Method for actuating a brake system of a commercial vehicle

Abstract

The invention relates to a method for actuating a braking system (1) of a commercial vehicle, the braking system (1) comprising a service braking system (8), an auxiliary braking system (28) and braking devices (5, 6) for the wheels (2, 3) of the commercial vehicle. The service braking system (8) drives the associated service brake actuators during normal operation. The actuation is effected via the service brake actuators to effect actuation of the associated braking devices (5, 6) in response to actuation of the brake actuators (21, 22). The auxiliary braking system (28) initiates actuation of the braking devices (5, 6) by actuating the auxiliary brake actuator (29). During emergency actuation, actuation of the brake actuators (21, 22) is detected and the auxiliary brake actuator (29) is accessed. In this case, actuation of the braking devices (5, 6) is adjusted in accordance with the degree of actuation of the brake actuators (21, 22).

Description

[Technical field]

[0001] The invention relates to a method for actuating a brake system of a commercial vehicle, in particular an agricultural or public commercial vehicle, the brake system comprising a service brake system, an auxiliary brake system and brake devices for wheels of the commercial vehicle. In the service brake system, in normal operation, actuation of at least one brake actuator leads to actuation of at least one associated service brake actuator. Actuation is effected via the service brake actuator and in response to actuation of the at least one brake actuator, an actuation of the respective associated brake device is effected. In the auxiliary brake system, actuation of at least one of the brake devices can be initiated via at least one control device. Upon detection of at least a partial failure of the service brake system, an emergency actuation is effected. Furthermore the invention relates to a control device, a brake system of a commercial vehicle and a commercial vehicle. [Background technology]

[0002] A braking system of a motor vehicle usually comprises a service brake system so that the wheels and thus the vehicle can be braked by correspondingly activating one or more associated brake actuators while the respective vehicle is moving. In addition, the braking system usually must comprise an auxiliary brake system. Via the auxiliary brake system, the respective vehicle that is stationary, for example parked, can be held in its current position by statically braking at least the individual wheels. In this case, the brake system in the vehicle must be realized as a redundant system in order to be able to brake the vehicle as far as possible, even if a part of the brake system fails. In some cases, an auxiliary brake system is aimed at in this case and is required in order to be able to brake the vehicle in the event of at least a partial failure of the service brake system.

[0003] US 2005 / 0168064 A1 discloses a brake system for a commercial vehicle, for example a towing vehicle such as a semi-trailer truck. The brake system in this case comprises a service brake system and an auxiliary brake system, which can brake the wheels of the commercial vehicle independently of one another via a brake device. The brake system of US 2005 / 0168064 A1 is realized in this case as an overall electronic brake system, in which actuation of a brake actuator of the service brake system in the form of a brake pedal on the one hand and actuation of a parking brake actuator of a parking brake system in the form of a handbrake lever on the other hand are each detected via a control device and converted in a data bus system into corresponding actuations of brake actuators. In this case, the brake actuators of the front axle of the commercial vehicle and the brake actuators of the rear axle of the commercial vehicle are integrated in separate circuits.

[0004] In the event of a partial failure of the service brake system in the form of a failure of the brake circuit of the front axle, the wheels of the front axle are braked in an alternative manner within the scope of emergency operation. In a variant, in the auxiliary brake system during emergency operation, the actuation of the parking brake actuator is converted via a brake actuator into braking of the wheels of the front axle. For this purpose, the control device drives a valve, whereby the brake actuator of the front axle is supplied with fluid from a brake circuit for the trailer of the commercial vehicle, which is independent from the brake circuit of the front axle. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US2005 / 0168064A1 Summary of the Invention [Problem to be solved by the invention]

[0006] Based on the above-mentioned prior art, the object of the present invention is to create a brake system for commercial vehicles, by means of which the commercial vehicle can be braked reliably even in the event of at least partial failure of the service brake system, and at the same time the design of the brake system can be simplified. [Means for solving the problem]

[0007] From a technical method point of view, this problem is solved by the preamble of claim 1 and its features. From a technical apparatus point of view, this problem is solved by the technical features of claim 7, which relates to a control device for a braking system. The following dependent claims each reflect advantageous developments of the invention. Furthermore, claims 9 to 14 relate to a braking system of a commercial vehicle, which comprises the aforementioned control device. Finally, claim 15 is directed to a commercial vehicle which comprises the aforementioned braking system.

[0008] According to independent claim 1, a method for actuating a brake system comprising a service brake system, an auxiliary brake system and brake devices for wheels of a commercial vehicle, the service brake system, in normal operation, drives at least one associated service brake actuator upon actuation of at least one brake actuator, and via the service brake actuator, performs an actuation of the respective associated brake device in response to the actuation of the at least one brake actuator. Furthermore, the auxiliary brake system can initiate an actuation of at least one of the brake devices via at least one control device. Furthermore, an emergency actuation is performed upon detection of an at least partial failure of the service brake system.

