DE19616428A1 - Hydraulic reservoir for vehicle braking system - Google Patents

Abstract

The reservoir has a separating piston (20) isolating a chamber (32) of variable vol. and contg. a hydraulic liquid from a counter chamber (34). The piston is movably mounted in a housing block. The counter chamber is closed wrt. the surroundings by a cover (30a,..) which is flexible under pressure. The piston occupies a bore (18) in the block and is spring (22) biassed towards the inner end of the bore. The variable vol. chamber lies between the inner bore end and piston.

Description

State of the art

The invention is based on a hydraulic accumulator for a vehicle brake system according to the preamble of claim 1.

Such a hydraulic accumulator is open documents DE-A-42 02 905 and GB-A-2 263 753 known become. The well-known hydraulic accumulator is in one Ver housing block with a blind bore as a cylinder bore see in which a separating piston can be moved in the axial direction is arranged by a spring in the direction of ge closed end of the hole is pressed. The hydrau lische Speicher has a volume-adjustable chamber with a variable storage volume for temporary Absorption of pressure present in the vehicle brake system liquid, for example when certain rules occur states of the vehicle brake system.

The well-known hydraulic accumulator is in the housing block arranged in the vehicle so that the hole is facing down the housing block opens. To prevent splashing water or dirt gets into the hole, this is with a Protective cap covered. The protective cap has one Ventilation opening, which in addition to their ventilation function  also serves the purpose, possibly between the piston and liquid emerging from the bore from the bore to let it flow so that this liquid doesn't flow on the piston back collects and thus the movement of the Piston is not hindered. The protective cap is on the Provide recesses on the face of the housing block. This creates gap segments. These gap segments form between the housing block and the protective cap Vents.

A disadvantage of the known hydraulic accumulator is that that although the hole in the housing block points downwards, Splashing water and dirt through the ventilation openings in can penetrate the bore used to guide the piston nen. Splashing water can lead to corrosion, and penetrating dirt leads to movement of the separator damage to the piston as a tread for the Separating piston serving bore wall and damage the seal between the separating piston and the bore. It also gets through the air exchange between the environment and the inside of the hole moisture into the inside of the Bore, which also leads to corrosion of the bore wall can lead.

In order to minimize the danger that spray Water and dirt must be able to penetrate the hole the well-known hydraulic accumulator down the hole lead out of the housing block. This makes it difficult for some Vehicles the installation of the housing block essential.

In a not yet published patent application a hydraulic accumulator registered with a protective cap, where the protective cap vents with special Has shape, so that from the housing block pointing bore that receives the separating piston also in  Lead out of the housing block in a horizontal direction can. Because of the special, not rotationally symmetrical Shaping, the assembly of the storage is significant difficult. The problem also exists with this version the ingress of humidity.

Advantages of the invention

Compared to the previously known hydraulic accumulator offers the hydraulic accumulator designed according to the invention the characterizing features of claim 1 the advantage that the interior of the memory regardless of the installation position excellent against the intrusion of an unwanted Medium is protected. The undesirable medium includes ins special dirt, splash water and air humidity. The Counter chamber of the memory can advantageously in point in any direction from the housing block.

By the measures listed in the subclaims advantageous further developments and improvements of the Main claim specified hydraulic accumulator possible.

About the spring support in the counter chamber, the Support the spring that acts on the separating piston without losing it especially the flexible cover is affected.

The passage ensures pressure equalization on both sides of the Spring support. The passage can, for example, in the spring support or be provided in the housing block.

The sleeve has the advantage that the pressure-compliant Ab cover connected to the housing block in a simple manner can be, with a minimum of required components. Of further is advantageously no increase in Housing blocks required.  

If the flexible cover as a membrane, esp specially designed as a rolling membrane, then this offers the Advantage that little overall space is required.

drawing

Selected, particularly advantageous exemplary embodiments of the invention are shown in simplified form in the drawing and are explained in more detail in the following description. They show: Fig. 1 a selected vehicle brake system having two hydraulic accumulators, Fig. 2 by way of example an off cut from the state shown in FIG. 1, the vehicle brake system with the hydraulic accumulator and the Fig. 3 in a modified form, also a section of the in memory shown in FIG. 1.

Description of the embodiments

The hydraulic accumulator is for a vehicle brake system provided, especially when the vehicle braking system with a regulation to prevent the wheels from locking of the vehicle is equipped. This system is called anti blocking system (ABS). The vehicle braking system can additionally or instead with a drive slip control (ASR).

