Electropneumatic parking brake with directly controlled valves

An electropneumatic parking brake module (1) includes a supply connection (2), a spring-type actuator connection (4), an inlet-outlet valve unit (10) having a first switching position and a second switching position, and an electropneumatic pilot control unit (12) for outputting at least a first control pressure (p1) at the inlet-outlet valve unit (10). In the first switching position of the inlet-outlet valve unit (10), a spring brake pressure (pF) can be fed through directly from the supply connection (2) to the spring-type actuator connection (4) by virtue of the fact that the spring-type actuator connection (4) is connected to the supply connection (2), and, in the second switching position of the inlet-outlet valve unit (10), when the first control pressure (p1) is below a first threshold value, the spring-type actuator connection (4) is connected to a ventilating connection (14.3) of the inlet-outlet valve unit (10).

TECHNICAL FIELD

The present disclosure relates to an electropneumatic parking brake module.

BACKGROUND

Such electropneumatic parking brake modules, also referred to as electropneumatic handbrake modules, serve to actuate what are known as parking brakes, in general spring brakes of a pneumatic brake system for a utility vehicle.

Spring brakes can be used as parking brakes and have a fault-prone brake actuator which activates the brake in a pressure-free manner so that the vehicle is correspondingly braked in the case of the pressure-free state. In order to release the spring brakes, these are acted upon with compressed air so that the spring brakes are released counter to the force of the spring.

Such electropneumatic parking brake modules therefore generally have a supply connection for connecting a compressed air supply, and at least one spring-type actuator connection for connecting at least one spring brake cylinder. It is conceivable in this case that all of the spring brake cylinders of the utility vehicle, in particular of the power car of a traction vehicle-trailer combination, are connected to a single spring-type actuator connection of the electropneumatic parking brake module. It is also possible that separate connections are provided for this purpose.

Such electropneumatic parking brake modules generally use a relay valve in order to supply the spring-type actuator connection and thus the spring brake cylinders with a volumetric flow.

Such an electropneumatic parking brake module is disclosed, for example, in DE 10 336 611 A1. The relay valve is coupled to a pilot control unit which connects a control input of the relay valve to the supply connection via an electrically switched 2/2-way valve and a bistable 3/2-way valve. The electrically controlled 2/2-way valve serves the purpose of pulsed ventilation of the control input in order to use the spring-type actuators also for auxiliary braking or additional brake application. The bistable 3/2-way valve serves to maintain an aerated or ventilated state of the control input of the relay valve in order to maintain the state of the spring brake cylinders. In driving operation, a pressure should be permanently output at the spring-type actuator connection so that the spring brake cylinders are released. In the switched off state of the vehicle, however, the spring brake cylinders should be actuated, i.e. ventilated.

There is a need to provide electropneumatic parking brake modules which do not have a relay valve. Relay valves are generally complex to manufacture and in terms of space requirements and it is therefore desirable to be able dispense with them.

An electropneumatic parking brake module without a relay valve is disclosed in EP 2 129 562 B1. The device disclosed there solely uses a tristable solenoid valve which enables a direct connection of the supply connection to the connection for the spring brake cylinders. Such tristable solenoid valves are nevertheless extremely complex and very large, hence there is also the need here to provide a simpler solution.

An electropneumatic parking brake module is furthermore known from EP 2 939 892 A1, which module uses an electrically actuable valve apparatus which has, proceeding from the supply connection, a branch between a pneumatic line for the parking brake cylinders and a pneumatic line for the connection of a trailer control valve (TCV). A control valve is connected to the pneumatic line for the spring brake cylinders, which control valve is formed as a 3/2-way valve and has both a pneumatic and an electric control input. EP 2 939 892 A1 thus dispenses with a pilot control unit. Nevertheless, dual-acting valves which have both a pneumatic and an electric control input are also complex and a simpler solution is furthermore desired.

DE 10 2014 006 614 A1 is known from the field of service brakes. A pneumatic brake apparatus for motor vehicles is disclosed there which has a brake signal transmitter, a supply pressure accumulator and a pneumatically operable wheel brake for each wheel as well as at least one axle of the motor vehicle with in each case one electrically actuable wheel brake module for each wheel for adjusting a setpoint brake pressure of the respective wheel brake. An electronic control unit determines specified values of the setpoint brake pressures of the wheel brakes taking into account the brake signal transmitter. Each wheel brake module comprises at least one aeration valve and a ventilation valve, electrically actuable activation means for activating the aeration valve and/or the ventilation valve as well as a control logic with means for generating an actuating signal for the activation means in accordance with the specified value for the setpoint brake pressure. In order to reduce the production costs and the size of the pneumatic brake apparatus, DE 10 2014 006 614 proposes that the aeration valve and its activation means are formed in such a manner that the pneumatic pressure can be fed through from the supply pressure accumulator in the activated state of the aeration valve directly to the respective wheel brake and/or the ventilation valve vents the brake pressure of the wheel brake in the activated state directly into the atmosphere.

SUMMARY

It is still desirable to provide an electropneumatic parking brake module of the above-mentioned type which has a simple structure, dispenses with a relay valve and allows reliable maintenance of the state at the spring-type actuator connection.

