WO2010100276A1

WO2010100276A1 - Electromechanically actuable parking brake for motor vehicles and operation method for a parking brake

Info

Publication number: WO2010100276A1
Application number: PCT/EP2010/052886
Authority: WO
Inventors: Oleg Bauer; Eduard Wiens; Rüdiger PUFF
Original assignee: Continental Teves Ag & Co. Ohg
Priority date: 2009-03-06
Filing date: 2010-03-08
Publication date: 2010-09-10
Also published as: DE102010002648A1

Abstract

The invention relates to an electromechanically actuable parking brake for motor vehicles and to an associated operating method, comprising at least one electronic control unit (ECU) which has implemented software comprising a control strategy for the purpose of open-loop controlled or closed-loop controlled supply of electricity to the parking brake, and for this purpose is electrically connected to at least one reversible actuator (15) and to one or more sensors (S) and/or signal generators (G) for supplying information in order to covert, through application of the control strategy, a rotational drive movement of an activation unit (2) into a translatory drive movement in such a way that brake callipers (3, 4) with a defined brake application force are pressed against a rotor (5), or vice versa. In order to improve known control strategies while avoiding direct measurement of the brake application force F, there is provision that at least one item of information about the power consumption of the actuator and an item of rotational information of the actuator for the calculation of a virtual brake application force (25) are fed to the control unit (ECU), and that the virtual brake application force (25) which is determined, or a control variable derived therefrom, is used to actuate the activation unit (2).

Description

Electromechanically actuated parking brake for motor vehicles and operating method for a parking brake

The present invention relates to an electromechanically actuable parking brake for motor vehicles and an associated operating method.

With regard to electromechanically actuated parking brakes (EPB), some constructively very differently structured technical systems are in competition with one another, each of which has very different constructively based advantages and also properties. Examples include the electromechanical brakes (EMB), the so-called cable pull actuators (CP for "cable-pull") and the integrated in a hydraulic caliper electromechanical Parkbremsaktuatorik (EPB-Ci, Ci for "caliper integrated") called. A special variant is so-called electromechanically actuated duo-servo parking brake systems, because they have an integrated gain function and, for example in drum-in-hat design in addition to a disc brake for the parking brake function a completely redundant, separately provided for service brake, wheel brake.

The particular design advantage of duo-servo parking brake systems is a direction of rotation independent self-boosting effect, so that with relatively low application forces high braking forces can be generated, with a so-called C * value is significantly greater than disc brakes. This makes this design variant particularly suitable for heavy passenger vehicles, all-terrain vehicles as well as delivery vans and light Lorries but also by way of example predestined for electric motor-driven vehicles, which may be due to recuperative braking operation possibly on high-performance disc brake systems (on one or more axis) can do without. Such systems also have in comparison with a combination containing so-called combination calipers (hydraulically actuated service brake caliper with a locking actuator) and cable actuators whose parking brake device act on already existing brake discs of a service brake system, on the principal advantage that in principle after parking the vehicle with a hot brake no application force loss due to thermal shrinkage processes as a result of thermal cooling occurs. In other words, the risk of insufficiently secured vehicles is minimized, and so-called post-tensioning strategies when hot-setting are basically rationalized. By eliminating re-tensioning, the total number of actuation cycles of the electro-mechanical parking brake system is reduced. Another fundamental advantage is that the electrical vehicle electrical system, including its electrical supply is protected by the integrated self-amplification, because the power consumption is lowered.

WO 2008/017613A1 an electromechanically actuated parking brake of the duo-servo type, and a scheme has been proposed, wherein a locking force based on the time course of a single measured variable, namely based on a change in current over time (modified current profile) of the electric actuator, and wherein in the system of the parking brake at least one biased spring element is provided, which influences the stiffness of the parking brake. This ensures a secure operation of the duo servo Parking brake system, regardless of thermal environment and operating conditions enabled. In this context, (see WO2008 / 017613, page 13, last paragraph) proposed a model such that recorded during the development of the brake system in the sense of a reference, characteristics of current consumption, engine speed and clamping force of the actuator and stored in an electronic control unit so that during operation of a parking brake system only with current measurement can be worked.

