DE19802847C2 - Pneumatic brake booster with improved electromagnetic actuation - Google Patents

Description

The invention relates to a pneumatic brake booster according to the preamble of claim 1. Such a brake Power amplifier is known from DE 196 17 589 A1.

Brake boosters of this type are increasingly used today Motor vehicles for installation because the braking system of modern cars can be equipped with functions that only work with one Brake booster can be implemented independently can be operated by the driver's will, usually by means of a Solenoid assembly. As an example of this additional Functions of modern brake systems are the drive here slip control, the vehicle dynamics control (also as stability program), the automatic distance control, and finally called the so-called brake assistant, who at Detect an emergency stop automatically as soon as possible provides maximum braking power support.

In known, usually as a vacuum brake booster designed pneumatic brake boosters with (additional Licher) electromagnetic actuation there is the problem that certain seals inside the control valve due to the between them and the component to be sealed Friction the controllability of the brake booster by means of adversely affect the electromagnet assembly, d. H. Be The driving points of the brake booster can be adjusted using the Do not set the electromagnet arrangement so sensitively and quickly len as it would be desirable. In addition, often in control valve certain effective areas are present, to which the the movable wall of the brake booster Pressure difference acts, so that corresponding disturbance variables arise hen the targeted and quick setting of predefined It makes support staff more difficult. The required greater control effort and also the higher of the electromagnet arrangement  Forces to be exerted increase the manufacturing costs.

From DE 43 37 361 A1 a brake booster with a control valve is known, the has two valve seats interacting with one valve member each. The control valve is Electromagnetically operated and has an axially displaceable, resiliently biased te electromagnet arrangement with which a pedal-controlled brake actuation electronically controlled brake actuation can be overlaid or even a driver-independent valid, electronically controlled brake actuation can be carried out.

The invention has for its object a pneumatic brake booster To provide, the control valve for setting or starting predetermined operation points, d. H. given support staff, easier and therefore cheaper than previously made possible.

This object is achieved with a brake booster, which in Claim 1 specified features. The Bremskraftver invention stronger where the connection between his vacuum chamber and his work came mer is controlled by two valve seats, which are located on axially opposite sides of one are located floating in the control valve housing electromagnet assembly, and the each with one of two movable valve members arranged in mirror image to each other cooperate, the one of the two aforementioned valve seats only by an actuator the electromagnet arrangement can be closed, allows a clear door between the electromagnetic actuation system and the manual Actuation of the brake booster used components, d. H. the manual Operation necessary components have no negative influence on the electromagnetic Actuation system. The brake booster according to the invention thus creates the Prerequisite for realizing an electromagnetic actuation with so-called horizontal characteristics. This means that the electromagnetic system at a Power supply with constant current over its entire stroke remains constant en Magnetic force generated. Such an electromagnetic system is independent of that in the different brake boosters axially differing position of the first valve member, so that settings or adjustments in series production are not required. Because of the lack of feedback or even freedom from feedback there are also magnetic forces between manual and electromagnetic actuation te, which the electromagnet arrangement must generate, is considerably reduced.

In a preferred embodiment of the brake booster according to the invention first valve seat which is the feed  from atmospheric pressure (or overpressure) to the working chamber ert, arranged concentrically to a second valve seat, the together with a third valve seat the connection between controls the vacuum chamber and the working chamber. A first one Valve seat, which is advantageously radially inside the second Ven arranged and at one with the input member of the Brake booster coupled actuating piston formed works like the second valve seat with the first valve member together. Such a construction promotes one compact design and helps the number of necessary Reduce components.

The braking force according to the invention is structurally advantageous both the second valve seat and the third Valve seat formed on the control valve housing, d. H. this both valve seats are fixed. Point particularly preferably the second valve seat and the third valve seat at least one approximately the same sealing diameter. Are the seal through same diameter of the second and third valve seat, one existing between the working chamber and the vacuum chamber Pressure difference to no disturbance on the electromagnet lead arrangement.

