DE102019203203A1 - Procedure for setting a creep mode, control unit, drive arrangement and vehicle - Google Patents

Abstract

The invention relates to a method for setting a creeping operating state (B _Kr ) of a vehicle (100) with an electric drive (1), comprising: starting the creeping operating state (B _Kr ); Building up a wheel torque (M _R ) up to a creeping torque (M _Kr ) for building up and maintaining a creeping speed (v _Kr ); Detecting a wheel standstill signal (S _St ); Checking an abort criterion (K _Fig ) for aborting the creep operating state (B _Kr ); Reduce the wheel torque (M _R ) by deactivating the electric drive (1) and ending the creep mode (B _Kr ) if the abort criterion is present (K _Fig ). The invention also relates to a control device (9), a drive arrangement (1) and a vehicle (100), each suitable for carrying out the method according to the invention.

Description

The invention relates to a method for setting a creeping operating state (also creeping functionality) of a vehicle with an electric drive, comprising: starting the creeping operating state, building up a wheel torque up to a creeping torque for building up and maintaining a creeping speed. The invention further relates to a control device, a drive arrangement and a vehicle, each of which is set up and designed to carry out such a method.

Modern vehicles with internal combustion engine drive and automatic clutch arrangements have creep functions that make it possible to set a vehicle in motion without having to operate an accelerator pedal. When the brake pedal is released to stop the vehicle, a wheel torque or a creep torque is built up via a hydrodynamic torque converter or a controlled engagement of a friction clutch, which sets the vehicle in motion at a very low speed. Such creep controls or creep functionalities are particularly useful when starting up slowly or when starting from standstill on an incline or when performing very slow driving maneuvers (for example: parking, stop-and-go).

The same functionality should also be usable in vehicles with an electric drive. There are different approaches to implement the creep functionality.

From the DE 10 2008 053 937 A1 There is known a method of vehicle creep torque control in which variable creep torque can be provided by detecting a vehicle creep torque condition, determining an initial braking torque, and then adjusting the applied creep torque based on the initial braking torque. The creep torque is then reduced as the braking effect increases. Ultimately, the desired creep torque is adapted here to the braking effect so that the energy required for the creep torque provided can be minimized.

From the US 2011/0029172 A1 an approach is known in which a creep functionality is implemented on an incline by preventing the vehicle from rolling back even when the brake pedal is released by building up a suitable creeping torque, in that the creeping torque that has built up counteracts and compensates for an output force. The vehicle is thus able to hold its position on an incline without pressing the brake or accelerator pedal.

Another approach is from the US 2016/0303998 A1 known, in which a creep functionality is used to accelerate and decelerate an electric vehicle simply by actuating the accelerator pedal and to put it back into a crawling movement without further actuation of the accelerator pedal.

An important safety aspect in the crawl functionality concerns the start-up or anti-trapping protection in a driving situation in which the vehicle drives against a stationary obstacle in the crawling mode and the crawling drive is thus stopped. In the worst case, a person can be trapped between the obstacle and the vehicle.

In vehicles with an internal combustion engine drive and a separating clutch between the engine and the drive train, the engine is either stalled or it opens after a certain period of time without vehicle movement, the crawling state and U. slipping clutch automatically to prevent damage from overheating. In any case, no drive torque (creep torque) acts on the drive wheels and the vehicle can be pushed back with the clutch open so that a trapped person can free himself or at least be easily freed with the help of other people.

For vehicles with an electric drive with creep functionality or a creep mode, however, when starting up against such a stationary obstacle - for example against a wall - the wheel torque or the creep torque is built up again in order to reach the creep speed again. Electric drives can build up a very high torque even in the very low speed range and a very large speed range is available. Therefore no gear and therefore no clutch is required. The vehicles are driven with what is known as an automatic input system, which consists in the electric drive being controlled accordingly by means of suitable power electronics and a control unit.

However, due to the lack of a mechanical coupling, the drive torque is built up when starting against an obstacle and thus also when a person or an object is trapped. Therefore, in vehicles with an electric drive, starting and / or trapping situations can be particularly critical.

One solution could be to limit the creep torque in order to reduce the starting / trapping forces. However, this would be the creep operation on inclines or when overcoming obstacles and the like. U. limited - especially with heavy vehicles.

