Method for providing a residual pressure valve for a gas spring, and residual pressure valve for a gas spring

Abstract

The invention relates to a method for providing a residual pressure valve for a gas spring, in particular for an air suspension strut of a motor vehicle, wherein the residual pressure valve has the following features: a flow path between a first valve side which can be connected to a compressor and a second valve side which can be connected to the gas spring; a valve seat; a valve element which is complementary to the valve seat and which can be lifted from the valve seat by an opening pressure acting on the valve side in order to open the flow path and can be pressed onto the valve seat by a biased mechanical force accumulator in order to close the flow path in the event of a residual pressure level on the valve side which is lower than the opening pressure; and a first housing part and a second housing part, between which the valve element is movably mounted. The method according to the invention is characterized in that the bias of the mechanical energy accumulator is mechanically adjusted during or after the assembly of the residual pressure valve and, as a result, one of a plurality of possible adjustable opening pressures is set in order to calibrate the residual pressure valve.

Description

[0001] Method for providing a residual pressure holding valve for a gas spring and residual pressure holding valve for a gas spring

[0002] The present invention relates to a method for providing a residual pressure holding valve for a gas spring, in particular for an air spring strut of a motor vehicle, according to the preamble of claim 1 and a residual pressure holding valve for a gas spring according to the preamble of claim 7.

[0003] Residual pressure holding valves of this type are well known, for example from the publication of international patent application WO 2012 / 116964 A1. As the name suggests, they serve to maintain residual pressure in a section of a pressurized system after a pressure drop, preventing that section from becoming depressurized. As is typical for valves, different valves are available for different residual pressures, so a suitable residual pressure holding valve must be selected from the range of available products for a specific application with a required residual pressure.

[0004] A key application for residual pressure valves is maintaining residual pressure in the air suspension systems of vehicles such as SUVs and upper- and mid-range sedans. Here, the residual pressure valve serves as a crucial safety element. For example, it disconnects the air spring from the pneumatic system in the event of a hose rupture, disconnects a defective air spring from the vehicle's pneumatic system, or prevents the vehicle from completely dropping to its ride height after prolonged periods of inactivity due to air diffusion through the air spring's rubber bellows. The valve is an integral component of each air spring, which in turn is part of the air suspension system—a suspension system that utilizes the compressibility of gases, particularly air.The residual pressure valve allows free airflow between the air spring strut and the air compressor during normal vehicle operation. In the event of a malfunction, regardless of which side of the valve is affected, the residual pressure valve closes as intended at a defined residual pressure. The pneumatically intact side of the valve is kept under pressure and thus protected from further damage.

[0005] The residual pressure relief valve known from publication WO 2012 / 116964 A1 has a sleeve-shaped first valve housing part into which a second valve housing part projects. The two housing parts can be tightly welded together, or the second valve housing part can be screwed into the first housing in a sealing manner. The second housing part circumferentially surrounds a valve body that is movable along the valve axis. When the valve is depressurized, a spring-type energy storage device presses the valve body into a valve seat against the second housing part. A central bore extends through the first valve housing part, and a central, multi-stepped blind bore extends through the second valve housing part. From this blind bore, transverse bores, perpendicular to the valve axis, open into a narrow annular space between the first and second valve housing parts, which coaxially surrounds the valve body.This ensures that, in the state of the valve body being lifted from the valve seat, air can flow around the outside of the valve body, for example from the central bore in the first housing part, through the annular space, the transverse bores and the blind bore, until the pressure on the first valve housing part has dropped to the defined minimum pressure, from which point the force exerted on the valve body by the energy storage device predominates and the valve closes.

[0006] Although the described residual pressure relief valve has proven effective in practice, it is not without its drawbacks. To ensure the valve closes at a specific residual pressure and to guarantee the valve body's mobility, consistently high precision in all components is necessary. This is achieved by manufacturing the components from brass. However, brass has the disadvantage of containing lead, which is a concern from an environmental perspective. Furthermore, brass is prone to contact corrosion when it comes into contact with other metals, such as aluminum. To prevent this, a protective coating is required on the components to which the brass parts rest, or a material other than brass must be used.

[0007] DE 10 2012 212 752 A1 discloses a housing part for a high-pressure pump with a high-pressure bore in which a high-pressure valve designed as a check valve is received, wherein the high-pressure valve comprises an axially displaceable valve element having a spherical sealing surface that interacts with a valve seat and is acted upon by the spring force of a spring in the direction of the valve seat. The valve element of the high-pressure valve is guided over a bushing received in the high-pressure bore, which is connected to the housing part by force and / or positive locking, thus reducing the required manufacturing precision of the first housing part.

[0008] DE 102 54 711 B3 discloses a pressure valve with additional

[0009] Injection timing adjuster function for installation in a pressure line of a self-igniting internal combustion engine.

[0010] CN 204 164420 U discloses a 4-way valve for water which provides various functions, such as filtration, a check valve and a control valve, as well as a pressure relief valve.

[0011] WO 2011 / 054615 A1 discloses a generic residual pressure holding valve, the features of which are summarized in the preamble of claim 7 and from which the preamble of claim 1 is implicitly derived. The residual pressure holding valve is arranged in a tubular air line of an air supply system between a pressure generator and a pressure consumer or pressure actuator. The residual pressure holding valve comprises a valve seat, a valve body complementary to the valve seat and movable by an opening pressure, a valve housing enclosing the valve seat and valve body and sealed against ambient pressure, and an elastic element acting between the valve seat and valve body against the opening pressure of the valve. Such a residual pressure holding valve is used, for example, in air suspension systems for vehicles.

[0012] The desired minimum residual pressure is determined by the opening pressure at which the valve body lifts off the valve seat against the force of the mechanical energy storage device. The resulting minimum residual pressure thus essentially corresponds to the opening pressure or is only minimally lower. To adjust the residual pressure according to the generic residual pressure holding valve disclosed in WO 2011 / 054615 A1 for the specific application, a suitable elastic element, hereinafter generally referred to as a mechanical energy storage device, with a suitable spring curve must be selected for the respective application and installed during the assembly of the residual pressure holding valve between the valve housing, against which the mechanical energy storage device is supported on one side, and the valve body, against which the mechanical energy storage device is supported on the other.Therefore, stockpiling and logistics for various mechanical energy storage devices with different spring curves are necessary. Furthermore, due to component tolerances and assembly clearances, the known residual pressure holding valve exhibits undesirable tolerances in the opening pressure, which are practically impossible to compensate for, thus proving disadvantageous.

