Pneumatic brake device for vehicles, and method for operating a brake device

Abstract

The invention relates to a method for operating a pneumatic brake device (1) for vehicles (2) having pneumatic brakes (4) which can be actuated by means of brake pressure (P) and which are vented by means of an outlet valve (13). In order to reduce the noise emission of the vehicle having pneumatic brakes during venting of the brakes, according to the invention a brake control unit (11) controls the outlet valve (13) according to a venting gradient (EG), the brake control unit selecting (26) from among at least two operating modes (29, 30, 31) having different venting gradients (EG1, EG2, EG3), while taking into account the current vehicle driving commands (38), and in a normal mode (29) the brake control unit controlling the outlet valve according to venting gradients EG1 which are optimized with respect to reduced noise emission during venting, and in a quick venting mode (30) the brake control unit controlling the outlet valve according to venting gradients EG2 which are optimized for quick venting.

Description

[0001] Pneumatic braking device for vehicles and method for operating a braking device

[0002] The invention relates, according to claim 1, to a method for operating a braking device for vehicles with pneumatic brakes that are released by venting via an outlet valve, wherein a brake control unit controls the outlet valve according to a predetermined venting gradient. The invention also relates to a braking device for vehicles with pneumatic brakes according to claim 6. Furthermore, the invention relates to a vehicle according to claim 7.

[0003] In commercial vehicles, the wheels are usually braked by pneumatically actuated wheel brakes. To actuate a pneumatic brake, brake pressure is applied via an inlet valve, and the brake is vented by actuating an outlet valve. Bleeding produces noises that are particularly noticeable when the brake is released, when the brake pressure is significantly reduced. These noises are often perceived as disturbing by those around the vehicle, especially when venting while the vehicle is stationary, for example, when releasing a stop brake, engaging the holding function of a service brake ("auto-hold"), or activating a parking brake by venting.

[0004] In principle, noise development could be reduced if the exhaust valves were controlled with flatter venting gradients, meaning that the pressure reduction during venting occurs more slowly. However, in many situations, slower venting is not sufficient to achieve the desired vehicle behavior. In particular, slower venting would often not correspond to the vehicle control requested by the driver. The present invention is based on the object of reducing the noise emissions of a vehicle with pneumatic brakes during brake venting.

[0005] This object is achieved by a method for operating a pneumatic braking device having the features of claim 1. The object is also achieved by a pneumatic braking device having the features of claim 6. Furthermore, a vehicle having the features of claim 7 achieves this object.

[0006] According to the invention, the brake control unit selects from at least two operating modes with different venting gradients after evaluating the current vehicle control commands it receives. In normal operation, it controls the exhaust valve according to venting gradients optimized for reduced noise emissions during venting and preset for the quietest possible venting. In rapid venting mode, it controls the exhaust valve according to venting gradients optimized for rapid venting. The venting gradient is understood as the temporal progression of the pressure reduction during brake venting, which is created by the specific activation of the exhaust valve with a corresponding control signal.Venting gradients optimized for reduced noise emissions generally correspond to a longer venting process than would be possible for venting and is also intended for rapid venting mode. Slower venting generally results in significantly quieter venting noise.

[0007] The invention therefore uses the evaluation results to distinguish between rapid venting mode, in which venting gradients are specified for rapid venting, and normal mode, in which venting gradients optimized for low noise emissions are specified, i.e., a quiet but slower venting occurs. In this way, rapid venting with corresponding noise emissions only occurs in exceptional cases, when the vehicle control commands make it necessary.

[0008] Vehicle control commands are the driver's messages regarding his control decisions or requirements to the vehicle's operating systems, which he communicates by operating the pedals in the cab. Accordingly, when selecting the operating mode with different venting gradients, the actuation signals from the brake pedal and / or the drive signal are evaluated. In manual vehicles, the clutch actuation can also be advantageously included in the evaluation and selection of the intended operating mode with different venting gradients.

