WO2004050448A1

WO2004050448A1 - Brake booster

Info

Publication number: WO2004050448A1
Application number: PCT/EP2003/013506
Authority: WO
Inventors: Wilfried Giering
Original assignee: Lucas Automotive Gmbh
Priority date: 2002-12-03
Filing date: 2003-12-01
Publication date: 2004-06-17
Also published as: AU2003289923A1; DE10256366A1; DE10256366B4

Abstract

The invention relates to a brake booster (10) comprising a control valve provided with a housing (16), and a valve element (44) which can be axially displaced in relation to said housing. The control valve housing (16) comprises a sealing seat (34, 36) with which a corresponding valve seat (48, 50) provided on the valve element (44) interacts. According to the invention, a flexible actuating element (58) is associated with the valve element (44), said actuating element being coupled to a force input member (12) of the booster in order to generate a common axial movement, and deforming itself according to the current position of the force input member (12) in such a way that, in a standby position, it applies the at least one valve seat (48, 50) to the at least one sealing seat (34, 36), and, in an axial position which differs from the standby position, lifts the at least one valve seat (48, 50) from the at least one sealing seat (34, 36).

Description

Brake booster

The present invention relates to a brake booster with a force input element for introducing a brake actuation force, a force output element for deriving a brake force, which is increased compared to the brake actuation force, to a brake system, a vacuum chamber and a working chamber which is fluid-tightly separated from the vacuum chamber by a movable wall, a control valve with a control valve housing and an axially movable relative to this

Valve element, wherein the control valve housing has a sealing seat with which a corresponding valve seat provided on the valve element cooperates, the control valve housing also being designed for force-transmitting coupling to the movable wall, the valve element also being designed for force-transmitting coupling to the force input element and to it Control valve housing is biased into a standby position, in which the valve seat bears against the sealing seat in a fluid-tight manner, and to achieve at least atmospheric pressure in order to achieve a pressure difference between the working chamber and vacuum chamber which determines the braking force as a function of an axial position of the valve element which deviates from the standby position by lifting the valve seat from the sealing seat Working chamber can be fed.

Such a brake booster is known for example from EP 0 327 997 B1. Such brake boosters enable a driver of a motor vehicle to generate a sufficiently large braking force with a relatively small amount of brake actuation force in order to achieve the desired braking effect. For this purpose, the control valve is used, which is actuated when the brake is actuated in such a way that a pressure difference between the working chamber and the vacuum chamber is allowed, which pressure difference is then used to amplify the brake actuation force via the movable wall. As a result, a braking force that is greater than the brake actuation force can be derived to the brake system.

The control valve according to EP 0 327 997 B1 is, however, of relatively complex construction in order to be able to reliably guarantee the functionality described above. It requires a large number of different pretensioning means which pretension different control valve components into specific positions and thus ensure that the valve element rests on its sealing seat. Furthermore, the control valve according to this prior art has a complex multi-part valve element, which is reflected in its manufacturing costs and assembly costs. In addition, the control valve from this state of the art takes up a large amount of space, which is undesirable in the design of modern vehicles.

From DE 28 45 794 C3 and WO 99/43526, brake boosters with a relatively complex, large-scale control valve are known.

In contrast, it is an object of the present invention to provide a brake booster of the type described at the outset, which ensures reliable operation with a simple and space-saving design.

This object is achieved by a brake booster with a force input element for introducing a brake actuation force, a force output element for deriving a brake force, which is increased compared to the brake actuation force, to a brake system, a vacuum chamber, and a working chamber which is fluid-tightly separated from the vacuum chamber by a movable wall, a control valve with a Control valve housing and an axially movable relative to this

Valve element, wherein the control valve housing has a sealing seat with which a corresponding valve seat provided on the valve element cooperates, the control valve housing also being designed for force-transmitting coupling to the movable wall, the valve element also being designed for force-transmitting coupling with the force input element and onto it Control valve housing is biased into a standby position, in which the valve seat bears against the sealing seat in a fluid-tight manner, and in order to achieve a pressure difference between the working chamber and vacuum chamber that determines the braking force, depending on an axial position of the valve element that deviates from the standby position, by lifting the valve seat from the sealing seat to at least atmospheric pressure Working chamber can be fed. In this brake booster, according to the invention, in order to achieve the object, the valve element is assigned a flexible actuating element which is coupled to the force input element for common axial movement and which deforms in dependence on the current position of the force input element in such a way that it is at least in the ready position creates a valve seat on the at least one sealing seat and in the axial position deviating from the ready position, the at least one valve seat lifts from the at least one sealing seat.

