DE19850910A1 - Pressure fluid accumulator for vehicle brake systems - Google Patents

Abstract

The invention relates to a pressure means accumulator (31) for vehicle brake systems with automatic brake control. The inventive pressure means accumulator has a housing (32) with two pressure means connections (33, 34) and an accumulator chamber (35) interconnecting them, an elastic membrane (41) delimiting said accumulator chamber (35), said membrane being fixed in the housing (32) on the edges, and an air-permeable support body (42), which is accommodated in the housing (32) and which has a support surface (43) for supporting the membrane (41). According to the invention, a large area of the support surface (43) is drawn deeply into the support body (42) and the membrane (41) is guided along on the support surface (43) in its non-extended state in order to improve the freeing of the accumulator volume and hereby improve the dynamics for the build-up of pressure when the traction control system is in operation or during regulation of driving dynamics. The support surface (43) is preferably shaped by the inner contour of a pot-shaped recess (48) in the support body (42).

Description

The invention relates to a pressure medium storage for Vehicle braking systems with automatic brake control after the preamble of claim 1.

In such vehicle brake systems with automatic, i.e. H. driver-independent brake control, for example Traction control system (ASR) and / or vehicle dynamics control (FDR) promotes a high pressure pump in the case of an ASR Pressure build-up pressure medium from a master brake cylinder in the Brake circuit of the spinning wheel. Especially at deep Temperatures and thus high viscosity of the pressure medium this leads to pressure losses in the suction line of the High-pressure pump that works on all throttling cross sections occur, such as B. the central valve of the Master brake cylinder. This worsens the  Pressure build-up dynamics considerably; because the max. possible Volume flow is limited by the suction resistances. The unpressurized, passive pressure medium storage of the aforementioned Art now serves the pressure drop on the brake line to bypass and the existing negative pressure of the high pressure pump to use and suck directly from the pressure medium storage, so that the first time-critical pressure build-up in the Brake line of the slipping wheel is done very quickly.

In a known unpressurized, passive pressure medium accumulator this type (DE 41 28 386 A1) the membrane is more elastic Hose formed on a cylindrical Support body rests. The support body is permeable to air and can be used as a solid wall component with a variety of Cross bores or be formed as a porous sintered part. in the Area of the gap-free accommodated in a housing section Support body is the housing with a variety of over the Provided circumferentially distributed cross holes that the Connect the support body to the atmosphere so that the Hose membrane is under atmospheric pressure. in the Traction control mode generates - as at the beginning described - the high pressure pump in the pressure medium storage a negative pressure, and the hose membrane lifts off Support body from, so that in the from the hose membrane enclosed storage space contained pressure medium volume of the high pressure pump can be sucked. That in The pressure medium volume contained is for the Build-up of brake pressure in the wheel brake when Sufficient traction initially. Another removal Pressure medium from the master brake cylinder follows with a delay. To End of traction control operation promotes  High pressure pump the pressure medium back from the wheel brake, whereby the pressure medium reservoir is filled again.

In a known, depressurized, passive Pressure fluid reservoir for a vehicle brake system with Traction control device (DE 43 36 464 A1) is the Storage space from a membrane clamped in the housing limited, which results from a middle position can move both sides and thus on the one hand additional pressure medium volume for an equalization the suction flow of the high pressure pump Provides traction control operation and on the other hand catches adverse pressure peaks in the brake system. The disc-shaped membrane is made of an elastomer, that has sufficient compliance. Prefers EPDM blends are usually used with high elasticity Shore hardness of 70-80 Shore A selected. The membrane has at its edge-side clamping point a ring bulge, which by a retaining wall is pressed against a housing shoulder.

