Method, circuitry, motor vehicle or trailer having circuitry of this type, for bleeding a brake channel of a compressed-air braking system

Abstract

The invention relates to a method for bleeding at least one brake channel in a brake circuit of a compressed-air braking system of a vehicle, in which method the brake channel can be bled. The compressed-air braking system comprises a braking-pressure modulator which has a plurality of switchable valves for a control pressure. The compressed-air braking system also comprises an electronic controller interacting with the braking-pressure modulator, one or more brake cylinder(s) acting on a wheel brake, as well as one or more pressure sensor(s). The braking-pressure modulator comprises at least one relay valve for each brake channel, by means of which relay valve a quantity of air from a supply pressure line, which is independent of the control pressure, can be introduced into at least one brake cylinder in order to actuate the brake, and by means of which relay valve the brake cylinder can be bled via a bleed outlet of the relay valve. During bleeding by switching one or more valve(s) of the braking-pressure modulator, the pressure is controlled to a target-pressure specification. In this process, the target-pressure gradient is varied during bleeding on the basis of the pressure in the brake cylinder and on the basis of the operating state of the vehicle, according to an algorithm stored in the controller.

Description

[0001] METHOD, CIRCUIT, VEHICLE OR TRAILER WITH SUCH A CIRCUIT, FOR BLEEDING A BRAKE DUCT OF A COMPRESSED AIR BRAKE SYSTEM

[0002] The invention relates to a method for venting at least one brake channel in a brake circuit of a compressed air brake system of a vehicle, wherein the compressed air brake system has a brake pressure modulator which comprises a plurality of switchable valves for a control pressure, an electronic control device which interacts with the brake pressure modulator, one or more brake cylinders acting on a wheel brake and one or more pressure sensors, wherein the brake pressure modulator has at least one relay valve for each brake channel, through which, on the one hand, an amount of air can be introduced from a supply pressure line which is independent of the control pressure into at least one brake cylinder for actuating the brake and, on the other hand, the brake cylinder can be vented via a vent outlet of the relay valve, wherein during the venting, control to a target pressure specification takes place by switching one or more valves of the brake pressure modulator.Also disclosed is an electropneumatic circuit for carrying out the method and a vehicle with such a circuit.

[0003] As transport volumes increase, so do the number of transport operations by commercial vehicles. This makes operating noises from auxiliary units and systems more noticeable, occasionally becoming prominent not only in loading bays or parking areas. These noises are perceived as unpleasant and disturbing not only by vehicle occupants, but also, and especially, by those in the vicinity.

[0004] For example, bleeding processes in a vehicle's air brake system are associated with considerable noise emissions and would have a particularly negative impact on the environment if appropriate measures were not taken, such as silencers at the outlet cross-section of the compressed air into the environment. This is especially true for bleeding brake systems at low speeds and during shunting, which require correspondingly large silencers.

[0005] Such silencers are additional components in an air brake system that must be designed according to the flow and pressure conditions for any sudden venting of a brake system. Different silencer designs are suitable to varying degrees for reducing the noise emissions occurring during venting, as disclosed, for example, in DE 102013 016 086 A1 or DE 10 2009 029 968 A1. In any case, the installation of appropriately dimensioned silencers designed for the respective brake system requires a dedicated installation space in the vehicle and is an element that incurs additional costs during both assembly and manufacturing.

[0006] The object of the present invention was therefore to provide a method and an electropneumatic circuit by means of which a significant noise reduction is possible during venting processes in compressed air brake systems of vehicles.

[0007] This problem is solved by the features of the main claim. Further advantageous embodiments are disclosed in the dependent claims.

[0008] During bleeding, a target pressure gradient is changed depending on the pressure in the brake cylinder and the operating condition of the vehicle according to an algorithm stored in the control unit.

[0009] A setpoint pressure is provided to regulate the venting process. The setpoint pressure gradient specifies the pressure drop per unit of time at which the pressure in the system / venting pressure is vented to atmosphere. If, as previously provided in the state of the art, the switching of the relay valve provided for venting is controlled solely based on the setpoint pressure, the resulting setpoint pressure gradient depends on the flow pattern or pipe conditions during venting, and usually results in a sudden venting that leads to an outflow associated with increased noise emissions. The sound pressure at the beginning of the venting process is therefore particularly high.

[0010] The method according to the invention now includes a different control of the venting process, in which the relay valve intended for venting is actuated in such a way that the target pressure gradient is changed during venting, depending on the pressure in the brake cylinder and the operating condition of the vehicle. This prevents, on the one hand, a steep increase in sound pressure and the extreme formation of a sound pressure peak at the beginning of the venting process. The change in the target pressure gradient is achieved by pulsing certain valves in the electropneumatic circuit and switching them stepwise so that a venting volume flow can be changed via the control chamber of the relay valve.

