Patent Description:
It is known to provide electro-pneumatic braking systems, in which a foot brake modulator detects the vehicle driver's brake request, for example by receiving one or more signals from one or more sensors. A central control unit electrically controls electro-pneumatic control modules which convert the electrical brake signals of the central control unit into pneumatic pressures based upon the desired brake value. It is known, for example from <CIT> to provide electronic braking systems which include two electronic service brake circuits. The braking system generates a first setpoint for a for a first one of the electronic braking circuits and a second setpoint for a second one of the electronic braking circuits, based upon braking demand from a foot pedal. In normal operation, higher functions, such as ABS, for example, which generate signals which modify the or each setpoint are performed in a first control unit of the first braking circuit while the second braking circuit generates only the second brake setpoint, which may be suppressed or act as a plausibility check for the first control unit. In a fault condition where the first circuit fails, the second service braking circuit is used to provide signals to generate a braking pressure in at least one pressure control module of the braking system.

It is also known to provide an electronically controlled braking system which includes two independent electronic brake control circuits, each of which drives a brake of the front axle and the rear axle of the vehicle in a diagonal arrangement. In such a system, two separate power supplies, two central control units and a foot brake module with two separate channels (brake encoder circuits) are provided to comply with the safety requirements. The two control units are communicable with one another for the exchange of information and the monitoring of functions of the two brake circuits.

<CIT> describes a trailer control valve for a braking system which includes pistons for actuating a double seat valve which can control the communication between a compressed air reservoir, a compressed air consumer and a pressure relief location. A control piston is provided that is jointly associated with an electrical control circuit and a pneumatic control circuit of a service brake system. A valve is provided which is connected to the pneumatic control circuit of the service brake system, which closes the pneumatic control circuit of the service brake off from the trailer control valve when the electrical control circuit is functional, and in the event of a failure of the electrical control circuit, unblocks the pneumatic control circuit of the service brake system.

<CIT> discloses an electronically controlled electro-pneumatic brake system for a vehicle, comprising at least two electric service brake control circuits. <CIT> discloses an electro-pneumatic parking brake modulator for controlling a parking brake mode of brakes of at least one trailer.

According to claim <NUM> of the invention, there is provided a trailer control module for a braking system, the trailer control module including an electronic control unit, which is operable to receive a signal indicative of a braking demand from at least one electrical braking control circuit and to provide signals to a supply valve and an exhaust valve which control the supply of pressurised air from a reservoir to one or more trailer brake actuators through a service line and a supply line, wherein the electronic control unit is operable to control an emergency line restrictor valve which is, in turn, operable to control the flow of pressurised fluid from the reservoir to a supply line in the event of a drop in pressure in the service line.

The electronic control unit may receive signals from the or each braking control circuit via a respective CANBUS connection.

The emergency line restrictor valve may be communicable with the electronic control unit via a CANBUS connection.

The emergency line restrictor valve may be integral with the trailer control module.

The trailer control module may include one or more pressure transducers operable to provide signals to the electronic control unit which are indicative of the pressure in at least one of the service line and the supply line, and to control at least one of the supply valve and the exhaust valve in response to signals received from the electronic control unit.

The electronic control unit (<NUM>) may be operable to control the emergency line restrictor valve which is, in turn, operable to control the flow of pressurised fluid from the reservoir to a supply line in the event of a drop in pressure in the service line, when there is no capability to communicate with a CANBUS connection, or in the event of a failure in the CANBUS connection.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, of which:.

Referring to the figures, there is shown a vehicle braking system <NUM>, for a vehicle which includes a towing vehicle and a trailer. The braking system <NUM> includes a service line (yellow line) <NUM>, for the supply of pressurised air to one or more service brake actuators located on the trailer and an emergency line (red line) <NUM> which provides the supply of pressurised air to the trailer, and is also used to operate an emergency brake on the trailer in the event of a failure in the service line <NUM>, or associated circuitry.

The braking system <NUM> includes a trailer control module <NUM>. The trailer control module <NUM> includes a first port <NUM>, for receiving a supply of pressurised air from a reservoir, and a second port <NUM> which is a delivery port for providing a pressurised air control signal via the service line <NUM>. A third port <NUM> of the trailer control valve <NUM> is an exhaust port, and a fourth port <NUM> is provided for the pressurised air control signal from a parking brake via a parking brake supply line <NUM>. The trailer control valve <NUM> also includes an electronic control unit (ECU) <NUM>. The ECU is a microcontroller which receives and provides signals indicative of pressure in the service line <NUM>, supply line <NUM>, parking brake supply line <NUM>, etc., as well as receiving and providing signals indicative of braking demand and required pressure. The ECU may receive and/or provide signals indicative of other characteristics of the braking system <NUM>.

