WO2002001076A2

WO2002001076A2 - Hydraulic energy accumulator with metal bellows

Info

Publication number: WO2002001076A2
Application number: PCT/DE2001/002269
Authority: WO
Inventors: Heinz Siegel; Harald Ott; Horst Beling
Original assignee: Robert Bosch Gmbh
Priority date: 2000-06-24
Filing date: 2001-06-22
Publication date: 2002-01-03
Also published as: EP1297263A2; WO2002001076A3; DE50103556D1; EP1297263B1; DE10030937A1

Abstract

A hydraulic energy accumulator consisting of a housing (7) with a space (4) for inserting metal bellows (5), comprising a non-moveable end and a moveable end with a front wall arranged in a sealed manner on the bellows and separating a hydraulic pressure medium from a pressurized gas is already known per se. The advantage of using metal bellows is that they are gas-tight in so far as no leak arises over time. According to the invention, the bellows are embodied in such a way that the pressure of said bellows in the gas is reduced in comparison with the hydraulic medium as a result of the longitudinal elasticity of said bellows and a sensor system (6) is provided which indicates a longitudinal expansion of the bellows (5) when the hydraulic pressure medium flows through a leak in said bellows into the area containing the gas. The inventive hydraulic energy accumulator (2) and the sensor system (6) thereof are also capable of indicating when such a leak occurs in the bellows. The indication of a leak is also an indication that a motor vehicle braking system fitted therewith has become unsafe.

Description

Hydraulic energy storage with a bellows made of metal

State of the art

The invention relates to a hydraulic energy accumulator with a housing which has an installation space for a metallic bellows according to the preamble of claim 1.

From the document DE 3048651 AI a hydraulic energy accumulator is known with a housing which is cylindrical on the inside and has an axially displaceable piston which is sealed relative to the housing by means of a sealing ring and which separates a hydraulic chamber from a gas chamber. Gas is under pressure in the gas space, so that the gas forms a cushion which can be elastically compressed when hydraulic pressure medium is poured into the hydraulic space. The piston therefore forms a kind of movable wall. The hydraulic chamber is delimited by a wall, through which a plunger extends, which is aligned in the longitudinal axis of the piston, is sealingly guided within the wall and, on the one hand, projects into the hydraulic chamber and, on the other hand, protrudes from the housing. In alignment with the plunger, a switch is arranged in a stationary manner on the wall of the hydraulic energy store with the aid of a holding bracket. The plunger is used to actuate the switch shortly before the piston has emptied the hydraulic space and is able to strike the wall through which the plunger is guided. In other words, the switch is a type of sensor system that can be used to detect that the hydraulic chamber is almost drained. The description of the document DE 3048651 AI also indicates that the movable wall can be elastic and can be a bubble, for example.

From the document DE 1525776 AI a further hydraulic energy storage device is known with a movable wall, a plunger that can be actuated by the movable wall and a switch, and between the plunger and the switch an arrangement of a pivoted lever mechanism which then actuates the switch via a control cam that can be pivoted by it. when the movable wall has almost reached its end position determined by design, which corresponds to the emptying position. The switch then gives a signal for an indicator lamp and / or the switching on of a pump drive motor. The movable wall is formed by a part of an elastic bladder or a displaceable piston. The publication DE 1525776 AI also indicates that either a potentiometer or a photo cell with a relay can be provided.

A further hydraulic energy accumulator is known from the publication EP 0980981 A1, which is optionally designed as a so-called high-pressure accumulator or a so-called medium-pressure accumulator and, within an installation space surrounded by a housing, has a bellows made of metal for variable limitation of a hydraulic space. In the design as a so-called medium pressure accumulator, the elasticity of the bellows alone serves to store energy. Including a gas cushion in the metallic bellows game in the form of the so-called high-pressure accumulator. The hydraulic energy store is intended, for example, for use in a slip-controlled hydraulic motor vehicle brake system, the gas tightness of the metal from which the bellows is made being advantageous for years for keeping cushion gas away from the pressure fluid by means of which the hydraulic vehicle brake system is operated.

