AIR BRAKE SYSTEM OF A TOWING VEHICLE

Description

[0001] The invention relates to a compressed air brake system of a towing vehicle, with two service brake circuits, each having a compressed air reservoir, a supply line leading from the respective compressed air reservoir to a foot brake valve and an axle brake line leading from the foot brake valve to wheel brake lines and wheel brake cylinders connected thereto of a respective vehicle axle, as well as with a parking brake circuit, which has a third compressed air reservoir, a supply line leading from the third compressed air reservoir to a parking brake valve and an axle brake line leading from the parking brake valve to wheel brake lines and spring brake cylinders connected thereto of a vehicle axle, and with a trailer control valve, which has at least one direct control input and one inverted control input,wherein a brake control line connected to a brake line of one of the two service brake circuits is connected to the at least one direct control input, and wherein a brake control line connected to a brake line of the parking brake circuit is connected to the inverted control input, and with a valve device for controlling braking of a coupled trailer vehicle independent of the foot brake valve.

[0002] During normal braking, a vehicle combination consisting of a towing vehicle, such as a truck or semi-trailer, and a trailer, such as a drawbar trailer or semi-trailer, is usually braked by actuating a foot brake valve in the towing vehicle. Via the foot brake valve, a suitable brake pressure is controlled in two service brake circuits, each from a supply pressure present on the inlet side of an assigned compressed air reservoir, and fed into an axle brake line which leads via wheel brake lines to the wheel brake cylinders of the front or rear axle of the towing vehicle. The trailer is braked by tapping the brake pressure from at least one of the brake lines of the front or rear axle of the towing vehicle via a brake control line and feeding it to a direct control input of the trailer control valve.In the trailer control valve, a brake control pressure is generated depending on this brake pressure, which acts as the control pressure, and is fed via a brake control output to a "Brake" coupling head (yellow). This brake control pressure is converted into brake pressure for the wheel brakes in a trailer brake valve on the trailer vehicle.

[0003] When a vehicle combination is driving down a downhill slope or on a slippery road due to dirt, wet, or icy road surface, the trailer may briefly travel at a higher speed than the towing vehicle, which can often lead to the vehicle combination jackknifing around the trailer coupling or drawbar axle, or around the fifth wheel coupling. To prevent such jackknifing, the trailer is typically subjected to a lateral braking maneuver, in which the vehicle combination is pulled straight by applying the trailer's wheel brakes independently of the foot brake valve.

[0004] If the trailer vehicle is to be braked independently of the foot brake valve, i.e. without actuating the foot brake valve, this is basically possible in two ways. Firstly, the trailer vehicle can be braked by passing a more or less high brake control pressure via a brake control line and a valve device with at least one electronically controllable valve unit arranged in the brake control line to one of the usually two direct control inputs of the trailer control valve. In addition, the trailer vehicle can also be braked by more or less venting a brake control line leading to an inverted control input of the trailer control valve, which is ventilated while driving and with the parking brake disengaged, via a valve device with at least one electronically controllable valve unit arranged in the brake control line.

[0005] DE 10 2015 015 922 A1 describes a compressed air brake system for a towing vehicle, in which a brake control line is routed from the compressed air reservoir of a parking brake circuit to a first input of a shuttle valve via a switchover valve designed as a 3 / 2-way solenoid valve. A brake control line branching off from the axle brake line of the rear axle is connected to the other input of this shuttle valve. From the output of this shuttle valve, a brake control line is routed to one of the two direct control inputs of a trailer control valve. A valve unit is arranged in this brake control line, which comprises an inlet valve designed as a 2 / 2-way solenoid valve and an outlet valve designed as a 2 / 2-way solenoid valve. By energizing the switchover valve, the supply pressure of the compressed air reservoir is routed via the shuttle valve into the brake control line leading to the trailer control valve.The brake control pressure applied to the relevant control input can be modulated by means of the valve unit arranged therein.

