Patent ID: 12202452

DETAILED DESCRIPTION

FIG.1shows an exemplary embodiment of an electric parking brake for a utility vehicle. The electric parking brake100includes a first valve110, a second valve120and a valve device130(for example, a booster valve) which are pneumatically connected between a feed line105for brake-pressure air and a discharge line107for the brake-pressure air leading to a pneumatic braking device. In this exemplary embodiment, the first valve110and the second valve120are 3/2-way valves which are capable of being switched between a stable state and an activated state in response to electrical control signals.

The valve device130includes a first inlet131, which is connected to the feed line105, a second inlet132and a third inlet133which is connected to the discharge line107. It will be understood that, depending on the directions of pneumatic flow, the inlets may also be outlets. The second inlet132is a control input, in order to switch between a stable state and an activated state in response to (pneumatic) control signals. The control input132may also represent an inlet for a pneumatic line, in order to move one or more pistons between two positions or states with the aid of compressed air.

In addition, the valve device130shown includes a vent port190and a biasing device136which, for example, may include a spring. In the stable state, the third inlet133is connected to the vent port190, so that the discharge line107is automatically vented (for example, in the event of a drop in pressure) and remains vented so long as no pneumatic control signal is applied to the control input132. In the activated position, the first inlet131is connected to the third inlet133, and consequently the feed line105is connected to the discharge line107.

The 3/2-way valves110,120also include three pneumatic ports and, additionally, respectively an electrical control terminal112,122. The control terminals are designed to switch the first 3/2-way valve110and/or the second 3/2-way valve120between the stable state and the activated state in response to (electrical) control signals. For instance, the two 3/2-way valves110,120may be solenoid valves, in which case an electromagnet brings about the switching operations.

In the stable state, the first 3/2-way valve110connects, for instance, the discharge line107to the control input132of the valve device130, in order to retain a current state of the valve device130in the case of sufficient brake-pressure air. In the activated state, the first 3/2-way valve110connects the control input132to the second 3/2-way valve120.

In the stable state, the second 3/2-way valve120connects, for instance, the feed line105to the first 3/2-way valve110, in order to activate the valve device130in the case of an activated first 3/2-way valve110. In the activated state, the second 3/2-way valve120interrupts a supply of compressed air to the first valve110and vents the connection to the first valve110. If the first valve110has also been activated, the valve device130is therefore brought into the stable state and the discharge line107is vented.

In further exemplary embodiments (not shown), the states of the second valve120(and similarly also of the first valve110) can be chosen precisely the other way round. Therefore the second valve120in the stable state can also vent the connection to the first valve110, and in the activated state can connect the feed line105to the first valve110.

FIG.2shows an electric parking-brake system for a utility vehicle (for example, a towing vehicle) with a trailer parking-brake port240, a spring-type actuator140and a shuttle valve150which is connected to a first pressure port101and to a second pressure port102. The shuttle valve150is designed to transmit the respectively higher pressure from the first pressure port101and the second pressure port102to a feed line105. The trailer parking-brake port240and the spring-type actuator140are respectively connected to a discharge line107a,107b, in order to be supplied with compressed air (in the driving state) or to be vented (in the parked state).

Correspondingly, two electric parking brakes100A,100B have been formed between the feed line105and the discharge lines107a,107b. A first electric parking brake100A actuates the spring-type actuator140of the tractor and includes a first valve device130awhich is controlled by two 3/2-way valves110a,120a, in order to supply the spring-type actuator140with compressed air, or to vent it. A second electric parking brake100B actuates a trailer parking brake via the trailer parking-brake port240and includes a second valve device130bwhich is likewise controlled by two 3/2-way valves110b,120b, in order to supply the trailer parking-brake port240with compressed air or to vent it.

The two electric parking brakes100A,100B may have been constructed in the same way and may function in the same way as the electric parking brake fromFIG.1. A renewed description is therefore unnecessary.

FIGS.3A,B show further exemplary embodiments of the electric parking-brake system100fromFIG.2, wherein further details of the first and second valve devices130a,130bare represented. The first and second valve devices130a,130bmay have been constructed identically and each include a first inlet131, a second inlet132, a third inlet133and a vent outlet190. The valve devices130a,130beach include, in addition, a first piston135and a second piston134, which have been biased correspondingly by a first spring136and a second spring137. The valve devices130a,130bshown have been represented in a sectional representation, wherein the elements shown may have been designed to be rotationally symmetrical, for instance.

According to one embodiment (seeFIG.3A), the vent outlet190has been formed below the second piston134and therefore constitutes an opening in one of the directions of motion of the pistons. In a further embodiment (seeFIG.3B), the vent outlet190has been formed on a side wall (laterally alongside pistons134,135), in order to open a chamber below the first piston135toward the outside.

When the second inlet132has been vented, the first piston135moves away from the second piston134, and the vent opening190is connected to the third inlet133. For this purpose, channels have been formed in pistons134,135, so that the compressed air is discharged from the third inlet133either to the vent opening190on the underside (seeFIG.3A) or to the vent opening190on the side wall (seeFIG.3B).