From the document DE 19833410 AI two further hydraulic energy stores are known with bellows, which have movable end walls and are equipped with helical springs acting on the end walls, which can be tensioned by means of hydraulic energy when compressed and thus form energy stores. The bellows are made of steel. Therefore, these hydraulic energy stores also have the advantage that they are in principle gas-tight in the long run. These hydraulic energy stores are intended for installation in hydraulic vehicle brake systems.

In another hydraulic energy accumulator known from the publication DE 19847325 A1 with a bellows made of metal, which encloses a gas cushion, an end wall of a movable end of this bellows is developed to form a valve plate which can be placed against a sealing ring which surrounds a storage connection opening is sealed into an end wall of a housing of the hydraulic energy accumulator. This hydraulic energy store is also provided in particular for installation in a slip-controlled hydraulic motor vehicle brake system

It cannot be ruled out with certainty that material fatigue will occur due to constantly recurring elastic deformations during operation, for example of hydraulic vehicle brake systems, with the result of leakage of the bellows. It cannot be ruled out that a weld seam on a bellows will tire and leak. In any case, leakage results in gas serving the energy storage getting into the hydraulic pressure medium of the respective vehicle brake system and at least jeopardizing the operational safety of a vehicle if the vehicle brake system is designed in such a way that in the event of failure of the hydraulic energy store or a pump supplying it With the help of muscle strength and braking using a master brake cylinder. Such a master brake cylinder has only a limited pumping capacity, so that in the case of gas bubbles within the hydraulic vehicle brake system, the elasticity of the brake brake does not generate sufficient brake pressure.

Advantages of the invention

The hydraulic energy accumulator with the characterizing features of claim 1 has the advantage that a leak in the metallic bellows caused by material fatigue can be recognized indirectly by a movement of the movable end wall of the bellows. This takes place in that, as a result of the construction of the metallic bellows according to the invention, a pressure in the gas is normally always somewhat lower than the pressure prevailing in the hydraulic chamber. When a leak occurs, this has the consequence that the pressure difference provided causes hydraulic pressure medium to flow into the gas space, so that the end wall of the bellows moves and finally actuates the sensor system.

The measures listed in the dependent claims allow advantageous developments and improvements of the hydraulic energy store specified in claim 1. The hydraulic energy accumulator according to the invention with the characterizing features of claim 2 has the advantage that a desired pressure difference between the hydraulic space and the gas space is achieved using a thin-walled bellows, in which the same

Longitudinal compression creates less mechanical stress in the metal, which results in increased security against breakage and leakage.

The characterized features of claim 3 result in a space-saving and therefore also inexpensive combination with a hydraulic unit of a hydraulic vehicle brake system. It is of particular advantage here that the sensors, which are intended to detect the alignment of the end wall of the bellows within the housing, are inserted with their electrical connections directly into an electronic evaluation and control circuit, and in this way the laying of special sensor connection cables, which cause costs and possibly become unusable due to cable breaks.

The characteristic features of claims 4 to 7 indicate practical selection options for different exemplary embodiments of the sensor system.

drawing

Four exemplary embodiments of the hydraulic energy store according to the invention are shown in the drawings. 1 shows a first exemplary embodiment in longitudinal section in a filled state, FIG. 2 shows a single part of the exemplary embodiment according to FIG. 1, FIG. 3 shows the exemplary embodiment according to FIG. 1 in another operating state, likewise in longitudinal section, FIG. 4 shows a modification of first embodiment with respect to the sensor 5, a second modification with a further sensor system and FIG. 6 a fourth embodiment for the sensor system.

Description of the embodiments

The first exemplary embodiment of the hydraulic energy store 2 according to the invention according to FIGS. 1 to 3 has a housing 3, which surrounds an installation space 4 for a metallic bellows 5, and a sensor system 6.

The housing 3 is simplified and shown as a hollow cylinder and has a peripheral wall 7, a first end wall 8 and a second end wall 9. In this case, the designer is free to choose where he makes the housing 3 divisible so that the installation space 4 is accessible for installing the metallic bellows 5.

