Trailer with electromagnetic valve assembly and method for controlling the electromagnetic valve assembly of the trailer

Description

[0001] The invention relates to a multi-axle trailer with an electromagnetic valve arrangement, controllable by an electronic control unit, for controlling a trailing axle. The trailing axle is arranged on the trailer, viewed in the forward direction, in front of or behind a main axle. It is supported on the trailer frame by at least one bellows and can be raised or lowered by means of at least one lifting bellows. The valve arrangement is designed such that the bellows pressure in the supporting bellows and the pressure in the lifting bellows can be adjusted independently of one another, and the trailing axle is automatically lowered to the road surface when the power supply is switched off. The invention also relates to a method for controlling such a valve arrangement.

[0002] A trailing axle of a vehicle can be positioned in front of or behind the drive axle of a motor vehicle. In a trailer, such a trailing axle can be positioned in front of or behind a non-driven main axle when viewed in the forward direction.

[0003] If such a trailing axle is air-sprung, i.e., supported by at least one bellows on the vehicle frame, the axle load acting on the trailing axle can be reduced by venting its bellows and increased by inflating them. When the vehicle is loaded, the bellows pressure in the bellows of a trailing axle is normally set to the bellows pressure in the bellows of a drive axle or main axle, so that the load and the vehicle's own weight are distributed evenly across all axles.

[0004] When the vehicle is unloaded, the air spring pressure in the trailing axle's air springs is advantageously reduced to minimize tire wear, particularly on the trailing axle's wheels, and to allow for tighter turning radii during maneuvering. Similarly, when starting under difficult traction conditions, the air spring pressure of a trailing axle can be reduced to increase the axle load on the drive axle and thus improve its traction. On a semi-trailer or center-axle trailer, the air spring pressure in the trailing axle's air springs can be reduced or increased for the same purpose, depending on the air spring configuration. This increases the axle load on the drive axle of the towing vehicle by increasing the vertical load on the fifth wheel or trailer coupling.

[0005] From DE 43 17 847 B4, a valve arrangement for controlling bellows pressures in the air springs of an air-sprung drive axle and an air-sprung trailing axle of a motor vehicle is known. The valve arrangement comprises a first valve assembly with two solenoid valves for adjusting the bellows pressure in the air springs of the drive axle and a second valve assembly with one solenoid valve for adjusting the bellows pressure in the air springs of the trailing axle.

[0006] The first solenoid valve of the first valve assembly is designed as a 3 / 2-way solenoid switching valve. In the de-energized state of the 3 / 2-way solenoid switching valve, an output port is connected to a vent line, and in the energized state, it is connected to a supply line. The second solenoid valve of the first valve assembly is designed as a 2 / 2-way solenoid switching valve. In the de-energized state of the 2 / 2-way solenoid switching valve, a working output connected to the support bellows of the drive shaft is closed off from an input port connected to the output port of the first solenoid valve. In the energized state of the 2 / 2-way solenoid switching valve, this input port is connected to the input port of the second solenoid valve.This first valve assembly allows the bellows pressure in the drive axle's support bellows to be continuously adjusted between ambient pressure and the supply pressure in the supply line. Opening the second solenoid valve, when the first solenoid valve is de-energized, reduces the bellows pressure, while opening the second solenoid valve increases the bellows pressure in the drive axle's support bellows.

[0007] The solenoid valve of the second valve assembly of this valve arrangement is designed as a partially pressure-controlled 3 / 3-way solenoid switching valve. It has an inlet port connected to the working outlet of the second solenoid valve of the first valve assembly, a vent port connected to the vent line, a working outlet connected to the trailing axle's air springs, and a control input connected via a pneumatic control line to the output port of the first solenoid valve of the first valve assembly. This second valve assembly allows the air spring pressure in the trailing axle's air springs to be continuously adjusted or locked between ambient pressure and the air spring pressure in the drive axle's air springs.In the de-energized state of the 3 / 3-way solenoid valve, the working output is connected to the working output of the second solenoid valve, so that the air springs of the trailing axle are pressurized to match those of the drive axle. When the 3 / 3-way solenoid valve is energized, the working output is connected to the venting output when the control input is pressureless, thus reducing the air spring pressure in the trailing axle's air springs. When the 3 / 3-way solenoid valve is energized, the working output is closed off from both the input port and the venting output when the control input is pressurized, thus maintaining the air spring pressure in the trailing axle's air springs.

[0008] A lift axle is located upstream or downstream of a drive axle in a motor vehicle or, in a trailer, of a non-driven main axle when viewed in the forward direction of travel. If the lift axle is air-sprung, meaning it is supported by at least one bellows on the vehicle frame, and can be raised and lowered by means of at least one bellows, raising the lift axle is achieved by inflating the bellows and simultaneously deflating the associated support bellows. Conversely, lowering the lift axle is achieved by inflating the support bellows and simultaneously deflating the lift axle. When the vehicle is loaded, the lift axle is normally lowered so that the load and the vehicle's own weight are distributed evenly across all axles.

[0009] In an unloaded or partially loaded vehicle, the lift axle is advantageously raised to reduce tire wear, particularly on the lift axle wheels, and to allow for a smaller turning radius when maneuvering. The lift axle of a motor vehicle can also be raised to increase the axle load on the drive axle and thus improve traction when starting under difficult traction conditions. On a semi-trailer or center-axle trailer, the lift axle of the trailer can be raised for the same purpose, increasing the axle load on the drive axle of the towing vehicle by increasing the vertical load on the fifth wheel or trailer coupling.

[0010] German patent application DE 10 2019 124 651 A1 describes a valve arrangement for controlling bellows pressures in air springs and in at least one lift bellows of an air-sprung lift axle of a trailer. The valve arrangement comprises a main control valve designed as a pressure-controlled 5 / 2-way switching valve and a pilot valve designed as a 3 / 2-way solenoid switching valve upstream of the main control valve. In an unenergized state, a control input of the main control valve is connected via the pilot valve to a vent outlet and is therefore pressureless. In an energized state, the control input of the main control valve is connected via the pilot valve to a supply line and is therefore under switching pressure.

[0011] With the control input depressurized, the lifting axle's support bellows are connected via the main control valve to the support bellows of an adjacent main axle, and the lifting bellows is connected to a vent outlet, so the lifting axle is then lowered and can bear a load. With the control input pressurized, i.e., in a switched state of the main control valve, the lifting axle's support bellows are connected via the main control valve to a vent outlet and are therefore depressurized, while the lifting bellows is then connected to the supply line, causing the lifting axle to be raised and unable to bear a load.