In furtherance of this goal, the electropneumatic parking brake module of the present disclosure has a supply connection for connecting a compressed air supply, at least one spring-type actuator connection for connecting at least one spring brake cylinder, an inlet-outlet valve unit which can assume at least a first switching position and a second switching position, and an electropneumatic pilot control unit for outputting at least a first control pressure at the inlet-outlet valve unit. It is provided that, in the first switching position of the inlet-outlet valve unit, the spring-type actuator connection is connected to the supply connection for outputting a spring brake pressure, and, in the second switching position of the inlet-outlet valve unit, the spring-type actuator connection is connected to a ventilating connection of the inlet-outlet valve unit, wherein the inlet-outlet valve unit has at least a first 3/2-way valve with precisely two switching positions, and wherein the inlet-outlet valve unit is in the second switching position if the first control pressure is below a first threshold value.

In this manner, an electropneumatic parking brake module is achieved which does not require a relay valve and manages with conventional, simple valves. The inlet-outlet valve unit is preferably controlled purely pneumatically, while the pilot control unit is controlled electromagnetically. The pilot control unit as such can be formed in general as described in DE 10 2014 006 614 A1. The pilot control unit therefore serves to output the first control pressure, wherein, depending on the first control pressure, the inlet-outlet valve unit supplies the spring-type actuator connection with a volume or ventilates it. The two defined switching positions of the 3/2-way valve are used here. The 3/2-way valve preferably serves both to aerate and ventilate the spring-type actuator connection.

According to the present disclosure, it is furthermore provided that the inlet-outlet valve unit is in the second switching position if the first control pressure is below a first threshold value. The threshold value is predetermined and structurally defined by the inlet-outlet valve unit. A typical threshold value lies in the region of 0.25 MPa, but can be freely defined and selected in accordance with the respective requirements of the brake system in which the electropneumatic parking brake module is supposed to be used. In this manner, it is ensured that if no first control pressure can be output, this therefore lies below the first threshold value, the spring-type actuator connected is ventilated and the spring brake cylinders can thus be actuated. This is advantageous particularly if the pilot control unit is formed so that it does not output any first control pressure in the currentless state.

In the first switching position of the inlet-outlet valve unit, the spring brake pressure can preferably be fed through directly from the supply connection to the spring-type actuator connection. In the present case, direct feeding through refers to the production of a volume connection between the supply connection and the spring-type actuator connection, without the interconnection of a relay valve. Therefore, not only is a control pressure output by the inlet-outlet valve unit, rather a volumetric flow for ventilating the spring-type actuator connection is directly provided.

In one preferred embodiment, it is provided that the inlet-outlet valve unit has at least one 2/2-way check valve. The 2/2-way check valve preferably serves the purpose of graduated aeration or ventilation of the spring-type actuator connection. Via a graduated ventilating of the spring-type actuator connection, graduated brake application can be brought about by the spring brake cylinders and the spring brake cylinders can thus be used for additional braking or auxiliary braking of the vehicle. For this reason, the 2/2-way check valve is only optional.

The first 3/2-way valve is preferably controlled pneumatically. The pilot control unit is preferably formed to provide the first control pressure at the first 3/2-way valve. The 2/2-way check valve is preferably also controlled pneumatically. In one alternative, the 2/2-way check valve is formed electromagnetically. In the event that the 2/2-way check valve is formed to be pneumatically controlled, it is preferably provided that the pilot control unit provides a second control pressure at the 2/2-way check valve.

In one preferred further development, the first 3/2-way valve has an inlet connection, a working connection and a ventilating connection and the first 3/2-way valve is formed to reciprocally connect the working connection to the inlet connection and the ventilating connection. A supply pressure can preferably be output at the input connection. The input connection is preferably connected to the supply connection.

In one preferred further development, a non-return valve is arranged between the supply connection and the input connection in order to prevent a return flow from the spring-type actuator connection to the supply connection. As a result of this, it is possible to maintain a control pressure, in particular the first control pressure, even if the pressure at the supply connection drops, for example, as a result of a fault in the compressed air supply which leads to a drop in the pressure in the compressed air supply.

If, however, no non-return valve is used, it is possible to achieve an actuation of the spring brake cylinders despite the presence of the first control pressure in that the corresponding brake circuit is pumped down, i.e. the pressure in the compressed air supply is reduced and thus the present supply pressure is reduced. In this case, even if the spring-type actuator connection is connected directly to the supply connection, the spring-type actuator connection is vented through opened valves via a pumping down of the supply connection and thus the spring brake cylinders are actuated.

It is furthermore preferred that the 2/2-way check valve has a first check valve connection and a second check valve connection, wherein the first check valve connection is connected to the working connection of the first 3/2-way valve, and the second check valve connection is connected to the spring-type actuator connection. The 2/2-way check valve is therefore connected between the first 3/2-way valve and the spring-type actuator connection. For graduated aeration and ventilation, the first 3/2-way valve can then be moved into a position which connects the spring-type actuator connection to an aeration or ventilation and this connection is produced by pulsed actuation of the 2/2-way check valve. The 2/2-way check valve is preferably formed as a pneumatically controlled 2/2-way check valve, wherein it is in the open switching position if the second control pressure undershoots a second threshold value.

In one preferred further development, the electropneumatic pilot control unit has at least one second 3/2-way valve, wherein the second 3/2-way valve is provided to output the first control pressure. To this end, the second 3/2-way valve can preferably be switched between a first and a second switching position, wherein no control pressure is output in the first switching position, i.e. the corresponding input of the inlet-outlet valve unit for the first control pressure is connected to a vent, and, in a second switching position, the first control pressure is output, i.e. the corresponding input of the inlet-outlet valve unit is connected to the supply connection.