The metallic bellows 5 has a first fixed end 10 and a second movable end 11 and with this end

11, an end wall 12 is connected in a gas-tight manner. The folds 13 typical of the bellows 5 are located between the first fixed end 10 and the second movable end 11. The folds 13 can be produced, for example, according to the prior art by partially expanding a thin-walled one

Tube within a divisible form. The end wall 12 is fastened in a gas-tight manner, for example by means of a weld seam 14 to the second movable end 11 of the bellows 5. The first fixed end 10 of the bellows 5 is welded to the first end wall 8 in a gas-tight manner, for example by means of a weld seam 15 within the installation space 4. A cavity 16 delimited by the bellows 5 between the first end wall 8 of the housing 3 and the end wall 12 of the bellows 5 is intended to be filled with a gas which can be compressed for the purpose of energy storage. Because that Filling such bellows with the gas used to store energy is part of the prior art, for example a gas filling support has been omitted here.

Between the first end wall 8 and the second end wall 9, the installation space 4 has a length dimension A. In the manner according to the invention, the metallic bellows 5 together with its end wall 12, as long as it is outside the installation space 4, has a length which is, for example, 10% is longer than a length dimension A. This has the desired effect when installing in the installation space 4 that if there is atmospheric pressure in the installation space 4 and also in the cavity 16 of the bellows, the end wall 12 of the bellows 5 either inside on the second end wall 9 or when an elastic sealing ring 17 is installed in the end wall 9 rests with a minimum force on this elastic sealing ring 17. Because this elastic sealing ring 17 is the same. The task, like the sealing ring provided in the aforementioned document DE 19847325 AI, against which a valve plate, which is located on a bellows face, can be placed, can be dispensed with here. Because, as already mentioned, the bellows 5 consists of a metallic material, usually of a resilient material such as steel or spring-hard brass, a compression of the bellows 5 in the longitudinal direction during installation has a subsequent pressing of the end wall 12 on the elastic sealing ring 17 or at omitted sealing ring on the surface of the second end wall 9 result.

A hydraulic connection opening 18 of the hydraulic energy accumulator 2 is in the exemplary embodiment according to FIG. 1 in an imaginary longitudinal axis of the metallic bellows 5 arranged. So that, as shown in FIG. 3, when the end wall 12 of the bellows is close enough to the second end wall 9 of the housing 3, the sensor system 6 can be actuated, there is a between the end wall 12 of the bellows 5 and the sensor system 6 plunger 19 mounted longitudinally displaceably, which extends through the hydraulic connection opening 18.

In the exemplary embodiment according to FIGS. 1 and 3, the sensor system 6 is designed in the form of a switch which can be removed from the prior art and has a movable contact 20 and a fixed contact 21. The contacts 20 and 21 can be arranged in a microswitch housing 22, which is known in the art Can be fastened in a manner to a circuit board 23. For example, the circuit board 23 is the carrier of an evaluation and control circuit of a hydraulic vehicle brake system, which is not shown in detail, and which is also used, for example, for brake slip control. Such hydraulic vehicle brake systems with electrically controllable valves and with brake slip control devices are known and are therefore not further explained. Such a hydraulic vehicle brake system has a hydraulic block 24, in which electrically controllable valves and, for example, also a piston pump (not shown) are installed. In the exemplary embodiment shown, the housing 3 of the hydraulic energy accumulator 2, projecting from the second end wall 9 in the direction of the hydraulic block 24, has a screw-in connector 25 by means of which the hydraulic energy accumulator 2 is fastened to the hydraulic block 24. So that the tappet 19 can be moved to actuate the sensor system 6 when it is struck by the end wall 12 of the bellows 5, the hydraulic block 24 has a guide bore 26, relative to which the tappet 19 can be displaced longitudinally. So no through this guide bore 26 Pressure medium escapes, an elastic sealing ring 27 is installed, which surrounds the plunger 19 in a sealing manner.

