DE102020211652A1 - Adjustable simulator unit and braking device with simulator unit. - Google Patents

Abstract

The invention relates to a simulator unit (1) for a braking device (100) of a hydraulic motor vehicle brake system, for separately generating a counterforce (Fg) acting on an actuating member (2) actuated by a driver against an actuating force (Fb). In order to offer a simulator unit (1), in particular for brake-by-wire braking systems, the characteristic curve of which can be changed several times and in particular directly during driving, it is proposed according to the invention that the simulator unit (1) comprises an elastic element (3) which, when the actuating member ( 2) can be compressed with the actuating force (Fb) and that the simulator unit (1) has at least one integrated adjusting means (4) for adjusting a prestressing force (Fv) acting on the elastoelement (3) independently of the actuating force (Fb).

Description

The invention relates to a simulator unit according to the preamble of claim 1 for a brake device for a hydraulic motor vehicle brake system, in particular a hydraulic brake-by-wire motor vehicle brake system, and a corresponding brake device.

Electronically controlled braking systems, in particular so-called brake-by-wire braking systems, are increasingly being used in modern vehicles. Such braking systems have several advantages over conventional braking systems. If necessary, braking can be carried out completely independently of the driver and flexibly adapted to the respective driving situation. The installation space required is reduced compared to a conventional brake system, and it can also be placed more flexibly in the vehicle. Modern brake-by-wire motor vehicle brake systems are operated in their regular braking mode by sensor-based detection of a braking request from the driver indirectly and electronically controlled completely independently of the driver. In order to supply a required system pressure in such a regular braking mode, a driver-independently controllable pressure generator is used, which is mostly driven by an electric motor.

With conventional braking systems, when the brake pedal is depressed, the pressure from the hydraulic circuit exerts a reaction force back into the driver's pedal.

This force varies depending on the braking scenario, vehicle load and road conditions. There is no such direct feedback in brake-by-wire systems because the brake pedal is decoupled from the hydraulic brake system.

There is therefore a need to give the driver a familiar and comfortable pedal feel despite the lack of direct feedback. It is known that special simulator units can be used to separately induce a feedback force in the sense of targeted generation of a resistance profile or a characteristic curve on the brake pedal, which is as similar as possible to a conventional brake system. Simulator units of different types of actuation are known from practice, for example mechanical, electrical, hydraulic or a combination.

It is known to equip a simulator unit with at least one viscoelastic element, in particular an element made of an elastomeric material, in which at least the essential part of the c is generated. The desired characteristic curve is specifically defined by the structural design of this element and remains over the entire service life.

The disadvantage of such a solution is that the characteristic curve of the simulator unit remains independent of the acute braking scenarios or the state of the road. Certain specific behaviors of a conventional braking system cannot be reproduced. For example, the pulsation of the brake pedal during anti-lock braking interventions, changes in pedal feel in the event of a pressure loss in the hydraulic circuit or other failure conditions.

The object is therefore to offer a simulator unit, in particular for brake-by-wire braking systems, whose characteristic curve can be changed several times and, in particular, directly during driving operation.

The object is achieved according to the invention by a simulator unit with the combination of features according to claim 1. Subclaims specify further advantageous embodiments and developments of the invention.

The invention provides that the simulator unit has at least one integrated adjusting means for adjusting a prestressing force acting on the elastic element independently of the actuating force.

As a result, the characteristic curve of the simulator unit can be changed statically or dynamically at any time. For example, the same simulator unit can be offered for different vehicle types with different feedback properties without additional manufacturing, conversion and logistics costs. The behavior of the simulator unit can also be dynamically parameterized according to the driver's wishes, for example to simulate a "sport" mode or in "comfort" mode.

According to a preferred embodiment of the invention, the adjusting means can be equipped with a robust tappet unit which acts mechanically on the elastic element.

For an effective, flexible and automatable adjustment, the preferred embodiment also provides that the adjustment means comprises an electrically controllable actuator which actuates the tappet unit.

For a simple and space-saving design, the elastic element can be effectively braced between the tappet unit and a pressure piece, which acts mechanically on the elastic element through the actuating force, with the Pressure piece is actuated by a piston arranged in the simulator unit and acted upon hydraulically by the actuating force.

