The invention relates to a method for operating an electrically operable parking brake system of a vehicle.

The present invention further relates to a control device of an electrically operable parking brake system of a vehicle, wherein the control device is designed for imple- menting the method according to the invention.

Vehicles, for example, utility vehicles, generally possess a service brake used for braking during a driving operation of the vehicle and a parking brake system independent of the service brake which secures the vehicle by applying a braking force in the parked state. The service brake and the parking brake system may conceptually be referred to as the brake system of the vehicle. In modern vehicles, the service brake as well as the parking brake system are often electrically operable. Accordingly, for example, electric signals generated by operating devices are transmitted to control devices of the service brake and of the parking brake system which in turn control the operation, i.e., in particular, the release and application, of the service brake and of the parking brake system. In their respective released operating states the service brake and the parking brake system do not generate a braking force. In their respective applied operating states, the service brake and the parking brake system respectively generate a braking force. A released brake can also be referred to as "open" and an applied brake as "closed". Usually a changeover between a phase in which mainly the service brake is operated and a phase in which mainly the parking brake system is operated takes place when starting or stopping. It is the responsibility of the driver of the vehicle to apply the parking brake system by manually operating an operating device provided for this purpose to safely place the vehicle when parking the vehicle.

Even though the application of the parking brake system is generally routinely performed by the driver, it is still an additional action to be explicitly performed by the driver which at least briefly requires his attention and may also be accidentally forgotten.

Accordingly, the present invention is based on the object to unburden the driver and to improve the vehicle safety. This object is solved by the features of the independent claims.

Advantageous embodiments and further developments of the invention will emerge from the dependent claims. The invention is based on the generic method in that a transfer of the electrically operable parking brake system from a released operating state into an applied operating state is initiated and a predeterminable waiting time period is started when the presence of a trigger event is detected which is independent of an operating device provided for manually operating the electrically operable parking brake system and/or used to release the parking brake system when an operating device is faulty. In this way, the application of the parking brake system may be enabled independent of a manual operation of an operating device of the parking brake system. The driver may therefore knowingly skip or unintentionally forget the manual application of the parking brake system without this having a negative effect on the safety of the vehicle, for example, a vehicle parked in an unbraked state. The possibility to consciously skip the manual application of the parking brake system when parking the vehicle unburdens the driver of the vehicle and improves the comfort when operating the vehicle. The vehicle may, in particular, be or comprise a towing vehicle.

In this connection, it may be contemplated that the trigger event comprises at least one of the following events: ignition is turned off,

cabin door of the vehicle is locked from the outside,

a key is removed from the ignition lock,

- driver of the vehicle leaves the driver's seat,

belt buckle is opened,

engine of the vehicle is turned off from the outside,

a gear position "neutral" or "parking" is selected

cabin door of the vehicle is opened,

- a tachograph chart is removed from a tachograph of the vehicle, master switch is turned off,

instruction to implement a levelling of the vehicle,

the vehicle is stopped. The above events may be part of the trigger event individually as well as in any combination. The master switch may, for example, be a manually operable switch independent from the ignition for activating or deactivating the electronics of the vehicle. The locking of the cabin door may, for example, be realised with the aid of a key and/or a remote control. Further, the deactivation of the engine from the outside may also comprise the receipt of an external signal from outside of the vehicle, for example, a signal sent to the vehicle via a remote control.

Further, it may be contemplated that it is checked whether the vehicle is standing. By checking whether the vehicle is standing, an unintentional application of the parking brake system while driving may reliably be prevented. The check may be implemented with the aid of rotational speed sensors which may, for example, be part of an antilock braking system of the service brake.

Usefully, it may be contemplated that it is checked whether the engine is running and that the electrically operable parking brake system is transferred into the applied operating state when the engine is running or stopped. In this way, the vehicle may be automatically secured by applying the parking brake system as soon as the driver stops, for example, with the aid of the service brake, while the engine is running. Alternatively, the vehicle may be automatically secured when the engine is stopped. This may unburden the driver, particularly in city traffic or in the case of a traffic jam.