In one preferred embodiment, the second 3/2-way valve is formed as a bistable valve. In the case of the bistable valve, both the first and the second switching positions are in each case stable in a currentless state and are preferably retained by a permanent magnet. In the event of the omission of a voltage or current, such a bistable valve does not fall back into a switching position under spring load, but rather sticks in the last switching position occupied as a result of the permanent magnets. An occupied switching position can therefore be maintained by such a bistable valve, also in a currentless state, and the output first control pressure can thus be maintained in a currentless state.

The bistable valve preferably has a first bistable valve connection, a second bistable valve connection and a third bistable valve connection, wherein the first bistable valve connection is connected to the supply connection, the second bistable valve connection outputs the first control pressure and the third bistable valve connection is connected to a vent. The second bistable valve connection is preferably connected to a first control input of the first 3/2-way valve.

In further embodiments of the present disclosure, it is also possible to combine the bistable valve by a combination of monostable switching valves as well as a pneumatic self-retention in order to ensure maintenance of the output first control pressure.

Insofar as it is provided in a further embodiment that the electropneumatic pilot control unit has a monostable inlet-outlet valve combination with an inlet valve and an outlet valve for outputting the first control pressure. The first control pressure can initially be output via the monostable inlet-outlet valve combination by providing corresponding switching signals. In order to maintain this in a currentless state, a return line is preferably provided which provides the pressure output by the first 3/2-way valve as a first control pressure at the inlet-outlet valve unit. As soon as the first control pressure is output via the monostable inlet-outlet valve combination, the first 3/2-way valve switches upon exceeding of a corresponding threshold value and outputs a pressure. By returning the output pressure as a first control pressure, the switching position achieved in this manner of the 3/2-way valve can be maintained and self-retention can be achieved. A bistable valve is no longer necessary in this variant, as a result of which the costs and the installation space for the electropneumatic parking brake module can be reduced.

The pressure output by the 3/2-way valve is preferably provided as a first control pressure in a throttled manner at the inlet-outlet valve unit. The return line preferably has a throttle for this purpose.

In a first variant, the inlet valve has in this case a first inlet valve connection connected to the supply connection and a second inlet valve connection connected to the inlet-outlet valve unit, wherein the first control pressure can be output at the second inlet valve connection by switching the inlet valve. The second inlet valve connection is preferably connected via a first pneumatic control line to the first 3/2-way valve, more precisely to the first control input of the first 3/2-way valve. The inlet valve can in this case be formed either as a 2/2-way valve or as a 3/2-way valve. It is preferably formed as a 2/2-way valve and is currentless in the first, closed switching position.

It is furthermore preferred that the outlet valve has a first outlet valve connection connected to the inlet-outlet valve unit and a second outlet valve connection connected to a vent for ventilating the first control pressure. In order to move the first 3/2-way valve back into the ventilating position so that no spring brake pressure is output, it is necessary to ventilate the first control input of the first 3/2-way valve. The outlet valve which can be formed according to this embodiment as a 2/2-way valve or as a 3/2-way valve serves this purpose. The outlet valve is preferably currentless in a closed switching position if it is formed as a 2/2-way valve. The first outlet valve connection can be connected to the same first pneumatic control line as the inlet valve. A branch or a branch line can be provided for this purpose.

In one preferred further development, the return line is connected directly to the inlet-outlet valve unit. This is advantageous in particular if both the inlet valve and the outlet valve are formed as 2/2-way valves. In this variant, the return line consequently branches off directly from the second pneumatic line, which is connected to the working connection of the first 3/2-way valve and leads directly to the first control input of the first 3/2-way valve. To this end, it can discharge into the first pneumatic control line. In this variant, the pressure output by the first 3/2-way valve is provided directly and without the interconnection of a valve at the first control input of the first 3/2-way valve irrespective of the switching position of the inlet valve or of the outlet valve. A blocking-out of the returned pressure is not possible here. In order to be able to block out the returned pressure, either a further valve is required, or the inlet or outlet valve is to be formed as a 3/2-way valve.

It is accordingly provided in a further variant that the inlet valve has a third inlet valve connection connected to the return line, wherein, in a first switching position of the inlet valve, the second inlet valve connection is connected to the first inlet valve connection, and, in a second switching position of the inlet valve, the second inlet valve connection is connected to the third inlet valve connection. In this embodiment, the inlet valve is formed as a 3/2-way switching valve. The inlet valve formed as a 3/2-way valve is preferably currentless in the second switching position so that in a currentless state the returned pressure is provided as a first control pressure at the first control input of the first 3/2-way valve. Self-retention of the first 3/2-way valve is thus achieved in a currentless state.

Alternatively to this, it is also possible to form the outlet valve as a 3/2-way valve. In this variant, the outlet valve has a third outlet valve connection connected to the return line, wherein, in a first switching position of the outlet valve, the first outlet valve connection is connected to the third outlet valve connection and, in a second switching position of the outlet valve, the first outlet valve connection is connected to the second outlet valve connection. The outlet valve is preferably currentless in the first switching position so that the pressure output by the first 3/2-way valve is returned via the return line in a currentless state and is output as a first control pressure at the first control input of the first 3/2-way valve. In this manner, self-retention is achieved in a currentless state.

