Expansion tanks, especially for hydraulic vehicle brake systems

Abstract

The invention relates to an expansion tank 1, in particular for hydraulic motor vehicle brake systems, with at least one pressure medium chamber 2, which can be filled with pressure medium via a filler neck 3, 20, 24, and a cover 4, 16, 19, which can be fastened to the filler neck 3, 20, 24, wherein the expansion tank (1) has means for pressure equalization between the pressure medium chamber 2 and the atmosphere and a sealing element is provided to prevent pressure medium from penetrating from the pressure medium chamber 2. In order to ensure the sealing and the ventilation function with little assembly effort and few components, it is proposed according to the invention that a sealing sleeve 5 with two sealing lips 6, 7 is provided as the sealing element, wherein the first sealing lip 6 lies in sealing contact with a sealing surface 8 of the cover 4, 16, 19 aligned radially to a central axis M of the expansion tank 1 and the second sealing lip 7 lies in sealing contact with a sealing surface 9 of the filler neck 3, 20, 24 aligned axially to the central axis M and wherein the first sealing lip 6 enables ventilation by folding over and the second sealing lip 7 enables ventilation of the pressure medium chamber 2 by folding over.

Description

[0001] The invention relates to an expansion tank, in particular for hydraulic motor vehicle brake systems, having at least one pressure medium chamber which can be filled with pressure medium via a filler neck, and a cover which can be fastened to the filler neck, wherein the expansion tank has means for pressure equalization between the pressure medium chamber and the atmosphere and a sealing element is provided to prevent pressure medium from escaping from the pressure medium chamber.

[0002] For such an expansion tank to function, it is necessary that the pressure fluid chamber is depressurized, i.e., that pressure equalization can occur between the pressure fluid chamber and the atmosphere, so that changes in the volume of the pressure fluid, which can occur, for example, due to pressure loss or temperature changes, can be compensated for by an exchange of air. At the same time, however, it must be prevented that pressure fluid can escape from the expansion tank—for example, when the vehicle is tilted.

[0003] A generic expansion tank is known, for example, from DE 37 34 421 A1. This has several components as a sealing element, which serve to seal the pressure medium chamber and simultaneously enable pressure equalization. For example, DE 37 34 421 A1 discloses an embodiment in which a sealing ring is arranged between the filler neck and the lid, and a separating element is provided in a filling opening of the filler neck, which is permeable to air but designed to be liquid-tight, wherein the separating element is captively connected to the lid. Inlet and outlet channels in the lid enable pressure equalization. One disadvantage of the known expansion tank is the complex structure. The inlet and outlet channels in the lid must be manufactured in a separate operation.As the tools wear, the channels may no longer have the required dimensions, meaning the ventilation function can no longer be guaranteed. Furthermore, precise positioning of the sealing ring is necessary to ensure the sealing function in the axial direction relative to the center axis of the expansion tank, which makes the assembly of the cover time-consuming and costly.

[0004] JP H06 270789 A discloses an expansion tank with a lid and a sealing collar arranged therein, featuring two foldable sealing lips. An upper sealing lip allows venting, and the lower sealing lip allows ventilation of the pressure medium chamber. In the resting state, the upper sealing lip is pressed against an angled, circumferential extension on the lid. However, sealing reliability combined with reliable venting, particularly at small pressure differences, is considered to be in need of improvement in such a design.

[0005] Therefore, it is an object of the present invention to provide an expansion tank in which a particularly reliable sealing and ventilation function are ensured with little assembly effort and few components.

[0006] This object is achieved according to the invention with an expansion tank having the feature combination of claim 1. By aligning the first sealing lip with a sealing surface of the cover aligned radially to the center axis, sealing is ensured in a simple manner, since no precise positioning is required. This also allows for compensation of manufacturing tolerances and unevenness. A separate vent hole simultaneously ensures a secure and stable pneumatic connection to the pressure medium chamber, enabling reliable venting even at small pressure differences.

[0007] The assembly of the sealing sleeve is considerably simplified in that the sealing sleeve is positioned on an extension of the cover projecting into the filler neck, wherein the cover has at least one vent hole for venting the pressure medium chamber and the ventilation of the pressure medium chamber takes place via a gap between the axially aligned sealing surface of the filler neck and the extension of the cover.

[0008] According to an advantageous embodiment of the invention, the extension is integrally formed with the cover, with the vent hole provided in the extension. This allows the number of components to be kept to a minimum and simplifies assembly.

[0009] A further advantageous embodiment of the invention provides for the extension to be attached to the lid as a separate insert. This makes it conceivable to retrofit existing lids with the insert and sealing sleeve.

[0010] A simple fastening is preferably achieved in that the extension is fastened to a centrally arranged, circular projection of the lid, wherein the vent hole is provided in the projection.

[0011] According to advantageous embodiments of the invention, the lid can be fastened to the filler neck by means of a threaded connection or a bayonet connection and the pressure equalization takes place via recesses in the threaded connection or the bayonet connection.