From DE 103 61 042 B3 a method for controlling a parking brake is known, wherein a control unit for achieving a predetermined application force, the size of a cut-off current of an electric motor in response to an event number of a counted event - such as in particular a number of braking operations - varies.

Under worst-case consideration, however, special actuation cases are possible which, in conjunction with an electromechanically actuated parking brake of the duo-servo type require a sophisticated problem solving, which in parking brake systems disc-type, and in particular the brake integrated integrated design solutions (EPB-Ci), in principle are not given. Because when a vehicle comprising a duo-servo parking brake system is parked under particularly low ambient temperatures of, for example, minus 40 ⁰ C with a particularly hot service brake, for example, several hundred ⁰ C, this has changed effects on the parking brake function and in particular the change of the clamping force result. Because the spatial proximity of the components of service and parking brake to each other and the preferred arrangement of the parking brake in a pot of the disc brake (drum-in-hat) causes heating of the parking brake components - in particular of the brake drum - although these are in principle not involved in a service braking. Cooling processes of the brake drum, which can lead to an undesirably high increase in the application forces of the duo-servo parking brake, follow a shut-off and application process of the parking brake. A further undesirable, yet possible in principle, therefore disadvantageous, consequence of these relationships is that the release of the parking brake after clamping force increase at a particularly low electrical on-board voltage potential (exhausted battery) - for example

Cryogenic conditions - can be difficult. Another peculiarity of the duo-servo brake systems is that the coefficient of friction of the friction linings on the parking brake function is optimally adjustable, but this coefficient of friction can have comparatively different friction conditions over its service life. This is caused, for example, because the friction linings of the parking brake system are used largely exclusively for the parking brake function, therefore hardly wear, and therefore may tend to glazing. So friction fluctuations are comparatively strong.

It is an object of the present invention to provide a smart improved control of a parking brake, which eliminates the disadvantages of known systems, allows a more precise positioning and Zuspannkrastetdosierung the actuating means involved, and also under worst-case considerations such as in particular at low temperatures a secure operation of a Duo servo parking brake system allows. In this context, in particular the peculiarities of a duo-servo parking brake system, preferably in thermal terms, to be taken into account with a still cost-effective solution.

To solve the problem according to the invention a proposed electromechanical parking brake, wherein the reversible actuator has means for detecting a rotational information, which are supplied to an electronic control unit, that the electronic control unit comprises means for detecting the electrical current consumption of the actuator, which are supplied to the electronic control unit, and that at least this information in the frame a control technology Feststellbremsmodell be used predictively for the calculation of a fictitious Zuspannkraft for the purpose of controlling or regulating the energization of the actuator for the application and / or release process. According to the invention, the function of the system is achieved by using at least two measured system variables increased positioning accuracy. Another significant advantage is that with improved function can be dispensed with an immediate force measurement using a separate force sensor, so that an improved yet cost-effective problem solution is given.

A correlating method for operating an electromechanical parking brake provides that the reversible actuator is controlled or regulated on the basis of a fictitious clamping force model, and that for predictive formation of a control application force model in an electronic control unit at least one measured rotation information of the actuator, in particular an actuator speed, and at least in addition a measured current consumption of the actuator is used.

According to the invention, a fictitious application force is thus predicted in a periodic repetitive manner during operation of the actuator using the variables described, and a modified manipulated variable is fed to the control system on this basis. The same applies mutatis mutandis vice versa for each intended release process of the parking brake system, each with the aim of a metered Zuspannkraftreduktion so that the Zuspannbetätigungsprozess is performed in a sense reversed, with changed sign.

The essential point of the present invention, therefore, is to use the physical analogy to the work done mechanically (force x path), namely the electrically performed work (voltage x current consumption) on the basis of corresponding measured quantities to form a control model of the application force of an actuator for a parking brake ,

In a further embodiment of the invention, it is provided in each case that the clamping force model is formed iteratively periodically, and that the respectively detected or measured instantaneous values of the system are used for the iterative calculation.

Advantageously, a clock frequency for the periodically repeated calculation on the basis of the clamping force model is fixed predetermined or variable. In particular, it is conceivable in principle to vary the clock frequency during expiring application or release processes according to specific specifications, such as, for example, on the basis of a respectively determined or measured control deviation in order to eliminate in particular very large control deviations particularly quickly.

