METHOD FOR OPERATING AN ELECTROPNEUMATIC PARKING BRAKE SYSTEM, AND ELECTROPNEUMATIC PARKING BRAKE SYSTEM

Abstract

A method is for operating a parking brake system with a spring-loaded brake and a control module in a motor vehicle or trailer. The control module is connected to a parking brake circuit. The method includes supplying the parking brake circuit with reservoir pressure. The method further includes applying spring-loaded accumulator holding pressure to the spring-loaded brake cylinders in order to have the spring-loaded brake assume a release position, wherein the spring-loaded accumulator holding pressure is less than the reservoir pressure in the parking brake circuit.

Claims

1. A method for operating a parking brake system with a spring-loaded brake and a control module in a motor vehicle or trailer, wherein the control module is connected to a parking brake circuit, the method comprising: supplying the parking brake circuit with reservoir pressure; and, applying spring-loaded accumulator holding pressure to the spring-loaded brake cylinders in order to have the spring-loaded brake assume a release position, wherein the spring-loaded accumulator holding pressure is less than the reservoir pressure in the parking brake circuit.

2. The method of claim 1, wherein the spring-loaded accumulator holding pressure is 1 to 5 bar below the reservoir pressure.

3. The method of claim 1, wherein the spring-loaded accumulator holding pressure is 1.5 to 3 bar below the reservoir pressure.

4. The method of claim 1, wherein the spring-loaded accumulator holding pressure is above a spring-loaded accumulator release pressure by at least a safety margin.

5. The method of claim 4, wherein the safety margin is at least 1 to 2 bar.

6. The method of claim 1, wherein the spring-loaded accumulator holding pressure is determined by a valve assembly which acts in at least one of a pressure-limiting manner, a pressure-reducing manner, and a pressure-regulating manner.

7. The method of claim 1, wherein the spring-loaded accumulator holding pressure is set by computer program-controlled regulation of a valve assembly.

8. A parking brake system comprising: a spring-loaded brake; a control module for a motor vehicle or trailer; said control module being connected to a brake circuit, wherein the brake circuit is supplied with a reservoir pressure; said spring-loaded brake including spring-loaded brake cylinders configured to have a spring-loaded accumulator holding pressure applied thereto in order to assume a release position of said spring-loaded brake; and, a setting device for setting the spring-loaded accumulator holding pressure to a value which is less than the reservoir pressure in the brake circuit.

9. The parking brake system of claim 8, wherein said setting device is a valve assembly having an input pressure and an output pressure, wherein said valve assembly is configured to supply the spring-loaded accumulator holding pressure as an output pressure.

10. The parking brake system of claim 9 further comprising an electronic control device configured to regulate the output pressure of said valve assembly.

11. The parking brake system of claim 10 further comprising a pressure sensor for sensing the output pressure and for transmission to said electronic control device.

12. The parking brake system of claim 10, wherein said valve assembly has a pneumatic relay valve and an electropneumatic proportional valve; the output pressure is present at an output of said valve assembly; said relay valve is configured to receive control pressure from said electropneumatic proportional valve; and, said proportional valve is configured to be activated by said electronic control device in order to set the output pressure.

13. The parking brake system of claim 10, wherein said valve assembly and said electronic control device are constituent parts of said control module.

14. The parking brake system of claim 9, wherein said valve assembly includes a pressure limiting valve.

15. The parking brake system of claim 14, wherein said valve assembly has a non-return valve connected in parallel to said pressure limiting valve.

16. The parking brake system of claim 9, wherein said valve assembly is integrated into said control module.

17. The parking brake system of claim 9, wherein said valve assembly is integrated into a pneumatic control line between a parking valve assembly and said control module.

18. The parking brake system of claim 9, wherein said valve assembly is integrated into a parking valve assembly which is connected to said control module via a pneumatic control line.

19. The parking brake system of claim 9, wherein said valve assembly is integrated into a brake cylinder assembly.

20. The parking brake system of claim 9, wherein said valve assembly is integrated into pneumatic working lines between said control module and said spring-loaded brake cylinders.

21. The parking brake system of claim 8, wherein said control module is an axle modulator.

22. A computer program product which comprises commands which, carried out on an electronic control device of a control module in a parking brake system, carry out the method of claim 7.