For example, the plunger 19 can have a collar 28 which is loaded in the direction towards the end wall 12 of the bellows 5 by means of a helical spring 29. So that this helical spring 29 can exert this load, a helical washer 30 is associated with the helical spring 29 and is permanently installed in the hydraulic block 24. So that the plunger 19 can extend to the sensor system 6, the support disk 30 is designed as an annular disk.

1 shows the hydraulic energy store 2 as a filled and pressurized gas cushion in the cavity 16 is pressed together by filling hydraulic pressure medium (not shown) into the installation cavity 4. This is due to the above-described design of the metallic bellows 5 and due to the elastic compression of the folds 13, a pressure in the hydraulic pressure medium is a higher pressure than the gas pressure within the cavity 16 of the bellows 5. As soon as for any reason, for example material fatigue or due to a material defect, the bellows 5 or one of the weld seams 14, If there is a leak, that is to say any leakage, there is a pressure difference in the leak in the sense of a pressure drop from the hydraulic pressure medium to the gas cushion. The consequence of this is that a portion of the hydraulic pressure medium present in the installation space 4 flows into the cavity 16 of the bellows 5, with the further consequence that the bellows 5 expands in the direction of the second end wall 9. As a result of the formation of the metallic bellows 5 such that due to its relaxed length it is larger than the dimension A, the end wall 12 moves continuously in the direction of the End wall 9 continues and finally hits the plunger 19 and moves it in the direction of the sensor system 6. This case is shown in FIG. 3. There lies the end wall 12 of the bellows 5 so that 9 of the movable contact 20 strikes already on the plunger 19 at by a remaining distance to go to the end wall 12 against the sealing ring 17 or in the absence of the sealing ring 17 against the end wall of ^'the unmovable contact 21st The evaluation and control circuit mentioned is then designed such that it detects the actuation state of the sensor system 6 and activates an alarm device (not shown). It can be seen that if the hydraulic pressure inside the installation space 4 is present, the bellows 5 is not tight, regardless of whether by any chance all of the cushioning gas is still in the bellows 5 or a subset thereof, for example when the leak is present a highest point of the bellows 5 should be located in the installation space 4.

According to Figures 1 and 3, a spring 35 is shown within the bellows 5. It is installed, for example, in order to support the migration of its end wall 12 in the direction of the second end wall 9 of the housing 3 if there is a leak in the bellows 5. For this purpose, the spring 35 is manufactured in such a way that it has a predetermined length in the non-installed state, as a result of which the spring 35 has a prestress in the installed state. The prestressing of the spring 35, which takes place in this way, gives the possibility of designing the bellows 5 with thinner walls, as a result of which the stress on the material of the bellows 5 becomes smaller with the same longitudinal compression. This counteracts an unwanted failure of the bellows 5 as a result of material fatigue. FIGS. 1 and 3 show the cheapest sensor system 6 per se, which can be bought cheaply in the form of a microswitch on the market. When using only one movable contact 20 and one stationary contact 21, it can be seen that only an already very close approach of the end wall 12 of the bellows 5 to the second end wall 9 or else to the elastic seal 17 can be sensed. However, if for some reason you want to have a larger distance between the end wall 12 of the bellows 5 and the elastic seal 17 or the second end wall 9 of the housing 3, a plunger 19a can be connected to a soft magnetic coil core 37 and along the path of movement of the coil core 37, for example, provide two coils 38, 39 of a so-called differential transformer 40. In the event that the end wall 12 of the bellows 5 has reached the plunger 19a, it is possible to detect even very small movements of the end wall 12 in the direction of the second housing wall 9 by means of the differential transformer 40 even in a rough operating environment, because differential transformers have no contact surfaces like those that are typical of microswitches and tend to make unreliable contact in an aggressive atmosphere.

If access from an aggressive atmosphere can be avoided, a cheaper ohmic potentiometer 41 can be used instead of the expensive differential transformer 40.

