Method for actuating a parking brake device

Abstract

The present invention relates to a method for actuating a parking brake device (12) of a work machine (1). The work machine (1) comprises a service brake device (5) for braking the work machine (1) while in motion. The method comprises the steps of detecting (II) an operating state variable of the service brake device (5) and actuating (IV) the parking brake device (12) based on the detected operating state variable of the service brake device (5).

Description

[0001] ZF Friedrichshafen AG File 303304 Friedrichshafen 2025-01-10

[0002] Procedure for actuating a parking brake device

[0003] Technical field

[0004] The present invention relates to a method for actuating a parking brake device. Furthermore, the present invention relates to a control device configured to perform such a method, to a braking system with such a control device, and to a working machine with such a braking system.

[0005] State of the art

[0006] Hill-hold functions, which automatically hold the machine on an incline using a parking brake, are not very common in agricultural machinery. This is partly because the design of a hill-hold function depends on the vehicle's total weight, which often varies considerably, especially in agricultural machinery. In some cases, a parking brake is engaged every time the machine comes to a standstill. However, this is disadvantageous for several reasons. Firstly, it prevents a quick restart without a waiting period. Secondly, it creates noise. Furthermore, it prevents the driver from using small inclines to slow the vehicle down. Using an angle sensor to detect the vehicle's position on an incline is also unsuitable for agricultural machinery, as it often produces inaccurate angle measurements.

[0007] Description of the invention

[0008] The present disclosure relates to a method for actuating a parking brake device of a working machine. The working machine may be a construction or agricultural machine. For example, the working machine may be a tractor. The working machine may be designed to tow one or more trailers. For this purpose, the working machine may, for example, have a trailer hitch for coupling a trailer. ZF Friedrichshafen AG File 303304 Friedrichshafen 2025-01-10

[0009] The parking brake system of the work machine may have an automatic parking brake, which can be operated automatically by means of a control device.

[0010] Additionally, the parking brake system can include a user-operated parking brake, which can be actuated, for example, by means of a Bowden cable. The automatic parking brake can be hydraulically, pneumatically, and / or electrically actuated. The machine can have a drive train with a motor and a gearbox. The parking brake system can be part of the gearbox of the machine's drive train. The drive train can be used to drive the front and / or rear wheels of the machine for propulsion.

[0011] For example, the rear wheels of an agricultural machine, such as a tractor, can be driven via the drivetrain. The drivetrain's motor can be an internal combustion engine and / or an electric motor. The motor transmits power via the transmission to the front and / or rear wheels of the machine, propelling it forward. Furthermore, the drivetrain can include one or more differentials, such as a transverse differential per axle and / or a longitudinal differential between the front and rear axles.

[0012] The transmission can have multiple gears to provide different gear ratios. For example, it can be a powershift transmission, which allows shifting between different gears under load. Alternatively, the transmission can be a continuously variable transmission (CVT). Such a CVT can have a mechanical, a hydraulic, and / or an electrical power branch. With such a CVT, the gear ratio can be continuously adjusted. Other transmission types are also conceivable. A transmission control unit can be provided to control the transmission, which can, for example, adjust the gear ratio based on various boundary conditions. The transmission control unit can also control the transmission's parking brake.Furthermore, the working machine may have a vehicle control unit that is both functionally and spatially separate. ZF Friedrichshafen AG File 303304 Friedrichshafen 2025-01-10.

[0013] This can be provided by the transmission control unit. For example, the vehicle control unit can directly control the engine and indirectly control the transmission via the transmission control unit. Thus, commands can be transmitted to the transmission control unit via the vehicle control unit, which are then implemented by the transmission control unit. For this purpose, a data exchange channel, such as a data bus like a CAN bus, can be provided between the transmission control unit and the vehicle control unit, enabling unidirectional and / or bidirectional communication between the control units.

[0014] The machine has a service brake system for braking the machine while in motion. The service brake system can have one or more service brakes on each of the wheels, for example, both front and / or both rear wheels. The service brake can be designed, for example, as a mechanical brake, such as a drum and / or disc brake, and / or as an electromagnetic brake, such as an eddy current brake. The service brake system can include actuators for actuating the service brake(s). For example, the service brake system may have a fluid system, such as a hydraulic and / or pneumatic system, for actuating the service brake(s).

