gas bag (2) for being filled with gas for protection of a passenger, and a gas generator (3) for producing the gas utilized for inflating the gas bag. A cooling device (5) has an openable reservoir (5a) for storing a cooling agent (K) e.g. 1, 2-Propandiol, where the cooling agent arrives in contact with the gas for cooling the gas. The cooling agent has an additional substance e.g. sugar or sugar substitute such as saccharose, sorbitol, xylitol, maltitol, lactit, isomalt, fructose, erythritol, cyclamate, glucose and acesulfam, for freezing point depression. An independent claim is also included for a method for cooling a gas used for inflating a gas bag in an airbag module of a motor vehicle.

Description

The The invention relates to an airbag module for a motor vehicle after The preamble of claim 1, a method for cooling a for inflating a Airbags in an airbag module for a motor vehicle used gas by means of a coolant according to the generic term of claim 10 and the use of a propanediol as a coolant according to the claim 11th

From the DE 10 2006 010 953 A1 an airbag module according to the preamble of claim 1 is known, in which a coolant is used in a cooling device for cooling a gas to be used for inflating a gas bag. However, the coolant is not specified in more detail.

From the WO 2007/141 335 A1 a gas generator with integrated cooling device is known in which glycol (ethylene glycol, 1,2-ethanediol) is used as a coolant. However, 1,2-ethanediol has unfavorable toxicological properties.

The DE 198 49 027 A1 describes a method for igniting an airbag provided with a gas generator controlled by a power control device. In the method, if necessary, coolant is introduced into the gas flowing out of the gas generator in order to control the power delivery of the gas generator as needed.

Of the The present invention is based on the object, an airbag module for a To provide motor vehicle in which a coolant with favorable toxicological properties is used.

These Task is with an airbag module with the features of the claim 1 solved. Such an airbag module for a motor vehicle has an airbag, which serves to protect a Inmates inflatable with gas. Furthermore, in the airbag module a Gas generator for generating the intended for inflating the airbag Gases and an additional cooler provided, which is a reservoir for storing a coolant includes. The reservoir can be opened be, for. B. at or after inflation of the airbag, so that the coolant for cooling the gas used to inflate the gas bag in contact with this can occur. According to the invention, it is provided that the coolant has at least one propanediol.

When possible Propanediols are, for example, 1,2-propanediol and 1,3-propanediol into consideration, in particular the use of 1,2-propanediol provided is. Mixtures of 1,2-propanediol and 1,3-propanediol are also conceivable.

In order to minimize the use of propane diol and at the same time to ensure good viscosity properties of the coolant, the coolant in one variant has a mixture of 1,2-propanediol and water. It is provided in a variant that the coolant consists exclusively of water and 1,2-propanediol (propylene glycol, C ₃ H ₈ O ₂ ).

In an embodiment is the mass ratio of 1,2-propanediol to water about 0.5 to about 5, especially about 0.75 to about 3, and most preferably about 1 to about 2.5. In these mixing ratios can be prepared particularly well usable propylene glycol-water mixtures, on the one hand have a sufficiently low freezing point and on the other hand are not too viscous and at the same time evaporate well, if they are with a hot one Gas in contact come. in principle is due to the evaporation of the coolant, including Evaporation enthalpy must be applied, the hot gas, which serves as an energy provider, deprived of energy. That is, through the evaporation of the coolant cools the hot Gas, which is used to inflate the airbag, from. mixtures 1,2-propaldiol and water require sufficient Amount of enthalpy of vaporization, so that the desired cooling effect in a favorable way entry.

In a further embodiment, it is provided that a further substance is used to lower the freezing point of the coolant. That is, in this case, the coolant would consist of at least two substances if no water is used, and of at least three substances, although water is contained in the coolant. It is - depending on the amount of added further substance for freezing point depression - in a variant possible to lower the proportion of propane in the coolant to a particularly low value or even let it go to zero. The further substance for lowering the freezing point serves to maintain a liquid state of aggregation of the coolant even at temperatures which are significantly below the freezing point of pure water. Thus, the coolant and consequently the entire airbag module remains even at low temperatures, as shown for example in Win dominate, operational. At the same time, the further substance for lowering the freezing point is to be selected such that it substantially does not impair evaporation of the other substances of the coolant and, if appropriate, can itself easily be vaporized. Also, the other substance should have similar good toxicological properties as the propanediol used to keep the consequences of skin contact or inhalation of aerosol, which is basically possible after the triggering of an airbag, on a non-harmful level for the vehicle occupants.

In a variant is used as another substance for freezing point depression a sugar or a sugar substitute used. Sugar or Sugar substitutes are toxicologically usually classified as favorable, as they are also used as nutritional supplements.