The additional use of a disconnect clutch to ensure the start-up / anti-trap protection described above in connection with internal combustion engines is structurally complex and expensive. Even the known approaches to setting a creep operating state do not provide a solution for realizing an effective anti-jamming and / or collision protection with the simultaneous availability of a full-fledged creep functionality.

The object of the present invention is therefore to provide a method for setting a creep operating state in which the above-mentioned disadvantages can be at least partially overcome. A further object is to provide a correspondingly suitable control device, a drive arrangement and a vehicle which are each suitable for carrying out such a method.

This object is achieved by the method according to the invention according to claim 1, the control device according to claim 8, the drive arrangement according to claim 9 and the vehicle according to claim 10. Further advantageous embodiments of the invention emerge from the subclaims and the following description of preferred exemplary embodiments of the present invention.

According to a first aspect of the present invention, a method for setting a creep operating state of a vehicle having an electric drive comprises: starting a creeping operating state; Building up a wheel torque up to a creeping torque for building up and maintaining a creeping speed, detecting a wheel standstill signal, checking an abort criterion for aborting the creeping operating state; Reduce the wheel torque by deactivating the electric drive and ending the creep mode if the termination criterion is met.

By checking the abort criterion for aborting the creep mode for a wheel standstill signal, the wheel torque can be reduced when driving against an obstacle or when a person is trapped, for example by deactivating the electric drive so that the wheel torque is no longer effective. At the same time, the creep mode is ended (permanently), so that it is not reactivated when the torque is reduced. By checking (querying) the termination criterion, on the one hand, a simple and flexible means is available which allows the creeping mode to be ended quickly and sustainably.

On the other hand, the definition and the technical design of this general termination criterion leaves room for different and possibly complementary individual criteria that form the termination criterion. In this way, single and multiple criteria can be taken into account when checking the termination criterion.

Basically, parameters such as torque, standstill time, torque curve (change in torque over time), speeds, speed curves but also variables that are specific to the electric drive, such as current, voltage curves, resistances, operating temperatures and the like, come into question as termination criteria .

There are methods in which the detection of the termination criterion comprises the following: detection of a wheel standstill period, ie a wheel standstill period, and comparing the wheel standstill period with a wheel standstill period threshold, ie a maximum permissible wheel standstill period. The termination criterion is present when the wheel standstill period exceeds the wheel standstill period threshold. A period is therefore defined, the wheel standstill period threshold, which must be exceeded so that the termination criterion is present. This is done, for example, by starting a timer that is started when the wheel standstill is detected. The timer then determines the wheel standstill period, which is compared with the wheel standstill period threshold. As soon as the wheel standstill period exceeds the wheel standstill period threshold, the termination criterion is established and the creep mode is ended. In effect, a time-triggered termination criterion corresponds to the interruption by a separating clutch which is opened after a certain time.

There are versions in which the wheel standstill period threshold is adjustable. It can thus be adapted in a simple manner to different operating states, in particular creeping operating states. For example, the wheel standstill period threshold can be higher at a low crawling speed than at a higher crawling speed. In this way, the sensitivity of the method can be set in a simple manner as a function of the creep speed or, in another embodiment, also as a function of the creep torque.

There are methods in which the detection of the termination criterion comprises the following: the detection of the wheel torque and the comparison of the wheel torque with a maximum wheel torque, the termination criterion being present when the detected wheel torque exceeds the maximum wheel torque. With this solution, a maximum wheel torque is specified, which must not be exceeded. In this way, excessive stop or trapping forces can be avoided. These termination criteria can also be used in addition to the time-triggered termination criterion in order to shorten the time when the termination criterion is determined - for example, if very high wheel torques should be built up before the wheel standstill period threshold has been reached.

There are methods in which the maximum wheel torque corresponds to the sum of the creep torque and a differential torque. It can thus be ensured that the approach according to the invention also works in situations in which the creep torque must first be used or must be built up in order to overcome a gradient. Here is the creep torque to be built up u. U. significantly higher than what is required to crawl without a slope. In such a case, effective anti-trap protection does not primarily depend on the absolute creep torque, but on a differential torque. This is built up when the drive torque, which is at least required to prevent the vehicle from rolling back, is supplemented by the actual creep or differential torque, which causes the creep against the incline and then also causes the stop or trapping forces.