In the further preferred embodiment, the electropneumatic pilot control unit has at least one third 3/2-way valve for outputting a second control pressure. For this purpose, the third 3/2-way valve has an inlet connection, a working connection and a ventilating connection, and the third 3/2-way valve is formed to reciprocally connect the working connection to the inlet connection and the ventilating connection. The third 3/2-way valve is preferably formed as an electronically switched valve. In a first switching position, the input connection is preferably connected to the working connection and, in a second switching position, the ventilating connection is connected to the working connection. The third 3/2-way valve is preferably currentless in the second switching position.

It is furthermore preferred that the inlet connection of the third 3/2-way valve is connected to the supply connection, the working connection of the third 3/2-way valve is connected to a second control input of the 2/2-way check valve and the ventilating connection of the third 3/2-way valve is connected to a vent. In this case, in the currentless state, no second control pressure is output and the 2/2-way check valve is preferably in the open switching position if the second control pressure undershoots the second threshold value. A pressure in the region of approximately 0.25 MPa is in turn possible as a second threshold value, wherein other threshold values can also be used here.

In order therefore to transfer a control pressure to a trailer control valve (TCV), which control pressure corresponds to the spring brake pressure at the spring-type actuator connection, the electropneumatic parking brake module according to this embodiment has the trailer control valve connection.

The electropneumatic parking brake module preferably has a trailer valve which is connected to the trailer control valve connection and which is provided, in a first switching position, to output at least the spring brake pressure as the trailer control pressure at the trailer control connection. Alternatively, it is also possible to output another equivalent pressure at the trailer control valve connection.

The spring brake pressure is preferably provided directly at the trailer control valve connection, i.e. without inversion. The trailer control valve (TCV) connected to the trailer control valve connection must then invert the output pressure in order to provide a corresponding operating brake pressure at the service brakes of the trailer.

The trailer valve preferably has a second switching position which is provided to perform a trailer control position function. In the trailer control position, there is a check in the European trailer control as to whether the trailer-towing vehicle combination is held securely even without engaged service brakes of the trailer only as a result of the spring brake cylinders of the towing vehicle. In order to achieve this state, it is consequently necessary to output a pressure at the trailer control valve connection if the spring-type actuator connection is ventilated. The trailer control valve connected to the trailer control valve connection inverts the output pressure and thus leaves the service brakes of the trailer in a depressurized state, i.e. in an open state. The trailer control position function is only performed temporarily and is generally activated from the vehicle cabin. The vehicle driver actuates the trailer control position function in order to check the secure holding of the towing vehicle trailer combination. If it is ascertained that the towing vehicle trailer combination is securely held, the trailer control position function is terminated and the trailer valve is correspondingly moved into the first switching position so that in turn the spring brake pressure is output as the trailer control pressure at the trailer control valve connection.

In a further preferred embodiment, the trailer valve is formed as a fourth 3/2-way valve and has a first trailer valve connection, a second trailer valve connection and a third trailer valve connection, wherein the first trailer valve connection is connected to the supply connection, the second trailer valve connection is connected to the trailer control valve connection and the third trailer valve connection is connected to a branch line which branches off from a spring brake pressure line connected to the spring-type actuator connection.

It is furthermore preferred that the trailer valve is in a currentless position in the first switching position or the second switching position. In the case that the trailer valve is currentless in the first switching position, the electropneumatic parking brake module is formed for European trailer control. In the case that the trailer valve is currentless in the second switching position, the electropneumatic parking brake module is formed for Scandinavian trailer control. In the second variant, the supply pressure is output in a currentless state at the trailer control valve connection so that, in a currentless state, the operating brakes of the trailer are not applied.

It is furthermore preferred that the electropneumatic parking brake module has an electric control unit with an electric connection for receiving parking brake signals and for providing corresponding switching signals at least to the pilot control unit. The electric connection for receiving parking brake signals can be connected, for example, to a vehicle bus or directly via cabling to a parking brake switch or handbrake switch in a driver's cabin of the vehicle.

It is further preferred that the electropneumatic parking brake module has a pressure sensor which is provided to detect the spring brake pressure and provide a corresponding signal. The pressure sensor preferably provides the signal at the electric control unit. The electric control unit can transfer the signal to a vehicle bus or the like, or independently process it. It is possible to determine via the signal detected by the pressure sensor whether the spring brake cylinders are actuated or open.

Embodiments of the present disclosure will now be described below on the basis of the drawing. It is not supposed to necessarily represent the embodiments to scale, rather the drawing is, for the purpose of explanation, designed in a schematic and/or slightly distorted form. Reference is made to the current prior art in terms of additions to the teachings which are clearly apparent from the drawing. It should be taken into account that numerous modifications and changes can be made relating to the form and the detail of one embodiment without deviating from the general idea of the present disclosure. Further advantages, features and details of the present disclosure will become apparent from the following description of the preferred embodiments and on the basis of the drawings.

DETAILED DESCRIPTION OF THE DRAWINGS

For the sake of simplicity, the same reference numbers are used below for identical or similar parts or parts with an identical or similar function. An electropneumatic parking brake module1(FIG. 1) has, according to the present disclosure, a supply connection2to which a compressed air supply3is connected. Compressed air supply3is part of a brake system of a utility vehicle which is not represented further here. In particular, compressed air supply3is part of a parking brake circuit.

