Compressed air brake system for a tractor

Abstract

The invention relates to a compressed-air brake system for a towing vehicle, having two service brake circuits, a parking brake circuit (18) with a compressed-air reservoir (52), a reservoir line (54) leading from the compressed-air reservoir to a parking brake valve (20), and a vehicle axle brake line (56) leading from the parking brake valve to a spring-loaded brake cylinder (60a, 60b), a trailer control valve (22) with at least one direct control input (p41, p42) and a reverse control input (p43), wherein a brake control line (82, 84) is coupled to the at least one direct control input, which brake control line is coupled to a brake line (36, 46) of one of the service brake circuits, a brake control line (86) is coupled to the reverse control input, which brake control line is coupled to the brake line (56) of the parking brake circuit, and a valve device (30) for controlling the brake of a coupled trailer vehicle independently of the foot brake valve. The valve device has an electronically controllable valve unit (100), which is arranged in the brake control line coupled to the reverse control input of the trailer control valve. By means of the valve unit, the section of the brake control line on the trailer control valve side can be connected alternately to the section on the parking brake valve side or to a venting output.

Description

Technical Field

[0001] This invention relates to a compressed air braking system for a tractor unit, comprising: two service brake circuits, each having a compressed air reservoir, a reserve 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 of respective vehicle axles connected to these wheel brake lines; and a parking brake circuit, comprising a third compressed air reservoir, a reserve 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 a wheel brake cylinder. The valve guides the spring-accumulated brake cylinders of the wheel brake lines and the vehicle axles connected to these wheel brake lines; and has a trailer control valve having at least one direct control input and a reverse control input, wherein a brake control line is connected to the at least one direct control input and is connected to the brake line of one of the two service brake circuits, and wherein a brake control line is connected to the reverse control input and is connected to the brake line of the parking brake circuit; and has a valve device for controlling braking of the coupled trailer vehicle independent of the foot brake valve. Background Technology

[0002] During normal braking operation, the combined braking of the vehicle consisting of the tractor (such as a truck or semi-trailer tractor) and trailer (such as a full trailer or semi-trailer) is typically achieved by means of a foot brake valve in the tractor unit. Through the foot brake valve, appropriate braking pressure is regulated from the reserve pressure waiting on the input side of the associated compressed air reservoir in each of the two service braking circuits, and this braking pressure is directed to the axle braking lines in the wheel brake cylinders of the tractor unit's front or rear axle via wheel braking lines. Braking of the trailer is achieved by intercepting braking pressure at at least one of the braking lines of the tractor unit's front or rear axle via a brake control line and directing it to the direct control output of the trailer control valve. In the trailer control valve, a braking control pressure is regulated based on this braking pressure, which acts as a control pressure, and this braking control pressure is directed to the coupling head "brake" (yellow) via the brake control output. This braking control pressure is converted into braking pressure for the wheel brakes in the trailer's trailer brake valve.

[0003] If a vehicle assembly is traveling downhill or on a slippery road due to dirt, wetness, or ice, the trailer may temporarily travel at a higher speed than the tractor unit. This often causes the vehicle assembly to veer around the trailer coupling, tie rod axis, or saddle coupling. To avoid this veer, a stretch brake is typically applied to the trailer, in which the vehicle assembly is straightened by operating the trailer's wheel brakes independently of the foot brake valves.

[0004] If braking of the trailer is desired independently of the foot brake valve, i.e., without operating the foot brake valve, this can, in principle, be achieved in two ways. Firstly, the trailer can be braked by directing a slightly higher braking control pressure via a brake control circuit and valve assembly to one of the two normally direct control inputs of the trailer control valve, which has at least one electronically controllable valve unit located in the brake control circuit. Secondly, the trailer can also be braked by forcefully bleeding the brake control circuit, which is inflated during driving and when the parking brake is released, via a valve assembly that has at least one electronically controllable valve unit located in the brake control circuit, through the reverse control input of the trailer control valve.

[0005] DE 10 2015 015 922 A1 describes a compressed air braking system for a tractor unit, wherein a brake control line is directed from the compressed air reservoir of the parking brake circuit to the first input of a shuttle valve via a switching valve configured as a 3 / 2 directional 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. A brake control line is directed from the output of this shuttle valve to one of the two direct control inputs of a trailer control valve. A valve unit is arranged in this brake control line, comprising an inlet valve configured as a 2 / 2 directional solenoid valve and an outlet valve configured as a 2 / 2 directional solenoid valve. By energizing the switching valve, the reserve pressure of the compressed air reservoir is directed via the shuttle valve to 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 in this brake control line.