It may be contemplated that the method is terminated when at least one of the following events is detected: detection of the velocity of the vehicle (104) is not possible, receipt of a external instruction to terminate the method (200), detection that the electrically operable parking brake system (100) is already in the applied operating state,

- receipt of an ADR main switch signal is not possible in an ADR vehicle,

detection of a stored control parameter for deactivating the method (200). The above-mentioned events may be used as an indicator of the termination of the method individually as well as in any combination. In this way, it may be ensured that the method yields predictable results or changes of the vehicle status only under controlled conditions. The abbreviation "ADR" may, for example, refer to the "European Agreement concerning the International Carriage of dangerous goods by road". Vehicles intended for the transport of dangerous goods may be provided with additional safety devices which, by means of an ADR signal, may indicate their operability and/or a proper state of the vehicle and/or of the transported hazardous materials.

It may be contemplated that the electrically operable parking brake system is trans- ferred into the applied operating state after the expiration of the predeterminable waiting time when the vehicle is standing and the engine is not started during the predeterminable waiting time. In this way, the parking brake system may be reliably applied when the vehicle is parked. In this connection, it may be contemplated that the predeterminable waiting time is reset and/or interrupted when the engine is started or the vehicle is rolling. By resetting the waiting time, a misinterpretation of the intended vehicle status and an uncontrolled application of the parking brake system may be prevented. Usefully, it may be contemplated that a transfer of the electrically operable parking brake system from a released operating state into an applied operating state is initiated and that an additional predeterminable waiting time period is started when a defect of the electrically operable parking brake system is detected and a presence of a further trigger event is detected which is independent of the operating device provided for manually operating the electrically operable parking brake system. In this way, safely parking the vehicle with the parking brake system applied may be possible even in the case of a defect of the manual operating device of the parking brake system. The defect may, in particular, affect the manual operating device of the parking brake system and/or an interface connecting the operating device to a control device implementing the method. The additional predeterminable waiting time may, for example, be preset at the factory and stored as a system parameter which is modifiable during vehicle maintenance in a control device of the electrically operable parking brake system. In this connection, it may be contemplated that the further trigger event comprises at least one of the following events: detecting a vehicle speed of less than a predeterminable threshold value,

recognizing that the engine not is running,

- a gear position "neutral" or "parking" is selected

receiving an external instruction to apply the electrically operable parking brake system,

driver of the vehicle leaves the driver's seat. The above-mentioned events may be part of the additional trigger event individually as well as in any combination.

It may further be contemplated that the electrically operable parking brake system is transferred into the applied operating state after the expiration of the additional predeterminable waiting time when the additional trigger event is detected between the start and the expiration of the additional predeterminable waiting time. In this way, it may be ensured that the driver of the vehicle actually intends to safely park the vehicle. Advantageously, it may be contemplated that the electrically operable parking brake system is transferred into the applied operating state prior to an expiration of the additional predeterminable waiting time when a brake pedal of the vehicle is operated. In this way, the operation of the brake pedal allocated to the service brake may replace the manual operation of the operating device allocated to the parking brake system in the case of a defect. This may be particularly advantageous in the case that a defect of the operating device is detected

It may be contemplated that the additional predeterminable waiting time is reset and/or interrupted when an accelerator pedal of the vehicle is operated. In this way, it may be ensured that the application of the parking brake system is actually in- tended as the driver may also reliably interrupt the automatic application of the parking brake system in the case of a defect.

The invention will now be explained by way of example with the aid of preferred embodiment with reference to the accompanying drawings in which:

Figure 1 shows a flow chart of a method;

Figure 2 shows a flow chart of a modified method;

Figure 3 shows an exemplary circuit diagram of a electrically operable parking brake system; and

Figure 4 shows a schematic representation of a vehicle.