If compressed air is applied to the second inlet132, the first piston135is pressed down against the spring tension until the first piston135comes into contact with the second piston134and then presses the latter down contrary to the spring tension of the second spring137. Since in this state the first piston135and the second piston134are connected to one another, the vent opening190is closed and no longer in contact with the third inlet133. Instead of this, the first inlet131is connected to the third inlet133, since the second piston134opens the first inlet131in the course of being pressed down.

FIG.4shows a flowchart for a method for actuating the described electric parking brake. The method comprises:upon establishing a desire to drive off, activating S110the valve device130by activating at least the first valve110;upon establishing a desire to park, switching S120the valve device130into the stable state by venting the control input132of the valve device130by activating at least the first valve.

It will be understood that all the described functions of the electric parking brake100or of the parking-brake system can be executed as further optional steps.

This method may also be computer-implemented—that is to say, it may have been realized by instructions that have been stored on a storage medium and are capable of executing the steps of the method when it is running on a processor. The instructions typically comprise one or more instructions that may have been stored in varying ways on varying media in, or peripheral to, a control unit (with a processor) and that, when they are read and are executed by the control unit, cause the control unit to carry out functions, functionalities and operations that are necessary for executing a method according to the present invention.

The software may, for instance, have been designed to switch on the parking brake of the towing vehicle and of the trailer individually or jointly, and opens it in accordance with the desire of the driver. In addition, the software can automatically engage the parking brake of the towing vehicle and/or trailer at a standstill under certain supplementary conditions. Similarly, under certain conditions the software can automatically open the parking brake of the towing vehicle and/or trailer if, for instance, a desire of the driver to move off was detected.

Advantageous aspects of the electric parking-brake system may also be summarized as follows:

The first and second valve devices130a,130bare each, for instance, a double-seat booster valve for the parking brake of the towing vehicle or for the parking brake of the trailer, in which case each booster valve130a,130bcan be controlled with a first 3/2-way solenoid valve110a,110b. This first 3/2-way valve110a,110bis capable of being switched between two switch positions: a “feedback” (in the stable state) and a “reversal” (in the activated state). In the case of the “feedback”, the outlet133of the booster valve130a,130bis connected to the control input132a,132bthereof, in order to sustain the switching state thereof stably. In the case of the “reversal” switching position, the control input132a,132bof the booster valve130a,130bis connected to a second 3/2-way solenoid valve120a,120b.

The second 3/2-way solenoid valve120a,120bcan now, in a first switching position, connect the control input132a,132bof the respective booster valve130a,130bto the atmosphere (venting), in order to switch the booster valve130a,130binto the venting position, or, in a second switching position, connect to a storage pressure (from the feed line105), in order to switch the booster130a,130binto the venting position.

The first 3/2-way solenoid valve110a,110bis in the de-energized state (stable state) in the “feedback” switching position. After the reversal of the booster valve130a,130b, the first 3/2-way solenoid valve110a,110bis firstly switched off again, so that it therefore automatically goes into the “feedback” switching position. After this, the switch position of the second 3/2-way solenoid valve120a,120bno longer has any influence.

Both booster valves130a,130band the 3/2-way solenoid valves110a,110bthereof can, for instance, be supplied pneumatically from the two storage circuits101,102by a shuttle valve150, as in conventional parking-brake systems.

The respective booster piston135a,135bis pushed in the “venting” direction by a spring136a,136b. As a result, the booster valve130a,130bcan only be in the aerating position if it holds that:
Storage pressure×Area of booster piston>Spring force.

If the storage pressure of both brake circuits101,102falls below this pressure, the corresponding booster130a,130bwill automatically go into the venting position after overcoming the friction (on piston135). Hence it is ensured that a vehicle that no longer has sufficient brake pressure for the service brake automatically comes to a halt with the parking brake.

The booster valve130a,130bmay, in addition, be present in two variants: with a central vent (seeFIG.3A) or with a side vent (seeFIG.3B). The second 3/2-way solenoid valve120can be switched in currentless manner to aerating. Alternatively, it is likewise possible that the second 3/2-way solenoid valve120is switched in currentless manner to venting.

With this parking-brake system and with a corresponding electronic control system in an electronic control unit (ECO) (for controlling the 3/2-way solenoid valves110,120) and also with two electrical push-buttons as human/machine interface (HMI), all the functions such as are known from conventional parking-brake systems, and also diverse additional automatic functions, can be carried out in software-controlled manner.

The features of the invention disclosed in the description, in the claims and in the figures may be essential, both individually and in arbitrary combination, for the realization of the invention.

LIST OF REFERENCE SYMBOLS

100A,100B electric parking-brake units101,102,501,502compressed-air supply105feed line107discharge line110,120,610,620first and second 3/2-way valves111,113,114ports of the first 3/2-way valve121,123,124ports of the second 3/2-way valve112,122electrical control terminals116,136biasing device130,630valve device131,133,631,632, . . . inlets132control input134,135piston of the valve device137,636spring140,660spring-type actuator150,550shuttle valve190,590vent240brake port for trailer505feed line507a,bparking-brake ports510,520manual valves560bypass unit639piston element662spring-loaded piston670brake componentA1, A2effective pressure areas