According to an embodiment of the Bremskraftver invention The second valve member of the third valve seat is stronger away and resilient towards the electromagnet assembly biased so that the third valve seat when unactuated Electromagnet arrangement is always open. With a like be wrote floating electrical stored in the control valve housing magnet arrangement is the resilient bias of the second Valve member advantageously also used to the housing of the Electromagnet arrangement in the unactuated state of the same you tends between the second valve member and a fixed one Clamp the stop of the control valve housing. The fixed de stop, like the valve seats, is preferably of circular shape and has no retroactive effects  one with the sealing diameter of the second valve same sealing diameter.

In preferred embodiments of the brake according to the invention The amplifier is the armature of the electromagnet arrangement coupled to an actuating sleeve, which when actuating the elec tromagnet arrangement acts on the first valve member to it from the first valve seat and thus the supply of atmosphere pressure (or overpressure) to the working chamber. An opening of the first valve seat by means of the Elektromag Thus, the net arrangement takes place without the aid of a mechanical actuation used components. The first valve link is preferably of two series connected, Springs biased towards the first valve seat by which the second spring, which is preferably stronger than the first Spring is only when the through the actuating sleeve Lifting the first valve member effective from the first valve seat is. This arrangement has the advantage that the first, preferably weaker spring generates the contact pressure with which the first valve member pressed against the second valve seat is, so that the opening of this second valve seat at Exit supply a mechanical actuation of the brake booster requires only a comparatively small force. on the other hand must open the electromagnetic valve when the first valve seat called actuating sleeve also the force of the second Overcome spring, d. H. the electromagnet arrangement must be against work a steeper spring characteristic. Such a steeper one The main characteristic has the advantage that the for a certain Current stroke of the armature against the spring force change (current increase) is relatively large, so that with a relatively low control effort, a sufficiently high control accuracy can be achieved.

The actuating piston already mentioned, on which the advantageous is formed, preferably penetrates the entire electromagnet assembly, the second valve member and third valve seat in the axial direction. Sealing the Actuating piston opposite the electromagnet arrangement is at  the described configuration with the two interacting, the connection between the vacuum chamber and the working Chamber-controlling valve seats are not required.

The tax exists for simpler manufacturing valve housing of a brake booster according to the invention preferably axially adjoining at least two Eating, rigidly connected parts, the second Valve seat in one part and the third valve seat in that other part of the control valve housing is formed. The at least two parts of the control valve housing are on purpose conveniently connected, for example by Screwing, gluing, or also by welding.

An embodiment of a Bremskraftver invention strengkers is described below with the help of the attached schematic rule drawings explained in more detail. It shows:

Fig. 1, the control valve of a braking force amplifier according to the invention in longitudinal section, Fig. 1 unbetä the saturated state of the control valve, so its rest position, reproduces,

Fig. 2 is the view of FIG. 1 in a state immediately after the start of manual operation,

Fig. 3 is the view of FIG. 2 after a retracting (loosening) a manual actuation of the control valve,

Fig. 4 is the view of FIG. 1 shortly after the start of an electromagnetic actuator of the control valve,

Fig. 5 shows the view of Fig. 1 in a comparison with FIG. 4, somewhat later phase of an electromagnetic actuator,

Fig. 6 shows the view from Fig. 1, in a comparison with FIGS. 4 and 5 still later phase of an electromagnetic actuator

Fig. 7 shows the view from Fig. 1 in a comparison with FIG. 6 again later phase of an electromagnetic actuation Be (so-called. The control position),

Fig. 8 is the view of Fig. 1 in a state during an electromagnetic actuation, in which a supply of atmospheric pressure (or overpressure) to the working chamber mer controlling valve seat is open, and

FIG. 9 shows the view from FIG. 1 in a state which follows the state shown in FIG. 8 and which occurs immediately after an electromagnetic actuation has ended.