Advantages of the invention

The pressure medium reservoir according to the invention with the features of claim 1 has the advantage that other than the volume release in the known pressure fluid accumulators of the pressure medium not from the elasticity of the membrane is brought out, but mainly from the Geometry of the support body with its deeply drawn Support surface for the membrane takes place, which by folding or Unrolling releases the pressure medium volume much easier than through material expansion. The membrane is like this designed that they in the relieved, that is, depressurized state  takes on its stable position by itself and adopts the deep in creates the support body retracted support surface. The at The expansion of the membrane occurring during the operating load is now significantly lower than the known ones Pressure fluid storage.

Overall, the inventive design of support body and Membrane in the pressure medium storage the suction behavior in automatic braking operation significantly improved.

By the measures listed in the other claims are advantageous further developments and improvements in Claim 1 specified pressure medium storage possible.

According to a preferred embodiment of the invention, the Support surface for the membrane from the inner contour of one in the Support body incorporated, cup-shaped recess formed, preferably the recess has a frustoconical shape and the bottom of the Recess the smaller diameter end face of the Truncated cone. Such a shape of the in the Support body deeply recessed support surface has for the easy rolling of the membrane Traction control mode and driving dynamics control as proven optimal.

According to an advantageous embodiment of the invention the housing in two parts with through the storage space extending parting plane. From the parting line is in one housing part the support body positive first recess and in the other Housing part opposite the first recess introduced second depression, which in the housing part  running channels with the two in the housing part trained pressure medium connections is connected. The second recess is dimensioned so that an application of the Membrane to the bottom of the second recess in which the Channels lead to the pressure medium connections, also at elastic expansion of the membrane is reliably excluded is.

According to an advantageous embodiment of the invention the support body is formed as a plastic ring, the one Having a plurality of through axial bores, the on the one hand in the supporting surface and on the other hand in the End face of the support body formed radial grooves flow out. The latter run centrally, i.e. at the center of the Face, into each other. Basically the first deepening is a vent hole penetrating the housing part arranged coaxially so that all axial bores over the Radial grooves and the vent hole with atmosphere are connected.

According to a preferred embodiment of the invention the housing part receiving the support body in the installed position on top of the other housing part, and in the Vent hole is a springless check valve arranged, the one formed in the vent hole Valve seat and one in the vent hole Valve ball includes. The diameter of the ball is like this dimensioned that air between the ball and vent hole remaining annular gap happens, but in the Vent hole inflowing pressure medium due to its Viscosity creates such a large drop in pressure at the annular gap, that the ball is pressed up onto the valve seat.  

This springless check valve is a reliable one Protection against total failure of the brake system in the event of a Bursting of the diaphragm of the pressure fluid accumulator ensured. According to an alternative embodiment of the invention which is the second well with connections and channels having housing part in the installation position lying on top and the Support body formed as a porous sintered part, the Pore size is such that air is not a pressure medium can penetrate through the sintered part at the rear. Basically the first recess is a penetrating part of the housing Vent hole arranged, and the vent hole is provided with a splash protection. Through this constructive design is the ventability and Fillability of the pressure medium reservoir when filling the Brake system with pressure medium improved because of the air their lower density flows upwards and therefore not in Pressure fluid reservoir remains, but when filling is promoted. Because of the changed installation position of the Vent hole now no springless check valve is more usable, the porous support body Sintered part used, its properties with respect to the Permeability of pressure medium and air also a Protection against total failure of the brake system in the event of a Offers bursting of the membrane in the pressure medium accumulator.

drawing

The invention is illustrated in the drawing Exemplary embodiments in the following description explained. Show it:  

Fig. 1 is a block diagram of a vehicle brake system with traction slip control device,

A longitudinal section of an accumulator in the hydraulic system according to FIG. 1, schematically illustrated FIG. 2,

Fig. 3 is an enlarged representation of the detail III in Fig. 2,

Fig. 4 shows a section along the line IV-IV in Fig. 3,

FIG. 5 shows the same representation as in FIG. 2 of a modified pressure medium store.

