EP3548347A1

EP3548347A1 - Master brake cylinder, brake system

Info

Publication number: EP3548347A1
Application number: EP17784250.7A
Authority: EP
Inventors: Simon Hansmann; Dirk Foerch; Matthias Kistner; Florent Yvonet; Raynald Sprocq; Chris Anderson
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2016-11-30
Filing date: 2017-10-05
Publication date: 2019-10-09
Also published as: GB2558413A; GB201719772D0; KR20190087587A; CN109996708B; DE102016223760A1; JP2019535595A; WO2018099638A1; KR102410780B1; CN109996708A; US20200079337A1

Abstract

The invention relates to a master brake cylinder (2) for a brake system (1) of a motor vehicle, comprising a hydraulic cylinder (4), which has a plurality of hydraulic connection points and in which at least one hydraulic piston (5, 6) is mounted for axial sliding in an actuation direction and in a relief direction, wherein the hydraulic piston (5, 6) can be slid in the actuation direction against the force of a spring element (7, 8), and wherein a restraint (22, 23) is associated with the spring element (7, 8), which restraint limits the maximum spring relief. According to the invention, the restraint (22, 23) has a restraining cylinder (24) and a restraining piston (25), which can be axially slid in the restraining cylinder (24), wherein the restraining cylinder (24) has at least one lateral-wall opening (30) such that an interior of the restraining cylinder (24) is connected to an interior of the hydraulic cylinder (4).

Description

description

title

The invention relates to a master brake cylinder for a brake system of a brake master cylinder

Motor vehicle, having a plurality of hydraulic connections

Hydraulic cylinder, in which at least one hydraulic piston is mounted axially displaceable in an actuating direction and in a discharge direction, wherein the hydraulic piston is displaceable in the actuating direction against the force of a spring element, and wherein the spring element is assigned a bondage, which limits the maximum spring relief.

Furthermore, the invention relates to a brake system for a motor vehicle with such a master cylinder.

State of the art

Master brake cylinder of the type mentioned are known from the prior art. To the force exerted by a driver on a brake pedal actuating force in a hydraulic pressure for actuating hydraulic

To convert wheel brakes, it is known to connect the brake pedal mechanically with a hydraulic piston which is mounted axially displaceable in the hydraulic cylinder. When the driver actuates the brake pedal, the hydraulic piston is displaced against the force of a spring element, so that the spring element is pretensioned or further pre-stressed. By relocating the

Hydraulic piston in the hydraulic cylinder, a volume in the interior of the hydraulic cylinder is reduced, whereby a fluid located thereon is pressurized and through at least one of the hydraulic connections from the

Main cylinder is fed out to actuate at least one of the wheel brakes. If the driver removes his foot from the brake pedal, that sums it up tensioned spring element by its inherent elasticity of the hydraulic piston back to its original position, at the same time hydraulic medium passes through the hydraulic connections in the hydraulic cylinder, so that then the master cylinder is prepared for a further braking operation available.

Is the spring element associated with a bondage, this causes that the maximum relaxation of the spring element is mechanically limited in relief of the hydraulic piston by the driver.

Disclosure of the invention

The master cylinder according to the invention with the features of claim 1 has the advantage that the bondage has an ankle cylinder and an in the ankle cylinder axially displaceably mounted restoring piston, wherein the restraint cylinder has at least one jacket wall opening, so that a

Interior of the tether cylinder communicates with an interior of the master cylinder. Through the casing wall opening, a connection is created between the interior of the hydraulic cylinder and the interior of the tether cylinder, through which the fluid in the hydraulic cylinder also flows into the interior of the tether cylinder. As a result, the movement of the restraining piston in the restraining cylinder is also determined as a function of the pressure conditions in the interior of the restraining cylinder which result from the inflow or outflow of fluid. This will be a

Damping the movement of the tether piston achieved, which reduces in particular the maximum movement speed of the tether piston to a predetermined value, so that the maximum recoil speed of

Hydraulic piston is limited to a permissible value in a movement in the discharge direction. This will be a hard stop of

Hydraulic piston at the end of the hydraulic cylinder avoided and also a pedal swing on the brake pedal, which could be felt by the driver. Preferably, the master cylinder is also a

