DE20314133U1 - Connecting system for pipes and suchlike carrying especially carbon dioxide under pressure has co-relationship between cross section of non-compressed circumferential seal, groove depth and gap width as well as groove length - Google Patents

Abstract

A connecting system for pipes, fittings and units for the carrying of pressurized media has a first (1) and second (2) coupling section, and an elastomer, gas-permeable seal (3) fitted in a groove (4). The connecting system for pipes, fittings and units for the carrying of pressurized media has a first (1) and second (2) coupling section, and an elastomer, gas-permeable seal (3) fitted in a groove (4). The cross section of the non-compressed seal, the groove depth (T) and gap width (s) as well as the groove length are co-related in such a way that in a ratio of a permeation-effective partial circumferential surface of the seal to the contact length, determining a permeation through the seal, the partial circumferential face is not greater than half the value of a cross sectional face of the deformed seal extending perpendicularly to the axial direction (X-X). An independent claim is included for a circumferential seal for a connecting system.

Description

The present invention relates to a connection system for Pipes, fittings or units that are used to guide one with one versus one Comparative pressure increased Pressurized fluids are intended, especially for carbon dioxide premier Systems comprising a first coupling part, such as a housing part, an insertable into the first coupling part along an axis second coupling part, such as a plug part, and at least one made of an elastomer, gas permeable peripheral seal, the arranged in a groove having a groove depth and a groove length which is circumferentially in one is formed of the two coupling parts, the one coupling part with a shaft in a round receiving opening of the other coupling part is insertable, the peripheral seal after insertion under deformation and generating a radial prepress a gap with a Gap width between the outer radius of the shaft and the inner radius of the receiving opening seals while doing so at least about one perpendicular to the respective radius of the coupling parts in the axial Direction of contact length rests on the coupling parts.

The need for a seal arises everywhere wherever rooms with different pressures must be separated from each other. The pressure difference in a connection system creates the type described above in the gap between the coupling parts a current which are prevented by using the peripheral seal should. For such seals are predominantly elastomeric materials in fluid technology, e.g. in the form of O-rings. Prerequisite for achievement the sealing effect is the presence of a pre-pressing force or Preload against the surfaces to be sealed, taking advantage of of formula elasticity the seal is created when it is installed.

A system that is used to manage a is pressurized fluid is determined in motor vehicles for example the refrigeration cycle of air conditioning systems. In such a system so far, different Halo-hydrocarbon compounds, like one known under the name R134a, consisting mainly of tetrafluoroethane Refrigerant used. Since all organic substances are gas-permeable, it is used in spite of use of seals - mainly as a result from permeation through the peripheral seal - to an inevitable fluid flow of the refrigerant from the space of the higher in the space of the lower pressure (partial pressure).

It is known that the by Leakage caused by the operating conditions of the System, such as pressure and temperature, the permeability of the connection system used elastomer seals and the seal geometry determined becomes.

The permeability in turn depends on the material and becomes causal through solubility of the fluid and its rate of diffusion in the sealing material affected. It is assumed that the side of the higher Pressure on the seal an absorption, then within the seal a diffusion and finally desorption occurs on the lower pressure side. in the stationary Condition, i.e. when saturated of the elastomer with the fluid, the absorption and the desorption process through Henry's law and the diffusion process described by Fick's first law.

To determine the amount occurring Q of the permeation through the peripheral seal Fluids are based on these laws - as described in DIN 53 536 - on the Equation.

from, in which P is the permeation constant of the sealing material, t is the underlying time, for example one year, Δp is the pressure difference to be sealed between an increased pressure p _{1 of} the fluid to be sealed and a comparison pressure p ₂ and A / L is a ratio of the cross-sectional area A of the deformed peripheral seal represents a permeation length L through the seal, the latter being determined by the axial longitudinal extent of the deformed seal between the two coupling parts. The equation is based on the fact that the seal is conceived as a plane-parallel plate. The equation illustrates a linear, proportional dependency of the amount Q of the fluid passed through the circumferential seal - hereinafter also referred to as the leakage amount - on the cross-sectional area A of the deformed circumferential seal and a linear, proportional dependence on the reciprocal of the mean permeation length L, which results from a given system pressure p and the predetermined operating time t to achieve a small leakage quantity Q results in principle from making the cross-sectional area A of the deformed peripheral seal as small as possible and the mean permeation length L as large as possible.

In practice, such are Dimensioning, however, set limits, as to ensure a basic Functionality of the connection system from the point of view the compensation of manufacturing tolerances of the coupling parts Cross sectional area the deformed peripheral seal in a manner opposite to the equation preferably be chosen large got to.

It should also be noted that the permeation constant P has an exponentially increasing Ver run with temperature shows what, for example, in the article "Gas permeability of elastomers" by W. Beckmann in a special print made of rubber + rubber plastics, 44th volume, issue 4/91, pages 323-329, Dr. Alfred Hüthig Verlag, Heidelberg is described.

From the DE 100 47 872 A1 a line connector is known in which, taking into account the principle mentioned, the sealing material is preferred. Execution extends over a length which is much greater than its radially measured seal thickness, which disadvantageously arises in the known system, however, due to the fact that positive connections tend to loosen under pulsating pressure, the seal by means of a self-locking wedge.

With a occurring in the enterprise Refrigerant pressure R134a, the upper level of which is around 30 bar and the lower level is around 3 bar, so far there is a leakage quantity Q of no less achieved and tolerated as 5 to 9 g per year per compound. There the fluorocarbons mentioned have a high so-called greenhouse potential have and with the formation of toxic or irritating fission products dismantled, therefore arises with the multitude of with air conditioning equipped Motor vehicles, currently around twelve million in Germany alone, a high environmental hazard.

Because of this, considerable efforts are being made in motor vehicle technology to replace the known refrigerants with less harmful substances, in particular with carbon dioxide, which occurs naturally in nature and is naturally degradable, for example, through the photosynthesis of plants. The use of carbon dioxide as a refrigerant in an air conditioning system is associated with the advantage of a much higher volumetric flow-related cooling capacity, but also requires the transition to increased pressures and temperatures in the heat exchange processes. An upper level of about 180 bar and a lower level of about 10 bar at a temperature of - 40 ° C are characteristic of the pressure that occurs during operation of a CO ₂ air conditioning system, which exacerbates the problem of sealing shown. The required temperature resistance of the connection in the upper range is 200 ° C, so that very large permeation constants can be expected. In addition, when using carbon dioxide, it must be noted that this has the relatively largest permeation constant for most common sealing materials in a number of gases after nitrogen, oxygen, helium and hydrogen, as can be seen, for example, from a corresponding comparison in the aforementioned article.

In the German utility model DE 200 02 810 U1 described a connection system with a special sealing part, which consists of an elastomer-coated corrugated tube. This sealing part is intended to meet the sealing requirements for gases such as carbon dioxide or hydrogen and to be axially elastic to the extent that it can be used in a conventional plug-in system with axial play. This plug-in coupling has generally proven itself in practice, but in connection with the elastomer-coated metallic sealing elements disadvantageously high plug-in forces and manufacturing tolerances that are difficult to maintain occur.

The present invention lies the task is based on a connection system of the aforementioned Kind of creating that without additional necessary support or assembly aids for the seal, such as a self-locking wedge or the like a small amount of the penetrated by the peripheral seal Fluids under high system pressures, especially under system pressures of up to more than 150 bar and with resistance in the temperature range low from –40 ° C to over 200 ° C insertion forces occurring during assembly and high functional reliability, i.e. a reliable one Compensation of the manufacturing tolerances of the coupling parts guaranteed.