[0006] According to DE 10 2006 054 433 A1, four implementation schemes of a tension brake device in a tractor's compressed air braking system are known, wherein a brake control line equipped with a valve device is directed from the compressed air reservoir of the parking brake circuit to the reverse control input of the trailer control valve. Based on that... Figure 1 In the first embodiment, the valve device has a valve unit configured as a 3 / 2 reversing solenoid valve. According to there... Figure 2In the second embodiment, in addition to the valve unit just mentioned, the valve device also has a shut-off valve located downstream of the valve unit, configured as a 2 / 2 reversing solenoid valve. According to there... Figure 3 In the third embodiment, the valve device has an electrically actuated electromagnetic relay valve. According to there... Figure 4 In the fourth embodiment, the valve assembly includes a pressure-controlled relay valve and a pilot valve configured as a 3 / 2 directional solenoid valve associated with the relay valve. The braking control pressure applied to the reverse control input of the trailer control valve can be modulated via the respective valve assemblies.

[0007] DE 10 2008 048 207 C5 illustrates and describes a compressed air braking system for a tractor unit, wherein a brake control line equipped with a valve device branches off from the compressed air reservoir of the parking brake circuit, and is directed on one hand to the control input of a pressure-controlled relay valve and on the other hand to the reverse control input of a trailer control valve. The valve device includes a valve unit configured as a 3 / 2 directional solenoid valve and a shut-off valve configured as a 2 / 2 directional solenoid valve downstream of the valve unit. The relay valve is arranged between a reservoir line connected to the compressed air reservoir and an axle brake line leading to a spring-loaded brake cylinder of the vehicle axle. Upstream of the control input of the relay valve is another shut-off valve configured as a 2 / 2 directional solenoid valve. The valve device is used not only to modulate the brake control pressure applied to the control input of the relay valve but also to modulate the brake control pressure applied to the reverse control input of the trailer control valve. To operate the trailer's wheel brakes in the extended braking function, firstly, the shut-off valve associated with the relay valve needs to be switched to its closed position, and the shut-off valve of the valve assembly needs to be switched to its open position. Next, the braking control pressure applied to the reverse control input of the trailer control valve is adjusted or modulated via the valve unit through more or less forceful venting. Summary of the Invention

[0008] Given the sometimes rather expensive structure and relatively complex controllability of the valve devices mentioned in compressed air braking systems, the objective of this invention is to provide a compressed air braking system having a valve device that is simple to construct and easy to control, by means of which a tension braking function independent of the foot brake valve can be implemented for braking a trailer coupled to a tractor.

[0009] The solution to this task is achieved using a compressed air braking device having the features of claim 1. Advantageous improvements to this compressed air braking device are defined in the dependent claims.

[0010] Therefore, the present invention relates to a compressed air braking system for a tractor unit, comprising: two service brake circuits, each service brake circuit having a compressed air reservoir, a reservoir 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 of respective vehicle axles connected to these wheel brake lines; and a parking brake circuit, the parking brake circuit having a third compressed air reservoir, a reservoir line leading from the third compressed air reservoir to a parking brake valve, and an axle brake line leading from the parking brake valve. The compressed air braking system includes spring-accumulated brake cylinders that lead to wheel brake lines and vehicle axles connected to these wheel brake lines; a trailer control valve having at least one direct control input and a reverse control input, wherein a brake control line is connected to the at least one direct control input and is connected to the brake line of one of two service brake circuits, and wherein a brake control line is connected to the reverse control input and is connected to the brake line of the parking brake circuit; and a valve device for controlling braking of the coupled trailer vehicle independent of the foot brake valve.

[0011] To address the proposed task, the compressed air braking system includes a valve device with an electronically controllable valve unit. This valve unit is arranged in a brake control circuit connected to the reverse control input of the trailer control valve. The valve unit has an input terminal; the section of the brake control circuit on the parking brake valve side is connected to this input terminal. The valve unit has an output terminal; the section of the brake control circuit on the trailer control valve side is connected to this output terminal. The valve unit also has an exhaust output terminal. Furthermore, the section of the brake control circuit on the trailer control valve side can be alternately connected via the valve unit to either the section on the parking brake valve side or the exhaust output terminal.