[0006] From DE 10 2006 054 433 A1, four designs of a stretch braking device in a compressed air brake system of a towing vehicle are known, in which a brake control line provided with a valve device is led from the compressed air reservoir of a parking brake circuit to the inverted control input of a trailer control valve. In a first embodiment according to the Fig. 1 the valve device has a valve unit designed as a 3 / 2-way solenoid valve. In a second embodiment according to the Fig. 2 In addition to the valve unit just mentioned, the valve device also has a shut-off valve arranged downstream of the latter, designed as a 2 / 2-way solenoid valve. In a third embodiment according to the Fig. 3The valve device comprises an electrically controllable solenoid relay valve. In the fourth embodiment according to the Fig. 4 The valve device comprises a pressure-controlled relay valve and an associated pilot valve designed as a 3 / 2-way solenoid valve. The brake control pressure applied to the inverted control input of the trailer control valve can be adjusted via the respective valve device.

[0007] DE 10 2008 048 207 C5 shows and describes a compressed air brake system for a towing vehicle, in which a brake control line, provided with a valve device, branches from a compressed air reservoir of a parking brake circuit and is led, on the one hand, to the control input of a pressure-controlled relay valve and, on the other hand, to the inverted control input of a trailer control valve. The valve device comprises a valve unit designed as a 3 / 2-way solenoid valve and, downstream of the valve unit, a shut-off valve designed as a 2 / 2-way solenoid valve. The relay valve is arranged between a supply line connected to the compressed air reservoir and an axle brake line leading to the spring-loaded brake cylinders of a vehicle axle. A further shut-off valve designed as a 2 / 2-way solenoid valve is connected upstream of the control input of the relay valve.The valve assembly serves both to adjust the brake control pressure applied to the control input of the relay valve and to adjust the brake control pressure applied to the inverted control input of the trailer control valve. To actuate the wheel brakes of the trailer vehicle in a braking function, the shut-off valve assigned to the relay valve must first be switched to its closed position and the shut-off valve of the valve assembly must first be switched to its open position. The adjustment or modulation of the brake control pressure applied to the inverted control input of the trailer control valve by varying the venting force is then performed via the valve assembly.

[0008] In view of the sometimes quite complex construction and the relatively complicated controllability of the said valve devices of compressed air brake systems, the object of the present invention is to present a compressed air brake system with a simply constructed and easily controllable valve device, by means of which a foot brake valve-independent extension braking function for braking a trailer vehicle coupled to a towing vehicle can be carried out.

[0009] This problem is solved by a compressed air brake system according to claim 1. Exchange page 5 and 5a (fair copy)

[0010] Accordingly, the invention relates to a compressed air brake system of a towing vehicle, comprising a parking brake circuit having a third compressed air reservoir, a supply line leading from the third compressed air reservoir to a parking brake valve, and an axle brake line leading from the parking brake valve to wheel brake lines and spring brake cylinders of a vehicle axle connected thereto, and comprising a trailer control valve having at least one direct control input and an inverted control input, as well as a valve device for controlling braking of a coupled trailer vehicle independent of the foot brake valve, wherein the valve device comprises an electronically controllable valve unit, and this valve unit is arranged in the brake control line connected to the inverted control input of the trailer control valve, and the valve unit has an inlet, an outlet, and a vent outlet,wherein the trailer control valve-side section of the brake control line is connected to the outlet, and wherein the trailer control valve-side section of the brake control line can be alternately connected to the inlet or to the vent outlet via the valve unit.

[0011] To achieve the stated object, this compressed air brake system is provided with at least two service brake circuits, each having a compressed air reservoir, a supply line leading from the respective compressed air reservoir to a foot brake valve, and an axle brake line leading from the foot brake valve to wheel brake lines and wheel brake cylinders connected to these of a respective vehicle axle, wherein a brake control line connected to a brake line of one of the two service brake circuits is connected to the at least one direct control input of the trailer control valve, and wherein a brake control line connected to a brake line of the parking brake circuit is connected to the inverted control input of the trailer control valve, and wherein a parking brake valve-side section of the brake control line is connected to the input of the valve unit.

[0012] Because the valve device has an electronically controllable valve unit, which in the manner mentioned is connected to the inverted control input of the

[0013] By utilizing the brake control line routed to the trailer control valve, the trailer vehicle can be braked easily and independently of the foot brake valve without impairing the function of the towing vehicle's service brake circuits. This is achieved by connecting the section of the brake control line on the trailer control valve side to the vent outlet via the valve unit, thus venting the inverted control input of the trailer control valve.