[0011] By applying the method according to the invention for venting, a silencer can be manufactured much more easily and its dimensions can also be significantly reduced, so that overall installation space and costs are saved.

[0012] A further development of the process involves reducing the target pressure gradient. This particularly effectively reduces the sound pressure at the beginning of the venting process.

[0013] A further development involves changing the target pressure gradient only below a predetermined vehicle speed, preferably below 15 km / h. Above 15 km / h, the anti-lock braking system (ABS) used in commercial vehicles is activated. However, for safety reasons, ABS control also requires occasional sudden venting, without taking noise emissions into account. Because the algorithm controlling the venting only intervenes below 15 km / h, control conflicts between the method according to the invention and the ABS control are avoided.

[0014] A further development of the method also serves to avoid control conflicts, which consists in the fact that the change in the target pressure gradient only occurs if no simultaneous routine of a vehicle safety or driver assistance system in a vehicle control system concerning the control unit of the compressed air brake system is carried out.

[0015] A further development of the process involves reducing the target pressure gradient at least for certain periods during the venting time. This prevents, as already explained above, a steep increase in sound pressure at the beginning of the venting process and allows the target pressure gradient, and thus the venting cross-section, to be increased again towards the end of the venting process.

[0016] A further development of the method consists in that at least two brake channels of a vehicle's compressed air brake system are vented alternately, whereby, depending on the design of the compressed air brake system and the brake channels, the venting can take place either alternately on each side and / or alternately on each axle.

[0017] A further embodiment consists in that the method according to the invention is used for venting at least one service brake circuit and / or a parking brake circuit of a compressed air brake system of a vehicle.

[0018] A further development of the method consists in that at least one brake circuit of a compressed air brake system of a trailer of a towing vehicle and / or at least one brake circuit of a compressed air brake system of a towing vehicle is vented.

[0019] By using the method according to the invention for several brake channels, for different brake circuits and for brake channels or brake circuits of trailer and towing vehicle, the method can be used very variably and leads to a comprehensive noise reduction when bleeding differently designed vehicles.

[0020] An electropneumatic circuit of a compressed air brake system which is particularly suitable for carrying out the method according to the invention will be described in more detail using an exemplary embodiment.

[0021] Fig. 1 shows an electropneumatic circuit for carrying out the method according to the invention,

[0022] Fig. 2 is a diagram comparing the sound pressure curve and the brake pressure curve for conventional venting systems according to the prior art and when using the method according to the invention.

[0023] Fig.1 shows a section of the circuit of a compressed air brake system of a vehicle that is relevant for the method according to the invention and the associated electropneumatic circuit, namely the electropneumatic circuit diagram of a trailer of a commercial vehicle.

[0024] The central element of the electropneumatic circuit shown here is the brake pressure modulator 10, which comprises an arrangement of pneumatic elements and sensors, as well as an electronic control unit (ECU) that interacts with the brake pressure modulator. The redundancy valve 13, the outlet valve 14, and the inlet valves 15 and 16, as well as the relay valves 17 and 18, which are actuated by a control pressure acting on their control chambers, are shown in Fig. 1 as belonging to the brake pressure modulator. Also visible are the vent outlets of the relay valves, each equipped with silencers 19, 20, as well as the pressure sensors 27 and 28 at various measuring points and the speed sensors 29 on both wheels of an axle. The brake pressure modulator and the ECU are enclosed by a dashed line in Fig. 1.

[0025] Also enclosed by a broken line are other important functional units of a trailer air brake system, namely an emergency brake valve with overload protection as functional unit 11 and a parking / release valve as functional unit 12. The functional unit 11 includes a switchable check valve 22, an overload protection valve 23 and an emergency brake valve 24. The functional unit 12 has a manually operated 4 / 3-way valve 25 and a pneumatic reset 26.

[0026] However, the functional units 11 and 12 are not essential in the sense of the inventive method and therefore will not be described further here in terms of their individual circuits and functions.

[0027] Fig. 1 also shows a supply pressure line 1, which also fills the storage pressure vessel 21, a control pressure line 2 and a voltage supply 3 for the ECU.

[0028] Finally, the actuating devices of the braking system are shown, namely the service brake cylinders 4 and 5 and the double-diaphragm cylinders 6, 7, 8, and 9. In an electropneumatic control system of an air brake system, the control pressure in the control line, which essentially represents a "driver's command," is combined or superimposed with a control characteristic specified in the control electronics. The control pressure, also called redundancy pressure, corresponds to the pressure generated by a driver pressing a brake pedal.

