The invention relates to a brake system for a motor vehicle to be equipped with a trailer, comprising a trailer control module, and to a trailer control module for such a brake system.

Nowadays, brake systems of commercial vehicles are operated with compressed air, in both, motor vehicles and their trailers. In the brake system, the interface between motor vehicle and trailer is standardized with appropriate compressed air connections.

However, the electrification of brake systems in modern vehicles is an attractive way to reduce auxiliary energy consumption, space need and noise emissions. As trailers usually have a longer life cycle, and hence could have many different owners throughout their life cycles, a solution for the electrification of brake systems of motor vehicles should be compatible with existing brake systems of trailers, which usually still work with pneumatic brakes, in order to be able to continue using existing trailers with pneumatic brakes. Therefore, a solution for the electro-mechanic brake system that is used preferably in modern motor vehicles is required, which is able to control the pneumatic brake system of a trailer.

In state of the art brake systems for motor vehicles and trailers, for example described in document DE10310235A1, the brakes of the trailer are controlled by trailer control valves (TCV) or a so-called trailer control module (TCM), which is/are positioned in the motor vehicle and therefore forms/form part of its brake system. In order to be able to provide brake pressure even if one brake circuit signal does not work, a redundant independent signal is necessary. Hence, the TCVs/TCM comprise at least two independent control input terminals that are able to receive inputs from an electronic control unit (ECU) that processes the signals of a service brake, which is operated by the operator of the vehicle, if there is a need to slow the vehicle down. Those inputs from the ECU to the TCV/TCMs are either both pneumatic in case of the use of TCVs or one is pneumatic and one is electric from an electric control line in case of the use of a TCM. Moreover, TCMs comprise an inverted pneumatic control input coming from the parking brake, a compressed air supply inlet and two coupling head outputs (pneumatic outlets), one for the air supply of the trailer and one for the pneumatic control line for the trailer brakes. Furthermore, there is optionally a digital communication line between the motor vehicle and the trailer in the form of a 24V CAN bus, standardized according to ISO 11992. The description of an internal design of a state-of-the-art TCM is provided for example in the document EP1127764. A TCM according to the state of the art disclosed in the document is provided with three different solenoid valves, with which in combination of a relay valve allows to adjust the brake pressure for the braking units of a trailer.

With modern electro-mechanic brake systems of motor vehicles being able to provide only electrical outputs instead of at least one pneumatic output, the need for new TCMs arises. Therefore, it is the objective of the present invention to provide a TCM and a brake system in a motor vehicle with a TCM that are compatible with the pneumatic state-of-the-art trailer brake systems described above.

Such a TCM and a brake system for a motor vehicle with the TCM is provided by the subject-matters of the independent claims. Further developments of the invention with advantageous effects are provided by the dependent claims.

A trailer control module for a brake system of a motor vehicle according to the present invention is configured to provide a preset brake control outlet pressure to a pneumatic trailer brake system and comprises at least two electrical terminals, which are configured to receive two independent but redundant electrical control input signals, which comprise the signal for the preset brake control outlet pressure. It further comprises at least one pneumatic inlet terminal, which is configured to receive constant pressure from an air pressure source, at least one valve, configured to adjust the constant air pressure from the air pressure source to the preset break outlet pressure, at least one brake supply pressure terminal, configured to provide the brake supply outlet pressure to the pneumatic brake system of the trailer and at least one brake control pressure terminal, configured to provide the preset brake control outlet pressure to the pneumatic brake system of the trailer. In an advantageous embodiment of the invention the trailer control module comprises at least two control solenoid groups, each including a load- and an exhaust valve and each group allowing to control the brake control outlet pressure by itself and independently from one another via its own control channel. Each solenoid group is provided with its own independent but redundant signal from the two different brake ECUs. Hence, in order for the TCM to be able to process both different but redundant electric signals independently from each other and to satisfy the existing safety requirements, it also needs internally two separate pressure control channels in which the pneumatic signals can be processed to the brake control outlet pressure. Thus, the control channel is formed by the technical elements like valves (relay valve) that define the brake control outlet pressure. An advantage of the use of solenoids in the TCM is that solenoids are well known in the state of the art, easy to handle also in terms of maintenance and don't need a lot of energy to be operated.

