DE10320373B4 - Gas pressure accumulator for a vehicle brake system - Google Patents

Abstract

Gas pressure accumulator (18a) for a vehicle brake system (10, 10 ') having a housing (50a) and a pressure piston (68a) guided in the housing (50a),
wherein the pressure piston (68a) and the housing (50a) are coupled to one another via a metal bellows (78a) which forms the interior of the housing (50a) into a gas space (84a) filled with gas and a fluid space which can be filled with a hydraulic fluid via a fluid channel ( 86a),
wherein further the housing (50a) is formed with a guide shaft (66a) in which a pressure piston (68a) formed piston plunger (70a) in the direction of a piston longitudinal axis (A) is guided displaceably and
wherein a sealing arrangement is provided, by means of which the fluid space (86a) can be separated from the fluid channel,
characterized in that the seal assembly is disposed in an orifice portion in which the guide shaft (66a) opens into the fluid space (86a), the seal assembly comprising a seal member (126a) forming the mouth portion, the seal member (126a) attaching one the piston ram (70a) adjacent ...

Description

Background of the invention

The The present invention relates to a gas pressure accumulator for a vehicle brake system according to the preamble of claim 1.

State of the art

Such gas pressure accumulators are known and are already used in vehicle brake systems. For example, shows the generic DE 199 54 326 A1 in 2 a gas pressure accumulator of the type described. In this gas pressure accumulator moves over the piston plunger in the guide shaft of the central receiving element of the housing guided pressure piston under the influence of an inserted into the fluid space hydraulic fluid within the housing. In this case, the gas trapped in the gas space is compressed until a pressure equilibrium is established between fluid space and gas space. Thus, hydraulic pressure can be cached and used in a later operating situation of a vehicle brake system, for example, when a hydraulic pressure source fails or can not deliver fast enough sufficiently high hydraulic pressure for an operating situation. When the hydraulic pressure is sufficiently high, the pressure piston is displaced to a position of maximum piston stroke. When the hydraulic pressure accumulator is emptied, the pressure piston moves towards a minimum piston stroke position until it finally reaches it. In both the maximum piston stroke position and the minimum piston stroke position, the fluid space should be isolated from the fluid channel to prevent excessively high pressure from arising in the fluid space. If, for example, no reliable sealing is achieved in the piston position with minimal piston stroke, so that further hydraulic fluid can be withdrawn from the fluid chamber, this can lead to destruction of the bellows and thus to destruction of the pressure accumulator due to the pressure difference between gas space and fluid space prevailing on the bellows , The same may result in too much filling of the fluid space with hydraulic fluid.

To prevent overstressing of the bellows, the prior art according to the DE 199 54 326 A1 a redundant seal arrangement for the case of piston position minimum piston stroke, with which both an axial and a radial seal can be achieved. However, the device arrangement shown in this document has the disadvantage that it is designed in several parts and can lead to leaks even with a minimal inclination of the plunger with respect to the guide shaft in the housing.

From the DE 101 19 357 A1 a gas pressure accumulator is known in which the pressure piston is guided via radially outer guide means in the housing of the gas pressure accumulator. On the plunger, a pin is arranged, which carries a seal. This seal moves with the plunger and engages a fluid supply port only in the minimum piston stroke position. Moreover, another seal is disposed at a considerable distance from the mouth portion between the fluid supply port and the fluid space. Accordingly, the pressure accumulator according to citation 1) has the same disadvantages as already described above with reference to the DE 199 54 326 A1 explained.

As another state of the art is on the WO 02/12732 A1 to indicate that shows a plunger free piston.

From the DE 100 03 648 A1 Another accumulator is known in which also can leak due to the radially outer seal assembly, which can lead to incorrect operation of the accumulator.

Object of the invention and inventive solution

It is in contrast An object of the present invention, a gas pressure accumulator to provide the type described at the outset, which in a simple and inexpensive Building a reliable Ensures sealing of gas space and fluid space.