[0013] The present invention is based on the objective of providing a method for supplying a residual pressure holding valve for a gas spring and a residual pressure holding valve for a gas spring, with which the undesirable tolerances in the opening pressure are at least largely or completely compensated. In addition, the residual pressure holding valve should have a simple design and be inexpensive to manufacture.

[0014] The problem according to the invention is solved by a method with the features of claim 1 and a residual pressure holding valve with the features of claim 7. Advantageous and particularly expedient embodiments of the invention are set forth in the dependent claims.

[0015] According to the inventive method for providing a residual pressure holding valve, in particular for an air spring of a motor vehicle, wherein the residual pressure holding valve comprises a flow path between a first valve side connectable to a compressor and a second valve side connectable to the gas spring, a valve seat, a valve body complementary to the valve seat, which can be lifted from the valve seat to open the flow path by an opening pressure on the valve side and which can be pressed onto the valve seat by a pre-tensioned mechanical energy storage device to close the flow path when the residual pressure on the valve side is less than the opening pressure, and a first housing part and a second housing part between which the valve body is movably arranged,The preload of the mechanical energy storage device is mechanically adjusted during or after the installation of the residual pressure holding valve, thereby setting one of several possible adjustable opening pressures for calibrating the residual pressure holding valve.

[0016] The invention thus makes it possible to calibrate the residual pressure holding valve during or after assembly with regard to the desired opening pressure and therefore the residual pressure maintained in practice on the valve side. The opening pressure can be adjusted continuously or in steps, depending on the embodiment. Due to the adjustable preload, assembly clearances and / or component tolerances affecting the preload of the mechanical energy storage device and / or the functionality of the valve can be compensated for.

[0017] Components influencing the residual pressure holding valve can be easily compensated for without the need to replace any components.

[0018] Preferably, the preload of the mechanical energy storage device is adjusted by changing its axial length by compressing or pulling it apart in the direction of movement of the valve body, thereby calibrating the residual pressure holding valve.

[0019] For example, if the valve seat is formed on the second housing part and the first housing part is mounted on the second housing part in such a way that the mechanical energy storage device is supported on the first housing part on one side and on the valve body on the other, one of several possible opening pressures can be set during or after the installation of the residual pressure holding valve by adjusting a relative position of the first housing part with respect to the second housing part.

[0020] According to a particularly compact, safe, and cost-effective embodiment, the first housing part is screwed into or onto the second housing part, and the preload of the mechanical energy storage device is adjusted by screwing or screwing the first housing part into or onto the second housing part to a greater or lesser extent, particularly without any stop. For example, by screwing or screwing the first housing part in or out to a limited extent, or by partially unscrewing it from the second housing part, the mechanical energy storage device can be somewhat relaxed, thereby reducing its preload. Conversely, by screwing or screwing the first housing part in or out further, the mechanical energy storage device can be tightened more, thereby increasing the preload, corresponding to the change in the axial length of the installed mechanical energy storage device.Preferably, when the desired preload of the mechanical energy storage device is set, which can be determined, for example, by measuring the residual pressure on the second side of the valve, its axial length is fixed, for example, by fixing the first housing part to the second housing part, in order to fix the relative position between the first housing part and the second housing part.

[0021] During assembly or subsequently, a first pressure can be set on the first valve side, i.e., the compressor side. This pressure is typically set to a constant value. On the second valve side, i.e., the gas spring side, a second pressure can either be set to a constant value or varied. In the first case, the second pressure can be set to the desired opening pressure or residual pressure, and the preload of the mechanical energy storage device can be adjusted until the residual pressure valve just opens (at the set opening pressure) or just remains closed (at the set residual pressure).Alternatively, calibration can be carried out by varying and measuring the second pressure on the second side of the valve by adjusting the preload of the mechanical energy storage device, and, when the second pressure on the second side of the valve has reached a desired opening pressure or a desired residual pressure, finally maintaining and, in particular, fixing the setting of the preload of the mechanical energy storage device.

[0022] Therefore, when mechanically adjusting the preload of the mechanical energy storage device, the pressure on the second side of the valve is preferably measured and used as a control variable during calibration.

[0023] A residual pressure holding valve according to the invention for a gas spring, in particular for an air spring strut of a motor vehicle, comprises a flow path between a first valve side, which can be connected to a compressor, and a second valve side, which can be connected to the gas spring, a valve seat, and a valve body complementary to the valve seat, which can be lifted from the valve seat to open the flow path by an opening pressure on the valve side and can be pressed onto the valve seat by a pre-tensioned mechanical energy storage device to close the flow path when there is a residual pressure on the valve side that is less than the opening pressure, a first housing part, and a second housing part, between which the valve body is movably arranged.

[0024] According to the invention, the preload of the mechanical energy storage device is mechanically adjustable during or after the installation of the residual pressure holding valve in order to set one of several possible adjustable opening pressures for calibrating the residual pressure holding valve.

[0025] As in the method according to the invention, one of several adjustable opening pressures means that the opening pressure of one and the same residual pressure holding valve can be varied without replacing any components. Thus, unlike previously, it is not necessary to replace a first mechanical energy storage device with another mechanical energy storage device to change the opening pressure.

[0026] Preferably, the preload of the mechanical energy storage device is adjustable by changing its axial length by compressing or pulling it apart in the direction of movement of the valve body.

[0027] As explained by the method, it is advantageous if the valve seat is formed on the second housing part and the mechanical energy storage device is supported at least indirectly on the first housing part and on the valve body, and the first housing part is adjustable on the second housing part, at least during assembly, in order to adjust the opening pressure by changing the relative position of the first housing part with respect to the second housing part.

[0028] Preferably, the first housing part is screwed into or onto the second housing part without any stop. In particular, the first housing part is not completely screwed into or onto the second housing part, so that a reserve remains in the corresponding thread engagement between the first and second housing parts for further screwing in or on.

[0029] Other options for adjusting the preload of the mechanical energy storage device involve, instead of a screw connection, a displacement of the first housing part relative to the second housing part, followed by a subsequent fixation in the position in which the desired opening pressure or residual pressure results.

