WO1999059855A1

WO1999059855A1 - Vacuum brake booster having an electric signal generating device

Info

Publication number: WO1999059855A1
Application number: PCT/EP1999/003042
Authority: WO
Inventors: Leo Gilles; Ulrich Danne
Original assignee: Lucas Industries Public Limited Company
Priority date: 1998-05-15
Filing date: 1999-05-04
Publication date: 1999-11-25
Also published as: EP1077852A1; DE19822010C1

Abstract

The invention relates to a vacuum brake booster (10) comprising a housing (12) and a wall (14) which can move in an axial manner and which is arranged in said housing. The wall divides the housing (12) into a first chamber (18) and into a second chamber (20) which is separated therefrom. In order to detect the actuating state of the vacuum brake booster (10), the vacuum brake booster is provided with a device (34) for generating an electric signal which indicates the actuation of said booster. The device (34) comprises a tube (38) which is guided into the housing (12) through a wall (36) thereof and which is sealed from outside. An axially displaceable tappet (40) is arranged in the tube (38). Said tappet (40) interacts with an electric switching mechanism (44) and is spring-loaded in a direction toward the spring element (46). The spring element (46) is supported on the moveable wall (14) when said wall is in the rest position, and thus does not transmit force to the tappet (40) which leads to the displacement of the same. After the moveable wall (14) is displaced from the rest position, the spring element (46) acts upon the tappet head (42) of the tappet (40) and provokes an axial displacement of the same which actuates the electric switching mechanism (44).

Description

Vacuum brake booster with electrical signal generating device

The invention relates to a vacuum brake booster with an integrated device for generating an electrical signal indicating the actuation of the vacuum brake booster.

Motor vehicle brake systems, which are usually equipped with a vacuum brake booster today, are equipped with more and more functions. These functions are usually controlled and monitored by an electronic control unit. For a number of reasons, it is desirable to have information as to whether the vacuum brake booster is operated at a given time or not. This information can be used, for example, to control the brake lights of a vehicle accordingly.

The invention has for its object to provide a brake booster with an integrated electrical signal generating device that can reliably differentiate between an unactuated and an actuated state of the brake booster and is able to emit a corresponding on / off signal.

This task is for a vacuum brake booster of conventional design with a housing and an axially movable wall arranged therein, which divides the housing into a first chamber and a second chamber separated therefrom and which moves from a rest position when the vacuum brake booster is actuated , solved according to the invention with a device for generating an electrical signal indicating the actuation of the vacuum brake booster, which has a tube sealingly guided from the outside through a wall of the housing and extending through the extends first chamber and penetrates the movable wall sealing. An axially displaceable tappet is arranged in the tube and protrudes with a head from the inner end of the tube. To interact with this head there is a stationary spring element opposite it. The plunger is resiliently biased towards the spring element and interacts with an electrical switching mechanism, the spring force of the spring element counteracting the resilient preload of the plunger. The spring element is supported on it in the rest position of the movable wall, so that it does not exert any force on the plunger which causes it to move. Following a displacement of the movable wall from the rest position, the spring element acts on the head of the plunger and causes an axial displacement of the plunger by its spring force, which actuates the electrical switching mechanism. This then emits a signal which indicates that the vacuum brake booster is in the actuated state.

If the actuation of the vacuum brake booster stops, the movable wall returns to its rest position, so that the spring element can be supported on it again. The plunger is also returned to a rest position due to its resilient pretension, in which the electrical switching mechanism is not actuated. Alternatively, the electrical switching mechanism can also be designed such that it is actuated in the rest position of the tappet and changes to the non-actuated state when the tappet is displaced when the vacuum brake booster is actuated.

The spring element which effects the displacement of the plunger can comprise a more or less rigid section which comes into contact with the head of the plunger. This rigid section can also be formed in one piece with the spring element.

Due to its protected installation position, the solution according to the invention is insensitive to external influences, which the Reliability increased significantly. In particular, the signal generating device according to the invention does not change even after long operating times. For a vehicle manufacturer there is also the advantage of easier installation since only the electrical connection has to be made. A time-consuming installation of a separate switch, for example a brake light switch, can be omitted.

The electrical switching mechanism is preferably arranged outside the brake booster housing, where it is easily accessible for any maintenance work. If desired, however, the electrical switching mechanism can also be arranged inside the tube in which the displaceable plunger is located.

In preferred embodiments of the brake booster according to the invention, the tappet is connected to its head in such a way that the axial distance between the head and the tappet can be changed. For example, the head can be screwed into the plunger by means of an adjusting thread. In this way, the switching point of the signal generating device according to the invention can be easily adjusted.