These Task is performed by a gas accumulator with the characteristics of Patent claim 1 solved.

The inventive seal assembly is located yourself in an area near the place of the actual guidance of the Plunger inside the housing, so that minor eccentricities of the pressure piston with respect the longitudinal axis can be easily compensated by the seal assembly and so that leaks can be prevented. In addition, positioning provides the seal arrangement in the mouth area of the guide shaft in the fluid space the possibility the seal assembly and required for their realization constructive measures on pressure piston, piston plunger and casing easy to keep, so the overall manufacturing cost is reduced can be and the gas pressure accumulator according to the invention more cost-effective can be produced.

According to the invention, it is provided the sealing arrangement has a sealing element which the mouth area forms, wherein the sealing element abutting one of the piston plunger Radialdichtbereich and one with a trained on the piston bottom Axialdichtsitz has brought in conditioning Axialdichtbereich. The sealing element fulfilled both the function of a radial seal in which it matures on the peripheral surface of the piston tappet, as well as the function of an axial seal, by using appropriate Piston position, that is with minimal piston stroke of the housing, engages the formed on the piston bottom Axialdichtsitz. The invention provides that both an axial seal and a Radial seal is effective when the piston is in position minimum piston stroke is located. Especially in this position is the Metal bellows in front of big ones Suppress in the fluid space with respect to To protect gas space, what a reliable one To ensure sealing effect of the seal assembly. An education the sealing arrangement as described above leads to that in the piston position minimum piston stroke of the fluid space of the fluid line is redundantly sealed, that is both with a seal acting in the axial direction as well as with a acting in the radial direction seal. Such a redundant arrangement offers greater security to avoid unwanted fluidic connections between fluid channel and fluid space.

Advantageous developments the invention

Around a reliable one guide of the piston plunger inside of the housing guarantee to be able to is provided in a development of the invention that the piston plunger on the total maximum piston stroke of the pressure piston inside the housing in the guide shaft guided is. This can tilt the pressure piston with respect to the piston longitudinal axis be largely prevented.

to Formation of the fluid channel for a loading and unloading of the fluid space with hydraulic fluid provides a development of the invention that the piston plunger in the Guide shaft under Training at least one axial channel is guided, which is at least one Part of the axial length of the piston plunger or of the guide shaft extends. This can be achieved, for example, by the fact that the piston plunger with at least an axial groove is formed, which at least over one Part of the axial length extends the piston plunger. Alternatively or in addition to this can be provided that the guide shaft is formed with at least one axial groove, which at least over one Part of the axial length of the guide shaft extends. A possible constructive realization provides, for example, that the guide shaft in one to the piston longitudinal axis orthogonal section a circular cross-sectional contour and that the piston plunger in one to the piston longitudinal axis orthogonal section one in the cross section of the guide shaft inscribed polygonal Cross section has.

As It is stated above with reference to the prior art to avoid the formation of a metal bellows destructive negative pressure within the fluid space required to minimize in a piston position Piston strokes the fluid space opposite the fluid channel is sealed off. To realize a corresponding Seal is provided in a development of the invention that the piston plunger on one piston-near region formed with a axialnutfreien radial collar is. This allows the arranged in the mouth area Sealing arrangement with a piston position minimum piston stroke engage the axialnutfreien radial collar of the piston near area and thus sealing the fluid space from the fluid channel.

alternative or additionally to the formation of the fluid channel via axial grooves can be provided according to the invention be that the piston plunger has a central Has bore and a piston near radial bore which the fluid channel form. In such a variant of the invention is to ensure that the seal assembly at a piston position minimum piston stroke in terms of of the housing the Radial bore seals so that they are not fluidly with the Fluid space can communicate.

