Patent Application
20230053950
The invention relates to a brake system and to a method for controlling a brake system.
The trend toward vehicles which are configured for autonomous driving in terms of the brake system places high demands in terms of the failsafe design, on the one hand, and redundant functions, for example in terms of brake pressure generation, voltage supply and computer functions, on the other hand.
So-called one-box and two-box systems are usually favored. These are composed of an electric brake booster (BKV), a so-called e-booster, and an electronic stability control system (ESP/ESC).
The known solutions have relatively large installation lengths and/or a high weight.
Described in WO2011/098178 as well as DE 10 2014 205 645 A1 (hereunder referred to as variant A, or as follower booster or e-booster) is a solution having a coaxial drive in which an electric motor by way of a gear mechanism and piston acts on the master cylinder piston (HZ piston). The BKV control is performed by way of an electric element and reaction disk as a so-called follower booster, the pedal travel is a function of the brake pressure and the volumetric absorption of the brake system, this requiring long pedal travels in the event of fading or brake circuit failure.
WO2009/065709 shows an e-booster, likewise having a follower booster function (hereunder referred to as variant B, or as follower booster or e-booster). The BKV control here is performed by way of a pedal travel and/or by way of a pedal pressure, thus the pressure used for activating the pedal. A separate pressure supply with an electric motor and plunger acts on the HZ piston by way of the booster piston.
WO2012/019802 shows an assembly similar to WO2011/098178, having a coaxial drive in which an electric motor by way of a gear mechanism and piston acts on the HZ piston (hereunder referred to as variant C). An additional piston/cylinder unit is used here, which acts on a travel simulator piston. In this way, the pedal travel is independent of, for example, fading and brake circuit failure. However, the complexity is high and the installation length is large.
DE 10 2009 033 499 shows a brake booster having an additional ESP unit with hydraulic activation of the booster piston and an external pressure supply (hereunder also referred to as variant D). This assembly having four or five pistons and six solenoid valves (MV) is complex and unfavorable in terms of the installation length. The travel simulator (WS), which does not act hydraulically, lies within the piston/cylinder unit that is disposed upstream of the master cylinder and can neither be damped nor switched by way of a solenoid valve (MV).
All solutions mentioned above have a redundant brake booster function because the braking function in the event of a failure of the BKV motor is guaranteed by the ESP unit with a pump similar to the assistance functions by a vacuum BKV in the autonomous driving mode.
In the event of a failure of the ESP motor, the ABS can continue to function by way of the possibility of pressure modulation by the motor of the brake booster, as described in WO2010/088920, in that the piston of the master brake cylinder is moved in a reciprocating manner for building up and dissipating pressure. If the brake booster is used in combination with an ESP unit with the typical valve circuit of the ESP unit, as outlined in detail for example in
All one-box systems known to date have a so-called travel simulator (in particular for brake-by-wire systems), so as to implement a progressive pedal travel characteristic.
The known systems with an e-booster and ESP have only one redundancy in the pressure supply, i.e. in the event of a failure of the e-booster there is a redundant pressure supply with a redundant output for brake boosting by the ESP. Higher requirements in terms of safety are not taken into account.
The packaging, thus an arrangement of the individual components of the brake system so as to form a ready-to-install unit and an installation volume of this unit are of great importance. In particular in the case of brake systems that are used in motor vehicles which are configured for semi-automatic or even fully automatic driving, many variants, for example with a tandem master (brake) cylinder or a single master (brake) cylinder have to be taken into account. Examples of known packaging variants are an arrangement of a pressure supply unit perpendicular to an axis of the master (brake) cylinder (as described in EP 2 744 691, for example) or an arrangement of the pressure supply unit parallel to the axis of the master (brake) cylinder (as described in DE 10 2016 105 232, for example). The latter is distinguished in particular by a smaller installation width in comparison to the first-mentioned packaging variant.
Proceeding from the prior art, it is an object of the present invention to specify an improved brake system.
The invention is in particular based on the object of achieving a brake system for the use in autonomous driving (hereunder also referred to as AD) and/or for electric vehicles/hybrid vehicles having an increasingly high recuperation output (recuperating energy by braking by way of a generator/or drive motor in the generator operation, respectively). Preferably, the weight is minimized and/or the dimensions of the system are reduced and/or the reliability is increased.