[0009] The method according to the invention is used in the braking system of a commercial vehicle, in particular an agricultural or public commercial vehicle. Particularly preferably, the commercial vehicle is an agricultural tractor. The commercial vehicle has a number of axles, preferably in the form of a front axle and a rear axle. At least one of them is equipped with brakeable wheels. Particularly preferably, however, all wheels of the vehicle can be braked. To this end, each wheel is assigned a respective brake device. In the sense of the invention, the brake devices for the wheels are in particular disc brakes. These can be designed as wet multi-disc brakes.

[0010] Within the scope of the present invention, each brake device is preferably assigned to a service brake actuator, via which the associated brake device is actuated in the event of activation. This actuation is carried out when, in normal operation of the brake system, actuation takes place in at least one brake actuator of the service brake system. In this case, the intensity of actuation of the respective brake device via the associated service brake actuator occurs depending on the intensity of actuation of the at least one brake actuator. In the sense of the present invention, the at least one brake actuator is in particular present as a brake pedal, which can be actuated by the driver of the commercial vehicle to brake the commercial vehicle via the service brake system.

[0011] Within the scope of the invention, there can be exactly one brake actuator in the brake system. When the brake actuator is activated, all service brake actuators of the service brake system are activated in normal operation of the brake system. Correspondingly, the wheels are also braked via the associated brake devices. However, it is particularly preferred that two brake actuators are provided in order to be able to represent the function of steering brakes via the service brake system. Thus, activation of one brake actuator activates only one or more service brake actuators. The service brake actuators activate brake devices located on one side of the commercial vehicle in the longitudinal direction of the commercial vehicle. On the other hand, activation of the respective other brake actuator activates brake devices on the other side of the commercial vehicle by activation of the service brake actuator or actuators therein.

[0012] The auxiliary braking system is provided in the braking system for braking the vehicle in response to an instruction from the driver of the vehicle in the event of at least partial failure of the service braking system. Particularly preferably, the auxiliary braking system is further configured to realize a parking brake function of the commercial vehicle in normal operation of the braking system in order to hold the commercial vehicle in its current position by braking the wheels stationarily in response to a corresponding instruction from the driver of the vehicle. In this case, in the method for actuating a braking system according to the invention, this parking brake function is realized by initiating the actuation of at least one of the brake devices of the wheels via at least one control device. Particularly preferably, the at least one control device initiates an actuation within the scope of the parking brake function when a corresponding instruction is given by the driver of the vehicle to the actuating device. In particular, this actuating device is a device, such as a brake lever, to which the driver of the vehicle can give infinitely variable instructions.

[0013] Within the scope of the method according to the invention, an emergency actuation of the brake system is carried out if an at least partial failure of the service brake system is detected, i.e. if it is recognized that the service brake system of the brake system is not working properly, in particular because pressure is not built up or is built up to an insufficient extent in the brake system, this is preferably carried out within the meaning of the invention already from the extent of the failure of the service brake system that there is a risk of braking the commercial vehicle insufficiently.

[0014] The present invention includes the technical teaching that in an auxiliary braking system, activation of at least one brake device is initiated by driving at least one auxiliary brake actuator via at least one control device, and during emergency activation, the at least one control device detects activation of the at least one brake actuator and accesses the auxiliary brake actuator, where the at least one control device uses the auxiliary brake actuator to regulate activation of the at least one brake device in accordance with the degree of activation of the at least one brake actuator.

[0015] In other words, in the auxiliary brake system of the brake system, the at least one control device also activates the at least one brake device by activating the at least one auxiliary brake actuator. During emergency activation, when activation of the at least one brake actuator of the service brake system is detected, i.e. when there is an instruction from the vehicle driver to brake the commercial vehicle, the at least one control device also activates the auxiliary brake actuator. However, since this desire cannot be realized or can only be realized to an insufficient extent via the service brake system due to at least a partial failure of the service brake system, the at least one control device activates the auxiliary brake actuator as follows: the activation of the at least one brake device is synchronized via the auxiliary brake actuator to the activation strength of the at least one brake actuator of the service brake system.

[0016] Such a method for actuating a brake system has the following advantages: via the auxiliary brake system, at least substantially sufficient braking can be provided to the commercial vehicle even in the event of at least partial failure of the service brake system of the brake system. This allows the driver of the commercial vehicle to brake the commercial vehicle even in the event of failure of the service brake system. The driver of the vehicle can thus bring the commercial vehicle to a halt. This is done in this case automatically and without any additional action of the driver of the vehicle. In other words, when the at least one control device detects an actuation of the at least one brake actuator in an emergency actuation, it actuates the at least one brake actuator independently by accessing the auxiliary brake actuator and in accordance with the actuation of the at least one brake actuator. At the same time, a simplified structure of the brake system can be realized since the auxiliary brake actuator is driven via the at least one control device, since an electronic actuation of the at least one auxiliary brake actuator of the auxiliary brake system can be achieved. This allows hydraulic / pneumatic components to be dispensed with at least as far as possible.