In the following drawings, the same numerals designate identical or equivalent parts. The trigger events, conditions, and related states mentioned below may be regularly detected by the sensors provided in the vehicle. Figure 1 shows a flow chart of a method. The method 200 illustrated in Figure 1 may be capable of transferring an electrically operable parking brake system from a released operating state into an applied operating state. The method 200 may, for example, be implemented by a control device of the electrically operable parking brake system. The method 200 may start in Step 201. In Step 201 , for example, conditions required for the implementation of the method 200 may be checked. For example, it may be checked whether a system parameter is set which prevents an implementation or a start of the method 200. Further, a check for detected/detectable defects may be performed, if possible. When a defect is detected, for example, a modified method illustrated in Figure 2 may be started. Further, a system parameter may be set which may prevent an implementation of the method 200 until the defect is removed. Starting from Step 201 , Step 202 may be executed in which it may be checked whether a trigger event is present. The trigger event may, for example, of comprise one of the events listed below: ignition is turned off,

- cabin door of the vehicle 104 is locked from the outside,

a key is removed from the ignition lock,

driver of the vehicle 104 leaves the driver's seat,

belt buckle is opened,

engine of the vehicle 104 is turned off from the outside, - a gear position "neutral" or "parking" is selected

cabin door of the vehicle 104 is opened,

a tachograph chart is removed from a tachograph of the vehicle 104, master switch is turned off,

instruction to implement a levelling of the vehicle 104.

When a trigger event is not present - NO in Step 202 - the method 200 may be restarted in Step 201. When a trigger event is present - YES in Step 202 - the period of a predeterminable waiting time may be started, and the process can be continued with Step 204. In Step 204, it may be checked whether the vehicle is standing. When the vehicle is not standing - NO in Step 204 - the method 200 may also be restarted in Step 201 . When the vehicle is standing - YES in Step 204 - the process can be continued with Step 206. In Step 206, it may be checked whether the engine of the vehicle, in particular, the drive engine of the vehicle, is deactivated. When the engine is not deactivated - NO in Step 206 - the process can be continued with Step 208. When the engine is deactivated - YES in Step 206 - the process can be continued with Step 210. In Step 208, the parking brake system may be applied. Further, a corresponding information signal indicating that the parking brake system is applied may be output in Step 208. The signal may comprise optical as well as acoustic components, in particular, an acoustic signal, the change of a signal lamp and/or written information indicating the application of the parking brake system on a display of an on-board computer. In Step 210, it may be checked whether a waiting time has expired. The predeterminable waiting time or the expiration of the prede- terminable waiting time checked in Step 210 may, for example, have been started in Step 202 as a response to a detected trigger event. When the waiting time has expired - YES in Step 210 - the process can be continued with Step 212. In Step 212, analogous to Step 208, the parking brake may first be applied. Then, also analogous to Step 208, an information signal may be output. The method 200 may, starting from Steps 208 and 212 in which the parking brake system is respectively applied, be continued with Step 220. In Step 220, the method may end properly. When the predeterminable waiting time has not yet expired - NO in Step 210 - the method 200 may be continued with Step 214. In Step 214, it may be checked again whether the engine is off. When the engine is not off - NO in Step 214 - the process can be continued with Step 216. When the engine is off - YES in Step 214 - the process can be continued with Step 218. In Step 216, it may be checked again whether the vehicle is standing. If the vehicle is standing - YES in Step 216 - the process can again be continued with Step 210 to again check whether the waiting time has expired. If the vehicle not is standing - NO in Step 216 - the process can be continued with Step 218. In Step 218, the predeterminable waiting time may be reset. If required, the waiting time or the remaining waiting time may be optically and/or acoustically indicated to the driver, for example, on a display of an on-board computer in the vehicle interior or by means of a variable acoustic signal.