Electropneumatic parking brake module1furthermore has a spring-type actuator connection4to which a spring brake cylinder6is connected according to this exemplary embodiment. It should be understood that it is also possible to connect two or more, in particular four or more spring brake cylinders to spring-type actuator connection4.

A supply pressure pV is provided at electropneumatic parking brake module1via supply connection2and a spring brake pressure pF is provided to spring-type actuator connection4via spring-type actuator connection4. Spring-type actuators6are formed so that they are actuated as a result of a spring force so that a positive spring brake pressure pF is required to release spring brake cylinders6. In the case of omission of spring brake pressure pF or undershooting of a threshold value, the spring brake cylinders are partially or fully actuated.

In order, proceeding from supply connection2, to output spring brake pressure pF at spring-type actuator connection4, electropneumatic parking brake module1has an inlet-outlet valve unit10and an electropneumatic pilot control unit12. Inlet-outlet valve unit10can be switched so that spring brake pressure pF can be directly fed through from supply connection2to spring-type actuator connection4. This is described in even greater detail below. For this purpose, in one switching position of inlet-outlet valve unit10, spring-type actuator connection4is connected directly to supply connection2. In a second switching position of inlet-outlet valve unit10, spring-type actuator connection4is however connected to a vent5in order to enable an actuation of spring brake cylinders6.

Inlet-outlet valve unit10is pneumatically controlled and can be switched on the basis of a first control pressure p1. Insofar as first control pressure p1lies below a first predetermined threshold value, for example, 0.25 MPa, the inlet-outlet valve unit switches into the second switching position in which spring-type actuator connection4can be vented and thus spring brake cylinders6are actuated.

In detail, inlet-outlet valve unit10initially has for this purpose a first 3/2-way valve14which is pneumatically controllable and has an input connection14.1, a working connection14.2, a ventilating connection14.3and a first control input14.4. Inlet connection14.1of first 3/2-way valve14is connected via a first pneumatic line50to supply connection2. Ventilating connection14.3of first 3/2-way valve14is connected to a vent5which can be a central vent5of electropneumatic parking brake module1. Working connection14.2of first 3/2-way valve14is connected to a pneumatic line52. First 3/2-way valve14has a first switching position, not occupied inFIG. 1, in which inlet connection14.1of first 3/2-way valve14is connected to working connection14.2of first 3/2-way valve14. First 3/2-way valve14furthermore has a second switching position which is occupied inFIG. 1and in which ventilating connection14.3of the first 3/2-way valve is connected to working connection14.2of first 3/2-way valve14. In this second switching position, working connection14.2of first 3/2-way valve14and thus also pneumatic line52can be ventilated. First 3/2-way valve14is pretensioned in a spring-loaded manner into the second switching position. By corresponding application of first control pressure p1at first control input14.4of first 3/2-way valve14, first 3/2-way valve14can be transferred into the first switching position, not shown, in order to output supply pressure pV in pneumatic line52.

In the exemplary embodiment shown inFIG. 1, second pneumatic line52is connected to a first check valve connection16.1of a 2/2-way check valve16. Second check valve connection16.2of 2/2-way check valve16is connected to a spring brake pressure line38which itself is connected to spring-type actuator connection4. That means that working connection14.2of first 3/2-way valve14is ultimately connected to spring-type actuator connection4if 2/2-way check valve16is in the opening switching position shown inFIG. 1. 2/2-way check valve16is part of inlet-outlet valve unit10and is also pneumatically controlled like first 3/2-way valve14. 2/2-way check valve16is pretensioned in a spring-loaded manner into the second open switching position shown inFIG. 1. 2/2-way check valve16has a second control connection16.3at which a second control pressure p2can be output.

It should be understood that there can also be embodiments according to the present disclosure which do not use a 2/2-way check valve16, rather in the case of which spring brake pressure line38is connected directly to working connection14.2of the first 3/2-way valve.

2/2-way check valve16primarily serves the purpose of graduated aeration and ventilation of spring-type actuator connection4. If first 3/2-way valve14is in the second switching position shown inFIG. 1, first check valve connection16.1is connected to vent5. If 2/2-way check valve16is now moved into the first switching position not shown inFIG. 1, spring-type actuator connection4is not ventilated despite the switching of first 3/2-way valve14into the second switching position shown inFIG. 1. It is only upon switching of 2/2-way check valve16into the second switching position shown inFIG. 1that spring-type actuator connection4would be vented. For example, for the purpose of auxiliary braking, 2/2-way check valve16can now be moved in a pulsed manner from the first switching position, not shown inFIG. 1, into the second switching position shown inFIG. 1in order to vent spring-type actuator connection4in a graduated manner and partially and temporarily actuate spring brake cylinders6.

Electropneumatic pilot control unit12serves to output at least first control pressure p1and provide it at inlet/outlet valve unit10in order to cause inlet/outlet valve unit10to switch and output a corresponding spring brake pressure pF at spring-type actuator connection4. To be more precise, by outputting first control pressure p1, pilot control unit12causes first 3/2-way valve14to change from the second switching position into the first switching position if output first control pressure p1assumes or exceeds the first defined threshold value. Insofar as electropneumatic parking brake module1has a 2/2-way check valve16, and insofar as this 2/2-way check valve16is formed to be pneumatically controlled, electropneumatic pilot control unit12is preferably also formed to output second control pressure p2and output it at inlet-outlet valve unit10, preferably at second control input16.3of 2/2-way check valve16.

