Unit for regulating or controlling fluid pressure

Abstract

Unit (10) for regulating or controlling a fluid pressure, comprising a valve housing (12) including an inlet (28) and an outlet (30) for the fluid, and a switching foil (22) for switching at pressure differences of 1 to 250 mbar, preferably from 1 to 100 mbar, for regulating, releasing, or shutting off a flow of the fluid between the inlet (28) and the outlet (30), wherein the switching foil (22) is made of PTFE (polytetrafluoroethylene), wherein the switching foil (22) has a plate-like flat body (16) with a bending area (18) surrounding a central closing area (24), wherein, when the switching foil (22) is switched, the bending area (18) moves the closing area (24) relative to a valve seat (32) in an axial direction (L) towards or away from the valve seat (32) by means of a low-stretch, in particular stretch-free, bending movement. (32) moved away,wherein the bending movement is carried out over a large area of ​​the switching foil (22) and with low elastic deformation in the form of a change in curvature with low elongation of less than 10%, wherein the bending area (18) extends radially in a wave-like manner around the closure area (24), wherein the switching foil (22) has a thickness that varies by at most 50% over its entire extent, wherein the switching foil (22) has a thickness (52) of at least 0.5 mm, preferably of at most 0.3 mm, particularly preferably of at most 0.2 mm, at least in the bending area (18), and / or wherein the switching foil (22) has a diameter (54) of less than 150 mm, preferably between 40 mm and 100 mm, particularly preferably between 50 mm and 80 mm.

Description

Technical field

[0001] The invention relates to a unit for regulating or controlling a fluid pressure, in particular for the pressure control of the internal combustion engine and / or the crankcase of the internal combustion engine of a motor vehicle. State of the art

[0002] Pressure regulating valves are used, for example, in the vent line between the crankcase and the intake manifold of an internal combustion engine. Their purpose is to prevent the pressure or vacuum in the containers being vented from rising above a predetermined value.

[0003] In internal combustion engines, blow-by gases occur when combustion gases escape past the piston in the cylinder and into the crankcase. These blow-by gases cause the pressure in the crankcase to rise, which can lead to leaks and oil spillage. To prevent this pressure increase and to remove the blow-by gases in an environmentally friendly manner, they are recirculated from the crankcase back into the engine's air intake system. However, the specified vacuum level should not be significantly reduced, as this would allow unintended air to be drawn into the crankcase through leaks.

[0004] In currently used pressure control valves, a switching diaphragm, also known to those skilled in the art as a "switching membrane," is typically made of elastomer, often fluorosilicone rubber (FVMQ). These switching diaphragms are highly flexible due to the specific properties of elastomers. Depending on the applied pressure, this switching diaphragm opens or closes an opening in the pressure control valve. The pressure is usually determined by the pressure difference between the applied pressure in a first chamber and the prevailing pressure in a second chamber of the pressure control valve. The pressure in the first chamber can, for example, be equal to atmospheric pressure. The switching diaphragm must respond to low switching pressures in the range of 1 to 250 mbar.

[0005] Blow-by gases consist of unburned fuel, engine oil, and other pollutants produced during combustion. These gases attack many types of elastomers, potentially damaging their material properties. Components made from these materials become brittle, porous, and cracked. If the switching films are damaged, the environmentally harmful blow-by gases escape directly into the environment because the system is no longer sealed. Switching films made of elastomers are typically rolled to allow for a certain degree of movement. The material in the rolled section is subjected to additional mechanical stress from the unwinding motion combined with contact with blow-by gases, which can lead to damage.

[0006] From US 2004 / 0 211 400 A1, a valve is known that can regulate at least part of the flow rate of the recirculation of crankcase emissions, wherein the valve includes a spring and a diaphragm which divides the valve into two different chambers, one of which communicates with the atmosphere and the other with the intake manifold downstream of the throttle body.

[0007] DE 198 21 324 A1 shows a membrane arrangement with a membrane made of flexible material, wherein the membrane has an edge which is intended to be connected to a pump or valve housing part, such that the edge of the membrane has a substantially constant width which forms a form-fitting and flush transition with the housing part.