[0012] From EP 1 212 205 B1, a control system for raising and lowering the body of air-sprung vehicles is known, which is applicable to trailers. The vehicle has a lift axle with air springs and a lifting bellows. An axle lift valve is provided to supply the air springs and the lifting bellows. This valve is designed as a 5 / 2-way valve and can be electrically controlled via a control unit. In a first, de-energized switching position of the axle lift valve, the lifting bellows is vented and thus the lift axle is lowered. The pressure in the air springs can be set via a switching valve arrangement with two switching valves. In a second, energized switching position, the lifting bellows is pressurized and thus the lift axle is lowered. In this switching position of the axle lift valve, the air springs are vented.

[0013] JP 5 318 794 B2 discloses a lift axle control system for a vehicle that allows a lift axle to be raised when the vehicle is on a scale. This shortens the vehicle's wheelbase to such an extent that all axles can rest on the scale, while the lift axle, if lowered, would stand off the scale. JP 5 318 794 B2 discloses air springs for the load-bearing axle, which can be pressurized or vented via a first electromagnetic valve. Each air spring of the lift axle is also equipped with a pneumatically operated actuator, which can be pressurized or vented via a second electromagnetic valve. The electromagnetic valves are jointly controlled in a circuit via a relay valve by a switch. The switch is operated manually by the vehicle's driver.When the switch is closed, the actuators are pressurized via the second electromagnetic valve and the air springs of the lift axle are vented. When the switch is open, the actuators are vented via the first electromagnetic valve and the air springs of the lift axle are pressurized.

[0014] US 2004 / 0164511 A1 discloses a vehicle with a liftable axle. CN 206374491 U discloses an air suspension arrangement for a vehicle with a switching valve by means of which it can be switched between a state in which an air spring of a drive axle and an air spring of a lift axle are connected, and a state in which the air spring of the drive axle and the air spring of the lift axle are isolated from each other.

[0015] A liftable, air-sprung trailing axle is a combination of a trailing axle and a lift axle. In its lowered position, the pressure in the air springs can be reduced or increased in the trailing axle function. In the lift axle function, the trailing axle can be raised by inflating the lift air spring and simultaneously deflating the associated air springs. Conversely, the trailing axle can be lowered by inflating the air springs and simultaneously deflating the lift air spring.

[0016] A valve arrangement for controlling such a trailing axle should be designed so that the bellows pressure in the associated support bellows and the bellows pressure in the lift bellows can be adjusted independently of each other, and that the trailing axle is automatically lowered when the vehicle's electrical system is switched off, i.e., when the solenoid valves are de-energized. Automatic lowering of the trailing axle prevents overloading of the other axles of the trailer, for example, when the trailer is uncoupled from the towing vehicle or even when an ISO 7638 connector of the trailer is disconnected from a corresponding socket on the towing vehicle.

[0017] In view of the known, relatively complex valve arrangements for controlling a trailing axle and a lift axle, the invention aims to present a valve arrangement for controlling a liftable trailing axle of the aforementioned design that is as simple and cost-effective as possible. Furthermore, a method is to be described that determines how this valve arrangement must be controlled in order to operate the trailing axle in either trailing or lift axle mode.

[0018] The device-related problem is solved by a trailer vehicle with a valve arrangement having the features of claim 1 or with the features of claim 1. 4Solved. Independent method claims specify method steps for actuating the valve arrangement by means of which a trailing axle operation or a lift axle operation of the trailing axle can be set. Advantageous embodiments are defined in the respective dependent claims.

[0019] The invention relates to a multi-axle trailer with an electromagnetic valve arrangement, controllable by an electronic control unit, for controlling a trailing axle. The trailing axle is arranged on the trailer, viewed in the forward direction, either in front of or behind a main axle. The trailing axle is supported on the trailer's frame by at least one bellows and can be raised or lowered by means of at least one lifting bellows. The valve arrangement is designed such that the pressure in the bellows and the pressure in the lifting bellows can be adjusted independently of one another, and that the trailing axle is automatically lowered to a road surface when the power supply is switched off. The road surface is a surface on which the vehicle rests, and "resting" here also refers to driving.

[0020] To solve the device-related problem, it is provided that the valve arrangement has a first solenoid valve unit, controllable by the electronic control unit, for stepless adjustment of the bellows pressure in the support bellows of the trailing axle between an ambient pressure and a bellows pressure applied in the support bellows of the main axle, and that the valve arrangement has a second solenoid valve unit, controllable independently of the first solenoid valve unit by the electronic control unit, which serves to switch the bellows pressure in the lift bellows of the trailing axle between the ambient pressure and a supply pressure.

[0021] The invention relates to a multi-axle trailer with a valve arrangement for controlling a trailing axle, which is arranged on the trailer in front of or behind a main axle and supported on a vehicle frame of the trailer via at least one bellows and can be raised or lowered by means of at least one lifting bellows. The trailer can optionally also have an additional axle, which is arranged, for example, in front of the main axle. The valve arrangement according to the invention is designed such that the bellows pressure in the supporting bellows and the bellows pressure in the lifting bellows can be adjusted independently of each other and that the trailing axle is automatically lowered when the power supply is switched off.

[0022] Separate adjustment of the bellows pressures in the support bellows and the lift bellows of the trailing axle is achieved by assigning a solenoid valve unit to each, with the solenoid valve units being electrically controlled independently of each other by the electronic control unit. The automatic lowering of the trailing axle when the power supply is switched off results from the specific design of the two solenoid valve units.

[0023] According to a first embodiment of the valve arrangement, the first solenoid valve unit is designed as a 3 / 3-way solenoid switching valve with a pressure inlet, a working outlet and a vent outlet, wherein the pressure inlet is connected to the support bellows of the main axle, the working outlet to the support bellows of the trailing axle and the vent outlet to a vent line.

[0024] The trailing axle's air springs can thus be selectively vented either via a pneumatic connection to the main axle's air springs or vented via a connection to the vent line. Furthermore, the air pressure in the trailing axle's air springs can be kept constant by a pneumatic shut-off valve separating them from the main axle's air springs and the vent line.

[0025] In order to achieve the intended lowering of the trailing axis when the power supply is switched off, the 3 / 3-way solenoid valve can be designed such that its working output is connected to the pressure input and closed off from the venting output in a de-energized state, that the working output is closed off from the pressure input and the venting output in a weakly energized state, and that the working output is connected to the venting output and closed off from the pressure input in a maximally energized state.

[0026] Alternatively, the 3 / 3-way solenoid valve can be provided with two electromagnets that can be controlled by the control unit and are arranged such that when the first electromagnet is energized, the 3 / 3-way solenoid valve is switched to its venting position, in which the pressure inlet is closed and the working outlet is connected to the venting outlet; when the second electromagnet is energized, the 3 / 3-way solenoid valve is switched to its shut-off position; and when the electromagnets are not energized, the pressure inlet and the working outlet of the 3 / 3-way solenoid valve are connected to each other and the venting outlet is closed.