In order to be able to map the braking behavior of a conventional brake system, including various characteristic control interventions, as precisely as possible, a development of the invention provides that the tappet unit is designed in multiple parts. It can have a head part that acts directly on the elastoelement and a drive part that can be rotated relative to the head part in the central axis and is provided for transferring and introducing the prestressing force from the actuator into the head part. There is also a switchable locking device which, if required, can couple the drive part to the head part in a twist-proof manner.

For simulating anti-lock braking or stability interventions, one embodiment of the invention provides that the simulator unit has at least one integrated means for generating a pulsation of the counterforce, which preferably acts through a mechanical interaction between the elastoelement and the ram unit.

According to a development, the means for generating a pulsation in a contact section between the elastic element and the ram unit has alternating elevations and depressions on corresponding surfaces of the two components, which cause a pulsating change in the prestressing force when the surfaces slide against one another.

The invention also claims a braking device with at least one simulator unit according to the invention.

• 1 einen prinzipiellen Aufbau eines gattungsgemäßen Bremsgeräts.
• 2 beispielhafte Darstellung eines gattungsgemäßen Brake-by-Wire-Bremsgeräts in Außenansicht (a) sowie Innentopologie mit einigen stark vereinfacht dargestellten Elementen (b).

• 3 ein Ausführungsbeispiel einer erfindungsgemäßen Simulatoreinheit in Axialschnitt.
• 4 räumliche Darstellungen einer Stößeleinheit gemäß 3.
• 5 räumliche Darstellungen eines Elastoelements gemäß 3.

Further features and advantages of the invention result from the following description. Shown below:

• 1 a basic structure of a generic braking device.
• 2 exemplary representation of a generic brake-by-wire braking device in an external view (a) and internal topology with some elements (b) represented in a greatly simplified manner.

• 3 an embodiment of a simulator unit according to the invention in axial section.
• 4 spatial representations of a ram unit according to 3 .
• 5 spatial representations of an elastoelement according to 3 .

1

1 shows an example of a part of a generic braking device 100 with a known simulator unit 1 as a simplified basic design sketch.

Braking device 100 has a master cylinder unit 15 that can be actuated by a driver using an actuating member 2 with an actuating force Fb. In the example shown, this is designed as a tandem master cylinder. In principle, the invention can also be used with other master cylinder variants. Likewise, within the invention, the actuating element 2 can also be coupled in some other way, for example to a brake lever, instead of to a brake pedal shown here.

In the tandem master cylinder unit 15 shown, a primary cylinder piston 17 actuated directly by the driver and an indirectly actuated secondary cylinder piston 17' delimit two pressure chambers 16, 16', which are fed with a brake fluid from a pressure medium tank 23.

Braking device 100 can be operated in a regular braking mode and in an irregular braking mode, a so-called fallback level. In the regular braking mode, movements of the actuating member 2 are detected by a sensor arrangement (not shown here), whereupon an electronic control unit 24 controls an electromotive pressure generator 22 . The pressure generator 22 generates the required service brake pressure for the wheel brakes, not shown here. If required, the pressure generator 22 can also be controlled entirely independently of the driver, for example in an autonomous driving mode.

The pressure chamber 16 of the master cylinder unit 15 is connected hydraulically to a simulator unit 1 in the regular braking mode. An electrically controllable, normally closed check valve 20 controls this override.

The simulator unit 1 has a piston 8 which is axially displaced by the brake fluid from the master cylinder unit 15 and compresses a viscoelastic elastomeric element 3 in the course of its stroke via an interposed pressure piece 7 . This creates a characteristic path-dependent resistance. This resistance is perceived by the driver via the actuating member 2 as a feedback force or counterforce Fg directed in the opposite direction to his applied actuating force Fb. The geometric and physical properties of the elasto-element 3 decisively influence the characteristic curve of the simulator unit 1.