There are also methods in which, when checking a termination criterion, both a wheel standstill period and a creeping torque or a differential torque are taken into account together. For example, it is possible to start the detection of a wheel standstill period only when a certain minimum wheel torque is exceeded. This can be helpful, for example, when the intended wheel standstill period threshold is low, that is to say, for example, should be in the low seconds range or less than one second. For example, it can be prevented that a comparatively short wheel standstill, as can occur when crossing a higher threshold in the creep mode, should not lead to the end of the creep mode and the reduction of the wheel torque.

There are methods in which the reduction of the wheel torque comprises, for example, one of the following steps: actuation of a separating clutch, actuation of a wheel brake arrangement. The additional actuation of a separating clutch, as it can be present, for example, in hybrid vehicle concepts, makes it possible to reduce a built-up wheel torque and thus a trapping force very quickly and effectively. A supplementary actuation of a wheel brake arrangement can, for example, prevent a vehicle from rolling back in an uncontrolled manner on an incline in which the crawling mode was terminated.

There are also methods in which the checking of the abort criterion for aborting the creep operating state includes the detection of a braking torque applied by means of a braking system. There is then no termination criterion if the detected wheel torque is less than the braking torque or a braking force corresponding to a specific braking torque. With such an embodiment it is ensured that the creeping operating state is maintained when the wheel standstill is caused by the actuation of the brake system. This ensures that the creeping process is resumed when the brake is released.

In addition, it can be provided that the drive torque is reduced during the braking process in accordance with the applied braking torque and, as a result, the energy consumption when braking into the creeping process is reduced as the braking effect increases. The creep torque is not built up against an increasing braking force.

The invention further relates to a control device which is set up and designed to set the creep operating state of a vehicle with an electric drive according to the method according to the invention.

The present invention also relates to a drive arrangement for a vehicle with an electric drive and a control device which is set up and designed to carry out the method according to the invention.

The invention also relates to a vehicle with such a drive arrangement which can be operated exclusively or partially via an electric drive. Such vehicles include vehicles with a purely electric drive but also hybrid vehicles in which an electric drive is provided for the (temporarily) exclusive or auxiliary drive and in particular also forms the exclusive drive during a crawling mode.

Further advantageous embodiments of the invention emerge from the subclaims and the following description of preferred exemplary embodiments of the present invention.

• 1 schematisch ein Fahrzeug mit einer Antriebsanordnung, die zur Ausführung des erfindungsgemäßen Verfahrens geeignet ist;
• 2 eine schematische Darstellung einer Schaltlogik für eine Steuerung zur Ausführung des erfindungsgemäßen Verfahrens und
• 3 einen Ablaufplan eines Ausführungsbeispiels des erfindungsgemäßen Verfahrens.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings. It shows:

• 1 schematically, a vehicle with a drive arrangement which is suitable for carrying out the method according to the invention;
• 2 a schematic representation of a switching logic for a control for carrying out the method according to the invention and
• 3 a flow chart of an embodiment of the method according to the invention.

The 1 an embodiment of a vehicle according to the invention 100 with a drive arrangement according to the invention 1 which is suitable for carrying out the method according to the invention.

The stylized vehicle 100 comprises a drive arrangement according to the invention 1 with an electric drive 2 that here as on a drive axle 3 acting electric motor is formed, which the two front wheels 4th drives, which form the drive wheels here. The electric drive is optional 2 via a disconnect clutch 12 with the drive axle 3 coupled. Each of the drive wheels 4th includes a brake assembly 5 and a speed sensor 6th . The rear wheels 7th are also with brake assemblies 5 Mistake. Again, for each bike 7th corresponding speed sensors 6th be provided (not shown).

The electric drive 2 , the brake assemblies 5 and the speed sensor (s) 6th are via signal lines 8th with a vehicle control unit 9 Mistake.
The vehicle 1 is in a creeping operating state B _Kr , in which it was moving at low speed v - the creeping speed v _Kr - in the direction of travel F (direction of arrow). The vehicle 100 is against a fixed obstacle 10 rolled and came to a standstill (v = 0). An object or a person can also be between the fixed obstacle 10 and the vehicle 100 be trapped. The control 9 is designed and set up in such a way that it recognizes this critical creep condition, namely the impact on the stationary obstacle 10 or trapping a person between the obstacle 10 and vehicle 100 , and the creep mode B _kr ends, so that the vehicle 100 after the end of the creep condition B _Kr no more force against the obstacle 10 or a trapped person or object. To establish and end this critical state, torque signals from the electric drive, which are transmitted to the control unit, are used, speed signals from the speed sensors 6th to the control unit 9 are transmitted, as well as time signals that are in the control unit 9 and serve to recognize the critical driving state from the creep operating state B _Kr and to terminate it if a termination criterion K _{Fig is present} .