In the brake booster according to the invention, the control valve can be constructed in a space-saving and relatively simple manner by actuating the valve element via the flexible actuating element. This flexible actuating element deforms in accordance with the movements carried out by the force input member and thus guides the valve seat from a position in which it is in mutual contact with the sealing seat, to a position in which it is lifted off the sealing seat, and back again , By using a flexible actuating element, which interacts directly with the input member and the valve element and takes over all actuating functions, a complex construction of the control valve, as is shown for example in EP 0 327 997 B1, can be avoided.

In a development of the invention it is provided that the valve element is flexible. For example, the valve element can be made from a rubber mixture or a flexible plastic material. Due to its flexibility, the valve element can adapt to the respective shape of the actuating element and thus assume its various functional positions.

It can further be provided that the valve element is coupled to the force input member in a fluid-tight manner via a sealing bellows. With this measure, the valve element can also be used to separate the vacuum chamber from the atmosphere.

With regard to the design of the valve seat and sealing seat, it is provided in a further development of the invention that the valve element is designed with a valve seat flange having the valve seat, on the side facing away from the valve seat, pretensioning means which bias the valve element into the ready position for contact with the sealing seat. The biasing means thus press the valve seat flange onto the control valve housing, so that the valve seat bears against the sealing seat in the ready position. When the brake booster is actuated via the actuating element, it is deformed to such an extent that, contrary to the action of the pretensioning means, it lifts the valve seat flange from the control valve housing and thus the valve seat from the sealing seat. To derive the reaction force from the pretensioning means, a further development of the invention provides that the pretensioning means are supported on the force input member on their side facing away from the valve element.

There are basically different designs for the flexible actuating element. It is conceivable to design this in the form of a flexible, resilient annular disc, the inner edge of which can be deflected in the axial direction with respect to the outer edge. Such a disc can for example be made of an elastic plastic or rubber material. In a preferred development of the invention, however, it is provided that the flexible actuating element comprises a meandering ring. The design of the actuating element in the form of a meandering ring has the advantage that it can be made of sheet metal, in particular spring steel, and thus has a relatively long service life with simple manufacture. In addition, the actuating element has good spring properties when designed as a meandering ring. Finally, such a meandering ring can save space and weight.

The functionality and reliability of such an actuating element designed as a meandering ring can be improved in a development of the invention in that radial projections projecting inward are formed on the radially inner regions of the meandering ring, by means of which the actuating element engages in a circumferential groove provided on the force input element. It can thereby be achieved that, despite its flexibility, the meander ring is reliably coupled to the force input element and cannot undesirably detach from it during the operation of the brake booster.

In a preferred embodiment of the invention it is provided that the valve element has two valve seats and the control valve housing has two corresponding sealing seats. For example, the two sealing seats can enclose an access or channel to the working chamber. In this embodiment, it can then be further provided that in the ready position of the valve element both valve seats rest on their corresponding sealing seats, that in a first axial position deviating from the ready position only one of the two valve seats rests on the corresponding sealing seat and the other is lifted off its corresponding sealing seat and that in a second axial position deviating from the ready position and the first axial position, the other valve seat bears against its corresponding sealing seat in a fluid-tight manner and one Valve seat is lifted from its corresponding sealing seat. These different relative positions of the valve seats and their corresponding sealing seats can be achieved, for example, in that in the first axial position the valve seat flange is tilted with respect to the ready position with one of the two sealing seats as a tilting line and in the second axial position the valve seat flange with respect to the ready position with the other one both sealing seats is tilted as a tilt line. By the measures described above it can be achieved that in the ready position vacuum chamber, working chamber and atmosphere are separated from each other by the valve element, that in the first axial installation working chamber and atmosphere are connected to each other to achieve the pressure difference determining the braking force between the working chamber and the vacuum chamber and that in the second axial position the working chamber is connected to the negative pressure chamber to reduce the pressure difference.