[0017] Preferably, the same wheel can be braked via the auxiliary braking system with one auxiliary brake actuator or via multiple auxiliary brake actuators. The same wheel can also be braked via the service brake system. In this respect, at least one auxiliary brake actuator within the auxiliary braking system has access in particular to the same brake device. Particularly preferably, two associated brake devices for multiple wheels of one axle are actuated via the auxiliary brake actuator when driven via at least one control device.

[0018] Indeed, in US 2005 / 0168064 A1 too, in the auxiliary brake system, the brake equipment is actuated via a control device of the auxiliary brake system, i.e. this control device electronically drives the brake actuators. However, in emergency operation, no independent actuation of the brake actuators via the control device is initiated in response to a brake pedal command. In a variant of US 2005 / 0168064 A1, in response to a parking brake handbrake command, the brake actuators of the front axle of the commercial vehicle are supplied from the brake circuit for the trailer of the commercial vehicle. Furthermore, the same brake actuators are assigned to the auxiliary brake system and the service brake system.

[0019] In the sense of the present invention, in the method according to the invention for actuating a brake system, the initiation of the actuation of the at least one auxiliary brake actuator is realized via at least one control device, preferably by electronic access of this control device to the auxiliary brake system. Within the scope of the present invention, the at least one control device can directly electronically access the at least one auxiliary brake actuator or can actuate and thus access it via intervening components, for example further control devices and / or electronic components. The auxiliary brake actuator particularly preferably also functions as a parking brake actuator, i.e. the brake actuator of the auxiliary brake system is used for stationary braking of the vehicle within the scope of the parking brake function. In particular, the auxiliary brake actuator comprises a spring-loaded cylinder.

[0020] In the context of the present invention, the actuation of the at least one brake device is adapted to the degree of actuation of the at least one brake actuator via the at least one control device, i.e. via the at least one control device, the at least one brake device initiates an actuation that corresponds as far as possible to an instruction to the at least one brake actuator of the service brake system via the auxiliary brake actuator. Within the scope of the method according to the invention, an attempt is made via the control device, i.e. during an emergency actuation, to compensate as far as possible for at least a partial failure of the service brake system and to implement as far as possible an instruction of the vehicle driver to the at least one brake actuator for braking the commercial vehicle. Particularly preferably, via the at least one control device, the at least one brake device is actuated by means of the auxiliary brake actuator in response to an instruction to the at least one brake actuator.

[0021] Within the scope of the method according to the invention, it is furthermore preferred to detect an at least partial failure of the service braking system and thus initiate an emergency operation by outputting a corresponding warning message in order to draw the attention of the driver of the commercial vehicle to said at least partial failure of the service braking system, said warning message being capable of being presented as a visual and / or acoustic warning message.

[0022] According to an embodiment of the present invention, during an emergency actuation, a required brake torque is determined based on the degree of actuation of at least one brake actuator. The required brake torque is then used to adjust the drive of at least one auxiliary brake actuator. Within the scope of an emergency actuation, i.e. by command of the driver of the vehicle to at least one brake actuator, a brake torque to be adjusted in the brake system is determined. This required brake torque is then used to adjust the drive of at least one auxiliary brake actuator, and thus this required brake torque is at least substantially generated in the associated brake system via the at least one auxiliary brake actuator. Particularly preferably, the determination of the required brake torque is likewise performed by at least one control device. To this end, the at least one control device is provided with information regarding the degree of actuation of the at least one brake actuator. In particular, the at least one control device exchanges data with a sensor system that detects the degree of actuation of the at least one brake actuator for this purpose.

[0023] According to one possible embodiment of the invention, upon detection of the actuation of the at least one brake actuator, a pressure supply to the at least one associated service brake actuator is detected as at least a partial failure via a pressure source to which the at least one associated service brake actuator is connected, i.e. if no pressure supply or a pressure supply to the respective service brake actuator in the service brake system is recognized as being too low to realize the required brake torque, then a switchover to emergency actuation is made, thus via at least one control device, to an independent actuation with the auxiliary brake actuator. The at least one associated service brake actuator and the pressure source are for this purpose preferably integrated into a brake circuit of the service brake system. Depending on the type of actuator, this can be a hydraulic or pneumatic brake circuit. In this brake circuit, the actuator can be supplied with hydraulic fluid or compressed air.

[0024] In a further development of one of the above-mentioned possible embodiments, at least a too low pressure supply in the service brake system is detected via a sensor system, preferably a pressure sensor, which provides a simple possibility of determining whether the pressure supply is too low.