FIG. 1 shows a longitudinal section through the part of a vacuum brake booster with an amplifier housing 10 which is of primary interest here, of which only a small section is shown in FIG. 1. The amplifier housing 10 is usually formed from two sheet metal half-shells and delimits an interior space which is divided by a movable wall 12 into a vacuum chamber 14 and a working chamber 16 .

In the amplifier housing 10 protrudes along an axis A a control valve 18 for controlling a pneumatic pressure difference acting on the movable wall 12 . The control valve 18 has a here of two parts 20, 22 existing control valve housing and is slidably and sealingly in an axially outwardly projecting cylindrical neck 10 of the booster housing be taken. In the interior of the amplifier housing 10 , the movable wall 12 is sealingly and force-transmitting on a circumferential radial flange 24 of part 20 of the control valve housing. An arranged in the vacuum chamber 14 , not shown return spring biases the control valve housing together with the movable wall 12 in the output position shown in Fig. 1 before.

The control valve 18 and thus the brake booster can be actuated with a rod-shaped here, axially projecting into the control valve housing, mechanical input member 26 , which acts with its one end in the control valve 18 on an actuating piston 28 and the other end of which is connected, for example, to a brake pedal, not shown , The actuating piston 28 transmits the actuating force introduced by the input member 26 to a so-called feeler 30 , which is accommodated in the part 22 of the control valve housing arranged on the force output side. The sensing disk 30 in turn acts on a rubber-elastic reaction disk 32 of larger diameter, which is also included in the part 22 and which transmits the actuating force to an input piston 34 of a hydraulic master cylinder, not shown here, which is attached to the vacuum-side booster half.

On the actuating piston 28, a first, annular valve seat 36 is formed which cooperates with a first, circular annular disc-shaped valve member 38 and which connects in the open state via a radial channel 40, the working chamber 16 to atmospheric pressure (or overpressure) formed by an air filter element 42 from can flow into the outside of the control valve housing. Through the radial passage 40 of the control valve housing projects a mounted on the actuating piston 28 cross bar 44, the relative axial movement of the actuating piston is limited on actuation of the control valve 18 28 with respect to the control valve housing by coming into contact with the left in the figures, the side wall of the channel 40 and at a Return movement of the actuating piston 28 at the end of a braking operation abuts a stop 46 formed in the wall of the booster housing 10 , which defines the so-called release position (unactuated position) of the brake booster.

For automatic, a driver that is, the will of independent actuation of the brake booster, the control valve 18 is a solenoid assembly 48, the larger in diameter portion of the part 20 of the control valve housing is accommodated and which has a hollow cylindrical armature 50, a coil housing 52 and accommodated therein, of a coil holder 54 carried coil 56 which surrounds the armature 50 ringför shaped. The electromagnet arrangement 48 is arranged coaxially with the actuating piston 28 and is pushed through by the latter. Radially between the armature 50 and the coil housing 52 or the coil holder 54 is a thin-walled separating sleeve 58 made of non-magnetic material, on the inner surface of which the armature 50 can slide axially.

The armature 50 is rigidly connected, for example by screwing, to a hollow cylindrical actuating sleeve 60 which coaxially surrounds the actuating piston 28 and extends out of the electromagnet arrangement 48 in the direction of the input member 26 . Outside the electromagnet arrangement 48 , the actuating sleeve 60 has a radial flange 62 to which a plurality of arms 64 , which extend essentially parallel to the axis A in the direction of the first valve member 38 , are fastened, of which only one can be seen in the figures. In the state shown in FIG. 1 (unactuated electromagnet arrangement 48 and no actuation of the input member 26 ), the arms 64 end radially outside the first valve seat 36 axially shortly before the first valve member 38 .

At a position corresponding to the rest position shown in FIG. 1 axially with the first valve seat 36 , on an inner part 66 of the control valve housing part 20 radially outside the first valve seat 36 and the arms 64, a concentric with the first valve seat 36 , also circular and with the first valve member 38 cooperating second valve seat 68 which can connect the vacuum chamber 14 to the working chamber 16 in the open state via an annular channel 70 .