Description of the embodiments

The hydraulic brake system for a motor vehicle shown in the block diagram in FIG. 1 has a master brake cylinder 11 with a pressure medium reservoir 12 , a brake pedal 10 acting on the master brake cylinder 11 and two brake circuits I and II connected to the master brake cylinder 11 . The brake circuit I serves to actuate a wheel brake 13 assigned to the left front wheel VL and a wheel brake 14 of the motor vehicle assigned to the right rear wheel HR. A wheel brake 15 of the right front wheel VR and a wheel brake 16 of the left rear wheel HR of the vehicle are connected to the brake circuit II. The brake system is equipped with a device 17 for automatic, ie driver-independent, brake control, for example for limiting the drive slip on the driven front wheels VL, VR of the vehicle or for braking intervention on all four wheels for the purpose of driving dynamics control or for automatic tracking or distance control. The structure of the brake system is described below with reference to brake circuit II, which is designed in the same way as brake circuit I, insofar as this is necessary for understanding device 17 . In brake circuit II, a brake line 20 extending from master brake cylinder 11 leads to wheel brake 15 . On the wheel brake side, the brake line 20 is assigned a pressure control valve arrangement 21 for the brake pressure modulation of the wheel brake 15 . Such a valve arrangement 21 consists of an inlet valve 22 and an outlet valve 23 . Both valves are designed as 2/2-way solenoid valves. A shut-off or changeover valve 24 is arranged in the brake line 20 on the master cylinder side. The changeover valve 24 has a basic position shown in FIG. 1, in which it is permeable to pressure medium. In its working position, the changeover valve 24 blocks the brake line 20 and is permeable in the direction of the master brake cylinder 11 when a predetermined response pressure is exceeded.

A suction line 25 branches off from the brake line 20 between the master brake cylinder 11 and the changeover valve 24 and contains a charging or shut-off valve 26 designed as a 2/2-way solenoid valve. This shut-off valve 26 in its blocking in Fig. 1 the basic position shown, the suction pipe 25 and is in its working position, the suction pipe 25 freely. The suction line 25 leads to the suction side of a self-priming high-pressure pump 27 , which is driven by an electric motor 28 . A pressure line 29 extends from the pressure side of the high-pressure pump 27 and is connected to the brake line 20 between the changeover valve 24 and the pressure control valve arrangement 21 . The elements of the brake system lying between the master brake cylinder 11 and the wheel brakes 13-16 are combined in a so-called hydraulic unit 30 , the housing of which is indicated by a dash-dotted line. Not shown is an electronic control unit which monitors the wheel turning behavior with the aid of speed sensors assigned to the vehicle wheels and switches the corresponding elements of the hydraulic unit 30 and the electric drive motor 28 of the high-pressure pump 27 according to a predetermined control algorithm when drive slip occurs or when driving dynamics are controlled.

In brake circuit II, just as in brake circuit I, an unpressurized, passive pressure medium reservoir 31 is provided. In the exemplary embodiment in FIG. 1, this pressure medium reservoir 31 is attached as an external screw-on part in front of the hydraulic unit 30 and connects the master brake cylinder 11 to the brake line 20 . As indicated in dashed lines in FIG. 1, the integration of the pressure medium reservoir 31 in the hydraulic unit 30 itself is also possible, for which purpose the pressure medium reservoir 31 is switched on in the suction line 25 and is located in front of the shut-off valve 26 . The construction of the pressure medium reservoir 31 , which serves to improve the pressure build-up dynamics of the device 17 , is shown schematically in longitudinal section in FIGS. 2 and 3. It has a housing 32 with two pressure medium connections 33 , 34 and with a pressure medium storage space 35 which is connected to the two pressure medium connections 33 , 34 via channels 36 , 37 . A pipe piece 38 is tightly screwed into the pressure medium connection 33 , on which in turn a screw connection 39 sits, via which the housing 32 is connected to the suction side of the hydraulic unit 30 . The brake line piece coming from the master brake cylinder 11 is screwed into an internal thread 40 in the pressure medium connection 34 with a sealing cone. The storage space 35 is bounded on one side by an elastic membrane 41 made of an elastomer, preferably EPDM, which, in the depressurized state of the pressure medium reservoir 31 shown in FIG. 2, bears against a support surface 43 formed on a support body 42 . As will be explained in more detail, the support surface 43 and thus the outside of the membrane 41 facing away from the storage space 35 is connected to the atmosphere.