[0012] The lid assembly is carried out in a particularly simple manner if, according to a further advantageous embodiment of the invention, the lid can be fastened to the filler neck by means of a snap connection and the pressure equalization takes place via recesses in the lid or the filler neck.

[0013] The lid is preferably substantially pot-shaped and has a wall with three projections, and the filler neck has three recesses into which the projections engage to precisely position the lid relative to the filler neck. This positioning easily accommodates the requirement that the lid be positioned in a specific way.

[0014] Further features, advantages, and possible applications of the invention will become apparent from the following description of exemplary embodiments and from the drawings, which illustrate embodiments. Each of these shows, in highly schematic form: Fig. 1 shows a section of a first embodiment of an expansion tank according to the invention; Fig. 2 a cover of a second embodiment in section; Fig. 3 a section of a third embodiment of an expansion tank according to the invention and Fig. 4 a section through a filler neck of a fourth embodiment of an expansion tank according to the invention.

[0015] Fig. Figure 1 shows a section of a first embodiment of an expansion tank 1 according to the invention, which provides, for example, brake fluid as a pressure medium for a hydraulic motor vehicle brake system in at least one pressure medium chamber 2 and which is attached to and connected to a master cylinder (not shown) of the motor vehicle brake system. The expansion tank 1 has a filler neck 3, through which the expansion tank 1 can be filled with brake fluid and which can be closed by means of a cover 4. The cover 4 can, as in Fig. 1, can be attached to the filler neck 3 via a threaded connection or alternatively via a bayonet connection.

[0016] For the expansion tank 1 to function, the pressure medium chamber 2 must be depressurized. This means that pressure equalization must be possible between the pressure medium chamber 2 and the atmosphere so that changes in the volume of the pressure medium, which can occur, for example, due to pressure loss or temperature changes of the pressure medium, can be compensated by an air exchange.

[0017] At the same time, a sealing element must be used to prevent pressure medium from escaping from the expansion tank 1, for example when the motor vehicle is tilted.

[0018] In order to ensure the sealing and ventilation function with minimal assembly effort and a few components, the expansion tank 1 according to the invention has a sealing sleeve 5 with two sealing lips 6,7 as a sealing element. Fig. 1, after fastening the cover 4 on the filler neck 3, the first sealing lip 6 lies sealingly against a sealing surface 8 of the cover 4 aligned radially to a central axis M of the expansion tank 1 and the second sealing lip 7 lies sealingly against a sealing surface 9 of the filler neck 3 aligned axially to the central axis M when the expansion tank 1 is in a pressure-equalized state.

[0019] The sealing sleeve 5 is positioned on an extension 10 of the cover 4 that projects into the filler neck 3. For this purpose, the extension 10 has a shoulder 11 against which the sealing sleeve 5 rests and which allows for easy, positioned mounting of the sealing sleeve 5 on the extension 10. The cover 4 has at least one vent hole 12 in its extension 10 for venting the pressure medium chamber 2.

[0020] If, for example, pressure loss or temperature changes cause volume changes in the pressure medium in the pressure medium chamber 2, pressure equalization between the pressure medium chamber 2 and the atmosphere is required. For this purpose, the pressure medium chamber 2 must be able to be vented and released so that the volume changes of the pressure medium can be compensated for by air exchange. The air flows during venting and release are indicated by arrows B and E.

[0021] How Fig. 1, in the event of overpressure in the pressure medium chamber 2, the first sealing lip 6 folds towards the pressure medium chamber 2, thus no longer resting against the sealing surface 8 and thereby exposing the vent hole 12. After flowing over the sealing lip 6, the air flows towards the atmosphere via one or more recesses 13 in an internal thread 14 of the cover 4.

[0022] If a negative pressure develops in the pressure medium chamber 2, the second sealing lip 7 folds towards the pressure medium chamber 2 and thus opens a gap 15 between the axially aligned sealing surface 9 of the filler neck 3 and the extension 10 of the cover 4, so that the air flows along the recesses 13 over the gap 15 towards the pressure medium chamber 2. It is Fig. 1 shows that the positioning of the sealing sleeve by means of the shoulder 11 is crucial for the function of the sealing lip 7, since the shoulder 11 ensures that the sealing lip 7 cannot contact the radial projection 26 of the extension 10. Both sealing sleeves 6, 7 are shown in dashed lines in their folded position.

[0023] Sealing by means of the sealing lips 6, 7 offers the advantage of ensuring a simple seal, since precise positioning of the sealing lips 6, 7 is not required; instead, sealing is achieved by their contact with the sealing surfaces 8, 9. This also allows for compensation for manufacturing tolerances and unevenness.

[0024] The molding of the extension 10 onto the cover 4 has the advantage that the number of components can be kept low and assembly can be simplified.

[0025] Fig. Figure 2 shows a cover 16 of a second exemplary embodiment. This differs from the first only in that the extension on which the sealing sleeve 5 is arranged is attached to the cover 16 as a separate insert. To secure the extension, the cover 16 has a centrally arranged, circular projection 17, with at least one vent hole 18 provided in the projection 17. This design makes it possible to retrofit an existing cover with the insert (not shown) and the sealing sleeve 5.