[0012] Because the valve assembly has an electronically controllable valve unit arranged in the manner described above in the brake control circuit leading to the reverse control input of the trailer control valve, the trailer vehicle can be braked easily and independently of the foot brake valve without impairing the function of the tractor's service brake circuit. This is achieved by connecting the section of the brake control circuit on the trailer control valve side to the exhaust output via the valve unit, thereby allowing exhaust from the reverse control input of the trailer control valve.

[0013] An improved embodiment of the compressed air braking device described herein may be configured such that the valve unit has an inlet valve and an outlet valve; the inlet valve is configured as a 2 / 2 reversing solenoid valve and is arranged between the input and output ends of the valve unit; and the outlet valve is configured as a 2 / 2 reversing solenoid valve and is arranged between the output end and the exhaust output end of the valve unit, wherein the input end of the valve unit is connected to the output end when the inlet valve is de-energized and is de-energized when the inlet valve is energized, and wherein the exhaust output end is de-energized when the outlet valve is de-energized and is connected to the output end when the outlet valve is energized.

[0014] Alternatively, the valve unit can be configured as a 3 / 2 directional solenoid valve having an input end, an output end, and an exhaust output end, wherein the input end of the valve unit is connected to the output end in the de-energized state and is cut off in the energized state, and wherein the exhaust output end is cut off in the de-energized state and connected to the output end in the energized state.

[0015] Based on similar functions, it is preferable that the valve unit is structurally identical to the ABS valve unit, which is arranged in the braking circuit of at least one wheel of the vehicle axle. The ABS valve unit is a type of valve unit that controls the function of the vehicle's long-known anti-lock braking system. This avoids unnecessary research and development costs and saves manufacturing and logistical costs due to the use of a larger number of identical parts. Attached Figure Description

[0016] To further illustrate the invention, accompanying drawings with two embodiments are attached to the specification.

[0017] in:

[0018] Figure 1 A schematic overview diagram illustrates a compressed air braking system of a tractor unit having a valve device according to the invention.

[0019] Figure 2 A schematic partial view of the compressed air braking device shows a first embodiment of the valve device according to the invention;

[0020] Figure 3 A schematic partial view of the compressed air braking device shows a second embodiment of the valve device according to the invention; and

[0021] Figure 4 The compressed air braking system of the tractor unit with known valve devices is shown in a schematic overview. Detailed Implementation

[0022] Therefore, in Figure 4The image depicts a compressed air braking system 10' for a tractor unit, which has a known valve device 30', used by the applicant to date, for braking the coupled trailer independently of a foot brake valve. Exemplarily, the tractor unit is implemented as a dual-axle vehicle and has: a front axle 2 having front wheels 4a, 4b arranged on both sides; and a rear axle 6 having rear wheels 8a, 8b arranged on both sides.

[0023] The compressed air braking system 10' includes: two service brake circuits 12 and 14, each equipped with a common foot brake valve 16; a parking brake circuit 18, equipped with a parking brake valve 20; a trailer control valve 22; a valve device 30'; an electronic brake control device 24; and four speed sensors 26a, 26b, 28a, 28b, which are located on the wheels 4a, 4b, 8a, 8b of the two vehicle axles 2 and 6 and connected to the brake control device 24 via electrical sensor wiring. To avoid confusing numerous reference numerals, the electrical sensor wiring of the speed sensors 26a, 26b, 28a, 28b, and other electrical sensor wiring and control wiring shown by dashed lines are... Figure 4 No reference numerals are provided for the attached figures.

[0024] The first service braking circuit 12 includes: a first compressed air reservoir 32, in which the compressed air stored is, for example, at a level of 13 × 10⁻⁶ under the current conditions. 5 The pressure of Pa; the first reservoir line 34 leading from the compressed air reservoir 32 to the foot brake valve 16; and the first axle brake line 36 leading from the foot brake valve 16 to the two wheel brake lines 38a, 38b and the wheel brake cylinders 40a, 40b of the rear axle 6 connected to the two wheel brake lines.

[0025] The second service brake circuit 14 includes a second compressed air reservoir 42, in which the stored compressed air is also at 13 × 10⁻⁶ under the current conditions. 5 The pressure of Pa; the second reservoir line 44 leading from the compressed air reservoir 42 to the foot brake valve 16; and the second axle brake line 46 leading from the foot brake valve 16 to the front wheel brake lines 48a, 48b and the wheel brake cylinders 50a, 50b of the front axle 2 connected to these front wheel brake lines.