[0027] According to a second embodiment of the valve arrangement, the first solenoid valve unit comprises an inlet valve designed as a 2 / 2-way solenoid switching valve with a pressure inlet and a working outlet, and an outlet valve designed as a 2 / 2-way solenoid switching valve with a working inlet and a vent outlet, wherein the pressure inlet of the inlet valve is connected to the support bellows of the main shaft, wherein the working outlet of the inlet valve and the working inlet of the outlet valve are connected to the support bellows of the trailing shaft, and wherein the vent outlet of the outlet valve is connected to a vent line.

[0028] In this embodiment of the first solenoid valve unit, the trailing axle's support bellows can be selectively vented either via a pneumatic connection to the main axle's support bellows or via a pneumatic connection to the vent line. Alternatively, the bellows pressure in the trailing axle's support bellows can be kept constant by a pneumatic shut-off valve relative to the main axle's support bellows and the vent line.

[0029] To achieve the intended lowering of the trailing axis when the power supply is switched off, the inlet valve can be designed such that its working outlet is connected to its pressure inlet in a de-energized state and is closed off from this pressure inlet in a energized state. Furthermore, the outlet valve is designed such that its working inlet is closed off from its vent outlet in a de-energized state and is connected to this vent outlet in a energized state.

[0030] The second solenoid valve unit can be designed as a 3 / 2-way solenoid switching valve with a pressure inlet, a working outlet and a vent outlet, wherein the pressure inlet of this 3 / 2-way solenoid switching valve is connected to a supply line, the working outlet is connected to the lift bellows of the trailing axle and the vent outlet is connected to the vent line.

[0031] The lift bellows of the trailing axle can therefore be optionally vented by a connection to the supply line or vented by a connection to the vent line, whereby the trailing axle is raised by venting the lift bellows in conjunction with venting the support bellows and lowered by venting the lift bellows in conjunction with venting the support bellows.

[0032] In order to achieve the intended lowering of the trailing axis when the power supply is switched off, the 3 / 2-way solenoid valve can be designed such that its working output is connected to its venting output and shut off from its pressure input in an unenergized state, and that its working output is connected to its pressure input and shut off from the venting output in an energized state.

[0033] For controlling an electromagnetic valve arrangement according to the invention, which has a first solenoid valve unit with a 3 / 3-way solenoid switching valve and a second solenoid valve unit with a 3 / 2-way solenoid switching valve, the following procedure steps are provided for lift axle operation of a trailer vehicle with a raised trailing axle: A) Check whether the weight on the main axle and / or an auxiliary axle of the trailer, with the trailing axle fully raised, would exceed a predefined weight limit. B) If the result in step A is negative, i.e., if the weight on the main axle and / or the auxiliary axle, with the trailing axle fully raised, would not exceed the predefined weight limit: Switch the 3 / 3-way solenoid valve of the first solenoid valve unit to its venting position. This closes off the air springs of the main axle and the air springs of the auxiliary axle of the trailer, and vents the air springs of the trailing axle. C) Switch the 3 / 2-way solenoid valve of the second solenoid valve unit to its venting position, which vents the lift bellows of the trailing axle and raises the trailing axle at least until its wheels lose contact with the road surface.

[0034] The following procedure steps are provided for controlling this electromagnetic valve arrangement for the execution of a trailing axle operation of a trailer vehicle with a lowered trailing axle: D) Check whether the weight on the main axle and / or an auxiliary axle of the trailer would exceed a predefined limit when the trailing axle is fully raised. E) If the assessment in step D is positive, i.e., if the weight on the main axle and / or the auxiliary axle would exceed the predefined limit when the trailing axle is fully raised: Switch the 3 / 2-way solenoid valve of the second solenoid valve unit to its venting position, thereby venting the trailing axle's lift bellows and allowing the wheels on the trailing axle to maintain contact with the road surface. F) Set any desired pressure between ambient pressure and a maximum pressure in the air springs of the main axle, auxiliary axle, and trailing axle of the trailer by opening or closing the 3 / 3-way solenoid valve of the first solenoid valve unit.

[0035] For controlling an electromagnetic valve arrangement according to the invention, which has a first solenoid valve unit with an inlet valve designed as a 2 / 2-way solenoid switching valve and with an outlet valve designed as a 2 / 2-way solenoid switching valve and a 3 / 2-way solenoid switching valve of a second solenoid valve unit, the following method steps are provided for a lift axle operation of a trailer vehicle with a raised trailing axle: G) Check whether the weight on the main axle and / or an auxiliary axle of the trailer, with the trailing axle fully raised, would exceed a predefined weight limit. H) If the test in step G reveals that the weight on the main axle and / or the auxiliary axle, with the trailing axle fully raised, would exceed the predefined weight limit: Switch the inlet valve to its closed position and switch the outlet valve to its open position. This isolates the air springs of the main axle and the auxiliary axle of the trailer and vents the air springs of the trailing axle. I) Switch the 3 / 2-way solenoid valve of the second solenoid valve unit to its venting position, venting the lift air spring of the trailing axle and raising the trailing axle at least until its wheels lose contact with the road surface.

[0036] The following procedure steps are provided for controlling the aforementioned valve arrangement for the execution of a trailing axle operation of a trailer vehicle with a lowered trailing axle: J) Check whether the weight on a main axle and / or an auxiliary axle of the trailer would exceed a predefined limit when the trailing axle is fully raised. K) If the assessment in step J is positive, i.e., if the weight on the main axle and / or the auxiliary axle would exceed the predefined limit when the trailing axle is fully raised: Switch the 3 / 2-way solenoid valve of the second solenoid valve unit to its venting position. This vents the trailing axle's lifting bellows, allowing the wheels on the trailing axle to maintain or regain contact with the road surface. L) Adjust the pressure in the lifting bellows of the main axle, the auxiliary axle, and the trailing axle of the trailer to any desired level between ambient pressure and a maximum pressure by opening or closing the vent valve.

[0037] The pressure in the support bellows of the main axle, the auxiliary axle and the trailing axle is preferably adjusted depending on the weight on the main axle and / or the auxiliary axle and / or a distribution of a load or load weight of the trailer and / or a geometry of the trailer.

[0038] It may be provided that the pressure in the air springs of the trailing axle is at most as high as the pressure in the air springs of the main axle and the auxiliary axle.

