PRESSURE STORE

Abstract

A pressure store comprising sub-chambers (8, 54, 28) arranged in a housing (2), a first sub-chamber (8) arranged between the housing (2) and a flexible separating diaphragm (40), a second sub-chamber (54) arranged between the separating diaphragm (40) and a supporting body (48), and a third sub-chamber (28) encompassed by the supporting body (48), wherein the first sub-chamber (8) can be filled with a first fluid, wherein the second sub-chamber (54) and the third sub-chamber (28) are connected to one another in fluid-conducting fashion and can be filled with a second fluid, and wherein the first and the second sub-chamber (8, 54) vary in terms of their respective sizes as a result of movements of the separating diaphragm (40) as a function of the respective filling state, is characterized in that the first fluid is a storage medium and the second fluid is a working medium, and in that the second sub-chamber (54) is increased in size during the extraction of storage medium from the pressure store and is reduced in size during the filling of the pressure store with storage medium.

Description

The invention relates to a pressure store comprising compartments arranged in a housing, a first compartment which is arranged between the housing and a flexible separating diaphragm, a second compartment which is arranged between the separating diaphragm and a support body, and a third compartment encompassed by the support body, with the first compartment being fillable with a first fluid, the second compartment and the third compartment being connected to one another to conduct fluid and being fillable with a second fluid, and the first and the second compartment varying in their respective size as a result of movements of the separating diaphragm as a function of the respective filling state.

Such an accumulator is known from DE 101 13 415 A1. In the known accumulator in the form of a hydropneumatic accumulator, there is a flexible separating element in an accumulator housing, formed by the end piece of a pipe, and the element surrounds a support body which has fluid passages. The support body, at least in individual sections, has a nonround cross-sectional shape. The separating element is anchored on the accumulator housing with the formation of a seal such that, on the outside and inside of the separating element, receiving spaces are formed which are separate from one another. A centrally located through bore forms a passage which leads to the inner receiving space of the accumulator for a storage medium. There is a gas valve for filling the outside gas space. The known accumulator can be used for energy storage, for example, in conjunction with vehicle suspension systems, or also as pulsation dampers. Furthermore, the known solution is especially well suited for damping of pressure peaks in hydraulic or other fluid-engineering systems. The known solution leaves much to be desired for use as an accumulator for storage media in the form of chemically corrosive fluids, such as a urea-water solution.

Another accumulator is known from DE 38 10 509 C2. An accumulator is known comprising a main body of a tank with an outer pipe of cylindrical shape on whose one end there is a side plate and on whose other end there is a cover, at least one inlet opening and one outlet opening which are formed on the outer pipe, and a bladder or diaphragm for subdividing the interior of the main body of the tank into a gas chamber and a liquid chamber, with an opening of the bladder being sealed tight by the cover. An insert is arranged such that it projects into the bladder for the purpose of reducing the volume of the gas chamber. The insert is formed from a base part, a middle part, and a head part, with the head part being kept in contact with the bottom of the diaphragm; this makes it possible to prevent damage of the diaphragm by repeated contraction. In the contracted state, the bladder or diaphragm adjoins the insert.

Accumulators of this type are widely used in different sizes and structural configurations in order to receive and discharge variable volumes of pertinent fluids which are under the operating pressure of a fluid system that is connected on the fluid side, with the bladder, which is under a preloading pressure of the working gas, forming a pressure cushion on its gas side. The operational reliability of the accumulator depends primarily on the accumulator bladder, which typically consists of a plastic material, especially butyl, which bladder is exposed not only to mechanical stresses in operation, but is also to be resistant to chemically corrosive storage fluids, if possible. As has been shown, in conjunction with corrosive fluids such as urea-water solutions, it has so far not been possible to ensure a problem-free service life of sufficient length for continuous operation, for example, over 20,000 hours.

So-called “urea injection” is being increasingly used in automotive engineering in order to reduce the nitrogen oxide (NOx) emissions by injection into the exhaust gas flow. In this type of application, it is especially important that a long service life can be achieved without problems in continuous operation.