According to the invention, this is achieved by that the Cross section of the unpressed Circumferential seal, the groove depth and the gap width and the groove length in such a way are coordinated that in one, a ratio determining a permeation through the circumferential seal permeation effective partial peripheral surface of the peripheral seal the contact length the partial circumferential area is not bigger than half the value of a perpendicular to the axial direction Cross sectional area the deformed peripheral seal.

The invention is based on the knowledge that it is possible to create a seal by a specific coordination of the above-mentioned variables in a connection system, in which a permeation through the peripheral seal is not due to the ratio of the axial cross-sectional area of the deformed peripheral seal to the axial length of the circumferential seal is determined, but rather by the ratio of a permeable partial circumferential surface of the circumferential seal to the contact length over which the circumferential seal rests in the axial direction on the coupling parts perpendicular to the respective radius of the coupling parts. Furthermore, the invention is based on the knowledge that this partial circumferential surface can be made much smaller than the cross-sectional surface extending in the axial direction by coordinating the sizes mentioned, and this if the reduced ratio of the partial circumferential surface to the contact length when using the known Calculation equation for dimensioning the seal geometry is taken into account, leads to constructive advantages, which are expressed in a reduced maximum plug-in force for a given maximum permissible leakage quantity. If in the inserted state of the coupling parts in the peripheral seal an adjustment of the above Ratio takes place on values that are determined by the fact that the partial circumferential area is not greater than half the value, preferably not greater than one fifth, of the cross-sectional area of the deformed circumferential seal that runs perpendicular to the axial direction, can optimally take into account the adversarial technical requirements mentioned at the beginning be worn. It can even be achieved that the permeable partial circumferential surface is independent of a cord thickness of the unpressed circumferential seal.

For setting the conditions the cross-sectional area perpendicular to the axial direction and the partial circumferential area the deformed peripheral seal to the contact length mentioned can be used as variable, but coordinated sizes of the cross-section of the unpressed peripheral seal, the groove depth, the groove length and selected the gap width become.

This is advantageous Wear that yourself from the sum of the groove depth and gap width a width of the vertical to the axial direction of the cross-sectional area of the deformed peripheral seal results, which determines the compression of the peripheral seal and thus a pre-pressing force, preferably a specific definition of the individual dimensions considering Hertzian Equations for the deformation of elastic bodies can be made. Doing it from the point of view of setting low insertion forces assembly as particularly cheap proven when the cross-section of the peripheral seal in the uncompressed state already has a preform that can be described in that a quotient from an axial main extension and a radial main extension of the seal cross-section has a value of greater than 1, preferably greater than 2, like this e.g. in the case of a ring with an elliptical cross-sectional area Case is.

Furthermore, advantageously considering one possible thermal expansion the circumferential seal as a quotient of one lying in the groove Proportion of the pressed, radial cross section of the circumferential seal and the groove depth and groove length resulting cross-sectional area the groove a degree of filling the Nut be determined over the size of the permeable partial circumferential surface can be controlled is.

Further advantageous design features the invention are in the dependent claims and the following description contain.

Using several preferred embodiments the invention is to be explained in more detail below. Show:

1 in longitudinal section, an illustration of a connection system according to the invention,

2 in longitudinal section, a partial representation of a connection system according to the invention,

3 3 shows a diagrammatic representation of the dependence of the amount of a fluid which is permeated as a result of permeation through a fluid-saturated peripheral seal of a connection system on an area-permeation length ratio,

4 in perspective, sectional representation, two mutually projected embodiments of a peripheral seal for a connection system according to the invention,

5 2 shows a planimetric representation to illustrate an approximation of the apex curvatures of a circumferential seal with an elliptical cross section through circles,

6 in the same representation as in 4 another embodiment of a peripheral seal for a connection system according to the invention,

7 a cross-sectional view of one of the in 6 illustrated peripheral seal similar embodiment of a peripheral seal for a connection system according to the invention,

8th in the same representation as in 2 a partial view of the connection system according to the invention with an embodiment of a peripheral seal according to the type as in 6 and 7 is shown

9 in the same representation as in 5 and 7 , a further embodiment of a peripheral seal for a connection system according to the invention,

10a to 10c in a schematic sectional view, three different embodiments of peripheral seals for a connection system according to the invention with a specific amount of a fluid penetrated by permeation through the respective peripheral seal.

In the various figures of the Drawing are the same and corresponding parts always with the are provided with the same reference numerals and are therefore described in usually only described once.

How it turns out first 1 results, an inventive connection system for fluidic systems, in particular for CO ₂ -containing systems, in the case shown a plug-in coupling, a first coupling part 1 in the form of a housing, one along an axis X-X in the first coupling part 1 insertable second coupling part 2 in the form of a plug part, and at least one, in the embodiment shown two, consisting of an elastomer peripheral seals 3 , The peripheral seals 3 are each in a groove having a groove depth T and a groove length NL 4 arranged, which is circumferentially in one of the two coupling parts 1 . 2 - In the embodiment shown in the second coupling part 2 , the plug part - is formed. The second coupling part 2 has a shaft which is round in cross section in its basic shape 5 on and is thus in a receiving opening which is round in cross section in its basic shape 6 of the first coupling part 1 inserted. The grooves 4 run in the coat of the shaft 5 circumferentially and parallel to each other.

The peripheral seals 3 close a gap after insertion with deformation and generation of a radial pre-pressing force F _V 7 with a gap width s that in 1 not easily recognizable and is therefore only indicated with a reference symbol "(s)" in parentheses. The enlargement in 2 ,

2 also shows that the gap 7 between the outer radius R _{SA of} the shaft 5 and the inner radius R _{OI of} the receiving opening 6 located. The respective peripheral seal 3 closes the gap 7 and lies at least over a perpendicular to the respective radius R _SA , R _{OI of} the coupling parts 1 . 2 Contact length KL on the coupling parts running in the axial direction X – X 1 . 2 on. A width B of the cross-sectional area A _{V of} the deformed peripheral seal that runs perpendicular to the axial direction X-X 3 results from the sum of the groove depth T and the gap width s or from the difference from the inner radius R _{OI of} the receiving opening 6 and the radius R _{SN of} the second coupling part 2 in the area of the bottom of its groove 4 , The cross-sectional area A _V itself results for one between the coupling parts 1 . 2 trained circular ring to A _V = Π * (R ² _OI -R ² _SN ) and is therefore in 2 with a reference symbol "(A _V )" in parentheses below the reference symbol for the width B. The radial cross-sectional area of the compressed peripheral seal 3 is instead marked with the reference symbol A _R.

A permeation through the peripheral seal 3 The determining area-permeation length ratio A _E / KL is determined by a permeable partial circumferential area A _{E of} the peripheral seal 3 formed to the contact length KL. The partial circumferential surface A _E is close to the gap 7 arranged and is by the in 2 (and also 8th ) highlighted in bold, especially not on the coupling parts 1 . 2 adjacent arc line BL of the pressed radial cross-sectional area A _{R of} the deformed peripheral seal 3 certainly. According to the invention, the partial peripheral area A _{E is} not greater than half the value, preferably not greater than one fifth of the cross-sectional area A _{V of} the deformed peripheral seal running perpendicular to the axial direction X-X 3 , The length of the arc line BL assumes the value of the gap width s in the minimum case when the arc curvature disappears. In this case, the cross-section of the uncompressed peripheral seal 3 , the groove depth T and the gap width s and the groove length NL are coordinated with one another in such a way that the permeable partial circumferential surface A _{E is} independent of a cord thickness of the unpressed circumferential seal 3 is. In the maximum case, the arc line BL should not be longer than half the value, preferably a quarter of the value, the width B, ie the sum of the gap width s and the groove depth T.