[0026] The parking brake circuit 18 includes a third compressed air reservoir 52, in which the compressed air stored is, for example, at a level of 8.5 × 10⁻⁶ under the current conditions. 5The pressure of Pa; the third reservoir line 54 leading from the compressed air reservoir 52 to the parking brake valve 20; and the axle brake line 56 leading from the parking brake valve 20 to the wheel brake lines 58a, 58b and the spring-accumulated brake cylinders 60a, 60b of the rear axle 6 connected to these wheel brake lines. In the present case, the wheel brake cylinders 40a, 40b of the first service brake circuit 12, which are preferably configured as diaphragm brake cylinders, and the spring-accumulated brake cylinders 60a, 60b of the first parking brake circuit 18 are respectively assembled into combined brake cylinders and act on the same wheel brakes on the wheels 8a, 8b of the rear axle 6.

[0027] The axle braking line 46 of the second service braking circuit 14 is connected to the control input of the pressure-controlled first relay valve 64, instead of being directly branched into the front wheel braking lines 48a and 48b. The fourth accumulator line 62 is also directed to this pressure-controlled first relay valve, branching off from the second accumulator line 44 associated with the second compressed air reservoir 42. In the first relay valve 64, the air pressure applied at its control input is converted into braking pressure by increasing the air volume. This braking pressure is directed into the connected wheel braking lines 48a and 48b of the front axle 2. ABS valve units 66a and 66b are respectively arranged in the wheel braking lines 48a and 48b of the front axle 2, and these ABS valve units are connected to the control device 24 via electrical control lines. When the control unit 24 confirms that one of the wheels 4a and 4b of the front axle 2 is locked or has a tendency to lock up by evaluating the speed signals from the speed sensors 26a, 26b, 28a, and 28b, the braking pressure is reduced via the two ABS valve units 66a and 66b.

[0028] In the axle brake line 46 of the second service brake circuit 14, a switching valve 70 is also arranged. This switching valve is configured as a 3 / 2 reversing solenoid valve and is connected to the control device 24 via an electrical control line. The section 46a of the axle brake line 46 on the foot brake valve side is connected to the first input terminal of the switching valve 70. The fourth reserve line 68 is connected to the second input terminal of the switching valve 70, and this fourth reserve line branches off from the reserve line 54 connected to the compressed air reservoir 52 of the parking brake circuit 18. The section 46b of the axle brake line 46 on the relay valve side is connected to the control input terminal of the first relay valve 64.

[0029] When the switching valve 70 is de-energized, the first input terminal of the switching valve is connected to the output terminal of the switching valve 70, and the second input terminal is cut off. This causes the braking pressure, which is controlled to enter the axle braking line 46 in the section 46a on the foot brake valve side via the foot brake valve 16, to be applied to the control input terminal of the relay valve 64 via the section 46b on the relay valve side of the axle braking line 46. The corresponding braking pressure is controlled to enter the wheel braking lines 48a and 48b of the front axle 2.

[0030] When the switching valve 70 is energized and thus switched, the second input terminal of the switching valve is connected to the output terminal of the switching valve 70, and the first input terminal of the switching valve 70 is cut off. Therefore, the reserve pressure of the compressed air reservoir 52 of the parking brake circuit 18 is 8.5 × 10⁻⁶. 5 The level of Pa is applied to the control input of the relay valve 64, and the corresponding braking pressure is then controlled to enter the wheel braking lines 48a and 48b of the front axle 2.

[0031] Therefore, by switching the switching valve 70 as described, the wheels 4a and 4b of the front axle 2 can be braked independently of the operation of the foot brake valve 16, which can be used, for example, in conjunction with a distance assist system to avoid rear-end collisions during emergency braking of the tractor.

[0032] Similarly, the axle brake line 36 of the first service brake circuit 12 for the rear axle 6 is also connected to the control input of a pressure-controlled relay valve, instead of being directly branched into the wheel brake lines 38a and 38b. A fifth accumulator line 72 is directed to this pressure-controlled relay valve, branching off from the accumulator line 34 of the associated first compressed air accumulator 32. However, unlike the arrangement of the front axle 2, the relay valve for the rear axle 6 is located in the axle valve module 74. In this relay valve, the air pressure applied at the control input is converted into braking pressure by increasing the air volume, which is then directed to the wheel brake lines 38a and 38b of the connected brakes for the rear axle 6. ABS valve units are also arranged in these wheel brake lines 38a and 38b for the rear axle brakes, respectively. These ABS valve units are also located in the axle valve module 74 and connected to the control device 24 via electrical control lines. When the control unit 24 confirms, through evaluation of the speed signals from speed sensors 26a, 26b, 28a, and 28b, that one of the wheels 8a and 8b of the rear axle 6 is locked or has a tendency to lock up, the braking pressure is reduced via the unmarked ABS valve unit of the axle valve module 70.