[0039] Finally, to implement a lift axle operation of a trailer vehicle with a raised trailing axle, a control system for the electromagnetic valve arrangement can be provided, which includes the following process steps: M) In several venting steps, the air springs of the main axle, the trailing axle, and, if present, an auxiliary axle are gradually vented. N) After each venting step, check whether the weight acting on the respective air springs exceeds a predetermined weight limit. O) If the assessment in step N is negative, i.e., if the weight acting on the respective air springs does not exceed the predetermined weight limit: partially vent the air springs again in a further venting step. P) After a final venting step with the trailing axle air springs almost completely deflated, and if the assessment in step N remains negative, i.e., if the weight acting on the respective air springs still does not exceed the predetermined weight limit: inflate at least one lift bellows of the trailing axle, thereby raising it sufficiently for its wheels to lift off the road surface.

[0040] This procedure involves a step-by-step determination of whether the main axle and any auxiliary axle on the trailer are capable of bearing the axle load acting upon them without exceeding a permissible load limit. This is achieved by gradually relieving the load on the trailing axle. Once it has been established that the main axle, alone or in conjunction with any auxiliary axle, is capable of bearing the load, at least one lifting bellows of the trailing axle is inflated, and the axle is raised to the point where it no longer bears any load.

[0041] The valve arrangement with the features of the invention will now be explained in more detail with reference to exemplary embodiments shown in the accompanying drawing. This drawing shows Fig. 1 shows a vehicle combination consisting of a towing vehicle and a trailer with a first embodiment of a valve arrangement according to the invention in a side view, Fig. 1 the valve arrangement according to Fig. 1 with a 3 / 3-way solenoid valve according to the first embodiment in an enlarged partial view, Fig. 1, section of the valve arrangement according to the Fig. 1 and 1a with a 3 / 3-way solenoid valve according to a second embodiment, Fig. 2, the vehicle combination according to Fig. 1 with a second embodiment of a valve arrangement according to the invention in a side view, and Fig. 2 the valve arrangement according to Fig. 2 in an enlarged partial view.

[0042] In the Fig. 1 and 2Figure 2 depicts a vehicle combination designed as a semi-trailer truck, consisting of a tractor unit 4 and a semi-trailer 6 coupled to it. The vehicle combination 2 is positioned on a roadway 3. The tractor unit 4 has a chassis 8 on which a cab 10 is mounted. The chassis 8 is supported by a steerable front axle 12 and a rear axle 14, which serves as the drive axle. The two axles 12 and 14 of the tractor unit 4 can be supported alternately or simultaneously on the chassis 8 by steel springs or air springs. A coupling element 16, designed as a fifth wheel coupling, is attached to the chassis 8 at the rear of the tractor unit 4.

[0043] The trailer 6 has a vehicle frame 18 on which a box-shaped body 20 is mounted. The vehicle frame 18 is supported by three axles 22, 24, 26 arranged adjacent to one another. At the front of the trailer 6, a coupling element 28 in the form of a fifth wheel with a kingpin is attached to the vehicle frame 18, via which the trailer 6 is pivotably coupled to the towing vehicle 4 by means of the fifth wheel coupling 16.

[0044] The middle axle of the trailer 6 forms its main axle 22. It is connected to the vehicle frame 18 by air suspension. For this purpose, two air springs with their air springs are arranged, of which in the Fig. 1 and 2Only one support bellows 30 is visible in each case. The front axle, viewed in the forward direction, is designed as an auxiliary axle 24, which is supported on the vehicle frame 18 by means of two air springs and their support bellows 32. The rear axle, viewed in the forward direction, is designed as a liftable trailing axle 26, which is also supported on the vehicle frame 18 by means of two air springs and their support bellows 34, and is arranged to be raised and lowered by means of at least one lift bellows 36.

[0045] In the Fig. 1 In addition to the vehicle combination 2, a first embodiment of a valve arrangement 38 according to the invention is schematically shown, which is actually attached to the vehicle frame 18 and in Fig. 1a The valve arrangement 38 is also shown enlarged. It comprises a first solenoid valve unit 42, controllable by an electronic control unit 40, for stepless adjustment of the bellows pressure in the support bellows 34 of the trailing axle 26 between ambient pressure and the bellows pressure present in the support bellows 30, 32 of the main axle 22 and the auxiliary axle 24. In addition, a second solenoid valve unit 44, controllable independently of the first solenoid valve unit 42 by the electronic control unit 40, is provided. This second solenoid valve unit 44 serves to switch the bellows pressure in the lift bellows 36 of the trailing axle 26 between ambient pressure and a supply pressure.

[0046] The first solenoid valve unit 42 according to the Figuren 1 and 1ais designed as a 3 / 3-way solenoid valve 46 with a pressure inlet 48, a working outlet 50 and a vent outlet 52. The first solenoid valve unit 42 is connected to the control unit 40 via an unlabeled electrical control line.

[0047] The pressure inlet 48 is connected via a first connecting line 54 and a connecting line 56 to the support bellows 30, 32 of the main axle 22 and the auxiliary axle 24. The working outlet 50 is connected via a second connecting line 58 to the support bellows 34 of the trailing axle 26. The vent outlet 52 is connected to a vent line 60, which leads to the environment via a silencer 62. This 3 / 3-way solenoid valve 46 is designed such that, in the de-energized state, the working outlet 50 is connected to the pressure inlet 48 and closed off from the vent outlet 52; in the slightly energized state, it is closed off from both the pressure inlet 48 and the vent outlet 52; and in the fully energized state, it is connected to the vent outlet 52 and closed off from the pressure inlet 48.

[0048] As the Fig. 1b As shown, the 3 / 3-way solenoid valve 46' can also be configured to have two electromagnets 92, 94 that can be controlled by the control unit 40. These electromagnets 92, 94 are arranged such that when the first electromagnet 92 is energized, the 3 / 3-way solenoid valve 46' is switched to its venting position, in which the pressure inlet 48 is closed and the working outlet 50 is connected to the venting outlet 52; when the second electromagnet 94 is energized, the 3 / 3-way solenoid valve 46' is switched to its closed position; and when the electromagnets 92, 94 are not energized, the pressure inlet 48 and the working outlet 50 of the 3 / 3-way solenoid valve 46' are connected to each other, and the venting outlet 52 is closed.

[0049] Even in such an embodiment of the 3 / 3-way solenoid valve 46', it is ensured that in the event of a power failure the support bellows 30, 32, 34 of the main axis 22, the auxiliary axis 24 and the lift axis 26 are pneumatically connected to each other.

