DE102007005871B3 - Vehicle wheel baking method, involves comparing measuring value and predetermined measuring reference value, and adjusting braking force by measuring value depending upon exceeding or falling of predetermined measuring reference value - Google Patents

Abstract

The method involves producing braking force (F) by using an electrical parking brake (EPB) for dynamic braking of a wheel (R) of a vehicle, where the force is produced for decelerating or temporary blocking of the wheel. A measuring value (MW1) indicating actual acceleration of the vehicle during dynamic braking is determined. The measuring value is compared with a predetermined measuring reference value (MWS1), and the produced braking force is adjusted by the measuring value depending upon exceeding or falling of the measuring reference value.

Description

The The invention relates to a method and a control arrangement for dynamic Braking a vehicle by means of at least one electric parking brake according to the generic term of claim 1 and 10.

In increasing dimensions become conventional purely mechanically controllable parking brakes through electronically controllable parking brakes or so-called parking brake systems replaced, in which the generation of the actuation of the brake mechanism required force over an electronic control system is controlled. Depending on the presence an electronic steep signal, the parking brake is controlled via the Control system tightened or released.

to Generation of a mechanical brake acting on the brake mechanism Adjusting force, for example, an electric motor-gear unit is provided which, for example with the brake mechanics over a cable system connected and controlled by the control system is. The electronic steep signal to operate the electric parking brake This is for example by a provided in the vehicle electronic Operating element, in particular a touch, rocker or switching module generated. alternative The electric parking brake can be over through a control routine generated steep signal to be controlled.

A electronic parking brake allows beside additional Safety and comfort functions also a dynamic braking of the vehicle during the journey, especially in emergency situations and to increase the Braking force provided by a defective service brake. Also The electronic parking brake can be independent of the service brake used for the dynamic braking of a vehicle. For security reasons In this case, the operating state of the electronic parking brake as well individual operating parameters of the vehicle by means of a monitoring routine checked constantly, so that a potential or actual Blocking the wheels to be braked automatically detected by the monitoring routine and the electric parking brake is then released immediately.

adversely are such monitoring routines however faulty. For example, an incorrectly determined Wheel speed or various environmental situations such as To carry black ice, that by the monitoring routine at least a short-term locking of the wheels is detected, namely because they do not produce any appreciable braking effect. The electric Parking brake is due to the longer time of the electric time Parking brake for a relatively long period of time, d. H. the driver is one Dynamic braking of the vehicle by means of the electric parking brake not possible anymore.

Out In the prior art are already electric parking brake systems known in which dependent from a given speed limit despite blocking Wheels continue the electric parking brake is available for dynamic braking, and that is when falling below the predetermined speed limit by the currently determined vehicle speed, the monitoring routine described above locked, d. H. although a blocking wheel can be detected continue to be braked by means of the electric parking brake. The Speed limit is here, for example, in the range of 10-15 km / h.

The post-published document DE 10 2005 034 326 A1 describes a vehicle with a service brake system and a parking brake. If the service brake pedal is operated such that a ratio of the actuation of the brake pedal to decelerate the vehicle exceeds a predetermined threshold value, it is recognized that an emergency braking situation has occurred and the emergency braking is initiated.

The document EP 0 976 634 A2 describes a parking brake system in which two wheel brakes each associated with an arranged in the region of the suspension actuator. In this case, a respective flexible transmission means for transmitting the actuating force is provided between the actuators and the wheel brakes.

task The present invention is a method and a control arrangement for the dynamic braking of a vehicle by means of at least one specify electric parking brake, by means of a dynamic braking a vehicle by the electric parking brake even at a at least short-term blocking of the wheels, especially in slippery Road conditions, continue guaranteed is.

The Task is in each case starting from the preamble of the independent claim 1 and 10 solved by its characterizing features. advantageous Embodiments of the invention are the further dependent claims remove.