[0009] In the case of vehicle guidance commands from a driver assistance system or a virtual driver, the signals “brake release” and / or an acceleration request are advantageously evaluated in order to select the operating mode and the venting gradients associated with the operating mode.

[0010] Accordingly, for the inventive selection of the operating mode with venting gradients provided for the operating mode, a variable, i.e., an operating selection variable, is derived from the vehicle control commands, from which conclusions are drawn about the vehicle behavior desired by the driver. The operating mode is selected based on the operating selection variable. The operating selection variable is advantageously derived from vehicle control commands for the current actuation of the pedals, in particular the brake pedal and / or the accelerator pedal. The position of the respective actuation pedal or a movement variable, for example, the speed of the change in the position of the actuation pedal or a variable derived from the speed, can be monitored as the operating selection variable.By evaluating this variable, it is possible to distinguish between situations in which bleeding must occur as quickly as possible and those in which bleeding gradients are controlled that are optimized with regard to noise development during bleeding. To derive the operating selection variable for determining the bleeding gradient, the brake control unit uses a connection to each of the actuating pedals to receive their travel sensor signals.

[0011] To derive the operating selection variable from the vehicle control commands, for example, a standard value for the travel of the respective actuation pedal and the time in which the travel is covered during actuation are specified. During the evaluation, the determined deviation from the standard value is assessed with regard to the selection of the venting gradient. If the evaluation shows that the brake pedal, for example, covers a certain pedal travel in a comparatively short time, this indicates the need for rapid venting as opposed to a comparatively long brake pedal movement time. If the brake pedal is moved more slowly over the pedal travel, there is time for slower venting, so that in this case the evaluation leads to the selection of a noise-optimized venting gradient during normal operation.

[0012] In a preferred embodiment of the invention, a movement variable of the change in the position of the brake pedal is evaluated to select the operating mode and corresponding venting gradients in order to make the choice between a venting gradient for rapid venting, i.e. the rapid venting mode, and another operating mode in which venting gradients optimized with regard to noise development are controlled.

[0013] In a further advantageous embodiment, the position of the accelerator pedal and / or a movement variable of the change in the position of the accelerator pedal is evaluated. The demand for drive power by actuating the accelerator pedal indicates a need to bleed the brakes. The evaluation of the variable determined by the accelerator pedal is particularly advantageous and meaningful when carried out in combination with the evaluation of the variable determined by the brake pedal. Conclusions are drawn from pedal changes or the interaction of the pedals as to whether the bleed gradient should be specified according to the quick bleed mode, resulting in rapid bleed, or whether a noise-optimized bleed gradient can be specified.

[0014] In a manual vehicle, the clutch pedal is used as an additional data source for evaluating and selecting optimal venting gradients. If, for example, the brake is released but the clutch pedal has not been depressed, there is no desire to set the vehicle in motion, i.e. the driver simply wants to release the brake while stationary. The same applies if the driver is still keeping 100% of his foot on the clutch pedal, or has been doing so for some time. In the preferred embodiment of the invention, a predetermined limit value for the operating mode selection variable is used when selecting the operating mode to differentiate between the quick venting mode and the at least one other operating mode in which venting gradients optimized for low noise emissions are specified.If several operating modes are provided in addition to the quick venting mode, several limit values ​​are determined accordingly to evaluate the operating selection variable and to define the respective operating mode with individually specified venting gradients and specified to the brake control unit.

[0015] A refinement of the reduction in noise emissions during venting by specifying optimized venting gradients is achieved if, during normal operation, additional operating modes with individual venting gradients are selected depending on the operating selection variable, which is derived from the vehicle control commands, i.e. determined by a driver by pressing at least one actuation pedal. The driving situation can also be taken into account, in particular whether the vehicle is traveling at low speed or even stationary. Noise-optimized venting gradients are particularly advantageous when the vehicle is stationary, as venting noises can be particularly disruptive in this situation, for example when braking at a stop or in auto-hold mode of the service brake. If the driver releases the brake while stationary, noise development can be significantly reduced with slower venting and a correspondingly flat venting gradient.