[0029] In the event of venting as a result of a sudden reduction in control pressure, for example when the driver quickly takes his foot off the brake pedal after a previous brake application, the pressure in control line 2 drops suddenly, e.g. from 8 bar to 1 bar.

[0030] A pressure sensor 27, which measures the pressure in the control line, registers the sudden pressure drop and initiates a corresponding reaction from the electronics, which then also operates to rapidly reduce the pressure. While valves 15 and 16 remain in the de-energized position shown in Fig. 1, the control device energizes and switches solenoid valve 14, which then connects the line leading to the control chambers of relay valves 17 and 18 to atmospheric pressure. The control chambers of relay valves 17 and 18 are then vented.

[0031] When their control chambers are vented, relay valves 17 and 18 vent service brake cylinders 4 and 5, as well as double-diaphragm brake cylinders 6, 7, 8, and 9. These brake cylinders were filled with a large amount of air from the supply pressure or the accumulator via the relay valves during the previous brake application. The venting of brake cylinders 4 to 9 now also takes place via relay valves 17, 18 and their outlets to silencers 19 and 20, directly to the atmosphere.

[0032] In the event of such a sudden pressure drop in the control line, i.e., when the driver quickly lifts their foot from the brake pedal, the method according to the invention kicks in. The bleeding of brake cylinders 4 to 9 then does not occur as abruptly as specified by the driver, but in a manner specified by the electronic control system. A corresponding algorithm is stored in the electronic control system for this purpose.

[0033] The pressure in the control chambers of the relay valves is regulated such that the pressure gradient, i.e., the gradient of the pressure drop during the bleeding of the brake cylinders, is controlled depending on the brake pressure in the brake cylinders. The brake pressure in the brake cylinders is detected by one of the pressure sensors 28.

[0034] The pressure gradient is changed by a change in the volume flow of the relay valves during venting, namely by a pulsed or stepwise / gradual opening of the valves, determined by the algorithm in the control unit, depending on the brake pressure. Since relay valves 17 and 18 are pressure-controlled, the pulsed or stepwise / gradual opening is achieved via the electronic control unit by a corresponding pulsed and stepwise switching of the vent valve 14 and the inlet valves 15 and 16.

[0035] The bleeding of the brake cylinders therefore depends on the brake pressure in the brake cylinders, but not solely on the brake pressure specified by the driver in control line 2. In addition, this happens depending on the speed and the presence of higher-level control strategies, e.g. only when there is no intervention by an ABS control.

[0036] Fig. 2 shows a comparison diagram of the sound pressure curve according to ECE-R 51 (Regulation No. 51 of the Economic Commission for Europe of the United Nations) and the brake pressure curve for conventional bleeding according to the state of the art and when using the method according to the invention. The sound pressure curves 30 and 31 are plotted in the upper part of the diagram. Curve 30 shows the sound pressure curve in Pa (A) over the bleeding time according to the methods customary in the state of the art, while curve 31 shows the sound pressure curve over the bleeding time according to the inventive method. The inventive method is approximately 6 dB (A) quieter than the bleeding known in the state of the art.

[0037] In the lower part of the diagram, the brake pressure is plotted against the bleeding time. Curve 32 clearly shows that the brake pressure drops with a much higher gradient, i.e., much steeper, in the prior art bleeding methods than the brake pressure shown in curve 32 in the method according to the invention.

[0038] List of reference symbols (part of the description):

[0039] 1 supply pressure line / supply pressure circuit

[0040] 2 Control pressure line / control pressure circuit

[0041] 3 Power supply

[0042] 4, 5 service brake cylinders

[0043] 6 - 9 double diaphragm cylinders

[0044] 10 Brake pressure modulator

[0045] 11 Functional unit emergency brake valve with overload protection

[0046] 12 Functional unit parking / release valve

[0047] 13 Redundancy valve

[0048] 14 Exhaust valve

[0049] 15 Inlet valve

[0050] 16 Inlet valve

[0051] 17 Relay valve

[0052] 18 Relay valve

[0053] 19 Silencer / vent outlet

[0054] 20 silencer / vent outlet

[0055] 21 Reservoir pressure vessel for the service brake

[0056] 22 switchable check valve

[0057] 23 Overload protection valve

[0058] 24 Emergency brake valve

[0059] 25 manually operated 4 / 3 way valve

[0060] 26 pneumatic reset (in driving position)

[0061] 27 Pressure sensor

[0062] 28 Pressure sensor

[0063] 29 Speed ​​sensor

[0064] 30 Sound pressure curve over the venting time according to the state of the art