An essential aspect of the method according to the invention is that at least one first measured value indicating the current acceleration of the vehicle during the dynamic braking process is determined. The at at least one determined first measured value is subsequently compared with a predetermined measured setpoint value and the braking force generated for the dynamic braking is adapted as a function of the overshooting or undershooting of the measured setpoint value by the determined first measured value. The method described advantageously makes possible an improved availability of the electric parking brake EPB during dynamic braking without causing the driving situations, which are normally critical, by blocking the braked wheels.

One Another advantage is the fact that at least one wheel slip indicating at least the wheel of the vehicle to be braked second Measured value is determined and the at least one determined second Measured value compared with a predetermined second measurement setpoint becomes. The generated braking force is subsequently increased until the determined second measured value exceeds the second measured setpoint.

Especially Advantageously, the time duration of exceeding or falling below the first measured setpoint determined by the determined first measured value and when crossing a predetermined time threshold adapted to the braking force generated.

Farther Advantageously, the first measured setpoint is an acceleration threshold and the second measurement setpoint is defined by a wheel slip threshold, wherein the Radschlupfschwelle variably adjustable, in one Value range of the speed or the acceleration of the vehicle or a combination of these is dependent.

in the The invention is based on an embodiment with reference to drawings explained in more detail. It demonstrate:

1 exemplified a block diagram of a control system for the dynamic braking of a vehicle by means of at least one parking brake and

2 and 3 two flowcharts of a control and evaluation routine for the dynamic braking of a vehicle by means of at least one parking brake.

In 1 is an example of a schematic block diagram of an electric parking brake EPB shown with an integrated control system SS, which has a control unit CU and a memory unit connected to this MU. In an alternative embodiment, the control system SS may be arranged spatially separate from the electric parking brake EPB or in an already existing control device of a vehicle (not in FIG 1 shown).

The electric parking brake EPB can either have at least one in the vehicle provided operating element or via another provided in the vehicle control unit, in particular a brake control unit activated or actuated (not shown in the figures).

The electric parking brake EPB is in addition to a conventional Service brake provided a vehicle. Normally done a dynamic braking of the vehicle via the service brake and a static braking of the vehicle by means of the electric parking brake EPB. Below is considered the case that one of the service brake independent Dynamic braking of the vehicle via the electric parking brake EPB performed becomes.

The electric parking brake EPB has to generate a force STF, STF *, for example, at least one electric motor-gear unit EGE, EGE *. The actuating force STF, STF * is provided by the electric motor-gear unit EGE, EGE *, for example, directly or indirectly to a brake mechanism unit BMU, Transmit BMU *, which is in each case associated with a wheel R, R * of the vehicle and For example, about a cable system SZS, SZS * with the electric motor gear unit EGE, EGE * is in active connection. Depends on the on the brake mechanism unit BMU, BMU * applied force STF, STF * becomes a braking force F, F * generated by the brake mechanism unit BMU, BMU *, by means of the at least one wheel R, R * of the vehicle is braked.

In the control unit CU of the control system SS is for dynamic braking of the vehicle by means of at least one provided in the vehicle electric parking brake EPB a control routine RR and a control and evaluation routine SAR provided, which in each case in the control unit CU executed become. By means of the control routine RR, for example, a dynamic Brake control according to the state realized the technology.

At For example, the control system SS is a first and second measuring unit ME1, ME2 connected, via which concerns at least one first and second measured value MW1, MW2 the current movement status of the vehicle or individual wheels of the Vehicle, in particular the acceleration B or the wheel slip S measured and in the form of a first and second measurement signal ms1, ms2 to the control system SS, in particular the control unit CU transmitted become.

For example, the first measurement signal ms1 of the acceleration B and the second measurement signal ms2 depending on the wheel slip S, ie by evaluating the first and second measurement signal ms1, ms2 by means of the control and evaluation routine SAR, a first and second measured value MW1 (B), MW2 (S) can be determined, wherein the first measured value MW1 the current acceleration B of the vehicle at the measuring time and the second measured value MW2 the wheel slip S of show the respective wheel R, R * of the vehicle.