[0008] DE 26 29 621 A1 discloses a membrane valve, also known to those skilled in the art as a "diaphragm valve," with a membrane clamped at its edge between the valve housing and the housing cover. This membrane is brought into contact with a sealing surface provided in the valve housing by a pressure piece. The membrane consists of a thinner layer of low elasticity, e.g., made of PTFE, facing the inside of the housing and resistant to aggressive fluids, and a further, thicker layer of rubber-elastic material. Such membrane valves are primarily used where high chemical resistance of the materials in contact with the fluid is required. Since rubber-elastic materials do not meet this requirement, and chemically resistant materials such as PTFE do not possess the elasticity necessary for proper function, two-layer membranes are used.The thick, rubber-like layer ensures that the contact pressure exerted by the pressure piece is transferred as evenly as possible to the sealing surface of the switching foil, which interacts with the seat in the valve housing. To close the two-layer foil, relatively high switching pressures of several bar are applied to the foil via a pressure spindle connected to a handwheel, thus guaranteeing the necessary sealing function through the rigid PTFE layer. Disclosure of the invention

[0009] One objective of the invention is to create a switching unit for low pressure differentials that achieves long service lives when operated on an internal combustion engine with aggressive blow-by gases.

[0010] Another objective of the invention is to create a switching foil for such a unit for switching at low pressure differences, which achieves long service lives when operated on an internal combustion engine with aggressive blow-by gases.

[0011] According to one aspect of the invention, the aforementioned problem is solved by a unit for regulating or controlling a fluid pressure, comprising a valve housing with an inlet and an outlet for the fluid, and a switching film, wherein the switching film is formed from a polymer film containing fluorine and carbon.

[0012] According to another aspect of the invention, the further problem is solved by a switching film for such a unit made of a polymer film containing fluorine and carbon.

[0013] Favorable embodiments and advantages of the invention will become apparent from the further claims, the description and the drawing.

[0014] A unit for regulating or controlling fluid pressure is proposed, comprising a valve body with an inlet and an outlet for the fluid, and a switching film for switching at pressure differences of 1 to 250 mbar, preferably 1 to 100 mbar, to open or close the flow of fluid between the inlet and the outlet, wherein the switching film is formed from a polymer film containing fluorine and carbon. The unit not only serves to open or close the flow, but also regulates the flow of fluid between the inlet and the outlet between the two switching states of open or closed by continuously changing the flow cross-section as a function of the pressure difference.

[0015] The fluorine and carbon polymer film is chemically resistant and can withstand many switching cycles of the film valve. The long-term stability of the unit is improved. The fluorine and carbon polymer is PTFE (polytetrafluoroethylene). Alternatively, the fluorine and carbon polymer can be PTFE as a base material with additives; it can also be a thermoplastic PTFE.

[0016] A spring element, supported against the valve housing, exerts a force on the switching foil to adjust the unit's control behavior. The outlet has a valve seat at one end located in the valve housing, which can be closed by the switching foil's closing area, thus controlling the flow of fluid from the inlet to the outlet.

[0017] According to the invention, the switching foil has a plate-like flat body with a bending area surrounding a central closure area. When the switching foil is activated, the bending area moves the closure area axially towards or away from a valve seat by a low-stretch, i.e., practically stretch-free, bending movement. Since the switching foil in this configuration can deflect not only in a small area but over a large area due to its plate-like shape, individual areas of the switching foil are subjected to little strain. The bending movement is thus carried out over a large area of ​​the switching foil and consequently with low elastic deformation in the form of a change in curvature with low elongation, for example, less than 10%.

[0018] According to the invention, the bending area extends radially in a wave-like pattern around the closure area. Advantageously, the bending area has at least one radially arranged wave around the closure area, wherein one or more waves are formed as concave and convex curved regions with alternating raised areas and recesses in the switching foil. A raised area on one flat side of the switching foil corresponds to a recess on the other flat side of the switching foil. The term "wave-like" encompasses not only sinusoidal waves but can also include, for example, U-shaped or other concave or convex curved contours. Even a curved deflection to only one side of an imaginary foil plane constitutes a wave.In this way, favorable bending behavior with a uniform force distribution can be achieved, along with minimal to no elongation of the fluorine and carbon-containing polymer film. This means that the geometry of the bending zone allows the central area of ​​the switching film to be moved axially with minimal elongation, practically without elongation or even without elongation in practical applications. Furthermore, this allows the fluorine and carbon-containing polymer film to move even at very small pressure differences between the front and back of the film. Thus, switching the valve is possible at a pressure difference of less than 250 mbar.