The plug part is in the 1 shown special embodiment of an inventive connection system in the receiving opening 6 lockable by means of a locking device (not designated as a whole) in the inserted state against loosening. The locking device consists of at least one locking element - in the embodiment shown, two locking elements arranged axially one behind the other on the plug part 8th . 9 - And each with a locking element 8th . 9 interacting locking shoulder 10 , The locking elements 8th . 9 are each one in an annular groove 11 . 12 of the plug part held snap ring. The housing part is made in two parts, consisting of an inner housing part 1a which is the main part of the receiving opening 6 forms, and from one with the inner housing part 1a detachably connectable and the inner housing part 1a essentially comprehensive outer housing part 1b consists. The rest shoulder 10 is single-ended in the entrance area of the receiving opening 6 on the outer housing part 1b educated. As shown, the outer housing part 1b than with the inner housing part 1a screwable union nut.

The second coupling part 2 , i.e. the plug, as well as both the inner housing part 1a , as well as the outer housing part 1b of the first coupling part 1 can preferably consist of metallic materials, in particular of aluminum or high-alloy stainless steel alloys. The peripheral seals 3 can, for example, from a polymeric fluorocarbon compound, from synthetic rubber, such as silicone rubber, NBR or H-NBR, PUR, EPDM, SBR, or the like. consist.

Regarding one as a quotient of one in the groove 4 lying portion of the pressed radial cross section A _{R of} the peripheral seal 3 and the cross-sectional area A _N = T * NL of the groove 4 calculated filling degree FG of the groove 4 it is advantageous for achieving a high sealing effect and thus minimizing the leakage quantity Q if this degree of filling FG is in the range from 58.0 percent to 100.0 percent, preferably from 78.0 percent to 98.0 percent. Considering the possible thermal expansion of the peripheral seal, an extrusion into the gap should be made 7 should be avoided if possible. For a peripheral seal 3 with the in 10a shown cross-sectional shape should the above-mentioned degree of filling FG of the groove 4 in particular be greater than 78.0 percent. With asymmetrical position of the peripheral seal 3 in the groove 4 the same applies to one as a quotient of one in one half of the cross-sectional area A _{N of} the groove 4 lying - in 2 hatched - comparatively larger portion A _{RH of} the pressed radial cross-section A _{R of} the peripheral seal 3 and half the cross-sectional area A _N / 2 of the groove 4 calculated filling degree FGH of the groove 4 , An asymmetrical position of the peripheral seal 3 can be adjusted by the difference Δp between the increased pressure p ₁ and the comparison pressure p ₂ in the axial direction X-X against a wall of the groove 4 ge is pressed while on the other side of the groove 4 still a distance between the wall of the groove 4 and the peripheral seal 3 consists.

By 2 illustrated, each between the peripheral seal 3 and the respective coupling part 1 . 2 Occurring contact relationships can be described with the help of Hertzian equations if circumferential sealing 3 and coupling parts 1 . 2 be understood as elastic bodies. Hertz's equations can be applied to the shape and size of the pressing surface (flattening), to the mutual approximation of the bodies, and to the size and distribution of the compressive stresses that arise under the influence of the preload force F _V , for example, the calculation of the maximum stresses that occur. These equations are first-class elliptical integrals and were determined on the basis of strict elasticity theory.

For the calculation of special cases of the contact of certain bodies with convex, flat or concave surfaces, such as spheres against plates, cylinders against cylinders, etc., special calculation formulas were derived from Hertzian theory peripheral seal 3 on the respective coupling part 1 . 2 considered, can be assumed at the contact point in a first approximation of a contact cylinder against plane. According to the invention, the cylinder is the development of the peripheral seal 3 , and the level is the development of the respective coupling part 1 . 2 , i.e. either the inner surface of the receiving opening 6 or the outer surface of the shaft 5 on the bottom of the groove 4 ,

For a maximum mechanical stress σ _{max that} arises under normal force F _N when there is contact between a cylindrical body with the radius R, which lies over a length L _A on a flat body (with the radius infinity), according to Hertz

where Θ one from the elastic modulus of the two bodies calculated size is which is according to the formula

results in the quantities v _Z and v _{E are} the respective transverse contraction numbers or Poisson constants and E _Z and E _{E are} the respective moduli of elasticity of the cylindrical and the planar body.

Due to the connection system in the assembly of the seal 3 Radially directed pre-pressing force F _V occurring, which corresponds to the normal force F _N in equation (2), the sealing contour is flattened and there is a linear contact over the contact length KL. This forms upon contact between a circumferential seal designed, for example, as an O-ring 3 and the first coupling part 1 over a length L ₁ , which corresponds to the length L _A in equation (2) and which is equal to the inner circumference U _OI = 2 * Π * R _{OI of} the first coupling part 1 is, a contact area F ₁ = 2 * Π * KL * R _OI .

Assuming that the peripheral seal 3 made of an elastomer and the first coupling part 1 is made of metal, so in Equation (3) the summand, which refers to the flat body, is negligible, because it is very small compared to the summand, which is due to the cylindrical, due to the elastic modulus of elasticity, which is much higher for metals than for elastomers Body relates. Furthermore, a cross-contraction number of 0.5 for the quantity v _Z in equation (3) can be expected for elastomers in a first approximation.

For a maximum mechanical stress σ _1max in the contact between the peripheral seal 3 and the first coupling part 1 therefore applies

F _{V is} the preload force acting in the radial direction with which the seal 3 against the first coupling part 1 is pressed, and R _OI the inner radius of the first coupling part 1 , E _D is the value of the elastic modulus of the peripheral seal 3 , R _RS is a measure of the convex curvature of the seal 3 in the radial direction, for example the line radius R _{SO of} an O-ring seal in the uncompressed state, as in 4 and 5 is specified. The maximum mechanical stress σ _1max is according to Hertz 1 . 5 times as large as the specific value of the pretensioning force F _V related to the contact area F _{1 being formed} .

The ab occurring at the point of contact between a cylindrical and a flat body plating AP, with AP as half the contact width - in the present case half the contact length KL - can be in a general form according to Hertz according to the equation

be determined.

Under the above-mentioned boundary conditions, this equation (5) gives the size of the contact length KL ₁ between the inner radius R _{OI of} the first coupling part 1 and the peripheral seal 3 to

For contact between the peripheral seal 3 and the second coupling part 2 can be - a radially inward and outward symmetrical effect of the preload force F _V in the peripheral seal 3 provided - the maximum mechanical stress σ _2max and the contact _length KL ₂ between the radius R _{SN of} the shaft 5 on the bottom of the groove 4 and the peripheral seal 3 determine. In equations (4) and (6) the inner radius R _{OI of} the first coupling part then takes the place 1 the - smaller - radius R _{SN of} the shaft 5 of the second coupling part 2 on the bottom of the groove 4 , The values of the maximum mechanical stress σ _2max and the contact _length KL = KL ₂ will accordingly be greater than the corresponding values σ _1max and KL = KL _1. For the design of the connection system according to the invention, the ratio A _E / KL of the permeation-determining partial circumferential surface area A _{E is} deformed peripheral seal 3 for the contact length KL, the smaller value KL = KL ₁ must be taken into account.