[0050] The second solenoid valve unit 44 according to the Fig. 1 and 1aThe valve 64 is designed as a 3 / 2-way solenoid valve with a pressure inlet 66, a working outlet 68, and a vent outlet 70, which is connected to the control unit 40 by means of an electrical control line. The pressure inlet 66 is connected to a supply line 74 connected to a compressed air source 72. The working outlet 68 is connected to the lift bellows 36 of the trailing axle 26 via a connecting line 76. The vent outlet 70 is pneumatically connected to the vent line 60. This 3 / 2-way solenoid valve 64 is designed such that its working outlet 68 is connected to the vent outlet 70 and closed off from the pressure inlet 66 when de-energized, and is connected to the pressure inlet 66 and closed off from the vent outlet 70 when energized.

[0051] Thus, the bellows pressure in the support bellows 34 of the trailing axle 26 can be continuously adjusted between ambient pressure and the bellows pressure in the support bellows 30, 32 of the main axle 22 and the auxiliary axle 24 by means of the first solenoid valve unit 42. Furthermore, the bellows pressure in the lift bellows 36 of the trailing axle 26 can be adjusted independently of the first valve unit 42, alternately to ambient pressure or the supply pressure present in the supply line 74, by means of the second solenoid valve unit 44.

[0052] Furthermore, the design of the two solenoid valve units 42, 44 ensures that, when the power supply is switched off and the solenoid switching valves 46, 64 are therefore de-energized, the support bellows 34 of the trailing axle 26 are pneumatically connected to the support bellows 30, 32 of the main axle 22 and the auxiliary axle 24, and the lift bellows 36 of the trailing axle 26 is connected to the vent line 60, which, when the trailing axle 26 is raised, leads to its lowering in the direction of the roadway 3.

[0053] In order to use the electromagnetic valve arrangement 38 in accordance with the Figuren 1 and 1a The following procedural steps are provided to set up a lift axle operation with a raised trailing axle 26: A) Check whether the weight on the main axle 22 and / or an auxiliary axle 24 of the trailer 6, with the trailing axle 26 fully raised, would exceed a predefined weight limit. B) If the result in step A is negative, and the weight on the main axle 22 and / or the auxiliary axle 24, with the trailing axle 26 fully raised, would not exceed the predefined weight limit: Switch the 3 / 3-way solenoid valve 46 of the first embodiment of the first solenoid valve unit 42 to its venting position. This closes off the air springs 30 of the main axle 22 and the air springs 32 of the auxiliary axle 24 of the trailer 6, and vents the air springs 34 of the trailing axle 26.C) Switching the 3 / 2-way solenoid valve 64 of the second solenoid valve unit 44 to its venting position, thereby venting the lift bellows 36 of the trailing axle 26 and raising the trailing axle 26 at least until its wheels have lost contact with the track 3.

[0054] If, on the other hand, a trailing axle operation with a lowered trailing axle 26 is to be carried out, the following procedure steps must be performed: D) Check whether the weight on the main axle 22 and / or an auxiliary axle 24 of the trailer 6, with the trailing axle 26 fully raised, would exceed a predefined limit. E) If the assessment in step D is positive, i.e., if the weight on the main axle 22 and / or an auxiliary axle 24 of the trailer 6, with the trailing axle 26 fully raised, would exceed the predefined limit: Switch the 3 / 2-way solenoid valve 64 of the second solenoid valve unit 44 to its venting position, thereby venting the lifting bellows 36 of the trailing axle 26 and allowing the wheels on the trailing axle 26 to maintain contact with the road surface 3. F) Setting any pressure between ambient pressure and a maximum pressure in the air springs 30, 32, 34 of the main axle 22, the auxiliary axle 24 and the trailing axle 26 of the trailer 6 by opening or closing the 3 / 3-way solenoid valve 46.

[0055] In the Fig. 2 A second embodiment of a valve arrangement 38' according to the invention is schematically shown on the vehicle combination 2, which is actually attached to the vehicle frame 18 of the trailer 6 and in Fig. 2a The valve arrangement 38' is shown enlarged. This valve arrangement 38' also comprises a first solenoid valve unit 78 (second embodiment) controllable by the electronic control unit 40 for stepless adjustment of the bellows pressure in the support bellows 34 of the trailing axle 26 between ambient pressure and the bellows pressure in the support bellows 30 of the main axle 22 and, if applicable, the auxiliary axle 24, as well as a second solenoid valve unit 44 controllable independently of the first solenoid valve unit 78 by the electronic control unit 40 for switching the bellows pressure in the lift bellows 36 of the trailing axle 26 between ambient pressure and a supply pressure. With the same operating principle, the valve arrangement 38' differs according to the Fig. 2 and 2a only by an alternative design of the first solenoid valve unit 78 from the valve arrangement 38 according to the Fig. 1 and 1a .

[0056] The first solenoid valve unit 78 according to the Fig. 2 and 2a The system now comprises an inlet valve 80 designed as a 2 / 2-way solenoid valve with a pressure inlet 82 and a working outlet 84, and an outlet valve 86 designed as a 2 / 2-way solenoid valve with a working inlet 88 and a vent outlet 90. The inlet valve 80 and the outlet valve 86 are each connected to the control unit 40 via an electrical control line.

[0057] The pressure inlet 82 is connected via the connecting line 54 and the connecting line 56 to the support bellows 30, 32 of the main axle 22 and the auxiliary axle 24. The working outlet 84 of the inlet valve 80 and the working inlet 88 of the outlet valve 86 are connected via the aforementioned connecting line 58 to the support bellows 34 of the trailing axle 26. The vent outlet 90 of the outlet valve 86 is connected to the vent line 60, which leads to the environment via the silencer 62.

[0058] The inlet valve 80 is designed such that its working outlet 84 is connected to the pressure inlet 82 of the inlet valve 80 in the de-energized state and is closed off from the pressure inlet 82 in the energized state. The outlet valve 86 is designed such that its working inlet 88 is closed off from the vent outlet 90 in the de-energized state and is connected to the vent outlet 90 of the outlet valve 86 in the energized state.

[0059] In this alternative valve arrangement 38', the bellows pressure in the support bellows 34 of the trailing axle 26 can also be continuously adjusted between ambient pressure and the bellows pressure in the support bellows 30, 32 of the main axle 22 and the auxiliary axle 24 by means of the first solenoid valve unit 78. Furthermore, the bellows pressure in the lift bellows 36 of the trailing axle 26 can be adjusted independently of the first solenoid valve unit 78, alternately to ambient pressure or the supply pressure present in the supply line 74.

[0060] Furthermore, the design of the two described solenoid valve units 78, 44 according to Fig. 2 and 2aensured that when the power supply is switched off and thus the solenoid valves 80, 86, 64 are not energized, the support bellows 34 of the trailing axle 26 are connected to the support bellows 30, 32 of the main axle 22 and the auxiliary axle 24, and that the lift bellows 36 of the trailing axle 26 is connected to the vent line 60, which leads to the lowering of the trailing axle 26 when it is raised.