In the event of a malfunction, for example failure of the sensors, the electrical supply or a fault in the pressure generator 22, the system is switched to an irregular braking mode. The simulator unit 1 is hydraulically separated from the master cylinder unit 15 by the check valve 20 . The service brake pressure is then generated directly in the pressure chamber 16′ solely by the driver’s muscle power and is conducted to the friction brakes, which are not shown here. Another electrically controllable valve arrangement 21, which is closed in the regular operating mode, is opened in the fallback level and thus enables the master cylinder unit 15 to be switched off directly on the wheel brakes.

Fig.2

2 shows an example of an embodiment of a generic brake-by-wire braking device 100 in an external view (a) and a greatly simplified arrangement of add-on components on the outside of the housing and the master cylinder unit 15 and the simulator unit 1 inside (b).

Fig.3

3 shows an embodiment of a simulator unit 1 according to the invention.

When the simulator unit 1 is actuated, hydraulic pressure is applied to a piston 8 by brake fluid, which is conveyed into the simulator unit 1 via a hydraulic channel from a master cylinder unit 15 described above. The piston 8 is thereby axially displaced in the direction of the elastoelement 3 and presses with its radial outer edge against a pressure piece 7 which is mounted so as to be axially displaceable relative to the piston 8 and which is then pressed against the elastoelement 3 and compresses it. A counterforce Fg′ exerted by the elastic element on the pressure piece 7 is fed back via the piston 8 and the brake fluid and is felt by the driver as a characteristic path-dependent resistance when the actuating member 2 is actuated.

A spring element 25 clamped between the piston 8 and the pressure piece 7 supports the return of the piston 8 to its unactuated starting position after the driver has stopped actuating the brakes. Furthermore, the spring element ensures that the pressure piece 7 is permanently in contact with the elastic element 3, even when the piston 8 is in the non-actuated initial position.

As already mentioned above, the elastic element exerts a significant influence on the characteristic curve of the entire simulator unit 1. The elastic element is preferably made of a viscoelastic material such as EPDM, rubber or silicone materials. In particular, in contrast to a steel spring, it has a progressive resistance curve when deformed and also generates a hysteresis, which means that a better simulation of the feedback of a conventional brake system can be achieved.

The simulator unit 1 according to the invention has an adjusting means 4 integrated into it, with which the elastic element 3 can be compressed separately and independently of the actuating force Fb. As a result, the path-dependent resistance of the elasto-element 3 can be changed at any time when it is actuated by the driver, and thus the characteristic of the simulator unit 1 can be changed.

The adjusting means 4 in the exemplary embodiment shown has an actuator 5 which can be electrically controlled by the electronic control unit 24 and which actuates a plunger unit 6 and displaces it axially.

The tappet unit 6 is arranged axially on a side of the elastic element 3 opposite the pressure piece 7 . An actuating rod 26 coupled thereto presses the ram unit 6 against the elastic element 3 with a prestressing force Fv set by the actuator 5, as a result of which the elastoelement 3 is braced and compressed between the pressure piece 7 and the ram unit 6. The actuating rod 26 is preferably designed in such a way that both axial and circumferential forces can be introduced onto the tappet unit 6, for example as a type of toothed rack. The adjustment of the tappet unit 6 can take place before or during a braking process, as a result of which the characteristic curve of the simulator unit 1 can be changed both statically and dynamically.

The plunger unit 6 is designed in several parts. On its side facing the actuator 5, the plunger unit 6 has a drive part 10 at its end, which interacts with the actuating rod 26 and into which actuating forces from the actuator 5 are introduced.

On its side facing the elastoelement 3 , the ram unit 6 has a head part 9 at the end, which is mounted such that it can rotate about the center axis A relative to the drive part 10 .

Furthermore, the plunger unit 6 has a switchable locking device 11. By activating the locking device 11, the head part 9 can be locked relative to the drive part 10 or fixed against rotation at any time.

Fig.4

4 shows the ram unit 6 according to FIG 3 in a spatial external view. On its end face facing the elastoelement 3, there are rib-shaped elevations 13 distributed regularly around the circumference on the head part 9 of the plunger unit 6. Between the adjacent elevations 13 there is necessarily a depression 14.

Fig.5

5 shows the elastic element 3 according to FIG 3 in a spatial external view of its side facing the plunger unit 6 . A trough provided for accommodating the head part 9 is designed as a kind of negative form or complementary profile of the head part 9 and forms elevations 13' and depressions 14', also distributed alternately over the circumference. The respective elevations 13' correspond to the depressions 14 of the head part 9, the depressions 14' correspond to the elevations 13 of the head part 9.