A further advantageous embodiment of the TCM according to the invention comprises a normally opened exhaust valve (for example as a solenoid) for normally not parked trailer control for each control channel of its relay valve. In the context of this application, a normally not parked trailer is a trailer, whose parking brakes are inactive, while the vehicle it is attached to, has its parking brakes active as the brakes of the vehicle alone should be able to hold both the vehicle and the trailer in parking position when they are active. This has the advantage that a combination parking stability is not depending on the trailer parking brakes (which are not always spring brake based) but the tractor parking brakes only (which are always spring brake based). According to this definition, a normally parked trailer is a trailer, whose parking brakes are active, while the vehicle it is attached to, has its parking brakes also active.

In a further advantageous embodiment of the invention, the TCM comprises a normally closed exhaust valve (for example as a solenoid) and a feedback orifice to achieve a bistable parking brake operation for normally parked trailer control for each control channel of its relay valve.

In another advantageous embodiment of the invention the TCM comprises a normally closed exhaust valve and a feedback orifice for normally parked trailer control for one control channel and a normally opened exhaust valve for normally not parked trailer control for another control channel of its relay valve.

In another advantageous embodiment of the invention the TCM comprises normally closed exhaust valves and a feedback orifice for normally parked trailer control for both control channels.

In another advantageous embodiment of the invention the trailer control module comprises normally opened exhaust valves for normally not parked trailer control for the control channel.

In yet another advantageous embodiment of the invention the TCM comprises at least two independent pressure sensors, configured to measure the brake control outlet pressure of the trailer. In this way the correct functionality of the brake system and the TCM can easily be controlled and adjusted by the ECUs of the motor vehicle brake system if necessary.

In a further advantageous embodiment of the invention, the trailer control module comprises a hold back valve to trigger the automatic trailer emergency braking at an unexpected disconnection between the vehicle and the trailer. If an unexpected disconnection during operation (driving) occurs, the legislation requires an emergency braking function of the trailer. This can be realized by a hold back valve, which provides the supplied pressure directly to a brake supply terminal.

A motor vehicle brake system according to the invention comprises, at least two independent brake control units (ECUs) which are configured to provide the TCM with at least two independent but redundant electronic signals comprising the signal for the preset brake control outlet pressure. It further comprises a trailer control module according to the invention and an air pressure source, configured to supply a constant pneumatic pressure to the brakes of the trailer.

In an advantageous embodiment of the motor vehicle brake system according to the invention, it further comprises a communication line between the trailer and the brake control units, wherein a multiplexer is configured to connect the trailer to either one or the other brake control unit, so that only one brake control unit is connected with the trailer at a time.

In the following, an embodiment of the invention is explained more in detail with respect to the corresponding figures. The latter show:

Fig. 1 a schematic layout of the motor vehicle brake system according to the invention.

Fig. 2 a schematic layout of the architecture of a TCM according to the invention.

Fig. 1 shows a schematic layout of the motor vehicle brake system according to the invention. The brake system according to the invention is powered by at least two independent electric energy sources 40a, 40b and controlled by at least two independent electronic control units 10a, 10b (ECU). The foot brake sensor 30 is operated by the operator of the motor vehicle in case that braking is necessary. The signal is provided at both, the first ECU 10a and the second ECU 10b. Further, a parking brake control 31 is connected to both ECUs 10a, 10b. Embodiments, where the parking brake control is only connected to one ECU are also possible. Both, the parking brake control 31 and the foot brake sensor 30 are connected with the ECUs 10a, 10b via analogous electrical lines 90, which could also be digital in other embodiments of the invention. The first ECU 10a is further connected with the second ECU 10b via a digital electric signal line 80. Both ECUs 10a, 10b are capable of controlling four wheel brake units 50a, 50b, 50c, 50d (which could be more or less in other embodiments of the invention) via a digital electrical line 80, so that both ECUs 10a, 10b are capable of commanding the wheel brake units 50a-50d through at least two independent communication lines.

The wheel brake units 50a, 50b as well as the first ECU 10a are powered by the first electric energy source 40a, while the wheel brake units 50c, 50d and the second ECU 10b are powered by the second electric energy source 40b. In order to achieve braking performance of the trailer, both ECUs 10a, 10b send redundant electric signals via analogous electric lines 90, which could also be digital in other embodiments, to a trailer control module (TCM) 20, which provides a braking outlet pressure to the trailer brake system. The TCM 20 is further connected to an air pressure source 60, which provides the TCM 20 with a constant pneumatic pressure. Thus, apart from the air pressure source 60, the TCM 60 is only provided with electric signals to adjust the brake pressure for the trailer.