For example Is it possible, as sugar or sugar substitute sucrose, sorbitol, xylitol, Maltitol, lactitol, isomalt, fructose, erythritol, cyclamate, glucose and / or To use acesulfame K. Mixtures of these substances are also possible.

Either by the propanediol used and optionally by the used further substance for freezing point depression is carried out a lowering of the freezing point of the coolant relative to the Freezing point of pure water. This is the freezing point of the coolant in a variant at or below about -40 ° C, especially at or below from about -38 ° C, in particular at or below about -35 ° C and completely especially at or below about -30 ° C. This ensures that that even at low outside temperatures the functionality the airbag module or the efficiency of the cooling of the exiting hot gases not impaired becomes.

In the evaporation of the coolant as a result of contact with the hot gases that are generated to inflate the airbag, it may in principle come to a mist. In order to keep this fog formation as low as possible or to avoid altogether, in one embodiment of the airbag module an additive for reducing or preventing mist formation is added to the coolant. As such additive, for example, a mixture of polyethylene glycol and silica, in particular with more than 95 wt .-% polyethylene glycol and less than 3 wt .-% of silica, z. As known under the trade name POLYOX ^™ WSR 301.

The The invention also relates to a method for cooling a for inflating a Airbag in an airbag module for a motor vehicle used gas by means of a coolant with the features of claim 10. This coolant is in one cooler included, with the cooling device an openable reservoir for storing the coolant includes. This reservoir is, for. B. at or after inflation of the airbag, opened, causing the coolant for cooling of the gas comes in contact with the gas. It is according to the invention provided that the coolant has at least one propanediol.

Regarding further Variants or embodiments of the method is based on the above Explanations to Variants and embodiments of the airbag module referenced in analogous manner also apply to the claimed method.

The Invention relates to this In addition, the use of a propanediol as a coolant for cooling a gas which is used to inflate a gas bag in an airbag module for a Motor vehicle is used, according to claim 11.

In A variant of the use is the coolant in a cooling device contain an openable reservoir for storing the coolant having. The reservoir is intended and aligned (at or after inflation of the airbag) to be opened, so that the coolant for cooling the gas used to inflate the gas bag in contact with this gas can occur.

Regarding further variants or embodiments the use of a propanediol as a coolant is based on the above Explanations referred to the variants or embodiments of the airbag module, apply in an analogous manner to the claimed use are.

Further Details of the invention are based on a shown in a figure embodiment explained become. It shows:

1 a schematic sectional view through an airbag module.

The 1 shows a schematic sectional view of an airbag module 1 that has a gas bag 2 which is inflatable to protect a person, and a gas generator 3 that's for inflating the airbag 2 provides required gas. For this purpose, the gas generator 3 a detonator 3a on, which can be controlled via a vehicle-mounted control electronics. The gas bag 2 and the gas generator 3 of the airbag module 1 are on a generator carrier 4 fixed, together with one adjacent to the gas generator 3 arranged cooling device 5 which is used to cool the airbag to inflate 2 used gas serves.

The sectional plane of the in the 1 shown airbag module 1 runs - based on a built-in steering wheel state of the airbag module 1 - Parallel to a steering axis of the steering wheel (not shown).

The gas bag 2 has an inflow opening, through which into an interior I of the airbag 2 Gas from the gas generator 3 for inflating the airbag 2 can be initiated.

The cooling device 5 includes a reservoir 5a for storing a coolant K which is liquid in the working temperature range of the airbag module (from approx. + 85 ° C. to approx. -40 ° C.) and which flows through an outflow opening 5b in the interior I of the airbag 2 can get. The coolant K is a mixture of water and 1,2-propanediol (propylene glycol). The vaporization of this coolant produces a toxicologically harmless vapor, so that even with skin contact with this vapor or with an oral intake of steam or a corresponding aerosol no serious consequences for a vehicle occupant are to be feared.

The discharge opening 5b is designed nozzle-shaped, so that the coolant K, when it comes out of the reservoir 5a through the discharge opening 5b in an outflow direction R in the interior I of the airbag 2 is introduced, is atomized, that is, is fractionated into small droplets.

For squeezing the coolant K from the reservoir 5a the cooling device 5 For example, various methods known in the art may be used. It is always a closure V, which is the outflow 5b in the non-activated state of the airbag module closes, opened. This can be done, for example, by one in the reservoir 5a generated overpressure happen. It is also possible to use a reversibly openable or (re) closable valve as the closure V of the outflow opening 5b use.