[0015] The degree of service brake application can depend on the level of an operating condition variable in the service brake system. For example, the higher an operating condition variable is in the service brake system, the more forcefully the service brake can be applied. The degree of service brake application can, for example, correlate linearly with the level of the operating condition variable in the service brake system. The level of the operating condition variable in the service brake system can, in turn, depend on how forcefully a brake actuator, such as a brake pedal and / or a brake switch, is applied by the operator of the machine. The more forcefully the service brake system is applied, the higher the operating condition variable in the service brake system can be. For example, the operating condition variable in the service brake system can correlate linearly with the degree of application. ZF Friedrichshafen AG File 303304 Friedrichshafen 2025-01-10

[0016] The brake sensor's input, for example, the amount of pressure exerted by a brake pedal, correlates with the service brake system. The service brake system can be controlled via the vehicle control unit described above, which may be electronically connected to the brake sensor. Based on the detected degree of actuation of the brake sensor, the vehicle control unit can adjust the operating condition in the service brake system as described above.

[0017] The method now includes detecting the operating state variable of the service brake system. For this purpose, a sensor device can be provided in the service brake system, for example, by means of which the operating state variable can be detected. The detected operating state variable can then be read, for example, by the vehicle control unit. Furthermore, the method of the present disclosure includes actuating the parking brake system based on the detected operating state variable of the service brake system. In other words, the parking brake system, which can, for example, be part of a transmission, can be actuated based on an operating state variable of the service brake system. For example, the parking brake system can be engaged when the detected operating state variable of the service brake system has a certain shape, such as a certain value and / or a certain sign.

[0018] The method described in this disclosure enables a hill hold function for a work machine, such as an agricultural machine, to be provided with a high level of comfort. For example, the parking brake can be selectively activated only when a specific operating condition is present in the service brake system. This allows for a rapid restart of the work machine in many situations. Similarly, the driver can utilize slight inclines in many driving situations to allow the vehicle to roll slowly, resulting in increased comfort. The latter can be particularly advantageous for work machines that allow so-called inching via a brake pedal, where the power transmission in the drive train can be controlled via the brake pedal. Acoustic noises are also eliminated. ZF Friedrichshafen AG File 303304 Friedrichshafen 2025-01-10

[0019] Parking brake activation can be prevented in many situations. Furthermore, this allows the parking brake to be activated with particularly high reliability, because, for example, it is not necessary to rely on measurement values ​​with high inaccuracy.

[0020] In one embodiment, detecting the operating state variable includes receiving the operating pressure of the service brake system. If the service brake(s) are mechanical, they can be actuated via a fluidic actuation system, for example, a hydraulic system. Depending on the operating pressure of such an actuation system, the parking brake system can then be actuated. If the parking brake system is actuated via the transmission control unit described above, the vehicle control unit can transmit the operating state variable, for example, the operating pressure, of the service brake system to it. In another embodiment, the operating state variable is a current, for example, if the service brake is of an electromagnetic design.

[0021] In one embodiment, the method includes comparing the detected operating condition variable with a threshold value. The parking brake can only be actuated if the detected operating condition variable exceeds the threshold value. In all other cases, the parking brake cannot be actuated. For example, the parking brake is only actuated if the operating pressure in the service brake system is greater than a threshold value.

[0022] The operating condition variable can be influenced by a driver by actuating a brake actuator, such as a brake pedal. The more forcefully such a brake actuator is actuated, for example, fully depressed, the higher the operating condition variable in the service brake system can be. By forcefully depressing the brake actuator of the machine, the driver can therefore increase the operating condition variable in the service brake system, which can lead to the operating condition variable being greater than the threshold value. (ZF Friedrichshafen AG File 303304 Friedrichshafen 2025-01-10)

[0023] The parking brake is activated. For example, a parking brake can be activated by firmly pressing the brake pedal. This allows, for instance, a hill hold function to be selectively activated very easily and with high precision.

[0024] Furthermore, the operating condition variable in the service brake system can depend on the general driving situation of the machine. For example, if the machine is fully loaded with a loaded trailer and is traveling downhill, and needs to be brought to a standstill, the driver must apply significant pressure to the brake actuator, such as the brake pedal. This significant pressure results in a high operating condition variable that can exceed the threshold and trigger the parking brake. In this case, the significant pressure on the brake actuator, such as the brake pedal, is caused by the general driving situation of the machine, which necessitates such pedal application. The load on a drivetrain engine can also be a factor in deciding whether to apply the parking brake.