[0025] An embodiment of the present invention provides for initiating the actuation of at least one auxiliary brake actuator via a first control device, in particular a brake control device. For this purpose, data transmission is carried out in a data transmission system between the first control device and a second control device. The second control device can be a transmission control device. Via the second control device, the auxiliary brake actuator is then actuated in response to an instruction of the first control device. Advantageously, an indirect actuation of at least one auxiliary brake actuator can thereby be carried out via the first control device by communication with the second control device. The second control device then realises the instruction of the first control device by directly actuating the auxiliary brake actuator.

[0026] In a further development of the invention, in the auxiliary brake system, activation of the at least one brake device is carried out in at least one auxiliary brake actuator by depressurizing a respective hydraulic cylinder, which hydraulic cylinder is equipped with an actuating piston preloaded in an actuated position. In this respect, when the respective hydraulic cylinder of the auxiliary brake actuator is depressurized, the at least one brake device is actuated via the at least one auxiliary brake actuator. For this purpose, the respective hydraulic cylinder is configured as an inverse hydraulic cylinder.

[0027] For this purpose, the working piston of the hydraulic cylinder is pre-biased into an operating position. The working piston is moved to an open position by supplying pressure with fluid to the hydraulic cylinder. In the open position, the activation of the at least one braking device via the auxiliary brake actuator is cancelled. Correspondingly, when the respective hydraulic cylinder of the auxiliary brake actuator is supplied with fluid according to this pressure, the activation of the at least one braking device is reduced or even cancelled. On the other hand, in the absence of a supply of fluid and the associated reduced pressure, the at least one braking device is activated via the auxiliary brake actuator due to the pre-biasing of the working piston.

[0028] Particularly preferably, at least one valve is provided in the auxiliary brake system, via which the supply pressure to each one of the fluid cylinders of the at least one auxiliary brake actuator can be adjusted. This is also necessary within the scope of the invention to adjust the actuation of the at least one brake device via the auxiliary brake actuator by controlling the pressure, since to achieve emergency actuation, a dosed actuation of the at least one brake device via the auxiliary brake actuator is necessary. A proportional valve or a combination of several valves can therefore be provided to adjust the pressure.

[0029] The subject of the invention is further a control device, which in an auxiliary brake system of a brake system of a commercial vehicle is configured to initiate activation of at least one auxiliary brake actuator for actuating at least one brake device of one wheel each, and which is further configured to initiate an emergency actuation upon detecting at least a partial failure of a service brake system of the brake system, and to access the at least one auxiliary brake actuator upon detecting actuation of the at least one brake actuator of the service brake system during the emergency actuation, and to initiate actuation of the at least one brake device via the auxiliary brake actuator in an adapted manner to the degree of actuation of the at least one brake actuator.

[0030] Such an arrangement of the control device and its use in a brake system of a commercial vehicle has the advantage that, in the event of at least a partial failure of the service brake system of the brake system, at least one auxiliary brake actuator of the auxiliary brake system is independently accessible via the control device and braking is subsequently effected by actuating at least one brake device via the auxiliary brake actuator, said braking being adapted to an instruction of the driver of the vehicle via the at least one brake actuator. This is further achieved with a compact construction due to the control device having direct or indirect electronic access to the at least one auxiliary brake actuator. The control device is in particular a brake control device of the brake system.

[0031] Furthermore, the control device according to the invention is preferably configured so that a method for operating a brake system according to one or more of the above-mentioned variants is implemented.

[0032] The above mentioned control device is preferably part of a brake system for a commercial vehicle. This brake system comprises a service brake system, an auxiliary brake system, brake devices for wheels of the commercial vehicle and at least a control device according to the invention. The service brake system comprises at least one brake actuator, via which, when operating in normal operation, at least one associated service brake actuator can be driven. The at least one associated service brake actuator, when operating in normal operation, activates a respectively assigned brake device in response to the activation of the at least one brake actuator. Furthermore, the auxiliary brake system comprises an auxiliary brake actuator, which can be driven via the control device and, when driven, activates at least one of the brake devices.

[0033] The control device according to the invention then accesses the auxiliary brake actuator by detecting the actuation of the at least one brake actuator in the event of an at least partial failure of the service brake system as described above and actuates the at least one brake actuator via the auxiliary brake in an adapted manner to the degree of actuation of the at least one brake actuator. A reliable brake system for commercial vehicles can thus be achieved, in which the commercial vehicle can be braked via the control device and thus at the command of the vehicle driver even in the event of an at least partial failure of the service brake system, without active handling by the vehicle driver. In this case, the brake system of the commercial vehicle can be actuated in the above-described manner within the scope of the method according to the invention.