[0019] A conventional elastomer switching film used in a standard internal combustion engine pressure control unit and / or crankcase pressure control unit is replaced by a film made of a fluorine-carbon polymer. A fluorine-carbon polymer such as PTFE can be produced via a sintering process and subsequently machined. In its standard form, such a film is very rigid and unsuitable for flexible components. PTFE possesses excellent chemical resistance and can be used in a very wide temperature range, although its modulus of elasticity increases significantly at low temperatures compared to other elastomer materials. For this reason, PTFE is not particularly suitable for use as a film in the temperature range required for automotive applications on internal combustion engines (-40°C to +150°C).This disadvantage is advantageously circumvented in the inventive unit by a special geometry and, optionally, by extremely thin wall thicknesses of the film made of fluorine-carbon polymer. By reducing the wall thickness of the PTFE material in a moving area to a few tenths of a millimeter, while the stationary sealing area and the clamping area of ​​the material can be made thicker, and by a specially developed geometry of the film without a rolling area, as is otherwise commonly used in the prior art, the rigid material can be formed into a shape in which it exhibits the necessary flexibility but still meets the mechanical requirements with regard to crack formation, elongation, and flexural fatigue strength. Due to the special geometry, no rolling movement occurs, but rather a low-elongation bending movement with a change in radius, with which a stroke movement of the switching film for a unit can be realized.

[0020] According to an advantageous embodiment, the switching film has a substantially constant thickness across its entire extent. This means that, perpendicular to its planar extent, the switching film is essentially the same thickness, i.e., that the switching film is at most twice as thick in the edge region as in the bending region. This can be advantageously achieved by manufacturing the switching film using a forming process, in particular by deep drawing. The bending region can be somewhat thinner than the edge region of the switching film. Preferably, the switching film is at most 0.5 mm thick. By eliminating areas with a locally confined, significantly increased material thickness, such as those known, for example, from known elastomer switching membranes, such a switching film with a uniform material thickness for practical purposes can be easily manufactured.In elastomer membranes, the thickness of the membrane typically varies by several times the thinner areas, since elastomer membranes are typically manufactured using a primary forming process, such as vulcanizing the elastomer in a press tool.

[0021] According to an advantageous embodiment, a spring element can be provided which is supported on the valve housing and exerts a force on the closing area of ​​the switching foil. The spring element exerts the appropriate counterforce on the switching foil to achieve the desired control behavior of the unit within the required pressure range. The side of the switching foil facing away from the fluid to be controlled is typically pressurized to atmospheric pressure.

[0022] According to an advantageous embodiment, the spring element can be supported by a plate at the closure area. This ensures stable contact of the spring element with the switching foil, thus guaranteeing a defined force transmission into the switching foil. At the same time, the switching foil, which according to the invention is designed as a thin polymer film containing fluorine and carbon, is protected against potential damage by the spring element.

[0023] According to an advantageous embodiment, the sealing area can have a cup-shaped protrusion. This cup-shaped protrusion ensures a stable shape for the sealing area, thereby guaranteeing a reliable seal when the sealing area is placed on the valve seat. The protrusion itself is not affected by the bending movement of the switching foil and retains its shape for reliable sealing.

[0024] According to an advantageous embodiment, the spring element can be arranged around the cup-shaped protrusion. This ensures a uniform force transmission from the spring element into the switching foil, whereby the shape of the protrusion-shaped sealing area is not affected by the force transmission. This is further guaranteed because the plate of the spring element is arranged ring-shaped around the protrusion, thus additionally stabilizing its shape. The protrusion, as the sealing area, is located in an inner region of the spring element.

[0025] According to an advantageous embodiment, the spring element can be overmolded on its end face, which faces the protrusion. Similarly, overmolding the spring element's plate with plastic can very effectively and economically create a connection between the spring element and the switching foil. Furthermore, this provides additional protection for the thin polymer foil containing fluorine and carbon against mechanical stress in the area of ​​the spring element.