[0061] The advantage of this second embodiment of the first solenoid valve unit 78 according to the Fig. 2 and 2a The advantage lies in the fact that their design and function are similar to those of an ABS control valve. Therefore, this version of the first solenoid valve unit 78 can be identical in construction to an ABS control valve of a pneumatically operated wheel brake of a commercial vehicle, thereby advantageously saving costs for the development, manufacture, and storage of a new solenoid valve unit.

[0062] To use the valve arrangement 38' according to the Fig. 2 and 2a To set up a trailing axle operation or a lift axle operation of the trailing axle 26, different procedure steps must be provided. For example, to implement a lift axle operation with the trailing axle 26 raised, the following procedure steps must be carried out: G) Check whether the weight on the main axle 22 and / or an auxiliary axle 24 of the trailer 6, with the trailing axle 26 fully raised, would exceed a predefined weight limit. H) If the result in step G is negative, i.e., if the weight on the main axle 22 and / or the auxiliary axle 24, with the trailing axle 26 fully raised, would not exceed the predefined weight limit: Switch the inlet valve 80 to its closed position and switch the outlet valve 86 to its open position. This closes off the air springs 30 of the main axle 22 and the air springs 32 of the auxiliary axle 24 of the trailer 6, and vents the air springs 34 of the trailing axle 26.I) Switching the 3 / 2-way solenoid valve 64 of the second solenoid valve unit 44 to its venting position, thereby venting the lift bellows 36 of the trailing axle 26 and raising the trailing axle 26 at least until its wheels have lost contact with the track 3.

[0063] In contrast, the following procedure steps must be carried out to control the electromagnetic valve arrangement 38' for the execution of a trailing axle operation with a lowered trailing axle 26: J) Check whether the weight on the main axle 22 and / or an auxiliary axle 24 of the trailer 6, with the trailing axle 26 fully raised, would exceed a predefined limit. K) If the assessment in process step J is positive, i.e., if the weight on the main axle 22 and / or the auxiliary axle 24, with the trailing axle 26 fully raised, would exceed the predefined limit: Switch the 3 / 2-way solenoid valve 64 of the second solenoid valve unit 44 to its venting position, thereby venting the lifting bellows 36 of the trailing axle 26 and allowing the wheels on the trailing axle 26 to maintain contact with the road surface 3. L) Setting any pressure between ambient pressure and a maximum pressure in the air springs 30, 32, 34 of the main axle 22, the auxiliary axle 24 and the trailing axle 26 of the trailer 6 by opening or closing the outlet valve 86.

[0064] The pressure in the air springs 30, 32, 34 of the main axle 22, the auxiliary axle 24, and the trailing axle 26 is adjusted depending on the weight of the trailer 6 and / or the distribution of the load weight on the trailer 6 and / or the geometry of the trailer 6. The pressure in the air springs 34 of the trailing axle 26 is at most as high as the pressure in the air springs 30, 32 of the main axle 22 and, if applicable, the auxiliary axle 24.

[0065] According to another method variant, the following method steps are provided for the execution of a lift axle operation of a trailer vehicle 6 with a raised trailing axle 26: M) In several venting steps, the air springs 30, 32, 34 of the main axle 22, the trailing axle 26, and, if present, an auxiliary axle 24 are vented step by step. N) After each venting step: Check whether a weight acting on the respective air springs 30, 32, 34 exceeds a predetermined weight limit. O) If the assessment in process step N is negative, i.e., if the weight acting on the respective air springs 30, 32, 34 does not exceed the predetermined weight limit: partially vent the aforementioned air springs 30, 32, 34 again in a further venting step.P) After a final venting step with the support bellows 34 of the trailing axle 26 almost completely deflated, and if the assessment in process step N remains negative, i.e., if the weight acting on the respective support bellows 30, 32, 34 still does not exceed the predetermined weight limit: Venting of at least one lift bellows 36 of the trailing axle 26, thereby raising the trailing axle 26 to such an extent that its wheels lift off the track 3.

[0066] Subsequently, the bellows 30, 32 of the main axle 22 and, if present, of the auxiliary axle 24 can be ventilated again.

[0067] In this procedure, it is determined step by step whether the main axle 22 and any auxiliary axle 24 on the trailer 6 are capable of bearing the axle load acting upon them without exceeding a permissible load limit. This is achieved by gradually relieving the load on the trailing axle 26. As soon as it has been established that the main axle 22, alone or in conjunction with any auxiliary axle 24, is capable of bearing the load acting upon these axles 22 and 24, the at least one lifting bellows 34 of the trailing axle 26 is vented and the axle is raised to such an extent that it no longer has to bear any load. Reference symbol list (part of the description)

[0068] 2 Vehicle combination, articulated lorry 3 Roadway 4 Tractor unit, semi-trailer truck 6 Trailer, semi-trailer 8 Vehicle frame of the tractor unit 10 Cab 12 Front axle of the tractor unit 14 Rear axle, drive axle of the tractor unit 16 Coupling element, fifth wheel coupling 18 Vehicle frame of the trailer unit 20 Box body of the trailer unit 22 Main axle of the trailer unit 24 Auxiliary axle of the trailer unit 26 Trailing axle of the trailer unit 28 Counter coupling element, fifth wheel plate 30 Bellows on the main axle of the trailer unit 32 Bellows on the auxiliary axle of the trailer unit 34 Bellows on the trailing axle of the trailer unit 36 ​​Lifting bellows on the trailing axle 38 Valve assembly (first embodiment) 38 Valve assembly (second embodiment) 40 Electronic control unit 42 First solenoid valve unit (first embodiment) 44 Second solenoid valve unit 46 3 / 3-way solenoid switching valve (first embodiment) 46 3 / 3-way solenoid switching valve (second embodiment) 48 Pressure inlet at3 / 3-way solenoid valve 46 50 Working outlet on the 3 / 3-way solenoid valve 46 52 Vent outlet on the 3 / 3-way solenoid valve 46 54 First connection line 56 Connecting line 58 Second connection line 60 Vent line 62 Silencer 64 3 / 2-way solenoid valve 66 Pressure inlet on the 3 / 2-way solenoid valve 64 68 Working outlet on the 3 / 2-way solenoid valve 64 70 Vent outlet on the 3 / 2-way solenoid valve 64 72 Compressed air source 74 Supply line 76 Connection line 78 First solenoid valve unit (second embodiment) 80 Inlet valve, 2 / 2-way solenoid valve 82 Pressure inlet on the inlet valve 84 Working outlet on the inlet valve 86 Outlet valve, 2 / 2-way solenoid valve 88 Working inlet on outlet valve 90 Vent outlet on outlet valve 92 First solenoid on 3 / 3-way solenoid valve 46' 94 Second solenoid on 3 / 3-way solenoid valve 46'