[0016] The bleeding of the brake according to the invention on the basis of a bleeding gradient which is selected depending on the actuation of at least one pedal, in particular the brake pedal, is particularly advantageous in commercial vehicles, in particular trucks or buses.

[0017] An embodiment of the invention is explained in more detail below with reference to the drawings. They show:

[0018] Fig. 1 is a pneumatic and electrical diagram of an embodiment of a pneumatic braking device of a commercial vehicle. Fig. 2 is a flow chart of an embodiment of a method for operating a braking device according to Fig. 1.

[0019] Fig. 1 shows an electro-pneumatic diagram of a pneumatic braking system 1 of a vehicle 2, which is a commercial vehicle 2a. In the exemplary embodiment shown, the vehicle is a bus 2b equipped with a stop braking function. Electrical lines are shown in solid lines and pneumatic lines in dotted lines. To brake the wheels 3, each wheel 3 is assigned a brake 4, which can be actuated pneumatically via brake cylinders 5. The brakes 4 exert a braking force on the rotating wheel 3 according to the pneumatic brake pressure P present in the brake cylinder 5. In the exemplary embodiment shown, the wheel brakes 4 of the front axle are assigned to a common first brake circuit 6, while the wheel brakes 4 of the rear axle can be actuated via a second brake circuit 7. A first pressure fluid reservoir 8 is assigned to the first brake circuit 6 and connected to the brake cylinders 5 of the brakes 4 of the front axle.The second brake circuit 7 of the rear axle is supplied with pressure fluid via a second pressure fluid reservoir 9. The second brake circuit 7 is constructed analogously to the first brake circuit 6.

[0020] Each brake cylinder 5 of a brake 4 is preceded by an electrically controllable pressure control valve 10. To receive control signals, the pressure control valves 4 are connected to a brake control unit 11. The brake control unit 9 is designed and provided to influence the brake pressure P of the brakes 4 as needed. In the exemplary embodiment shown, the pressure control valves 10 are each a combination of at least two solenoid valves, namely an inlet valve 12 and an outlet valve 13. The inlet valve 12 essentially serves to increase the pressure or maintain the pressure in the respective brake cylinder 5, while the outlet valve 13 is opened to reduce the brake pressure and vent the brake 4, specifically the connected brake cylinder 5. The inlet valve 12 and the outlet valve 13 are preferably electrically controlled 2 / 2-way valves.For the control of the intake valves 12 and the exhaust valves 13, the brake control unit 11 takes into account vehicle control commands 38, which the driver of the vehicle 2 specifies via actuating pedals in the driver's cab, namely a brake pedal 18, an accelerator pedal 22, and in the case of a manual vehicle, a clutch pedal 21. Upon detecting a braking request at the brakes 3, the brake control unit 11 sets a corresponding brake pressure P and, for this purpose, outputs control signals 20 for at least the intake valves 12. The braking request is communicated by the driver of the vehicle 2 via a brake signal 16 from the brake signal transmitter 17 of the brake pedal 18. By actuating the accelerator pedal 22, the driver communicates a driving request. The braking request and / or driving request can also be the specification of a virtual driver, for example in autonomous driving or an external braking request from a driver assistance or stability system 14 of the commercial vehicle 2a.A braking request is also the request for an auto-hold function of the braking device 1 or a stop brake, which have in common that a specific braking pressure is applied to the brake actuators, with which the vehicle 2 is held at a standstill, and this braking pressure is retained until the brake 4 is released. In the case of a parking brake, pneumatic pressure is applied analogously to a braking request to release the brake, which is vented to apply it.

[0021] The release of the brake 4 by venting occurs by opening the respective outlet valve 13, which is actuated by the brake control unit 11 with control signals 23. A release request can result from an evaluation of the brake signal 16 of the brake pedal 18 or from the input of a virtual driver.