23. An electropneumatic control module comprising an electronic control device and configured for use in the parking brake system of claim 8.

24. A vehicle comprising the parking brake system of claim 8.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0039] The invention will now be described with reference to the drawings wherein:

[0040] FIG. 1 shows a schematic illustration of an electropneumatic brake system in a towing vehicle;

[0041] FIG. 2 shows an electropneumatic control module of an electropneumatic parking brake system inside the electropneumatic brake system;

[0042] FIG. 3 shows a schematic illustration of a valve assembly with a pressure limiting valve and a non-return valve;

[0043] FIG. 4 shows a highly simplified illustration of a parking brake system in a trailer and with a modulator with an integrated valve assembly according to FIG. 3;

[0044] FIG. 5 shows an embodiment which is similar to FIG. 4 but with a valve assembly integrated into a control line between a parking valve and the modulator;

[0045] FIG. 6 shows an embodiment which is similar to FIG. 4 but with a valve assembly integrated into a parking valve;

[0046] FIG. 7 shows an embodiment which is similar to FIG. 4 but with valve assemblies integrated into combination brake cylinders;

[0047] FIG. 8 shows an embodiment which is similar to FIG. 4 but with valve assemblies integrated into working lines between the modulator and spring-loaded brake cylinders; and,

[0048] FIG. 9 shows a qualitative illustration of time-dependent pressure gradients when air is exhausted from spring-loaded brake cylinders.

DETAILED DESCRIPTION

[0049] Illustrated in simplified form in FIG. 1 is an electropneumatic brake system 10 for a towing vehicle ZG with a front axle 11 and a rear axle 12. The basic structure of the brake system 10 is known and is disclosed in a similar form in US 2020/0079341.

[0050] Only the constituent parts which are relevant for understanding the disclosure are taken into account below. The brake system 10 here has three pneumatic brake circuits BK1, BK2, and BK3, each with a reservoir I, II, III. Compressors as compressed-air sources are not shown, and neither is a multi-circuit protection valve which may be present.

[0051] An axle modulator MV for the front axle 11 is provided in the brake circuit BK2. Front-axle service brake cylinders BZV of the front axle 11 are connected to the axle modulator MV.

[0052] An axle modulator, not illustrated in detail, for the rear axle 12 is combined with a central controller, likewise not shown in detail, to form a central unit ECM. The latter also controls the axle modulator MV for the front axle 11.

[0053] Connected to the central unit ECM are combination brake cylinders KBZ into which rear-axle service brake cylinders BZH and spring-loaded brake cylinders FSZ of the rear axle 12 are integrated. In order to pneumatically charge the rear-axle service brake cylinders BZH, the central unit ECM is connected to the brake circuit BK1 or is part thereof.

[0054] In order to supply air to the front-axle service brake cylinders BZV and rear-axle service brake cylinders BZH, the driver can actuate a brake encoder P (brake pedal). A corresponding signal of the brake encoder P passes to the central unit ECM. The latter activates the integrated axle modulator for the rear axle 12 and the front axle modulator MV.

[0055] The spring-loaded brake cylinders FSZ are a constituent part of a spring-loaded brake FSB inside a parking brake system FSY which is a subsystem of the electropneumatic brake system 10 and is provided with an electropneumatic control module EH. The control module EH is connected to the brake circuit BK3 and, when the spring-loaded brake FSB is released, emits an output pressure to supply air to the spring-loaded brake cylinders FBZ. In order to exhaust air from the spring-loaded brake cylinders FBZ and hence to actuate the spring-loaded brake FSB, an electric switch H, connected to the control module EH, is provided which, like the brake encoder P, can be operated by the driver.

[0056] Also connected to the electropneumatic control module EH is a trailer control module TC which is fed from the brake circuit BK3 but has no significance in this figure.

[0057] According to FIG. 2, in particular an electronic control device ECU and a valve assembly 13 are provided in the electropneumatic control module EH, wherein the valve assembly 13 is controlled by the control device ECU.

