DE19902710A1 - Brake amplifier with emergency brake function for vehicles - Google Patents

Abstract

The brake amplifier has a first sealing seat (15) which can move relative to the control casing (8). A fixing device (26) can lock the sealing seat if a present relative movement between the valve piston (6) and the control casing is exceeded, so that the fixing device can at least prevent a movement of the sealing seat in the operating direction (30).

Description

The invention relates to a brake booster with panic Brake function for motor vehicles with an amplifier housing se, whose interior through a movable wall into a he most chamber and a second chamber is divided, as well as with a control housing in which a one on the movable wall acting pneumatic pressure difference, by means of an actuating rod operable control valve arranged is a first sealing seat, one on a valve piston trained second sealing seat and one with both Sealing seats interacting elastic valve body points, wherein means are provided, which at a fast Actuation of the control valve a sudden increase in amplification force applied by the brake booster guarantee.

Such a brake booster is such. B. from the US-A-5,645,145. The valve piston of the known brake power amplifier acts when actuated with a hydrau piston together, together with a power output member or a push rod a first hydraulic cam limited. On the side facing away from the first chamber  of the hydraulic piston is a second hydraulic cam mer trained across multiple channels with the first Kam mer is connected, the connection using a Valve device can be shut off. On the hydraulic piston a second is supported under pre-tensioning of a compression spring hydraulic piston or ring piston axially from a Ver pushing the volume of liquid out of the second chamber the first chamber allows. The arrangement described s therefore represents a hydraulic reaction device. The valve device mentioned above is preferred designed such that they are in a "normal" operation remains closed, so that a transmission of both the Valve piston initiated actuation force as well as that of Brake force booster applied by means of of the liquid volume enclosed in the first chamber mens takes place. With a quick press, the z. B. is due to panic braking or emergency braking, the valve device remains open, so that displacement the liquid from the first chamber into the second chamber takes place and on the first hydraulic piston supporting valve pistons a longer actuation path can put an enlargement of the opening gap between the second sealing seat and a valve body and thus faster ventilation of the ventilated working chamber of the known brake booster results.

A disadvantage of the known brake booster  in particular the complicated structure of the means mentioned or to view the reaction device, the chambers with Means sealing elements must be sealed, the increase cause friction in the system and also also represent a potential source of interference. Not The filling of the hydraulic also seems unproblematic Chamber with liquid pressure medium, especially for a Large-scale production is unsuitable.

It is therefore an object of the present invention to take measures to propose which the operational security and the Le Increase the service life of the brake booster. In addition, should  the proposed brake booster with reasonable Effort can be produced.

This object is achieved in that the first sealing seat movable relative to the control housing is ordered, and that means are provided with which the Sealing seat when exceeding a predetermined relative Set the shift between the valve piston and the control housing bar, so that the agent moves the sealing seat against the direction of actuation relative to the control housing se enables. Consequently, it is prevented from being caused by a movement of the sealing seat in the actuating direction ner reduction of the gap at the second sealing seat, the so called poppet valve comes.

To concretize the idea of the invention, that the first sealing seat when the specified one is exceeded Relative displacement between the valve piston and control housing abge indirectly or directly on a reaction disc is supported. Consequently, the Verfor leads in the actuated state tion of the reaction disc to lift the sealing seat from nem effective stop in the direction of actuation against the forces of a return spring.

In an advantageous development, the valve piston associated with an axially displaceable sleeve relative to this, which is provided with such a stop, the  Sealing seat as a result of contact with the stop by means of the sleeve is supported on the reaction disc.

The invention is described in the following description an embodiment in connection with the drawing tion explained in more detail. The drawing shows:

Fig. 1, the brake booster according to the invention on a larger scale and in longitudinal section, partially broken away, in the inactive standby position;

FIG. 2 shows the control group of the brake booster according to FIG. 1 in an active emergency braking position (panic braking position);

Fig. 3, the control group shown in Fig. 2 in a return stroke position, ie, force after removal of the actuator,

Fig. 4 control group of the brake booster shown in Fig. 1 in a full braking position (maximum force),

Fig. 5 shows a second embodiment of the invention in section as in Fig. 1,

Fig. 6 taken along the line VI-VI in Fig. 5,

Fig. 7 section along the line VII-VII in Fig. 5, and

Fig. 8 section as in Fig. 7 taken along line VIII-VIII in Fig. 5.