[0014] According to a further development of the described compressed air brake system, it can be provided that the valve unit has an inlet valve and an outlet valve, that the inlet valve is designed as a 2 / 2-way solenoid valve and is arranged between the inlet and the outlet of the valve unit, and that the outlet valve is designed as a 2 / 2-way solenoid valve and is arranged between the outlet and the vent outlet of the valve unit, wherein the inlet of the valve unit is connected to the outlet when the inlet valve is not energized and is blocked when the inlet valve is energized, and wherein the vent outlet is blocked when the outlet valve is not energized and is connected to the outlet when the outlet valve is energized.

[0015] Alternatively, it can be provided that the valve unit is designed as a 3 / 2-way solenoid valve with an inlet, an outlet and a vent outlet, wherein the inlet of the valve unit is connected to the outlet in the de-energized state of this solenoid valve and is blocked in the energized state, and wherein the vent outlet is blocked in the de-energized state of this solenoid valve and is connected to the outlet in the energized state.

[0016] Due to a similar function, it is preferably provided that the valve unit is constructed identically to an ABS valve unit, which is arranged in at least one wheel brake line of a vehicle axle. An ABS valve unit is a valve unit by means of which the function of a long-established anti-lock braking system of the vehicle can be controlled. This avoids unnecessary development costs and saves manufacturing and logistics costs due to the higher number of identical parts used.

[0017] To further clarify the invention, a drawing with two embodiments is attached to the description. Fig. 1 a compressed air brake system of a towing vehicle with a valve device according to the invention in a schematic overview, Fig. 2 a first embodiment of the valve device according to the invention in a schematic partial view of the compressed air brake system, Fig. 3 a second embodiment of the valve device according to the invention in a schematic partial view of the compressed air brake system, and Fig. 4 a compressed air brake system of a towing vehicle with a known valve device in a schematic overview.

[0018] In the Fig. 4 Accordingly, a compressed air brake system 10' of a towing vehicle with a known valve device 30' previously used by the applicant for braking a coupled trailer vehicle independently of the foot brake valve is depicted. The towing vehicle is, for example, designed with two axles and has a front axle 2 with front wheels 4a, 4b arranged on both sides and a rear axle 6 with rear wheels 8a, 8b arranged on both sides.

[0019] The compressed air brake system 10' comprises two service brake circuits 12, 14, to which a common foot brake valve 16 is assigned, a parking brake circuit 18, to which a parking brake valve 20 is assigned, a trailer control valve 22, the valve device 30', an electronic brake control unit 24, and four speed sensors 26a, 26b; 28a, 28b, which are arranged on the wheels 4a, 4b; 8a, 8b of the two vehicle axles 2, 6 and are connected to the brake control unit 24 via electrical sensor lines. To avoid a confusingly high number of reference symbols, the electrical sensor lines of the speed sensors 26a, 26b; 28a, 28b, as well as other electrical sensor lines and control lines, which are each represented by dashed lines, are shown in the Fig. 4 not provided with reference symbols.

[0020] The first service brake circuit 12 comprises a first compressed air reservoir 32, in which the stored compressed air is, in the present case, for example, at a pressure of 13 × 10 5< Pa, a first supply line 34 leading from this compressed air reservoir 32 to the foot brake valve 16, and a first axle brake line 36 leading from the foot brake valve 16 to two wheel brake lines 38a, 38b and wheel brake cylinders 40a, 40b of the rear axle 6 connected to them.

[0021] The second service brake circuit 14 comprises a second compressed air reservoir 42, in which the stored compressed air is also presently under a pressure of 13 × 10 5< Pa, a second supply line 44 leading from this compressed air reservoir 42 to the foot brake valve 16, and a second axle brake line 46 leading from the foot brake valve 16 to front wheel brake lines 48a, 48b and wheel brake cylinders 50a, 50b of the front axle 2 connected thereto.