[0065] 31 Sound pressure curve over the venting time according to the method according to the invention

[0066] 32 Brake pressure curve over the bleeding time according to the prior art 33 Brake pressure curve over the bleeding time according to the invention

[0067] Proceedings

Claims

Patent claims:

1. A method for venting at least one brake channel in a brake circuit of a vehicle's pneumatic brake system, wherein the pneumatic brake system has a brake pressure modulator (10) comprising a plurality of switchable valves (13, 14, 15, 16) for a control pressure, an electronic control device cooperating with the brake pressure modulator, one or more brake cylinders (4, 5, 6, 7, 8, 9) acting on a wheel brake, and one or more pressure sensors (27, 28), wherein the brake pressure modulator (10) has at least one relay valve (17, 18) for each brake channel, through which, on the one hand, an amount of air from a supply pressure line (1) independent of the control pressure can be introduced into at least one brake cylinder for actuating the brake, and, on the other hand, the brake cylinder can be vented via a vent outlet of the relay valve (17, 18),wherein during the bleeding, a control to a target pressure specification is carried out by switching one or more valves of the brake pressure modulator (10), characterized in that a target pressure gradient is changed during the bleeding depending on the pressure in the brake cylinder (4, 5, 6, 7, 8, 9) and depending on an operating state of the vehicle according to an algorithm stored in the control unit.

2. Method according to claim 1, wherein the change in the target pressure gradient consists in at least an initial reduction in the target pressure gradient.

3. Method according to claim 1 or 2, wherein the change in the target pressure gradient occurs only below a predetermined driving speed of the vehicle, preferably only below 15 km / h.

4. Bleeding method according to one of claims 1 to 3, wherein the change in the target pressure gradient only occurs when no simultaneous routine of a vehicle safety or driver assistance system in a vehicle control system relating to the control unit of the compressed air brake system is carried out.

5. Method according to one of claims 1 to 4, wherein the desired pressure gradient is reduced at least over individual time periods during the venting time.

6. A method for venting according to one of claims 1 to 5, wherein at least two brake channels of a compressed air brake system of a vehicle are vented alternately.

7. Method according to one of claims 1 to 6 for venting at least one service brake circuit and / or a parking brake circuit of a compressed air brake system of a vehicle.

8. Method according to one of claims 1 to 7, in which at least one brake circuit of a compressed air brake system of a trailer of a towing vehicle and / or at least one brake circuit of a compressed air brake system of a towing vehicle are vented.

9. Electropneumatic circuit of a compressed air brake system for carrying out the method according to claims 1 to 8, which has the following features: a control pressure circuit (2) and a supply and reservoir pressure circuit (1) independent thereof, a brake pressure modulator (10) which comprises a plurality of switchable valves (13, 14, 15, 16) for the control pressure, an electronic control device (ECU) cooperating with the brake pressure modulator (10) for the switchable valves, one or more brake cylinders (4, 5, 6, 7, 8, 9), one or more pressure sensors (27, 28) cooperating with the control device at different points of the pneumatic circuit, wherein the brake pressure modulator (10) is assigned at least one relay valve (17, 18) for each brake channel, through which, on the one hand, an amount of air from the supply pressure circuit (1) independent of the control pressure can be introduced into at least one brake cylinder (4, 5, 6, 7, 8, 9) for actuating the brake and, on the other hand, the brake cylinder can be vented via a vent outlet of the relay valve (17, 18), wherein the relay valve is designed as a pressure-controlled valve provided with a control chamber and has a vent outlet with a silencer (19, 20), characterized in that the electronic control device has a programmed algorithm,by which a target pressure gradient can be changed during bleeding depending on the pressure in the brake cylinder and the operating condition of the vehicle.

10. Electropneumatic circuit according to claim 9, in which at least one vent valve (14) and at least one inlet valve (15, 16) are provided for control pressure in the respective control chamber of the relay valve (17, 18), wherein the vent valve (14) and inlet valve (15, 16) are pulsed and can be switched stepwise so that a vent volume flow in the relay valve (17, 18) can be changed via the control chamber of the relay valve (17, 18).

11. Electropneumatic circuit according to claim 9 or 10, wherein a pressure measuring sensor (28) is provided in the connecting line between the relay valve and the brake cylinder or in the control chamber of the relay valve for measuring the pressure in the brake cylinder.

12. Motor vehicle, in particular commercial vehicle, with an electropneumatic circuit according to one of claims 9 to 11.

13. Trailer for a towing vehicle with an electro-pneumatic circuit according to one of claims 9 to 11.

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