It can thus be achieved with this embodiment according to the invention that in the ready position there is a balanced pressure ratio between the vacuum chamber and the working chamber, that is to say that the same vacuum prevails in the working chamber as in the vacuum chamber. If desired, there can also be a slight overpressure in the working chamber with respect to the vacuum chamber, the valve element being held in contact with the control valve housing via the pretensioning means. In the first axial position, ie when a braking process is initiated, the working chamber and the atmosphere are then connected to one another, the vacuum chamber remaining separate from the atmosphere and the working chamber. This increases the pressure in the working chamber - with a sufficiently long opening to atmospheric pressure, whereas negative pressure continues to exist in the vacuum chamber. This results in the desired pressure difference between the vacuum chamber and the working chamber, which leads to an increase in the brake actuation force. If the braking process is ended, the second axial position is initially set, in which the working chamber is now isolated from the atmosphere and is connected to the vacuum chamber, which is also separated from the atmosphere. This means that pressure equalization occurs again in the working chamber and vacuum chamber (negative pressure relative to the atmosphere), so that the pressure difference between the vacuum chamber and the working chamber is reduced and the boosting effect of the brake booster decreases to zero. As a result, the control valve returns to its standby position. The invention is explained below by way of example with reference to the accompanying figures. They represent:

Figure 1 is a partially cutaway perspective view of an embodiment of the brake booster according to the invention;

FIG. 2 shows an axis-containing section through the brake booster according to the invention according to FIG. 1;

FIG. 3 shows a detail from the axis-containing section according to FIG. 2 in the ready position;

Figure 4 shows a section corresponding to Figure 3 in a first axial position;

5 shows a section according to FIGS. 3 and 4 in a second axial position.

In Figure 1, a brake booster according to the invention is shown in perspective and generally designated 10. FIG. 2 shows the same brake booster 10 as a section, which contains its longitudinal axis A.

The brake booster 10 comprises a force input member 12 and a force output member 14. The force input member 12 is coupled to a brake pedal, not shown, via which a brake actuation force Fi can be applied to the force input member 12. Via the force output member 14, a braking force F ₂ which is increased compared to the brake actuation force Fi is then transmitted to a hydraulic vehicle brake system, for example.

The force input member 12 is guided axially displaceably in a control valve housing 16. The force input member 12 has at its left end in FIG. 2 an axial extension 18 which extends axially displaceably through an axial opening within a channel support section 20 of the control valve housing. At its left end in FIGS. 1 and 2, the axial extension 18 has a spherically shaped sensing area 19 projecting from its end face 21, with which it cooperates on the end face with a reaction disk 24 made of rubber-elastic material. The reaction disk 24 is in a receiving cylinder 22 of the

Force output member 14 added. When the brake is actuated, the spherical sensing area 19 first immerses itself in the reaction disk 24 until the the area of the end face 21 surrounding the sensing area 19 abuts the reaction disk 24. This leads to a progressive response of the brake system. The response behavior of the brake system can thus be influenced with the shape of the sensing area 19.

The control valve housing 16 is formed with a cavity 26 which is in communication with the atmosphere. The control valve housing also has 16 channels 28 which lead to the working chamber of the brake booster. These channels 28 are delimited in the radial direction by a radially outer wall 30 and a radially inner wall 32. Both the radially inner wall 32 and the radially outer wall 30 are angled in the axial direction and taper at their free ends so that they each form a sealing seat 34 and 36. Radially within the radially inner wall 32, the control valve housing 16 is also formed with a cavity 38, which leads to the vacuum chamber of the brake booster 10, not shown. In order for the cavity 38 to communicate with the

To enable the vacuum chamber, channels 40 are provided in the channel support section 20, which open both in the axial direction towards the cavity 38 and in the radial direction towards the vacuum chamber.

A circumferential groove 42 is provided in the force input member 12, in which a flexible valve element 44 with a corresponding section is received. The valve element 44 fulfills the function of a sealing bellows. It extends from the circumferential groove 42 initially in the radial direction, is then angled in the axial direction and then merges into a valve seat flange 46. The valve seat flange 46 is provided on its side facing the sealing seats 34 and 36 with two round depressions 48 and 50, which interact as valve seats with the corresponding sealing seats 34 and 36. When the sealing seat 34 and valve seat 48 or sealing seat 36 and valve seat 50 are in mutual contact, there is fluid-tight contact between the control valve housing 16 and the valve element 44 in this area.

A biasing spring 52 engages on the side of the valve seat flange 46 facing away from the valve seats 48 and 50. At its end of the biasing spring 52 facing away from the valve element 44, it is supported on a holding element 54 in the axial direction, which in turn is supported on the force input member 12 via a locking ring 56. The valve element 44 is additionally connected to the force input element 12 via a flexible actuating element 58. As can be seen in FIG. 1, the actuating element 58 is designed in the form of a meandering ring, on the radially inner regions of which radial projections 60 are formed, by means of which the actuating element 58 engages in a circumferential groove 62 provided on the force input element 12 and is coupled to it for common axial movement ,

The mode of operation of the brake booster according to the invention will be explained below with reference to FIGS. 3 to 5, which each represent an image section from the axis-containing section according to FIG. 2, which represents the area around the valve element 44.