A cost-effective brake system for autonomous driving is preferably to be achieved, said brake system meeting all required redundancies and a very high requirement in terms of safety.
Moreover, a function of ABS which is sufficient in terms of the braking distance and stability, as well as a sufficient recuperation function, are to be achieved by the brake system in the event of a failure of ESP.
It is in particular an object of the present invention to specify an improved brake system as well as a method for controlling a brake system having a redundant pressure supply, a very large range of functions and availability, in particular in the event of the failure of a brake circuit, with simultaneously a very short installation length and low costs. Furthermore to be provided is a method which enables a very high degree of availability even in the event of partial failures/leakages.
In terms of the brake system, the object is achieved according to the invention by a brake system having the features of claim 1. In terms of the method, the object is achieved according to the invention by a method having the features of claim 18.
The object focused on the brake system is achieved according to the invention in particular by a brake system having:
The pressure supply unit here can generally be understood to mean a unit, in particular a construction unit, of the brake system that provides a brake pressure. The pressure supply unit thus serves for impinging the at least one brake circuit with the pressurizing medium. The third pressure supply unit is preferably an ESP unit of the type described at the outset. The isolation valves here can be configured so as to be bidirectional, i.e. can be hydraulically permeable in two flow directions. Depending on the design embodiment of the brake system and/or also of the field of application of the brake system, the optional second pressure supply unit can be configured as an electronic pedal or as a central computer.
The at least partial failure of the third pressure supply unit here can be understood to mean that the motor/pump unit fails while the other components of the third pressure supply unit are still able to function.
The isolation valves as well as the brake pressure adjustment valves, in particular the pressure buildup valves and pressure dissipation valves (hereunder also referred to as inlet valves EV and outlet valves AV) are in particular configured as solenoid valves. Solenoid valves have been proven advantageous in particular by virtue of the simple actuation capability of said solenoid valves.
In one embodiment the first pressure supply unit in the first error event is controlled in such a manner that said first pressure supply unit when dissipating pressure for providing the ABS braking operation generates a pressure sink having a lower pressure than the pressures in the wheel brakes.
In a further embodiment, at least some of the isolation valves of the first module are disposed and configured for establishing a hydraulic connection between the brake pressure adjustment valves, in particular the outlet valves and the connection points.
The brake system in the first error event, for dissipating pressure in one of the wheel brakes, here is preferably configured for opening the assigned outlet valve.
In one embodiment, at least some of the isolation valves of the first module are disposed and configured for establishing a hydraulic connection between the brake pressure adjustment valves, in particular the outlet valves and the connection points, wherein the brake system in the first error event, for dissipating pressure in one of the wheel brakes, is preferably configured for opening the assigned outlet valve.
A communications link, in particular a bus link, is expediently configured between the first control apparatus and the second control apparatus, wherein the first control apparatus is preferably configured for receiving pressure measurement values of the second module and/or wheel rotational speed signals by way of the communications link. The communications link can alternatively be an Ethernet or Flexray link. Furthermore alternatively, the communications link can also be configured so as to be wireless or as an analog connection, for example for determining a measurement value.
Furthermore alternatively, the communications link, in particular the bus link, can be configured between the first control apparatus and the second control apparatus, wherein the first control apparatus and the second control apparatus are preferably configured for receiving pressure measurement values of the third pressure supply unit and/or wheel rotational speed signals by way of the communication link. In the event of a failure of the communications link, it is possible in this way to perform ABS controlling by way of the data imported by the two control apparatuses. Receiving here can also be understood to mean importing sensor values and signals of this type from one of the control apparatuses by way of the communications link.
In one embodiment, the first control apparatus and/or the second control apparatus and/or a third control apparatus in the first error event are/is configured for controlling the first pressure supply unit and the brake pressure adjustment valves so as to implement wheel-individual and/or brake circuit-individual pressure feedback control in the wheel brakes or the brake circuits. According to the invention, indirect controlling of the actuators, for example valves, can also take place by way of the respective other control apparatus. The third control apparatus can be understood to mean a central control unit, for example.