The housing 32 is formed in two parts with a parting plane 44 running through the storage space 35 and has a first housing part 321 and a second housing part 322 which lie flat on one another in the parting plane and are screwed together. The screw connection of the two housing parts 321 , 322 is indicated in FIG. 2 by dash-dotted connecting lines 45 . In each case from the parting plane 44, a first recess 46 which positively accommodates the support body 42 is introduced in the first housing part 321, and a second recess 47 directly opposite the first recess 46 is introduced in the second housing part 322 . The second recess 47 forms part of the pressure medium storage space 35 and is connected to the pressure medium connections 33 , 34 also formed in the housing part 322 by the already mentioned channels 36 , 37 which open into the bottom 471 of the recess 47 .

The support surface 43 of the support body form-fitting inserted in the first recess 46 42 has a large area drawn deep into the support body 42 and is preferably formed by the inner contour of a introduced into the support body 42 cup-shaped recess 48 of frustoconical shape with the base of the recess 48, the smaller-diameter end face of the truncated cone. The membrane 41 is guided along the support surface 43 in the unstretched state and inserted with an annular bead 411 formed on the edge into an annular groove 49 which is introduced into the first housing part 321 concentrically with the first recess 46 receiving the support body 42 from the parting plane 44 . By superposing and screwing together the two housing parts 321, 322 the diaphragm is clamped peripherally between the two housing parts 321, 322 41st The second depression 47 present in the second housing part 322 is dimensioned such that a contact of the membrane at the base 471 of the second depression 47 is reliably excluded even when the membrane 41 is elastically stretched, so that the orifices 361 and 371 of the channels 36 , 37 in the pressure medium - Storage space 35 can never be closed by the membrane 41 .

In the exemplary embodiment in FIGS. 2 and 3, the first housing part 321 receiving the support body 42 lies in the installed position of the pressure medium reservoir 31 on the second housing part 322 and forms the upper part of the housing 32 . The support body 42 is designed as a plastic disk 50 , which has a plurality of continuous axial bores 51 which on the one hand open into the support surface 43 and on the other hand into radial grooves 52 which are formed on the end face of the support body 42 facing away from the support surface 43 ( FIG. 4) . The axial bores 51 are reduced in diameter (tapered) near their mouths in the support surface 43 , and the mouths in the support surface 43 are rounded to prevent damage when they come into contact with the membrane 41 . The radial grooves 52, which are offset by the same circumferential angle from one another, are connected to one another in the center of the support body 43 , and basically 461 of the first recess 46 , a coaxial vent hole 53 is made which penetrates the housing part 321 and covers the connection point of the four radial grooves 52 in the center of the support body 42 .

With vehicle dynamics control or in traction control mode, e.g. B. when an impermissibly large drive slip on the wheel brake 15 of the right front wheel VR of the vehicle, the control unit, not shown here, switches the switching valve 24 and the shut-off valve 26 into the working position and switches on the high-pressure pump 27 . The high-pressure pump 27 now sucks pressure medium from the pressure medium reservoir 31 , the storage space 35 being partially or completely emptied by the membrane 41 moving downward. Since the upper side of the diaphragm 41 is connected to atmospheric ambient pressure via the vent hole 53 and the support body 42 , the diaphragm 41 has the possibility of rolling off the support surface 43 and moving downward in the presence of negative pressure in the storage space 35 in order to release the desired volume to effect. Even in the unrolled state, the membrane 41 does not close the openings 361 , 371 of the channels 36 , 37 , basically 471 of the depression 47 , since this is made deeper than the shape and expansion of the membrane 41 allow. The pressure medium drawn in from the pressure medium reservoir 31 is conveyed through the pressure line 29 into the wheel brake 15 , and brake pressure is built up there to stabilize the wheel turning behavior. Such pressure build-up can be followed by phases for pressure maintenance and pressure reduction, which are not described in more detail. When the pressure is reduced - and thus the wheel brake 15 is released - the pressure medium is conveyed back again and the storage space 35 in the pressure medium reservoir 31 is filled again, the membrane 41 again contacting the support surface 43 of the support body 42 , as shown in FIG. 3.