2 shows the in the control unit 9 trained switching logic in a schematic block diagram which terminates the creep operating state B _Kr when a termination criterion K _{Fig is present} .

For this purpose, the actual creep operating state B _Kr is first started by setting a switching bit SB. The following variables are taken into account to terminate the creeping operating state B _Kr : the wheel torque or drive torque M _{R of} one of the drive wheels 4th , a vehicle speed v, for example via the speed sensors 6th on the drive wheels 4th or on the non-powered rear wheels 7th recorded and sent to the control unit 9 be signaled. The determination of the drive speed v or the creep speed v _Kr via the non-driven wheels 7th has the advantage that even if the drive wheels are spinning 4th reliably a vehicle speed v via the wheels that just roll along 7th can be determined.

In the creep state, there is normally a creep torque M _Kr and a creep speed v _Kr . According to the in 2 The illustrated embodiment is the termination criterion K _Abb when the speed sensor or sensors 6th a wheel standstill signal Sst is detected. Such a signal is detected when the creeping speed v _{Kr is} equal to zero.

If there is now a creep torque M _kr on the drive wheels at the same time 4th via the electric drive 2 before and a standstill signal Sst is detected, a timer 11 started, which records a wheel standstill period T _St. This wheel standstill period T _St is then compared with a wheel standstill period threshold T _StS . If the detected wheel standstill period Tst exceeds the wheel standstill period threshold T _StS and at the same time there is a via the switching bit SB activated creep mode B _Kr before, the termination criterion K _{Abb is} determined and the electric drive 2 is deactivated and the creep mode B _Kr is ended. The vehicle exercises with it 100 no more force against the obstacle 10 or against one between the vehicle 100 and the obstacle 10 jammed object or person.

As an alternative or in addition to the time-controlled check of the termination criterion by comparing the wheel standstill period TSt with the wheel standstill period threshold T _StS , a torque-controlled check can also optionally or in addition of the termination criterion K _Fig . For this purpose, a wheel torque M _{R is} compared with a maximum wheel torque M _Rmax . If the wheel torque M _R exceeds the maximum wheel torque, the abort criterion K _{Abb is} determined and the electric drive is deactivated or the creep mode B _Kr is ended when a standstill signal Sst (v = 0) is simultaneously detected.

The detected wheel torque M _R can also be compared with a sum of the creep torque M _Kr and a differential torque M _Diff . In this case, the creep torque M _{Kr is} required for the vehicle 100 to move against a driving resistance - for example on an incline - in creep mode. The vehicle now hits the obstacle 10 , an additional wheel torque M _{Diff is} built up in order to move the vehicle further. If the detected wheel torque M _R now exceeds this composite vehicle torque (M _Kr + M _Diff ), the condition is met in order to determine the termination criterion K _Abb . M _Rmax is composed of the creep torque M _Kr and a definable differential _torque M _Diff . This maximum wheel torque is, for example, lower on level ground than on an incline.

Furthermore, it is also possible to make the wheel standstill period threshold T _StS adjustable or variable. It can be made dependent, for example, on a creeping speed v _Kr or on a wheel torque M _R. Thus, the wheel standstill period threshold Tsts can be designed to be lower at high speeds or high wheel torques, so that the termination criterion K _Abb can be determined after a shorter wheel standstill time T _St.

3 shows a schematic sequence of the method for setting a creeping operating state B _{Kr of} a vehicle 100 with an electric drive. In this case, the creeping operating state B _{Kr is} started first, a wheel torque or a creeping torque M _Kr is built up and a creeping speed v _Kr is built up. If there is now a wheel standstill signal Sst, which possibly signals a critical driving state, the abort criterion K _Abb for aborting the creep operating state B _{Kr is} checked and, if the abort criterion K _Abb is present, the wheel torque M _{R is set} by deactivating the electric drive 2 and ending the creep mode B _Kr reduced.

The detection of the termination criterion K _Abb can include: the detection of a wheel standstill period T _St and the comparison of the wheel standstill period T _St with a wheel standstill period threshold T _StS , the termination criterion being present when the wheel standstill period exceeds the wheel standstill period threshold T _StS .