In a further embodiment, a first isolation valve of the first module is disposed in a first hydraulic line between the first pressure supply unit and the first connection point. Moreover, according to this embodiment a second isolation valve is disposed in a second hydraulic line between the first pressure supply unit and the second connection point. The brake system here is configured to detect a second error event, in particular a total failure of the third pressure supply unit. The total failure here can be understood to mean that all components of the third pressure supply unit have failed and are no longer able to function. Furthermore, the brake system in the second error event is configured to control the first pressure supply unit and the first and second isolation valve, so as to implement at least one brake circuit-individual pressure feedback control in the at least two brake circuits. The controlling here preferably takes place by way of the first control apparatus.
According to one embodiment, the brake system and in particular the first control apparatus is specified to detect a non-homogenous road condition, in particular a p-split situation, and in the second error event and in the detected non-homogenous road condition, is specified to control the first pressure supply unit. This controlling here serves to adjust a target brake pressure in at least one selected brake circuit of the brake circuits, said target brake pressure being determined as a function of a wheel blocking pressure of that wheel brake of the selected brake circuit that has the coefficient of friction that is higher in comparison to the other wheel brake of the selected brake circuit. The non-homogenous road condition here is detected in such a manner that a pressure differential between the two wheel blocking pressures is detected. A non-homogenous road condition is present when this pressure differential has a percentage value of more than 30% or 40%.
In a third error event, in particular in the event of an additional failure of the wheel sensors mentioned above, or in the communication of the wheel rotational speed signals from the second module to the first module, the brake system, in particular the first control apparatus, in one embodiment in the third error event, by means of the first pressure supply unit, is specified for controlling the pressure buildup and the pressure dissipation, so as to implement a single-channel ABS while using wheel rotational speed sensors, and/or in a fourth error event is specified for implementing an intermittent brake by modulating the pressure between two fixedly adjusted pressure levels in both brake circuits. An improved maneuverability and braking performance of the vehicle as compared to the brake systems known in the prior art is thus also achieved in a further error event and an additional failure of further components of the brake system associated therewith.
At least one pressure sensor for detecting a brake pressure within the at least one brake circuit is expediently provided.
In one embodiment the first hydraulic line between the first pressure supply unit and the first connection point is configured without a valve. Moreover, the second hydraulic line between the first pressure supply unit and the second connection point is configured without a valve. Without a valve here can be understood to mean that no valves are disposed in the first or the second hydraulic line between the first pressure supply unit and the first or the second connection point, respectively.
According to a further embodiment, the first module has a rotary pump, in particular a single-circuit 1-piston pump, or a multi-piston pump, for building up pressure and dissipating pressure. Moreover, the first module according to this embodiment comprises a solenoid valve hydraulically connected to a reservoir, as well as at least one optional pressure transducer. The optional pressure transducer for feedback-controlling the pressure buildup and the pressure dissipation is preferably communicatively connected to the first control apparatus.
According to an alternative embodiment, the first pressure supply unit is configured as a gear pump for building up pressure and dissipating pressure. The gear pump is expediently controlled while using a pressure transducer or as a function of a measurement of a current, in particular a phase current i of the electromotive drive of the gear pump, and of an angle a of a rotor of the electromotive drive. In the case of a present pressure transducer, said measurements can be used for providing a redundancy (hot or cold).
Considering the different variants of design configuration of the first pressure supply unit, the latter thus takes into account different variants of configuration.
In a further embodiment, at least one third isolation valve is provided, said third isolation valve being disposed and configured in such a manner that, in a closed state of the third isolation valve, the first brake circuit is hydraulically decoupled from the first and the second pressure supply unit.
Furthermore, the first hydraulic line and/or the second hydraulic line are/is preferably (in each case) connected to a reservoir by way of a suction valve. The suction valves are used such that the third pressure supply unit can convey volumes directly from the reservoir rapidly with minor hydraulic resistances and that the first and the second pressure supply unit during conveying are decoupled as a result of the operation of the third pressure supply unit and are not compromised by the operation.
According to a further design embodiment, an activation element, in particular a brake pedal, is disposed on the second pressure supply unit. The second pressure supply unit here comprises a master brake cylinder having a single piston that is activatable by means of the activation element and has a pressurized chamber as well as a travel simulator connected to the pressurized chamber. Furthermore, the pressurized chamber by way of a switchable solenoid feed valve FV is connected to at least one brake circuit.
As a result of the embodiments of the brake system according to the invention described above, operation taking into account safety aspects is made possible in particular in the error events listed hereunder (in all or a selection of these error events).