[0026] According to an advantageous embodiment, a first chamber of the unit can be pressurized to atmospheric pressure. For effective control of the unit, the switching film should be able to move as freely as possible. Therefore, a first chamber, which is separated from a second chamber containing the fluid to be controlled by the switching film, is expediently connected to the surrounding environment, i.e., atmospheric pressure. The spring element compensates for the atmospheric pressure, allowing the switching film to operate within a low pressure differential range.

[0027] According to an advantageous embodiment, the switching foil can be moved between its maximum positions in the open and closed states without a switching plunger. The switching foil can be opened and closed without a movable contact plunger ever acting on it from both sides and moving it in one direction or the other. Instead, the switching foil can be moved back and forth solely by a pressure difference on either side of it.

[0028] Alternatively, it can be provided that the switching film can be moved back and forth between its maximum positions in the closed and open state by means of movable mechanical actuating means acting on the switching film, such as switching plungers.

[0029] According to an advantageous embodiment, the sealing area of ​​the switching film can interrupt the flow of fluid between the inlet and the outlet. The switching film can rest directly on a sealing seat to interrupt the flow.

[0030] According to an advantageous embodiment, the switching foil can be moved between its maximum positions in the open and closed states by applying atmospheric pressure as a control pressure to one side of the switching foil. Advantageously, the switching foil is self-regulating, and it can be closed indirectly via a pressure difference between atmospheric pressure in one chamber of the unit and a working pressure in the other chamber. The working pressure could, for example, be the pressure in the crankcase of an internal combustion engine.

[0031] According to an alternative embodiment, the switching foil can be moved between its maximum positions in the open and closed states by applying a control pressure other than atmospheric pressure to one side of the switching foil and / or by providing a mechanical actuating means for switching the switching foil.

[0032] According to the invention, the switching foil has a thickness of at most 0.5 mm, preferably at most 0.3 mm, and particularly preferably at most 0.2 mm, at least in the bending area. Such a small thickness of the fluorine and carbon-containing polymer foil, for example PTFE foil or PTFE-containing foil, allows the foil to bend easily enough at low differential pressures without undergoing significant elongation. Advantageously, the corrugated bending area and the small foil thickness can work together to enable low switching pressures. The foil can ensure the desired switching behavior by sealing the valve seat with the sealing area of ​​the switching foil.In contrast to the bellows areas typically used in thicker PTFE components, which are produced mechanically by machining or cutting and allow movement of the rigid PTFE material, such a design is not necessary for such a thin polymer film containing fluorine and carbon, as the bending movement is made possible solely by the plate-shaped design with radially wave-like areas of the switching film.

[0033] According to the invention, the switching foil has a diameter between 40 mm and 100 mm, preferably between 50 mm and 80 mm. Switching foils of the specified diameter, at the previously specified foil thicknesses, achieve sufficient flexibility to achieve the desired control behavior in a single unit at the desired low pressure differentials. This allows for the efficient implementation of vent valves for conventional internal combustion engines in the automotive sector. It is conceivable that with correspondingly larger diameters, somewhat greater thicknesses of the switching foil in the range of over 0.5 mm, e.g., a maximum of 1 mm to 0.5 mm, could also be realized.

[0034] According to a further aspect of the invention, a switching film for a unit is proposed, which is formed from a polymer film containing fluorine and carbon, with a plate-like flat body and a bending area surrounding a central closure area. The closure area can be moved back and forth axially to switch the switching film by means of a low-stretch, and in particular, stretch-free, bending movement of the bending area. Since the switching film in this embodiment can bend not only in a small area but over a large area due to its plate-like shape, individual areas of the switching film are subjected to little strain. The bending movement is thus carried out over a large area of ​​the switching film and consequently with low curvature.