In this respect, the object of the invention is to provide an accumulator which is characterized by improved operational reliability in connection with corrosive storage media and which is therefore suitable especially for use in urea injection in automotive engineering.

This object is achieved according to the invention by an accumulator having the features specified in claim 1 in its entirety.

According to the characterizing part of claim 1, one important feature of the invention consists in that the first fluid is a storage medium and the second fluid is a working medium and that the second compartment is enlarged when the storage medium is removed from the accumulator and reduced in size when the accumulator is filled with the storage medium. The amount of the working medium to be accommodated is defined by the volumes of the second and third compartment. When the first compartment is filled with the storage medium, the flexible separating diaphragm is moved such that the second compartment, which adjoins the third compartment outside the support body, is reduced in size. Accordingly, the second compartment is enlarged when the storage medium is removed from the first compartment or when the filling of the latter with the storage medium decreases.

Advantageously, the accumulator is designed as a hydropneumatic bladder accumulator for a gaseous working medium and/or a liquid storage medium. Especially preferably, the accumulator is designed for filling of a storage medium in the form of a chemically corrosive fluid such as a urea-water solution. This affords the possibility of using the accumulator according to the invention in urea injection, especially in the automotive domain.

In one special configuration of the accumulator according to the invention, the support body and the separating diaphragm are shaped and dimensioned such that at a volumetric size of the first compartment which exceeds a definable boundary value, in other words, at a volumetric size which exceeds a maximum value for the storage medium which is to be accommodated, the support body forms a support for the separating diaphragm.

Furthermore, it is advantageous if the housing and the separating diaphragm are shaped and dimensioned such that the separating diaphragm at least partially adjoins the housing when the first compartment is completely emptied. Alternatively, the separating diaphragm can be shaped and dimensioned such that it is spaced apart from the support body and from the housing when the first compartment is completely emptied.

The support body and the housing thus form an effective protection for the separating diaphragm against overstress at excess pressures in the first and second compartment by the separating diaphragm or the accumulator bladder being able to rest against the support body and the housing and thus being protected against being crushed at excess pressures. The reduced mechanical loading leads to a prolongation of the safe service life of the separating diaphragm even if it is exposed to chemically corrosive media such as a urea-water solution.

Typically, the housing has a head part which forms the closure of the housing and which borders the second and/or third compartment. The housing is advantageously made cup-shaped, with the first compartment being arranged on the bottom. In the head part, there can be a connection device for the second fluid.

Furthermore, it is advantageous if on the head part there is a retaining body on which the opening edge of the separating diaphragm is anchored. The retaining body preferably forms a retaining part on which the support body is arranged. This yields an especially compact construction of the accumulator.

In one special configuration of the accumulator according to the invention, the retaining body has the shape of a bell whose jacket surrounds a fourth compartment which borders the third compartment. In this way, the intake capacity of the accumulator for the second fluid or the typically gaseous working medium is enlarged, and, at the same time, the material demand for forming the accumulator is reduced.

In especially advantageous exemplary embodiments, the support body has the shape of a body of revolution which is made rounded and closed on the end facing the first compartment and is provided with at least one lateral wall opening as a passage site between the second and third compartment. In this configuration, the support body for the separating diaphragm or accumulator bladder can form a large-area support so that the accumulator bladder, which has essentially no folds at excess pressures, is optimally protected.

With respect to the configuration of the head part, the arrangement can be advantageously made such that the head part has a cover part which can be screwed to the housing with inside wall parts in the form of a spherical cap which is concentric to the axis of the housing, and that within the cover part the retaining body is arranged such that between its outside wall in the form of spherical surface parts and the inside wall parts of the cover part, a gap is formed for accommodating an edge region of the separating diaphragm which borders the opening edge.

Especially reliable anchoring of the separating diaphragm can be achieved when the retaining body in a region which is axially offset from its retaining part in the direction of the connection device has an annular groove which has been machined into the outside wall and which is engaged by an edge bead which surrounds the opening edge of the separating diaphragm for the anchoring of the separating diaphragm.