Error event 1: failure of the motor of the third pressure supply unit (ESP unit); 4-channel ABS by feedback control by way of valves and first pressure supply unit;
Error event 2: complete failure of the third pressure supply unit (ESP unit); 2-channel ABS with “select-low”/“select-high” feedback control atypical of the normal operation;
Error event 3: complete failure of the third pressure supply unit (ESP unit), wheel rotational speed sensors are available in a redundant manner and are imported into the first module directly from the wheel brakes; establishment of a 1-channel ABS;
Error event 4: complete failure of the third pressure supply unit (ESP unit) and failure of the wheel rotational speed sensors; establishment of an automatic intermittent brake.
Alternatively or additionally to the ABS control in the error event 1, a yaw torque control can furthermore take place in this error event so that a brake pressure is generated in selectively selected wheels.
In terms of the method, the object is achieved in particular by a method for controlling a brake system, in particular the brake system described above, said method comprising the steps:
In one embodiment, the method furthermore comprises the steps:
According to a further embodiment, the method comprises the steps:
In a further embodiment, the method moreover comprises the steps:
According to an alternative embodiment, the method furthermore comprises the steps:
Advantages similar to those that have been described in conjunction with the brake system are derived for the method.
Exemplary embodiments of the invention will be explained in more detail hereunder by means of the figures. In the figures, in some instances in a highly simplified illustration:
Components with equivalent functions are in some instances provided with the same reference signs in the figures.
The brake system 2 according to a first exemplary embodiment as illustrated in
The first pressure supply installation 6 serves here to impinge a first brake circuit BK1 and a second brake circuit BK2 with a pressurizing medium. To this end, the cylinder of the first pressure supply unit 6 by way of a hydraulic line is hydraulically connected to the first brake circuit BK1 (cf. connection point A1) and to the second brake circuit BK2 (cf. connection point A2).
In the exemplary embodiment according to
Additionally, the first pressure supply unit 6 and in particular the cylinder of the first pressure supply unit 6 has a hydraulic connection line to a reservoir 40 in which a check valve is disposed. The hydraulic connection to the reservoir 40 serves for suctioning pressurizing medium from the reservoir 40.
Furthermore, the brake system 2 has a third pressure supply unit 90 which is only schematically illustrated in fig. la. The third pressure supply unit 90 is also referred to as an ESP unit, or the ESP unit comprises the third supply unit 90, respectively. Moreover, a second control apparatus 95 which controls the third pressure supply unit 90 is provided.
A communications link 100, in particular a CAN bus link, is configured between the first control apparatus 9 and the second control apparatus 95. The communications link 100 serves for exchanging data and/or signals between the two control apparatuses 9, 95.
In particular, no valves are disposed in the hydraulic lines of the first brake circuit BK1 as well as of the second brake circuit BK2 in the exemplary embodiment according to
Moreover, a pressure transducer p/U which is disposed between the isolation valve PD1 and the first or the second brake circuit BK1, BK2, respectively, is provided in the hydraulic line. This pressure transducer p/U, in particular in an error event (cf. embodiments hereunder) serves for providing pressure information pertaining to the brake circuits BK1, BK2 in order for pressure to be adjusted in the brake circuits BK1, BK2.
As an alternative to the pressure transducer p/u, an item of information pertaining to the pressure adjusted by means of the first pressure supply unit 6 in this embodiment takes place by estimating the pressure by way of a motor rotary encoder a/U and/or the motor current i/u.
This exemplary embodiment corresponds substantially to the aforementioned exemplary embodiment of the brake system 2 according to
A circuit diagram of the first exemplary embodiment of the brake system 2 having the first pressure supply unit 6 according to a second embodiment is illustrated in
The brake system 2 according to the first exemplary embodiment having a first pressure supply unit 6 according to a third embodiment, as is illustrated in
One aspect of the invention lies in that the first control apparatus 9 by way of a communications link 100 is communicatively connected to the second control apparatus 95 (“ECU-ESP”) of the ESP unit and, for achieving safety aspects, at least the inlet valves EV1 to EV4 are able to be controlled by the first control apparatus 9.
A (further) aspect of the invention lies in the wheel-individual pressure dissipation while using the outlet valves AV1 to AV4 and HSV valves of the ESP unit.