Equation (6) also illustrates that an increase in the contact length KL results either from an increase in the preload force F _V or from an increase in the radius of curvature R _RS in the cross section of the undeformed peripheral seal 3 or by reducing the elastic modulus E _{D of} the sealing material or by a smaller inner radius R _{OI of} the first coupling part 1 can bring about.

With regard to the increase in the preload force F _V , it must be noted that the magnitude of the preload force F _V when the shaft is inserted 5 with the one already in the groove 4 arranged circumferential seal 3 Using the relationship F _S = μ * F _V , with μ as an integral coefficient of friction, which is only generally mentioned here, influences the necessary insertion force F _{S in the} same direction and therefore - not in a gradation corresponding to the diameter of the seal - does not exceed a predetermined value should. Thus one expects, for example, known to be at nominal diameters of 12 mm with required maximum insertion forces F _S of less than 50 N, even preferably less than 10 N. For larger nominal diameters or for small nominal diameter, but with the relevant CO ₂ pressure range, occur more insertion forces F _S that can reach more than 100 N and 120 N. Such insertion forces F _S can be avoided according to the invention and can advantageously be achieved for inner radii R _{OI of} the first coupling part 1 in the range of approximately 6 mm to 13 mm insertion forces F _S of less than 100 N, preferably less than 50 N and even less than 30 N. ,

According to the invention, the cross section AU _R , or also AU _E in 4 , AU in 6 to 8th or AU _opt in 9 , the unpressed peripheral seal 3 , the groove depth T, the groove length NL and the gap width s are specially matched to one another, so that only small insertion forces F _S occur during assembly and that with a small amount Q of the circumferential seal 3 of a fluid throughput system according to the invention under high system pressure differences Δp, in particular under system pressures p ₁ of up to more than 150 bar or 180 bar, a reliable compensation of the manufacturing tolerances of the coupling parts 1 . 2 he follows. The relationships described above, in particular equation (6), can be taken into account in a preferred manner in this coordination.

The way in which the cross section AU _R , AU _E , AU or AU _{opt of} the unpressed peripheral seal is tuned according to the invention 3 , Groove depth T, groove length NL and gap width s illustrated one on top of the other 3 , in which - as already mentioned - a diagram is shown which shows the dependence of the quantity Q of a fluid which is due to permeation through a known peripheral seal saturated with fluid or peripheral seal according to the invention 3 of a connection system with a gas-permeable peripheral seal is achieved, from a ratio A / L of a permeation surface A of the deformed peripheral seal to a permeation length L through the peripheral seal.

The area labeled I in the right-hand part of the diagram illustrates the conditions in the conventionally used circumferential seal dimensioned with the aid of equation (1) explained at the outset, whereby - as described - a linear, proportional dependence of the leakage quantity Q on the perpendicular to the axial Cross-sectional area A of the pressed seal and one oriented in the direction X-X linear, proportional dependence on the reciprocal of the permeation length L is assumed. As for the cross-sectional area A of the deformed circumferential seal that runs perpendicular to the axial direction X-X, this results from a cross-sectional area A _V , as is described with reference to FIG 2 is described above.

With a peripheral seal used according to the invention 3 which - as exemplified in

2 shown - is convex in the axial direction X-X, or with a peripheral seal 3 who - as in 10c shown - is not curved at all in the axial direction X-X, the shortest - and therefore decisive for the permeation - permeation length L is the perpendicular to the respective radius R _SA , R _{OI of} the coupling parts 1 . 2 contact length KL running in the axial direction X – X.

According to the invention, at the ratio A / L of one, the permeation through the peripheral seal 3 determining ratio A _E / KL of the permeable partial peripheral surface A _{E of} the peripheral seal 3 to the contact length KL, with the partial circumferential area A _E in the ratio A _E / KL not being greater than half the value of the cross-sectional area A _{V of} the deformed circumferential seal running perpendicular to the axial direction X-X 3 , This is in the left part of the diagram, in an area that is in 3 is designated by II. In this area II is the amount Q due to permeation through the peripheral seal 3 fluids after penetration of the peripheral seal 3 with fluid significantly lower than would be expected according to the conventional dimensioning method (illustrated by the continuation of the straight line from area I carried out in dashed lines).

The one out 3 Removable value Q ₁ represents a leakage quantity Q of 5 to 9 g per year and connection, as is characteristic for the use of the refrigerant R134a in a motor vehicle air conditioning system. When specifying such a previously tolerated value Q ₁ , a certain operating time t, the operating pressure p ₁ (e.g. 30 bar), taking into account equation (1), a ratio is reached for a certain material, ie on the basis of a certain permeation constant P. (A / L) ₁₁ , with the setting of which the previous technical requirements can be taken into account.

By specifying a lower value Q ₂ than the previously tolerated value Q ₁ , such as 2.5 or 1 g per year and connection, as is sought for the use of CO ₂ as a refrigerant in a motor vehicle air conditioning system, and by specifying the Further variables - the operating time t, the operating pressure p ₁ (for example 180 bar), or the pressure difference Δp, and the permeation constant P - result in a ratio (A / L) ₁₂ taking equation (1) into account. In practice, however, it has been shown that setting this ratio (A / L) ₁₂ can no longer take into account the increased technical requirements. The required low value Q _{2 of} the leakage quantity Q can then only be achieved by measures, such as an excessively long groove and seal length, which cause extraordinarily high insertion forces F _S and cannot be implemented structurally.

In contrast, the invention enables, at low assembly forces F _S, the setting of a ratio A _E / KL which meets the technical requirements - even when a very low leakage value Q _{2 is} specified, as is the case for the use of CO ₂ as a refrigerant in a motor vehicle air conditioning system is demanded - does justice.

In order to achieve the lowest possible values Q _{2 of} the leakage quantity Q; the ratio A _E / KL can preferably be below the in 3 limit G shown.

This limit value G, ie the permeation through the peripheral seal 3 determining ratio A _E / KL, especially for carbon dioxide as a fluid, should not be greater than 50.0 mm at room temperature, preferably not greater than 17.5 mm, at 100 ° C not greater than 4.5 mm, preferably not greater than 1.2 mm, and at 150 ° C not greater than 1.00 mm, preferably not greater than 0.25 mm.

The following will refer to 4 and 5 shown as in that the cross section AU _{E of} the peripheral seal 3 already has an elliptical shape in the uncompressed state, an increase in the contact length KL can be brought about in comparison to an O-ring.

As already mentioned, R _{RS is} a measure of the convex curvature of the peripheral seal 3 and is used with an O-ring as the core in 4 is shown, determined by the cord radius R _{SO of} the circular cross section AU _{R of} the cord. With a peripheral seal 3 that have an ellipse as seen in the circular cross section 5 In contrast, AU _R , as the shape of the cross section AU _E , does not have a uniform curvature over its cross-sectional circumference, since a long semiaxis HA and a short semiaxis HB take the place of the uniform radius of curvature R _{SO of} the circle.

It is now possible to express these semiaxes HA, HB in the sense of a coordinate transformation in relation to the circle radius R _{SO mentioned} by the relationships HA = U * R _SO and HB = V * R _SO . For those in 4 The relationships shown here apply to the transformation factors U, V, for example U ≈ 2 and V = 1, ie HB = R _SO , the inner radius R _I and the outer radius R _{A of} the respective ring of the two mutually projected embodiments of the circumferential seal 3 are the same for both versions.

Furthermore, in a sufficiently precise approximation construction for the ellipse, it is possible to introduce apex curvature circles K1, K2; who are in the area. nestle the crown as much as possible like this 5 shows. It can be shown here that the radii R _K1 and R _{K2 of} the crown crest circles K1, K2 according to the relationships

have it calculated.