The rubber-elastic first valve member 38 , which is provided with a stiffening element 72 , is pressed by a first compression spring 74 into sealing contact with the first valve seat 36 and the second valve seat 68 , which have one end on the stiffening element 72 and the other end on an annular one Spring retaining element 76 with an L-shaped cross section is supported. The spring holding element 76 is in turn pressed axially against a stop 82 formed on one of the latter, the second compression spring 78 , the other end of which is supported on an insert 80 , against an inside formed on the control valve housing part 20 . The second compression spring 78 has a greater spring force than the first compression spring 74 .

In the exemplary embodiments shown, the first valve member 38 is provided with a one-piece, rubber-elastic bellows 84 , the free edge of which is thickened and is sealingly clamped between a radially inwardly projecting projection of the insert 80 arranged sealingly in the control valve housing part 20 and an annular plate 86 . The ring plate 86 is pressed by a conical spring 88 supported on it against the insert 80 , the other end of which is supported on a step of the input member 26 , so that the conical spring 88 also preloads the input member 26 against the direction of actuation.

Seen from the input member 26 axially beyond the Elek tromagnetanordnung 48 on the part 22 of the control valve housing, a third, annular valve seat 90 is formed, which cooperates with a similar to the first valve member 38 , second valve member 92 and the seat 68 together with the second valve Controls connection between the vacuum chamber 14 and the working chamber 16 . The third valve seat 90 has, in any case at least approximately, the same sealing diameter as the second valve seat 68 .

On the electromagnet arrangement 48 , an annular fourth valve seat 94 is formed by a short axial and annular circumferential collar 93 of the coil housing 52, the sealing diameter of which corresponds to that of the third valve seat 90 and which also interacts with the second valve member 92 . In the starting or rest position of the control valve 18 shown in FIG. 1, the second valve member 92 is prestressed by a third compression spring 96 in contact with the fourth valve seat 94 , ie the third valve seat 90 is open in the rest position of the control valve 18 .

The entire solenoid assembly 48 is mounted in the Steuererventilgehäu se 20 , 22 axially floating between the second valve member 92 and a fixed, annular stop 98 against which the coil housing 52 of the solenoid assembly 48 in the rest position of the control valve 18 due to the resilient voltage before the second valve member 92nd is pressed. The housing fixed stop 98 is provided with an elastic sealing bead 100 in order to be able to seal against the bobbin case 52 .

It will now be explained in more detail with reference to the other figures, the function of the brake booster and in particular the Steuererven valve 18 . Move a driver operates the brake pedal, not shown here, so the input member 26 and the actuating piston 28 from its in Fig. 1 shown rest position relative to the control valve housing 20, 22 in the direction of the likewise not shown here, the main hydraulic cylinder, ie in the figures to the left , This displacement causes the first valve seat 36 to be lifted from the first valve member 38 , so that atmospheric pressure can flow past the first valve seat 36 through the air filter element 42 and through the radial channel 40 into the working chamber 16 ( FIG. 2). A differential pressure then builds up on the movable wall 12 , which moves the wall 12 and thus also the control valve housing 20 , 22 to the left. The corresponding servo force is delivered via the input piston 34 to the master cylinder, not shown.

After releasing the brake pedal, the conical spring 88 presses the input member 26 relative to the control valve housing 20 , 22 against the operating direction, ie to the right in the figures. The first valve seat 36 comes back in sealing contact with the first valve member 38 and opens in continuation of this movement against the force of the first compression spring 74, the second valve seat 68 , which due to the also open third valve seat 90, the connection between the vacuum chamber 14 and the working chamber 16 is open. Because the vacuum chamber 14 is constantly connected to a vacuum source, for example with the intake tract of an internal combustion engine, the differential pressure applied to the movable wall 12 is reduced with a corresponding reduction in the servo force output by the brake booster ( FIG. 3).