It is understood that the application process can be carried out in a reversed manner to a certain extent in order to carry out a dissolving process, without leaving the basic idea of the invention.

Further details of the invention will become apparent from dependent claims together with the description with reference to the drawings. In the drawing shows:

1 is a schematic representation of an electromechanically actuated parking brake of the duo-servo type for motor vehicles on the example of Fig. 1 of WO2008 / 017613A1,

2 schematically shows an action plan of the control circuit of an electromechanical actuator of a parking brake,

3 schematically shows a diagram with a family of characteristics for qualitative clarification of the force-displacement curve for various thermal operating states, including worst-case characteristics (hot / cold),

4 shows a diagram as in FIG. 3 exclusively with two worst-case characteristics (hot / cold), FIG.

Fig. 5 qualitatively model diagram to illustrate current consumption I, Zuspannkraft F and voltage U, respectively over the path s of an actuator, during the clamping operation of an electromechanical actuator.

1, an electromechanically actuated parking brake is described by way of example, which essentially comprises a drum brake type wheel brake known per se of the design "duo-servo" and an electromechanical actuator 15. This drum brake is shown in FIG. 017613A1 known in principle, and the disclosure content is, including in view of the basic operating method and the explanations accompanying, expressly included in the disclosure. Although an inventive control method is primarily explained on the structural example of an electromechanically actuated duo-servo parking brake device with an electromechanical actuator, a transfer to other electromechanical service brake or parking brake systems seems in principle possible and useful.

In detail, Fig. 1 illustrates an electromechanically operable drum brake parking brake of the "duo-servo" type comprising an actuator unit 2 in the form of an expanding lock with an electromechanical actuator 15. A rotor 5, in the form of a brake drum, is fixedly connected to a motor vehicle wheel and In a preferred embodiment, the rotor 5 additionally has a friction ring for a disc brake type service brake device (drum-in-hat construction) Drive rotational movement of the electromechanical actuator 15 into a translatory application movement of the brake shoes 3, 4. As a result, the friction linings 10, 11 of the brake shoes 3, 4 are brought into engagement with a friction surface of the rotor 5. A characteristic feature of a drum brake of the "Duo -Servo "is a floating between the brake shoes 3,4 arranged supporting device 16, which is the expansion lock 2 arranged parallel to each other. The actuating unit 2 essentially comprises a threaded nut spindle arrangement 8 and two pressure pieces 13, 14. The pressure piece 13 interacts with the spindle 7, and the pressure piece 14 cooperates with the threaded nut 6.

As illustrated in FIG. 1, the threaded nut spindle arrangement 8 is actuated by a drive wheel 1, which is actuated by the electromechanical actuator 15 with the interposition of a schematically illustrated reduction gear 12 is driven. For this purpose, the threaded nut 6 has a toothing on the circumference which runs parallel to the axis of the threaded nut 6. With this spur toothing of the threaded nut 6, the just mentioned drive wheel 1 forms a drive gear. The rotary drive of the drive wheel 1 causes the threaded nut 6 in a rotational movement. The rotational movement of the threaded nut 6 is converted by the spindle 7 of the threaded nut spindle assembly 8 in the desired translational movement, and brings the two brake shoes 3, 4 with the desired clamping force with the friction surfaces of the rotor 5 into engagement.

For the electroless locking of an electric motor running parking brake actuator, either the reduction gear 12 or the threaded nut spindle assembly 8 is self-locking. With regard to other brake systems, basically ball screw drives can be used.

WO 2008 / 017613A1 describes that, when parking on a slope, the mechanism occurs that after removal of a (usually hydraulically induced) service brake effect in the service brake system, the parking brake system is taken over by electromechanical brake application of the parking brake. In conventional duo-servo brake systems takes place in this context, a barely noticeable Rückrolltendenz the motor vehicle in the direction of downhill power. In this process, the rotor 5 rotates slightly by a certain angle, until unavoidable settling phenomena are completed, and the friction linings are rotationally fixed in the circumferential direction. As a disadvantageous consequence of a tendency to roll back, it is thereby possible in principle that the set electromechanical application force is at least slightly influenced, namely reduced. As a countermeasure is therefore according to WO 2008 / 017613Al has been proposed that in the power flow between the threaded nut-spindle assembly 8 and, cooperating with the threaded nut 6, pressure element 14, a spring element 9 is arranged, which compensates for a reduction of the clamping force.