Associated with pedal force simulator, which at least one

Hydraulic accumulator has or forms, which the actuation of the

Counteracts hydraulic piston. This is also the pushing back of the Supported hydraulic piston in its initial position, but reduced by the advantageously trained bondage to a maximum dimension. The damped spring throttling reduces the acceleration of the brake pedal when the actuation force is removed, so that the brake pedal can move into its rest position without any further acceleration, whereby the brake pedal is prevented from oscillating or an acoustically perceptible striking of the brake pedal in its rest position. Preferably, shell wall opening is arranged in the anvil cylinder in such a way that the damping operation

or displacement of the hydraulic piston in the direction of actuation not hindered, wherein the damping is in particular maximum until reaching the hydraulic connection to the piston is effective.

According to a preferred embodiment, it is provided that the

Mantle wall opening opens into a section in the tether cylinder, in which the tether piston in a displacement of the hydraulic piston in

Actuation direction is reached. This ensures that when

Entering the brake pedal or when moving the

Hydraulic piston in the direction of actuation, the restorer piston is pressed into the restraint cylinder without later counterpressure, while the fluid in the chamber can flow out of the ankle cylinder and into the hydraulic cylinder. As a result, when the brake pedal is engaged, an advantageous volume compensation takes place, which does not impair the onset of the brake pedal. During the movement of the hydraulic piston in the loading direction by the spring element, the tether piston passes into a section of the

Bonding cylinder, which is formed free of mantle, so that in the remaining chamber, a fluid counteracts the movement of the piston, thereby ensuring the damping. By positioning the

Mantle wall opening or shell wall openings is thus adjustable in a simple manner, the damping effect of the bondage.

Preferably, the tether piston is guided radially at least substantially close to the tether cylinder. This ensures the effect described above, that the fluid in the closed chamber between

Tether piston and ankle cylinder movement in the unloading direction is essentially locked and the movement of the tether piston counteracts. Preferably, there is a radial leakage gap which determines the damping performance.

Furthermore, it is preferably provided that the ankle cylinder and the

Bonding piston each at their ends facing away from one another

Having end plate, wherein the spring element is held axially biased between the end plates. The bondage is thus formed at their ends by the end plates, between which the spring element is held axially biased. As a result, the spring element always urges the captive piston away from the front disk of the tether cylinder. Conveniently, the front disk of the tether piston is arranged on a piston rod, which leads through an end wall of the tether cylinder into the tether cylinder and is fixedly connected there to the tether piston. The ratio of the outer diameter of the piston rod to the inner diameter of the opening in the end face of the tether cylinder further affects the damping of the bondage when the piston is moved away in the direction of the front side of the forelock piston. By an appropriate choice of cross sections of

Piston rod and end wall opening to form a defined leakage gap thus the damping of the bondage can be influenced advantageously.

Preferably, the spring element is designed as a helical spring and arranged coaxially to captive piston and ankle cylinder. This form the

Bonding piston, the anvil cylinder and the clamped between the end plates of this coil spring an advantageous assembly unit, which can be prefabricated and easily arranged in the hydraulic cylinder.

Furthermore, it is preferably provided that at least one of the end plates is fixedly connected to the hydraulic piston. Alternatively, the piston rod is fixedly connected to the hydraulic piston, which then forms the front plate for the tether piston. Through the bondage is achieved that not only the

Acceleration of the brake pedal or the hydraulic piston is attenuated or limited in the discharge, but that actively the movement of the brake pedal and the hydraulic piston are braked. This is particularly advantageous in terms of the pedal, because this prevents too fast running back of the brake pedal and the user The feeling of a conventional brake pedal is simulated, which is given in conventional brake systems with vacuum brake booster.

Preferably, the other of the end discs with the hydraulic cylinder, in particular with an end wall of the hydraulic cylinder is firmly connected.

This ensures that the bondage has a fixed anchor point on the hydraulic cylinder, by means of which the braking effect is exerted on the hydraulic piston during the discharge.

Furthermore, it is preferably provided that the master cylinder as

Tandem cylinder formed with a further hydraulic piston, which is arranged axially displaceable in the master cylinder against the force of another spring element and between the hydraulic piston and a front end of the hydraulic cylinder. Tandem cylinders are already known from the prior art, so that at this point should not be discussed in detail on its structure. It is important that a tandem cylinder has not one, but two hydraulic pistons arranged in series in the

Hydraulic cylinders are arranged. The further hydraulic piston ensures that a further brake circuit is operated independently of a first brake circuit actuated by the hydraulic piston through the master brake cylinder.