The above functional description relates to a manual actuation of the brake booster taking place by means of the input member 26 . In the case of an electromagnetic actuation, an electronic control unit connected to the brake booster and not shown here excites the coil 56 of the electromagnet arrangement 48 with a specific current which corresponds to the desired servo force to be output by the brake booster. A magnetic field then builds up in the electromagnet arrangement 48 , which pulls the armature 50 to the right until the arms 64 of the actuating sleeve 60, which are firmly connected to the armature 50 , abut the first valve member 38 ( FIG. 4). Due to the resistance opposed by the first compression spring 74 biased valve member 38 , the floating spool housing 52 then ver moves the electromagnet assembly 48 in the opposite direction, ie to the left, and presses the second valve member 92 against the force of the compared first compression spring 74 weaker third compression spring 96 in sealing contact with the third valve seat 90 ( FIG. 5).

The armature 50 and the actuating sleeve 60 rigidly connected to it then resume their previously interrupted movement to the right, as a result of which the first valve member 38 is displaced to the right against the force of the first compression spring 74 and is thereby lifted off the first valve seat 36 ( FIG. 6). , The second valve seat 68 is also open in this state, but the third valve seat 90 is closed as previously mentioned, so that there is no connection between the vacuum chamber 14 and the working chamber 16 . Rather, as described in connection with the manual actuation, through the opened first valve seat 36, a supply of atmospheric pressure to the working chamber 16 and, as a result, a displacement of the movable wall 12 , which is transmitted via the flange 24 to the control valve housing 20 , 22 . The actuation supply piston 28 , which is biased via its connection to the input member 26 by the conical spring 88 against the actuating direction, does not follow this movement, so that there is a relative displacement between the control valve housing 20 , 22 and the actuating piston 28 , which is the first Valve seat 36 closes again. This happens until the cross bar 44 abutting the stop 46 of the booster housing 10 is forcibly brought into contact with the right side wall of the radial channel 40 in the figures in the case of a further displacement of the control valve housing 20 , 22 relative to the booster housing 10 ( Fig. 7).

Only when, as shown in Fig. 7, the cross bar 44 strikes the right wall of the radial channel 40 , each further opening stroke of the armature 50 , which is transmitted by the actuating sleeve 60 and its arms 64 to the first valve member 38 , to lift the first valve member 38 from the first valve seat 36 . In this position, which is also referred to as the control position, the first compression spring 74 is compressed to the extent that the stiffening element 72 of the first valve member 38 is in contact with the spring holding element 76 . This means that the opening of the first valve seat 36 caused by a displacement of the armature 50 must take place against the force of both the first compression spring 74 and the stronger, second compression spring 78 .

From the control position, the electromagnet arrangement 48 thus works against a steeper spring characteristic when the first valve seat 36 is opened ( FIG. 8). The increase in the current intensity, which is required for a desired change in stroke of the armature 50 in the opening direction of the first valve member 38 , must therefore be larger, which is advantageous in terms of control technology due to the lower control effort thereby achieved.

FIG. 9 shows a state which occurs after the electromagnetic actuation of the control valve 18 has ended , ie when the coil 56 is de-energized. The second valve seat 68 and the third valve seat 90 are open, while the first valve seat 36 is closed, so that by the then existing connection between the vacuum chamber 14 and the working chamber 16 a pressure difference applied to the movable wall 12 can be reduced.

