WO2009129887A1

WO2009129887A1 - Main brake cylinder arrangement with actuation detection for a motor vehicle brake system and motor vehicle brake system

Info

Publication number: WO2009129887A1
Application number: PCT/EP2009/001342
Authority: WO
Inventors: Klaus Lemke; Daniel Noll
Original assignee: Lucas Automotive Gmbh
Priority date: 2008-04-25
Filing date: 2009-02-25
Publication date: 2009-10-29
Also published as: DE102008020934A1

Abstract

The invention relates to a main brake cylinder arrangement (10) for a motor vehicle brake system, comprising at least one piston arrangement (12, 16) having a piston (14) moveably guided in a cylinder bore (20) in a cylinder housing (22), wherein the piston (14) defines a pressure chamber (24) together with the cylinder bore (20), said chamber being fluid-coupled to a hydraulic brake circuit. In said main brake cylinder arrangement (10) it is provided that the piston (14) is permanently coupled to a position detection rod (42) so as to provide common motion, said rod being moveably guided in a guide shaft (44) in the cylinder housing (22) parallel to the first cylinder bore (20), wherein the position detection rod (42) comprises a position detection member (54), the position thereof within the guide shaft (44) being detectable by way of a position detection sensor (56) attached to the cylinder housing (22).

Description

Master brake cylinder arrangement with actuation detection for a motor vehicle brake system and motor vehicle brake system

The present invention relates to a master brake cylinder assembly for a motor vehicle brake system having at least one piston assembly with a piston which is displaceably guided in a cylinder bore in a cylinder housing, wherein the piston with the cylinder bore bounded by a hydraulic brake circuit fluidly coupled pressure chamber.

To control the brake warning lights of a motor vehicle, an electro-mechanical switch is often used, which detects an actuation of a brake pedal of the vehicle brake system by the driver of the motor vehicle. This electromechanical switch is designed as a separate component and mounted in the footwell of the vehicle. To ensure proper operation of the switch and thus also the brake warning lights, the switch must be mounted in a fixed position either on the brake pedal or relative to the brake pedal and adjusted in this position. Such to be performed after installation of the pedals assembly and adjustment work are relatively difficult and time consuming, since the footwell of the motor vehicle is generally difficult to access.

The document DE 100 53 995 A1 therefore proposes to use a signal generated by a device integrated in a master brake cylinder and indicating an actuation of the master brake cylinder for controlling the brake warning lights of the motor vehicle. The master cylinder described in this document comprises a housing with a longitudinal bore formed therein, in which a first and a second piston are sealingly and axially displaceably guided, wherein in a recess formed on the second piston, a pin or ringsegment-shaped element of a magnetic Material is arranged. In the housing a with respect to the longitudinal bore extending in the radial direction blind bore for receiving a plug is formed, which carries on one of the longitudinal bore facing end face a Hall sensor. Upon displacement of the second piston due to actuation of the master cylinder, the Hall sensor generates an electrical signal indicative of an operation of the master cylinder in response to detection of displacement of the pin or ring segment shaped magnetic material integrally formed with the second piston relative to the Hall sensor , To achieve the required Chen measuring accuracy is in such a signal generating device, a relatively high cost for adjusting the equipped with the Hall sensor plug relative to the integrally formed with the second piston element made of magnetic material required, these adjustments must be repeated when replacing the plug due to a defect ,

The document DE-OS 2 010 073 discloses a master cylinder with a mechanical switch for actuating the brake light lamps of a motor vehicle. The switch comprises a plunger which, when the brake is not actuated, cooperates with an outer circumference of a piston guided in a bore of a housing and is thereby held in a first depressed position. Upon actuation of the master cylinder and an associated displacement of the piston in the bore of the plunger is displaced by the force of a compression spring in a second position and protrudes in the region of a formed on the piston recess into the bore. As a result, a switching contact is closed so that the brake light lamps of the motor vehicle are actuated.