[0030] The set axial length of the mechanical energy storage device can be fixed, for example, by a positive-locking and / or material-locking connection between the two housing parts, or, as will be shown below, by fixing an additional component, such as a pressure plate, which is adjustable to change the axial length of the energy storage device. For example, crimping, gluing, welding, and / or riveting are possible methods for fixing the component.

[0031] According to an advantageous embodiment of the invention, the valve body is pot-shaped and has a central blind hole.

[0032] The valve body can preferably be slidably guided on the first housing part. It is advantageous if a transverse bore opening into the blind hole is provided, so that the flow path runs through the valve body.

[0033] The advantage of this design lies in guiding the gas or air flow through the valve body, effectively creating an open design towards the first valve side. This means it is subjected to the pressure on the first valve side, as the pressure also acts in the blind hole and potentially on other surfaces of the valve body. Consequently, this design of the valve body offers a further means of influencing the residual pressure and the response speed of the valve body compared to the prior art, independent of the material of the housing components and the valve body itself. Thus, the valve body, the first and second housing components do not necessarily have to be made of brass, although this is possible; they can also be made of aluminum or a plastic, independently of each other. For example, the valve body could be made of plastic and the housing components of brass.

[0034] The valve body can be guided in various structural ways, as will be shown below. The preferred residual pressure relief valve offers higher operational reliability because the valve body cannot tilt due to the guidance provided by the first housing part. It can also be easily miniaturized without impairing its functionality. This allows for a reduction in the radial dimensions and the installation space required for the residual pressure relief valve.

[0035] If the valve seat is formed on the second housing part, the sealing partner against which the valve body comes into contact is the second housing part itself, and no additional sealing component is required. This has the advantage of minimizing the number of components for the residual pressure relief valve. In one embodiment, a guide sleeve, open at its end and connected to the first housing part, can extend into the blind hole of the valve body or circumferentially encircle a cylindrical section of the valve body, so that the valve body is guided by the guide sleeve and the flow path also passes through the guide sleeve. This gives the residual pressure relief valve a compact design and allows its axial length to be easily varied by correspondingly lengthening or shortening the guide sleeve, while maintaining the same functionality.Although the guide sleeve can be a separate component that can be connected to the first housing part, it is preferably formed integrally with the first housing part. In other words, the guide sleeve then forms part of the first housing part. This also reduces the number of parts that make up the residual pressure relief valve and simplifies assembly, since the guide sleeve does not need to be connected to the first housing part separately.

[0036] It is possible that the guide sleeve extends through the energy storage device in one embodiment of the residual pressure relief valve. In other words, the energy storage device is hollow and cylindrical, arranged externally around the guide sleeve, particularly coaxially. This has the advantage that, unlike in the prior art, the energy storage device is not located in the blind hole of the valve body and therefore does not require an axial extension of the residual pressure relief valve, allowing it to be designed in a particularly compact manner. Furthermore, this arrangement ensures that the energy storage device is not affected by the flow.

[0037] In another embodiment, where a cylindrical section of the valve body is circumferentially enclosed by the first housing part, particularly by the guide sleeve, the energy storage device can also be arranged within the housing part, especially within the guide sleeve. Preferably, the valve body is guided not only radially on the inside of the guide sleeve, but also radially on the outside, for example on the inside of the second housing part or an outer sleeve of the first housing part. This completely eliminates any tilting of the valve body.

[0038] The energy storage device can be a spring element, in particular a coil spring or a wave spring. Spring elements such as coil springs or wave springs have the advantage of being widely available on the market, so that a spring element with the required mechanical properties can always be found. Alternatively, the energy storage device could be an elastically deformable component made of an elastomer or rubber. However, a further advantage of metal spring elements is their permanent elasticity, which is why metallic spring elements are preferable. A structurally simple design of the residual pressure relief valve is achieved if the energy storage device presses against an annular end face of the valve body facing the first housing part or against an annular disc abutting this end face. The annular disc can be used to increase the end face of the valve body, i.e., the force transmission area to the valve body.

[0039] It is advantageous if the energy storage device is supported by the first housing part. This is preferably done directly to keep the number of components to a minimum.

[0040] In particular, the energy storage device can bear against an annular surface facing the valve body, which may be formed by a recess in the outer diameter of the first housing part. The energy storage device is thus arranged between the valve body and the first housing part in a radially outer region that coaxially surrounds the flow path through the first housing part.

[0041] This has the advantage that the axial length of the residual pressure holding valve is independent of the axial length of the energy storage device, and thus the latter can be selected from the market supply without restrictions regarding its axial dimensions and only with regard to the required mechanical properties.

[0042] In a further development, the first housing part can have an outer sleeve that coaxially surrounds the guide sleeve, forming an annular space in which the energy storage device and a cylindrical section of the valve body are movably located. In other words, the guide sleeve and the outer sleeve extend parallel to a main part or section of the first housing part and each has a free end opposite this main section, from which the valve body with its cylindrical section extends into the annular space between the guide sleeve and the outer sleeve. This arrangement has the advantage that the valve body is guided exclusively by surfaces of the first housing part, namely the outer surface of the guide sleeve and the inner surface of the outer sleeve. These surfaces can even be produced simultaneously, for example with a milling cutter, so that they are exactly coaxial.There is therefore no guidance provided by different components, so tolerances and angular errors of the surfaces and the alignment of the first and second housing parts relative to each other have no negative influence on the movement of the valve body. To seal the valve body against the guide sleeve and thus prevent leakage along the outside of the guide sleeve, the valve body can have a radially inwardly open recess, in particular a bored-out, on the inlet side of the blind hole, in which a sealing ring bearing against the guide sleeve can be seated. Due to the arrangement of the recess on the inlet side of the blind hole, the recess is also open in the axial direction. Since this makes the end face of the valve body facing the first housing part radially narrower, the aforementioned ring washer can be used to bear against the end face and thus enlarge it again for force transmission through the energy storage device.The annular disc immediately closes the recess in the axial direction and prevents the sealing ring from being forced out of the recess towards the energy storage device. Additionally or alternatively, to seal the valve body against the first housing part, particularly the guide sleeve, the valve body can have an internal annular groove in which a sealing ring rests against the first housing part, particularly the guide sleeve. The internal annular groove is thus directed towards the first housing part and axially spaced from the aforementioned end face. The annular groove can be open radially inwards, so that the sealing ring rests against the outside of the guide sleeve, or it can be open radially outwards, so that the sealing ring rests against the inside of the first housing part, particularly the guide sleeve. The latter is suitable for the embodiment in which the housing part completely surrounds the cylindrical section of the valve body.In this case, the valve body has a radially outwardly open annular groove on its cylinder section.