The plunger is preferably sealed off from the tube, in which it is guided so as to be axially displaceable. This eliminates the

Need to make the electrical switching mechanism pressure tight.

The plunger can interact with the electrical switching mechanism in various ways. According to one embodiment of the brake booster according to the invention, the end of the tappet opposite the tappet head carries a first switching contact which comes into contact with a second switching contact of the electrical switching mechanism due to the axial displacement of the tappet. According to another embodiment, a ramp-shaped button is formed on the end of the tappet opposite the tappet head, which has a Switch of the electrical switching mechanism cooperates, the switching direction is at least substantially perpendicular to the longitudinal axis of the plunger. According to yet another embodiment, the end of the plunger opposite the plunger head carries a magnet which interacts with a Hall sensor of the electrical switching mechanism. The approach of the magnet to the Hall sensor, which occurs when the brake booster is actuated, is registered by the Hall sensor and leads to the generation of a corresponding signal.

In preferred embodiments of the brake booster according to the invention, the movement of the tappet in the direction of the spring element is limited by a stop. The spring element can thereby be relieved of the pressure of the tappet in its rest position. In addition, the rest position of the plunger is precisely defined by such a stop.

In order to simplify the manufacture of the brake booster according to the invention, the tube, which receives the axially displaceable tappet, is preferably locked in place by means of a locking projection in the power amplifier housing. The tube then only needs to be pushed into the brake booster housing with a fixed pressure. If the electrical switching mechanism is not already inside the tube, it can then be easily connected to the end of the tube protruding from the brake booster housing, for example by clipping it on.

According to a further development, a separate channel for the passage of electrical connecting lines is formed in the tube. These connecting lines can be used, for example, to connect an electromagnetic actuation unit of the brake booster to a control unit located outside the brake booster. Furthermore, these connecting lines can lead to sensors which are arranged in the brake booster. Several exemplary embodiments of a vacuum brake booster according to the invention are explained in more detail below with reference to the attached schematic drawings. It shows:

1 shows in longitudinal section a vacuum brake booster in tandem construction, which is provided with a device according to the invention for generating an electrical signal indicating the actuation of the brake booster,

2 shows the electrical signal generating device from FIG. 1 in an enlarged representation,

3 shows a modified embodiment of the electrical signal generating device in section, FIG. 4 shows another modified signal generating device in section,

Fig. 5 shows a further embodiment of an electrical signal generating device in longitudinal section.

In Fig. 1 is a generally designated 10, here in

Tandem design of vacuum brake booster for a hydraulic motor vehicle brake system shown in longitudinal section. The brake booster 10 has a housing 12, in which two movable walls 14, 16 are arranged, of which the movable wall 14 the housing interior into a first chamber 18 and a separate second chamber 20 and the movable wall 16 the housing interior into a third chamber 22 and a separate fourth chamber 24 divided. A rigid intermediate wall 26 also arranged in the housing 12 separates the one unit of the brake booster 10, which is formed by the first chamber 18, the second chamber 20 and the movable wall 14, from that by the third chamber 22, the fourth chamber 24 and the movable wall 16 'formed second unit. In the example shown, the first chamber 18 and the third chamber 22 are designed as so-called vacuum chambers, which are in constant communication with a vacuum source during operation of the brake booster 10. The second chamber 20 and the fourth chamber 24, on the other hand, are referred to as working chambers, which can be connected either to the negative pressure source or to atmospheric pressure (or also to excess pressure). The connection of the working chambers with atmospheric pressure (or with excess pressure) controls a control valve 28 which, when the brake booster 10 is actuated, which is perceived by the displacement of a rod-shaped input member 30, allows atmospheric pressure to flow into the previously evacuated chambers 20 and 24. The resulting pressure difference between the first chamber and the second chamber 20 or the third chamber 22 and the fourth chamber 24 leads to a displacement of the movable walls 14 and 16 from the rest position shown in FIG. 1 and to the transmission of a corresponding force to one Output member of the brake booster 10, which delivers the force to a hydraulic master cylinder, not shown here. This function of the vacuum brake booster 10 is well known to those skilled in the art and therefore need not be explained further.