[0025] In one embodiment, the method includes detecting when the machine is stationary. Such a standstill can be detected, for example, by means of the transmission control unit described above, which uses a sensor in the transmission, such as a speed sensor, to determine whether the wheels mechanically connected to the transmission are rotating and thus whether the machine is in motion. The steps for detecting the operating condition and actuating the parking brake can only be performed if such a standstill of the machine is detected. In this embodiment, it is therefore possible to actuate the parking brake when the machine is stationary if an operating condition in the service brake system reaches a certain level.For example, in this embodiment, the parking brake is activated when the machine is stationary and the operating pressure in the service brake system exceeds a threshold value. Such a high operating pressure can be caused by a driver depressing the brake pedal (ZF Friedrichshafen AG File 303304 Friedrichshafen 2025-01-10).

[0026] The working machine can be activated as described above. For example, a hill hold function can be provided in a simple, convenient and reliable way, where the driver firmly presses a brake pedal to activate the parking brake.

[0027] In one embodiment, the method can include opening the parking brake device upon detection of a moving-away condition. The parking brake device can be opened, for example, by means of the transmission control unit described above, when it is informed by the vehicle control unit described above that the machine is about to start moving. Such a move can be initiated, for example, by actuating a drive switch on the machine, such as an accelerator pedal and / or throttle lever. Alternatively or additionally, such a moving-away condition can be detected when a switching device for releasing the parking brake device is actuated, for example, by the operator of the machine.

[0028] Furthermore, the present disclosure relates to a control device configured to execute a method according to one of the embodiments described above. The control device may include one or more microprocessors, which may be located in the same or different locations. The microprocessors may be interconnected, for example via the internet, to execute the method of the present disclosure. The microprocessor(s) are configured, i.e., specifically prepared, for example, programmed, to execute such a method. The control device may have one or more interfaces, which may be configured as input and / or output interfaces, for communication with various components of the machine to execute the method of the present disclosure.

[0029] Furthermore, the present disclosure relates to a braking system for a working machine with a service brake device for braking the working machine while in motion. The braking system also includes a ZF Friedrichshafen AG file 303304 Friedrichshafen 2025-01-10

[0030] The braking system includes a sensor device for detecting an operating condition variable of the service brake system. For example, the braking system includes a pressure sensor for detecting the operating pressure in the service brake system. Furthermore, the braking system includes a parking brake system and a control device for actuating the parking brake system according to the embodiment described above. The parking brake system can be configured to hold the machine stationary independently of the service brake system. For example, the parking brake system can be part of the transmission described above. For the specific design of such a parking brake system, reference is made to the above descriptions. Alternatively or additionally, the parking brake system can be configured to hold the machine stationary by means of an actuating element of the service brake system.In such a case, the parking brake device can be part of the service brake device described in detail above. Regarding the designs and advantages of the individual features of the service brake device, reference is made to the above explanations in connection with the method of the present disclosure. Furthermore, the present invention relates to a working machine with a control device according to the embodiments described above or a braking system according to one of the embodiments described above. Regarding the designs and advantages, reference is again made to the above explanations in connection with the method of the present disclosure.

[0031] Brief description of the characters

[0032] Figure 1 shows a working machine with a service brake and a parking brake device according to an embodiment of the present disclosure.

[0033] Figure 2 shows a method for actuating the parking brake device of the working machine from Figure 1.

[0034] Detailed description of embodiments ZF Friedrichshafen AG File 303304 Friedrichshafen 2025-01-10

[0035] Figure 1 shows a work machine 1, which in the present embodiment is designed as an agricultural machine, more precisely as a tractor. The work machine comprises two front wheels 3 mechanically connected to each other via a transverse differential 2. Furthermore, the work machine comprises two rear wheels 4 mechanically connected to each other via a transverse differential 2. The work machine also includes a service brake 5 for braking the work machine while driving. In the present embodiment, only the rear wheels 4 are braked by means of the service brake 5. In an alternative embodiment, the front wheels 3 are also braked by means of the service brake 5 in addition to the rear wheels 4.