[0058] The electropneumatic brake system 10 is connected to a CAN bus of the vehicle ZG (see CAN in FIG. 1) or to another bus system which is typical for vehicles. The central unit ECM, the electropneumatic control module EH, and further electronic control units (not shown) of the vehicle can communicate with one another via the CAN bus and, for example, also transmit commands to actuate the spring-loaded brakes FSB to the electropneumatic control module EH. The electronic control device ECU in the control module EH can moreover have software which, under defined boundary conditions and/or with the input of defined signals, actuates or releases the spring-loaded brake FSB and exhausts air from or supplies it to the spring-loaded brake cylinders FBZ.

[0059] A possible structure of the electropneumatic control module EH is illustrated in FIG. 2. The main constituent parts of the valve assembly 13 are a relay valve 14 and an electropneumatic proportional valve 15. Arranged upstream from the proportional valve 15 is a bistable switching valve 16 via which the spring-loaded brake FSB is activated or deactivated. To do this, the switching valve 16 connects the proportional valve 15 to an input 17 of the control module EH or blocks this connection. In the position according to FIG. 2, the connection is blocked and the spring-loaded brake FSB is exhausted of air, that is, activated.

[0060] A reservoir pressure pV from the brake circuit BK3 is present at the input 17 of the control module EH. Output pressure pA for the spring-loaded brake cylinders FBZ is supplied at the outputs 18 of the control module EH. The relay valve 14 is connected to the input 17 and, via its valve output 19, to the outputs 20 and receives control pressure from the proportional valve 15.

[0061] The proportional valve 15 is here a 2/2-way valve which is switched through when no current is applied and closed when current is applied. A specific control pressure for the relay valve 14, and hence also a specific output pressure pA at the outputs 18 for supplying air to the spring-loaded brake cylinders FBZ can be set by modulating the proportional valve 15. The relay valve 14 thus forms, together with the proportional valve 15, a pressure regulating valve for the output pressure pA.

[0062] Connected to the outputs 18 and to the relay valve 14 is a pressure sensor 20, the signals of which are received and processed by the electronic control device ECU. A valve output VTA of a switching valve VT which is monostable in this case is connected to the trailer control module TC. Reservoir pressure pV is applied to a first valve input VTE1, while a second valve input VTE2 is connected to the valve output 19. It is consequently possible to maintain the valve output VTA and the trailer control module TC at reservoir pressure pV, while pressure regulation takes place for the outputs 18 via the relay valve 14. This advantageously prevents the pressure regulation affecting the pressure at an output (not shown) of the trailer control module TC.

[0063] The electronic control device ECU controls the output pressure pA present at the outputs 18 by actuating the valves 15, 16 by taking into account the signals of the pressure sensor 20. In order to release the spring-loaded brake FSB or supply air to the spring-loaded brake cylinders FBZ, the switching valve 16 is switched into a passage position (not shown) and modulates the proportional valve 15. The objective is a spring-loaded accumulator holding pressure pH as an output pressure pA at the outputs 18 which is less than the reservoir pressure pV at the input 17 and greater than a spring-loaded accumulator release pressure pL. The spring-loaded accumulator holding pressure pH is preferably 1 to 2 bar more than the spring-loaded release pressure pL and/or 1 to 3 bar less than the reservoir pressure pV.

[0064] Exhausting the air from the spring-loaded brake cylinders FBZ in order to actuate the spring-loaded brake FSB takes place in this case via an exhaust vent 21 at the relay valve 14 or an exhaust vent connected thereto. Starting from the relatively low spring-loaded accumulator holding pressure pH, the spring-loaded brake FSB can be exhausted of air much more quickly than in the case of an output pressure pA which corresponds to the reservoir pressure pV in the brake circuit BK3.

[0065] FIG. 3 shows a further valve assembly 22 for reducing the output pressure pA, in this case as a purely pneumatic/mechanical solution. The main constituent part of the valve assembly 22 is a pressure limiting valve 23 with an input 24 and an output 25. A non-return valve 26 is connected in parallel to the pressure limiting valve 23, that is, is also connected to the input 24 and the output 25.

[0066] The pressure limiting valve 23 is set and/or selected such that the desired output pressure pA and not the higher reservoir pressure pV is present at the output 25. The non-return valve 26 equalizes the pressure at the output 25 if the pressure at the input 24 falls.