To illustrate the function is shown in Fig. 5 is a schematic curve of a Zuspannkraft F, a characteristic of a current consumption I and a characteristic curve of a voltage U respectively depending on the path s of an actuator when applying the parking brake applied. Markings with "refer in each case to characteristic curves, data, values, reference numbers or other information in connection with changed characteristic curves, such as in particular a worst-case characteristic (hot characteristic curve) under changed boundary conditions according to FIG. 4 (right-hand characteristic curve) can by worn friction linings 10,11 and worn rotor 5, deteriorated friction, hot braking system or the like

Operating conditions caused. The qualitative effect on force-displacement characteristics can be seen in FIGS. 3 and 4. 3 shows a family of curves to illustrate many, in principle imaginable, curves and Fig. 4 two extreme cases and dashed the application and the release process based on the set trigger T. Here, a reference characteristic (removed in the context of a brake calibration in new condition at Room temperature) compared to a worst-case characteristic as a critical limiting case in the most critical boundary conditions on the right-hand edge of the diagram. The qualitative effect of all negative influencing variables therefore consists in the fact that a characteristic curve is shifted to the right in the diagrams in the direction of extended actuation paths, depending on the operating factors and the boundary condition. This motivates the present invention in terms of an improved as well as in the Clamping or releasing process improves control or regulation of the actuator 15. The control strategy according to the invention allows the consideration of the boundary conditions and influencing variables described above in the sense of a specification and correction of previously used ideal models by the fictitious clamping force is calculated on the basis of electrical work, which will be described in Individual will be explained in more detail.

At the beginning of each application operation, the parking brake is in a released state, ie the position of the brake shoes 3, 4 is "zero" and the application force F is "zero", as shown according to waymark S ₀ in the drawing. According to FIG. 3, this state of the proposed control strategy correlates to Fzero (FIG. 3) on the basis of a fictitious, negative assumed application force between the landmarks so, sl and s2 and on the assumption that a characteristic branch with a negative sign and a constant assumed slope α2 the application force F is present over the path s. This provides a first regulatory corrective. Subsequent to sθ in FIG. 5, the further curve in section A illustrates the initial setting of the actuator 15 at the beginning of a clamping operation which requires a comparatively high starting current I with decreasing tendency, which in particular reflects an overcoming of mechanical inertia and frictional forces. This is followed between way mark sl and s2 to a certain extent an idle and application phase B, in which, for example, Lüftspiele ascended with the lowest power consumption and the friction linings 10,11 are finally applied to the rotor 5. In accordance with the waymark S ₂ , the friction linings 10, 11 essentially come into contact with the rotor 5, a trigger Tl is set and the application force F increases. The application force F increases during the following Zuspannphase C up to the waypoint S ₃ with an approximately proportional slope. This correlates in Fig. 3 with the force curve of the slope α2 between 0 and Fl. Almost parallel to that 5, the characteristic curve of the rising current consumption I extends. Starting with the reference mark S _3, the slope of the application force F buckles during phase D - the characteristic curve of the current consumption I also essentially describes an inflection point from S ₃ . Trigger T2 is set. In phase D between S ₃ and S ₄ , the elastic element in the form of at least one spring element 9 is compressed. Since spring element 9 is prestressed in a defined manner, it is also known how large the reference force F1 correlating with the waymark S ₃ is. The additional connection of the spring element 9 is illustrated in Fig. 3 by a characteristic part, which correlates with an amended, constant assumed slope αl. With continuous path s, the continued spreading of the brake shoes 3, 4 leads to the progressive compression of the spring element 9. In this connection, the increase in the application force F between the distance marks S ₃ and S _{4 is} consequently reduced because the mechanical work is at least partially reversible in the spring element 9 is cached. Starting with the waypoint S ₄ , the spring element 9 is completely compressed or pressed onto a block. Therefore, the current consumption in the phase E, starting with the waymark S ₄ in Fig. 5 again describes a turning point. Subsequent to this inflection point (waymark S ₄ ), the further increase in clamping force in the section E proceeds with an increased gradient, which correlates with a characteristic curve region above F 2 in FIG. 3. As can be seen, the Zuspannkraftzunahme occurs in the phase E after switching off the electrical supply.