Brief description of the figures

The Invention will be described below by way of example with reference to the accompanying Figures explained. They show:

1 a schematic view of a vehicle brake system;

2 a schematic view of a second embodiment of a vehicle brake system;

3 a longitudinal sectional view of a non-inventive embodiment of a gas pressure accumulator;

4 an enlarged view of the in 3 with IV designated mouth area;

5 a view accordingly 4 a modified embodiment not according to the invention;

6 a sectional view of the piston plunger cut along the section line VI on the right side of 4 embodiment shown;

7 a sectional view of the piston plunger cut along section line VII on the left side of 4 embodiment shown; and

8th an embodiment of a gas pressure accumulator according to the invention;

Description of preferred embodiments

In 1 a vehicle brake system is shown schematically and generally with 10 designated. This includes a fluid reservoir 12 for storing hydraulic fluid. From the fluid reservoir 12 is via a pump 14 , which has an electric motor 16 is driven, hydraulic fluid conveyed. On a print page 24 the pump 14 there is a hydraulic pressure accumulator 18 with a gas space 20 and a fluid space 22 , The print side 24 is via a switching valve 26 with a brake unit 28 connected in the position according to 1 closed is. When opening the switching valve 26 can from the pump 14 or the accumulator 18 Hydraullic fluid under increased pressure of the brake unit 28 are fed to actuate them for braking a vehicle wheel, not shown. Similarly, by closing the switching valve 26 the brake unit 28 again from the pressure side 24 be disconnected, so that an actuation of the brake unit 28 omitted. The brake unit 28 is with the fluid reservoir 12 via another switching valve 30 connected in 1 is shown in its open position. In this open position of the switching valve 30 can hydraulic fluid from the brake unit 28 discharged and the fluid reservoir 12 be supplied. The brake unit 28 is relieved of pressure. In its other switching position, the switching valve separates 30 the brake unit 28 hydraulically from the fluid reservoir 12 from.

To control and operate the brake system are pressure sensors 32 and 34 intended. The pressure sensor 32 detects the current hydraulic pressure on the pressure side 24 , The pressure sensor 34 detects the current hydraulic pressure at the brake unit 28 , The with the pressure sensors 32 and 34 detected hydraulic pressures are converted into signals and to an electronic control unit 36 transmitted. The electronic control unit 36 controls both the engine in accordance with the hydraulic pressures and other input variables 16 the pump 14 as well as the switching valves 26 and 30 to, so the brake system 10 to press.

The accumulator 18 fulfills the function of a hydraulic pressure buffer. This is necessary, for example, because the pump 14 has a certain start-up delay, so that they are not immediately upon switching on sufficiently high hydraulic pressure on the pressure side 24 delivers to the brake unit 28 to press. In order to still be able to realize a fast-response vehicle brake system is in the pressure accumulator 18 Hydraulic pressure cached, which then when opening the switching valve 26 quickly the brake unit 28 can be fed, although the pump 14 not yet to operate the brake unit 28 sufficiently high hydraulic pressure supplies. In a state of the vehicle brake system 10 , in which no braking takes place, can with closed switching valve 26 and active pump 14 on the print side 24 the pump 14 a hydraulic pressure for charging, ie "charging", the pressure accumulator 18 be generated.

2 shows one opposite 1 slightly modified vehicle brake system 10 ' , For ease of description and avoidance of repetition, the same reference numerals as in the description of FIG 1 used, but with an apostrophe readjusted.

The vehicle brake system 10 ' according to 2 differs from the vehicle brake system 10 according to 1 only in that an accumulator unit 38 ' is provided, which next to the pressure accumulator 18 ' in addition a pressure relief valve 40 ' having. The pressure relief valve 40 ' has the task that it opens when on the pressure side 24 ' too high a hydraulic pressure prevails, which optionally the accumulator 18 ' would destroy. The pressure relief valve 40 ' is switched so that it is the pump 14 ' short closes. This means that when it reaches the opening of the pressure relief valve 40 ' required minimum pressure no further pressure increase more on the pressure side 24 ' the pump takes place because the pressure relief valve 40 ' the further pumped hydraulic fluid to the fluid reservoir 12 ' or to the suction side of the pump 14 leads back.