For this purpose, electropneumatic pilot control unit12firstly has a second 3/2-way valve20which is connected to supply connection2and a vent5for outputting first control pressure p1. To be more precise, second 3/2-way valve20is formed in this embodiment as bistable valve21and has a first bistable valve connection21.1, a second bistable valve connection21.2and a third bistable valve connection21.3. Bistable valve21has a first switching position, not shown inFIG. 1, in which first bistable valve connection21.1is connected to second bistable valve connection21.2, and a second switching position, shown inFIG. 1, in which second bistable valve connection21.2is connected to third bistable valve connection21.3. First bistable valve connection21.1is connected to supply connection2. To be more precise, first bistable valve connection21.1is connected via a third pneumatic line54to supply connection2, wherein third pneumatic line54branches off from first pneumatic line50. In this respect, supply pressure pV is present at first bistable valve connection21.1. Third bistable valve connection21.3is connected to a vent5which can be the central vent of electropneumatic parking brake module1. Second bistable valve connection21.2is in contrast connected to a first pneumatic control line56into which first pneumatic control pressure p1is output. On the other hand, first pneumatic control line56is connected to first control input14.4of first 3/2-way valve14.

Bistable valve21is formed so that it is stable both in the first switching position, not shown inFIG. 1, and in the second switching position shown inFIG. 1. This is achieved by a permanent magnet which correspondingly holds the valve armature in the switching positions. This means that bistable valve21can remain currentless both in the first and in the second switching position.

In order to output second control pressure p2, electropneumatic pilot control unit12has according to this exemplary embodiment a third 3/2-way valve22. Third 3/2-way valve22is connected to supply connection2, a vent5and second control input16.3of 2/2-way check valve16.

In detail, third 3/2-way valve22has an inlet connection22.1, a working connection22.2as well as a ventilating connection22.3. Inlet connection22.1of third 3/2-way valve22is connected to a fourth pneumatic line58. Third pneumatic line58branches off from second pneumatic line54. This means that supply pressure pV is also present at inlet connection22.1of third 3/2-way valve22.

Working connection22.2of third 3/2-way valve22is connected to a second pneumatic control line60which itself leads to second control input16.3of 2/2-way check valve16. Second control pressure p2is consequently output at working connection22.2of third 3/2-way valve22. Ventilating connection22.3of third 3/2-way valve22is connected to a vent5, in particular the central joint vent of electropneumatic parking brake module1.

Electropneumatic parking brake module1has an electric control unit ECU. Electric control unit ECU is provided to provide an actuating signal S1at the second 3/2-way valve, in particular bistable valve21, in order to switch it between the first and second switching positions. Electric control unit ECU is furthermore formed to provide a second actuating signal S2at third 3/2-way valve22in order to move third 3/2-way valve22from the second switching position shown inFIG. 1into the first switching position, not shown inFIG. 1. In the first switching position, not shown inFIG. 1, inlet connection22.1of third 3/2-way valve22is connected to working connection22.2of third 3/2-way valve22so that second control pressure p2is output and subsequently, upon exceeding of the second threshold value, switches 2/2-way check valve16and thus shuts off second check valve connection16.2from first check valve connection16.1.

Electric control unit ECU furthermore has an electronic connection40to which at least one vehicle bus or an HCU switch can be directly connected. If, for example, a vehicle which has electromagnetic parking brake module1is started, a signal is preferably provided at electronic connection40that spring brake cylinders6should be released. Electric control unit ECU generates, on the basis of the received signal, signal S1and switches second 3/2-way valve20into the first switching position, not shown, in order to output first control pressure p1so that first 3/2-way valve14is also switched into the second switching position, not shown, in order to output spring brake pressure pF so that spring-type actuator connection4is aerated. Spring brake cylinders6connected to spring-type actuator connection4are consequently aerated and released. The vehicle can begin to move.

Second signal S2is triggered on the basis of auxiliary braking requirement signals received via electronic connection40and serves to switch third 3/2-way valve22and as a result 2/2-way check valve16in order to ventilate spring brake cylinders6which are connected to spring-type actuator connection4in a graduated manner.

The first embodiment shown inFIG. 1of electropneumatic parking brake module1also enables a trailer control position function.

In the case of towing vehicle-trailer combinations, it is preferred that the service brakes of the trailer are braked in coordination with spring brake cylinders6of the towing vehicle. In this case, a differentiation is made in principle between what is known as European trailer control and what is known as Scandinavian trailer control. While in the case of European trailer control, the service brakes of the trailer should be permanently applied in the parked state of the vehicle, in the case of Scandinavian trailer control, it is required that, in the parked state of the towing vehicle-trailer combination, the service brakes of the trailer are released in order to prevent freezing. It is nevertheless also required in the case of Scandinavian trailer control that the service brakes of the trailer are also applied for other cases in which spring brake cylinders6of the towing vehicle are activated, i.e. actuated.

For this purpose, electropneumatic parking brake module1according to this embodiment has a trailer control valve connection30as well as a trailer valve32. A trailer control pressure pA which corresponds to spring brake pressure pF or is an equivalent pressure to this is output at trailer control valve connection30. A trailer control valve TCV which inverts provided trailer control pressure pA and then outputs it inversely at service brakes of a trailer (not shown) can be connected to trailer control valve connection30.