As an alternative or in addition, the detection of the termination criterion K _{Abb can} include: the detection of the wheel torque M _R and the comparison of the wheel torque M _R with a maximum wheel torque M _Rmax , the termination criterion K _{Abb being} present when the recorded wheel torque M _{R is} the maximum wheel torque M. _Rmax exceeds.

Further variants and embodiments of the invention emerge for the person skilled in the art within the scope of the claims.

List of reference symbols

100

vehicle

1

Drive arrangement

2

electric drive, electric motor

3

Drive matter

4th

Front wheels / drive wheels

5

Brake assembly

6th

Speed sensor

7th

Rear wheel

8th

Signal line

9

Control unit

B _Kr

Creep mode

F.

Direction of travel

10

fixed obstacle

12

Disconnect clutch

SB

Switch bit

M _R

Wheel torque

M _Kr

Creep moment

v

speed

v _Kr

Creep speed

S _St

Wheel standstill signal

K _Fig

Termination criterion

Tst

Wheel standstill period

T _StS

Wheel standstill period threshold

M _Rmax

maximum wheel torque

M _diff

Differential torque

QUOTES INCLUDED IN THE DESCRIPTION

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

Patent literature cited

• DE 102008053937 A1 [0004]
• US 2011/0029172 A1 [0005]
• US 2016/0303998 A1 [0006]

Claims (15)

Method for setting a creeping operating state (B _Kr ) of a vehicle (100) with an electric drive (1), comprising: - starting the creeping operating state (B _Kr ); - Building up a wheel torque (M _R ) up to a creep torque (M _Kr ) to build up and maintain a creep speed (v _Kr ); - Detection of a wheel standstill signal (S _St ); - Checking an abort criterion (K _Fig ) for aborting the creep operating state (B _Kr ); - Reduction of the wheel torque (M _R ) by deactivating the electric drive (1) and ending the creep mode (B _Kr ) if the termination criterion is present (K _Fig ). Procedure according to Claim 1 , whereby the acquisition of the termination criterion (K _Fig ) comprises: - Acquisition of a wheel standstill period (T _St ) - Comparison of the wheel standstill period (T _St ) with a wheel standstill period threshold (T _StS ), the termination criterion (K _Fig ) being present when the wheel standstill period ( T _St ) exceeds the wheel standstill period threshold (T _StS ). Procedure according to Claim 1 or 2 , whereby the detection of the termination criterion (K _Abb ) comprises: - Detecting the wheel torque (M _R ) - Comparing the wheel torque (M _R ) with a maximum wheel torque (M _Rmax ), the termination criterion (K _Abb ) then being present when the detected Wheel torque (M _R ) exceeds the maximum wheel torque (M _Rmax ). Procedure according to Claim 3 , wherein the maximum wheel torque (M _Rmax ) corresponds to the sum of the creep torque (M _Kr ) and a differential torque (M _Diff ). Method according to one of the Claims 2 , 3 , or 4, whereby the wheel standstill period threshold (T _StS ) is adjustable. Procedure according to Claim 5 , the wheel standstill period threshold (T _StS ) being adjustable as a function of a creeping speed (v _Kr ). Procedure according to Claim 5 or 6th , the wheel standstill period threshold (T _StS ) being adjustable as a function of the wheel torque (M _R ). Method according to one of the preceding claims, wherein reducing the wheel torque (M _R ) comprises: actuating a wheel brake arrangement (5) and applying a braking torque (M _Br ). Procedure according to Claim 8 , whereby the wheel torque (M _R ) is reduced according to the applied braking torque (M _Br ) Method according to one of the preceding claims, wherein the reduction of the wheel torque (M _R ) comprises: actuation of a separating clutch (12). Method according to one of the preceding claims, wherein checking the abort criterion (K _Fig ) for aborting the creep operating state (B _Kr ) comprises the detection of a braking torque (M _Br ) applied by means of a brake system (5), with no abort criterion being present if the detected wheel torque ( M _R ) is smaller than the braking torque (M _Br ). Control device (9) which is set up and designed to control the creep operating state (B _Kr ) of a vehicle (100) with an electric drive (1) according to the method according to one of the Claims 1 to 11 adjust. Drive arrangement for a vehicle (100) with an electric drive (1) and a control unit (9) Claim 12 . Vehicle (100) with a drive arrangement Claim 13 . Vehicle (100) after Claim 14 , wherein the vehicle (100) is designed as a hybrid vehicle.

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