The first and second measurement signal ms1, ms2 become for this purpose, for example each over a wireless and / or wired interface from the first one and second measuring unit ME1, ME2 transmitted to the control unit CU. In a preferred embodiment the determined first and second measured values MW1 (B), MW2 (S) possibly stored together with the measurement time in the memory unit MU.

The control and evaluation routine SAR provided for carrying out the method according to the invention is shown by way of example in FIG 2 and 3 each shown in a flow chart.

About the Control and evaluation routine SAR is first determined whether an activation the electric parking brake EPB for the dynamic braking of the vehicle or one of the wheels R is present. Activation is, for example, when controlled by the control routine RR braking force F, F * for dynamic braking of the vehicle is generated, d. H. the electric motor transmission unit EGE, EGE * is controlled such that by means of this a force STF, STF * is generated via the Cable system SZS, SZS * transmitted to the brake mechanism unit EMU, BMU * becomes.

Lead the Activation of the electronic parking brake EPB at least one short-term blocking of the wheels R, R *, so will be first the current acceleration B of the vehicle determined. To do this by the control and evaluation routine SAR depending on the currently measured first measurement signal ms1 at least the first measured value MW1 determined. The first measured value MW1 indicating the current acceleration B is compared with a first measured setpoint MWS1 and depends on the over- or Falling below the first measured setpoint MWS1 by the determined first measured value MW1 which is provided for the dynamic braking of the vehicle Braking force F, F * adapted, d. H. either increased, kept constant or lowered.

in this connection For example, the first measured setpoint MWS1 gives an acceleration threshold in which it is assumed that, despite the dynamic braking process no reduction in the speed V of the vehicle occurred is. In particular, it is detected here whether a change in the Acceleration B of the vehicle is present, due to an effective dynamic braking of the vehicle is assumed.

At the in 2 For example, the first measured setpoint value MWS1 = 0 is set and, when the first measured setpoint value MWS1> = 0 is exceeded, an adjustment, for example a stepwise increase in the braking force F by a predetermined value ΔF, is made by the first measured value MW1 determined performed. If the first measured value MW1 falls short of the first measured setpoint MWS1 = 0, ie if a deceleration of the vehicle occurs, conventional control of the electronic parking brake EPB is carried out by means of the dynamic braking control routine RR. An adjustment of the braking force F dependent on the determined acceleration B does not take place.

optional can be a time threshold .DELTA.T are given, which, for example, compared with the duration T will, while the acceleration B over the acceleration threshold given by the first measured setpoint MWST lies. Only when crossing the time threshold .DELTA.T by the period T, an adaptation of the braking force F. Alternatively can the time threshold .DELTA.T dependent from the time of actuation the electric parking brake EPB are selected and / or the period of time T from the time of actuation the electric parking brake EPB be detected.

In an alternative embodiment of the control and evaluation routine SAR according to 3 After the activation of the electric parking brake EPB, it is again checked whether the wheel R, R * dynamically braked by the electric parking brake EPB blocks, at least in the short term.

Subsequently, will for example, the wheel slip S indicative second measured value MW2 determined and compared with a predetermined second measurement setpoint MWS2, wherein by the second measurement setpoint MWS2 a Radschlupfschwelle is given. When the second measured setpoint is undershot MWS2 through the second measured value MW2 becomes the method according to the invention carried out, d. H. the acceleration B of the vehicle evaluated analogously before and possibly adapted to the braking force F of the electric parking brake EPB. By monitoring of the wheel slip S is an excessive increase in the braking force F, in particular a conditional complete Blocking the wheels R effectively avoided.

If the currently measured wheel slip S or the second measured value MW2 exceeds the predefined wheel slip threshold or the second measured setpoint value MWS2, for example, the control routine RR without an adaptation of the braking force F, F * executed.

In a preferred embodiment is the wheel slip threshold given by the second measurement setpoint MWS2 variably adjustable. For example, the value range of the adjustable Wheel slip threshold dependent from the speed V, the acceleration B and / or a combination of both measured values MW1, MW2 selected become.