[0043] In another embodiment, conversely, to seal the valve body against the guide sleeve, the guide sleeve can have an annular groove in which a sealing ring, bearing against the valve body, is seated. The annular groove is thus directed towards the valve body, and the sealing ring located therein is stationary. The annular groove can be open radially outwards if the guide sleeve projects into the blind hole. Alternatively, it can be open radially inwards if the guide sleeve circumferentially surrounds the cylindrical section of the valve body. A combination of the aforementioned embodiments is also conceivable, provided that the annular groove in the valve body and the annular groove in the guide sleeve are sufficiently spaced from each other, as are the annular grooves and the recess in the valve body.

[0044] To prevent leakage along the radial outer surface of the valve body, the valve body can have an outer annular groove in which a sealing ring rests against the opposite inner surface of the second housing part, or, in another embodiment, against the outer sleeve of the first housing part. Here, too, the outer annular groove can be axially offset from the inner annular groove, which has the advantage that the radial thickness of the valve body in the area of ​​the annular grooves can be less than if the outer and inner annular grooves were at the same axial height.

[0045] The valve body may have a mushroom-shaped valve head at its axial end opposite the blind hole. The mushroom-shaped sealing head is formed by a central stub which, spaced apart from the rest of the valve body, has a radially oriented, annular projection. The end face of the stub may be flat, concave, or convex. Optionally, the axial end face of the stub may also be widened to form the radial projection. The mushroom-shaped valve head serves to securely hold a sealing ring or cap, which can then come into sealing contact with the second housing part.

[0046] The valve body can thus have a sealing ring held at the valve head, which, in the closed state of the residual pressure relief valve, rests against a conical inner surface, particularly of the second housing part, to seal the flow path. The conical inner surface presses the sealing ring obliquely against the mushroom-shaped sealing head. The sealing ring is penetrated by the stub and partially engaged behind it by the radial annular projection, thus holding it securely in place.

[0047] Alternatively, the valve body can have a sealing cap held to the valve head, which completely encloses the valve head, so that the sealing cap forms the end face of the valve head. The sealing cap is suitably hat-shaped and engages behind the radial annular projection at least partially, thereby holding it to the valve head.

[0048] In addition to or as an alternative to the sealing element on the valve head, it is also possible to provide a sealing element, such as a coating, a positively connected component, or one or more sealing rings, on the valve seat. These sealing rings can be O-rings of any cross-section, for example, with a circular, oval, or rectangular cross-section and rounded edges. The sealing rings can also be molded seals, for example, those with sealing lips.

[0049] In the simplest case, the sealing rings are mounted on the valve body. In a preferred embodiment of the residual pressure holding valve according to the invention, the sealing rings, or at least one of the sealing rings, can be injection-molded or vulcanized onto the valve body and / or the first and / or second housing part, in particular onto the guide sleeve. This has the advantage that they do not need to be mounted separately. Furthermore, they are secured against slippage because they adhere to the valve body and / or the first or second housing part. In the case of a valve body and / or a first or second housing part made of plastic, injection molding can even create a material bond, so that the sealing rings cannot be separated from the valve body or the first or second housing part without being damaged.

[0050] In one embodiment, the sealing ring located in the outer annular groove, open to the inside of the second housing part or to the outer sleeve, can even be integrally integrated into a sealing cap that forms the axial end of the valve body opposite the blind hole. Such a transitional sealing element can, of course, be open in the area of ​​the transverse bore(s) in the valve body to allow flow.

[0051] It goes without saying that in all the aforementioned cases where a sealing ring or sealing cap is held on the valve body, the respective sealing ring moves together with the valve body relative to the guide sleeve and the second housing part. In a special design variant, the valve body may even be made entirely of an elastomer. In this case, all the aforementioned sealing rings are then an integral part of the valve body or form annular sealing projections.

[0052] As explained, the first valve side is designed to be connected to a compressor, which can build up the necessary pressure in the gas spring. Furthermore, the second valve side is designed to be connected to the gas spring, whose pressure is to be maintained at a minimum level in the event of a malfunction. The residual pressure holding valve according to the invention is particularly flexible with regard to its design, insofar as the installation direction of the valve body can be such that, in a first variant, it seals the second valve side, and in a second variant, it seals the first valve side. According to these possibilities, the first housing part can provide the first valve side and the second housing part the second valve side. This represents the aforementioned first variant. Alternatively, the first housing part can provide the second valve side and the second housing part the first valve side.This represents the second variant mentioned above.

[0053] A preferred design variant is one in which the first and second housing parts are made of metal, such as brass or aluminum, and the valve body is made of plastic. However, it is also possible to make the valve body of metal, such as brass or aluminum, or alternatively, to make the first and / or second housing parts of plastic independently of each other.

[0054] Further features, advantages, and properties of the invention are explained in more detail below with reference to exemplary embodiments and the accompanying figures. In the figures, identical reference numerals or symbols denote identical or at least functionally equivalent components, parts, surfaces, or directions. It should be noted that, within the scope of this description, the terms "have," "comprise," or "include" in no way exclude the presence of further features. Furthermore, the use of the indefinite article for an object does not preclude its plural.

[0055] The terms or word components “radial”, “axial”, “circumferential” or “circumferential” used in this description generally refer to the longitudinal axis of the residual pressure holding valve, unless otherwise stated.

[0056] Features of one embodiment of the invention may also be present in another embodiment, unless this is technically excluded or expressly stated.

[0057] They show:

[0058] Figure 1 shows a first embodiment of a residual pressure holding valve according to the invention;

[0059] Figure 2 shows a second embodiment of a residual pressure holding valve according to the invention;

[0060] Figure 3 shows a third embodiment of a residual pressure holding valve according to the invention;

[0061] Figure 4 shows a fourth embodiment of a residual pressure holding valve according to the invention.

[0062] The illustrations in the figures each show a partially sectioned view of a residual pressure holding valve 1 along an axial plane. While the right half of the valve is sectioned with respect to the valve axis 7, the left half of the valve is shown in a front view.