The only schematically indicated amplifier housing 1 of the under pressure brake booster according to the invention shown in the drawing is divided by a not shown axially movable wall into a first chamber 2 (vacuum chamber) and a second chamber 3 (working chamber). The axially movable wall, not shown, consists of a membrane plate and an adjacent, only partially indicated flexible membrane 4 , which does not show a roller membrane as a seal between the outer periphery of the membrane plate and the amplifier housing 1 .

A control valve 5, which can be actuated by an actuating rod 7, is accommodated in a control housing 8 , which is sealed in the booster housing 1 and supports the movable wall, and has a first sealing seat 15 , which is provided so as to be movable axially relative to the control housing 8 . In addition, the actuating rod 7 is firmly connected to a valve piston 6 , on which a second sealing seat 16 is formed. In addition, the valve assembly is a with two sealing seats 15 , 16 cooperating, arranged in a sealed in the control housing 8 valve body 10 , which is pressed against the valve seats 15 , 16 by means of a valve spring 22 supported on a bottom 21 Ven. The working chamber 3 is connected to the vacuum chamber 2 via a channel 29 extending laterally in the control housing 8 .

The braking force is via a front part 14 of the control housing 8 adjacent rubber-elastic re action disc 9 and a head flange 13 having a push rod 12 to an actuating piston of a master cylinder of the brake system not shown is transmitted, which is attached to the vacuum-side amplifier housing half. A central opening in the front part 14 serves for the passage of a pressure piece, preferably with a conical pressure surface, so that the driver can intensify the force effect exerted by the pressure difference across the front part by additionally applying pressure to the pressure piece, which can be applied to the front of the valve piston 6 .

A return spring 17 shown schematically in the drawing, which is supported on the vacuum-side end wall of the amplifier housing 1 , holds the movable wall in the starting position shown. In addition, a second compression spring or piston rod return spring 18 is provided, which is supported on the one hand indirectly on the actuating rod 7 and on the other hand on the bottom 21 and whose force ensures a preloading of the valve piston 6 or its sealing seat 16 with respect to the valve body 10 .

In order to be able to connect the working chamber 3 to the atmosphere when the control valve 5 is actuated, an approximately radially extending channel 19 is finally formed in the control housing 8 . The return movement of the valve piston 9 at the end of a braking process is limited by a cross member 11 which, in the readiness position shown in FIG. 1, of the vacuum brake booster rests against a stop 20 formed in the intensifier housing 1 .

As can be seen from the drawing, the valve body 10 has a with the two sealing seats 15 , 16 cooperating annular sealing surface 23 , which is stiffened by means of a metallic stiffening washer 24 and is seen ver for pressure compensation with several axial passages. For the purpose of pressure equalization, a guide part can also be provided instead of the bottom 21 , in which the valve body 10 can be moved and guided in a sealed manner with sealing lips, so that a pressure-balanced pneumatic space for the valve body 10 is created within the control housing 8 . With regard to this modification, reference is made in full to EP 655 039 A1. This arrangement therefore enables a reduction in the difference between the response force of the brake booster and the restoring force acting on the valve piston ben in the sense that, with a constant response force, an increase in the restoring force or with a constant restoring force a reduction in the response force is possible.

As can be clearly seen in FIG. 1, the sealing seat 15 is assigned a means 26 with which it can be fixed when a predetermined relative displacement between the valve piston 6 and the control housing 8 is exceeded. For this purpose, the valve piston 6 sits at the end of the reaction disk, a sleeve 32 which can be moved coaxially relative to the valve piston 6 and can be placed on a shoulder 31 on the valve piston side and which, when actuated together with the piston 6 , is displaced in the direction of pressure element 27 . The sleeve 32 is provided with a stop 36 , on which the means 26 can engage with a projection 36 , as can be seen in FIGS. 2 and 3. According to the exemplary embodiment, a lever is used as the means, which is pivotably connected to the sealing seat 15 or to a base body 25 carrying the sealing seat by means of a cutting edge bearing or a bolt 33 . The lever has an L-shape as seen from the side and has a first leg 34 and an indicated second leg 35 . A projection 36 for engaging the stop 37 of the sleeve 32 is arranged on the second leg 35 . In addition, a mandrel 38 is arranged at the end of the second leg 35 , which engages in a compression spring 39 . The compression spring 39 acts on the means 26 per manent in the clockwise direction. Consequently, the legs 35 endeavors to engage with a angeord NetEm at its rear projection 40 to rest on the cross member. 11