With the waypoint S ₅ , the clamping force F finally reaches a. At the same time there is no further displacement or spreading of the brake shoes 3, 4 and the position S of the brake shoes 3, 4 does not substantially change after the waypoint S ₅ . It has been found that there is a need to provide improved control over the engagement and disengagement operations of a duo-servo type parking brake with respect to an improved control model.

Reference will now be made in detail to FIG. 2, which describes a preferably software-implemented, and integrated in an electronic control unit ECU of the parking brake device trained, electronic control device and a corresponding control process in more detail. According to FIG. 2, a control circuit designed according to the invention has a reference variable 20, which is referred to below as the requested application force Freq. The reference variable 20 is impressed on a control module 17 for control or regulation by the electric motor 18 / M. In addition, a controller module 19 can be seen, which includes a software measure with an algorithm that models the clamping force, and in principle serves a virtual Zuspannkraftabschätzung or a derived variable for evaluating a control error predictive, as well as periodic-cyclical with a predetermined fixed or variable clock frequency essentially in real time based on input data, values or information. According to the invention, it is provided that the ECU, and in particular its controller module 19, the current current consumption 24, information about a motor shaft speed 23, and the applied supply voltage 22 is supplied. In the sense of a feedback, the predictive (fictitious) application force 21 formed in this way in the model is subtracted from the reference variable 20 at the summation point. The difference formed is impressed on the controlled system. The model thus formed for a clamping force control on the basis of a fictitious application force 25 therefore contains at least one measured or determined one System size, which represents the current current consumption I and a measured or determined system size representing the current engine speed n from the actuator 15. Disturbance variables 26, which may occur in particular as a result of friction and wear influences, are not sensed on the basis of this fictitious application force model, and are principally ignored or otherwise taken into account, for example as a model with a separate control module. It can be provided, for example, that these disturbance variables 26 can acquire an increased significance, in particular on the basis of system aging, stored on the basis of empirical values in a separate controller module, stored in a separate nonvolatile memory module 30 that can be electrically erased and rewritten by the ECU, and after Need separately the control device switched, without departing from the invention. The memory module 30 is preferably designed for this purpose as an EEPPROM or flash module. At the output of the controlled system thus formed, the controlled variable 27 in the form of the application force F can be seen. An arrow 28 illustrates an area of the control system in which data and information are actually measured or determined by means of sensors S, encoders G or similar measures internally integrated or arranged externally of the ECU, while the arrow 29 illustrates a system area in which data and information that is not sensory measured or determined, but provided on a different basis. To monitor the standstill state, sensors S are available which monitor a movement of the vehicle, in particular wheel rotation sensors, which are required in any case for a stability control program ESP.

According to the invention, it is provided in each case in summary that both a rotation information, for example a motor shaft speed and additionally the current consumption I from Motor 18 / M is determined or measured to form a fictitious clamping force. In a preferred embodiment of the invention, an incrementally operating rotary encoder is provided for the rotation information.

The parking brake control unit ECU may be provided separately in the vehicle and electronically networked with an ESP control unit ESP-ECU. Alternatively, it is possible to provide the ECU as an integrated part of an already required ESP control unit of a service brake device, which simplifies the effort for indirect or direct, separate, electronic supply and networking and connection to externally provided encoder G and sensors S and contributes to the rationalization ,

It is understood that the electronic control unit ECU has a plausibility stage, wherein an error message can be output to a suitable human machine interface MMI if error conditions have been detected.

Reference symbol

1 drive wheel

2 operating unit / expanding lock

3 brake shoe / brake member

4 brake shoe / brake member

5 rotor / brake drum

6 threaded nut

7 spindle

8 threaded nut spindle unit

9 spring element

10 friction lining

11 friction lining

12 reduction gear

13 pressure piece

14 pressure piece

15 Electromechanical actuator

16 support device

17 regulator module

18 engine / m

19 regulator module

20 leadership size

21 application force / F

22 supply voltage

23 motor shaft speed [l / min]

24 current consumption / I [A]

25 fictitious application force

26 Disturbance

27 controlled variable

28 arrow

29 arrow

30 memory module

A, B, C, D, E phase ECU electronic control unit

F force [N]