[0022] The parking brake circuit 18 comprises a third compressed air reservoir 52, in which the stored compressed air is, in the present case, for example, at a pressure of 8.5 × 10 5< Pa, a third supply line 54 led from this compressed air reservoir 52 to the parking brake valve 20, and an axle brake line 56 led from the parking brake valve 20 to wheel brake lines 58a, 58b and spring brake cylinders 60a, 60b of the rear axle 6 connected to them. The wheel brake cylinders 40a, 40b of the first service brake circuit 12, which are preferably designed as diaphragm brake cylinders, and the spring brake cylinders 60a, 60b of the parking brake circuit 18 are each combined in the present case as combination brake cylinders and act on the same wheel brakes on the wheels 8a, 8b of the rear axle 6.

[0023] Instead of branching directly into the front wheel brake lines 48a, 48b, the axle brake line 46 of the second service brake circuit 14 is connected to the control input of a pressure-controlled first relay valve 64, to which a fourth supply line 62 is also routed, branching off from the second supply line 44 assigned to the second compressed air reservoir 42. In the first relay valve 64, the air pressure applied to its control input is converted, with air volume amplified, into a brake pressure, which is fed into the connected wheel brake lines 48a, 48b of the front axle 2. An ABS valve unit 66a, 66b is arranged in each of the wheel brake lines 48a, 48b of the front axle 2, each of which is connected to the control unit 24 via an electrical control line.The respective brake pressure is reduced via the two ABS valve units 66a, 66b if, by evaluating the speed signals of the speed sensors 26a, 26b, 28a, 28b in the control unit 24, a locking or a tendency to lock of one of the wheels 4a, 4b of the front axle 2 is detected.

[0024] Also arranged in the axle brake line 46 of the second service brake circuit 14 is a switching valve 70, which is designed as a 3 / 2-way solenoid valve and is connected to the control unit 24 via an electrical control line. The foot brake valve-side section 46a of the axle brake line 46 is connected to a first inlet of the switching valve 70. A fourth supply line 68, which branches off from the supply line 54 connected to the compressed air reservoir 52 of the parking brake circuit 18, is connected to a second inlet of the switching valve 70. The relay valve-side section 46b of the axle brake line 46 is connected to the control inlet of the first relay valve 64.

[0025] In the de-energized state of the changeover valve 70, its first input is connected to the output of the changeover valve 70 and the second input is blocked, so that the brake pressure introduced via the foot brake valve 16 into the foot brake valve-side section 46a of the axle brake line 46 is then applied to the control input of the relay valve 64 via the relay valve-side section 46b of the axle brake line 46, and a corresponding brake pressure is introduced into the wheel brake lines 48a, 48b of the front axle 2.

[0026] When the switching valve 70 is energized and thus switched, its second input is connected to the output of the switching valve 70, and the first input of the switching valve 70 is closed. As a result, the supply pressure of the compressed air reservoir 52 of the parking brake circuit 18, at a level of 8.5 × 10 5 Pa, is applied to the control input of the relay valve 64, and a corresponding brake pressure is then fed into the wheel brake lines 48a, 48b of the front axle 2.

[0027] By switching the switching valve 70 as described, the wheels 4a, 4b of the front axle 2 can thus be braked independently of an actuation of the foot brake valve 16, which can be used, for example, to avoid a rear-end collision in conjunction with a distance assistance system for emergency braking of the towing vehicle.

[0028] Similarly, the axle brake line 36 of the first service brake circuit 12 for the wheels of the rear axle 6 is connected to the control input of a pressure-controlled relay valve, instead of directly branching into the wheel brake lines 38a, 38b, to which a fifth supply line 72 is led, branching off from the supply line 34 of the associated first compressed air reservoir 32. In contrast to the arrangement for the front axle 2, however, the relay valve for the rear axle 6 is arranged in an axle valve module 74. In the relay valve, the air pressure present at the control input is converted, with air volume amplified, into a brake pressure, which is fed into the connected wheel brake lines 38a, 38b for the brakes of the rear axle 6.In each of these wheel brake lines 38a, 38b for the rear axle brakes, an ABS valve unit is also arranged, which is also arranged in the axle valve module 74 and is connected to the control unit 24 via an electrical control line. The respective brake pressure is reduced via the ABS valve units of the axle valve module 70, which are not separately designated, when the control unit 24 detects locking or a tendency to lock of one of the wheels 8a, 8b of the rear axle 6 through the evaluation of the speed signals from the speed sensors 26a, 26b, 28a, 28b.