The document US 5,016,442 describes a master cylinder with two pistons which are axially displaceably guided in a first bore formed in a housing. In a housing formed in the second bore a compensating piston is guided axially displaceable, wherein the second bore is fluid-conductively connected to arranged in the first bore pressure chambers. About a arranged in a blind hole reed switch, a first magnet is disposed, while the balance piston carries a second magnet. Upon actuation of the master cylinder, the balance piston is normally displaced only slightly against the actuating direction of the master cylinder as a result of the pressure building up in the pressure chambers until a shoulder comes into abutment against a step formed on the housing. On the other hand, if a leak occurs in a brake circuit connected to the pressure chambers, the compensating piston is displaced from its rest position as a result of the pressure difference in the pressure chambers until it comes into contact with stop elements. The displacement of the second magnet connected to the balance piston relative to the first magnet, the reed switch is actuated, whereupon a warning signal is issued to a driver indicating a failure of the affected brake circuit.

Furthermore, the document DE 103 52 589 B4, from which the preamble of claim 1 proceeds, shows a master brake cylinder arrangement in which the secondary piston ben is mechanically coupled in a starting position with a position detection element, which moves under spring bias over a short portion of a movement of the secondary piston for detecting a brake actuation with this. Alternatively, a hydraulic coupling of position sensing element and of the secondary piston limited pressure chamber is proposed. Although the master brake cylinder arrangement proposed in this prior art has been proven in practice, it has the disadvantage that due to the required coupling of position sensing element and secondary piston a connection between the cylinder bore to a guide shaft is provided, in which the position detection element is guided displaceable. This leads to a complex production of at least the cylinder housing.

The invention has for its object to provide a master cylinder of the type described, which has the same advantages as the generic state of the art, however, has a simpler structure.

This object is achieved by a master brake cylinder assembly of the type described, in which it is further provided that the piston is permanently coupled for common movement with a position sensing rod which is guided displaceably in a parallel to the first cylinder bore guide shaft in the cylinder housing, wherein the position sensing rod is a position detecting member whose position within the guide shaft can be detected by means of a position detection sensor attached to the cylinder housing.

By using a position sensing rod, it is possible to design the coupling with the associated piston so that no connection between piston and position sensing rod within the cylinder housing is required. This makes the entire system much easier to set up. An advantage of this solution is that no additional opening opens into the cylinder bore, in which the piston assembly is received, so that required manufacturing steps can be avoided. In addition, a position sensing rod due to the permanent coupling of the same with the piston can monitor the movement of the piston of the piston assembly within the cylinder bore over a greater distance. As a result, additional information about a brake actuation by a driver or about the current actuation status of the brake can be determined not only qualitatively but also quantitatively. A further development of the invention provides that the piston has a piston shaft which projects out of the cylinder housing and to which the position detection rod is coupled. Thus, it may be provided in this context that the piston skirt has at its projecting out of the cylinder housing free end a coupling portion, in particular a coupling flange, with which the position detection rod is coupled. In this way, the position detection rod can be accommodated in a guide shaft, which although parallel to the at least one piston assembly receiving cylinder bore, but is completely independent of this. This guide shaft can thus be formed separately in the cylinder housing. A connection of cylinder bore and guide shaft is not required.

According to one embodiment of the invention it is provided that the position detection rod is biased by means of a return spring in abutment with the coupling portion, in particular the coupling flange. This ensures that the position detection rod is biased for example in a starting position, which corresponds to an unactuated state of the motor vehicle brake system. By mutual contact but also ensures that the position sensing rod permanently moves with the piston during its operation.

A constructive development of the invention provides that the restoring spring is accommodated in the guide shaft and is supported at one end on an investment plug received in the guide shaft and bears against the position detection rod at the other end in a biasing manner. This embodiment is advantageous in terms of manufacture and assembly, because the position detection rod can be inserted into the guide shaft, the restoring spring is subsequently inserted and finally is pressed into the cylinder housing in a force-locking or positive-locking manner by building up a preload of the installation plug.