[0036] Each of the rear wheels 4 has a brake 6, which is part of the service brake system 5 and can be opened and closed by means of the service brake system 5. In the present embodiment, the service brake system 5 is designed as a hydraulic brake system, in which the brakes 6 can be actuated by means of a hydraulic fluid, in this case oil. The degree of actuation of the brakes 6 correlates in the present embodiment with an operating condition variable, namely the operating pressure, in the service brake system 5. The higher the operating pressure in the service brake system 5, the more strongly the brakes 6 are actuated. The lower the pressure in the service brake system 5, the less strongly the brakes 6 are actuated. The correlation between the operating condition variable of the service brake system 5 and the degree of actuation of the brakes 6 is linear in the present embodiment.

[0037] The operating condition variable, more precisely the operating pressure, in the service brake system 5 is controllable by a user of the machine. In the present embodiment, a brake pedal (not shown) is provided for this purpose, the actuation position of which correlates with the operating condition variable of the service brake system 5. The further the brake pedal is depressed, the greater the operating condition variable, i.e., the operating pressure, in the service brake system 5. Therefore, with the brake pedal fully depressed, the maximum pressure in the service brake system 5 is also reached. The maximum pressure in the present embodiment is > 30 bar. ZF Friedrichshafen AG File 303304 Friedrichshafen 2025-01-10

[0038] In the present embodiment, the brake pedal is electronically connected to a vehicle control unit 7, which detects the degree of actuation of the brake pedal and controls the service brake system 5 accordingly. The service brake system 5 has a sensor unit 8, which in this case is designed as a pressure sensor. The operating condition variable, i.e., the operating pressure, in the service brake system 5 can be detected by means of the sensor unit 8. The vehicle control unit 7 is configured to read the operating condition variable detected by the sensor unit 8.

[0039] Furthermore, the working machine 1 comprises a drive train with an engine 9 and a transmission 10. The drive train is designed such that the rear wheels 4 can be driven by the engine 9 via the transmission 10 and the transverse differential 2 to propel the working machine 1. In the present embodiment, the engine 9 is an internal combustion engine. Alternatively or additionally, it is an electric motor. In the present embodiment, the transmission 10 is a power-shift transmission. Alternatively or additionally, it is a continuously variable transmission (CVT). The engine 9 is electronically connected to the vehicle control unit 7. The transmission 10 has a transmission control unit 11, which is electronically connected to the vehicle control unit 7.Based on accelerator pedal positions detected by the vehicle control unit 7, for example a brake and / or accelerator pedal position, the vehicle control unit 7 is configured to control the engine 9 and the transmission 10 via the transmission control unit 11 so that the wheels 4 are driven via the transverse differential 2 in the requested manner.

[0040] The transmission 10 has a parking brake device 12, which in the present embodiment is integrated into the transmission 10 and can be actuated by means of the transmission control unit 11. The parking brake device 12 is designed as a positive-locking parking brake device, by means of which a positive-locking connection between an output of the transmission 10 and a stationary component can be selectively established for rotationally fixed fixation of the drive train. In the present embodiment, the parking brake device 12 has a claw by means of which a ZF Friedrichshafen AG File 303304 Friedrichshafen 2025-01-10

[0041] A rotationally fixed connection can be established between the output of the gearbox 10 and the stationary component for fixing the rear wheels 4.

[0042] The transmission control unit 11 is configured to execute the method described below with reference to Figure 2. In a first step I, the transmission control unit 11 detects that the driven machine 1 has come to a standstill. In the present embodiment, this is done based on a sensor provided in the transmission 10, for example a speed sensor, by means of which the speed at the output of the transmission can be detected. When the output of the transmission 10 has come to a standstill, it can be concluded that the driven machine 1 is also at a standstill.

[0043] If a standstill of the working machine 1 was detected in step I, the transmission control unit 11 now detects an operating condition variable of the service brake system 5 in a subsequent step II. In the present embodiment, the transmission control unit 11 receives the current operating pressure of the service brake system 5, detected by the sensor device 8 in the service brake system 5, from the vehicle control unit 7. In a subsequent step III, the transmission control unit 11 compares the operating pressure received from the vehicle control unit 7 with a threshold value predefined in the transmission control unit 11. If the detected operating pressure is greater than the predefined threshold value, the process proceeds to step IV, described below. Otherwise, the process returns to step I.