In the case shown, the radius R _K2 , which is important with regard to the design of the connection system according to the invention, is therefore four times the value of the radius R _SO of the circle inscribed in the ellipse. Taking into account this value R _K2 as curvature R _RS in equation (6), this means that at constant jacking force F _V, the contact length KL doubled or that, with constant contact length KL, the jacking force F _V, and thus the necessary insertion force F _S to can be reduced by up to a quarter.

Both to achieve a favorable ratio A _V / KL of the cross-sectional area A _{V of} the deformed peripheral seal that runs perpendicular to the axial direction X-X 3 to the contact length KL, as well as to achieve a favorable ratio A _E / KL of the permeation-determining partial peripheral surface A _E to the contact length KL, it is therefore advantageous if the cross section AU _{E of} the peripheral seal 3 already has a preform in the uncompressed state, in which a shape number, a quotient FZ _U = HA / HB from an axial main extension of the sealing cross section AU _E , in the case shown the large semi-axis HA of the ellipse, and a radial main extension, in the illustrated case the small one Semi-axis HB, the ellipse, has a value greater than 1, preferably greater than 2.

This is also the case with the 6 to 8th illustrated further embodiments of a peripheral seal 3 the case for a connection system according to the invention. It is characteristic of these embodiments that the cross section AU of the uncompressed peripheral seal 3 in a symmetrical manner to a central axis Y-Y of two equally large semicircular surfaces KF1, KF2 - it could also be circular segment surfaces - and an intermediate rectangular surface RF.

As in 4 is in 6 and 7 - in contrast to 4 but twice - an O-ring inscribed in the cross-sectional shape shown as a further embodiment. With the radius R _SO, the O-ring determines the main radial extension HB of the cross-section AU of the cord and the curvature in the axial direction X-X. The main axial extent HA results as the side length SL of the half surface of the cross section AU, which has the total axial length GL. The choice of this total length GL - for example in relation to a predetermined groove length NL - represents the size of the radial deformation of the peripheral seal 3 during assembly is another way to check the degree of filling FG of the groove in the compressed state 4 to vary.

As with the peripheral seal 3 with the elliptical cross section ( 4 and 5 ) is also according to 6 to 8th there is no uniform curvature across the cross-sectional circumference. The curvature formed in the radial direction is determined by the rectangular surface RF with the side length GL-2 * R _SO ; and a corresponding radius of curvature takes the value infinity. 8th shows in a similar form as in 2 the net-like, compressed circumferential seal 3 compared to the unpressed peripheral seal 3 , The illustration shows that there is a high degree of filling FG of the groove and that the length of the curved line BL is not greater than half the value of the sum of the gap width s and the groove depth T.

9 shows another, to be considered as optimal execution of a peripheral seal 3 for a connection system according to the invention, which is characterized in that the cross section AU _{opt of} the unpressed peripheral seal 3 in its basic form consists of a rectangle which has two longitudinal sides convexly curved with a first radius of curvature R ₁ , two transverse sides convexly curved with a second radius of curvature R ₂ and four corners convexly rounded with a third radius of curvature R ₃ . The third radius of curvature R ₃ , which determines the arc length BL and influences the degree of filling FG, in particular when the peripheral seal is pressed, is smaller than the first, in particular the contact length KL determining, radius of curvature R, and the first radius of curvature R ₁ is again smaller than the second Radius of curvature R ₂ , which also determines arc length BL and degree of filling FG - but to a lesser extent than the third radius R ₃ . Such a cross-sectional shape allows the groove to be filled with a high degree of filling FG 4 and low pre-pressing force F _V a short arc length BL and thus a smaller permeation-effective partial circumferential surface area A _E can be achieved in comparison with an O-ring or a ring with an elliptical cross-section. In this embodiment too, the cross section AU _{opt of} the peripheral seal 3 in the uncompressed state, a preform in which the shape number, the quotient FZ _U = HA / HB from an axial main extension HA of the sealing cross section AU _opt , and a radial main extension HB have a value of greater than 1, are preferred of greater than 2.

10a to 10c show that depending on the embodiment of the peripheral seal 3 for a specific leakage quantity q, ie for a cross-section A _{V of} the compressed peripheral seal 3 related leakage amount Q due to permeation through the respective peripheral seal 3 enforced fluid, a different profile of the course of the specific leakage q sets, that of the shape of the cross section A _{V of} the compressed peripheral seal 3 is dependent.

10a shows a pressed O-ring OR. Such an O-ring OR forms with a ratio of the inside diameter 2 * R _I to the strength of its cord 2 * R _SO of ≤ 6, preferably <3, and a strong minimum compression VP, ie with a value VP = 100% * ( 1 – B / (2 * R _SO )) of more than 15 percent, preferably more than 25 percent up to a maximum of 40 percent, in the assembled state a much more pronounced oval than a standard O-ring under normal compression VP. This means that the cross section AU _{R of} the unpressed O-ring OR, the groove depth T and the gap width s are matched to one another in such a way that a contact length KL is established which is suitable for an optimal value of the ratio A _E / KL, ie below of the limit value G in 3 , i.e. in area II.

10b shows a peripheral seal 3 with a contact length KL, which is already longer than an O-ring OR, due to the geometrical design of its cross section in the uncompressed state. With such a peripheral seal 3 which - like the execution according to 4 and 5 with the elliptical cross section AU _E and the designs according to 6 to 8th such as 9 - In the assembled state, there is no need to press more than a standard O-ring, the assembly forces and also the expansion required during assembly can be kept low. Also, the peril is the perimeter seal 3 damaged during assembly or out of the groove 4 tearing out, less than with the O-ring OR with a circular cross-section.

10c shows a peripheral seal 3 with a rectangular cross-sectional area A _V in the compressed state. The sides of the rectangle lying in the axial direction X-X are longer than the sides of the rectangle lying in the radial direction. If such a circumferential seal is introduced into a groove, the permeable partial circumferential surface A _{E is} independent of the cord thickness of the unpressed circumferential seal and the arc line BL assumes the value of the gap width s.

In all embodiments of the peripheral seal 3 the shortest permeation length L is the contact length KL over which the peripheral seal 3 on the respective coupling part 1 . 2 is applied. The largest permeation length L is in 10a to 10c designated L _max . From the profiles of the specific leakage quantity q it becomes clear that by extending the contact length KL the permeation path L and thus the total leakage quantity Q, which is due to integration of the specific leakage quantity q over the cross section A _V as the area shown in the figures below the curve q results, can be reduced.

The difference between the largest permeation length L _max and the contact length KL increases from 10a up to 10c from. At the in 10c shown execution of the peripheral seal 3 , which is to be regarded as the optimum from the point of view of a small leakage quantity Q, the largest permeation length L _{max is} identical to the contact length KL. In the 10c The shape shown, in particular a rectangle as a compressed radial cross section A _R , which has a greater side length in the axial direction X - X than in the radial direction, therefore appears to be particularly advantageous. In the 10b and 10c Versions shown can also be assumed that the cross section of the peripheral seal 3 in the unpressed state - analogous to the cross section AU _E in the version according to 4 and 5 , analogous to the cross section AU in the versions according to 6 and 7 and analogous to the cross section AU _opt in the version according to 9 Already has a preform in which the quotient FZ _U = HA / HB has a value of greater than 1, preferably greater than 2, from an axial main extent of the sealing cross section and a radial main extent. However, it must be mentioned that the conditions during assembly, especially the pressing, the filling of the groove 4 and the size of the assembly force F _S - as with the purely rectangular shape - can be made more unfavorable than with another cross section.