[0063] Figure 1 shows a residual pressure holding valve 1 for a gas spring (not shown) in the form of an air suspension strut of a motor vehicle, commonly referred to simply as an air spring. An air-sprung vehicle has the advantage that the vehicle's driving characteristics can be influenced by adjusting the pressure in the gas spring. The suspension can be made firmer by increasing the pressure or softer by decreasing it. Furthermore, the pressure influences the height of the vehicle chassis relative to the ground, and thus the vehicle's ground clearance, which can be specifically adjusted by increasing the pressure or decreasing it.

[0064] The residual pressure holding valve 1, hereinafter referred to as the valve, has a first valve side 4, which is intended to be connected to an electronically controlled air compressor via a hose, and is connected to it during operation, and a second valve side 5, which is intended to be connected to the gas spring, and is connected to it during operation. The valve 1 interrupts the flow path A between the first and second valve sides 4, 5 in the event of a sudden pressure difference between sides 4, 5. During normal, trouble-free operation, the valve 1 is open, so that a specific operating pressure prevails on both valve sides 4, 5.If there is a pressure drop on the compressor side of the pneumatic system, for example due to a hose rupture, the pressure on the first valve side 4 drops rapidly to zero. This must cause valve 1 to close within a few milliseconds in such a way that a certain residual pressure is maintained on the second valve side 5, thus preserving the vehicle's suspension. Conversely, if there is a pressure drop in the gas spring, i.e., on the second valve side 5, this also leads to the immediate closure of valve 1, and the rest of the pneumatic system, which is connected to the first valve side 4 via a hose, is protected.

[0065] To achieve this functionality, an embodiment of a residual pressure holding valve 1 is proposed, the structural design of which is shown in Figure 1. The valve 1 has a first housing part 2 and a second housing part 3, wherein in this embodiment the first housing part 2 provides the first valve side 4 and the second housing part 3 provides the second valve side 5.

[0066] The first housing part 2 is essentially screw-like in its external geometry. It comprises a head part 26, a main part 33 extending axially from it, and a guide sleeve 8 also extending axially from it, all of which are integrally formed. The head part 26 has a wrench-like contour on its exterior in the form of a hexagon for gripping with an open-end wrench. The first housing part 2 has a central bore 41 that extends axially through the entire first housing part 2, namely the head part 26, the main part 33, and the guide sleeve 8. The first housing part 2 thus forms a hollow body. Due to the wrench-like contour, the shape of the first housing part is essentially rotationally symmetrical in a 60° cyclic fashion. The bore 41 is open towards the first valve side 4 and forms an inlet opening for the valve 1.

[0067] In the head section 26 and the main section 33, the central bore 41 is stepped multiple times, so that the inner diameter of the central bore 41 decreases several times from the inlet opening to the guide sleeve 8, specifically three times conically and once in a stepped manner. The head section 41 has an internal thread 32 on its inside for screwing in a connecting piece for the pluggable attachment of a hose. The outer contour of the first housing section 2 is also stepped multiple times, so that the outer diameter of the second housing section 2 also decreases several times. More precisely, there is a first stepped reduction in the outer diameter at the transition from the head section 26 to the main section 33, a second stepped reduction in the outer diameter at the transition from the main section 33 to the guide sleeve 8, and a third stepped reduction 34 in the outer diameter in the area of ​​the guide sleeve 8.The second stepped retraction forms a ring surface 12 against which a power storage device 11 is supported. The third stepped retraction 34 forms a stop for a ring disk 14.

[0068] On its radial outer surface, the main part 33 has an external thread 25 to allow it to be screwed into the second housing part 3. In other words, the first housing part 2 extends axially into the second housing part 3.

[0069] A cup-shaped valve body 6 is movably arranged between the first and second housing parts 2, 3. When a minimum pressure is undershot, here on the second valve side 5, a mechanical energy storage device 11 presses the valve body onto a valve seat 22, thus closing the flow path A, which extends from the first valve side 4 to the second valve side 5. The cup shape results from a central blind hole in the valve body 6, so that the valve body 6 essentially consists of a cylindrical section 40 and a base 42, which closes the cylindrical section at its axial end facing the second housing part 3. The open-ended guide sleeve 8 of the first housing part extends into the blind hole 9 of the valve body 6, such that the valve body 6 is guided slidably on the outside of the guide sleeve 8.The valve body 6 has one or more circumferentially distributed transverse bores 10 that connect the interior of the blind hole 9 with a space radially outside the valve body 6. Only one such transverse bore 10 is shown in Figure 1. Preferably, three further transverse bores are arranged symmetrically to this, offset by 90° and 180° respectively. Thus, the flow path A, indicated by corresponding arrows in Figure 1, extends through the valve body 6. The valve body 6 is therefore part of the flow path A. It not only serves the purpose of closing the valve 1, but also acts as a flow-guiding element inside the valve 1. This is because the flow path A extends through the valve body 6, more precisely through the blind hole 9 and the transverse bores 10, and through the guide sleeve 8.

[0070] The energy storage device 11 is formed here by a spring element in the form of a wave spring, which is supported against the first housing part 2. For this purpose, the energy storage device 11, hereinafter referred to as the spring element, rests against an annular surface 12 facing the valve body 6, which is formed by the second recess of the outer diameter of the first housing part. The spring element thus surrounds the guide sleeve 8 at its axial end near the main part 33. Viewed in other terms, the guide sleeve 8 extends coaxially through the spring element. On the side opposite the annular surface 12, the spring element presses against an annular disk 14, which rests against an axial end face of the valve body 6, and transmits the spring force to the valve body 6.

[0071] The second housing part 3 is also a hollow body and essentially cylindrical. It comprises a cylindrical main part 35, which defines an interior space 23 into which the first housing part 2 projects and the valve body 6 is located. Consequently, the aforementioned space radially outside the valve body 6, into which the transverse bores 10 open, is an annular sub-region of the interior space 23 of the main part 35. In other words, the space lies between the valve body 6 and the main part 35. The main part 35 forms an outer wall of the valve 1.

[0072] The main part 35 transitions into a head part 27, which has a hexagonal keyway on its outer surface for gripping with an open-end wrench. On its inner surface, the head part 27 has an internal thread 24 into which the corresponding external thread 25 of the first housing part 2 is screwed. The second housing part 3, together with the head part 27, defines an annular space 36 extending radially outwards, in which the spring element is arranged in a compressed state.