Claims (11)

1. Pneumatic brake booster, in particular for motor vehicles, with an amplifier housing ( 10 ), the interior of which is divided by at least one movable wall ( 12 ) into a vacuum chamber ( 14 ) and a working chamber ( 16 ), and with one along an axis (A) in the amplifier housing ( 10 ) projecting control valve ( 18 ) for controlling a pneumatic pressure difference acting on the movable wall ( 12 ), which has a control valve housing ( 20 , 22 ) to which the movable wall ( 12 ) is connected in a force-transmitting manner, and on the one hand by a mechanical input member ( 26 ) and independently of it on the other hand can be actuated by a housing ( 52 ) and an armature ( 50 ) having an electromagnet arrangement ( 48 ), the control valve ( 18 ) having a first valve seat ( 36 ) which supplies atmospheric pressure or overpressure to the working chamber ( 16 ) controls a second valve seat ( 68 ) together with a first valve member ( 38 ) men acts and controls the connection between the vacuum chamber ( 14 ) and the working chamber ( 16 ), and has a third valve seat ( 90 ), the connection between the vacuum chamber when the control valve ( 18 ) is actuated by means of the electromagnet arrangement ( 48 ) ( 14 ) and the working chamber ( 16 ) controls, the second valve seat ( 68 ) and the first valve member ( 38 ) with respect to the axis (A) on one side of the electromagnet arrangement ( 48 ) and the third valve seat ( 90 ) can only be closed by actuating the electromagnet arrangement ( 48 ), characterized in that
the third valve seat ( 90 ) cooperates with a second valve member ( 92 ),
the third valve seat ( 90 ) and the second valve member ( 92 ) are arranged on the side of the electromagnet arrangement ( 48 ) axially opposite the second valve seat ( 68 ) and the first valve member ( 38 ), and
the electromagnet arrangement ( 48 ) is axially floating in the control valve housing ( 20 , 22 ). 2. Brake booster according to claim 1, characterized in that the first valve seat ( 36 ) is arranged concentrically to the second valve seat ( 68 ) and also cooperates with the first valve member ( 38 ). 3. Brake booster according to claim 1 or 2, characterized in that the second valve seat ( 68 ) and the third valve seat ( 90 ) on the control valve housing ( 20 , 22 ) are formed. 4. Brake booster according to one of claims 1 to 3, characterized in that the second valve seat ( 68 ) and the third valve seat ( 90 ) have an at least approximately the same sealing diameter. 5. Brake booster according to one of the preceding claims, characterized in that the second valve member ( 92 ) from the third valve seat ( 90 ) away and in the direction of the electro magnet arrangement ( 48 ) is resiliently biased. 6. Brake booster according to claim 5, characterized in that when the solenoid assembly is not actuated ( 48 ), the housing ( 52 ) of the solenoid assembly ( 48 ) due to the spring preload of the second valve member ( 92 ) sealing between the second valve member ( 92 ) and a fixed stop ( 98 ) of the control valve housing ( 20 , 22 ) is clamped. 7. The brake booster according to one of the preceding claims, characterized in that the armature (50) of the electromagnet arrangement (48) is coupled to an actuating sleeve (60) acting upon actuation of the electromagnet arrangement (48) on the first valve member (38), to lift it off the first valve seat ( 36 ). 8. Brake booster according to claim 7, characterized in that the first valve member ( 38 ) of two series-connected, differently strong springs ( 74 , 78 ) is biased towards the first valve seat ( 36 ), of which the second and stronger spring ( 78 ) is only effective when lifting the first valve member ( 38 ) from the first valve seat ( 36 ) through the actuating sleeve ( 60 ). 9. Brake booster according to one of the preceding claims, characterized in that the first valve seat ( 36 ) is formed on an actuating piston ( 28 ) coupled to the input member ( 26 ). 10. Brake booster according to claim 9, characterized in that the actuating piston ( 28 ) axially passes through the entire electromagnet arrangement ( 48 ), the second valve member ( 92 ) and the third valve seat ( 90 ). 11. Brake booster according to one of the preceding claims, characterized in that the control valve housing ( 20 , 22 ) consists of at least two axially consecutive parts ( 20 , 22 ), the second valve seat ( 68 ) in one part ( 20 ) and the third Valve seat ( 90 ) is formed in the other part ( 22 ) of the control valve housing.