Trailer valve32serves to implement the trailer control position function. For this purpose, trailer valve32, in this embodiment (FIG. 1), is formed as fourth 3/2-way valve34and has a first trailer valve connection34.1, a second trailer valve connection34.2and a third trailer valve connection34.3. In a first switching position, not shown inFIG. 1, first trailer valve connection34.1is connected to second trailer valve connection34.2. In a second switching position shown inFIG. 1, second trailer valve connection34.2is connected to third trailer valve connection34.3. The first trailer valve connection is connected to a fourth pneumatic line62which branches off from third pneumatic line58. In this regard, supply pressure pV is present at first trailer valve connection34.1. Second trailer valve connection34.2is connected to trailer valve connection30. Third trailer valve connection34.3is connected via a branch line36to spring brake pressure line38into which spring brake pressure pF is output. This means that spring brake pressure pF is present at third trailer valve connection34.3.

Either supply pressure pV or spring brake pressure pF can now be output via trailer valve32at trailer control valve connection30. In the event that spring brake pressure pF is output as trailer control pressure PA, the service brakes of the trailer vehicle are controlled in coordination with spring brake cylinders6. This means that, if spring brake cylinders6are actuated, the service brakes of the trailer are also actuated. In order to prevent this, trailer valve32can be moved into the first switching position via a third signal S3by electric control unit ECU so that supply pressure pV is output at trailer control valve connection30as trailer control pressure PA. In this case, the service brakes of the trailer vehicle remain released.

The exemplary embodiment shown inFIG. 1uses a trailer valve32which is currentless in the second switching position shown inFIG. 1and thus outputs spring brake pressure pF as trailer control pressure pA in a currentless state. The exemplary embodiment shown inFIG. 1thus implements European trailer control in which, in a parked state of the vehicle (currentless state), the trailer is braked in coordination with spring brake cylinders6of the towing vehicle.

A variant of this, namely Scandinavian trailer control, is shown inFIG. 3. As is apparent fromFIG. 3, the only difference in the third exemplary embodiment of electropneumatic parking brake module1lies in the switching positions of trailer valve32being reversed. This means that trailer valve32according to the third exemplary embodiment (FIG. 3) is currentless in the switching position referred to as the first switching position in the first exemplary embodiment (FIG. 1) and thus connects first trailer valve connection34.1to second trailer valve connection34.2in a currentless state so that in a currentless state supply pressure pV is output as trailer control pressure pA and thus the service brakes of the trailer are released in the currentless state (parked state).

In the context of the present disclosure, both European trailer control and Scandinavian trailer control can therefore be implemented in a particularly simple manner with electropneumatic parking brake module1.

Both in the first and in the third exemplary embodiment (FIGS. 1 and 3), compressed air supply3is connected directly to supply connection2. These two embodiments (FIG. 1andFIG. 3) therefore also enable a ventilation of spring-type actuator connection4by pumping down compressed air supply3. In the event that, for example, bistable valve21functions incorrectly and sticks permanently in the first switching position, not shown inFIGS. 1 and 3, in which first control pressure p1is output, spring-type actuator connection4can be ventilated as a result of the fact that compressed air supply3is overall pumped down and is thus adjusted to an ambient pressure level. Secure braking of the vehicle can thus be achieved even in the event of a malfunction of bistable valve21or also in the event of a malfunction of electric control unit ECU, or of first 3/2-way valve14.

In the second exemplary embodiment (FIG. 2) of electropneumatic parking brake module1, in contrast, an additional non-return valve18is inserted into first pneumatic line50, and indeed directly downstream of supply connection2, i.e. between supply connection2and the branch point of third pneumatic line54. A return flow of compressed air from spring brake cylinders6into compressed air supply3is prevented via said non-return valve18. As a result of this, it is possible that a released state of spring brake cylinders6can be permanently maintained even in the case of a leak of compressed air supply3, and the vehicle does not brake via spring brake cylinders6in an unintentional manner as a result of a leak or crack in a pneumatic line.

The fourth exemplary embodiment (FIG. 4) of electropneumatic parking brake module1differs from the first three exemplary embodiments (FIGS. 1-3) in that electropneumatic parking brake module1does not have a trailer control valve connection30. No trailer control valve32is also accordingly provided. Fourth pneumatic line62and branch line36are thus also omitted. The remaining elements and components of the fourth exemplary embodiment are identical to the first three exemplary embodiments.

Exemplary embodiments5,6and7according toFIGS. 5, 6 and 7show in each case an electropneumatic parking brake module1, as is fundamentally known from the fourth exemplary embodiment (FIG. 4). Bistable valve21is nevertheless replaced by a monostable inlet-outlet valve combination65.

A particularly simple circuit layout is first described with reference toFIG. 5in a fifth exemplary embodiment. Monostable inlet-outlet valve combination65has an inlet valve70and an outlet valve72. Inlet valve70is in this exemplary embodiment formed as 2/2-way inlet valve74and has a first inlet valve connection70.1and a second inlet valve connection70.2. Inlet valve70is formed as a monostable valve and is pretensioned into the first closed switching position shown inFIG. 5. By providing a fourth switching signal S4, inlet valve70can be switched from the first switching position shown inFIG. 5into the second switching position, not shown inFIG. 5. In the second switching position, not shown inFIG. 5, first inlet valve connection70.1is connected to second inlet valve connection70.2.