[0033] Furthermore, the axle valve module 70 of the first service brake circuit 12 includes a switching valve (not separately labeled), which is configured as a 3 / 2 reversing solenoid valve and connected to the control device 24 via electrical control wiring. The first axle brake line 36 is connected to the first input terminal of the switching valve. A fifth accumulator line 72, branching from the accumulator line 34 of the associated first compressed air accumulator 32, is connected to the second input terminal of the switching valve. The output terminal of the switching valve is connected to the control input terminal of the relay valve.

[0034] When the switching valve is de-energized, the first input terminal of the switching valve is connected to the output terminal of the switching valve, and the second input terminal of the switching valve is cut off, so that the braking pressure controlled to enter the first axle braking circuit 36 ​​via the foot brake valve 16 is applied to the control input terminal of the relay valve, and the corresponding braking pressure is controlled to enter the wheel braking circuits 38a and 38b of the rear axle 6.

[0035] When the switching valve is energized and thus switched, the second input terminal of the switching valve is connected to the output terminal of the switching valve, and the first input terminal of the switching valve is cut off, thereby causing the storage pressure of the compressed air reservoir 32 of the first service brake circuit 12 to be 13 × 10⁻⁶. 5 The pressure Pa is applied to the control input of the relay valve, and the corresponding braking pressure is controlled to enter the wheel braking lines 38a and 38b of the rear axle 6. Therefore, by switching the switching valve, the wheels 8a and 8b of the rear axle 6 can be braked independently of the operation of the foot brake valve 16.

[0036] The axle brake line 56 of the parking brake circuit 18 is connected to the control input of the pressure-controlled second relay valve 78, instead of being directly branched into the rear wheel brake lines 58a, 58b. The sixth reservoir line 76 is also directed to this pressure-controlled second relay valve, branching off from the third reservoir 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 into brake release pressure in a manner that increases the air volume. This brake release pressure is directed to the connected wheel brake lines 58a, 58b and the spring-loaded brake cylinders 60a, 60b of the rear axle 6 connected to these wheel brake lines.

[0037] The trailer control valve 22 has: a reserve input terminal p13; two direct control input terminals p41 and p42; a reverse control input terminal p43; a reserve output terminal p21; a brake control output terminal p22; and an exhaust output terminal p3. A seventh reserve line 80 is connected to the reserve input terminal p13 of the trailer control valve 22, which branches off from the reserve 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 input terminal p41, which branches off from the section 48a' inside 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 terminal 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 reverse control input p43. This brake control line branches off from the axle brake line 56 of the parking brake circuit 18 for the rear axle 6.

[0038] An eighth reserve line 88 is routed from the reserve output p21 of the trailer control valve 22 to the coupling head "Reservoir" (red) 90. A brake control line 92 is routed from the brake control output p22 of the trailer control valve 22 to the coupling head "Brake" (yellow) 94. In the trailer control valve 22, a brake control pressure is regulated based on the brake control pressure or brake pressure applied at the direct control inputs p41 and p42 and based on the brake control pressure or brake release pressure applied at the reverse control input p43. This brake control pressure is routed via the brake control output p22 and the brake control line 92 to the coupling head "Brake" (yellow) 94 and, in the coupled trailer, to the brake pressure converted into braking pressure for the wheel brakes therein in the trailer brake valve.

[0039] The valve device 30' for braking the coupled trailer vehicle independently of the foot brake valve has an electronically controllable valve unit 96, which is arranged in the brake control line 82' that leads to the first direct control input p41 of the trailer control valve 22. The valve unit 96 has an input end, an output end, and an exhaust output end. A section of the brake control line 82' is connected to the input end on the brake line side, and a section of the brake control line 82' is connected to the output end on the trailer control valve side. Furthermore, the valve unit 96 is connected to the control device 24 via electrical control lines. To operate the valve unit 96, the valve device 30' is equipped with an electric operating unit 98, which is arranged in the cab of the tractor and connected to the control device 24 via electrical control lines.

[0040] When valve unit 96 of valve device 30' is not operated, i.e., not switched, the input end of the valve unit is connected to the output end of the valve unit and the exhaust output end is cut off, so that the braking pressure applied to the right wheel braking line 48a of the front axle 2 is also applied as braking control pressure to the first direct control input p41 of trailer control valve 22. When valve unit 96 is switched, the input end of the valve unit is cut off and the output end of the valve unit is connected to the exhaust output end, so that exhaust is subsequently emitted from the direct control input p41 of trailer control valve 22.

