DE102016219792A1 - Electronically slip-controlled brake system and method for controlling an electronically slip-controlled brake system - Google Patents

Abstract

The invention relates to an electronically slip-controlled brake system (10), and to a method for controlling an electronically slip-controlled brake system (10). The brake system (10) comprises an actuatable master cylinder (16) to which at least one wheel brake (26a, 26b), the one wheel (34a, 34b) of a front axle (36) of the vehicle and at least one wheel brake (26c, 26d) a wheel (34c, 34d) is associated with a rear axle (38) of the vehicle, are separably connected. An electronically controllable first actuator (30) of the brake system (10) is used to set and control mutually different brake pressures in the wheel brakes (26a-26d) in dependence on the prevailing slip conditions. An electronically controllable second actuator (24) causes adjustment and regulation of a uniform brake pressure at the wheel brakes (26a-26d) and a third actuator (42) limits the brake pressure generated by the second actuator (24) at the at least one wheel ( 34c, 34d) of the rear axle (38) associated with the wheel brake (26c, 26d). An electronic control of the actuators (30, 34, 42) is performed by at least one electronic control unit (22). According to the invention, the third actuator (42) is fluidically connected in series with the first actuator (30) arranged upstream of the third actuator (42) and with the wheel brake (26c, 26d) of the rear axle (38) of the wheel arranged downstream of the third actuator (42) vehicle.

Description

State of the art

The invention relates to an electronically slip-controllable brake system according to the features of the preamble of claim 1 and to a method for controlling an electronically slip-controllable brake system, according to the features of the preamble of claim 5.

An electronic slip-controllable brake system for a motor vehicle is known, for example from the DE 10 2009 001135 A1 ,

This known brake system comprises a first actuator, hereinafter referred to as primary actuators, in the form of a conventional ABS / ESP brake system for wheel-specific modulation of the brake pressure as a function of prevailing at the wheels slip conditions. The brake pressures of the individual wheel brakes can be set or regulated independently of each other. In connection with a conventional 4-wheeled motor vehicle is therefore spoken of a 4-Kanal-Regelungsaktuatorik. The braking system includes i.a. a hydraulic unit of a housing equipped with pumps and valves housing block and an electronic control unit that operates these pumps and valves in response to sensor signals representing the slip conditions at the individual wheels. Each brake of the vehicle brake system is assigned a brake pressure build-up valve and a respective brake pressure reduction valve for braking pressure control.

This primary actuation makes it possible to stabilize the running state of a vehicle during a braking operation, during start-up or while driving, by reducing the brake pressure at wheel brakes of slip-loaded wheels. This reduced brake pressure can be generated together with the driver or independently of the driver. The primary actuators work accordingly in a so-called partially or in a fully active mode.

Furthermore, the known vehicle brake system has a second actuator or secondary actuator in the form of an electromechanical brake booster. This secondary actuation is typically connected to the master cylinder and, in normal operation, enhances ride comfort by assisting the driver in establishing a brake pressure necessary for braking. An electromechanical brake booster for this purpose comprises an electronically controllable actuator, which provides an external force for actuating a master brake cylinder. The actuation of the master cylinder can be done solely by the external force of the secondary actuators or by a combination of this external force with a muscle power provided by the driver.

First and second actuators or primary actuators and secondary actuators therefore form two mutually redundant systems for generating and modulating a brake pressure in a vehicle brake system, wherein this brake pressure modulation can be carried out in each case with or without the driver's involvement. The two actuators thus fulfill an essential prerequisite for the realization and implementation of a partially or fully automated driving operation. Because during such an automated driving operation, the driver only performs a control or monitoring function, there are particularly high demands with regard to the reliability of such electronically pressure-controllable vehicle brake systems, which are met by providing the two explained actuators.

However, in contrast to the primary actuation, the secondary actuation is only able to supply all the wheel brakes of the vehicle brake system connected thereto with a uniform brake pressure by actuation of the master brake cylinder or to uniformly modulate this brake pressure. This mode of operation is referred to in professional circles as a 1-channel control actuator. A 1-channel designed secondary actuators is still sufficient to decelerate in the event of a malfunction of the primary actuators a vehicle while maintaining its directional stability to a standstill.