[0026] The covers 4, 16 of the above-described embodiments are attached to the filler neck 3 by means of a threaded connection, and pressure equalization occurs via recesses 13 of the threaded connection. However, it is also conceivable within the scope of the invention for the cover 4, 16 to be attached to the filler neck 3 by means of a bayonet connection, and for pressure equalization to occur via recesses in the bayonet connection.

[0027] The Fig. 3 and Fig. Figure 4 shows a third and a fourth embodiment, where Fig. 3 a section of a third embodiment and Fig. Figure 4 shows a section through a filler neck of the expansion tank of a fourth embodiment. The two embodiments differ from the previous ones only in the attachment of the cover, so only this is shown.

[0028] According to the third embodiment, the lid assembly is carried out in a particularly simple manner in that a lid 19 can be fastened to a filler neck 20 by means of a snap connection and the pressure equalization takes place via recesses in the lid 19 or, as indicated by dashed lines, through recesses in the filler neck.

[0029] For this purpose, the lid 19 is provided in a substantially pot-shaped manner and has an elastic wall 21, at the end of which a radially inwardly directed circumferential projection 22 is provided, which snaps into an undercut 23 of the filler neck 20 in order to fasten the lid 19 to the filler neck 20.

[0030] A filler neck 24 of the fourth embodiment has, in contrast to the third embodiment according to Fig.3 has three recesses 25, into which three projections of the cover (not shown) engage to ensure its precise positioning relative to the filler neck 24. This positioning easily accommodates the requirement that the cover be positioned in a specific way. This can, for example, ensure that the label on the cover is always positioned in a predetermined direction relative to the vehicle. List of reference symbols 1 expansion tank 2 pressure medium chamber 3 filler necks 4 lids 5 Sealing sleeve 6 Sealing lip 7 Sealing lip 8 Sealing surface 9 Sealing surface 10 extension 11 paragraph 12 vent hole 13 recesses 14 internal threads 15 gap 16 lids 17 lead 18 vent hole 19 lids 20 filler necks 21 Wall 22 lead 23 Undercut 24 filler necks 25 recess 26 lead M central axis

Claims

[1] Expansion tank (1) for hydraulic motor vehicle brake systems, with at least one pressure medium chamber (2) which can be filled with pressure medium via a filler neck (3, 20, 24), and a cover (4, 16, 19) which can be fastened to the filler neck (3, 20, 24), wherein the expansion tank (1) has means for pressure equalization between the pressure medium chamber (2) and the atmosphere and a sealing element against the escape of pressure medium from the pressure medium chamber (2) is provided as a sealing sleeve (5) with two sealing lips (6, 7), wherein the first sealing lip (6) enables venting by folding over and the second sealing lip (7) enables ventilation of the pressure medium chamber (2) by folding over, wherein the second sealing lip (7) bears sealingly against a sealing surface (9) of the filler neck (3, 20, 24) which is aligned axially to the central axis (M). characterized bythat the first sealing lip (6) bears sealingly against a sealing surface (8) of the cover (4,16,19) aligned radially to a central axis (M) of the expansion tank (1) and the cover (4,16,19) has at least one vent hole (12,18) for venting the pressure medium chamber (2). [2] Expansion tank (1) according to claim 1, characterized by that the sealing sleeve (5) is positioned on an extension (10) of the cover (4,16,19) projecting into the filler neck (3,20,24) and the ventilation of the pressure medium chamber (2) takes place via a gap (15) between the axially aligned sealing surface (9) of the filler neck (3,20,24) and the extension (10) of the cover (4,16,19). [3] Expansion tank (1) according to claim 2, characterized by that the extension (10) is formed onto the cover (4,19), wherein the vent hole (12) is provided in the extension (10). [4] Expansion tank (1) according to claim 2, characterized bythat the extension is attached to the cover (16,19) as a separate insert. [5] Expansion tank (1) according to claim 4, characterized by that the extension is fastened to a centrally arranged, circular projection (17) of the cover (16, 19), wherein the vent hole (18) is provided in the projection (17). [6] Expansion tank (1) according to one of the preceding claims 1 to 5, characterized by that the cover (4,16) can be fastened to the filler neck (3) by means of a threaded connection or a bayonet connection and the pressure equalization takes place via recesses (13) of the threaded connection or the bayonet connection. [7] Expansion tank (1) according to one of the preceding claims 1 to 5, characterized by that the lid (19) can be fastened to the filler neck (20,24) by means of a snap connection and the pressure equalization takes place via recesses in the lid or the filler neck (20,24). [8] Expansion tank (1) according to claim 7, characterized by that the lid is substantially pot-shaped and has a wall on which three projections are provided and that the filler neck has three recesses (25) into which the projections engage for the clear positioning of the lid with respect to the filler neck (24).

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