[0034] In the above-mentioned brake system, a first control device and a second control device can be provided which are connected to each other in a data transmission system, preferably a CAN bus. The first control device is in particular a brake control device. On the other hand, the second control device can be present as a transmission control device of a transmission arranged in the area of ​​the axles of the commercial vehicle. In this case, an auxiliary brake actuator can be driven via the second control device. If the second control device is a transmission control device, this is realized in particular if the auxiliary brake actuator is located in the area of ​​the transmission or even integral with the transmission.

[0035] In a further development of the brake system, the auxiliary brake actuators comprise a hydraulic cylinder with an actuating piston pre-biased in an actuated position. The actuating piston can be moved to an open position by supplying pressure to the hydraulic cylinder with a fluid. In the open position, actuation of the at least one braking device via the auxiliary brake actuator is cancelled. Correspondingly, the hydraulic cylinder of each auxiliary brake actuator is configured as a counter hydraulic cylinder, in that when pressure is supplied, actuation of the at least one braking device via the hydraulic cylinder is reduced or cancelled depending on the pressure. On the other hand, in the absence of pressure supply, the hydraulic cylinder actuates the at least one braking device.

[0036] In the service brake system of the brake system, at least one associated service brake actuator is arranged in a respective brake circuit. In each respective brake circuit, in normal operation of the brake system, the control of the respectively associated service brake actuator takes place as a function of the actuation of at least one brake actuator. Preferably, each respective brake circuit is configured as a hydraulic circuit. In each respective brake circuit, a fluid is supplied in the form of a hydraulic fluid. The service brake actuator is then configured as a hydraulic actuator. Alternatively, the fluid of the brake circuit can also be present as compressed air. The components and the service brake actuator in the brake circuit can then be present as pneumatic components.

[0037] The brake circuit may further comprise a valve plate, via which, in normal operation of the brake system, the actuation of at least one brake actuator is converted by a corresponding valve into a corresponding pressure for controlling a service brake actuator.

[0038] Alternatively, and preferably in addition to the aforementioned variant, at least one brake circuit, which can control a service brake actuator, can be provided with a sensor system. Via the sensor system, the fluid pressure of the at least one brake circuit can be monitored. Via this sensor system, an at least partial failure of the service brake system can be concluded in the event of no or insufficient supply to the service brake actuator. Particularly preferably, the sensor system is constituted by a pressure sensor, which can determine the fluid pressure in the at least one brake circuit. Such a pressure sensor can be provided in a valve block of the at least one brake circuit.

[0039] The invention further relates to a commercial vehicle provided with a braking system corresponding to one or more of the above mentioned variants, the commercial vehicle being preferably an agricultural or municipal commercial vehicle, in particular an agricultural tractor.

[0040] The invention is not limited to the specific combination of the independent claims or the claims dependent thereon. Individual features which emerge from the claims, from the following description of preferred embodiments of the invention or directly from the drawings, can also be combined with one another. Reference in the claims to the drawings by the use of reference numbers is not intended to limit the scope of the claims.

[0041] Advantageous embodiments of the invention are described below and shown in the drawings. [Brief description of the drawings]

[0042] [Figure 1] 1 is a schematic diagram of a commercial vehicle braking system according to a preferred embodiment of the present invention; [Diagram 2] 2 is a diagram of the brake system from FIG. 1 shown in normal operation and in a first operating state. [Diagram 3] 2 is a diagram of the brake system from FIG. 1 shown in normal and second operating conditions; [Figure 4] FIG. 2 is a diagram of the brake system from FIG. 1 shown in emergency operation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] 1 shows a schematic diagram of a braking system 1 of a commercial vehicle, in particular an agricultural commercial vehicle in the form of a tractor. The braking system 1 is designed according to a preferred embodiment of the invention and serves to brake the wheels 2 and 3 of an axle 4 of the commercial vehicle. The axle 4 is in this case the rear axle of the commercial vehicle. However, within the scope of the invention, a further axle with brakeable wheels, in particular the front axle of the commercial vehicle, can also be provided within the braking system 1. This further axle can likewise be equipped with a braking system for braking the wheels.

[0044] Each of the wheels 2 and 3 is assigned by the brake system 1 one braking device 5 or 6 respectively. The braking devices 5 and 6 are configured in this case in the form of disc brakes. In particular, the disc brakes in this case can be wet multi-disc brakes. When actuated, each braking device 5 or 6 brakes the associated wheel 2 or 3 or ensures that it is braked stationarily.

[0045] The braking system 1 according to the invention comprises a control device 7 in the form of a brake control device and a service braking system 8. Inside the service braking system 8, two service brake actuators 9 and 10 with hydraulic fluid cylinders are provided. The service brake actuator 9 activates the braking device 5 when actuated by pressure. The service brake actuator 10 activates the braking device 6 when actuated by pressure. In this case, in a manner known in principle to the person skilled in the art, the supply of hydraulic fluid to the respective fluid cylinder of the service brake actuator 9 or 10 causes a displacement of a respective piston which is connected to the respective associated braking device 5 or 6. This is preferably realised via a respective ball ramp. Correspondingly, the piston of the respective fluid cylinder is displaced due to the connection, which activates the respective associated braking device 5 or 6.