Claims

1. Trailer vehicle (6), comprising - a main axle (22), - a trailing axle (26), wherein the trailing axle (26) - is arranged in front of or behind the main axle (22) of the trailer vehicle (6) considered in the forward travel direction, - is arranged in a manner supported on a vehicle frame (18) of the trailer vehicle (6) via supporting bellows (34), and - is raisable or lowerable by means of at least one lift bellows (36), wherein the trailer vehicle is characterized by - an electromagnetic valve assembly (38, 38') for controlling the trailing axle (26), and - an electronic control unit (40), wherein the valve assembly (38, 38') - is controlled by the electronic control unit (40) and - is designed in such a way that - a bellows pressure in the supporting bellows (34) and a bellows pressure in the lift bellows (36) are adjustable independently of one another, and - when the power supply is switched off, the trailing axle (26) is automatically lowered toward a roadway (3) on which the trailer vehicle (6) is situated, wherein the valve assembly (38, 38') - has a first solenoid valve unit (42, 78), actuatable by the electronic control unit (40), for steplessly adjusting the bellows pressure in the supporting bellows (34) of the trailing axle (26) between an ambient pressure and a bellows pressure present in the supporting bellows (30) of the main axle (22) and - has a second solenoid valve unit (44), actuatable by the electronic control unit (40) independently of the first solenoid valve unit (42, 78), for switching the bellows pressure in the lift bellows (36) of the trailing axle (26) between the ambient pressure and a supply pressure, wherein the first solenoid valve unit (42) is designed as a 3 / 3-way solenoid switching valve (46, 46') with a pressure inlet (48), a working outlet (50), and a vent outlet (52), wherein - the pressure inlet (48) is connected to the supporting bellows (30) of the main axle (22), - the working outlet (50) is connected to the supporting bellows (34) of the trailing axle (26), and - the vent outlet (52) is connected to a vent line (60).

2. Trailer vehicle (6) according to claim 1, characterized in that the 3 / 3-way solenoid switching valve (46) is designed in such a way - that in a de-energized state of the 3 / 3-way solenoid switching valve (46), the working outlet (50) is connected to the pressure inlet (48) and is shut off from the vent outlet (52), - that in a low-energized state of the 3 / 3-way solenoid switching valve (46), the working outlet (50) is shut off from the pressure inlet (48) and the vent outlet (52), and - that in a maximally energized state of the 3 / 3-way solenoid switching valve (46), the working outlet (50) is connected to the vent outlet (52) and is shut off from the pressure inlet (48).

3. Trailer vehicle (6) according to claim 1, characterized - in that the 3 / 3-way solenoid switching valve (46') has two electromagnets (92, 94) actuatable by the control unit (40) and arranged in such a way that when the first electromagnet (92) is energized, the 3 / 3-way solenoid switching valve (46') is switched into its venting position, in which the pressure inlet (48) is shut off and the working outlet (50) is connected to the vent outlet (52), - in that when the second electromagnet (94) is energized, the 3 / 3-way solenoid switching valve (46') is switched into its shut-off position, and - in that when the electromagnets (92, 94) are not energized, the pressure inlet (48) and the working outlet (50) of the 3 / 3-way solenoid switching valve (46') are connected to one another and the vent outlet (52) is closed.

4. Trailer vehicle (6), comprising - a main axle (22), - a trailing axle (26), wherein the trailing axle (26) - is arranged in front of or behind the main axle (22) of the trailer vehicle (6) considered in the forward travel direction, - is arranged in a manner supported on a vehicle frame (18) of the trailer vehicle (6) via supporting bellows (34), and - is raisable or lowerable by means of at least one lift bellows (36), wherein the trailer vehicle is characterized by - an electromagnetic valve assembly (38, 38') for controlling the trailing axle (26), and - an electronic control unit (40), wherein the valve assembly (38, 38') - is controlled by the electronic control unit (40) and - is designed in such a way that - a bellows pressure in the supporting bellows (34) and a bellows pressure in the lift bellows (36) are adjustable independently of one another, and - when the power supply is switched off, the trailing axle (26) is automatically lowered toward a roadway (3) on which the trailer vehicle (6) is situated, wherein the valve assembly (38, 38') - has a first solenoid valve unit (42, 78), actuatable by the electronic control unit (40), for steplessly adjusting the bellows pressure in the supporting bellows (34) of the trailing axle (26) between an ambient pressure and a bellows pressure present in the supporting bellows (30) of the main axle (22) and - has a second solenoid valve unit (44), actuatable by the electronic control unit (40) independently of the first solenoid valve unit (42, 78), for switching the bellows pressure in the lift bellows (36) of the trailing axle (26) between the ambient pressure and a supply pressure, wherein the first solenoid valve unit (78) comprises an inlet valve (80), designed as a 2 / 2-way solenoid switching valve, with a pressure inlet (82) and a working outlet (84) and comprises an outlet valve (86), designed as a 2 / 2-way solenoid switching valve, with a working inlet (88) and a vent outlet (90), - wherein the pressure inlet (82) of the inlet valve (80) is connected to the supporting bellows (30) of the main axle (22), - wherein the working outlet (84) of the inlet valve (80) and the working inlet (88) of the outlet valve (86) are connected to the supporting bellows (34) of the trailing axle (26), and - wherein the vent outlet (90) of the outlet valve (86) is connected to a vent line (60).

5. Trailer vehicle (6) according to claim 4, characterized - in that the inlet valve (80) is designed in such a way that its working outlet (84) is connected to its pressure inlet (82) in a de-energized state of the inlet valve (80) and is shut off from this pressure inlet (82) in an energized state of the inlet valve (80), and - in that the outlet valve (86) is designed in such a way that its working inlet (88) is shut off from its vent outlet (90) in a de-energized state of the outlet valve (86) and is connected to the vent outlet (90) in an energized state of the outlet valve (86).

6. Trailer vehicle (6) according to any of claims 1 to 5, characterized in that the second solenoid valve unit (44) is designed as a 3 / 2-way solenoid switching valve (64) with a pressure inlet (66), a working outlet (68), and a vent outlet (70), wherein - the pressure inlet (66) of this 3 / 2-way solenoid switching valve (64) is connected to a supply line (74), - the working outlet (68) is connected to the lift bellows (36) of the trailing axle (26), and - the vent outlet (70) is connected to the vent line (60).