[0029] The axle valve module 70 of the first service brake circuit 12 also contains a switchover valve (not specifically designated), which is designed as a 3 / 2-way solenoid valve and is connected to the control unit 24 via an electrical control line. The first axle brake line 36 is connected to a first input of this switchover valve. The fifth supply line 72, branching off from the supply line 34 of the associated first compressed air reservoir 32, is connected to a second input of the switchover valve. The output of the switchover valve is connected to the control input of the relay valve.

[0030] When the changeover valve is de-energized, its first input is connected to the output of the changeover valve and the second input of the changeover valve is blocked, so that the brake pressure introduced into the first axle brake line 36 via the foot brake valve 16 is applied to the control input of the relay valve and a corresponding brake pressure is introduced into the wheel brake lines 38a, 38b of the rear axle 6.

[0031] When the changeover valve is energized and thus switched, the second inlet of the changeover valve is connected to the outlet of the changeover valve and the first inlet of the changeover valve is blocked, so that the supply pressure of the compressed air reservoir 32 of the first service brake circuit 12 in the amount of 13 × 10 5< Pa is applied to the control input of the relay valve and a corresponding brake pressure is fed into the wheel brake lines 38a, 38b of the rear axle 6. By switching the changeover valve, the wheels 8a, 8b of the rear axle 6 can also be braked independently of actuation of the foot brake valve 16.

[0032] Instead of directly branching into the rear wheel brake lines 58a, 58b, the axle brake line 56 of the parking brake circuit 18 is connected to the control input of a pressure-controlled second relay valve 78, to which a sixth supply line 76 is also routed, branching off from the third supply line 54 associated with the third compressed air reservoir 52. In the second relay valve 78, the air pressure applied to its control input is converted, with air volume amplified, into a brake release pressure, which is fed into the connected wheel brake lines 58a, 58b and the spring brake cylinders 60a, 60b of the rear axle 6 connected to them.

[0033] The trailer control valve 22 has a supply inlet p13, two direct control inlets p41, p42, an inverted control inlet p43, a supply outlet p21, a brake control outlet p22, and a vent outlet p3. A seventh supply line 80 is connected to the supply inlet p13 of the trailer control valve 22, which branch off from the supply line 54 connected to the third compressed air reservoir 52 of the parking brake circuit 18. A brake control line 82' is connected to the first direct control inlet p41, which branch off from the inner section 48a' of the wheel brake line 48a located between the first relay valve 64 and the ABS valve unit 66a of the right wheel brake line 48a of the front axle 2. A brake control line 84 is connected to the second direct control input p42, which branches off from the axle brake line 36 of the first service brake circuit 12 for the brakes of the rear axle 6.A brake control line 86 is connected to the inverted control input p43, which branches off from the axle brake line 56 of the parking brake circuit 18 for the brakes of the rear axle 6.

[0034] An eighth supply line 88 leads from the supply output p21 of the trailer control valve 22 to a "supply" coupling head (red) 90. A brake control line 92 leads from the brake control output p22 of the trailer control valve 22 to a "brake" coupling head (yellow) 94. In the trailer control valve 22, a brake control pressure is controlled depending on the brake control pressures or brake pressures present at the direct control inputs p41, p42 and depending on the brake control pressure or brake release pressure present at the inverted control input p43. This brake control pressure is routed via the brake control output p22 and the brake control line 92 to the "brake" coupling head (yellow) 94 and, in a coupled trailer vehicle, is converted into a brake pressure for the wheel brakes in the trailer brake valve there.

[0035] The valve device 30' for foot brake valve-independent braking of a coupled trailer vehicle has an electronically controllable valve unit 96, which is arranged in the brake control line 82' leading to the first direct control input p41 of the trailer control valve 22. This valve unit 96 has an inlet, an outlet, and a vent outlet. The brake line-side section of the brake control line 82' is connected to the inlet, and the trailer control valve-side section of the brake control line 82' is connected to the outlet. Furthermore, this valve unit 96 is connected to the control unit 24 via an electrical control line. To actuate the valve unit 96, the valve device 30' is assigned an electrical operating unit 98, which is arranged in the driver's cab of the towing vehicle and is connected to the control unit 24 via an electrical control line.