Since at constant volume, the pressure in the gas bag 2 is located in the gas bag is proportional to the temperature of the gas is, by cooling a reduction in the gas bag 2 prevailing gas pressure achieved. That is, by means of the controllable cooling of the gas bag 2 located gas, the gas bag 2 adapted to a specific accident situation.

Of the cooling effect occurs by the fact that the coolant K atomized is and by the hot, in the interior I located gas is evaporated, the temperature of the gas is lowered because of the conversion of the liquid phase of the coolant in the gaseous Phase, that is to provide needed Enthalpy of evaporation, energy must be applied.

Basically the most diverse airbag designs conceivable in which a Coolant, which at least one propanediol, can be used.

In the following, various examples of possible coolant compositions are presented in tabular form. Table 1: Various mixtures of 1,2-propanediol and water suitable for use as a coolant in an air bag. example Of water / g 1,2-propanediol / g freezing point 1 3.3 6.7 -40 ° C 2 3.6 6.4 -38 ° C 3 4.0 6.0 -35 ° C 4 5.0 5.0 -30 ° C

These water-1,2-propanediol mixtures each represent 10 g of a coolant. Here is the mass of 10 g only by way of example; In a corresponding airbag module in each case more or less coolant may be included. Table 2: Examples of water-1,2-propanediol-sugar mixtures which are suitable as coolant in an airbag module. example Of water / g 1,2-propanediol / g sugar metabolism freezing point 1 3.9 1.5 4.6 -40 ° C 2 3.7 0.7 5.6 -35 ° C

Also in the exemplary water-1,2-propanediol-sugar mixtures shown in Table 2 each is about 10 g of a coolant, wherein in an airbag module also a bigger one or one lower mass of a coolant can be used. As a sugar, for example, are the listed above Sugar and sugar substitutes, with the sugars as possible a high solubility in water so that the coolant is a homogeneous liquid mixture, which is free of solids represents.

1

airbag module

2

airbag

3

inflator

4

generator support

5

cooler

5a

reservoir

5b

Outlet opening interior of the gas bag

K

coolant

R

outflow of the coolant

V

shutter

Claims (12)

Airbag module for a motor vehicle, with - a gas bag ( 2 ) which is inflatable to protect an occupant with gas, - a gas generator ( 3 ) for generating the for inflating the airbag ( 2 ), and - an additional cooling device ( 5 ), which has an openable reservoir ( 5a ) for storing a coolant (K), wherein the reservoir ( 5a ) is adapted to be opened, so that the coolant (K) for cooling the airbag to inflate ( 2 ) used gas can come into contact with this, characterized in that the coolant (K) comprises at least one propanediol. Airbag module according to claim 1, characterized in that the propanediol is 1,2-propanediol. Airbag module according to claim 1 or 2, characterized that the coolant (K) has a mixture of 1,2-propanediol and water. Airbag module according to claim 3, characterized in that that the mass ratio of 1,2-propanediol to water 0.5 to 5, especially 0.75 to 3 and especially 1 to 2.5. Airbag module according to one of the preceding claims, characterized characterized in that the coolant (K) has at least one further substance for freezing point depression. Airbag module according to claim 5, characterized in that that the further substance is a sugar or a sugar substitute is. Airbag module according to claim 6, characterized in that that the sugar or the sugar substitute is selected from the group comprising sucrose, sorbitol, xylitol, maltitol, lactitol, Isomalt, fructose, erythritol, cyclamate, glucose and acesulfame K. Airbag module according to one of the preceding claims, characterized characterized in that the freezing point of the coolant (K) at or below of -40 ° C, in particular at or below -38 ° C, in particular at or below -35 ° C and all over especially at or below -30 ° C. Airbag module according to one of the preceding claims, characterized characterized in that the coolant (K) an additive for reducing or preventing fogging at an evaporation of the coolant (K) having. Method for cooling a gas bag to inflate ( 2 ) in an airbag module ( 1 ) used for a motor vehicle by means of a coolant (K), which in a cooling device ( 5 ), the cooling device ( 5 ) an openable reservoir ( 5a ) for storing the coolant (K) and wherein the reservoir ( 5a ) is opened, so that the coolant (K) for cooling the airbag for inflating ( 2 ) used gas comes into contact with this, characterized in that the coolant (K) comprises at least one propanediol. Use of a propanediol as coolant (K) for cooling an airbag for inflating ( 2 ) in an airbag module ( 1 ) used for a motor vehicle gas. Use according to claim 11, characterized in that the coolant (K) in a cooling device ( 5 ) containing an openable reservoir ( 5a ) for storing the coolant (K), wherein the reservoir ( 5a ) is adapted to be opened, so that the coolant (K) for cooling the airbag to inflate ( 2 ) used gas can come into contact with this.