Preferably, the further hydraulic piston associated with a further bondage, which is formed as described above bondage. This ensures that the total of the tandem cylinder, the pressing movement of the

Brake pedal dampens and optionally brakes, especially if the other bondage is also firmly connected to the other hydraulic piston on the one hand and the front side of the hydraulic cylinder on the other. The former restraint is expediently firmly connected to the one hydraulic piston and the other hydraulic piston and thus lies axially between them.

The brake system according to the invention with the features of claim 10 is characterized by the inventive design of the master cylinder. This results in the already mentioned advantages. Furthermore, the invention relates to a brake system for a motor vehicle, with a master cylinder, which is connected to at least one hydraulic circuit having at least one hydraulically actuated wheel brake.

Further advantages and preferred features and combinations of features result from the previously described and from the claims.

In the following, the invention will be explained in more detail with reference to the drawing. Show this

Figure 1 is a brake system of a motor vehicle in a simplified

Presentation,

2 shows a master cylinder of the brake system according to a first

Embodiment and

3 shows the master cylinder according to a second embodiment, each in a simplified longitudinal sectional view.

Figure 1 shows a simplified illustration of a brake system 1 for a motor vehicle, not shown in detail. The brake system 1 has a

Master brake cylinder 2, which is designed as a tandem cylinder and can be actuated by a brake pedal 3 by a driver of the motor vehicle. Of the

Master brake cylinder in this case has a hydraulic cylinder 4, in which a hydraulic piston 5, which is mechanically fixedly connected to the brake pedal 3, and a further hydraulic piston 6 are each mounted axially displaceable. Between the hydraulic piston 5 and the hydraulic piston 6 is a

Spring element 7 and disposed between the hydraulic piston 6 and an end face of the hydraulic cylinder 4, a further spring element 8 axially biased, so that between the hydraulic piston 5 and 6 each chambers in the

Hydraulic cylinder 4 are formed, with hydraulic connections of the

Brake system 1 communicate. In particular, two brake circuits 9 and 10 are connected to the master cylinder 2 by the hydraulic connections such that one of the brake circuits 9 with one of the hydraulic chambers and the other the brake circuits 10 is fluidly connected to the other hydraulic chamber. As a result, the two brake circuits 9, 10 through the

Master cylinder 2 are operated. The two brake circuits 9 and 10 are constructed substantially identical to each other. Each brake circuit 9, 10 has two wheel brakes LR, RF

or LF, RR, which can be actuated by intake valves 11 and exhaust valves 12 in the respective brake circuit 9, 10. The brake circuits 9, 10 are connected by high-pressure switching valves 13 each with one of the chambers of the master cylinder 2.

In a likewise connected to the master cylinder 2 tank 14, a fluid or a brake fluid is held, which in the

Brake circuits 9, 10 can be penetrated by actuation of the master cylinder 2. In the present brake system 1 is provided that on a

Vacuum brake booster is omitted. Therefore, the brake pedal 3 is also directly connected mechanically to the hydraulic piston 5. However, in order to give the driver the usual pedal feel, the brake system 1 also has a brake pedal feel simulator 15, which has a switching valve 16 and a pressure accumulator 17. The brake pedal feel simulator 15 functions to influence the pedal movement of the brake pedal 3 so as to correspond or nearly correspond to that of a brake pedal connected to a vacuum booster. This provides the driver with the accustomed brake pedal feel available.

According to the present embodiment, a

Brake force boost by an electromechanical brake booster 18 having a pump 19, in this case piston pump, which is driven by an electric motor 20 to increase a hydraulic pressure in the brake circuits 9, 10, if necessary. For this purpose, the brake circuits 9, 10 are connected by a respective switching valve 21 to the brake booster 18.

The spring elements 7, 8 of the master cylinder 2 ensure that the hydraulic piston 5, 6 are shifted back to an initial position after actuation by the brake pedal 3. Figure 2 shows this in a simplified longitudinal sectional view of the

Master brake cylinder 2 according to a first embodiment. 1 already known elements are provided with the same reference numerals, so that reference is made to the above description.