Minimum requirements for longitudinal or directional stabilization of the vehicle are adhering to a blocking order, that is, a brake pressure build-up such that the wheel brakes of the front axle temporally block in front of the wheel brakes of the rear axle, also maintaining the controllability of the vehicle and thus ensuring a maximum blocking time of the vehicle wheels as well as the possibility of an active or driver-independent construction of a brake pressure.

In particular, the mentioned criterion of the blocking time limit of the wheels causes the maximum achievable deceleration values of the vehicle to depend on the braking power that can be converted by the wheel brakes of the rear axle. This convertible Hinterachsbremsleistung is relatively low due to the taking place during a braking inertial reasons dynamic axle load shift in the direction of the front axle. Since an axle load increase at the front axle is forcibly accompanied by an axle load reduction of the rear axle, their wheels tend significantly earlier or at lower brake pressures for Blocking, as the more heavily loaded front wheels.

Due to the explained property of the secondary actuators all existing wheel brakes can apply only with a uniform brake pressure, in combination with a low convertible by the wheel brakes of the rear brake pressure, without risk of locking the associated wheels, resulting in the case of a braking operation in which the brake pressure due to a occurred malfunction of the primary actuators applied by the secondary actuators is the disadvantage that the achievable total braking power of the vehicle fails only relatively low or that consistently sets a relatively long braking distance of the vehicle. This has a particularly negative effect on vehicles in which the dynamic axle load displacement in the direction of the front axle during a braking operation is particularly large.

To avoid this disadvantage, it is also known to equip generic electronic pressure-controllable vehicle brake systems on the wheel brakes of the rear axle with a further actuator, hereinafter referred to as the third actuator.

This third actuator is another electronically controllable unit which is activated in case of failure of the primary and which adjusts the provided by the secondary brake pressure at the wheel brakes of the rear axle to the taking place during this braking weight reduction of the rear axle. This makes it possible by appropriate control of the actuator of the secondary actuators that this provides a brake pressure which is fully implemented only by the wheel brakes of the heavily loaded front axle in a braking power by the third actuator interrupts a further increase in the brake pressure at the wheel brakes of the rear axle, as soon as this brake pressure approaches a threshold value up to which this brake pressure can still be fully converted into a braking power. In other words, the third actuator technology overrides the described restriction of the brake pressure level of the vehicle brake system to the lower brake pressure level that can be converted by the wheel brakes of the rear axle, and moreover makes it possible for the braking power transferable by the wheel brakes of the front axle to be fully exploitable. As a result, a greater overall brake line of the vehicle brake system and, consequently, a significant shortening of the braking process or the braking distance can be achieved in this way.

Advantages of the invention

An electronically slip-controllable vehicle brake system according to the features of claim 1 is in addition to the primary and the secondary actuators equipped with a third actuator, which is simple in design, compact builds, easily integrated into an existing brake circuit and, accordingly, cost feasible.

According to the invention, the third actuator is fluidically connected in series with the primary actuator disposed upstream of the third actuator and the wheel brake of the rear axle arranged downstream of the third actuator.

Further advantages or advantageous developments of the invention will become apparent from the dependent claims and / or the following description.

The third actuator comprises per wheel brake of the rear axle in each case a directional control valve, which is identical to the known brake pressure build-up valve of the primary actuators, in the non-controlled state open or permeable for pressure medium valve. With an activation or electronic activation, the directional control valve switches over into a blocking position and thus prevents a further flow of pressure medium to or from the assigned wheel brake of the rear axle. Consequently, there is no further build up of brake pressure on the wheel brakes of the rear axle and the prevailing brake pressure is maintained.