Fig. 1 shows an exemplary selected vehicle braking system with an anti-lock braking system (ABS). The driving tool brake system has an electric motor 1 for two return pumps 2 , 2 ', which are arranged between a memory 3 , 3 ' and a damper 4 , 4 '. Furthermore, two master cylinders 5 , 5 , and two wheel brake cylinders 6 , 6 'see easily, which are each connected via an inlet solenoid valve 7 , 7 ' and an outlet solenoid valve 8 , 8 'to the hydraulic fluid. In addition, there is in this vehicle brake system one each the inlet solenoid 7 and 7 'via bridging check valve 9 , 9 ' and a throttle 10 , 10 'on the damper 4 , 4 '. As the drawing shows, the return pumps 2 , 2 ', storage 3 , 3 ', damper 4 , 4 ', master cylinder 5 , 5 ', wheel brake cylinder 6 , 6 ', inlet solenoid valve 7 , 7 ' and outlet solenoid valves 8 , 8 ' hydraulically connected to one another via a connecting line 12 . In the Ver connection line 12 is a hydraulic fluid. The pressure fluid is, for example, a brake fluid or a hydraulic oil.

Such a vehicle brake system with the anti-lock braking system (ABS) works in such a way that when braking, the inlet solenoid valves 7 , 7 'are open and the outlet solenoid valves 8 , 8 ' are closed. A pressure rise in the master cylinder 5 , 5 ', which is optionally formed as a tandem cylinder or parallel cylinder, in any case preferably as a dual-circuit master cylinder, passes through two separate channels to the wheel brake cylinders 6 , 6 '. If there is a risk of locking, the inlet solenoid valves 7 , 7 'and the outlet solenoid valves 8 , 8 ' switch over so that the pressure fluid via the reservoir 3 , 3 'to the return pump 2 , 2 ' and from there via the damper 4 , 4 'to the master cylinder 5 , 5 'Can go back. So that the wheel brake cylinder 6 , 6 'is relieved and the risk of locking is eliminated. In order to maintain the pressure and to increase the pressure, the solenoid valves 7 , 7 'and 8 , 8 ' are activated accordingly by an electronic switching device (not shown) in the drawing for better clarity.

This two-channel system shown and described as an example Vehicle braking system can by much folding, especially the solenoid valves, into a three Channel or four-channel anti-lock braking system (ABS) expanded  and it can be done easily with a Traction control system (ASR) can be completed.

In the preferred embodiment selected, the return pumps 2 , 2 ', the memory 3 , 3 ', the damper 4 , 4 ', the inlet solenoid valves 7 , 7 ', the outlet solenoid valves 8 , 8 ', the check valves 9 , 9 ' and the throttles 10 , 10 'arranged in a common housing block 11 . The housing block 11 is indicated in Fig. 1 for better clarity because of dash-dotted lines. The housing block 11 consists for example of a few, firmly connected individual blocks, or it is in one piece. In the side walls of the housing block 11 , a plurality of holes are embedded, in which the parts mentioned are located. The memory 3 is also located in a bore 18 provided in the housing block 11 .

Fig. 2 shows on a different scale a detail of the housing block 11, the section was chosen so that a longitudinal section is visible through the memory 3.

The same or equivalent parts are included in all the figures provided the same reference numerals. Unless nothing against it Part mentioned or shown in the drawing applies the one mentioned and represented with the help of one of the figures in the other embodiments. Provided that from the The explanations are otherwise, the details of the different embodiments with each other can be combined.

The preferably selected accumulator 3 essentially comprises a separating piston 20 , a spring 22 , a spring support 24 , a locking ring 26 and a pressure-flexible cover 30 .

A hollow space is formed in the housing block 11 through the bore 18 . The separating piston 20 is mounted axially displaceably within the bore 18 . The separating piston 20 divides the cavity into a volume-changeable chamber 32 and into a counter chamber 34 . The volume-changeable chamber 32 is in constant communication with the connecting line 12 . A sealing ring 36 is provided on the outer circumference of the separating piston 20 for the purpose of sealing between the volume-variable chamber 32 and the counter chamber 34 .

The bore 18 has an outer end 18 a pointing outward from the housing block 11 and an inner end 18 b pointing in the opposite direction. In the course of the bore 18 a circumferential groove 18 c and a paragraph 18 d are seen before. Modified, the bore 18 can also be smooth, ie the paragraph 18 d is omitted, or the bore 18 is stepped several times. The snap ring 26 slotted at one point on its outer circumference is inserted with pretension into the recess 18 c. The separating piston 20 is urged by the spring 22 in the direction of the inner end 18 b. The spring 22 is supported on the one hand on the separating piston 20 and on the other hand on the spring support 24 . The spring support 24 has a shoulder 24 a. The spring support 24 can be supported with its shoulder 24 a via the locking ring 26 on the housing block 11 and thus hold the spring 22 against the separating piston 20 .