[0036] In the unactuated, i.e., non-switched, state of the valve unit 96 of the valve device 30', its inlet is connected to its outlet and the vent outlet is blocked, so that the brake pressure present in the right wheel brake line 48a of the front axle 2 is also present as brake control pressure at the first direct control inlet p41 of the trailer control valve 22. In the switched state of the valve unit 96, its inlet is blocked and its outlet is connected to the vent outlet, so that the direct control inlet p41 of the trailer control valve 22 is then vented.

[0037] In order to be able to brake a coupled trailer vehicle independently of actuation of the foot brake valve, in particular to carry out a stretch braking maneuver, while the vehicle combination is traveling with released wheel brakes, i.e. vented wheel brake cylinders 40a, 40b; 50a, 50b and pressure-bearing spring brake cylinders 60a, 60b, this known valve device 30' requires switching the switching valve 70 of the second service brake circuit 14 and switching the ABS valve units 66a, 66b of the front axle 2 to their venting position.

[0038] When the switching valve 70 is switched, the supply pressure from the third compressed air reservoir 52 of the parking brake circuit 18 is switched to the control input of the first relay valve 64, so that a corresponding brake pressure is introduced into the wheel brake lines 48a, 48b of the front axle 2. When the ABS valve units 66a, 66b are switched to their venting position, the wheel brake cylinders 50a, 50b of the front axle 2 are kept depressurized so that the wheels 4a, 4b of the front axle 2 are not braked. The braking or anti-skid braking of the trailer vehicle by switching the valve unit 96 of the valve device 30' can then be carried out continuously or in pulsed fashion through repeated switching.

[0039] A disadvantage of this arrangement, particularly of the brake control line 82' and the valve unit 96 of the valve device 30', is the high control complexity required for switching the switching valve 70, the two ABS valve units 66a, 66b, and the valve unit 96. Another disadvantage is that the wheels 4a, 4b of the front axle 2 are not braked if the driver, for example, actuates the foot brake valve 16 during a sudden braking maneuver of the trailer. Actuation of the foot brake valve 16 is detected by a sensor or brake light switch arranged therein and transmitted to the control unit 24 via an electrical sensor line. However, a resulting switching of the switching valve 70, the ABS valve units 66a, 66b, and the valve unit 96 leads to a disadvantageously delayed response of the wheel brakes on the front axle 2.

[0040] In the Fig. 1a compressed air brake system 10 of a towing vehicle with a valve device 30 according to the invention for braking a coupled trailer vehicle independently of the foot brake valve is shown, with which the disadvantages just mentioned are avoided.

[0041] When compared with the air brake system 10' according to Fig. 4With the compressed air brake system 10 otherwise largely identical in structure, the brake control line 82 connected to the first direct control input p41 of the trailer control valve 22 is now connected to the axle brake line 46 of the second service brake circuit 14 or the front axle 2. In addition, the valve device 30 according to the invention for braking a coupled trailer vehicle independently of the foot brake valve has an electronically controllable valve unit 100, 100', which is now arranged in the brake control line 86 leading to the inverted control input p43 of the trailer control valve 22. This valve unit 100, 100' has an inlet 102, an outlet 104, and a vent outlet 106. The parking brake valve-side section 86a of the brake control line 86 is connected to the inlet 102, and the trailer control valve-side section 86b of the brake control line 86 is connected to the outlet 104.Furthermore, this valve unit 100, 100' is connected to the control unit 24 via an electrical control line. This valve unit 100, 100' is actuated, as previously described, by means of the electrical operating element 98, which is arranged in the driver's cab of the towing vehicle and is connected to the control unit 24 via an electrical control line.