A circuit diagram of the third pressure supply unit 90 (ESP unit) while dissipating pressure in a first error event is illustrated by way of example in a brake circuit in
In the first error event, the actuation of the valves, in particular of the isolation valves USV1, USV2, HSV1, HSV2 and of the outlet valves AV1 to AV4 can also take place by the first control apparatus 9 and not, as in the normal case, by the second control apparatus 95. When controlling by the first control apparatus 9, the control signals required for this purpose here are transmitted to the third pressure supply unit 90 by means of the communications link 100. However, in the normal operation, in the absence of an error event, the second control apparatus 95 assumes the actuation of the valves. The normal operation here can be understood to mean a pressure buildup required for example for braking a vehicle in comparison to a pressure buildup for the purpose of feedback control (so as to prevent slipping or blocking of the wheel).
The inlet valves EV1 to EV4 are closed (by energizing) when dissipating pressure. A hydraulic connection to the first pressure supply unit 6 is configured by opening the isolation valve HSV2; an outflow of the pressurizing medium here is then facilitated by means of the first pressure supply unit 6 and not, as customary, by means of the pump P.
The pressure dissipation illustrated and explained by way of example for two wheel brakes RB3, RB4 in
A pressure is preferably detected by means of the pressure transducer p/U in the ESP unit during this feedback control, so that information pertaining to the pressure for feedback-controlling the pressure dissipation is present at every point in time.
A pressure buildup in the first error event is illustrated by way of example by the circuit diagram of the third pressure supply unit 90 according to
The isolation valve PD1, if provided, which isolates the first pressure supply unit 6 from the brake circuits BK1, BK2 is operated so as to be open during the pressure buildup. The first pressure supply unit 6 by way of the hydraulic line conveys pressurizing medium into the wheel brakes RB3, RB4. Also in this exemplary embodiment, the pressure transducer p/U, which according to
A temporal profile of vehicle speed VF, wheel circumferential speed VR, reference speed VREF, brake circuit pressure Ph for “high wheel”, PL for “low wheel” is in each case illustrated in
In homogenous conditions (all vehicle wheels are situated on asphalt, for example) switching takes place to a “select-low” feedback control (
In non-homogenous conditions, for example p-split, i.e. wheels on a vehicle side on ice, the other vehicle side on a wet or dry road, the “select-high” feedback control (
As has already been explained,
In this way,
As a consequence, the wheel VR2 does not block at the time point 3 and again undershoots the λ-slippage limit at the time point 3. A pressure buildup in stages follows from the time point 3. In a first stage, the pressure is increased by 70% of the previous Δpab value, for example, and in a second step increased by a further 30%, so that the pressure p2 is reached again and subsequently exceeded. In this phase, the pressure transducer p/U is preferably used for pressure measurement. The slippage limit is again exceeded at the time point 4. Thereafter, the pressure is reduced again, as at the time point 2, and subsequently increased again in stages so that the wheel undershoots the slippage limit again at the time point 5. This feedback control method is continued during the feedback controlling.
As has already been explained, in one exemplary embodiment, in the second error event switching from a “select-low” feedback control to a “select-high” feedback control takes place by way of the first control apparatus 9 when the first control apparatus 9 detects that the vehicle is situated on a non-homogenous hard ground, for example a partially icy road. For this purpose, it is necessary that the brake system 2 according to the invention by means of the first pressure supply unit 6 can adjust different pressures in the individual brake circuits BK1, BK2. The design embodiments already shown schematically by means of
The second module and in particular the third pressure supply unit 90 comprises an electrically driven motor/pump unit 91 having a pump with an electromotive drive. The third pressure supply unit 90 can be any arbitrary ESP unit. A suitable ESP unit is described in detail in DE 10 2014 205 645 A1. Alternatively, a standard ABS unit without ESP function can be used as the second module.
The two modules (X-boost and ESP unit) are specified for impinging two brake circuits BK1 and BK2 with pressurizing medium, wherein the modules are preferably hydraulically connected in series. In one exemplary embodiment, the X-boost is fastened to the scuttle of a vehicle, the second module (ESP unit) at two hydraulic interfaces or connection points A1, A2 (cf. solid black points in
The first pressure supply unit 6 by way of a first hydraulic line HL1 is connected to the first brake circuit BK1, or to the corresponding interface, respectively. Furthermore provided is a second hydraulic line HL2 for connecting the first pressure supply unit to the second brake circuit, or to the corresponding interface, respectively.