To protect the brake system before a total failure of the brake circuit II event of a possible bursting of the diaphragm 41 in the vent hole 53, a springless non-return valve 54 is inserted, a valve seat formed in the vent hole 53 55 and cooperating with the valve seat 55 in the vent hole 53 comprises displaceably held valve ball 56 . The ball diameter is selected so that the annular gap remaining between the valve ball 46 and the bore wall of the vent hole 53 allows air to pass through, but when pressure medium flowing into the vent hole 53 produces a pressure drop in the annular gap which is so great that the valve ball 56 moves upward due to its viscosity is pressed onto the valve seat 55 .

In the modified pressure medium reservoir 31 shown schematically in longitudinal section in FIG. 5, in the installed position, the second housing part 322 lies on top of the first housing part 321 and forms the upper part of the housing 32 . The second housing part 322 in FIG. 5 is configured identically to the second housing part 322 in FIGS. 2-4. The first housing part 321, which is now at the bottom, essentially corresponds to the housing part 321 in FIGS. 2-4 and is now modified in such a way that the support body 42 is designed as a porous, cup-shaped sintered part 58 . The vent hole 59, which is much larger in diameter and is designed as a stepped bore, is equipped with a splash guard 60 . The splash guard 60 is realized by means of an injection lid 61, which rests with the edge pronounced corrugations 62 on a radially projecting in the venting bore 59 and annular shoulder 63 is defined on the annular shoulder 63 by means of a snap ring 64th Between the outer edge of the spray cover 61 and the inner wall of the vent hole 59 there remains an annular gap 65 through which air can pass to the support body 42 .

The 180 ° with respect to the accumulator in Fig. 2 and 3 rotated installation position of the accumulator 31 of FIG. 5 provides improved deaeration and fillability of the storage space 35 during filling of the brake system with pressure medium, as the air moves because of their lower density up and thus does not remain in the storage space 35 , but is conveyed out during filling. As a result of the installation position of the pressure medium reservoir 31 rotated through 180 °, the springless check valve 34 shown in FIGS. 2 and 3 can no longer be used. In order to also ensure protection against total failure of the brake system when the membrane 41 may burst, the pore size of the porous sintered part 58 is selected so that air can pass through without problems, but pressure medium of the brake system does not. This is achieved through the throttling effect of the very small flow cross sections in the pores.

Claims (12)