An activation of the third actuator is performed when a malfunction of the primary actuators has been detected and the brake pressure generated by the Sekundäraktuatorik is higher than the convertible from the wheel brakes of the rear brake pressure, so if the wheel brakes of the rear axle tend to uncontrolled locking. With activation or activation of the third actuator, the brake pressure at the wheel brake of the rear axle is adjusted as far as the relief of the rear axle taking place during a braking process, de facto taken back that this brake pressure of the wheel brakes concerned can still be converted into a braking power without that a wheel brake assigned to the rear axle blocked.

The third actuator is advantageously constructed separately from the pressure-medium-controlling components of the primary actuators and uses specially this third actuator associated with components. On the one hand, this has the advantage that the components of the primary actuators are not exposed to an increased load profile for the extended functional safeguarding of a vehicle brake system according to the invention, but that, on the other hand, the components However, due to the existing identical construction with the components of the primary actuators, the third actuators are nevertheless available in large quantities and thus relatively inexpensive on the market. With regard to the durability of the components of the third actuator can be largely used on the known test results of the primary actuators, the components of the third actuator over the lifetime have a significantly lower load profile than the corresponding components of the primary actuators, since they are activated only in case of failure of this primary. Alternatively, the components of the third actuator can be arranged on the hydraulic unit of the primary actuators.

Likewise, the electronic control unit of the vehicle brake system can be combined with that for the third actuator or it can be used separate control units. The invention thus allows a high degree of design freedom with manageable costs and yet compact design.

drawing

An embodiment of the invention is illustrated in the drawing and will be explained in detail in the following description.

1 shows, schematically simplified, the essential components of the invention underlying electronic slip-controllable vehicle brake system and also represents the pressure medium connections existing between these components;

2 illustrates the construction of a third actuator and their arrangement within an electronic pressure-controllable vehicle brake system according to the invention.

Description of the embodiment

The electronic slip-controllable vehicle brake system 10 to 1 includes, for example, a. Via a brake pedal 12 by a driver by muscle power operable actuator 14 and one of this actuator unit 14 applied master cylinder 16 which is from an attached reservoir 18 is supplied with pressure medium. The operating unit 14 is with an electronically controllable actuator 20 equipped, by which the braking force applied by the driver can be enhanced by a foreign force. With this actuator 20 is, for example, an electronically controllable electric motor with downstream transmission. The control of the electric motor takes place in dependence on the operation of the brake pedal 12 , These are sensors (not visible) on the brake pedal 12 provided, which detect the actuation force and / or the actuation path and thus a braking request of a driver and their sensor signals from an electronic control unit 22 be evaluated for calculating the drive signals for the electric motor. The electronically controllable brake booster or the actuating unit 14 forms within the vehicle brake system, a so-called second actuator 24 or secondary actuators. The latter is capable of wheel brakes 26 the vehicle brake system 10 uniformly apply to brake pressure.

The second of this actuator 24 operated master cylinder 16 supplies two separate brake circuits with pressure medium and is via two pressure-medium-carrying lines 28a . 28b to a first actuator or primary actuators 30 connected.

In this primary actuators 30 it is the hydraulic unit of a well-known from the prior art slip-controllable vehicle brake system, which is also known under the name ABS / ESP brake system. To this first actuator or primary actuators 30 are druckmittelitend a total of four wheel brakes 26a - 26d connected. Two of these wheel brakes 26a . 26b There are wheels 34a . 34b a front axle 36 or wheels 34c . 34d a rear axle 38 assigned to the vehicle. The primary actuators 30 is different from secondary 24 capable of the different wheel brakes 26 the vehicle brake system 10 to supply individually with different brake pressures. For this purpose, this primary features 30 including a in the 1 unrecognizable and drivable by a controllable electric motor pressure generating unit as well as an electronically controllable Druckaufbau- and a likewise controllable pressure reduction valve per wheel brake 26 , The modulation of the brake pressure takes place as a function of the slip conditions that prevail at the relevant wheel 34 predominate and which are detected by means of speed sensors (not shown). The signals of these speed sensors are the electronic control unit 22 supplied and further processed to drive signals for the electric motor of the pressure generator unit and for the valves.