According to the invention, the second pressure supply unit 14 of the X-boost only has one master brake cylinder 22 having a piston 24 and a piston chamber. In the exemplary embodiment, the second pressure supply unit 14 is embodied with a single circuit and by way of a third hydraulic line HL3 and a feed valve 69 is connected to the brake circuit BK1, or to the corresponding hydraulic interface, respectively. A fluidic connection to the second hydraulic line HL2 runs by way of an optional first isolation valve BP1 (highlighted by a border with dashed lines). The second pressure supply unit 14 by closing the feed valve 69 is able to be isolated from the brake circuits BK1, BK2 in such a manner that the activation element 26 in the normal brake-by-wire operation without errors (for example without a brake circuit failure) acts only on a travel simulator 28.
In the exemplary embodiment as per
The first pressure supply unit 6 likewise selectively acts on the second brake circuit BK2 (first isolation valve BP1 closed) or both brake circuits BK1, BK2 (first isolation valve BP1 opened or open when not energized). The first isolation valve BP1 is open in the normal operation so that the first pressure supply unit 6 supplies both brake circuits BK1, BK2 with pressure, and the second pressure supply unit 14 by the closed feed valve 69 is decoupled from the first brake circuit BK1. If it is established that volume is lost from the brake circuits BK1, BK2, the brake circuit BK1 by means of the first isolation valve BP1 can be decoupled from the first pressure supply unit 6 so that, in the event of a leakage in the first brake circuit BK1, the second brake circuit BK2 can continue to be operated without hydraulic fluid losses.
In the exemplary embodiment, the isolation valve BP1 is embodied as a solenoid valve, wherein the ball seat of the isolation valve BP1 by way of a connector (valve seat connector) is connected to the portion of the hydraulic line that leads to the first pressure supply unit 6. In this way, the isolation valve BP1 can also be reliably closed by energizing in the event of a failure of the first brake circuit BK1, and is not forced open by higher pressures in the operation of the first pressure supply unit 6.
The second pressure supply unit 14 upon activation of the activation element 26 feeds the travel simulator 28 by way of a breather bore in a wall of the master brake cylinder 22, such that a progressive haptic resistance in the form of a restoring force as a function of a variable of the activation of the activation element 26 can be felt.
The variable of the activation here can be understood to mean how “firmly and/or how far” a driver activates the activation element 26 configured as a brake pedal, and thus pushes the piston 24 into the master brake cylinder 22. The progressive haptic resistance is also referred to as a pedal characteristic.
A travel simulator valve 29 can be provided for blocking the connection to the travel simulator 28.
The second pressure supply unit 14 has at least one breather bore 38 which by way of hydraulic lines is connected to a reservoir 40. The reservoir 40 is likewise part of the brake system 2.
In the exemplary embodiment, a check valve RVHZ as well as a throttle DR can be disposed in the hydraulic line between the breather bore 38 and the reservoir 40. By means of this check valve RVHZ and the first pressure supply unit 6 it is possible to carry out a diagnosis pertaining to a state of preservation of sealing elements disposed within the first pressure supply unit 6 as well as within the travel simulator 28. The travel simulator valve 29, if present, can be closed when checking the seal of the master brake cylinder 22.
As illustrated, the master brake cylinder 22 has two sealing elements 42a, 42b, which are configured as annular seals. The breather bore 38 is disposed between the two sealing elements 42a, 42b. A throttle DR is disposed in the connection between the breather bore 38, which is disposed between the two sealing elements 42a, 42b, and the reservoir 40.
The throttle DR in terms of the flow rate thereof is sized such that the pedal characteristic is not substantially changed (3 mm pedal travel in 10 s) in the event of a failure of the sealing element 42a. Moreover, a temperature-related volumetric compensation of the pressurizing medium can take place by way of the throttle DR.
High pressure peaks in the brake circuits BK1 and BK2, which can significantly stress the first pressure supply unit 6, can be created in an ABS operation of the third pressure supply unit 90. In the variant of design embodiment according to
A suction valve NV is likewise fluidically connected to the piston chamber of the first pressure supply unit 6 and enables pressurizing medium to be resupplied from the reservoir 40. In this way, the first pressure supply unit 6 can independently introduce additional pressurizing media into the brake circuits BK1, BK2. An additional breather bore provided in the cylinder of the first pressure supply unit 6 enables a volumetric compensation in the initial position of the piston of the first pressure supply unit 6.