For the sake of completeness, the combination of at least one permanent magnet 43 and one Hall effect sensor 44 is made available as a sensor 6c according to FIG. 6. The at least one permanent magnet 43 is in turn attached to a plunger 19a so that it can be secured by means of the The plunger 19a can be moved relative to the stationary Hall effect sensor 44 so that when it moves relative to the Hall effect sensor 44 it emits a sensor signal. "At least one permanent magnet" is given as the minimum solution because such a relatively simple sensor system can be used to replace, for example, a microswitch with only a single movable contact 20 and a single immovable contact 21. If a sequence of permanent magnets in the direction of movement of the STOE is provided SSELS 19a, so it is possible when using a counting circuit, displacement measurements to perform similar to the rule by means of the differential transformer 40 or the Ohm ^Λ potentiometer 41 are possible. it is therefore possible gradually an approximation of the end wall 12 'of the pleat bellows 5 to the second end wall 9 of the housing 3. The use of the sensor 6c has the advantage that it is no longer necessary to convert analog sensor signals into digital values.

In addition, it is pointed out that the principle of leak detection for a bellows is not dependent on whether, according to the exemplary embodiments shown, a gas cushion is arranged within a bellows 5. Rather, as can be seen from FIG. 2 of the document DE 19833410 A1 mentioned in the description of the description, the cavity 16 enclosed by the bellows 5 can be the cavity in which hydraulic pressure medium is to be stored under pressure.

Claims

Expectations

1. The hydraulic energy accumulator with a housing having an installation space for a metallic bellows, comprising a μnbewegliches end and a movable end ^'.with a sealed arranged end wall, wherein the metallic bellows hydraulic pressure medium separate from a trapped gas under pressure, characterized in that the metallic bellows (5) procured in this way _. is that, when it is not filled with gas, it has a length before installation in the installation space (4) which is longer than a length dimension (A) of the installation space (4) and that when the bellows (5) is inserted, it is elastic is shortened and that the housing (3) is assigned a sensor system (6, 6a, 6b, 6c) for sensing the orientation of the end wall (12) when it moves in the direction of an emptying position of the hydraulic energy store.

2. Hydraulic energy storage device according to claim 1, characterized in that in the hydraulic energy storage device (2) a spring (35) is installed in such a way that it has a prestress within the hydraulic energy storage device (2) which the end wall (12) of the bellows (5 ) in the direction of an emptying position of the hydraulic accumulator (2).

3. Hyraulikenergiespeicher.er according to claim 1 or 2, characterized in that the housing (3) of the hydraulic energy accumulator (2) in an end wall (9) delimiting the installation space (4) has a hydraulic connection opening (18) lying in an extension of the longitudinal axis of the bellows ) that the connection opening (18) communicates with a hydraulic block (24) of a hydraulic vehicle brake system 'and that the hydraulic block (24) is assigned a circuit board (23) of an evaluation and control circuit of the hydraulic vehicle brake system that at least one fixed part the sensor system (6, 6a, 6b, 6c) is fastened, in alignment with the longitudinal axis of the bellows (5), on the circuit board (23) of the evaluation and control circuit, and that a sensor system (6, 6a, 6b, 6c) actuating is displaceable in the longitudinal direction mounted plunger (19) between the sensor system (6, 6a, 6b, 6c) and the end wall (12) of the bellows (5) is inserted through the hydraulic connection opening (18 ) of the hydraulic energy store (2) and is hydraulically sealed relative to the sensor system (6, 6a, 6b, 6c) within the hydraulic block (24).

4. Hydraulic accumulator according to one of claims 1 to 3, characterized in that the sensor system (6) is designed as a switch having a movable contact (20).

5. Hydraulic energy store according to one of claims 1 to 3, characterized in that the sensor system (6a) is designed in the form of a differential transformer (40) with a movable coil core (37).

6. Hydraulic energy store according to one of claims 1 to 3, characterized in that the sensor system (6b) is designed as an ohmic potentiometer (41).

7. Hydraulic energy store according to one of claims 1 to 3, characterized in that the sensor system (6c) consists of a stationary Hall effect sensor (44) and at least one permanent magnet (43) movable by the plunger (19a).