The spring support 24 has a pot-like shape with a bottom 24 b. In the bottom 24 b there is a centrally arranged passage 24 c. The counter chamber 34 is divided into a first region 34 a and a second region 34 b. The first area 34 a is located essentially between the separating piston 20 and the spring support 24 , and the second area 34 b is located essentially between the spring support 24 and the pressure-compliant cover 30 . The two areas 34 a and 34 b are connected to each other via the passage 24 c.

The cover 30 serves as a partition for separating the counter chamber 34 against a surrounding the housing block 11 order. In the embodiment shown in FIG. 2, the cover 30 consists essentially of a membrane 30 a and a sleeve 30 b. The sleeve 30 b has an outer circumference 30 c, an inner circumference 30 d, an inner end 30 e and an outer end 30 f. The sleeve 30 b is pressed into the outer end 18 a of the bore 18 until the inner end 30 e of the sleeve 30 b comes to rest on the shoulder 18 d. To facilitate the installation of the sleeve 30 b in the bore 18 , the sleeve 30 b is chamfered on the outer circumference of its inner end 30 e.

The membrane 30 a preferably has approximately the shape of a rolling membrane. The membrane 30 a can for example also be plate-like like a round disk. The membrane 30 a has a circumferential outer end 30 g. The sleeve 30 b is preferably made of metal. The circumferential end 30 g is vulcanized to the outer end 30 f of the sleeve 30 b. The vulcanization achieves a circumferential seal between the sleeve 30 b and the membrane 30 a. The inner circumference 30 d is smaller in the area of the outer end 30 f than in the area of the inner end 30 e. As a result, the vulcanization between the sleeve 30 b and the membrane 30 a can be facilitated. However, this gradation of the inner circumference 30 d is not absolutely necessary.

The membrane 30 a consists of a plate-like rubber-like material. The membrane 30 a gives way very easily when pressure acts on it from one side, so that practically no pressure difference, or in other words, practically no pressure difference can occur on both sides of the membrane. With the membrane 30 a, the cover 30 is so flexible that no, or virtually no difference in pressure can arise on both sides of the cover 30 . That is, cover 30 is resilient to pressure. As a result, no counterpressure which is higher than the pressure in the vicinity of the housing block 11 can arise in the counter chamber 34 . Respectively. the back pressure in the counter chamber 34 is at most insignificantly higher than the pressure in the environment, so that the back pressure cannot negatively affect the functioning of the accumulator 3 .

The pressure fluid is located in the connecting line 12 and in the volume-variable chamber 32 . If the pressure of the pressure fluid in the volume-variable chamber 32 is relatively low, then the separating piston 20 is located at the inner end 18 b, as shown in FIG. 2. If the pressure of the hydraulic fluid in the volume-changeable chamber 32 is relatively high, then the separating piston 20 is displaced against the force of the spring 22 (to the right in FIG. 2) until the separating piston 20 in extreme cases on the shoulder 24 a of the spring support 24 comes to the plant. The spring support 24 also serves as an end stop for the separating piston 20 . In the counter chamber 34 is air. If the separating piston 20 moves from the position shown in FIG. 2 in the direction of the spring support 24 , then part of the air passes from the first region 34 a of the counter chamber 34 through the passage 24 c into the second region 34 b. The membrane 30 a of the pressure flexible cover 30 is so flexible that no higher pressure can form in the counter chamber 34 compared to the pressure in the environment. The cover 30 is so flexible that with a movement of the separating piston 20, the membrane 30 a of the cover 30 can perform a corresponding movement without disturbing pressure increase in the counter chamber 34th

The sleeve 30 is firmly pressed b in the bore 18 so that the opposing chamber is sealed with respect to the order gebung 34 at this point. The sleeve 30 b can, for example, also be glued into the housing block 11 , and / or a sealing ring can additionally be provided between the outer circumference 30 c and the bore 18 . As FIG. 2, the diameter of the bore 18 in the region of the outer end 18 a is greater than b in the region of the inner end 18 so as to form the shoulder 18 d. The embodiment can also be modified so that the diameter of the bore 18 in the region of the outer end 18 a is the same as in the region of the inner end 18 b, so that the paragraph 18 d falls. By pressing the sleeve 30 b in a manner dependent on the path into the bore 18 , the sleeve 30 b can be positioned exactly relative to the housing block 11 even without the shoulder 18 d.

The sleeve 30 b offers the advantage that sufficient room for movement for the membrane 30 a can be provided without the housing block 11 having to be enlarged. The relatively rigid sleeve 30 b considerably facilitates the attachment of the pressure-compliant cover 30 to the housing block 11 . The existing from the sleeve 30 b and the membrane 30 a pressure-compliant cover 30 can be provided as a finished part to the construction on the housing block 11 .

FIG. 3 shows another particularly selected, particularly advantageous exemplary embodiment, with a pressure-flexible cover 30 that is modified compared to FIG. 2.