The ECU <NUM> receives electrical signals via a first pressure transducer <NUM> which converts a measure of pressure in the service line <NUM> and/or emergency line <NUM> to a voltage. A second pressure transducer <NUM> is connected between the fourth port <NUM> and the ECU to provide electronic signals relating to the pressure in the parking brake supply line <NUM>.

The ECU <NUM> provides signals to a supply valve <NUM> and an exhaust valve which control the supply of pressurised air to the or each trailer brake actuator. The supply valve <NUM> and the exhaust valve <NUM> may be solenoid operated valves, with the solenoids being controlled by signals from the ECU <NUM>. The supply valve <NUM> includes an inlet <NUM> which is connected to the first port <NUM>, and hence to the emergency line <NUM>, and an outlet <NUM> which is connected to the exhaust valve <NUM> and to the first pressure transducer <NUM>. In a first condition, the inlet <NUM> is disconnected from the outlet <NUM>. In a second condition, the inlet <NUM> is fluidly communicable with the outlet <NUM>. In an embodiment, the supply valve <NUM> is biased to its first condition, for example by a spring <NUM>. In other words, the supply valve is normally closed, until the ECU <NUM> provides an electrical signal, i.e. a voltage, to the solenoid to override the bias, and place the supply valve in the second, open condition, such that pressurised air can be supplied to the exhaust valve <NUM>.

The exhaust valve <NUM> also includes an inlet <NUM> and an outlet <NUM>. In a first condition, the inlet <NUM> is fluidly communicable with the outlet <NUM>. In a second condition, the inlet is disconnected from the outlet <NUM>. In an embodiment, the exhaust valve is biased to its first condition, for example by a spring <NUM>. In other words, the exhaust valve <NUM> is normally open, unless and until the ECU <NUM> provides a signal, i.e. a voltage, to the solenoid of the exhaust valve <NUM> to override the bias, and place the exhaust valve <NUM> in the second, closed condition.

It will be appreciated that the supply and exhaust valves <NUM>, <NUM> need not be solenoid valves and may be pneumatically controlled valves.

The ECU <NUM> is communicable with a first transceiver which provides signals from a first electrical braking control circuit via a CANBUS connection <NUM>. The first electrical braking control circuit may control the operation of brakes on a front axle of the vehicle, for example. The ECU is communicable with a second transceiver which provides signals from a second electrical braking control circuit via a further CANBUS connection <NUM>. The second braking control circuit may control the operation of brakes on a rear axle of the vehicle. The first and second braking control circuits provide braking demand signals in response to the application of a braking demand made by the driver. The first and second electrical braking control circuits may be independently operable.

The ECU <NUM> may be communicable with the emergency line restrictor (ELR) valve <NUM> via a third transceiver <NUM>. The ECU <NUM> may be communicable with the ELR valve <NUM> via a CANBUS, or via a direct solenoid connection (as shown in <FIG>). The ECU is communicable with a fourth transceiver <NUM> which enables the transfer of data between the towing vehicle and the trailer. In embodiments, the fourth transceiver may follow the ISO11992 standard.

The ELR valve <NUM> acts to throttle the flow of pressurised fluid from the reservoir into the emergency line <NUM> in the event of a rupture of in the service line <NUM> (see below) so that pressure drops in both, to activate the emergency braking mechanism in the trailer. The ELR valve <NUM> includes a throttle valve <NUM> which includes an input <NUM> which is fluidly communicable with the reservoir of pressurised fluid and an output <NUM> which is fluidly communicable with the emergency line <NUM>. In a first condition, the inlet <NUM> is fluidly communicable with the outlet <NUM> such that the emergency line <NUM> is pressurised. In a second condition, the flow of fluid from the inlet <NUM> to the outlet <NUM> is throttled, to reduce the flow of pressurised fluid, and to reduce the pressure in the emergency line <NUM>. The throttle valve <NUM> is biased to its first condition, preferably by a spring. The throttle valve <NUM> is controlled by a control valve <NUM>, which includes an inlet <NUM>, which is communicable with the reservoir via a first port. An outlet <NUM> is communicable with the throttle valve to control the condition of the throttle valve <NUM>. The control valve <NUM> is solenoid controlled by a solenoid <NUM>, and is electrically communicable with the ECU <NUM>. In a first condition, the inlet <NUM> is closed, and the outlet <NUM> vents through an exhaust port <NUM>. In a second condition, the inlet <NUM> is fluidly communicable with the outlet <NUM>, to move the throttle valve into its second condition and the exhaust port <NUM> is closed.

In the embodiment shown in <FIG>, the ELR valve is shown as being external to the trailer control module <NUM>, and is controlled by a solenoid which receives a signal from the ECU <NUM>. The ELR valve <NUM> is connected between the first port <NUM> and an emergency line connection between the towing vehicle and the trailer.