In the emergency braking position, when a predetermined relative displacement between valve piston 6 and control housing 8 is exceeded, ventilation of the working chamber 3 takes place, where housing 8 is acted upon by the reaction disc 9 as a result of the action of the control and is elastically compressed by the front part 14 . At the same time, a force equilibrium is formed on the pressure surface of the pressure piece 27 , where the driver is free from any repercussions due to the play 28 between the valve piston front part and pressure piece 27 . Under the action of the compression spring 39 of the leg 35 seeks a rotational movement in a clockwise direction and engages with its projection 36 the stop 37 of the sleeve 32, so that the sealing seat 15 through the means 26 and the sleeve 32 and the thrust piece supported on the reaction disc 9 27 is. The pivoting movement of the means 26 is ultimately made possible by the fact that the cross member 11 in the course of the actuation movement on the one hand releases from the housing-side stop 20 and on the other hand has play 42 within a valve piston side recess 41 . In the panic braking position, the valve seat 15 can only be pushed against the actuating direction relative to the control housing 8 . A reduction in the gap on the sealing seat 16 is consequently excluded. As will be described below, the braking force can be increased up to the maximum braking power without the driver feeling any reaction of the braking system. As a result, the maximum amplification force of the amplifier can be generated even with the lowest input force, and there is a higher transmission ratio than the normal braking function.

Fig. 4 can be seen that the output force of the brake booster can even be increased by adding foot force, the pressure piece 27 penetrates into the reaction disk 9 and on the other hand, the second sealing seat 16 for a particularly fast ventilation of the Ar chamber 3 very strong is lifted off. The base body 25 of the sealing seat 15 comes to bear against the front part 14 of the control housing under the action of springs. Of course, this process is not without retroactive effects.

An essential aspect is the regulation of the applied Braking power after a panic actuation, because it is a he major disadvantage of known electrical panic brake aids (brake assistants) that after the on-off Working principle. In other words, the reinforcement by virtue of these known devices in the panic brake system not or only with the greatest electronic effort gelbar because the brake booster directly in the Full scale range arrives and this state only through complete loosening and associated complete be interrupted when the brake assist function ceases to exist  can.

Fig. 3 now illustrates the process for reducing the applied reinforcing force in the emergency braking position. Starting from the position illustrated in FIG. 2, the valve piston 6 was withdrawn to the right by withdrawing the actuation pedal (not shown), the play 28 on the reaction disk side being enlarged and at the same time the gap on the second sealing seat 16 being closed. Because on the one hand the ventilation of the working chamber 3 is omitted and on the other hand there is a connection to the vacuum chamber 2 via the channels 19 , 29 , there is also an evacuation of the working chamber 3 and to the same extent a reduction in the strengthening force.

It is also possible in the panic brake position to end the force reduction by depressing the brake pedal and consequently displacing the valve piston 6 to the left, as a result of which the first sealing seat 15 closes and the second sealing seat 16 opens, so that a corresponding servo force takes place.

Starting from the panic brake position, the device is brought into the standby position as follows. Because a little or no braking force is desired, the Ven tilkolben 6 is retracted until the cross member 11 abuts the housing stop 20 on the housing side. At the same time, the sealing seats 15 , 16 are closed, so that the first and second chambers 2 , 3 are evacuated. This leads to a movement of the diaphragm 4 together with the control housing 8 to the right, the base body 25 also being pressed against the spring forces to the right by contact with an edge 43 provided on the front part 14 . At a certain point in time the back of the leg 35 strikes with the shoulder 40 on the cross member 11 and under the progressive return movement there is a pivoting movement of the means 26 in the counterclockwise direction, the projection 36 being pivoted out of engagement relative to the stop 37 . Consequently, the panic brake position with the associated axial support of the first sealing seat 15 is eliminated and the brake booster is available for the normal braking function or repeated panic braking function.

According to a modified, not shown embodiment, it is also conceivable to end the panic brake function by suddenly reducing the pressure on the pedal only to such an extent that the withdrawal does not lead to a complete return movement of the control housing 8 into the standby position described above, but le diglich to a limited retraction of the Ven tilkolbens 6 relative to the control housing 8th In this imple mentation form, the means 26 are designed such that they become ineffective at a predetermined relative displacement between the valve piston 6 and control housing 8 , that is to say that they solve the setting against the direction of actuation. Consequently, the mobility of the valve seat 15 is ensured again, so that the panic brake function is canceled.