The third pressure supply unit 90 is only schematically illustrated in
The first brake circuit BK1 is connected to the wheel brakes RB1 and RB2, and the second brake circuit BK2 is connected to the wheel brakes RB3 and RB4. A corresponding allocation is advantageous for the hydraulic assembly illustrated in
The third pressure supply unit 90 furthermore possesses a control apparatus 95 (“ECU-ESP”).
The second pressure supply unit 14 likewise possesses a printed circuit board which has a level sensor NST which detects the position of a magnetic float gauge NS within the reservoir 40. The PCB furthermore has sensors 30a, 30b for detecting the pedal travel as well as a difference in the distance of travel between the piston 24 and the pedal travel.
A suction valve 70b, which connects the pump of the third pressure supply unit 90 to the reservoir 40, is provided in the first brake circuit BK1 for providing additional pressurizing medium for the third pressure supply unit 90.
When the pump of the third pressure supply unit 90 requires pressurizing medium for the second brake circuit BK2, the latter can thus be provided from the reservoir 40 by way of the suction valve 70c.
In this way, for suctioning pressurizing medium, the two brake circuits BK1, BK2 by the respective hydraulic lines HL1, HL2 are in each case connected to the reservoir 40 by way of one suction valve 70b or 70c, respectively. In order to achieve optimum suctioning of the pressurizing medium, the suction valve 70c preferably has a diameter in the range from 30 mm to 50 mm and in particular a diameter of 40 mm.
The exemplary embodiment optionally possesses a control of the clearance between the brake pads and the disk brake. The wheel brakes RB1, RB2, RB3, RB4 (cf.
The clearance in the wheel brake RB1, RB2, RB3, RB4, which is variable during operation, can be measured in a wheel-individual or brake circuit-individual manner by evaluating the pressure profile by means of the first pressure supply unit 6. According to the invention, corresponding measuring can take place when servicing, or else during the operation of the vehicle. The measurement is preferably performed in a stationary vehicle or after braking.
Using the known clearance values of the wheel brakes RB1, RB2, RB3, RB4, the clearance when activating the wheel brake RB1, RB2, RB3, RB4 is first rapidly overcome by means of a piston travel control of the first pressure supply unit 6. In this respect, the use of a brushless motor as an electromotive drive 8 of the first pressure supply unit 6 with a small time constant is to be preferred, because the action of overcoming the clearance can be implemented without the driver perceiving the latter when activating the brake.
Moreover, the brake system 2 can be controlled so that the vehicle electric motor is active in the phase of the clearance. In this way, a braking action is generated immediately when activating the brake.
In one exemplary embodiment of the invention, differences in the clearances of the wheel brakes RB1, RB2, RB3, RB4 are compensated for in that the inlet valves EV1 to EV4 of the second module (ESP unit) are actuated, and/or the electric motor of one or a plurality of vehicle axles is utilized for generating a braking action at the beginning of braking. By way of the clearance, stick-slip effects of new brake systems at low speeds can generally be reduced or avoided.
In one exemplary embodiment, the brake system 2 according to the invention in the event of a failure (error event 4) of the ESP unit implements a very simple variant of an intermittent brake. Locking of the wheels is avoided and the steerability is maintained by moving the piston of the first pressure supply unit 6 in a reciprocating manner between an upper and lower pressure range. As opposed to a 1-channel ABS operation, no measurement values, for example pressure and wheel speeds, are required in this form of deceleration.
The automated intermittent brake leads to sufficient stopping distances (approx. 200% of the stopping distance in the ABS mode in comparison to a full-fledged wheel-individual ABS) and to acceptable stability by maintaining the steerability.
The brake system according to the invention can provide the decisive advantage that the brake pedal acts only on the piston 24 and by way of the feed valve 69 is isolated from the brake circuits BK1, BK2. In this way, the function of the automated intermittent brake with the X-boost or X-booster, respectively, cannot be interfered with by the driver as opposed to the prior art (WO2011/098178).