In this embodiment of the invention may also be provided that the investment plug provides a connection of the guide shaft to the atmosphere. In one embodiment, in which the position detection rod is sealingly guided relative to a vacuum chamber of a braking force generator, it is possible by this measure that builds upon compression of the brake in the guide shaft no compression-related back pressure, which counteracts a movement of the position sensing rod. In order to define a defined starting position of the position detection rod, a development of the invention provides that the guide shaft is formed with a diameter step, wherein the position detection rod has a smaller diameter shaft portion and a larger diameter detection portion on which the position detecting member is provided. This diameter stage acts as captive during assembly and transport of the master cylinder assembly according to the invention. In operation, there is always a gap between the position sensing rod and the diameter stage in their home position, the return spring biasing the position sensing rod into abutment with the coupling portion, as described above.

According to the invention, it can be provided that the position detection member has a magnetic body and that the position detection sensor is formed by a Hall sensor. But it is also possible to perform the position detection differently, for example, optically or inductively.

In principle, the master brake cylinder arrangement according to the invention can be designed as desired. A preferred embodiment provides, for example, that in the master cylinder, a first piston assembly is received with a primary piston and a second piston assembly with a secondary piston, wherein the position sensing rod is designed for common movement with the primary piston and / or the secondary piston. In this case, the position sensing rod is coupled with the projecting out of the cylinder housing primary piston for common movement.

According to the invention, it can further be provided that the position detection sensor provides a position signal which provides information about the current position of the piston coupled to the position detection rod. According to one embodiment of the invention it is possible in this context that the position signal for actuating a brake light system, as an input signal for a brake assist system or a vehicle stabilization system, or further for controlling a regenerative braking system in connection with the use of a braking action of an electric motor acting as a generator or the like is usable. In the latter case, that is, when used for the control of a regenerative braking system, it is necessary in some applications, from a certain requested braking effect (delay) - in addition to or as an alternative to the braking effect of acting as a generator electric motor - the friction brake system activate. This can be done, for example, based on the detected position of the position detection rod.

The invention further relates to a motor vehicle brake system with a master brake cylinder assembly of the type described above. This is carried out with a vacuum braking force generator with a chamber assembly having a vacuum chamber and a working chamber connectable to the ambient atmosphere, wherein the vacuum chamber and the working chamber separated by a movable wall wherein the piston coupled to the position sensing rod is connected for common movement with the movable wall.

In this motor vehicle brake system can be provided that the position sensing rod is in contact with the movable wall or coupled to this component of the vacuum braking force generator, preferably biased against this.

The invention is explained below by way of example with reference to the accompanying figures. They show:

FIG. 1 shows a perspective, partially cutaway view of a master cylinder arrangement according to the invention,

FIG. 2 shows an axis-containing sectional view of a braking force generator which is coupled to a master cylinder arrangement according to the invention, and

FIG. 3 shows a detailed view of section III from FIG. 2.

1 shows a master brake cylinder assembly according to the invention is shown in a partially cutaway perspective view and generally designated 10. This comprises a first piston arrangement 12 with a primary piston 14 and a second piston arrangement 16 with a secondary piston 18. The two piston arrangements 12 and 16 are guided in a cylinder bore 20 of a cylinder housing 22. The primary piston 14 defines with the cylinder bore 20 and the back of the secondary piston 18, a primary pressure chamber 24, whereas the secondary piston 18 with the cylinder bore 20 defines a secondary pressure chamber 26. The primary piston 14 is via a return spring 28 in the position shown in Figure 1 biased, as is the secondary piston 18 is biased by a return spring 30 in the position shown in Figure 1.

As can be seen from FIG. 1, circumferential grooves are provided in the cylinder bore 20, in which sealing rings 32 for sealingly guiding the piston arrangements 12 and 16 are accommodated. Further, in the cylinder housing 20 connection openings 34 and 36 are provided, which serve to fill the pressure chambers 24 and 26 via a reservoir.