[0041] In order to enable braking of the coupled trailer, independent of the operation of the foot brake valve, particularly for tension braking, during the operation of the vehicle assembly using released wheel brakes, i.e., exhaust wheel brake cylinders 40a, 40b; 50a, 50b and spring-loaded brake cylinders 60a, 60b that guide pressure, in the known valve device 30', it is necessary to switch the switching valve 70 of the second service brake circuit 14 and the ABS valve units 66a, 66b of the front axle 2 to their exhaust positions.

[0042] As the switching valve 70 is switched, the reserve pressure from the third compressed air reservoir 52 of the parking brake circuit 18 is transferred to the control input of the first relay valve 64, thereby controlling the corresponding braking pressure to enter the wheel brake lines 48a and 48b of the front axle 2. With the ABS valve units 66a and 66b switched to their exhaust positions, the wheel brake cylinders 50a and 50b of the front axle 2 remain pressureless, thus preventing the wheels 4a and 4b of the front axle 2 from being braked. Therefore, braking or tension braking of the trailer can be achieved continuously or in a pulsed manner by repeatedly switching the valve unit 96 of the valve device 30'.

[0043] In particular, the arrangement of the brake control line 82' and the valve unit 96 of the valve device 30' is disadvantageous due to the high workload in control technology caused by the switching of the switching valve 70, the two ABS valve units 66a, 66b, and valve unit 96. Also disadvantageous is that when the driver operates the foot brake valve 16, for example during the trailer's extended braking, the wheels 4a, 4b of the front axle 2 are not braked. Although the operation of the foot brake valve 16 is detected via a sensor or brake light switch located in the foot brake valve and transmitted to the control device 24 via electrical sensor lines, the resulting switching of the switching valve 70, ABS valve units 66a, 66b, and valve unit 96 will result in an undesirable delayed response of the wheel brakes at the front axle 2.

[0044] exist Figure 1The image depicts a compressed air braking system 10 for a tractor unit, which has a valve device 30 according to the invention for braking the coupled trailer independently of the foot brake valve, thereby avoiding the aforementioned disadvantages.

[0045] In accordance with Figure 4 Compared to the compressed air braking system 10', which is largely identical in other respects, the brake control line 82, which is 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. Furthermore, the valve device 30 according to the invention for braking the coupled trailer independently of the foot brake valve also has electronically controllable valve units 100, 100', which are now arranged in the brake control line 86 leading to the reverse control input p43 of the trailer control valve 22. These valve units 100, 100' have an input 102, an output 104, and an exhaust output 106. A section 86a of the brake control line 86 on the parking brake valve side is connected to the input 102, and a section 86b of the brake control line 86 on the trailer control valve side is connected to the output 104. Furthermore, the valve units 100 and 100' are connected to the control device 24 via electrical control lines. As described above, the operation of the valve units 100 and 100' is achieved by means of an electric operating element 98, which is arranged in the driver's cab of the tractor and connected to the control device 24 via electrical control lines.

[0046] exist Figure 2 In the first embodiment schematically shown, valve unit 100 includes an inlet valve 108 and an outlet valve 110. The inlet valve 108 is configured as a 2 / 2 reversing solenoid valve and is arranged between the input terminal 102 and the output terminal 104 of valve unit 100. Similarly, the outlet valve 110 is configured as a 2 / 2 reversing solenoid valve and is arranged between the output terminal 104 and the exhaust output terminal 106 of valve unit 100. The input terminal 102 is connected to the output terminal 104 when the inlet valve 108 is de-energized and is de-energized when the inlet valve 108 is energized. The exhaust output terminal 106 of valve unit 100 is de-energized when the outlet valve 110 is de-energized and is connected to the output terminal 104 when the outlet valve 110 is energized.

[0047] exist Figure 3In the second embodiment schematically depicted, valve unit 100' is configured as a 3 / 2 reversing solenoid valve 112 having an input terminal 102, an output terminal 104, and an exhaust output terminal 106. The input terminal is connected to the output terminal 104 when the solenoid valve 100' is de-energized and is cut off when energized. The exhaust output terminal 106 of valve unit 100' is cut off when the solenoid valve 100' is de-energized and is connected to the output terminal 104 when energized.