[0044] As previously described, the operating pressure in the service brake system 5 depends on the actuation state of the brake pedal of the machine 1, as described above. If the machine 1 is stationary and the operator has significantly increased the brake pressure in the service brake system 5 by forcefully depressing the brake pedal, this results in comparison step III finding that the detected operating pressure in the service brake system 5 is above the threshold value. Alternatively or additionally, a driving condition of the machine 1 prior to the standstill may also have caused the service brake pressure in the service brake system 5 to exceed the threshold value. ZF Friedrichshafen AG File 303304 Friedrichshafen 2025-01-10

[0045] If, for example, the work machine 1 is traveling downhill fully loaded and needs to be decelerated, the driver must press the brake pedal firmly to decelerate the work machine 1 as desired. Such a firm press of the brake pedal in turn results in a high operating pressure in the service brake system 5, which in turn leads to a service brake pressure above the threshold value when the machine comes to a standstill in comparison step III.

[0046] If, in comparison step III, it was determined that the received operating pressure of the service brake device 5 is above the threshold value, then in subsequent step IV, the parking brake device 12 is actuated by the transmission control device 1. For this purpose, the transmission control device 11 establishes the rotationally fixed connection of the output of the transmission 10 with the stationary component as described above, in order to fix the rear wheels 4 in a rotationally fixed manner. Thus, by the method of the present disclosure, the parking brake device 12 of the transmission 10 can be actuated based on the operating pressure of the service brake device 5. This allows, for example, a hill-hold function to be selectively activated by the driver by firmly depressing the brake pedal while stationary.

[0047] If a starting condition is detected in a subsequent step V, the transmission control unit 11 opens the parking brake device 12 to start the machine 1. The starting condition can be detected, for example, by the vehicle control unit 7 communicating to the transmission control unit 11 that the driver has pressed an accelerator pedal to accelerate the machine 1. The process then returns to step I. (ZF Friedrichshafen AG File 303304)

[0048] Friedrichshafen 2025-01-10

[0049] Reference sign

[0050] 1 working machine

[0051] 2 Transverse differential

[0052] 3 front wheels

[0053] 4 rear wheels

[0054] 5 Service brake system

[0055] 6 Service brake

[0056] 7 Vehicle control unit

[0057] 8 Sensor device

[0058] 9 engine

[0059] 10 gearboxes

[0060] 11 Transmission control unit

[0061] 12 Parking brake device

[0062] I. Detecting standstill

[0063] II. Identifying operating state variables

[0064] III. Compare operating condition variable with threshold value. IV. Activate parking brake device.

[0065] V Open parking brake device

Claims

ZF Friedrichshafen AG File 303304 Friedrichshafen 2025-01-10 Patent claims 1. Method for actuating a parking brake device (12) of a working machine (1), wherein the working machine (1) has a service brake device (5) for braking the working machine (1) while driving, comprising detecting (II) an operating state variable of the service brake device (5) and actuating (IV) the parking brake device (12) based on the detected operating state variable of the service brake device (5).

2. Method according to claim 1, characterized in that the detection (II) of the operating state variable comprises receiving an operating pressure of the service brake device (5).

3. Method according to claim 1 or 2, characterized in that the method comprises a comparison (III) of the detected operating state variable with a threshold value, and in that the actuation (IV) of the parking brake device (12) takes place when the threshold value is exceeded by the detected operating state variable.

4. Method according to one of the preceding claims, characterized in that the method comprises detecting (I) a standstill of the working machine (1).

5. Method according to one of the preceding claims, characterized in that the method comprises opening (V) the parking brake device (12) upon detection of a starting condition.

6. Control device (11) configured to perform a method according to any of the preceding claims.

7. Braking system for a working machine (1) comprising a service brake device (5) for braking the working machine (1) while driving, a sensor device (8) for detecting an operating condition variable of the service brake device (5), a ZF Friedrichshafen AG File 303304 Friedrichshafen 2025-01-10 Parking brake device (12) and a control device (11) for actuating the parking brake device (12) according to claim 6.

8. Braking system according to claim 7, characterized in that the parking brake device (12) is configured to be able to hold the working machine (1) at a standstill independently of the service brake device (5).

9. Braking system according to claim 7 or 8, characterized in that the parking brake device (12) is configured to keep the working machine (1) stationary by means of an actuating element of the service brake device (5).

10. Working machine (1) with a control device (11) according to claim 6 or a braking system according to one of claims 7 to 9.

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