It can also be seen in FIG. 1 that the free right end of the primary piston 14 is formed with a flange 38. At this flange 38 is located on a free end 40 of a position detection rod 42, which is guided displaceably in a stepped guide shaft 44 of the cylinder housing 22. The position detecting rod 42 has an elongated portion protruding from the cylinder housing 22 and an enlarged diameter detection portion 46. The detection portion 46 is displaceably guided in a larger diameter portion 48 of the guide shaft 44. Between the smaller diameter guide shaft 44 and the larger diameter portion 48, a diameter step 45 is formed. The larger diameter portion 48 of the guide shaft 44 is closed at its left in Figure 1 end with a investment plug 50. The investment plug 50 in this case has no opening, so that no air from the atmosphere in the guide shaft 44,48 enter and over this on the position detection rod 42 over into the vacuum chamber (see description below) can penetrate. However, if the position detection rod 42 is sealingly guided in the cylinder housing 22 in the context of an alternative embodiment, the contact plug 50 is preferably formed with an opening for pressure equalization. At the investment plug 50, a return spring 52 is supported, which is biased in the position shown in Figure 1.

It can also be seen in FIG. 1 that a position detection element 54 in the form of a magnetic body is accommodated in the detection section 46 of the position detection rod 42. On the cylinder housing 22 a embedded in a plastic housing position detection sensor 56 is mounted, which is electrically contacted via a connector socket 58. The position detection sensor 56 detects the instantaneous relative position of the magnetic body of the position detection gate 54. By the return spring 52 of the Positionseraufυngsstab 42 is pressed into contact with the flange 38. Upon movement of the flange 38 together with the primary piston 14, the position detection rod 42 moves against the force of the return spring 52, wherein the position detecting member 54 moves relative to the position on the detection sensor 56. This relative movement is detected by the position detection sensor 56 and output as a corresponding signal. This signal is used to detect the brake application, for example, as a result of a pedal operation of the driver or as a result of activation of the brake by a driver assistance system or a brake assist system. This signal can be used, for example, to actuate brake warning lights, but also as further input signals for various vehicle systems.

Due to the structure shown in FIG. 1, it is possible to detect a brake operation by means of the position detecting rod 42 completely separately from the cylinder bore 20 in the cylinder housing 22. The structure of the position detection device formed in this way is relatively simple, in particular in comparison to the prior art discussed at the beginning. The master brake cylinder assembly 10 of the invention provides reliable operation and reliable detection of the current brake actuation condition. Due to the return spring 52, the position detection rod 42 always returns reliably to its initial position shown in Figure 1 and remains in abutment with the flange 38, so that a common movement of the position detection rod 42 and the primary piston 14 is ensured.

FIG. 2 shows a braking force generator 60 having a master brake cylinder arrangement 10 according to the invention. The braking force generator 60 has a force input member 62 that can be coupled or coupled to a brake pedal (not shown). As is known, the function of the braking force generator 60 is controlled via a control valve 64. The control valve 64 is fluidly coupled to a chamber assembly 66, which is formed in Figure 2 as a tandem chamber assembly. It comprises two vacuum chambers and two working chambers, wherein in each case a vacuum chamber is separated from its associated working chamber via a movable wall 68 and 70. The two pairs of vacuum chamber and working chamber are separated by a fixed housing wall 72. The two movable walls 68 and 70 are fixed on a displaceable in the direction of a longitudinal axis A control valve housing 74. As soon as a pressure difference acts on the movable walls 68 by 70, the control valve housing 74 is moved as a result of this pressure difference. This then actuates the primary piston 14 and thereby the secondary piston 18 of the master cylinder assembly 10. As described above, this operation can be detected via the position detection rod 42 due to its displacement in the guide shaft 44 and 48.

Figure 3 shows an enlarged view of how the primary piston 14 is coupled to the control valve housing 74. For this purpose, a multiply folded funnel-shaped element 76 is mounted on the control valve housing 74, which is received in the end-side opening of the control valve housing 74. At this funnel-shaped element 76, a tension spring 78 is supported in a conventional manner. Furthermore, the free end 40 of the position detection rod 42 is also supported on this funnel-shaped element 76.

As an alternative to the coupling of the position detection rod 42 shown in FIG. 1 with a flange 38 attached to the primary piston 14, according to FIGS. 2 and 3 the position detection rod 42 is directly biased against the control valve housing 74 or against the funnel-shaped element 76 coupled thereto.