Two brake lines 40c . 40d are about a third actuator 42 the vehicle brake system 10 with the two wheel brakes 26c . 26d at the rear axle 38 connected. This third actuatorics 42 is downstream of the primary actuators 30 and upstream of the wheel brakes 26c . 26d the rear axle 38 arranged. Primäraktuatorik 30 , third actuatorics 42 and the wheel brakes 26c . 26d the rear axle 38 are therefore connected in series or in series.

In normal operation of the vehicle brake system 10 is the necessary brake pressure by an adapted electronic control of the second actuator or secondary actuators 24 in response to an operation of the brake pedal 12 provided and possibly by electronic control of the first actuator or primary actuators 30 according to the at the wheels 34a - 34d prevailing slip conditions adapted as needed. The brake pressure build-up or the brake pressure modulation can be carried out with or without driver participation, for example, if the driving condition of the vehicle or the traffic conditions require it, or the vehicle is operated in an autonomous driving.

Despite all technical precautions are disturbances in the intended operation of the vehicle brake system 10 not be ruled out. In case of disturbance of the primary actuators 30 is the secondary actuators 24 able to build up brake pressure automatically and decelerate the vehicle to a standstill. Primäraktuatorik 30 and secondary actuators 24 are therefore redundant to each other, the Sekundäraktuatorik 24 in case of failure, the function of the primary 30 safeguards.

As explained above, the third actuator is 42 present to the brake pressure level at the wheel brakes 26c . 26d the rear axle 38 opposite the brake pressure level at the wheel brakes 26a . 26b the front axle 36 lower, if in case of failure of the primary 30 the secondary actuators 24 is activated to decelerate the vehicle and when doing so from the secondary actuators 24 Provided brake pressure not from all wheel brakes 26a - 26d especially not from the wheel brakes 26c . 26d the rear axle 38 , in full in a braking performance is feasible.

The third actuatorics 42 is controlled in this case such that it provides the brake pressure at the wheel brakes 26c . 26d the rear axle 38 a takes place during braking dynamic displacement of the axle load and thus premature blocking of the wheel brakes 26c . 26d the rear axle 38 prevents as well as an associated unstable driving condition and / or an extension of the braking distance of the vehicle. In other words, the third actuator technology lowers 42 the brake pressure at the wheel brakes 26c . 26d the rear axle 38 so far off that the wheel brakes 26c . 26d associated wheels 34c . 34d Just roll off and do not block unchecked.

Based on 2 is the structure of the invention of a third actuator 42 illustrated. In this case forms the first actuator or primary actuators 30 in 2 the central element of the vehicle brake system 10 to which about two pressure medium lines 28a . 28b the master cylinder, not shown here, and indirectly via the master cylinder, the secondary and the brake pedal are connected. Furthermore, a total of four brake lines go 40a - 40d from the primary actuators 30 off, at the ends of the wheel brakes 26a - 26d the vehicle brake system 10 are located. The in the 2 above drawn wheel brakes 26a . 26b are doing a front axle 36 assigned to the vehicle while in 2 bottom drawn wheel brakes 26c . 26d a rear axle 38 are assigned to the vehicle. In the two brake lines 40c . 40d to the wheel brakes 26c . 26d the rear axle 38 There is an electronically controlled directional control valve 44 , The latter is fluidically between the primary actuators 30 and the respectively associated wheel brake 26c . 26d arranged so that the explained three components are fluidly connected in series or in series. The wheel brakes 26c . 26d the rear axle 38 associated directional control valves 44 are identical to each other and are also in a common valve body 46 accommodated.