Fig. 5 is a modified embodiment removed bar, which has a pivotable and L-shaped lever 50 in accordance with the previous Figu as a support means, which is hinged to a base body 51 of a basically axially displaceable in a control housing 52 first sealing seat 53 . For a torsion-resistant and largely smooth guidance, the base body 51 is provided with cylindrical pins with which it engages in corresponding holes in the control housing. The axial support of the sealing seat 53 takes place indirectly on a re action disk 54 , whereby as a mediating component in contrast to the device described above, no sleeve displaceable on the valve piston 55 , but rather an abutment against a valve piston end face 56 and axially displaceable locking body 57 is provided. The locking body 57 performs the same function as the sleeve and is associated with the advantage that it (compared with the sleeve mentioned) has larger dimensions, so that the dimensional monitoring and tolerance of very small dimensions is not necessary. Furthermore, there are no signs of friction (slip-stick effects). In FIG. 5, the lever is drawn gestri smiles in its (non-pivoted) Normal braking position 50th The locked or engaged panic braking position of the lever 50 is marked with a dot-dash line.

As is also clear in connection with FIGS. 6, 7 and 8, the lever 50 has two, oppositely lying, L-shaped (approximately at right angles) cranked leg pairs 58 , 58 ', 59 , 59 ', which on their leg ends are connected to each other via a yoke 60 , 61 . The yoke 60 connecting the first two legs 58 , 58 'serves for locking on the locking body 57 (in the panic brake position), and on the two second legs 59 , 59 ' connecting yoke 61 there is an elastically prestressed spring element 62 in such a manner that the lever 50 is constantly striving to perform a pivoting movement about its bearing axis counterclockwise (in Fig. 5). In addition, this second yoke 61 is used for the release process, as will be described below. The pivotable mounting of the lever 50 takes place by means of two bearing eyes aligned with one another, which engage in recesses of the base body 51 and in this way form the bearing axis. The spring element 62 is largely flat according to the embodiment, and has a plurality of resilient legs, which are arranged in one piece on a traverse 63 . The legs are arranged on the traverse from radially inwards to outwards as follows. A first (central) leg 64 is used to apply the aforementioned counterclockwise biasing force to the lever 50 . Two second legs 65 pass through recesses in the control housing 52 and each have an angled locking lug 66 for fixing in the control housing 52 . Finally, two third legs 67 resiliently rest on an end face 68 of the base body 51 , so that there is also an elastic bias against the direction of actuation. As an advantage in this context, it should be noted that the flat spring element 62 not only takes up very little space in the axial direction, so that installation space is saved, but simultaneously performs several tasks and functions which would conventionally have to be taken over by other separate spring elements. For a clear, secure locking in the panic brake position, it is recommended that the locking body 57 be provided with a locking shoulder 69 or a locking step, behind which the yoke 60 can engage with a sufficient relative displacement between the valve piston 55 and the base body 51 such that a Displacement of the first valve seat 53 in the direction of the reaction disk 54 is no longer possible. In other words, the valve piston position is, in a sense, fixed in relation to the sealing seats in question at the moment of latching in such a way that the gap opening on the second sealing seat 70 cannot be reduced. A single quick actuation associated with a corresponding displacement of the valve piston 55 relative to the control housing 52 consequently leads to the full amplifying force. This process is independent of whether the driver is pushed back by the reaction force to a certain extent (retreats in the course of braking) or "stays on the brake" without retreating with a corresponding increase in foot strength.

To release the locking position, the operator takes the valve piston 55 back (can be pushed back) until the closure of the second valve seat 70 (control valve) and the opening of the first valve seat 53 , the working chamber is evacuated again, and the Steuerge housing 52 of the retraction movement of the valve piston 55 follows. When the wedge 71 shown in FIG. 7 offset by 90 ° comes to rest against a stop 72 on a housing half-shell 73 , and the base body 51 is also pressed back under the spring action of the third leg 67 , the second yoke 61 comes to rest an end face of the wedge 71 on the housing side. Due to the fixed contact of the yoke 61 on the wedge 71 , and the striving back of the control housing 52 together with the base body 51 counter to the actuation direction, the lever 50 swings back clockwise into the release position.

Claims (15)

1. Brake booster with panic brake function for motor vehicles with an amplifier housing ( 1 ), the interior of which is divided by a movable wall into a first chamber ( 2 ) and a second chamber ( 3 ), and with a control housing ( 8 , 52 ), in which is arranged a pneumatic pressure difference that acts on the movable wall and controls a valve ( 5 ) which can be actuated by means of an actuating rod ( 7 ) and which has a first sealing seat ( 15 , 53 ), a second sealing seat formed on a valve piston ( 6 ) ( 16 , 70 ) and one with both sealing seats ( 15 , 16 , 53 , 70 ) cooperating ela-elastic valve body ( 10 ), means being provided which, when the control valve is actuated quickly, ensure a sudden increase in the boosting force applied by the brake booster afford, characterized in that

• - The first sealing seat ( 15 , 53 ) is arranged movable relative to the control housing ( 8 , 52 ), and
• - That means ( 26 , 50 ) are provided with which the sealing seat ( 15 ) when a predetermined relative displacement between the valve piston ( 6 , 55 ) and control housing ( 8 , 52 ) can be determined, so that
• - The means ( 26 , 50 ) allows movement of the sealing seat ( 15 , 53 ) against the actuating direction ( 30 ) relative to the control housing ( 8 , 52 ).