In the embodiment shown in <FIG>, the ELR valve <NUM> is integral with the trailer control module <NUM>. The solenoid of the control valve <NUM> is controlled by the ECU <NUM>. The embodiment of the trailer control module <NUM> shown in <FIG> includes an additional pressure transducer <NUM>, which provides the ECU <NUM> with signals which indicate the pressure in the emergency line <NUM>.

Referring to <FIG>, the trailer control module <NUM> is shown in normal operating mode. In <FIG>, the third transceiver <NUM> has been replaced by a diagnostic connection <NUM> which is operable to provide information about the operating status of the ECU <NUM>. The transceiver <NUM> is not required in this configuration of the trailer control module <NUM> because the ELR valve <NUM> is integral with the trailer control module <NUM>. No service brake demand input is being made to the ECU <NUM> from the first or second braking circuit via CANBUS connection <NUM> or <NUM>. The exhaust valve <NUM> is vented via the exhaust port <NUM>, therefore the service line <NUM> is not pressurised. The ELR valve <NUM> is maintained in its first condition, such that the emergency line <NUM> is pressurised, and the supply of pressurised fluid to the emergency line <NUM> is un-throttled. The control valve <NUM> vents. In the condition shown in <FIG>, the parking brake is not applied, therefore the transducer <NUM> provides a signal indicating that the parking brake line <NUM> is pressurised. If the transducer were to provide a signal indicating that the park brake is on because line <NUM> is vented, it would be possible to pressurise service line <NUM> to apply the service brake as a park brake.

Referring to <FIG>, the trailer control module is shown in normal operating mode, with a braking demand being made via the first CANBUS connection <NUM> and/or the second CANBUS connection <NUM>, i.e. via the first and/or second braking circuit(s). In this situation, there is still no parking brake demand, because the parking brake line <NUM> remains pressurised, and the parking brake remains off. The transducer <NUM> ensures that the emergency line <NUM> remains pressurised. The transducer <NUM> provides an output to open the supply valve <NUM>, so as to pressurise the service line <NUM>, by the supply of pressurised fluid from the reservoir, through the supply valve <NUM>. When the service line <NUM> is pressurised the or each brake actuator is operated to apply the or each brake to an associated trailer wheel. Opening the supply valve <NUM> also allows the flow of pressurised fluid between the supply valve <NUM> and the exhaust valve <NUM>, which is closed to maintain pressure in the supply line <NUM>. In this situation, where there is no failure in any part of the braking system, the ELR valve <NUM> remains in its first condition, i.e. un-throttled, so as to maintain pressure in the emergency line <NUM>.

Referring to <FIG>, the trailer control module is shown in a normal operating mode, but where there is a failure in the service line <NUM>, for example the service line <NUM> may have ruptured, meaning that the requisite pressure cannot be achieved and/or maintained to apply the service brake or to prevent the service brake from disengaging. The trailer control module <NUM> is able to overcome this problem, as follows. The ECU <NUM> attempts to pressurise the service line <NUM> by opening the supply valve <NUM>, as described above. Since the requisite pressure cannot be reached and/or maintained in the service line <NUM>, the transducer <NUM> indicates a drop in pressure in the service line <NUM> to the ECU <NUM>. The ELR valve solenoid <NUM> is activated by a signal from the ECU <NUM>, to move the control valve <NUM> into its second condition, and hence move the throttle valve <NUM> into its second, throttled condition. The supply of pressurised fluid from the reservoir into the emergency line <NUM> is throttled, and since the supply valve <NUM> is open, the emergency line <NUM> is exhausted, which applies the emergency brake in the trailer. The parking brake line <NUM> remains pressurised, such that the parking brake is not applied.

An additional or alternative solution is also possible. Since the trailer control module has CANBUS connection <NUM> (ISO <NUM>) via which the towing vehicle is able to communicate with the trailer, the braking demand signal from the brake pedal via the CAN connector(s) <NUM>, <NUM> to the ECU <NUM>, can be communicated to the trailer via the CANBUS connection <NUM>. The service line <NUM> is effectively redundant, and may be vented. In this instance, the configuration of the trailer control module is similar to that shown in <FIG>, i.e. the exhaust valve <NUM> is vented via the exhaust port <NUM>, and the service line <NUM> is not pressurised. The ELR valve <NUM> is maintained in its first condition, such that the emergency line <NUM> is pressurised, and the supply of pressurised fluid to the emergency line <NUM> is un-throttled. The control valve <NUM> vents. In the condition shown in <FIG>, the parking brake is not being applied, because the transducer <NUM> provides a signal indicating that the parking brake supply line <NUM> is pressurised. The difference between this situation and the situation shown in <FIG> is that when there is a braking demand from the CANBUS connection(s) <NUM>, <NUM>, the ECU <NUM> provides a signal to the trailer via CANBUS connection <NUM>, and circumvents the need to pressurise the service line <NUM>. The service line <NUM> is isolated from the emergency line by the supply valve <NUM>.