[0046] The service brake actuators 9 and 10 are integrated into a hydraulic brake circuit 11, in this case by being connected to a valve block 14 via lines 12 and 13. In addition, a pressure source 15 in the form of a hydraulic pump for the commercial vehicle, a tank 16 for hydraulic fluid, a pressure accumulator 17, a pressure sensor 18 and two further lines 19 and 20 are also connected in the brake circuit 11 to this valve block 14. The supply pressure of hydraulic fluid prevailing in the brake circuit 11 can be determined via the pressure sensor 18.

[0047] In this case, the brake actuators 21 and 22 are respectively connected to the lines 19 and 20. The brake actuators 21 and 22 are respectively present as brake pedals. Via the brake pedal, the driver of the commercial vehicle can actuate the service brake actuators 9 and 10 of the service brake system 8. The degree of actuation of the respective brake actuator 21 or 22 is detected by a sensor and determined by the control device 7. The control device 7 likewise detects the pressure in the brake circuit 11, which is determined via the pressure sensor 18.

[0048] As can be seen from figure 1, the control device 7 is connected in a data transmission system in the form of a CAN bus 23 with two further control devices 24 and 25. Of them, the control device 24 is a vehicle control device and the control device 25 is a transmission control device for the transmission 26. The transmission 26 is located in the area of ​​the axles 4.

[0049] Of the control devices 24, 25, the control device 24 is connected to an actuator 27 of an auxiliary brake system 28. This actuator 27 is present as a brake lever, the actuating position of which is detected via the control device 24. The auxiliary brake system 28 is arranged in this case within the brake system 1 and, in normal operation, realizes a parking brake function for statically braking both wheels 2 and 3 in order to hold the commercial vehicle in the respective current position. This static braking is carried out in normal operation of the brake system 1 via the actuator 27 when a corresponding command is given by the driver of the vehicle.

[0050] For this purpose, an auxiliary brake actuator 29 is assigned to the auxiliary brake system 28. In this case, the auxiliary brake actuator 29 is integrated in the transmission 26 in the area of ​​the axle 4. This auxiliary brake actuator 29 comprises a hydraulic cylinder 30, in which an actuating piston is preloaded via a spring element into an actuated position. In the actuated position, the actuating piston acts on both brake devices 5 and 6 via a bridge 31 to actuate them. The hydraulic cylinder 30 is supplied with hydraulic fluid from a pressure source 32 of the transmission 26, contrary to the actuation of the actuating device 27 with fluid. In normal operation, therefore, with the actuating device 27 in the released state, a pressure bias on the hydraulic cylinder 30 and thus a movement of the actuating piston against the spring element is initiated. The actuation of the brake devices 5 and 6 via the auxiliary brake actuator 29 is thereby cancelled. In contrast, when the actuating device 27 is actuated by the driver of the vehicle, the hydraulic cylinder 30 is gradually depressurized. Thereby, the brake devices 5 and 6 are also gradually actuated due to the effect of the spring element via the working piston of the hydraulic cylinder 30. In order to be able to adjust the degree of actuation, at least one valve, not shown here, is assigned to the auxiliary brake actuator 29. This at least one valve is adjusted via a control device 25. The required degree of actuation is transmitted by the control device 24 to the control device 25, which in this case is inside the CAN bus 23.

[0051] In Fig. 2 to Fig. 4, different states of the brake system 1 are shown from Fig. 1. In this case, only the components that are currently actively participating in the braking process are shown. For example, Fig. 2 shows the state of the brake system 1 when the brake actuators 21, 22 are actuated by the driver and the service brake is used. In this case, the actuation of the individual brake actuators 21 or 22 is converted in the valve block 14 into a corresponding adjustment of the pressure in the lines 12 and 13. The service brake actuators 9 and 10 then actuate both brake devices 5 and 6. Thus, the wheels 2 and 3 are braked accordingly. In this case, the brake actuators 21 and 22 can be actuated differently or only one of the brake actuators 21 or 22 can be actuated via the driver of the vehicle in order to realize the function of a steering brake of a commercial vehicle via one of the brake devices 9 or 10 by actuating one more strongly or only one of them.