The For example, the speed V of the vehicle may be based on the wheel speeds the individual wheels R, R * are derived or by evaluation of the first measurement signal ms1, wherein the acceleration B indicative first measurement signal ms1, for example, by means of a trained as an acceleration sensor first measuring unit ME1 can be determined. Alternatively, the first Measurement signal ms1 also from the measured wheel speeds the individual wheels R, R * are derived.

B

acceleration

BMU, BMU *

Brake mechanism unit

CU

control unit

EGE, EGE *

Electric motor-gear unit

EPB

electrical parking brake

F, F *

braking force

ME1

first measuring unit

ME2

second measuring unit

ms1

first measuring signal

ms2

second measuring signal

MU

storage unit

MW1

first reading

MW2

second reading

MWS1

first measurement threshold

MWS2

second measurement threshold

R R *

wheel

RR

control routine

S

wheel slip

SAR

Tax- and evaluation routine

SS

control system

STF, STF *

force

SZS, SZS *

cable system

T

time

V

speed

.DELTA.F

value

.DELTA.T

time threshold

Claims (10)

Method for the dynamic braking of a vehicle by means of at least one parking brake (EPB), in which a braking force (F, F *) is generated by the at least one parking brake (EPB) for dynamically braking at least one wheel (R, R *) of the vehicle for delaying or at least temporarily blocking at least one wheel (R, R *) leads, characterized in that at least one of the current acceleration (B) of the vehicle during the dynamic braking indicative first measured value (MWl) is determined that the at least one determined first Measured value (MW1) is compared with a predetermined first measured setpoint (MWS1), and that depending on the above or below the measured setpoint (MWS1) by the determined first measured value (MW1), the braking force generated for dynamic braking (F, F *) is adjusted , Method according to claim 1, characterized in that that falls below the first measurement setpoint (VAT) by the determined first measured value (MW1) the generated braking force (F) increased, constant held or reduced. Method according to claim 1 or 2, characterized that when crossing of the first measured setpoint (MWST) by the determined first measured value (MW1) the generated braking force (F) is increased or kept constant. Method according to one of claims 2 or 3, characterized that the braking force (F) is adjusted step by step, respectively a predetermined value (ΔF) elevated or humiliated. Method according to one of claims 1 to 4, characterized, that at least one wheel slip (S) of the wheel to be braked (R, R *) the second measured value (MW2) indicating the vehicle is detected, that the at least one determined second measured value (MW2) having a predetermined value second measured setpoint (MWS2) is compared, and that the generated Braking force (F, F *) is increased as long until the determined second measured value exceeds the second measured setpoint (MWS2). Method according to claim 1 or 5, characterized that the duration (T) of the over- or Fall below the first measured setpoint (VAT) by the determined first measured value (MW1) is determined and when a predetermined value is exceeded Time threshold (ΔT) the generated braking force (F) is adjusted. Method according to one of claims 4 to 6, characterized that by the first measurement setpoint (MWST) an acceleration threshold and by the second measurement setpoint (MWS2) a wheel slip threshold is defined. A method according to claim 7, characterized in that the predetermined by the second measurement setpoint (MWS2) Radschlupfschwelle variable adjustable, is. Method according to claim 8, characterized in that the value range of the wheel slip threshold depends on the speed (V) of the vehicle, the acceleration (B) of the vehicle and / or a combination of these chosen becomes. Control arrangement (with a control system (SS)) for dynamic braking of a vehicle by means of at least one parking brake (EPB), in which by at least one parking brake (EPB) to the dynamic Braking at least one wheel (R, R *) of the vehicle a braking force (F, F *) is generated, which is to delay or at least short-term Blocking at least one wheel (R, R *) of the vehicle leads, thereby in that the control system (SS) has a control and evaluation routine (SAR) to determine at least one of the current acceleration (B) of the vehicle during of dynamic braking indicating first measured value (MW1) and for comparing the at least one determined first measured value (MW1) having a predetermined first measurement setpoint (MWS1), wherein dependent from the or undershooting of the measured setpoint (MWS1) by the determined first measured value (MW1) the braking force generated for dynamic braking (F, F *) over adapted the control system (SS) becomes.