[0073] The main part 35 transitions at its axial end opposite the head part 27 into a base 45, which is pierced by a central bore 43, forming a valve opening 44 in the base 45 that can be closed by the valve body 6. The opening of the valve opening 44 is conical, or formed by a conical inner surface 22b, which forms the valve seat 22. An axially projecting connecting piece 29 with an external thread is integrally attached to the base 45, by means of which the valve 1 can be screwed to a gas spring. The central bore 43 also extends through the connecting piece 29. Thus, the central bore 43 is also part of the flow path A through the valve 1. On its outer side, the connecting piece 29 has a concave rounded area 30 in the transition region to the base 45, in which a sealing ring 31 is arranged to seal the screw connection to the gas spring.

[0074] To interact with the valve seat 22 to interrupt the flow path A, the valve body 6 has a mushroom-shaped valve head 20 at its axial end opposite the blind hole 9. This head is formed as a central butt integrally connected to the base 42, and has a radially extending, annular projection 46 spaced apart from the base 42. The end face of the butt is flat and is widened by the radial projection 46. The radial projection 46 holds a sealing ring 21 in position, which is part of the valve head 20 and is penetrated by the butt. In the closed state of the valve 1, the sealing ring 21 comes into sealing contact with the conical inner surface 22b of the valve opening 44 of the second housing part 3, which forms the sealing seat 22. However, in the state shown in Figure 1, it is lifted from the inner surface 22b.In other words, valve 1 is open, allowing the first valve side 4 to communicate with the second valve side 5 along the flow path A.

[0075] In order to move into the closed state, the valve body 6 is arranged to be axially movable by a few millimeters between the guide sleeve 8 and the main part 35.

[0076] To seal the valve body 6 against the guide sleeve 8 and thus prevent leakage through the gap along the outside of the guide sleeve 8 into the annular space 36 and outwards via the threads 24, 25, the valve body 6 has a radially inwardly and axially open recess 15 on the inlet side of the blind hole 9, in which a sealing ring 16 is arranged, bearing against the guide sleeve 8. As a result of the recess 15, the end face 13 of the valve body 6 facing the first housing part 2 is radially reduced. The annular washer 14 rests against the end face 13 and enlarges it for force transmission by the spring element. The annular washer 14 then immediately closes the recess 15 in the axial direction and prevents the sealing ring 16 from slipping out of the recess 15.

[0077] To prevent leakage through the gap along the radial outer surface of the valve body 6, the valve body 6 has an outer annular groove 17 in which a sealing ring 19 is arranged, bearing against the opposite inner surface 18 of the second housing part 3, more precisely against the main part 35. The outer annular groove 17 is axially offset from the recess 15, which allows the radial wall thickness of the cylinder section 40 of the valve body 6 to be less than if the outer annular groove 17 and the recess 15 were at the same axial height.

[0078] As already explained, the operating principle of this residual pressure holding valve 1 according to the invention is such that, in the event of a pressure difference between the first and second valve sides 4, 5, such as in the case of a hose rupture on the first valve side 4, the flow path A is immediately interrupted by the spring element pressing the valve body 6 against the base 45 of the second housing part 3, which forms the sealing seat 22, thereby covering the valve opening 44. The valve head 20 rests with its sealing ring against the conical inner surface 22b of the edge of the valve opening 44. A certain residual pressure is present on the second valve side 5. This residual pressure also acts on the valve head 20, which is consequently pressed towards the spring element.However, the spring element and its degree of compression, which is determined by the axial installation space available in the annular space 36 on the one hand and the screw-in depth of the first housing part 2 into the second housing part 3 on the other hand, as well as the area of ​​the valve head 20, on which the pressure force on the second valve side 5 acts, are dimensioned and selected in relation to each other such that the force exerted by the spring element is greater than the force acting on the valve body 6 at the specified residual pressure, so that this residual pressure can be safely maintained in the gas spring.

[0079] According to the invention, by changing the screw-in depth of the first housing part 2 into the second housing part 3, the preload of the mechanical energy storage device 11, here of the spring element mentioned, can be adjusted or set in order to calibrate the residual pressure holding valve 1, in particular already during its initial assembly.

[0080] Figure 2 shows a second embodiment of a residual pressure holding valve 1 according to the invention. It differs from the first embodiment in Figure 1 essentially in the design of the valve head 20 and the valve seat 22, as well as in the sealing of the gap between the guide sleeve 8 and the valve body 6. This is explained below, and reference is made to the description of the first embodiment in Figure 1. In this second embodiment, the valve head 20 is also mushroom-shaped, but it does not have a sealing ring 21, but rather a sealing cap 21a. For this purpose, it engages the annular projection 46 in a form-fitting manner, the edges of which, in cross-section, are not rounded but angular for better grip compared to the first embodiment. Thus, the sealing cap 21a encloses the entire valve head 20. The sealing cap 21a is made of an elastomer.

[0081] In contrast to the first embodiment, the edge of the valve opening 44 in the second housing part 3 is not formed by a conical inner surface to form the valve seat 22. Instead, the second housing part 3 has an annular projection 22a surrounding the valve opening 44 to form the valve seat 22, against which the valve body 6 with the sealing cap 21a abuts in a sealing manner.

[0082] The annular protrusion 22a can be created by compressing the material around the valve opening 44 in a radial direction outwards, so that the central bore 43 has a larger inner diameter on the side of the valve opening 44 than at the other axial end.

[0083] In the second embodiment, a radially outwardly open annular groove 15 is provided in the outer surface of the guide sleeve 8 to seal the valve body 6 against the guide sleeve 8. A sealing ring 16, bearing against the valve body 6, is arranged in this groove. This has the advantage that the recess 15 in the valve body 6 can be omitted, thus maximizing the area of ​​the annular end face 13 of the valve body 6. This, in turn, makes it possible to omit the ring washer 14, thereby reducing the assembly effort for the valve 1. Figure 3 shows an embodiment of a residual pressure holding valve 1 according to the invention, in which the valve body 6 is "upside down" with respect to the first and second valve sides 4, 5. In other words, in this embodiment, only the first valve side 4 is sealed.Although the valve seat 22 is also formed on the second housing part 3 here, the positions of the first and second housing parts 2, 3 are reversed compared to Figure 1. Thus, the first housing part 2 now provides the second valve side 5, i.e., the connection to the gas spring, and the second housing part 3 provides the first valve side 4, i.e., the connection to the compressor.