[0052] Fig. 3 shows further states of the brake system 1. In Fig. 3, the situation of actuation of the actuator 27 by the driver of the vehicle and actuation of the auxiliary brake system 28 as a parking brake is shown. The respective degree of actuation of the actuator 27 is detected by the control device 24 and transmitted to the control device 25 by means of the CAN bus 23. The control device 25 drives the auxiliary brake actuator 29 on the basis thereof to actuate the brake devices 5 and 6 via the auxiliary brake actuator 29, via the bridge 31, in accordance with the degree of actuation of the actuator 27. In this case, the reduced pressure of the hydraulic cylinder 30 is increased via the control device 25 as the degree of actuation of the actuator 27 increases.

[0053] Finally, Fig. 4 shows the state of the brake system 1 in an emergency operation due to at least a partial failure of the service brake system 8. The reason for the failure of the service brake system 8 can in this case be a failure of the pressure source 15, a leak in the area of ​​the lines 12 and 13 or even a failure of one or both of the service brake actuators 9 and 10. In particular, the first two mentioned causes of failure are detected by the control device 7 by means of the pressure sensor 18. When a low pressure of the fluid in the brake circuit 11 is detected, the control device 7 initiates an emergency operation. This is preferably further indicated to the driver of the vehicle visually using a warning lamp and / or acoustically via a warning signal.

[0054] As a special feature, when the brake actuators 21 and 22 are actuated, the control device 7 independently ensures that the wheels 2 and 3 are braked as specified by the vehicle driver for the brake actuators 21 and 22. For this purpose, the control device 7 initiates the actuation of the auxiliary brake actuator 29 via the control device 25 using the CAN bus 23. In this case, the actuation of the brake actuators 5 and 6 is carried out at the brake actuators 21 and 22 in response to the vehicle driver's command via the auxiliary brake actuator 29. The control device 7 detects the degree of actuation of the brake actuators 21 and 22. The control device 7 gradually increases the pressure reduction of the hydraulic cylinder 30 of the auxiliary brake actuator 29 using the control device 25. Thereby, finally, in an emergency actuation, the braking command from the vehicle driver for the brake actuators 21 and 22 is automatically translated into the required braking of the wheels 2 and 3 of the axle 4 using the auxiliary brake system 28.

[0055] As a result, in the event of only a partial pressure failure in the service brake system 8, the braking demand is automatically calculated in such a way that only the missing difference to the driver's demand is conveyed via the auxiliary brake system 28. The braking force exerted via the auxiliary brake system 28 is mechanically added to the force generated by the residual pressure in the service brake system 8 via the service brake actuators 9 and 10. This is done automatically and dynamically. If the pressure in the service brake system 8 drops further during braking, the compensating braking demand on the auxiliary brake system 28 is also automatically readjusted. In the event of a complete loss of pressure in the service brake system 8, this adjustment immediately and automatically sends 100% of the driver's braking demand to the auxiliary brake system 28.

[0056] By means of the method for actuating a brake system according to the invention, it is possible to achieve a compact and highly reliable braking of commercial vehicles, also in the event of at least a partial failure of the service brake system. [Explanation of symbols]

[0057] 1 Brake system 2 wheels 3 wheels 4 axles 5 Brake device 6 Brake system 7 Control Device 8 Service Brake System 9 Service Brake Actuator 10 Service brake actuator 11 Brake circuit 12 Line 13 Line 14 Valve block 15 Pressure Source 16. Tank 17 Accumulator 18 Pressure Sensor 19 Line 20 Line 21 Brake actuator 22 Brake actuator 23 CAN Bus 24 Control Device 25 Control Device 26 Gearbox 27 Actuating device 28 Auxiliary Brake System 29 Auxiliary brake actuator 30 Fluid Cylinder 31 Bridge 32 Pressure Source

Claims

1. A method for operating a braking system (1) of a commercial vehicle, wherein the braking system (1) comprises a service braking system (8), a brake control device (7), an auxiliary braking system (28), and braking devices (5, 6) for wheels (2, 3) of an axle (4) of the commercial vehicle, the axle (4) being a rear axle of the commercial vehicle. In the service braking system (8), in normal operation, when at least one brake operating device (21, 22) operates, at least one associated service brake actuator (9, 10) is driven, and driving is performed via the at least one associated service brake actuator (9, 10). In response to the operation of the at least one brake operating device (21, 22), the operation of the respectively associated braking device (5, 6) is executed. The auxiliary braking system is provided to realize a parking brake function in normal operation. In the auxiliary braking system (28), the operation of at least one of the braking devices (5, 6) can be started via at least one transmission control device (25). When at least a partial failure in the form of a failure of a pressure source (15) of the service braking system (8), a leak in the area of lines (12, 13), or a failure of one or both of the service brake actuators (9, 10) is detected in the service braking system (8), in an emergency operation execution method, in the auxiliary braking system (28), at least one auxiliary brake actuator (29) is driven via the transmission control device (25) to start the operation of at least one of the braking devices (5, 6). During emergency operation, the operation of the at least one brake operating device (21, 22) is detected by the brake control device (7), and access is made to the auxiliary brake actuator (29). In this case, the brake control device (7) uses the auxiliary brake actuator (29) to adjust the operation of at least one of the braking devices (5, 6) in adaptation to the degree of operation of the at least one brake operating device (21, 22). The auxiliary brake actuator (29) and the service brake actuators (9, 10) act on the same braking device (5,A method, characterized by acting on (6).