Each of the spring elements 7, 8 is associated with a bond 22 or 23. The two bondings 22, 23 are the same design, so that in the following structure and function of the two bonds with reference to the bond 22 will be explained in more detail.

The bondage 22 has an ankle cylinder 24, in which a

Tether piston 25 is mounted axially displaceable. In this case, the anvil cylinder 24 is aligned coaxially with the hydraulic cylinder 4, so that the

Displacement direction of the tether piston 25 of the direction of the

Hydraulic piston 5, 6 corresponds. The tether cylinder 24 has on a first end face an end plate 25 and on its second end face a

End wall 27, in which a passage opening is formed. Through the passage opening, a piston rod 28 which is fixed to the

Bonding piston 25 is connected. The piston rod 28 carries at her the

Fetter piston 25 opposite end another end plate 29. Between the two end plates 29 and 26, the respective spring element. 7

or 8 held axially biased. For this purpose, the spring element 7, 8 is designed as a helical spring which extends coaxially to the anvil cylinder 24 and the piston rod 28. Because the tether piston 25 is formed larger than the passage openings of the end wall 27, the tether piston 25 can be displaced maximally to the end wall 27. This limits the maximum

Expansion of the spring element 7 or 8. The tether piston 25 is radially sealing or at least substantially sealingly on the

Ankle cylinder 24 on. Preferably, a leakage gap remains. Likewise, preferably piston rod 28 and through hole are formed such that a leakage gap is formed between them, so that a fluid from the chamber between the captive piston 25 and the end wall 27 in the ankle cylinder 24 through the leakage gap either directly into the interior of the Hydraulic cylinder 4 can enter, or in the hydraulic chamber between the captive piston 25 and end plate 26th

In the tether cylinder 24 a plurality of shell wall openings 30 are formed, which are arranged close to the end plate 26. Through the jacket wall openings 30, the chamber is in the restraint cylinder 24 (between end plate 26 and restraint piston 25) in fluid communication with the interior of the

Hydraulic cylinder between the two hydraulic pistons 5 and 6

or between hydraulic piston 6 and the closed end face of the hydraulic cylinder 4th

Due to the advantageously formed restraints 22, 23, it is achieved that the speed of movement of the spring element 7, 8 is damped or braked during relief. As soon as the captive piston 25 has passed the shell wall openings 30 when the spring element 7 or 8 relaxes, a captive piston 25 and the end wall 27 are created

Through chamber or damper chamber, from which the fluid can escape only slowly due to the leakage column. This will be the

Movement speed of the tether piston 25 is limited in the anvil cylinder 24 and thus slows down the expansion behavior of the respective spring element 7, 8. This ensures that the respective spring element 7, 8 initially expands quickly and then only slowly to his

To reach the starting position. This has the advantage that the hydraulic piston 5, 6 only allowed a maximum by the respective bound spring

Movement speed at discharge, so if the driver takes his foot off the brake pedal 3, learn. As a result, stop noises of the hydraulic piston 5, 6 and pendulum movements are prevented on the brake pedal 3 itself, which can be perceived by the driver as unfamiliar and unpleasant.

Upon the onset of the brake pedal 3, the damping is effective until reaching a hydraulic connection to the piston. Due to the

Mantle wall openings 30 is also the bondage 22 or 23 upon actuation of the brake pedal 3 when the hydraulic piston 5 in

Actuating direction, as shown by an arrow 31, are shifted, within the tether cylinder 24 slightly slidable until the

Mantle wall openings 30 were run over. Only then will another kick

Damping, which ensures that a hard impact of the tether piston 25 on the end plate 26 and at the end plate 26 associated end of the tether cylinder 24 is prevented. For this purpose, the jacket wall openings 30 are spaced from the end wall 26 in the

Ankle cylinder 24 is formed.

When braking or relieving acts on the hydraulic piston 5, 6, the accelerating forces of the pedal feel simulator 15 and the spring forces of the spring elements 7, 8. The damped spring throttling reduces the

Acceleration of the brake pedal 3. From the time when a so-called sniffer hole in the master cylinder 4 is opened due to the position of the hydraulic piston 5, 6, the pedal feel simulator 15 due to the fact that it is purely hydraulically coupled to the master cylinder 4, exert no further driving hydraulic pressure , By the muted

Federfesselung 22 and 23 is also the accelerating moment of the spring elements 7, 8 limited, whereby the brake pedal 3 can run without further acceleration in its rest position, without causing a noise and / or vibrations on the pedal when reaching the selbigen.