[0035] According to an advantageous embodiment, the bending zone can extend radially in a wave-like pattern around the closure zone. The bending zone expediently comprises at least one radially arranged wave around the closure zone, wherein one or more waves are formed as concave and convex curvature zones with alternating raised and recessed areas in the switching foil. A bulge on one flat side of the switching foil corresponds to a depression on the other flat side. In this way, favorable bending behavior with a uniform force distribution can be achieved, along with low (low-stretch) or even no (stretch-free) elongation of the fluorine and carbon-containing polymer foil. That is, the geometry of the bending zone allows the central area of ​​the switching foil to be moved axially with low or even no stretching.This also allows movements of the polymer film containing fluorine and carbon to be caused by very small pressure differences between the front and back of the film.

[0036] According to an advantageous embodiment, the central sealing area can be cup-shaped. This cup-shaped protrusion ensures a stable form for the sealing area, thereby guaranteeing a reliable seal when the sealing area is placed on the valve seat. The protrusion itself is not affected by the bending movement of the switching foil and retains its shape for reliable sealing.

[0037] According to an advantageous embodiment, at least the bending section can have a thickness of at most 0.5 mm, preferably at most 0.3 mm, and particularly preferably at most 0.2 mm, and the flat body can have a diameter of less than 150 mm, preferably between 40 mm and 100 mm, and particularly preferably between 50 mm and 80 mm. Such a small thickness of the fluorine and carbon polymer film allows the film to bend easily enough at low differential pressures without undergoing significant elongation. It is conceivable that with correspondingly larger diameters, somewhat greater thicknesses of the switching film in the range of over 0.5 mm, e.g., at most 1 mm to 0.5 mm, are also achievable.

[0038] The foil ensures the desired switching behavior by sealing the valve seat with the foil's sealing area. Unlike the bellows-like sections typically found in thicker PTFE foils, which allow movement of the rigid PTFE material, such a design is unnecessary with this thin foil made of a fluorine and carbon polymer. The bending movement is achieved solely through the foil's disc-shaped design with radially wave-like sections. Switching foils of the specified diameter, at the previously stated thicknesses, provide sufficient flexural freedom to achieve the desired control behavior in a single unit at the required low pressure differentials. This allows for the efficient production of vent valves for common internal combustion engines in the automotive sector.

[0039] According to another aspect of the invention, the unit according to the invention is used for pressure control of an internal combustion engine and / or for pressure control of a crankcase of an internal combustion engine. Brief description of the drawings

[0040] Further advantages become apparent from the following description of the drawings. The drawings illustrate exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. A person skilled in the art will expediently consider the features individually and combine them into meaningful further combinations.

[0041] They show, for example: Fig. 1 a unit with a switching foil made of a polymer containing fluorine and carbon according to an embodiment of the invention in a sectional view; Fig. 2 a switching foil made of a polymer containing fluorine and carbon according to an embodiment of the invention in isometric view; Fig. 3 the circuit foil Fig. 2 in an unloaded state in longitudinal section; and Fig. 4 the circuit foil Fig. 2 in deflected state in longitudinal section. Embodiments of the invention

[0042] In the figures, identical or similar components are numbered with the same reference symbols. The figures merely show examples and are not to be understood as limiting.

[0043] Fig. Figure 1 shows a sectional view of a unit 10 for regulating or controlling a fluid pressure, comprising a switching film 22 made of a polymer containing fluorine and carbon, according to an embodiment of the invention. This unit 10 serves to regulate or control a fluid pressure, in particular for use in pressure regulation of an internal combustion engine and / or for pressure regulation of a crankcase of an internal combustion engine. The unit 10 has a valve housing 12 with a housing cover 14, the valve housing 12 having an inlet 28 and an outlet 30 for the fluid. The switching film 22 is formed from a polymer film containing fluorine and carbon, for example PTFE, and is clamped between the valve housing 12 and the housing cover 14 by a clamping area 60. The switching film 22 separates a first chamber 36 from a second chamber 38.A pressure difference exists between a first chamber 36 and a second chamber 38, with the first chamber 36 being connected to the environment, i.e., atmospheric pressure (not shown). The switching foil 22 can be moved with pressure differences of 1 to 250 mbar, preferably from 1 to 100 mbar, and serves to open or close the flow of fluid between the inlet 28 and the outlet 30. In operation, the inlet 28 of the unit 10 is, for example, fluidically connected to the crankcase of an internal combustion engine, while the outlet 30 is fluidly connected to the intake manifold. The switching foil 22 has a plate-like flat body 16 with a wave-shaped bending section 18 surrounding a central closure area 24.When the switching foil 22 is activated, the bending section 18 moves the closure area 24 towards or away from a valve seat 32 in the axial direction L by means of a low-stretch, and in particular, stretch-free, bending movement. For this purpose, the switching foil 22 has a thickness of at most 0.5 mm, preferably at most 0.3 mm, and particularly preferably at most 0.2 mm, at least in the bending section 18. The diameter of the switching foil 22 is between 40 mm and 100 mm, preferably between 50 mm and 80 mm.