Each directional valve 44 has two pressure medium connections 48a . 48b ; a first connection 48a to the primary actuators 30 and a second pressure medium connection 48b to the assigned wheel brake 26c . 26d at the rear axle 38 of the vehicle. In the illustrated basic position, the directional control valves 44 electronically not activated and the two pressure medium connections 48a . 48b are connected. Pressure medium can therefore from the Primärraktuatorik 30 through the third actuator 42 through to the wheel brake 26c . 26d flow through. Likewise, the pressure medium from the wheel brake 26c . 26d back to primary actuators 30 flow, because the way valve 44 can be flowed through in both directions. The directional valve 44 is powered by an elastic return element 50 symbolically represented by means of a return spring, held in the illustrated basic position or put back into this basic position, for example. If a previously made electronic control by the electronic control unit 22 withdrawn or discontinued. An electronically controllable valve actuator 52 acts on this return element 50 opposite. With its control, the directional control valve 44 switched from the basic position to a switching position. Intermediate positions of the directional valve 44 are not provided here; In principle, however, it would be possible the directional control valve 44 form for this purpose as a proportional valve. In the switching position is the connection between the pressure medium connections 48a . 48b of the directional valve 44 interrupted, so that no pressure medium from the primary actuators 30 to the wheel brake 26c . 26d to or from the wheel brake 26c . 26d to the primary actuators 30 can flow back. The drawn way valve 44 can also be referred to as normally open 2/2-way switching valve.

The directional valve 44 is also a bypass 54 connected in parallel. A pressure medium flow through this bypass 54 is from a check valve 56 controlled, which is designed such that there is a pressure fluid flow from the wheel brake 26c . 26d in the direction of primary actuators 30 while blocking the reverse flow direction. The check valve 56 is controlled by a prevailing pressure difference across it.

As already stated, each wheel brake 26c . 26d the rear axle 38 the vehicle each such a directional control valve 44 with such a bypass 54 assigned. The two units are preferably, as shown by the dash-dotted outline, in one of the primary actuators 30 separate valve housing 46 arranged; Alternatively, however, it would be possible the directional valves 44 and bypasses 54 the third actuatorics 42 on the hydraulic unit of the primary actuators 30 train. Likewise, for controlling the third actuator 42 an electronic control unit can be used which in the control unit 22 primary and / or secondary actuators 30 . 24 is integrated or by a separate control unit, the structurally separate from the control unit 22 the primary actuators 30 is trained.

By controlling the directional control valves 44 can the pressure medium connection between primary actuators 30 and wheel brakes 26c . 26d the rear axle 38 interrupt. This interruption takes the electronic control unit before the pressure level at these wheel brakes 26c . 26d achieved in the context of a brake pressure build-up in a braking operation, a threshold, which due to the dynamic axle load shift of these wheel brakes 26c . 26d is no longer fully implemented in a braking performance and up to which the wheel brakes 26c . 26d the rear axle 38 the braking power without blocking the associated wheels 34c . 34d can implement.

The intended third actuator 42 is in trouble-free normal operation of the vehicle brake system 10 inactive. Only when from the electronic control unit 22 a disturbance of the primary actuators 30 has been determined and the brake pressure from the Sekundäraktuatorik 24 is also the third actuator 42 activated. Even then, however, there is an electronic control of the associated directional control valves 44 only if that of the secondary actuators 24 provided brake pressure because of the axle load shift of the wheel brakes 26c . 26d at the rear axle 38 is no longer fully implementable in a braking performance, that is, when the associated wheels 34c . 34d block unchecked.

That the way valves 44 the third actuatorics 42 parallel check valve 56 has the function of having a brake pressure reduction in the wheel brakes 26c . 26d the rear axle 38 unthrottled and thus possible delay as soon as the pressure drop at the check valve 56 has changed to that effect, that is, when the brake pressure upstream of the directional control valves 44 less than downstream of it.