In especially advantageous exemplary embodiments, the connection device has a screw fitting which extends through an opening of the cover part which is concentric to the central axis, which fitting pulls the retaining body against the inside wall of the cover part by screwing to the cover part and clamps the edge region of the separating diaphragm located in the gap.

Especially advantageously, the arrangement can be made such that the retaining body in the region of the retaining part forms a circular cylinder on whose edge region catch elements are formed which with counter-elements on the support body form a snap connection which anchors the latter. This type of anchoring of the support body is especially easy to mount and makes possible low production costs.

The catch elements on the outer wall of the retaining part can be offset from its end edge and can be formed by depressions of the outer wall of the retaining part into which a bead-like projection which protrudes radially to the inside, can be snapped on the inside of the support body.

Alternatively, the catch elements on the inside wall of the retaining part can be formed by a depression which is axially at a distance from its end edge and a projection which adjoins the end edge and which protrudes radially to the inside, and said catch elements can be latched to counter-elements by catch fingers which are distributed over the periphery of the opening of the support body. In a collar of individual catch fingers which has been formed in this way, mounting is made especially simple and convenient. The corresponding applies to exemplary embodiments in which latching takes place on the outside of the retaining part. In this case, there can also be individual catch fingers on the end edge of the support body.

The support body is preferably formed from a plastic material. Especially advantageously in this case, it can be glass fiber-reinforced polyarylamide IXEF®, a material which, compared to conventional glass fiber-reinforced plastics, is characterized by a smooth, closed outer skin. Due to these properties, the retaining body and/or the connection device can also be advantageously formed from this material.

The invention is detailed below using the drawings.

FIG. 1 shows a longitudinal section of one exemplary embodiment of the accumulator according to the invention which is shown only slightly enlarged compared to a practical embodiment;

FIG. 2 shows a longitudinal section of only one retaining body with the support body fixed thereon for the exemplary embodiment from FIG. 1;

FIG. 3 shows an extract of the region designated as III in FIG. 2, greatly enlarged compared to FIG. 2, and

FIG. 4 shows a longitudinal section which is similar to FIG. 2 and in which a modified example of the latching of the support body on the retaining body is shown.

The invention is explained below using the example of the use of the accumulator for a urea injection system. In FIG. 1, which shows the exemplary embodiment of the accumulator as a whole, an accumulator housing is designated as 2 and for the most part has the shape of a circularly cylindrical cup on whose closed bottom 4 a throughflow opening 6 is located. The opening 6 which is aligned to the central longitudinal axis 10 enables supply and discharge of a first fluid, such as a urea-water solution, to or from the first compartment 8 which is located in the housing 2 bordering the bottom 4. A head part 12, which can be screwed to the accumulator housing 2, forms the fluid-tight closure of the upper open end of the housing 2.

The head part 12 has an outer cover part 14 on which the screw coupling to the housing 2 is formed and which can consist of a metallic material, for example, of aluminum, as can also be the case for the housing 2. Alternatively, the cover part 14 can also be formed from a structurally strong plastic material. The cover part 14 has a central opening 16 which is concentric to the axis 10. At a short distance from the opening 16, the cover part 14 has inner wall parts in the form of a spherical cap 18 which is concentric to the axis 10. Within the cover part 14, the head part 12 has a retaining body 20 with a screw fitting 22 which forms the connection device for the second fluid, which is located integrally on the retaining body, which extends through the opening 16 of the cover part 14, and by means of which the retaining body 20 is fixed within the cover part 14 in interaction with a nut 24. A central fluid channel 26 extends through the screw fitting 22 in order to fill a third compartment 28 with the working medium which is under a preloading pressure as the second fluid. A valve insert which is arranged within the channel 26 is not shown in the drawing.

The retaining body 20 has the shape of a bell whose jacket surrounds a fourth compartment 30 which borders the third compartment 28. The bell jacket on its outside wall forms spherical surface parts 34 which define between themselves and the spherical cap 18 of the cover part 14 a clamping gap 36 for the anchoring region 38 of a separating diaphragm 40, which region is arranged in the gap 36. The bladder, which is formed from a plastic such as butyl, which is suitable for these types of accumulators, forms the flexible separating diaphragm 40 between the first compartment 28 and the second compartment 54. The retaining body 20 between the end of the outer spherical surface part 34 and the screw fitting 22 has an annular groove 42 which for especially reliable anchoring of the separating diaphragm 40 engages an edge bead 44 which surrounds its opening edge.