The brake booster 10 is provided with a device 34 for generating an electrical signal indicating the actuation of the vacuum brake booster, which can be seen more precisely from FIG. 2. The device 34 has a pipe 38 which seals from the outside through a wall 36 of the brake booster housing 12 and which extends through the first chamber 18 and penetrates the movable wall 14 in a sealing manner. An axially displaceable tappet 40 is guided in the tube 38 and projects with a head 42 from the inner end of the tube 38 into the second chamber 20. The opposite, other end of the plunger 40 interacts with an electrical switching mechanism 44 which emits an electrical signal corresponding to the axial position of the plunger 40 and which will be explained in more detail below. Opposite the head 42 of the plunger 40, a spring element 46 is arranged in a fixed position, which is intended to interact with the head 42. The spring element 46 is formed in one piece in the exemplary embodiments shown and is fastened to the intermediate wall 26 of the brake booster housing 12 with an approximately S-shaped end section 48, which essentially provides the spring force of the spring element 46. The S-shaped section 48 is followed by an essentially rigid actuating section 50, against which the head 42 of the plunger 40 bears. The free end of the spring element 46 is formed by an arm 52 which extends at a right angle from the actuating section 50 and which is supported on the movable wall 14 when the latter is in its rest or starting position.

A compression spring 54 arranged in the electrical switching mechanism 44 according to FIG. 2, which engages an annular collar 58 of the plunger 40, prestresses the plunger 40 in the direction of the spring element 46. At the same time, the annular collar 56, in cooperation with an annular disk 58 inserted into the tube 38, serves as a stop which limits the movement of the tappet 40 in the direction of the spring element 46 and defines a rest position of the tappet 40. A sealing bellows 60, one edge of which is clamped between the annular disk 58 and a radial projection of the tube 38 and the other, thickened edge of which is fixed in an annular groove 62 of the tappet 40, seals the tappet 40 from the tube 38.

On the end of the plunger 40 which interacts with the electrical switching mechanism 44, a first switching contact 64 is formed, which can come into contact with a second switching contact 66 of the electrical switching mechanism 44 after having overcome a fixed axial distance. Both switching contacts 64, 66 are connected to plug contacts 68, 70 in order to enable an electrical connection of the device 34 to, for example, an electronic control unit via a plug (not shown here). The function of the device 34 will now be explained. In the idle state shown in FIGS. 1 and 2, the spring element 46 cannot exert any force on the head 42 which leads to the displacement of the tappet 40 because it is supported on the movable wall 14. However, if the brake booster 10 is actuated, the movable wall 14 moves to the left without noticeable delay, as shown in FIG. 2, whereby the arm 52 of the spring element 46 is released from it, so that the full spring force of the spring element 46 via its actuating section 50 on the head 42 of the plunger 40 is transmitted. Since the spring force of the spring element 46 is greater than the opposite spring force of the spring 54 biasing the plunger 40, the plunger 40 is displaced axially to the left and the first switching contact 64 comes into contact with the second switching contact 66. This state in which the electrical switching mechanism 44 emits an ON signal, remains until the movable wall 14 runs back again at the end of an actuation of the brake booster 10 and rests against the arm 52 of the spring element 46 and takes it somewhat to the right. The force of the spring 54 now predominates again, so that the plunger 40 is displaced axially to the right and the two switching contacts 64 and 66 are separated from one another. When the two switching contacts 64 and 66 are separated from one another, the electrical switching mechanism 44 emits an OFF signal.

In the exemplary embodiments shown, the head 42 is connected to the plunger 40 via an adjusting thread 72, so that the rest position of the plunger 40 and the first switching contact 64 can be set precisely by screwing the head 42 in or out.

So that the device 34 can be easily assembled, the tube 38 has a latching projection 74 on its outer circumferential surface. The pipe 38 then only needs to be pressed from the outside through a rubber sleeve 76, which is placed in the opening of the housing wall 36, until the locking projection 74 inside the brake booster housing 12 behind the rubber sleeve 76 locked. If the tappet 40 is sealed off from the pipe 38, as in the illustrated exemplary embodiments, a housing 78 accommodating the electrical switching mechanism 44 need not be particularly sealed, but can, for example, be provided with the corresponding end section of the brake booster housing 12 Tube 38 be clipped.

FIGS. 3 and 4 show modified exemplary embodiments of the device 34, the function of which essentially corresponds to the previously explained exemplary embodiment according to FIG. 2.

In FIG. 3, the function of the first switching contact is taken over by a ramp-shaped button 80 which interacts with a switch 82, the switching direction of which is perpendicular to the longitudinal axis of the plunger 40. For this purpose, the switch 82 has a roller 84, which runs up on the ramp-shaped button 80 when the plunger 40 is axially displaced and is thereby pushed away from the plunger 40 at right angles to the plunger axis. The roller 84 thereby comes into contact with a key switch 86, which then signals the ON state. In a further difference from the exemplary embodiment according to FIG. 2, the tappet 40 according to FIG. 3 is pretensioned by a spring 54 'in the direction of the spring element 46, which is supported at one end on the tube 38 and at the other end on the head 42 of the tappet .