2. The method according to claim 1, wherein during emergency operation, a required braking torque is determined based on the degree of actuation of the at least one brake actuation device (21, 22), and the required braking torque is subsequently used to adjust the drive of the at least one auxiliary brake actuator (29).

3. The method according to claim 1 or 2, wherein when detecting the actuation of the at least one brake actuation device (21, 22), it is detected as at least a partial failure that the pressure supply to the at least one associated service brake actuator (9, 10) is at least too low via a pressure source (15) to which the at least one associated service brake actuator (9, 10) is connected.

4. The method according to claim 3, wherein it is detected via a pressure sensor (18) that the pressure supply in the service brake system (8) is at least too low.

5. The method according to claim 1 or 2, wherein the drive of the at least one auxiliary brake actuator (29) is started via the brake control device (7), and for this purpose, data transmission is carried out in a data transmission system between the brake control device (7) and the transmission control device (25), and in this case, the auxiliary brake actuator (29) is driven via the transmission control device (25) in correspondence with an instruction of the brake control device (7).

6. The method according to claim 1 or 2, wherein in the auxiliary brake system (28), the actuation of at least one of the brake devices (5, 6) is carried out in the at least one auxiliary brake actuator (29) by decompressing one fluid cylinder (30) each, and the fluid cylinder (30) is equipped with an actuating piston pre-biased to an actuated position.

7. A brake control device (7) configured to start driving at least one auxiliary brake actuator (29) in an auxiliary brake system (28) of a brake system (1) of a commercial vehicle to operate at least one brake device (5, 6) of each wheel (2, 3). In the brake control device (7), when detecting at least a partial failure of the service brake system (8) of the brake system (1), the brake control device (7) starts an emergency operation. During the emergency operation, when detecting the operation of at least one brake operating device (21, 22) of the service brake system (8), the brake control device (7) accesses the at least one auxiliary brake actuator (29) via a transmission control device (25). At this time, the brake control device (7) is further configured to start the operation of the at least one brake device (5, 6) by adapting to the degree of operation of the at least one brake operating device (21, 22) via the auxiliary brake actuator (29). Claim 8 A braking system (1) for a commercial vehicle, comprising a service braking system (8), an auxiliary braking system (28), braking devices (5, 6) for the wheels of an axle (4) which is the rear axle of the commercial vehicle, a brake control device (7), a vehicle control device (24), and a transmission control device (25). The service braking system (8) comprises at least one brake actuating device (21, 22), and when operating in normal operation via the at least one brake actuating device (21, 22), at least one associated service brake actuator (9, 10) can be driven. When the at least one associated service brake actuator (9, 10) is driven in normal operation, it operates the respectively assigned braking devices (5, 6) corresponding to the operation of the at least one brake actuating device (21, 22). In the braking system (1), the brake control device (7) is connected to the transmission control device (25) in a data transmission system. The auxiliary braking system (28) comprises an auxiliary brake actuator (29). The auxiliary brake actuator (29) and the service brake actuators (9, 10) act on the same braking devices (5, 6). The auxiliary brake actuator (29) can be driven via the transmission control device (25) in normal operation, and in an emergency operation, the operation of the auxiliary brake actuator (29) can be started by the brake control device (7) via the transmission control device (25) to apply brakes to the wheels (2, 3). Braking system (1), characterized by this.

9. In the braking system (1) according to claim 8, the auxiliary brake actuator (29) comprises a fluid cylinder (30) having an operating piston pre-biased to an operating position. The operating piston can be moved to an open position by supplying fluid pressure to the fluid cylinder (30). In the open position, the operation of at least one of the braking devices (5, 6) via the auxiliary brake actuator (29) is cancelled. Braking system (1), characterized by this.

10. In the braking system (1) according to claim 8 or 9, in the service braking system (8), each of the at least one associated service brake actuator (9, 10) is arranged in one brake circuit (11), and in the brake circuit (11), in normal operation, the control of each associated service brake actuator (9, 10) is performed in response to the operation of the at least one brake operating device (21, 22). Braking system (1).

11. In the braking system (1) according to claim 8 or 9, in the service braking system (8), a sensor system can be provided in at least one brake circuit (11) capable of controlling the service brake actuator (9, 10), and the fluid pressure of the at least one brake circuit (11) can be monitored via the sensor system. Braking system (1).

12. A commercial vehicle comprising the braking system (1) according to claim 8 or 9.

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