7. Trailer vehicle (6) according to claim 6, characterized in that the 3 / 2-way solenoid switching valve (64) is designed in such a way - that in a de-energized state of the 3 / 2-way solenoid switching valve (64), the working outlet (68) is connected to the vent outlet (70) and is shut off from the pressure inlet (66), and - that in an energized state of the 3 / 2-way solenoid switching valve (64), the working outlet (68) is connected to the pressure inlet (66) and is shut off from the vent outlet (70).

8. Method for controlling the electromagnetic valve assembly (38) of the trailer vehicle (6) according to any of claims 1, 2, 3, 6 and 7 in order to carry out a lift axle operation of the trailer vehicle (6) with a raised trailing axle (26), characterized by the following method steps: A) checking whether when the trailing axle (26) is fully raised, a weight bearing on the main axle (22) and / or an additional axle (24) of the trailer vehicle (6) would be greater than a predefined weight limit value; B) if when the trailing axle (26) is fully raised, the weight bearing on the main axle (22) and / or the additional axle (24) of the trailer vehicle (6) would not be greater than the predefined weight limit value: switching the or a 3 / 3-way solenoid switching valve (46) of the first solenoid valve unit (42) into its venting position, as a result of which the supporting bellows (30) of the main axle (22) and the supporting bellows (32) of the additional axle (24) of the trailer vehicle (6) are shut off and the supporting bellows (34) of the trailing axle (26) is vented; C) switching the or a 3 / 2-way solenoid switching valve (64) of the second solenoid valve unit (44) into its ventilation position, as a result of which the lift bellows (36) of the trailing axle (26) is ventilated and the trailing axle (26) is raised at least until its wheels are no longer in contact with the roadway (3).

9. Method for controlling the electromagnetic valve assembly (38) of the trailer vehicle (6) according to any of claims 1 to 7 in order to carry out a trailing axle operation with a lowered trailing axle (26), characterized by the following method steps: D) checking whether when the trailing axle (26) is fully raised, a weight bearing on the main axle (22) and / or an additional axle (24) of the trailer vehicle (6) would be greater than a predefined limit value; E) if when the trailing axle (26) is fully raised, the weight bearing on the main axle (22) and / or the additional axle (24) of the trailer vehicle (6) would be greater than the predefined limit value: switching the or a 3 / 2-way solenoid switching valve (64) of the second solenoid valve unit (44) into its venting position, as a result of which the lift bellows (36) of the trailing axle (26) is vented and thus the wheels on the trailing axle (26) come into or maintain contact with the roadway (3); F) adjusting any pressure between the ambient pressure and a maximum pressure in the supporting bellows (30, 32, 34) of the main axle (22), the additional axle (24), and the trailing axle (26) of the trailer vehicle (6) by opening or closing the or a 3 / 3-way solenoid switching valve (46) of the first solenoid valve unit (42).

10. Method for controlling the electromagnetic valve assembly (38') of the trailer vehicle (6) according to either of claims 4 and 5 in order to carry out a lift axle operation with a raised trailing axle (26), characterized by the following method steps: G) checking whether when the trailing axle (26) is fully raised, a weight bearing on the main axle (22) and / or an additional axle (24) of the trailer vehicle (6) would be greater than a predefined weight limit value; H) if when the trailing axle (26) is fully raised, the weight bearing on the main axle (22) and / or the additional axle (24) of the trailer vehicle (6) would not be greater than the predefined weight limit value: switching the inlet valve (80) into its shut-off position and switching the outlet valve (86) into its open position, as a result of which the supporting bellows (30) of the main axle (22) and the supporting bellows (32) of the additional axle (24) of the trailer vehicle (6) are shut off and the supporting bellows (34) of the trailing axle (26) is vented; I) switching the or a 3 / 2-way solenoid switching valve (64) of the second solenoid valve unit (44) into its ventilation position, as a result of which the lift bellows (36) of the trailing axle (26) is ventilated and the trailing axle (26) is raised at least until its wheels are no longer in contact with the roadway (3).

11. Method for controlling the electromagnetic valve assembly (38') of the trailer vehicle (6) according to any of claims 1 to 7 in order to carry out a trailing axle operation with a lowered trailing axle (26), characterized by the following method steps: J) checking whether when the trailing axle (26) is fully raised, a weight bearing on the main axle (22) and / or an additional axle (24) of the trailer vehicle (6) would be greater than a predefined weight limit value; K) if when the trailing axle (26) is fully raised, the weight bearing on the main axle (22) and / or the additional axle (24) of the trailer vehicle (6) would be greater than the predefined weight limit value: switching the or a 3 / 2-way solenoid switching valve (64) of the second solenoid valve unit (44) into its venting position, as a result of which the lift bellows (36) of the trailing axle (26) is vented and thus the wheels on the trailing axle (26) come into or maintain contact with the roadway (3); L) adjusting any pressure between the ambient pressure and a maximum pressure in the supporting bellows (30, 32, 34) of the main axle (22), the additional axle (24), and the trailing axle (26) of the trailer vehicle (6) by opening or closing the outlet valve (86).

12. Method according to any of claims 8 to 11, characterized in that the pressure in the supporting bellows (30, 32, 34) of the main axle (22), the additional axle (24), and the trailing axle (26) is adjusted on the basis of the weight bearing on the main axle and / or the additional axle, and / or on the basis of a distribution of a load weight of the trailer vehicle (6), and / or on the basis of a geometry of the trailer vehicle (6).

13. Method according to any of claims 8 to 12, characterized in that the pressure in the supporting bellows (34) of the trailing axle (26) is at most as high as the pressure in the supporting bellows (30, 32) of the main axle (22) and the additional axle (24).

14. Method for controlling the electromagnetic valve assembly (38, 38') of the trailer vehicle (6) according to any of claims 1 to 7 in order to carry out a lift axle operation of the trailer vehicle (6) with a main axle (22), a raisable trailing axle (26), and, if present, an additional axle (24), characterized by the following method steps: M) in a plurality of venting steps, venting the supporting bellows (30, 32, 34) of the main axle (22), the trailing axle (26), and, if present, an additional axle (24) step by step; N) after each venting step: checking whether a weight acting on the respective supporting bellows (30, 32, 34) exceeds a predetermined weight limit value; O) if the weight acting on the respective supporting bellows (30, 32, 34) does not exceed the predetermined weight limit value: partially venting the supporting bellows (30, 32, 34) again in a further venting step; P) after a final venting step with the supporting bellows (34) of the trailing axle (26) almost completely emptied and if additionally the weight acting on the respective supporting bellows (30, 32, 34) does not exceed the predetermined weight limit value: ventilating the at least one lift bellows (36) of the trailing axle (26), as a result of which said axle is raised high enough that its wheels lift off the roadway (3).