[0067] The valve assembly 22 can preferably be used in a parking brake system FSY with a purely pneumatically controlled spring-loaded brake FSB. Use in an electropneumatic parking brake system FSY is, however, also possible.

[0068] Particular advantages for use in a trailer consist in the faster activation of the spring-loaded brake FSB, also as an emergency brake, and a reduction in the risk of the trailer unintentionally rolling away when uncoupled because the transfer of the braking effect of the service brake to the spring-loaded brake FSB takes place more quickly.

[0069] The embodiment in FIG. 4 relates to a trailer brake system ASY in a trailer AG, for example a semitrailer. Constituent parts of the trailer brake system ASY are a reservoir connection 27, a parking valve 28, also referred to as a parking release valve, a reservoir IV, a modulator AM, combination brake cylinders KBZ at two axles 29, 30, while a further axle 31 has only trailer service brake cylinders BZA. The combination brake cylinders KBZ are, in the same way as in the embodiment in FIG. 1, divided into trailer service brake cylinders BZA and trailer spring-loaded brake cylinders FBA.

[0070] A constituent part of the trailer brake system ASY is also in this case an electropneumatic parking brake system FSY which includes the trailer spring-loaded brake cylinders FBA. For the sake of simplification, only those lines which are important in connection with the spring-loaded brake system FSY are indicated in FIG. 4. The feeding and distribution of control pressure, similar to the reservoir connection 27, is also not illustrated. The parking brake system FSY can also be purely pneumatic.

[0071] The modulator AM regulates all the functions of the trailer brake system ASY, including the parking brake system FSY for the trailer AG and contains all the valve assemblies and control devices required for it. In the embodiment in FIG. 4, the valve assembly 22 is integrated into the modulator AM, that is, is a constituent part of the modulator AM. The reservoir pressure pV fed via the parking valve 28 is present at the input 24. The output 25 is connected to lines 32, 33 leading to the trailer spring-loaded brake cylinders FBA. A reservoir line 35 to the parking valve 28 leads from the reservoir connection 27. A further reservoir line 36 runs from the parking valve 28 to the reservoir IV and from there to the modulator AM. Alternatively, the modulator AM can be switched between the reservoir IV and the parking valve 28.

[0072] In the embodiment in FIG. 5, the valve assembly 22 is switched into a control line 34 from the parking valve 28 to the modulator AM. The input 24 faces the parking valve 28, while the output 25 faces the module AM. The valve assembly 22 can be retrofitted simply in this way.

[0073] In the embodiment in FIG. 6, the valve assembly 22 is integrated into the parking valve 28, or is a part thereof. The interconnection of the input 24 and the output 25 is not illustrated. The output 25 is preferably connected to the control line 34. The input 24 is connected, inside the module AM, to a line (not shown) carrying reservoir pressure pV, to a line (not shown) connected to the reservoir IV, or to an exhaust opening (not shown). Which connection actually exists depends on the position of a manual actuating member VBO at the parking valve 28 and requires only a small additional degree of complexity inside the parking valve 28.

[0074] In the embodiment in FIG. 7, a valve assembly 22 is integrated into each combination brake cylinder KBZ. The inputs 24 can be connected to the lines 32, 33, while the outputs 25 are connected to the trailer spring-loaded brake cylinders FBA. The latter are not indicated in FIG. 7 for the sake of simplification but can be seen, for example, in FIG. 4. According to FIG. 7, the valve assemblies 22 are integrated into all the combination brake cylinders KBZ which are present. It is also possible to select them for or limit them to individual axles 29, 30 or wheels.

[0075] In the embodiment in FIG. 8, valve assemblies 22 are arranged in each of the lines 32, 33 between the modulator AM and the combination brake cylinders KBZ. The inputs 24 are here connected to the modulator AM and the outputs 25 to the trailer spring-loaded brake cylinders FBA inside the combination brake cylinders KBZ. This solution is also particularly well suited to retrofitting.