Of course, changes or additions to the described embodiment are conceivable without departing from the spirit of the invention.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009001135 A1 [0002]

Claims (5)

Electronically slip-controlled brake system ( 10 ), in particular for a motor vehicle, comprising - an actuatable master cylinder ( 16 ), to the at least one wheel brake ( 26a ; 26b ), which is a wheel ( 34a ; 34b ) of a front axle ( 36 ) of the vehicle and at least one wheel brake ( 26c ; 26d ), which is a wheel ( 34c ; 34d ) a rear axle ( 38 ) is associated with the vehicle, are connected; An electronically controllable first actuator system ( 30 ) for setting and regulating mutually different brake pressures in the wheel brakes ( 26a - 26d ) depending on the prevailing slip conditions; An electronically controllable second actuator system ( 24 ) for the at least indirect setting and regulation of a uniform brake pressure at the wheel brakes ( 26a - 26d ) of the vehicle brake system ( 10 ); A third actuator ( 42 ) for limiting the brake pressure at the at least one, the wheel ( 34c . 34d ) of the rear axle ( 38 ) associated wheel brake ( 26c . 26d ) and - at least one electronic control unit ( 22 ), which the electronic control of the first, the second and / or the third actuator ( 30 . 24 . 42 ) characterized in that the third actuator ( 42 ) is connected in series with the upstream of the third actuator ( 42 ) arranged first actuator ( 30 ) and with the downstream of the third actuator ( 42 ) arranged wheel brake ( 26c . 26d ) on the rear axle ( 38 ) of the vehicle. Electronically slip-controlled brake system ( 10 ) according to claim 1, characterized in that the third actuator ( 42 ) an electronically controllable directional control valve ( 44 ) per wheel brake ( 26c . 26d ) of the rear axle ( 38 ), wherein the directional control valve ( 44 ) in its basic position open valve with two pressure medium connections ( 48a . 48b ), which by electronic control of a Ventilaktuators ( 52 ) against the force of an elastic return element ( 50 ) is switchable into a blocking position. Electronically slip-controlled brake system ( 10 ) According to claim 1 or 2, characterized in that the directional control valves ( 44 ) of the third actuator ( 42 ) in a common valve housing ( 46 ), which in particular separated from the first actuator ( 30 ) and of the second actuator ( 24 ) is trained. Electronically slip-controlled brake system ( 10 ) according to one of claims 1 to 3, characterized in that each directional control valve ( 44 ) one bypass each ( 54 ) is connected in parallel, whose flow with pressure medium from a check valve ( 56 ), wherein the check valve ( 56 ) a flow in the direction of the first actuator ( 30 ) to the associated wheel brake ( 26c . 26d ) of the rear axle ( 38 ) locks. Method for controlling an electronically slip-controllable brake system, in particular for a motor vehicle, comprising - an actuatable master cylinder ( 16 ), to the at least one wheel brake ( 26a ; 26b ), which is a wheel ( 34a ; 34b ) of a front axle ( 36 ) of the vehicle and at least one wheel brake ( 26c ; 26d ), which is a wheel ( 34c ; 34d ) a rear axle ( 38 ) is associated with the vehicle, are connected; An electronically controllable first actuator system ( 30 ) for setting and regulating mutually different brake pressures in the wheel brakes ( 26a - 26d ) depending on the prevailing slip conditions; An electronically controllable second actuator system ( 24 ) for the at least indirect setting and regulation of a uniform brake pressure at the wheel brakes ( 26a - 26d ) of the vehicle brake system ( 10 ); A third actuator ( 42 ) for limiting the brake pressure at the at least one, the wheel ( 34c . 34d ) of the rear axle ( 38 ) associated wheel brake ( 26c . 26d ) and - at least one electronic control unit ( 22 ), which the electronic control of the first, the second and / or the third actuator ( 30 . 24 . 42 ), whereby the electronic control unit ( 22 ) the intended function of the primary ( 30 ) is monitored, whereby in case of a detected malfunction of the primary ( 30 ) a braking process is initiated by triggering the secondary actuators ( 24 ) takes place as a result of the wheel brakes ( 26a - 26d ) of the vehicle brake system ( 10 ) are subjected to a brake pressure, characterized in that a directional control valve ( 44 ) of the third actuator ( 42 ) is controlled as soon as the brake pressure at the directional control valve ( 44 ) associated wheel brake ( 26c ; 26d ) of the rear axle ( 38 ) of the vehicle approaches a threshold at which this wheel brake ( 26c ; 26d ) is no longer able to fully implement this brake pressure in a braking performance.

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