On the one hand, for insertion forces F _S of approximately 120 no, the value Q _{2 of} the quantity Q was due to permeation through the peripheral seal 3 fluids of less than 2.5 g per year and connection, in particular less than 1 g per year and connection of an O-ring 8.0 × 5.0 consisting of N-NBR with an average compression VP of 25.0 Percent reached, the latter fluctuating in the range of 21.2 percent to 27.4 percent due to tolerance. The average degree of filling FG of the groove 4 was 86.0 percent and was able to fluctuate in the range from 78.2 percent to 92.1 percent. The axial length NL of the groove 4 was 5.8 mm, the depth T of the groove 4 in the range from 3.47 mm to 3.63 mm, the gap width s was in the range from 0.05 mm to 0.25 mm, the inner radius R _{OI of} the receiving opening 6 was 7.75 mm, the radius R _{SN of} the shaft 5 on the bottom of the groove 4 at 4.0 mm and the radius R _{SO of} the cord of the cross section AU _R in the uncompressed state at 2.5 mm. A contact length KL of about 4.5 mm was formed at room temperature.

On the other hand, in contrast to the greatly reduced insertion forces F _S (less than 60 N), an equally low value Q _{2 of} the leakage amount Q was achieved by an oval ring likewise made of H-NBR with an average pressing VP of 22.5 percent, the latter in the Range fluctuated from 16.3 percent to 26.8 percent due to tolerance. The ring had a cross-sectional shape in the uncompressed state, such as it in 6 to 8th is shown, the total axial length GL of the cross section AU was 3.55 mm and the radius R _SO was 1.25 mm. The average degree of filling FG of the groove 4 ranged from 58.6 percent to 90.0 percent. The axial length NL of the groove 4 was 4.9 mm, the depth T of the groove 4 in the range from 3.47 mm to 3.63 mm, the gap width s was in the range from 0.05 mm to 0.25 mm, the inner radius R _{OI of} the receiving opening 6 was 6.2 mm, and the radius R _{SN of} the shaft 5 on the bottom of the groove 4 at 4.35 mm. A contact length KL of about 3.9 mm was formed at room temperature.

Although in the representations in 10a to 10c no groove 4 shown, however, the corresponding relationships apply to the contact length even in the presence of a groove. It can also be deduced from this that a connection system according to the invention has a particularly favorable design if the deformed peripheral seal is in the radial cross section A _R 3 the contact length KL by less than about 15 percent, preferably by less than about 10 percent, particularly preferably by less than about 5 percent, of the maximum axial permeation length L _max through the peripheral seal 3 differs, ie if, for example, the seal 3 a very large radius of curvature in the axial direction, such as the radius R ₂ in 9 , having. This must also be taken into account when dimensioning a cross section AU _E which is elliptical in the unpressed state when determining the length of the semiaxes HA, HB - and taking into account the coordinate transformation when determining the coefficients U and V -.

For a connection system according to the invention, it is also important that a gas leakage flow GLS occurring therein is always made up of two components. On the one hand, this is the amount Q due to permeation through the peripheral seal 3 penetrated fluids, on the other hand there is a possible path for micro leakage currents MQ across the contact length KL, the size of which is determined by the topography of the surfaces of the coupling parts 1 . 2 is determined. An advantageous high seal against the micro leakage currents MQ can be achieved in the connection system according to the invention in that a maximum roughness value R _{max of} the surfaces of the coupling parts 1 . 2 , at least in the area of the outer radius R _{SA of} the shaft 5 and the inner radius R _{OI of} the receiving opening 6 where the peripheral seal 3 is less than 16 μm, preferably less than 10 μm. In particular, an average roughness R _{a should be} in the range from 0.3 to 0.8 μm, which can advantageously be achieved with diameters from 12 to 25 mm in that the surfaces provided with an allowance of 0.018 to 0.040 mm are in the pre-machined area Condition should have a roughness R _a in the range of 1.6 to 3.2 μm, be smooth rolled. The smooth rolling can also optimally form the support profile of the surfaces of the two coupling parts that are in contact with the peripheral seal 1 . 2 can be achieved. The micro leakage flows MQ in the gas leakage flow GLS are then very, in particular negligible, small compared to the amount Q due to permeation through the peripheral seal 3 established fluids.

An advantageous sealing arrangement in a connection system according to the invention also results from the axial connection of a plurality of peripheral seals 3 how to do this for two peripheral seals 3 in 1 is shown, as this extends the contact length KL. Although the effort involved in achieving the larger permeation path - the total contact length KL - is higher than when only one O-ring is used, the uncompressed cross-section AU _{E of which is,} for example, elliptically pre-shaped, such an arrangement can nevertheless be advantageous from a different aspect. For example, with the aging of EPDM as a sealing material under the influence of oxygen, the permeation coefficient P becomes significantly lower. This could be the case, for example, in a series connection of circumferential seals 3 can be exploited by an outer peripheral seal accessible to the ambient atmosphere 3 after a certain operating time t has a reduced permeability coefficient P due to age and the inner peripheral seal 3 with a higher permeability coefficient P from the environmental influences, which can also lead to undesirable embrittlement of the sealing material, is better protected.

The invention is not limited to the exemplary embodiments shown, but also encompasses all embodiments having the same effect in the sense of the invention. For example, it is possible to use the type of connection according to the invention not only - as shown - in a plug-in coupling, but also in systems with block or screw connections. Furthermore, it is possible that only the first coupling part 1 instead of the second coupling part 2 the groove 4 having. Different construction details can be executed differently than shown. For example, in the execution according to 9 the first radius R, larger than the second radius R ₂ can be selected.

The in the 4 to 9 illustrated versions of the peripheral seal 3 with the features described above have an independent inventive meaning.

Finally, other criteria for the tuning according to the invention when determining the cross section AU _R , AU _E , AU, AU _{opt of} the unpressed peripheral seal 3 , the groove depth T, groove length NL and the gap width s, such as, for example, as is known from nomograms, for certain material hardness of the material of the peripheral seals 3 contain a relationship between the gap width s and the operating pressure p ₁ . With regard to equation (6), particular attention should be paid to a possible correlation between the elastic modulus E _D and the Shore A hardness of the material. A Shore A hardness in the range from 70 to 90 has proven to be favorable.

The equations (4) and (6) specified, before the respective root expression, theoretically certain coefficients 0.184 and 0.78 can occur from those occurring in practice Values deviate because of the underlying requirements only approximate Fulfills are. The specifically stated values can therefore be in general form can be expressed by constants C1 and C2 to be determined in each case.

Also the compression VP, in which - as has been shown - the width B is calculated, which in turn results from the ratio of the sum of the groove depth T and the gap width s to the radial main extent of the peripheral seal 3 , such as the small semiaxis HB of the ellipse or the radius R _{SO of} the circle, the Hertz equations - in particular the equation for the approximation of two elastic bodies pressed together - can be used with advantage.

A circumferential seal can be used to reduce permeation 3 of a connection system according to the invention can additionally be provided with a special gas barrier coating, for example a coating with a lubricating coating based on polyurethane or with a spray coating applied permeation-reducing coating, in a preferred thickness range from 15 μm to 60 μm, in particular with an all-round coating of O-rings in a. Thickness range from 20 μm to 30 μm.