1. Pressure fluid accumulator for vehicle brake systems with automatic brake control, for. B. with traction control device and / or vehicle dynamics control, with a housing ( 32 ) which has two connections ( 33 , 34 ) for connecting pressure-medium-carrying lines of the brake system and a storage space ( 35 ) connecting the two connections ( 33 , 34 ) with one another the memory space (35) bounding the flexible diaphragm (41), which is clamped on the edge side in the housing (32), and with a accommodated in the housing (32), air-permeable support body (42) having a support surface (43) for supporting the membrane ( 41 ) in the depressurized state of the brake system and with brake pressure control and on its outside facing away from the support surface ( 43 ) communicates with the atmosphere, characterized in that the support surface ( 43 ) is drawn deep into the support body ( 42 ) and that the membrane ( 41 ) is guided along the support surface ( 43 ) in the unstretched state. 2. Memory according to claim 1, characterized in that the support surface ( 43 ) is formed by the inner contour of a cup-shaped recess ( 48 ) introduced into the support body ( 42 ). 3. Memory according to claim 2, characterized in that the cup-shaped recess ( 48 ) has a frustoconical shape, the bottom of the recess ( 48 ) representing the smaller-diameter end face of the truncated cone. 4. Memory according to one of claims 1-3, characterized in that the housing ( 32 ) is formed in two parts with through the storage space ( 35 ) extending parting plane ( 44 ) that from the parting plane ( 44 ) in the one housing part ( 321 ) a first recess ( 46 ) receiving the support body ( 42 ) and in the other housing part ( 322 ) a second recess ( 47 ) opposite the first recess ( 46 ) is introduced, which extends via channels ( 36. ) running in the housing part ( 322 ) , 37 ) is connected to the two connections ( 33 , 34 ) formed in the housing part ( 322 ). 5. Memory according to claim 4, characterized in that the second recess ( 47 ) is dimensioned such that application of the membrane ( 41 ) at the base ( 471 ) of the recess ( 47 ) is reliably excluded even with elastic expansion of the membrane ( 41 ) and that the channels ( 36 , 37 ) open at the bottom ( 471 ) of the recess ( 47 ). 6. Memory according to claim 4 or 5, characterized in that the supporting body ( 42 ) receiving the housing part ( 321 ) to the first recess ( 46 ) concentric, introduced from the parting plane ( 44 ) from the annular groove ( 49 ) and the membrane ( 41 ) has a circumferential annular bead ( 411 ) lying in the annular groove ( 49 ), and that the membrane ( 41 ) is clamped in the parting plane ( 44 ) at the edge between the adjacent housing parts ( 321 , 322 ) of the housing ( 32 ). 7. Memory according to one of claims 4-6, characterized in that the support body ( 42 ) is designed as a plastic disc ( 50 ) which has a plurality of continuous axial bores ( 51 ), on the one hand in the support surface ( 43 ) and on the other hand in Radial grooves ( 52 ) open, which are introduced into the end face of the support body ( 42 ) facing away from the support surface ( 43 ) and are centrally connected to one another, and that basically ( 461 ) of the first recess ( 46 ) has a vent hole penetrating the housing part ( 321 ) ( 53 ) is arranged coaxially. 8. The memory of claim 7, characterized in that the axial bores ( 51 ) near their mouths in the support surface ( 43 ) are reduced in diameter and that the mouths in the support surface ( 43 ) are provided with a rounding. 9. Memory according to claim 7 or 8, characterized in that the support body ( 42 ) receiving housing part ( 321 ) is in the installed position on top of the other housing part ( 322 ) and that in the vent hole ( 53 ) a valve seat ( 55 ) for one in the vent hole ( 53 ) lying valve ball ( 56 ) is formed, the diameter of which is such that air passes between the valve ball ( 56 ) and the wall of the vent hole ( 53 ) remaining annular gap ( 57 ), but flowing into the vent hole ( 53 ) Due to its viscosity, pressure medium produces such a strong pressure drop in the annular gap ( 57 ) that the valve ball ( 56 ) is pressed upwards onto the valve seat ( 55 ). 10. Memory according to one of claims 4-6, characterized in that the second recess ( 47 ) with connections ( 33 , 34 ) and channels ( 36 , 37 ) having housing part ( 322 ) in the installed position on top of the other housing part ( 321 ) rests that the support body ( 42 ) is designed as a porous sintered part ( 58 ), the pore size of which is dimensioned such that air but no pressure medium can pass through, and that basically ( 461 ) of the first recess ( 46 ) is a housing part ( 321 ) penetrating vent hole ( 59 ) is formed. 11. The memory according to claim 10, characterized in that the vent hole ( 59 ) is provided with a splash guard ( 60 ). 12. The accumulator according to claim 11, characterized in that the splash water protection ( 60 ) has a spray cover ( 61 ) fixed in the vent hole ( 59 ), which has edge-shaped beads ( 62 ) on a radially projecting annular shoulder ( 63 ) in the vent hole ( 59 ) rests and leaves an annular gap ( 65 ) to the bore wall of the ventilation bore ( 59 ).