If a defect in the parking brake system is detected, in particular, a defect of the operating device of the parking brake system and/or of an interface between the operating device and a control device of the electrically operable parking brake system, the modified method described below may be started. The detection of a defect may, for example, be intended as a required prerequisite during the start 201 of the method illustrated in Figure 1 prior to the implementation of the method 200. Figure 2 shows a modified method. The modified method 300 illustrated in Figure 2 may start in Step 301 . Starting from Step 301 , the process can be continued with Step 302. In Step 302, it may be checked whether a defect of the parking brake system was detected. The defect may, in particular, be a defect of a control, i.e., of a manual operating device and/or of an interface between the operating device and a control device of the parking brake system. If no defect was detected - NO in Step 302 - the modified method 300 may be restarted in Step 301 . If a defect of the parking brake system was detected - YES in Step 302 - the process can be continued with Step 304. In Step 304, it may be checked whether an additional trigger event has occurred. If no additional trigger event has occurred - NO in Step 304 - the process can be continued with Step 306. If the additional trigger event has occurred - YES in Step 304 - a period of a further predeterminable waiting time may be started or continued, and the process can be continued with Step 308. In Step 306, the further predeterminable waiting time period started in Step 302 may be reset. When Step 306 is completed, the modified method may be restarted in Step 301 . In Step 308, it may be checked whether the accelerator pedal is operated. If the accelerator pedal is operated - YES in Step 308 - the process can be continued with Step 306. If the accelerator pedal is not operated - NO in Step 308 - the process can be continued with Step 310. In Step 310, it may be checked whether the brake pedal is operated. If the brake pedal is operated - YES in Step 310 - the process can be continued with Step 312. If the brake pedal is not operated - NO in Step 310 - the process can be continued with Step 314. In Step 312, the parking brake system may be applied. Further, an optical and/or acoustical signal may be output which notifies the driver of the vehicle of the application of the electrically operable parking brake system. The signal may, for example, comprise an acoustic signal, a changed signal lamp, and/or a written message on a display of an on-board computer in the vehicle interior. Following Step 312, the method 300 may end in Step 318. If the brake pedal is not operated - NO in Step 310 - it may be checked in Step 314 whether the additional waiting time has already expired. If the additional waiting time has not yet expired - NO in Step 314 - the modified method 300 may be continued with Step 301 . If the additional waiting time has already expired - YES in Step 314 - the process can be continued with Step 316. In Step 316, the parking brake may, analogous to Step 312, be applied, and a corresponding signal may be output. Following Step 316, the method 300 may end in Step 318. If required, the additional waiting time or the remaining additional waiting time may be optically and/or acoustically indicated to the driver, for example, on a display of an on-board computer in the vehicle interior or by means of a variable acoustic signal.

The modified method 300 illustrated in Figure 2 may, for example, starting from the method 200 known from Figure 1 , begin with Step 301 , for example, periodically or if a check of the required preconditions in Step 201 is unsuccessful. Prior to a restart of the modified method in Step 300, an implementation of Step 201 of the method 200 shown in Figure 1 may periodically be provided, for example, to change between the modified method 300 and the method 200.

Figure 3 shows an exemplary circuit diagram of an electrically operable parking brake system. The illustrated electrically operable parking brake system 100 may be connected to a pressurised air processing system (not shown) via a non-return valve 10. The non-return valve 10 may be followed by an optional filter unit 12 through which the pressurised air may be supplied to a supply solenoid valve 14 which may be formed as a 2/2 directional valve. A first working connection 20 of a control valve device 22 may be connected to the outlet of the supply solenoid valve 14 via a supply line section 16 and an optional throttle 18. The control valve device 22 may be formed as a pneumatically controllable 3/2 directional valve. A second working connection 24 of the control valve device 22 may lead to a control inlet 26 of a trailer control module 30. It may operate a supply connection 34 and a control connection 36 of the trailer coupling. The trailer control line branches 42, 44 may be connected to inlets of a select low valve 46, the outlet of which may be connected to a control inlet 50 of the control valve device 22 via a control line 48. The select low valve 46 may function so that the lower inlet pressure, i.e., the lower pressure from the two trailer control line branches 42, 44, may be applied at its outlet, i.e., in the control line 48. The control line 48 may further be connected to a relay control inlet 56 of a relay valve 58 via a relay control line 52 and a shuttle valve 54. The relay valve 58 may be supplied with pressurised air from a location upstream of the supply sole- noid valve 14 via a relay supply line 60. A relay outlet line 62 may lead to branch lines 64, 66 to which a spring energy store cylinder (not illustrated) may be connected. Further, a service brake line 68 may be connected to the shuttle valve 54. A connection 74 of a control and exhaust valve device 72 may be connected to a vent port 70 of the control valve device 22. A further port 76 of the control and exhaust valve device 72 may be supplied with pressurised air from a location between the filter unit 12 and the supply solenoid valve 14. Further, an exhaust solenoid valve 78 formed as a 2/2 directional valve may be provided which may be connected to the supply line section 16. Further, pressure sensors 80, 82 for detecting the pressures at the second working connection 24 of the control valve device 22 as well as the relay outlet line 62 may be provided. The pressure sensor 80 may, for example, measure a shift pressure of the electrically operable parking brake system 100. A supply pressure of the electrically operable parking brake system 100 may, for example, be determined by a pressure sensor (not shown) between the non-return valve 10 and the filter unit 12.