[0076] An essential advantage of the disclosure can be seen in FIG. 9. The gradient over time t of the output pressure pA can be seen. In the prior art, reservoir pressure pV is applied to the spring-loaded brake cylinders FBZ and trailer spring-loaded brake cylinders FBA which are supplied with air. According to the disclosure, the valve assemblies 13, 22 have an output pressure pA equal to the spring-loaded accumulator holding pressure pH. The spring-loaded accumulator holding pressure pH is less than the reservoir pressure pV and has a safety margin DS above the spring-loaded accumulator release pressure pL. Two different cases with their pressure gradient lines P1, P2 are illustrated.

[0077] Starting from the reservoir pressure pV in the first case and starting from the spring-loaded accumulator holding pressure pH in the second case, the possible gradient over time according to the dotted pressure gradient lines P1 and P2 results when the spring-loaded brake cylinders FBZ and trailer spring-loaded brake cylinders FBA are exhausted of air. Of interest are the points of intersection S1, S2 of the pressure gradient lines P1 and P2 with the spring-loaded accumulator release pressure pL. While the pressure gradient line P1 reaches the spring-loaded accumulator release pressure pL at the point of intersection S1 only at the point in time t3, the point of intersection S2 is above the much earlier point in time t2. A spring-loaded accumulator release time t2t1 resulting in connection with the disclosure is correspondingly much less than the previously possible spring-loaded accumulator release time t3t1.

[0078] The safety margin DS mentioned is to be selected such that dispersion of the spring-loaded accumulator release pressure pL and subsequent fluctuations due to wear and corrosion are taken into account such that the spring-loaded accumulator holding pressure pH never reaches the spring-loaded accumulator release pressure pL or falls below it.

[0079] The illustration in FIG. 9 is an idealized and purely qualitative one which serves only to explain the shortened period of time until the spring-loaded accumulator release pressure pL is reached.

[0080] All the embodiments illustrated here relate to use both in a tractor/motor vehicle and in a trailer, in particular a semitrailer, or can be transferred thereto.

[0081] It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.

LIST OF REFERENCE SIGNS (PART OF THE DESCRIPTION)

[0082] 10 electropneumatic brake system [0083] 11 front axle [0084] 12 rear axle [0085] 13 valve assembly [0086] 14 relay valve [0087] 15 proportional valve [0088] 16 switching valve [0089] 17 input [0090] 18 outputs [0091] 19 valve output [0092] 20 pressure sensor [0093] 21 exhaust vent [0094] 22 valve assembly [0095] 23 pressure limiting valve [0096] 24 input [0097] 25 output [0098] 26 non-return valve [0099] 27 reservoir connection [0100] 28 parking valve [0101] 29 axle [0102] 30 axle [0103] 31 axle [0104] 32 lines [0105] 33 lines [0106] 34 control line [0107] 35 reservoir line [0108] 36 reservoir line [0109] I reservoir [0110] II reservoir [0111] III reservoir [0112] IV reservoir [0113] AG trailer [0114] AM trailer modulator [0115] ASY trailer brake system [0116] BK1 brake circuit [0117] BK2 brake circuit [0118] BK3 brake circuit [0119] BK4 brake circuit [0120] BZA trailer service brake cylinder [0121] BZH rear axle service brake cylinder [0122] BZV front axle service brake cylinder [0123] CAN bus system [0124] DS safety margin [0125] ECM central unit [0126] ECU electronic control device [0127] EH electropneumatic control module [0128] FBA trailer spring-loaded brake cylinder [0129] FBZ spring-loaded brake cylinder [0130] FSB spring-loaded brake [0131] FSY parking brake system [0132] H electric switch [0133] KBZ combination brake cylinder [0134] MV front axle modulator [0135] P brake encoder [0136] P1 pressure gradient [0137] P2 pressure gradient [0138] pA output pressure [0139] pH spring-loaded accumulator holding pressure [0140] pL spring-loaded accumulator release pressure [0141] pV reservoir pressure [0142] S1 point of intersection [0143] S2 point of intersection [0144] t1 point in time [0145] t2 point in time [0146] t3 point in time [0147] TC trailer control module [0148] VBO actuating member at the parking valve [0149] VT valve [0150] VTA valve output [0151] VTE1 valve input [0152] VTE2 valve input [0153] ZG towing vehicle