[0084] The two housing parts 2, 3 and the valve body 6 are also slightly modified in their design, with the valve body 6, its seal against the guide sleeve 8, and the valve seat 22 essentially corresponding to the second embodiment shown in Figure 2. The valve body 6 also features a sealing cap 21a held on the valve head 20, which, when the valve 1 is closed, presses against an annular projection 22a on the base 45 of the second housing part 3, which surrounds the valve opening 44. However, the projection 22a is not formed by material compression. Furthermore, the gap between the guide sleeve 8 and the valve body 6 is also sealed by a seal 16, which is inserted into a radially outwardly open annular groove 15b in the guide sleeve 8.

[0085] In this third embodiment, the cylinder section 40 of the valve body 6 is movably located within a cylindrical annular space 36. This space is bounded radially inwards towards the valve axis 7 by the guide sleeve 8 and radially outwards by an outer sleeve 28, which is also integral with the first housing part 2. The guide sleeve 8 and the outer sleeve 28 extend coaxially from the main part 33 of the first housing part 2. The spring element, i.e., the mechanical energy storage device 11, is also located within the cylindrical annular space 36, so that the annular space 36, at least in the area accommodating the spring element, corresponds to the annular space 36 according to the first and second embodiments. The valve body 6 seals against the inner surface 18a of the outer sleeve 28 via a sealing ring 19, as is the case in the first and second embodiments with respect to the inner surface 18 of the cylindrical main part 35.However, here the outer sleeve 28 lies flat against the inner side 18 of the cylindrical main part 35 of the second housing part.

[0086] In the third embodiment, it is essential that the first and second housing parts 2, 3 are not screwed together, but rather inserted into one another. The first housing part 2 is held in place by the second housing part 3 via a positive locking mechanism 37, 38, which here is exemplified by an annular projection 37 and a corresponding annular groove 38 into which the annular projection 37 engages. The positive locking mechanism 37, 38 exists between the free axial end of the cylindrical main part 35 of the second housing part 3 and the main part 33 of the first housing part 2, wherein the annular projection 37 extends radially inwards from said free axial end of the cylindrical main part 35, and the annular groove 38 engages in the main part 33 of the first housing part 2. Due to the interlocking nature of the housing parts 2, 3, they do not have a head with a key-like contour.A seal 39 lies axially in front of the said positive locking 37, 38 in an annular groove on the outside of the outer sleeve 28 in order to seal to the main part 35 of the second housing part 3.

[0087] Another difference between the third version and the first and second versions is that the connecting piece 29 for screw connection with the gas spring is now part of the first housing part 2 and is molded onto its main part 33.

[0088] In order to be able to mechanically adjust the preload of the mechanical energy storage device 11 according to the invention, the mechanical energy storage device 11 is supported with its side facing away from the valve body 6 against a pressure plate 47, which accordingly forms an annular surface 12a for this purpose. The pressure plate 47 is adjustable in its axial position relative to the valve body 6 in order to preload the mechanical energy storage device 11 to a greater or lesser extent. For example, the axial position of the pressure plate 47 relative to the valve body 6 and, in the illustrated embodiment, also relative to the first housing part 2, can be adjusted from outside the two housing parts 2, 3, that is, in the assembled state of the residual pressure holding valve 1.For this purpose, for example, as schematically illustrated by dashed lines, screws can be inserted into the first housing part 2, operable from the outside, which, by screwing them in to a greater or lesser extent, move the pressure plate 47 axially in the direction of movement of the valve body 6. Alternatively, it can also be provided that the pressure plate 47 can only be adjusted from the inside, i.e., when the housing parts 2, 3 are not yet mounted together.

[0089] The adjustability of the mechanical energy storage device 11 according to Figure 3 can of course also be provided if the first housing part 2 forms the first valve side 4 and the second housing part 3 forms the second valve side 5, as shown in Figures 1, 2 and 4.

[0090] Furthermore, it is possible to implement the mechanical adjustment of the preload of the mechanical energy storage device 11 differently than in the embodiments shown here, for example with a pressure plate 47 guided in a cam guide or a thread. Other possibilities exist.

[0091] Figure 4 shows a fourth embodiment of a residual pressure holding valve 1 according to the invention. It differs from the other embodiments only in that the guide sleeve 8 is shortened with respect to its axial length and the guide sleeve 8 circumferentially surrounds the cylinder section 40 of the valve body 6. Consequently, the cylinder section 40 has a radially outwardly open annular groove 15c on its outer surface, in which a sealing ring 16 is arranged, which abuts the inner surface of the guide sleeve 8 to provide a seal. The outer diameter of the valve body 6 also widens in a stepped manner at a certain axial distance from the end face of the guide sleeve 8, so that the valve body 6 can come into contact with the inner surface 18 of the main part 35 of the first housing part 2. The stepped widening creates the annular end face 13 against which the spring element abuts.Furthermore, this variant essentially corresponds to the second embodiment shown in Figure 2, so reference is made to the details there.

[0092] All sealing rings 16, 19, 21, 31, 39 are formed by O-rings in the illustrated design variants. Alternatively, one or more of the sealing rings can also be injection-molded onto the respective component 2, 3, 6.

[0093] The first and second housing parts 2, 3 are preferably made of brass, with the second housing part 3 being made of plastic according to the third embodiment. The valve body 6 can also be made of brass, but preferably of plastic. The valve body 6 can also be made of an elastomer. Thus, the separate sealing rings 16, 19, 21 and the sealing cap 21a can be omitted, because the seals are then an integral part of the valve body 6.

[0094] It should be noted that the foregoing description is given merely as an example for illustrative purposes and in no way limits the scope of protection of the invention. Features of the invention that are indicated as "may," "exemplary," "preferred," "optional," "ideal," "advantageous," "if applicable," "suitable," or the like are to be considered purely optional and likewise do not limit the scope of protection, which is exclusively defined by the claims. Insofar as the foregoing description mentions elements, components, process steps, values, or information that have known, obvious, or foreseeable equivalents, these equivalents are also encompassed by the invention.Likewise, the invention includes any changes, alterations or modifications of embodiments which involve the replacement, addition, modification or omission of elements, components, process steps, values ​​or information, as long as the basic idea of ​​the invention is retained, regardless of whether the change, alteration or modification leads to an improvement or deterioration of an embodiment.