In Figure 3, the so-called ready position of the control valve is shown. This is represented by the distance between a reference edge 64 of the control valve housing 16 near the sealing seats 34 and 36 and the left boundary edge 66 of the circumferential groove 62 of the force input member 12 shown in FIGS. 3 to 5. In the ready position shown in FIG. 3, in which the distance between the boundary edge 66 and the reference edge 64 was designated by x ₀ , both valve seats 48 and 50 lie against the corresponding sealing seats 34 and 36 of the control valve housing in a fluid-tight manner. This is due to the fact that the actuating element 58 runs essentially in the radial direction due to the axial position of the force input member 12 and that the valve seat flange 46 is pressed onto the sealing seats 34 and 36 by the biasing spring 52. In this standby position, there may already be a slight pressure difference between the vacuum chamber and the working chamber.

When the brake is actuated, ie when the brake pedal is depressed, the force input member 12 is pressed to the left in FIG. 4 under the action of the brake actuation force Fi. As a result, the distance between the reference edge 64 and the boundary edge 66 shrinks to a value Xi, which is smaller than the value x _{0 of} the ready position according to FIG. 3. Due to the coupling via the radial projections 60 and the circumferential groove 62, the actuating element 58 moves in the same way Way in the axial direction with the force input member 12. However, this movement is blocked by the sealing seat 36, so that the actuating element 58 tilts according to FIG. 4 within the circumferential groove 62, a reaction force F _R ι acting on the amount of the braking actuation force Fi acting on the sealing seat 36 and resulting in this tilting. The tilt has a deformation of the flexible actuator tion element 58 and the flexible valve element 44 over their entire circumference, the sealing seat 36 serving as a tilt line over its entire circumference, on which the valve seat 50 rolls, so that the valve seat 48 lifts off from the sealing seat 34. The sealing seat 36 and the valve seat 50 remain in mutual fluid-tight contact. By lifting the sealing seat 34 from the valve seat 48, there is a connection between the channel 28 communicating with the working chamber and the atmosphere, so that the pressure in the working chamber rises. This ultimately leads to a pressure difference between the vacuum chamber and the working chamber, which, as already explained at the beginning, leads to brake force amplification via the movable wall separating the vacuum chamber from the working chamber. When the valve seat 48 is lifted sufficiently long and far from the sealing seat 34, atmospheric pressure is established in the working chamber, which leads to a maximum pressure difference between the vacuum chamber and the working chamber and thus to a maximum reinforcing effect. However, it should be pointed out that when the brake is briefly actuated, intermediate states can also arise in which the pressure difference between the vacuum chamber and the working chamber is less than the maximum pressure difference.

If the braking process is ended, the brake pedal is released and the

Brake actuation force Fi reduced to zero. Due to the reset mechanisms (not shown) on the part of the hydraulic brake system and the action of the biasing spring 52, the force input member 12 moves from its axial position shown in FIG. 4 via the axial position shown in FIG. 3 to its axial position shown in FIG. 5, the adjusting distance x ₂ between the reference edge 64 of the control valve housing and the limiting edge 66 of the force input member 12 exceeds the distance x _D according to the ready position according to FIG. 3. This leads to the valve seat 48 of the valve seat flange 46 again making contact with the corresponding sealing seat 34 in a fluid-tight manner. Due to the axial movement in FIG. 5 to the right, the valve element 44 and the actuating element 58 are tilted in the opposite direction relative to FIG. 4 such that the valve seat 50 lifts off from the sealing seat 36. The sealing seat 34 serves as a tilt line over its circumference. By tilting the valve element 44, the channel 28 and the cavity 38 are connected to one another. Ultimately, there is a connection between the working chamber and the vacuum chamber, so that the same vacuum can be established in the working chamber as in the vacuum chamber. Thereby the pressure difference on the movable wall, not shown, is reduced and the braking force boosting effect is canceled.

After sufficient pressure compensation between the vacuum chamber and the working chamber, the valve element 44 moves back together with the force input member 12 into its ready position shown in FIG. 3, so that the two valve seats 48 and 50 with their corresponding sealing seats 34 and 36 come into fluid-tight contact.