The electrically operable parking brake system 100 illustrated in Figure 3 may further comprise a first control device not illustrated in this figure and a manual operating device which is also not illustrated. The operating device may be con- nected to the first control device via an interface. The operating device may be designed for manually releasing and applying the parking brake system 100 as well as for manually initiating a trailer test function.

Figure 4 shows a schematic representation of a vehicle. Figure 4 schematically shows the vehicle 104 which may comprise a towing vehicle 106 and a trailer 108. The vehicle 104 may comprise an electrically operable parking brake system 100 and a service brake 1 10. The electrically operable parking brake system 100 may in turn comprise a first control device 1 12 and an electrically operable valve array 1 14 which may be controllable by the first control device 1 12. The electrically operable valve array 1 14 may, for example, be connected to or identified with the circuit diagram illustrated in Figure 3. The electrically operable parking brake system 100 may be coupled to at least one wheel brake 124 on at least one axle of the towing vehicle 106 via a pneumatic line 120. Further, the electrically operable parking brake system 100 may be connected to a pneumatic trailer connection 122 via the pneumatic line 120. The pneumatic trailer connection 122 may be identified with the trailer control module 30 or the control connection 36. Analogously, the service brake 1 10 may comprise a second control device 1 16 and a valve array 1 18. Further, the service brake 1 10 may also be connected to the at least one wheel brake 124 and the pneumatic trailer connection 122 via the pneumatic lines 120. In this connection, it is clear to a person skilled in the art that the pneumatic line 120 only suggests the pneumatic couplings between the service brake 1 10, the electrically operable parking brake system 100, the pneumatic trailer connection 122, and the wheel brakes 124, as, for example, a combination cylinder located in the area of the at least one wheel brake 124 comprises two independent pneumatic connections for the service brake 1 10 and the parking brake system which are independently coupled to the electrically operable parking brake system 100 and the service brake 1 10.

The trailer 108 may be pneumatically coupled to the trailer connection 122, wherein pneumatic control pressures may be transmitted to at least one trailer wheel brake 128 of the trailer 108 via at least one pneumatic line 126. In connection with the at least one trailer wheel brake 128, combination cylinders may also be provided to some extent so that the at least one pneumatic line 126, analogous to the pneumatic lines 120 of the towing vehicle 106, may illustrate existing couplings in a simplified manner.

The features of the invention disclosed in the above description, the drawings as well as the claims may be important for the realisation of the invention individually as well as in any combination. List of Numerals

10 non-return valve

12 filter unit

14 supply solenoid valve

16 supply line section

18 throttle

20 first working connection

22 control valve device

24 second working connection

26 control input

30 trailer control module

34 supply connection

36 control connection

42 trailer control line branch

44 trailer control line branch

46 select low valve

48 control line

50 control inlet

52 relay control line

54 shuttle valve

56 relay control input

58 relay valve

60 relay supply line

62 relay outlet line

64 branch line

66 branch line

68 service brake line

70 vent port 72 control and exhaust valve device

74 connection

76 connection

78 exhaust solenoid valve

80 pressure sensor

82 pressure sensor

100 electrically operable parking brake system

102 trailer test function

104 vehicle

106 towing vehicle

108 trailer

1 10 service brake

1 12 first control device

1 14 electrically operable valve array

1 16 second control device

1 18 valve array

120 pneumatic line

122 trailer connection

124 wheel brake

126 pneumatic line

128 trailer wheel brake

200 method

201 start

202 trigger event

204 vehicle standing?

206 engine off?

208 apply parking brake

210 waiting time expired?

212 apply parking brake

214 engine off?

216 vehicle standing? reset waiting time

end

modified method

start

defect in the parking brake system? additional trigger event? reset additional waiting time accelerator pedal operated? brake pedal operated?

apply parking brake

additional waiting time expired? apply parking brake

end