A multiplexer 70 is connected with the trailer via a standardized CAN-bus according to ISO 11992 known from the state of the art and either passes the signals from the first ECU 10a or of the second ECU 10b to the trailer. It can be either physical (by an active switch) or functional (by e.g. an interconnected bus to both brake control units and a master is commanding and a slave is listening).

In operation, the operator (driver) of the motor vehicle operates the foot brake sensor 30 for normal service brake needs and the parking brake control 31, if a movement of the vehicle in standstill is to be prevented. The electric signal is passed to both ECUs 10a, 10b, where a necessary braking force is calculated, according to which the ECUs 10a, 10b control the wheel brake units 50a, 50b, 50c, 50d of the motor vehicle via the corresponding digital electric signal lines 80. Further, the information of a brake pressure, which needs to be applied to the pneumatic brake system of the trailer is passed via electric signals to the TCM 20 via the analogous electric line 90. With the given signals by the ECUs 10a, 10b and the constant pressure of the air pressure source 60, the TCM adjusts the demanded brake pressure and provides it to the brake system of the trailer. Further, information of either one of the ECUs 10a, 10b is provided to the trailer according to the position of the multiplexer 70 via the CAN-bus.

Fig. 2 shows a schematic layout of the architecture of a TCM according to an embodiment of the invention. The pneumatic pressure of the air pressure source 60 is provided at an air pressure source inlet A. The air pressure source inlet A is connected via an air pressure source pressure line 23 with a hold back valve 25 and two solenoid valves 21b and 21c. Both of them are in the following also referred to as load valves 21b, 21c and are in a normally closed state. At each side of the load valves 21 b, 21 c, two further solenoid valves 21a, 21 d are positioned, which are also referred to as exhaust valves 21a, 21 d, the exhaust valve 21a being in a normally opened state and the exhaust valve 21 d being in a normally closed state. All of the four solenoid valves 21a-21d are controlled by the electric signals of the two ECUs 10a, 10b of the brake system of the motor vehicle. The solenoid valves 21a, 21b form one group controlled by the first ECU 10a and the solenoid valves 21c, 21 d form a second group controlled by the second ECU 10b.

From both of the load valves 21b, 21c, a control pressure line 24 to the hold back valve 25 and to the corresponding exhaust valve 21a, 21d of each group is formed. Further the control pressure lines 24 from the load valves 21b, 21c also connect a dual channel relay valve 26 and an orifice 27. A further pressure line, referred to as exhaust pressure line 22, leads from the outlets of the exhaust valves 21 a, 21 d and the dual channel relay valve 26 to an exhaust outlet terminal B, where pressure, which is not needed anymore in the system, can be released to the atmosphere.

Moreover, one outlet of the hold back valve 25 is connected to one inlet of the dual channel relay valve 26 via a brake supply pressure outlet 29a, which also leads to a brake supply pressure terminal C, which is a pneumatic outlet and connected to the air pressure tanks of the trailer. As mentioned above, one outlet of the dual channel relay valve 26 is connected to the exhaust outlet terminal B. Another outlet of the dual channel relay valve 26 is connected to a brake control pressure terminal D by a brake control pressure outlet 29b. The brake control pressure terminal D is a second pneumatic outlet and provides a trailer brake control pressure signal to the trailer. The pressure in the brake control pressure outlet 29b is measured by two pressure sensors 28a, 28b, which are permanently connected via an analogue or digital line with both ECUs 10a, 10b.

In the embodiment of the invention shown in Fig. 2, the pressure provided by the air pressure source 60 at the air pressure source inlet A is provided directly at the brake supply pressure terminal C under normal operation and switches to its orifice position in case of an unexpected trailer disconnection to introduce an emergency braking to the trailer. REFERENCE LIST

10a first electronic control unit 10b second electronic control unit 20 Trailer control module 201a, 201b electrical terminal 21a, 21d solenoid valve: exhaust valve 21b, 21c solenoid valve: load valve

22 exhaust pressure line

23 air pressure source pressure line

24 control pressure line

25 hold back valve

26 dual channel relay valve

27 orifice 28a, 28b pressure sensors

29a brake supply pressure outlet

29b brake control pressure outlet

30 foot brake sensor

31 parking brake control

40a first electric energy source

40b second electric energy source 50a, 50b, 50c, 50d wheel brake unit 60 air pressure source

70 multiplexer

80 digital electric signal line

90 analogous electric line

A air pressure source inlet

B exhaust outlet terminal C brake supply pressure terminal to trailer air tanks

D brake control pressure terminal providing trailer brake control pressure signal to the trailer