[0042] In a Fig. 2In the schematically illustrated first embodiment, the valve unit 100 comprises an inlet valve 108 and an outlet valve 110. The inlet valve 108 is designed as a 2 / 2-way solenoid valve and is arranged between the inlet 102 and the outlet 104 of the valve unit 100. The outlet valve 110 is also designed as a 2 / 2-way solenoid valve and is arranged between the outlet 104 and the vent outlet 106 of the valve unit 100. The inlet 102 is connected to the outlet 104 when the inlet valve 108 is not energized and is blocked when the inlet valve 108 is energized. The vent outlet 106 of the valve unit 100 is blocked when the outlet valve 110 is not energized and is connected to the outlet 104 when the outlet valve 110 is energized.

[0043] In the Fig. 3In the schematically illustrated second embodiment, the valve unit 100' is designed as a 3 / 2-way solenoid valve 112 with an inlet 102, an outlet 104, and a vent outlet 106. The inlet is connected to the outlet 104 when the solenoid valve 100' is de-energized and is blocked when energized. The vent outlet 106 of the valve unit 100' is blocked when the solenoid valve 100' is de-energized and connected to the outlet 104 when energized.

[0044] In the unactuated, i.e., non-switched, state of the two valve units 100, 100' according to the invention, the inlet 102 is thus connected to the outlet 104 and the vent outlet 106 is blocked, so that the brake release pressure introduced into the brake control line 86 via the parking brake valve 20 is also present as brake control pressure at the inverted control inlet p43 of the trailer control valve 22. In the switched, i.e., actuated, state of these valve units 100, 100', their inlet 102 is blocked and their outlet 104 is connected to the vent outlet 106, so that the inverted control inlet p43 of the trailer control valve 22 is then vented.

[0045] In order to be able to brake a coupled trailer vehicle independently of actuation of the foot brake valve, in particular to carry out a stretch braking operation, while the vehicle combination is traveling with released wheel brakes, i.e. vented wheel brake cylinders 40a, 40b; 50a, 50b and pressure-bearing spring brake cylinders 60a, 60b, only the switching of the valve unit 100, 100' is required in the valve device 30 according to the invention, which can be done continuously or in a pulsed manner by repeated switching.

[0046] If the driver now actuates the foot brake valve 16, for example, during a braking maneuver of the trailer, the wheel brake cylinders 40a, 40b; 50a, 50b of both vehicle axles 2, 6 are immediately subjected to the brake pressures introduced into the axle brake lines 36, 46 via the foot brake valve 16, thus braking the towing vehicle. The trailer is then braked by overriding the brake release pressure present at the inverted control input p43 in the trailer control valve 22 by the brake pressures present at the direct control inputs p41, p42 from the axle brake lines 36, 46 of the two service brake circuits 12, 14. List of reference symbols (part of the description)

[0047] 2Vehicle axle, front axle 4a, 4bFront wheels 6Vehicle axle, rear axle 8a, 8bRear wheels 10, 10'Air brake system 12First service brake circuit 14Second service brake circuit 16Foot brake valve 18Parking brake circuit 20Parking brake valve 22Trailer control valve 24Electronic brake control unit 26a, 26bSpeed ​​sensors 28a, 28bSpeed ​​sensors 30, 30'Valve device 32First compressed air reservoir 34First supply line 36First axle brake line 38a, 38bRear wheel brake lines 40a, 40bRear wheel brake cylinder 42Second compressed air reservoir 44Second supply line 46Second axle brake line 46aFoot brake valve side section of the second axle brake line 46 46bRelay valve side section of the second axle brake line 46 48a, 48bFront wheel brake lines 48a'Inner section of 48a 50a, 50bFront wheel brake cylinders 52Third compressed air reservoir 54Third supply line 56Third axle brake line 58a, 58bWheel brake lines 60a, 60bSpring brake cylinder 62Supply line 64First relay valve 66a,66bABS valve units 68Fourth supply line 70Changeover valve, 3 / 2-way solenoid valve 72Fifth supply line 74Axle valve module 76Sixth supply line 78Second relay valve 80Seventh supply line 82, 82'Brake control line 84Brake control line 86Brake control line 86aParking brake valve side section of 86 86bTrailer control valve side section of 86 88Eighth supply line 90Coupling head "Supply" (red) 92Brake control line 94Coupling head "Brake" (yellow) 96Valve unit (state of the art) 98Operating unit 100, 100'Valve unit 102Inlet of the 100, 100' 104Outlet of the 100, 100 106Vent outlet of the 100, 100 108Inlet valve, 2 / 2-way solenoid valve 110Exhaust valve, 2 / 2-way solenoid valve 112Solenoid valve,3 / 2-way solenoid valve p3Vent output of trailer control valve 22 p13Supply input of trailer control valve 22 p21Supply output of trailer control valve 22 p22Brake control output of trailer control valve 22 p41First direct control input of trailer control valve 22 p42Second direct control input of trailer control valve 22 p43Inverted control input of trailer control valve 22,