In the embodiment shown in FIG. 3, the sleeve 30 b shown in FIG. 2 is omitted. As shown in FIG. 3, the membrane 30 a of the pressure-compliant cover 30 in the area of the circumferential end 30 g is directly connected to the housing block 11 in a tight and sealing manner.

As FIG. 3 shows, can be used for better connection between the housing block 11 and the drucknachgiebigen cover 30 may be provided in the region of the outer end 18 a of the bore 18 to an operating recess 18 e. Furthermore, the membrane 30 a in the region of its circumferential end 30 g can have a bead 30 h which can be inserted into the recess 18 e. In order to further improve the connection between the cover 30 and the housing block 11 , a clamping ring 30 i made of metal or solid plastic can be provided, which additionally presses the circumferential end 30 g against the housing block 11 , in particular in that the clamping ring 30 i press the bead into the recess 18 e for 30 h. In a modification of the exemplary embodiment depicted in FIG. 3, the clamping ring 30 i can also be cast directly into the bead 30 h, which contributes to a reduction in the number of components required.

If the memory 3 with the separating piston 20 and the spring support 24 is fully assembled in the housing block 11 , then before the pressure-compliant cover 30 is added, through the passage 24 c provided in the spring support 24 , the faultless operation of the memory 3 , in particular the Mobility of the separating piston 20 , can be easily checked.

The pressure of the pressure fluid in the chamber 32 is relatively high. In the course of a long operating time of the accumulator 3 , some of the pressure fluid can possibly get from the chamber 32 into the counter chamber 34 between the separating piston 20 and the bore 18 . Because of the sealing ring 36 , this amount is relatively small. The resilient cover 30 can be dimensioned sufficiently resilient that the liquid coming from the chamber 32 into the counter chamber 34 liquid bulges the membrane 30 a more outwards, but because of the high resilience of the membrane 30 a the back pressure in the counter chamber 34 does not increase noticeably as a result.

Claims (9)

1. Hydraulic accumulator for a vehicle braking system, with a displaceably mounted in a housing block, a volume-changing chamber ( 32 ) containing a hydraulic fluid and a separating piston ( 20 ) separating a counter chamber, characterized in that the counter chamber ( 34 ) has a pressure-flexible cover ( 30 , 30 a, 30 b) towards an environment is complete. 2. Hydraulic accumulator according to Claim 1, characterized in that the separating piston ( 20 ) is mounted in a bore ( 18 ) provided in the housing block ( 11 ), the bore ( 18 ) has an outer end pointing outwards from the housing block ( 11 ) ( 18 a) and an inner end ( 18 b) pointing in the opposite direction, the separating piston ( 20 ) being acted upon by a spring ( 22 ) in the direction of the inner end ( 18 b) of the bore ( 18 ), the volume-variable chamber ( 32 ) is provided between the inner end ( 18 b) of the bore ( 18 ) and the separating piston ( 20 ) and the spring ( 22 ) is supported on a spring support ( 24 ) provided in the counter chamber ( 34 ). 3. Hydraulic accumulator according to claim 2, characterized in that starting from the spring support ( 24 ), one of the separating piston ( 20 ) facing the first region ( 34 a) of the counter-chamber ( 34 ) and one of the pressure-flexible cover ( 30 , 30 a, 30 b) facing second region ( 34 b) of the counter chamber ( 34 ) are connected via a passage ( 24 c). 4. Hydraulic accumulator according to one of claims 1 to 3, characterized in that an at least part of the pressure-flexible cover ( 30 , 30 a, 30 b) sealed bearing sleeve ( 30 b) is provided and the sleeve ( 30 b) sealed at least is inserted indirectly into the housing block ( 11 ). 5. Hydraulic accumulator according to one of claims 1 to 4, characterized in that the resilient cover ( 30 , 30 a, 30 b) has an outer circumference ( 30 c), on which it is sealed with the housing block ( 11 ) at least indirectly connected . 6. A hydraulic reservoir according to any one of the preceding claims, characterized in that the drucknachgiebige cover (30, 30 a, 30 b) is at least partially designed as a membrane (30 a), in particular as a rolling diaphragm (30 a). 7. Hydraulic accumulator according to one of the preceding claims, characterized in that the flexibility of the pressure-flexible cover ( 30 , 30 a, 30 b) is dimensioned sufficiently that an operational leakage of the pressure fluid from the chamber ( 32 ) into the counter chamber ( 34 ) changed a back pressure in the counter chamber ( 34 ) at most insignificantly. 8. Hydraulic accumulator according to one of claims 1 to 7, characterized in that when the displaceably mounted separating piston ( 20 ) moves, a back pressure in the counter-chamber ( 34 ) changes at most insignificantly. 9. Hydraulic accumulator according to claim 7 and / or 8, characterized in that the back pressure in the counter chamber ( 34 ) corresponds essentially to an ambient pressure prevailing in the environment.