[0022] The brake control unit 11 determines the control signals 23 for controlling the exhaust valve 13 according to a venting gradient EG, i.e., a specification that determines the temporal dynamics of the opening of the exhaust valve 13. Several operating modes are provided, each with a different venting gradient EG. For the operating mode selection 26, an operating selection variable 25 is derived from the vehicle control commands 38. The operating selection variable 25 is therefore characterized by the actuation of at least one actuating pedal. For the derivation 26 of the operating selection variable 25 and thus of the venting gradient EG, the brake signal 16 of the brake pedal 18 is used and evaluated with regard to the vehicle behavior desired by the driver. In the exemplary embodiment shown, the evaluation 15 also takes into account the driving signal 22 of the accelerator pedal 19, with which the driver can request propulsion of the vehicle 2, when determining the venting gradient EG.In a manual vehicle, a clutch signal 24 of a clutch pedal 24 is also used for the derivation 15 of the operating selection variable 25 and ultimately for the evaluation of the driver's actuation behavior.

[0023] The specification of the venting gradient and determination of the control signal 23 for the outlet valve 13 is explained below with reference to Fig. 2. The same reference numerals as in Fig. 1 are used for identical features. If the current actuation of one or more pedals results in the need to reduce the applied brake pressure by venting the brake, a specific operating mode 29, 30, 31 is determined and a venting gradient EG1, EG2, EG3 provided in the operating mode is determined, which forms the basis for the output 33 of the control signal 23 for the outlet valve 13. The operating mode selection 26 and thus the determination of the venting gradient EG1, EG2, EG3 is determined by the evaluation 15 of at least one operating selection variable 25, which is characterized by the current actuation of the actuating pedals.When selecting the operating mode 26, a distinction is made between a rapid venting mode 30, in which venting gradients EG are specified for rapid venting, and at least one further operating mode, in which venting gradients optimized for low noise emissions are specified. In the illustrated embodiment, a normal mode 29 is provided, as well as a further operating mode 31 for standstill or slow travel (standstill mode 31). Standstill mode 31 is provided for a stop brake function or an auto-hold of the braking system when the brake is intended to secure the vehicle 2—in this embodiment, the bus 2c equipped with a stop brake—at a standstill.

[0024] In order to select the operating mode 26 and thus the choice between a venting gradient EG2 for rapid venting, i.e. the rapid venting mode 30, and another operating mode in which venting gradients EG1, EG3 optimized with regard to noise development are activated, the change 34 in the position of the brake pedal 18 is derived from the brake signal 16 and determined as the decisive operating selection variable 26. The change 34 in the position of the brake pedal 18 is a movement variable, the speed of the movement of the brake pedal 18 or another movement variable derived therefrom, which contains the qualitative statement about the movement of the brake pedal 18. An optional standard value for the travel of the brake pedal 18 is specified, and the time in which the travel is covered when actuated is considered.During the evaluation and derivation 15 of the operating selection variable 25, and thus the selection of the venting gradient EG1, EG2, EG3 to be controlled, the determined deviation from the normal value is evaluated. The differentiation of the rapid venting mode 30 from normal operation then takes place in the exemplary embodiment by comparing the determined deviation from the normal value with a predetermined limit value 27.

[0025] In addition, when selecting the operating mode 26 and thus the ideal venting gradient EG1, EG2, EG3, the position of the accelerator pedal 22 and / or a movement variable of the change in the position of the accelerator pedal 22 is evaluated. Taking into account the information provided by the accelerator pedal 22 is particularly advantageous and meaningful when it is combined with the variables provided by the brake pedal 18 and the operating mode selection 26 is made on the basis of the combined evaluation of information from the accelerator pedal 22 and the brake pedal 18. In this case, conclusions are drawn from pedal changes or the interaction of the pedals as to whether the venting gradient EG2 should be specified according to the quick venting mode 30 and causes rapid venting or whether a noise-optimized venting gradient EG1 can be specified.If the driver releases the brake pedal in a comparatively short time of, for example, 0.3 seconds and presses the accelerator pedal in a short transition time of, for example, less than 0.5 seconds, this underlines the desire to drive off immediately. If no signal is received from the accelerator pedal, the brake has more time to vent and a noise-optimized venting gradient EG2 can be specified and controlled by the outlet valve 13. The vehicle 2 shown is a manual vehicle, with the clutch pedal 21 being used as an additional data source in the operating mode selection 26 of the different operating modes with different venting gradients EG1, EG2, EG3. If, for example, the brake is released but the clutch pedal 21 has not been depressed, there is no desire to set the vehicle in motion, i.e. the driver simply wants to release the brake while stationary.