In the embodiment shown in FIG. 4, in accordance with the exemplary embodiment according to FIG. 2, there is a first switch contact 64 'at the end of the plunger 40 and a second switch contact 66' arranged at an axial distance therefrom. In contrast to the exemplary embodiment according to FIG. 2, however, only the second switching contact 66 'is provided with two connecting pins 88, 89. The first switch contact 64 'therefore only serves to bridge two contact fields present on the second switch contact 66' and thereby to close a circuit. The spring biasing the plunger 40 54 'is arranged in accordance with the exemplary embodiment according to FIG. 3.

5 shows a further exemplary embodiment of the device 34, in which a Hall sensor arrangement is used instead of switching contacts. For this purpose, a magnet 90 is fastened to the end of the plunger 40 which interacts with the electrical switching mechanism 44, and a Hall sensor 92 is arranged opposite it at an axial distance in the housing 78 of the electrical switching mechanism 44. An axial displacement of the plunger 40 leads to an approach of the magnet 90 to the Hall sensor 92, which is detected by the latter and is emitted as a corresponding signal. In this embodiment, the spring 54 which prestresses the tappet 40 is in turn arranged at a location which corresponds to the embodiment according to FIG.

As can be seen from FIG. 5, in this embodiment the tube 38 has a separate channel 94 which is separate from the tappet 40 and which is used to carry out electrical connecting lines, which lead, for example, to an electromagnetic actuation unit of the brake booster 10 and / or to a safety switch (neither shown). The channel 94 is preferably separated from the plunger 40 in an airtight manner.

Claims

claims

l. Vacuum brake booster (10), with a housing

(12) and an axially movable wall (14) arranged therein, which divides the housing (12) into a first chamber (18) and a second chamber (20) separate therefrom and moves from a rest position when the vacuum brake booster is actuated and having means (34) for generating an electrical signal indicative of the actuation of the vacuum brake booster, the device comprising

a pipe (38), which extends from the outside through a wall (36) of the housing (12) into the housing (12) and extends through the first chamber (18) and sealingly penetrates the movable wall (14),

- An axially displaceable plunger (40) arranged in the tube (38), which projects with a plunger head (42) from the inner end of the tube (38), - A fixedly arranged relative to the plunger head (42)

Spring element (46) for cooperation with the plunger head (42), and

- An with the plunger (40) cooperating, electrical switching mechanism (44), wherein

- The plunger (40) is resiliently biased towards the spring element (46), the spring force of which counteracts the resilient preload of the plunger (40),

- The spring element (46) in the rest position of the movable wall (14) is supported on it and does not exert any force leading to the displacement of the plunger (40) on the plunger head (42), and wherein

- The spring element (46) acts on the plunger head (42) after a displacement of the movable wall (14) from its rest position and an axial displacement of the

Plunger (40) which actuates the electrical switching mechanism (44).

2. Brake booster according to claim 1, characterized in that the electrical switching mechanism (44) is arranged outside the brake booster housing (12).

3. Brake booster according to claim 1 or 2, characterized in that the tappet head (42) is connected to the tappet (40) such that the axial distance between the tappet head (42) and the tappet (40) is variable.

4. Brake booster according to one of claims 1 to 3, characterized in that the tappet (40) is sealed off from the tube (38).

5. Brake booster according to one of the preceding claims, characterized in that the plunger head (42) opposite end of the plunger (40) carries a first switching contact (64) by an axial displacement of the plunger (40) in contact with the electrical Switching mechanism (44) associated second switching contact (66) device.

6. Brake booster according to one of claims 1 to 4, characterized in that on the plunger head (42) opposite end of the plunger (40) a ramp-shaped button (80) is formed, and that the electrical switching mechanism (44) one with of the ramp-shaped button (80) cooperating switch (82), the switching direction is at least substantially perpendicular to the longitudinal axis of the plunger (40).

7. Brake booster according to one of claims 1 to 4, characterized in that the plunger head (42) opposite end of the plunger (40) carries a magnet (90) which with an electrical switching mechanism (44) associated Hall sensor (92 ) interacts.

8. Brake booster according to one of the preceding claims, characterized in that the movement of the tappet (40) in the direction of the spring element (46) is limited by a stop (56).

9. Brake booster according to one of the preceding claims, characterized in that the tube (38) is locked by means of a locking projection (74) in the brake booster housing (12).

10. Brake booster according to one of the preceding claims, characterized in that in the tube (38) a separate channel (94) is formed for carrying out electrical connecting lines.

11. Brake booster according to one of the preceding claims, characterized in that the electrical signal generated by the device (34) is used to control brake lights.