[0095] Although the foregoing description of the invention mentions a multitude of physical, intangible, or process-related features relating to one or more specific embodiments, these features can also be used in isolation from the specific embodiment, at least insofar as they do not necessarily require the presence of further features. Conversely, these features mentioned in relation to one or more specific embodiments can be combined arbitrarily with one another and with further disclosed or undisclosed features of illustrated or unillustrated embodiments, at least insofar as the features do not mutually exclude each other or lead to technical incompatibilities.

[0096] Reference symbol list

[0097] 1 residual pressure holding valve

[0098] 2 first housing part

[0099] 3 second housing part

[0100] 4 first valve side

[0101] 5 second valve side

[0102] 6 valve bodies

[0103] 7 Valve axis

[0104] 8 Guide sleeve

[0105] 9 blind hole

[0106] 10 transverse bore

[0107] 11 Energy storage

[0108] 12, 12a Ring area

[0109] 13 Front surface of the valve body

[0110] 14 ring disc

[0111] 15 Exclusion

[0112] 15a-15c Ring groove

[0113] 16 sealing ring

[0114] 17 outer ring groove

[0115] 18 Inside of the second housing part

[0116] 18a Inside of the outer sleeve

[0117] 19 outer sealing ring

[0118] 20 Valve head

[0119] 21 Sealing ring on the valve head

[0120] 21a Sealing cap

[0121] 22 Valve seat

[0122] 22a annular protrusion for valve seat

[0123] 22b conical inner surface for valve seat flow-through interior

[0124] internal thread

[0125] external thread

[0126] Head section with key contour of the first housing part

[0127] Head section with key contour of the second housing part

[0128] Outer sleeve

[0129] Connection piece

[0130] Concave rounding

[0131] sealing ring

[0132] internal thread

[0133] Main part of the first housing part

[0134] Stop, return of the cylindrical main part of the second housing part

[0135] Annular space for energy storage

[0136] Ring-shaped protrusion

[0137] Ring groove

[0138] sealing ring

[0139] Cylinder section of the valve body

[0140] Central borehole

[0141] Floor

[0142] Central borehole

[0143] Valve opening

[0144] Floor

[0145] Ring-shaped protrusion

[0146] printing plate

Claims

Patent claims 1. Method for providing a residual pressure holding valve (1) for a gas spring, in particular for an air spring strut of a motor vehicle, wherein the residual pressure holding valve (1) comprises the following features: a flow path (A) between a first valve side (4) connectable to a compressor and a second valve side (5) connectable to the gas spring; a valve seat (22); a valve body (6) complementary to the valve seat (22), which can be lifted from the valve seat (22) to open the flow path (A) by an opening pressure on the valve side (5) and which can be pressed onto the valve seat (22) by a pre-tensioned mechanical energy storage device (11) to close the flow path (A) when the residual pressure on the valve side (5) is less than the opening pressure; a first housing part (2) and a second housing part (3) between which the valve body (6) is movably arranged;characterized in that the preload of the mechanical energy storage device (11) is mechanically adjusted during or after the installation of the residual pressure holding valve (1) and thereby one of several possible adjustable opening pressures is set for calibrating the residual pressure holding valve (1).

2. Method according to claim 1, wherein the preload of the mechanical energy storage device (11) is adjusted by changing its axial length by compressing or pulling it apart in the direction of movement of the valve body (6).

3. Method according to claim 2, wherein the valve seat (22) is formed on the second housing part (3) and the first housing part (2) is formed on the second Housing part (3) is mounted such that the mechanical energy storage device (11) is supported on the first housing part (3) and on the other hand on the valve body (6), and during or after the mounting of the residual pressure holding valve (1) one of several possible opening pressures is set by adjusting a relative position of the first housing part (2) to the second housing part (3).

4. Method according to claim 3, wherein the first housing part (2) is screwed into or onto the second housing part (3) and the preload of the mechanical energy storage device (11) is adjusted by screwing or screwing the first housing part (2) into or onto the second housing part (3) to a greater or lesser extent, in particular without stop.

5. Method according to one of claims 2 to 4, wherein, when the preload of the mechanical energy storage device (11) is set, its axial length is fixed, in particular by fixing the first housing part (2) to the second housing part (3).

6. Method according to any one of claims 1 to 5, wherein a first pressure, in particular a constant pressure, is set on the first valve side (5), a second pressure on the second valve side (5) is set constant or varied, and the residual pressure holding valve (1) is calibrated by mechanically adjusting the preload of the mechanical energy storage device (11) such that a predetermined opening pressure is established.

7. Residual pressure holding valve (1) for a gas spring, in particular for an air spring strut of a motor vehicle, with a flow path (A) between a first valve side (4) that can be connected to a compressor and a second valve side (5) that can be connected to the gas spring; with a valve seat (22); with a valve body (6) complementary to the valve seat (22), which can be lifted from the valve seat (22) by an opening pressure on the valve side (5) to open the flow path (A) and can be pressed onto the valve seat (22) by a pre-tensioned mechanical energy storage device (11) to close the flow path (A) at a residual pressure on the valve side (5) that is less than the opening pressure; with a first housing part (2) and a second housing part (3) between which the valve body (6) is movably arranged; characterized in that the pre-tension of the mechanical energy storage device (11) is mechanically adjustable during or after the installation of the residual pressure holding valve (1) in order to set one of several possible adjustable opening pressures for calibrating the residual pressure holding valve (1).

8. Residual pressure holding valve (1) according to claim 7, wherein the preload of the mechanical energy storage device (11) is adjustable by changing its axial length by compressing or pulling it apart in the direction of movement of the valve body (6).

9. Residual pressure holding valve (1) according to claim 8, wherein the valve seat (22) is formed on the second housing part (3), the mechanical energy storage device (11) is supported at least indirectly on the first housing part (2) and on the other hand on the valve body (22), and the first housing part (3) is adjustable on the second housing part (3) at least during assembly in order to adjust the opening pressure by adjusting a relative position of the first housing part (2) relative to the second housing part (3).

10. Residual pressure holding valve (1) according to claim 9, wherein the first housing part (2) is screwed into or onto the second housing part (3) without stop.

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