Claims

1. Compressed air braking system (10, 10') of a towing vehicle, comprising a parking brake circuit (18) having a third compressed air reservoir (52), a supply line (54) leading from the third compressed air reservoir (52) to a parking brake valve (20), and an axle brake line (56) leading from the parking brake valve (20) to wheel brake lines (58a, 58b) and to spring brake actuators (60a, 60b), attached thereto, of a vehicle axle (6), the compressed air braking system also comprising a trailer control valve (22) having at least one direct control input (p41, p42) and one inverted control input (p43), and comprising a valve apparatus (30, 30') for controlling braking, which is independent of a foot brake valve (16), of a coupled trailer vehicle, the valve apparatus (30) having an electronically controllable valve unit (100, 100'), and the valve unit (100, 100') being arranged in the brake control line (86) attached to the inverted control input (p43) of the trailer control valve (22), the valve unit (100, 100') having an input (102), an output (104) and a vent output (106), the trailer control valve-side portion (86b) of the brake control line (86) being attached to the output (104), and the trailer control valve-side portion (86b) of the brake control line (86) being connectable alternately to the input (102) or to the vent output (106) via the valve unit (100, 100'), characterized in that the compressed air braking system (10, 10') comprises at least two service brake circuits (12, 14), each having a compressed air reservoir (32, 42), a supply line (34, 44) leading from the relevant compressed air reservoir (32, 42) to the foot brake valve (16), and an axle brake line (36, 46) leading from the foot brake valve (16) to wheel brake lines (38a, 38b; 48a, 48b) and to wheel brake actuators (40a, 40b; 50a, 50b), attached thereto, of a relevant vehicle axle (2, 6), a brake control line (82, 82', 84) attached to a brake line (36, 46, 48a) of one of the two service brake circuits (12, 14) being attached to the at least one direct control input (p41, p42) of the trailer control valve (22), and in that a brake control line (86) attached to a brake line (56) of the parking brake circuit (18) is attached to the at the inverted control input (p43) of the trailer control valve (22), and in that a parking brake valve-side portion (86a) of the brake control line (86) is attached to the input (102) of the valve unit (102).

2. Compressed air braking system according to claim 1, characterized in that the valve unit (100) comprises an inlet valve (108) and an outlet valve (110), in that the inlet valve (108) is designed as a 2 / 2-way solenoid valve and is arranged between the input (102) and the output (104) of the valve unit (100), and in that the outlet valve (110) is designed as a 2 / 2-way solenoid valve and is arranged between the output (104) and the vent output (106) of the valve unit (100), the input (102) of the valve unit (100) being connected to the output (104) when the inlet valve (108) is de-energized and being blocked when the inlet valve (108) is energized, and the vent output (106) being blocked when the outlet valve (110) is de-energized and being connected to the output (106) when the outlet valve (110) is energized.

3. Compressed air braking system according to claim 1, characterized in that the valve unit (100') is designed as a 3 / 2-way solenoid valve (112) comprising an input (102), an output (104) and a vent output (106), the input (102) of the valve unit (100') being connected to the output (104) when this solenoid valve (112) is de-energized and being blocked when the solenoid valve is energized, and the vent output (106) being blocked when this solenoid valve (112) is de-energized and being connected to the output (104) when the solenoid valve is energized.

4. Compressed air braking system according to any of claims 1 to 3, characterized in that the valve unit (100, 100') is designed to be structurally identical to an ABS valve unit (66a, 66b) which is arranged in at least one wheel brake line (48a, 48b) of a vehicle axle (2).