It can be seen in Figure 3, the area 80 on the control valve housing 74, in which the movable wall 70 is fixed. Finally, it can be seen in FIG. 3 that a transmission piston 82 and a coupling part 84 are provided, which permit an immediate coupling of the force input member 62 and the master brake cylinder assembly 10 for purely mechanical actuation of the brake system via the brake pedal in the event of an emergency operation in the event of malfunction of the chamber arrangement.

Figures 2 and 3 thus show a solution that can be integrated into a braking force generator with little effort and while ensuring reliable operation without major structural changes a position detection device according to the present invention.

Claims

claims

A master brake cylinder arrangement (10) for a motor vehicle brake system having at least one piston arrangement (12, 16) with a piston (14) which is displaceably guided in a cylinder bore (20) in a cylinder housing (22), the piston (14) being connected to the Cylinder bore (20) bounded by a hydraulic brake circuit fluidly coupled pressure chamber (24), characterized in that the piston (14) for common movement with a position sensing rod (42) is permanently coupled in a for the first cylinder bore (20) parallel guide shaft (44) in the cylinder housing (22) is displaceably guided, wherein the position detection rod (42) has a Positionsserfassungsungs- organ (54), whose position within the guide shaft (44) by means of a cylinder housing (22) mounted position detection sensor (56) can be detected ,

Second master brake cylinder assembly (10) according to claim 1, characterized in that the piston (14) from the cylinder housing (22) protruding out piston shaft, with which the position detection rod (42) is coupled.

3. Master brake cylinder assembly (10) according to claim 1 or 2, characterized in that the piston shaft at its out of the cylinder housing (22) protruding from the free end a coupling portion, in particular a coupling flange (38), with which the position detection rod (42) is coupled ,

4. master brake cylinder assembly (10) according to claim 3, characterized in that the position sensing rod (42) by means of a return spring (52) in contact with the coupling portion, in particular the coupling flange (38), is biased.

5. Master brake cylinder assembly (10) according to claim 4, characterized in that the return spring (52) in the guide shaft (44, 48) is accommodated and at one end on a in the guide shaft (48) received investment plug (50) is supported and the other end biasing the position detection rod (42) abuts.

6. master brake cylinder assembly (10) according to claim 5, characterized in that the investment plug (50) provides a connection of the guide shaft (48) to the atmosphere.

7. master brake cylinder assembly (10) according to any one of the preceding claims, characterized in that the guide shaft (44, 48) with a diameter step (45) is formed, wherein the position detection rod (42) has a smaller diameter shaft portion (42) and a larger diameter detection portion (46 ), on which the position detecting member (54) is provided.

8. Master brake cylinder assembly (10) according to any one of the preceding claims, characterized in that the position detecting member (54) has a magnetic body and that the position detection sensor (56) is formed by a Hall sensor.

9. Master brake cylinder assembly (10) according to any one of the preceding claims, characterized in that in the cylinder bore (20) a first piston assembly (12) with a primary piston (14) and a second piston assembly (16) is received with a secondary piston (18), wherein the position sensing rod (42) is adapted for co-movement with the primary piston (14) and / or the secondary piston (18).

10. Master brake cylinder assembly (10) according to any one of the preceding claims, characterized in that the position detection sensor (56) provides a position signal which provides information about the current position of the position sensing rod (42) coupled to the piston (14).

11. master brake cylinder assembly (10) according to claim 10, characterized in that the position signal for actuating a brake light system and as an input signal for a brake assist system, a vehicle stabilization system, or the like can be used.

12. Motor vehicle brake system comprising a master brake cylinder assembly (10) according to any one of the preceding claims, characterized by a vacuum braking force generator (60) having a chamber arrangement (66) having a vacuum chamber and a work chamber connectable to the ambient atmosphere, wherein the vacuum chamber and the working chamber a movable wall (68, 70) are separated from each other, the piston (14) coupled to the position sensing rod (42) being connected for common movement with the movable wall (70).

13. Motor vehicle brake system according to claim 12, characterized in that the position detection rod (42) in abutment with the movable wall (70) or coupled to this component (74) of the vacuum braking force generator (60) is preferably biased against this.