Whilst the service line <NUM> is effectively redundant in this arrangement, it can provide a back-up in the event that the towing vehicle is connected to a vehicle which does not have the capability to communicate with the CANBUS <NUM>, or in the event that the CANBUS connection <NUM> is present between the towing vehicle and the trailer, but fails. In such a situation, the braking system operates as described in relation to <FIG>, above.

<FIG> and <FIG> show solenoid valves as the supply valve <NUM> and the exhaust valve <NUM>, whereas <FIG> indicate fast acting valves, which may be as described in <CIT>. It will be understood that any appropriate type of valve may be used.

Referring to <FIG>, there is shown a vehicle <NUM>, having a front axle <NUM>, which in an embodiment is a steering axle; a first rear axle <NUM>, which in an embodiment may be driven; and a second rear axle <NUM>.

A foot brake modulator <NUM> is provided to receive an input to indicate a braking demand, for example from a brake demand source, i.e. a brake pedal. The foot brake modulator <NUM> provides an input data signal (indicated by a dashed line in <FIG>) indicative of the braking demand to a vehicle ECU <NUM>.

The ECU <NUM> may also be in communication with a yaw sensor <NUM> and/or a steer angle sensor <NUM>. The yaw sensor <NUM> and the steer angle sensor <NUM> are operable to provide data signals (shown by dotted lines in <FIG>) to the ECU <NUM>. The data signals can be used by the ECU <NUM> to modify braking demand signals transmitted by the ECU <NUM>, for example.

Each wheel end unit includes a brake torque control and diagnostic module <NUM>, which are also in communication with the ECU <NUM>. Each brake torque control and diagnostic module <NUM> is capable of receiving brake control information from and sending sensor information to the ECU <NUM>. Each brake torque control module <NUM> may be powered via its connection to the ECU <NUM>. Each wheel end unit includes a mechanical actuator for applying the brake associated with the wheel. The ECU <NUM> is capable of setting the brake torque at each individual wheel unit.

One or more of the wheel end units may be in communication with a wheel speed sensor which provides data indicative of the speed of an associated wheel to the diagnostic module <NUM>, which can then transmit the wheel speed data to the ECU <NUM>.

A trailer control module <NUM> is in communication with the ECU <NUM>. The trailer control module <NUM> may be of any appropriate type, including any of the embodiments of a trailer control module described herein. The trailer control module may be supplied with power via its connection to the ECU <NUM>, and may exchange data, e.g. sensor data with the ECU <NUM>.

In the embodiments shown in <FIG>, the approximate relative positions of the components of the braking system are shown, but without the communication links, for clarity.

In the embodiment shown in <FIG> and <FIG>, each wheel end unit includes a fast acting brake valve <NUM> which is communicable with the ECU <NUM>, and is able to control the associated brake actuator in response to a signal from the ECU <NUM>. It will be understood that the braking system is flexible enough that other wheel end controls can be utilised without significantly altering the architecture, or significantly altering the functionality of the braking system. For example, the embodiment shown in <FIG> includes a relay-based modulator <NUM> with an associated ECU at each wheel end unit, in place of the corresponding fast acting valve <NUM>. In <FIG> each wheel end unit includes an electro-mechanical brake <NUM> in place of the corresponding fast acting valve <NUM>.

In use, the vehicle ECU <NUM> receives signals from the yaw sensor <NUM>, the steer angle sensor <NUM> and the vehicle speed sensor <NUM>. The ECU <NUM> provides signals to each brake torque control and diagnostics module <NUM>, which is operable to communicate with the associated wheel end unit to set the brake torque at each wheel end by the wheel end control which is utilised, e.g. fast acting valve <NUM>, relay based modulator with ECU <NUM> or electro-mechanical brake <NUM>.

Claim 1:
A trailer control module (<NUM>) for a braking system (<NUM>), the trailer control module (<NUM>) including an electronic control unit (<NUM>), which is operable to receive a signal indicative of a braking demand from at least one electrical braking control circuit and to provide signals to a supply valve (<NUM>) and an exhaust valve (<NUM>) which control the supply of pressurised air from a reservoir to one or more trailer brake actuators through a service line (<NUM>) and a supply line (<NUM>), characterized in that the electronic control unit (<NUM>) is operable to control an emergency line restrictor valve (<NUM>) which is, in turn, operable to control the flow of pressurised fluid from the reservoir to a supply line (<NUM>, <NUM>) in the event of a drop in pressure in the service line (<NUM>).