The following is intended to variants according to the invention with respect to the structure and operation of the pressure accumulator 18 be discussed in more detail.

3 shows an embodiment of a non-inventive pressure accumulator 18 , which serves to illustrate the invention. This includes a housing 50 , which has a cylindrical interior 52 trained and with a on the housing 50 attached housing cover 54 is closed. The housing points in his in 3 upper area a threaded hole 56 on, which by means of a sealing screw 58 as well as sealants 60 is sealed fluid-tight. The housing cover 54 is with a central cylindrical Kör by 62 formed along the longitudinal axis A in the interior 52 of the housing 50 protrudes. Furthermore, the housing cover 54 at his in 3 lower area a terminal extension 64 for connecting a fluid supply, not shown.

The cylindrical body 62 is with a running in the direction of the longitudinal axis A central bore 66 Mistake. In this hole is a piston 68 with its extending in the direction of the longitudinal axis A piston plunger 70 used. The piston plunger 70 is in the central hole 66 slidably guided in the direction of the longitudinal axis A. Also the piston plunger 70 has a central hole 72 on (see 3 , right side) or in an equivalent alternative embodiment of the invention in its peripheral surface a series of extending in the direction of the longitudinal axis A axial grooves 74 on (see 3 , left side).

At the bottom of the piston 76 of the piston 68 is in its respect to the longitudinal axis A radially outer region of a metal bellows 78 intended. The metal bellows 78 is at the bottom 76 of the piston 68 firmly and fluid tight. At his from the butt bottom 76 distant end is the metal bellows 78 on a mounting ring 80 attached fluid-tight. The fastening ring 80 is over a weld 82 , Preferably, a CO ₂ laser seam, fluid-tight to the housing cover 54 attached. Thus, the piston separates 68 together with the metal bellows 78 and the mounting ring 80 a gas filled closed gas space 84 from a fluid space that can be filled with hydraulic fluid 86 from. It should be noted that in the fluid space 86 a packing 88 is provided, which the cylindrical body 62 surrounds.

In the following, special attention is paid to the connection area of piston plunger 70 and pistons 68 be directed.

4 and 5 show various possible designs of the connection area between pistons 68 and piston plunger 70 and the mouth area in which the central bore 66 in the fluid space 86 empties. How out 4 right side, opens into the axial bore 72 further a radial bore 90 , which are transverse to the longitudinal axis A through the piston plunger 70 extends through. This is also out 6 apparent, which correspond to the embodiment 4 right side, an orthogonal to the longitudinal axis A section through the valve stem 70 along the axis of the radial bore 90 shows.

In the cylindrical body 62 is in the area of his in 3 upper end a circumferentially around the longitudinal axis A extending around radial groove 92 introduced, in which an O-ring 94 and a radial seal 96 made of rubber-elastic material are inserted. The O-ring 94 and the radial seal 96 Press together on the peripheral surface of the piston plunger 70 , Above the radial groove 94 is at the frontal area 98 of the cylindrical body 62 around the cylindrical bore 66 around a ring recess 100 brought in. In the ring recess 100 is an axial sealing ring 102 Made of rubber-elastic material with a reinforcing ring 104 inserted and in the ring recess 100 attached. The axial seal 102 is with a central hole 106 executed by which, as shown 4 the piston plunger 70 with game extending through.