The invention shows a brake booster with a relatively simple and space-saving control valve. This simple and space-saving design stems from the fact that the entire functionality of the control valve can be controlled with the valve element 44 and the actuating element 58 assigned to it. These components interact in a simple manner with the control valve housing 16 and the force input member 12, only the biasing spring 52 being required for biasing into the ready position.

Claims

claims

1. brake booster (10), comprising: a force input element (12) for introducing a brake actuation force (Fi), a force output element (14) for deriving a brake force (F ₂ ) that is increased compared to the brake actuation force (Fi) to a brake system,

a vacuum chamber and a working chamber separated from the vacuum chamber by a movable wall in a fluid-tight manner,

- A control valve with a control valve housing (16) and a valve element (44) which can be moved axially relative thereto, the control valve housing (16) having a sealing seat (34, 36) with which a corresponding valve seat (48) provided on the valve element (44) , 50) cooperates, the control valve housing (16) also being designed for force-transmitting coupling to the movable wall, the valve element (44) also being designed for force-transmitting coupling to the force input member (12) and being biased into a standby position in which the valve seat (48, 50) abuts the sealing seat (34, 36) in a fluid-tight manner, and in order to achieve a pressure difference between the working chamber and vacuum chamber which determines the braking force (F ₂ ) as a function of an axial position of the valve element (44) which deviates from the ready position by lifting off the valve seat (48, 50) from the sealing seat (34, 36) at least atmospheric pressure to the working comb r can be supplied, characterized in that the valve element (44) is assigned a flexible actuating element (58) which is coupled to the force input element (12) for the common axial movement and which deforms in such a manner as a function of the current position of the force input element (12) that in the ready position it places the at least one valve seat (48, 50) on the at least one sealing seat (34, 36) and in the axial position deviating from the ready position the at least one valve seat (48, 50) from the at least one sealing seat (34, 36) takes off.

2. Brake booster (10) according to claim 1, characterized in that the valve element (44) is flexible.

3. Brake booster (10) according to claim 1 or 2, characterized in that the valve element (44) is fluid-tightly coupled to the force input member (12) via a sealing bellows.

4. Brake booster (10) according to one of the preceding claims, characterized in that the valve element (44) is formed with a valve seat flange (48, 50) having valve seat flange (46), on the side facing away from the valve seat (48, 50) Attack pretensioning means (52) which pretension the valve element (44) into the ready position for contact with the sealing seat (34, 36).

5. Brake booster (10) according to claim 4, characterized in that the biasing means (52) are supported on their side facing away from the valve element (44) on the force input member (12).

6. Brake booster (10) according to one of the preceding claims, characterized in that the flexible actuating element (58) comprises a meandering ring.

7. Brake booster (10) according to claim 6, characterized in that on the radially inner regions of the meandering ring (58) inwardly projecting radial projections (60) are formed, by means of which the actuating element (58) in a on the force input member (12) engage the provided circumferential groove (62).

8. Brake booster (10) according to one of the preceding claims, characterized in that the valve element (44) has two valve seats (48, 50) and the control valve housing (16) has two corresponding sealing seats (34, 36).

9. Brake booster (10) according to one of the preceding claims, characterized in that the two sealing seats (34, 36) enclose access to the working chamber (28).

10. Brake booster (10) according to claim 9, characterized in that in the ready position of the valve element (44) both valve seats (48, 50) rest on their corresponding sealing seats (34, 36), that in a first axial position deviating from the ready position only one of the two valve seats (50) on the corresponding sealing seat (36) fits tightly and the other (48) is lifted off its corresponding sealing seat (34) and that in a second axial position deviating from the ready position and the first axial position, the other valve seat (48) lies fluid-tight on its corresponding sealing seat (34) and the one valve seat (50) is lifted from its corresponding sealing seat (36).

11. Brake booster (10) according to claim 4 and 10, characterized in that in the first axial position of the valve seat flange (46) with respect to the ready position with one of the two sealing seats (36) is tilted as a tilt line and that in the second axial position of the valve seat flange ( 46) is tilted relative to the ready position with the other of the two sealing seats (34) as a tilt line.

12. Brake booster (10) according to claim 10 or 11, characterized in that in the ready position vacuum chamber, working chamber and atmosphere are separated from each other by the valve element (44), that in the first axial installation working chamber and atmosphere to achieve the braking force (F ₂ ) determining pressure difference between the working chamber and the vacuum chamber are connected to each other and that in the second axial position the working chamber is connected to the vacuum chamber to reduce the pressure difference.