[0048] Therefore, in the unoperated, i.e., unswitched state of the valve units 100, 100' according to the invention, the input terminal 102 is connected to the output terminal 104, and the exhaust output terminal 106 is cut off, so that the brake release pressure controlled to enter the brake control circuit 86 via the parking brake valve 20 is also applied as brake control pressure to the reverse control input terminal p43 of the trailer control valve 22. In the switched, i.e. operated state of these valve units 100, 100', the input terminal 102 of these valve units is cut off and the output terminal 104 of these valve units is connected to the exhaust output terminal 106, so that the reverse control input terminal p43 of the trailer control valve 22 is then vented.

[0049] In order to enable braking of the coupled trailer, independent of the operation of the foot brake valve, particularly for tension braking, during the operation of the vehicle assembly by releasing the wheel brakes, i.e., the exhaust wheel brake cylinders 40a, 40b; 50a, 50b and the pressure-guiding spring-loaded brake cylinders 60a, 60b, the valve device 30 according to the invention only requires switching the valve units 100, 100', which can be done continuously or in a pulse manner by repeated switching.

[0050] When the driver now operates the foot brake valve 16, for example, during the trailer's extension braking, the wheel brake cylinders 40a, 40b; 50a, 50b of the two vehicle axles 2, 6 are immediately loaded with braking pressure controlled by the foot brake valve 16 into the axle brake lines 36, 46, thereby braking the tractor. Then, braking of the trailer is achieved by over-controlling the brake release pressure applied at the reverse control input p43 through the braking pressure applied at the direct control inputs p41, p42 from the axle brake lines 36, 46 of the two service brake circuits 12, 14 in the trailer control valve 22.

[0051] List of reference numerals

[0052] 2. Vehicle axles, front axle

[0053] 4a, 4b Front wheels

[0054] 6. Vehicle axles, rear axle

[0055] 8a, 8b Rear wheels

[0056] 10, 10' Compressed air braking system

[0057] 12 First service brake circuit

[0058] 14 Second service brake circuit

[0059] 16-foot brake valve

[0060] 18 Parking brake circuit

[0061] 20 Parking brake valve

[0062] 22 Trailer control valve

[0063] 24 Electronic braking control equipment

[0064] 26a, 26b speed sensors

[0065] 28a, 28b speed sensors

[0066] 30, 30' valve device

[0067] 32 First Compressed Air Storage Unit

[0068] 34 First Reserve Circuit

[0069] 36 First Axle Braking Circuit

[0070] 38a, 38b Rear Wheel Braking Circuits

[0071] 40a and 40b rear wheel brake cylinders

[0072] 42 Second Compressed Air Storage Unit

[0073] 44 Second Reserve Circuit

[0074] 46 Second Axle Braking Circuit

[0075] 46a The section of the second axle braking line 46 on the foot brake valve side

[0076] 46b The section of the second axle braking line 46 on the relay valve side

[0077] 48a, 48b Front Wheel Braking Circuits

[0078] 48a'48a internal section

[0079] 50a and 50b front wheel brake cylinders

[0080] 52 Third Compressed Air Storage Unit

[0081] 54 Third Reserve Circuit

[0082] 56. Third Axle Braking Circuit

[0083] 58a, 58b wheel brake circuits

[0084] 60a and 60b spring-accumulated brake cylinders

[0085] 62. Reservoir Circuit

[0086] 64 First Relay Valve

[0087] 66a and 66b ABS valve units

[0088] 68. Fourth Reserve Circuit

[0089] 70 Switching valve, 3 / 2 reversing solenoid valve

[0090] 72. Fifth Reserve Circuit

[0091] 74 Axle Valve Module

[0092] 76. Sixth Reserve Circuit

[0093] 78 Second Relay Valve

[0094] 80 Seventh Reserve Circuit

[0095] 82, 82' Braking Control Circuit

[0096] 84 Braking control circuit

[0097] 86 Braking control circuit

[0098] The part of 86a 86 on the parking brake valve side

[0099] The part of 86b 86 on the trailer control valve side

[0100] 88 Eighth Reserve Circuit

[0101] 90 Coupler Head "Reservoir" (Red)

[0102] 92 Braking control circuit

[0103] 94 Coupler head "brake" (yellow)

[0104] 96 Valve Unit (Prior Art)