[0044] The bending section 18 extends radially in a wave-like pattern around the sealing section 24, with a depression on one flat side corresponding to a protrusion on the other flat side of the switching foil 22. The sealing section 24 seals the valve seat 32 fluid-tight when it rests on the valve seat 32. A spring element 26 is provided, which is supported against the valve housing 12 and exerts a force on the sealing section 24 of the switching foil 22, thus compensating for the atmospheric pressure in the first chamber 36. The spring element 26 is supported on the sealing section 24 by an annular plate 34. The sealing section 24 is designed as a cup-shaped protrusion 20 of the switching foil 22, with the plate 34 acting as a support ring annularly enclosing this protrusion.The spring element 26 can alternatively engage the switching foil 22 without the plate 34 and, in this case, be overmolded on its end face facing the protrusion 20 to protect the switching foil 22, so that the overmolding could replace the plate 34. The edge 56 between the flat part of the switching foil 22 and the protrusion 20 is adapted to the plate 34 so that the switching foil 22 can rest directly against the plate 34. The spring element 26 is therefore arranged around the cup-shaped protrusion 20, which extends into the interior of the spring element 26.

[0045] Fig. Figure 2 shows an isometric view of a switching foil 22 made of a polymer film containing fluorine and carbon according to an embodiment of the invention. The switching foil 22 for a unit 10 is formed from a polymer film containing fluorine and carbon, for example PTFE, with a plate-like flat body 16 and a bending area 18 surrounding a central closure area 24. The closure area 24 can be moved back and forth in the axial direction L to switch the switching foil 22 by a low-stretch, in particular stretch-free, bending movement of the bending area 18. The central closure area 24 is realized in a cup-shaped protrusion. The diameter 54 of the switching foil 22 is between 40 mm and 100 mm, preferably between 50 mm and 80 mm. The bending area 18 extends radially in a wave-like manner around the closure area 24. In the embodiment shown in Fig. Figure 2 shows three waves 40, 44, 48, which are arranged concentrically around the closure area 24 and each have opposite curvatures, so that a bending movement of the flat body 16 is thereby favored.

[0046] In Fig. 3 is the switching foil made of Fig. 2 is shown in longitudinal section in the unloaded state. In the unloaded state, the edge 56 between the flat area of ​​the switching foil 22 and the cup-shaped protrusion 20 lies at the same level as the outer clamping area 60. The bending area 18 is formed in three waves 40, 44, 48, which, viewed from the first chamber 36 of the unit 10, are convex, concave, and convex with radii 42, 46, 50 in alternating sequence. At least in the bending area 18, the thickness 52 of the polymer foil containing fluorine and carbon is in the range of at most 0.5 mm, preferably at most 0.3 mm, and particularly preferably at most 0.2 mm. The flat body 16 of the switching foil 22 in Fig. 3, as shown, in particular has a diameter 54 which is between 40 mm and 100 mm, preferably between 50 mm and 80 mm.

[0047] Fig. 4 shows the circuit diagram Fig. 2 in deflected state in longitudinal section. The closure area 24 is significantly lowered and would be in unit 10 in Fig. 1, for example, resting on the valve seat 32. The lowering movement of the closure area 24 is caused by the bending movement of the switching foil 22 by an extension of the radii 42, 46, 50 of the three shafts 40, 44, 48, which are each arranged radially concentrically around the closure area 24. The arrows symbolizing the radii 42, 46, 50 are intended to express the extension of the radii. The stroke 58 of the closure area 24 is greater than the stroke 58 of the in Fig. 2 shown circuit foil 22 in unloaded state, as in Fig.Figure 3 shows a significantly enlarged view. In contrast, the edge 56 between the flat area of ​​the switching foil 22 and the closure area 24 retains its approximately right-angled shape despite the bending movement, since the flat body 16 of the switching foil 22 has an extensive bending area 18 and consequently the curvature of the entire bending area 18 has a very large radius of curvature.