Figure 3 shows an advantageous development of the master cylinder 3, wherein from Figure 2 already known elements are provided with the same reference numerals and insofar reference is made to the above description.

In the following, the differences should be dealt with essentially.

In contrast to the previous embodiment, it is provided that the end disks 29, 26 and the restraints 22, 23 respectively fixed to the hydraulic piston 5, 6 and the

closed end wall of the master cylinder 4 are connected. For this purpose, welds 32 are shown in FIG. 3 by way of example.

When the brake pedal 3 is actuated, the function is similar to that described above. When braking or relieving but is additionally achieved that due to the fixedly connected to the respective bond 22, 23 hydraulic piston 5, 6, the brake pedal 3 and the hydraulic piston 5, 6 is not only accelerated less strong, but also in addition to the damping and active braking through the damped bonds 22, 23 learns , This is particularly advantageous in terms of the experience experienced by the driver pedal feel, because thereby one too fast returning

Brake pedal 3 avoided and the feeling of a conventional

Vacuum brake booster is achieved.

If the advantageous master cylinder 4 used in a brake system 1 as described above, this has the advantage that the user is guaranteed a familiar brake pedal behavior, although a

Dispensed vacuum brake booster and instead, for example, an electromechanical or electro-hydraulic brake booster 19 is used in the brake system 1. In addition, impact sounds and / or generated by a hard impact

Stress / damage avoided in an advantageous manner with a compact design.

Claims

claims

A master brake cylinder (2) for a brake system (1) of a motor vehicle, comprising a hydraulic cylinder (4) having a plurality of hydraulic connections, in which at least one hydraulic piston (5, 6) is displaceably mounted axially in an actuating direction and in a relief direction, wherein the hydraulic piston (5,6) in the direction of actuation against the force of a spring element (7,8) is displaceable, and wherein the spring element (7,8) a bondage (22,23) is associated, which limits the maximum spring relief, characterized in that the Bonding (22, 23) has an anvil cylinder (24) and an in the anvil cylinder (24) axially displaceably mounted restraint piston (25), wherein the restraint cylinder (24) has at least one shell wall opening (30), so that an interior of the restraining cylinder (24) with an interior of the hydraulic cylinder (4) is in communication.

2. master cylinder according to claim 1, characterized in that the

Mantle wall opening (30) opens into a portion in the tether cylinder (24), in which the tether piston (25) is pressed in a displacement of the hydraulic piston (5,6) in the actuating direction.

3. Master cylinder according to one of the preceding claims, characterized

in that the tether piston (25) is guided radially at least substantially close to the tether cylinder (24).

4. master cylinder according to one of the preceding claims, characterized

characterized in that the anvil cylinder (24) and the captive piston (25) at their opposite ends each have an end plate (26,29), wherein the spring element (7,8) between the end plates (26,29) is held axially biased.

5. master cylinder according to one of the preceding claims, characterized in that the spring element (7,8) designed as a helical spring and coaxial with the captive piston (25) and ankle cylinder (24) is arranged.

6. master cylinder according to one of the preceding claims, characterized

characterized in that at least one of the end discs (29) with the

Hydraulic piston (5) is firmly connected.

7. master cylinder according to one of the preceding claims, characterized

in that the other of the end discs (26) is fixedly connected to the hydraulic cylinder (4), in particular to a closed end wall of the hydraulic cylinder (4).

8. Master brake cylinder according to one of the preceding claims, characterized by the design as a tandem cylinder with a further hydraulic piston (6), axially in the hydraulic cylinder (4) against the force of another

Spring element (7) displaceable and between the hydraulic piston (5) and the closed front end of the hydraulic cylinder (4) is arranged.

9. master cylinder according to one of the preceding claims, characterized

characterized in that the further hydraulic piston (6) is associated with a further bondage (23), which is formed according to the one bond (22).

10. brake system (1) for a motor vehicle, with a master cylinder (2), the

having at least one hydraulic circuit (10) which has at least one hydraulically actuable wheel brake (LR, RF, LF, RR),

characterized by the construction of the master cylinder (2) according to one or more of claims 1 to 9.