4 shows a position of the piston 68 with respect to the cylindrical body 62 in which the piston is 68 not in its lowest position, that is, in which it does not occupy a piston position minimum piston stroke. The position of minimum piston stroke is reached when the bottom 76 with the top of the Axialdichtrings 102 of the piston 68 comes into contact. In this position minimum piston stroke prevents the Axialdichtring 102 along with the bottom 76 of the piston 68 a fluidic connection of the piston plunger 70 near surrounding area with the axial sealing ring 102 surrounding fluid space 86 , In such a piston position minimum piston stroke are both the radial bore 90 according to 4 right side and the axial grooves 74 according to 4 left side below the radial groove 92 so that the radial seal 96 over the O-ring 94 to the axialnutfreie or radial bore-free Außenumgangsfläche 108 near the piston 68 is pressed. The piston plunger 70 is gripped tightly over its entire circumference. This is the piston plunger 70 also under radial seal in the central bore 66 guided so that no hydraulic fluid axially on the piston plunger 70 over from the fluid space 86 can pour out. The distance from the top of the radial bore 90 or the axial grooves 66 is thus chosen such that in the piston position minimum piston stroke of the radial seal 96 sealing the piston plunger in the central bore 66 holds. Due to the arrangement shown with Axialdichtring 102 and radial seal 96 a redundant seal is achieved, which reliably prevents minimum piston stroke in the piston position from the fluid space 86 Hydraulic fluid through the central bore 66 can escape.

7 shows a cross section through the piston plunger 70 along the section line VII 4 when the piston tappet 70 corresponding 4 left side is executed. It can be seen that the piston plunger 70 instead of a central hole 72 is formed with a substantially square shape and rounded corners and thus axial channels 74 inside the central hole 66 forms.

5 shows the non-inventive embodiment according to 3 and 4 in slightly modified form. Looking at the right side of 5 , so you can see that the piston plunger 70 a collar 110 having enlarged diameter. Starting from this collar 110 the diameter reduces over a transition area 112 to an area 114 , The collar 110 is in the direction of the longitudinal axis A, starting from the piston underside 76 dimensioned so that it is at the in 4 again not shown piston position minimum piston stroke just in contact with the sealing ring 112 and thus the central hole 66 from the fluid space 86 fluidly separated. In this position, in turn, the Axialdichtring 102 sealing at the bottom 76 of the piston 68 at. In the in 5 shown position and with greater axial distance between the cylindrical body 62 and the piston 68 can the central hole 66 with the fluid space 86 communicate fluidly.

Turning to the left side of 5 to, it can be seen that in this variant of the invention, the collar 110 is dimensioned larger in the direction of the longitudinal axis A and with an annular groove 116 is provided. In the ring groove 116 is again an O-ring 118 and a radial seal 120 inserted, which press radially outward. Furthermore, in the mouth region of the cylindrical body 62 with a tapered hole 122 Mistake. The axial seal 102 is over his reinforcement ring 104 on the bottom 106 of the piston 68 appropriate.

In the 5 The embodiment shown on the left works in the same way as described above. A radial seal is made via the radial seal 120 and the O-ring 118 scored when the piston plunger 70 deep enough in the central hole 66 of the cylindrical body 62 dips. In this case, the Axialdichtring lies 102 sealing on the end face of the cylindrical body 62 at.

The referring to 3 to 5 explained variants of the non-inventive embodiment all have the effect that in the piston position minimum piston stroke both an axial sealing action on the Axialdichtring 102 and its reinforcing ring 104 as well as a radial sealing effect over the radial seal 120 respectively. 96 and the supporting O-ring 94 respectively. 118 can be achieved. As a result, after reaching the minimum piston stroke position, further suction or extraction of hydraulic fluid from the fluid chamber can take place 86 over the central hole 66 be prevented. It has been shown that when the negative pressure in the fluid space 86 with respect to the gas space 84 too large in terms of size, the metal bellows 78 can be destroyed. This is achieved by the redundant sealing arrangement according to with reference to 3 to 7 described embodiments avoidable.

8th shows an embodiment of a pressure accumulator according to the invention 18a , For description of this embodiment, the same reference numerals as in the description of the embodiment according to FIGS 3 to 7 used, but with the letter "a" readjusted. To avoid repetition only the differences from the embodiment according to 3 to 7 be explained.