Furthermore, the invention is so far also not yet on the combination of features defined in the independent claims limited, but can also be determined by any other combination of certain Characteristics of all of the individual characteristics disclosed are defined his. This means that basically practical each individual feature of claim 1 or 31 omitted or by at least one disclosed elsewhere in the application Single feature can be replaced. In this respect, the claims are only to be understood as a first attempt at formulating an invention.

1

first Coupling part (housing part)

1a

inner housing part

1b

outer housing part

2

second Coupling part (plug part)

3

peripheral seal

4

Groove for 3 in 5

5

Shaft of 2

6

Opening of 1

7

Gap between 1 and 2

8th, 9

locking elements

10

locking shoulder

11 12

Ring grooves for 8th . 9

I

linear Area of dependency Q of A / L

II

nonlinear Area of dependency Q of A / L

A

Permeation surface, deformed axial seal cross section

A _E

Partial circumferential area of 3 , pressed

A _N

Cross section of 4

A _R

radial cross section of 3 deformed

A _V

Cross section of 3 , deformed, perpendicular to the axial direction

A _RH

radial cross section of 3 , deformed in half of 4

AP

flattening

AU

radial cross section of 3 (Execution in 6 and 7 ), unpressed

AU _E

radial cross section of 3 (elliptical), unpressed

AU _opt

radial cross section of 3 , unpressed (version in 9 )

AU _R

radial cross section of 3 (OR), unpressed

(A / L) ₁₁

Ratio value for Q ₁ according to equation (1)

(A / L) ₁₂

Ratio value for Q ₂ according to equation (1)

B

(radial) latitude of A _V

BL

Arc length from A _V

C1, C2

constants

E _D

Modulus of elasticity of 3

E _E

Young's modulus - flat body

E _Z

Young's modulus - more cylindrical body

F _N

normal force

F _V

Prepress force of 3

F _S

Insertion force of 2 With 3

F ₁

Contact area of 3 With 1

FG

Degree of filling of 4

FZ _U

form factor Quotient of HA and HB

G

limit from A / L between I and II

GL

axial overall length from AU

HA

main axial extension of 3 , long elliptical semiaxis

HB

main radial extension of 3 , short elliptical semiaxis

K1, K2

Vertex curvature circles

KF1, KF2

Semicircular areas of AU

KL

Contact length of 3 With 1 or 2

KL ₁

Contact length of 3 With 1

KL ₂

Contact length of 3 With 2

L

permeation length

L _A

System length cylinder / plane

L _max

maximum permeation length

L ₁

Investment length of 3 on 1 about U _OI

NL

Groove length of 4 (in the direction of X – X)

OR

O-ring (with unpressed circular cross-section AU _R )

P

permeation coefficient

p ₁

higher fluid pressure

p ₂

lower fluid pressure

Q

Amount of fluid leakage amount

Q ₁

so far tolerated value of Q

Q ₂

achievable according to the invention Value of Q

q

specific Fluid quantity / amount of leakage

R

radius

R _K1 , R _K2

radii from K1, K2

R ₁ , R ₂ , R ₃

Radii in AU _opt

R _A

Outside radius of 3 , unpressed

R _a

average roughness value of 1 . 2

R _I

Inner radius of 3 , unpressed

R _max

maximum roughness value of 1 . 2

R _RS

(Radial) measure of curvature of 3 , unpressed

R _SA

Outside radius of 5

R _SN

Radius of 5 based on 4

RSO

Value for R _RS with circular cross-section (OR)

R _OI

Inner radius of 6

RF

Rectangular area from AU

s

Gap width of 7

SL

Side length of the half area from AU

T

Depth of 4

t

time

U

transforming factor for HA

U _OI

Inner circumference of 6

V

transforming factor for HB

VP

pressing

X X

Longitudinal axis of 1 . 2

Y-Y

radial directional center axis of AU

Ap

pressure difference

μ

Coefficient of friction

v _E

Cross contraction number - even body

v _Z

Cross contraction number - cylindrical body

Π

circle constant

Θ

operand

σ _max

maximum voltage

σ _1max

Maximum stress in F ₁

σ _2max

maximum voltage

Claims (31)

Connection system for pipes, fittings or aggregates (p ₁₎ for guiding a raised with respect to a comparison pressure (p ₂₎ the pressurized fluid are intended, leading in particular for carbon dioxide systems, comprising a first coupling part ( 1 ), like a housing part, into the first coupling part along an axis (X-X) ( 1 ) insertable second coupling part ( 2 ), like a plug part, and at least one gas-permeable peripheral seal consisting of an elastomer ( 3 ), which in a groove having a groove depth (T) and a groove length (NL) ( 4 ) is arranged, which is circumferentially in one of the two coupling parts ( 1 . 2 ) is formed, the one coupling part ( 2 ) with a shaft ( 5 ) in a round opening ( 6 ) of the other coupling part ( 1 ) is insertable, the peripheral seal ( 3 ) after insertion with deformation and generation of a radial pre-compression (F _V ) a gap ( 7 ) with a gap width (s) between the outer radius (R _SA ) of the shaft ( 5 ) and the inner radius (R _OI ) of the receiving opening ( 6 ) seals and thereby at least over a perpendicular to the respective radius (R _SA , R _OI ) of the coupling parts ( 1 . 2 ) axial length (X – X) of contact length (KL) on the coupling parts ( 1 . 2 ), characterized in that the cross section (AU, AU _R , AU _E , AU _opt ) of the unpressed peripheral seal ( 3 ), the groove depth (T) and the gap width (s) and the groove length (NL) are coordinated with one another in such a way that in one, permeation through the peripheral seal ( 3 ) determining ratio (A _E / KL) of a permeable partial peripheral surface (A _E ) of the peripheral seal ( 3 ) for the contact length (KL) the partial circumferential area (A _E ) is not greater than half the value of a cross-sectional area (A _V ) of the deformed circumferential seal running perpendicular to the axial direction (X-X) ( 3 ). Connection system according to claim 1, characterized in that the cross section (AU, AU _R , AU _E , AU _ppt ) of the unpressed peripheral seal ( 3 ), the groove depth (T) and the gap width (s) and the groove length (NL) are coordinated with one another in such a way that by permeation through the peripheral seal ( 3 ) determining ratio (A _E / KL) of the permeable partial peripheral surface (A _E ) of the peripheral seal ( 3 ) to the contact length (KL) the partial circumferential surface (A _E ) is not greater than one fifth of the value of a cross-sectional area (A _V ) of the deformed circumferential seal running perpendicular to the axial direction (X-X) ( 3 ). Connection system according to claim 1 or 2, characterized in that the partial peripheral surface (A _E ) in the vicinity of the gap ( 7 ) and a curved line (BL) of a pressed radial cross-sectional area (A _R ) of the deformed peripheral seal ( 3 ) is determined. Connection system according to claim 3, characterized in that a Length of Arc line (BL) with vanishing curvature minimally the value of Gap width (s) assumes and at most is not greater than half the value, preferably a quarter of the value of the sum of the gap width (s) and groove depth (T). Connection system according to one of claims 1 to 4, characterized in that the cross section (AU, AU _R , AU _E , AU _opt ) of the unpressed peripheral seal ( 3 ), the groove depth (T) and the gap width (s) as well as the groove length (NL) are coordinated so that the permeable partial circumferential surface (A _E ) is independent of a cord size (2 * R _SO , 2 * HB) of the unpressed circumferential seal ( 3 ) is. Connection system according to one of claims 1 to 5, characterized in that the size of a contact length (KL ₁ ) between the inner radius (R _OI ) of the first coupling part ( 1 ) and the peripheral seal ( 3 ) according to the equation