The retaining body 20 with the bell located within the bladder formed by the separating diaphragm 40 forms a retaining part 46 for the anchoring of a support body 48 which projects into the interior of the bladder. The support body is formed from a relatively structurally strong plastic material, with glass fiber-reinforced polyarylamide IXEF® having proven itself especially well suited. As FIG. 1 shows, the support body 48 has the shape of a body of revolution with a spherically rounded, closed lower end located at a distance from the bottom 4 of the housing 2 and surrounds a third compartment 28 which borders the fourth compartment 30. The other upper end 50 of the support body 48 is fixed on the retaining part 46 by means of a snap connection. As FIG. 1 moreover shows, the support body 48 in a longitudinal section is somewhat V-shaped and has side wall openings 52 for the passage of the working fluid to the second compartment 54, which borders the third compartment 28.

The details of the snap connection are best illustrated in FIGS. 2 and 3. As is apparent, at a short distance from the end edge 56 of the retaining part 46, depressions 56 and 60 are formed in which the end region of the support body 48 can be accommodated, and a projection 62 of the support body 48 which protrudes radially to the inside can be snapped into the depression 60. The retaining body 20 in this example, in the same manner as the support body 48 and the valve located in the channel 26 of the fitting 22, is formed from glass fiber-reinforced polyarylamide IXEF®, so that the retaining body 20 with the support body 48 fixed thereon forms a unit which consists completely of plastic.

In operation, when used for urea injection, the first compartment 8 of the accumulator is filled with the urea-water solution by means of a pump until an upper value of the system pressure of the system pressure is reached and the pump shuts off. The storage medium for metered injection is forced into the system by the accumulator pressure. When a lower pressure value is reached, the pump starts again. If unwanted excess pressures should occur and a certain boundary value of the volume increase of the first compartment 8 is exceeded, the separating diaphragm 40 rests against the support body 48 and is thus protected against overload and damage.

FIG. 4 shows one version of the configuration of the snap connection, with the catch elements now being arranged on the inner wall of the retaining part 46 of the retaining body 20. As FIG. 4 shows, it is a depression 64 which is axially at a distance from the end edge 56, and a projection 66 which adjoins the end edge 56 and which protrudes radially to the inside. The counter-elements on the side of the support body 48 are formed by retaining fingers 68 which are arranged distributed over the periphery of the opening of the support body 48. For counter-elements formed by individual catch fingers 68, the establishment of the latching is made especially simple and convenient.

In the embodiment of the latching shown in FIGS. 2 and 3, on the outside of the retaining part 46 of the retaining body 20, the counter-elements of the support body 48 could also be formed from individual, peripherally distributed catch fingers.

Claims

1. A pressure store comprising compartments (8, 54, 28) arranged in a housing (2), a first compartment (8) which is arranged between the housing (2) and a flexible separating diaphragm (40),a second compartment (54) which is arranged between the separating diaphragm (40) and a support body (48), anda third compartment (28) encompassed by the support body (48),with the first compartment (8) being fillable with a first fluid,the second compartment (54) and the third compartment (28) being connected to one another to conduct fluid and being fillable with a second fluid, andthe first and the second compartment (8, 54) varying in their respective size as a result of movements of the separating diaphragm (40) as a function of the respective filling state,characterized in that the first fluid is a storage medium and the second fluid is a working medium, andthat the second compartment (54) is enlarged when the storage medium is removed from the pressure store and reduced in size when the pressure store is filled with the storage medium.

2. The accumulator according to claim 1, characterized in that the accumulator is made as a hydropneumatic bladder accumulator for a gaseous working medium and/or a liquid storage medium.

3. The accumulator according to claim 1, characterized in that the accumulator is made for filling of a storage medium in the form of a chemically corrosive fluid such as a urea-water solution.