Alternatively to the intermittent brake, a 1-channel ABS operation with “select-low” feedback control (error event 3) can be implemented. This leads to a further deterioration of the stopping distance (approx. 400% stopping distance in comparison to the stopping distance with a full-fledged wheel-individual ABS) but to an unrestricted vehicle stability and in terms of this characteristic is superior to the intermittent brake. In this form of the 1-channel ABS operation, measurement values such as, for example, pressure and wheel speeds are required, which can be imported from the ESP unit by way of a communications link/interface, for example a CAN interface.
In order to further increase the availability of the brake system 2 according to the invention according to
The control apparatus 95 of the ESP unit 90, as well as the control unit 9 (ECU-DV) of the X-boost, are connected to one another by way of the communications link 100, for example a CAN bus. To this extent, it is possible for control commands to be released to the third pressure supply unit 90, said control commands causing an activation of the drive 91 and/or of the provided valves (cf. also
The following safety-relevant redundancies can be implemented using the brake system 2 as per
Furthermore, the exemplary embodiment according to
The following safety-relevant redundancies can be implemented using the brake system 2 as per
A circuit diagram of the third pressure supply unit (ESP unit) while dissipating pressure (cf.
A wheel-selective yaw torque feedback control during a pressure buildup in the wheel brake RB4 is shown in an exemplary manner in
Likewise, the HSV valves for the selective pressure generation in the wheel brake RB4 are closed, i.e. switched so as not to conduct pressurizing medium.
In this way, an impingement of pressure from the first pressure supply unit 6 by way of the isolation valve USV2 and the inlet valve EV4 takes place exclusively to the wheel brake RB4 (schematically indicated by an arrow). In addition to a wheel brake RB1, RB2, RB3, RB4, a yaw torque can be generated in a plurality of wheel brakes RB1, RB2, RB3, RB4. To this end, those inlet valves EV1-EV4 in the wheel brakes RB1, RB2, RB3, RB4 are closed in each case by way of which a pressure is not to be built up. By way of this enhancement, a yaw torque can be simultaneously generated in, for example, 2 wheel brakes RB1, RB2, RB3, RB4 of one vehicle side. Since brake circuits are typically embodied so as to be black and white, or diagonal, in this instance consequently one wheel brake RB1, RB2, RB3, RB4 of one brake circuit is in each case impinged with pressure. A further potential enhancement of the yaw torque feedback control is possible as a result of a sequential or simultaneous multiplex operation of the circuit isolation valves BP1/BP2 and TVBK2 of the first module (embodiment according to
Moreover, another pressure level can be adjusted in a wheel brake RB1, RB2, RB3, RB4 of the other brake circuit (for example RB2 of the right front wheel), wherein the second brake circuit isolation valve BP1 or alternatively BP2 is closed in order to maintain the pressure. The brake circuit isolation valves BP1/BP2 and TVBK2 are required for maintaining pressure because the inlet valves of the wheel brakes RB1, RB2, RB3, RB4 have check valves connected in parallel. In this way, maintaining pressure in the second module (ESP unit) is impossible when the pressure has dissipated, or when a lower pressure level is adjusted in the second brake circuit.
The following states thus result for the relevant valves of the third pressure supply unit 90 for the pressure buildup according to
In the case of pressure dissipation, as shown in
In one embodiment, a plurality of, in particular all four, wheel brakes RB1, RB2, RB3, RB4 can additionally be actuated individually and wheel-selectively in an analogous manner, and a wheel-selective yaw torque feedback control can thus be implemented. Alternatively or additionally, the yaw torque feedback control in one embodiment can take place in a brake circuit-selective manner, so that two wheel brakes of one brake circuit are in each case conjointly actuated.
Specifically, the following states are thus derived for the relevant valves of the third pressure supply unit 90 for the pressure dissipation according to
At this point it is to be pointed out that all parts described above are in each case to be considered individually—even without features which have been additionally described in the respective context, even when said features have not been explicitly identified individually as optional features in the respective context, for example by using: in particular, preferably, for example, e.g., optionally, parentheses, etc.—and in combination or any arbitrary sub-combination as independent design embodiments or refinements of the invention, respectively, as defined in particular in the introduction to the specification and the claims. Deviations therefrom are possible. Specifically, it is to be pointed out that the word “in particular” or parentheses do not identify features which are mandatory in the respective context.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2020 101 988.2 | Jan 2020 | DE | national |
| 10 2020 102 590.4 | Feb 2020 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/051788 | 1/27/2021 | WO |