Claims

[1] Unit (10) for regulating or controlling a fluid pressure, comprising a valve housing (12) including an inlet (28) and an outlet (30) for the fluid, and a switching foil (22) for switching at pressure differences of 1 to 250 mbar, preferably from 1 to 100 mbar, for regulating, releasing or shutting off a flow of the fluid between the inlet (28) and the outlet (30), wherein the switching foil (22) is made of PTFE (polytetrafluoroethylene), wherein the switching foil (22) has a plate-like flat body (16) with a bending area (18) surrounding a central closing area (24), wherein, when the switching foil (22) is switched, the bending area (18) moves the closing area (24) relative to a valve seat (32) in an axial direction (L) towards or away from the valve seat (32) by means of a low-stretch, in particular stretch-free, bending movement. Valve seat (32) moved awaywherein the bending movement is carried out over a large area of ​​the switching foil (22) and with low elastic deformation in the form of a change in curvature with low elongation of less than 10%, wherein the bending area (18) extends radially in a wave-like manner around the closure area (24), wherein the switching foil (22) has a thickness that varies by at most 50% over its entire extent, wherein the switching foil (22) has a thickness (52) of at least 0.5 mm, preferably of at most 0.3 mm, particularly preferably of at most 0.2 mm, at least in the bending area (18), and / or wherein the switching foil (22) has a diameter (54) of less than 150 mm, preferably between 40 mm and 100 mm, particularly preferably between 50 mm and 80 mm. [2] Unit according to one of the preceding claims, wherein a spring element (26) is supported on the valve housing (12) and exerts a force on the switching foil (22), wherein preferably the spring element (26) is supported on the switching foil (22) via a plate (34). [3] Unit according to one of the preceding claims, wherein the closure area (24) has a pot-shaped protrusion (20). [4] Unit according to one of claims 2 or 3, wherein the spring element (26) is arranged around the cup-shaped protrusion (20). [5] Unit according to one of the preceding claims, wherein the switching foil (22) is movable between its maximum positions in the open and closed state by applying atmospheric pressure as control pressure to one side of the switching foil (22). [6] Unit according to one of claims 1 to 4, wherein the switching foil (22) is movable between its maximum positions in the open and closed state by applying a control pressure other than atmospheric pressure to one side of the switching foil (22) and / or by providing a mechanical actuating means for switching the switching foil (22). [7] Switching foil (22) for a unit (10) for regulating or controlling a fluid pressure according to one of the preceding claims, which is formed from a polymer material containing fluorine and carbon, with a plate-like flat body (16), with a bending area (18) surrounding a central closure area (24), wherein the closure area (24) is movable back and forth in the axial direction (L) for switching the switching foil (22) by a low-stretch, in particular stretch-free, bending movement of the bending area (18). [8] Switching foil according to claim 7, wherein the bending area (18) extends in a radial direction in a wave-like manner around the closure area (24). [9] Switching foil according to claim 7 or 8, wherein the central closure area (24) is protruded in a pot shape. [10] Switching foil according to one of claims 7 to 9, wherein at least the bending area (18) has a thickness (52) of at most 0.5 mm, preferably of at most 0.3 mm, particularly preferably of at most 0.2 mm, and / or the flat body (16) in particular has a diameter (54) of less than 150 mm, preferably between 40 mm and 100 mm, particularly preferably between 50 mm and 80 mm. [11] Switching foil according to one of claims 7 to 10, wherein the polymer material comprising fluorine and carbon is polytetrafluoroethylene or polytetrafluoroethylene with admixtures or thermoplastically processable polytetrafluoroethylene. [12] Use of a unit (10) according to any one of claims 1 to 6 for pressure control of an internal combustion engine and / or for pressure control of a crankcase of an internal combustion engine.

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