A difference from the non-inventive embodiment according to 3 to 7 lies in the fact that the housing cover 54 is formed in a meandering longitudinal section, so that he on the one hand the cylindrical body 62a and on the other hand low-weight forms an annular space in which the metal bellows 78a over the fastening ring 80a on the housing 50a is attached. Again the piston tappet 70a in a central hole 66a in the central cylindrical body 62a guided. In the mouth area is a sealing element 126a trained, which in the in 8th shown piston position minimum piston stroke both radial sealing effect on the piston plunger 70a as well as axial sealing effect on the piston underside 76a exercises. With the sealing element 126a For example, a redundant seal can be realized relatively easily with a single component. As 8th can be seen, includes the sealing element 126a an axially extending sealing lip, with the bottom 76a of the piston 68a comes into contact, as well as one parallel to the piston plunger 70a in its connection area to the piston 68a extending radial sealing area.

It's re 8th Finally, to point out that the face 98a forming axial region of the housing cover 54a an axial stop for defining the piston position minimum piston stroke presents.

above were different embodiments In order to explain of the invention, which in non-limiting Way ways represent how a pressure accumulator designed for a vehicle braking system so that this can be in different operating situations a reliable one Provides sealing effect and is protected against overloading.

Claims (8)

Gas pressure accumulator ( 18a ) for a vehicle brake system ( 10 ; 10 ' ) with a housing ( 50a ) and one in the housing ( 50a ) guided pressure piston ( 68a ), wherein the pressure piston ( 68a ) and the housing ( 50a ) via a metal bellows ( 78a ) are coupled together, the interior of the housing ( 50a ) into a gas space filled with gas ( 84a ) and via a fluid passage with a hydraulic fluid fillable fluid space ( 86a ), wherein further the housing ( 50a ) with a guide shaft ( 66a ) is formed, in which a on the pressure piston ( 68a ) trained piston plunger ( 70a ) is guided displaceably in the direction of a piston longitudinal axis (A) and wherein a sealing arrangement is provided, by means of which the fluid space ( 86a ) is separable from the fluid channel, characterized in that the sealing arrangement is arranged in a mouth region, in which the guide shaft ( 66a ) into the fluid space ( 86a ), wherein the sealing arrangement is a sealing element ( 126a ), which forms the mouth region, wherein the sealing element ( 126a ) one on the piston plunger ( 70a ) adjacent Radialdichtbereich and one with a at the piston bottom ( 76a ) trained Axialdichtsitz has brought into abutment Axialdichtbereich. Gas pressure accumulator ( 18a ) according to claim 1, characterized in that the piston tappet ( 70a ) over the entire maximum piston stroke of the pressure piston ( 68a ) within the housing ( 50a ) in the guide shaft ( 66a ) is guided. Gas pressure accumulator ( 18a ) according to claim 1 or 2, characterized in that the piston tappet ( 70a ) in the guide shaft ( 66a ) forming at least one axial channel ( 72 . 74 ) is guided, which at least over a part of the axial length of the piston plunger ( 70a ) or the guide shaft ( 66a ). Gas pressure accumulator ( 18a ) according to claim 3, characterized in that the piston tappet ( 70a ) with at least one axial groove ( 74a ) is formed, which at least over a part of the axial length of the piston plunger ( 70a ). Gas pressure accumulator according to claim 3 or 4, characterized characterized in that the guide shaft with at least one axial groove is formed, which at least over one Part of the axial length of the guide shaft extends. Gas pressure accumulator ( 18 ) according to one of claims 3 to 5, characterized in that the guide shaft ( 66 ) has a circular cross-section in a section orthogonal to the piston longitudinal axis (A) and in that the piston tappet ( 70 ) in a to the piston longitudinal axis (A) orthogonal section in the cross section of the guide shaft ( 66 ) has a described polygonal cross-section. Gas pressure accumulator ( 18a ) according to one of the preceding claims, characterized in that the piston tappet ( 70a ) at a region close to the piston with an axial groove-free radial collar ( 110 ) is trained. Gas pressure accumulator ( 18a ) according to one of the preceding claims, characterized in that the piston tappet ( 70a ) a central bore ( 72a ) and a piston-near radial bore ( 90 ), which form the fluid channel.