2. Brake booster according to claim 1, characterized in that the first sealing seat ( 15 , 53 ) when the predetermined relative displacement between rule's valve piston ( 6 , 55 ) and control housing ( 8 , 52 ) with telbar or directly on a reaction disc ( 9 , 54 ) is supported. 3. Brake booster according to one or more of the preceding claims, characterized in that the means ( 26 , 50 ) is pivotally articulated on the first sealing seat ( 15 , 53 ), and is under the force of a spring element ( 39 , 62 ), so that the means ( 26 , 50 ) rests resiliently on a valve piston-side control contour or resiliently on a cross member ( 11 , 71 ) and that the means ( 26 , 50 ) rests on a stop ( 37 , 69 ) when the predetermined rela tive displacement. 4. Brake booster according to one or more of the preceding claims, characterized in that the sealing seat ( 15 , 53 ) is arranged on a sleeve-shaped base body ( 25 , 51 ) which has a cylindrical socket ( 44 ) and that guide surfaces ( 45 ) on Base body ( 25 ) and / or on the nozzle ( 44 ) for axially movable guidance of the base body ( 25 ) in the interior of the control housing ( 8 , 52 ) are provided. 5. Brake booster according to one or more of the preceding claims, characterized in that the valve piston ( 6 ) relative to this axially displaceable bare sleeve ( 32 ) is assigned, that the sleeve ( 32 ) with the stop ( 37 ) is provided and the sealing seat ( 15 ) is supported by means of the sleeve ( 32 ) on the reaction disk ( 9 ). 6. Brake booster according to one or more of the preceding claims, characterized in that the sleeve ( 32 ) in addition to the stop ( 37 ) is provided with a control contour for the projection ( 36 ). 7. Brake booster according to one or more of the preceding claims, characterized in that a second leg ( 35 ) is provided at an angle to a leg ( 34 ), the leg ( 35 ) against a spring force at a fixed point on the housing, in particular one on the amplifier housing ( 1 ) fixed cross member ( 11 ) can be applied. 8. Brake booster according to one or more of claims 1 to 4 or 7, characterized in that the lever ( 26 , 50 ) is pivotally articulated on the base body ( 25 , 51 ) and is acted upon by an elastic spring element ( 39 , 62 ) . 9. Brake booster according to claim 8, characterized in that a locking body ( 57 ) between the valve piston ( 55 ) and reaction disc ( 54 ) is arranged, and that the lever ( 50 ) can be placed on the locking body in such a way that a reduction in Opening gap on the sealing seat ( 70 ) can not be made. 10. Brake booster according to claim 9, characterized in that the lever 50 has two opposite, as well as L-shaped bent pairs of legs ( 58 , 58 ', 59 , 59 '). 11. Brake booster according to claim 10, characterized in that the leg ends ( 58 , 58 ', 59 , 59 ') are interconnected by a yoke ( 60 , 61 ). 12. Brake booster according to claim 8, characterized in that a largely flat spring element ( 62 ) with a plurality of resilient legs ( 64 , 65 , 67 ) is provided. 13. Brake booster according to claim 12, characterized in that the legs ( 64 , 65 , 67 ) are arranged on a cross member ( 63 ) from which they protrude in a single direction Rich, and that the legs ( 64 , 65 , 67 ) are at least partially redundant. 14. Brake booster according to claim 9, characterized in that the locking body ( 57 ) is L-shaped with two legs, and that on one of the legs a locking shoulder ( 69 ) is arranged for positive engagement of the yoke ( 60 ). 15. Operating method for a brake booster, in particular according to one or more of the preceding claims, characterized in that a panic brake function is provided with an increased gear ratio compared to a normal brake function by rapid actuation of a brake pedal, with means tel ( 26 ) a movement of a sealing seat ( 15 ) prevent against the direction of actuation, and that the panic brake function can be ended by pulling back the brake pedal and thereby disengaging the means ( 26 ).