[0105] 98 operating units

[0106] 100, 100' valve unit

[0107] 102 100, 100' input terminals

[0108] 104 100, 100 output terminals

[0109] 106 100, 100 exhaust outlet

[0110] 108 Inlet valve, 2 / 2 reversing solenoid valve

[0111] 110 Outlet Valve, 2 / 2 Reversing Solenoid Valve

[0112] 112 Solenoid valve, 3 / 2 directional solenoid valve

[0113] p3 Trailer control valve 22 exhaust output end

[0114] p13 Reserve input terminal of trailer control valve 22

[0115] p21 Reserve output terminal of trailer control valve 22

[0116] p22 Trailer control valve 22 brake control output terminal

[0117] p41 First direct control input terminal of trailer control valve 22

[0118] p42 Second direct control input terminal of trailer control valve 22

[0119] p43 Reverse control input terminal of trailer control valve 22

Claims

1. A compressed air braking system (10, 10') for a tractor unit, the compressed air braking system comprising: a parking brake circuit (18) having a third compressed air reservoir (52), a reservoir line (54) extending from the third compressed air reservoir (52) to a parking brake valve (20), and an axle brake line (56) extending from the parking brake valve (20) to wheel brake lines (58a, 58b) and spring-loaded brake cylinders (60a, 60b) of a vehicle axle (6) connected to the wheel brake line; and a trailer control valve (22) having at least one direct control input (p41, p42) and a reverse control input (p43); and a valve device (30, 30') for controlling braking of the coupled trailer vehicle independent of the foot brake valve (16), wherein, The valve device (30) has electronically controlled valve units (100, 100'), and the valve units (100, 100') are arranged in a brake control line (86) connected to the reverse control input (p43) of the trailer control valve (22). The valve units (100, 100') have an input (102), an output (104), and an exhaust output (106). The section (86b) of the brake control line (86) on the trailer control valve side is connected to the output (104). The section (86b) of the brake control line (86) on the trailer control valve side can be alternately connected to the input (102) or the exhaust output (106) via the valve units (100, 100'). Its features are, The compressed air braking system (10, 10') has at least two service braking circuits (12, 14), each of which has a compressed air reservoir (32, 42), a reservoir line (34, 44) extending from the respective compressed air reservoir (32, 42) to the foot brake valve (16), and an axle brake line (36, 46) extending from the foot brake valve (16) to the wheel brake lines (38a, 38b; 48a, 48b) and to the wheel brake cylinders (40a, 40b; 50a, 50b) of the respective vehicle axles (2, 6) connected to the wheel brake lines. Among them, at least one direct control input terminal (p41, p42) of the trailer control valve (22) is connected to a brake control line (82, 82', 84) which is connected to the brake line (36, 46, 48a) of one of the two service brake circuits (12, 14); Furthermore, a brake control line (86) is connected to the reverse control input terminal (p43) of the trailer control valve (22) and to the brake line (56) of the parking brake circuit (18). Furthermore, the section (86a) of the brake control line (86) on the parking brake valve side is connected to the input terminal (102) of the valve unit (100, 100'); and the section (86b) of the brake control line (86) on the trailer control valve side can be alternately connected to the section (86a) on the parking brake valve side or to the exhaust output terminal (106) via the valve unit (100, 100').

2. The compressed air braking device according to claim 1, characterized in that, The valve unit (100) has an inlet valve (108) and an outlet valve (110). The inlet valve (108) is configured as a 2 / 2 reversing solenoid valve and is arranged between the input end (102) and the output end (104) of the valve unit (100). The outlet valve (110) is configured as a 2 / 2 reversing solenoid valve and is arranged between the output end (104) and the exhaust outlet end (106) of the valve unit (100). The input end (102) of the valve unit (100) is connected to the output end (104) when the inlet valve (108) is de-energized and is shut off when the inlet valve (108) is energized. The exhaust outlet end (106) is shut off when the outlet valve (110) is de-energized and is connected to the output end (104) when the outlet valve (110) is energized.

3. The compressed air braking device according to claim 1, characterized in that, The valve unit (100') is configured as a 3 / 2 reversing solenoid valve (112) having an input end (102), an output end (104) and an exhaust output end (106), wherein the input end (102) of the valve unit (100') is connected to the output end (104) in the de-energized state of the solenoid valve (112) and is cut off in the energized state, and wherein the exhaust output end (106) is cut off in the de-energized state of the solenoid valve (112) and is connected to the output end (104) in the energized state.

4. The compressed air braking device according to any one of claims 1 to 3, characterized in that, The valve units (100, 100') are designed in the same way as the ABS valve units (66a, 66b), and the ABS valve units are arranged in at least one wheel braking line (48a, 48b) of the vehicle axle (2).

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