[0026] List of reference symbols (part of the description)

[0027] 1 . Braking device

[0028] 2. Commercial vehicle

[0029] 3. Wheel

[0030] 4. Brake

[0031] 5. Brake cylinder

[0032] 6. First brake circuit

[0033] 7. Second brake circuit

[0034] 8. First pressure medium supply

[0035] 9. Second pressure medium supply

[0036] 10. Pressure control valve

[0037] 11. Brake control unit

[0038] 12. Inlet valve

[0039] 13. Exhaust valve

[0040] 14. Driver assistance system

[0041] 15. Derivative P brake pressure

[0042] EG1 vent gradient normal operation

[0043] EG2 vent gradient quick vent mode

[0044] EG3 venting gradient standstill operation

Claims

Claims 1. Method for operating a braking device (1) for vehicles (2) with pneumatic brakes (4) and a brake control unit (11) which receives vehicle control commands (38) (for acceleration and / or braking) and actuates the respective brake by means of brake pressure (P) and vents it via an outlet valve (13), wherein the brake control unit (11), taking into account the current vehicle control commands (38), selects (26) from at least two operating modes (29, 30, 31) with different venting gradients (EG1, EG2, EG3) and controls the outlet valve (13) in normal operation (29) according to venting gradients (EG1) which are optimized with regard to reduced noise emissions during venting, and in rapid venting operation (30) according to venting gradients (EG2) optimized for rapid venting.

2. Method according to claim 1, characterized in that the operating mode selection (26) is carried out on the basis of an operating mode selection variable (25) which is derived (15) from vehicle control commands (38) of the current actuation of the brake pedal (18) and / or the accelerator pedal (19).

3. Method according to claim 2, characterized in that the operating selection variable is derived (15) from the change (34) in the position of the brake pedal (18).

4. Method according to claim 2 or 3, characterized in that the operating selection variable is derived (15) from the position (35) of the accelerator pedal (19) and / or the change (36) in the position (35) of the accelerator pedal (19).

5. Method according to one of claims 2 to 4, characterized in that in the operating selection (26) with a predetermined limit value (27) for the operating selection variable (25) is used to delimit the quick venting operation (30) from the at least one further operating mode (29, 31) in which venting gradients (EG) optimized with regard to reduced noise emission are specified.

6. Braking device (1) for vehicles (2) with pneumatic brakes (4) which can be actuated by means of brake pressure (P) and can be vented via an outlet valve (13), and with a brake control unit (11) for controlling the outlet valve (13) according to a predetermined venting gradient (EG), wherein the brake control unit (11) is designed to receive vehicle control commands (38) and, taking into account the current vehicle control commands (38), to select (26) from at least two operating modes (29, 30, 31) with different venting gradients (EG1, EG2, EG3) and to control the outlet valve (13) in a normal operation (29) according to venting gradients (EG1) which are optimized with regard to reduced noise emissions during venting, and to control the outlet valve (13) in a quick venting operation (30) according to to control the venting gradient (EG2) optimized for rapid venting.

7. Vehicle (2), in particular commercial vehicle (2a), with a braking device (1) according to claim 6, in particular for carrying out a method according to one of claims 1 to 5.

8. Vehicle (2) according to claim 7, characterized in that the vehicle (2) is a bus (2b).

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