Second inlet valve connection70.2is connected to first pneumatic control line56which, as has already been described with reference to the first four exemplary embodiments, is connected to first control connection14.4of first 3/2-way valve. By switching inlet valve70, first control pressure p1can consequently be output. As soon as this exceeds the first threshold value, first 3/2-way valve14switches into the second switching position, not shown inFIG. 5, and working pressure pVS is output at working connection14.2, which working pressure pVS can then be provided as spring brake pressure pF if 2/2-way check valve16is in the open switching position shown inFIG. 5.

In order to achieve a pneumatic self-retention of first 3/2-way valve14, in the first four exemplary embodiments (FIGS. 1 to 4), bistable valve21was used which is stable both in the first and in the second switching position. Monostable inlet-outlet valve combination65is, however, not stable in the open switching position, but rather in the closed one. For this reason, electropneumatic parking brake module1according to the fifth exemplary embodiment (FIG. 5) has a return line67which returns working pressure pVS output by first 3/2-way valve14to first control input14.4and provides it there as first control pressure p1. In this manner, first control pressure p1is maintained even if inlet valve70, once it has firstly been switched into the open switching position, is switched back into the closed switching position. A pneumatic self-retention is achieved.

Outlet valve72is provided to ventilate first control input14.4in order to allow first 3/2-way valve14to fall back into the first switching position shown inFIG. 5. Said outlet valve72is, according to the fifth exemplary embodiment (FIG. 5), in turn formed as 2/2-way outlet valve76. It has a first outlet valve connection72.1and a second outlet valve connection72.2. First outlet valve connection72.1is connected to first pneumatic control line56, and second outlet valve connection72.2is connected to a vent5. 2/2-way outlet valve76is currentless in the closed first switching position shown inFIG. 5. 2/2-way outlet valve76can be moved into the second open switching position, not shown inFIG. 5, in which first outlet valve connection72.1is connected to second outlet valve connection72.2, by a corresponding fifth switching signal S5. In this manner, first pneumatic control line56and thus first control connection14.4can be ventilated so that first 3/2-way valve14can fall back into the first switching position shown inFIG. 5. As a result of this, spring-type actuator connection4is ventilated even if check valve16is in the open switching position shown inFIG. 5.

In order to not immediately release the pneumatic self-retention in the case of small fluctuations in pressure at spring-type actuator connection4and enable a change in the switching states, a throttle68is arranged in return line67according to this exemplary embodiment (FIG. 5). Throttle68can also be arranged at other positions.

As is apparent fromFIG. 5, return line67is connected directly to first control input14.4without interconnection of a valve. The returned pressure can therefore not be shut out, rather is provided immediately when first 3/2-way valve14has switched. In this regard, throttle68is also useful to avoid excess output.

Exemplary embodiments6and7now show variants in the case of which return line67is not connected directly to first control input14.4, rather a valve is interconnected.

FIG. 6initially shows in a sixth exemplary embodiment that inlet valve70is formed as 3/2-way inlet valve78. It has in this regard a third inlet valve connection70.3which is then connected to return line67. First inlet valve connection70.1is, as also in the case of the fifth exemplary embodiment (FIG. 5), connected to supply connection2, in particular via third pneumatic line54. Second inlet70.2is, as already known from the fifth exemplary embodiment (FIG. 5), connected to first pneumatic control line56. By switching 3/2-way inlet valve78into the second switching position, not shown inFIG. 6, second inlet valve connection70.2is therefore connected to supply connection2so that first control pressure p1is output. As a result of this, first 3/2-way valve14switches into the second switching position, not shown inFIG. 6, and working pressure pVS is output. This pressure is returned via return line67and is then present at third inlet valve connection70.3. If inlet valve70is now switched to be currentless, it falls back into the first switching position shown inFIG. 6, and third inlet valve connection70.3is connected to second inlet valve connection70.2. The returned pressure is fed through and provided as first control pressure p1at first control input14.4. As a result of this, a pneumatic self-retention of first 3/2-way valve14is then achieved. In this exemplary embodiment (FIG. 6), throttle68is formed in 3/2-way inlet valve78.

In a similar manner, in the seventh exemplary embodiment (FIG. 7), outlet valve72is formed as 3/2-way outlet valve80. Inlet valve70is, as in the fifth exemplary embodiment (FIG. 5), formed as 2/2-way inlet valve74.

3/2-way outlet valve80has a third outlet valve connection72.3which is then connected in this exemplary embodiment (FIG. 7) to return line67. This means that the key difference between the sixth exemplary embodiment (FIG. 6) and the seventh exemplary embodiment (FIG. 7) lies in the fact that return line67is not connected to inlet valve70, but rather to outlet valve72. In this variant, in the event of switching of inlet valve70and outputting of first control pressure p1, first 3/2-way valve14is also switched and working pressure pVS is provided as first control pressure via return line67, outlet valve72and first pneumatic control line56. Provision is carried out immediately and not only upon inlet valve70being switched into a currentless state, as is the case in the sixth exemplary embodiment (FIG. 6). 3/2-way outlet valve80is currentless in the second switching position shown inFIG. 7, in the case of which third outlet valve connection72.3is connected to first outlet valve connection72.1so that return line67is connected to first pneumatic control line56. A pneumatic self-retention of first 3/2-way valve14can also be achieved in this manner.

While the above description constitutes the preferred embodiments of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.

LIST OF REFERENCE NUMBERS (PART OF THE DESCRIPTION)