4. The accumulator according to claim 1, characterized in that the support body (48) and the separating diaphragm (40) are shaped and dimensioned such that the support body (48) at a volumetric size of the first compartment (8) which exceeds a definable boundary value forms a support for the separating diaphragm (40).

5. The accumulator according to claim 1, characterized in that the housing (2) and the separating diaphragm (40) are shaped and dimensioned such that the separating diaphragm (40) at least partially adjoins the housing (2) when the first compartment (8) is completely emptied.

6. The accumulator according to claim 1, characterized in that the separating diaphragm (40) is shaped and dimensioned such that it is spaced apart from the support body (48) and from the housing (2) when the first compartment (8) is completely emptied.

7. The accumulator according to claim 1, characterized in that the housing (2) has a head part (12) which forms the closure of the housing (2) and which borders the second and/or third compartment (54, 28).

8. The accumulator according to claim 7, characterized in that in the head part (12) there is a connection device (22) for the second fluid.

9. The accumulator according to claim 7, characterized in that on the head part (12) there is a retaining body (20) on which the opening edge of the separating diaphragm (40) is anchored.

10. The accumulator according to claim 9, characterized in that the retaining body (20) forms a retaining part (46) on which the support body (48) is arranged.

11. The accumulator according to claim 9, characterized in that the retaining body (20) has the shape of a bell whose jacket surrounds a fourth compartment (30) which borders the third compartment (28).

12. The accumulator according to claim 1, characterized in that the support body (48) is a body of revolution which is made rounded and closed on the end facing the first compartment (8) and is provided with at least one wall opening (52) as a passage site between the second compartment (54) and third compartment (28).

13. The accumulator according to claim 9, characterized in that the head part (12) has a cover part (14) which can be screwed to the housing (2) with inside wall parts in the form of a spherical cap (18) which is concentric to the axis (10) of the housing (2), and that within the cover part (14) the retaining body (20) is arranged such that between its outside wall in the form of spherical surface parts (34) and the inside wall parts of the cover part (14), a gap (36) is formed for accommodating an edge region (38) of the separating diaphragm (40) which borders the opening edge.

14. The accumulator according to claim 9, characterized in that the retaining body (20) in a region which is axially offset from its retaining part (46) in the direction of the connection device (22) has an annular groove (42) which has been machined into the outside wall and which is engaged by an edge bead (44) which surrounds the opening edge of the separating diaphragm for the anchoring of the separating diaphragm (40).

15. The accumulator according to claim 13, characterized in that the connection device has a screw fitting (22) which extends through an opening (16) of the cover part (14) which is concentric to the central axis (10), which fitting pulls the retaining body (20) against the inside wall of the cover part (14) by screwing to the cover part (14) and clamps the edge region (38) of the separating diaphragm (40) located in the gap (36).

16. The accumulator according to claim 10, characterized in that the retaining body (20) in the region of the retaining part (46) forms a circular cylinder on whose edge region catch elements (58, 60) are formed which with counter-elements (62) on the support body (48) form a snap connection which anchors the latter.

17. The accumulator according to claim 16, characterized in that the catch elements on the outer wall of the retaining part (46) are offset from its end edge (56) and are formed by depressions (58, 60) of the outer wall of the retaining part (46) into which a bead-like projection (62) which protrudes radially to the inside can be snapped on the inside of the support body (48).

18. The accumulator according to claim 16, characterized in that the catch elements on the inside wall of the retaining part (46) are formed by a depression (64) which is axially at a distance from its end edge (56) and a projection (66) which adjoins the end edge (56) and which protrudes radially to the inside, and said catch elements can be latched to counter-elements by catch fingers (68) which are distributed over the periphery of the opening of the support body (48).

19. The accumulator according to claim 1, characterized in that the support body (48) is formed from plastic, preferably from glass fiber-reinforced polyarylamide IXEF®.

20. The accumulator according to claims 9, characterized in that the retaining body (20) and/or the connection device (22) is formed from plastic, especially from glass fiber-reinforced polyarylamide IXEF®.