I current consumption [A]

U voltage [V]

PWM pulse width modulation

Fl reference force (preload force of the spring element 9 achieved)

Kl gain factor

ΔST adjustment path [mm]

FSOLL = Freq. Sollzuspannkraft

M engine

MMI human machine interface

G donors

S sensor

T1, T2 trigger s path [mm] sx path mark α gradient

Claims

claims

An electromechanically actuated parking brake for motor vehicles, and method of operation therefor, comprising at least one electronic control unit (ECU) having implemented software comprising a control strategy for controlled or regulated electrical supply of the parking brake, and for this purpose electrically with at least one reversible actuator

(15), as well as with one or more sensors (S) and / or encoders (G) is connected to the information supply in order to use the control strategy, a rotational drive rotational movement of an operating unit

(2) convert into a translational output movement such that brake shoes (3, 4) are pressed against a rotor (5) with a defined application force, or vice versa, characterized in that the control unit

(ECU) has at least one regulator module (19), the at least one information about a current consumption of the actuator (15) and a rotational information of the actuator

(15) are supplied for calculating a fictitious application force (25), and that the determined fictitious application force (25), or a controlled variable derived therefrom, is used to control the actuation unit (2).

2. Electromechanically actuated parking brake and operating method according to claim 1, characterized in that the calculation of the fictitious application force (25), or the derived control variable, iteratively-cyclically, in particular periodically, based on a predetermined defined clock frequency substantially in real time by the control unit ( ECU).

3. Electromechanically actuated parking brake and operating method according to claim 1, characterized in that the calculation of the fictitious application force (25) iteratively variable based on a variable clock frequency substantially in real time by the control unit (ECU) is made, and that the clock frequency in the range is increased by end positions of an actuator.

4. Electromechanically actuated parking brake and operating method according to claim 1, characterized in that the control unit (ECU) comprises means for measuring the current consumption of the actuator (15), and that a control module (19) of the control unit (ECU) rotational pulses for calculating the notional application force (25) are supplied.

5. Electromechanically actuated parking brake and operating method according to claim 1, characterized in that the control strategy has a plausibility logic, wherein it is checked whether the calculated fictitious application force (25) or the derived controlled variable, and the information regarding current consumption and rotation information are plausible, and wherein in the case of lack of plausibility of the control unit (ECU) an error message is issued.

6. Electromechanically actuated parking brake according to claim 1, characterized in that the regulator module

(19) the control unit (ECU) has at least one non-volatile, electronic memory section or memory module (30), and in that in the memory section or memory module defined measurement, Kenn-, reference or operating values of the parking brake are stored readable.

7. Electromechanically actuated parking brake according to claim 6, characterized in that the memory section or memory module (30) by the control unit (ECU) is formed erasable and / or writable.

8. Electromechanically actuated parking brake according to claim 6 or 7, characterized in that the memory module (30) is designed as EEPROM or flash EEPROM.

9. Electromechanically actuated parking brake and operating method according to one or more of the preceding claims, characterized in that when a parking brake actuation, the control strategy, a calculation based on the formula

F _soll = F ₁ + k _γ -As ₁ , has, with Fsoll = Zuspannkraftsollwert = lawl. defined, Fl = reference force = known, kl = gain factor, ΔST = unknown.

10. Electromechanically actuated parking brake and operating method according to one or more of the preceding claims, characterized in that after detection of a clamping force of the height Fl, the control strategy is a calculation based on the formula

^F * = ^F ι + K - ^As a _h

11. Electromechanically actuable parking brake and operating method according to one or more of the preceding claims, characterized in that the control unit (ECU) is provided separately to a control unit of an ESP control system (ESP-ECU), and provided electronically networked with this ESP control system, or the control unit (ECU) is provided as an integrated partial component, module or control module at least partially spatially integrated in a control unit of a stability control program (ESP-ECU).

12. Electromechanically actuable parking brake and operating method according to one or more of the preceding claims, characterized by, an electronic control unit (ECU) comprising at least one direct electrical connection to at least one encoder (G), and / or sensor (S) and / or an ESP -ECU or by at least one indirect electrical connection to at least one encoder (G) and / or a sensor (S) each with the interposition of a control unit of a stability control program (ESPECU).