If necessary, the head part 9 can be secured against rotation by means of the locking device 11 with the drive part 10 and the drive part 10 can be rotated about the central axis A by the actuator 5 . At the beginning of the application of the torque in the drive part, the head part 9 and the elastic element 3 remain interlocked by the corresponding elevations 13, 13' and depressions 14, 14'. When a specific torque threshold is reached, however, the surfaces of the elastic element 3 and the head part 9 that are in contact with one another slide off one another. The elevations 13, 13' and depressions 14, 14' jump over to their next possible adjacent toothed position. This generates an axial force impulse. As a result of this mechanical interaction between the elastoelement 3 and the head part 9, the elastoelement 3 is loaded axially in the direction of the pressure piece 7 in addition to the static component of the preload force Fv with a regularly increasing dynamic component of the preload force Fv. This dynamic component of the prestressing force Fv is subsequently transmitted via the pressure piece 7 to the piston 8 and via the brake fluid as a perceptible pulsation of the counterforce Fg to the actuating element.

reference list

1

simulator unit

2

actuator

3

elastic element

4

adjusting means

5

actuator

6

ram unit

7

Pressure piece

8th

Pistons

9

headboard

10

drive part

11

locking device

12

medium

13

increase

14

deepening

15

master cylinder unit

16

pressure chamber

17

cylinder piston

18

19

hydraulic channel

20

check valve

21

valve assembly

22

pressure generator

23

pressure fluid tank

24

control unit

25

spring element

26

operating rod

100

braking device

A

central axis

color

operating force

fg

counterforce

Fv

preload force

Claims (10)

Simulator unit (1) for a braking device (100) of a hydraulic motor vehicle brake system, for separately generating a counterforce (Fg) acting on an actuating member (2) actuated by a driver against an actuating force (Fb), characterized in that the simulator unit (1) Elastoelement (3) which can be compressed with the actuation force (Fb) when the actuation member (2) is actuated and that the simulator unit (1) has at least one integrated adjusting means (4) for adjusting a force acting on the elastoelement (3) independently of the actuation force ( Fb) acting preload force (Fv). Simulator unit (1) after claim 1 characterized in that the adjusting means (4) has a tappet unit (6) which acts mechanically on the elastic element (3). Simulator unit (1) after claim 2 characterized in that the adjusting means (4) comprises an electrically controllable actuator (5) which actuates the tappet unit (6). Simulator unit (1) after claim 2 or 3 characterized in that the elastic element (3) is clamped between the tappet unit (6) and a pressure piece (7) which acts mechanically on the elastic element (3) by the actuating force (Fb). Simulator unit (1) after claim 4 characterized in that the pressure piece (7) is actuated by a piston (8) which is arranged in the simulator unit (1) and is hydraulically acted upon by the actuating force (Fb). Simulator unit (1) according to at least one of claims 2 until 5 characterized in that the ram unit (6) is designed in several parts with a head part (9) for directly acting on the elastic element (3), with a drive part (10) for transmitting and introducing the prestressing force (Fv) into the head part (9), the drive part (10) being arranged such that it can rotate about a central axis (A) relative to the head part (9) and having a switchable locking device (11) for selectively locking and releasing the ability to rotate between the drive part (10) and the head part (9). Simulator unit (1) according to at least one of the preceding claims, characterized in that the simulator unit (1) has at least one integrated means (12) for generating a pulsation of the counterforce (Fg). Simulator unit (1) after claim 7 and at least one of the claims 2 until 6 characterized in that the means (12) acts through a mechanical interaction between the elasto-element (5) and the ram unit (6). Simulator unit (1) at least after claims 6 and 8th characterized in that in at least one contact section between the elastic element (5) and the ram unit (6), alternating elevations (13, 13') and depressions (14, 14') are formed on corresponding surfaces of the two components, which when the surfaces slide off together cause a pulsating change in the preload force (Fv). Braking device (100) with at least one simulator unit (1) according to at least one of the preceding claims.

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