is dimensioned, where C1 is a constant, F _{V is} the preloading force acting in the radial direction, R _{OI is} the inner radius of the first coupling part ( 1 ), E _D the value of the elastic modulus of the peripheral seal ( 3 ) and R _RS a measure of the convex curvature of the seal ( 3 ), for example the line radius (R _SO ) of an O-ring seal (OR) is in the uncompressed state. Connection system according to one of claims 1 to 6, characterized in that a taking into account the possible thermal expansion of the peripheral seal ( 3 ) as a quotient from one in the groove ( 4 ) lying portion of the pressed radial cross-section (A _R ) of the peripheral seal ( 3 ) and the cross-sectional area (A _N ) of the groove ( 4 ) calculated degree of filling (FG) of the groove ( 4 ) is in the range from 58.0 percent to 100.0 percent, preferably from 78.0 percent to 98.0 percent. Connection system according to one of claims 1 to 7, characterized in that at asymmetri the circumferential seal 3 ) in the groove ( 4 ) taking into account the possible thermal expansion of the peripheral seal ( 3 ) as a quotient from one in half of the cross-sectional area (A _N ) of the groove ( 4 ) lying, comparatively larger portion (A _RH ) of the pressed radial cross-section (A _R ) of the peripheral seal ( 3 ) and half the cross-sectional area (A _N / 2) of the groove ( 4 ) calculated degree of filling (FGH) of the groove ( 4 ) is in the range from 58.0 percent to 100.0 percent, preferably from 78.0 percent to 98.0 percent. Connection system according to one of claims 1 to 8, characterized in that the cross section (AU _E , AU, AU _opt ) of the peripheral seal ( 3 ) has a preform in the uncompressed state, in which a quotient (FZ _U ) of an axial main extension (HA) and a radial main extension (HB) of the seal cross-section has a value of greater than 1, preferably greater than 2. Connection system according to one of claims 1 to 9, characterized in that the cross section (AU _E ) of the peripheral seal ( 3 ) has an elliptical shape in the uncompressed state. Connection system according to one of claims 1 to 9, characterized in that the cross-section (AU) of the unpressed peripheral seal ( 3 ) consists of two semicircular surfaces (KF1, KF2) or circular segment surfaces and an intermediate rectangular surface (RF). Connection system according to one of claims 1 to 9, characterized in that the cross section (AU _opt ) of the unpressed peripheral seal ( 3 ) consists in the basic form of a rectangle which has two longitudinal sides convexly curved with a first radius of curvature (R ₁ ), two transverse sides convexly curved with a second radius of curvature (R ₂ ) and four corners convexly rounded with a third radius of curvature (R ₃ ). Connection system according to claim 12, characterized in that the third radius of curvature (R ₃ ) is smaller than the first radius of curvature (R ₁ ) and the first radius of curvature (R ₁ ) is smaller than the second radius of curvature (R ₂ ). Connection system according to one of claims 1 to 8, characterized in that the peripheral seal ( 3 ) is formed by an O-ring (OR) with a circular cross-section (AU _R ) in the uncompressed state, in which the ratio of the inside diameter (R) to the strength of its cord (2 * R _SO ) is less than or equal to 6, preferably less than 3, and in which a minimum compression (VP} is in a range from more than 15 percent, preferably from more than 25 percent up to a maximum of 40 percent. Connection system according to one of claims 1 to 14, characterized in that in the radial cross section (A _R ) of the deformed peripheral seal ( 3 ) the contact length (KL) by less than 15 percent, preferably by less than 10 percent, particularly preferably by less than 5 percent, of a maximum axial permeation length (L _max ) through the peripheral seal ( 3 ) differs. Connection system according to one of claims 1 to 15, characterized in that the first coupling part ( 1 ) and / or the second coupling part ( 2 ) made of metallic materials, especially aluminum or high-alloy stainless steel alloys. Connection system according to one of claims 1 to 16, characterized in that a maximum roughness value (R _max ) of the surfaces of the coupling parts ( 1 . 2 ), at least in the area of the outer radius (R _SA ) of the shaft ( 5 ) and the inner radius (R _OI ) of the receiving opening ( 6 ) where the peripheral seal ( 3 ) is less than 16 μm, preferably less than 10 μm. Connection system according to one of claims 1 to 17, characterized in that the surfaces of the coupling parts ( 1 . 2 ), at least in the area of the outer radius (R _SA ) of the shaft ( 5 ) and the inner radius (R _OI ) of the receiving opening ( 6 ) where the peripheral seal ( 3 ) is applied by smooth rolling of surfaces that have an oversize of 0.018 mm to 0.040 mm and a roughness (R _a ) in the range of 1.6 to 3.2 μm compared to the machined surfaces. Connection system according to one of claims 1 to 18, characterized in that the peripheral seal ( 3 ) from a polymeric fluorocarbon compound, from synthetic rubber, such as silicone rubber, NBR or H-NBR, PUR, EPDM, SBR, or the like. consists. Connection system according to one of claims 1 to 19, characterized in that the peripheral seal ( 3 ) has a Shore A hardness in the range from 70 to 90. Connection system according to one of claims 1 to 20, characterized in that two or more peripheral seals ( 3 ) are arranged one behind the other in the axial direction (X – X). Connection system according to claim 21, characterized in that an outer peripheral seal accessible to the ambient atmosphere ( 3 ) has a reduced permeability coefficient (P) due to aging than one in front of the ambient atmosphere due to the outer peripheral seal ( 3 ) protected inner peripheral seal ( 3 ). Connection system according to one of claims 1 to 22, characterized in that the fluid acted upon by the pressure (p ₁ , p ₂ ) is carbon dioxide (CO ₂ ). Connection system according to one of Claims 1 to 23, characterized in that the pressure (p ₁ ) acting on the fluid is in the range from approximately 10 bar to 180 bar. Connection system according to one of claims 1 to 24, characterized in that a value (Q ₂ ) of the amount (Q) of the result of permeation through the peripheral seal ( 3 ) throughput fluid is no greater than about 2.5 g per year per compound, preferably no greater than 1 g per year per compound. Connection system according to one of claims 1 to 25, in particular according to one of claims 23 to 25, characterized in that the permeation through the peripheral seal ( 3 ) determining ratio (A _E / KL) at room temperature is not greater than 50.0 mm, preferably not greater than 17.5 mm. Connection system according to one of claims 1 to 26, in particular according to one of claims 23 to 26, characterized in that the permeation through the peripheral seal ( 3 ) determining ratio (A _E / KL) at 100 ° C is not greater than 4.5 mm, preferably not greater than 1.2 mm. Connection system according to one of claims 1 to 27, in particular according to one of claims 23 to 27, characterized in that the permeation through the peripheral seal ( 3 ) determining ratio (A _E / KL) at 150 ° C is not greater than 1.00 mm, preferably not greater than 0.25 mm. Connection system according to one of claims 1 to 28, characterized in that one for insertion while deforming the peripheral seal ( 3 ) and generation of the radial pre-pressing force (F _V ) to be applied (F _S ) with an inner radius (R _OI ) of the first coupling part ( 1 ) in a range from about 6 mm to 13 mm is less than 100 N, preferably less than 50 N, particularly preferably less than 30 N. Connection system according to one of claims 1 to 29, characterized in that the peripheral seal ( 3 ) is provided with a gas barrier coating. Circumferential seal for a connection system one of the claims 1 to 30, characterized by one or more features of the characteristic Part of the claims 9 to 13, 15, 19, 20 or 30.